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`@ publoafionnumben
`o 549 909 A2
`
`®
`
`EUROPEAN PATENT APPLICATION
`
`@ Application number: 92120574.6
`
`@ lnt. Cl.5: BGOQ 1/52
`
`(29 Date of filing: 02.12.92
`
`@ Designated Contracting States:
`DE FR GB
`
`® Applicant: MITSUBISHI DENKI KABUSHIKI
`KAISHA
`
`2-3, Marunouchi 2-chome Chiyoda-ku
`Tokyo 100(JP)
`
`
`
`@ Inventor: Kajiwata, Yasuya, c/o Mitsubishi
`Denki K.K.
`
`Himeji SYeisakusho, 840, Chiyoda-cho
`Himeii-shi, Hyogo 670(JP)
`
`
` 6:) Priority: 03.12.91 JP 319034191
`
`@ Date of publication of application:
`
`07.07.93 Bulletin 93/27
`
`
`
`
`Representative: Lehn, Werner, Dipl.-lng. et al
`Hoffmann, Eitle & Partner Patentanwalte
`Arabellastrasse 4
` W-8000 Miinchen 81 (DE)
`
`
`
`@ Warning apparatus for a vehicle.
`
`@ A warning apparatus for a vehicle generates a warning for a driver of the vehicle when the separation
`between the vehicle (1) and an obstacle (20) located in front of the vehicle falls below a prescribed value. The
`prescribed value is varied in accordance with changes in the physical or mental state of the driver of the vehicle,
`environmental conditions, or the driving characteristics of the driver and thereby adjust to changes in the driver's
`reaction time and the stopping distance of the vehicle.
`
`FIG.
`
`I
`
`DRIVER
`
`CONDITION
`
`SENSOR
`
`v;
`
`20 *““
`
`’
`
`O .
`
`
`fiat; g
`COMPUTER
`
`
`VEHICLE
`
`
`CONDITION
`SENSOR
`
`
`
`
`Rank Xerox (UK) Business Services
`
`(3.10/35/33» 1i
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`MERCEDES
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`EP0549909A2
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`MERCEDES
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`EP 0 549 909 A2
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`BACKGROUND OF THE INVENTION
`
`This invention relates to a warning apparatus for a vehicle such as an automobile which can warn the
`operator of the vehicle when there is the possibility of a collision with an obstacle located in front of the
`vehicle. More particularly,
`it relates to a warning apparatus which varies the conditions which must be
`satisfied for a warning to be generated in accordance with the physical or mental state of the driver, the
`driving characteristics or the driver, environmental conditions, or other factors.
`In these
`Various collision warning devices for passenger vehicles have been proposed in the past.
`devices, some form of radiation, such as a laser beam or radar,
`is used to determine the separation
`between a vehicle in which the warning device is installed and an obstacle located in front of the vehicle,
`such as another vehicle or a pedestrian. Based on the speed of the vehicle and the rate of change of the
`distance between the vehicle and the obstacle, the warning device determines when there is danger of a
`collision between the vehicle and the obstacle and generates a warning to alert the driver to take evasive
`action.
`
`In a conventional warning device, a warning is generated whenever prescribed conditions are satisfied.
`However, the reaction time of the driver of a vehicle and the ability of the vehicle to stop in order to avoid
`an accident vary greatly in accordance with the circumstances. For example, when the driver is tired, he
`takes longer to react to a warning than when he is alert. Similarly, it takes much longer for a vehicle to stop
`on a wet road surface than on a dry one.
`If the conditions to be satisfied in order for the warning to be
`generated are chosen conservatively so as to allow the driver ample time to stop the vehicle even when the
`driver is tired or when the road conditions are bad, the warning will be generated even in situation when
`unnecessary and will become an annoyance to the driver. On the other hand,
`it the conditions to be
`satisfied with a smaller margin of safety so that the warning will be generated in fewer situations, there may
`be situations in which the warning does not leave the driver sufficient time to safely stop the vehicle and
`avoid an accident.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, it is an object of the present invention to provide a warning apparatus for a vehicle which
`can adapt to changes in the physical or mental state of the driver of the vehicle.
`It
`is yet another object of the present invention to provide a warning apparatus which can adapt to
`changes in the environment in which the vehicle is travelling.
`A warning apparatus for a vehicle according to the present invention generates a warning for a driver of
`the vehicle when the separation between the vehicle and an obstacle in front of the vehicle falls below a
`predetermined value. The predetermined value is varied in accordance with changes in a condition which
`affects the ability of the vehicle to stop.
`In one form of the present invention, the predetermined value for the vehicle separation is varied in
`accordance with changes in the physical or mental state of the driver. For example, the predetermined
`value can be increased when it is determined that the driver is tired or napping or looking away from the
`road.
`
`In another form of the present invention, the predetermined value for the vehicle separation is varied in
`accordance with changes in an environmental condition of the environment in which the vehicle is traveling.
`For example, the predetermined value can be increased when the environmental conditions are such as to
`increase the stopping distance of the vehicle or the reaction time of the driver.
`In yet another form of the present invention, the predetermined value for the vehicle separation is varied
`in accordance with changes in the driving characteristics of the driver. For example, when the driving
`characteristics indicate that the driver is tired, the predetermined value for the vehicle separation can be
`increased.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Figure 1
`invention.
`
`is a block diagram of an embodiment of a warning apparatus according to the present
`
`Figure 2 is flow chart illustrating the operation of the embodiment of Figure 1.
`Figure 3 is a block diagram of another embodiment of a warning apparatus according to the present
`invention.
`
`Figure 4 is flow chart illustrating the operation of the embodiment of Figure 3.
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`EP 0 549 909 A2
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`Figure 5 is a block diagram of still another embodiment of a warning apparatus according to the present
`invention.
`
`Figures 6 and 7 are flow charts illustrating the operation of the embodiment of Figure 5.
`
`DESCRlPTlON OF PREFERRED EMBODIMENTS
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`A number of preferred embodiments of a warning apparatus for a vehicle according to the present
`invention will be described while referring to the accompanying drawings,
`In these embodiments,
`the
`present invention is applied to a vehicle in the form of an automobile, but it could be applied to a different
`type of vehicle, such as a motorcycle.
`Figure 1 schematically illustrates a first embodiment of a warning apparatus installed on a first vehicle 1
`in the form of an automobile travelling in the direction of the arrow at a velocity V0. On the road ahead of
`the first vehicle 1
`is an obstacle in the form of a second vehicle 20 travelling at a speed VF in the same
`direction as the first vehicle 1. However, the obstacle need not be moving, and it can be an object other
`than a vehicle, such as a pedestrian or an animal crossing the road. Although the first vehicle 1
`is illustrated
`as being larger than the second vehicle 20, this is merely for ease of illustration, and the relative sizes of
`the first and second vehicles is not important.
`The warning apparatus includes an obstacle sensor 2, which can be any device capable of sensing the
`separation between the first vehicle 1 and the second vehicle 20. For example,
`it can be a device which
`generates a beam of radiation, such as a beam of light waves, radar, radio waves, or ultrasonic waves,
`reflected off the second vehicle 20 and returns to the obstacle sensor 2, Alternatively, it can be an imaging
`device which forms an image of the second vehicle 20 and measures the separation based on the image.
`The obstacle sensor 2 generates an output signal
`indicating the measured separation from the second
`vehicle 20 and provides the output signal to a controller in the form of a computer 10,
`Examples of methods that can be used by the obstacle sensor 2 to measure the separation from the
`second vehicle 20 include triangulation and stereo processing of a plurality of video images. Based on the
`time rate of change of the separation, the relative speed of the first and second vehicles as well as the
`speed of the second vehicle 20 can be determined.
`The obstacle sensor 2 could also be a device which receives information transmitted from a sensor
`mounted on or along the road and which calculates the separation between the vehicles and their relative
`speed based on the transmitted information.
`A vehicle condition sensor 3 senses ore or more operating conditions of the first vehicle 1, such as the
`vehicle speed, the engine rotational speed, the engine torque, the vehicle acceleration, the steering angle of
`the steering wheel, or the yaw rate of the speed change ratio. Sensors for sensing such parameters are well
`known to those skilled in the art, and one or more such conventional sensors can be employed as the
`vehicle condition sensor 3. An output signal indicating the condition or conditions detected by the vehicle
`condition sensor 3 is input to the computer 10 by the vehicle condition sensor 3.
`A driver condition sensor 4 senses one or more conditions indicative of the physical or mental state of
`the driver of the first vehicle 1 and generates a corresponding output signal which is input to the computer
`10. The driver condition sensor 4 can be a device which senses when the driver is tired, napping, or looking
`away from the road, or it can sense any other condition in which the driver‘s reaction time is expected to be
`impaired. These conditions can be sensed either directly or indirectly, For example, when the driver is
`manipulating one of the accessories of the vehicle such as the air conditioner,
`the radio,
`the cigarette
`lighter, or a car telephone,
`it can be inferred that the driver is looking away from the road and therefore
`requires longer to react to a warning.
`Based on the input signals from sensors 2 - 4, the computer 10 determines when a dangerous condition
`exists, i.e., a condition when the separation between the first and second vehicles is too small given the
`present speeds of the two vehicles, and in response it controls an alarm 5 to generate a warning. Any type
`of warning device can be used as the alarm 5, such as a buzzer, a chime, a computer-generated voice, or a
`flashing light. The alarm 5 warns the driver of the first vehicle 1
`to slow down or take evasive action so as
`not to collide with the second vehicle 20.
`
`Figure 2 illustrates an example of a routine performed by the computer 10 to control the operation of
`the embodiment illustrated in Figure 1.
`in Step 81, the computer 10 reads in data from each of sensors 2 -
`4.
`in Step 82, the computer 10 determines whether the relative speed VF — V0 of the first and second
`vehicles is greater than 0, wherein V; is the speed of the second vehicle 20 and V0 is the speed of the first
`vehicle 1. The relative speed can be calculated by the computer 10 based on the time rate of change of the
`vehicle separation R determined by the obstacle sensor 2.
`if the relative speed is positive,
`i.e.,
`if the
`separation between the two vehicles is increasing, then in Step 83,
`it
`is determined whether the vehicle
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`separation R is greater than we, wherein k is a coefficient determined by the computer 10. k can be a
`constant, or it can varied by the computer 10 as described below.
`if the separation R is less than or equal
`to We, then in Step S4, the computer 10 controls the alarm 5 to generate a first warning to caution the
`driver.
`
`is growing closer to the
`it means that the first vehicle 1
`if the relative speed is negative,
`In Step 82,
`second vehicle 20, so in Step 85, the computer 10 calculates the minimum required vehicle separation RF
`required for the first vehicle 1
`to decelerate from its present speed of V0 to the same speed V; as the
`second vehicle 20 without colliding with the second vehicle 20 upon the driver of the first vehicle 1 being
`given a warning by the alarm 5 to slow down. R; can be calculated from the formula
`
`(V0 ‘ V392 + (V0 " Va)to
`
`RF 2
`
`Zlal
`
`(1)
`
`i.e., the time between when the warning is generated by the
`wherein to is the reaction time of the driver,
`alarm 5 and when the driver actually depresses the brake pedal, and or is the assumed rate of deceleration
`of the first vehicle 1 when the driver depresses the brake pedal.
`in Step 86, the computer 10 determines whether the actual separation R between the first and second
`vehicles is greater than RF + Fig, wherein is a predetermined safety factor, such as the value We used in
`Step 83.
`If the vehicle separation R is less than or equal to this sum, then in Step S7 it is determined
`whether the vehicle separation R is less than RF.
`If R is greater than or equal to RF, then the driver can
`safely slow down the first vehicle 1 with a normal deceleration or, so in Step S4, the alarm 5 is driven to
`generate the first warning. However,
`in Step S7,
`if the vehicle separation R is smaller than RF, then a
`dangerous situation exists, because if the second vehicle 20 continues at its present speed, braking of the
`first vehicle at the normal deceleration a can not avert a collision. Therefore,
`in Step 88, the alarm 5 is
`driven to generate a second warning which alerts the driver to take immediate evasive action, such as
`stepping more firmly on the brakes or turning the steering wheel to avoid the second vehicle 20.
`In Step 83,
`if the vehicle separation R is larger than we, or in Step SS,
`if the vehicle separation is
`larger than R; + Re, there is no immediate danger of a collision, so a warning is not generated and the
`routine is ended.
`
`When the driver of the vehicle is tired or napping or looking away from the road, his reaction time will
`generally be slower than when he is alert and concentrating on the road. Thus, for safety reasons,
`it
`is
`desirable to maintain a larger separation between the first and second vehicles when the driver's reaction
`time is impaired.
`the value of the vehicle separation R at which the first and
`Therefore,
`in the present embodiment,
`second warnings are generated is varied by the computer 10 in accordance with the condition of the driver
`as indicated by the driver condition sensor 4. For example, when it
`is sensed that the driver is tired or
`sleepy or looking away from the road, the computer 10 can increase one or more of the variables R0, k, or
`to.
`increasing any of these variables will
`increase the value of the separation R at which a warning is
`generated and thereby ensure that the driver has sufficient time after generation of a warning to brake the
`first vehicle 1 without colliding with the second vehicle 2.
`Figure 3 illustrates another embodiment of the present invention installed on a first vehicle 1. The
`overall structure of this embodiment is similar to that of the previous embodiment, and elements 2 ~ 5 can
`have the same structure as described with respect to Figure 1. This embodiment further includes an
`environment sensor 6 which senses one or more conditions of the environment in which the first vehicle 1
`is
`
`travelling and generates a corresponding output signal, which is provided to the computer 10. Preferably,
`the environment sensor 6 detects an environmental condition which affects the distance required for the
`driver to stop the first vehicle 1, such as the presence of rain or wind, or it can detect an environmental
`condition which affects the driver‘s reaction speed, such as fog. These conditions can be detected either
`directly or indirectly. For example, in order to directly sense rain, a rain or fog sensor could be installed on
`the road, and the environment sensor 6 could be a device which receives signals transmitted by the rain or
`fog sensor. Alternatively, the occurrence of rain or fog could be indirectly sensed by detecting when the
`driver of the first vehicle 1 turns on windshield wipers or fog lamps.
`The computer 10 receives the signals generated by sensors 2 ~ 4 and 6 and determines when a
`dangerous condition exists, upon which it drives the alarm 5 to generate a warning.
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`The operation of the embodiment of Figure 3 will be described while referring to Figure 4, which is a
`flow chart of a routine which can be performed by the computer 10 to control this embodiment. in Step 311,
`the computer 10 reads in data from each of sensors 2 - 4 and 6.
`in Step 812, the computer 10 determines
`whether the relative speed VF ~ V0 of the first and second vehicles is greater than 0. if the relative speed is
`greater than zero, then in Step 813, it is determined whether the vehicle separation R is greater than we. if
`the separation R is less than or equal to kVO, then in Step 814, the computer 10 drives the alarm 5 and a
`first warning is generated to caution the driver.
`is growing closer to the
`in Step $12, if the relative speed is negative, it means that the first vehicle 1
`second vehicle 20, so in Step $15, the computer 10 calculates by means of Equation (1) the minimum
`required vehicle separation R; for the driver to decelerate from the current speed V0 to the speed Vi: of the
`second vehicle 20 without colliding with the second vehicle 20 assuming a rate of deceleration a produced
`by braking.
`in Step 816, the computer 10 determines whether the actual separation R between the first and second
`vehicles is greater than RF + Re.
`if the vehicle separation R is less than or equal to this sum, then in Step
`817 it is determined whether the vehicle separation R is less than RF.
`if R is greater than or equal to RF,
`then the driver can safely slow down the first vehicle 1 with a normal deceleration a, so in Step 814, the
`alarm 5 is driven to generate the first warning. However,
`if the driver did not respond to the first warning
`and in Step 817 the vehicle separation R is smaller than RF, then a dangerous situation exists, so in step
`818, the alarm 5 is driven to generate a second warning which alerts the driver to take immediate evasive
`action, such as stepping more firmly on the brakes or turning the steering wheel to avoid the second vehicle
`20.
`
`in Step 813, if the vehicle separation R is larger than we, or in Step 816, if the vehicle separation is
`larger than RF + R0, there is no immediate danger of a collision, so a warning is not generated and the
`routine is ended.
`
`As in the preceding embodiment, the value of one or more of R0, k, and to can be varied in accordance
`with the physical or mental state of the driver as sensed by the driver condition sensor 4 so that the first
`and second warnings are generated earlier, i.e., at a large vehicle separation R when the driver is fatigued
`or looking away from the road.
`Furthermore, the first and second warnings are generated earlier when the environmental conditions are
`such as to increase the stopping distance of the first vehicle 1 or decrease the reaction time of the driver.
`For example, when the road on which the first vehicle 1
`is travelling is wet, the rate of deceleration of the
`first vehicle 1 upon the driver's activating the brakes will be lower than on a dry road surface.
`In order to
`compensate for this, the computer 10 can vary the value of a in Equation (1) so as to increase when the
`environment sensor 6 detects strong rain. By decreasing or,
`the value of RF will be increased, so the
`warnings will be generated earlier. Alternatively, one or more of Ra, k, and to can be adjusted in accordance
`with the environmental condition sensor by the environment sensor 6. For example, Ro, k, or to can be
`increased when the environment sensor 6 detects rain.
`
`the conditions for generation of a warning by the alarm 6 are varied in
`in this embodiment,
`Thus,
`accordance with both the physical or mental state of the driver and environmental conditions, so the safety
`of the first vehicle 1 can be greatly increased.
`it is
`Although this embodiment employs both a driver condition sensor 4 and an environment sensor 6,
`possible for a warning apparatus according to the present
`invention to be equipped with only the
`environment sensor 6 without the driver condition sensor 4, and for the conditions for generating a warning
`to be varied in accordance with the environmental conditions.
`
`Figure 5 illustrate yet another embodiment of the present invention installed on a first vehicle 1. The
`structure of this embodiment is similar to that of the embodiment of Figure 3, but it further includes an
`operating amount sensor 7 and a learning device 8.
`The operating amount sensor 7 senses one or more parameters related to the operation of equipment
`manipulated by the driver as he drives the first vehicle 1, and it generates a corresponding output signal
`which is provided to the computer 10. A few examples of the operating amount sensor 7 are a sensor for
`sensing the speed of depression of the accelerator pedal, a sensor for sensing the force applied by the
`driver to the brake pedal, or a sensor which senses the steering angle of the steering wheel of the first
`vehicle 1.
`
`The learning device 8 receives the output signals from the vehicle condition sensor 3 and the operating
`amount sensor 7 and performs statistical processing to numerically evaluate the driving characteristics of
`the driver based on sensed operating characteristics such as the speed and force with which the driver
`operates the brakes, the accelerator pedal, or the steering wheel and the speed with which he accelerates
`and decelerates the vehicle.
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`in general, driving characteristics vary in accordance with the physical and mental state of the driver.
`When the driver is rested and alert, his reactions are fast, so the speed or depression of the acceleration
`pedal is fast, the depression of the brake pedal is strong, the rate of deceleration is fast, and as a whole the
`motions of the vehicle tend to be comparatively rough or violent. Conversely, when the driver is fatigued,
`the depression of the acceleration pedal is slow, the depression of the brake pedal is weak, and the rate of
`deceleration is slower, so the motions of the vehicle tend to be smoother than when the driver is rested.
`Therefore, the learning device 8 determines from the manner of operation of the first vehicle 1 when the
`driver is alert and when the driver is tired. When the learning device 8 determines that the driver is alert, the
`computer 10 delays the generation of the warnings by the alarm 5, l.e., decreases the vehicle separation R
`at which a warning is generated towards some predetermined limit so as to reflect the fast reaction time of
`the driver in his current condition. When the learning device 8 determines that the driver is fatigued, the
`computer 10 causes the warnings to be generated earlier by the alarm 5,
`l.e., at a larger value of R to
`compensate for the delayed reaction time of the driver caused by his fatigue.
`The operation of the embodiment of Figure 5 will be described while referring to Figures 6 and 7, which
`are flow charts of a routine which can be performed by the computer 10 to control this embodiment. in Step
`821, the computer 10 reads in data from each of sensors 2 — 4 and 6 - 8.
`In Step 822, the computer 10
`determines whether the current operating conditions of the first vehicle 1 are suitable for performing
`learning. For example, suitable conditions can be when a predetermined length of time has passed since
`the first vehicle 1 has started or when a predetermined vehicle speed has been reached.
`it suitable
`conditions for learning have not been established, then in Step 823, the present operating conditions are
`compared with either conditions which were set at an initial stage (if this is the first pass through the
`routine) or with operating condition learned by the learning device 8 (if this is the second or higher pass
`through the routine). Based on this comparison, the values of k, R0, and to are set in Step 824.
`in Step 22,
`it
`it
`is determined that conditions for performing learning have been established, then in
`Step 825, the learning device 8 performs statistical evaluation of the data from the vehicle condition sensor
`3 and the operating amount sensor 7 and determines the driving characteristics of the driver of the first
`vehicle 1. In Step 826, the characteristics determined in Step S25 are stored in an unillustrated memory. in
`Step 824, based on the driving characteristics determined by the learning device 8, the values of R, R0, and
`to are adjusted.
`in Step 827, the computer 10 determines whether the relative speed VF — Vo ot the first and second
`vehicles is greater than 0.
`if the relative speed is greater than zero, then in Step 828,
`it
`is determined
`whether the vehicle separation R is greater than kVo.
`If the separation R is less than or equal to kVo, then in
`Step $29, the computer 10 drives the alarm 5 and a first warning is generated to caution the driver.
`in Step 827, it the relative speed is less than or equal to zero, in Step 830, the computer 10 calculates
`by means of Equation (1) the minimum required separation R; for the driver to decelerate from the current
`speed V0 to the speed Vi: of the second vehicle 20 without colliding with the second vehicle 20 assuming a
`rate of deceleration or.
`
`in Step 831, the computer 10 determines whether the actual separation R between the first and second
`vehicles is greater than R; + Re.
`if the vehicle separation R is less than or equal to this sum, then in Step
`832 it is determined whether the vehicle separation R is less than RF.
`it R is greater than or equal to RF,
`then the driver can safely slow down the first vehicle 1 with a normal deceleration a, so in Step 829, the
`alarm 5 is driven to generate the first warning. However,
`if the driver of the first vehicle 1 did not react to
`the first warning and the vehicle separation R is found to be smaller than R; in Step 832, then a dangerous
`situation exists, so in Step 833, the alarm 5 is driven to generate a second warning which alerts the driver
`to take immediate evasive action, such as stepping more firmly on the brakes or turning the steering wheel
`to avoid the second vehicle 20.
`
`if the vehicle separation R is larger than kVO, or in Step 831, ii the vehicle separation is
`in Step 828,
`larger than R; + R0, there is no immediate danger of a collision, so a warning is not generated and the
`routine is ended.
`
`As in the previous embodiment, the values of one or more of R0, k, and to are varied in accordance with
`the physical or mental state of the driver as sensed by the driver condition sensor 4 and the environmental
`condition sensed by the environment sensor 6 so that the conditions which must be met for a warning to be
`generated,
`l.e., the vehicle separation R at which a warning is generated are set so that the driver will
`always have enough time to react to a warning generated by the alarm 5 to prevent a collision.
`In the embodiment of Figure 5, the computer 10 adjusts the conditions for generating a warning based
`on input signals from the driver condition sensor 4, the environment sensor 6, and the learning device 8.
`However,
`it
`is also possible for the computer 10 to adjust the conditions for generating a warning based
`only on input signals from the learning device 8, or based on input signals from the learning device 8 and
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`only one of the driver condition sensor 4 and the environment sensor 6. Therefore, it is possible to omit one
`or both of sensors 4 and 6.
`
`in the present invention, because the conditions for generating a warning are varied in accordance with
`changes in sensed conditions of the driver or the environment, the timing of the warnings wiil be suitable for
`the existing circumstances at any given time. Therefore, the driver of a vehicle equipped with the present
`invention will not be annoyed by unnecessary generation of warnings, and the vehicle can be made both
`safe and pleasant to drive.
`
`Claims
`
`1. A warning apparatus for a vehicle comprising:
`obstacle sensing means for sensing the separation between a vehicle and an obstacle located in
`front of the vehicle;
`driver condition sensing means for sensing a condition of a driver of the vehicle;
`an alarm; and
`a controller comprising condition setting means responsive to the driver condition sensing means
`for setting a value for vehicle separation which varies in accordance with the sensed condition of the
`driver, and warning generating means for controlling the alarm to generate a warning for the driver
`when the separation sensed by the obstacle sensing means is below the set value for vehicle
`separation.
`
`2. A warning apparatus as claimed in claim 1 wherein the driver condition sensing means comprises
`means for sensing when the driver is manipulating an accessory of the vehicle, and the condition
`setting means increases the set value for vehicle separation when the driver condition sensing means
`senses that the driver is manipulating an accessory.
`
`3. A warning apparatus as claimed in claim 1 further comprising environment sensing means for sensing
`an environmental condition of an environment containing the vehicle, wherein the condition setting
`means comprises means for varying the set value for vehicle separation in accordance with changes in
`the sensed environmental condition.
`
`4. A warning apparatus as claimed in claim 3 wherein the environment sensing means comprises means
`for sensing rain, and the condition sensing means increases the set value for vehicle separation when
`the environment sensor senses rain.
`
`further comprising means for determining a driving
`5. A warning apparatus as claimed in claim 1
`characteristic of the driver, wherein the condition setting means varies the value for vehicle separation
`in accordance with the determined driving characteristic.
`
`including speed sensing means for sensing the speed of the
`
`6. A warning apparatus as claimed in claim 1
`vehicle V0, wherein:
`the controller includes means for sensing the relative speed (V0 - VF) of the vehicle and the
`obstacle based on the separation sensed by the obstacle sensor. wherein VF is the speed of the
`obstacle;
`the condition setting means sets the value for vehicle separation to We, wherein R is a value which
`is varied by the condition setting means in accordance with changes in the sensed condition of the
`driver; and
`
`the warning generating means controls the alarm to generate a warning when the relative speed is
`decreasing and the vehicle separation is less than we.
`
`7. A warning apparatus as claimed in claim 1 wherein:
`the controller includes means for sensing the relative speed (Vo - VF) of the vehicle and the
`obstacle based on the separation sensed by the obstacle sensor, wherein V0 is the speed of the
`vehicle and V; is the speed of the obstacle; and
`the condition setting means sets the value for vehicle separation to
`
`70
`
`15
`
`2O
`
`25
`
`30
`
`35
`
`4O
`
`45
`
`50
`
`55
`
`MERCEDES
`
`EXHIBIT 1008
`
`MERCEDES
`EXHIBIT 1008
`
`

`

`EP 0 549 909 A2
`
`(V0 "' Val 1‘
`
`(V0 ‘ VF)t0 + R0
`
`Zial
`
`10
`
`75
`
`2O
`
`25
`
`30
`
`35
`
`4O
`
`45
`
`and varies the value of at least one of to and R0 in accordance with changes in the sensed condition of
`the driver, wherein to is an assumed reaction time of the driver between a warning being generated by
`the alarm and initiation of braking of the vehicle by the driver, R0 is a safety factor, and a is an
`assumed deceleration of the vehicle produced by braking.
`
`A warning apparatus for a vehicle comprising:
`obstacle sensing means for sensing the separation between a vehicle and an obstacle located in
`front of the vehicle;
`environment sensing means for sensing an environmental condition of an environment containing
`the vehicle;
`an alarm; and
`a controller comprising condition setting means responsive to the environment sensing means for
`setting a value for vehicle separation which varies in accordance with the sensed environmental
`condition, and warning generating means for controlling the alarm to generate a warning for the driver
`when the separation sensed by the obstacle sensing means is below the set value for vehicle
`separation.
`
`A warning apparatus for a vehicle comprising:
`obstacle sensing means for sensing the separation between a vehicle and an obsta