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Pilot Study of Systems to Drive Autonomous Vehicles on Test Tracks

1. Numbers of satellites 0 L 1 1 1 L fi 0 1 2 3 4 5 6 Sample x10 Figure 5 1 Number of satellites at H llered sampled at 1 Hz during one week The frequency spectrum shows four major frequencies where the shortest period time is approximately 24 hours The HDOP value recieved during this time is plotted in Figure 5 4 and the figure shows that the value variates between approximately one and seven The conclusion from static measurements at H llered is that the satellite cover age is satisfactory but the HDOP value sometimes exceeds over the recommended for excellent satellite constellation 5 1 2 Test Track GPS Coverage The different test tracks at Hallered are surrounded with trees see aerial photo in Figure 5 5 Therefore it is important to investigate if there are any GPS shadows on the test track due to the vegetation and or the topography A GPS antenna was placed on the center on the roof of an estate car and the NMEA GGA sentence was logged during the test The test was performed by driving laps on every single lane of the test track to detect GPS shadows The results are shown in Figure 5 6 and Figure 5 7 The results shows that the numbers of satellites and the HDOP 5 1 GPS coverage 43 Numbers of satellites Ke T T Teen 6 1 1 1 1 1 1 1 1 1 1 1 0 5 1 1 5 2 2 5 3 3 5 4 45 5 5 5 6 Sample x 107 Figure 5 2 Low pass filtered signal of the number of satellites at H
2. gt 99 gt 99 gt 99 gt 99 50 0 due to D lt Din Figure 4 5 Distance and angles defined for the Kalman prediction example 4 1 Collision Avoidance Prediction 35 40 20 400 EEE E 20 4 ES 22210 ES AS 410 y 440 0 60 4 u 80 1 1 1 1 1 1 10 0 10 20 30 40 50 60 Figure 4 6 The Kalman position prediction In every prediction the confidence region Din P D n 25 3 is calculated according to Reale max With this information the system is able to calculate the probability of the position estimation being within this region At state amp 5 0 the two position estimations with corresponding confidence region will indicate a possible collision 36 Collision Avoidance As shown in Example 4 1 4 3 the position prediction are exactly the same due to no difference in the model The difference of using the Kalman prediction is that this technique handles the error in a more realistic way Another advantage of the Kalman technique is that the confidence interval of the prediction is x distributed The vehicle model that is used in these examples is as mentioned very simple Increasing the model to a non linear model also increases the accuracy of the calcu lated positions The side effects are that the CPU time increases and an extended Kalman filter has to be used see Appendix E for information of an extended Kalman filter technique The choice o
3. amp t m is a x distributed variable 12 29 In Example 4 3 a Kalman m step prediction is done 32 Collision Avoidance Algorithm 1 Kalman filter KF Initial values 0 1 zo P0 1 Io Time update amp t 1 t A amp t t 4 3a PEHI APEA Q 4 3b Filter gain computation L t P tlt 1 C7 C4P t t 1 C7 RJ 4 4 Measurement update g tt tt 1 L t y t Cia t t 1 4 5a P tt P tt 1 P t t 1 CZ C P tft CP R C4P tt 1 4 5b where Qi Cov w R Cover Algorithm 2 Kalman filter m step predictor t mlt A amp t t 4 6a P t mlt A P Et A gt Am kg Am k T 4 6b k 1 4 1 Collision Avoidance Prediction 33 r Example 4 3 Kalman prediction By using the constant velocity vehicle model see Equation 4 1 and 4 2 and the Kalman filter m step prediction see Algorithm 2 the future estimated position and a confidence region around that prediction can be calculated The constant velocity model has been extended with process and measurement noise according to the following equations 1010 1000 0 1 0 1 0 1 0 0 x t 1 0010 Lt 0010 4 7 0 0 0 1 0 0 0 1 and 1 0 0 0 0 1 0 0 liege ae uj L 4 8 0 0 0 1 where w is normal distributed and has a covariance 0x y 0 5 Ov v 0 1 or 0 0 0 0 oy 0 0 Q 0 0 0 0 0 0 0 dv and has the covariance 1 0 0 0 0 1 0 0
4. Figure 5 13 Lat Long HDOP signals from Lundby 2 50 Measurements and Data Collection 1 08 1 04 1 02 0 98 0 96 0 94 0 92 0 9 0 88 4 1250 Number of samples removed HDOP Figure 5 14 Standard deviation improvement by removing samples for which HDOP exceeds the given level H llered Number of samples removed Figure 5 15 Standard deviation improvement by removing samples for which HDOP exceeds given the level Lundby 1 Table 5 3 Correlation between the signals Lateral Longitudinal 1 0000 0 3053 1 0000 0 2434 0 3053 1 0000 0 2434 1 0000 5 1 GPS coverage 51 1 15 1 1 1 05 0 95 0 9 0 85 0 8 0 75 4 1250 Number of samples removed HDOP Figure 5 16 Standard deviation improvement by removing samples for which HDOP exceeds given the level Lundby 2 performance differential GPS with combined INS system was performed The DGPS receiver was a single antenna system with a standard deviation of 2 cm The measurements took place at H llered and lasted for approximately 5 days See Appendix G and Appendix H for specification of the equipment used The DGPS INS unit was mounted in an estate car with the antenna placed on the roof of the car The car was placed in a stationary position with a clear sky and southern view The position sample rate was set to 10 Hz The position data is presented in Figure 5 17 The position of the stationary measurement was
5. amh nl l july i I LT hri S 1000 1500 2000 2500 HDOP signal 1 Hz on all tracks The measured signal 1 1 1 44 12 4401 12 4402 12 4403 L 12 4404 Long 1 12 4405 1 12 4406 1 12 4407 12 4408 Stationary GPS position measured at H llered during one week 5 1 GPS coverage 47 57 4287 57 4286 57 4285 F 57 4284 Lat 57 4283 57 4282 57 4281 57 428 57 4279 l l y L K 11 5528 11 5528 11 5528 11 5529 11 5529 11 553 11 553 11 5531 Long Figure 5 9 Stationary GPS position measured at Lundby 1 57 4287 57 4286 57 4285 57 4284 57 4283 w 57 4282 57 4281 57 428 F 57 4279 57 4278 57 4277 I L L L I L i 11 5526 11 5527 11 5528 11 5529 11 553 11 5531 11 5532 11 5533 115534 Long Figure 5 10 Stationary GPS position measured at Lundby 2 48 Measurements and Data Collection 12 4406 12 4402 57 4646 57 4644 57 4642 HDOP a T 1 Figure 5 11 Lat Long HDOP signals from H llered HDOP signal is plotted in Figure 5 11 5 13 The figures shows that the position seems to drift away when the HDOP value gets high To reduce this position error we have investigated if the position gets any better by removing some samples when the HDOP value exceeds a given limit In Figure 5 14 5 16 the result is plotted and by removing approximately 300 samples the sta
6. The RT3000 Inertial and GPS Navigation System three angular rate sensors gy ros three servo grade accel erometers a GPS receiver and all the required processing in includes one very compact box Six single GPS antenna models in the RT3000 family allow us to offer very competitively priced products The difference between the products is the positioning performance of the GPS receiver with our most accurate model offering 2cm accuracy The RT3000 works as a stand alone autonomous unit and Autonomous Vehicles requires no user input before it starts operating The outputs from the RT3000 Inertial and GPS Navigation System are derived from the measurements of the acceler ometers and gyros Using the inertial sensors for the main outputs gives the RT3000 sys tem a high update rate 100Hz and a wide bandwidth All the Aerial Survey Applications Inertial outputs are computed in real time with a very low latency The RT3000 Inertial and GPS Navigation Systems outputs its real time measurements over RS232 Ethernet and CAN bus The CAN bus output can be combined into a vehicle s CAN bus or captured using any CAN data acquisition sys tem The real time nature allows the RT3000 to be used for hardware in the loop and controller development Con nection to powerful tools like dSPACE is easy CAN DBC files are provided The precision ADC in the RT3000 gives more than 20 bits of resolu
7. This technique is not suitable to use as a communication device due to the low data rate 3 2 7 WiMax Worldwide Interoperability for Microwave Access WiMax is the standard IEEE 802 16 The use of WiMax is to cover large areas with wireless access approxi mately 70 Mbit second over 500 km It operates between the 2 5 GHz and the 5 8 GHz frequency band The main purpose of this system is to provide the final user with a wireless connection without cable connection In Sweden it operates in the licensed frequency band of 3 5 Ghz This has to be licensed from the Post och telestyrelsen PTS 64 This technique supports a great range but is not intended for implementation as a closed network in a small area The implementation is not cost efficient and the interface would be difficult to implement This makes the technique not suitable for our needs Chapter 4 Collision Avoidance Collision avoidance is a common aspect in the automotive industry nowadays The preventative work is to reduce the numbers of traffic accidents Today most collision avoidance systems are driver assisting warning systems e g Adaptive Cruise Control ACC Lane Departure Warning LDW Blind Spot Surveillance BSS etc By installing vision units in the vehicle to gather information about the surrounding environment the driver can obtain this information to reduce the risk of ending up in a hazardous situation By using sensor target tracking algorithms and pr
8. 544 Dual GPS ac 22 320 2 A AR od oda a RO Y A 48 5 1 5 Differential GPS 48 5 2 Laser Scanner Data Collection 53 5 8 WLAN coverage e 54 5 3 1 WLAN range 000000 eee eee d 54 6 Conclusions 57 6 1 Positioning Conclusions ooo 57 6 Ll Positioning eones de e e E E 57 61 27 VISIONI ad a d dr do en hh ieee ale CAE 58 6 2 Communication Conclusions sosse ss sosse ss ss vor 58 62 1 WLAN ees d 2 20 Bann ea 58 6 3 Survaillence Conclusions 59 6 4 Collision Avoidance Conclusions ss sosse nennen 59 6 5 System Movability Conclusions 00 59 6 6 Future Work ico ella Se 2 2 en ka d des s 59 6 6 1 Positioning System 2 Connor 59 6 6 2 Lidar System gie gt V Sl eA er oda 60 6 6 3 Communication System 60 6 6 4 Collision Avoidance System o 60 6 6 5 Fault Detection 222r 60 Bibliography 61 A Satellite Navigation 67 AL History xoc Be ch att A P aa BE A 67 Ar2 GPS oo ofc cst RARO Se dod e it Kurier Aor Sud e Nite 67 B Inertial Navigation Systems 73 B 1 Dead Reckoning 2 73 C Prototype Systems 76 Ed BADEN s rag Aa aa ii ar a Da 76 C NW Golf GI 53 2 3 don ue Re a 76 Cid Team LUX ee A are a eM e 77 C 4 Previous Volvo projects aa 77 CALL UERAB 600 04 eee ORatMERGGEGEGNSUSOY e an Warren TT Contents xi 0 4 2 VTEC Prototype truck TT D Mathematics 79 D 1 H
9. R T 0010 4 9 0 00 1 where I is small 0 0001 due to the communication possibilities To determine if the system should warn about a future collision risk some definitions need to be explained see Figure 4 5 When the safety distance between two vehicles is defined as Din it is of interest to know if two vehicles are separated with at least Din When the noise is assumed to be Gaussian the confidence region around x t can be calculated Due to the Gaussian noise the confidence region g x t mt z t m T P t m t a t mit Z t m is a x n distributed variable where n is the dimension of x To determine the probability of the confidence region a position x t mit must be assigned In this example the position we have chosen is the edge of the ellipse with a radius of Reale max 29 D_Dih In the Figure 4 6 the confidence region is plotted and the corresponding probability is shown in Table 4 1 If the probability is less than a given threshold an indication of a future hazard situation will be made This indication can also be weighted with the step number m A smaller m is a prediction in the near future and due to prediciton errors it is a much greater risk for collision than if m is larger 34 Collision Avoidance Table 4 1 Position probability when using the Kalman prediction State x t P a t lt pu z 010 x 1 0 210 310 410 510 8 8 410 x 5 0 8
10. RMS 0 15 RMS 0 15 RMS 0 15 RMS at 50km h i i i j i Lateral Velocity 0 3 0 2 0 2 0 2 0 2 0 2 Update Rate 100 Hz 100 Hz 100 Hz 100 Hz 100 Hz 100 Hz Calculation Latency 3 9 ms 3 9ms 3 9 ms 3 9 ms 3 9 ms 3 9 ms Note 1 300m s and 300 s options are available Note 2 A subscription is required to use OmniStar VBS and OmniStar HP Services The internal Pentium class Inertial Sensors in RT3000 in clude servo grade accelerometers and precision MEMS angular rate sensors Powerful 40MHz floating point DSP takes care of coning sculling and aliasing processor runs QNX real time operating system to ensure that the outputs are always deliv ered on time The Kalman filter monitors the performance of the system and updates the using GPS and wheel speed measurements By using the measurements from GPS the RT3000 system is able to maintain highly accu rate measurements and correct its inertial sensor errors The RT3000 comes with ac quisition software that displays the data on a PC or on Pocket PC devices The PC software Simple configuration software allows the user to change the mounting angle displace the measurement point to a virtual location change the differen tial GPS options etc Models To choose the best model for your application think about the positioning accuracy you require and what differential GPS corrections you can sup ply OmniStar systems give excellent results over a
11. Weight 2 0 Ib 0 9 kg Environmental Nonoperating storage temperature 40 to 185 F 40 to 85 C Operating temperature 4 to 131 F 20 to 55 C Operating humidity 10 to 90 percent noncondensing System memory 32 MB RAM 16 MB flash memory Input power requirements 100 to 240 VAC 50 to 60 Hz power supply 36 to 57 VDC device Powering options Local power 802 3 AF switches Cisco higher power switches capable of supporting 13W or greater Cisco Aironet power injectors PWRINJ3 and PWRINJ FIB Third party PoE devices must meet input power and power draw requirements Power draw 12 95W maximum Note 12 95W is the maximum power required at the powered device If the access point is being used in a PoE configuration the power drawn from the power sourcing equipment will be higher by some amount dependent on the length of the interconnecting cable This additional power can be as high as 2 45W bringing the total system power draw access point and cabling to 15 4W Warranty 90 days Wi Fi certification que CERTIFIED System Requirements Table 3 lists the system requirements for Cisco Aironet 1240G Series Access Points Table 3 System Requirements for Cisco Aironet 1240G Series Access Points Access Method Description Browser Using the Web browser management GUI requires a computer running Internet Explorer Version 6 0 or later or Netscape
12. in front of the vehicle can observe a range to the object a range rate measurement e g by Doppler shift and an azimuth angle to the object By estimating the vehicle states a prediction of the new position can easily be done The predicted position can then be used to determine how an avoidance manouvere should be implemented This is a feature that is relevant to use in regular traffic scenarios where every surrounding vehicle is unknown 37 In the case of test track environment and surrounding conditions the vehicle already has all the relevant vehicle states from the communication and all vehicles are known When surrounding vehicles states are unknown a tracking feature has to be implemented to observe the vehicles states Due to the already known vehicle states a more precise prediction can be done when the position and heading does not have to be estimated Hence this tracking feature can improve the avoidance manouvere if an unknown object appears e g an animal a trailer or a broken down vehicle Further information about tracking can be found in 11 Chapter 5 Measurements and Data Collection In this chapter measurements and data collections that have been made during the thesis are presented The chapter will also cover analysis of the collected data and signals 5 1 GPS coverage In this section the result of GPS coverage measurements is presented It will cover the results of long time static measurements dynamic
13. lidar system has a greater field of view as well as the fusion unit A single lidar covers approximately 170 and a fusion unit placed on each front corner covers approximately 300 20 26 Figure 4 7 shows an example plot of a single lidar detection area The lidar is mounted on a truck s front left corner The dotted line points out the field of view of a single lidar The reflected image shows a detection of a car in front of the vehicle The high resolution makes it possible to identify the object due to its significant structure A fusion system also increases the redundancy of the complete system The data that is collected from the same area makes it possible to verify the view of the front of the vehicle the most relevant area in the collision avoidance system with a second measurement The sensor fusion also features as a backup if malfunction in one sensor should occur 13 A general feature in automotive collision avoidance systems is the possibility of object tracking The vision unit e g radar or lidar detects the object and 4 3 Collision Avoidance Vision 39 Bern ws te fam VR 30 At n a 6m Mm d E 10 82 VR 33 Ai n a 4m ow em 10 27 4 VR 34 IR Ar nl e N A s af k mem N MP 3c 3D om a jac 20 Z ia Bic 10 6m 4m 2m Om 2m 4m 6m Figure 4 7 A front edge mounted laser scanner The picture shows the echoes and how the unit detects an object in this case a car
14. 2 Laser Scanner Data Collection Due to restricted availability to a lidar system we were not able to perform these measurements by ourselves The data sequences which we have studied are from the Volvo Integrated Safety Truck VIST at Volvo Technology The data pre sented in Figure 5 19 is from a single dual echo four layer technology laser scanner mounted on the truck s front left corner see Appendix C 4 2 for more informa tion The angle of view is approximately 200 dashed line in Figure 5 19 The figure clearly shows the objects in the nearby area of the truck In this particular case it is an avenue with planted trees on both sides of the roadway The left side of the picture shows a wall The conclusions of this data collection is that the lidar is able to clearly detect and use the trees on the avenue as markings for e g positioning This points to the possibilities of using static known objects for determining present position In the picture some objects very near the front are occurring This is dirt that are stuck on the laserscanner This dirt can be handled by filtering the signal Table 5 4 The DGPS accuracy Latitude Longitude Drift 23 5m Tm o 3 2cm 3 lcm 54 Measurements and Data Collection 5 3 WLAN coverage The distance coverage of a WLAN system is often specified by the manufactur ers The problem of these specifications is that the system is not applied in an environment that is similar to a tes
15. AP was measured to approximately 600 m When the speed was reduced to approximatly 30 km h the distance was measured to approx imately 650 m when connection was established During these tests the tendencies of latency were less than 5 ms independant of the vehicle speed The tests were performed with constant visual contact with the AP Transfer Rate During the tests a constant transfer rate was applied The transfer rates that we tested were 1 2 and 11 Mbit s The distances of the AP range were near constant for all tested transfer rates In Section 4 2 the VSM is calculated to be less than 50 Bytes with header and checksum included With a realistic usage of 50 percent of the channel the number of VSM s that the system will be able to send are presented in Table 5 5 With an update frequency of the VSM of 2 times per second and vehicle the system will be able to handle at least 625 vehicles calculated with the slowest transfer rate A realistic assumption is that the number of vehicles at the test site will be less than 100 which leaves room for additional data transfer e g measurement data Table 5 5 Messages per second Tranfer rate 50 usage Number of messenges I Mbit s 0 5 Mbit s 1250 2 Mbit s 1 Mbit s 2500 11 Mbit s 5 5 Mbit s 13750 Environment To see how the environment effects the connection possibilities we drove around the curve endurance track to see if we had similar coverage as in the distance test
16. Data Sheet Cisco Aironet 1240G Series Access Point Cisco Aironet 1240G Series Access Points provide single band 802 11g wireless connectivity for challenging RF environments such as factories warehouses and large retail establishments Figure 1 Connectorized antennas a rugged metal enclosure and a broad operating temperature range offer extended range and coverage versaiility The Cisco Aironet 1240G Series provides local as well as inline power including support for IEEE 802 3af Power over Ethernet POE Figure 1 Cisco Aironet 1240G Access Point The Cisco Aironet 1240G Series is a component of the Cisco Unified Wireless Network a comprehensive solution that delivers an integrated end to end wired and wireless network Using the radio and network management features of the Cisco Unified Wireless Network for simplified deployment the Cisco Aironet 1240G Series extends the security scalability reliability ease of deployment and manageability available in wired networks to the wireless LAN WLAN The Cisco Aironet 1240G Series is available in two versions unified or autonomous Unified access points operate with the Lightweight Access Point Protocol LWAPP and work in conjunction with Cisco wireless LAN controllers and the Cisco Wireless Control System WCS When configured with LWAPP the Cisco Aironet 1240G Series can automatically detect the best available Cisco wireless LAN controller and download appropriate poli
17. Navigator Version 7 0 or later PoE Power sourcing equipment is compliant with Cisco Inline Power or IEEE 802 3af and provides at least 12 94W at 48 VDC All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 5 of 6 Data Sheet Ordering Information To place an order visit the Cisco Ordering Website at http www cisco com en US ordering index shtml Table 4 lists the product part numbers for Cisco Aironet 1240G Series Access Points Table 4 Product Part Numbers for Cisco Aironet 1240G Series Access Points Part Number Description AIR AP1242G A K9 802 11g non modular Cisco IOS access point RP TNC FCC configuration AIR AP1242G E K9 802 11g non modular Cisco IOS access point RP TNC ETSI configuration AIR AP1242G P K9 802 119 non modular Cisco IOS access point RP TNC Japan2 configuration AIR LAP1242G A K9 802 119 non modular LWAPP access point RP TNC FCC configuration AIR LAP1242G E K9 802 119 non modular LWAPP access point RP TNC ETSI configuration AIR LAP1242G P K9 802 119 non modular LWAPP access point RP TNC Japan2 configuration Service and Support Cisco offers a wide range of services programs to accelerate customer success These innovative programs are delivered through a unique combination of people processes tools and partners resulting in high levels of customer satisfaction
18. The space segment consists of 24 satellites arranged in 6 orbitals The orbital planes have an inclination angle of 55 degrees relative the earth equator The satellites have an average orbital altitude of approximately 20 200 km and i takes 67 68 Satellite Navigation Table A 1 Location of the Components of the Operation Control Segment Master control station Falcon Air Force Base Colorado Springs CO Master control station backup Gaithersburg MD Monitor station Falcon Air Force Base Colorado Springs CO Remote monitor station Cape Canaveral FL Remote monitor station Hawaii Remote monitor station Ascension Island Remote monitor station Diego Garcia Remote monitor station Kwajalein Ground antenna Cape Canaveral FL Ground antenna Ascension Island Ground antenna Diego Garcia Ground antenna Kwajalein approximately 12 hours to complete one orbit Each satellite have a precise atomic clock and sends out messages with the current position current time and an iden tity number The satellites transmit on two frequencies centered on 1575 42 MHz and 12227 60 MHz 3 30 Control segment The control segment consists of six monitoring stations four ground antennas and a master control station In Table A 1 is the control segment stations listed The control segment main purpose is to monitoring the health and status of the space segment 3 30 User segment The user segment provides the user with position veloci
19. access points 802 1af PoE The access points can be powered by IEEE 802 3af PoE Cisco Inline Power switches single port power injectors or local power Hardware assisted The access points provide high security without performance degradation AES encryption Product Specifications Table 2 lists the product specifications for Cisco Aironet 1240G Series Access Points Table 2 Product Specifications for Cisco Aironet 1240G Series Access Points Item Specification Part Number AIR AP1242G x K9 AIR LAP1242G x K9 Regulatory domains x regulatory domain A FCC E ETSI e P Japan2 Customers are responsible for verifying approval for use in their individual countries To verify approval and to identify the regulatory domain that corresponds to a particular country please visit http www cisco com go aironet compliance Not all regulatory domains have been approved As they are approved the part numbers will be available on the Global Price List Data rates supported 802 119 1 2 5 5 6 9 11 12 18 24 36 48 and 54 Mbps Network standard IEEE 802 11b and 802 11g Uplink Autosensing 802 3 10 and 100BASE T Ethernet Frequency band and operating channels Americas FCC 2 412 to 2 462 GHz 11 channels ETSI 2 412 to 2 472 GHz 13 channels Japan2 2 412 to 2 472 GHz 13 channels Orthogonal Frequency Division Multiplexing OFDM 2 412 to 2 484 GHz 14 channels CC
20. at 6 Mbps 425 ft 130m at 5 5 Mbps 910 ft 277m at 5 5 Mbps 445 ft 136m at 2 Mbps 940 ft 287m at 2 Mbps 460 ft 140m at 1 Mbps 950 ft 290m at 1 Mbps Measured with 2 2 dBi dipole antenna for 2 4 GHz Compliance Standards Safety UL 60950 1 CAN CSA C22 2 No 60950 1 UL 2043 IEC 60950 1 EN 60950 1 NIST FIPS 140 2 level 2 validation Radio Approvals FCC Part 15 247 RSS 210 Canada EN 300 328 Europe ARIB STD 33 Japan ARIB STD 66 Japan AS NZS 4268 2003 Australia and New Zealand EMI and susceptibility Class B FCC Part 15 107 and 15 109 ICES 003 Canada VCCI Japan EN 301 489 1 and 17 Europe EN 60601 1 2 EMC requirements for the Medical Directive 93 42 EEC Security 802 11i WPA2 WPA 802 1X AES TKIP Other IEEE 802 11g and IEEE 802 11a FCC Bulletin OET 65C RSS 102 All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 4 of 6 Data Sheet Item Specification Antenna connectors 24 GHz Dual RP TNC connectors Status LEDs Status LED indicates operating state association status error or warning condition boot sequence and maintenance status Ethernet LED indicates status of activity over the Ethernet Radio LED indicates status of activity over the radio Dimensions H x W x D 1 1 x 6 6 x 8 5 in 2 79 x 16 76 x 21 59 cm
21. aviation_technology_vdl model Neil Ackroyd and Robert Lorimer Global Navigation A GPS User s Guide Lloyd s of London Press Ltd 2 edition 1994 Fraport AG Tacsys capts fraport project 2007 URL http www fraport com cms company dok 81 81480 tacsyscapts htm SICK AG Homepage 2007 URL http www sick com home en html The Defense Advanced Research Projects Agency D a r p a challange 2007 URL http www darpa mil grandchallenge index asp The Defense Advanced Research Projects Agency D a r p a home November 2007 URL http www darpa mil ZigBee Alliance Zigbee alliance 2007 URL http www zigbee org David Andersson and Johan Fjellstr m Vehicle Positioning with Map Mach ing Using Integration of a Dead Reckoning System and GPS Master s thesis Link pings Universitet ISY Link pings Universistet 581 83 Link ping 2004 LiTH ISY EX 3457 2004 Dave Bagby Bob O Hara and Dave Roberts Proposed revisions to the mac frame formats to support wireless distribution systems Document 802 11 94 248 1994 Yaakov Bar Shalom and William Dale Blair Multitarge Multisensor Track ing Applications and Advances Volume III Artech House Inc 2000 Yaakov Bar Shalom X Rong Li and Thiagalingam Kirubarajan Estimation with Applications to Tracking and Navigation John Wiley amp Sons Inc 2001 61 62 Bibliography 13 Alberto Broggi Stefano Cattani Pier Paolo Porta and Zani Paolo A l
22. echo feature to be able to reduce unwanted detection rain fog etc and a multi layer scanning to increase the resolution 6 2 Communication Conclusions The communication system needs to be robust with sufficient capacity to handle all communication It must be fast enough to reduce the risk of latencies in the system 6 2 1 WLAN The WLAN technique is suitable for this implementation The WLAN technique is known as an off the shelf technology The great advantages of this is that the technique is very cost efficient and it still is under development with new standards for future use e g IEEE 802 11n The test result when using a WLAN shows that a significant distance can be covered with an omni directional antenna However there is a performance problem when the vegetation blocks the line of sight between the AP and the receiving unit To evade this problem more AP s are needed to cover the complete area The Vehicle States Messages VSM size is very small compare to the transfer rate This indicates that the WLAN technique is suitable for future improvement e g transferring the measurement data with the spared bandwidth 6 3 Survaillence Conclusions 59 6 3 Survaillence Conclusions Surveillance of all vehicles can be accomplished by using the VSM s The vehicles positions can be presented in real time on a digital map All additional information in the VSM can also be presented as additional information about the vehic
23. larger amounts of data would be limited 3 2 Wireless Local Area Network 3 2 1 IEEE 802 11 IEEE 802 11x is the standard of Wireless Local Area Network WLAN The IEEE 802 11 is followed by an index letter a b g n in this case which indicates what version of WLAN it is In table 3 1 the capacity and performance of different 802 11 protocols is presented This is the most common communication technique adapted for wireless data transfer Table 3 1 IEEE 802 11x specifications of frequency and transfer rate Protocol Operation Freq Transfer Rate 802 1la 5 GHz 54 Mbit 802 11b 2 4 2 5 GHz 11Mbit 802 11g 2 4 2 5 GHz 54 Mbit 802 11n 2 4 and or 5 GHz 248 Mbit 1802 11n is a draft version 3 2 Wireless Local Area Network 21 3 2 2 WLAN With Dual Antennas A problem with the WLAN technique is that latency occurs when switching be tween different Access Points AP When leaving the area of AP and entering the area of AP the receiving module must do a scan to obtain a new signal This causes a latency time when the receiver does not have a wireless connection To minimize this latency time the receiving unit can be equipped with a dual antenna system A normal latency time for a single antenna including roaming is about 1 second By adding one antenna to the system it can decrease the handover time to approximately 60 milliseconds with fast authentication 44 One technique of the dual antenna h
24. measurements at the tracks at Hallered test site Analysis of the GPS accuracy will also be handled 5 1 1 Static GPS Coverage H llered To verify that the GPS coverage at H llered is satisfactory data was collected during one week see Table 5 1 with a stationary GPS receiver The NMEA GGA sentence the NMEA sentence is specified in Appendix A 2 was monitored The receiver was placed with free sight in the Southern hemisphere direction In this test a USB connected GPS receiver was used with a specification according to Appendix F In the GGA sentence contains several fields to determine the GPS coverage numbers of satellites and quality HDOP of the GPS signal To obtain an accurate position the GPS receiver needs at least four satellites see Appendix A 2 and it needs to have an HDOP value below four for excellent satellite constellation see Appendix A 2 Figure 5 1 shows is the number of satellites It seems like it is several added sinus waves with a large period time To obtain a clearer signal the signal is filtered through a low pass Butterworth filter of the fourth degree with a cutoff frequency of 10 mHz In Figure 5 2 the filtered signal is plotted and the corresponding frequency spectrum obtained through FFT calculation is shown in Figure 5 3 1FFT Fast Fourier Transform 41 42 Measurements and Data Collection Table 5 1 Stationary GPS measurement From To Date 03 07 07 10 07 07 Time 13 30 13 30
25. non autonomous vehicles simultaneously on test tracks The thesis includes studies of communication positioning collision avoidance and techniques for surveillance of vehicles which are suitable for implementation The investiga tion results in a suggested system outline Differential GPS combined with laser scanner vision is used for vehicle state estimation position heading velocity etc The state information is transmitted with IEEE 802 11 to all surrounding vehicles and surveillance center With this information a Kalman prediction of the future position for all vehicles can be estimated and used for collision avoidance Acknowledgments We would first of all thank our supervisors at AB Volvo G ran hlin and G ran hling These two persons have been of great importance for the performance of this master thesis and have always encouraged and helped us during the time We would also thank Per Olov Fryk who initiated this project our examiner Thomas Sch n and our supervisor at the university Christian Lundquist Finally we would thank all of the employees at Volvo 3P who have helped us and made our work a great time Erik Agardt and Markus L fgren G teborg January 2008 vii Contents Introduction Ll Background ss amp ns Rn A a e 1 2 Volvo IP a e sg perenne WR nes 1 3 Problem Specification LL lid e o ari a ita aaa II LARA hee de die en Sh te 1 5 Ehesis Quiline 44 Pee a a AA RAI Position System 2 1 Sat
26. of the vehicles models The accuracy could of course be increased by extending the model with vehicle specific parameters but the versatility of the model and the accuracy should be enough for the intended function as a collision avoidance predictor 59 60 1See 31 for more information about given vehicle models Table 4 2 Vehicle model errors and CPU time 31 Model RMSE m Max error m CPU time Constant velocity 0 88 5 2 1 Constant acceleration 0 65 4 7 1 2 Nearly coordinated turn 0 56 3 5 2 8 4 2 Vehicle States Message 37 X t x t ut v t bt E x t tibi i ti vs ti cos p t i y ti ti41 ti Ve ti sin p t ots tia tbs i belt 4 10 ti ot mip ts The vehicle s current states estimates as an initial state X t 0 and the vehicles future states are Xp t tp 0 tp Tpred where Tprea is the total prediction time The model based prediction is given by Equation 4 11 where f X U tn tp is a nonlinear model and Up tn tp is the assumed future input Xpltn tp HXp tn tp Up tn tp tn tp 4 11 When the vehicle s current states are given the accuracy of the prediction depends on the assumption of driver input and the vehicle model To increase the accuracy of this prediction the history of the driver and future driving schedule could be incorporated With constant input assumption the prediction model based on the vehicle m
27. on to a rotating mirror to spread the view of sight The echo of the laser beam is received and the distance and the heading can be calculated 26 14 Position System Figure 2 6 Animation of the principle of lane detection using a laserscanner 26 Lidar Technique The lidar vision system uses several different techniques to increase its perfor mance Dirt on the lens could result in a false detection The dirt reflections can to a certain extent be filtered by processing the signal This applies to limited surface elements The obstacles of the lidar such as bad weather performance is improved by using four echo technology An object such as a raindrop or another vehicle would normally generate one reflection or echo per laser pulse By increas ing the number of echoes to as many as four per pulse and by filtering the echoes and removing the false echoes the lidar has significantly optimized and refined object detection 26 For implementation at a truck that is supposed to drive under very rough road conditions the system is exposed to hard oscillation The system handles this problem with a multilayer technique see Figure 2 7 The laser beam is split into four different layers and the distance measurements are taken independently for each of these layers with an aperture angle of 3 2 This allows compensation for pitching of the vehicle caused by an uneven surface or driving manoeuvres such as braking and accelerating Sinc
28. pulse with a defined duration is sent and reflected by an object The reflection of the object is captured by a photo diode and transformed into signals in an optoelectronic circuit The time interval between the pulse of light being sent and its reflection being received indicates the distance to the object which reflected the light In addition to the radar the laser pulse is quite narrow This gives the laser scanner a higher resolution of the object By rotating a mirror the laser range finder operates as a scanner and the mirror deflects each outgoing beam The mirror s continuous rotation in conjunction with the pulsing laser generates a complete environmental profile of the vehicle 2 4 Vision System 13 within the laser scanners visible range see Figure 2 5 The laser scanning system has been adapted by several autonomous prototype vehicles The lidar technique has also been implemented by Volvo Technology at their Volvo Integrated Safety Truck see Appendix C 4 2 Usage of the lidar is for example collision avoidance pedestrian safety blind spot surveillance 31 Lidar Performance The laser scanner has a very high sample rate This makes it suitable for scanning the environment at high speeds This technique is similar to millimeter radar mm radar but is a less expensive technique to use The range and the narrow lobe of the laser makes the system very precise It provides a high resolution of the pixel map and could giv
29. this example these are set to four and six meters The vehicle initial states are given as below Xi to 0 0 10 01 Xa to 0 55 10 10 The predicted positions are presented in Figure 4 3 If both vehicles continue with present headings and velocities there is a great probability that a collision will take place after five seconds The future predictions in this case require a perfect model and state estimation o T ER amp 4 4 0 20 E 4 2310 E 30r 4 ae 50 F 60b 4 70 1 1 1 1 1 1 10 0 10 20 30 40 50 60 Figure 4 3 A linear prediction from the present position at 0 0 Circles around every prediction symbols the fixed safety distance At state 5 0 the two position estimations with corresponding safety distances will indicate a possible collision LL e _ _ In Example 4 1 the model as well as the measurement are assumed to be be very good and are not very realistic Almost all state measurement equipments have some kind of errors see Table 2 1 for typical GPS accuracy and this in secureness should be taken into consideration In Example 4 2 an error in the position is assigned and the safety area is then increased in each step 4 1 Collision Avoidance Prediction 31 ol Eolo 00 3420 0 e sem ey 20L 4 50 4 4 60 1 1 L 1 1 1 10 0 10 20 30 40 50 60 Figure 4 4 Linear prediction with increasing pr
30. this information supplies the user with a high accuracy in position 47 2 4 Vision System 11 Table 2 1 Accuracy of different navigation types Navigation Type Theoretical performance GPS 215 m 1 GPS with EGNOS 2 m 19 GPS L1 Carrier Phase 1 8 m 42 GPS L1 L2 Carrier Phase 1 5 m 42 OmniSTAR GPS sub m 42 Local Area DGPS L1 Carrier Phase 0 45 m 42 Local DGPS L1 L2 Carrier Phase sub dm 42 Local DGPS L1 L2 with INS sub dm 47 2 4 1 Line Following Systems A system that is commonly used by Automated Guided Vehicles AGVs is the line following principle By using a guidance system the vehicle can follow a predefined guidance line by itself Vehicles with monotonous driving schedules are suited for this system The principle of implementation is usage of a vision system e g a laser scanner that detects a significant marking or reflection material and uses it as guidance This technique can also be implemented with magnetic force which the PATH project see Appendix C 1 in California is one example of Using permanent magnets in the roadway and detectors in the vehicle results in a robust system However this technique suffer from problems as relocation and mobility of the system due to the need of static implementation 49 Due to our demands of movability of the system this technique is not of interest to our needs 2 4 2 Camera Systems Camera systems can use one or several cameras in combination with a comp
31. 001 Fredrik Gustafsson Lennart Ljung and Mille Millnert Signalbehandling 2001 Bernhard Hofmann Wellenhof and Herbert Lichtenegger GPS Theory and Practice 5 edition 2001 Jonas Jansson Collision Avoidance Theory with Application to Automotive Collision Mitigation Phd thesis Link pings Universitet ISY Link pings Universistet 581 83 Link ping 2005 Christopher Jekeli Inertial Navigation Systems with Geodetic Applications Walter de Gynter GmbH amp Co KG 2001 Anders Johansson Kommuniaktionsgr nssnitt mot GP amp C transponder Mas ter s thesis Link pings Universitet Department of Science and Technology Link pings Universistet 601 74 Norrk ping 2003 LiTH ITN EX 03 005 SE Rickard Karlsson Simulation Based Methods for Target Tracking Lic thesis Link pings Universitet ISY Link pings Universistet 581 83 Link ping 2002 J rg Kibbel Winfried Justus and Kay F rstenberg Lane estimation and departure warning using multilayer laserscanner Intelligent Transportation Systems 2005 Proceedings 2005 IEEE pages 607 611 Hye Soo Kim Sang Hee Park Chun Su Park Jae Won Kim and Sung Jea Ko Selective channel scanning for fast handoff in wireless lan using neighbor graph July The 2004 International Technical Conference on Cir cuits Systems Computer and Communications ITC CSCC2004 Japan Alexander Kirchner and Christian Ameling Integrated obstacle and road tracking using a laser scanner I
32. 1 216 Omnistar Omnistar 2007 URL http www omnistar nl DesktopDefault aspx tabid 344 J rgen Ott and Dirk Kutscher Drive thru internet IEEE 802 11b for au tomobile users IEEE Infocom 2004 Conference Oxford Technical Solutions Limited Oxford Technical Solutions Limited 77 Heyford Park Upper Heyford Oxfordshire OX25 5HD RT3000 Inertial and GPS Measurement System User Manual revision 060502 edition Bradford W Parkinson and James J Spilker Jr Global Positioning System Theory and Applications Volume II American Institute of Aeronautics and Astronautics Inc 1996 California PATH Path california partners for advanced transit and highways 2007 URL http www path berkeley edu Jon Person Writing your own gps applications Part 2 causes of precision error 2007 URL http www developerfusion co uk show 4652 2 Martin Pettersson Distributed integrity monitoring of differential GPS cor rections Master s thesis Link pings Universitet ISY Link pings Universis tet 581 83 Link ping 1998 LiTH ISY EX 2021 Andreas R nnebjerg A Tracking and Collision Warning System for Mar itime Applications Master s thesis Link pings Universitet ISY Link pings Universistet 581 83 Link ping 2005 LiTH ISY EX 05 3709 SE Sangho Shin Andrea G Forte Anshuman Sing Rawat and Henning Schulzrinne Reducing mac layer handoff latency in IEEE 802 11 wireless lans 2004 ACM 1 58113 920 9 04 0010 Bibliograph
33. Cisco services help you protect your network investment optimize network operations and prepare your network for new applications to extend network intelligence and the power of your business For more information about Cisco services visit Cisco Technical Support Services or Cisco Advanced Services For More Information For more information about the Cisco Aironet 1240G Series visit http www cisco com go wireless or contact your local Cisco account representative Arnoricus Peseta risa no Ta BUNG Readers Europe Hosen Capo ng MOL oN BE alui CISCO ore ace ted on Te Cisco Website at une velica oom aofal lies Pat Stino bien Bi Li x Pronto Fat Kasten Way to cinereus Cs anida f Parigi Of Oise viteria Lig Amer as eh Nob inte dO Pina dari oli coh vos PAL eter terna rona ar rus dique er Ve cod caio muy est Fer epoca oe vec Tra doe ot Dre wet patina est vat pate press shy ealpiionnnly Gore Cano and soy dier compare BAN Printed in USA C78 401676 01 07 07 All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 6 of 6 Appendix J Antenna Specifications 100 101 Specification Quick Installation Guide 8dBi Omni Heewre pane 157 Extended range Package Contents Holder Hose Clamp Screw nuts Screws Plastic fixings Washer Sticker e Free Gift Waterproof Tape zeuu
34. GDOP is divided into HDOP Horizontal DOP VDOP Vertical DOP PDOP Position DOP 3 D and TDOP Time DOP These values are presented in different parts of the NMEA code These quantities follow mathematically from the positions of the usable satellites on the local sky 48 NEMA 0183 The NMEA 0183 is a standard the are based on serial communication It has one speaker and an optional number of receivers It can be used by sonars echo sounder gyrocompass autopilot GPS receivers and many other types of instru ments The GPS system uses the standard and is sends a string of information the most common are listed in Table A 3 One of the NMEA sentences is the GPGGA GGA sentence which is a essential fix data which provide 3D location and accuracy data It includes information as the position Latitude Longitude fix quality number of satellites being tracked horizontal dilution of position alti tude mean sea level time in seconds since last DGPS update DGPS station ID number and a checksum data see Table A 4 for example 16 70 Satellite Navigation Table A 3 NMEA 0183 GPAAM GPBOD GPBWW GPGGA GPGLL GPGSA GPGST GPGSV GPHDG GPHDT GPRMB GPRMC GPRTE GPVTG GPWCV GPWNC GPWPL GPXTE GPXTR GPZDA GPZFO GPZTG A DA PA DK LD DD DD A A AA A LD LD A A O90 ND ND A ND amp Waypoint Arrival Alarm Bearing Origin to Destination Bearing Waypoint to Waypoint Global Positioning System Fix Data Geographic P
35. HD England Tel 44 1869 238 015 Fax 44 1869 238 016 http www oxts co uk mailto info oxts com RT Base GPS Base Station The RT Base is a portable GPS Base Station capable of pro viding Differential Corrections for Differential GPS Receiv ers The RT Base can be used with the RT3000 products to give up to 2cm positioning accu racy One RT Base unit can be used to correct multiple DGPS sys tems Additional Remote Ra dio Modems can be purchased for each mobile DGPS system FastTo Install The RT Base has been de signed with installation speed in mind Simply connect the GPS Antenna and the Radio Modem Aerial then turn on EZ OND E A s 2 B E s The unit can start transmitting corrections in under 2 minutes with a known location or under 5 minutes if the position needs to be averaged Training for operators is also minimal Instructions are printed on the inside of the RT Base unit and a Quick Oty RT Base components with SATEL radio 1 RT Base Unit 1 GPS C006 15m GPS Antenna Cable 1 GPS 702 GG GPS Antenna 1 SATEL Satelline 3ASd Radio Modem 2 Radio Modem Aerial Antenna with 3m cable 1 Lightweight Tripod 1 IEC Mains Cable 1 77C0002B Power Cable 1 Internal Radio Link fit to use internal radio 1 RT Base User Manual 1 RT Base Quick Guide Note 1 Different radios are required for operation in different countries Guide is provided to make the operatio
36. I L t C t P t t 1 where 8f t PO En CO B z tt 1 and Qi Cov w Ri Cover E 9a E 9b E 10a E 10b Appendix F Globalsat PRODUCT SPECIFICATION USB GPS RECEIVER BU 353 Ver 1 03 GlobalSat Technology Corporation 16 No 186 Chien 1 Road 235Chung Ho City Taipei Hsien Taiwan R O C Tel 886 2 8226 3799 Rep Fax 886 2 8226 3899 Web www globalsat com tw E mail service globalsat com tw Page 1 of4 BU 353specification ver1 03 doc Product Feature e SiRF starlll high performance and low power consumption chipset e All in view 20 channel parallel processing e Built in patch antenna e Very High sensitivity to satellite signal Tracking Sensitivity 159 dBm e Extremely fast TTFF Time To First Fix at low signail level e Build in SuperCap to reserve system data for rapid satellite acquisition e Supported NMEA 0183 data protocol e Super cohesive magnetic for mounting on the car e Water resisted and non slip on the bottom e USB interface connection port e LED indicator for GPS fix or not fix LEDOFF Receiver switch off LED ON No fixed Signal searching LED Flashing Position Fixed Page 2 of 4 System Specification Electrical Characteristics Receiver Chipset SIRF Star III Frequency L1 1575 42 MHz C A Code 1 023 MHz chip rate Channels 20 channel all in view tracking Sensitivity 159 dBm Accuracy Position Horizontal 10m 2D RMS SA off Velocity 0 1m sec Time 1 micr
37. Institutionen f r systemteknik Department of Electrical Engineering Examensarbete Pilot Study of Systems to Drive Autonomous Vehicles on Test Tracks Examensarbete i Reglerteknik utf rt vid Tekniska h gskolan i Link ping av Erik Agardt Markus L fgren LITH ISY EX 08 4042 SE Link ping 2008 U ely 7 CS Nas uns Link pings universitet TEKNISKA H GSKOLAN Department of Electrical Engineering Link pings tekniska h gskola Link pings universitet Link pings universitet SE 581 83 Link ping Sweden 581 83 Link ping Pilot Study of Systems to Drive Autonomous Vehicles on Test Tracks Examensarbete i Reglerteknik utf rt vid Tekniska h gskolan i Link ping av Erik Agardt Markus L fgren LITH ISY EX 08 4042 SE Handledare Christian Lundquist IsY Link pings universitet G ran hling EDAC Volvo 3P G ran hlin Volvo 3P Examinator Thomas Sch n ISY Link pings universitet Link ping 28 March 2008 GS UN P E Ive Avdelning Institution Datum LI KA Division Department Date S a u CES Division of Automatic Control A ar x nn of Electrical Engineering 2008 03 28 2 ay ink pings universitet ic SE 581 83 Link ping Sweden Spr k Rapporttyp ISBN Language Report category EN Svenska Swedish Licentiatavhandling ISRN amp Engelska English amp Examensarbete LITH ISY EX 08 4042 SE C uppsats Serietitel och serienu
38. K Nonoverlapping channels 802 11b g 3 channels Receive sensitivity typical 802 11g 1 Mbps 96 dBm 2 Mbps 93 dBm 5 5 Mbps 91 dBm 6 Mbps 91 dBm 9 Mbps 85 dBm 11 Mbps 88 dBm 12 Mbps 83 dBm 18 Mbps 81 dBm 24 Mbps 78 dBm 36 Mbps 74 dBm 48 Mbps 73 dBm 54 Mbps 73 dBm All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 3 of 6 Data Sheet Item Specification Available transmit power settings 802 11g Maximum power setting varies by channel and CCK OFDM according to individual country regulations 20 dBm 100 mW 17 dBm 50 mW 17 dBm 50 mW 14 dBm 25 mW 14 dBm 25 mW 11 dBm 12 mW 11 dBm 12 mW 8 dBm 6 mW e 8 dBm 6 mW e 5 dBm 3 mW 5dBm 3 mW 2dBm 2 mW 2 dBm 2 mW 1 dBm 1 mW Range typical Indoor distance across open Outdoor office environment 802 119 802 119 105 ft 32m at 54 Mbps 120 ft 37m at 54 Mbps 180 ft 55m at 48 Mbps 350 ft 107m at 48 Mbps 260 ft 79m at 36 Mbps 550 ft 168m at 36 Mbps 285 ft 87m at 24 Mbps 650 ft 198m at 24 Mbps 330 ft 100m at 18 Mbps 750 ft 229m at 18 Mbps 355 ft 108m at 12 Mbps 800 ft 244m at 12 Mbps e 365 ft 111m at 11 Mbps 820 ft 250m at 11 Mbps 380 ft 116m at 9 Mbps 875 ft 267m at 9 Mbps 410 ft 125m at 6 Mbps 900 ft 274m
39. Security EAP TLS EAP Tunneled TLS EAP TTLS e EAP Subscriber Identity Module EAP SIM e Cisco LEAP Encryption Advanced Encryption Standard Counter Mode with Cipher Block Chaining Message Authentication Code Protocol AES CCMP encryption WPA2 o TKIP WPA Cisco TKIP WPA TKIP IEEE 802 11 WEP keys of 40 and 128 bits Current support for 12 Lower potential interference with neighboring access points nonoverlapping channels with simplifies deployment potentially up to 23 channels Fewer transmission errors delivers greater throughput All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 2 of 6 Data Sheet u Feature Benefit Rugged metal housing Metal case and rugged features support deployment in factories warehouses the outdoors NEMA enclosure required and other industrial environments UL 2043 plenum rating and The access points support installation in environmental airspaces such as areas extended operating temperature above suspended ceilings Multipurpose and lockable The access points provide greater flexibility in installation options for site surveys mounting bracket as well as theft deterrence Support for both local and Power can be supplied using the Ethernet cable eliminating the need inline power including IEEE for costly electrical power line runs to remotely installed
40. T3002 from Oxford Technical Solutions This is a combination system that are using 76 C 3 Team LUX 77 a DGPS beacon antenna and an inertial navigation system to obtain a very high position update frequency This sophisticated equipment supplies the car the exact position in sub dm level less then 2 5 cm The track is limited by cones that easily can be detected by the laser scanner By using the vision of the car on a scouting lap the car stores the route of the track to compute the optimal driving schedule A MicroAutoBox from dSPACE is implemented to control the power steering brake booster and the accelerator pedal 55 C 3 Team LUX The Team LUX is Ibeo s and SICK s first D A R P A Grand Challenge team 6 They are using a modified Volkswagen Passat and made it fully autonomous The car navigates by a DGPS Omnistar 45 i combination with three laser scanners Ibeo The use of three laser scanners gives the car complete 360 vision around the vehicle This application make it possible to get an exact position in combination with the DGPS without any INS systems The use of the laser scanner vision it calculates its position from reference points in the near area This gives the system very little drift 5 26 C 4 Previous Volvo projects C 4 1 LKAB A previous project that has been implemented by AB Volvo is the autonomous trucks that runs i the mine industry at LKAB The projects purpose was to build a number of tr
41. The curvature test results were not as good as the results of the straight line test When the test vehicle lost visual contact the coverage distance rapidly decreased 56 Measurements and Data Collection AP position Figure 5 21 AP position at H llered endurance track during WLAN distance test Chapter 6 Conclusions This chapter summarizes all systems and techniques which are mentioned in the previous chapters The advantages and disadvantages will be called to attention Systems and techniques which are suitable for autonomous implementation will be presented and can bee seen as a recommendation for implementation or for future investigations 6 1 Positioning Conclusions The positioning system is divided into two different parts satellite positioning and vision These two systems are intended to be integrated by sensor fusion to increase the performance and reliability of the complete system 6 1 1 Positioning To be able to drive autonomously a positioning system is needed This system needs to be robust precise and redundant DGPS A local area DGPS solution is the technique that offers the most advantages The possibility to increase the accuracy of more vehicles simultaneously is of great advantage The GPS coverage in this case at H llered is satisfying see section 5 1 1 thus a GPS positioning device would be suitable To make sure that the vehicle stays within one lane of the roadway the accuracy has t
42. able to send information of vehicle states and receive information of other vehicles states The system s ability to transfer information in addition to vehicle status shall also be estimated e The surveillance must be able to monitor all active vehicles and their states e The complete system must be movable to other sites We will be studying three different structures which will handle the problem specification See Figure 1 1 1 Vehicle states include position velocity and status of the vehicle 1 4 Limitations 3 1 4 Limitations In this thesis the data collection is limited to G teborg H llered and nearby areas For that reason the moveability and the system performance at other test tracks cannot be evaluated in this thesis The hardware tested is limited to equip ment available at AB Volvo The system designed may consist of other parts which have not been validated This thesis will not include control of an autonomous vehicle 1 5 Thesis Outline In the following chapters we will investigate the different sub systems and present the techniques for these Chapter 2 describes different navigation systems and navigation tools to be used in our application Chapter 3 compares the different communication techniques that have been in vestigated and describes the theoretical background Chapter 4 describes the principles and techniques which are used to prevent collisions between autonomous vehicles no
43. andover theory is presented in the following subsection Handover Theory If a Mobil Node MN is equipped with a dual antenna system the handover time can be reduced The system has to work with two WLAN InterFaces IF and IF2 The MN uses these two different IF s for data communication and for searching for new AP These two IF are switched alternately e g when IF is communicating IF2 is searching for a better AP When connection is established IF is searching and IF is communicating To make a connection to the next AP the system must satisfy the condition P P gt P where P Power level in dBm of candidate AP radio signal P Power level in dBm of used AP radio signal P Power level in dBm of predefined threshold Then IF can establish a connection and authentication to the next AP During this authentication processes IF is still active in a receive mode only for a certain protection time When the protection time is over IF is disconnected and starts searching for another AP Using this overlapping sequence the system completes the handover with minimal package loss The handover flowchart is presented in Figure 3 1 44 One solution to speed up the handover process is to shorten the authentication time and the location registration time The Mobile Switch MS authenticates a MN on behalf of the radius server when the MN switches from AP to AP After establishing an air link the MN sends an authentication
44. aserscanner vision fusion system implemented on the terramax autonomous vehicle Intelligent Robots and Systems 2006 IEEE RSJ International Con ference pages 111 116 14 Jin Chen Stefan Deutschule and Kay Fuerstenberg Evaluation methods and results of the intersafe intersection assistants Intelligent Vehicles Symposium 2007 IEEE 15 Yin Jun Chen Ching Chung Chen Shou Nian Wang Han En Lin and Hsu Roy C Gpsensecar a collision avoidance support system using real time gps data in a mobile vehicular network Systems and Networks Communication 2006 ICSNC 06 International Conference 16 Dale DePries Nmea data 2007 URL http www gpsinformation org dale nmea htm 17 Andreas Eidehall Tracking and threat assessment for automotive collision avoidance Phd thesis Link pings Universitet Department of Electrical En gineering Link pings Universistet 581 83 Link ping 2007 18 Matts Eriksson and Jonas Lundmark Tecnical Verification and Validation of ADS B VDL Mode 4 for A SMGCS Master s thesis Link pings Univer sitet Department of Science and Technology Link pings Universistet 601 74 Norrk ping 2002 LiTH ITN KTS EX 02 34 SE 19 ESA European space agency Egnos 2007 URL http www esa int esaNA GGG63950NDC_egnos_0 html 20 Andreas Ewald and Volker Willhoeft Laser scanners for obstacle detection in automotive applications Intelligent Vehicles Symposium 2000 IV 2000 Proceedi
45. ation system will be used to upload and download information about the vehicles states In this chapter several techniques will be presented and inves tigated as to the possibillity to obtain the wanted performance 3 1 STDMA STDMA stands for Self organizing Time Division Multiple Access This method was developed by H kan Lans and is used for positioning and identification of aircrafts VDL Mode 4 and ships AIS The STDMA data link is divided into a number of time slots to send data messages It is self organized and the commu nicator can by itself find a free slot and send the message to the free slot Every node must have access to global time and the regular transmissions are sent as heartbeats This means that different types of data can be sent on the data link using just one frequency All communicators within radio distance will be able to hear the message The STDMA scheme ensures that access is free of collisions and that the bandwidth per node is guaranteed 18 23 33 3 1 1 VDL Mode 4 VDL Mode 4 Very high frequency Data Link Mode 4 is the standard of the Inter national Civil Aviation Organization ICAO The main purpose for VDL Mode 4 is to send an Automatic Dependent Surveillance Broadcast ADS B signal to com plement the ground radar and the surveillance service The technique is also used as a Flight Information Service Broadcast FIS B It sends the aircraft s position and identification to all surrounding aircra
46. aversine Equation oem 22e 79 DEZACOVArance omr ret ar dd o go hd AS woes ae qe de ak ee i 79 E Kalman filter 80 E 1 Extended Kalman filter 80 F Globalsat 82 G Oxford Tech RT 3002 87 H Oxford Tech RT Base 90 I Cisco Aironet 1240G Series Access Point 93 J Antenna Specifications 100 Chapter 1 Introduction 1 1 Background This master thesis has its background at Volvo s test track at H llered On the test track an endurance circuit is built with the purpose to expose the vehicles tested to general wear and tear The drivers are exposed to very hard working conditions primarily because of heavy vibrations when driving repeatedly numbers of laps on the endurance track Long time exposure to these conditions is not suitable for the human physique The drivers working environment would benefit from a decrease of the exposure to vibrations In order to obtain as much measurement data as possible without causing the driver harm the idea to investigate the possibility to drive vehicles autonomously With an autonomous vehicle it is possible to repeat the path on the track with a higher precision than a human driver can achieve There were several questions to be answered such as Is this project possible Which techniques should then be used Which modifications should be done at Hallered To answer these questions Volvo initiated this as a master thesis project for two master students The result is a pilot stu
47. being used is a magnetic trail that are built in the road By putting magnets in the road sizes of a marker pen placed with distances of approximately 1 1 2m the vehicle can follow the magnetic line Using the magnetic domains of the permanent magnets the system is able to use them as an ID tag The vehicles are able to sense the field strength and by this it can control the direction and speed of the vehicle This technique gives a longitudinal accuracy of less then 0 3m and lateral less then 0 05m Five magnetometers is placed beneath the vehicle and by signal processing the vehicle is able to determine its position Due to the simple path the implementation is quite robust and can handle high speed driving The implementation of this system demands high effort in setting up the road with magnets Although the permanent magnets are at low cost but the path is very static and variation of driving schedules are minimal 49 C 2 VW Golf GTi 53 Volkswagen AG has made a prototype car called Golf GTi 53 It is a fully autonomous car that uses a laser scanner and a DGPS for navigation The basic use of this car is handling and brake tests due to its capability of precision driving By using the autonomous car the repeating sequences is much more like an exact duplicate then with a human driver The Golf GTi uses an Ibeo laser scanner mounted below the front license plate for front vision For positioning and navigation it uses a DGPS system R
48. ce the scanning time and decrease the handover time it is possible to use a selective scanning procedure It takes less time to scan three channels instead of fourteen This is called a selective scan 53 3 2 4 Handover Using Neighbour Graph To make a faster handover it is possible to use a technique that builds and sends out a Neighbour Graph NG A NG is an undirected graph where each edge represents a mobility path between two AP s 40 41 Definition 3 1 Neighbour Graph G VE V vi vi 2 AP channel AP APo AP e AP AP N AP APik AP r V AP APix E 3 2 Wireless Local Area Network 23 ER E e eb AP Search Authentication start request Authentication start response m Genreate local challange a Authentication request Authentication request I regi i ER Authentication response lt Local registration Authentication Authentication accept LE AP Search e Authentication request DS b Figure 3 2 Fast authentication when switching between two APs The flowchart de scribes how the authentication requests and responses are handled Channels 6 7 8 9 10 11 12 13 14 Viti IT LIL LITI C11 AERREAY NN a n LK KA 2 402 GHz 22 MHz 2 483 GHz Figure 3 3 Channel frequency distribution in IEEE 802 11b 53 24 Communication Systems Figure 3 4 a Map of an AP s example positions b Nei
49. cies and configuration information with no manual intervention Autonomous access points are based on Cisco los Software and can optionally operate with the CiscoWorks Wireless LAN Solution Engine WLSE Autonomous access points along with the CiscoWorks WLSE deliver a core set of features and can be field upgraded to take full advantage of the benefits of the Cisco Unified Wireless Network as requirements evolve All contents are Copyright 1992 2007 Cisco Systems Inc All rights reserved This document is Cisco Public Information Page 1 of 6 Data Sheet Applications Designed for rugged environments and installations that require antenna versatility the Cisco Aironet 1240G Series features antenna connectors for extended range or coverage versatility and more flexible installation options Manufacturing applications for example can place WLANs in hazardous locations and remotely place antennas in those locations while securing the Cisco Aironet 1240G Series Access Points The metal housing and industrial grade components of the Cisco Aironet 1240G Series provide the ruggedness and extended operating temperature range required in factories warehouses big box retail environments and similar facilities High transmit power receive sensitivity and delay spread for 2 4 GHz radios provide the long range and large coverage area consistent with these applications Access points can be placed above ceilings or suspended ceili
50. dem s communication to enhance reliability and mini mise the number of corrupt packets The Radio Modem provides reliable transmission over a 2km range in an open envi ronment Since some packets can be dropped or have errors the Radio Modem can be used up to a range of 5km in open environments IP65 Rugged Case When the lid is closed the RT Base has IP65 ingress protec tion making it suitable for use in all weathers The RT Base is mounted in a rugged ultra high impact PELI case For further information please contact Oxford Technical So lutions or your nearest local agent Radio Details 380 480 MHz band up to 1 W typically 5 km License free bands available for many European SATEL MAC countries Radio will typically cover 8 bands with 25 KHz channel spacing ES A d 869 MHz band up to 500 mW typically 2 km For correct operation of the RT 2 License free across most of European Union Base it is essential to locate the GPS antenna in a location where it has a full view of the Breswave 200 MHz band up to 1 Ns typically gt 10 km sky down to an elevation of 10 License free in USA Brazil Canada degrees in all directions It must also be away from reflective Futaba 2 4 GHz band 10 mW maximum 2 km Li objects like buildings and trees cense free in Japan Revision 070410 Subject to change without notice Appendix I Cisco Aironet 1240G Series Access Point A CISCO
51. drifting from the static position Our measurments show a standard deviation of approximately 3 2 cm which is larger than the specified 2 cm The increase in standard deviation is negligible due to the limited number of tests The IMU in the DGPS receiver should be connected with a fifth wheel to reduce some if the drift in the position see Figure 5 18 During the test performed for this thesis a fifth wheel was not available Despite the advanced equipment the system was still drifting from the position up to 23 5 m from the static position This distance is a worst case scenario The plot of position Figure 5 17 clearly shows that it makes five different deviations from its static position The HDOP signal was not logged during this test why the comparison between the drift and the HDOP signal was not possible Measurements and Data Collection 57 7736 57 7735 9 x 57 7735 T x fi 57 7734 y 4 Lat 57 7734 57 7733 57 7733 57 7732 57 7732 i i l 12 7345 12 7345 12 7346 12 7346 12 7347 12 7347 Long Figure 5 17 Stationary DGPS position measurments at Hallered Figure 5 18 Fifth Wheel for vehicle testing 27 5 2 Laser Scanner Data Collection 53 nem ry y ID 35 VR 18 Ai n a ID 27 10 28 i ld een e OR ID 16 lam 16m 8m Om 8m 16m Figure 5 19 Plotted lidar detection from the Volvo Integrated Safety Truck driving at Lindholmen 5
52. dvantages Disadvantages Resolution Dirt sensitivity Minimal clutter Weather sensitivity Light insensitive Prototype stadium Photo detection Used in automotive application 2 5 Complete Position System 17 DGPS CAN INS Vision I x a Collision 5 Position System ei Vehicle gt x YAA Communication Route Figure 2 10 An extended system structure to run autonomously To obtain accurate position the position system uses information from DGPS CAN INS and from a vision unit 2 5 Complete Position System To fulfill the demands of the problem specification in Chapter 1 3 the performance of the CDGPS is of interest as a positioning system and will be further investigated The input signals to the position system will in this stage be from a DGPS the CAN Controller Area Network information and from the vision system A block diagram over the system principle is presented in Figure 2 10 The vision system that at this point seems to have the most advantages is the lidar system By integrating the lidar vision with the DGPS the vehicle s position system increases its robustness 25 Chapter 3 Communication Systems The complete system is depending on a communication system in order to im plement interacting between vehicles To surveil the traffic of the test track the communic
53. dy that are investigating if the theory of autonomous driving is possible and if so an investigation of what kind of equipment would be needed to implement this idea 1 2 Volvo 3P This master thesis has been performed at Volvo 3P Volvo 3P is a business unit within AB Volvo that works with Volvo Trucks Mack Trucks Renault Trucks and BA Asia 3P stands for Product Planning Purchasing Product Development and Product Range Management for the companies within AB Volvo 1 3 Problem Specification The primary goal of this thesis work is to investigate the possibilities of au tonomous operation of vehicles The aim is to design a system allowing several au 1 Introduction Position Communication Collision Avoidance gt Vehicle Figure 1 1 A proposed system structure Three different subsystems supply the vehicle with information needed to run autonomously tonomous and non autonomous vehicles to use the test track simultaneously while maintaining adequate safety Our task is to suggest techniques for implementa tions which are suitable and cost efficient for positioning collision avoidance communication and surveillance of vehicles e The positioning performance of the system must be in the range of the width of the road e The collision avoidance system must be able to prevent collisions with other vehicles and obstacles e The communication performance must at least be
54. e more detailed information than the mm radar The laser scanner system is also very tolerant to clutter Again the narrow beam does not suffer from reflections of nearby objects in the same degree as a radar 31 The intensity of the reflected laser pulse can be detected by the lidar and can easily be projected into a gray scale picture This is very useful to implement in the lane detection feature see Figure 2 6 The laser scanner is relatively insensitive to the surrounding light conditions 31 35 58 54 Despite all of these advantages the laser scanner suffers from a couple of weak nesses In the automotive industry most of these systems are at prototype stage This makes the price high at this stage but will probably drop when prototypes go to large series production In similarity with the camera system the laser scanner must have a free line of sight Rain and fog could also interfere with the correct echo detection A single pulse can be reflected by rain or other weather obstacles Due to the technique of reflection the lidar has difficulties to detect dark and rough objects These objects are hard to detect due to absorbation of the laser beam The lens also needs to have a clear view to avoid false detections 31 43 Motor with Angle Encoder Outgoing Rotating Mirror Beam IR Transmitter Diode Reflected Echo Photo Diode Receiver Figure 2 5 An exploded view of a laserscanner The laser beam is reflected
55. e of the base station is limited and the position accuracy de creases with increasing distance to the base station The base station is stationary and sends out correction signals to the DGPS receiver with e g a radio modem With the local area correction signals the DGPS receiver obtains great accuracy A position accuracy below 50 cm is achievable with this technique The local area 8 Position System DGPS system is fairly expensive to implement but it is free from any subscrip tion services and is very suitable for implementation within a restricted area The cost of implementing a local DGPS system is according to given indications in the same range as one single year of subscription fees for eight units using e g Omnistar services The local DGPS system is not limited to a number of users and it offers a high grade of accuracy 48 This technique is very suitable to our demands and will be further investigated 2 1 3 Carrier Phase L1 L2 A typical GPS receiver calculates its position by the data that is sent from the GPS satellites A second form of precise monitoring is called Carrier Phase CP Enhancement In order to obtain greater accuracy such a GPS receiver uses the CP from the satellite signal The CP approach utilizes the L1 carrier wave which has a period a thousand times smaller than the bit period of the Coarse Acquisition code C A as an additional clock signal in order to reduce the uncertainty The phase differe
56. e the beam generated by each laser pulse is split into four layers the lidar sensors can evaluate the data from the reflections up to 16 reflections per measurement four echoes and four layers This technique gives a high grade resolution and reliability 24 All products are in a prototype stadium A truck implementation is available as well as the possibility to produce products according to customer specifications The scan of the surrounding environment detects objects due to the many reflec tion points in a high resolution picture This also results in that the detected object can be identified by its significant structure The detected objects can be assigned with an ID number a velocity and a heading Due to the high scanning frequency a high resolution model of the surrounding environment can be esti mated In the model can objects be classified as a car a truck a pedestrian a fixed object etc By using the heading and distances to known objects navigation 2 4 Vision System 15 Figure 2 7 Example of a multilayer lidar The lidar beam is spread in different angles to obtain additional information of the surroundings field of view 220 resolution in angle 0 5 range 0 3 m 80 0 m iem ibeo Figure 2 8 Lidar object detection The picture to the left shows the lidar echoes of the surrounding environment corresponding to the right picture is possible In Figure 2 8 the d
57. ed with a trajectory prediction to estimate all other vehicles positions An autonomous vehicle also needs a vision system to take care of the unpredictable objects that could occur e g animals and items that are blocking the roadway 4 1 Collision Avoidance Prediction The prediction of the vehicle s position is intended to estimate the risk of a future collision By using a model of the vehicle motion the future position can be predicted There are several vehicle models that can be used for prediction of the position with different degrees of complexity e g general models and vehicle specific models that handles vehicle dynamics 31 34 60 One of the simplest vehicle model is the constant velocity model given in Equa tion 4 1 and 4 2 This model describes a straight line between two measurement updates The model is based on four states as position x and y and constant velocity in both directions v and vy This model will be used in some examples in this report to show the principle of collision avoidance when the vehicle states are known 4 1 Collision Avoidance Prediction 29 Roll Pitch Lat Compensation Vehicle Model Extended Kalman Filter Position States Vehicle Y Speed Heading Angle Sensor Adjustment LS a dt pers GPS Error Pre A processor Figure 4 2 Block diagram of the po
58. ediction error In every prediction the safety distance is increased Circles around every prediction symbols the safety distance At state 5 0 the two position estimations with corresponding safety distances will indicate a possible collision r Example 4 2 Linear prediction with error in position _ The situation is identical to the situation in Example 4 1 and the vehicle states are the same The vehicle position has an error due to uncertainty in the position system This will lead to a greater uncertainty of the future predicted positions The probability of a future collision will also increase The error in position is defined as o7 0 5m and of 0 5m To cover the predicted area with a safety distance the radius is enhanced for every step in time By using the standard deviation to predict the worst case scenario an area could be calculated with dia k An example is showed in Figure 4 4 OOOO Another technique to estimate the future position is to use the Kalman m step prediction By calculating the error covariance matrix P and the state vector amp see Algorithm 1 and then performing the m step prediction see Algorithm 2 with these variables the future states can be estimated This calculation also considers the given state and measurement errors Q and R If the noise is assumed to be Gaussian it can be shown that the equation g x t m t amp t m P t m t x t m t
59. ediction models e g state space prediction the surrounding vehicles can be assigned with relative position and heading This information is validated to get a threat assessment of the situation 17 Work is also done to receive information from other nearby vehicles and road side units The theory is often applied in intersections where peer to peer networks are used to establish connections In these situations vehicle positions and traffic information e g stop signs traffic signals etc are exchanged 14 15 The environment of a test track is similar to the standard traffic environment as well as the basic functions of a collision avoidance system The major differences between these situations are that the test track has more restrictions of the drivers the drivers are professionals more restricted traffic rules limited number of vehicles etc and the advantage of providing the vehicle with suitable equipment for a specific scenario The test track is also a closed area and does not allow any unknown vehicles These specific test track features simplifies the implementation of a collision avoidance system All vehicles can be equipped with suitable tools in this case communication devices and positioning systems As mentioned in Chapter 3 all vehicles are able to communicate with each other server based communication and all vehicles will also have a position system to calculate the vehicles positions The server based communicatio
60. ellite Navigation iu a sa aa etr m a 2 1 1 Global Positioning System 2 2 llle 2 1 2 Differential GPS os 22 2232 22 ee e e 2 1 3 Carrier Phase LI L2 leen 2 2 Inertial Navigation System een 2 3 Combined DGPS INS System ooa 2 4 Vision Systemes amp s sigg Au da dar sn sn ee e 2 4 1 Line Following Systems 22 2 4 2 Camera Systems ooo ver 2 4 3 Radar Sensors 4 e dle ta es 2 4 4 Lasersc nners a x RU see a A e ee ae AA 2 5 Complete Position System len Communication Systems 3 1 jS3DDM n se fl le AER La eda 3 1 1 VDLMode4 3 03 55 00064444 04 2 rr 3 1 2 TACSYS CAPTS 00002200 3 1 3 STDMA Summary n 3 2 Wireless Local Area Network 3 2 1 IEEE 802 Ll 0 zes sa an A Rus 3 2 2 WLAN With Dual Antennas 3 2 3 Selective Channel Scanning 3 2 4 Handover Using Neighbour Graph 3 2 5 IEEE 802 11 Summary 3 2 6 ZigBee ar r i A ede ios 3 2 WiMax 22 fi ee ae pay OSO a ix x Contents 4 Collision Avoidance 27 4 1 Collision Avoidance Prediction lr 28 4 2 Vehicle States Message ee ee 37 4 3 Collision Avoidance Vision 2 o 38 5 Measurements and Data Collection 41 5u GPS Coverage ve ouium fiat iene an BG 41 5 1 1 Static GPS Coverage H llered 41 5 1 2 Test Track GPS Coverage o nenn 42 5 1 3 GPS ACCUTANE e e db 44
61. ems 2006 Proceedings 2006 IEEE pages 756 761 Yilin Xhao Vehicle Location and Navigation Systems Artech House INC 1997 Tomas Zirn Wimax 6ppnar ny v g in till bredbandskunderna 2007 URL http computersweden idg se 2 2683 1 112141 Appendix A Satellite Navigation Satellite navigation technology is based on measuring the distance to different satellites With the information of the satellite position and distance the user po sition can be calculated by triangulation Today only one system is fully operative and it is the NAVSTAR GPS A 1 History The first satellite navigation system was the Navy Navigation Satellite System NAVSAT also called TRANSIT The system was using six low orbiting 1100 km satellites The position was calculated by measuring the change in frequency of the satellites transmission as it speeds past in low orbit Because the system only had six satellites the average time between the position update was about 90 min The position accuracy was about 250 meter 3 30 A 2 GPS The term GPS includes both the American system NAVSTAR Navigation Satellite Timing And Ranging Global Positioning System and the Russian system GLONASS Global Navigation Satellite System 3 30 NAVSTAR GPS The GPS system is developed by the US DoD United States Department of Defense The NAVSTAR GPS is divided into tree parts the space segment the control segment and the user segment Space Segment
62. er E 1 Extended Kalman filter The KF is made for a linear model Many models are nonlinear function in either the state or measurement update To use the KF the system can be linearized around the lastest state estimation when this is done the KF can be applied 12 52 Consider a system z t 1 flelt w t E la y t c a t v t E 1b where the function f x t and h x t represent nonlinear functions To linearize the states a first order Taylor series around the current state are used This will result in this approximation ft me fall EFE x t tt E 2a c t e a tlt 1 C t E amp t t 1 E 2b where F t one E 3a T le 4 tlt ch u E 3b T I2 tlt 1 With these approximations Equation E la and E 1b can be rewritten as z t 1 Fett f llt FEAE w t yt Cat e 2 t t 1 C t t t 1 80 E 1 Extended Kalman filter 81 The new state update and measurement update now looks like 2 1 FHE E FREI fit amp tt tlt 1 K t w tt 1 KE h 2 tt 1 The EKF is summerized in Algorithm 3 Algorithm 3 Extended Kalman filter EKF Initial values P0 1 Mo Time update amp t lt FEO P t 1 t F P UN FO Q Filter gain computation L t Ptt VCA CARPE 1 C 07 RJ Measurement update amp tt tlt 1 L t y t e t t 1 P t t
63. esting and validation for the Dual Antenna system and Neighbour Graph has not been done within this thesis Dual Antenna To reduce the handover time when changing between AP s we recommend a dual antenna solution The implementation of this technique should be done and veri fied Neighbour Graph The neighbour graph technique might not be needed if the system is permanently installed but it will make the system more adaptive to changes and disturbances and make the system more movable due to the self building NG 6 6 4 Collision Avoidance System In this thesis work we have not investigated how the avoidance manoeuvre should be preformed This manoeuvre must be made in several different ways according to different traffic situations e g unknown object on the road future trajectory conflict etc 6 6 5 Fault Detection In an autonomous vehicle the fault detection system must be extended A human driver can detect malfunctions in the vehicle which are not indicated by sensors e g flat tire drive shaft brake down fire etc To obtain this information more sensors might be needed along with analysis of e g CAN data Descriptions of many of these errors and malfunctions can be gathered from interviewing the test drivers about their experiences Bibliography 10 11 12 Garmin 35 36 TracPak GPS Smart Antenna Technical Specification CNS Systems AB Vdl mode 4 2007 URL http www cns se aviation core php page
64. f model will depend of computing capacity and demands of accuracy By comparing very simple models an indication can be given of how the accuracy and computational demands are combined By run ning several Monte Carlo simulations 1000 MC simulations and comparing the average path on each model Constant velocity Constant acceleration and Nearly coordinated turn a grade of computional load can be achieved An example is presented in Table 4 2 31 By using non vehicle dependent models it is very easy to adapt the system to a wide range of different vehicles This increases the versatility of the system As seen in Table 4 2 the maximum error of for example the nearly coordinated turn model 3 5 m is acceptable as the safety radius will be greater than this distance In Equation 4 10 4 12 a suggested vehicle model is presented The suggested vehicle model is similar to the nearly coordinated turn model In the model the variables x and y are earth inertial coordinates is the heading angle v is the longitudinal velocity we is the yaw rate we is the bias in the yaw rate measurement and Nja IS a white Gaussian noise This is a general model that is independent of vehicle handling parameters This model has shown good accuracy in position and good performance in prediction 60 By using this kind of model it is easy to assign it to a great number of different vehicle s and it makes the system very versatile due to the independence
65. ffected by this during a longer time The ionospheric delay affects the speed of microwave signals differently based on frequency the receiver is able to reduce this effect with comparing different 72 Satellite Navigation Figure A 3 Multipath example when the GPS signals are reflected on objects before reaching the user 50 frequency bands L1 1575 42 MHz and L2 1227 6 MHz Ionospheric delay is a well defined function of frequency and the total electron content TEC along the path so measuring the arrival time difference between the frequencies determines TEC and thus the precise ionospheric delay at each frequency This feature is mostly applied on expensive survey grade receivers 28 29 51 Multipath is also an effect that causes inaccuracy The signals reflects and bounces of nearby objects and causes a difference in travel time see Figure A 3 Multipath effects are less severe in moving vehicles When the GPS antenna is moving the false solutions using reflected signals quickly fail to converge and only the direct signals result in stable solutions Clock errors is another factor of position error The onboard clocks in the GPS satellites are extremely accurate but they do suffer from some clock drift This results in some inaccuracy of the position All this faults summarize in an inaccuracy of approximately 15m 28 29 51 GLONASS GLONASS Global naya Navigatsionnaya Sputnikovaya Sistema is the russian versio
66. fts It can also send complementary information such as weather information from the control tower to the aircraft The data link transmits digital data in a standard 25 kHz VHF communication channel 2 18 23 33 19 20 Communication Systems The problem with this is that the total bandwidth is limited due to the number of slots that can be used This results in a limited number of users and or a small amount of data that can be sent 2 18 23 33 3 1 2 TACSYS CAPTS The Taxi and Control System Cooperative Area Precision Tracking System TAC SYS CAPTS is an innovation project from Fraport AG The general function of this system is to increase the accuracy of airport ground navigation in poor weather conditions It uses the signals from the on board transponders By measuring the time of the incoming transponder signals the distance to the object can be calcu lated by triangulation The transponder signal includes an ID tag so the identity of the vehicle also can be determined 4 3 1 3 STDMA Summary The STDMA technique e g VDL Mode 4 is a very robust and reliable commu nication system It has been approved by the aeronautical industry which shows out its reliability Because of the system s limitations in transfer rate and in the number of vehicles that can simultaneously use it this system is not interesting for our application The future expansion possibilities would also be narrowed down and the possibility to send
67. ge http www ep liu se Erik Agardt Markus L fgren
68. ghbour graph corresponding to the AP s position in a where G is the data structure of NG V consists of AP s and their channels E is the set which consists of edge e and N is the neighbor AP s of a AP 40 41 A simple example of a possible AP placement and its corresponding neighbor graph is shown in Figure 3 4 The NG can be generated by two different methods The first uses the reasso ciation request from the mobile node The reassociation request contains MAC address of the old AP The second way to build the NG is to use the Move Notify message 36 40 Both the reassociation request and the Move Notify message adds an edge to the NG The first mobile node to change from AP to AP will suffer from a high latency but the cost of this is amortized over all upcoming changes from AP to AP If the network is restarted the NG info can be loaded from a file with the latest known NG 40 41 When no mobile node hand offs from AP to AP is done in a given time interval T the edge should be removed from the NG 40 41 The major advantage of an automatically generated NG is adaption to changes in the AP placement physical topology AP malfunction etc Figure 3 5 shows an example of a simple flowchart of an NG server and in Figure 3 5 b the corresponding flowchart of the NG client is shown 36 Media Access Control 3An Inter AP Protocol IAPP message that are used to reduce link layer handoff latency 38 3 2 Wireles
69. ifferent cars velocity and headings are marked with circles and arrows The fixed object is marked with a square In the picture to the left it is shown how the lidar detects objects and different contours in the sur rounding environment The precision of the position can also be increased when using precise high level maps 62 Detection of the lanemarkings can also be used for road navigation and vehicle control 13 35 37 An installation of two laser scanners in the front of the truck will give a sat isfying visual coverage to prevent collisions and the ability to navigate by nearby objects see Figure 2 9 The lidar function and performance is suitable as a vision system to an autonomous system The lidar system is used for safety applica tions by many developing companies and is frequently used by the D A R P A autonomous vehicles 6 26 Advantages and disadvantages of the system is pre sented in Table 2 4 8The D A R P A Defense Advanced Research Projects Agency is the central research and development organization for the U S Department of Defense DoD 7 16 Position System Lane Departure Warning Turning Assist Cut In Assist Slow Motion Assist Automatic Emergency Braking Traffic Jam Assist Stop amp Go Assist Figure 2 9 Field of vision of a laser scanner mounted on the right front of atruck By using this location the scanner covers approximatly 270 of view 26 Table 2 4 Lidar system 31 A
70. ignals The two most common techniques are Wide Area Correction System WACS and Local Area Correction System LACS 48 EGNOS WAAS European Geostationary Navigation Overlay Service EGNOS is a Satellite Based Augmentation System SBAS that is under development in Europe The EGNOS system is a WACS The system started operations in July 2005 and will be cer tified for use in 2008 The North American Wide Area Augmentation System WAAS is similar but has no European coverage 21 EGNOS uses three geosta tionary satellites which send out a ranging signal similar to ordinary GPS signal EGNOS also uses a network of ground stations that calculates the errors clock ionospheric disturbances etc and sends out a correction signal see Figure 2 1 This correction increases the accuracy of the GPS to approximately 2 m 19 The problem with this system is that the accuracy is not good enough to keep the vehicle within one lane of the roadway SwePos The Swedish GPS correction service EPOS is available for use The service is provided by the Swedish company SwePos It uses the FM radio frequency to send out the correction signals The coverage of this technique is very good for use in Sweden but the update frequency is between between 3 and 5 seconds The accuracy is good but the update frequency is too slow 57 For that reason this technique is not suitable for this project 2 1 Satellite Navigation 7 Figure 2 1 Wide Area Co
71. it Number of bits Time 00 00 00 00 23 59 59 99 Seconds 25 Lat 0 000 000 90 000 000 Degree 27 Long 0 000 000 180 000 000 Degree 28 North South North 1 South 0 1 West East West 1 East 0 1 Speed 0 00 100 00 m s 14 Heading d 0 0 360 0 Degree 12 Yaw rate 4 40 95 40 95 Degree s 13 Acceleration ax 20 00 20 00 m s 12 ID 0 255 8 Track 0 255 8 Information Message 0 255 8 4 3 Collision Avoidance Vision A part of the collision avoidance system is the trajectory prediction technique This is implemented for all vehicles autonomous and with human drivers Even if every vehicle has a communication system a positioning system and has con nection with everyone an unpredictable object can occur on the test track An animal can run across the roadway a truck can lose its trailer a vehicle can break down etc A vehicle with a human driver can react to this scenario and do an avoidance manoeuvre but an autonomous vehicle has to be extended with a vi sion system For collision avoidance systems several different vision techniques are used The systems that we have been investigating are presented in Chapter 2 4 The demands of the vision system in this case is to achieve a satisfactory field of view about 180 and detect objects in front of the vehicle An ACC radar sensor has normally a 15 field of view 31 but with this performance demand a fusion unit several sensors or a custom specified radar must be used The
72. les With the VSM the current and predicted positions of the vehicles can be presented to the traffic controller 6 4 Collision Avoidance Conclusions The suggested collision avoidance system is based on prediction of the future tra jectory of the vehicle This feature can be obtained by using a vehicle model and with the information in the Vehicle States Message VSM A proposed VSM is presented in Section 4 2 The prediction of any future trajectory conflict decreases the possibilities of collisions To detect unpredicted objects a vision unit is needed The lidar vison unit supplies the system with a high detailed image and a large field of view to detect objects in the nearby area These systems offer two different kinds of collision warnings The warnings can be presented to an autonomous vehicle as well as a warning to a human driver With these two systems collision avoidance actions can be taken 6 5 System Movability Conclusions The recommended systems are movable because all of the systems are independent of location The positioning system is based on satellite navigation and a vision unit which is integrated in the vehicle The surrounding equipment such as the differential base station and the WLAN AP s can be placed on any desired test area If the test area is large or the topography causes communication losses in some areas more AP s can be added to resolve this problem The collision avoid ance system is independent of
73. llered sampled at 1 Hz during one week o tete ic oat Tooc ooo 0 5 0 6 0 7 0 8 0 9 Hz x 10 altile ml el Inl 0 0 1 0 2 1 4 Figure 5 3 Frequency spectrum of the low pass filtered signal in Figure 5 2 44 Measurements and Data Collection Figure 5 4 HDOP signal measured at H llered sampled at 1 Hz during one week values are satisfying the demands for GPS navigation With this result we know that the tracks due not have any sections that suffer from GPS shadows This result shows that there should be no problem to use GPS as a positioning tool 5 1 3 GPS Accuracy To verify the GPS accuracy three long time each one week of duration mea surements were made one measuring at H llered and two at Lundby The GPS receiver see Appendix F for GPS receiver specifications was located within clear Southern hemisphere sight and mounted on a stationary platform During the measurements the number of satellites was always at least four Figure 5 8 shows the position measured at H llered plotted and Figure 5 9 5 10 the position mea sured at Lundby In Table 5 2 the drift is presented in meters max min and the standard deviation c The distances between the points of interest where calculated using the haversine formula see Appendix D 1 The standard deviation of all long time measurements is close to the given accuracy by the GPS manufacture
74. location because the trajectory conflict is calculated from the vehicle states and not based on a planned route conflict 6 6 Future Work This thesis work is based on literature and small scale testing Many of the recom mended systems are not tested by us in this thesis work To verify the accuracy capacity and adequacy under realistic conditions further tests needs to be done 6 6 1 Positioning System In Measurement and Data Collection Chapter 5 the maximum drift of the po sition is very large It seems to be a correlation between the HDOP signal and the position drift As described in the chapter a simple filtering of the position was made which increased the accuracy with approximately ten percent By doing 60 Conclusions more studies of the GDOP signals HDOP VDOP PDOP and TDOP and the positioning drift it might be possible to increase the position accuracy The un certanty of the position can be decreased if the GDOP signal is weighted and com bined with additional sensors e g IMU Only a few tests with high performance equipment has been done within this thesis work and some of the conclusions are based on low accuracy equipment and need to be verified using recommended equipment 6 6 2 Lidar System The specifications of the lidar system is not yet validated to the testing environ ment of the test track influence of vibrations bad weather conditions etc 6 6 3 Communication System The implementation t
75. mmer ISSN D uppsats Title of series numbering vrig rapport http www control URL for elektronisk version isy liu se http www ep liu se Titel F rstudie av System f r K rning av Autonoma Fordon p Provbanor Title Pilot Study of Systems to Drive Autonomous Vehicles on Test Tracks F rfattare Erik Agardt Markus L fgren Author Sammanfattning Abstract This Master s thesis is a pilot study that investigates different systems to drive au tonomous and non autonomous vehicles simultaneously on test tracks The thesis includes studies of communication positioning collision avoidance and techniques for surveillance of vehicles which are suitable for implementation The investiga tion results in a suggested system outline Differential GPS combined with laser scanner vision is used for vehicle state estimation position heading velocity etc The state information is transmitted with IEEE 802 11 to all surrounding vehicles and surveillance center With this information a Kalman prediction of the future position for all vehicles can be estimated and used for collision avoidance Nyckelord Keywords Autonomous vehicles GPS DGPS WLAN fast handover IEEE 802 11 laser scanner lidar collision avoidance Kalman filter Abstract This Master s thesis is a pilot study that investigates different systems to drive au tonomous and
76. n autonomous vehicles and other ob jects Chapter 5 presents the data that has been collected for this project Chapter 6 summarizes the thesis This chapter also includes suggestions for future work to expand this project Chapter 2 Position System To obtain a position of a vehicle several different techniques can be used This chapter will introduce the techniques which have been investigated The major problem of the positioning is the accuracy The systems considered in this chapter are positioning by satellite navigation vision units and dead reckoning 2 1 Satellite Navigation Positioning by satellite navigation is nowadays a very common feature The most used system is the NAVSTAR Global Positioning System henceforth referred as GPS in this thesis 2 1 1 Global Positioning System The basic function of satellite navigation and GPS function is described in Ap pendix A Many vehicles nowadays can have a GPS wayfinder integrated within the vehicle This is often a typical commercially available GPS receiver unit with an update frequency of 1 Hz and with a standard deviation accuracy of 15 m This accuracy is too low to fulfill the demands of keeping a vehicle within one lane of the road To obtain the demands of the positioning system the standard deviation needs to be less than 1 m 1 Even the update frequency of the position in a typical GPS is too low see Example 2 1 A GPS unit with a higher update frequency and wi
77. n easy Integral Battery The RT Base includes a 10 hour battery for all day opera tion A 12 volt input is pro vided for an external battery if required An internal mains charger can charge the RT Base s battery in 2 hours The internal power supply can be used to run the system if mains power is avail able Multipath Rejection The RT Base uses Pulse Aperture Correlator Technol ogy to minimise the effects of multipath The GPS 700 Pin Wheel Tech nology Antenna includes a ground plane to minimise ground surface multi path and reflections I IW IRertial GPS Parameter RT Base Specifications 110 240 V AC 50 60Hz 3A Max Mains Power Battery Charge Time Operating Time Operating Temperature Charge Temperature Environment Relative Humidity Corrections Frequency Format Dimensions Weight 12V 7Ah Sealed Lead Acid 2 hours gt 10 hours 0 to 50 C 10 to 40 C IP65 with lid closed 95 non condensing RTCA Differential L1 L2 1 Hz RS232 486 x 392 x 192 mm 12 6 kg The RT Base includes a Remote Radio Modem and Antenna for use on the vehicle The Radio Modem in the RT Base will be factory configured for use in a particular country or territory Radio Modem The RT Base includes an in ternal radio modem Several options are available so that the RT Base can be used with out a license in many coun tries Advanced Error Correcting Codes are used in the Radio Mo
78. n of the GPS system The GLONASS system has their own satellites 18 satellites at this point The project started in 1976 The goal of this project was to have global coverage by 1991 but has not reach this object yet The system rapidly fell into disrepair with the collapse of the Russian economy In the end of 2009 the GLONASS system would have 24 satellites up and running for the wanted performance 56 61 Appendix B Inertial Navigation Systems Inertial navigation systems use an IMU Inertial Measurement Unit This is a closed system that detect movement and acceleration with a combination of accelerometers and angular rate sensors The IMU detect the current acceleration and the rate of change in the angular sensors pitch roll and yaw see Figure B 1 and sum these up to calculate the total change from the initial position As a stand alone system it suffer from accumulated errors 47 All inertial navigation systems suffer from integration drift as small errors in measurement are integrated in progressively larger errors in velocity an especially position Additional roll error due to centripetal and Coriolis acceleration The IMU is adding all detected changes to the current position and any error is accumulated It can be based on several different techniques e g gyro stabilized platforms B 2 or strap down platforms The platforms are based on vibrating structure gyroscopes B 3 fiber optic gyros ring laser gyros B 4 a and
79. n supplies every user with information about all other vehicles states such as position heading velocity etc When this information is known the tracking and state estimation of the vehicles is unnecessary The basic conditions of the collision avoidance system in this thesis can be summarized in Figure 4 1 The flowchart shows an example of how a suggested 27 28 Collision Avoidance Visual System DGPS CAN INS al Self Future Trajectory L Estimator n Position System Y Y a p Potential a IL Al Potential Trajectory la Collision J Avoidance gt Avoidance le Hence Conflict Processor Algoritm Actuator Detector x Other Vehicle State y Interpreter mau Hd aria Driver Y Algoritm Roue Other Vehicle Future 2 T Trajectory Estimator I gt Communication System A P 4 SP Neighbourhood Vehicle 1 Neighbourhood Vehicle 2 Figure 4 1 Flowchart of Collision Avoidance System in the complete system The flowchart shows how the subsystems are connected and how they exchange information with each other collision avoidance system could be implemented This flowchart is an extension of the flowchart in Section 2 5 and it has been divided into several subsystems All vehicles on the test track will have a communication device combin
80. nce error in the normal GPS results in a position error within 2 to 3 meters Using the CP method this position error could in the ideal case reach 3 cm resolution Realistic use of a CP GPS L1 coupled with differential correction Carrier Phase DGPS CDGPS gives a normal position accuracy of approximatly 50 centimeters If this technique is expanded with a L1 L2 receiver the accuracy is at centimeter level see appendix A 2 An accuracy comparision is presented in Figure 2 2 and Table 2 1 48 42 To keep the vehicle within the roadway a CDGPS would be recommended 2 2 Inertial Navigation System An inertial navigation system is a completely independent system The position ing is based on integration of the small changes in direction and velocity This is detected by an Inertial Measurement Unit IMU Due to the minor offset in the change of the position the new calculated position can quickly drift to a great er ror See Figure 2 3 for a schematic drawing of an inertial navigator This system is not suitable for use as a stand alone system due to the increasing error but the technique can be used as a complement to increase the total accuracy of the combined systems 28 48 2 3 Combined DGPS INS System To obtain greater accuracy than the DGPS provides several systems use a com bination of a DGPS unit and an IMU To increase the position accuracy between DGPS samples inertial gyros and or accelerometers are used to calculate
81. nd som upphovsman i den omfattning som god sed kr ver vid anv ndning av dokumentet p ovan be skrivna s tt samt skydd mot att dokumentet ndras eller presenteras i s dan form eller i sadant sammanhang som r kr nkande f r upphovsmannens litter ra eller konstn rliga anseende eller egenart F r ytterligare information om Link ping University Electronic Press se f rla gets hemsida http www ep liu se Copyright The publishers will keep this document online on the Internet or its possi ble replacement for a period of 25 years from the date of publication barring exceptional circumstances The online availability of the document implies a permanent permission for anyone to read to download to print out single copies for his her own use and to use it unchanged for any non commercial research and educational purpose Subsequent transfers of copyright cannot revoke this permission All other uses of the document are conditional on the consent of the copyright owner The publisher has taken technical and administrative measures to assure authenticity security and accessibility According to intellectual property law the author has the right to be mentioned when his her work is accessed as described above and to be protected against infringement For additional information about the Link ping University Electronic Press and its procedures for publication and for assurance of document integrity please refer to its www home pa
82. ndard deviation is reduced by approximately ten percent 5 1 4 Dual GPS The results in the static measurements indicated a drift in the static position By using two simple identical GPS receivers data sheet in Appendix F and logg the measurements simultaneously to investigate if both receivers were drifting to the same position In that case it might be possible to use one of them as a local differential station To see if the position varied together we investigated the correlation see Appendix D 2 for more information about these calculations of the signals The results are presented in Table 5 3 It shows that the correlation is small and that the signals do not follow each other closely Due to the poor result of this test the conclusion is that these GPS receivers are not suitable for obtaining a local area correction 5 1 5 Differential GPS The test performed with a typical GPS receiver showed poor performance To verify if the cause of the poor performance was the hardware a test using a high 5 1 GPS coverage 49 11 553 11 5529 Long 11 5528 Al 0 5 1 15 2 25 3 3 5 4 57 4284 5 57 4282 57 428 i i i i i Y J 0 5 1 1 5 2 2 5 3 3 5 4 20 15 3 10 4 HDOP 0 5 1 15 2 25 3 3 5 4 Figure 5 12 Lat Long HDOP signals from Lundby 1 11 5532 o 2 S 11 553 11 5528 57 4286 57 4284 57 4282 57 428 57 4278 4 Lat HDOP
83. ngs allowing antennas to be discreetly placed below drop ceilings The UL 2043 rating of the Cisco Aironet 1240G Series allows for placement of the access points above ceilings in plenum areas regulated by municipal fire codes Public access applications such as large hotel buildings can also present a challenging RF environment the antenna versatility of the Cisco Aironet 1240G Series together with industry leading range and coverage provides reliable performance for the most demanding environments Features and Benefits Table 1 lists the features and benefits of Cisco Aironet 1240G Series Access Points Table 1 Features and Benefits of Cisco Aironet 1240G Series Access Points Feature Benefit 802 11g radios The access points provide 54 Mbps of capacity and compatibility with older 802 11b clients Dual RP TNC antenna Antenna connectors support a variety of Cisco 2 4 GHz antennas providing connectors for 2 4 GHz radios range and coverage versatility Security Authentication Security standards Wi Fi Protected Access WPA WPA2 802 111 Cisco Temporal Key Integrity Protocol TKIP Cisco Message Integrity Check MIC IEEE 802 11 WEP keys of 40 and 128 bits 802 1X Extensible Authentication Protocol EAP types EAP Flexible Authentication via Secure Tunneling EAP FAST Protected EAP Generic Token Card PEAP GTC PEAP Microsoft Challenge Authentication Protocol Version 2 PEAP MSCHAP EAP Transport Layer
84. ngs of the IEEE pages 682 687 21 FAA Federal aviation administration Waas 2007 URL http www faa gov airports_airtraffic technology waas 22 Jay Farrell and Matthew Barth The Global Positioning System amp Inertial Navigation The McGraw Hill Companies Inc 1998 23 Daniel Fredriksson and Anders Schweitz Tecnical Verification and Validation of TIS B using VDL Mode 4 Master s thesis Link pings Universitet Depart ment of Science and Technology Link pings Universistet 601 74 Norrk ping 2004 LiTH ITN KTS EX 04 013 SE 24 Kay Ch Fuerstenberg Klaus C J Dietmayer and Volker Willhoeft Pedes trian recognition in urban traffic using a vehicle based multilayer laserscanner Intelligent Vehicle Symposium 2002 IEEE 1 31 35 25 Bin Gao and Benjamin Coifman Vehicle identification and gps error detection from a lidar equipped probe vehicle Intelligent Transportation Systems 2006 Proceedings 2006 IEEE pages 1537 1542 Bibliography 63 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Ibeo Automobile Sensor GmbH Homepage 2007 URL http www ibeo as com english default asp PEGASEM Messtechnik GmbH Pegasem wheel 2007 URL http www pegasem de english mainframe_uk htn Mohinder S Grewal Lawrence R Weill and Andrews Angus P Global Posi tioning Systems Inertial Navigation and Integration John Wiley and Sons Inc 2
85. ntelligent Vehicles Symposium 2000 IV 2000 Proceedings of the IEEE pages 675 681 Joo Chul Lee and Dominik Kaspar Pmipv6 fast handover for pmipv6 based on 802 11 networks Technical report ETRI 161 Gajeong dong Yuseong gu Daejeon 305 700 Korea July 2007 URL http tools ietf org id draft lee netlmm fmip 00 txt Oxford Technical Solutions Limited Oxford technical solutions rt4000 2007 URL http www oxts co uk default asp pageRef 63 64 Bibliography 40 41 42 43 44 45 46 47 48 49 50 51 52 53 Arunesh Mishra Min ho Shin and William A Arbaugh Context caching us ing neighbor graphs for fast handoffs in a wireless network INFOCOM 2004 Twenty third AnnualJoint Conference of the IEEE Computer and Communi cations Societies 1 361 365 2004 Arunesh Mishra Min ho Shin and William A Arbaugh Improving the la tency of 802 11 hand offs using neighbor graphs International Conference On Mobile Systems Applications And Services pages 70 83 2004 Novatel Novatel gps 2007 URL http www novatel com Documents Papers ProPakV3 pdf Takashi Ogawa and Kiyokazu Takagi Road environment recognition using on vehicle lidar Intelligent Vehicles Symposium 2006 IEEE pages 120 125 Toshiya Okabe Takayuki Shizuno and Tsutomu Kitamura Wireless lan network system for moving vehicles IEEE Symposium on Computers And Communications ISCC 2005 10 21
86. o be less than one meter To obtain the desired performance a Differential GPS DGPS with a carrier phase technology CDGPS has to be used The accuracy of an CDGPS LI receiver fulfills the demands of accuracy if the update frequency is proportional to the vehicle speed When driving with a speed of up to 15 m s the update frequency has to be at least 20 Hz When driving at high speeds a faster update frequence is needed This can be achieved with more sophisticated systems or in combination with INS systems 97 58 Conclusions Dilution of Precision The GPS signal is very sensitive to the Geometric Dilution Of Precision GDOP The test which has been done see Section 5 1 3 shows that the accuracy can be increased by isolating the time when the GDOP signal is high Due to the orbits of the satellites the GDOP can easily be predicted and the reliability of the position can be increased 6 1 2 Vision To obtain satisfactory robustness of an autonomous vehicle s position the use of a vision system is needed A good vision system is able to locate the position by itself if the surrounding environment is known lane marks guidepoles etc To obtain this feature a high resolution picture of the surrounding environment is needed Lidar The vehicle vision unit with most advantages for this application is a lidar system It provides a high resolution image with distances and bearing to objects and obstacles The lidar needs a multi
87. o second synchronized to GPS time WAAS enabled 5m 2D RMS Datum WGS 84 Acquisition Rate Hot start 1 sec average with ephemeris and almanac valid Warm start 38 sec average with almanac but not ephemeris Cold start 42 sec average neither almanac nor ephemeris Reacquisition 0 1 sec average interruption recovery time Protocol GPS Protocol Default NMEA 0183 GPS Output Data SIRF binary gt gt position velocity altitude status and control NMEA 0183 protocol supports command GGA GSA GSV RMC VTG GLL VTG and GLL are optional GPS transfer rate Software command setting Default 4800 n 8 1 for NMEA Dynamic Condition Acceleration Limit Less than 4g Altitude Limit 18 000 meters 60 000 feet max Velocity Limit 515 meters sec 1 000 knots max Jerk Limit 20 m sec 3 Temperature Operating 40 85 C Storage 40 85 C Humidity Up to 95 non condensing Voltage 4 5V 6 5V Current 80mA typical Physical Characteristics Dimension 53mm diameter 19 2mm height USB Cable Length 65 Page 3 of 4 USB GPS Receiver Due to continuous product improvements all specifications may be subject to change without notice Page 4 of 4 Appendix G Oxford Tech RT 3002 RT3000 Inertial and GPS Navigation System The RT3000 Inertial and GPS Navigation Systems are ad vanced six axis inertial naviga blended with precision GPS to give robust outputs of position orientation and velocity tion systems
88. odel in Equation 4 10 is showed in Equation 4 12 where 4 h is the unbiased yaw rate and a ap is the unbiased longitudinal acceleration 59 60 na ad AN CHE ado X tn tp tp 1 tp Vapltn tp cos p tn tp Yltn tp tp 1 tp Vap tns tp Be Ens tp tp 1 tp Wz tn Voltn Vep tn tp tp 1 tp az tn av tn tad 4 12 4 2 Vehicle States Message To calculate a prediction of a vehicle the vehicle states of the particular vehicle must be known According to Equation 4 12 the time position Lat Long vehicle speed v vy heading y yaw rate and the longitudinal acceleration a4 are demanded This demanded information could be gathered in an informa tion message the Vehicle States Message VSM and sent to other surrounding vehicles This message can also include an ID tag Track and an Information Mes sage This information can be used to specify the vehicle discard non relevant vehicles and obtain vehicle status running autonomously brake down hazard situations etc A suggested content of a VSM is presented in Table 4 3 The total length of this suggested message is 157 bits According to the IEEE 802 11 standard the general MAC header with checksum is 30 Bytes 10 This means that the entire frame is less than 50 Bytes 3Media Access Control 38 Collision Avoidance Table 4 3 Vehicle State Message Message information Range SI un
89. on Automotive usage Clutter Range Ghost and multipath reflections emit as to receive by switching between sending and receiving mode It sends out a conical lobe that is reflected by the object To obtain information about the target the system receives an echo of the emitted signal and can calculate the distance to the target One sensor can do a mechanical sweep or electronically switches can be used to alternate between different sensors each located at different emission angles These techniques make it possible to survey a wider area In general for automotive purposes the field of view is 10 15 For short distances less than 200m the radar has good performance in bad weather conditions e g darkness rain haze and snow Although good performance the resolution to verify the objects identities is not very good due to the wide lobe For this project the radar needs assistance of other devices to obtain acceptable performance The radar suffers from unwanted reflections called clutter Reflections from the road surface might give ghost obstacles Multipath propagation might also occur The precision of the radar is not suitable as a stand alone implementation of navigation The best use of this application would be as an Automatic Cruise Control ACC system 31 Advantages and disadvantages of this system are presented in Table 2 3 2 4 4 Laserscanners The laser scanner also known as Lidar works like a radar A laser
90. or pendular accelerometers B 4 b All of these solutions have their benefits and disadvantages 9 22 32 63 B 1 Dead Reckoning Dead Reckoning DR is a primitive technique to determine the position of a vehicle If the starting position and all the previous displacement are known the position can be calculated through N k 1 N k v k Tcos 0 k cos v k B 1 E k 1 E k v k Tcos 0 k sin a k B 2 Z k 1 Zk v k Tsin 0 k B 3 OREI vA T R Ba O k 1 6 k T6 k B 5 where T is the sample time and N E and Z are the north east and height position coordinates v is the velocity v is the yaw angle and 0 is the pitch angle All the signals are supposed to be constant during one sample period 9 22 32 63 73 74 Inertial Navigation Systems Up Left Front Down Figure B 1 Roll pitch and yaw angles Figure B 2 Gimbaled Gyrostabilized platform B 1 Dead Reckoning 75 i Input Rate Figure B 3 Vibrating structure gyroscope j Input axis Pendulous axis Compensation Ring laser gyro Pendular accelerometers Figure B 4 Inertial gyro systems Appendix C Prototype Systems The theory of driving vehicles autonomous is already implemented by different car manufacturers C 1 PATH An example of line follower is the American PATH project The ambition of this project is to have autonomous traffic on the highways in California The technique that
91. osition Latitude Longitude GPS DOP and Active Satellites GPS Pseudorange Noise Statistics GPS Satellites in View Heading Deviation amp Variation Heading True Recommended Minimum Navigation Information Recommended Minimum Specific GPS TRANSIT Data Routes Track Made Good and Ground Speed Waypoint Closure Velocity Distance Waypoint to Waypoint Waypoint Location Cross Track Error Measured Cross Track Error Dead Reckoning UTC Date Time and Local Time Zone Offset UTC and Time from Origin Waypoint UTC and Time to Destination Waypoint Table A 4 GGA Example GGA essential fix data which provide 3D location and accuracy data GPGGA 123519 4807 038 N 01131 000 E 1 08 0 9 545 4 M 46 9 M 47 Where GGA 123519 4807 038 N 01131 000 E 1 08 0 9 545 4 M 46 9 M empty field empty field 47 Global Positioning System Fix Data Fix taken at 12 35 19 UTC Latitude 48 deg 07 038 N Longitude 11 deg 31 000 E Fix quality Number of satellites being tracked Horizontal dilution of position Altitude Meters above mean sea level Height of geoid mean sea level above WGS84 ellipsoid time in seconds since last DGPS update DGPS station ID number the checksum data always begins with A 2 GPS 71 GPS position determination To calculate the position the GPS receiver needs to know the position of the satel lites and the time a message have traveled from the satellite In two dimensions the posi
92. r but the maximum drift is almost fifteen times higher For autonomous positioning and navigation both the standard deviation and the maximum drift is of interest Because the maximum drift is approximately fifteen times higher than the standard deviation the lateral longitudinal and 2 Ari Zi max x1 22 2n where n is the number of samples Vi min z1 22 25 where n is the number of samples 4The GPS resolution given by the GPS manufacturer is the standard deviation 5 1 GPS coverage 45 Figure 5 5 Aerial photo of H llered test site MAN T NN n TH n m HDOP Numbers of satellites tuali hn MK LU fi M 50 100 150 20 250 300 350 400 450 985 50 100 150 20 250 300 350 400 450 Sample Sample Number of Satellites HDOP signal Figure 5 6 GPS measurements sampled at 1 Hz on the Life Endurance Track Table 5 2 The GPS accuracy Hallered Lundby 1 Lundby 2 Latitude Longitude Latitude Longitude Latitude Longitude Min 67 m 63 m 110m 30 m 186 m 30 m Max 161m 47 m 65 17 m 94 m 70 m c 10m 10m 9 4m 10m 5m 46 Measurements and Data Collection Numbers of satellites ML L m rd IM pil o 500 1000 1500 2000 2500 Sample Number of Satellites Figure 5 7 GPS measurements sampled at has no indication of any GPS outage 57 4648 57 4647 57 4646 57 4645 5 57 4644 57 4643 57 4642 57 4641 Figure 5 8 HDOP
93. rrection System WACS Two GPS satellites 1 and 2 with stationary reference stations 3 and 4 that supplies the user with position information and correction signals to obtain a high accuracy position 50 SwePos also offers a Network Real Time Kinematic correction This is based on a subscription provided by the GSM network This provides with centimeter accuracy but the correction service is expensive and every user needs a subscription 57 This technique is not suitable to our demands due to the subscription cost OmniSTAR The OmniSTAR is a GPS system which offers GPS correction which can improve the accuracy of the GPS receiver The OmniSTAR concept is a subscription service to their GPS receiver The subscription supplies the customer with access to the correction signal of their satellites It works like a WACS system where multiple OmniSTAR GPS reference sites calculate the error of the signal By sending up correction signals to the satellites from the American and Australian Network Control Center the correction data is received and applied in real time The system is available with an accuracy below 10 cm with the OmniSTAR service subscription 45 This technique provides great accuracy but is still dependent on a subscription service for every user and because of this service it is not suitible for this prodject Local Area DGPS One option to get differential correction signals is to use a separate DGPS base station The rang
94. s Local Area Network 25 NG Server NG Client y Read NG info from a file No Is a client connected Get NG info from server Yes y Send NG info to Save NG info to client Device Driver a b NG server NG client Figure 3 5 Flowchart of the NG server and NG client 3 2 5 IEEE 802 11 Summary The IEEE 802 11 technique offers off the shelf technology This is a very common technique used both by professionals and by the general public The widespread popularity of these products makes the price low and the accessibility high which is a major advantage of this products It is a widespread technique and with increasing performance Adoption of this technique for automotive use fore ex ample roadside systems points to an effective range of 150 m in radius 46 This features makes the IEEE 802 11 technique very interesting as a communication tool The problem is the limited range of the system 3 2 6 ZigBee ZigBee is a high level communication protocol which is based on the IEEE 802 15 4 standard It is a low power radio based solution for wireless personal area networks WPANs The advantages of the ZigBee is low power consumption giving a long 26 Communication Systems life battery and secure networking The disadvantage are on the other hand that the data rate is low and the product is not approved as a standard 8
95. sition states estimator X t et yti ve ts vt Y 4 1 1 0 t t 0 X ti41 i eia c X ti 4 2 0 0 0 1 All vehicle states are calculated by the vehicle itself and then transmitted to all other vehicles which leads to the errors in the states being less than when these states have to be estimated by the other vehicle Another advantage is that the vehicle does not need visual contact with the other vehicles to track and estimate their future positions Since all vehicles receive the vehicle states from the other vehicles the prediction will be the same independent of which vehicle that does the prediction An example flowchart of how the states can be calculated is shown in Figure 4 2 When the states are known a prediction can be done By comparing the pre diction of a vehicle with the surrounding vehicles a future possibility of a collision can be predicted If the vehicle model and the measurement of the states are really good an implementation of a collision avoidance system can be done by assigning a safety area around the vehicles When these areas overlap each other the system will alert An example of this is shown in Example 4 1 r Example 4 1 Ideal linear prediction with fixed safety distance 34 30 Collision Avoidance Two vehicles are traveling in the nearby area Both are estimated with a constant velocity model see Equation 4 1 and 4 2 The two vehicles each have a preset safety radius in
96. sjuy ejqessejdey UM 18INON dY 103 euusjuy Jepua x3 Buey 8dBi Omni Quick Installation Guide i Two mounting methods are av le for 8dBi Omni Ant Wes mounting 102 Antenna Specifications 2 4GHz RF HI GAIN DIPOLE ANTENNA AFN D MBP Nui Elaste waste ITN f 1 AS Aluminum Ye bbs cop Lp Nm A pa AL Ss NS Supporting pole not included E i jf AEU Screw YA j SPECIFICATION ER E Frequency 2300 2500 MHz T f m Max gain 12dBi T W Connector N female f W Max inputer power lt 50 W lol E Size Hi420un m Wight 590g amp For mage Date Voice communications and Wireless LAN system Link pings universitet Upphovsr tt Detta dokument h lls tillg ngligt p Internet eller dess framtida ers ttare under 25 r fr n publiceringsdatum under f ruts ttning att inga extraordin ra omst ndigheter uppst r Tillg ng till dokumentet inneb r tillst nd f r var och en att l sa ladda ner skriva ut enstaka kopior f r enskilt bruk och att anv nda det of r ndrat f r icke kommersiell forskning och f r undervisning verf ring av upphovsr tten vid en senare tidpunkt kan inte upph va detta tillst nd All annan anv ndning av doku mentet kr ver upphovsmannens medgivande F r att garantera ktheten s kerhe ten och tillg ngligheten finns det l sningar av teknisk och administrativ art Upphovsmannens ideella r tt innefattar r tt att bli n m
97. start request Then the MS generates a key that is used to maintain the identity of the MN for the following process The MN sends an authentication message to the MS that includes a response word derived from the key The MS forwards it to the radius server as a radius authentication message The radius server then authenticates the MN and sends back a response message After this authentication the MS confirms that the MN is identical to what was previously authenticated The MS compares the key from the previous transaction and if the key is verified there is no need to do a transaction to the radius server see Figure 3 2 44 22 Communication Systems AP Search with 1 F2 i Establish air link with 1 F2 ii Authentication Location Registration with 1 F2 111 Start data communication with 1 F2 iv Disconnect air link with I F 1 v Figure 3 1 Flowchart of the handover process using dual antenna technique This schematic flow describes how the system switches between the two network interfaces 44 3 2 3 Selective Channel Scanning The IEEE 802 11b g works with several different channel frequency distributions In Sweden the channel distribution is according to Figure 3 3 and the distribution is divided to 14 possible channels but several of these are overlapping Among these channels only three of them are not overlapping and together they cover the entire bandwidth These channels are 1 6 and 11 To redu
98. stry is to measure vehicle handling roll pitch yaw angles slip etc 47 A combined DGPS INS system would be an appropriate choice for this application but this technique leads to very expensive hardware 2 4 Vision System This section presents different vision systems that are used for automotive imple mentation such as collision avoidance adaptive cruise control and lane detection systems Vision systems can be used for positioning with reference points by measuring distance and heading to the reference points 6See Appendix G for example See Figure B 1 10 Position System Sensor 27 Z electronics a Se Computer A I se Y XAccel__ x Figure 2 3 A schematic drawing of a Inertial Navigation System INS The system contains gyros and accelerometers to obtain information in three dimensions and a com putional unit to process the information signals Acceleration Angular Rates ys yi Ay 04 hy Oy Differential Corrections Radio Modem Navigation Computer Serial e g SATEL 3ds or cellphone 300MHz CPU 54MB Storage Ethernet Sync 1PPS 100Hz out or event in Power 9 18Vdc Figure 2 4 Schematic block diagram of a combined DGPS and INS unit The com putional unit combines the information from the GPS receiver single or dual antenna the INS system and receives differential correction signals from a differential base sta tion via the radio modem All
99. t track In order to verify the capacity of the WLAN system and get an indication of realistic working operating distances we did several measurements at H llered test site 5 3 1 WLAN range To verify the WLAN range we mounted a WLAN Access Point AP see Ap pendix I for technical specifications of the equipment to an omni directional an tenna see Appendix J for technical specifications of the equipment The antenna was mounted to a 3 m high pole to get good transference conditions see Figure 5 20 The AP was connected to a laptop that constantly sent UDP messages at a constant transfer rate The receiving unit was mounted in an estate car with an external antenna placed on the top center of the roof of the car We drove the car towards the AP to see at what maximum distance we could obtain a connection Figure 5 20 WLAN test base station During the test the weather conditions were very moist and sometimes rainy These conditions were unfavourable for good WLAN coverage although not a worst case weather scenario We also performed the test at different vehicle speeds 5 3 WLAN coverage 55 to investigate if the connection was dependent on the speed Distance test To determine the maximum distance at which coverage communication could be obtained we drove against the antenna on a straight line and measured the dis tance with the odometer of the car The first test speed was approximatly 60 km h and the distance from the
100. th a standard deviation accuracy of 15 m has an accuracy which is too imprecise Our conclusion is that the typical GPS not qualifies to be a part of the positioning system 1The phrase typical GPS receiver is referring to the Garmin GPS 35 36 that is used as a standard component within Volvo trucks 1 2The positioning standard deviation 95 of the time 6 Position System r Example 2 1 1 Hz GPS example 4 If the GPS update frequency is 1 Hz and the test vehicle is traveling at 15 m s 54 km h The vehicle will advance 15 m between measurement positions This can be a serious problem in for instance cornering manoeuvres To obtain the wanted resolution in meters the GPS update frequency can be estimated by the following equation Velocity m s Resolution m Frequency Hz 2 1 A _______ _ _ _ _ _ 2 1 2 Differential GPS A differential GPS is an enhancement to the standard GPS system It operates by a stationary ground network or by fixed ground local stations By knowing the exact position of the stationary receiver it can calculate the errors from satellite signals and send out the differential corrections to the vehicle A base station covers a small area and the differential correction is a local correction There are several different techniques that are currently in use to obtain the differential correction s
101. the new 3See Appendix A 2 for carrier wave information 4The performance is valid for kinematic measuring Static measuring obtains even better accuracies 5See Appendix B for more information 2 4 Vision System 9 A Carrier Phase Code Phase Measurements Measurements d BEE Local Area Code Differential BE aa COGPS Worldwide Applicability ESS Wide Area DGPS en Survey HH Static Survey plus 1 pom imm tem 10cm 10m 100m HORIZONTAL ACCURACY 1c Figure 2 2 Summary of expected differential GPS concepts and position accuracies 48 position Due to the DGPS combination the system will not suffer from severe drifting in the calculation of the new position After every new DGPS sample the inertial system has a known position to calculate from This technique can deliver position with a very high sample rate e g 250 Hz 39 When adding a Kalman filter to this setup the system obtains even greater resolution The Kalman filter uses the input errors to give the system an even more exact position The stan dard deviation is below 2 cm in some products To further improve the position accuracy a single double antenna GPS differential GPS correction and an IMU unit can be used See Figure 2 4 for a block diagram of DGPS INS unit The input to the figure is the measured value of the gyros and accelerators 47 48 The ordinary use of this technique in the automotive indu
102. tion The resolu tion of the acceleration meas urements is 0 12mm s 121g The ADC oversamples the analogue sensors and uses coning sculling motion com pensation algorithms to avoid aliasing of the signals The internal processing in cludes the strapdown algo rithms using a WGS 84 earth model Kalman filtering and in flight alignment algorithms 75 Parameter RT3100 RT3020 RT3002 RT3040 3 0mCEP SPS 1 8mCEP SPS 1 8mCEP SPS 1 5mCEP SPS 1 8mCEP SPS 1 5mCEP SPS Position Accuracy 1 4mCEP SBAS 1 2mCEP SBAS 1 2mCEPSBAS 0 8mCEPSBAS 1 2mCEPSBAS 0 8mCEP SBAS 1 0mCEP DGPS 0 4mCEP DGPS 0 2m lo DGPS 0 02m lo DGPS 0 5mCEP VBS 0 1mCEP HP Velocity Accuracy 0 2 km h RMS 0 1 km h RMS 0 08km h RMS 0 05km h RMS 0 08km h RMS 0 07km h RMS Acceleration Bias 10 mm s lo 10 mm s lo 10 mm s lo 10 mm s lo 10 mm s lo 10 mm s lo Linearity 0 01 0 01 0 01 0 01 0 01 0 01 Scale Factor 0 1 lo 0 1 lo 0 1 lo 0 1 lo 0 1 lo 0 1 lo Range 100 m s 100 m s 100 m s 100 m s 100 m s 100 m s Roll Pitch 0 1 lo 0 05 1c 0 05 lo 0 03 1c 0 04 lo 0 03 lo Heading 0 2 lo 0 1 lo 0 1 lo 0 1 lo 0 1 lo 0 1 lo Angular Rate In run Bias 2 deg hr 2 deg hr 2 deg hr 2 deg hr 2 deg hr 2 deg hr ARW 0 2 deg Vhr 0 2 deg Vhr 0 2 deg Vhr 0 2 deg vhr 0 2 deg Vhr 0 2 deg vhr Range 100 s 100 s 100 s 100 s 100 s 100 s Track at 50km h 0 2 RMS 0 1 RMS 0 07 RMS 0 1 RMS 0 1 RMS 0 08 RMS ab 0 3 RMS 0 22 RMS 0 15
103. tion U x y t can calculated according to Equation A 1 A 2 where n is the satellite number and R is the distance to satellite n To get the right po sition in the two dimensional case it takes three satellites and in the general case four The extra satellite is needed to synchronize the simple clock in the receiver with the precise atomic clock in the satellites A larger number of satellites would provide better resolution see Figure A 2 for an example 28 29 51 R c Aty c ta t A 2 Possible Solutions Chosen Solution Three satellite coverage Six satellite coverage Figure A 2 Position accuracy according to the number of satellites When more satellites are used in the position estimation a higher accuracy can be achieved 50 Accuracy The GPS system is not exact in its position determination There are several factors of disturbance that generates errors in the positioning An included feature in the GPS system is Selected Availability SA This is a deliberately encoded random error that occurs and generates an error of about 100 m This signal is now turned off and greater resolution is available to the general public The atmospheric conditions affect the speed of the GPS signals as they travel through the atmosphere and ionosphere The error of this effect is minimal when the satellite is right above the receiver and the error effect increases when the satellite is nearer the horizon due to the signal is a
104. ty precise timing etc To provide this information the GPS receiver use an antenna and a receiver processor The receiver processor measures and decodes the satellite transmission Various GPS receivers uses different types of protocols to present the informa tion Some of the most common protocols is NMEA 0183 the Garmin protocol the SiRF protocol etc 3 30 Geometric Dilution Of Precision The Geometric Dilution Of Precision GDOP describe the geometric strength of the satellite configuration A high number of satellites does not always indicates that the position accuracy is high To obtain an accurate positioning with GPS navigation the satellites have to be separated from each other The GDOP value is a measure of the error contributed by the geometric relationship of the satellites positions When the satellite are close together the geometry is said to be weak and the GDOP value is in this cases high A low GDOP value represents a better GPS positional accuracy due to the wider angular separation between the satellites A 2 GPS 69 Good GDOP Poor GDOP Figure A 1 Satellite constellation for good and poor Geometric Dilution Of Precision Table A 2 DOP value and rating 1 Ideal 2 3 Excellent 4 6 Good 7 8 Moderate 9 20 Fair 21 50 Poor used to calculate a GPS units position see Figure A 1 The ideal level is one and up to six is acceptable The DOP values and rating are presented in Table A 2 The
105. ucks that was supposed to drive autonomous in a restricted area it included active steering and modification in existing control units The navigation was based on laser scanning By placing reflectors in the specified route and using laser scanners for detection the system was able to navigate by building a local reference network and keep the vehicle on a specified route C 4 2 VTEC Prototype truck The Volvo Technology VTEC are working with a concept truck the Volvo Inte grated Safety Truck VIST This concept truck is equipped with several different observation technologies main purpose of collision avoidance One of this features are the lidar system In Figure C 1 the VIST is shown and the circled area shows the lidar system integrated in the front of the truck The lidar is used for collision avoidance and as a pre crash system 78 Prototype Systems Figure C 1 The Volvo Integrated Safety Truck with lidar sensor implementation cir cled Appendix D Mathematics D 1 Haversine Equation The haversine function is given by Equation D 1 By setting Equation D 2 as the variable h we can easily calculate the distance d between the points of interest 2 0 haversin 0 sin 5 D 1 d haversin R haversin A cos 1 cos d2 haversine AA D 2 d R haversin h 2R arcsin Vh D 3 D 2 Covariance Cov X Y E X w Y v D 4 PX Y zu D 5 OXOY 79 Appendix E Kalman filt
106. uter to perform image processing The camera systems can give a very high resolution and advanced target classification is possible thanks to the detailed images The camera systems are very dependent on good light conditions and free sight of view Darkness and weather conditions as rain and snow lower the resolution of the images which leeds to lower reliability of the camera system When combined with infrared or thermal cameras the system can see in the dark Such camera systems suffer from reflection of heat radiation which makes it hard to use within navigation and safety purposes The image processing algorithms are computation intensive which may make it difficult to maintain reliability when the environment changes rapidly such as at high speed driving 31 Advantages and disadvantages of this system are presented in Table 2 2 2 4 3 Radar Sensors Radio detection and ranging Radar is one of the most common tracking sensors It has been used for automotive purposes such as adaptive cruise control A radar emits electro magnetic radiation to illuminate targets It uses the same antenna to 12 Position System Table 2 2 Camera system 31 Advantages Disadvantages Cost efficient system Sensitivity to light conditions High resolution Sensitivity to dirt and weather Advanced target classification High computational demands Table 2 3 Radar system 31 Advantages Disadvantages Bad weather performance Bad resoluti
107. wide area The RT3002 can give more accurate positioning in a local area where licence free radios can be used to transmit the corrections The RT3000 products are also available as dual antenna mod els Where accurate heading in low dynamics is required the dual antenna model may be more suitable For further information please contact Oxford Technical So lutions or your nearest local agent Parameter RT3000 can be used to save tests in Power 9 18 V d c 15W files display real time results Daso ran 234 x 120 x 80 and monitor the performance Weight 2 2 kg The internal logging enables Operating Temperature 10 to 50 C the RT3000 to work stand 777 0 1 g Hz 5 500 Hz alone Post mission data can be output in ASCII text format Shock Survival 100G 11ms Magnetic GPS antenna for vehicle and pucr to the software Internal Storage 500 MB mounting Other types available of your choice Dual Antenna No Appendix H Oxford Tech RT Base RT Base GPS Base Station Features e 45cm DGPS Corrections e 20cm L1 Corrections e 2cm L2 Corrections e RTCA Format e Integral 10h Battery e Integral Charger e Integral Mains PSU e Integral Radio Modem e 450MHz Band e Error Correcting Transmission e Save Restore Antenna Position e Multi path Rejecting GPS Antenna e IP65 Rated Case Compatibility e RT3000 e RT4000 e RTCA Oxford Technical Solutions 77 Heyford Park Upper Heyford Oxfordshire OX25 5
108. y 65 54 55 56 57 58 59 60 61 62 63 64 Jan Sparbert Klaus Dietmayer and Daniel Streller Lane detection and street type classification using laser range images Intelligent Transportation Systems 2001 Proceedings 2001 IEEE Carsten Spichalsky Golf gti 53 the driverless car dSpace News 1 18 19 2007 Swepos Swepos Glonass November 2007 URL http swepos lmv lm se gps glonass glonass htm Swepos Swepos produkter 2007 URL http swepos lmv lm se index prod htm Kiyokazu Takagi Katsuhiro Moirikawa Takashi Ogawa and Makoto Saburi Lane recognition using on vehicle lidar Intelligent Vehicles Symposium 2006 IEEE pages 540 545 Han Shue Tan and Jihua Huang Dgps based vehicle to vehicle cooperative collision warning Enginering feasibility viewpoints IEEE Transactions on in telligent transportation system Vol 7 No 4 December 2006 7 2006 1524 9050 Han Shue Tan and Jihua Huang A low order dgps based vehicle positioning system under urban enviroment IEEE ASME Transactions on mechatronics Vol 11 No 5 October 2006 5 2006 1083 4435 Andrews Space amp Technology Glonass November 2007 URL http www spaceandtech com spacedata constellations glonass con sum shtml S Wender T Weiss and K Dietmayer Improved object classification of laserscanner measurements at intersections using precise high level maps In telligent Transportation Syst

Pilot Study of Systems to Drive Autonomous Vehicles on Test Tracks

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