USOOS693876A
`
`Umted States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,693,876
`
`Ghitea, Jr. et a].
`[45] Date of Patent:
`Dec. 2, I997
`
`
`[54]
`
`[75]
`
`[73]
`
`[21]
`
`[221
`
`[51]
`[52]
`[58]
`
`[5 6]
`
`FUEL ECONOMY DISPLAY FOR VEHICLES
`
`Inventors: Nicolae Ghitea, J11. Tigard, Oreg.;
`James M. Ehlbeck, La Comet, Wash.
`Assignee: Freightliner Corporation, Portland,
`0mg
`
`I
`
`Appl‘ No“ 655’s“
`Fflech
`May 31, 1996
`
`4,845,630
`5,143,702
`
`711989 Stephens
`911992 (Solid-1J1:
`
`731113
`................................ 731114
`
`
`
`OTHER PUBUCAHONS
`P rformnnce, Detroit Diesel Corporati
`E
`Dri
`on
`P33335217“. WI
`6
`PmDriverm User Manual, Dell'oit Diesel Corporation,
`Man, 1994.
`Operating & Error Codes, FloScan Inslrument Company,
`Inc, Alan 1993-
`
`.
`
`GfllM 15100
`lnt. C135
`731114; 3401439
`U.S. CL
`
`Field of Search ..,
`.. 731113, 114, 116,
`7311112, 117.3; 3401‘439
`
`Primary Etaminer—George M. Dombmske
`Attorney, Agan or Fims—Klarquist Sparh‘nan Campbell
`Leigh & Whinston
`[57]
`
`ABSTRACT
`
`manages GM
`U_S_PATENI~ DOWS
`
`4,400,779
`,
`4,564,905
`4,510,226
`4,663,718
`4,706,083
`
`731114
`
`311983 Knsuge eta].
`
`[$2132 (610101123: 313]”
`'-
`:0
`et
`.
`..
`
`111936 Masada et a1.
`.. 731114
`
`211986 Aussedat ............
`731113
`
`511987 Augelloet a1.
`731F114
`............................... 731113
`1111937 Beau et a1.
`
`An improved fuel economy device computes a filtered rate
`of change of instantaneous fuel economy or a filtered
`mstantancous fuel economy and repeuuvely updates :1
`graphical display depicting the current fuel economy. The
`fuel economy can be displayed as a percentage of a. target
`-
`memd by me mm m “h” Wat”
`
`21 Claims, 8 Brewing Sheets
`
`
`
`
`
`@353
`
`25°
`
`2'32
`264
`
`r.
`
`266
`
`READSPEED11.FUELRATE 5E8
`
`CALCULATE MPG_INST
`
`NO
`
`RETURN
`
`TO MAIN PROGRAM
`
`MPG_FILTEFlEDo = MPG_FILTEF1ED1
`274
`NC
`
`2?2
`
`276
`
`MPG_FILTEF[ED1 = MPG_INST
`
`CALCULATE MPG_FILTERED1
`
`YES
`
`282
`
`MPG_FILTERED1 = 99.9
`
`
`
`
`IS
`MPG FILTEHED1
`
`—> 99.9
`? _
`
`
`CALCULATE SUM
`
`CALCULATE BAHGRAPH
`
`DISPLAY BARGHAF’H
`
`290
`
`"°YES
`
`TO FIG.1OB
`
`284
`
`236
`
`238
`
`UNIFIED 1004
`
`UNIFIED 1004
`
`1
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 1 of 3
`
`5,693,876
`
`INTERFACE
`
`2
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 2 of 8
`
`5,693,876
`
`
`
`88
`
` 1%
`®®®®®®®
`®®®®®®
`
`®®®®®®®
`
`®®®®®®®
`
`®®®®®®®
`
`FIG. 5
`
`100
`
` /
`82—- M 123456.?
`10:!
`104
`T
`
`108
`
`3
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 3 of 8
`
`5,693,876
`
`FIG. 6
`
`FRCt - LIMH> DELTA
`
`LlMt_1+ DELTA > MAX
`
`
`
`
`
`
`
`
`LIMt = AVEt
`
` FROt - LlMt_1<- DELTA
`
`
`LIMH - DELTA < -MAx
`
`
`
`LIMt = LIMH - DELTA
`
`FIG. 7
`
`158 .
`
`I
`
`156
`
`150* —
`
`0% I'll
`
`+
`
`152—— 1591234561 MI
`
`160
`
`54
`
`1
`
`162
`
`
`
`
`
`
`
`4
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 4 of 8
`
`5,693,876
`
`mm".mm?wmwmap02mm:09.3:.mm
`
`m5
`
`a
`
`
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`
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`
`ZO_._.<EIO..“_Z_
`
`5
`
`
`
`
`
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 5 of 8
`
`5,693,876
`
`w
`
`202
`
`
`
`READ SPEED 204
`
`.9 FUEL RATE
`
`CALCULATE MPG_|NST
`
`205 FIG- 9A
`
`
`
`CALCULATE MPG_FILTERED m
`
`208
`
`212
`
`
`'3
`“Mi
`
`FILTEREDm
`
`
`219
`YES
`
`MPG_F|LTERED (t) = 99.9
`
`_
`
`>9?
`
`
`CALCULATE SUM
`
`
`
`216
`
`YES
`CALCULATE MPG_SHORT_TERM 213
`
`
`CALCULATE PERCENT
`
`220
`
`224
`
`PERCENT = 100
`
`
`
`
`
`
`PERCENT = —100
`
`CALCULATE BARS 1
`
`
`
`6
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 6 of 8
`
`5,693,876
`
`FIG. QB
`
`o
`
`CALCULATE Z
`
`232
`
`236
`
`DISPLAY 0%
`
`DISPLAY BARS 1
`
`240
`
`CALCULATE D
`
`DISPLAY D
`
`a 248
`
`YES
`
`250
`
`NO
`
`YES
`
`252
`
`RETURN TO
`MAIN PROGRAM
`
`7
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 7 of 3
`
`5,693,876
`
`mm FIG. 10A
`
`SUM = o
`
`260
`
`262
`STEP = 1 TO N
`READ SPEED & FUEL RATE
`
`264
`
`[—299
`
`YES
`
`CALCULATE MPG_INST
`
`NO
`
`MPG_FILTERED0 = MPGHFILTERED1 fem
`
`268
`
` PROGRAM
`
`276
`
`
`
`
`
`IS
`{—230 S
`MPG_FILTERED1
`
`> 99.9
`
`
`
`MPG_F|LTEF{ED1 = MPG_INST
`
`CALCULATE MPG_FILTEHED1
`
`E
`
`292
`MPG_F|LTERED1 = 99.9
`
`CALCULATE SUM
`
`284
`
`CALCULATE BARGRAPH
`
`236
`
`DISPLAY BARGRAPH
`
`288
`
`
`
`
`g 290
`
`Y SE
`
`T0 FIGJOB
`
`8
`
`

`

`US. Patent
`
`Dec. 2, 1997
`
`Sheet 3 of 8
`
`5,693,876
`
`FIG. 1OB
`
`FROM
`FIG.10A
`
`BARSO = BARS1
`
`292
`
`CALCULATE MPG_SHOR‘ITERM
`
`294
`
`CALCULATE PERCENT
`
`296
`
`
`
`PERCENT>100
`
`298
`
`YES
`
`
`
`
`
`
`
`
`
`
`PERCENT<-400
`
`302
`YES
`
`300
`
`PERCENT=1OO
`
`304
`
`PERCENT=-400
`
`CALCULATE BARS1
`
`305
`
`CALCULATE DELTA
`
`308
`
`9
`
`9
`
`

`

`5,693,376
`
`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-haul trucks, to increase fuel economy. A number of fuel
`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 economy instnlments fail 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 economy indicator is too sensitive to changes in the
`fuel rate. In these latter cases, the indicator reading changes
`rapidly and en‘atically, distracting the driver. To be truly
`effective, a fuel economy indicator should be accurate,
`responsive to drle actions, meaningful to 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. Merer
`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 Wine of fuel economy.
`Another measure of fuel economy is the “average” fuel
`economy. This quantity is computed by simply dividing me
`distance traveled by the amount of fuel consurrmd. This
`quantity is not very helpful to the driver because it 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 file] mnsumption to
`average fuel consumption. While this ratio may provide
`more helpful feedback than merely computing the instanta-
`neous or the average fuel consumption,
`it sulfers from
`drawbacks. The average fuel economy is 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
`acwmulatcs more miles, the value of theratio 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 instrument flucmates rapidly,
`it conveys little, if any useful information and is distracting
`to the driver. On the other hand, if the display is static, itfails
`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.
`SUMNIARY OF THE INVENTION
`
`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
`
`5
`
`£0
`
`15
`
`20
`
`35
`
`45
`
`55
`
`10
`
`2
`sensor for measuring road speed. The control unit comptnes
`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
`economy representation 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 economy as a percentage
`of apredefined targetfuel economy. The target fuel economy
`can be preset or mm 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 and a filtered value the instan-
`taneous fuel economy computed fora 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 instantaneous or the short term average
`fuel economy can then be compared to the target 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 number of 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 Cd'
`shifts gears. these actions are almost immediately reflected
`in the fuel economy display. Moreover, the fuel economy
`display is more neonate 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 economy display is
`responsive to driver actions,
`it
`is designed to change
`smoothly so as not to distract the driver. The fuel economy
`values can be filtered based On programmable ooeflicients
`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
`
`

`

`5,693,876
`
`3
`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 embcxfiment.
`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 embodiment of the display
`device.
`
`FIG. 8 is a diagram of the keypad for the ICU.
`FIGS. 9A and 9B are a flow diagram illustrating a process
`for computing fuel economy in a second embodiment.
`FIGS. 10A and 1013 are a flow diagram illustrating a
`process for computing fuel economy in a third embodian
`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
`
`10
`
`15
`
`FIG. 1 is a block diagram illustrating the system archi-
`tecture in a truck for one embodiment of the invention. The
`system architecture includes a number of electronic control
`units (ECU) interconnected via a data link 2|]. 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
`includes an optional data pun-30, for coupling external data
`processing equipment to the ECUs on board the truck. This
`data port enables an external computer, for example,
`to
`receive and transmit messages on the data link. It also
`enables an external computer to download data or a file to an
`ECU and to receive data or a file from an ECU.
`FIG. 2 is a block diagram illustrating the engine ECU in
`more detail. The engine ECU includes memory 40, a CPU
`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. The port interface
`44servesasalinkbetwoentheCPU42andaserial
`communication path called the data link 20.
`The engine ECU also includes a variety of sensors and
`controls for monitoring and controlling engine performance.
`This implementation of the ECU includes a fuel rate control
`48 and a speed sensor 50. The ECU in combination with the
`fuel rate control serves as a fuel rate meastn-ing 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 ECU also serves as
`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 meastn'e the fuel rate. and the use of the engine
`ECU is 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 rettn'ned 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
`
`4
`
`controlling the solenoid valves that inject fuel to the engine
`cylinders. The rate of fuel flow is directly related to the
`amount of time that the solenoid valve is closed. This time
`
`period determines the volume of fuel injected into a cylinder
`per revolution. By determining the amount of time that the
`solenoid valves are closed, the engine ECU can compute the
`amount of fuel flowing into the engine. The engine ECU
`cutoulales the fuel flow rate from the dwell of the injection
`pulse and the engine speed.
`In this embodiment, the engine ECU is 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.
`One particular method used in this implementation is to
`sense the speed of rotation of the tail shaft of the truck. A
`magnetic sensor located on the tail 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 (AID) 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.
`
`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 memory 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.
`
`35
`
`the ICU includes a
`In one specific implementation,
`68HC11 microprocessor from Motorola Corporation, and its
`memory 62 comprises EEPROM, ROM, and RAM. This
`specific ICU has 8 KB of external EEPROM, 128K of ROM
`and 2K of RAM. 'I'heinternal memory of the CPU comprises
`256 Bytes of RAM and 512 bytes of EEPROM. This is only
`one specific implementation of the ICU. A variety of con-
`ventional processors and memory systems can be used to
`implement the functi0nality of the instrumentation control
`unit.
`
`The ICU also preferably includes an input device 70 and
`a display defice 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 output to
`the driver display. In one specific implementation, the dis
`play device comprises a two by 2D vacuum fluorescent
`display.
`The particular ICU used in this implementation is manu—
`factured by Joseph Polls]: of Boston, Mass. for Freightliner
`Corporation. The instrumentation control unit is presently
`available as a replacement part from Freightliner Corpora-
`non.
`
`45
`
`55
`
`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 11708, a
`standard for serial data communication between microcom-
`puter systems in heavy duty vehicle applications. While this
`specific embodiment is based on the 11703 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. The communication
`link need not be a shared communication path. It is also
`possible to connect fuel rate and speed sensors tothe control
`unit responsible for computing and displaying fuel economy.
`
`11
`
`11
`
`

`

`5,693,876
`
`5
`In the embodiment shown in FIG. 1, the data link 40 is
`comprised of a twisted pair cable operating at 9600 band.
`Designed according to the SAE J 1708 standard, the datalink
`forms a communication channel among electronic connol
`units coupled to it. Electronic control units generate a digital
`signal on the data link by applying a voltage dilferential
`betWeen the two wires in the cable. A voltage difl’erential
`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 impervious to signal degradation.
`However, other alternative communication media could be
`used in place of the 11708 cable.
`The ECUs connected on the network communicate with
`each other according to protocols defined in SAE 11708 and
`SAE 11587. The SAE 11587 standard is entitled “Joint
`SAFJ’IMC 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 11703.
`According to SAE 11708401587, 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 instrumentation con-
`trol unit and the engine ECU are both transmitters and
`receivers. For the purpose of measmjng 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 (MJD), 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 11708
`standard The message identification numbers are assigned
`to transmitter categories as identified in SAE 1158?. 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 convey informa-
`tion about one or more parameters contained within the
`messages. According to the SAE 1158? 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 1158? supports different data
`fonnats 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 11708. The standard destribes methods for access-
`ing the data link and constructing messages for transfer over
`it. It also defines a method for resource contention among
`the BCUs 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 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 ECUs that opmate as receivers
`on the data link will receive the message. However. receiv-
`ers only act on a message if programmed to do so.
`
`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 message identifiers. The Mle of
`higher priority transmitters have a greater numba' 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 must wait and
`retransmit 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.
`Among the parameters defined in SAE 11587, there are
`two that are particularly relevant to fuel economyr in this
`implementation. The first is P11) 84, which represents the
`road speed. The second is P11) 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 The:
`Bit Resolution:
`Maximum Range:
`Minibar Update:
`Message Priority:
`Format:
`
`1 I:th
`Unsigned short integer
`0.305 krn'h (0.5 mph)
`0w205.2kmfh{0to 127.5 mph)
`0.1 s
`1
`Data
`PID
`a
`84
`
`a road speed
`
`The details of the fuel rate parameter are set forth below:
`
`
`1?th Data length:
`Data Type:
`Bit Resolution:
`Matti:an Range:
`Transmission Ilpdatc:
`Message Priority:
`Format:
`
`2 characters
`Unsigned integer
`16.428 x 10“ 11501.34 x 10‘6 galls)
`0.0 to 1.076 65 Us (9.0 to 018442190 galls)
`0.2 a
`3
`
`Data
`PJD
`as
`183
`
`an mel rate
`
`Engine control units capable of transmitting the road
`speed and fuel rate parameters include:
`the DDEC 1]]
`provided with Benoit Diesel engines from Detroit Diesel
`Corporation of Detroit, Mich; the ADEM 11 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.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`45
`
`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 ccrnpised of a 5x7 array of pixels (88,
`90 for exalnple).
`FIG. Sis a diagramillustrating 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
`avnrage fuel economy in miles per gallon on the left side
`1015. and a seven digit odometer reading on the right side
`108.
`
`55
`
`65
`
`12
`
`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 on the
`road speed and fuel rate parameters from the engine ECU.
`Both the numerical and graphical quantifies are computed
`fi'omthe instantaneous fuel economy. The instantaneous fuel
`economy is calculated using the equation:
`
`l'FEFmad spearer Myfird mar, (Pro 183)
`
`The subscript notation ..,- refers to the time at which the
`instantaneous fuel economy is calculated. The instrumenta—
`tion control unit preferably computes the instantaneous fuel
`economy periodically, such as every 200 ms, which corre-
`sponds to the rate at der 911) 84 and P11) 183 are
`transmitted to the instrumentation control unit. If the mag»
`nitride of the instantaneous fuel economy is greater than 99.9
`or if the fuel rate is zero, the magnitude of the instantaneous
`fuel economy is 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 economy or the rate of change of instan-
`taneous fuel economy from diiferent intervals. For instance
`in one method, the instrumentation control unit combines a
`value for the current instantaneous fuel economy with a
`value of the instantaneous fuel economy for one or more
`previous intervals. Similarly,
`the instrumentation control
`unit combines a value for the current rate of change of
`instantaneous fuel economy with a value of the rate of
`change of instantaneous fuel economy for one or more
`previous intervals. More specifically,
`the instrumentation
`control unit combines a weighted value of the current
`instantaneous fuel economy with a weighted value of the
`instantaneous fuel economy computed from prior intervals.
`Similarly, the instrumentation control unit combines a
`weighted value of the currentrate of change of instantaneous
`fuel economy with a weighted value of the rate of change of
`instantaneous fuel economy computed from prior intervals.
`The instrumentation control unit can compute this repre—
`sentation of the fuel economy without using trip or leg
`values such as the trip or leg distance, or total fuel volume
`consumed over a trip or leg of a trip. Atrip or leg of a trip
`is sometimes defined as a period starting at a point where the
`fitel economy device is reset or initialized and continuing to
`the current point in time.
`In one embodiment, the representation of instantaneous
`fuel economy is computed in the instrumentation control
`unit by digitally filtering the instantaneous fuel economy
`values. The instrumentation control unit performs digital
`filtering using predefined filter coeflicients either perma-
`nently programmed into the instrumentation control unit or
`downloaded from the data port on the data link. The specific
`expression for computing the filtered instantaneous fuel
`economy (FIFE) in this embodiment is set forth below:
`
`FlFEflcflIFEfie-JFIFEHMG, when: c.+o,=256
`
`Both c1 and c: are filter coeflicients which are specified as
`inputs to the configuration file of the instrumentation control
`unit. To initiate the process, the filtered instantaneous fuel
`economy is initially set to the instantaneous fuel economy at
`the starting time 13:0. The numerical value of the filtered fuel
`economy is displayed as shown in the message center and is
`updated every 200 ms. The bar graph (shown in FIG. 5)
`displays the rate of drange (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 in this
`
`8
`embodiment is most preferably located at the center of the
`first line of the message center as shown. The zero point may
`be shifted if desired. The. left and right-most character in 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 economy is digitally filtered using pre-
`defined coefficients. The specific expression for the digitally
`filtered rate of change in fuel economy (PRC) is set forth in
`the following expression:
`FRCFfic, '{fFErIFEh1)‘300H4’FRCh1F256
`
`where c3+c4=256.
`Cs and c4 are filter coefficients which are specified as
`inputs to the configuration file for the instrumentation con-
`trol unit. IFE, and IFEH are respectively, the instantaneous
`fuel economy at the current and previous update times.
`FRCM is the filtered rate of change of the fuel economy at
`the prior update time. To initiate the filtering process, the
`instrumentation control unit sets FRch to zero. This digi-
`tally filtered rate of change of the vehicle‘s fuel economy is
`updated every 200 ms.
`To avoid distracting the driver, it is important that the
`movement of the bar graph not appear to jump from one
`update to the next. To prevent distracting movement in the
`bar graph, 21 maximum change in length of the bar is limited
`in this implementation. For example, the maximum change
`in length of the bar graph is limited to five columns of dots
`(one character position) per update. FIG. 6 illustrates a
`method for converting an unrestricted filtered rate of change
`in fuel economy to a restricted value called “LEM”.
`In this embodiment, the parameters for setting up or
`calibrating the display of the filtered rate of change in fuel
`economy are defined as followa. The parameter MAX is
`variable and is a maximum value of the increased filtered
`rate of change in fuel economy to be displayedwhile —MA.X
`is variable and is a maximum value of the decreased filtered
`rate of change in fuel economy to be displayed. In addition,
`DELTA is the minimumresolution of the display. For the 16
`character 5%? dot matrix display of FIG. 4 in this
`implementation, DELTA=W. The two opposite end
`characters are respectively reserved for displaying symbols
`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
`he 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 DELTAIS in this implementation. For
`example, when the instrumentation control unit is config-
`
`5
`
`10
`
`15
`
`25
`
`30
`
`45
`
`55
`
`13
`
`13
`
`

`

`5,693,876
`
`9
`ured such that MAX=105 and the value of LM, is
`computed, for example by the method of FIG. 6, to be 4.5
`mpglmin, 15 columns of pixels to the right of the center in
`the message center will be illuminated.