JP2011131715A - Parking support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a parking support device by a simple and inexpensive constitution having no image processing function. <P>SOLUTION: The parking support device includes a reference position recognizing means 51 for recognizing that a vehicle 1 is put in a state of stopping in a reference position by an operation signal of a parallel parking switch 30, a retreat locus estimating means 52 for successively calculating a relative position from the reference position of a midpoint between rear wheels 12 and 13 of the vehicle 1 based on detecting speeds of an R-side wheel speed sensor 14 and an L-side wheel speed sensor 15 when the vehicle 1 starts to advance and successively calculating an estimated retreat locus being a locus of the midpoint between the rear wheels 12 and 13 when assuming that the vehicle 1 is retreated with a steering wheel steering angle from the relative position as a maximum steering angle in the direction when the vehicle 1 approaches a parking space. and a retreat start indicating means 53 for outputting a chime sound of indicting the fact of retreating the vehicle 1 with the steering wheel steering angle as the maximum steering angle in the direction when the vehicle 1 approaches an entrance of the parking space when the estimated retreat locus comes to pass through the reference position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a parking assist device that assists a driver in guiding a vehicle to a parking space.

  Conventionally, for example, when the driver recognizes the positional relationship between the host vehicle and the parking frame from an image captured by a camera attached to the host vehicle and performs an operation of guiding the driver into the parking frame while reversing the host vehicle. There has been proposed a parking assistance device that displays the reverse start area of the vehicle on the display to assist the operation of the driver (see, for example, Patent Document 1).

  And in the case of the parking assistance apparatus described in Patent Document 1, the apparatus cost is increased by providing the camera and the image processing apparatus, and the parking frame may not be recognized at night.

JP 2006-160147 A

  The present invention has been made in view of the above background, and an object of the present invention is to provide a parking support device having a simple and low-cost configuration that does not include an image processing function.

  The present invention has been made in order to achieve the above object, and a first aspect of the present invention is a parking assistance device for assisting an operation when a four-wheeled vehicle is moved backward to park in parallel in a parking space. A wheel speed sensor that detects the rotational speed of each rear wheel of the vehicle, and the vehicle is stopped at a reference position where the driver's seat of the vehicle is opposed to the center of the entrance of the parking space via the side of the vehicle. A reference position recognizing means for inputting a reference position notification signal for notifying that the vehicle is in the position, and after the reference position recognizing means inputs the reference position notification signal, the vehicle is moved from the reference position to the vehicle and the parking space. When the vehicle starts moving forward with a steering angle at which the distance from the entrance is constant or increases, the relative position from the reference position of the midpoint between the rear wheels of the vehicle is determined based on the detection speed of the wheel speed sensor. Between the rear wheels of the vehicle when it is assumed that the steering wheel steering angle is the maximum steering angle in the direction in which the vehicle approaches the entrance of the parking space. When the estimated backward trajectory calculated by the backward trajectory estimating means passes the reference position, the steering angle of the steering wheel is calculated. The vehicle has a reverse start instruction means for outputting a reverse start instruction signal for instructing the vehicle to move backward as a maximum steering angle in a direction in which the vehicle approaches the entrance of the parking space.

  According to the present invention, it is recognized that the vehicle is stopped at the reference position when the reference position recognition means receives the reference position notification signal. Then, when the vehicle starts moving forward with a handle operation angle at which the distance between the vehicle and the entrance of the parking space is constant or enlarged by the driver's operation or the control of the vehicle control device, the backward trajectory The estimation means sequentially calculates the relative position of the midpoint between the rear wheels of the vehicle from the reference position, and determines the steering angle from the relative position to the maximum in the direction in which the vehicle approaches the entrance of the parking space. As the steering angle, the estimated backward trajectory when it is assumed that the vehicle is moved backward is sequentially calculated.

  Then, when the estimated backward trajectory passes the reference position, the reverse start instructing means sets the steering wheel steering angle as the maximum steering angle in the direction in which the vehicle approaches the entrance of the parking space. A reverse start instruction signal for instructing to reverse the vehicle is output. In this case, the driver or the vehicle control device that has recognized the output of the reverse start instruction signal maintains the steering wheel at the maximum steering angle in the direction in which the vehicle approaches the entrance of the parking space. By moving backward, the vehicle can be easily guided into the parking space. And since the parking assistance apparatus of the 1st aspect does not use the image processing apparatus, the parking assistance apparatus by a simple and low-cost structure can be provided.

  Next, a second aspect of the present invention is a parking assistance device that assists an operation when a four-wheeled vehicle is moved backward to park in parallel in a parking space, and detects the rotational speed of each rear wheel of the vehicle. A wheel speed sensor and a reference position notification signal for notifying that the driver's seat of the vehicle is stopped at a predetermined reference position in front of the parking space via a side surface of the vehicle are input to the vehicle. And a steering wheel steering angle at which a distance between the vehicle and the entrance of the parking space is constant or enlarged from the reference position after the reference position recognition means inputs the reference position notification signal. When the vehicle starts moving forward, the relative position from the reference position of the midpoint between the rear wheels of the vehicle is sequentially calculated based on the detection speed of the wheel speed sensor, and the A first estimated backward trajectory, which is a trajectory of the midpoint between the rear wheel axles of the vehicle, assuming that the vehicle has been retracted with the steering angle as the maximum steering angle in a direction approaching the entrance of the parking space. On the first estimated backward locus calculated by the first backward locus estimating means and the first backward locus estimating means, the steering angle of the steering wheel is changed to the maximum steering angle opposite to the current state and the vehicle is moved backward. When a second estimated backward trajectory that is a trajectory of the midpoint of the vehicle rear axle is calculated and the second estimated backward trajectory passes a target parking position that is set based on the reference position. A reverse start instructing means for outputting a reverse start instructing signal for instructing to reverse the vehicle, with the steering wheel operating angle as a maximum steering angle in a direction in which the vehicle approaches the parking space, and the reverse start instructing signal. When the vehicle starts to reverse after the reverse start instruction signal is output, the relative position of the midpoint between the rear wheels of the vehicle from the reference position is sequentially determined based on the detection speed of the wheel speed sensor. When the calculated relative position reaches the contact point between the second estimated backward trajectory passing through the target parking position and the first estimated backward trajectory that is the calculation target of the second estimated backward trajectory, the steering angle of the steering wheel And a steering angle reversal instructing means for outputting a steering angle reversal instructing signal for instructing to reverse by changing to a maximum steering angle opposite to the steering direction at that time.

  According to the present invention, it is recognized that the vehicle is stopped at the reference position when the reference position recognition means receives the reference position notification signal. Then, when the vehicle starts moving forward with a handle operation angle at which the distance between the vehicle and the entrance of the parking space is constant or enlarged by the operation of the driver or the control of the control device of the vehicle, the first The first estimated backward locus is sequentially calculated by the backward locus estimating means.

  Then, the reverse start instructing means assumes that the second estimated backward trajectory when the vehicle is moved backward by changing the steering angle of the steering wheel to the maximum steering angle opposite to the current steering direction on the first estimated backward trajectory. And when the second estimated backward trajectory passes through the parking completion position, the steering wheel steering angle is set as the maximum steering angle in the direction in which the vehicle approaches the parking space, and the reverse is instructed to reverse the vehicle. A start instruction signal is output. In this case, the driver or the vehicle control device that has recognized the output of the reverse start instruction signal maintains the steering wheel at the maximum steering angle in the direction in which the vehicle approaches the entrance of the parking space. By moving backward, the vehicle can be easily guided into the parking space.

  The steering angle inversion instruction means calculates a relative position from the reference position of a midpoint between the rear wheels of the vehicle when the reverse start instruction signal is output and the vehicle starts to reverse. When the relative position reaches the contact point between the second estimated backward trajectory passing through the parking completion position and the first estimated backward trajectory from which the second estimated backward trajectory is calculated, the steering angle of the steering wheel is determined at that time. The steering angle reversal instruction signal for instructing to move backward by changing to the maximum steering angle opposite to the steering direction is output.

  In this case, the driver or the vehicle control device that has recognized the output of the steering angle reversal instruction signal changes the steering wheel steering angle to the maximum steering angle opposite to the current steering direction, and moves backward to change the vehicle. Can be easily guided to the parking position in the parking space. And since the parking assistance apparatus of the 2nd aspect does not use the image processing apparatus, the parking assistance apparatus by a simple and low-cost structure can be provided.

  Further, in the first aspect and the second aspect, an imaging means for imaging the rear of the vehicle, an expected course calculation means for calculating an expected course when the vehicle moves backward according to a steering angle of the vehicle, It is characterized by comprising display means for displaying the predicted course superimposed on the image taken by the imaging means.

  According to the present invention, the driver of the vehicle recognizes the predicted course displayed by the display unit and corrects the steering angle of the steering wheel, thereby bringing the vehicle into a more appropriate position in the parking space. Can be guided.

  In the first and second aspects, the vehicle includes an ABS (Antilock Brake System), and the wheel speed sensor is used by the ABS.

  According to the present invention, the wheel speed sensor provided for the ABS is diverted to calculate the position of the vehicle. Therefore, it is not necessary to separately provide the wheel speed sensor, and the cost of the parking assistance device can be reduced.

The block diagram of the parking assistance apparatus of this invention. Explanatory drawing which showed the implementation process of the support process of parallel parking. Explanatory drawing of the reference position which starts the parallel parking assistance process. Explanatory drawing of the determination method of the reverse start position in the parallel parking assistance process. Explanatory drawing which showed the implementation process of the support process of parallel parking. Explanatory drawing of the determination method of the reverse start position and steering angle inversion position in the parallel parking assistance process.

  An embodiment of the present invention will be described with reference to FIGS.

  With reference to FIG. 1, the parking assist device of the present embodiment is used by being mounted on a four-wheel vehicle 1 (hereinafter simply referred to as a vehicle 1), functions of an ECU (Electronic Control Unit) 50, and a chime. A sound generator 22, an R-side wheel speed sensor 14 that detects the rotational speed of the right rear wheel 12, an L-side wheel speed sensor 15 that detects the rotational speed of the left rear wheel 13, a parallel parking switch 30, and parallel parking The switch 31, the camera 40, and the display 41 constitute a parking assistance device.

  The ECU 50 is an electronic unit configured by a CPU (Central Processing Unit) and a memory (not shown), and when the CPU executes a control program for parking assistance, the CPU performs reference position recognition means 51, backward locus estimation. It functions as means 52, reverse start instructing means 53, steering angle inversion instructing means 54, and expected course calculating means 55.

  And a parking assistance apparatus performs the process which assists operation when the driver | operator of the vehicle 1 parks the vehicle 1 in parallel parking and parallel parking. Hereinafter, the parallel parking and parallel parking assistance processing by the parking assistance device will be described.

[Parallel parking support processing]
First, with reference to FIGS. 2-4, the parallel parking assistance process by a parking assistance apparatus is demonstrated. With reference to FIG. 2, the parallel parking is performed by three steps of a first step to a third step.

  First step: The driver moves the vehicle 1 to a predetermined parallel parking reference position P0 and stops the vehicle 1. Here, the reference position P 0 is determined at a position where the driver's seat of the vehicle 1 faces the central portion of the entrance of the parking space 60 through the side surface of the vehicle 1. In this case, the positional relationship between the reference position P0 and the midpoint P1 between the rear wheels 12 and 13 of the vehicle 1 is as shown in FIG. 3, and the ECU 50 memory stores the position of P1 relative to the reference position P0 (a, b) and data of the width c between the rear wheels 12 and 13 are held.

  Then, the driver turns on the parallel parking switch 30 provided on the dashboard or the like of the vehicle 1. In response to the ON operation of the parallel parking switch 30, the reference position recognition means 51 inputs an operation signal (corresponding to the reference position notification signal of the present invention) of the parallel parking switch 30, and the vehicle 1 stops at the reference position P0. Recognize that

  Second step: The driver sets the steering wheel 21 at a constant interval between the vehicle 1 and the parking space 60 (the steering angle of the steering wheel 21 is 0 degrees) or increases this interval (the steering angle of the steering wheel 21 in the case of FIG. 2). Is operated counterclockwise) to the steering angle to advance the vehicle 1. When the vehicle 1 is moved forward in this way, the driver does not need to keep the steering angle of the handle 21 constant or at a predetermined angle.

  At this time, the backward trajectory estimation means 52 determines the relative position Pa of the midpoint between the rear wheels 12 and 13 of the vehicle 1 with respect to the reference position P0 based on the detection speed by the R-side wheel speed sensor 14 and the L-side wheel speed sensor 15. To calculate sequentially (every predetermined control period).

  Then, the backward trajectory estimation means 52 makes the maximum steering angle in the direction in which the vehicle 1 approaches the parking space 60 at the relative position Pa for each calculated relative position Pa (clockwise direction in the case of FIG. The estimated backward trajectory that is the trajectory of the relative position Pa when the vehicle 1 is assumed to be moved backward while maintaining the maximum steering angle in the right direction) is sequentially calculated.

  FIG. 4 shows an example of the estimated backward trajectory. The estimated backward trajectory (P3 (a, R1-b) when C1 moves backward from the reference position P0 with the steering wheel 21 as the maximum steering angle in the clockwise direction is shown. The arc of the minimum turning radius R1 of the vehicle 1 as the center is shown. C2 indicates an estimated backward trajectory passing through the reference position P0 (an arc of the minimum turning radius R1 of the vehicle 1 centered on P4 (A, B)).

  As indicated by C2, when the current position Pa at the midpoint between the rear wheels 12, 13 of the vehicle 1 is such that the estimated backward trajectory at Pa passes through the reference position P0, the steering wheel If the vehicle 1 is moved backward with 21 as the maximum steering angle in the clockwise direction, the vehicle 1 is parked such that the midpoint between the rear wheels 12 and 13 of the vehicle 1 passes through the center of the entrance of the parking space 60. It can be guided into the space 60.

  Therefore, when the estimated backward trajectory at the current position Pa of the vehicle 1 passes through the reference position P0, the reverse start instructing means 53 notifies the driver from the chime sound generator 22 that the vehicle is temporarily stopped. Chime sound indicating that the steering wheel is fully turned to the right (the direction in which the vehicle approaches the parking space, the clockwise direction) and the vehicle moves backward while maintaining the full steering state (reverse start of the present invention). Corresponding to the instruction signal).

  Specifically, with reference to FIG. 4, the reverse start instructing unit 53 determines the distance between the rear wheels of the vehicle 1 at the present time calculated by the reverse trajectory estimating unit 52 according to the following formulas (1) to (5). The coordinates (A, B) of the center point P4 of the arc having the minimum turning radius R1, which is the estimated retraction locus at the midpoint position Pa, are obtained.

  Where r: approximate turning radius when the vehicle 1 moves, c: width between the rear wheels of the vehicle 1, RL: movement distance of the right rear wheel, LL: movement distance of the left rear wheel.

  However, the moving distance of the midpoint between the rear wheels of the vehicle 1.

  Where θ is the displacement angle of the midpoint between the rear wheels of the vehicle 1, and LC is the travel distance of the midpoint between the rear wheels of the vehicle 1.

  Then, the reverse start instructing means 53 uses the following formula (6) as a condition that the minimum radius circle centered on (A, B) calculated by the above formulas (4) and (5) passes through the reference position P0. ) Is output, the above-mentioned chime sound is output.

  In addition to the chime sound, or in place of the chime sound, an indication indicating that “the vehicle is temporarily stopped and the steering wheel is fully steered to the right, and this steered state is maintained to reverse” You may make it output to the display 41. FIG. In this case, the output signal to the display 41 corresponds to the reverse start instruction signal of the present invention.

  Third step: The driver who recognizes the reverse start timing by the chime sound once stops the vehicle 1 and fully turns the handle 21 in the direction in which the vehicle 1 approaches the parking space 60 (clockwise rotation direction, right direction in FIG. 4). Steer (to the maximum steering angle). Then, the driver moves the vehicle 1 backward while maintaining the state in which the steering wheel 21 is fully steered in the right direction. Thereby, the vehicle 1 can be guided to the parking space 60.

[Parallel parking]
Next, with reference to FIGS. 5-6, the parallel parking assistance process by a parking assistance apparatus is demonstrated. Referring to FIG. 5, parallel parking is performed by four steps of a first step to a fourth step.

  First step: The driver moves the vehicle 1 to a predetermined parallel parking reference position P0 and stops the vehicle 1. Here, the reference position P 0 is set at a position where the driver's seat of the vehicle 1 faces the rear end of the vehicle 70 parked in front of the parking space 71 through the side surface of the vehicle 1. In this case, the midpoint Pa between the rear wheels 12 and 13 of the vehicle 1 and the midpoint between the rear wheels 12 and 13 in the parking target frame 72 of the vehicle 1 in the parking space 71 when the reference position P0 is the origin. The position data of the target parking position Pt is previously stored in the memory.

  Then, the driver turns on the parallel parking switch 31 provided on the dashboard or the like of the vehicle 1. In response to the ON operation of the parallel parking switch 31, the reference position recognition means 51 inputs an operation signal (corresponding to the reference position notification signal of the present invention) of the parallel parking switch 31, and the vehicle 1 is in the reference position for parallel parking. Recognize that it is stopped at P0.

  Second step: The driver holds the steering wheel 21 at a constant interval between the vehicle 1 and the parking space 71 (steering angle is 0 degree) or increases this interval (in the case of FIG. 5, the clockwise rotation direction, the right steering angle) ) The vehicle 1 is moved forward by operating the steering angle. When the vehicle 1 is moved forward in this way, the driver does not need to keep the steering angle of the handle 21 constant or at a predetermined angle.

  At this time, the backward trajectory estimation means 52 determines the relative position Pa of the midpoint between the rear wheels 12 and 13 of the vehicle 1 with respect to the reference position P0 based on the detection speed by the R-side wheel speed sensor 14 and the L-side wheel speed sensor 15. To calculate sequentially (every predetermined control period).

  Then, the backward trajectory estimation means 52 makes the maximum steering angle in the direction in which the vehicle 1 approaches the parking space 60 at the relative position Pa with respect to the calculated angular relative position Pa (counterclockwise rotation direction in the case of FIG. 5). , The first estimated backward trajectory that is the trajectory of the relative position Pa when the vehicle 1 is assumed to be retracted.

  FIG. 6 shows an example of the first estimated backward trajectory, and shows the first estimated backward trajectory when the vehicle 1 is moved backward with C3 being Pa and the steering wheel 21 being turned fully to the left (maximum steering angle). Show. C4 fully steers the steering angle of the steering wheel 21 at the point Pc on C3 in the direction opposite to the present time (clockwise rotation direction, rightward in FIG. 6), and maintains the state of this full steering. 2 shows a second estimated backward trajectory that is a trajectory of the midpoint Pa between the rear wheels 12 and 13 of the vehicle 1 when it is assumed that the vehicle has moved backward.

  As shown in FIG. 6, when the second estimated backward trajectory C4 passes the target parking position Pt, the steering angle of the handle 21 is changed from the maximum counterclockwise steering angle to the maximum clockwise steering angle at Pc. The vehicle 1 can be guided to the parking target frame 72 by reversing and reversing the vehicle 1.

  Therefore, the reverse start instructing means 53 determines whether or not the second estimated reverse locus C4 passing through the target parking position Pt is obtained for each first estimated reverse locus C3 sequentially calculated by the reverse locus estimating means 52. To do. When the second estimated backward trajectory C4 passing through the target parking position Pt is obtained, the reverse start instructing means 53 notifies the driver from the chime sound generator 22 “stop the vehicle once, A chime sound (corresponding to the reverse start instruction signal of the present invention) is output instructing that the vehicle is fully steered leftward (counterclockwise rotation direction, and is moved backward while maintaining the full steered state). Further, the position of the contact point Pc between the first estimated backward locus C3 and the second estimated backward locus C4 is held in the memory.

  In addition to the chime sound, or instead of the chime sound, an indication indicating that “the vehicle is temporarily stopped and the steering wheel is fully steered to the left, and this vehicle steers backward while maintaining the full steered state” You may make it output to the display 41. FIG. In this case, the output signal to the display 41 corresponds to the reverse start instruction signal of the present invention.

  Third step: The driver who recognizes the reverse timing by the chime sound once stops the vehicle 1 and fully turns the handle 21 to the left (counterclockwise direction, the direction in which the vehicle 1 approaches the parking space 71). Do (set to the maximum steering angle). Then, the driver moves the vehicle 1 backward while maintaining the steering wheel 21 at the maximum left steering angle. Thereby, the vehicle 1 can be guided into the parking frame 72 of the parking space 71.

  Fourth step: The steering angle reversal instructing means 54 detects the relative position Pa of the midpoint between the rear wheels 12, 13 of the vehicle 1 with respect to the reference position P0 by the R-side wheel speed sensor 14 and the L-side wheel speed sensor 15. It calculates sequentially (every predetermined control period) based on speed. When the relative position Pa reaches the steering angle reversal position Pc, the steering angle reversal instructing means 54 notifies the driver from the chime sound generator 22 that the vehicle is temporarily stopped and the steering wheel is A chime sound (corresponding to the steering angle reversal instruction signal of the present invention) instructing that the vehicle is fully turned in the reverse direction (clockwise in FIG. 5 and the vehicle is moved backward while maintaining the full turning state). Output.

  The driver who recognizes the turning timing of the steering angle of the steering wheel by this chime sound once stops the backward movement of the vehicle 1 and fully turns the steering wheel steering angle in the direction opposite to the current state, and maintains this full steering state. The vehicle 1 is moved backward. Thereby, the driver can easily guide the vehicle 1 to the target parking frame 72 of the parking space 71.

  Next, the expected course calculation means 55 calculates the expected course when the vehicle 1 moves backward based on the steering angle of the steering wheel 21 (steering angle at full turning), and displays the rear image of the vehicle 1 by the camera 40. The predicted course is superimposed and displayed on the display 41. The driver can confirm the course of the vehicle 1 to the parking space by visually checking the display 41 when the vehicle 1 is moved backward.

  Further, the vehicle 1 includes an ABS (Antilock Brake System), and the R-side wheel speed sensor 14 and the L-side wheel speed sensor 15 are also used in the ABS. Therefore, it is not necessary to provide the R-side wheel speed sensor 14 and the L-side wheel speed sensor 15 exclusively for the parking assistance device, and the cost when the parking assistance device is mounted on the vehicle can be suppressed.

  In the present embodiment, the driver of the vehicle performed the steering wheel operation and the forward and backward operation of the vehicle in the parallel parking assistance process and the parallel parking assistance process, but part or the front of these operations, You may make it carry out by control of ECU50 of the vehicle 1. FIG. In this case, the ECU 50 outputs a control signal to the steering mechanism of the handle 21 to change the steering angle of the handle 21, and outputs a control signal from the ECU 50 to the drive mechanism (engine, motor, transmission, etc.) of the vehicle 1. The vehicle 1 is moved forward and backward. Note that these control signals output from the ECU 50 correspond to the reverse start signal and the steering angle inversion instruction signal of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Four-wheel vehicle, 14 ... R side wheel speed sensor, 15 ... L side wheel speed sensor, 21 ... Handle, 22 ... Chime sound generator, 30 ... Parallel parking switch, 31 ... Parallel parking switch, 40 ... Camera, 41 ... Display, 50 ... ECU, 51 ... Reference position recognition means, 52 ... Backward trajectory estimation means, 53 ... Reverse start instruction means, 54 ... Steering angle inversion instruction means, 55 ... Expected course calculation means.

Claims (4)

A parking assistance device for assisting operations when a four-wheeled vehicle is moved backward and parked in parallel in a parking space,
A wheel speed sensor for detecting the rotational speed of each rear wheel of the vehicle;
Reference position recognition means for inputting a reference position notification signal for notifying that the vehicle's driver's seat is stopped at a reference position facing the central entrance of the parking space via the side of the vehicle; ,
After the reference position recognition means inputs the reference position notification signal, when the vehicle starts moving forward from the reference position with a steering wheel steering angle at which the distance between the vehicle and the entrance of the parking space is constant or enlarged. , Sequentially calculating the relative position of the midpoint between the rear wheels of the vehicle from the reference position based on the detection speed of the wheel speed sensor, and the vehicle calculates the steering angle of the steering wheel from the relative position of the parking space. A reverse trajectory estimation means for sequentially calculating an estimated reverse trajectory that is a trajectory of a midpoint between the rear wheels of the vehicle when it is assumed that the vehicle is retreated as a maximum steering angle in a direction approaching the entrance;
When the estimated backward trajectory calculated by the backward trajectory estimating means passes through the reference position, the steering angle is set as the maximum steering angle in the direction in which the vehicle approaches the entrance of the parking space. A parking assistance apparatus, comprising: a reverse start instruction means for outputting a reverse start instruction signal instructing to reverse the vehicle. A parking assistance device for assisting an operation when a four-wheeled vehicle is moved backward to park in parallel in a parking space,
A wheel speed sensor for detecting the rotational speed of each rear wheel of the vehicle;
Reference position recognition means for inputting a reference position notification signal for notifying that the vehicle is in a state where the driver's seat of the vehicle is stopped at a predetermined reference position in front of the parking space via the side of the vehicle. When,
After the reference position recognition means inputs the reference position notification signal, when the vehicle starts moving forward from the reference position with a steering wheel steering angle at which the distance between the vehicle and the entrance of the parking space is constant or enlarged. In addition, the relative position from the reference position of the midpoint between the rear wheels of the vehicle is sequentially calculated based on the detection speed of the wheel speed sensor, and the steering wheel operating angle approaches the entrance of the parking space from the relative position. First retraction trajectory estimation means for sequentially calculating a first estimated retraction trajectory that is a trajectory of a middle point between the rear wheel axles of the vehicle when it is assumed that the vehicle is retreated as a maximum steering angle in a direction to
On the first estimated backward locus calculated by the first backward locus estimating means, it is assumed that the vehicle is moved backward by changing the steering angle of the steering wheel to the maximum steering angle opposite to the current state. A second estimated backward trajectory, which is the trajectory of the middle point of the rear wheel axle, is calculated, and when the second estimated backward trajectory passes a target parking position set based on the reference position, the steering wheel operating angle is determined by the vehicle. A reverse start instruction means for outputting a reverse start instruction signal for instructing the vehicle to reverse as a maximum steering angle in a direction approaching the parking space;
After the reverse start instruction signal is output by the reverse start instruction signal, when the vehicle starts to reverse, the middle position between the rear wheels of the vehicle from the reference position is determined based on the detection speed of the wheel speed sensor. The relative positions of the points are sequentially calculated, and the relative position reaches the contact point between the second estimated backward trajectory passing through the target parking position and the first estimated backward trajectory that is the calculation target of the second estimated backward trajectory. And a steering angle reversal instructing means for outputting a steering angle reversal instructing signal for instructing to reverse by changing the steering angle to the maximum steering angle opposite to the steering direction at that time. Parking assistance device. In the parking assistance device according to claim 1 or 2,
Imaging means for imaging the rear of the vehicle;
An expected course calculation means for calculating an expected course of the vehicle when the vehicle moves backward according to a steering angle of the steering wheel;
A parking assistance apparatus comprising: a display unit configured to display the predicted course in a superimposed manner on an image captured by the imaging unit. In the parking assistance device according to any one of claims 1 to 3,
The vehicle is equipped with ABS (Antilock Brake System),
The parking assistance device according to claim 1, wherein the wheel speed sensor is used by the ABS.

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