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1. 0 to 63 75 day Character 2 0 to 255 month Character 3 0 to 255 year Valid Range Character 1 0 25 to 31 75 day 5 Character 2 1 to 12 month Character 3 0 to 255 year Transmission Update Period request Message Priority 8 Format PID Data 10 252 nabc n Number of parameter data characters 3 a Day b Month c Year 1985 15 A value of 0 for the date Character 1 is null The values 1 2 3 and 4 are used to identify the first day of the month 5 6 7 and 8 identify the second day of the month etc A value of 0 for the month Character 2 is null The value 1 identifies January 2 identifies February etc A value of 0 for the year Character 3 identifies the year 1985 a value of 1 identifies 1986 etc 20 In response to the broadcast of the time or date update the ICU retrieves and displays the current time and date 274 Although possible preferably in this particular implemen tation the ICU does not maintain a separate clock for driver local time Instead it requests time as necessary from the 5 data logging unit However it is also possible to maintain driver local time in the ICU In an alternative implementation the ICU could maintain the delta between local and vehicle standard time and use the local delta value to compute driver local time 30 FIGS 8A and 8B are flow diagrams illustrating the process for displaying local time in one embodiment FIG illustrates the steps executed2. vehicle clock the data logging unit being operable to the vehicle standard time monitor the vehicle performance data and to record monitoring for a manually triggered event entered into an selected vehicle performance data along with a time input device in the vehicle stamp in vehicle standard time from the master vehicle in response to detecting the manually triggered event clock 15 storing the slices of vehicle performance data and time local time display communicative with the master stamp in vehicle standard time over a predefined period vehicle clock the local time display being operable to that includes a time of occurrence of the manually display the driver local time triggered event 3 In a vehicle including a data logging device for monitoring and recording events a method for recording
3. 254101419 7903 dW3L cel i I Too oO YOU INSWNYLSNI vy 29 LINN LINN LINN JOHLNOO 26 NOLLO3 1O0Hd 32011 NV NIVHIH3MOd ONINOLLIQNOO HIV ESSET ES E Ep cte ap ue 95 914 U S Patent Sep 28 1999 Sheet 3 of 7 5 957 986 OOR HVAC PARKING A SENSORS BRAKE SENSORS ga COOLANT LEVEL SENSOR 100 WIPER FIG 3 CONVERTERS FLUID SENSOR 102 106 TURN SIGNALS 04 DISPLAY LOGGING UNIT KEYPAD DEVICE pa 2 MEMORY ROM 88 86 5 957 986 Sheet 4 of 7 Sep 28 1999 U S Patent Ad3 Llvga 210IH2A 961 88 H31H3ANOO 32012 QN AWIL Way WVd 002 L 261 981 3OVJH3 NI 1408 H3TIOHINOO OBOIIN 781 081 HOLIMS H399lu L 06 H3MOd S Old 5 957 986 Sheet 5 of 7 Sep 28 1999 U S Patent 5 gt lt HLNOW LAS 20 01 YNOH LAS vee NV 20 01 SALANIW LAS A HSVd 39NVHO Ol A33 LAS HSNd 9 918 9 5 U S Patent Sep 28 1999 Sheet 6 of 7 5 957 986 RECEIVE TIME DATE DATA COMPUTE CHANGE IN TIME DATE CONSTRUCT MESSAGE SEND MESSAGE TO DATA LOGGING UNIT RECEIVE UPDATE IN TIME DATE FROM DATA LOGGING UNIT FlG 7A 260 262 264 266 FIG 7B RECEIVE MESSAGE 268 F
4. a driver as a time zone is passed In one embodiment a master clock maintains vehicle standard time and also maintains driver local time One specific way to maintain driver local time is to keep track of the difference between the local time and the vehicle time and compute the local time upon request from the vehicle standard time and the difference value In one embodiment a truck includes a data logging device for recording vehicle performance data relative to vehicle standard time The data logging device monitors vehicle performance data such as road speed engine speed coolant temperature etc provided by data measuring devices throughout the vehicle In the process of recording selected data the data logging device stamps instances of the data with the vehicle standard time from a master vehicle clock Time stamping refers to the process of associating vehicle standard time with the data This master clock in this embodiment also maintains driver local time by keeping track of the difference between local time and vehicle standard time A local time display presents the local time in the cabin in the vehicle If the driver wants to change the local time he or she simply increments or decrements the time through an input control Changes in local time are communicated to the master clock In one specific implementation the input control and time display are integrated into an instrument control unit This instrument control unit
5. communicates changes in local time to the master clock which keeps track of the current difference between vehicle standard time and driver local time Further advantages and features of the invention will become apparent with reference to the following detailed description with reference to the accompanying drawings BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a functional block diagram illustrating a vehicle data recording system of an embodiment of the invention FIG 2 is a block diagram illustrating the architecture of data management system on a vehicle FIG 3 is a block diagram illustrating an embodiment of an instrument control unit in the data management system FIG 4 is a diagram of the keypad of the instrument control unit shown in FIG 3 FIG 5 is block diagram illustrating the data logging unit in one embodiment of the invention FIG 6 is a diagram illustrating one example of the display screens used to set or change drive local time FIGS 7A and 7B are flow diagrams illustrating a process for setting the driver local time in one embodiment FIGS 8A and 8B are flow diagrams illustrating the process for displaying local time in one embodiment DETAILED DESCRIPTION FIG 1 is a functional block diagram illustrating a vehicle data recording system of an embodiment of the invention 5 957 986 3 The system includes a plurality of data measuring devices e g 20 22 or 24 for measuring vehicle perform
6. different intervals For example data can be captured once a minute twice a minute every second or only when a predefined event is detected Some examples of the data monitored by the data logging unit are set forth below The name of the parameter is followed by the parameter identification number PID as set forth in the SAE 11587 standard Vehicle Road Speed PID 84 Percent Throttle PID 91 Percent Engine Load PID 92 Output Torque PID 93 Engine Oil Pressure PID 100 Turbo Boost Pressure PID 102 Coolant Temperature PID 110 Engine Speed RPM PID 190 data logging unit captures instances of selected data once every second and stores it in the buffer When the buffer is full the most recent second of data overwrites the oldest snapshot of data In addition to continuously storing slices of selected data the data logging unit also monitors predefined events These events can be defined by a PID broadcast on the data link or by a discrete signal such as an interrupt received at the data logging unit When one of the predefined events occurs the data logging unit stores the last 60 seconds worth of data to memory and begins storing data following the event such as the next 60 seconds worth of data In total the amount of data stored for an event includes two minutes and one second worth of data in this particular implementation This data is recorded in an event file in memory An external computer can be used to e
7. implementation of a user interface for the ICU A number of other approaches are possible as well FIGS 7A and 7B are flow diagrams illustrating a process for setting the driver local time in one embodiment FIG 7A illustrates the steps executed by the ICU and FIG 7B illustrates the steps executed by the data logging unit The process begins when a user changes the time or date from the setup screens as described above The ICU receives the data entered at the keypad when the user presses the set key 260 It then computes the change in time or date of the driver local time 262 The ICU then constructs a message to send to the data logging unit 264 Depending on what the user changes a message or messages can be sent for the change in time the change in date or changes in both the time and date The specification for one implementation of the change in time is set forth below Delta Time Change Priority 8 Update Period As needed Format MID Cluster 254 Datalogger Message Length 31 Minute Byte Hour Byte Checksum Where Minute Byte and Hour Byte as defined below Byte Type Resolution Valid Range Minute Signed Short 1 minute bit 60 to 60 minutes Integer Hour Signed Short 1 hour bit 24 to 24 hours Integer Example 140 254 179 3 31 01 00 Checksum Example requests displayed time be incremented by one minute The specification for one implementation of the change in date 1s set forth below De
8. level low or electrical subsystem failure In addition an event can be a manually triggered signal or data message sent to the data logging device For instance in one specific embodiment described further below one type of event is a manually triggered event initiated by the driver When used in conjunction with the time tracking devices in the system this type of event is useful for tracking precisely when the driver experiences problems The master clock 28 is a time keeping device that main tains vehicle standard time on the truck Vehicle standard time refers to a shared time resource or reference that monotonically increases from a starting time and acts as a time reference for instances of vehicle data and events The master clock can be located in a variety of locations in the truck For instance it can function as a stand alone device or can be incorporated into the data logging device 26 or other electronic control device in the vehicle such as an engine computer or an instrument control unit in the cabin In one embodiment the master clock communicates vehicle stan dard time to the data logging device so that the data logging device can record the performance data relative to vehicle standard time In addition to keeping vehicle standard time the master clock can also provide driver local time which may or may not differ from the vehicle standard time In one specific embodiment the master clock maintains driver local time b
9. that includes a time of the user input event memory communicative with the real time clock the memory operable to maintain a difference between the vehicle standard time and a driver local time local time display device communicative with the real time clock the local display device being operable to display the local driver time in a cabin of the truck and an input control communicative with the real time clock the input control being operable to receive input from user representing a change in the driver local time and operable to communicate the change to the real time clock 5 957 986 13 14 2 data recording system on vehicle the system vehicle data relative to vehicle standard time and for main comprising taining driver local time the method comprising a plurality of vehicle data measuring devices operable to recording vehicle performance data relative to vehicle measure vehicle performance data standard time by stamping slices of the vehicle perfor a master vehicle clock operable to maintain vehicle stan 5 mance data with the vehicle standard time from a dard time for the vehicle and operable to maintain master vehicle clock driver local time storing a delta value representing a difference between the a data logging device communicative with the plurality of vehicle standard time and a driver local time the vehicle data measuring devices and the master computing the driver local time from the delta value and
10. the data link or from discrete sensors coupled directly to it For example the data logging unit monitors voltage supplied by the vehicle battery through an analog to digital converter 200 which converts the 12 volt signal from the battery to a digital signal compatible with the microcon troller 184 The real time clock maintains vehicle standard or refer ence time Though the driver local time may be reset for 10 15 20 25 30 35 40 45 50 55 60 65 8 example as the truck passes through time zones the vehicle standard time does not change with changes in the local time Instead the vehicle standard time monotonically increases from an origin Vehicle standard time is helpful in recording faults and events because it prevents ambiguity in tracking when these faults or events occurred relative to each other Further detail regarding the operation of the master clock and the local time display is provided below As introduced above the data logging unit performs a data monitoring function Coupled to the data link the data logging unit listens for periodic data messages broadcast over the data link and continuously records a snapshot of data from the data link into a temporary storage device such as a FIFO buffer In this implementation the data logging unit is programmed to continuously store the most recent 60 seconds of data from the data link Instances of vehicle performance data can be captured at
11. ROM ICU UPDATE DELTA IN 270 BUFFER TIME DATE MESSAGE 272 U S Patent Sep 28 1999 Sheet 7 of 7 5 957 986 FIG RECEIVE INPUT FROM KEYPAD CONSTRUCT MESSAGE BROADCAST REQUEST FOR TIME DATE 280 282 284 RECEIVE RESPONSE FROM DATA LOGGING UNIT DISPLAY TIME DATE 292 294 FIG 8B RECEIVE REQUEST FOR 286 TIME DATE COMPUTE DRIVER LOCAL TIME BROADCAST TIME DATE 288 290 5 957 986 1 METHOD AND SYSTEM FOR RECORDING VEHICLE DATA RELATIVE TO VEHICLE STANDARD TIME RELATED APPLICATION DATA This application is a continuation of U S application Ser No 08 652 776 now U S Pat No 5 802 545 entitled METHOD AND SYSTEM FOR RECORDING VEHICLE DATA RELATIVE TO VEHICLE STANDARD TIME by Cary N Coverdill filed May 23 1996 which is hereby incorporated by reference FIELD OF THE INVENTION The invention relates generally to data management and storage systems for vehicles and more specifically relates to vehicle clock capable of maintaining standard vehicle time and a driver local time BACKGROUND OF THE INVENTION In the trucking industry it is important to accurately maintain time for the benefit of both the driver and for service technicians Since a truck driver frequently travels across time zones it is helpful to provide a clock in the cabin that is easy to change with the change in time z
12. US005957986A United States Patent 1 Patent Number 5 957 986 Coverdill 4 Date of Patent Sep 28 1999 54 METHOD AND SYSTEM FOR RECORDING 5 303 163 4 1994 Ebaugh et 340 439 VEHICLE DATA RELATIVE TO VEHICLE 5 452 446 9 1995 Johnson E STANDARD TIME 5 526 269 6 1996 Ishibashi et al 5 594 646 1 1997 Itoh et al 5 600 558 2 1997 Mearek et al 340 438 Cary N Coverdill Boring Ors 5 650 930 7 1997 Hagenbuch 701 35 73 Assignee Freightliner Corporation Portland 5 802 545 9 1998 Coverdill 701 35 Oreg OTHER PUBLICATIONS Notice This patent is subject to a terminal dis Owner s Manual Caterpillar Driver Information Display claimer Caterpillar Feb 1995 ProDriver User Manual Detroit Diesel Corporation Mar 1994 21 Appl No 09 137 553 d CELECT RoadRelay User s Guide Cummins Cadec 22 Filed Aug 20 1998 22 quie Primary Examiner Gary Chin Related U S Application Data Attorney Agent Firm Klarquist Sparkman Campbell Leigh amp Whinston LLP 63 Continuation of application No 08 652 776 May 23 1996 Pat No 5 802 545 57 ABSTRACT 51 eMe G06F 17 00 master clock on a truck maintains vehicle standard time 701 35 701 29 340 438 the purposes of monitoring and recording vehicle per 58 Field of Searc
13. ance data Vehicle performance data can include a variety of vehicle operating trip maintenance or diagnostic data such as oil pressure road speed fuel rate coolant level coolant temperature battery voltage odometer etc In addition such vehicle performance data can include fault data such as oil pressure low coolant temperature high high intake manifold air temperature electrical system or subsystem failure etc The vehicle performance data can be measured indirectly via sensors controlled by electronic control units or directly via discrete sensors or input devices The data logging device 26 monitors vehicle performance data and potentially records selected instances or slices of this data As alluded to above the data logging device can receive the vehicle performance data either directly from a data measuring device such as a discrete sensor or input device or indirectly through messages from electronic con trol units on a data link For example sensors can include a coolant level sensor a battery voltage sensor an input device located in the cab of the truck etc Similarly the data logging device 26 can be coupled to one or more electronic control units that measure performance data and transfer it to the data logging device via a data link The data logging device 26 can be programmed to record selected vehicle performance data in response to events An event can be a fault detected in the vehicle such as coolant
14. ault at 2 00 P M in South Bend and a second fault at 2 00 P M in Chicago The resulting data erroneously shows that the fault occurred twice at the same time when in reality they occurred one hour apart The problems outlined above occur because of the lack of effective means for displaying and keeping track of time in the truck The difficulty in diagnosing problems in the vehicle are further frustrated by the lack of effective systems for tracking and recording faults detected in the truck In general there is a need for an effective system for tracking and recording events on a consistent basis and most prefer ably across all subsystems installed in a truck SUMMARY OF THE INVENTION The invention provides a method for accurately recording vehicle performance data relative to a master or vehicle 10 15 20 25 30 35 40 45 50 55 60 65 2 standard time and for conveniently displaying local time in the cabin of the vehicle The invention further provides a master clock for maintaining vehicle standard time and a system for recording vehicle data In this context vehicle standard time refers to a time reference or time standard in truck against which the timing of performance data mea sured throughout the vehicle may be recorded Vehicle standard time can also serve as a reference point for com puting the local time displayed to the driver Vehicle local time is variable and is typically adjusted by
15. ble data such as a configuration file is stored in the EEPROM 86 The ICU also includes an input device 90 and a display device 92 In this implementation the input device 90 is a ten key keypad and the display device 92 presents a two line display sometimes referred to as the message center In one implementation the display device com prises a two by 20 character vacuum fluorescent display Alternative implementations are also possible such as a Liquid Crystal Display LCD or raster display device The ICU can be connected to a number of sensors 94 104 through analog to digital converters 106 For example the ICU in this implementation is coupled to door sensors 94 for detecting when the cab doors are open or closed HVAC sensors 96 for determining whether fresh air is circulating in the cab parking brake controls 98 for sensing whether the parking brakes are applied a coolant level sensor 100 for detecting when the coolant level drops below a specified level wiper fluid sensors 102 for deter mining when the wiper fluid drops below a specified level and turn signal controls 104 which indicate when a turn signal is applied The ICU can also include a buzzer 108 used to notify the driver when certain warning conditions are detected Typical examples of these warning conditions include cab door open parking brake applied and vehicle in motion coolant level low etc In this implementation the
16. buzzer is integrated into the ICU However a buzzer or other audio transducer can be implemented as a discrete device to the ICU The particular ICU used in this implementation is manu factured by Joseph Pollak of Boston Mass for Freightliner Corporation The instrument control unit is available as a replacement part from Freightliner Corporation FIG 4 is a diagram of one implementation of the keypad The keypad includes the following dedicated keys 1 Time 120 2 Temperature 122 3 Fuel 124 4 Trip miles hours and fuel 126 5 Leg miles hours and fuel 128 The keypad also includes the following general purpose keys 1 Left Arrow Key 130 2 Down Arrow Key 132 3 Right Arrow Key 134 4 Set Reset Key 136 The keypad includes an event key 138 which enables the driver to specify that an event or problem has occurred with the vehicle For example if the driver is experiencing problems with the transmission he can depress the event key to record data associated with the transmission problem In 5 957 986 7 response the data logging unit 44 FIG 2 receives interrupt signal from the keypad 90 of the ICU FIG 3 and creates an event file In this implementation there is a discrete connection 110 from the keypad 90 to the data logging unit 44 In addition the ICU can send a message to the data logging unit over the data link 40 to notify it that the driver or other user has triggered a manual ev
17. by the ICU to request time from the data logging unit and FIG 8B illustrates the steps executing by the data logging unit in response to this request 35 for time As shown in FIG 8A the process begins when a user presses the time key on the keypad to request local time 280 In response to this input the ICU constructs a message requesting the time and date 282 The message 40 specifically includes the MID of the ICU followed by PID 128 and the MID of the data logging unit which represents request for parameter transmission from the data logging unit The message further includes PID 251 and 252 repre senting a request for the time and date respectively 45 The specification for PID 128 is forth in SAE J1587 and are provided below PID 128 Component Specific Parameter Request Used to request 50 parameter data transmissions from a specified component on the data link Parameter Data Length 2 Characters Data Type Unsigned Short Integer both characters Resolution Binary both characters 55 Maximum Range 0 to 255 both characters Transmission Update Period As needed Message Priority 8 Format PID Data 128 ab a Parameter number of the requested 60 parameter b MID of the component from which the parameter data is requested The ICU then broadcasts this message on data link 65 284 As shown in FIG 8B the data logging unit receives this message and begins to prepare a response 286 In this 12
18. ceive and transmit messages on the data link It also enables an external computer to establish a connection with an ECU on the network to either download data or retrieve data from memory of an ECU on the data link data link 40 in this implementation is a serial communication path connecting the ECUS together This particular data link is designed according to SAE J1708 a standard for serial data communication between microcom puter systems in heavy duty vehicle applications While this specific embodiment is based on 11708 standard it is not critical that the invention be implemented in this specific manner One possible alternative is to use a data link constructed according to SAE 11939 In one specific embodiment the data link 40 15 comprised of a twisted pair cable operating at 9600 baud Designed according to the SAE J1708 standard the data link forms a communication channel among electronic control units coupled to it Electronic control units generate a digital signal on the data link by applying a voltage differential between the two wires in the cable A voltage differential above a specified threshold represents a logic high value while a voltage threshold below a specified threshold rep resents a logic low value This type of data link is particu 1 advantageous for hostile environments because the signal is more robust and impervious to signal degradation However other alternative communication media coul
19. d be used in place of the J1708 cable The ECUs connected on the network communicate with each other according to protocols defined in SAE J1708 and 5 957 986 5 SAE 11587 The SAE 11587 standard is entitled Joint SAE TMC Electronic Data Interchange Between Micro computer Systems and Heavy Duty Vehicle Applications This standard defines the format of data and messages communicated among microprocessors connected to a shared data link and is specifically adapted for use with SAE J1708 According to SAE J1708 J1587 the ECUs on the data link communicate by passing messages to each other The ECUs can be either receivers or receivers and transmitters In this particular implementation the instrument control unit and the data logging unit are both transmitters and receivers A message includes the following 1 a module ID MID 2 one or more parameters and 3 a checksum The number of parameters in a message is limited by the total message length defined in the SAE J1708 standard The message identification numbers are assigned to transmitter categories as identified in SAE J1587 The MID portion of a message specifies the origin or transmitter of the message In the majority of cases messages are broadcast on the data link without specifying a receiver However the message format can be extended to include the MID of a receiver after the MID of the transmitter for special applications The messages passed among the ECUs to co
20. ent at the keypad 90 Using the keypad a user such as the driver or other operator is able to display and set driver local time In this particular embodiment the ICU displays driver local time in response to an input received from the time key in the keypad Driver local time includes the time in hours and minutes hh mm A M or P M and the date month day year The time and date can be displayed at any time in response to the time key so long as the power to the dash of the truck is on To change or set the driver local time in this embodiment the user presses a sequence of keys on the keypad to retrieve set up screen For safety reasons the set up mode of the ICU can only be activated when the parking brake is applied Further detail regarding setting and changing driver local time is provided below Any available local time resetting approach may be used FIG 5 is block diagram illustrating the data logging unit in one embodiment of the invention In this implementation the data logging unit incorporates the data logging device and master clock shown in FIG 1 The data logging unit 180 generally includes memory 182 a microcontroller 184 an interface 186 to the data link a real time clock 188 and a power supply 190 The memory 182 and the real time clock are coupled to the microcontroller 184 via a bus 192 The power supply 190 includes a chip that supplies power to the microcontroller from either the vehicle bat
21. es have a priority according to their message identifiers The PIDs of higher priority parameters have a greater number of bits set at a logic level one When more than one message is broadcast at a time the more dominant message takes priority over lesser dominant messages Since a lower pri ority message is blocked by a higher priority message the transmitter of the lower priority message waits and retrans mits the message after another lull An ECU on the data link will continue to attempt to send a message until it is successfully broadcast to the data link While this particular embodiment is implemented accord ing to the SAE J1708 standard this is only one example a suitable data link implementation Other alternatives are possible as well For example the data link can be imple mented according to SAE J1939 FIG 3 is a block diagram illustrating the instrument control unit ICU in an embodiment of the invention 10 15 40 45 50 55 60 65 6 Preferably located at the dash of the truck the instrument control unit can include the input control that enables a driver to display driver local time and to change the dis played time as well The instrument control unit includes a CPU 80 memory 82 and a port interface 84 for connecting the unit to the data link 40 The memory includes programmable ROM EEPROM 86 and permanent ROM 88 The routines for controlling the ICU are stored in ROM 88 while config ura
22. h 701 29 35 3 40 438 formance data throughout the vehicle Vehicle performance 40 439 data is stored for predefined period of time in response to detecting predefined events Instances of vehicle perfor 56 References Cited mance data are time stamped with vehicle standard time The master vehicle clock can also maintain the local time U S PATENT DOCUMENTS displayed to the driver In response to inputs from the driver 4 258421 3 1981 Juhasz et al 701 35 the difference between driver local time and vehicle standard 4 533 962 8 1985 Decker et A i A 360 5 time is computed and the updated local time is displayed to 5 173 856 12 1992 Purnell et al 701 35 driver 5 250 761 10 1993 Koyanagi 701 35 5 253 224 10 1993 Van Doesburg 340 438 3 Claims 7 Drawing Sheets DATA MEASURING 20 DATA MEASURING DEVICE DATA LOGGING DEVICE DEVICE 22 DATA MEASURING DEVICE MASTER CLOCK LOCAL TIME DISPLAY INPUT CONTROL 28 32 U S Patent Sep 28 1999 Sheet 1 of 7 5 957 986 FIG 1 20 DATA PIECE 22 DATA MEASURING DEVICE DATA LOGGING DEVICE m lt LOCAL TIME DISPLAY DATA MEASURING MASTER DEVICE CLOCK 28 32 5 957 986 Sheet 2 of 7 Sep 28 1999 U S Patent viva LINN NOISN3dSNS OUO 09 0Z 1N3A3
23. he dash of the truck and a data logging unit 44 used to monitor and record events reported on the data link 40 The illustrated system architecture also includes a number of other electronic units as shown such as a powertrain ECU 46 an air suspension ECU 48 an antilock brake ECU 50 and an air conditioning protection unit 52 An ECU typically includes a microprocessor memory and one or more sensors and actuators 54 56 58 60 62 and 64 for example used to control and or monitor truck performance As one possible implementation the devices depicted in FIG 1 can be implemented in the system architecture shown in FIG 2 In one embodiment for example the data logging device and master clock are incorporated into the data logging unit 44 The input control and the local time display are features of the instrument control unit 42 Finally the data measuring devices may correspond to the electronic control units For instance a data measuring device can be implemented in an electronic control unit equipped with sensors for measuring vehicle performance data As another example a data measuring device can be implemented as a discrete sensor directly coupled to the data logging unit More detail regarding the instrument control unit and data logging unit follows below The system architecture in FIG 2 also includes a data port 70 for coupling external devices to the on board data link This data port 70 enables an external computer to re
24. implementation the data logging unit computes driver local time by adding the cumulative offset stored in the buffer to the vehicle standard time provided by the real time clock 288 Similarly it computes the date to be displayed with driver local time by adding the cumulative offset for the date to the date provided by the real time clock 288 After computing driver local time the data logging unit constructs time and date messages and broadcasts them on the data link 290 The format of these messages adheres to the J1587 standard for PIDs 251 and 252 as set forth above Returning again to FIG 8A the ICU is programmed to receive the time and data messages 292 It then reads the value for time and date provided in these messages and displays the time and date on the display device 294 approach described above enables the data processing system on the truck to monitor and record system wide events and faults with respect to vehicle standard time and to display correct driver local time While I have described the invention with reference to several specific embodiments I do not intend to limit the scope of my invention to these specific embodiments The master clock can be implemented in a variety of ways It need not be incorporated into a data logging unit but instead could act as a stand alone device or could be incorporated into another ECU The data logging device can be implemented in a variety of ways as well It c
25. lta Date Change Priority 8 Update needed Period Format MID Cluster 254 MID Datalogger Message Length 30 Day Byte Month Byte Year Byte Checksum Where Day Byte Month Byte and Year Byte are as defined below Byte Type Resolution Valid Range 31 75 to 431 75 days Day Signed Short Integer 0 25 day bit 10 15 20 25 30 35 40 45 50 55 60 65 continued Byte Type Resolution Valid Range Month Signed Short 1 month bit 12 to 12 months Integer Year Signed Short 1 year bit 127 to 127 years Integer Example 140 254 179 4 30 FC 00 00 Checksum Example shows ICU sending a negative change of one day to the data logging unit date buffers As set forth in the above message specifications the ICU sends the change in time and or data to the data logging unit by specifying its MID 266 The data logging unit receives the message or messages from the ICU 268 FIG 7B and in response updates values in a buffer for storing the difference delta between vehicle standard time and driver local time 270 In this particular implementation the battery backed RAM in the data logging unit includes this memory buffer The data logging unit adds a signed change in time to the cumulative time delta or offset stored in the buffer Similarly for a change in date it adds a signed change in date to the cumulative date value stored in the buffer As an alternative to c
26. nvey infor mation by one or more parameters contained within the messages According to the SAE J1587 standard the first character of every parameter is a parameter identification character PID The parameter identified by the PID directly follows the PID The SAE J1587 supports different data formats including a single character a double data character or more than two data characters representing the parameter data Several parameters can be packed into a message limited by the maximum message size as noted above In this implementation the ECUs communicate with each other over the data link according to the SAE standard J1708 The standard describes methods for accessing the data link and constructing messages for transfer over it It also defines a method for resource contention among the ECUs on the data link An ECU wishing to transmit data on the data link first waits for a lull in transmission of data on the data link In this particular implementation the length of the lull is 200 milliseconds After detecting this lull the ECU attempts to transmit its message The transmitter broadcasts its message onto the data link Each of the ECUs that operate as receivers on the data link will receive the message However receiv ers only act on a message if programmed to do so In some cases two or more transmitters may attempt to broadcast a message at one time giving rise to a collision To resolve a conflict among transmitters messag
27. ommunicating changes in local time over the data link the keypad of the ICU can be directly connected to the data logging unit to transfer data repre senting changes in local time In response the data logging unit would then update the time date buffer as described above After updating the buffer the data logging unit sends a message transferring the updated time or date to the ICU 272 In this particular implementation the data logging unit issues a message using the J1587 standard parameters PID 251 in the case of an update in time or PID 252 in the case of an update of the date The specification for PIDs 251 and 252 used in this embodiment are set forth below PID 251 Clock 3 Characters Each Character Unsigned Short Integer Character 1 0 25 s bit Character 2 1 min bit Character 3 1 h bit Character 1 0 to 63 75 s Character 2 0 to 255 min Character 3 1 h bit Parameter Data Length Data Type Resolution Maximum Range Transmission Update Period request Message Priority 8 Format PID Data 251 nabc n Number of parameter data characters 3 a Seconds not displayed in this implementation b Minutes c Hours PID 252 Date 3 Characters Each Character Unsigned Short Integer Character 1 0 25 day bit Character 2 1 month bit Character 3 1 year bit Parameter Data Length Data Type Resolution 5 957 986 11 continued Maximum Range Character 1
28. ones In view of this fact it is quite common for trucks to have clocks in the cabin that display time and can be reset to the local time Aside from the convenience to the driver it is also useful to have a clock for keeping track of vehicle operating and diagnostic data For example if a problem occurs in the transmission it is useful to know precisely when the prob lem occurred Many of the sophisticated electronic controls in trucks do have a mechanism for keeping track of time Despite the presence of these electronics on board the truck the frequent changes in local time and or the lack of a consistency among time keepers in the vehicle often leads to confusion in identifying when problems on the truck actu ally occurred This confusion arises for example when a driver tells the service technician that a problem occurred at one time and the problem actually occurred at another time This can result when an electronic subsystem in a truck records a fault using a time clock that is not consistent with the driver s time or time used by other subsystems in the vehicle It is equally confusing when a fault in a subsystem is recorded at one time in a first time zone and then is recorded again at the same time in a second time zone Consider for example a truck travelling west from South Bend Ind to Chicago Ill If faults are recorded in terms of local time either by the driver or the truck s electronics it is possible to record a f
29. ould be designed to monitor vehicle performance data through dis crete sensors or through ECUs coupled to a shared data link for example The local time display and input control can be implemented in a variety of ways as well For instance they can implemented in an integrated dash control device such as the instrument control unit or in discrete devices Having described and illustrated the principles of my invention with reference to a preferred embodiment and several variations thereon it should be apparent that the invention can be modified in arrangement and detail without departing from its principles Accordingly I claim all modi fications as may come within the scope and spirit of the following claims I claim 1 A master vehicle clock in a truck comprising a real time clock operable to maintain vehicle standard time for vehicle performance data measured from at least two vehicle data measuring devices in the truck a data logging device in communication with the vehicle data measuring devices and the real time clock the data logging device being operable to buffer vehicle perfor mance parameters from the vehicle data measuring devices and the data logging device being operable to write a set of the buffered vehicle performance param eters along with a vehicle standard time indicator to a file in response to a user input event where the set of buffered vehicle performance parameters is defined by a moving period of time
30. tery or a lithium battery or other back up power supply The lithium battery serves as a back up in the event that the voltage supplied from the battery is insufficient or unavailable As noted above the data logging unit is coupled to the keypad 90 of the ICU FIG 3 to receive an interrupt when a user actuates the event key on the keypad This connection is represented by the manual trigger switch 194 shown in FIG 5 The data logging unit can also receive interrupts from other devices as well The keypad of the ICU could also be coupled to the data logging unit to communicate signals representing changes in driver local time For example a key or keys on the keypad could be configured to send signals to the data logging unit to update or modify local time or the delta between vehicle standard time and local time stored in the data logging unit memory 182 of the data logging unit includes both RAM 196 and ROM 198 This implementation includes 128 KB of ROM which stores the application code executed by the microcontroller This executable code includes the set up routines used to boot the data logging unit and the data logging routines used to monitor predefined events This implementation also includes 256 KB of battery backed RAM which is used to implement a FIFO buffer for capturing data from the data link to store event files and to store a device parameter file The data logging unit can monitor vehicle performance data from
31. xtract one or more of these event files from the data logging unit for diagnostic purposes As noted above the system architecture on board the vehicle maintains both vehicle standard time for tracking events and faults and driver local time for display to the driver In the implementation described and illustrated above the data logging unit maintains vehicle standard time and the difference delta between vehicle standard time and driver local time In response to a request to display local time at the keypad the ICU issues a request for the time The data logging unit then returns the appropriate time to the ICU FIG 6 is a diagram illustrating one example of the display screens used to set or change driver local time This diagram shows a series of display screens as well as the keys on the keypad used to change screens and enter data Starting with the setup screen 220 the user accesses time date setup screens by using the arrow keys 222 226 for example on the keypad as shown The user begins by scrolling through setup screens 228 to reach the main time date screen 230 5 957 986 9 When the user reaches the main time date screen 230 or she can then set the minutes 232 hours 234 day 236 month 238 and year 240 using the set key 242 and left and right arrow keys 244 246 for example To exit the time date screens the user can press the down arrow key 248 for example FIG 5 represents only one example of one
32. y storing the difference between driver local time and vehicle standard time The local time display 30 shown in FIG 1 displays the driver local time in the cab of the truck It can receive the local time either directly or indirectly from the master clock 28 In one specific embodiment the local time display receives the local time via the data logging device 26 The input control 32 enables the driver to control the display of driver local time Located in the cabin of the truck the input control enables the driver to increment or decrement the local time For example if the truck passes through a time zone the driver can change the local time easily by simply pressing a button on the input control to 10 15 20 25 30 35 45 50 55 60 65 4 change the local time displayed in the cabin In one specific embodiment changes in local time are communicated to the master clock which maintains the current difference or delta between vehicle standard time and local time More detail regarding a specific implementation of the system in FIG 1 follows below FIG 2 is a block diagram illustrating the system archi tecture in a more specific implementation of the system shown in FIG 1 The system architecture includes a number of electronic control units ECUs coupled together in with a data link 40 In particular the system includes an instru ment control unit 42 used to control instruments and gauges at t
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