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2007-07 - Peer to Peer Research at UCSB

1. Description Return the offset in bytes of the field source e offset Bits function public static int offsetBits function Description Return the offset in bits of the field function e offset Bits_packetnum public static int offsetBits_packetnum Description Return the offset in bits of the field packetnum e offset Bits_sample public static int offsetBits_sample gt Description Return the offset in bits of the field sample e offsetBits_source public static int offsetBits_source Description Return the offset in bits of the field source e set_function public void set_function int value Description Set the value of the field function 94 Appendix A javadoc e set_packetnum public void set_packetnum int value Description Set the value of the field packetnum e set_sample public void set_sample int value Description Set the value of the field sample e set _source public void set_source short value Description Set the value of the field source e size function public static int size_function Description Return the size in bytes of the field function e size_packetnum public static int size_packetnum Description Return the size in bytes of the field packetnum e size_sample public static int size_sample Description Return the size in
2. Field summary AM _DIOMEDESTLMMSG FUNCTION_ADCO FUNCTION ADC1 84 Appendix A javadoc FUNCTION_ADC2 FUNCTION_ADC3 FUNCTION _ADC4 FUNCTION_ADC5 FUNCTION_ADC6 FUNCTION_ADC7 FUNCTION_LIGHT FUNCTION_TEMP Constructor summary Constants Fields public static final byte FUNCTION_ADC2 public static final byte FUNCTION_ADC5 public static final short FUNCTION_LIGHT public static final short FUNCTION_ADC7 public static final byte AM_DIOMEDESTLMMSG public static final byte FUNCTION_ADC6 public static final short FUNCTION TEMP public static final byte FUNCTION_ADC3 public static final byte FUNCTION_ADC4 public static final byte FUNCTION_ADC1 public static final byte FUNCTION_ADCO Constructors Constants public Constants 85 Appendix A javadoc A 1 10 Class DialGauge Dial Gauge Creates a generic Dial Gauge Declaration public class DialGauge extends org ucsb mayhem diomedes Gauge in A 1 19 page 103 Constructor summary DialGauge boolean Constructor Method summary handleSample Sample Handle Sample paintComponent Graphics Paint Component Constructors e DialGauge public DialGauge boolean floating Description Constructor Construct a Dial Gauge and detatch it if requested Parameters x floating Whether or not to detatch the frame Methods e handleSample public void handleSample Sample samp throws org ucsb mayhem diomedes WSNException
3. Chapter 3 A Solution ity mechanisms will need to be employed to reach acceptable packet reception rate The environment is also inhospitable in other ways Both vibration and high temperatures could cause problems for the system Luckily there is a history of sensor network solutions in far more extreme environments 20 36 often achieved by insulating the sensor nodes either physically from vibrations or thermally from high temperatures Another source of challenge common to any networking system is coordi nation of network traffic With a large number of wireless sensor nodes asyn chronously transmitting samples to the base station likely at different frequen cies of transmission the base station must be able to attribute the samples to the proper data source on the proper sensor node order them relative to other messages sent from the same node and determine which if any of the samples were corrupted This will require an additional application level protocol on top of any existing network level protocols Finally sensor node hardware is not well suited to automotive signals Signal voltage ranges are potentially wide and varied voltage spikes can potentially damage analog to digital converters and there can be significant noise To handle all of these issues the sensor nodes will require some signal conditioning in front of the analog to digital converter 14 Chapter 3 A Solution 3 3 Requirements At th
4. e setUnitsName public void setUnitsName java lang String newname Description Set Units Name Sets the full name of the units of the Channel 82 Appendix A javadoc Parameters x newname The full name of the units of the Channel e g Volts for Volts A 1 7 Class ConsoleSampleLogger Console Sample Logger Logs all samples to stdout instead of a file Declaration public class ConsoleSampleLogger extends java lang Object implements SampleLogger Constructor summary ConsoleSampleLogger Method summary handleSample Sample Constructors e ConsoleSampleLogger public ConsoleSampleLogger gt Methods e handleSample public synchronized void handleSample Sample s throws org ucsb mayhem diomedes WSNException A 1 8 Class consoletest Console Test Jumping off point for Diomedes Accepts command line argu ments and constructs the system 83 Appendix A javadoc Declaration public class consoletest extends java lang Object Constructor summary consoletest Method summary main String Main Constructors e consoletest public consoletest Methods e main public static void main java lang String args Description Main Console entry point Parses the command line constructs the network and builds the GUI Parameters x args Command line arguments A 1 9 Class Constants Declaration public class Constants extends java lang Object
5. Description Handle Sample Stores the sample and calls repaint O Parameters samp Sample to handle Throws x org ucsb mayhem diomedes WSNException 86 Appendix A javadoc e paintComponent protected void paintComponent java awt Graphics g Description Paint Component Place the gauge image and render a needle in the correct direction A 1 11 Class DigitalGauge Digital Gauge A digital readout which displays the readings as text in a textbox Declaration public class DigitalGauge extends org ucsb mayhem diomedes Gauge in A 1 19 page 103 Constructor summary DigitalGauge boolean Constructor Method summary handleSample Sample Handle Sample paintComponent Graphics Paint Component Constructors e DigitalGauge public DigitalGauge boolean floating Description Constructor Constructs a Digital gauge detatching it if requested Parameters x floating Whether or not to detatch the frame 87 Appendix A javadoc Methods e handleSample public void handleSample Sample samp throws org ucsb mayhem diomedes WSNException Description Handle Sample Store the value of the sample and call repaint Parameters x samp The sample to handle Throws x org ucsb mayhem diomedes WSNException e paintComponent protected void paintComponent java awt Graphics g Description Paint Component Write the sample to the text box A 1 1
6. P Zhang and M Martonosi Implementing software on resource constrained mobile sensors experiences with impala and ze branet In MobiSys 04 Proceedings of the 2nd international conference on Mobile systems applications and services pages 256 269 New York NY USA 2004 ACM Press A Mainwaring J Polastre R Szewczyk D Culler and J Anderson Wire less sensor networks for habitat monitoring In ACM International Work shop on Wireless Sensor Networks and Applications WSNA 02 Atlanta GA Sept 2002 K Martinez P Padhy A Elsaify G Zou A Riddoch J K Hart and H L R Ong Deploying a sensor network in an extreme environment 69 Bibliography 21 22 23 24 25 26 27 28 29 30 31 32 In SUTC 06 Proceedings of the IEEE International Conference on Sen sor Networks Ubiquitous and Trustworthy Computing Vol 1 SUTC 06 pages 186 193 Washington DC USA 2006 IEEE Computer Society MINI Cooper Service Manual Bentley Publishers 2004 MINI USA http www miniusa com MTS MDA Sensor Board User s Manual Crossbow Doc 7430 0020 04 Rev B T Nolte H Hansson and L L Bello Automotive communications past current and future In 10th IEEE Conference on Emerging Technologies and Factory Automation 2005 OBD IL http www obdii com Pico Technology http www picotech com auto B J Pine Mass Customization The New Frontier in Business Com
7. isArray_function Return whether the field function is an array false isArray_packetnum Return whether the field packetnum is an array false isArray_sample Return whether the field sample is an array false isArray_source Return whether the field source is an array false isSigned function Return whether the field function is signed false isSigned_packetnum Return whether the field packetnum is signed false isSigned sample Return whether the field sample is signed false isSigned_source Return whether the field source is signed false offset_function Return the offset in bytes of the field function offset_packetnum Return the offset in bytes of the field packet num offset sample Return the offset in bytes of the field sample offset_source Return the offset in bytes of the field source offset Bits_function Return the offset in bits of the field func tion 89 Appendix A javadoc offsetBits_packetnum Return the offset in bits of the field packetnum offset Bits sample Return the offset in bits of the field sample offset Bits_source Return the offset in bits of the field source set_function int Set the value of the field function set_packetnum int Set the value of the field packetnum set_sample int Set the value of the field sample set_source short Set the v
8. 40 20 0 20 40 60 80 100 Reception Rate Figure 5 3 Reception Rate CDF 48 Chapter 5 System Evaluation 5 3 3 Measurement Resolution The key to understanding the resolution of our measurements is that the ADCs on the Mica2 mote have 10 bits of resolution For a voltage connected directly to the ADC input with its 0 3V range this equates to a resolution of about 3mV as shown in Equation 5 6 In other words the difference between a measurement and the next highest measurement is 3mV due to the discrete nature of ADCs 3 0V So 0 00293V 5 6 With linear relationships in hand which convert raw ADC readings into rea sonable units for the light sensor Equation 5 2 engine coolant temperature Equation 5 3 throttle pedal position Equation 5 4 and fuel level Equa tion 5 5 it is a simple matter to determine the resolution of each measurement Unfortunately with all of these readings being unit less the resultant resolution is also unit less Nevertheless Table 5 1 shows the resolution of each of the measurements all sensors but the temperature sensor have a unit less range of 0 100 The only measurement which has real engineering units is the built in temper ature sensor on the MDA100 board The default calibration curve Equation 5 1 for this thermistor is not linear so it is impossible to give a single resolution for 49 Chapter 5 System Evaluation measurement range reso
9. 7 Sequence Diagram of the mote software Class Mote accepts objects of type Sample from the WirelessSensorNetwork class and must dispatch them to the proper registered Channel class Channels in this case represent potential sources of data from the mote in the current prototype these are TempChannel LightChannel and ADCChannel for temperature light and general voltage data respectively The channels en capsulate the type of data coming in from a particular mote and must therefore also provide conversion from raw ADC readings into the appropriate engineering units When a Sample is passed to a Channel the Channel must register itself with the Sample so that later the Sample s engineering units can be expediently 27 Chapter 4 A Prototype WirelessSensor Network SampleHandler handleSample Sample Channel function int convertUnits float setScale setTitle paintComponent TempChannel LightChannel ADCChannel FuelGauge DialGauge TempGauge i FuelPumpLevelChannel AcceleratorPedalChannel EngineCoolantChannel Figure 4 8 Class Diagram for Sample Handler children extracted The final job of the Channel is to pass the Sample to any registered handlers typically subclasses of the abstract class Gauge A Gauge represents a UI elemen
10. Figure 5 1 Data Collection Photos a Sensorboard closeup affixed to the engine b Laptop strapped safely into the car Three sensors were chosen for the experiment Engine Coolant Temperature Throttle Pedal Position and Fuel Level The location of the sensors and the correct signal wires were collected from the Bentley Publishing MINI Cooper Service Manual 21 Engine Coolant should mirror exactly the readout on the dashboard tem perature gauge This signal from this sensor is accessible where it meets the Electronics Control Module ECM under the car s bonnet Throttle Pedal Position is also available under the bonnet at the ECM For a drive by wire vehicle this is the desired throttle position transferred from a sensor the gas pedal in the passenger compartment This is an attractive sensor Al Chapter 5 System Evaluation to monitor because it is easy for the experimenter i e the driver to interactively affect Finally the Fuel Level sensor was chosen as it differs from the other two sensors in several ways First this signal is not available in the engine compart ment with the other two The only way to access this signal is to remove the rear seats and place the sensor node directly on the fuel pump enclosure this varied the relative locations of the motes Second while the other two sensors are well described in the service manual this signal was poorly documented The output could be a simple voltage leve
11. ae OS 86 Dial Gauge 73 Appendix A javadoc DisttalGalee instala s norttao altea 87 Digital Gauge Diomedes TELMMS2 crea ti a ted a ee ed ae ds 88 Dummy Moteis aaaea ae ec ag nt all cas soya tied Si 96 Dummy Mote Dummy WirelessSensorNetwork 0 0000 cece eee eee 97 Dummy Wireless Sensor Network EngineCoolantTempChannel 0 0 00 e cee cee 98 Engine Coolant Temp Channel FileSample log get ii eer ai ee eee ae a d dad Sy 99 File Sample Logger PTV sats A e ee A A cach 101 Fuel Gauge FuelPumpLevelChannel 0 neunana aanere eee teed 102 Fuel Pump Level Channel CANIS A tes Shea a ea 103 Gauge GPa iG ae Gey di rd eas 106 Graph Gauge ns AA O btlea ee a OTA OE EREE 107 Light Channel Inet Samiple 2c2g cscu ate ee hak ee ee de ee ee 108 Light Sample Lothile Milter e oeiee ie A AOS 108 Moteras a a Gee Saat he eas 109 Mote RealWirelessSensorNetwork 0 0000 cece eee eee eee 111 Real Wireless Sensor Network Sample ds Sitges whan ie onda A a God Beate Gee eo E 112 Sample WTemipC hannel o ete tet De de o ds A Wiehe BS a A ees 116 Temperature Channel TenipGaee e ote Aneel te be eck a bre eek ts el dl A dete ott one 117 Temperature Gauge T mpsamplen a ta ts tg abe de ds leo 118 TempSample 74 Appendix A javadoc WirelessSensorNetwork o 119 Wireless Sensor Network Exceptions W SINE XCEDEION via tecdcsd tl ced oes 121 Wireless Sensor
12. base station software is the BaseStation module provided with TinyOS while two components on the sensor nodes were written custom There is a Java language package to interface between the network and the graphical user interface which is also written in Java The rest of this chapter deals with the design and then the implementation of the DIOMEDES prototype 19 Chapter 4 A Prototype 4 2 Design 4 2 1 Sensor Package Considering that we want to read an external signal with the mote we need to interface with the Mica2 s on board analog to digital converter ADC The Mica2 s Atmel ATMegal28L has 8 ADC inputs Since the first ADC input ADC is already taken up by the built in temperature and light sensors we have to use ADC2 This is accomplished by connecting a probe wire directly to pin ADC2 on the Mica2 expansion connector Figure 4 2 as in Figure 4 2 broken out on the prototyping board Test Point ADC2 Car Ground Sensor Node Ground Figure 4 2 ADC2 signal conditioning This simplistic design does not account for the variety of voltage ranges which could be present in the car Because the ADC on the microcontroller only supports voltages in the range of 0 3V it is necessary to add a voltage divider to the front end of the ADC dividing the actual input voltage such that the maximum voltage that the sensor could see does not exceed 3V This is 20 Chapter 4 A Prototype accomplished with the
13. circuit shown in Figure 4 3 The ratio of R1 and R2 determine the amount that the voltage is divided according to the following formula _ Vre ho iS e A A Ri R 4 1 Where Vrp is the voltage at the test point and V gt is the voltage across R and thus the voltage that ADC2 sees Because the effect of the measurement circuit on the car s electronics must be minimal the total resistance R R should be as large as possible At the same time the total resistance should be several orders of magnitude lower than the input resistance of the ADC which is 10MQ Thus the value of Ra was fixed at 50K Q and R is subsequently sized according to the desired maximum test point voltage as follows solving Eqn 4 1 for R Vrp Ri Ro R 4 2 1 2 2 4 2 And inserting our known quantities for Ra and the maximum Vz Vrp Q R 50 000 30V 50 0000 4 3 Which means that given a desired maximum test point voltage Vrp we can size R using Table 4 1 21 Chapter 4 A Prototype maximum Vrp Ry 3 0V 00 5 0V 33 333 339 6 0V 50 0009 10 0V 116 666 672 12 0V 150 0002 15 0V 200 0000 Table 4 1 Sizing R of the ADC front end circuit Figure 4 3 ADC2 signal conditioning w Voltage Divider In order to filter out spikes and noise from the input signal this circuit needs a capacitor across the lower resistor Figure 4 4 This creates a simple RC filter Now we must p
14. in the system Again like Figure 5 2 the graph is pretty straightforward For both the fuel level and throttle pedal motes 90 of the time each had 90 or better reception rate This is in marked contrast to the coolant temperature mote which achieves 90 or better reception rate only 60 of the time Again the motes were all running the same software so the variation between the reception rates must be something more environmental The mote connected to the fuel pump was fully surrounded in the metal of the car s body with what can only be described as a metal blast shield screwed down on top of it It was in cramped quarters squeezed down next to the fuel pump and its antenna was in a peculiar orientation This almost certainly negatively impacted its reception 47 Chapter 5 System Evaluation rate And yet it is the coolant temperature mote sitting physically next to the throttle pedal mote which achieves the worst performance It is doubtful that electrical and physical interference alone are to blame since again the throttle pedal position mote was directly next to the poorly performing coolant temperature mote This may be a case where the previously documented mis calibrations of Mica2 radios comes into play 34 It may be that the coolant temperature mote inherently performs worse than the other two motes 100 Coolant Temperature Throttle Pedal Position e Fuel Level EEE SESION 80 60 CDF
15. intrusive We provide a solution to the problem and probe the answer to this question using the nodes of a wireless sensor network to read and relate diagnostics data to a central base station The base station either a notebook computer for a temporary system or an integrated carputer for a more permanent solution logs and displays the data in a coherent manner By removing the wires which characterize traditional automotive diagnostics systems we enable the system to be much more integrated customizable and non intrusive By utilizing sensor network nodes which are projected to be inexpensive and ubiquitous in the future we make the system low cost After detailing the solution and giving its justification in relation to alter nate approaches we enumerate a series of requirements which an implementation must meet Then we present the design and implementation of our prototype solution which uses Crossbow Mica2 motes as the remote sensor nodes for the system and an Apple notebook computer as the base station The Mica2 motes Chapter 1 Introduction are fitted with Crossbow MDA100CB prototyping boards which include tem perature and light sensors and provide a space to construct a signal conditioning circuit The motes run a custom application built on top of TinyOS which han dles the timing of all data acquisition and networking operations The notebook computer has another Mica2 mote attached to it via RS 232 serial which act
16. java util Vector motes Known motes in the network 119 Appendix A javadoc Constructors e WirelessSensorNetwork public WirelessSensorNetwork Description Default constructor Creates the wireless sensor network with three motes 1 2 3 Methods e addGlobalHandler public void addGlobalHandler SampleHandler hand Description Add Global Handler Registers a handler which is called on all mes sages This is typically a logging object Parameters hand The handler object to register e addHandler public void addHandler int moteID int function SampleHandler hand Description Add Handler Registers a SamplerHandler with the appropriate mote and on the proper channel Parameters x moteID The id of the mote with which to register the handler function The function or channel of data to handle hand The handler object to register e messageReceived public void messageReceived int dest_addr net tinyos message Message msg Description Message Received Converts the message to a Sample and then passes it to the appropriate Mote and to any registered SampleHandlers Parameters 120 Appendix A javadoc x dest_addr The destination address of the packet should always be 710 x msg The actual contents of the message A 1 31 Exception WSNException Wireless Sensor Network Exception Thrown when errors are found in a packet receive
17. motes are small and light and easily fit wherever they needed to fit Also the probes were connected with t taps which remove easily leaving behind almost no trace of their previous installation Electrically the total resistance of the whole sensor package is very high which allows very little current to flow Consequently the motes are nearly invisible to the car s electronics 5 4 Analysis 5 4 1 What worked Ultimately the system works to its requirements Even with packet losses the rates are reasonable for monitoring and some post processing All the read ings have sufficient resolution and could conceivably be made even better with a better knowledge of the signals being read The system is integrated customiz 53 Chapter 5 System Evaluation able and relatively cheap Certain mechanisms proved especially useful in the system s construction Filtering in both hardware and software did much to clean up the signals received from the motes The addition of the hardware filter Figure 4 4 in front of the analog to digital converter cleaned up most of the huge periodic voltage spikes common to automotive applications Basic filtering in software by throwing out corrupted messages as detected by a CRC check at the base station removes many of the packets which we can only assume are damaged during transmission Also making use of the built in packet acknowledgment system in TinyOS active messaging also did mu
18. register convert Units public abstract double convertUnits Sample samp Description Convert Units Method which all children must implement that con verts from a raw ADC sample into engineering units Parameters samp sample to convert to EU getFunction public int getFunction Description Get Function Returns the function of the Channel Returns The function of the Channel get Units public java lang String getUnits 81 Appendix A javadoc Description Get Units Returns the abbreviation of the Channel s units Returns The abbreviation of the units of the Channel e g V for Volts e getUnitsName public java lang String getUnitsName Description Get Units Name Gets the full name of the units of the Channel Returns The full name of the units of the Channel e g Volts for Volts e handleSample public void handleSample Sample samp throws org ucsb mayhem diomedes WSNException Description Handle Sample Pass the sample to all registered handlers Parameters x samp Sample to handle Throws org ucsb mayhem diomedes WSNException Sample is not handled within Channel e setUnits public void setUnits java lang String newunits Description Set Units Sets the abbreviation of the Channel s units Parameters newunits The new abbreviation of the Channel s units e g V for Volts
19. the case where samples are being logged the base station would require an interface to configure a logging session and then a means to extract the completed log data Chapter 4 discusses a prototype implementation of this solution then Chap ter 5 evaluates the prototype against these requirements 16 Chapter 4 A Prototype 4 1 Introduction This chapter describes the prototype which we built to determine the feasi bility of the solution The prototype system is called DIOMEDES which stands for Diagnostics Implemented On Motes Expressly Designed for Engine Sens ingt It is built using Crossbow Mica2 motes for the sensor nodes which are comprised of an Atmel ATMegal28L microcontroller with built in 10bit analog to digital converter and a Chipcon CC1000 900MHz low power radio Another Crossbow Mica2 mote is used as wireless interface for the base station and an Apple notebook computer is the user interface to the system connected to the base station mote with RS 232 serial The architecture for the prototype is shown in Figure 4 1 lAlso a Greek hero from Homer s Iliad 17 Chapter 4 A Prototype User Interface Laptop Figure 4 1 Prototype Architecture DIOMEDES Image of car courtesy of MINI USA 22 image of motes courtesy of Crossbow 7 The Mica2 motes were a good choice for wireless sensor nodes for a num ber of reasons First we had a number of them from previous experiments so finding three s
20. 2 Class DiomedesTLMMsg Declaration public class Diomedes TLMMsg extends net tinyos message Message Field summary AM_TYPE The Active Message type associated with this message DEFAULT_MESSAGE_SIZE The default size of this message type in bytes Constructor summary DiomedesTLMMsg Create a new DiomedesTLMMsg of size 7 DiomedesTLMMsg byte Create a new DiomedesTLMMsg us ing the given byte array as backing store DiomedesTLMMsg byte int Create a new Diomedes TLMMsg using the given byte array as backing store with the given base offset 88 Appendix A javadoc DiomedesTLMMsg byte int int Create a new DiomedesTLMMsg using the given byte array as backing store with the given base offset and data length DiomedesTLMMsg int Create a new DiomedesTLMMsg of the given data_length DiomedesTLMMsg int int Create a new DiomedesTLMMsg with the given data_length and base offset DiomedesTLMMsg Message int Create a new DiomedesTLMMsg embedded in the given message at the given base offset DiomedesTLMMsg Message int int Create a new Diomedes TLMMsg embedded in the given message at the given base offset and length Method summary get function Return the value as a int of the field function get_packetnum Return the value as a int of the field packet num get_sample Return the value as a int of the field sample get_source Return the value as a short of the field source
21. 5 1 Measurement ranges and resolutions xii Chapter 1 Introduction tu cum olfacies deos rogabis totum ut te faciant Fabulle nasum G Valerius Catullus carmen tredecim All people who interact with a vehicle require custom indicators of the vehi cle s performance custom diagnostics data Drivers need to see that the vehicle has sufficient fuel and that the engine is not overheating whereas mechanics require detailed readouts of all operational parameters Though the automotive industry has recognized the need for options and customization in other aspects of their vehicles such as paint colors and wheel designs customizable diagnos tics displays are seldom offered When an original equipment manufacturer does provide diagnostics read outs they are typically insufficient for general uses and are always limited in scope Temperature gauges only read engine coolant tem perature when other engine temperatures for example the air temperature at the throttle intake would also be valuable 1 when you smell it Fabullus you will beg the gods to make you all nose Chapter 1 Introduction This leaves a niche to be filled by third party developers Unfortunately though third party solutions greatly increase the flexibility of automotive diag nostics systems they typically fail to provide all desired aspects integration customizability low cost and non intrusiveness The system must be integrate
22. Corswant and P Fredriksson Sourcing trends in the car industry A survey of car manufacturers and suppliers strategies and relations In ternational Journal of Operations amp Production Management 22 741 758 2002 Q Wang W P Chen R Zheng K Lee and L Sha Acoustic target tracking using tiny wireless sensor devices In Proc of the 2nd International Workshop on Information Processing in Sensor Networks IPSN 03 2003 M Yarvis W Conner L Krishnamurthy J Chhabra B Elliott and A Mainwaring Real world experiences with an interactive ad hoc sensor network In International Conference on Parallel Processing pages 143 151 2002 ZigBee Alliance www zigbee org 71 Appendices 72 Appendix A javadoc A 1 Package org ucsb mayhem diomedes Package Contents Page Interfaces saniple Handle cect Ala li A tended 75 Sample Handler SampleLogger Sadrana aa A Md Ae ae ite a 76 Sample Logger Classes AcceleratorPedalChannel 0 0 0 00000 c cece cnet ees 76 Accelerator Pedal Channel ADOC banned sac tcc a tenho etn teens Bat e e cad 77 ADC Channel PRTC DAIS too se decease eect elena hed en ea teh tae 79 ADC Sample Channel tora ya Saad nhs eked ew Gees Baw Bue anaes ia od 79 Channel ConsoleSampleLogger 0 2 0 0 0 0 cece corr 83 Console Sample Logger CONSOLE dentro leaks edad keine wade te 83 Console Test E elas cela vale ead eee peso A 84 DD My AIO Css Se hoo hey Ba a leet hig
23. Max Max and min displayed scale scaleMin Max and min displayed scale title Gauge title XOFFSET Internal graphical placement offsets YOFFSET Internal graphical placement offsets Constructor summary Gauge Default constructor 103 Appendix A javadoc Method summary isScaleVisible Is Scale Visible paintComponent Graphics Paint Component setScale double double Set Scale setScaleVisible boolean Set Scale Visible set Title String Set Title toFloat To Float Fields e protected double scaleMax Max and min displayed scale protected double scaleMin Max and min displayed scale protected java lang String title Gauge title protected static final int XOFFSET Internal graphical placement offsets protected static final int YOFFSET Internal graphical placement offsets Constructors e Gauge public Gauge Description Default constructor Constructs a Gauge with Arial as its title font Methods e isScaleVisible public boolean isScaleVisible gt Description Is Scale Visible Checks the visibility of the scale 104 Appendix A javadoc Returns Whether he scale numbering is visible true visible e paint Component protected void paintComponent java awt Graphics g Description Paint Component Draws the title Called by subclasses Parameters g Graphics context e setScale public void setScale double min double m
24. Network Exception A 1 1 Interface SampleHandler Sample Handler Interface for any class capable of receiving samples Declaration public interface SampleHandler All known subinterfaces TempGauge in A 1 28 page 117 TempChannel in A 1 27 page 116 Sam pleLogger in A 1 2 page 76 Mote in A 1 24 page 109 LightChannel in A 1 21 page 107 GraphGauge in A 1 20 page 106 Gauge in A 1 19 page 103 Fu elPumpLevelChannel in A 1 18 page 102 FuelGauge in A 1 17 page 101 File SampleLogger in A 1 16 page 99 EngineCoolantTempChannel in A 1 15 page 98 DigitalGauge in A 1 11 page 87 DialGauge in A 1 10 page 86 ConsoleSampleL ogger in A 1 7 page 83 Channel in A 1 6 page 79 ADCChannel in A 1 4 page 77 AcceleratorPedalChannel in A 1 3 page 76 All classes known to implement interface Mote in A 1 24 page 109 Gauge in A 1 19 page 103 Channel in A 1 6 page 79 Method summary handleSample Sample Methods e handleSample void handleSample Sample s throws org ucsb mayhem diomedes WSNException 75 Appendix A javadoc A 1 2 Interface SampleLogger Sample Logger Parent interface for all logger classes Declaration public interface SampleLogger extends SampleHandler All known subinterfaces FileSampleLogger in A 1 16 page 99 ConsoleSampleLogger in A 1 7 page 83 All classes known to implement interface FileSampleLogger in A 1 16 page 99 ConsoleSampleLogge
25. UNIVERSITY OF CALIFORNIA Santa Barbara DIOMEDES An integrated automotive diagnostics system that is customizable low cost and non intrusive built on a wireless sensor network A Thesis submitted in partial satisfaction of the requirements for the degree of Masters of Science in Computer Science by Erik Olin Peterson Committee in Charge Professor Rich Wolski Chair Professor Chandra Krintz Professor Ben Zhao June 2007 This work was supported by a grant from the National Science Foundation num bered CNS 0627183 The Thesis of Erik Olin Peterson is approved Professor Chandra Krintz Professor Ben Zhao Professor Rich Wolski Committee Chairperson May 2007 DIOMEDES An integrated automotive diagnostics system that is customizable low cost and non intrusive built on a wireless sensor network Copyright 2007 by Erik Olin Peterson 111 Acknowledgements Thanks to Rich for getting me excited in the project and then getting me through it Thanks to Ben for his honest critique of this work s earliest form as well as his and Chandra s invaluable assistance in getting it buttoned up and signed off Thanks to Ye and Wei for help with motes Thanks to James and Brian for the crash course in analog design Thanks to Julie for being supportive and for wasting all of that precious gasoline driving up to Santa Barbara This document was written in a variety of places Thanks to the Goleta Cami
26. alendar timestamp Time of sample receipt at the computer e protected DiomedesTLMMsg m The original Message object e protected Channel chan The associate Channel for the purposes of EU conversion Constructors e Sample public Sample DiomedesTLMMsg newm Description Constructor Stores the message timestamps and returns Parameters newm Message to convert to a Sample Methods e getFileHeader public static java lang String getFileHeader Description Get File Header Returns The standard logfile header in String format 113 Appendix A javadoc e getFunction public int getFunction Description Get Function Returns The function from the Message e getPacket Number public int getPacketNumber Description Get Packet Number Returns The packet number from the Message e getRawSample public int getRawSample Description Get Raw Sample Returns The raw sample from the Message e getSource public int getSource Description Get Source Returns The source mote from the Message e getTimestamp public java lang String getTimestamp Description Get Timestamp Returns The timestamp of the receipt in String format e getTimestampInMillis public long getTimestampInMillis gt Description Get Timestamp in Milliseconds 114 Appendix A javadoc Returns Th
27. alue of the field source size function Return the size in bytes of the field function size_packetnum Return the size in bytes of the field packetnum size_sample Return the size in bytes of the field sample size_source Return the size in bytes of the field source sizeBits function Return the size in bits of the field function sizeBits packetnum Return the size in bits of the field packet num sizeBits_sample Return the size in bits of the field sample sizeBits_source Return the size in bits of the field source toString Fields e public static final int DEFAULT_MESSAGE_SIZE The default size of this message type in bytes e public static final int AM_TYPE The Active Message type associated with this message Constructors e DiomedesTLMMsg public DiomedesTLMMsg Description Create a new DiomedesTLMMsg of size 7 e DiomedesTLMMsg public DiomedesTLMMsg byte data Description Create a new DiomedesTLMMsg using the given byte array as backing store 90 Appendix A javadoc e DiomedesTLMMsg public DiomedesTLMMsg byte data int base_offset Description Create a new DiomedesTLMMsg using the given byte array as backing store with the given base offset e DiomedesTLMMsg public DiomedesTLMMsg byte data int base_offset int data_length Description Create a new DiomedesTLMMsg using the given byte array a
28. ameters extracted from the data second by second are e number of packets received count of the number of seconds with the same timestamp to the precision of the second e number of packets lost count of packets missing during a particular sec ond as determined by missing packet numbers e total packets sum of packets received and packets lost e reception rate ratio of packets received to total packets expressed as a percent 43 Chapter 5 System Evaluation If a particular second of the experiment is found to not have packets associ ated with it it is recorded appropriately to show instances of 0 packet reception The scripts also extract the data samples themselves as per second averages This made it possible to generate graphs of the fuel level engine coolant tem perature and throttle position throughout the experiment Sanity checks were performed on these data to see if they properly reflect the operation of the car Another helpful form of sanity check is to look at the laptop while the car is op erating to compare the digital gauges with the physical ones Ultimately they should match Clearly this is dangerous if performed by the driver so these kinds of evaluations were limited to instances in controlled driving conditions or with copilots The evaluation of these data rests on two parameters the effective throughput Section 5 3 1 or the number of packets per second and the reception rate Sect
29. as been proposed but its data source was the factory OBD II port 16 There have been some discussions of entirely intra vehicle wireless networks and often the subject of the discussion is Bluetooth 802 15 1 24 10 It has been suggested as a choice for a partial replacement for cable bundles 5 with the bluetooth nodes acting as wireless bridges between disparate on board wired networks such as CANbus the large number of bluetooth radio units required for a complete replacement is cited as cause for only partial replacement 10 At Unicamp Brazil Bluetooth modules were used as the sensor nodes with the Bluetooth module acting as the central host 28 Centralized wireless systems where all data are taken directly from the car s electrical control module have been built 17 Wireless sensor networks have even been recommended as a 62 Chapter 6 Related Work complete data cable replacement 8 but only in a speculative fashion and with a fair amount of trepidation with respect to using them in safety critical instances 63 Chapter 7 Conclusion and Potential Elaboration If there s no one around when the tour runs aground and if you re still around then we ll meet at the end of the tour They Might Be Giants End of the Tour 7 1 Conclusion In this thesis we identified a problem in the automotive industry Though users of automobiles require customized diagnostics data about their operating vehicles and tho
30. ax Description Set Scale Adjusts the visible scale Parameters x min Minimum value of the scale x max Maximum value of the scale e setScaleVisible public void setScaleVisible boolean val Description Set Scale Visible Changes whether the scale numbering is visible on the gauge Parameters x val true make visible false make invisible e set Title public void setTitle java lang String newTitle Description Set Title Sets the String title for the gauge Parameters newTitle The new value for the title e toFloat protected void toFloat Description To Float Causes the gauge to be rendered in a separate window instead of the default mode as a child container 105 Appendix A javadoc A 1 20 Class GraphGauge Graph Gauge A gauge which graphs the data arriving at a Channel Declaration public class GraphGauge extends org ucsb mayhem diomedes Gauge in A 1 19 page 103 implements java awt event ActionListener Constructor summary GraphGauge boolean Constructor Method summary actionPerformed ActionEvent Action Performed handleSample Sample Handle Sample paintComponent Graphics Paint Component Constructors e GraphGauge public GraphGauge boolean floating Description Constructor Constructs a Graph Gauge displays buttons and de tatches the frame if desired Parameters x floating Whether or not to construct the frame deta
31. bytes of the field sample e size_source public static int size_source Description Return the size in bytes of the field source 95 Appendix A javadoc e sizeBits_function public static int sizeBits function Description Return the size in bits of the field function e sizeBits_packetnum public static int sizeBits packetnum gt Description Return the size in bits of the field packetnum e sizeBits_sample public static int sizeBits sample Description Return the size in bits of the field sample e sizeBits_source public static int sizeBits_source Description Return the size in bits of the field source e toString public java lang String toString Description A 1 13 Class DummyMote Dummy Mote Runnable class to simulate the operation of a single mote in the system for development Declaration public class DummyMote extends java lang Object implements java lang Runnable 96 Appendix A javadoc Constructor summary Dummy Mote short short double WirelessSensor Network Constructor Method summary run Run Constructors e Dummy Mote public DummyMote short newid short newfunction double freq WirelessSensorNetwork wsn Description Constructor Creates a dummy mote with the given ID function data generation frequency and network Parameters newid The ID of the mote
32. ces A javadoc ix 29 30 33 35 37 37 38 38 40 43 44 45 45 47 49 50 ol 52 53 53 53 54 56 58 58 58 61 64 64 66 68 72 73 A 1 Package org ucsb mayhem diomedes B nesdoc B 1 Diomedes Application B 2 Diomedes Sensorboard List of Figures 3 1 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 4 10 4 11 4 12 5 1 5 2 5 3 B 1 B 2 Solution Architecture verse ak ae eed bee oh daw ale 11 DIOMEDES Prototype Architecture 18 ADC2 signal conditioning 4 20 ADC2 signal conditioning w Voltage Divider 22 ADC2 signal conditioning w Filter 24 ADC2 signal conditioning w Protection Diode 25 Mote Software Architecture 26 Sequence Diagram of the mote software 27 Class Diagram for Sample Handler children 28 Sensor network message handling Sequence Diagram 29 Mica2 and sensor board block diagram 32 Sensor Board Implementation 38 User Interface isla a is A 36 Data Collection Photos 204 stos A A 41 Effective Throughput CDF ara ata ds rs 46 Reception Rate CDF o eee ene 48 DiomedesAppC Dependencies 122 DiomedesSB Dependencies 123 xi List of Tables 4 1 Sizing R of the ADC front end circuit 4 2 Sizing R of the ADC front end circuit actual values
33. ch to increase packet reception rates Of the three sensor positions chosen for this study the throttle position and temperature proved to be good choices Both gave deterministic readings 5 4 2 What didn t work Not everything went perfectly in the system s development Some of the more notable problems and less conclusive results are described below For one the protection diode was unusable due to its leakage current One of the assumptions is that the current leaking through the zener diode before its breakdown voltage is minimal at least compared with the total current flowing 54 Chapter 5 System Evaluation through the circuit Because the circuit was designed with large resistors the nominal current flow was already very small With the zener diodes that we chose the leakage current was sufficient to negatively impact the voltage read ings Luckily we were able to rely on the total resistance of the circuit to protect the microcontroller Still it would be worthwhile to investigate zener diodes with less leakage current Also the default active message protocol in TinyOS needs to be bolstered with additional mechanisms in order to guarantee more reliable communication Retransmissions and CRC checks were not able to protect the system from packet loss there was inevitably at least one node in the system which experienced noticeable packet loss While the packet reception rates may be sufficient for monitoring th
34. chnologies this solution could work in numerous situations harsher conditions might require modification First the hardware is off the shelf with only minor additions The Crossbow Mica series of motes are a standard in wireless sensor networking research The only modifications made were to add a few inexpensive passive components This design could be easily duplicated elsewhere 56 Chapter 5 System Evaluation Second the software systems are all largely cross platform The user interface is written in Java and the mote software is written in cross platform NesC code with the exception of the digital I O controls used to enable and disable the on board sensors Finally the technologies employed would make it simple to expand the system into tens or even hundreds of nodes Changing from the Mica2 base to one using ZigBee radios would allow for 64k addressable nodes Also while the particular vehicle used with this prototype is arguably smaller than the average there would be nothing stopping the introduction of multi hop networking into the system This would allow the sensor nodes to communicate across much larger vehicles One situation which might require a redesign for the system is a more extreme environment Currently the sensor nodes would not be able to operate exposed to the elements Encasing the nodes in weatherproof casings would enable them to work as well outside of the vehicle as inside There is also a history of
35. customization in nearly every other facet of its production the development of factory customization of diagnostics data is not keeping pace It is left up to the third party automotive test and modification industries to fill this need For a third party solution to completely fill the needs of all interested parties it must achieve several high level requirements integration customizability low cost and non intrusiveness It must be integrated offering diagnostics data as easily on the road as it does in the garage with minimal modification This is a requirement which is Chapter 2 The State of the Art not often seen in general purpose diagnostics systems because most systems are built specifically for installation on static vehicles For a system to be truly integrated it must require that its wiring be routed carefully around the vehicle or it must be wireless It must be customizable allowing the collection of data from a variety of existing data sources on board as well as permitting the addition of data sources not previously envisioned by the original equipment manufacturer Thus it should be able to read the voltage from a temperature sensor already built into the engine of a vehicle but it should also be able to read temperature in a region of the car which does not already have a temperature sensor in it Typically systems either allow connection to existing signals or measurement of conditions e g temperature at arbit
36. d from the packetforwarder Ceases all further processing of the packet Declaration public class WSNException extends java lang Exception Constructor summary WSNException String Constructors e WSNException public WSNException java lang String message 121 Appendix B nesdoc B 1 Diomedes Application DiomedesC yo acket Acknowledgements end Packe itControl Leds Timer lt TMilli gt I i TimerMilliC MainC Read lt uint16_t gt ActiveMessageC I i Heartbeat j lio Es DiomedesSBC Figure B 1 DiomedesAppC Dependencies B 1 1 DiomedesAppC Configuration for the Diomedes Application Author Erik Peterson B 1 2 DiomedesC Implementation for the Diomedes Application Author Erik Peterson 122 Appendix B nesdoc Uses interface PacketAcknowledgements as Acks interface Leds interface Read lt uint16_t gt as ADC2 interface Timer lt TMilli gt as MilliTimer interface SplitControl as RadioControl interface Read lt uint16_t gt as Light interface Packet interface Read lt uint16_t gt as Temp interface AMSend interface Boot B 2 Diomedes Sensorboard Ce 10 HplAtm128GenerallOC Figure B 2 DiomedesSB Dependencies B 2 1 tos sensorboards diomedessb DiomedesSBP Implementation of the Diomedes Sensorboard software Author Erik Peterson wombatty alu
37. d into the car to such a degree that it can operate effectively whether the car is stationary or moving Clearly the goal is not to have the driver actively interacting with the system but rather to allow data collection and display at all times For troubleshooting some conditions may only occur when the car is operating The system must be customizable in order to support the full range of ex pected and unexpected uses It must be able to collect and display data from any of the car s on board sensors and it must additionally be capable of intro ducing additional sensors to measure previously unplanned parameters The system must be low cost so that it is feasible to collect a large number of parameters from the operating vehicle while maintaining affordability This system must support the needs of all users from the home user interested in a little more feedback from his or her vehicle to the well established auto me chanic While the mechanic may be able to afford another piece of expensive diagnostics equipment the home user would likely not be able to Chapter 1 Introduction Finally the system must be non intrusive The system must not affect the operation of the car to which it is attached and after it has been removed it must leave minimal evidence of its presence Taking these requirements into account the question then becomes Can integrated diagnostics systems be built that are customizable low cost and non
38. diomedes WSNException Description Handle Sample Saves the sample value and units and repaints e paintComponent protected void paintComponent java awt Graphics g Description Paint Component Draws the temperature gauge with the appropriate level Parameters g Graphics context A 1 29 Class TempSample TempSample Sample from a temperature sensor Declaration public class TempSample extends org ucsb mayhem diomedes Sample in A 1 26 page 112 Constructor summary TempSample DiomedesTLMMsg Constructors e TempSample public TempSample DiomedesTLMMsg msg 118 Appendix A javadoc A 1 30 Class WirelessSensorNetwork Wireless Sensor Network Encapsulates the first layer of packet handling from a WSN Declaration public abstract class WirelessSensorNetwork extends java lang Object implements net tinyos message MessageListener All known subclasses RealWirelessSensorNetwork in A 1 25 page 111 DummyWirelessSensorNet work in A 1 14 page 97 Field summary handlers All first level packet handlers i e motes Known motes in the network Constructor summary WirelessSensorNetwork Default constructor Method summary addGlobalHandler SampleHandler Add Global Handler addHandler int int SampleHandler Add Handler messageReceived int Message Message Received Fields e protected java util Vector handlers All first level packet handlers i e loggers e protected
39. e 4 10 Mica2 and sensor board block diagram age probe wires The voltage probe wires are connected to the signals of interest in the car A block diagram of the Mica2 with the sensor board is shown in Figure 4 10 The final result with green wires forming jumpers is shown in Figure 4 11 The resistors are 1 metal film and the capacitor is a 6 3V tantalum The leads for the sensor board are a pair of 18AWG wires with 0 250 insulated male disconnects crimped onto the ends with their other ends soldered to the sensor board and strain relieved with 501b nylon monofilament Connecting the sensor board to a signal wire becomes a matter of crimping a Female T Tap disconnect onto the wire and slipping on the sensor board leads 32 Chapter 4 A Prototype aani aaa Q ajaj UDANG CROSSBOW ORTH Figure 4 11 Sensor Board Implementation 4 3 3 Mote Software The software for the motes was written in NesC for the TinyOS operating system The details of the code can be found in Appendix B which is the nesdoc output There are two main components the Diomedes Sensorboard and the Diomedes Application Diomedes Sensorboard The Diomedes Sensorboard was based at least philosophically on the stan dard SensorMts300 sensor board provided with TinyOS The component provides three Read lt uint16_t gt interfaces called Light Temp and ADC2 Depending on which read command is called the software enables the appropriate sen
40. e Software 000000 ee eee 4 2 3 User Interface Software ace ea ko be ada de 4 3 Implementation Pe me ee he viii iv vi xi xii D 10 10 10 11 13 15 17 17 20 20 24 25 29 A331 Introduction 24 e Beg OR te BS be nS GS eee el x 43 2 Sensor Board 4 3 3 Mote Software 43 4 User Interface 0 0 2000000008 8 5 System Evaluation 5 1 Criteria tor Evaluation oe 2 88 amp bocce SAGA Be BAS 5 2 Evaluation Methodology a A A 5 2 1 Calibration 22 los eb We eo A 5 2 2 Data Collection o 5 2 3 Data Processing and Evaluation 5 2 4 Qualitative Evaluation 3 e a a e A A A 5 3 1 Effective Throughput pipa e Se ode de 5 3 2 Reception Rate Gos AGERE ra Sew ee es 5 3 3 Measurement Resolution 33 4 Mntegration Jete AAA we be se ey a a 5 3 5 Customizability a ds ada a eK e a EA Cosh S25 ts Are ee ete She wots Badr ce eh el a 5 3 7 Non intrusiveness 0 0 a eee eee F4 Analysis GoGo as Jara i gt tae RAE eo a ee oe a ak a 5 4 1 What worked 5 4 2 What didn t work 5 4 3 Generalization oo a a a 00084 6 Related Work OI OVER ee a 6 2 Existing Diagnostics Solutions pi is a 6 3 Related Research 7 Conclusion and Potential Elaboration Gel CONCLUSION a 2 a AA Sloe ta o 7 2 Potential Elaboration 0 0 0 0000004 Bibliography Appendi
41. e high level the solution must meet the requirements from Section 2 2 it must be integrated customizable low cost and non intrusive Beyond these high level requirements however lie the requirements on this particular solution in order to make it a viable system These requirements can be divided by the component to which they pertain they are either requirements for the wireless sensing nodes or for the base station The wireless sensing nodes need to collect data samples and forward them to the base station The nodes should have a sensor package which allows them to measure environmental parameters without the support of existing sensors They must also be able to clip onto existing wires in the vehicle reading the voltage present without damaging themselves or the car In order to be non intrusive they must also be small and light and ought to be battery powered with a reasonable battery life Finally they must be capable of completing all of their tasks while inside a vehicle The base station needs to receive samples from all of the wireless sensing nodes in the car and then either display those samples in real time or log them to secondary storage for post processing In the case where samples are being displayed the base station would need a display device and a visual represen 15 Chapter 3 A Solution tation of each of the data sources either as simple digital display or some more complex graphical representation In
42. e timestamp of the receipt in milliseconds since the epoch e get TimestampInS public long getTimestampInS gt Description Get Timestamp in Seconds Returns The timestamp of the receipt in seconds since the epoch e getUnits public java lang String getUnits Description Get Units Returns a String containing the units of the value suitable for concatenation to the end of the value in a display Returns The abbreviation of the value s engineering units e g V km e getUnitsName public java lang String getUnitsName Description Get Units Name Returns the full name of the units of the value Returns The full name of the value s engineering units e g Volts Kilometers e get Value public double getValue Description Get Value Converts the raw sample value into Engineering Units with the help of the associated Channel Returns The value of the sample in engineering units e setChannel public void setChannel Channel c Description Set Channel Associates a Channel with the Sample allowing EU conversions 115 Appendix A javadoc Parameters x c The Channel to associate e toLog public java lang String toLog Description To Log Returns The Sample as a logfile line A 1 27 Class TempChannel Temperature Channel Converts raw binary readings from on board temper ature sensor into degrees Celciu
43. eceipt and processing of messages from the distributed sensors For this reason most of the classes in the design of the software implement a simple interface called SampleHander which defines a method called handleSample as shown in 25 Chapter 4 A Prototype pd NE DiomedesSB AAN POS INES E Figure 4 6 Mote Software Architecture the high level Class Diagram Figure 4 8 This diagram also elucidates the has a relationships present in the system which will be discussed shortly The unmodified TinyOS class MoteIF handles all of the communication with the base station mote To abstract the concept of the network and its compo nents we introduce classes WirelessSensorNetwork Mote and Channel The user interface also uses classes SampleLogger and Gauge Class WirelessSensorNetwork receives the incoming DiomedesTLMMsg mes sages from MotelIF Its job is threefold First it must decode the packet into a Sample of the appropriate type based upon what kind of data it contains Next it must dispatch the Sample to the proper Mote class Finally it must pass the Sample to any other registered handlers typically implementers of the SampleLogger interface which can log the samples to file among other projected uses 26 Chapter 4 A Prototype DiomedesA DiomedesSB MoteRadio l 1 1 start ADC read start conversion Timer Fired ADC read done Figure 4
44. ensors and a base station mote was not a problem They also have sufficient on board memory and processing capability to collect samples and transmit them via their built in radios in a light compact package Also Crossbow makes a prototyping board MDA100 that connects to the Mica2 s expansion port This made it easy to experiment with our analog signal condi tioning The motes are battery powered as well making them better suited for a testing environment 18 Chapter 4 A Prototype The Mica2 motes were not without their downsides The Mica2 uses a 900MHz radio instead of the aforementioned 2 4GHz ZigBee radios In this sense we sacrifice some accuracy in our prototype With ZigBee s additional protocol features and its wideband radio it is expected that replacing our pro totypes with ones using ZigBee radios would have yielded better results in terms of reception rate but slightly worse results in terms of range 29 The software for the prototype system consists of three main components software running on the sensor modes software running on the base station mote and software running on the user interface laptop All of the sensor node software is written on top of TinyOS 11 a lightweight event driven operating system specifically designed for use with sensor networks Components are writ ten in a domain specific version of the C programming language called NesC and compiled with TinyOS to create the device images The
45. ere appropriate They are also very inexpensive Like the original equipment manufacturer gauge clusters these gauges install permanently in the vehicle making integration a given Still they too have their downside The installation of these gauges can be a difficult undertaking requiring the routing of wires through inaccessible paths They also often require modification of the vehicle whether by perforating the firewall or installing mounting hardware and thus are not non intrusive None of these solutions fully solves the problem stated in Section 2 2 6 3 Related Research Recent research in wireless sensor networks covers significant breadth 1 from the early discussions of TinyOS 11 to discussions of habitat monitoring 18 19 and acoustic target tracking 38 Still there is little to find about the empiri 61 Chapter 6 Related Work cal application of these low power wirelessly networked devices in automotive applications This is not the first paper to make a case for using wireless networking in automotive applications with many applications involving inter vehicular com munications One such application is Internet connectivity 6 4 Also the idea of vehicular sensor networks is not new Still work on the subject has often fo cussed on the large scale inter vehicle sensor networks 12 31 without applica tion of wireless sensor networks within the vehicle Even connecting diagnostics data to the wide area h
46. ey are not sufficient for higher rate data or for critical parameters For example under normal operation the throttle pedal position sensor proves difficult to analyze at 8Hz The standard rule of thumb says that sampling ought to be done at twice the frequency of the signal being sampled Parameters such as temperature change very slowly so a couple of samples per second would be sufficient but one could imagine that the position of a pedal under one s foot could have much higher frequency components to its position An order of magnitude faster sam 59 Chapter 5 System Evaluation pling infeasible with this system s sample and send scheme would be required to better understand signals like this with higher frequency components Finally the fuel level sensor proved to be something of a mystery When the car started up our measured value could be transformed into a reliable reflection of the true fuel level gauge However several minutes into running the system the readings from the fuel level sensor grew erratic and difficult to fathom Again higher rate sampling may reveal the problem with our readings but for now this sensor is only useful for the packet reception statistics not as a reflection of the fuel level 5 4 3 Generalization Now that this particular prototype has been evaluated how will these results generalize into other instantiations We expect that with the use of commodity components and expandable te
47. ey lost Are they corrupted Packets which are lost might be able to be resent whereas corruption of packets might be hard to detect without more sophisticated packet integrity check mechanisms 5 2 Evaluation Methodology 5 2 1 Calibration Before data in engineering units could be collected from the sensors each sensor had to be calibrated When the calibration was complete the conversions between raw ADC readings DN to engineering units EU were placed in the user interface classes corresponding to each sensor The two built in sensors on the MDA100 have generic calibration profiles packaged with them For the thermistor temperature sensor Equation 5 1 con verts from a raw ADC reading DN to Temperature in Kelvins This is taken directly from the datasheet 23 38 Chapter 5 System Evaluation 1 EU 0 001010024 0 000242127 In Rin 0 000000146 In Rep 9 5 1 10 000 1023 DN where Rihr PN The light sensor measures a simple intensity 0 100 and the conversion is shown in Equation 5 2 EU 100 DN 1023 5 2 The engine coolant sensor was calibrated by recording raw readings from startup until the engine reached operating temperature mid way on the car s temperature gauge The raw data were then scaled so that they corresponded to the appropriate gauge readings with the bottom of the gauge being 0 and the top of the gauge being 100 The final conversion is shown in Equatio
48. f 45 Chapter 5 System Evaluation the time and the Accelerator Pedal mote achieves 8 or less readings per second 10 of the time Another way of looking at this is that 90 of the time the Coolant Temperature mote achieves rates higher than 6 readings per second the Fuel Level mote achieves rates of higher than 10 packets per second and the Accelerator Pedal mote achieves more than 8 readings per second 100 Coolant Temperature Throttle Pedal Position e Fuel Level seer 80 60 CDF 40 20 Throughput samples second Figure 5 2 Effective Throughput CDF Since all three motes are running the same software and all had new batteries installed prior to the test the variation in rates must be explained by something environmental by either the relative positioning of the motes to the base station 46 Chapter 5 System Evaluation by the amount of occluding material or simply by the activity of the motes radio protocol We can rule out the simple explanation of the amount of occluding material because the Temperature and Pedal motes were collocated yet they showed different throughputs Physical orientation could have been a factor Previous studies have shown that sensor network mote radios are very sensitive to placement and orientation 39 5 3 2 Reception Rate The CDF for reception rate for an hour long run of the system is shown in Figure 5 3 Each line represents a single mote
49. g timer event then the same message is sent again until it succeeds 4 3 4 User Interface The user interface software is built in Java making use of the existing java packages net tinyos for connecting to the base station mote through a serial port and getting its messages The graphical user interface code is written using Java Swing The details of the code can be found in Appendix A the javadoc of the code The classes in the application directly mirror those laid out in Section 4 2 3 Every message received from the MoteIF is converted to a Sample and passed through the hierarchy of SampleHandlers If at any time the Sample object is deemed to be invalid a WSNException is thrown and its handling is stopped The UI of the application provides gauges and controls as shown in Fig ure 4 12 The gauges are subclasses of the class Gauge which extend the standard Swing class javax swing JPanel Most of them are images with transparent portions wherein simple vector art can be drawn to indicate the current value of the mote s channel Gauges which look like thermometers car dial gauges car fuel gauges simple digital readouts and stripcharts have been constructed 39 Chapter 4 A Prototype The controls on the application serve a few additional functions They allow logging to be started and stopped When logging is started a standard Java file dialog asks the user to choose a location for the logfile After that until the S
50. gh the automotive indus try has fully embraced the need for the mass customization of their vehicles this trend does not extend to diagnostics displays This leaves an open niche for third party solutions Unfortunately the third party solutions tend to be targeted at specific subsets of the problem and do not work in all cases Our solution employs a wireless sensor network which results in a system which is integrated customizable low cost and non intrusive Wireless sensing nodes are small and are located close to the signals they are measuring A base station ageregates the readings from the sensing nodes and then logs and displays them vi We describe the design and implementation of the system and evaluate it show ing that ultimately it is a feasible solution for low rate non critical automotive diagnostics vil Contents Acknowledgements Abstract List of Figures List of Tables 1 Introduction 2 The State of the Art 2 1 Background 1 OR ces A 222 Te Problem 80 30 dee see ap Aen deen a ee ee ed 3 A Solution 3L Architectures saoe Hand amp Bin OS Reha e e p a Sh cart 3 1 1 Overview 312 USTICA I N A A a ee ee A 32 Challenges A A eta Se ena Sa he cele Gok cw 3 3 Requirements O tet Mee hs ONS 5 ee 4 A Prototype 4 1 Introduction ners 23 0 ne Bie ace ee OR ae a AS MIE ic ans Ih ne Sy i vs eal ick Bnei he a ee dae e 4 2 1 Sensor Package e aur ala ee amp Wow ees Aa A SR 4 2 2 Mot
51. he mote can be connected to the tap and secured in place Because the motes are small they can easily be placed anywhere on the car With no wires to route the mote is now turned on and the data immediately stream to the laptop whether it be outside of the car or in our test case on the passenger seat Right now the customization of the system requires changing the source code in several places but it has been abstracted to be straightforward The infras tructure also exists for the front end software to detect new motes in the system and to automatically allow the user to customize its data channel s 5 3 6 Cost Much of the work on sensor networks does so with the assumption that in the future the sensor nodes will be ubiquitous and inexpensive 40 30 Although each node in this prototype cost about 250 in materials per unit it is projected that sensor nodes could cost less than 1 per node In this future this whole system will be very inexpensive to build The motes are off the shelf with min imal analog front ends consisting of a few passive components Combine this 52 Chapter 5 System Evaluation inexpensive mote hardware with an equally inexpensive serial packet forwarding base station already a mainstay of sensor network design and the total hardware cost is projected to be minimal 5 3 7 Non intrusiveness There are two aspects of non intrusiveness worth evaluating physical and electrical Physically the
52. hich listens on the serial port for active messages from the TinyOS Basestation node Declaration public class RealWirelessSensorNetwork extends org ucsb mayhem diomedes WirelessSensorNetwork in A 1 30 page 119 111 Appendix A javadoc Constructor summary Real WirelessSensor Network Constructors e RealWirelessSensor Network public RealWirelessSensorNetwork A 1 26 Class Sample Sample Encapsulates message data receive timestamp and the information necessary to convert the message s sample to engineering units Declaration public abstract class Sample extends java lang Object All known subclasses TempSample in A 1 29 page 118 LightSample in A 1 22 page 108 ADCSam ple in A 1 5 page 79 Field summary chan The associate Channel for the purposes of EU conversion m The original Message object timestamp Time of sample receipt at the computer Constructor summary Sample DiomedesTLMMsg Constructor Method summary getFileHeader Get File Header getFunction Get Function getPacketNumber Get Packet Number getRawSample Get Raw Sample getSource Get Source 112 Appendix A javadoc getTimestamp Get Timestamp get TimestampInMillis Get Timestamp in Milliseconds get TimestampInS Get Timestamp in Seconds getUnits Get Units get UnitsName Get Units Name get Value Get Value setChannel Channel Set Channel toLog To Log Fields e protected java util C
53. ication it must be possible to clamp it onto a car take measurements remove the system and have little in the way of evidence that it had ever been 12 Chapter 3 A Solution present the car should continue to perform as if the system is not and has never been attached Sensor nodes are small and light and fulfill this aim well Also since they are wireless there is no need to carefully route wires between areas of the car Ultimately it is the wires characteristic to most automotive diagnostics systems that limit the non intrusiveness of these systems We discuss related research in Section 6 3 3 2 Challenges Although inter vehicular networking has been studied 12 31 and intra vehicular networking has been examined using Bluetooth 24 10 28 17 there has been little empirical work with ZigBee and other low power wireless radios in automotive applications Because of this there are expected to be several challenges to evaluate and overcome For one the environment in a car is electromagnetically noisy due in part to the presence of high voltage high frequency signals such as those running through the plug wires Moreover line of sight between wireless sensor nodes in a typical application is often broken by large sheets of steel More than in other applications of low power radios it is expected that this application will experience significant interference and consequently packet loss Thus reliabil 13
54. int Component Draws the gauge and renders a needle pointing to the appropriate place on the gauge A 1 18 Class FuelPumpLevelChannel Fuel Pump Level Channel Channel which converts the raw samples into a reading of fuel level on a MINI Cooper S Declaration public class FuelPumpLevelChannel extends org ucsb mayhem diomedes ADCChannel in A 1 4 page 77 Constructor summary FuelPumpLevelChannel Default Constructor Method summary convert Units Sample Convert Units Constructors e FuelPumpLevelChannel public FuelPumpLevelChannel Description Default Constructor Constructs a fuel level channel assuming R1 and R2 values consistent measurements in the current system 102 Appendix A javadoc Methods e convert Units public double convertUnits Sample samp Description Convert Units Convert from raw samples to a 0 100 value meant to mirror the operation of the car s on board fuel gauge Parameters samp Sample to convert Returns fuel gauge reading 0 100 A 1 19 Class Gauge Gauge Abstraction of a gauge which embodies a sample handling object and a GUI display Declaration public abstract class Gauge extends javax swing J Panel implements SampleHandler All known subclasses TempGauge in A 1 28 page 117 GraphGauge in A 1 20 page 106 FuelGauge in A 1 17 page 101 DigitalGauge in A 1 11 page 87 DialGauge in A 1 10 page 86 Field summary scale
55. ion 5 3 2 Another parameter of the system which is worth evaluating is the resolution of the measurements This can be calculated directly and is covered in Section 5 3 3 5 2 4 Qualitative Evaluation Other criteria cannot be quantitatively evaluated The integration for ex ample is a purely qualitative measurement It can be described and compared 44 Chapter 5 System Evaluation with alternatives but the decision must be left up to the reader as to whether these criteria are met We must qualitatively examine the parameters set forth in the thesis question e integration can the system be used in the service bay as easily as it can be used in the field or even on the road e customizability are a diverse range of modes of operation supported which can support conceivable automotive applications e cost is the final system relatively inexpensive e non intrusiveness does the presence of the system affect operation of the vehicle or does the system leave any evidence of its installation 5 3 Results 5 3 1 Effective Throughput The CDF of the effective throughput for an hour long run of the system is shown in Figure 5 2 Each line represents a single mote in the system The graph is fairly straightforward For example for the Coolant Temperature mote 10 of the time the system achieves 6 or less readings per second In contrast the Fuel Level mote achieves roughly 10 or less readings per second 10 o
56. ketnum public static boolean isArray_packetnum Description Return whether the field packetnum is an array false e isArray_sample public static boolean isArray_sample Description Return whether the field sample is an array false 92 Appendix A javadoc e isArray_source public static boolean isArray_source Description Return whether the field source is an array false e isSigned_function public static boolean isSigned function Description Return whether the field function is signed false e isSigned_packetnum public static boolean isSigned packetnum Description Return whether the field packetnum is signed false e isSigned sample public static boolean isSigned_sample gt Description Return whether the field sample is signed false e isSigned_source public static boolean isSigned_source Description Return whether the field source is signed false e offset_function public static int offset_function gt Description Return the offset in bytes of the field function e offset_packetnum public static int offset_packetnum Description Return the offset in bytes of the field packetnum 93 Appendix A javadoc e offset_sample public static int offset_sample Description Return the offset in bytes of the field sample e offset_source public static int offset_source
57. l proportional to the amount of fuel in the tank which was the preferred outcome or it could be something entirely different The MINI has a two lobed gas tank equalized with a syphon pump between the two lobes 21 with two independent fuel level sensors It was as sumed that one of the sensors would typically read half of the total fuel in the vehicle So with two motes secured under the hood a mote sitting on the fuel pump under the rear seats and a laptop strapped securely into the passenger seat the car was driven and data was collected There were also data collection sessions wherein the motes were laid out at a workstation These typically provided baseline information giving an idea of what to expect from the in car experiments 42 Chapter 5 System Evaluation The particular data collection session used in the following evaluation took place over an hour of a variety of driving conditions It began at UC Santa Barbara went out to Cathedral Oaks Road east to Old San Marcos Road back down highway 154 to 101 and then back to campus This provided slow city traffic rough and twisty hills and relatively quick highway driving All three motes were programmed to collect and transmit data at a maximum rate of 20Hz 5 2 3 Data Processing and Evaluation The datafiles collected with the front end s logging facility were fed through a series of bash and awk scripts which rendered them down to statistics and graphs Par
58. lass Channel Channel Abstracts the concept of a data stream from a single mote Declaration public abstract class Channel extends java lang Object implements SampleHandler 79 Appendix A javadoc All known subclasses TempChannel in A 1 27 page 116 LightChannel in A 1 21 page 107 FuelPumpLevelChannel in A 1 18 page 102 EngineCoolantTempChannel in A 1 15 page 98 ADCChannel in A 1 4 page 77 AcceleratorPedalChannel in A 1 3 page 76 Field summary function handlers units unitsName Constructor summary Channel int Constructor Method summary addHandler SampleHandler Add Handler convert Units Sample Convert Units getFunction Get Function get Units Get Units getUnitsName Get Units Name handleSample Sample Handle Sample setUnits String Set Units setUnitsName String Set Units Name Fields e protected int function e protected java util Vector handlers e protected java lang String units e protected java lang String unitsName 80 Appendix A javadoc Constructors Channel public Channel int newfunc Description Constructor Creates a new Channel with the given function Parameters x newfunc The function that this Channel should handle Methods addHandler public void addHandler SampleHandler hand Description Add Handler Registers a Handler with the Channel Typically used with Gauges Parameters hand Handler to
59. letely acceptable Ultimately the solution and its prototype make strides towards filling the general purpose automotive diagnostics niche While this prototype represents an acceptable proof of concept there are certainly aspects which could be improved or elaborated upon In the next and final section we outline some of these aspects 65 Chapter 7 Conclusion and Potential Elaboration 7 2 Potential Elaboration There are many facets of this system which given additional resources would have been interesting to investigate These items would make for potential elab oration on the system Already mentioned additional work could be done in minimizing packet loss The addition of trivial retransmissions already greatly improved the per formance and more sophisticated retransmission mechanisms could do much to increase message reception rate at the expense of overall throughput Building the system using ZigBee radios should also yield better reception rates Also taking the system to its logical conclusion by allowing customization at run time would be a valuable exercise At present the code must be recompiled to support different data sources than the three experimental sensors Allowing a single mote to be used as a light temperature or voltage sensor with a fully customizable front end display would be a matter of taking advantage of mechanisms already available in the system framework but not exposed to the user A
60. lution temperature sensor 0 50 C 0 1 C light sensor 0 100 0 0978 engine coolant temperature sensor 0 100 0 0977 throttle pedal position sensor 0 100 0 309 fuel level sensor 0 100 0 0108 Table 5 1 Measurement ranges and resolutions the measurement Rather since the curve is nominally valid over the range 0 C to 50 C it is possible to calculate the average resolution by determining the ADC reading corresponding to 0 C and 50 C and calculating the slope of the linear fit between those points The result is also shown in Table 5 1 5 3 4 Integration When examining the criterion of integration it is necessary to consider how easily the system translates from operation in a static deployment e g in a garage to another location or even on the road in between Many existing systems fail this criterion because they are designed specifically to be used on an immobile vehicle This system was designed with integration in mind and proves successful in this regard Because all of the components of the system are modular and relatively decoupled it proved simple to take the instrumented car on the road The only additional work required was to secure the motes to their locations using in this case 50 lb test fishing line and the laptop to the 50 Chapter 5 System Evaluation passenger seat Beyond those minor fixes the system operated identically in the garage as it did on the road 5 3 5 Customizability An
61. mni cs ucsb edu 123 Appendix B nesdoc Uses Oo Oo interface Timer lt TMilli gt as WarmUpTimer interface Read lt uint16_t gt as GeneralADC interface GenerallI0 as TempPin interface Generall0 as LightPin interface TaskBasic as getSample interface Read lt uint16_t gt as SensorADC Provides interface ResourceConfigure as ADC2ResourceConfig interface ResourceConfigure as SensorADCResourceConfig interface Atm128AdcConfig as SensorADCAtm128AdcConfig interface Atm128AdcConfig as ADC2Atm128AdcConfig interface Read lt uint16_t gt as ADC2 interface Read lt uint16_t gt as Light interface Read lt uint16_t gt as Temp interface Init B 2 2 tos sensorboards diomedessb DiomedesSBC Modified to work with the temp sensor on an MTS series board Author Erik Peterson Provides interface Read lt uint16_t gt as Temp interface Init interface Read lt uint16_t gt as ADC2 interface Read lt uint16_t gt as Light 124
62. n 5 3 EU 65 820313 0 09765625 DN 5 3 The throttle pedal position sensor was calibrated by taking a reading with the pedal untouched and then taking a reading with the pedal on the floor These values were scaled to read 0 to 100 with the conversion shown in Equation 5 4 39 Chapter 5 System Evaluation EU 0 30864198 DN 22 839506 5 4 Finally the fuel level sensor was calibrated by taking a reading at full gas tank and then taking a reading at half gas tank scaling these values to read from 0 fuel to 100 fuel The final conversion is shown in Equation 5 5 EU 0 01082908 DN 5 5 While the units of throttle pedal position calibration are percents which is appropriate for a throttle value the other two sensors could only be decoded into units of some arbitrary range 0 100 was chosen not their true engineering units i e gallons for fuel degrees Fahrenheit for coolant temperature This is ultimately acceptable since the goal is to mirror the physical gauges and they are unit less 5 2 2 Data Collection Once the system was complete it had to be tested in a real data collec tion scenario A typical data collection experiment involves clamping three of the motes into the test car a 2004 MINI Cooper S at interesting test points strapping a laptop into the passenger seat Figure 5 1 and then driving around Santa Barbara for an hour 40 Chapter 5 System Evaluation
63. newfunction The function of the data to generate x freq The frequency to generate the data wsn The associated WSN Methods e run public void run Description Run Sleep based on the frequency and then wake up and generate some data A 1 14 Class Dummy WirelessSensor Network Dummy Wireless Sensor Network A dummy wsn which consists of three dummy motes generating data 97 Appendix A javadoc Declaration public class Dummy WirelessSensor Network extends org ucsb mayhem diomedes WirelessSensorNetwork in A 1 30 page 119 Constructor summary Dummy WirelessSensorNetwork Default Constructor Constructors e Dummy WirelessSensor Network public DummyWirelessSensorNetwork Description Default Constructor Create three dummy motes 1 2 3 all running at 10Hz A 1 15 Class EngineCoolantTempChannel Engine Coolant Temp Channel Channel which mirrors the operation of the MINI Cooper engine coolant temperature gauge Declaration public class EngineCoolantTempChannel extends org ucsb mayhem diomedes ADCChannel in A 1 4 page 77 Constructor summary EngineCoolantTempChannel Default Constructor Method summary convert Units Sample Convert Units Constructors e EngineCoolantTempChannel public EngineCoolantTempChannel gt 98 Appendix A javadoc Description Default Constructor Constructs an Engine Coolant Temperature Channel using the R1 and R2
64. no Real Starbucks Corner House Coffee in Los Olivos Mayhem Lab 1 0 Mayhem Lab 2 0 and Jalama House for giving me a place to sit and drink caffeinated beverages and work This document was prepared in BIFXusing version 3 1 of the ucthesis class by Daniel Gildea improved for UCSB usage by Mathias K lsch The PT X Companion by Mittelbach and Goossens was infinitely helpful The java doc appendix was generated using the TeXDoclet javadoc doclet originally written by Gregg Wonderly revised by XO Software and then revised into the form which I used by Stefan Marx The nesdoc documentation was created by a tool of my own sinister design from the XML produced by nesdoc iv Diagrams were produced in Omnigraffle Oh and thanks to my MINI Cooper Bertram for putting up with all of the poking and prodding with minimal complaint Abstract DIOMEDES An integrated automotive diagnostics system that is customizable low cost and non intrusive built on a wireless sensor network Erik Olin Peterson All persons who interact with a vehicle e g drivers mechanics require a unique set of data about its operation diagnostics data Drivers for example need to know that their cars are healthy and that they are not currently break ing any traffic laws mechanics on the other hand need to know the current operational state of numerous components in the car as well as a history of the car s performance in order to do their jobs Althou
65. nother often discussed addition to the system would be driving physical gauges with readings from the wireless sensors The idea would be to have a general purpose gauge mounted on the car s dashboard but to have its input 66 Chapter 7 Conclusion and Potential Elaboration connected to the output of a computer based voltage output card digital to analog board This would have the advantage of being able integrate the system more cleanly into a car while still supporting the full customization of the totally software display system A common question when pitching this system as a valid on the road data collection scheme is how security is handled There are currently no measures taken to segregate packets from two nearby instances of the system There is also no protection against sniffers collecting data about the system while it operates In the future sensor nodes should be paired with base stations so that base stations are able to filter out messages destined for them Finally the hardware could be made more robust Adding an external ADC could yield significantly higher measurement resolution and having the readings referenced to a precision voltage reference instead of the variable battery volt age would increase repeatability of measurements The quality of the passive components could also be increased which would yield less effects from temper ature swings and varying signal frequencies All of these efforts would help
66. oller There was no reason to believe that this would not be sufficient It would be possible in the future to purchase Zener diodes with more agreeable leakage characteristics The capacitors also caused issues The original construction of the sensor board used 3 3uF electrolytic capacitors assuming a sampling rate of 10Hz As will be shown in the Section 5 3 1 the target sampling rate of 10Hz was not always met making this capacitor slightly undersized The 3 3uF electrolytic capacitors were replaced with 22uF tantalum capacitors The change in capac itor type was necessary because larger electrolytic capacitors would not have fit easily on the board tantalum capacitors are significantly smaller in footprint The circuit was constructed on top of a Crossbow MDA100 prototyping sen sor board The board provides built in temperature and light sensors both connected to the ADC1 pin on the microcontroller Each of these built in sen sors has a general purpose digital input output GPIO pin used to enable and disable it The MDA100 also gives a break out panel giving solder points corre sponding to most of the pins on the expansion module interface including the needed ADC2 pin where we connect our signal conditioning and arbitrary volt 31 Chapter 4 A Prototype MDA100 Sensor Board Mica2 Photocell probe Conditioning DT OS rr gt A 1 l digital control signal analog signal signal ground Figur
67. on of wireless sensor nodes collecting data from the car The sensor network is arranged in a static star topology surrounding a central base station which aggregates the data The base station also provides display and logging functionality Figure 3 1 shows the architecture The diagram illustrates a couple of im portant aspects of the system First the wireless sensing nodes are scattered around the car as close as possible to the signals which they are measuring re sulting in no wires more than a few inches long Also the base station is shown outside of the car to emphasize the flexibility of the architecture Depending 10 Chapter 3 A Solution z z i Wireless sensing node O Base Station i d i O i pS Legend I I I N SUV Figure 3 1 Solution Architecture upon the need for the system the base station could be a built in carputer i e a computer built into an automobile for a permanent installation or it could be a ruggedized laptop for a more temporary diagnostics system 3 1 2 Justification When approaching the architecture for a diagnostics system an initial ques tion is how to collect readings from disparate signals into a central place Tra ditionally this was done with long cables all connected to a central comput ing device Wires either had to be routed through barriers limiting the non intrusiveness of the system or routed externally to the car limiting the sy
68. other important criterion for this system was customizability The system needs to be capable of not only reading a variety of signals in the electrical system of the car but it needs to be capable of reading additional channels of data which the user might want to see Like any similar diagnostics system this one works well for connecting to existing signals The front end to the ADC can be configured through a minor hardware change sizing a resistor to read a variety of voltage ranges The series resistance of the front end also limits the current to the ADC input thus protecting the micro controller from out of range voltages The front end software can also be modified to perform conversions of these data into appropriate engineering units What this system also enables is the ability to read additional channels Currently the software of the motes can be configured to read from the built in temperature and light sensors all of the infrastructure exists to make these measurements In future revisions of the sensor board additional built in sensors could be added to further expand its customizability 51 Chapter 5 System Evaluation Without the wires of traditional diagnostics systems installing the motes becomes a simple prospect The most difficult aspect is finding the signal wire which is to be read This wire is then tapped with a t tap a small ubiquitous connector requiring only a pair of pliers Once the wire is tapped t
69. peti tion Harvard Business School Press 1993 J Polar D Silva A Fortunato L Almeida and C Dos Reis Filho Blue tooth sensor network for remote diagnostics in vehicles In 2003 IEEE In ternational Symposium on Industrial Electronics volume 1 pages 481 484 June 2003 J Polastre R Szewczyk and D Culler Telos enabling ultra low power wireless research In IPSN 05 Proceedings of the 4th international sym posium on Information processing in sensor networks page 48 Piscataway NJ USA 2005 IEEE Press J Rabaey J Ammer J L da Silva Jr and D Patel Picoradio Ad hoc wireless networking of ubiquitous low energy sensor monitor nodes In WVLSI 00 Proceedings of the IEEE Computer Society Annual Workshop on VLSI WVLSI 00 page 9 Washington DC USA 2000 IEEE Com puter Society H Sawant J Tan and Q Yang A sensor networked approach for intelli gent transportation systems In IROS 2004 Proceedings 2004 IEEE RSJ International Conference on Intelligent Robots and Systems 2004 pages 1796 1801 vol 2 October 2004 Scion http www scion com 70 Bibliography 33 34 35 36 37 40 Snap on http www snapondiag com K Srinivasan and P Levis Rssi is under appreciated In Proceedings of the Third Workshop on Embedded Networked Sensors EmNets 2006 2006 Toyota prius http www toyota com prius Volcano sensorweb http sensorwebs jpl nasa gov F von
70. r in A 1 7 page 83 A 1 3 Class AcceleratorPedalChannel Accelerator Pedal Channel Represents the data coming from the requested throttle position signal in a MINI Cooper S Declaration public class AcceleratorPedalChannel extends org ucsb mayhem diomedes ADCChannel in A 1 4 page 77 Constructor summary AcceleratorPedalChannel Default Constructor Method summary convert Units Sample Convert Units Constructors e AcceleratorPedalChannel public AcceleratorPedalChannel 76 Appendix A javadoc Description Default Constructor Constructs the channel with known R1 and R2 values as measured on the existing system Methods e convert Units public double convertUnits Sample samp Description Convert Units Converts from a raw sample to the position of the accelerator pedal Parameters x samp Sample to convert Returns Pedal Position 0 100 w 100 pedal to the metal A 1 4 Class ADCChannel ADC Channel Handles samples from ADC channels converting them to Volts based on the values of R1 and R2 resistor values in the circuit Declaration public class ADCChannel extends org ucsb mayhem diomedes Channel in A 1 6 page 79 All known subclasses FuelPumpLevelChannel in A 1 18 page 102 EngineCoolantTempChannel in A 1 15 page 98 AcceleratorPedalChannel in A 1 3 page 76 Constructor summary ADCChannel int Constructor TT Appendix A javadoc Me
71. rary locations to do both will require a more general measurement platform than is currently available It should also be able to work on a variety of vehicle models and model years It must be low cost making it appropriate for home users as well as skilled mechanics This requirement may seem at odds with the others but it is essential that the system provide some utility to home users if it is to be truly general in scope Perhaps most importantly it must be non intrusive The system should be capable of being attached to a vehicle of taking data and then of being removed Chapter 2 The State of the Art from the vehicle During data collection the operation of the vehicle should not be negatively impacted and afterwards there should be minimal evidence that the diagnostics system was ever installed This is easy to achieve with a system which does not directly interface with the vehicle but it becomes more difficult once electrical connections are made This also implies that the system s components are small enough to fit in spaces existing in the vehicle allowing all panels and doors to be left unmodified and safely closed during operation The range of existing diagnostics solutions is discussed in Section 6 2 Chap ter 3 discusses our solution to this problem Chapter 3 A Solution 3 1 Architecture 3 1 1 Overview The basic notion of this solution is to build an automotive diagnostics system utilizing a collecti
72. rd user interface of the vehicle Unfortunately options such as these are typically expensive for the end user They also fail to meet the full customizability requirement restricting the user to a small set of predefined data sources often only displaying one at a time Another class of diagnostics solutions involves the standard On board Di agnostics II OBD II port installed on all production automobiles since the mid 1990 s 25 The OBD II port gives access to a selection of data sources a standard set of fault codes and the standard on board data busses These data busses such as the Controller Area Network Bus CANbus or ISO 11898 1 15 or the K bus ISO 9141 14 provide digital interfaces between peripherals and the central computer of a car Companies such as AutoTap 25 and Snap On 33 market products which connect to the OBD II port and provide a display of engine parameters and fault codes These devices are very easy to use and can 59 Chapter 6 Related Work often operate while the vehicle is driving making them well integrated Their prices are reasonable They are also completely non intrusive since they plug into existing ports on the vehicles made expressly for this purpose Again though they fail to meet the customizability requirement in that they can only read data sources which have been predetermined They can read engine coolant tempera ture for example but not the temperature in the undercarriage nex
73. rdware implementation typically provides a disconnect from the ideals of hardware design Where in design it is possible to pick any resistor value desired and have it be exact in reality there are only very particular resistor values available and those with tolerances upwards of 10 20 The closest resistor value available to the ideal 500 R resistor is a 49 9K 2 resistor To compensate R had to be sized as in Table 4 2 in order to achieve the desired voltage division maximum Vrp Ri 3 0V 00 5 0V 34KQ 6 0V 49 9K0 12 0V 150KQ 20 0V 280K 0 Table 4 2 Sizing R of the ADC front end circuit actual values All of these resistances take into account the tolerance of 1 in the resistance of metal film resistors since we would prefer to have the maximum voltage across Ry be less than 3 0V as opposed to greater than 3 0V This translates into larger resistances than would ideally be required The Zener diodes also proved to be a problem They were sized to have a 3 0V breakdown voltage but they appeared to be flowing too much current at lower voltages affecting the ADC reading It was determined that the Zener 30 Chapter 4 A Prototype diodes had leakage current at lower voltages which rivaled the typical current flowing through the circuit This resulted in hugely affected readings The only solution was to remove the Zener diodes and rely on the current limiting of the resistors to protect the microcontr
74. roperly size C4 in order that our low pass filter s cutoff frequency can be properly adjusted The Nyquist frequency of our 10Hz sample rate is 5Hz Thus we want to size the filter such that the cutoff frequency is less than or equal to 5Hz This ensures that we are able to sample the highest frequencies Test Point R1 ADC2 R2 Sensor Node Ground Car Ground 22 Chapter 4 A Prototype which pass through our filter So given the relation of cutoff frequency in terms of R and C 1 A H 4 4 f 2r RC Soulg sa We can solve for C ETE 4 5 107R In this case R is equal to the equivalent resistance of R parallel to R which is 20 0002 assuming R 33 333Q for a voltage range of 0 5V across Vrp So 1 Cw pos ee 2 1 6 Z 107 20 0002 58 C gt 159uF 4 7 Finally we must protect the mote from unexpectedly large voltages Al though the resistors are large enough that reasonably large voltages would not pull sufficient current to damage the microcontroller as an added protective measure a 3 0V Zener diode is placed across Ra Figure 4 5 2 Analog design tips from electronics minded colleagues James and Brian were instrumental in getting to this point in the sensor package design 23 Chapter 4 A Prototype Test Point O Em Tak ADC2 R2 c1 tO Sensor Node Ground O Car Ground Figure 4 4 ADC2 signal conditioning w Filter 4 2 2 Mote Software The mo
75. rs x newid The ID of the Mote to construct e Mote public Mote int newid java lang String newname Description Constructor ID and Name Constructs a Mote using both the supplied ID and name Parameters x newid The ID of the Mote to construct newname The explicit name to assign to the Mote Methods e addHandler public void addHandler int function SampleHandler hand Description Add Handler Registers a handler to this Mote on the given function Typically for a Channel Parameters x function The channel to register the handler to defined in Constants java 110 Appendix A javadoc hand The handler to register See also Constants java e getID public int getID gt Description Get ID Returns the ID of this Mote Returns The ID of this Mote e getName public java lang String getName Description Get Name Returns the name of this Mote Returns The name of this Mote e handleSample public void handleSample Sample s throws org ucsb mayhem diomedes WSNException Description Handle Sample Routes the Sample to the appropriate registered Channel Parameters x s The Sample to handle Throws org ucsb mayhem diomedes WSNException If the channel cor responding to the Sample is not found A 1 25 Class RealWirelessSensorNetwork Real Wireless Sensor Network Wireless Sensor Network w
76. running sensor networks in much more extreme environments e g volcanos 36 so we do not anticipate this being a problem 57 Chapter 6 Related Work 6 1 Overview This chapter discusses work related to this thesis in several fields Related to the thesis question are current commercial automotive diagnostics systems as well as research in the realms of wireless sensor networks wireless networking in vehicles and wireless automotive diagnostics systems 6 2 Existing Diagnostics Solutions Numerous products have been developed to fill the need for diagnostics data They can be broken into the rough categories of OEM offerings on board di agnostics readers wired clamp on devices and after market gauges As we will show the offerings tend to be targeted towards a particular need and no indi vidual solution fills all needs 58 Chapter 6 Related Work Original equipment manufacturers have made initial strides towards cus tomizable diagnostics for car owners Aside from the standard cluster of gauges available on most cars manufacturers typically offer additional on board read outs These can range from simple offerings like additional gauge clusters and single multifunction LED displays to the elaborate systems employed in models like the aforementioned Toyota Prius 35 These options are very integrated in that they are permanent components in the car and they are very easy to use as they blend into the standa
77. s Declaration public class TempChannel extends org ucsb mayhem diomedes Channel in A 1 6 page 79 Constructor summary TempChannel Default Constructor Method summary convert Units Sample Convert Units Constructors e TempChannel public TempChannel Description Default Constructor 116 Appendix A javadoc Methods e convert Units public double convertUnits Sample samp Description Convert Units Converts a sample into Celcius based on the conver sion curve found in the Crossbow documentation Parameters x samp Sample to convert Returns sample in degrees Celcius A 1 28 Class TempGauge Temperature Gauge Temperature gauge consisting of a thermometer which displays the value with the level of a red indication fluid Declaration public class TempGauge extends org ucsb mayhem diomedes Gauge in A 1 19 page 103 Constructor summary TempGauge boolean Constructor Method summary handleSample Sample Handle Sample paint Component Graphics Paint Component Constructors e TempGauge public TempGauge boolean floating Description Constructor Sets the size loads the overlay image initializes the container and then spawns the floating frame if desired Parameters 117 Appendix A javadoc floating Whether to launch the gauge as floating Methods e handleSample public void handleSample Sample samp throws org ucsb mayhem
78. s as a packet forwarder It also runs a Java application which provides graphical displays of the data as well as data logging capabilities The prototype is built and exercised in a real world scenario The data logs are reduced to statistics which are then evaluated We also analyze the qualitative aspects of the system Finally we discuss which aspects of the system meet specifications such as its integration and non intrusiveness and give ideas for how to improve other aspects such as the overall packet reception rate and the customizability We also review a body of related work including other commercial diagnostics systems wireless networking in cars and general work on sensor networks The rest of this thesis is structured as follows Chapter 2 states the prob lem being solved and gives some background on existing commercial solutions Chapter 3 presents a solution to the problem its justification the challenges inherent in solving the problem and then the requirements for any implementa tion of the solution to meet Chapter 4 describes the design and implementation Chapter 1 Introduction of the prototype used to show the feasibility of this solution Chapter 5 gives an evaluation of the prototype with respect to the problem Chapter 6 reviews a body of related work Finally conclusions and potential elaboration are covered in Chapter 7 Chapter 2 The State of the Art 2 1 Background All people who interact wi
79. s backing store with the given base offset and data length e DiomedesTLMMsg public DiomedesTLMMsg int data length gt Description Create a new DiomedesTLMMsg of the given data_length e DiomedesTLMMsg public DiomedesTLMMsg int data length int base offset Description Create a new Diomedes LMMsg with the given data length and base offset e DiomedesTLMMsg public DiomedesTLMMsg net tinyos message Message msg int base_offset Description Create a new DiomedesTLMMsg embedded in the given message at the given base offset e DiomedesTLMMsg public DiomedesTLMMsg net tinyos message Message msg int base_offset int data_length Description Create a new DiomedesTLMMsg embedded in the given message at the given base offset and length 91 Appendix A javadoc Methods e get_function public int get_function gt Description Return the value as a int of the field function e get_packetnum public int get_packetnum Description Return the value as a int of the field packetnum e get_sample public int get_sample Description Return the value as a int of the field sample e get_source public short get_source Description Return the value as a short of the field source e isArray_function public static boolean isArray_function gt Description Return whether the field function is an array false e isArray_pac
80. sensor Declaration public class LightSample extends org ucsb mayhem diomedes Sample in A 1 26 page 112 Constructor summary LightSample DiomedesTLMMsg Constructors e LightSample public LightSample DiomedesTLMMsg m A 1 23 Class LogfileFilter Declaration public class LogfileFilter extends javax swing filechooser FileFilter Constructor summary LogfileFilter 108 Appendix A javadoc Method summary accept File get Description getExtension File Constructors e LogfileFilter public LogfileFilter Methods e accept public abstract boolean accept java io File arg0 e getDescription public abstract java lang String getDescription e getExtension public java lang String getExtension java io File f A 1 24 Class Mote Mote Abstracts the concept of a mote from the sensor network Mainly used to organize channels and to funnel samples to them Declaration public class Mote extends java lang Object implements SampleHandler Constructor summary Mote int Constructor ID only Mote int String Constructor ID and Name 109 Appendix A javadoc Method summary addHandler int SampleHandler Add Handler getID Get ID getName Get Name handleSample Sample Handle Sample Constructors e Mote public Mote int newid Description Constructor ID only Constructs a Mote using only the ID The name of the mote defaults to the modelD Paramete
81. sor 33 Chapter 4 A Prototype waits for it to warm up starts the conversion and then when the conversion is done it posts the result in an event For ADC2 the act of enabling the sensor is trivial it basically ensures that the other sensors are disabled Temp and Light share the same ADC channel so it is necessary to enable the proper sensor This is done by setting the corresponding digital output pin on the microcontroller Port E pin 5 for the Light sensor Port C pin 0 for the Temp sensor Diomedes Application The Diomedes Application uses three Read lt uint16_t gt interfaces those cor responding to the interfaces provided by the Diomedes Sensorboard the AMSend interface the Timer lt TMilli gt interface and the PacketAcknowledgements in terface Once the software has initialized it starts a periodic timer 10Hz typical and goes to sleep When it receives a timer event if the previous packet has not been acknowledged it is retransmitted and the software goes to sleep Otherwise it calls read on the appropriate Read interface and goes to sleep When the software receives a readdone event it builds a message contain ing the data sample the mote s ID packet number an ever increasing counter and the type of data being sent Then an acknowledge for the message is re 34 Chapter 4 A Prototype quested and it is sent If the send ever fails or the message is not ACK d before the followin
82. stem s integration Making the system wireless adds significant flexibility 11 Chapter 3 A Solution Once wireless has been chosen as the medium of communication we must examine the available protocols Two prime choices are Bluetooth or low power radio protocols such as ZigBee Low power radios have numerous advantages over Bluetooth for large customizable deployments ZigBee networks can con tain more nodes they are typically more resilient and reliable and consume much less power 3 40 Automotive applications of these protocols have been suggested 24 even as a complete data cable replacement 8 but only in a specu lative fashion and with a fair amount of trepidation with respect to using them in safety critical instances The nodes are also projected to be inexpensive and tools exist to make them easier to program and less platform specific than if they were programmed directly in C or assembly The system can be expected to receive sufficient battery life for any reason able temporary application and more permanent applications could make use of the on board switched 12V available in a car Also the indoor interfer ence characteristics of Zigbee 9 13 and other sensor network specific low power radio standards make it an excellent choice for the cluttered and potentially electromagnetically noisy environment around a car s engine The system also aims to be non intrusive meaning that for a temporary appl
83. t to the fuel tank They are also not available on vehicles older than 1994 so a mechanic or tuner looking to operate on an older model car must find a different solution The third class of diagnostics options are wired clamp on devices These are general purpose diagnostics systems employing collections of cables that can be attached to arbitrary test points within the vehicle They come from companies such as Pico Technology 26 and Snap On 33 and are targeted mainly at auto mechanics These systems are relatively easy to use though they require more knowledge of the operation of the vehicle than other options They fail to meet the integration and non intrusive requirements as bundles of wires must be run to each test point a complicated and potentially impossible prospect They are also the most expensive of these options Last the customizability requirement is still not completely fulfilled Although these systems can read a large number of existing voltages within the car they cannot introduce new sensors out of the box 60 Chapter 6 Related Work Finally there are aftermarket gauges and gauge clusters perhaps most no tably those made by Auto Meter 2 These are additional gauges which are installed in the passenger compartment to monitor small numbers of parameters and are targeted at tuners These gauges are extremely customizable capable of measuring any conceivable signal in a car as well as adding additional sensors wh
84. t which displays the readings from a particular Channel It could be as simple as a text box showing the rapidly changing values or as complex as a graph of the previous data history or a graphical representation of a car s gauge The typical sequence of operations when a message is received from the sensor network is showing in Figure 4 9 If at any point in this sequence the sample is 28 Chapter 4 A Prototype MotelF WirelessSensorNetwork Mote Channel _ Gauge_ _ SampleLogger i i i i i i i i i messageReceived 1 l Hl handleSample i l handleSample i i fe handleSample l EIA lt m 1 1 1 1 1 i L L j l handleSample i A lt a h j 1 i 1 k H l i i 1 if 1 1 i Figure 4 9 Sensor network message handling Sequence Diagram found to be invalid e g impossible readings nonexistent channels or motes an exception is thrown and all processing on that sample is halted 4 3 Implementation 4 3 1 Introduction This section describes the physical construction of the custom software and hardware focusing especially on the places where the ideal assumptions of the design diverged from the reality of implementation 29 Chapter 4 A Prototype 4 3 2 Sensor Board The reality of ha
85. tartLogging public void startLogging java lang String fname Description Start Logging Starts logging to the filename given if the file exists Parameters fname File to log to e stopLogging public void stopLogging Description Stop Logging Close the current logfile e writeFileHeader public void writeFileHeader 100 Appendix A javadoc Description Write File Header Start the logfile with the file header A 1 17 Class FuelGauge Fuel Gauge Gauge meant to mirror the MINI Cooper S s fuel gauge Declaration public class FuelGauge extends org ucsb mayhem diomedes Gauge in A 1 19 page 103 Constructor summary FuelGauge boolean Constructor Method summary handleSample Sample Handle Sample paintComponent Graphics Paint Component Constructors e FuelGauge public FuelGauge boolean floating Description Constructor Constructs a Fuel Gauge either integrated or floating Parameters x floating Whether or not to detach the frame Methods e handleSample public void handleSample Sample samp throws org ucsb mayhem diomedes WSNException Description Handle Sample Stores the value of the sample and calls repaint O Parameters 101 Appendix A javadoc samp Sample to handle Throws x org ucsb mayhem diomedes WSNException e paint Component protected void paintComponent java awt Graphics g Description Pa
86. tched Methods e actionPerformed public void actionPerformed java awt event ActionEvent e Description Action Performed Handles the clear graph button e handleSample public void handleSample Sample samp throws org ucsb mayhem diomedes WSNException 106 Appendix A javadoc Description Handle Sample Adds the sample to the history array and fires off a repaint Parameters samp The sample to add to the graph Throws x org ucsb mayhem diomedes WSNException e paintComponent protected void paintComponent java awt Graphics g Description Paint Component Draw the graph based on the history array and the running max and min times A 1 21 Class LightChannel Light Channel Channel which handles onboard light sensor data Declaration public class LightChannel extends org ucsb mayhem diomedes Channel in A 1 6 page 79 Constructor summary Light Channel Method summary convert Units Sample Convert Units Constructors e LightChannel public LightChannel 107 Appendix A javadoc Methods e convert Units public double convertUnits Sample samp Description Convert Units Converts the raw binary reading into an intensity that is percenta of full scale Parameters x samp The sample to convert Returns light sensor reading 0 100 A 1 22 Class LightSample Light Sample A sample taken from an onboard light
87. te software consists of two custom components and several unmodi fied TinyOS components One of the custom components is the abstraction of the sensor board which provides management of the ADCs as well as any asso ciated hardware I O necessary The other is the main application DiomedesApp which must manage the timer coordinate ADC reads and initiate the sending of messages via the radio Both components run on top of the TinyOS operat ing system making use of its ADC and Radio abstractions among others The whole mote software architecture is shown in Figure 4 6 A sequence diagram of the basic operation of the mote software is shown in Figure 4 7 Essentially during operation the mote need only wait on a timer event and then kick off an ADC read from whichever of the three available 24 Chapter 4 A Prototype Test Point 0 Em Z1 C1 R2 t Sensor Node Ground ADC2 O Car Ground Figure 4 5 ADC2 signal conditioning w Protection Diode channels is chosen When the ADC read completes it needs to format the data into a message and pass the message to the Mote Radio for transmission Additional reliability mechanics are not shown These involve an ACK mechanism for each packet sent checked at the sensor node before another packet is sent and a CRC check for each packet checked at the base station 4 2 3 User Interface Software The operation of the user interface software is based upon the r
88. th vehicles need feedback from the vehicles about how they are performing Car owners lean towards increasingly elaborate dis plays of their vehicles operational parameters e g any ad hoc survey of Toyota Prius owners will reveal how much their cars advanced dashboard readouts in fluenced their purchase car tuners need data on the parameters that they are tuning during tuning operations in the shop and later during road testing me chanics need to be able to measure a host of operational parameters for a car in the shop and could benefit from historical debug information about the state of the car when a problem occurred All of these people have different needs for this feedback or diagnostics data Chapter 2 The State of the Art The automobile industry is well aware of the need to cater to the diverse needs of its customers Embracing the notion of mass customization 27 37 companies offer hundreds of options in each of their models Some manufac turers notably MINI 22 and Scion 32 center their marketing campaigns on the customizability of their cars they make statements that over 10 000 000 possible configurations 22 are available or that no two cars are exactly alike Everything can be customized from engine sizes and transmissions to interior trim and wheel colors 2 2 The Problem Despite the displayed need for customized vehicle diagnostics displays and the auto industry s espousal of mass
89. thod summary convert Units Sample Convert Units getMaxV Get Maximum Voltage setR1 long Set Resistor 1 setR2 long Set Resistor 2 Constructors e ADCChannel public ADCChannel int ch Description Constructor Creates an ADC Channel handling the given ADC chan nel number Parameters ch ADC channel to handle currently only FUNCTION_ADC2 Methods e convert Units public double convertUnits Sample samp Description Convert Units Converts the reading into volts based on the value of the sample and the resistors in the divider network Parameters x samp Sample to convert e getMaxV public double getMaxV Description Get Maximum Voltage Returns the maximum voltage reading based upon the resistors in the voltage divider circuit Returns max voltage e setR1 public void setR1 long newR1 78 Appendix A javadoc Description Set Resistor 1 Set the value of R1 Parameters x newR1 new value of R1 e setR2 public void setR2 long newR2 Description Set Resistor 2 Set the value of R2 Parameters x newR2 new value of R2 A 1 5 Class ADCSample ADC Sample Represents a sample from an ADC channel Declaration public class ADCSample extends org ucsb mayhem diomedes Sample in A 1 26 page 112 Constructor summary ADCSample DiomedesTLMMsg Constructors e ADCSample public ADCSample DiomedesTLMMsg m A 1 6 C
90. tive applications In Bluetooth 99 London UK June 1999 68 Bibliography 11 12 13 14 15 16 19 20 J Hill R Szewczyk A Woo S Hollar D E Culler and K S J Pis ter System architecture directions for networked sensors In Architectural Support for Programming Languages and Operating Systems pages 93 104 2000 B Hull V Bychkovsky Y Zhang K Chen M Goraczko A K Miu E Shih H Balakrishnan and S Madden CarTel A Distributed Mobile Sensor Computing System In 4th ACM SenSys Boulder CO November 2006 O Hyncica P Kacz P Fiedler Z Bradac P Kucera and R Vrba The ZigBee Experience In Proceedings of the 2nd International Symposium on Communications Control and Signal Processing March 2006 ISO 9141 1989 1989 Road vehicles Diagnostic systems Requirements for interchange of digital information ISO 11898 1 2003 2003 Road vehicles Controller area network CAN Part 1 Data link layer and physical signalling W Jenkins R Lewis G Y Lazarou J Picone and Z Rowland Real time vehicle performance monitoring using wireless networking In Communica tions Internet and Information Technology pages 375 380 2004 D La Clair Auto analyzer a mobile based automotive diagnostics tool utilizing wireless communications and embedded Java technology Master s thesis Arizona State University East December 2002 T Liu C M Sadler
91. to increase trust in the measurements 67 Bibliography 1 10 I F Akyildiz W Su Y Sankarasubramaniam and E Cayirci Wireless sensor networks a survey Computer Networks Amsterdam Netherlands 1999 38 4 393 422 2002 Auto Meter http www autometer com N Baker ZigBee and Bluetooth strengths and weaknesses for industrial applications Computing amp Control Engineering Journal pages 20 25 2005 V Bychkovsky B Hull A K Miu H Balakrishnan and S Madden A Measurement Study of Vehicular Internet Access Using In Situ Wi Fi Net works In 12th ACM MOBICOM Conf Los Angeles CA September 2006 Y Chen and L Chen Using Bluetooth wireless technology in vehicles In IEEE International Conference on Vehicular Electronics and Safety pages 344 347 October 2005 M Cilia P Hasselmeyer and A Buchmann Profiling and internet connec tivity in automotive environments In Proceedings of VLDB pages 1071 1074 2002 Crossbow technology inc http www xbow com T ElBatt C Saraydar M Ames and T Talty Potential for intra vehicle wireless automotive sensor networks In 2006 IEEE Sarnoff Symposium 2006 G Ferrari P Medagliani S Di Piazza and M Martal Wireless sensor networks Performance analysis in indoor scenarios EURASIP Journal on Wireless Communications and Networking 2007 Article ID 81864 14 pages 2007 doi 10 1155 2007 81864 L B Fredriksson Bluetooth in automo
92. top Logging button is pressed every reading which comes from the MotelIF and is not deemed to be invalid is logged to that file There is also a Quit button to do the obvious Engine Coolant Accelerator Pedal Fuel Level 67 59 Start Logging Figure 4 12 User Interface 36 Chapter 5 System Evaluation 5 1 Criteria for Evaluation Because the goal of this project is to build a system which is integrated customizable low cost and non intrusive clearly it must be shown that this solution meets these overarching criteria Also inherent in the construction of an automotive diagnostics system is showing that the device can indeed be used as an automotive diagnostics system It must be capable of reading a variety of signals with sufficient resolution and presenting them to the user in a sane way This implies a reasonable minimum update rate per type of channel For example temperatures need not be read as often as throttle pedal position because temperatures change slowly and throttle pedal position can change quickly This partly depends on the rate of collection at the motes themselves and partly on the networking 37 Chapter 5 System Evaluation For a wireless application update rate translates into a few parameters Most important are the ultimate packet throughput and the reception rate Also important is what is happening to the packets that do not make it to the front end application intact Are th
93. ugh the automotive manufacturers have fully embraced the idea of mass customization in other facets of their production factory customized di agnostics displays are not forthcoming This creates a niche for third party manufacturers to fill Unfortunately third party diagnostics systems fail to 64 Chapter 7 Conclusion and Potential Elaboration meet all of the requirements of integration customization low cost and non intrusiveness Notably they tend to trade off integration for customization As a solution to this problem we introduced a system architecture wherein the automobile is instrumented with a wireless sensor network The nodes in the wireless sensor network transmit their readings to a central base station which displays the samples in real time and logs them for later analysis We then detailed a prototype implementation of the system using Crossbow Mica2 motes for the wireless sensor nodes and an Apple notebook as the base station and user interface We described the hardware signal conditioning and software components which had to be designed and implemented Finally we described the steps taken to test the system and evaluate its performance We showed that the resulting prototype successfully meets our re quirements Although packet loss was not negligible we argued that for an appli cation such as low rate real time monitoring where the data are not being used to make critical decisions some packet loss is comp
94. values measured from the existing sys tem Methods e convert Units public double convertUnits Sample samp Description Convert Units Converts raw sample into 0 100 value suitable for display Parameters x samp The sample to convert Returns temp gauge reading 0 100 A 1 16 Class FileSampleLogger File Sample Logger Writes samples to file for later analysis Also presents appropriate GUI elements Declaration public class FileSampleLogger extends javax swing JPanel implements SampleLogger java awt event ActionListener Constructor summary FileSampleLogger Default Constructor Method summary actionPerformed ActionEvent ActionPerformed handleSample Sample Handle Sample startLogging String Start Logging stopLogging Stop Logging writeFileHeader Write File Header 99 Appendix A javadoc Constructors e FileSampleLogger public FileSampleLogger gt Description Default Constructor Construct a File Sample Logger registering all button actions Methods e actionPerformed public void actionPerformed java awt event ActionEvent e Description ActionPerformed Handles Start and Stop button presses e handleSample public synchronized void handleSample Sample samp throws org ucsb mayhem diomedes WSNException Description Handle Sample If there is a valid file write to it Parameters samp Sample to convert to a logfile line e s

2007-07 - Peer to Peer Research at UCSB

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