United States Patent [19]
`Nishida
`
`lllllllllllllllllllllllllllllllllllllllllllyllllllllllllllllll'llllllllllllll
`5,215,159
`Jun. 1, 1993
`
`USOO5215159A
`Patent Number:
`Date of Patent:
`
`[11]
`[45]
`
`[54] SYSTEM FOR CONTROLLING A DRIVING
`DEVICE OF A VEHICLE
`Minoru Nishida, Hyogo, Japan’
`[75] Inventor:
`Assignee: Mitsubishi Denki K.K., Tokyo, Japan
`[73]
`[21]
`Appl. No.: 708,426
`[22] Filed:
`May 31, 1991
`[30]
`Foreign Application Priority Data
`Jun. 4, 1990 [JP]
`Japan ................................ .. 2-146994
`
`[51] 1111.015 ............................................ .. B60K 31/04
`[52] us. c1. .................................. .. 100/179; 180/169;
`180/171
`[58] Field ofSeai-ch ............. .. 180/167, 170, 171, 179,
`180/169; 364/426.01, 426.04; 123/352
`References Cited
`U.S. PATENT DOCUMENTS
`
`[56]
`
`4,706,195 11/1987 Yoshino et al. ................... .. 180/169
`4,947,952 8/1990 Kajiwara ...................... .. 364/426.0l
`
`FOREIGN PATENT DOCUMENTS
`
`2642211 6/1978 Fed. Rep. ol'iGermany .... .. 180/171
`3304620 9/1983 Fed. Rep. of Germany .
`3247450 6/1984 Fed. Rep. of Germany .... .. 180/169
`
`3936925 5/1990 Fed. Rep. of Germany .
`59-231157 12/1984 Japan ................................. .. 180/179
`2-128930 5/1990 Japan ................................. .. 180/170
`Primary Examiner—Eric D. Culbreth
`Attorney, Agent, or Firm-Sughrue, Mion, Zinn,
`Macpeak & Seas
`ABSTRACT
`[57]
`A system for controlling running of a vehicle comprises
`a switch for setting a slow-run mode, a sensor for de
`tecting that the brake is being applied, a driving force
`control device mechanically separated from the accel
`erator for controlling a driving force of the vehicle, a
`sensor for detecting the running speed of the vehicle, a
`switch for setting a slow-run speed command signal. A
`target speed is generated on the basis of information
`concerning the brake activation and, the running speed
`of the vehicle and the slow-run speed command signal
`value. In the slow-run mode, when the brake is not
`applied, the driving force control device is driven to
`cause the vehicle to run at the target slow-run speed,
`and when the brake is applied, the driving force control
`device is driven so that no driving force is produced at
`least in the direction of travel of the vehicle.
`
`3 Claims, 8 Drawing Sheets
`
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`Swagway_1005
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`US. Patent
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`J1me 1, 1993
`
`Sheet 1 of 8
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`US. Patent
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`June 1,1993
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`US. Patent
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`June 1, 1993
`
`Sheet 3 of s
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`US. Patent
`
`June 1, 1993
`
`Sheet 6 of 8
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`5,215,159
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`
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`U.S. Patent
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`Jlime 1, 1993
`
`Sheet 7 of 8
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`5,215,159
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`U.S. Patent
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`June 1, 1993
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`Sheet 8 of 3
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`
`1
`
`SYSTEM FOR CONTROLLING A DRIVING
`DEVICE OF A VEHICLE
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to a system for controlling a
`driving apparatus of a vehicle which includes an engine,
`a transmission for receiving the engine output to drive
`the vehicle for controlling the running thereof, and,
`more particularly, to a system for controlling the run
`ning of a vehicle suitable when the vehicle negotiates a
`congested road at low speed and is repeatedly starting
`and stopping and when the vehicle cruises on a rela
`tively busy highway, and on an ordinary suburban road.
`2. Prior Art
`'
`Hitherto, a speed of a motor vehicle has been con
`trolled by opening or closing the throttle valve by pull
`ing a wire, such as a piano wire, by means of an acceler
`ator pedal for adjusting an engine output. Recently, as
`disclosed in "Isuzu Technical Report” No. 72, pages
`7-20, a system has been proposed which includes an
`accelerator pedal disconnected from a throttle valve
`opened and closed by a sensor for sensing the depres
`sion of the accelerator pedal, and an electric motorfor
`driving the throttle valve and a controller. This system
`is arranged so that, as shown in FIG. 1, the output of an
`accelerator pedal 50 is detected by a computer unit 52,
`the detected signal being processed to reflect the driv
`er’s intention. On the basis of information derived from
`a selector position sensor 54, a cooling water tempera
`ture sensor 56, an engine rotation sensor 58 for detect
`ing the rotation of the engine EN, a gear position sensor
`60, a vehicle speed sensor 62, and a clutch position
`sensor 64, a motor MT for regulating the opening of a
`throttle valve SV is operated, a clutch CL is connected
`and disconnected and a gear position of a transmission
`TM is controlled, whereby easy drive and low fuel
`consumption can be established.
`A conventional vehicle control system being con
`structed such as described above, when a road is
`crowded causing consecutive motor vehicles to repeat
`~ edly start and stop, the accelerator pedal and the brake
`have to be depressed alternately. Under these condi
`tions, a driver must constantly control an accelerator
`45
`pedal being careful not to depress it excessively. As
`such, a driver will become fatigued over a period of
`time, thus increasing the probability of an accident.
`
`30
`
`SUMMARY OF THE INVENTION
`The present invention is intended, to solve the above
`mentioned problems and provide a system for control
`ling a driving apparatus of a motor vehicle capable of
`preventing driver fatigue when a vehicle runs at low
`speed (a running condition not containing substantial
`acceleration and deceleration such as a rapid accelera
`tion on sudden stopping is hereinafter referred to as
`“slow-run”), thereby providing safe running of a vehi
`cle.
`According to one aspect of the invention, a system
`for controlling a driving apparatus of the vehicle com
`prises means for setting a slow-run mode,_ means for
`detecting that the brake is being applied, means me
`chanically separated from the accelerator for control
`ling a driving force of the vehicle, means for detecting
`a running speed of the vehicle, means for setting a slow
`run speed command signal, means receiving informa
`tion concerning the brake activation, the running speed
`
`5,215,159
`2
`of the vehicle and the slow-run speed command signal
`for generating a target slow-run speed. In the slow-run
`mode, when the brake is not applied, the means for
`controlling the driving force is driven so as to allow the
`running speed of the vehicle to become the target slow
`run speed, and, when the brake is applied, no driving
`force is produced at least in the direction of travel of the
`vehicle.
`Thus, when the slow-run mode is set, the start, stop
`and running operation of the vehicle without abrupt
`acceleration and deceleration can be attained by operat
`ing one pedal, that is, the brake. Thus, the driver fatigue
`is minimized even when the vehicle istravelling on a
`heavily congested road where the driver repeatedly
`starts and stops the vehicle, and the time required for
`operating the brake to avoid an obstacle, a person or a
`vehicle suddenly appearing in front of the vehicle can
`be minimized whereby highly safe driving is possible.
`The control system may further comprise means for
`measuring a distance between the driver’s vehicle and
`the vehicle in front, and means for generating a target
`slow-run speed generated in response to information
`concerning the brake operation, the inter-vehicle dis
`tance and the running speed of the vehicle, and a slow
`run speed command signal. This control system will
`result in decreasing the number of braking operations
`and thus increasing driving safety.
`The control system may further comprise means for
`selecting either one of two different control modes, i.e.,
`an inter-vehicle distance predominating control mode
`or a running speed predominating control mode, and
`the means for generating the target slow-run speed can
`generate a target slow-run speed in accordance with the
`selected control mode. Thus, the driver can either main
`tain an inter-vehicle distance (a distance between the
`driver’s vehicle and the vehicle in front) at a proper
`value or drive the vehicle at a desired running speed in
`accordance with the driver’s preference, thereby run
`ning the vehicle without adjusting an amount of accel
`erator depression.
`According to another aspect of the invention, a sys
`tem for controlling a driving apparatus of a vehicle
`comprises means for setting a slow-run mode, means for
`detecting that the brake is being applied, means me
`chanically separated from the accelerator for control
`ling a driving force of the vehicle, means for sensing a
`running speed of the vehicle, means for measuring a
`distance between the driver’s vehicle and the vehicle in
`front, means for setting a slow-run speed command
`signal, means, in response to information concerning the
`brake activation, the inter-vehicle distance and the run
`ning speed of the vehicle and the slow-run speed com
`mand signal, for generating a target slow-run speed, and
`decision means, in response to information concerning
`the inter-vehicle distance and the running speed of the
`vehicle, for calculating a speed approaching the vehicle
`in front to make a decision as to whether the measured
`inter-vehicle distance is within a proper distance value
`so as to output a warning signal to the driver and a
`braking command signal to the driving force control
`device. In the slow-run mode, if the braking command
`ing signal is output from the proper inter-vehicle dis
`tance decision means, the driving force control means is
`driven in accordance with the braking command signal.
`If there is no such braking command signal, when the
`brake is not applied, the driving force control means is
`driven to cause the vehicle to run at the target slow-run
`
`so
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`5,215,159
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`speed, and when the brake is applied, the driving force
`control means is driven such that no driving force is
`produced at least in the direction of travel of the vehi- -
`cle.
`Thus, safe driving can be achieved in the slow-run
`mode in various running conditions including low speed
`running on a congested road and cruising on a suburban
`road or highway.
`The proper inter-vehicle distance decision means
`may output a warning signal when the product of a
`speed approaching the vehicle in front and a ?rst set
`value is greater than a current inter-vehicle distance,
`and output a braking command signal when the product
`of a speed approaching the vehicle in front and a second
`set value is larger than a current inter-vehicle distance.
`This operation can minimize a risk of collision between
`vehicles.
`In an embodiment of the control system of the inven
`tion, once a vehicle is set in the slow-run mode by a
`driver, the driving force generating device and the
`transmission of the vehicle are controlled to cause the
`vehicle to run at a target slow-run speed generated on
`the basis of information of a slow-run speed command '
`25
`signal set by the driver and a running speed of the vehi
`cle, without depressing the accelerator further and ad
`justing an amount of accelerator depression, thereby
`enabling the vehicle to be driven with the brake only.
`The running speed is supervised by the computer unit
`with a signal from the vehicle speed sensor. The com
`puter unit operates to variably control the opening of '
`the engine throttle or a current supplied to the electric
`motor and adjust a speed regulating mechanism and a
`load located in the driving force transmitting path,
`thereby maintaining a vehicle speed substantially corre»
`sponding to a sequentially generated target slow-run
`speed.
`,
`If a target slow-run speed is generated on the basis of
`information concerning an inter-vehicle distance in
`40
`addition to the information described above, the brake
`pedal is less frequently depressed and ‘safety is en
`hanced.
`The target slow-run speed can be generated in accor
`dance with either of two different modes, i.e., vehicle
`speed predominating control mode or inter-vehicle
`distance predominating control mode, which is selected
`by the driver.
`Thus, according to an embodiment of the invention,
`50
`when the brake pedal is depressed, the computer unit
`detects this fact immediately to cease the generation of
`the driving force, or cause the driving force control
`means to operate to vary the transmission such that a
`braking force is further generated. When the driver
`stops applying the brake, the vehicle accelerates again
`to run at a target slow~run speed. As a result, it is unnec
`essary for the driver to shift his foot from the brake
`pedal to the'accelerator pedal.
`In a control system according to another embodiment
`of the invention, the computer unit calculates speed
`approaching the vehicle in front on the basis of informa
`tion concerning a running speed of the vehicle and a
`distance between the vehicle and the vehicle in front. If
`such a distance becomes less than a proper value, then a
`warning signal is issued to draw the driver’s attention
`and a braking force is produced through the driving
`force control means to ensure safer driving.
`
`4
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a prior art system for
`controlling the running of a vehicle;
`FIG. 2 is a block diagram of a system for controlling
`the running of a vehicle in accordance with an embodi
`ment of the present invention;
`FIG. 3 is a block diagram of a driving force control
`device of the embodiment of the invention;
`FIG. 4 is a graph showing examples of a target slow
`run speed according to the embodiment of the inven
`tion;
`FIGS. 5A and 5B depict a ?owchart showing an
`operation of the vehicle run controlling system accord
`ing to the embodiment of the present invention;
`FIG. 6 is a graph showing an example of changes in
`the target slow-run speed with respect to time accord
`ing to the embodiment of the invention;
`FIG. 7 is a ?owchart showing in detail a part of the
`flowchart in FIG. 5B; and
`FIG. 8 is a block diagram of a system for controlling
`the running of a vehicle in accordance with another
`embodiment of the invention.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`A ?rst embodiment of the invention will now be
`described with reference to the drawings. In FIG. 2, a
`brake switch 1 for detecting the depression of a brake
`by the driver or a brake pedal sensor 1 for generating an
`electric signal corresponding to a brake depression
`amount, a switch 2 located to be, easily operated by the
`driver for setting the vehicle in a slow-run mode, and an
`inter-vehicle distance sensor 3 which employs a radar
`system or a triangulation system using picture images
`are connected to a computer unit 4 comprising a well
`known microcomputer including a ROM, a RAM, a
`CPU, etc., A/D converter circuits and input and output
`interface circuits having pulse waveform shaping cir
`cuits and executing a main operation in accordance with
`a software program. In addition to the above-described
`brake activation detecting signal, a slow-run mode set
`ting signal and an inter-vehicle distance signal, an elec
`tric signal indicative of a vehicle speed is input from a
`vehicle speed sensor 5 to the computer unit 4, and an
`electric signal corresponding to a speed command in the
`slow-run mode is also input from a speed command
`inputting device 6 to the computer unit 4. A circuit for
`generating a target slow-run speed is provided within
`the computer unit 4 and includes a microcomputer, a
`ROM, etc. The computer unit 4 is further connected
`with a display device 7 which informs the driver that
`the slow-run mode has been set in response to a signal
`output by the computer unit 4 as well as informing the
`driver of a commanded slow-run speed, an accelerator
`pedal sensor 8 for detecting an amount of accelerator
`depression by the driver, a selector switch 9 for select
`ing a control mode in the slow-run mode as an input,
`and a driving force control device 10 for generating a
`driving force of the vehicle in response to a command
`signal from the computer unit 4. (It is noted that the
`driving force control device is mechanically separated
`from the accelerator). FIG. 3 schematically illustrates
`an example of the driving force control device 10. As
`seen in FIG. 3, an engine 20 for generating a driving
`force is coupled to a clutch section 21 which is attached
`to the output shaft of the engine to transmit and control
`an engine torque. The clutch section 21 may be a disk
`
`30
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`5,215,159
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`clutch or a hydraulic torque converter. A transmission
`22 receives a rotational driving force from the clutch
`section 21 and appropriately converts the number of
`rotation and an amount of torque to transmit the driving
`force to the ?nal driving section 23 which comprises a
`reduction gear set and a differential gear train. Wheels
`24 actually drive the vehicle using the rotational force
`of the ?nal driving section 23. The transmission 22 is
`adapted to change a combination of gear sets having
`different gear ratios through a hydraulic or electric
`actuator. An actuator driving circuit 11 drives a gear
`change actuator in the transmission 22 in response to a
`command signal from the computer unit 4. The output -
`of the engine 20 is varied by the degree of opening of a
`throttle valve 12, and the opening of the throttle valve
`is electrically controlled by a throttle actuator 13 in
`cluding an electric motor. In order to open and close
`the throttle valve 12 in response to the command signal
`from the computer unit 4, a driving circuit 14 generates
`a signal for driving the throttle actuator 13.
`An operation of the vehicle run control system will
`now be described.
`When the slow-run mode setting switch 2 is in its
`off-position and the vehicle is in the normal driving
`mode, the computer unit 4 feeds a command through
`the driving circuit 14 to the throttle actuator 13 so as to
`open the throttle valve 12 basically in proportion to an
`amount of accelerator depression. When the vehicle is
`caught in a traf?c jam and forced to repeatedly start and
`stop and the mode switch 2 is turned on by the driver,
`the computer unit 4 detects the signal from the mode
`switch 2. For safety, however, it is desirable that run
`ning control in the slow-run mode does not immediately
`commence, but is permitted to be set when certain pre
`determined conditions are satis?ed. It is preferable for
`such predetermined conditions to be as simple as possi
`ble and necessary to at least maintain the safety desired.
`For example, the vehicle can actually enter in the slow
`run mode when the brake pedal is operated or when the
`distance between the driver’s vehicle and the vehicle in
`front is larger than that preset with respect to the run
`ning speed of the driver’s vehicle. Such an operation is
`performed by the computer unit 4 which receives a
`brake operation detection signal and a signal output
`from the inter-vehicle distance sensor and processes
`these signals using a stored program. When the slow
`run mode is set, the computer unit 4 informs the driver
`through the display device 7 visibly or audibly that the
`slow-run mode has been set so that the driver can al
`ways recognize this fact during the period of time when
`the slow-run mode is being set. When the slow-run
`mode is entered, the computer unit 4 sequentially gener
`ates a target slow-run speed in accordance to data input
`from the speed command inputting device 6, informa
`tion as to whether the brake is applied and data input
`from the inter-vehicle distance sensor 3 and the vehicle
`speed sensor 5, so that the vehicle speed is set to the
`target slow-run speed.
`At this time, a selected one of two different target
`slow-run speeds is generated. More speci?cally, the
`switch 9 selects either of two control modes, that is, the
`mode in which the running speed of the driver’s vehicle
`predominantly becomes a commanded slow-run speed
`input from the input device 6 (running speed predomi
`nating control mode) or the mode in which the distance
`between the driver’s vehicle and the vehicle running in
`front becomes a predetermined value (inter-vehicle
`distance predominating control mode). The speed in the
`
`6
`selected control mode is output and set as a target slow
`run speed used in an actual operation, as described be
`low. Even when the inter-vehicle distance predominat
`ing control mode is selected, when a signal output from
`the inter-vehicle sensor 3 shows no vehicle in front, the
`running speed predominating control mode is entered
`immediately or after a lapse of a predetermined time, so
`that the running condition does not change abruptly.
`The reverse shift from the running speed predominating
`control mode to the inter-vehicle distance predominat
`ing control mode when there is the vehicle infront is
`similarly performed. In the low-speed running mode,
`operating only the brake can achieve accelerating and
`constant speed running operations by controlling the
`throttle valve 12 of the engine 20 and the transmission
`22 in response to a drive command signal output
`through the throttle actuator driving circuit 14 and the
`gear ratio change actuator driving circuit 11 in accor
`dance with a control process programmed in the com
`puter unit 4 in such a way that the vehicle runs at the
`target slow-run speed without the accelerator being
`operated.
`As described above, in, the running speed predominat
`ing control mode the vehicle runs to maintain a com
`manded speed in a so-called cruising condition in which
`the vehicle runs without acceleration or deceleration.
`In the inter-vehicle distance predominating control
`mode the vehicle runs to always maintain a commanded
`distance between the vehicle in front or a proper dis
`tance automatically set by the computer on the basis of
`a current vehicle speed. Thus, during a transient run
`ning condition reaching the cruising, even in the run
`ning speed predominating control mode, a target slow
`run speed is sequentially set in consideration of the
`distance to the vehicle in front. In the inter-vehicle
`distance predominating control mode, as long as the
`driver does not operate the brake, a target slow-run
`speed is sequentially set in consideration of the distance
`to the vehicle in front, even when the vehicle is acceler
`ated or cruising. Either of these two control modes can
`be selected in accordance with a driver’s preference and
`current traf?c conditions, which makes the present
`system effective in various situations.
`FIG. 4 shows an example of acceleration patterns
`when a vehicle runs slowly in the running speed pre
`dominating control mocle. As shown in this ?gure, a
`target slow-run speed value is time-sequentially set to
`allow the driving force control device to be operated in
`response thereto. During running in the slow-run mode,
`when the driver observes an obstacle or detects an
`abrupt decrease in the distance to the vehicle in front
`because it has decelerated, and the driver therefore
`depresses the brake pedal, the brake switch 1 outputs a
`signal informing the computer unit 4 that the brake has
`been operated. In response to this signal, the computer
`unit 4 outputs a command signal to stop the operation of
`the throttle actuator driving circuit 14 and the gear ratio
`change actuator driving circuit 11 so as to minimize a
`driving force of the vehicle or cause the power trans
`mission system to operate as a brake. Thus, the throttle
`valve 13 is closed by a maximum extent within which
`range the engine does not stall. As a result, no driving
`force is generated. If the vehicle runs at relatively high
`speed, the engine brake is operated. During such an
`operation, there is no change in function and operation
`of the brake, irrespective of whether the slow-run mode
`is maintained or not.
`
`50
`
`55
`
`60
`
`20
`
`25
`
`35
`
`40
`
`Swagway_1005
`
`

`
`5,215,159
`7
`8
`Such running control of a vehicle as described above
`running speed V0, the current inter-vehicle distance
`enables the driver to drive on a congested road without
`Dc and the commanded inter-vehicle distance (or
`operating the accelerator. Although it is necessary for
`proper inter-vehicle distance) D0 will now be described
`the driver to respond to obstacles and detect an ap
`by way of a practical example. FIG. 6 shows an exam
`proach to the vehicle in front, the control system of the
`ple of a change in the target slow-run speed VTfrom the
`present invention eliminates the necessity of shifting
`time when a vehicle is at rest to the time when the
`from the accelerator pedal to the brake pedal, so that a
`vehicle reaches a commanded speed, for example, 65
`time delay from the driver’s recognition of need for
`km/h and is cruising in the running speed predominat
`brake operation to the driver’s actual braking operation
`ing control mode. A dot-and-dash curve shows the case
`can not only be shortened, but also the accelerator
`in which the speed is linearly increased from zero at a
`pedal, the brake pedal or the clutch pedal will not be
`time t=0 to 65 km/h at a time t= 18 sec and thereafter
`depressed incorrectly, whereby safe driving can be
`maintained at 65 km/h. This indicates that there is no
`achieved.
`vehicle in front and that a prestored acceleration pat
`In order to perform the above-described control op
`tern is used to sequentially set a target slow-run speed.
`eration, the computer unit 4 is programmed to operate
`The speed VTshown by a solid curve shows the case in
`in accordance with a flowchart shown in FIGS. 5A and
`which there is a vehicle in front when the vehicle is
`5B.
`accelerated. In this case, the target slow-run speed is
`At a step S1, a decision is made as to whether the
`sequentially corrected and set on the basis of the current
`slow-run mode setting switch 2 is ON or OFF. If the
`inter-vehicle distance Dc and the commanded inter
`switch 2 is OFF, the program proceeds to a step S2 and
`vehicle distance (or proper inter-vehicle distance) D0
`the vehicle runs in the normal driving mode. If the
`during the period from a time t=4 sec to a time t: 14
`switch 2 is ON, then the slow-run mode has been set
`sec, because excessive access to the vehicle ahead will
`(step S3), and at a step S4 a decision is made as to
`be caused if the driver’s vehicle runs in accordance with
`whether or not the brake is being operated. If yes, a
`a prestored acceleration pattern for the running speed
`generated driving force is decreased to zero (step S5),
`predominating control mode. The target slow-run
`and if no, a suitable inter-vehicle distance is determined
`speed VTis set at every predetermined time interval At
`and set based on a current running speed Vc (step S6).
`(At=0.25 sec, for example) by a procedure shown in a
`Then, the program makes a decision at a step S7 as to
`?owchart of FIG. 7. The ?owchart of FIG. 7 shows in
`whether or not the selector switch 9 has selected the
`detail the operation at step S14 in the ?owchart of FIG.
`running speed predominating control mode, and if yes,
`30
`5B.
`‘
`a decision is made as to whether or not a commanded
`A running speed at the time of titaken at every inter
`speed V0 has been input (step S8). At a step S9, a deci
`val of At is expressed by Vc(i), a commanded running
`sion is made as to whether or not the current speed Vc ‘
`speed by V0(i), an inter-vehicle distance by Ddi) and a
`has reached the commanded speed V0. If no com
`commanded inter-vehicle distance by D0(i), and these
`manded speed is input at step S8, a speed of 40 km/h is
`information values taken at the time t,‘_.1 (prior to the
`set as the commanded speed V0 at a step S10, and the
`time t,- by At) are suffixed by (i— 1). Thus, At=t,-—t,-_1.
`program proceeds to step S9. If Vc has reached the
`In FIG. 7, at a step S17 a decision is made as to which
`commanded speed V0, the program sets target slow-run
`is larger, the inter-vehicle distance D56) or the com
`speed V T based on the current speed Vc and the com
`manded inter-vehicle distance D0(i). If D0(i)<D¢(i),
`manded speed V0 (step S11), and then outputs a driving
`i.e., there is a sufficient distance between the vehicle
`force control signal (step S12). If Vc has not reached
`and the vehicle in front, then and at a step S18 a decision
`V0 at step S9, i.e., the vehicle is in a transient running
`is made as to which mode has been selected by the
`condition reaching the cruising, a decision is made as to
`selector switch. If V0(i)ZVc(i), the target slow-run
`whether or not an inter-vehicle distance is detected at a
`speed VTis corrected in accordance with Do and Dc
`step S13. If no, that is, there is no vehicle in front, the
`(step S19). After checking with the selector switch, if
`program proceeds to a step S11 and the target speed V 7
`the inter-vehicle distance predominating control mode
`is obtained from the current speed Vc and the com
`is selected, the program proceeds to step S19, but if the
`manded speed V0. If an inter-vehicle distance is de
`running speed predominating control mode is selected,
`tected, the target slow-run speed VTis set at a step S14
`the program proceeds to a step S20 and the target slow
`from the current speed Vc, a current inter-vehicle dis
`50
`run speed VTis determined merely by V0 and V(:. At
`tance Dc and a commanded inter-vehicle distance (or a
`each of steps S20 and S19, the target slow-run speed V T
`proper inter-vehicle distance) D0, and then the pro
`is set by the following equations:
`gram proceeds to step S12. If the inter-vehicle distance
`predominating control mode is selected at step S7, a
`decision is made as to whether or not the commanded
`55
`inter-vehicle distance D0 has been input (step S15), and
`if no, at a step S16 the proper inter-vehicle distance
`determined at step S6 is set as a commanded inter-vehi
`cle distance. Then, the program proceeds to step S13 at
`which, as described above, a decision is made as to
`whether an inter-vehicle distance is detected. If there is
`no vehicle in front, the running control is automatically
`shifted to the running speed predominating control
`mode, and the program pr