Autonomous driving control device and autonomous driving path computation method

An autonomous driving control device and an autonomous driving path computation method capable of computing a driving path without extremely changing a movement of a steering wheel during autonomous driving. A parking control device computes a parking path for automatically parking a vehicle, and includes an acceleration section transition curve computing unit that computes an acceleration section transition curve based on a target steering speed set in advance and an acceleration section target vehicle speed, a deceleration section transition curve computing unit that computes a deceleration section transition curve based on the target steering speed and a deceleration target vehicle speed, and a parking path computing unit that computes a parking path using the acceleration section transition curve and the deceleration section transition curve. The parking path is computed by setting the deceleration section target vehicle speed faster than the acceleration section target vehicle speed.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2018-196325 filed on Oct. 18, 2018, the content of which is hereby incorporated herein by reference into this application.

BACKGROUND

Technical Field

The present invention relates to an autonomous driving control device and an autonomous driving path computation method for vehicles.

Background Art

JP 2005-14775 A discloses a parking assistance system for automatically steering a vehicle. In this document, a technique is disclosed in which a driving path using a clothoid curve as a transition curve is computed so as to prevent a sudden change in the steering speed of the steering wheel.

SUMMARY

In this document, change from 0° to a preset steady-state angle are defined as being identical to that from the steady-state angle to 0°. However, a clothoid curve may coincide with a driving path, if a constant speed is set, and under such condition, operation of turning a steering wheel at a constant speed is performed.

Therefore, if the clothoid curve is applied to a system for turning the steering wheel while accelerating or decelerating the vehicle, such as a driving assistance system, a phenomenon that movement of a steering wheel changes suddenly fast or suddenly slow would occur, which may give a sense of discomfort to a driver.

The present invention has been made in view of the foregoing. Exemplary embodiments relate to providing an autonomous driving control device and an autonomous driving path computation method capable of computing a driving path that can reduce a sense of discomfort felt by a driver by varying the lengths of transition curves between an acceleration section and a deceleration section on the basis of a speed profile for driving a vehicle.

Accordingly, there is provided an autonomous driving control device for computing a driving path along which a vehicle is driven autonomously, including an acceleration section transition curve computing unit configured to compute an acceleration section transition curve on the basis of a target steering speed set in advance and an acceleration section target vehicle speed; and a deceleration section transition curve computing unit configured to compute a deceleration section transition curve on the basis of the target steering speed and a deceleration section target vehicle speed. A driving path is computed by setting the deceleration section target vehicle speed faster than the acceleration section target vehicle speed.

According to the present invention, a driving path that is suitable for given circumstances or user's needs can be computed. Further features related to the present invention will become apparent from the description of the specification and the accompanying drawings. In addition, other problems, configurations, and advantageous effects will become apparent from the following description of embodiments.

DETAILED DESCRIPTION

Next, embodiments of the present invention will be described with reference to the drawings. The following embodiment illustrates a case where the autonomous driving control of the present invention is applied to automatic parking control in which a driving path is often considered as a curve. A parking control device of the present embodiment is encompassed by the autonomous driving control device of the present invention.

FIG. 1is a functional block diagram of a parking control device according to an embodiment of the present invention.FIGS. 2A and 2Billustrate the state of reverse parking, specifically, the state of a vehicle before and after the parking.

A parking control device1computes a parking path for automatically parking a vehicle, and outputs the computation results to the vehicle control device15. The vehicle control device15performs all of steering wheel operation, and accelerator operation and brake operation for the vehicle V, in place of a driver, on the basis of information on the parking path, and automatically parks the vehicle V at a target parking position by moving the vehicle V along the parking path. The parking control device1computes a parking path from the initial position of the vehicle V to the target parking position in the parking space.

For example, a parking space20illustrated inFIGS. 2A and 2Bis provided on the left side with respect to a road orientation25of a road21, and has a parking orientation26set therein so as to allow the vehicle V to be reverse parked in the parking space20. The parking space20means a zoned area having a parking orientation set therein in advance so as to allow a vehicle to be parked in a predetermined orientation in the parking space20. The parking space20is also referred to as a parking frame, parking slot, parking area, paring place, or parking lot, for example. In the parking space20illustrated inFIGS. 2A and 2B, the vehicle V is first turned to the right while being moved forward from the initial position P0, and is once stopped with its rear facing the parking space20, and is then turned to the left while being going backward so that the vehicle V can enter the parking space20.

The parking assistance device1computes a path for moving the vehicle V, so that the vehicle V is arranged with the vehicle orientation Vf directed in the same orientation as the parking orientation26at the target parking position P1in the parking space20from the state in which the vehicle V is at the initial position P0on the road21with the vehicle orientation Vf directed in the same orientation as the road orientation25, and sets the computed path as a parking path. A parking path to be set herein basically includes a curve at least at a part thereof.

In the parking environment in which the vehicle V is parked, obstacles23and24, such as other vehicles or other parking spaces, are arranged ahead of or behind the parking space20along the road21. Also, an obstacle22, such as a wall or a curb extending along the road orientation25of the road21or another vehicle, is arranged across the road21opposite to the parking space20. It should be noted that in the present embodiment, the obstacles23and24are always present on the opposite sides of the parking space20.

To generate a parking path, the parking control device1uses transition curves that are based on a target vehicle speed and the turning radius of the vehicle that moves autonomously. Accordingly, a parking path that is suitable for given circumstances or user's needs can be computed, and the vehicle V can be parked automatically.

Regarding movements of the vehicle V, all of steering wheel operations, accelerator operation and brake operation are basically performed by autonomous control. To park the vehicle V automatically, a target vehicle speed and acceleration can be set in advance, and transition curves can be set on the basis of them. Thus, a sense of discomfort felt by the driver can be reduced.

The parking control device1is installed on the vehicle V, and is implemented through cooperative operations of hardware, such as a microcomputer including a CPU and memory, and a software program. The parking control device1includes, as illustrated inFIG. 1, a transition curve computing unit11, a candidate connection position setting unit12, a connection path computing unit13, and a parking path generating unit14.

A parking path includes an acceleration section in which the vehicle V is accelerated from the stop state, a constant speed section that is continuous from the acceleration section and in which the vehicle V travels at a constant vehicle speed, and a deceleration section that is continuous from the constant vehicle speed and in which the vehicle V is decelerated to stop. In each of the acceleration section and the deceleration section, the vehicle is moved forward or backward while the steering angle of the steering wheel (i.e., steering wheel angle) is increased or decreased (i.e., while the steering wheel is turned). Therefore, transition curves are set. Meanwhile, in the constant speed section, the vehicle is moved forward or backward while the steering angle of the steering wheel is held constant. Therefore, an arc-shaped curve with a constant radius of curvature is set. In the present embodiment, the minimum turning radius of the vehicle V is set as the radius of curvature of the arc-shaped curve so that the length of the parking path becomes the shortest.

The transition curve computing unit11computes the length of each transition curve on the basis of a target steering speed and a target vehicle speed. At the same time as computing the length of each transition curve, the transition curve computing unit11also computes the relative movement positions of the vehicle traveling along the transition curve, on the basis of the target steering speed and the target vehicle speed. The transition curves computed by the transition curve computing unit11are used to compute a pull-out path and set candidate connection positions thereon in the candidate connection position setting unit12, and also to compute a connection path in the connection path computing unit13.

The transition curve computing unit11includes an acceleration section transition curve computing unit that computes an acceleration section transition curve on the basis of a target steering speed set in advance and an acceleration section target vehicle speed, and a deceleration section transition curve computing unit that computes a deceleration section transition curve on the basis of the target steering speed and a deceleration section target vehicle speed. The transition curve computing unit11sets the deceleration section target vehicle speed faster than the acceleration section target vehicle speed. Therefore, the length of the transition curve of the deceleration section becomes shorter than that of the acceleration section, and thus, a parking path with the shortest distance can be generated.

Conventionally, a transition curve for an acceleration section and that for a deceleration section have the same length. Therefore, a movement of the steering wheel becomes slow during deceleration of the vehicle, which may give a sense of discomfort to a driver. Further, conventionally, the deceleration section and the acceleration section have the same length. Therefore, the resulting parking path tends to be long.

In contrast, in the parking control device1of the present embodiment, regarding the settings of the acceleration section target vehicle speed and the deceleration section target vehicle speed for computing transition curves in the transition curve computing unit11, the deceleration section target vehicle speed is set faster than the acceleration section target vehicle speed. Therefore, since the amount of change in the steering angle relative to the travel distance during acceleration of the vehicle has a gentle slope, it is possible to prevent the steering speed from becoming too fast. Meanwhile, since the amount of change in the steering angle relative to the travel distance during deceleration of the vehicle has a steep slope, it is possible to prevent the steering speed from becoming too slow and thus prevent the movement of the steering wheel from becoming too slow. Further, since the length of the deceleration section becomes shorter than that of the acceleration section, the length of the resulting parking path can be made shorter than that of the conventional device.

The candidate connection position setting unit12computes at least one pull-out path for pulling the vehicle V out of the target parking space20on the basis of information on the target parking space, constraint conditions regarding vehicle behavior, and transition curves and a predetermined arc-shaped curve computed with the transition curve computing unit11, and then sets a plurality of candidate connection positions Pcn on the pull-out path.

The connection path computing unit13determines the type of a connection path that can connect the initial position P0of the vehicle V to one of the candidate connection positions Pcn when the vehicle V start moving by moving forward. When a plurality of candidate connection positions has been set, the determination is performed for all of the candidate connection positions set.

FIG. 3illustrates exemplary types of connection paths. It is determined whether the type of the connection path is a connection path that involves turning of the vehicle V to one of the right or left side (FIG. 3A); an S-shaped connection path that involves turning of the steering wheel to both the right and left sides, that is, turning the steering wheel in the direction toward the candidate connection position and then turning the steering wheel in the opposite direction (FIG. 3B); and an S-shaped connection path that involves turning of the steering wheel in the direction away from the candidate connection position and then turning the steering wheel in the opposite direction (FIG. 3C). It should be noted that when the connection path is a simple straight path, such a path is determined as an infinite S-shaped path.

The connection path computing unit13computes, on the basis of the determined type of the connection path, a connection path that allows the vehicle V to reach the candidate connection position from the initial position of the vehicle V when it starts moving forward from the initial position, using the transition curves and the arc-shaped curve computed with the transition curve computing unit11. The method of computing the connection path will be described below.

The parking path generating unit14generates a parking path for the vehicle V by connecting the pull-out path and the connection path. The parking path is a path that allows the vehicle V to move along the connection path from the initial position P0of the vehicle V to a park-out position Pe, and then inversely follow the pull-out path from the park-out position Pe to the target parking position P1.

The aforementioned transition curve computing unit11, the candidate connection position setting unit12, the connection path computing unit13, and the parking path generating unit14constitute a parking path computing unit that computes a parking path using an acceleration section transition curve and a deceleration section transition curve.

The parking control device1receives, as illustrated inFIG. 1, target parking position information181and target parking space information182. The target parking position information181includes information, such as the shape of the parking space20and the relative position of the parking space20with respect to the vehicle V. The target parking space information182includes information on constraint conditions regarding a parking space, such as the positions of and distances to obstacles around the parking space20. The target parking position information181and the target parking space information182can be obtained from an external recognition sensor mounted on the vehicle V, such as a detected signal of an ultrasonic sensor mounted on the vehicle V or an image from an in-vehicle camera, for example. In addition, infrastructure information output from a parking facility may be obtained.

The vehicle information183includes information on constraint conditions regarding vehicle behavior, such as a turning radius of the vehicle V. For the vehicle position information184, dead reckoning positions computed with a vehicle model on the basis of the steering angle and speed of the vehicle V as well as the number of revolutions of the wheels may be used, and also, positional information obtained with a sensor, such as a GPS, or vehicle position information obtained through road-vehicle communication or inter-vehicle communication may be used.

The vehicle control device15controls an actuator mounded on the vehicle V for vehicle operation, on the basis of output signals from the parking control device1, so as to control the steering wheel operation, accelerator operation, and brake operation of the vehicle V, and automatically park the vehicle V at the target parking position P1by moving it along the parking path.

The display unit16is an in-vehicle monitor that the driver can watch in the vehicle, and can display the positions for switching the direction of vehicle travel for a target parking path, while displaying an image from a camera in a overlapped manner. The display unit16may display not only the positions for switching the direction of vehicle travel but also the entire parking path. Then, the driver is able to visually check the positions for switching the direction of vehicle travel as well as a parking path displayed on the in-vehicle monitor.

Next, the configuration of each of the transition curve computing unit11, the candidate connection position setting unit12, and the connection path computing unit13will be described in detail.

The transition curve computing unit11computes the length of each transition curve on the basis of the vehicle information183, and also computes the relative movement positions of the vehicle V traveling along the transition curve.

FIGS. 4A, 4B, and 4Cillustrate an exemplary parking path having transition curves and arc-shaped curves of the present embodiment.FIG. 4Aillustrates an exemplary parking path for reverse parking,FIG. 4Billustrates a connection path of the parking path, andFIG. 4Cillustrates a pull-out path of the parking path.FIG. 5illustrates the relationship between changes in the travel distance and the vehicle speed regarding the parking path ofFIG. 4.FIG. 6illustrates the relationship between the steering wheel angle and the distance based on the parking path of the present embodiment.FIG. 7illustrates the relationship between the steering wheel angle and the distance based on the conventional parking path.

The parking path illustrated inFIG. 4Aincludes a forward drive section31for moving the vehicle V forward from the initial position P0to the park-out position Pe while turning it to the right, and a reverse drive section41for reversing the vehicle V from the park-out position Pe to the target parking position P1while turning it to the left. The forward drive section31includes, as illustrated inFIG. 5, an acceleration section311for accelerating the vehicle speed to a predetermined speed from the initial position P0, a constant speed section312for moving the vehicle V at a predetermined speed over a constant distance, and a deceleration section313for decelerating the vehicle speed from the predetermined speed so as to stop the vehicle V at the park-out position Pe. In addition, the reverse drive section41includes an acceleration section411for accelerating the vehicle speed to a predetermined speed while reversing the vehicle V from the park-out position Pe, a constant speed section412for moving the vehicle V at a predetermined speed over a constant distance, and a deceleration section413for decelerating the vehicle speed from the predetermined speed so as to stop the vehicle V at the target parking position P1.

The acceleration section311of the forward drive section31includes a straight line31dextending from the initial position P0to a pass point32, and an acceleration section transition curve31acontinuous from the straight line31dand extending to a pass point33. The constant speed section312includes an arc-shaped curve31bcontinuous from the acceleration section transition curve31aand extending to a pass point34. The deceleration section313includes a deceleration section transition curve31ccontinuous from the arc-shaped curve31band extending to the park-out position Pe.

The acceleration section411of the reverse drive section41includes an acceleration section transition curve41aextending from the park-out position Pe to a pass point42. The constant speed section412includes an arc-shaped curve41bcontinuous from the acceleration section transition curve41aand extending to a pass point43. The deceleration section413includes a deceleration section transition curve41ccontinuous from the arc-shaped curve41band extending to a pass point44, and a straight line41dcontinuous from the deceleration section transition curve41cand extending to the target parking position P1.

As described above, the acceleration section transition curve31ais used for the acceleration section311of the forward drive section31, the arc-shaped curve31bis used for the constant speed section312, and the deceleration section transition curve31cis used for the deceleration section313. In addition, the acceleration section transition curve41ais used for the acceleration section411of the reverse drive section41, the arc-shaped curve41bis used for the constant speed section412, and the deceleration section transition curve41cis used for the deceleration section413.

The acceleration section transition curve31ais a curve whose curvature gradually increases from the pass point32between the straight line31dand the acceleration section transition curve31atoward the pass point33between the acceleration section transition curve31aand the arc-shaped curve31b. The deceleration section transition curve31cis a curve whose curvature gradually decreases from the pass point34toward the park-out position Pe. The steering angle is 0° at the park-out position Pe. Meanwhile, the acceleration section transition curve41ais a curve whose curvature gradually increases from the park-out position Pe toward the pass point42. The deceleration section transition curve41cis a curve whose curvature gradually decreases from the pass point43between the arc-shaped curve41band the deceleration section transition curve41cto the pass point44between the deceleration section transition curve41cand the straight line41d.

The relationship between the steering wheel angle and the distance based on the conventional parking path illustrated inFIG. 7includes a forward drive section101and a reverse drive section111. The acceleration section of the forward drive section101includes a straight line101dextending from the initial position P0to a pass point102, and an acceleration section transition curve101acontinuous from the straight line101d. The constant speed section of the forward drive section101includes an arc-shaped curve101bcontinuous from the acceleration section transition curve101a. The deceleration section of the forward drive section101includes a deceleration section transition curve101ccontinuous from the arc-shaped curve101band extending to the park-out position Pe. Meanwhile, the acceleration section of the reverse drive section111includes an acceleration section transition curve111aextending from the park-out position Pe. The constant speed section of the reverse drive section111includes an arc-shaped curve111bcontinuous from the acceleration section transition curve111a. The deceleration section of the reverse drive section111includes a deceleration section transition curve111ccontinuous from the arc-shaped curve111b, and a straight line111dcontinuous from the deceleration section transition curve111cand extending to the target parking position P1. In the example illustrated inFIG. 7, the acceleration section transition curve101aand the deceleration section transition curve101cof the forward drive section101have the same length, and the acceleration section transition curve111aand the deceleration section transition curve111cof the reverse drive section111also have the same length.

In contrast, the relationship between the steering wheel angle and the distance based on the parking path of the present embodiment differs from the conventional one in that the acceleration section and the deceleration section have different lengths as illustrated inFIG. 6. Specifically, in the forward drive section31, the length of the deceleration section transition curve31cis shorter than that of the acceleration section transition curve31a, and in the reverse drive section41, the length of the deceleration section transition curve41cis set shorter than that of the acceleration section transition curve41a. The transition curve computing unit11computes an acceleration section transition curve and a deceleration section transition curve so that the length of the deceleration section transition curve becomes shorter than that of the acceleration section transition curve.

The distance S of each transition curve along which the vehicle V travels is computed with Formula (1) below. Computing the distance S by separately setting the vehicle travel speed V for each of the acceleration section and the deceleration section in Formula (1) below can vary the lengths of the transition curves between the acceleration section and the deceleration section. Meanwhile, the steering speed ω is set at the same speed for both the acceleration section and the deceleration section.

FIG. 8illustrates the relative movement positions of the vehicle traveling along a transition curve. The relative positions Xc, Yc, θc of the vehicle that travels over the travel distance computed with the method of Formula (1) above are computed with Formulae (2), (3), and (4), respectively. The relative positions Xc, Yc, θc are computed for each of the acceleration section and the deceleration section, and are stored as acceleration section relative positions Xac, Yac, θac, and deceleration section relative positions Xbc, Ybc, θbc.

In the present embodiment, the deceleration section target vehicle speed is set faster than the acceleration section target vehicle speed. Therefore, in the forward drive section31, the length of the deceleration section transition curve31cis shorter than that of the acceleration section transition curve31a, and in the reverse drive section41, the length of the deceleration section transition curve41cis shorter than that of the acceleration section transition curve41a.

<Candidate Connection Position Setting Unit>

The candidate connection position setting unit12computes a pull-out path on the basis of the target parking position information181, the target parking space information182, the vehicle information183, and the acceleration section relative positions Xac, Yac, θac as well as the deceleration section relative positions Xbc, Ybc, θbc computed with the transition curve computing unit11, and also computes candidate connection positions during computation of the pull-out path.

The pull-out path is a virtual movement path obtained by estimating a path along which the vehicle V is pulled out of the parking space20from the state in which the vehicle V is correctly arranged at the target parking position P1in the parking space20. The pull-out path is computed totally independently of and without relevance to the initial position P0of the vehicle V. The candidate connection position setting unit12does not use the vehicle position information when computing the pull-out path. The number of pull-out paths is not limited to one, and more than one pull-out path may be computed.

The pull-out path is computed on the basis of information on the target parking space and the constraint conditions regarding vehicle behavior. For example, when reverse parking is conducted, provided that the target parking position P1is the origin, a path is generated such that the vehicle V is pulled out of the parking space in the same direction as the orientation of the vehicle V at the initial position P0, is created.

For example, when conducting reverse parking in which the position or state of the vehicle V is reverse-parked at the target parking position P1, the following paths are computed: a path for moving the vehicle V straight forward from the target parking position P1until the reference point Vo that is an intermediate position between the right and left rear wheels of the vehicle V (hereinafter referred to as a “position Vo” of the vehicle) reaches a position outside of the parking space20; a forward drive path for moving the vehicle V forward while turning it in the direction to leave the parking space toward the same direction as the orientation of the vehicle V at the initial position P0until the vehicle V reaches a reachable limit position with respect to an obstacle ahead; and a reverse drive path for reversing the vehicle V with its front wheels held straight with respect to the vehicle V or reversing the vehicle V while turning it in a direction opposite to the direction during the forward drive until the vehicle V reaches a reachable limit position with respect to an obstacle behind.

The forward drive path and the reverse drive path are alternately computed to compute a pull-out path until a predetermined termination condition is satisfied. It should be noted that the “reachable limit position” means a position at which the vehicle V is away from an obstacle with a predetermined gap therebetween. The predetermined gap includes a predetermined error taken into consideration as a margin so that the vehicle V will not contact the obstacle. The predetermined gap is preferably as small as possible, and is set to about 1 to 5 cm, for example. In the present embodiment, a virtual frame with a predetermined gap is set in a region around the outer periphery of the vehicle V, and a position at which the virtual frame contacts the obstacle is determined as a reachable limit position.

The candidate connection position setting unit12computes a pull-out path until at least one of the following conditions is satisfied as the predetermined termination condition, for example: a first condition in which the vehicle orientation Vf of the vehicle V on the pull-out path has an angle of 90° [deg] with respect to the parking orientation26and is in parallel with and in the same orientation as the road orientation25, a second condition in which the vehicle V has reached a point that is away from the target parking position P1by a predetermined distance Hmax along the road orientation25, or a third condition in which the number of switching of the direction of vehicle travel on the pull-out path has reached a predetermined number.

FIGS. 9A-9Iillustrate an exemplary method of computing a pull-out path for reverse parking. The pull-out path is computed as follows for the reverse parking exemplarily illustrated inFIGS. 9A-9I, for example: inFIG. 9Athe vehicle V is moved straight forward from the state in which the vehicle V is parked in the parking space20, inFIG. 9Bthe position Vo of the vehicle V reaches a position outside of the parking space20, inFIG. 9Cthe vehicle V is moved forward from that position while being turned to the left until the vehicle V reaches a reachable limit position with respect to the obstacle22ahead, inFIG. 9Dthe vehicle V is reversed from that position with its front wheels adjusted straight again along the vehicle orientation of the vehicle V until the vehicle V reaches a reachable limit position with respect to the obstacle24behind, and then, the vehicle V is moved along inFIG. 9Ea forward drive path for moving the vehicle V forward while turning it to the left, inFIG. 9Fa reverse drive path for reversing the vehicle V straight, inFIG. 9Ga forward drive path for moving the vehicle V forward while turning it to the left, and inFIG. 9Ha reverse drive path for reversing the vehicle V straight so that inFIG. 9Ithe vehicle orientation Vf of the vehicle V has an angle of 90° [deg] with respect to the parking orientation26of the parking space20and is in parallel with and in the same orientation as the road orientation25.

Herein, the deceleration section transition curve is introduced into the portion of the change inFIG. 9BtoFIG. 9C, and the acceleration section transition curve is introduced into the portion immediately beforeFIG. 9C.

FIGS. 10A and 10Bspecifically illustrate the configuration of a path fromFIG. 9A-FIG. 9C. The reason that the deceleration section transition curve is introduced into the portion of the change inFIG. 9BtoFIG. 9Cis that the degree of necessity to decelerate the vehicle V is high since the obstacles23and24are present around the parking space. In addition, the reason that the acceleration section transition curve is introduced into the portion immediately before inFIG. 9Cis that as the computed pull-out path is finally set as an inverse path, the vehicle V actually moves in the direction away from the obstacle22, and the operation of the vehicle at this time corresponds to the acceleration section after the direction of vehicle travel is switched.

It should be noted that the method of computing the pull-out path is not limited to the ones described above, and computation may be performed using other conditions. Further, computation may be performed using a condition suitable for a target parking space that has been selected from among a plurality of preset conditions. For example, althoughFIGS. 9A-9Iillustrate an example in which the vehicle V reverses straight, the vehicle V may reverse while turning to a side opposite to the side to which the vehicle turns when moving forward. Alternatively, it is possible that the vehicle V moves straight forward when moving forward, and it turns only when it reverses. The acceleration section transition curve and the deceleration section transition curve are introduced only when the vehicle V turns and are not introduced when the vehicle V moves straight.

The candidate connection position setting unit12sets a plurality of candidate connection positions during computation of the pull-out path. A candidate connection position is a candidate position for determining whether the vehicle V can reach the candidate connection position by moving it forward from the initial position P0.

FIG. 11illustrates candidate connection positions on the pull-out path for reverse parking. As one of the methods of setting candidate connection positions, for example, a plurality of candidate connection lines PLn (n is a number) is set at predetermined intervals on the road21along the road orientation25of the road21. The positions of intersection between the position Vo of the vehicle V and the candidate connection lines PLn on the pull-out path are set as candidate connection positions Pcn (n is a number), and the candidate connection positions Pcn are stored in association with the vehicle orientations Vf of the vehicle V at those positions.

The candidate connection lines PLn are set at predetermined intervals on the road21along the road orientation of the road21in the leftward direction from the parking space20such that they extend in the width direction of the road21at positions ahead of the target parking position P1. In the present embodiment, the candidate connection lines PLn are set at intervals of 10° of, with reference to the vehicle orientation Vf at the target parking position P1, the relative angle with respect to the vehicle orientation Vf at the target parking position P1or the switch position of the direction of vehicle travel.

Herein, the candidate connection positions Pcn are positions computed on the basis of a single pull-out path B. Considering the behavior of drivers, the operation of pulling the vehicle V to a position close to the obstacle22on the side of the road is often performed. Therefore, in the present embodiment, candidate connection positions Pcn′ and Pcn″ are also set at positions close to the obstacle22on the side of the road on the basis of the candidate connection positions Pcn set on the pull-out path B. In the drawing, symbol P1denotes the target parking position, symbol B denotes an exemplary pull-out path for pulling the vehicle V out of the target parking position P1, symbol Pcn denotes an exemplary candidate connection position set on the pull-out path B, and symbols Pcn′ and Pcn″ denote exemplary candidate connection positions computed on the basis of symbol Pcn.

FIGS. 12A and 12Billustrate a method of increasing the candidate connection positions. In the present embodiment, the distance D is added to the distance for moving the vehicle V straight from the target parking position P1, to increase the candidate connection positions Pcn′ and Pcn″ around the obstacle22on the side of the road. Specifically, as illustrated inFIG. 12A, the distance D from a corner of the vehicle at the candidate connection position Pc1that is closest to the obstacle22on the side of the road is computed. Then, the computed distance D is added to the distance for moving the vehicle V straight from the target parking position P1as illustrated in ofFIG. 12Bso as to set a new candidate connection position Pc1′ around the obstacle22on the side of the road. At this time, the vehicle orientation Vf of the vehicle V at the candidate connection position Pc1′ is inclined with respect to the parking orientation26at the same angle as the vehicle orientation Vf of the vehicle V at the candidate connection position Pc1on the pull-out path B as a reference.

In addition, a distance D/2 that is a half the computed distance D is added to the distance for moving the vehicle V straight from the target parking position P1so as to set a new candidate connection position Pc1″ around the obstacle22on the side of the road as illustrated inFIG. 11. Similarly, regarding the candidate connection positions Pc2, Pc3, and Pc4, candidate connection positions Pc2′, Pc2″, Pc3′, Pc3″, Pc4′, and Pc4″ are also set using the distances D and D/2.

In the present embodiment, as illustrated inFIG. 12A, a method of r computing the candidate connection position Pc1′ by adding the maximum straight movement amount of the distance D from the corner of the vehicle at the candidate connection position Pc1that is closest to the road to the obstacle22on the side of the road, and a method of computing the candidate connection position Pc1″ by adding a half the distance D/2 are adopted. However, the straight movement distance to be added may be any value as long as it is less than or equal to the maximum distance to the obstacle on the side of the road. Further, the number of dividing the distance D may be any number.

FIG. 13illustrates a method of determining candidate connection positions taking an acceleration section transition curve into consideration.

As illustrated inFIG. 13, the candidate connection positions Pcn to be set at predetermined intervals on the road21are each set as having an acceleration section transition curve. That is, in the present embodiment, when positions obtained by adding the acceleration section relative positions Xac, Yac, θac to the movement positions (which include the angle) on an arc are at predetermined intervals (i.e., at intervals of 10° of the relative angle with respect to the vehicle orientation Vf at the target parking position), such positions are set and stored as the candidate connection positions Pcn.

The candidate connection position setting unit12computes a pull-out path taking into consideration a deceleration section transition curve61cand an acceleration section transition curve61a, and sets the candidate connection positions Pcn on the pull-out path. Specifically, the candidate connection position setting unit12computes a pull-out path for pulling the vehicle V from the target parking position P1using the deceleration section transition curve61cand an arc-shaped curve61bcomputed with the transition curve computing unit11. Then, at least one candidate connection position Pcn is set on the pull-out path using the acceleration section transition curve transition curve61acomputed with the transition curve computing unit11.

The candidate connection position setting unit12connects the deceleration section transition curve61cto a straight-line section61dextending from the target parking position P1in a continuous manner, and connects the arc-shaped curve61bto the deceleration section transition curve61cin a continuous manner. Then, the candidate connection position setting unit12sets the candidate connection positions Pcn taking into consideration the acceleration section transition curve61a.

In the present embodiment, the length of the deceleration section transition curve61cand the relative positions of the vehicle V on the deceleration section transition curve61care computed in advance on the basis of a target steering speed and a deceleration section target vehicle speed, and the length of the acceleration section transition curve61aand the relative positions of the vehicle V on the acceleration section transition curve61aare computed in advance on the basis of the target steering speed and an acceleration section target vehicle speed (seeFIG. 8). In addition, the arc-shaped curve61bis set so that it has a constant radius of curvature (i.e., the minimum turning radius in the present embodiment). The candidate connection positions Pcn are set at intervals of 10° of, with reference to the vehicle orientation Vf at the target parking position P1, the relative angle of the vehicle orientation Vf with respect to the vehicle orientation Vf at the target parking position P1or the switch position of the direction of vehicle travel.

Therefore, connecting the deceleration section transition curve61cto the tip end position64of the straight-line section61din a continuous manner can determine the position of the tip end63of the deceleration section transition curve61. In addition, the arc-shaped curve61bis connected to the tip end63of the deceleration section transition curve61in a continuous manner, and the acceleration section transition curve61ais connected to the arc-shaped curve61bin a continuous manner. The acceleration section transition curve61ais, with the length of the arc-shaped curve61bvaried, arranged at intervals of 10° of the relative angle between the orientation of the tangent at the tip end of the acceleration section transition curve61aand the vehicle orientation Vf at the target parking position P1. Then, the tip ends of the acceleration section transition curve61aare set as the candidate connection positions Pc1, Pc2, . . . , Pcn.

FIG. 14is a flowchart illustrating an exemplary method of computing candidate connection positions on the pull-out path. First, computation for virtually moving the vehicle V in the direction to leave the target parking position P1is performed according to a predetermined rule (S101). Herein, straight-line section relative positions for moving the vehicle V straight from the target parking position P1are added to the virtual frame of the vehicle V (S102), and the deceleration section relative positions Xbc, Ybc, θbc are added to the straight-line section relative positions in a continuous manner (S103). Then, arc-section relative positions having a constant radius of curvature are added to the deceleration section relative positions in a continuous manner, and the acceleration section relative positions Xac, Yac, and θac are added to the arc-section relative positions in a continuous manner (S104). Then, whether the virtual frame of the vehicle V contacts an obstacle is determined (S105).

If it is determined that virtual frame of the vehicle V does not contact an obstacle (NO in S105), whether the vehicle V has reached a predetermined candidate connection position Pcn is determined (S106). Then, when the position Vo of the vehicle V has passed a candidate connection line PLn, such position is set as the candidate connection position Pcn, and the vehicle orientation Vf of the vehicle V at that position is stored (S110).

Then, whether the vehicle V is at an angle of 90° [deg] with respect to the parking orientation26and the vehicle orientation Vf is in parallel with the road orientation25(i.e., whether the first condition is satisfied) is determined (S107), and if it is determined that the vehicle V is at an angle of 90° [deg] with respect to the parking orientation26and the vehicle orientation Vf is in parallel with and in the same orientation as the road orientation25(YES in S107), the first condition is determined to be satisfied, and thus, the present routine terminates.

Meanwhile, if the vehicle orientation Vf of the vehicle V is not determined to be at an angle of 90° [deg] with respect to the parking orientation26, whether the vehicle V has moved away from the parking space by a distance greater than or equal to a predetermined distance Hmax is determined (S108). In the present embodiment, the predetermined distance Hmax is set to 7 meters. If the vehicle V is determined to have moved by a distance greater than or equal to the predetermined distance Hmax, the second condition is determined to be satisfied, and thus, the present routine terminates.

As another method of setting candidate connection positions, the candidate connection position setting unit12may, each time the vehicle orientation Vf of the vehicle V has changed by a predetermined relative angle (for example, every 5° [deg]) when the vehicle V is moved in the direction to leave the parking space along the pull-out path, set such position as a candidate connection position. Accordingly, the position Vo of the vehicle V when the orientation Vf of the vehicle V is at an angle of 5°, 10°, 15°, . . . , 90° with respect to the parking orientation26is each set as the candidate connection position Pcn.

If it is determined that the virtual frame of the vehicle V contacts an obstacle (YES in S105), such position is determined as a reachable limit position, and the gearshift of the vehicle V is switched from the D (drive) range to the R (reverse) range or from the R range to the D range so that the direction of travel of the vehicle V is switched back from forward drive to reverse drive or from reverse drive to forward drive (S109). Then, whether the virtual frame of the vehicle V contacts an obstacle is determined (S111).

If it is determined that the virtual frame of the vehicle V does not contact an obstacle (NO in S111), whether the vehicle V has moved by a predetermined distance is determined (S112). If it is determined that the vehicle V has not moved by the predetermined distance (NO in S112), the process returns to step S111, and whether the virtual frame of the vehicle V contacts an obstacle is determined. If it is determined that the vehicle V has moved by the predetermined distance (YES in S112), the process is determined to have failed and thus is terminated.

Meanwhile, if it is determined that the virtual frame of the vehicle V contacts an obstacle (YES in S111), such position is determined as a reachable limit position, and the gearshift of the vehicle V is switched from the D (drive) range to the R (reverse) range or from the R range to the D range so that the direction of travel of the vehicle V is switched back from forward drive to reverse drive or from reverse drive to forward drive (S113). Then, the deceleration section relative positions are added to the reachable limit position and the process returns to the loop again (S114).

The connection path computing unit13computes a connection path that allows the vehicle V to reach at least one of the plurality of candidate connection positions Pcn from the initial position P0of the vehicle V.

Whether the vehicle V can reach the candidate connection position Pcn is determined on the basis of the position Vo and vehicle orientation Vf of the vehicle V. If the position Vo of the vehicle V coincides with the candidate connection position Pcn and the vehicle orientation Vf of the vehicle V coincides with the vehicle orientation Vf stored in association with the candidate connection position Pcn through computation by the candidate connection position setting unit12, it is determined that the vehicle V can reach the candidate connection position Pcn.

If the vehicle V can be moved from the initial position P0and arranged in a predetermined vehicle orientation Vf at one of the candidate connection positions Pcn, then, the vehicle V can be moved into the parking space20by inversely following the pull-out path. Thus, the connection path computing unit13sets, among the plurality of candidate connection positions Pcn on the pull-out path, a candidate connection position Pcn at which the vehicle V can be arranged in a predetermined vehicle orientation Vf from the initial position P0, as a park-out position Pe, and computes a connection path from the initial position P0to the park-out position Pe.

FIG. 15is a process flow for determining whether the vehicle V can reach the candidate connection position Pcn. This process flow is performed for the total number of the candidate connection positions Pcn in a loop (S121). First, whether the vehicle V can reach the nearest candidate connection position Pcn from the initial position P0through a single-side steering maneuver is determined (S122). The “single-side steering maneuver” as referred to herein is an operation of turning the steering of the vehicle V to only one of the right or left side of the vehicle V. With this operation, the steering wheel is turned to one of the right or left side with respect to the vehicle orientation Vf. If it is determined that the vehicle V cannot reach the candidate connection position Pcn through a single-side steering maneuver alone, then, whether the vehicle V can reach the candidate connection position Pcn through an S-turn steering maneuver is determined (S126). The “S-turn steering maneuver” as referred to herein is an operation of turning the steering of the vehicle V to both the right and left sides of the vehicle V. With this operation, the steering wheel is turned to both the right and left sides with respect to the vehicle orientation Vf.

If it is determined that the vehicle V can reach the candidate connection position Pcn through a single-side steering maneuver or an S-turn steering maneuver, such candidate connection position Pcn is selected as a park-out position Pe, and a connection path from the initial position P0of the vehicle V to the park-out position Pe is generated (S123).

Then, whether the virtual frame of the vehicle V contacts an obstacle on the connection path is determined (S124). If it is determined that the virtual frame of the vehicle V does not contact the obstacle, the connection OK flag is set ON and the generated connection path is stored in a storage, and thus, the loop terminates (S127). Meanwhile, if it is determined that the vehicle V cannot reach the candidate connection position Pcn through a single-side steering maneuver or an S-turn steering maneuver (NO in S122and S126), or if it is determined that the virtual frame of the vehicle V contacts the obstacle (YES in S124), the determination for the relevant candidate connection position Pcn terminates, and determination for the other remaining candidate connection positions Pcn is performed. Then, if it is determined that the vehicle V cannot reach any of the candidate connection positions Pcn, the connection OK flag is set OFF (S125), and the process flow terminates.

FIGS. 16A to 16Ceach illustrate an example of determination of whether the vehicle V can reach a candidate connection position through a single-side steering maneuver.FIGS. 16D and 16Eeach illustrate an example of determination of whether the vehicle V can reach a candidate connection position through an S-turn steering maneuver.

In the determination of whether the vehicle V can reach a candidate connection position through a single-side steering maneuver in S122, it is determined that the vehicle V can reach the candidate connection position if all of the following conditions (1) to (3) are satisfied (i.e., restrictions regarding the angular difference and positions are also imposed).

(1) An axis a2(vehicle orientation Vf) of the vehicle V at the current position Pa (i.e., initial position P0) intersects an axis c2(vehicle orientation Vf) of the vehicle V at a candidate connection position Pcn.

(2) A turning circle a1at the current position Pa does not intersect the axis c2at the candidate connection position Pcn.

(3) A turning circle c1at the candidate connection position Pcn does not intersect the axis a2at the current position Pa.

It should be noted that a “turning circle” herein means an arc on the turning side with the clothoid curve taken into consideration (i.e., minimum turning trajectory).

In the example illustrated inFIG. 16A, the aforementioned condition (1) is satisfied since the axes a2and c2intersect at a position of intersection f1. In addition, the aforementioned conditions (2) and (3) are also satisfied. Therefore, it is determined that the vehicle V can reach the candidate connection position through a single-side steering maneuver. Meanwhile, inFIG. 16B, the aforementioned condition (3) is not satisfied since the turning circle c1intersects the axis a2. In addition, in the example illustrated inFIG. 16C, the aforementioned condition (2) is not satisfied since the turning circle a1intersects the axis e2. Therefore, in the example illustrated inFIGS. 16B and 16C, it is determined that the vehicle V cannot reach the candidate connection position through a single-side steering maneuver, and the process proceeds to determination of whether an S-turn steering maneuver is available.

In the determination of whether the vehicle V can reach the candidate connection position through an S-turn steering maneuver in S126, it is determined that the vehicle V can reach the candidate connection position if the following condition (4) is satisfied (i.e., restrictions regarding the angular difference and positions are also imposed).

(4) The turning circle a1at the current position Pa and the turning circle c1at the candidate connection position Pcn do not intersect.

In the example illustrated inFIG. 16D, the aforementioned condition (4) is satisfied since the turning circle a1and the turning circle c1do not intersect. Therefore, it is determined that the vehicle V can reach the candidate connection position through an S-turn steering maneuver. Meanwhile, in the example illustrated inFIG. 16E, the aforementioned condition (4) is not satisfied since the turning circle a1and the turning circle c1intersect. Therefore, it is determined that the vehicle V cannot reach the candidate connection position through an S-turn steering maneuver.

FIGS. 17A, 17B, 17C, and 17Dillustrate a method of generating a connection path using a transition curve that requires only a single-side steering maneuver. To generate a path from the current position Pa of the vehicle V to the candidate connection position Pcn, first, a reference single-side steering maneuver curve81, which is obtained by adding together an acceleration section transition curve81a, an arc-shaped curve81b, and a deceleration section transition curve81c, is generated on the basis of the vehicle information183as illustrated inFIG. 17A. The reference single-side steering maneuver curve81is determined on the basis of the relative angle θt between the vehicle orientation Vf of the vehicle V at the current position Pa and the vehicle orientation Vf of the vehicle V at the candidate connection position Pcn as illustrated inFIG. 17B.

The acceleration section transition curve81aand the deceleration section transition curve81care each computed on the basis of a target steering speed and a target vehicle speed. The arc-shaped curve81bhas the minimum turning radius of the vehicle V set thereon, and the length of the arc-shaped curve81bis set such that the vehicle orientation Vf at an end of the acceleration section transition curve81abecomes parallel with the vehicle orientation Vf at the current position Pa. Then, a reference reachable position82that can be reached by the vehicle V from the candidate connection position Pcn using the reference single-side steering maneuver connection curve81is computed.

Next, as illustrated inFIG. 17C, on the coordinate system having the current position Pa as the origin, the distance ΔPcy in the horizontal axis direction between the Y-coordinates of the candidate connection position Pcn and the current position Pa, and the distance ΔKy in the horizontal axis direction between the Y-coordinates of the reference reachable position82and the current position Pa are computed, and a magnification is computed on the basis of ΔPcy/ΔKy. This magnification is referred to as an Y-coordinate reachable magnification. In addition, a position obtained by magnifying the values of the X-coordinate and the Y-coordinate of the reference reachable position82on the basis of the Y-coordinate reachable magnification is referred to as a magnified reachable position83. Further, a curve obtained by magnifying the reference single-side steering maneuver curve81by the Y-coordinate reachable magnification is referred to as a magnified curve84.

The connection path computing unit13computes the Y-coordinate reachable magnification on the basis of the ratio of the distance ΔPcy in the horizontal axis direction from the current position Pa of the vehicle V to the candidate connection position Pcn to the distance ΔKy in the horizontal axis direction of the reference single-side steering maneuver curve81. Then, the connection path computing unit13computes the magnified curve84by magnifying and deforming the reference curve through a similarity transformation on the basis of the Y-coordinate reachable magnification. Herein, a characteristic that the inclination of the tangent at the reachable position remains the same even when the curve is magnified through a similarity transformation is used for each of the arc-shaped curve and the clothoid curve.

Finally, as illustrated inFIG. 17D, on the coordinate system having the current position Pa as the origin, the distance Δx to the X-coordinate of the magnified reachable position83is computed, and is determined as the length of a straight line85. Connecting the straight line85and the magnified curve84can form a connection path86. Thus, the magnified curve84partially forms the connection path86. With this method, the connection path86for which a transition curve that requires only a single-side steering maneuver is used can be generated. The candidate connection position Pcn, with which the connection path86can be generated by the connection path computing unit13among the plurality of candidate connection positions Pcn, is set as the park-out position Pe.

FIGS. 18A, 18B, 18C, and 18Dillustrate a method of generating a connection path using a transition curve that requires an S-turn steering maneuver. A method of computing a driving path from the current position Pa of the vehicle V to the candidate connection position Pcn is basically the same as the method of generating a connection path using a transition curve that requires only a single-side steering maneuver illustrated inFIGS. 17A, 17B, 17C, and 17D. The computation method herein differs from that inFIGS. 17A, 17B, 17C, and 17Din that, as illustrated inFIG. 18A, a reference S-turn steering maneuver curve91is formed using an acceleration section transition curve91a, an arc-shaped curve91b, an acceleration section transition curve91c, an arc-shaped curve91d, and a deceleration section transition curve91e, and in that, regarding the difference in the relative angle of the vehicle orientation Vf, the relative angle of the vehicle orientation Vf changes by the same degree on the two curves making up the S-shaped curve.

To generate a path from the current position Pa of the vehicle V to the candidate connection position Pcn that requires an S-turn steering maneuver, first, as illustrated inFIG. 18A, a reference S-turn steering maneuver curve91, which is obtained by adding together the acceleration section transition curve91a, the arc-shaped curve91b, the acceleration section transition curve91c, the arc-shaped curve91d, and the deceleration section transition curve91e, is generated on the basis of the vehicle information183. The reference S-turn steering maneuver curve91is computed on the basis of the vehicle orientation Vf of the vehicle V at the current position Pa and the vehicle orientation Vf of the vehicle V at the candidate connection position Pcn as illustrated inFIG. 18B.

The acceleration section transition curves91aand91cand the deceleration section transition curve91eare computed on the basis of a target steering speed and a target vehicle speed. The arc-shaped curves91band91deach have set thereon the minimum turning radius of the vehicle V. The lengths of the arc-shaped curves91band91dare set equal so that the turning angles for a right turn and a left turn of the vehicle V become equal. In addition, a reference reachable position92that can be reached by the vehicle V from the candidate connection position Pcn using the reference S-turn steering maneuver curve91is computed.

Next, as illustrated inFIG. 18C, on the coordinate system having the current position Pa as the origin, the distance ΔPcy in the horizontal axis direction between the Y-coordinates of the candidate connection position Pcn and the current position Pa, and the distance ΔKy in the horizontal axis direction between the Y-coordinates of the reference reachable position92and the current position Pa are computed, and an Y-coordinate reachable magnification is computed on the basis of ΔPcy/ΔKy. Then, a position obtained by magnifying the values of the X-coordinate and the Y-coordinate of the reference reachable position92on the basis of the Y-coordinate reachable magnification is set as a magnified reachable position93, and a curve obtained by magnifying the reference S-turn steering maneuver curve91by the Y-coordinate reachable magnification is set as a magnified curve94.

The connection path computing unit13computes the Y-coordinate reachable magnification on the basis of the ratio of the distance ΔPcy in the horizontal axis direction from the current position Pa of the vehicle V to the candidate connection position Pcn to the distance ΔKy in the horizontal axis direction of the reference S-turn steering maneuver curve91. Then, a characteristic that the inclination of the tangent at the reachable position remains the same even when the curve is magnified through a similarity transformation is used for each of the arc-shaped curve and the clothoid curve.

Finally, as illustrated inFIG. 18D, on the coordinate system having the current position Pa as the origin, the distance Δx to the X-coordinate of the magnified reachable position93is computed, and is determined as the length of a straight line95. Connecting the straight line95and the magnified curve94can form a connection path96. Thus, the magnified curve94partially forms the connection path96. With this method, the connection path96for which a transition curve that requires an S-turn steering maneuver is used can be generated. The candidate connection position Pcn, with which the connection path96can be generated by the connection path computing unit13among the plurality of candidate connection positions Pcn, is set as the park-out position Pe.

It should be noted that in the present method, it is often the case that the reference reachable position92is set at a position away from the current position Pa of the vehicle V in the Y-coordinate direction since the turning radius is too small, and thus, a connection path cannot be computed. In the present embodiment, in such a case, a known method such as the one disclosed in JP 2017-081398 A is used to geometrically compute a turning radius and a change in the angle, and then, a method of comprehensively searching for a connection path using values around the value of the turning radius while changing the turning radius is adopted.

According to the parking control device1of the present embodiment, the acceleration section transition curve is computed using the acceleration section target vehicle speed, and the deceleration section transition curve is computed using the deceleration section target vehicle speed. The deceleration section target vehicle speed is set faster than the acceleration section target vehicle speed. Thus, the length of the deceleration section transition curve is shorter than that of the acceleration section transition curve. Therefore, since the amount of change in the steering angle relative to the travel distance during acceleration of the vehicle has a gentle slope, it is possible to prevent the steering speed from becoming too fast. Meanwhile, since the amount of change in the steering angle relative to the travel distance during deceleration of the vehicle has a steep slope, it is possible to prevent the steering speed from becoming too slow and thus prevent the movement of the steering wheel from becoming too slow. Further, since the length of the deceleration section is shorter than that of the acceleration section, the length of the resulting parking path can be made shorter than that with the conventional device.

Although the aforementioned embodiment illustrates an example in which reverse parking is assisted, the present invention is similarly applicable to assisting in front-in parking. A parking path for front-in parking also includes an acceleration section for accelerating the vehicle speed from the initial position, a constant speed section for turning the vehicle at a constant speed, and a deceleration section for decelerating the vehicle speed until the vehicle reaches a target parking position. Regarding an acceleration section transition curve computed using an acceleration section target vehicle speed and a deceleration section transition curve computed using a deceleration section target vehicle speed, the deceleration section target vehicle speed is set faster than the acceleration section target vehicle speed. Thus, the length of the deceleration section transition curve is shorter than that of the acceleration section transition curve. Therefore, since the amount of change in the steering angle relative to the travel distance during acceleration of the vehicle has a gentle slope, it is possible to prevent the steering speed from becoming too fast. Meanwhile, since the amount of change in the steering angle relative to the travel distance during deceleration of the vehicle has a steep slope, it is possible to prevent the steering speed from becoming too slow and thus prevent the movement of the steering wheel from becoming too slow. Further, since the length of the deceleration section is shorter than that of the acceleration section, the length of the resulting parking path can be made shorter than that with the conventional device.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited thereto, and various design changes can be made without departing from the spirit or scope of the present invention recited in the claims. For example, although the aforementioned embodiments have been described in detail to clearly illustrate the present invention, the present invention need not include all of the configurations described in the embodiments. It is possible to replace a part of a configuration of an embodiment with a configuration of another embodiment. In addition, it is also possible to add, to a configuration of an embodiment, a configuration of another embodiment. Further, it is also possible to, for a part of a configuration of each embodiment, add, remove, or substitute a configuration of another embodiment.

Although the aforementioned embodiments illustrate a case where the vehicle is automatically parked, the present invention is also applicable to a steering wheel operation during autonomous driving of a vehicle, for example. In such a case, a target vehicle position is set instead of the target parking position, a movement path is set instead of the pull-out path, and a driving path is set instead of the parking path, so that the driving path up to the target vehicle position is computed.

DESCRIPTION OF SYMBOLS