Europaisches Patentamt
`
`(19)
`
`0’
`
`European Patent Office
`
`Office européen des brevets
`
`(11)
`
`EP 1 022 903 A2
`
`(12)
`
`EUROPEAN PATENT APPLICATION
`
`(43) Date of publication:
`26.07.2000 Bulletin 2000/30
`
`(51) Int. 01.7: H04N 7/18
`
`(21) Application number: 001009083
`
`(22) Date of filing: 18.01.2000
`
`(84) Designated Contracting States:
`AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU
`MC NL PT SE
`
`Designated Extension States:
`AL LT LV MK RO SI
`
`(30) Priority: 19.01.1999 JP1045299
`21.05.1999 JP 14229099
`
`(71) Applicant:
`Kabushiki Kaisha
`
`Toyoda Jidoshokki Seisakusho
`Aichi-ken (JP)
`
`(72) Inventors:
`- Asahi, Goro
`Kariya-shi, Aichi-ken (JP)
`- Kuriya, Hisashi
`Kariya-shi, Aichi-ken (JP)
`
`- Ushino, Masashi
`Kariya-shi, Aichi-ken (JP)
`- Kimura, Tomio
`Kariya-shi, Aichi-ken (JP)
`- Teramura, Kousuke
`Kariya-shi, Aichi-ken (JP)
`- Shimazaki, Kazunori
`Kariya-shi, Aichi-ken (JP)
`- Haftori, Kanii
`Kariya-shi, Aichi-ken (JP)
`- Yamada, Satoshi
`Kariya-shi, Aichi-ken (JP)
`
`(74) Representative:
`Pellmann, Hans-Bernd, Dipl.-lng. et al
`Patentanwaltsbiiro
`
`Tiedtke-Biihling-Kinne & Partner
`Bavariaring 4-6
`80336 Miinchen (DE)
`
`
`
`(54) Apparatus for assisting steering of vehicle when backing
`
`A steering assist apparatus (10) that assists a
`(57)
`driver when backing a vehicle (1) in an S-shaped path or
`parallel parking. The apparatus displays guidance
`marking (17) on a monitor screen (19) and the driver
`refers to the guidance marking, which permits the driver
`to easily back the vehicle to a desired position. The
`apparatus includes a camera (2), a monitor (4), an
`angle sensor
`(9), obstacle sensors (6), an image
`processing unit (11), a controller (12) and a monitor
`controller (13). The image processing unit computes the
`predicted path of the vehicle at the current wheel angle.
`The monitor shows an image captured by the camera.
`The image processing unit generates data representing
`a guidance marking based on the predicted path and
`superimposes the marking on the monitor screen. The
`location of the marking on the screen is determined
`based on the current wheel angle. The marking repre-
`sents part of the predicted path. Specifically, the mark-
`ing matches the width of the vehicle.
`In the monitor
`screen, a marking is separated from the rear bumper of
`the vehicle by a distance corresponding to the wheel-
`base of the vehicle.
`
`
`
`Obstacle Sensors
`18
`Reverse Switch
`
`
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`Printed by Xerox (UK) Business Services
`2167(HRSV36
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`Valeo EX. 1006_001
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`EP1022903A2
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`Valeo Ex. 1006_001
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`

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`EP 1 022 903 A2
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`Description
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to an apparatus for assisting steering when a vehicle is moving backward.
`[0001]
`More specifically, the present invention relates to a steering assist apparatus that includes a camera for capturing the
`view from the rear and a monitor for displaying the captured view along with marking for assisting the driver.
`[0002]
`In the prior art, apparatuses for showing the view from the rear of a vehicle have been proposed. Such an
`apparatus allows the driver to see the view from the vehicle rear without actually turning around. Japanese Examined
`Patent Publication No. 2-36417 discloses a rear monitoring apparatus, which includes a video camera for capturing
`view from the rear of the vehicle, a video monitor for showing the captured view and a sensor for outputting signals rep-
`resenting the angle of vehicle wheels. The apparatus generates marker signals based on signals from the wheel angle
`sensor and superimposes a marker on the video monitor. The positions of the markers on the monitor correspond to
`the direction in which the vehicle is being backed. The direction is determined in accordance with the steered angle of
`the vehicle wheels. The apparatus includes a read only memory (ROM), which stores steered angle data of the vehicle
`wheels and marker position data. When the vehicle is moving backward, the course of the vehicle is predicted based
`on the steered angle data. The predicted course is displayed by rows of the markers superimposed on the monitor
`screen showing the image captured by the video camera.
`[0003]
`Japanese Unexamined Patent Publication No. 10-175482 discloses an apparatus for assisting the view from
`the rear of a vehicle. This apparatus includes a detector for detecting the angle of the front wheels, a vehicle speed sen-
`sor, a camera for capturing the view from the rear of the vehicle and monitor for displaying the view. The apparatus also
`includes a computer. When the vehicle is moving backward, the computer computes the path of the rear wheels based
`on the steered angle of the front wheels. The predicted path is converted into path image data, which represents the
`predicted path as viewed from the rear camera. The path image data is further converted into linear marking data,
`which corresponds to the monitor screen. The linear marking data is superimposed on the image of the view from the
`vehicle rear shown on the monitor screen.
`
`Japanese Unexamined Patent Publication No. 10-244891 discloses a parking assist apparatus. This appa-
`[0004]
`ratus includes first and second image pickup means provided at the sides of the vehicle to capture the image of the
`vehicle surroundings. The apparatus superimposes lines on the image captured by the image pickup means. The lines
`permit the driver to judge whether parallel parking is possible.
`[0005]
`The apparatuses of the publications No. 2-36417 and No. 10-175482 both show the rear view captured by a
`camera and predict the path of the vehicle or the path of the rear wheels based on the current wheel angle. The appa-
`ratuses then superimpose the predicted path on the monitor screen. The superimposed path does not correspond to
`the vehicle length or the wheelbase. When passing another car in a winding road such as a mountain road, the driver
`may have to move his vehicle backward until the vehicle reaches a spot that is wide enough for two vehicles to pass
`each other. At this time, the apparatuses of the publications No. 2-36417 and No. 10-175432 will show the view from
`the rear and the predicted path on a monitor. Accordingly, the driver will know whether maintaining the angle of the front
`wheels will cause the vehicle to leave the road.
`
`However, as shown in Fig. 26, all the currently predicted data of a path 41 representing the vehicle path or
`[0006]
`the predicted rear wheel path is shown on a monitor screen 42. Thus, if the curvature of the road 43 is not constant for
`a relatively long distance and the wheel angle does not correspond to the curvature of the road 43, the upper end of the
`superimposed path 41 does not match the road 43 on the screen 42. Generally, the curvature of a road is not constant
`for a long distance on winding roads such as mountain roads. Therefore, the superimposed path 41 is often partly off
`of the a road on the screen 42, which at least permits the driver to realize that maintaining the current wheel angle will
`cause the vehicle to leave the road. However, the superimposed path 41 does not give the driver information necessary
`for judging how he should manipulate the steering wheel. In other words, the superimposed path 41 cannot be used for
`determining the steering amount of the steering wheel.
`[0007]
`When parallel parking a vehicle, the driver has to switch the direction of steering. However, the superim-
`posed path 41 does not help the driver to judge when to switch the steering direction.
`[0008]
`The apparatus of the publication No. 10-244891 assists the driver when parking a vehicle. The apparatus
`needs two image pickup means to capture front and rear images from the vehicle side. The apparatus shows a line for
`indicating whether parallel parking is possible. The computation of the line is complicated.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, it is an objective of the present invention to provide an apparatus for assisting steering of vehicle
`[0009]
`when vehicle is moving backward, which provides guidance on a monitor screen for permitting a driver to easily move
`the vehicle to a desired position when the driver moves the vehicle backward along an S-shaped corner or when the
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`Valeo EX. 1006_002
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`Valeo Ex. 1006_002
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`EP 1 022 903 A2
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`driver parallel parks the vehicle.
`
`To achieve the foregoing and other objective and in accordance with the purpose of the present invention,
`[0010]
`an apparatus for aiding steering when a vehicle is being driven in reverse is provided. The moving direction of the vehi-
`cle is determined in response to the position of steered wheels. The apparatus includes a camera for capturing an
`image of an area behind the vehicle, a monitor for displaying the image captured by the camera and a display control
`unit for displaying a guide marking for aiding steering. The marking and the image are simultaneously displayed on the
`monitor when the vehicle is being driven in reverse. The marking provides a driver with at least first indication of the
`width of the vehicle and a second indication of a prospective path of the vehicle corresponding to the position of the
`steered wheels.
`
`The present invention may be another apparatus for aiding steering when a vehicle is being driven in
`[0011]
`reverse. The moving direction of the vehicle is determined in response to the position of steered wheels. The apparatus
`includes a camera for capturing an image of an area behind the vehicle, a monitor for displaying the image captured by
`the camera, and a display control unit for displaying a guide marking that is fixed at a predetermined position with
`respect to the monitor screen for aiding a driver in parking. The control unit displays the guide marking and the image
`simultaneously on the monitor when the vehicle moves in reverse. The parallel parking is completed by causing the
`marking to coincide with a target point in the image, followed by backing while keeping the steered wheels turned at
`their maximum angle.
`[0012]
`Other aspects and advantages of the invention will become apparent from the following description, taken in
`conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention, together with marking and advantages thereof, may best be understood by reference to the
`[0013]
`following description of the presently preferred embodiments together with the accompanying drawings in which:
`
`Fig. 1 is a block diagram showing a steering assist apparatus according to a first embodiment;
`
`Fig. 2 is a schematic side view showing a vehicle having the apparatus of Fig. 1;
`
`Fig. 3 is a schematic view showing the screen of a monitor;
`
`Fig. 4 is a flowchart showing a routine for generating data for guidance marking shown on the monitor screen;
`
`Fig. 5 is a schematic view showing the relationship between the wheel angle and the turn radius of vehicle wheels;
`
`Fig. 6 is a diagram showing the relationship between polar coordinates and an ellipse;
`
`Fig. 7 is a diagram showing a vehicle when the vehicle is moving backward in an S-shaped road;
`
`Fig. 8 is a diagram showing a state of the monitor screen corresponding to the state A of Fig. 7;
`
`Fig. 9A is a diagram showing a state of the monitor screen corresponding to the state B of Fig. 7;
`
`Fig. QB is a diagram showing a state of the monitor screen when lateral lines of a guide frame are parallel to the
`lower sides of the monitor;
`
`Figs. 10A, 108 and 10C are diagrams showing the positions of a vehicle and the corresponding guidance marking
`on the monitor screen when the vehicle is being parallel parked;
`
`Figs. 11A, 11B and 11C are diagrams showing the positions of vehicle and the corresponding guidance marking
`on the monitor screen when the vehicle is parallel parked;
`
`Figs. 12A, 12B, 12C and 12D are diagrams showing the monitor screen when parking the vehicle perpendicular to
`a reference such as a curb;
`
`Fig. 13 is diagram for calculating the location of a marker on the monitor screen;
`
`Fig. 14 is a flowchart showing a routine according to a second embodiment;
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`Valeo EX. 1006_003
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`Valeo Ex. 1006_003
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`

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`EP 1 022 903 A2
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`Fig. 15 is a graph showing changes of the angle of wheels when the vehicle is moving along a corner;
`
`Fig. 16 is a diagram showing the paths taken by wheels of a vehicle when the vehicle is moving along a corner;
`
`Fig. 17 is a diagram showing the relationship between the state of a steering wheel and the path of the vehicle;
`
`Fig. 18 is a flowchart showing a routine according to a third embodiment;
`
`Fig. 19 is a diagram for calculating the location of a marker on the monitor screen according to a fourth embodi-
`ment;
`
`Figs. 20A, 208 and 20C are diagram showing operations of guidance marking on a monitor screen when parallel
`parking a vehicle;
`
`Fig. 21 is a diagram showing a monitor screen showing markers according to a fifth embodiment;
`
`Fig. 22 is a diagram for calculating the location of markers on the monitor screen;
`
`Fig. 23A is a diagram for calculating the location of a marker on the monitor screen according to a sixth embodi-
`ment;
`
`Fig. 23B is a diagram for calculating the location of a marker on the monitor screen when the target point is different
`from that of Fig. 23A;
`
`Figs. 24A and 24B are diagrams showing the locations of markers on a monitor screen;
`
`Fig. 25A and 25B are diagrams showing the locations of a marker on a monitor screen according to another
`embodiment; and
`
`Fig. 26 is a diagram showing a monitor screen of a prior art steering assist apparatus.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
`
`A first embodiment according to a first embodiment of the present invention will now be described with ref-
`[0014]
`erence to Figs. 1 to 13. As shown in Fig. 2, a vehicle 1 has a monochrome camera 2 for capturing the view from the
`vehicle rear. A rear bumper 3 is at the nearest end of the view of the camera 2. The distance between the bumper 3 and
`the farthest extend of the camera view is greater than the length of the vehicle 1.
`[0015]
`A monitor 4 for showing the image captured by the camera 2 is located in the passenger compartment of the
`vehicle 1. The monitor 4 is a color liquid crystal display and is also used as the monitor of a navigation system. The
`monitor 4 is normally used as the navigation system monitor. When a shift lever 5 is shifted to a reverse position, the
`monitor 4 shows the image captured by the camera 2.
`[0016]
`Obstruction sensing means, which are obstruction sensors 6, are arranged in the corners of the vehicle 1.
`The obstruction sensors 6 are, for example, conventional sensors such as ultrasonic sensors. When an obstruction is
`in a range between a first distance (for example, about fifty centimeters) and a second distance (for example, about
`twenty centimeters) from one of the sensors 6, the sensor 6 outputs a first obstruction signal. If the obstruction is closer
`to the sensor 6 than the second distance, the sensor 6 outputs a second obstruction signal.
`[0017]
`Steered wheels, which are front wheels 7a in this embodiment, are steered by manipulating steering means,
`which is a steering wheel 8 in this embodiment. The steered angle a of the front wheels 7a is computed by multiplying
`the rotated angle 9 of the steering wheel 8 by a coefficient K. That is, the angle of the front wheels 7a is represented by
`K6. The rotated angle of the steering wheel 8 is detected by wheel angle detecting means, which is an angle sensor 9
`in this embodiment.
`
`As shown in Fig. 1, a steering assist apparatus 10 includes the camera 2, the monitor 4, the angle sensor 9,
`[0018]
`the obstruction sensors 6, a display control means, a controller 12 and a monitor controller 13. The display control
`means is an image processing unit 11 in this embodiment. The controller 12 receives signals from the angle sensor 9
`and computes the angle or of the front wheels 7a based on the angle 9 of the steering wheel 8 and then send the com-
`puted angle 0L to the image processing unit 1 1. The monitor controller 13 inputs image signals from the image processor
`and a car navigator system (not shown). The monitor controller 13 selectively shows one of the image signals on the
`monitor 4.
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`Valeo EX. 1006_004
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`Valeo Ex. 1006_004
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`EP 1 022 903 A2
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`The image processing unit 11 includes an arithmetic circuit, or central processing unit (CPU) 14, a program
`[0019]
`memory 15a, a working memory 15b, an image memory 15c and an image processor 16. The CPU 14 adjusts a pre-
`dicted path of the vehicle 1 and generates display data. The program memory 15a is a read only memory (ROM) for
`storing control programs. The working memory 15b is a random access memory (RAM) for temporarily storing compu-
`tation results of the CPU 14. The image memory 15c is a random access memory The image processor 16 processes
`image data from the camera 2 and stores the data in the image memory 15c. The CPU 14 operates based on the pro-
`gram data stored in the program memory 15a.
`
`The CPU 14 computes and predicts the backward path of the vehicle 1 with the front wheels 7a steered at
`[0020]
`an angle or based on signals from the controller 12. Superimposed marking in Fig. 3, which is a guide frame 17 in this
`embodiment, represents the width of the vehicle 1 and is moved on the screen in accordance with the steering angle or.
`Specifically, the CPU 14 computes data representing the guide frame 17 based on the predicted path. The CPU 14 is
`connected to a reverse switch 18 and an input interface (not shown). The reverse switch 18 detects whether the shift
`lever 5 is in the reverse position and sends a signal to the CPU 14. When receiving a signal showing that the shift lever
`5 is in the reverse position from the switch 18, the CPU 14 generates the guide frame data at predetermined intervals.
`[0021]
`Fig. 3 shows a screen 19 of the monitor 4. The guide frame 17 includes lateral line 17a and a pair of side
`guide lines 17b. Fig. 3 shows the guide frame 17 when the angle or is zero degrees, or when the angle of the front
`wheels 7a are directed straight ahead. The guide frame 17 is moved in accordance with the steering angle or as shown
`in Figs. 8 and 9A. The length of the lateral line 17a represents the width of the vehicle 1. In the image captured by the
`camera 2 shown in Fig. 3, the lateral line 17a is spaced apart from the rear bumper 3, by a distance corresponding to
`the wheelbase of the vehicle 1. The side lines 17b extend from the ends of the lateral line 17a to the rear bumper 3
`along the predicted path. The guide frame 17 preferably has cross lines 17c, 17d connecting the side lines 17b.
`[0022]
`The position of the guide frame 17 when the steering angle a is zero degrees will be referred to as reference
`position. The guide frame 17 is swung to left and to right in accordance with the steering angle or.
`[0023]
`The program memory 15a stores data representing a fixed frame 20. The fixed frame 20 is shown on the
`screen 19 and is not swung in accordance with the rotation of the steering wheel 8. The fixed frame 20 includes a pair
`of guide lines, which are side lines 20a, and a lateral line 20b, which connects the upper ends of the side lines 20a. A
`marker 21 is located in the center of the lateral line 20b. The mark 21 includes a line 21a, which extends vertically, or
`perpendicularly to the lateral line 20b. On the screen 19, the upper side represents the reanrvard direction of the vehicle
`1.
`
`The marker 21 assists the driver to move the vehicle 1 backward when the driver is parking the vehicle 1.
`[0024]
`For example, the driver matches the marker 21 with a corner of a parking space and then parks the vehicle 1
`in the
`parking space by moving the vehicle 1 backward while rotating the steering wheel 8 to the maximum rotation position.
`[0025]
`The location of the marker 21 is calculated in the following manner. The dotted line in Fig. 13 shows the vehi-
`cle 1 at a parked position. Fig. 13 also shows another position of the vehicle 1 by solid lines. When moving the vehicle
`1 from the parked position to the position of the solid lines, the driver maximally steers the front wheels 7a and advances
`the vehicle 1. The path of the vehicle 1 at this time is the same as the path of the vehicle 1 when the vehicle 1 is moved
`from the position of the solid line to the parked position of the dotted line. Thus, the calculation of the marker 21 will be
`described referring to a case when the vehicle is moved from the dotted line position to the solid line position in Fig. 13.
`[0026]
`As shown in Fig. 13, a corner of the vehicle 1 when parked at the dotted line position is defined as a point
`E. The distance a between the point E and the axis of the rear axle is the rear overhang of the vehicle 1.
`If the steering
`wheel 8 is maximally rotated when the vehicle is moved, the axial center of the rear axle is moved along a circle the
`radius of which is Rc. When the tangent of the circle of the radius Rc includes the point E, the axial center of the rear
`axle is defined as On. A point on the tangent separated from the point On by the distance a is defined as a point D. The
`distance DE between the point D and the point E is calculated.
`[0027]
`A line between the center 0 of the circle of the radius Rc and the axle axial center Cn is defined as a line
`OCn. A line between the center 0 and the point E is defined as a line OE. The angle defined by the line OCn and the
`line CE is defined as an angle 01'. The following equations are satisfied.
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`Therefore
`
`E: (R02+a2)
`
`cosoc'=m/CT =Rc/
`
`(R02+a2)
`
`oc' = cos'1{Flc/ «/(Fto2 + a2)}
`
`0nE W tan oc' = Rc tan ed
`
`(1)
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`(2)
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`Valeo EX. 1006_005
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`Valeo Ex. 1006_005
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`EP 1 022 903 A2
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`_E = Rc tan oc'-a
`
`When the angle defined by the line OE and the line OCn is the angle or', the position of the marker 21 on the
`[0028]
`screen 19 corresponds to a point that is separated from the rear bumper 3 of the vehicle 1 by the length of the line DE.
`In the above equations, the length of the line CnE is a value that is adjusted through experiments. The length of the line
`CnE is adjusted in consideration of a case where the angle of approach is relatively great.
`[0029]
`In this embodiment, when the angle or is zero degrees, or when the guide frame 17 is at the reference posi-
`tion, the lateral line 17a matches the lateral line 20b of the fixed frame 20 and the side lines 17b match the side lines
`20a of the fixed frame 20. Fig. 3 shows the guide frame 17 at the reference position. To show both frames 17 and 20,
`the frames are slightly displaced from each other in Fig. 3.
`[0030]
`The program memory 15a stores display reference data for displaying an obstacle finder 22 on the screen
`19. The obstacle finder 22 shows whether any of the sensors 6 is outputting either the first or second obstacle signals.
`The obstacle finder 22 includes a frame 22a representing the shape of the vehicle 1 and corner markers 23a to 23d
`representing the obstacle sensors 6.
`[0031]
`The CPU 14 sends data representing the guide frame 17, the fixed frame 20 and the marker 21 to the mon-
`itor controller 13 via the output interface. The monitor controller superimposes the frames 17, 20 and the marker 21 on
`the image of the camera 2. The CPU 14 also sends data representing the obstacle finder 22 to the monitor controller
`13. The monitor controller 13 displays the view of the camera 2, and images of the guide frame 17, the fixed frame 20,
`the marker 21 and the obstacle finder 22 on the monitor 4. The obstacle finder 22 does not interfere with the guide
`frame 17 and the fixed frame 20.
`
`Since the camera 2 is a monochrome camera, the image is in black and white. The data for the guide frame
`[0032]
`17, the fixed frame 20, the marker 21 and the obstacle finder 22 are color. Thus, the guide frame 17, the fixed frame 20,
`the marker 21 and the obstacle finder 22 are superimposed in color on the black and white image shown on the screen
`19 of the monitor 4. The color of the guide frame 17 is basically different from the color of the fixed frame 20. The marker
`21 is shown in the same color as the color of the fixed frame 20. The color of the side lines 17b is the same as the color
`
`of the fixed frame 20 at portions between the cross lines 17c and 17d. In this embodiment, the guide frame 17 is green
`except for the portions between the cross lines 17c, 17d. The segments between the cross lines 17c and 17d, the
`marker 21 and the fixed frame 20 are shown in yellow.
`[0033]
`If none of the obstacle sensors 6 outputs obstacle signals, the CPU 14 displays the corner markers 23a to
`23d, which represent the sensors 6, by outputting obstacle checking data to the monitor controller 13, and all the corner
`markers 23a to 23d have the same appearance. When receiving the first or second obstacle signal from one or more
`of the sensors 6, the CPU 14 outputs corresponding obstacle checking data to the monitor controller 13. Accordingly,
`the corner marker corresponding to the sensor 6 sending the first or second obstacle signal is distinguished from the
`other corner markers on the screen 19. For example, a corner marker is displayed in orange when the corresponding
`sensor 6 outputs a first obstacle signal and the corner marker is displayed in red when the corresponding sensor 6 out-
`puts a second obstacle signal.
`[0034]
`The CPU 14 computes the predicted path of the sides of the vehicle when the vehicle 1 is moved backward
`with the front wheels 7a steered by the angle or. The predicted path is expressed in polar coordinates. The predicted
`path is substantially circular. The lateral line 17a of the frame 17 is drawn between points in the predicted paths of the
`sides of the vehicle. The points are on the same radius (from the center of the turn) and represent a line separated from
`the bumper 3 substantially by the length of the wheelbase. The side lines 17b match the predicted path from the ends
`of the lateral line 17a to the sides of the bumper 3. The CPU 14 compresses the image of the predicted path circle in
`the direction of the vehicle's movement by a predetermined ratio. That is, the CPU 14 converts the circle of the predicted
`path into an ellipse as shown in Fig 6. Part of the ellipse corresponding to the size of the guide frame 17 is converted
`into a perspective view and is superimposed on the monitor screen 19 as the guide frame 17. The location of the guide
`frame 17 on the screen 19 is slightly displaced reanrvard from its accurate position.
`[0035]
`The operation of the steering assist apparatus 10 will now be described.
`[0036]
`When the shift lever 5 is in the reverse position, the reverse switch 18 sends a signal indicating that the lever
`5 is in the reverse position to the CPU 14. In this state, the CPU 14 executes the routine of the flowchart shown in Fig.
`4 at predetermined intervals (for example, thirty-three milliseconds) for generating data representing the guide frame
`display. At step S1, the CPU 14 reads the data of the steered angle a from the controller 12. At step S2, the CPU 14
`computes the predicted path of the sides of the vehicle 1 while assuming that the angle or will not be changed.
`[0037]
`The width and the wheelbase of the vehicle 1 are defined as W and L, respectively The distance between
`the radial centers of the rear wheels 7b is defined as Tr. The distance between the center of the turn and the axial center
`
`of the rear axle, or the radius of turn, is defined as a radius BC. The distance between the center of the turn and the
`intersection point of the outer side of the vehicle body and the line extended from the rear axle axis is defined as a
`radius Flo. The distance between the center of the turn and the intersection point of the inner side of the vehicle body
`and the line extended from the rear axle axis is defined as a radius Hi. The radiuses Rc, R0 and Hi are expressed by
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`Valeo Ex. 1006_006
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`the following equations.
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`EP 1 022 903 A2
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`Rc= (L/tanoc)-(Tr/2)
`
`R0: Rc+W/2=(L/tana)-(Tr/2)+W/2
`
`Ri=Rc-W/2=(L/tanoc)-(Tr/2)-W/2
`
`(3)
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`(4)
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`(5)
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`
`The CPU 14 computes the predicted path based on these equations and moves to step SS. At step S3, the
`[0038]
`CPU 14 determines the coordinates of the ends of each line 17a, 17c, 17d.
`[0039]
`At step S4, the CPU 14 converts the coordinates of the predicted path into polar coordinates. At step 85, the
`CPU 14 converts the circle of the predicted path into an ellipse. As shown in Fig. 6, the origin of the polar coordinates
`matches the center of the circles of radiuses Rc, R0 and Hi. The x axis of the polar coordinates matches the axis of the
`rear axle. Fig. 6 shows a line that makes an angle [5 from the x axis. The coordinates of the node P of the line and the
`circle of the radius R0 is defined as (Flo, [1). The coordinates of the node Q of the line and the circle of the radius Pi is
`defined as (Hi, [1).
`[0040]
`The polar coordinates (Ro, B) of the node P and the coordinates (x, y) of the node P in the x and y coordi-
`nates satisfy the following equation.
`
`x=Rocosfi, y=Rosinfi
`
`Likewise, the polar coordinates (Ri, B) of the node Q and the coordinates (x, y) of the node Q in the x and y
`[0041]
`coordinates satisfy the following equation.
`
`x=Flicosfi, y= Rosinfi
`
`[0042]
`[0043]
`
`When the circle of Fig. 6 is converted into the ellipse, the nodes P, Q are shifted to nodes R, S.
`The coordinates (X, Y) of the node R in the x and y coordinates satisfy the following equations.
`
`X=Ricosfi, Y=bsinfi
`
`[0044]
`
`Likewise, the coordinates (X, Y) of the node S in the x and y coordinates satisfy the following equations.
`
`[0045]
`
`Wherein the value b satisfies the following equation.
`
`X=RicosB, Y=(b-W)sin [i
`
`b= Ro(minor axis/major axis)
`
`The CPU 14 converts the circle of the predicted path into an ellipse and converts the coordinates of the
`[0046]
`ellipse into polar coordinates. The CPU 14 then generates the guide frame data based on the converted ellipse coordi-
`nates. The ratio of the minor axis to the major axis (compression ratio) is previously computed through test drives of the
`vehicle 1 and is stored in the program memory 15a.
`[0047]
`The CPU 14 moves to step 86 and displaces the guide frame 17 from its accurate location, or upward in the
`screen 19 of the monitor 4, by a predetermined amount. The displace amount is previously computed through test
`drives and is stored in the program memory 15a.
`[0048]
`The CPU 14 outputs the data of the guide frame 17, the fixed frame 20, the marker 21 and the obstacle
`finder 22 to the monitor controller 13. The monitor controller 13 superimposes the data onto the image captured by the
`camera 2 displayed on the monitor 4.
`[0049]
`The operation of the steering assist apparatus 10 when the vehicle 1 is moving backward in an S-shaped
`road is as follows. When the driver shifts the shift lever 5 into reverse, the guide frame 17, the fixed frame 20, the marker
`21 and the obstacle finder 22 appear on the screen 19 of the monitor 4. Fig. 7 illustrates a case where the vehicle 1 is
`moved backward along an S-shaped road 24.
`In this case, the driver uses the guide frame 17 and ignores the fixed
`frame 20 and the marker 21.
`
`Fig. 8 illustrates a state of the screen 19 when the vehicle 1 is at a position A in Fig. 7, or when the vehicle
`[0050]
`1 is moving through a rightward corner. Fig. 9A illustrates a state of the screen 19 when the vehicle 1 is at a position B
`in Fig. 7, or when the vehicle 1 is moving through a leftward corner. The fixed frame 20 and the reference marker 21 are
`not deformed regardless of the steering angle or. The guide frame 17 is deformed in accordance with the angle or.
`
`Valeo EX. 1006_007
`
`Valeo Ex. 1006_007
`
`

`

`EP 1 022 903 A2
`
`The driver manipulates the steering wheel 8 such that the lateral line 17a of the frame 17 is located at the
`[0051]
`center of the road 24. The guide frame 17 is generated based on the predicted path, which is calculated according to
`the current angle or of the front wheels 7a. Thus, if the guide frame 17 is located in the center of the road 24, the vehicle
`1 will not deviate from the road 24 until the vehicle 1 reaches the location indicated by the frame 17. However, the cur-
`vature of the road 24 is not constant. Therefore, if the angle or is not changed, the guide frame 17 will indicate that the
`path of the vehicle 1 deviate from the road 24. Manipulating the steering wheel 8 to adjust the lateral line 17a to the
`center of the road 24 changes the wheel angle or to a value corresponding to the curvature of the road 24. As a result,
`the vehicle 1 is moved backward along the road 24.
`
`Fig. 9B shows the screen 19 when the lines 17a, 17c, 17d of the guide fram