US005693876A
`5,693,876
`(11) Patent Number:
`United States Patent
`Dec. 2, 1997
`[45] Date of Patent:
`Ghitea, Jr. et al.
`
`
`119
`
`E
`
`Driver
`
`[73]
`
`[21]
`
`[22]
`
`[56]
`
`
`4,845,630
`FUEL ECONOMY DISPLAY FOR VEHICLES
`7/1989 Stephens ...
`wee THUS
`[54]
`
`5,148,702—9/1992 Gillick, Jr, scesonnsssseoceesececessessenuns 73/114
`[75]
`Inventors: Nicolae Ghitea, Jr., Tigard, Oreg.;
`OTHER PUBLICATIONS
`James M.Ehlbeck, La Center, Wash.
`”
`Assignee: Freightliner Corporation, Portland, me EES
`Performance, Detroit Diesel Corporation,
`Ong:
`ProDriver™ User Manual, Detroit Diesel Corporation,
`Mar., 1994.
`Operating & Error Codes, FloScan Instrument Company,
`Appl. No.: 655,841
`Inc., Apr. 1993.
`Filed:
`May 31, 1996
`Primary Examiner—George M. Dombroske
`Tint. C.© ecessssssssssssseseeessenseserssseceeneeseeeeee GOLM 15/00
`(51)
`GS. Cle cissaciece w 73/114; 340/439—Attomney, Agent, or Firm—Klarquist Sparkman Campbell
`
`[52]
`
`Field of Search ....
`.. 73/113, 114, 116,
`Leigh & Whinston
`[58]
`ABSTRACT
`73/117.2, 117.3; 340/439
`[57]
`References Cited
`An improved fuel economy device computesa filtered rate
`U.S. PATENT DOCUMENTS
`of change of instantaneous fuel economy or a filtered
`instantaneous fuel economy and repetitively updates a
`graphical display depicting the current fuel economy. The
`4,400,779
`8/1983 Kosuge et al. c.ssecssssrseceereen T3/LIL4
`fuel economy can be displayed as a percentage of a target
`peiee pee oe ey
`” xoe
`
`:
`;
`=
`ro!
`et
`al.
`
`1/1986 Masuda et al....
`. T3/L4 Reo. Propeamaned Dy One Res Oe EE Ones
`4,564,905
`
`2/1986 Aussedat ves
`we T3/LL3
`4570226
`
`4,663,718
`5/1987 Angello et al.
`73/114
`-.seccscsssccssseseesnsesessen 73/113
`4,706,083
`11/1987 Baatz et al.
`
`21 Claims, 8 Drawing Sheets
`
`START)
`
`RED
`
`ak
`266
`GOI
`READ SPEED & FUEL RATE
`EMPG_INST= 7“
`
`CALCULAT
`
`rn
`
` PROGRAM
`
`Slee
`
`
`
`Is
`
`So
`
`282
`
`ES
`
`7MPG_FILTERED, =99.9
`
`CALCULATE SUM
`
`CALCULATE BARGRAPH
`
`DISPLAY BARGRAPH
`
`290
`
`"GS
`
`YES
`
`TO FIG.10B
`
`284
`
`286
`
`288
`
`UNIFIED 1004
`
`272
`
`276
`
`MPG_FILTEREDg = MPG_FILTERED,
`
`274oe
`
`
`CALCULATE MPG_FILTERED,
`
`MPG_FILTERED, = MPG_INST
`
`
`
`UNIFIED 1004
`
`1
`
`

`

`U.S. Patent
`
`MEMORY
`
`Dec. 2, 1997
`
`INTERFACE
`
`Sheet 1 of 8
`
`5,693,876
`
`PORT
`
`2
`
`

`

`USS. Patent
`
`Dec. 2, 1997
`
`Sheet 2 of 8
`
`5,693,876
`
`
` @OOQOo)|/
`
`FIG. 5
`100
`
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`2 aT 123456.7
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`
`
`
`
`
`108
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`
`
`
`
`
`
`
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`
`
`
`
`
`
`3
`
`

`

`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 3 of 8
`
`5,693,876
`
`FIG. 6
`
`LIM, = LIM,_, - DELTA
`
`FIG. 7
`
`150—=
`
`152—
`
`
`
`158 |
`
`-
`
`0%Illl
`
`Tat0123456.7 MI
`
`162
`
`156
`
`
`
`4
`
`

`

`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 4 of 8
`
`5,693,376
`
`
`
`SSANLHDIYEAVIdSIG
`
`=4HVGLHOT)>
`
` NOLLWWHYOSNI
`
`rs]AN,b><]SINGSZHONSUT)(afSOVNONVISONVHO|HSIHIDNA
`-SDVNONV1OlASLASHSNd
`LADuYVLADNVHOdnLasOlASXLASHSNd
`
`
`
`5
`
`
`
`
`

`

`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 5 of 8
`
`5,693,876
`
`STAR
`
`.
`
`READ SPEED [204
`
`& FUEL RATE
`
`CALCULATE MPG_InsTL’
`CALCULATE MPG_FILTERED t)
`
`
`
`208 FIG. 9A
`}~208
`
`212
`
`=I 7MPG_FILTERED(t)=99.9
`
`CALCULATE MPG_SHORT_TERM|218
`
`
`CALCULATE PERCENT
`
`
`
`
`
`[-~220
`
`224
`
`PERCENT= 100
`
`PERCENT =—100
`
`CALCULATE BARS1
`
`
`
`6
`
`

`

`USS. Patent
`
`Dec.2, 1997
`
`Sheet 6 of 8
`
`5,693,876
`
`FIG. 9B
`
`w
`
`CALCULATE Z
`
`232
`
`236
`
`DISPLAY BARS1
`
`DISPLAY 0%
`
`240
`
`CALCULATE DI’ <4
`
`DISPLAY Dl
`
`2*®
`
`‘ 248
`
`YES
`250
`
`NO
`
`YES
`
`252
`
`RETURN TO
`MAIN PROGRAM
`
`7
`
`

`

`U.S. Patent
`
`Dec. 2, 1997
`
`Sheet 7 of 8
`
`5,693,876
`
`STARD
`
`FIG. 10A
`
`260
`
`/~268
`i
` YES
`Beaan
`
`ae
`
`MPG_FILTERED, = MPG_INST
`
`CALCULATE MPG_FILTERED,
`
`282
`MPG_FILTERED, = 99.9
`
`STEP=11ON oa
`
`READ SPEED & FUEL RATE
`
`Me
`CALCULATE MPG_INST
`MPG_FILTEREDg = MPG_FILTERED, }~ °”2
`
`274
`
`NO
`
`
`777280
`YES
`IS
`?
`
`MPG_FILTERED 4
`> 99.9
`
`eS 290
`
`CALCULATE SUM+~284
`
`CALCULATE BARGRAPH/~286
`
`
`DISPLAY BARGRAPH|-°8
`
`
`YES
`
`TO FIG.10B
`
`8
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 8 of 8
`
`5,693,876
`
`FIG. 10B
`
`FROM
`FIG.10A
`
`BARSO = BARS1
`
`292
`
`CALCULATE MPG_SHORTTERML
`
`224
`
`CALCULATE PERCENT
`
`296
`
`
`
`
`
`PERCENT > 100
`
`
`
`298
`YES
`
`
`300
`PERCENT= 100
`
`PERCENT =-—100
`
`304
`
`CALCULATE BARS1
`
`CALCULATE DELTA
`
`306
`
`308
`
`9
`
`

`

`5,693,876
`
`1
`FUEL ECONOMY DISPLAY FOR VEHICLES
`
`BACKGROUND OF THE INVENTION
`
`Because of the high cost of fuel, significant cost savings
`can be achieved by enabling drivers, especially drivers of
`long-haultrucks, to increase fuel economy. A numberoffuel
`economy instruments have been developed to allow drivers
`to monitor fuel economy. Many of these devices, however,
`are not effective because they provide inaccurate or mis-
`leading information. Some fuel economyinstrumentsfail to
`provide the driver with helpful feedback on how certain
`driver actions impact fuel economy. In some cases these
`devices are ineffective because they react too slowly to
`driver actions, and therefore, do not inform the driver how
`his or her actions impacted the fuel economy.In other cases,
`the fuel economyindicator is too sensitive to changes in the
`fuel rate. In these latter cases, the indicator reading changes
`rapidly and erratically, distracting the driver. To be truly
`effective, a fuel economy indicator should be accurate,
`responsive to driver actions, meaningfulto the driver and not
`distracting or annoying.
`One measure of fuel economy, called instantaneous fuel
`economy, refers to the computation of miles per gallon at
`one instant in time. This quantity is calculated from the
`vehicle’s speed and the fuel consumption rate. Merely
`computing and displaying instantaneous fuel economy pro-
`duces erratic results. The use of electronic signal processing
`to smooth these signals does help, however, to produce a
`more stable measure of fuel economy.
`Another measure of fuel economy is the “average” fuel
`economy. This quantity is computed by simply dividing the
`distance traveled by the amount of fuel consumed. This
`quantity is not very helpful to the driver becauseit does not
`provide adequate feedback as to how discrete driver actions
`impact fuel economy.
`One attempt to provide more helpful feedback involves
`computing a ratio of instantaneous fuel consumption to
`average fuel consumption. While this ratio may provide
`more helpful feedback than merely computing the instanta-
`neous or the average fuel consumption, it suffers from
`drawbacks. The average fuel economyis zero at the begin-
`ning of a trip, and as a result, the ratio of instantaneous to
`average fuel consumption is undefined. As the vehicle
`accumulates more miles, the value of the ratio moves toward
`the average fuel consumption. Thus, the ratio of instanta-
`neous to average fuel consumption tends to be an inaccurate
`and confusing fuel economy indicator to the driver.
`In addition to the accurate measurement and computation
`of fuel economy, the presentation of fuel economy to the
`driver is also important. If an instrumentfluctuatesrapidly,
`it conveyslittle, if amy useful information andis distracting
`to the driver. On the other hand,if the display is static,it fails
`to give valuable feedback in response to specific driver
`actions. For example, a driver may want to know whether
`shifting gears significantly impacts fuel economy. Static
`displays fail to provide the necessary rapid feedback to the
`driver. Therefore, a need exists for an improved fuel
`economy determining apparatus and method and for an
`improved vehicle fuel economy display.
`SUMMARY OF THE INVENTION
`
`10
`
`15
`
`35
`
`40
`
`45
`
`The invention provides an improved fuel economy device
`and method. One embodiment of the device includes a
`control unit that computes and controls the display of fuel
`economy in a vehicle. The control unit is in communication
`with a fuel sensor for measuring the fuel rate and a speed
`
`65
`
`2
`sensor for measuring road speed. The control unit computes
`a weighted instantaneous fuel economy representation by
`combining current and selected previous instantaneous fuel
`economy values on a weighted basis. To display the fuel
`economy, the control unit repetitively updates a graphical
`display, such as a bar graph display, at discrete time inter-
`vals. The rate of change in the displayed value is preferably
`restricted so that it changes smoothly and minimizes dis-
`tractions to the driver.
`One embodiment of the invention computes a represen-
`tation of the fuel economy by combining weighted values of
`the instantaneous fuel economy from different intervals. In
`one specific example, a control unit computes a fuel
`economyrepresentation by combining a weighted value of
`the current instantaneous fuel economy with a weighted
`value of the fuel economy computed for one or more prior
`intervals, The representation of the rate of change of instan-
`taneous fuel economy can be computed in a similar fashion.
`In one specific embodiment, the control unit computes a
`filtered rate of change of instantaneous fuel economy. It
`computes instantaneous fuel economy by dividing road
`speed by the fuel rate. It filters the rate of change of fuel
`economy by summing the weighted current change of
`instantaneous fuel economy, and the weighted prior rate of
`change of the fuel economy. The control unit then updates
`the display with the current value of the filtered fuel
`economy. To smooth the transitions between updates of the
`display, the control unit most preferably limits the maximum
`amount of change in the display from one update to the next.
`In another specific embodiment, the control unit computes
`a filtered value for the fuel economy from the instantaneous
`fuel economy, and displays the fuel economyas a percentage
`of a predefinedtarget fuel economy. The target fuel economy
`can be preset or more preferably programmed by the driver,
`fleet owner, or other operator via the user interface provided
`by the control unit. The control unit, in this embodiment
`computes the filtered fuel economy by weighting the current
`instantaneous fuel economy anda filtered value the instan-
`taneous fuel economy computed for a previous interval. The
`filtered instantaneous fuel economy can be averaged over a
`number of intervals to compute a short term average fuel
`economy. Either the instantaneousor the short term average
`fuel economy can then be compared to thetarget value. The
`control unit in this case may be coupled to a display device
`for graphically displaying the fuel economy as a percentage
`of the target fuel economy.
`The fuel economy devices summarized here and
`described below have a numberof advantages over existing
`fuel economy indicators. The fuel economy is computed and
`displayed so that the driver can see how his or her actions
`affect fuel economy. For example,if the driver accelerates or
`shifts gears, these actions are almost immediately reflected
`in the fuel economy display. Moreover, the fuel economy
`display is more accurate because it does not have to be based
`on the trip average fuel economy or the total distance
`travelled which can vary. While the fuel economydisplay is
`responsive to driver actions,
`it is designed to change
`smoothly so as not to distract the driver. The fuel economy
`values can befiltered based on programmable coefficients
`and limited in a manner that prevents the display from being
`erratic or changing abruptly.
`Further advantages and features of the invention will
`become apparent with reference to the following detailed
`description and accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrating the system archi-
`tecture in a truck for one embodiment of the invention.
`
`10
`
`10
`
`

`

`5,693,876
`
`2
`FIG.2 is a block diagram illustrating the engine electronic
`control unit (ECU) in more detail.
`FIG. 3 is a functional block diagram illustrating the
`architecture of the instrumentation control unit (ICU).
`FIG. 4 is a diagram illustrating one embodiment of the
`display device for the ICU.
`FIG.5 is a diagram illustrating the format of the display
`during normal driving conditions in one embodiment.
`FIG. 6 is a flow diagram illustrating a method for com-
`puting the filtered rate of change of the fuel economy for
`display.
`FIG.7 is a diagram of a second embodimentofthe display
`device.
`
`FIG. 8 is a diagram of the keypad for the ICU.
`FIGS.9A and 9Bare a flow diagram illustrating a process
`for computing fuel economy in a second embodiment.
`FIGS. 10A and 10B are a flow diagram illustrating a
`process for computing fuel economy in a third embodiment.
`FIG. 11 is a diagram illustrating one example of set-up
`screens displayed by the ICU to enter a value for the target
`fuel economy.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`4
`controlling the solenoid valves that inject fuel to the engine
`cylinders. The rate of fuel flow is directly related to the
`amountof time that the solenoid valve is closed. This time
`period determines the volume of fuel injected into a cylinder
`per revolution. By determining the amountof time that the
`solenoid valvesare closed, the engine ECU can computethe
`amount of fuel flowing into the engine. The engine ECU
`calculates the fuel flow rate from the dwell of the injection
`pulse and the engine speed.
`In this embodiment, the engine ECUis also responsible
`for measuring and computing the vehicle’s road speed.
`Again, there are a number of known methods to measure
`speed which may be used on the present invention.
`Oneparticular method used in this implementation is to
`sense the speed of rotation of the tail shaft of the truck. A
`magnetic sensor located onthetail shaft generate an analog
`signal comprised of a series of pulses representing the
`rotation rate of the engine. The engine ECU includes an
`analog to digital (A/D) converter 54 to convert this analog
`signal into a digital signal. It is programmed to read this
`digital value and derive the instantaneous speed in miles per
`hour.
`
`10
`
`15
`
`FIG. 3 is a functional block diagram illustrating the
`architecture of one implementation of an instrumentation
`control unit (ICU). This instrumentation control unit
`includes a CPU 60, memory 62 and a port interface 64 for
`connecting the unit to the data link 20. The
`62
`includes programmable ROM (EEPROM)66, RAM 67 and
`permanent ROM 68. The routines for controlling the ICU
`are stored in ROM 68, while re-configurable data is stored
`in the EEPROM 68.
`
`FIG. 1 is a block diagram illustrating the system archi-
`tecture in a truck for one embodimentof the invention. The
`system architecture includes a number of electronic control
`units (ECU) interconnected via a data link 20. In particular,
`the illustrated system includes an engine ECU 22, located at
`the engine, and an instrumentation control unit 24, located at
`the dash of the truck. As shown,other optional ECUs 26, 28
`can be connected to the data link 20. Finally, the system
`the ICU includes a
`In one specific implementation,
`includes an optional data port 30, for coupling external data
`68HC11 microprocessor from Motorola Corporation,andits
`processing equipment to the ECUs on board the truck. This
`memory 62 comprises EEPROM, ROM, and RAM.This
`data port enables an external computer, for example,
`to
`specific ICU has 8 KB of external EEPROM,128K of ROM
`receive and transmit messages on the data link. It also
`and 2K of RAM.Theinternal memory of the CPU comprises
`enables an external computer to download data orafile to an
`256 Bytes of RAM and 512 bytes ofEEPROM.This is only
`ECU andto receive data or a file from an ECU.
`one specific implementation of the ICU. A variety of con-
`FIG, 2 is a block diagram illustrating the engine ECU in
`ventional processors and memory systems can be used to
`more detail. The engine ECU includes memory 40, a CPU
`implement the functionality of the instrumentation control
`unit.
`42, and a port interface 44 connected via a bus structure 46.
`The CPU 42 executes routines stored in the memory 40 to
`control and monitor engine performance. Theport interface
`44 serves as a link between the CPU 42 and a serial
`communication path called the data link 20.
`The engine ECUalso includes a variety of sensors and
`controls for monitoring and controlling engine performance.
`This implementation of the ECUincludes a fuel rate control
`48 and a speed sensor 50. The ECU in combination with the
`fuel rate control serves as a fuel rate measuring device for
`the system. The engine ECU receives data representing
`motion of the vehicle from the speed sensor and computes
`vehicle speed from this data. The engine ECUalso servesas
`a fuel rate measuring device. Since it controls the flow of
`fuel to the engine, it is capable of determining the fuel rate.
`It should be noted that there are a number of well known
`methods to measure the fuel rate, and the use of the engine
`ECUis just one implementation. For example, net fuel flow
`may be measured in a diesel truck by obtaining the differ-
`ence between the fuel being delivered to the engine from the
`fuel returned from the engine using conventional flow
`meters. In light of the variety of fuel rate measurement
`devices available, we refer to them generally as fuel rate
`measuring devices.
`In this implementation the engine ECU determines the
`amount of fuel supplied to the cylinders in the engine by
`
`35
`
`45
`
`55
`
`11
`
`The ICU also preferably includes an input device 70 and
`a display device 72. In one implementation,the input device
`is a ten key keypad 70, but the specific design of the input
`device can vary. The design of the input device can vary. The
`display device 72 provides a textual and graphical outputto
`the driver display. In one specific implementation, the dis-
`play device comprises a two by 20 vacuum fluorescent
`display.
`The particular ICU used in this implementation is manu-
`factured by Joseph Pollak of Boston, Mass. for Freightliner
`Corporation. The instrumentation control unit is presently
`available as a replacement part from Freightliner Corpora-
`tion.
`is a serial
`in this implementation,
`The data link 20,
`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 embodimentis based on the J1708 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 J1939. The communication
`link need not be a shared communication path. It is also
`possible to connect fuel rate and speed sensorsto the control
`unit responsible for computing and displaying fuel economy.
`
`11
`
`

`

`5,693,876
`
`5
`Tn the embodiment shown in FIG. 1, the data link 40 is
`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 coupledto 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-
`larly advantageous for hostile environments because the
`signal is more robust and imperviousto signal degradation.
`However, other alternative communication media could be
`used in place of the J1708 cable.
`The ECUsconnected on the network communicate with
`each other according to protocols defined in SAE J1708 and
`SAE J1587. The SAE J1587 standard is entitled “Joint
`SAE/TMC Electronic Data Interchange Between Micro-
`computer Systems and Heavy Duty Vehicle Applications.”
`This standard defines one format for 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
`ECUscanbe either receivers, or receivers and transmitters.
`In this particular implementation, the instrumentation con-
`trol unit and the engine ECU are both transmitters and
`receivers. For the purpose of measuring fuel economy, the
`engine ECU acts as a transmitter, sending messages to the
`ICU regarding road speed and fuel rate.
`In this format, 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 messageis 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 areceiver after the MID ofthe transmitter for special
`applications.
`The messages passed among the ECUs convey informa-
`tion about 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.
`Again, in this implementation, the ECUs communicate
`with each other over the data link according to the SAE
`standard J1708. The standard describes methods for access-
`ing the data link and constructing messages for transfer over
`it. It also defines a method for resource contention among
`the ECUson 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 1.04
`milliseconds. After detecting, this lull, the ECU attempts to
`transmit its message. The transmitter broadcasts its message
`onto the data link. Each of the ECUsthatoperate asreceivers
`on the data link will receive the message. However, receiv-
`ers only act on a message if programmed to do so.
`
`30
`
`35
`
`45
`
`60
`
`65
`
`12
`
`6
`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, messages have a
`priority according to their messageidentifiers. The MIDs of
`higher priority transmitters have a greater number ofbits 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 must wait and
`retransmit the message after another lull. An ECU on the
`data link will continueto attempt to send a message until it
`is successfully broadcast to the data link.
`Among the parameters defined in SAE J1587, there are
`two that are particularly relevant to fuel economy in this
`implementation. The first is PID 84, which represents the
`road speed. The second is PID 183 which represents the fuel
`rate. The engine ECU transmits both of these parameters in
`this implementation. The details of the road speed parameter
`are set forth below:
`
`
`Data Length:
`Data Type:
`Bit Resolution:
`Maximum Range:
`‘Transmission Update:
`Message Priority:
`Format:
`
`1 character
`Unsigned short integer
`0.805 koh (0.5 mph)
`0 to 205.2 km/h (0 to 127.5 mph)
`Ols
`1
`Data
`PID
`a
`84
`
`a road speed
`
`The details of the fuel rate parameter are set forth below:
`
`
`Parameter Data Length:
`Data Type:
`Bit Resolution
`Maximum Range:
`Transmission Update:
`Message Priority:
`Format:
`
`2 characters
`Unsigned integer
`16.428 x 10° L/s (4.34 x 10 galls)
`0.0 to 1.076 65 Lis (0.0 to 0.28442190 gal/s)
`0.25
`a
`
`Data
`PID
`aa
`183
`
`aa fuel rate
`
`Engine control units capable of transmitting the road
`speed and fuel rate parameters include:
`the DDEC II
`provided with Detroit Diesel engines from Detroit Diesel
`Corporation of Detroit, Mich.; the ADEM II provided with
`Caterpillar engines from Caterpillar, Inc., Engine Division
`of Mossville, Ill.; and the CELECT+ provided with Cum-
`mins engines from Cummins Engine Company of
`Columbus, Ind.
`
`FIG. 4 is a diagram illustrating one specific embodiment
`of the display device for the instrumentation control unit.
`The display area includes two rows 80, 82 of 16 display
`elements (84, 86 for example). Each of the individual
`display elements are comprised of a 5x7 array of pixels (88,
`90 for example).
`FIG.5 is a diagram illustrating one preferred format of the
`message center during normal driving conditions. The top
`bar 80 of the message center displays a negative sign 100 in
`the left-most element and a positive sign 102 in the right-
`most element. The center 104 of the top bar provides a
`reference point or origin for the fuel economy display. ‘The
`lower bar of the message center displays the short term
`average fuel economy in miles per gallon on the left side
`106, and a seven digit odometer reading on the right side
`108.
`
`12
`
`

`

`5,693,876
`
`7
`For the message center depicted in FIG.5, the instrumen-
`tation control unit computes quantities for a numerical and
`a graphical representation of the fuel economy based onthe
`road speed and fuel rate parameters from the engine ECU.
`Both the numerical and graphical quantities are computed
`from the instantaneous fuel economy. Theinstantaneous fuel
`economy is calculated using the equation:
`
`IFE;=road speed{PID 84)/fuel rate, (PID 183)
`
`8
`embodiment is most preferably located at the center of the
`first line of the message center as shown. Thezero point may
`be shifted if desired. 'The. left and right-most characterin the
`first line of the message center display (—) and (+) characters,
`respectively, represent or indicate either a decreasing or
`increasing filtered rate of change in fuel economy as the
`graph extends from the zero point in the respective direc-
`tions.
`The graphical display of a representation of the fuel
`economy can be processed so as to avoid presenting dis-
`tracting or erratic movement
`to the driver.
`In one
`embodiment, the value of the fuel economy is evaluated to
`determine whether it has changed too much from a previous
`interval. If so, the displayed value is only allowed to change
`by a predefined amount.
`To cause the fuel economy bar in the display to move
`continuously or in a smooth manner, the rate of change of
`the vehicle’s fuel economyis digitally filtered using pre-
`defined coefficients. The specific expression for the digitally
`filtered rate of change in fuel economy (FRC)is set forth in
`the following expression:
`FRCles *(IFE-IFE,_:)*3004¢,*FRC,_,V256
`
`The subscript notation ..,. refers to the time at which the
`instantaneous fuel economyis calculated. The instrumenta-
`tion control unit preferably computes the instantaneousfuel
`economy periodically, such as every 200 ms, which corre-
`sponds to the rate at which PID 84 and PID 183 are
`transmitted to the instrumentation control unit. If the mag-
`nitude of the instantaneous fuel economyis greater than 99.9
`or if the fuel rate is zero, the magnitude of the instantaneous
`fuel economyis set to 99.9 in this particular implementation.
`The instrumentation control unit computes a representa-
`tion of the fuel economy by combining values for the
`instantaneous fuel economyor the rate of change of instan-
`taneous fuel economy from different intervals. For instance
`in one method, the instrumentation control unit combines a
`where c;+c,=256.
`value for the current instantaneous fuel economy with a
`C, and c, are filter coefficients which are specified as
`value of the instantaneous fuel economy for one or more
`inputs to the configuration file for the instrumentation con-
`previous intervals. Similarly,
`the instrumentation control
`trol unit. IFE, and IFE,, are respectively, the instantaneous
`unit combines a value for the current rate of change of
`fuel economy at the current and previous update times.
`instantaneous fuel economy with a value of the rate of
`FRC,_, is the filtered rate of change of the fuel economyat
`change of instantaneous fuel economy for one or more
`the prior update time. To initiate the filtering process, the
`previous intervals. More specifically,
`the instrumentation
`instrumentation control unit sets FRC,_, to zero. This digi-
`control unit combines a weighted value of the current
`tally filtered rate of change of the vehicle’s fuel economyis
`instantaneous fuel economy with a weighted value of the
`updated every 200 ms.
`instantaneous fuel economy computed from priorintervals.
`To avoid distracting the driver, it is important that the
`Similarly, the instrumentation control unit combines a
`movement of the bar graph not appear to jump from one
`weighted value of the currentrate of change of instantaneous
`update to the next. To prevent distracting movement in the
`fuel economy with a weighted valueof the rate of change of
`bar graph, a maximum change in length ofthe bar is limited
`instantaneous fuel economy computed from prior intervals.
`in this implementation. For example, the maximum change
`The instrumentation control unit can compute this repre-
`in length of the bar graphis limited to five columnsof dots
`sentation of the fuel economy without using trip or leg
`(one character position) per update. FIG. 6 illustrates a
`values such as thetrip or leg distance, or total fuel volume
`method for converting an unrestricted filtered rate of change
`consumed over a trip or leg of a trip. A trip or leg ofatrip
`in fuel economy to a restricted value called “LIM”.
`is sometimes defined as a period starting at a point where the
`In this embodiment, the parameters for setting up or
`fuel economydevice is reset or initialized and continuing to
`calibrating the display of the filtered rate of change in fuel
`the current pointin time.
`economy are defined as follows. The parameter MAX is
`In one embodiment, the representation of instantaneous
`variable and is a maximum value of the increasedfiltered
`fuel economy is computed in the instrumentation control
`rate of change in fuel economyto be displayed while -MAX
`unit by digitally filtering the instantaneous fuel economy
`is variable and is a maximum value ofthe decreased filtered
`values. The instrumentation control unit performs digital
`rate of change in fuel economy to be displayed. In addition,
`filtering using predefined filter coefficients either perma-
`DELTAis the minimum resolutionof the display. For the 16
`nently programmed into the instrumentation control unit or
`character 5x7 dot matrix display of FIG. 4 in this
`downloaded from the data port on the data link. The specific
`implementation, DELTA=MAX/7. The two opposite end
`expression for computing the filtered instantaneous fuel
`characters are respectively reserved for displaying symbols
`economy (FIFE) in this embodimentis set forth below:
`indicating fuel economy is increasing (+) or decreasing (—)
`(see FIG.5, line 80). The parameter MAX can be specified
`as an input to a configuration file for the instrumentation
`control unit. The value for the restricted filtered rate of
`change in fuel economy at time t=0 is represented by
`illuminating (see FIG. 4) the first or reference column of
`dots to the right of the center in the first line 80 of the
`display. Although less preferred, the reference column may
`be shifted to the left or right in FIG.4. This reference column
`of dots is preferably always illuminated when the display
`(FIG. 4, FIG. 5) is showing the fuel economy bar graph.
`Each column of pixels in the bar graph represents a numeri-
`cal value equal to DELTA/S in this implementation. For
`example, when the instrumentation control unit is config-
`
`15
`
`25
`
`45
`
`55
`
`13
`
`FIFEA(c,*IFE,+c,*FIFE,..V256, where cytc,=256
`
`Both c, and c,arefilter coefficients which are specified as
`inputs to the configurationfile of the instrumentation control
`unit. To initiate the process, the filtered instantaneous fuel
`economyis initially set to the instantaneous fuel economyat
`the starting time t=0. The numerical value ofthefiltered fuel
`economyis displayed as shown in the message center and is
`updated every 200 ms. The bar graph (shown in FIG. 5)
`displays the rate of change (increase or decrease) in the
`vehicle’s instantaneous fuel economy. To permit a symmet-
`ric display of both increasing and decreasing fuel economy,
`the zero point 104 of the fuel economy bar graph inthis
`
`13
`
`

`

`5,693,876
`
`10
`FIG. 8 is a diagram of an exemplary keypad for the ICU.
`The keypad may include the following dedicated keys:
`
`
`(180)
`1. Time
`(182)
`2, Temperature
`(184)
`3. Fuel Data
`(186)
`4. Trip Data
`
`5. Leg Data (188)
`
`10
`
`15
`
`20
`
`30
`
`35
`
`The illustrated keypad also includes the following general
`purpose keys:
`
`1. Left Arrow Key
`(190)
`2. Down Arrow Key
`(192)
`3, Right Arrow Key
`(194)
`
`4. SetfReset Key (196)
`
`9
`ured such that MAX=10.5 and the value of LIM,is
`computed, for example by the method of FIG. 6, to be 4.5
`mpg/min, 15 columns ofpixels to the right of the center in
`the message center wil