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Inertial+ User Manual - Industrial Measurement Solutions

1. The altitude option can be used to change the default altitude output between the ellipsoidal altitude of WGS84 and the geoidal altitude given by adding undulation from a lookup table Outputs where the altitude type is specifically defined e g NMEA GGA are not affected outputs where the altitude type is not defined NCOM are affected The geoid table used will come from the external GNSS receiver if the external GNSS does not supply undulation or geoid height then the Inertial will only be able to output the ellipsoidal altitude A constant altitude offset can be specified by entering a value in to the box Serial 1 and Serial 2 outputs Adjustment click button to open properties window The Serial 1 and Serial 2 output ports can be configured for different message types Figure 23 shows the properties windows for the Serial 1 output which are the same for Serial 2 Figure 23 NAVconfig Serial output properties windows Q Serial 1 output Ea O Serial 1 output al General NMEA General Message type Periodic Falling Rising Camera Packet NCOM v GPGGA tHe y GPHDT 1Hz v Baudrate 115200 v GPVTG Disabled v GPZDA Disabled Y Datarate 100 Hz v GPGST Disabled Y PASHR Disabled Y GPRMC Disabled v GPGSv Disabled v GPGSA Disabled V PTCF Disabled Y GPPPS Disabled Y PRDID Disabled V epont peppa n m n Me Baud rate 115200
2. Adjustment select a predefined value from the drop down list The output of the Inertial will continue to change even when the vehicle is stationary For some video systems this leads to ambiguous results The position and orientation can be locked by the Inertial automatically when the vehicle becomes stationary While the outputs are locked the Kalman filter continues to run and accumulate errors When the vehicle moves the Kalman filter will quickly return to the new solution The drift rate can be controlled using the Output smoothing option Output smoothing Adjustment click button to open properties window When the Kalman filter in the Inertial determines that there is some error to correct this error is applied smoothly rather than as a jump The output smoothing controls how fast the correction is applied to the outputs Figure 22 shows the Output smoothing window Click the checkbox to enable output smoothing and unlock the properties for editing B Oxford Technical Solutions Inertial User Manual QObxrs Inertial GPS Figure 22 NAVconfig Output smoothing properties window F Output smoothing properties Eal Enable output smoothing Smoothing Position 0 100 m Velocity 0 500 m s Angle 0 200 deg Time limit Position s Velocity s Angle s OK Cancel The smoothing of the position velocity and orientation corrections can be controlled independently Enter the maximum correcti
3. To check that all the internal circuits in the Inertial are working correctly and that the navigation computer has booted correctly use the following procedure Revision 131122 1 Connect power to the system connect the system to a laptop computer and run the visual display software Enginuity 2 Use Table 29 to check that the status fields are changing Table 29 Status field checks Field Increment Rate IMU packets 100 per second or 250 per second depending on product model IMU chars skipped Not changing but not necessarily zero GPS packets Between 2 and 20 per second depending on system GPS chars skipped Not changing but not necessarily zero GPS2 packets Between 2 and 20 per second depending on system GPS2 char skipped Not changing but not necessarily zero Note 1 The GPS2 related fields will only increase for dual antenna systems These checks will ensure that the signals from the internal GNSS and from the inertial sensors are being correctly received at the navigation computer 7 Oxford Technical Solutions Inertialt User Manual Qoxrs Using the orientation measurements This section has been provided to clarify the definitions of heading pitch and roll that are output by the Inertial The Inertial uses quaternions internally to avoid the problems of singularities and to minimise numerical drift on the attitude integration Euler angles are used to output the heading pitch an
4. has been designed to be simple and easy to operate The front panel label and LEDs convey some basic information that aid in configuration and troubleshooting Once powered the Inertial requires no further input from the user to start logging and outputting data This section covers some basic information required for operation of the Inertial Front panel layout Figure 5 shows the layout of the Inertial front panel Table 9 gives descriptions on the parts labelled in Figure 5 The front panel is the same for all Inertial models On single antenna models the secondary antenna connector is not connected internally Figure 5 Inertial front panel layout INERTIAL SDNav Pos Head Pwr AN Os serial Output Axes N erin Pree E7004 Serial HH h 9 o ee o 8 amp 8 Par ax Ethernet 1 Digital 1 0 E ww oxs com Revision 131122 EJ Table 9 Inertial front panel descriptions Label no Description 1 RS232 serial port 2 External GNSS serial port 3 Secondary RS232 serial port 4 Digital I O port 5 SDNav LED 6 Pos Head LED 7 Pwr LED 8 Primary antenna connector 9 Secondary antenna connector 10 M12 power connector 11 Ethernet port LED definitions The front panel of the Inertial has some LEDs that give an indication of the internal state of the system and are designed to provide enough feedback so that a laptop does not need to be connected They can be used for some simple operational
5. when entering measurements alternate units can be used as long as they are specified e g 10 or 10 in NAVconfig will then convert and display these in metric units Product selection The first page of the NAVconfig configuration wizard lets you select the type of product for configuration see Figure 11 40 Oxford Technical Solutions Inertial User Manual QOaxrs Inertial GPS Figure 11 NAVconfig Product Selection page F NAVconfig wizard o Product Selection I rti i Select the product for configuration Inertial and GNSS Product family Product model Navigation RT2000 RT3000 Inertial 250 RT4000 Inertial 2 Step 1 of 10 Inertial Inertial 2 250 Survey xNAV Read Configuration SEN GNSS Selection Onentation External Antenna ondary Antenne Wheel Configuration Options Commit Save Fintsh Always use this product Dev ID 131024 14am EE English v Next gt Cancel The configuration wizard can be run without a system connected so it is necessary to select the correct product for configuration Some configuration pages are not available with some of the products These will be displayed as grey in the sidebar In instances where the same product type will be used each time the Product Selection page can be skipped in the future by clicking the Always use this product checkbox If a different product needs configuring the selection page can be returned t
6. Added Javad output for faster RTK relock Added reverse polarity clarification Added specification for internal GPS receiver 110901 Updated for the new software Added improved settings Clarification on co ordinate frames 120928 Updated for the new software Added GPPPS messages Two new receivers added Updated Conformance Notices Added section on ECCN Added Software Disclaimer Added section on Ethernet output Updated Inertial drawing 131122 Updated for new NAVsuite software Added software installation and related documents sections Other minor updates 7 Oxford Technical Solutions Inertialt User Manual QOaxrs Inertial GPS Drawing list Table 31 lists the available drawings that describe components of the Inertial system Many of these drawings are attached to the back of this manual Note that the x following a drawing number is the revision code for the part If you require a drawing or different revision of a drawing that is not here then contact Oxford Technical Solutions Table 31 List of available drawings Drawing Description 14A0040x Inertial system outer dimension drawing 77C0038B Power cable AT575 70B GNSS antenna Revision 131122 Ea Oxford Technical Solutions 77 Heyford Park Upper Heyford Oxfordshire OX25 5HD www oxts com Copyright Oxford Technical Solutions 2013 gonial The information in this docume
7. C Program Files x86 OxTS on 64 bit operating systems or C Program Files OxTS on 32 bit operating systems The first time some OxTS applications are run a firewall warning message similar to that shown in Figure 2 may be triggered This is because the program is attempting to listen for and communicate with OxTS devices on the network The firewall must be configured to allow each program to talk on the network or programs will not work as intended g Oxford Technical Solutions Inertialt User Manual Inertial GPS Figure 2 Windows Firewall warning message Windows Security Alert e Windows Firewall has blocked some features of this program Windows Firewall has blocked some features of Enginuity on all public and private networks Name Enginuity Publisher Oxford Technical Solutions Path C program files x86 oxts enginuity exe Allow Enginuity to communicate on these networks V Private networks such as my home or work network Public networks such as those in airports and coffee shops not recommended because these networks often have little or no security What are the risks of allowing a program through a firewall allow access Cancel SSS SSS SS SSS Ensure both Private and Public networks are selected to ensure the software can continue functioning when moving from one type to another Revision 131122 19 Connections The connection
8. MA Maximum chars per second 101 Available chars per second 11520 C Allow extended length messages Output approximate values before initialisation OK Cancel oK Cancel Note NMEA tab only appears when NMEA is selected from the Packet drop down list Select the message type to output from the Packet drop down list and select the baud rate and data rate to output at Table 24 gives details of the different messages EX Oxford Technical Solutions Inertialt User Manual Qoxrs Table 24 Serial output options Option Description Disabled The serial output is disabled This option can be used to reduce the computational load and ensure that the Kalman filter runs quicker NCOM Normal output of the Inertial NCOM data is transmitted at up to 100 Hz or 125 Hz for 250 Hz systems RS232 does not support 250 Hz The format is described in the NCOM Description Manual Software drivers exist for decoding the NCOM data IPAQ NCOM output at a reduced rate The baud rate of the serial port is set to 19200 and the update rate is 25 Hz It is used because the IPAQ cannot manage to receive the data reliably above 25 Hz IPAQ NCOM output at a reduced rate and polled Windows Mobile 5 on IPAQs crashes if the Inertial is sending data when the IPAQ is turned on Using IPAQ the IPAQ will poll the Inertial the Inertial will not send data while the IPAQ is off preventing the turn on crash of the IPAQ NMEA The NMEA outpu
9. PDF files Figure 13 NAVconfig GNSS Selection page Q NAVconfig wizard 0 GNSS Selection I rt I Choose the external GNSS receiver connected to the Inertial Inertial n nd G NSS Manufacturer Model ai Navigation C amp C Technologies C Nav 3050 w Generic NMEA l Step 3 of 10 Leica GPS1230 NavCom SF 3050 Product Selection Novatel OEM3 o fi Read Configuration Da OEM4 e Orientation Novatel OEMV w External Antenna Omnistar 4305 HP 2 Secondary Antenna Topcon GB 500 Qa Wheel Configuration Options Commit Save Finish 9600 C Use advanced settings C Use intemal GNSS receiver Dev ID 131024 14am English v lt Back Next gt Cancel For some GNSS receivers it is necessary to change the port settings so that the external GNSS port on the Inertial matches the port settings on the GNSS receiver Click the Use advanced settings checkbox to unlock the advances settings and change the port settings Revision 131122 Ey The advanced settings can also be used to change the format of the receiver being used For example if a Novatel OEMV receiver is being used with NMEA then OEMV should be selected from the list and NMEA should be selected from the Format dropdown list in advanced settings Mixing receivers and formats is not recommended unless directed by OxTS The Inertial has internal GNSS receivers that are used to obtain a GPS time stamp for synchronising measurements or for co
10. This is the forward direction of the car y This is the right direction of the car Z This is the down direction of the car a Oxford Technical Solutions Inertialt User Manual QObxrs Figure 8 Vehicle frame definition y Ethernet configuration To configure the Inertial for unrestricted data transmission it is necessary to use the Ethernet connection The operating system at the heart of the Inertial products allows connection to the unit via FTP The use of FTP allows the user to manage the data logged to the unit files can be downloaded for reprocessing and deleted to make space for future files Configuration files for alternative configurations require FTP to put the configuration files on to the Inertial The default username and password are both user The Inertial outputs its data over Ethernet using a UDP broadcast The use of a UDP broadcast allows everyone on the network to receive the data sent by the Inertial The data rate of the UDP broadcast is 100 Hz or 250 Hz depending on the Inertial model In order to communicate via Ethernet each Inertial is configured with a static IP address that is shown on the delivery note If the delivery note is unavailable the default IP address normally takes the form 195 0 0 sn where sn is the last two digits of the Inertial s serial number The serial number can be found on the front panel of the Inertial or on the delivery note The IP address of the co
11. a camera or a brake switch The event input has a pull up resistor so it can be used with a switch or as a CMOS input A low voltage requires less than 0 8 V on the input and a high voltage requires more than 2 4 V on the input There is no protection on this input protection circuitry would disturb the accuracy of the timing Keep the input in the range of 0 V to 5 V By default the maximum event rate is 1 Hz for 100 Hz products and 4 Hz for 250 Hz products This can be increased to 50 Hz by selecting one or both the Output on falling edge of trigger and Output on rising edge of trigger check boxes on the Ethernet Output window This is accessed from the Options page in NAVconfig see Ethernet output on page 58 of this manual Trigger information can be found in status message 24 output over NCOM for the triggers Odometer input The odometer input accepts TTL pulses from an encoder on a single wheel An encoder from a gearbox should not be used and simulated TTL pulses e g from a CAN bus should not be used The timing of the odometer input pulses is critical and nothing should cause any delay in the pulses The odometer input requires less than 0 8 V for a low pulse and more than 2 4 V for a high pulse Limited protection is provided on this input however the input voltage should not exceed 12 V The wheel that is used should not steer the vehicle The Inertial will assume that this wheel travels straight Camera trigger
12. as thoroughly Accelerometer test procedure To check the accelerometers are working correctly follow this procedure 1 Connect power and a laptop to the system 2 Commit a default setting to the Inertial using NAVconfig then run Enginuity 3 Click the Calibration button then select the Navigation tab and ensure the x y and z accelerations values 19 to 21 are within specification when the Inertial is placed on a level surface in the orientations according to Table 27 Table 27 Acceleration measurement specifications Orientation Acceleration measurement Y Flat Flat Down z acceleration between 9 7 and 9 9 m s Flat Flat Up z acceleration between 9 7 and 9 9 m s Down Flat Flat x acceleration between 9 7 and 9 9 m s Up Flat Flat x acceleration between 9 7 and 9 9 m s Flat Down Flat y acceleration between 9 7 and 9 9 m s Flat Up Flat y acceleration between 9 7 and 9 9 m s This test is sufficient to ensure that the accelerometers have not been damaged Gyro test procedure To check that the gyros angular rate sensors are working correctly follow this procedure e Oxford Technical Solutions Inertialt User Manual Qoxrs 1 Connect power and a laptop to the system 2 Commit a default setting to the Inertial using NAVconfig then run Enginuity 3 Click the Calibration button then select the Navigation tab and scroll to view the x y and z angular rates values 30 to 32 4 Rotate
13. cables exit in the same direction but the bases of the antennas are not parallel C The bases of the antennas are parallel and the cables exit in the same direction This configuration will achieve the best results It is best to mount the two antennas on the top of the vehicle On aircraft it is best to mount the antennas on the main aircraft fuselage if the Inertial is mounted in the aircraft fuselage itself If the Inertial is mounted on a pod under the wings then mounting the antennas on the pod may give the best results Multipath affects dual antenna systems on stationary vehicles more than moving vehicles and it can lead to heading errors of more than 0 5 RMS if the antennas are mounted poorly fe Oxford Technical Solutions Inertialt User Manual Qoxrs It is critical to have the Inertial mounted securely in the vehicle If the angle of the Inertial can change relative to the vehicle then the dual antenna system will not work correctly This is far more critical for dual antenna systems than for single antenna systems The user should aim to have no more than 0 05 of mounting angle change throughout the testing If the Inertial is shock mounted then the mounting will change by more than 0 05 this is acceptable but the hysteresis of the mounting may not exceed 0 05 For both single and dual antenna systems it is essential that the supplied GNSS antenna cables are used and not extended shortened or replaced This is
14. can turn on the spot The default setting Normal is best for most applications as it is least likely to cause problems in the Kalman filter Tight and Very tight are better when trying to reduce position drift in poor GNSS environments and traffic jams Table 23 gives a more detailed description on each of the heading lock options Table 23 NAVconfig heading lock options Heading lock Description Normal This option assumes that the heading of the vehicle does not change by more than 2 while the vehicle is stationary The heading accuracy recovers quickly when the vehicle moves Tight This option assumes that the heading of the vehicle does not change by more than 0 5 while the vehicle is stationary The recovery is fast if the heading of the vehicle does not change but will be slow if the vehicle turns before it moves Very tight The option assumes that the heading of the vehicle does not change by more than 0 3 while the vehicle is stationary The recovery is fast if the heading of the vehicle does not change but will be slow if the vehicle turns before it moves This option can cause problems during the warm up period if the vehicle remains stationary for a long time and then drives suddenly Note The heading of most vehicles does change if the steering wheel is turned while the vehicle is stationary Junctions and pulling out of parking spaces are common places where drivers turn the steering wheel while not moving Output lock
15. definition Axis Description Diagram North The north axis n is perpendicular to the gravity vector and in the direction of the north pole along the earth s North surface East The east axis e is perpendicular to gravity perpendicular to the north axis and is in the east direction Down The down axis d is along the gravity vector East Level frame The level frame is attached to the vehicle but does not rotate with the roll and pitch of the vehicle It rotates by the heading of the vehicle The definition of the level frame is listed in Table 17 and shown in Figure 7 Revision 131122 EI Table 17 Level frame definition Axis Description Forward This is the forward f direction of the car projected in to the horizontal plane Lateral This is the lateral 1 direction of the car pointing to the right projected in to the horizontal plane Down This is the down d direction of the car along the gravity vector Figure 7 Level frame definition Lateral Forward Lateral Oo wy Down Down Forward Vehicle frame The vehicle frame is attached to the body of the vehicle It is related to the Inertial through the rotations in the Orientation page of NAVconfig It can be changed while the Inertial is running using the Quick Config page of Enginuity The definitions of the vehicle frame are listed in Table 18 and shown in Figure 8 Table 18 Vehicle frame definition Axis Description x
16. even more critical for dual antenna systems and the two antenna cables must be of the same specification Do not for example use a 5 m antenna cable for one antenna and a 15 m antenna cable for the other Do not extend the cable even using special GNSS signal repeaters that are designed to accurately repeat the GNSS signal Cable length options are available in 5 m and 15 m lengths Using an antenna splitter In many cases it is possible to use an antenna splitter with the Inertial so that only one antenna is needed or two antennas for dual antenna systems If an antenna splitter is used then there are a few important points to consider The Inertial supplies a 5 V output to the antenna with up to 100 mA supply This is probably enough to power both the antenna and the antenna splitter If the Inertial is supplying the power to the antenna splitter then both the antenna and the antenna splitter need to work correctly from a 5 V supply e The Inertial has an extremely sensitive GNSS receiver in it High gain antennas can sometimes have a signal that is too large for the Inertial Antenna splitters often contain some additional gain to overcome cable and connector losses Having an antenna with a gain of more than 40 dB is not recommended This may be 35 dB for the antenna and 5 dB for the antenna splitter Cable loss may increase the amount of gain that can be used In dual antenna configurations only one antenna splitter is
17. manoeuvres Warm up is recommended in order to achieve the highest level of accuracy In aircraft applications flying figures of eight will remove a few hundredths of a degree of roll and pitch error which can be critical for geo referencing applications The same is true for marine applications However the effect is small and only significant when you need the full performance of the Inertial 7 Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS Post processing data Data stored on the Inertial is in a raw unprocessed format these files have an rd extension The advantage of this is it can be reprocessed with different configuration settings For example if the configuration was configured incorrectly when running in real time then the configuration can be changed and the data can be reprocessed post mission The software suite provided with the Inertial includes the RT Post process software which can be used to reprocess the data The RT Post process Wizard also gives the user the ability to change the NCOM binary output format to text A full explanation of RT Post process is given in the RT Post process manual Revision 131122 ED Laboratory testing There are several checks that can be performed in the laboratory to ensure that the system is working correctly The most fragile items in the system are the accelerometers the other items are not subject to shock and do not need to be tested
18. on the serial port up to 30 ms late and out of order compared to the normal messages To enable these messages check the appropriate checkbox Note that it is easy to overload the serial port if there are too many events The software computes the number of characters that will be output each second and displays this at the bottom of the window A serial port data overflow warning message will appear if Revision 131122 Ea the data rate is too high for the selected baud rate to fix this it is necessary to lower the data rate of the selected NMEA sentences or increase the baud rate Selecting Allow extended length messages enables the full GGA and RMC messages to be output which are longer than the NMEA specification allows Please see the NMEA 0183 Description manual for more details Selecting Output approximate values before initialisation forces output of the raw GNSS measurements before the Inertial is initialised Currently just the position is output and this is the position of the antenna not the inertial measurement unit Note that there will be a jump from the antenna to the inertial measurement unit when initialisation occurs Ethernet output Adjustment click button to open properties window The Ethernet output of the Inertial can be configured for different data rates Figure 24 shows the Ethernet output properties window Figure 24 NAVconfig Ethernet output properties window F Ethernet Output x Gener
19. otherwise the course over ground will not be close enough to the heading Real time outputs During the initialisation process the system runs 1 s behind allowing GNSS information to be compared to information from the inertial sensors After initialisation the system has to catch up from this 1 s lag It takes 10 s to do this During the first 10 s the system cannot output data in real time the delay decays to the specified latency linearly over this 10 s period The system turns the SDNav LED orange to show the outputs are not real time When the system is running in real time this LED is green Warm up period During the first 15 minutes of operation the system will not conform to specification During this period the Kalman Filter runs a more relaxed model for the sensors By running a more relaxed model the system is able to e6 Oxford Technical Solutions Inertialt User Manual QObxrs 1 Make better estimates of the errors in the long term if it does not get these correct then they become more difficult to correct as time goes on 2 Track the errors in the inertial sensor during their warm up period when their errors change more quickly than normal During this period it is necessary to drive the vehicle or the errors will not be estimated and the specification will not be reached The NCOM output message includes status information that can be used to identify when the required specification has been met These are plott
20. outputs 36 1PPS output 36 Event input 37 Odometer input 37 Camera trigger output 37 IMU sync output pulse 38 Reverse polarity protection 38 Configuring the Inertial 39 Overview 39 Selecting the operating language 39 Navigating through NAVconfig 40 Product selection 40 Reading the initial configuration 4 GNSS selection 43 Orientation 44 Improve configuration 45 External antenna position 47 Secondary antenna position 49 Wheel configuration 50 Options 52 Initialisation speed 52 Displace output 53 Camera trigger 53 Heading lock 53 Output lock 54 Output smoothing 54 Altitude 55 Serial 1 and Serial 2 outputs 56 Ethernet output 58 Revision 131122 jE GNSS control 59 GNSS weighting 61 Odometer input 61 Advanced 63 Committing the configuration to the Inertial 63 Saving the configuration and finishing 64 Initialisation process 66 Real time outputs 66 Warm up period 66 Post processing data 71 Laboratory testing 72 Accelerometer test procedure 12 Gyro test procedure 72 Testing the internal GNSS and other circuitry 73 Using the orientation measurements 75 Revision history 76 Drawing list TI a Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS Scope of delivery The Inertial products are supplied with cables GNSS antennas software and manual In the standard configurations magnetic mount antennas are provided but other antenna types are available please enquire for more details Table 1 li
21. profits or business interruption however caused and on any theory of liability whether in contract strict liability or tort including negligence or otherwise arising in any way out of the use of this software even if advised of the possibility of such damage Copyright Notice Copyright 2013 Oxford Technical Solutions Revision Document Revision 131122 See Revision History for detailed information Contact Details Oxford Technical Solutions Limited Tel 44 0 1869 238 015 77 Heyford Park Fax 44 0 1869 238 016 Upper Heyford Oxfordshire Web http www oxts com OX25 5HD Email support oxts com United Kingdom a Oxford Technical Solutions Inertialt User Manual Qoxrs Inertial GPS Warranty Oxford Technical Solutions Limited OxTS warrants the Inertial products to be free of defects in materials and workmanship subject to the conditions set forth below for a period of one year from the Date of Sale Date of Sale shall mean the date of the Oxford Technical Solutions Limited invoice issued on delivery of the product The responsibility of Oxford Technical Solutions Limited in respect of this warranty is limited solely to product replacement or product repair at an authorised location only Determination of replacement or repair will be made by Oxford Technical Solutions Limited personnel or by personnel expressly authorised by Oxford Technical Solutions Limited for this purpose In no event wil
22. required if the antenna splitter does not cause a significant phase change to the signal Both antennas need to be of the same design or the dual antenna system will not work Cable lengths should not be significantly different e g 1 m on one antenna and 15 m on the other is not recommended OxTS has tried and tested an antenna splitter from GPS Networking in a dual antenna configuration and we could not find a reduction in the performance The details of the product tested are listed in Table 8 Revision 131122 Ee Table 8 GPS Networking antenna splitter Parameter Description Website http www gpsnetworking com Model HIALDCBS1X2 Description GPS Hi isolation amplified antenna splitter 2 outputs TNC Gain option 3 dB Note By default this antenna splitter comes with an 18 dB gain It must be ordered with a 3 dB gain for use with the Inertial otherwise the overall gain is likely to be too high This gain cannot be ordered through the web and GPS Networking must be contacted directly in order to have the 3 dB gain We have tested the hi isolation version by default which minimises the possibility of interference between the GNSS receivers This is the version that we would recommend We have also successfully used active antenna splitters from GPS Networking i e ones that do not get power from the GNSS receiver gE Oxford Technical Solutions Inertial User Manual Qaxrs Inertial GPS Operation The Inertial
23. settings upon exit Advanced a Once the computer is configured the IP address of an Inertial can be found by running Enginuity software this will display the IP address of any Inertial connected Note that it is possible to change the IP address of Inertial systems If the IP address has been changed then Enginuity should still be able to identify the address that the Inertial is using as long as the PC has a valid IP address and this is not the same as the Inertial s Dual antenna systems It is often useful to have an understanding of how the Inertial 2 uses the measurements from the dual antenna system This can lead to improvements in the results obtained 1 To use the measurements properly the Inertial 2 needs to know the angle of the GNSS antennas compared to the angle of the Inertial 2 This cannot be measured 32 Oxford Technical Solutions Inertialt User Manual Qoxrs accurately by users without specialised equipment the Inertial 2 needs to measure this itself as part of the warm up process 2 The Inertial 2 will lock on to satellites but it cannot estimate heading so it cannot start Either motion or static initialisation can be used to initialize the Inertial 2 3 When the vehicle drives forward and reaches the initialisation speed the Inertial 2 assumes that the heading and track are similar and initialises heading to track angle If the Inertial 2 is mounted in the vehicle with a large headin
24. several distinct advantages over systems that use GNSS alone e All outputs remain available continuously during GNSS blackouts when for example the vehicle drives under a bridge e The Inertial recognises jumps in the GNSS position and ignores them e The position and velocity measurements that the GNSS makes are smoothed to reduce the high frequency noise e The Inertialt makes many measurements that GNSS cannot make for example acceleration angular rate heading pitch roll etc e The Inertial takes inputs from a wheel speed odometer in order to improve the drift rate when no GNSS is available e The Inertial has a high 100 or 250 Hz update rate and a wide bandwidth e The outputs are available with very low 3 5 ms latency The Inertial system processes the data in real time The real time results are output via RS232 and over 10 100 Base T Ethernet using a UDP broadcast Outputs are time stamped and refer to GPS time The measurements are synchronised to the GPS clock a Oxford Technical Solutions Inertialt User Manual Qoxrs Easy operation Installation and operation of the Inertial could not be simpler A simple configuration wizard is used to configure the Inertial The configuration can be saved to the Inertial so it can operate autonomously without user intervention A lot of work has been put into the initialisation of the inertial algorithms so that the Inertial can reliably start to navigate in the
25. to read these improved measurements into NAVconfig commit them to the Inertial then use them next time you start the system If you move the Inertial from one vehicle to another it is essential you return to the default configuration rather than using parameters that have been tuned for a different vehicle Selecting the operating language The NAVconfig software can operate in several languages To change language select the language from the drop down menu at the bottom of the page The language is hot swappable making it easy and fast to switch between languages Revision 131122 EJ The software will use the regional settings of the computer to choose whether numbers are represented in the English or European format dot or comma for the decimal separator The selected language does not change the format used for numbers Navigating through NAVconfig NAVconfig provides a ten step process to make configuring your product as easy as possible After completing each step click the Next button at the bottom of the window to proceed to the next step The Back button can be used to return to the previous step at any time Clicking Cancel will bring up a warning asking to confirm you want to close the wizard and lose any changes you have not saved To quickly move between any of the steps click on the step name in the sidebar to instantly jump to that page Measurements are always displayed in metric units in NAVconfig However
26. to the errors caused by multipath This can be from buildings trees roof bars etc Multipath is where the signal from the satellite has a direct path and one or more reflected paths Because the reflected paths are not the same length as the direct path the GNSS receiver cannot track the satellite signal as accurately The dual antenna system in the Inertialt2 works by comparing the carrier phase measurements at the two antennas This tells the system the relative distance between the two antennas and which way they are pointing the heading For the heading to be accurate the GNSS receivers must measure the relative position to about 3 mm The level of accuracy can only be achieved if there is little or no multipath In an ideal environment with no surrounding building trees road signs or other reflective surfaces the only multipath received is from the vehicle s roof The antennas supplied with the Inertial 2 are designed to minimise multipath from the vehicle s roof when the roof is made of metal For use on non metallic roofs a different type of antenna is required When stationary the heading from the Inertial 2 will show some error the size of the error depends on the multipath in the environment Table 19 lists the error you can expect when stationary with a m base line Table 19 Typical heading error for when stationary in different environments Environment Typical error 30 Complete open sky 0 45 0 3 10 Near
27. vast majority of situations For example the Inertial can initialize during flight without problems To make installation easier the Inertial contains its own low cost GNSS receiver This receiver is used to synchronise the inertial measurements to the external GNSS receiver Using this technique the Inertial is able to precisely time align the measurements from the external GNSS giving much more accurate results The single unit contains the inertial sensors low cost GNSS receiver data storage and CPU A laptop computer can be used to view the results in real time Often an antenna splitter can be used to split the signal from the external GNSS receiver and feed it to the GNSS receiver in the Inertial Self correcting Unlike conventional inertial navigation systems the Inertial uses GNSS to correct all its measurements GNSS makes measurements of position and velocity and for dual antenna systems heading Using these measurements the Inertial is able to keep other quantities such as roll pitch and heading accurate Tight coupling of the GNSS and inertial measurements means the raw GNSS data can also be used Flexible accuracy The Inertial takes GNSS accuracy measurements into account and uses them to obtain the best possible output accuracy When using a 1 cm accurate GNSS receiver the Inertial will give 1 cm accurate results Drop in component The Inertial has been made so that it is a drop in component in man
28. vehicles or road vehicle applications on low friction surfaces e g ice a dual antenna system is recommended to maintain high accuracy heading GNSS only dual antenna systems require open sky environments to operate because they can take several minutes to acquire heading lock Advanced processing in the Inertial 2 allows relock to occur after 5 s of a sky obstruction in this time the Inertial 2 s heading will not have significantly degraded The fast relock time is made possible because the Inertial 2 s own heading is used to resolve the ambiguities in the GNSS measurements Resolution of these ambiguities is what normally takes several minutes The heading software in the Inertialt 2 enables significantly better performance and coverage compared to GNSS only solutions Revision 131122 a 250 Hz Both the Inertial and Inertial 2 have the option of coming with a 250 Hz version of the inertial measurement unit IMU The IMUs used in 100 Hz and 250 Hz products are essentially the same both with a fundamental sampling frequency of 2500 Hz The difference is the 3D filter used to integrate the accelerations and angular rates has a smaller time step in the 250 Hz version allowing a higher update rate However because of the smaller time step measurements that depend on angular acceleration are typically noisier on the 250 Hz products The noise can be managed by filtering the data to limit the bandwidth a Oxford Technical
29. wheel speed measurements are used it may be desirable to reject more GNSS measurements Select the Start believing measurements after_ option and enter the number of GNSS measurements to reject before the system starts believing it again The amount of time the Inertial will ignore updates for is dependent on the update rate of the external GNSS receiver For example if the receiver updates position at a rate of 2 Hz and velocity at a rate of 10 Hz and you wish the Inertial to start believing both measurements after 30 s then it should be configured to start believing measurements after 60 position updates and 300 velocity updates The internal GNSS receivers in the Inertial update position at 2 Hz and velocity at 4 Hz Ey Oxford Technical Solutions Inertialt User Manual QObxrs Inertial GPS GNSS weighting Adjustment select a predefined value from the drop down list The Inertial can place different emphasis on the GNSS receiver s measurements The default setting is Medium placing equal weighting on the GNSS receivers and inertial sensors Selecting High will cause the Inertial to believe the GNSS receivers more and selecting Low will make the Inertial rely more on the inertial sensors In urban environments it is better to believe the inertial sensors more whereas in open sky the GNSS receiver should be believed more Odometer input Adjustment click button to open properties window Using an odometer makes a hug
30. 0 100 m at oc a S Dev ID 131024 14am English v lt Back Next gt Cancel Enter the antenna separation and select the position of the secondary antenna relative to the primary antenna from the drop down list The illustrations will change according to the settings you choose to help visualise the configuration of the antennas The Inertial does not estimate the distance between the two antennas It is essential to get this right yourself otherwise the system will not work correctly and the performance will be erratic The measurement needs to be accurate to 5 mm preferably better than 3 mm A wider separation will increase the dual antenna heading solution accuracy The maximum recommended separation in 5 m giving an accuracy of up to 0 06 in both static and dynamic conditions Revision 131122 EI If the antennas are mounted at significantly different heights or if the mounting angle is not directly along a vehicle axis forward or right then click the Use advanced settings checkbox to enable advanced settings and specify the orientation and height offset Getting the angle wrong by more than 3 can lead the Inertial to lock on to the wrong heading solution The performance will degrade or be erratic if this happens If the angle between the antennas cannot be estimated within a 3 tolerance then contact OxTS support for techniques for identifying the angle of the antennas The Enable static initia
31. Antenna Ethemet output Enabled Wheel Configuration GNSS control Defaut Commit GNSS weighting Medium Save Finish Differential Disabled Odometer input Disabled Advanced Disabled Dev ID 131024 14am English v lt Back Next gt Cancel Initialisation speed Adjustment select a predefined value from the drop down list or type in a value a Oxford Technical Solutions Inertialt User Manual QObaxrs If static initialisation has not been enabled the Inertial will need to be initialised by driving forwards in a straight line to initialise the heading to the track angle The initialisation speed is the speed at which the vehicle must travel to activate the initialisation The default initialisation speed for the Inertial is 5 m s However some slow vehicles cannot achieve this speed For these vehicles adjust the initialisation speed to a different value If a speed less than 5 m s is selected then care should be taken to make sure that the Inertial is travelling straight when it initialises The accuracy of some GNSS receivers is not good enough to initialize at very low speeds Displace output Adjustment click button to open properties window The Inertial can displace or move its outputs to another location in the vehicle This simulates the Inertialt being mounted at the new location rather than at its actual location This function displaces all of the outputs position velocity acceleration to this new
32. Inertial Inertial and GNSS measurement system User Manual Confidently Accurately Legal Notice Information furnished is believed to be accurate and reliable However Oxford Technical Solutions Limited assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of Oxford Technical Solutions Limited Specifications mentioned in this publication are subject to change without notice and do not represent a commitment on the part of Oxford Technical Solutions Limited This publication supersedes and replaces all information previously supplied Oxford Technical Solutions Limited products are not authorised for use as critical components in life support devices or systems without express written approval of Oxford Technical Solutions Limited All brand names are trademarks of their respective holders The software is provided by the contributors as is and any express or implied warranties including but not limited to the implied warranties of merchantability and fitness for a particular purpose are disclaimed In no event shall the contributors be liable for any direct indirect incidental special exemplary or consequential damages including but not limited to procurement of substitute goods or services loss of use data or
33. NCOM file has been saved to disk or processed using the post process utility then this file can be read and the settings extracted from it Use this setting if you have an NCOM file Click Browse and select the NCOM file you wish to read the configuration from Do not use an NCOM file that has been combined from forward and backwards processing of the inertial data Read configuration from Ethernet This will get the information that the Inertial is currently using and apply it next time the Inertial starts Use this setting if the Inertial is running has initialised and has warmed up Select the correct IP address of the Inertial to read the configuration from in the drop down list Note the list will not function correctly if Enginuity or other software is using the Inertial UDP port unless the OxTS UDP Server is running Once the source has been selected click Next and the software will find which settings can be obtained from the source Settings that cannot be obtained will be shown in grey this may be because the Inertial is not calculating these values at present Figure 16 shows the Settings page with the parameters available to improve in the configuration as Oxford Technical Solutions Inertial User Manual QOaxrs Inertial GPS Figure 16 NAVconfig settings selection page for improved configuration F Get settings from Inertial Ea a Select Configuration s Choose whic
34. Solutions Inertial User Manual Qoxrs Inertial GPS Specification The specification of the Inertial depends on the GNSS receiver connected Typical figures are listed in Table 4 These specifications are listed for operation of the system under the following conditions e After a warm up period of 15 minutes continuous operation e Open sky environment free from cover by trees bridges buildings or other obstructions The vehicle must have remained in open sky for at least 5 minutes for full accuracy e The vehicle must exhibit some motion behaviour Accelerations of the unit in different directions are required so that the Kalman filter can estimate the errors in the sensors Without this estimation some of the specifications degrade e The distance from the system to the external GNSS antenna must be known by the system to a precision of 5 mm or better The vibration of the system relative to the vehicle cannot allow this to change by more than 5 mm The system can estimate this value itself in some dynamic conditions e The heading accuracy is only achieved under dynamic conditions Under slow and static conditions the performance will degrade Revision 131122 Table 4 Typical performance specification for Inertial Parameter Positioning Position accuracy Velocity accuracy Acceleration Bias Linearity Scale factor Range Roll pitch Heading Angular rate Bias Scale facto
35. al Output packet NCOM v Data rate 100 Hz v C Output on falling edge of trigger _ Output on rising edge of trigger _ Output on camera trigger Advanced Delay output by ms 0 0 ms v The Ethernet output can either output NCOM or MCOM or be disabled by using the Output Packet drop down list When NCOM or MCOM is selected the Data rate can be selected by using the drop down list Ey Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS The Inertial can output Ethernet messages when an event rising or falling edge is input on the event input pin It can also output Ethernet messages from pulses in the camera trigger These messages are interpolated to the time when the event occurred and may be output up to 30 ms late and out of order compared to the normal messages It is essential to enable these options if the events have a rate higher than 1 Hz otherwise the output cannot communicate all of the events and some will be lost The Delay output option should not be used with the Inertial GNSS control Adjustment click button to open properties window The GNSS control option contains advanced options that control how the GNSS information is managed in the Inertial The GNSS algorithm tab can be used to select the algorithm used for merging the GNSS and the inertial data in the Kalman filter The Recovery tab can be used to decide how to begin using GNSS measurements if they have been rejected or i
36. also not suitable for land vehicles with no fixed wheels The Inertial uses the position of the non steered wheels to reduce the lateral drift when GNSS is not available and to improve the heading accuracy When combined with an odometer input the drift of the Inertial when GNSS is not available is drastically reduced Figure 19 shows the Wheel Configuration page EX Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS Figure 19 NAVconfig Wheel Configuration page Q NAVconfig wizard Wheel Configuration Specify the position of the non steered axle Inertial Inertial and GNSS v The vehicle has a non steered ade Navigation Measured from the Inettial device How far ahead or behind is the non steered ade Ahead v 0 000m 0 100m Step 7 of 10 How far left or right is the centre of the vehicle Product Selection Right v 0 000m 0 100m Read Configuration GNSS Selection How far above or below is the ground Orientation Below v 1 000m 0 100m External Antenna Secondary Antenna Specify each accuracy separately Overall accuracy 0 100m v Options Commit Select surface Normal v Save Finish Dev ID 131024 14am English a For the Wheel configuration feature to work correctly the system needs to know the position of the non steered axle rear wheels on a front wheel steering vehicle and vice versa A position at road height mid way between the rear whe
37. checks on the system Table 10 gives a description of each LED Table 11 Table 12 and Table 14 give details on the meanings of the states of each LED Table 10 LED descriptions ETI Description SDNav Strapdown navigator state Pos Head Position solution single antenna or heading solution dual antenna from GNSS Pwr Power and communication EI Oxford Technical Solutions Inertialt User Manual Qoxrs Table 11 SDNav LED states Colour Description Off The operating system has not yet booted and the program is not yet running This occurs at start up Red green The Inertial is asleep password locked Contact OxTS support for further flash information Red flash The operating system has booted and the program is running The GNSS receiver has not yet output a valid time position or velocity Orange The internal GNSS receiver has locked on to time but the external GNSS receiver does flash not have valid position and velocity Red The external GNSS receiver has locked on to satellites and has a valid position and velocity The strapdown navigator is ready to initialise If the vehicle is travelling faster than the initialisation speed then the strapdown navigator will initialise and the system will become active Orange The strapdown navigator has initialised and data is being output but the system is not real time yet It takes 10 s for the system to become real time after start up Green The strapdown navigator
38. d roll and these have singularities at two orientations The Inertial has rules to avoid problems when operating close to the singularities if you regenerate the rotation matrices given below then they will be correct The Euler angles output are three consecutive rotations first heading then pitch and finally roll that transform a vector measured in the navigation co ordinate frame to the body co ordinate frame The navigation co ordinate frame is the orientation on the earth at your current location with axes of north east and down If V is vector V measured in the navigation co ordinate frame and V is the same vector measured in the body co ordinate frame the two vectors are related by Vn C bn Vb cos y sin y 0 cos 0 0 sin O 0 0 V a sincy cos y o 1 0 J0 cos d sin Vp 0 0 1 sin 0 cos 0 sin d cos d where y is the heading angle O is the pitch angle and is the roll angle Remember heading pitch and roll are usually output in degrees but the functions sin and cos require these values in radians Revision 131122 E Revision history Table 30 Revision history Revision Comments 080107 Initial Version 080213 Update including images from the software 090108 Added RMC message available in German split wheel and odometer input 091009 Added Inertial 2 Output Displacement other small changes 100721 Added NMEA GSV GSA messages Added undulation options for altitude
39. e difference to the longitudinal drift performance of the Inertial when GNSS is not available It is essential to use the Wheel configuration feature page 50 at the same time as an odometer input As with the wheel configuration the odometer input can only be used on land vehicles Aircraft and marine vehicles cannot use this option The odometer input cannot be used on a steered wheel it must be used on a wheel that is measuring the forward direction of the vehicle Figure 26 shows the Odometer input properties window To enable the odometer input ensure the checkbox is checked If this option is disabled the Inertial will ignore corrections from the odometer even if it is connected Revision 131122 a Figure 26 NAVconfig Odometer input properties window F Odometer input Ea V Enable odometer input Measured from the Survey device Where is the measurement point of the odometer Ahead v 0 000m 0 100 m Right v 0 000m 0 100 Below vi 1 000m 0 100 r _ Specify each accuracy separately Overall accuracy 0 100m y Pulses per metre 100 000 pulses per metre to within 10 00 v The distance from the Inertial to the measurement point of the odometer in the vehicle co ordinate frame should be input The directions can be selected from the drop down lists If the odometer is from a prop shaft then the distance should be measured half way between the two wheels The illustrations in the window w
40. e pages 50 and 45 Revision 131122 a respectively Roll and pitch offsets can be measured using the Surface tilt utility in Enginuity Antenna placement and orientation For optimal performance it is essential for the GNSS antenna s to be mounted where they have a clear uninterrupted view of the sky and on a suitable ground plane such as the roof of a vehicle For good multipath rejection the antennas must be mounted on a metal surface using the magnetic mounts provided no additional gap may be used The antennas cannot be mounted on non conducting materials or near the edges of conducting materials If the antennas are to be mounted with no conductor below them then different antennas must be used It is recommended to mount the antennas at least 30 cm from any edge where possible For dual antenna systems the secondary antenna should be mounted in the same orientation as the primary antenna as shown in Figure 4 The antenna baseline should also be aligned with one of the vehicle axes where possible either inline or perpendicular to the vehicle s forward axis In the default configuration the primary antenna should be at the front of the vehicle and the secondary antenna should be at the rear The antenna separation should be measured accurate to 3 mm or better Figure 4 Dual antenna orientations Se S Oh PR PE GR lea la iii A The bases of the antennas are parallel but the cables exit in different directions B The
41. ed in the example below The warm up period is a concern to some customers but it is often very simple to overcome Below is an example of a good warm up procedure that did not involve a lot of work for the user In this example the key features are The Inertialt was configured well the GNSS antenna position Wheel configuration options and dual antenna separation were measured accurately in advance The Inertial was turned on as soon as possible In this case it took us 15 minutes to get all the other equipment sorted out The Inertial was stationary for most of this period which is not a problem Although in this example the Inertial was receiving corrections from a base station while stationary it is not necessary The base station should be working before the dynamic driving starts so the Inertial can use the best information to self calibrate if a base station is not being use this does not apply There are 6 minutes during which the vehicle was driven in figures of eight From the graphs you can see the Inertial is accurate almost after the first figure of eight after that the improvement is very small The trick is to turn the Inertial on early do not reconfigure it which resets it or cycle the power Figure 29 shows the route driven and Figure 30 shows the accuracy estimated by the Kalman filter for various output parameters during the first 25 minutes The quality of initialisation would have been the
42. el To save a copy of the configuration in a local folder check the Save settings in the following folder box and use Browse to select a folder The configuration has a number of files associated with it so it is recommended to create a new folder Click Finish to save the configuration to the selected folder and close NAVconfig Revision 131122 e Initialisation process Before the Inertial can start to output all the navigation measurements it needs to initialise itself In order to initialise the Inertial needs all the measurements listed in Table 26 Table 26 Quantities required for initialisation Quantity Description Time Measured by GNSS Position Measured by GNSS Velocity Measured by GNSS Heading Approximated to course over ground with large error when the vehicle moves Dual antenna models have the option for static initialisation which does not require any movement Roll pitch Estimated over first 40 s of motion with large error The system will start when it has estimates of all of these quantities Course over ground will be used as the initial heading when the system exceeds the value set as the initialisation speed unless static initialisation has been selected for a dual antenna system The system takes about 40 s to find approximate values for roll and pitch For the initialisation process to work correctly the Inertial requires the user to tell it which way it is mounted in the vehicle
43. els should be used as shown in Figure 20 Vehicles with all wheels steering cannot use this feature reliably although minor steering of the rear wheels does not significantly affect the results Figure 20 Measurement point for wheel configuration Revision 131122 a Measuring from the Inertial measure the distances to the non steered axle position in each axis in the vehicle co ordinate frame Select the direction from the drop down lists and enter the distances Typically the measurements would all be made to an accuracy of 10 cm Selecting an accuracy better than 10 cm does not improve results Using an accuracy figure worse than 20 cm will increase the drift of the Inertial Use the accuracy fields to select or specify the accuracy of the measurements Options The Options page includes some important settings for getting the best results from your Inertial system Figure 21 shows the Options page of the configuration wizard Figure 21 NAVconfig Options page F NAVconfig wizard 0 Performance Options I rti I mi Advanced options to improve the performance of the Inertial nertia ete i ar Navigation Initialisation speed 5m s Displace output Disabled Camera trigger Disabled Step 8 of 10 Heading lock Normal Output lock Disabled Product Selection Output smoothing Disabled Read Configuration GNSS Selection a pin ccs Orientation Serial 1 output NCOM External Antenna Serial 2 output Disabled Secondary
44. for accurate navigation If a post differential encoder must be used then the accuracy cannot be guaranteed For best results a front wheel drive vehicle should be used with the odometer on a rear wheel The odometer pulses from driven wheels are less accurate Advanced Adjustment click button to open settings window The Advanced option is used to set special commands for the Inertial This should only be done with special instructions from OxTS Committing the configuration to the Inertial Changes to the Inertial settings must be sent using Ethernet It is necessary to configure your computer s Ethernet settings so it is on the same network as the Inertial The section Ethernet configuration on page 31 gives details on how to do this Figure 27 shows the Commit page Revision 131122 Figure 27 NAVconfig Commit page F NAVconfig wizard 0 Es Commit D Commit configuration to the Inertial Inertial Inertial and GNSS IP Address of the Inertial that you want to configure Navigation 195 0 0 29 Inertial v Step 9 of 10 Product Selection Read Configuration GNSS Selection Orientation External Antenna Secondary Antenna Wheel Configuration Options Save Finish Dev ID 131024 14am English v lt Back Commit Cancel Enter the IP address of the Inertial that you want to configure or select if from the drop down list The drop down box will list all of the system
45. g offset then the initial value of heading will be incorrect This can also happen if the Inertial 2 is initialized in a turn This can lead to problems later 4 When the combined accuracy of heading plus the orientation accuracy figure for the secondary antenna is sufficiently accurate then the Inertial 2 will solve the RTK Integer problem using the inertial heading There is no need for the Inertial 2 to solve the RTK Integer problem by searching If the antenna angle is offset from the Inertial 2 by a lot then the RTK Integer solution that is solved will be incorrect For a 2 m antenna separation the Inertial 2 orientation and the secondary antenna orientation should be known to within 5 For wider separations the secondary antenna orientation angle needs to be more accurate 5 Once the RTK Integer solution is available the Inertial 2 can start to use the dual antenna solution to improve heading The level of correction that can be applied depends on how accurately the angle of the secondary antenna is known compared to the inertial sensors 6 The Kalman filter tries to estimate the angle between the inertial sensors and the secondary antenna The default value used in the configuration software 5 is not accurate enough so that the Inertial 2 can improve the heading using this value If you want the vehicle heading to 0 1 but the angle of the two GNSS antennas is only known to 5 then the measurements from the antenna are not goin
46. g to be able to improve the heading of the vehicle Driving a normal warm up with stops starts and turns helps the Kalman filter improve the accuracy of the secondary antenna angle The accuracy of this angle is available in the Status tab of the Calibration window in Enginuity On aircraft or marine vehicles some turns are needed to help the Kalman filter estimate the relative angle of the antennas compared to the Inertial 2 7 In the unlikely event that the RTK Integer solution is incorrect at the start then the Kalman filter can update the secondary antenna orientation incorrectly If this happens then things start to go wrong The Kalman filter becomes more convinced that it is correct so it resolves faster but it always solves incorrectly Solving incorrectly makes the situation worse Revision 131122 Es To avoid the Kalman filter from getting things wrong it is possible to drive a calibration run then use the Improve configuration utility within NA Vconfig see page 45 for more information This tells the Kalman filter it has already estimated the angle of the secondary antenna in the past and it will be much less likely to get it wrong or change it This step should only be done if the Inertial 2 is permanently mounted in a vehicle and the antennas are bolted on Any movement of either the Inertial 2 or the antennas will upset the algorithms Multipath Effects on Dual Antenna Systems Dual antenna systems are very susceptible
47. gnored for a period of time Figure 25 shows both tabs in the GNSS control properties window Figure 25 NAVconfig GNSS control properties window F GNSS control F GNSS control Ea GNSS Algorithm Recovery GNSS Algorithm Recovery This option controls what algorithm is used to update the These settings control how long the INS will ignore Kalman filter These are advanced settings Refer to the unexpected GNSS measurements before being forced to manual for additional details believe them Use GNSS receiver s calculations GNSS position updates Use OxTS gx x raw data processing algorithm Use firmware defaults _ Never believe unexpected measurements Start believing measurements after 20 unexpected GNSS updates GNSS velocity updates Use firmware defaults Never believe unexpected measurements Start believing measurements after 20 unexpected GNSS updates OK Cancel OK Cancel The GNSS algorithm tab gives a choice of two algorithms for computing the GNSS measurements The default option is to use the algorithm provided by the GNSS receiver Using this algorithm the Inertial will accept position and velocity from the GNSS and use it to update the Kalman filter Revision 131122 EJ The gx ix raw data processing algorithm should only be used with the internal GNSS receivers It uses the raw data from the GNSS and custom algorithms to compute position and velocity tailored to the needs of the Kalma
48. h settings should be used Inertial Inertial tems Description ate on O Orientation in vehicle TuT E Primary GNSS antenna Step 2 of 2 _ Secondary GNSS antenna Wheel speed input Source Select all Clear all Accurately 1 eo Back Finish Cancel ey You may update several parameters at once Select the settings you want to be updated and uncheck the ones that you do not want to update Click Finish to transfer these settings to the configuration wizard If Orientation in vehicle is selected the improvement to orientation should only be applied if the change in the orientation is small less than 5 If the change in orientation is large then it is likely that the original configuration was wrong or has not been loaded into NAVconfig You are very likely to get poor results if the orientation is changed by a large amount External antenna position It is essential to measure the position of the external GNSS antenna the antenna connected to the external GNSS receiver compared to the Inertial accurately Getting these measurements incorrect is one of the main reasons for poor results from the Inertial so it is important to be careful with the measurements Figure 17 shows the External Antenna page If the internal GNSS receiver was selected on the GNSS selection page then this page will change to Primary Antenna and the position of the primary GNSS antenna should be measured Revision 131122 jar Figure 17 NAVconfig Ex
49. ial orientation and alignment The orientation of the Inertial in the vehicle is normally specified using three consecutive rotations that rotate the Inertial to the vehicle s co ordinate frame The order of the rotations is heading z axis rotation then pitch y axis rotation then roll x axis rotation The Inertial co ordinate conventions are detailed on page 28 It is important to get the order of the rotations correct In the default configuration the Inertial expects its y axis to be pointing right and its z axis pointing down relative to the host vehicle There are times however when installing an Inertial in the default configuration is not possible for example when using the RT Strut The Inertial can be mounted at any angle in the vehicle as long as the configuration is described to the Inertial using NAVconfig This allows the outputs to be rotated based on the settings entered to transform the measurements to the vehicle frame For ease of use it is best to try and mount the Inertial so its axes are aligned with the vehicle axes This saves the offsets having to be measured by the user If the system must be mounted misaligned with the vehicle and the user cannot accurately measure the angle offsets the Inertial has some functions to measure these offsets itself The heading offset can be measured if the vehicle has a non steered axle The Wheel configuration and Improve configuration utilities should be used for this se
50. ill change depending on the settings you choose to help visualise the position of the Inertial in relation the odometer Ideally the measurements would be made to an accuracy of 10 cm Using higher precision for the measurement does not improve the results Using an accuracy figure worse than 20 cm will increase the drift of the Inertial The accuracy can be specified as the same for all measurements using Overall accuracy or it can be specified for each individual measurement by clicking the Specify each accuracy separately checkbox In either case choose a predefined value from the drop down list or type in a value Enter the pulses per metre of the odometer A value that is accurate to 10 is sufficient unless the figure is known more accurately The Inertial will improve this scaling factor itself when GNSS is available The Improve configuration utility can be used to apply a more accurate value calculated by the Inertial from a calibration run If this option is used then the Inertial should be allowed to recalibrate the scaling value occasionally to account for tyre wear See page 45 of this manual for more information on improving the configuration e2 Oxford Technical Solutions Inertialt User Manual QObxrs Inertial GPS The odometer corrections will not be as effective in reducing the drift of the Inertial if the odometer is measuring two wheels i e after a differential since the actual position of the wheel is required
51. ion accuracy is better than 2 cm and the heading is better than 0 2 Ey Oxford Technical Solutions Inertial User Manual Qaxrs Inertial GPS Figure 30 Example warm up accuracy estimates 60 40 3 z a f 20 A 0 0 200 400 600 800 1000 1200 1400 1600 A b f b F 0 200 400 600 800 1000 1200 1400 1600 Latitude ial Longitude gt Altitude 2 Ed Fa 3 S 0 200 400 600 800 1000 1200 1400 1600 North Velocity seas East Velocity Down Velocity Orientation Accuracy deg RMS 0 200 400 600 800 1000 1200 1400 1600 Time Roll aa Pitch gt Heading a Forward velocity b Position accuracies c Velocity accuracies d Orientation accuracies Revision 131122 69 You can see the Inertial is nearly at specification after just this small amount of driving However experience tells us the Kalman filter will continue to make some improvements not obvious during the first few figures of eight The main part of the motion occurs after 1100 s when the vehicle was driven in a figure of eight for 6 minutes These are fairly large figures of eight driven at relatively low speeds Notice the brake stops in the velocity graph a in Figure 30 where the speed falls to zero These are important parts of the warm up so as many states in the Kalman filter as possible can be updated Notice how close to the specification the Inertial is even without the figure of eight
52. is running and the system is real time i In current versions of the software the strapdown navigator will not leave green and return to any other state This may change in future releases Table 12 Pos Head LED states single antenna models Colour Description Off The GNSS receiver is not sending data Start up only The GNSS receiver is sending data to the Inertial This is an operational check for the GNSS receiver Red The GNSS receiver has a standard position solution SPS Red flash The GNSS receiver has a differential solution DGPS or kinematic floating position Orange solution 20 cm accuracy Green The GNSS receiver has a kinematic integer position solution 2 cm accuracy Revision 131122 Es Table 13 Pos Head LED states dual antenna models Colour Description Off GNSS receiver fault valid only after start up Red flash GNSS receiver is active but has been unable to determine heading Red The GNSS has a differential heading lock Orange The GNSS receiver has a floating poor calibrated heading lock Green The GNSS receiver has an integer good calibrated heading lock Table 14 Pwr LED states Colour Description Off There is no power to the system or the system power supply has failed Green The 5 V power supply for the system is active Orange The system is outputting data on connector J2 Co ordinate frame conventions The Inertial uses a co ordinate frame that is po
53. l Oxford Technical Solutions Limited be liable for any indirect incidental special or consequential damages whether through tort contract or otherwise This warranty is expressly in lieu of all other warranties expressed or implied including without limitation the implied warranties of merchantability or fitness for a particular purpose The foregoing states the entire liability of Oxford Technical Solutions Limited with respect to the products herein Revision 131122 a Table of contents Scope of delivery 7 Introduction 8 Easy operation 9 Self correcting 9 Flexible accuracy 9 Drop in component 9 Related documents 10 Inertial family divisions 11 Single antenna 11 Dual antenna 11 250 Hz 12 Specification 13 Common specifications 14 Heading accuracy 15 GNSS antenna operating temperature 15 Export control classification number 15 Conformance notices 17 Regulator testing standards 17 Software installation 18 Connections 20 Hardware installation 21 Inertial orientation and alignment 21 Antenna placement and orientation 22 Using an antenna splitter 23 Operation 25 Front panel layout 25 LED definitions 26 Co ordinate frame conventions 28 a Oxford Technical Solutions Inertialt User Manual Qoxrs Inertial GPS Navigation frame 29 Level frame 29 Vehicle frame 30 Ethernet configuration 31 Dual antenna systems 32 Multipath Effects on Dual Antenna Systems 34 Inputs and outputs 35 Pin assignments 35 Digital inputs and
54. lisation option is useful for slow moving vehicles or where it is essential to start the Inertialt running before moving for example in autonomous vehicles Static initialisation is 99 reliable in open sky but the reliability decreases in environments with high multipath Static initialisation is also faster when the antenna separation is smaller If you can guarantee the antennas are level always within 15 of horizontal during static initialisation then the following advanced command can also speed up static initialisation and make it more reliable gps_pitch15 0 This is a pitch constraint or tilt constraint Enter this text into the Advanced window on the Options page It will tell the ambiguity resolution algorithm to only search within 15 of the horizontal Note that this is the angle between the antennas and it is independent of the height offset entered in to the software The static initialisation algorithms degrade rapidly in non ideal conditions They should only be used in open sky environments Using a shorter separation or using the pitch constraint can improve the accuracy in non ideal conditions Wheel configuration Thw Wheel configuration feature uses characteristics of land vehicle motion to improve heading performance and reduce drift when GNSS is not available The wheel configuration can only be used on land vehicles with non steered wheels Aircraft and marine vehicles cannot use this option It is
55. location To enable output displacement click the checkbox in the properties window and enter the offsets to the new location in the vehicle The offsets are measured from the Inertial in the vehicle co ordinate frame Select the directions from the drop down lists Note that the noise in the acceleration outputs will be much higher when output displacement is used Typical installations in moving vehicles have angular vibrations of about 2 rads s this equates to 2 m s of additional vibration of a m output displacement It will be necessary to filter the data if output displacement is used Camera trigger The Inertial can generate a regular pulse based on distance for example one pulse every 10 m of travel This can be used to trigger a camera so that a picture can be taken on a regular basis Enter the distance between pulses or leave disabled default Heading lock Adjustment select a predefined value from the drop down list The heading of the single antenna Inertial can drift when it remains stationary for long periods of time To solve this the Inertial includes an option to lock the heading to a fixed value when stationary This option cannot be used if the vehicle can turn on the spot i e on a boat With heading lock enabled the Inertial can remain stationary for indefinite periods of time without any problems Revision 131122 There are four settings to choose from Disabled should be selected if the vehicle
56. lue OV GND A e consent of i xfore ni View from front 4 Black 0V GND ord Technical Solutions of socket Pin Definitions Brown Positive 12V Power supply 9 18V d c 0 10 20 30 Print Size A4 Scale 1 1 Units mm Tolerances 1mm 77C0002B Projection N A Notes 10 04 02 Alternative Part Number added Parts Connections RS291 5881 M12 4w 5m PVC straight Connector J1 1 Brown J2 1 FEC 658 376 Car Cigarette Lighter Plug J1 2 White J2 1 RS399 524 Yellow Heat Shrink 6 4mm J1 3 Blue J2 2 RS399 934 Clear Heat Shrink 6 4mm J1 4 Black J2 2 Alternative Part RS 266 0250 Car Cigarette Lighter Plug 8A fused Fuse Date 21 11 13 Littelfuse Part Number 0214005 5A Torpedo Type Fuse 25 x 6mm 36V Part 7700002B Document Power Cable Sheet 1 of 1 Oxford Technical Solutions 77 Heyford Park Upper Heyford Oxfordshire OX25 5HD www oxts com Copyright Oxford Technical Solutions 2013 The information in this document is confidential and must not be published or disclosed either wholly or in part to other parties or used to build the described components without the prior written consent of Oxford Technical Solutions 0 10 20 30 Print Size A4 Scale 1 1 Units mm Tolerances 1mm Projection 3rd Angle TNC Connecto
57. mputer being used to communicate with the Inertialt may need to be changed so it matches the subnet For example 195 0 0 200 should be available since this IP address is never used by the Inertial by default To change the IP address of the computer follow these steps applies to Windows Vista 7 8 1 Open the Control Panel from the Start menu 2 In category view select Network and Internet and then Network and Sharing Center 3 Select Change adapter settings in the side panel Revision 131122 Ey 4 Right click the Ethernet option and select Properties 5 In the window that opens navigate the list to find Internet Protocol Version 4 TCP IPv4 Select it and click Properties 6 In the TCP IPv4 Properties window Figure 9 select Use the following IP address and enter the IP address and subnet mask to use 7 Click OK when finished Figure 9 Configuring the computer s IP address Internet Protocol Version 4 TCP IPv4 Properties x General You can get IP settings assigned automatically if your network supports this capability Otherwise you need to ask your network administrator for the appropriate IP settings Obtain an IP address automatically Use the following IP address IP address 1995 0 0 200 Subnet mask 255 255 255 0 Default gateway Obtain DNS server address automatically Use the following DNS server addresses Preferred DNS server Alternate DNS server Validate
58. mputing a heading solution in dual antenna systems The internal GNSS receiver is a low cost receiver and it not capable for giving good position measurements If you wish to use the internal receivers for position measurements instead of an external receiver for debugging or testing the Inertial click the Use internal GNSS receiver checkbox This will disable the GNSS receiver list and the Inertial will ignore any external GNSS measurements even if one is connected Orientation The Orientation page is used to define the vehicle co ordinate frame relative to the Inertial s co ordinate frame It is important to get the orientation correct as although settings entered on this page do not affect the accuracy of the Inertial if the outputs are not properly rotated to the vehicle frame then the measurements will appear incorrect When using the RT Strut the orientation will need to be changed A number of configurations are possible with the RT Strut so ensure the directions of the axes are entered correctly Select from the drop down lists the directions of the y axis and z axis of the Inertial in relation to the vehicle Figure 6 on page 28 shows the Inertial axes directions The Orientation page of the configuration wizard shown in Figure 14 also has illustrations to visualise the orientation of the Inertial in a vehicle based on the settings input The greyed out advanced settings will change to show the three rotations associated with o
59. n filter It also improves performance in poor GNSS environments using single satellite aiding technology and tightly coupled GNSS and inertial measurements Gx ix mode is recommended to achieve the highest accuracy in environments where RTK lock may be difficult to maintain e g urban canyons Note gx ix processing is a new technology and is still being developed and improved As such there are some limitations to its compatibility Table 25 details the current compatibilities of gx ix mode Table 25 gx ix compatibility GNSS mode Real time Post process SPS v y SBAS x x DGPS v v OmniSTAR x x RTK x Optional GLONASS x x Note only RTCM V3 format differential corrections are supported in gx ix mode The Recovery tab controls how the Inertial will accept or reject GNSS measurements The Inertial will automatically reject GNSS updates that it believes are not correct However there is a limit on the number of GNSS measurements that the Inertial will reject Once this limit has passed the Inertial accepts the GNSS update since it is possible the GNSS is correct and the inertial measurements are not The GNSS control determines how many updates the Inertial should ignore before forcing the GNSS to be accepted Both the velocity and the position can be controlled separately In the default state the Inertial will reject up to 20 GNSS measurements before it forces the GNSS to be accepted However in high multipath environments or when
60. nertial writes the configuration it is using to the internally stored RD file This option extracts the configuration used and loads it into the configuration wizard Specify an RD file by clicking the Browse button Read initial settings from Inertial If the Inertial is connected to the computer via Ethernet then it is possible to read the initial settings directly from the Inertial The initial settings loaded are the settings that were last committed to the Inertial before it makes any improvements Select this option and enter the correct IP address of your A Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS Inertial or select it from the drop down list The list will show all systems that are connected to the network so if more than one system is connected ensure you select the correct system Note the list will not function correctly if Enginuity or other software is using the Inertial UDP port unless the OxTS UDP Server is running GNSS selection It is essential to select the correct external GNSS receiver so that the Inertial can interpret its data correctly An integration document giving details on how to connect and configure the external GNSS receiver is available This gives essential information on the GNSS receiver and it should be followed carefully in order to obtain the best performance The integration manual can be opened by clicking on the icon if the computer has software for viewing
61. nertial 2 250 Hz Inertial 250 Inertial 2 250 Calculation latency 3 5 ms Power 10 18 V dc 15 W Dimensions 234 x 120 x 76 mm excluding connectors Weight 2 3 kg Operating temperature 10 to 50 C Vibration 0 1 g Hz 5 500 Hz Shock survival 100 g 11 ms Internal storage 2 GB The operating temperature range for the antenna is much wider since it can be mounted outside the vehicle See specification below Heading accuracy The heading accuracy that can be achieved by the dual antenna system in the Inertial is 0 2 lo per meter of separation in ideal open sky conditions The system can provide these accuracies in static and dynamic conditions A 4 m separation is required to reach an accuracy of 0 06 1o The maximum recommended separation is 5 m at which it may be possible to achieve better than 0 06 if the structure is rigid including temperature variation although OxTS do not claim this in the specification For single antenna systems the heading is calculated from the inertial measurements The accuracies listed in Table 4 are achievable under dynamic conditions Under static conditions the heading accuracy of single antenna systems will degrade Non ideal mounting of the GNSS antennas will reduce the heading accuracy particularly for dual antenna systems GNSS antenna operating temperature The GNSS antennas have a much wider operating temperature range from 55 C to 85 C allowing them to be used on the ou
62. nt 4 is confidential and must not be linde With Gere published or disclosed either wholly or in part to other parties or used to A Ss paa a build the described components Red 2 A g without the prior written consent of ue j d F lki cg Z eres e9 WWW OXU O Exces Oxford Technical Solutions Print Size A4 Scale Not to Scale Units mm Material Alu Finish Anodised Notes A M4 x 10 Tapped Hole B 2mm dia x 3 hole Date 21 11 2013 Part 14A0040A Document Inertial outer dimensions Oxford Technical Solutions 77 Heyford Park Upper Heyford Oxfordshire OX25 5HD www oxts com Copyright Oxford Technical Solutions 2013 Confidential Information The information in this document is confidential and must not be 1 published or disclosed either wholly i ui or in part to other parties or used to 2 White Positive 12V Power Charger supply 11 18V d c build the described components 3 B
63. o by clicking Product Selection in the sidebar Reading the initial configuration The Read Configuration page gives several options for reading the configuration from different places as shown in Figure 12 Revision 131122 a Figure 12 NAVconfig Read Configuration page F NAVconfig wizard Es Read Configuration I rti I Choose where the initial settings should be read from Inertial and GNSS D Use default settings Navigation Read settings from a folder Step 2 of 10 Read settings from an RD file Product Selection GNSS Selection Read initial settings from Inertial Orientation External Antenna IP Address Secondary Antenna 195 0 0 29 inertial Wheel Configuration Options Commit Save Finish Dev ID 131024 14am English v lt Back Next gt Cancel Use default settings This option tells the configuration wizard to use the default settings the Inertial was delivered with Note choosing Use default settings will overwrite any advance settings you may have set To maintain advanced settings the Read initial settings from Inertial option must be used Read from a folder It is possible to store a configuration in a folder The configuration requires several files so it is tidier to keep it in a folder by itself To read the configuration from a folder select this option and then specify a folder by clicking the Browse button Read settings from an RD file The I
64. of the Inertial and Inertial 2 is shown in Figure 3 Figure 3 Connection example External Secondary Primary Antenna Antenna Antenna es aan 4 Uexrs inertia SS External GPS Serial 1 Power Serial 2 Power Ethernet The external GNSS receiver is connected to the Inertial using a serial connection on the External GNSS port see Front panel layout section on page 25 for more information on the connectors Power is supplied directly to the Inertial Seriall Serial2 and Ethernet outputs are available from the Inertial Ensure a stable voltage is applied to the Inertial otherwise the system may appear to power correctly but the data will not be correct The Inertial has its own internal GNSS receiver This receiver is required to synchronise the inertial measurements to GPS time The position and velocity measurements from this receiver are not normally used It is possible to use an antenna splitter and feed the GNSS signal in to both the external GNSS and Inertial When using the internal GNSS receiver it is possible to connect a radio modem to the External GNSS port to receive differential corrections from a base station A 12 V supply is provided on this connector to power the radio As such users should not try and use this port to connect to their computer as it could cause damage When using an Inertial 2 the secondary GNSS antenna should be fitted The Inertial 2 will operate as an Inertial if thi
65. on that can be applied every second For example if 0 1 m is entered for the position smoothing then the Inertial will only correct a position error by a maximum rate of 0 1 m s If a large error is accumulated for example if GNSS is not available for a long period of time then it may take a very long time to apply the correction Under these circumstances it may be preferable to jump the measurement to the correct value quickly By specifying a time in the Time limit section for the correction the Inertial will jump the measurement if it will take too long to correct For example if the position has drifted by 5 m after a period without GNSS and the smoothing is set to 0 05 m then it will take at least 100 s to correct the 5 m drift If the time limit is set to 20 s then the Inertial will apply the 5 m correction immediately because the predicted time to correct the position is longer than the time limit Care should be taken not to make the smoothing too small If these parameters are too small then the Inertial will not be able to make suitable corrections to the outputs and it will not work correctly Note this function is designed to improve the data in real time When post processing the data using the forwards backwards combined option output smoothing should not be used as it may give unexpected results Altitude Adjustment select a predefined value from the drop down list or type in a value Revision 131122 e
66. or the height difference between the phase centre and the antenna base This option should not be used with the Inertial The GNSS receiver assumes that the roll and pitch of the antenna are zero in order to do the compensation The Inertial can perform the compensation correctly even when the roll and pitch are not zero s Oxford Technical Solutions Inertial User Manual QOaxrs Inertial GPS Secondary antenna position If your system has dual antennas Inertial 2 Inertial 2 250 click the Enable secondary antenna checkbox on the Secondary Antenna page Figure 18 to allow the configuration to be entered If it is not enabled the Inertial will ignore the secondary antenna and will not use it to compute a heading solution Figure 18 NAVconfig Secondary Antenna page Q NAVconfig wizard 0 ES Secondary Antenna I rt I Specify the secondary GNSS antenna position on the vehicle in relation to the primary antenna Inertial and GNSS V Enable secondary antenna Navigation 2 Please enter the total distance between 1 000m the primary and secondary antennas o Step 6 of 10 Measured from the primary antenna z n Product Selection Vasa DEE Read Configuration Position of the antenna Behind v GNSS Selection s 2 1 oe _ Enable static initialisation j External Antenna j Use advanced settings A A Wheel Configuration E oy Options i Commit 180 000 deg 5 000 dea Save Finish
67. output The camera trigger output generates a pulse for a fixed distance travelled The configuration software can change the number of metres travelled between pulses The output has 0 8 V or less for a low and 2 4 V or more for a high There is no protection on this output no more than 10 mA should be used on this output Revision 131122 Ea IMU sync output pulse The IMU inertial measurement unit sync output pulse is a 100 Hz or 250 Hz output pulse synchronised to the IMU sample time The output has a duty cycle of approximately 50 and the falling edge is synchronised to the sample file of the data from the IMU The IMU is already synchronised to GPS time so one of the pulses each second will line up with the 1PPS output This allows other systems to sample based on the timing of the Inertial Reverse polarity protection The Inertial products have limited reverse polarity protection Reversing the polarity on the power inputs for short periods of time is unlikely to damage the product Causing a short circuit through the Inertial will damage the product A short circuit will be created if the polarity is reversed and another connector has ground connected In this condition the ground input of the power supply will be connected to the positive power supply this causes a high current to flow through the circuits in the Inertial and it will damage several internal components EX Oxford Technical Solutions Inertialt User Man
68. pular with most navigation systems Figure 6 shows how the axes relate to the Inertial box All measurements to and from the Inertial should be made from the measurement origin point shown in Figure 6 The axes and measurement origin point are the same for all Inertial models Figure 6 Inertial co ordinate frame and measurement origin Oxford Technical Solutions Inertialt User Manual Qoxrs Table 15 lists the directions that the axes should point for zero heading pitch and roll outputs when the default mounting orientation is used Table 15 Direction of axes for zero heading pitch and roll outputs Axis Direction Vehicle axis x North Forward y East Right Zz Down Down If the axes of the Inertial and the vehicle axes are not the same as those listed in Table 15 then they can be aligned by reconfiguring the Inertial for a different mounting orientation using the NAVconfig software If the RT Strut is being used to mount the Inertial in the vehicle then NAVconfig will have to be used to configure the orientation or the Inertial will not work correctly Page 43 gives more information on configuring the orientation of the Inertial in a vehicle Navigation frame The navigation frame is used by the Inertial to integrate the acceleration to velocity and to integrate the velocity to position The definition of the navigation frame is listed in Table 16 Table 16 Navigation frame
69. put from internal GNSS receiver 2 Digital 2 Event input 3 Digital 3 Odometer input from tachometer on a single wheel 4 Digital 4 Camera trigger output 5 Digital 5 IMU sync output pulse 100 or 250 Hz 6 Digital Ground Ground 7 Digital Ground Ground 8 Digital Ground Reserved 9 Digital Ground Reserved See additional information in Digital inputs and outputs section Table 22 Power pin assignments Pin Direction Description 1 Input Power in 10 18 V dc 2 Input Power in 10 18 V dc 3 Ground 4 Ground Digital inputs and outputs 1PPS output The 1PPS output is a pulse from the internal GNSS receiver The falling edge of the pulse is the exact transition from one second to the next in GPS time The pulse is low for 1 ms then high for 999 ms and repeats every second The I PPS is only output when the internal GNSS has a valid position measurement Figure 10 1PPS waveform Falling edge denotes GPS time ea crossing second boundary lt 1 ms 4 ae at Oxford Technical Solutions Inertialt User Manual Qoxrs The output is a low voltage CMOS output with 0 8 V or less representing a low and 2 4 V or more representing a high No more than 10 mA should be drawn from this output Older models have no protection on this output protection circuitry would disturb the accuracy of the timing New models 2013 onwards have limited protection Event input The event input can be used to time events like the shutter of
70. r Date 21 11 13 Part 201 990146 789 Document AT575 70B GPS antenna Sheet 1of1
71. r Range Track at 50 km h 2 cm L1 L2 GPS L1 L2 Kinematic 2cmlo 0 05 km h RMS 10 mm s lo 0 01 0 1 lo 100 m s 0 03 lo 0 1 lo 0 01 s lo 0 1 lo 100 s 0 07 RMS 20 cm L1 Float GPS L1 Kinematic OmniStar HP 20 cm 10 cm for HP 0 08 km h RMS 10 mm s 10 0 01 0 1 lo 100 m s 0 04 lo 0 1 lo 0 01 s lo 0 1 lo 100 s 0 1 RMS Differential OmniStar VBS 0 4 m CEP 0 1 km h RMS 10 mm s lo 0 01 0 1 lo 100 m s 0 05 lo 0 1 lo 0 01 s lo 0 1 lo 100 s 0 15 RMS SPS 1 8 m CEP 0 1 km h RMS 10 mm s lo 0 01 0 1 lo 100 m s 0 05 lo 0 1 lo 0 01 s lo 0 1 lo 100 s 0 15 RMS Internal GNSS SPS 3 0 m CEP 0 2 km h RMS 10 mm s lo 0 01 0 1 lo 100 m s 0 15 lo 0 2 lo 0 01 s lo 0 1 lo 100 s 0 25 RMS E Some manufacturers specify L1 L2 GPS to be more accurate than 2 cm in which case the Inertial will also be more accurate However it is assumed that the Inertial will be used in dynamic conditions and under these conditions many GNSS products do not achieve 1 cm accuracy Common specifications The specifications in Table 5 apply regardless of the GNSS receiver attached to the products u Oxford Technical Solutions Inertialt User Manual Qoxrs Table 5 Inertial common specifications Parameter Specification Update rate 100 Hz Inertial I
72. rientation input gy Oxford Technical Solutions Inertial User Manual Qoxrs Inertial GPS Figure 14 NAVconfig Orientation page F NAVconfig wizard oO Es Orientation I rti i Specify how you have mounted the Inertial in the vehicle Inertial and GNSS Y axis points Right v Navigation Z axis points Down v Step 4 of 10 C Use advanced settings 5 FES Product Selection 0 000 deg _ Read Configuration GNSS Selection Extemal Antenna 5 000 deg mi Wheel Configuration g _ Options Z i 2 Commit A warmed up correctly operating Inertial will have improved configurations Read improved tee Save Finish configuration from the Inertial Confidently TT Dev ID 131024 14am EEE Enolish v lt Back Next gt Cancel For correct initialisation it is necessary to get the heading orientation correct The Inertial gets its initial heading by assuming that the vehicle is travelling forwards in a straight line If the definition of the vehicle s x axis forward direction is incorrect in the Inertial then it will not initialise correctly when the vehicle drives forwards To make small adjustments click the Use advanced settings checkbox to unlock the rotations for editing This allows any slip angle pitch or roll offsets to be zeroed Improve configuration Also included on the Orientation page is the ability to read the configuration settings from a warmed up sys
73. s antenna is not connected Further details on the connections may be found in the Integration Manual for the GNSS receiver being used fa Oxford Technical Solutions Inertialt User Manual Qoxrs Hardware installation It is essential to install the Inertial rigidly in the vehicle The Inertial should not be able to move or rotate compared to either GNSS antenna otherwise the performance will be reduced In most circumstances the Inertial should be mounted directly to the chassis of the vehicle If the vehicle experiences high shocks then vibration mounts may be required The Inertial is compatible with the RT Strut product from OxTS which can be used to provide a quick and secure vehicle mounting option Do not install the Inertial where it is in direct sunlight which in hot countries may cause the case to exceed the maximum temperature specification For single antenna installations the position of the primary GNSS antenna is not critical it can have a partial view of the sky as long as it has enough satellites to operate For dual antenna installations it is essential for both the primary and the secondary antenna to be mounted in a good open location and on a suitable ground plane such as the roof of a vehicle The antennas cannot be mounted on non conducting materials or near the edges of conducting materials If the antennas are to be mounted with no conductor below them then different antennas must be used Inert
74. s that are connected to the computer s network so ensure to select the correct system if there are multiple listed The list function will not work if Enginuity or other software is using the Inertial UDP port unless the OxTS UDP server is running Press Commit to save the configuration in the Inertial This will automatically reset the Inertial so the changes take effect It will be necessary to initialise and warm up the Inertial again after the changes have been applied Saving the configuration and finishing Before finishing it is possible to save a copy of the configuration in a folder on your computer This can then be reloaded next time The Save Finish page also lets you know if the settings have been committed successfully to the Inertial or not Figure 28 shows the Save Finish page es Oxford Technical Solutions Inertialt User Manual Figure 28 NA Vconfig Save Finish page Inertial Inertial and GNSS Navigation Step 10 of 10 Product Selection Read Configuration GNSS Selection Orientation External Antenna Secondary Antenna Wheel Configuration Options Commit NAVconfig wizard Finish Save configuration to a folder You have not yet committed your changes to the Inertial Go back to the Commit screen to retry Save settings v Save settings in the following folder CAOxTS inertialcfg v Browse Dev ID 131024 14am English v lt Back Finish Canc
75. same if the stationary period was 10 minutes followed by 5 minutes of driving The time on the graphs is the time from initialisation In this example the Inertial was initialised 25 s after starting up the quality of initialisation would be the same if it had been not been initialised for the first 10 minutes then initialised and driven for 5 minutes Revision 131122 Ea Figure 29 Example warm up driving route Course At the start there is just a small amount of motion to get the Inertial initialised During this time the Kalman filter cannot improve the position accuracy because the position of the GNSS antenna is not known accurately and cannot be estimated without motion The accuracy of the velocity roll and pitch steadily improves as the Kalman filter places more and more weight on the inertial sensors At this point the heading accuracy is worse than the scale of the graph d in Figure 30 the heading is not accurate and the dual antenna system cannot measure the angle of the GNSS antennas compared to the inertial sensors so the dual antenna cannot provide accurate information Just after 500 s the Inertial is driven it is the small loop on the east side in Figure 29 not the figures of eight This small amount of driving is sufficient for the Kalman filter to gain confidence in the antenna position and to improve the alignment of the two GNSS antennas compared to the inertial sensors After this period the posit
76. sed in accordance with the instructions may cause harmful interference to radio communications However there is no guarantee that interference will not occur in a particular installation If this equipment does cause harmful interference to radio or television reception which can be determined by turning the equipment off and on the user is encouraged to try to correct the interference by one or more of the following measures Re orient or relocate the receiving antenna Increase the separation between the equipment and the receiver The Inertial incorporates a GPS receiver Any GPS receiver will not be able to track satellites in the presence of strong RF radiations within 70 MHz of the GPS frequency 1575 MHz L1 The Inertial conforms to the requirements for CE Regulator testing standards e 47CFR15 109 2010 class A radiated emissions e EN 300 440 1 2008 test methods 8 3 2 conducted emissions and 8 3 3 radiated emissions EN55022 class A according to standard EN 301 489 1 2008 conducted emissions EN6100 4 3 criterion A according to standard EN 301 489 1 2008 radiated immunity ISO7637 2 criterion B 12V according to standard EN 301 489 1 2008 vehicular transients and surges immunity Older Inertial systems do not conform to this standard contact OxTS for further details e EN60950 1 2006 safety A11 2009 safety Revision 131122 e Software installation Included with every Iner
77. sts all the items that are delivered with the Inertial systems Table 1 Summary of the Inertial and Inertial 2 system components Qty Olay Description Inertial Inertial 2 1 1 Inertial system unit 1 2 GNSS antenna AT575 70 1 1 Power cable 77C0002B 1 1 Serial cable 1 1 Ethernet cable cross over 1 1 CD ROM with manual and software 1 1 User manual In addition to the components supplied the user will require a laptop to configure the Inertial An external GNSS receiver is needed for high accuracy the internal GNSS can be used for low accuracy applications Figure 1 Typical Inertial system in transit case Revision 131122 7 Introduction The Inertial is an add on for GNSS receivers to improve reliability and accuracy The Inertial uses accelerometers and angular rate sensors gyros to smooth the jumps in GNSS and fill in missing data Other important measurements such as heading pitch and roll can also be measured The Inertial is a true inertial navigation system INS that is aided by the external GNSS An inertial sensor block with three accelerometers and three angular rate sensors is used to compute all the outputs A WGS 84 modelled strapdown navigator algorithm compensates for earth curvature rotation and Coriolis accelerations while measurements from the external GNSS receiver update the position and velocity navigated by the inertial sensors This innovative approach gives the Inertial
78. tem While the Inertial is running it tries to improve some of its configured parameters This option is useful if a calibration run has been done and the Kalman filter s values are known to be good In particular the Inertial will try to improve the external GNSS antenna position the orientation of the dual antennas the yaw orientation of the Inertial in the vehicle and the wheel speed calibration values For applications where the Inertial is installed permanently in the vehicle it can be beneficial to use the values that the Inertial has learned next time you use the Inertial It can make the results more consistent However Revision 131122 e this feature should not be used if there is a risk the Inertial will rotate in the vehicle or that the GNSS antennas can move even by a few millimetres To read the improved values from the Inertial click the button on the Orientation page to open the Get settings from Inertial window as shown in Figure 15 Figure 15 NAVconfig source selection page for improved configuration Q Get settings from Inertial Read improved configuration Choose where to read the configuration from Inertial Inertial and GNSS Read configuration from File v Navigation Step 1of2 Settings NCOM File Browse Next Cancel Click the drop down list and choose which source to read the configuration from The two options are Read configuration from file If an
79. ternal Antenna page F NAVconfig wizard 0 Es External Antenna I rti I Specify the primary GNSS antenna position on the vehicle in relation to the Inertial Inertial and GNSS Measured from the Inertial device Navigation Where is the measurement point of the GNSS antenna Ahead v 0 000m 0 100 m ight 0 000 m 0 100 m Step 5 of 10 Rd x Above v 1 000m 0 100 m Product Selection Read Configuration a Specify each accuracy separat GNSS Selection sid Orientation Overall accuracy 0 100m v Secondary Antenna Wheel Configuration Options Commit Save Finish Dev ID 131024 14am English v lt Back Next gt Cancel It is necessary to tell the Inertial the distance between its measurement origin shown in Figure 6 and the GNSS antenna s measurement point This should be entered in the vehicle s co ordinate frame The accuracy of the measurements should also be specified and care should be taken here It is very easy to measure within 1 cm or better in a straight line but it is much harder to measure within cm through a vehicle roof This is compounded if the Inertial is slightly misaligned in the vehicle Any alignment errors should be included in the accuracy you believe you can measure to It is better to overestimate the accuracy i e tell the Inertialt a worse value than underestimate it as the Inertial will refine the accuracy over time Some GNSS receivers can compensate f
80. the Inertial according to Table 28 and check the angular rate measurements occur 5 With the unit stationary check all the angular rates are within 5 s In general they will be within 0 5 s but the algorithm in the Inertial will work to specification with biases up to 5 s Table 28 Angular rate measurement specifications Rotation Angular Rate Measurement Y ve Zero Zero The x axis should indicate positive rotation others are small ve Zero Zero The x axis should indicate negative rotation others are small Zero ve Zero The y axis should indicate positive rotation others are small Zero ve Zero The y axis should indicate negative rotation others are small Zero Zero ve The z axis should indicate positive rotation others are small Zero Zero ve The z axis should indicate negative rotation others are small It is hard to do a more exhaustive test using the angular rate sensors without specialised software and equipment For further calibration testing it is necessary to return the unit to OxTS Note that the Inertial is capable of correcting the error in the angular rate sensors very accurately It is not necessary to have very small values for the angular rates when stationary since they will be estimated during the initialisation process and warm up period This estimation process allows the Inertial to go for long periods without requiring recalibration Testing the internal GNSS and other circuitry
81. tial is a CD containing the software package NAVsuite This package contains a number of programs required to take full advantage of the Inertial s capabilities Table 7 lists the contents of NAVsuite Table 7 NAVsuite components Icon Software Description Ethernet or a serial port It can also be used to transmit Enginuity Used to view real time data from OxTS products via special commands and replay logged data NAVeonfig Used to create send and receive configurations from vi OxTS products As configurations vary between products there is no manual for NAVconfig The options relevant to the Inertial products are covered in this manual on page 35 post process the data The configuration can be changed and differential corrections can be applied before the data is reprocessed It can export NCOM XCOM and CSV file formats C RT Post process Used to download raw data files from the Inertial and post process It can display graphs cursor tables and map plots and data can be exported in CSV or KML Google gj NAVgraph Used to graph NCOM XCOM and RCOM files created in Earth format T Manuals This folder contains PDF versions of relevant OxTS manuals Other manuals can be downloaded from the OxTS website http www oxts com support manuals To install NAVsuite insert the CD and run NAVsetup exe Follow the onscreen instructions to install the software By default the installer creates the program files in
82. trees buildings 1 Next to trees buildings 2 Typical figures using a 1 m base line For accuracy specification of 0 15 RMS a 2 m separation is required Using a 2 m base line can halve the figures shown here B Oxford Technical Solutions Inertialt User Manual QObxrs Inputs and outputs This section describes the connectors and the signals on the Inertial All connections to the Inertial are marked on the front panel shown in Figure 5 on page 25 The system can output data on the serial port or over Ethernet The standard serial output of the Inertial is a proprietary binary format referred to as NCOM OxTS offers C and C code that will interpret the packet This can be used freely in users programs to interpret the output of the Inertial More information about NCOM can be found in the NCOM description manual It is also possible to output a standard NMEA string from the Inertial to mimic the output of standard GNSS receivers OxTS offers a service to tailor the serial output format to the customer s specification Contact Oxford Technical Solutions for details of this service Pin assignments Table 20 RS232 pin assignments Serial 1 Serial 2 and External GNSS Pin Direction Description 2 Input Data receive 3 Output Data transmit 5 Ground 9 Reserved Other pins not connected internally Revision 131122 e Table 21 Digital I O pin assignments Pin Function Description 1 Digital 1 1PPS out
83. ts conform to the National Marine Electronics Association Standard NMEA 0183 version 3 01 The NMEA sentences available are GPGGA GPHDT GPVTG GPZDA GPGST PASHR GPRMC GPGSV GPGSA PTCF GPPPS PRDID GPROT GPGGK and GPUTC The NMEA 0183 description manual gives details of the fields output in the NMEA sentences Javad I RTK A special set of messages output in GREIS format to be used with Javad receivers For assistance please contact OxTS for support MCOM Used for marine applications Identical to NCOM output but with the addition of heave measurements TSS1 TSS1 format outputting acceleration heave roll and pitch TSSHHRP TSSHHRP format EM3000 Suitable for use with Simrad EM3000 multibeam sounders EM1000 Suitable for use with Simrad EM1000 multibeam sounders If the NMEA packet type is selected the NMEA tab will appear in the properties window see Figure 23 In this tab the NMEA messages to output on the serial port of the Inertial are selected by choosing the data rate for each message type from the drop down lists and clicking the checkbox for when to generate the message NMEA messages can be generated by falling or rising voltages on the event inputs Check the falling or rising edge checkbox to compute the message when the event occurs The Inertial can also generate NMEA messages from pulses on the camera trigger These messages use interpolation to compute the values at the exact time of the event and may be output
84. tside of vehicles Export control classification number Export control regulations change and so the classification number of the Inertial may also change The information here relates to the time when the manual was published The Inertial products can fall under two different export control categories depending Revision 131122 on the type of accelerometer fitted internally The type of accelerometer does not affect the specification of the product only the export control classification number ECCN The ECCN can be found on the invoice delivery note and also on the label of your Inertial system The label shows a code used by OxTS to identify the type of accelerometer and is used because the ECCN numbers can change in the future Table 6 shows the current ECCN numbers for the different label text on the Inertial Table 6 ECCN and Inertial label text Label Text Current ECCN Number EXCT 1 7A003d EXCT 2 7A103a1 Oxford Technical Solutions Inertialt User Manual Qoxrs Conformance notices The Inertial complies with the radiated emission limits for 47CFR15 109 2010 class A of Part 15 subpart B of the FCC rules and with the emission and immunity limits for class A of EN 55022 These limits are designed to provide reasonable protection against harmful interference in business commercial and industrial uses This equipment generates uses and can radiate radio frequency energy and if not installed and u
85. ual Qoxrs Configuring the Inertial To obtain the best results from your Inertial it will be necessary to configure it to suit the installation and application before using it for the first time The program NAVconfig can be used to do this This section describes how to use NAVeconfig and gives additional explanations on the meanings of some of the terms used It is only possible to change the Inertial configuration using Ethernet It is necessary to have the Ethernet on your computer configured correctly in order to communicate with the Inertialt and change the settings See the section Ethernet configuration on page 31 for more information Overview In order to give the best possible performance the Inertial needs to know the following things e The type of GNSS receiver fitted e The orientation that the Inertial is mounted at in the vehicle e The position of the external GNSS antenna compared to the Inertial e The position of the rear wheels or non steering wheels compared to the Inertial e The position of the odometer compared to the Inertial e The orientation of the dual antenna system if applicable The Inertialt can work out many of these parameters by itself but this takes time Measuring the parameters yourself and configuring the Inertial reduces the time taken to achieve full specification If the Inertial has been running for some time it will have improved the measurements It is possible
86. upport NCOM Manual and Code Drivers ncomrx zip NMEA 0183 NMEA description manual for the NMEA outputs Description www oxts com Downloads Support NMEA nmeaman pdf RT Post process Manual User manual for the post processing software RT Post process www oxts com Downloads Support Manuals rtppman pdf 1o Oxford Technical Solutions Inertialt User Manual Qoxrs Inertial family divisions The Inertial product family includes several different divisions all based on the same core system but with minor differences to address different applications Table 3 lists the current model line up for the Inertial family Table 3 Inertial family divisions Product name Description Inertial Base model Single antenna 100 Hz Inertial 2 Dual antenna 100 Hz Inertial 250 Single antenna 250 Hz Tnertial 2 250 Dual antenna 250 Hz Single antenna The advanced algorithm in the Inertial software means that most road vehicle customers are able to use a single antenna system The Heading lock and Wheel configuration features mean that the Inertial can maintain accurate heading while stationary and while driving with low vehicle dynamics Dual antenna The dual antenna system gives high accuracy heading information and almost constant heading performance under all conditions Single antenna systems can have reduced heading accuracy on aircraft boats or in low speed land vehicles For applications on aircraft or marine
87. y applications The NMEA input and NMEA output means that the original GNSS output can be connected to the Inertial and the Inertial output can be connected to the final application Revision 131122 Ea Related documents This manual contains sufficient information about the installation and operation of an Inertial system It is beyond the scope of this manual to provide details on service or repair Contact OxTS support or your local representative for any customer service related inquiries There are separate manuals available for further information on some of the software and communication types mentioned in this manual Table 2 lists related manuals and where to find them Table 2 Supplementary manuals Manual Description Enginuity Manual User manual for the real time display software Enginuity www oxts com Downloads Support Manuals EnginuityMan pdf Inertial List of manuals for integrating the Inertial with a number of GNSS receivers integration http www oxts com products inertial inertial receiver manuals manuals NAVegraph User manual for the graphing and display software NAV graph Manual www oxts com Downloads Support Manuals NA Vgraphman pdf NCOM Manual NCOM description manual www oxts com Downloads Support NCOM Manual and Code Drivers ncomman pdf NCOM C Code A collection of C functions that can be used to decode the binary protocols from Drivers the Inertial www oxts com Downloads S

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