Parking assist system

Abstract

The present invention provides a parking assist device that enables the generation of a forward trajectory in which the hitch angle does not exceed the limit angle at which reverse movement is possible, even if the occupant's operation is delayed and the actual turning position exceeds a preset turning position. [Solution] When assisting the parking of a towing vehicle 2 and a trailer 3 to be towed by a towing vehicle 2 while they are connected, the system acquires the parking start position and the parking target position, and generates a driving trajectory for parking from the parking start position to the parking target position. The driving trajectory is configured such that, when the towing vehicle 2 travels along the driving trajectory in the forward section, the hitch angle does not exceed the limit angle at which reverse movement is possible, even after passing the recommended turning point.

Description

Technical Field

[0001] The present invention relates to a parking assistance device that performs parking assistance for a vehicle.

Background Art

[0002] Conventionally, as parking assistance for a vehicle, it is known to calculate a driving trajectory when parking and perform guidance or vehicle control so that parking is performed according to the calculated driving trajectory. Here, particularly in the case of performing reverse parking, the driving trajectory is such that it once moves forward to a turning position appropriate for entering a parking target position such as a parking space, and then switches to reverse at the turning position and reverses to the parking target position. However, when performing the above parking assistance for a towing vehicle (hereinafter referred to as a tractor) towing a towed vehicle (hereinafter referred to as a trailer), it is necessary to set the above driving trajectory in consideration of not only the behavior of the tractor but also the behavior of the trailer.

[0003] For example, in Japanese Patent Application Laid-Open No. 2019-87875, in the parking assistance of a tractor towing a trailer, as a method for calculating a guiding path for guiding the trailer to a parking space, a guiding path of the tractor that can move the trailer to the parking space in a predetermined posture is calculated by making the guiding reference point indicating the current position of the tractor reach the guiding target point in the shortest distance and with the minimum number of turnbacks.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, as described in Patent Document 1 above, the driving trajectory until the vehicle reverses into a parking space is broadly divided into a forward section, from the start of parking to the turning point where the vehicle reverses direction, and a reverse section, from the turning point to the parking space. Furthermore, when providing parking assistance based on the generated driving trajectory, there is also a known parking assistance system that assumes that only the steering operation is automated, while the accelerator and brake operations are performed manually rather than automatically.

[0006] In parking assistance systems where acceleration and braking are performed manually, delays in the occupant's operation can cause the actual turning position to exceed the turning position pre-set by the system. Figure 15 shows an example of the forward trajectory (hereinafter referred to as the forward trajectory) generated when performing conventional parking assistance, and the changes in the connection angle (hitch angle) and curvature of the towing vehicle and trailer when traveling along that forward trajectory. As shown in Figure 15, the forward trajectory includes a first forward trajectory that moves forward with the turning direction being the direction away from the parking target position, and a second forward trajectory that moves forward with a second direction different from the first direction as the turning direction in order to adjust the hitch angle after the first forward trajectory. Conventionally, when setting the turning position in advance, the turning position is set at a position on the second forward trajectory that corresponds to the target hitch angle. However, if the occupant's operation to stop the vehicle is delayed, the absolute value of the hitch angle becomes larger than the target value as the vehicle moves forward. As a result, there was a problem in that the hitch angle became too large at the time of turning, making it impossible to reverse.

[0007] The present invention was made to solve the aforementioned problems of the conventional invention, and aims to provide a parking assistance device that can generate a forward trajectory in which the hitch angle does not exceed the limit angle at which reversing is possible, even if the occupant's operation is delayed and the actual reversing position exceeds a preset reversing position. [Means for solving the problem]

[0008] To achieve the above objective, the parking assistance device according to the present invention is a parking assistance device that assists in parking a towing vehicle and a trailer when the towing vehicle and the trailer to be towed by the towing vehicle are connected, and acquires a parking start position and a parking target position, generates a travel trajectory for parking from the parking start position to the parking target position, the travel trajectory includes a forward section in which the towing vehicle moves forward from the parking start position according to a forward trajectory to adjust the hitch angle, which is the connection angle between the towing vehicle and the trailer, and a reverse section in which the vehicle reverses after the forward section to the parking target position, sets a recommended turning position in the forward trajectory in which it is recommended to perform a turning maneuver, and in generating the travel trajectory, generates a forward trajectory in which, when the towing vehicle travels along the forward trajectory, the hitch angle does not exceed the limit angle in which it is possible to reverse even after passing the recommended turning position. Furthermore, regarding the generation of the travel trajectory, it is not necessary to generate the "travel trajectory for the forward section" and the "travel trajectory for the reverse section" at the same time. You can first generate the "travel trajectory for the forward section" and travel in the forward section, and then generate the "travel trajectory for the reverse section" and travel in the reverse section. Furthermore, "reversing operation" refers to, for example, the operation of switching the vehicle from a forward-moving state to a reverse-moving state. This operation of switching the vehicle from a forward-moving state to a reverse-moving state may be performed manually (by the occupant) or automatically. [Effects of the Invention]

[0009] According to the parking assistance device of the present invention having the above configuration, even if the occupant's operation is delayed and the actual turning position exceeds the preset recommended turning position, it is possible to generate a forward trajectory in which the hitch angle does not exceed the limit angle at which reversing is possible. As a result, even if the recommended turning position is exceeded, parking assistance can be continued until parking is completed without interruption. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the towing vehicle and trailer according to this embodiment. [Figure 2] This is a magnified view of the area around the towing device of a towing vehicle. [Figure 3] This diagram shows the movement of the towing vehicle and trailer with the hitch ball and coupler connected. [Figure 4] This is a block diagram showing the configuration of the parking assistance device according to this embodiment. [Figure 5] This is a flowchart of the parking assistance processing program according to this embodiment. [Figure 6] This diagram shows the entire driving trajectory from the parking start position to the parking target position. [Figure 7] This diagram illustrates the limit angle of the hitch angle. [Figure 8] This diagram illustrates Pattern A as a method for generating the forward-moving section of the driving trajectory from the parking start position to the parking target position. [Figure 9] This figure shows the changes in the travel trajectory and hitch angle of the generated forward section. [Figure 10] This is a diagram illustrating a steady state. [Figure 11] This diagram illustrates Pattern B as a method for generating the forward-moving section of the driving trajectory from the parking start position to the parking target position. [Figure 12] This diagram illustrates pattern C as a method for generating the forward-moving section of the driving trajectory from the parking start position to the parking target position. [Figure 13] This diagram shows potential turning points. [Figure 14] This diagram illustrates a method for determining the correct turning point from among the candidate turning points. [Figure 15] This diagram illustrates the problems with conventional technology. [Modes for carrying out the invention]

[0011] [Explanation of towing vehicles and trailers] Hereinafter, a specific embodiment of the parking assistance device according to the present invention will be described in detail with reference to the drawings. First, a tractor 2 equipped with the parking assistance device 1 according to the present embodiment and a towed vehicle (hereinafter referred to as a trailer) 3 towed by the tractor 2 will be described below. FIG. 1 is a view showing the tractor 2 and the trailer 3.

[0012] Here, the tractor 2, which is also called a tractor, is configured to be able to tow the trailer 3 and travel. The tractor 2 may be, for example, an automobile (internal combustion engine vehicle) having an internal combustion engine (engine, etc.) as a drive source, an automobile (electric vehicle, fuel cell vehicle, etc.) having an electric motor (motor, etc.) as a drive source, or an automobile (hybrid vehicle) having both of them as drive sources. Also, regardless of the vehicle type, as long as it has a towing device 4 described later, it may be an ordinary vehicle or a commercial large tractor (trailer head).

[0013] Also, as shown in FIG. 1, a towing device 4 (hitch) for towing the trailer 3 is arranged to project from, for example, the lower part of the center of the rear bumper of the tractor 2 in the vehicle width direction. FIG. 2 is a view showing an enlarged view of the vicinity of the towing device 4.

[0014] As shown in FIG. 2, the towing device 4 is fixed to, for example, the frame of the tractor 2. As an example, the towing device 4 includes a hitch ball 5 with a spherical tip erected in the vertical direction (vehicle up and down direction). The hitch ball 5 is covered by a coupler 7 provided at the tip of a connecting member 6 fixed to the trailer 3, so that the hitch ball 5 and the coupler 7 are connected, and as a result, the tractor 2 and the trailer 3 are connected. However, the shapes of the hitch ball 5 and the coupler 7 are not limited to the shapes shown in FIG. 2, and any shape may be used as long as the tractor 2 and the trailer 3 can be connected.

[0015] When the hitch ball 5 and coupler 7 are connected, the hitch ball 5 transmits forward, backward, left, and right movements to the trailer 3 (connecting member 6) in accordance with the movement of the towing vehicle 2. Furthermore, as shown in Figure 3, even when the coupler 7 is connected to the hitch ball 5, the angle of the coupler 7 relative to the hitch ball 5 can be freely changed (with an upper limit), allowing the trailer 3 to swing (rotate) in the width direction relative to the towing vehicle 2.

[0016] On the other hand, as shown in Figure 1, a rear camera (imaging device) 9 is installed on the wall of the rear hatch of the towing vehicle 2. The rear camera 9 is a digital camera with a built-in image sensor such as a CCD or CIS. The rear camera 9 can output video data (image data) at a predetermined frame rate. The rear camera 9 has a wide-angle lens or a fisheye lens, and its optical axis is set diagonally downward, allowing it to image a range of, for example, 140° to 220° in the horizontal direction.

[0017] Furthermore, the imaging range of the rear camera 9 includes at least the towing device 4 and hitch ball 5 located at the rear end of the towing vehicle 2. The image data captured by the rear camera 9 can be used, for example, to detect the coupling state of the towing vehicle 2 and the trailer 3 (e.g., coupling angle (hitch angle), whether or not they are coupled, etc.). However, instead of the rear camera 9, a sensor installed on the towing device 4 may be used as a means to detect the coupling state of the towing vehicle 2 and the trailer 3.

[0018] On the other hand, trailer 3 is also called a towed vehicle and is towed by the towing vehicle 2 described above. Therefore, unlike the towing vehicle 2, it basically does not have an engine or motor as a drive source. It also does not have a steering system for changing the direction of the wheels. Examples include camping trailers that have living space inside, and light trailers that carry cars or boats. Trailer 3 comprises a main body, multiple (two in this embodiment) trailer wheels, a connecting member 6, and a coupler 7.

[0019] Here, as shown in Figure 1, the connecting member 6 is provided at the lower part of the center of the main body of the trailer 3 in the width direction, and is positioned to protrude forward (in the direction of travel) from the front end of the main body.

[0020] Furthermore, as shown in Figure 2, the coupler 7 is provided at the front end of the connecting member 6 and has a spherical recess that covers the hitch ball 5. The coupler 7 covers the hitch ball 5, allowing the trailer 3 to be rotatably connected to the towing vehicle 2, as described above (see Figure 3). The length of the connecting member 6 and its height from the ground (i.e., the position of the coupler 7 on the trailer 3) vary depending on the type of trailer 3. However, in this embodiment, the coupler 7 is positioned at least to be connectable to the hitch ball 5 on the towing vehicle 2.

[0021] [Explanation of parking assist system] Next, the parking assistance device 1 provided by the towing vehicle 2 will be described. The parking assistance device 1 is a device that assists the driver in operating the vehicle when the towing vehicle 2, as described above, is parked in a predetermined parking space while connected to the trailer 3. Figure 4 is a block diagram showing the configuration of the parking assistance device 1 according to this embodiment.

[0022] As shown in Figure 4, the parking assistance device 1 according to this embodiment includes a vehicle information DB 21 in which various data related to the towing vehicle 2 and trailer 3 are recorded, and a parking assistance ECU 23 that performs various calculations based on the input information. The parking assistance device 1 is also connected via an in-vehicle network such as CAN to an operation unit 14 that receives operations from the occupants of the towing vehicle 2, a liquid crystal display 15 that displays the driving trajectory for parking into the parking space and other parking assistance-related information to the occupants of the towing vehicle 2, and a speaker 16 that outputs voice guidance related to parking assistance. Furthermore, the parking assistance device 1 is also connected to various sensors such as a rear camera 9 installed on the towing vehicle 2, a vehicle control ECU 24 that performs various controls on the towing vehicle 2, a vehicle speed sensor 25, a steering sensor 26, and a shift position sensor 27.

[0023] The control unit 14 is located on the instrument panel or steering wheel of the towing vehicle 2 and is operated, for example, when switching to the parking assist mode described later, or when inputting various parameters related to the towing vehicle 2 and trailer 3. It has multiple control switches (not shown), such as various keys and buttons. The parking assist ECU 23 controls the system to perform various operations based on the switch signals output when each switch is pressed. The control unit 14 may also have a touch panel located in front of the liquid crystal display 15. It may also have a microphone and a voice recognition device.

[0024] The liquid crystal display 15 is installed on the instrument panel of the towing vehicle 2 and, when the towing vehicle 2 is connected to the trailer 3 and the system is in parking assist mode, it displays an overhead view of the area around the vehicle, images captured by the rear camera 9, and a driving trajectory for parking. Furthermore, if the parking operation is to be performed by the user rather than automatically, the system also displays steering operation instructions, as well as instructions for operating the brakes, accelerator, and shift position to follow the driving trajectory. In addition, the parking assist device 1 of this embodiment assumes that at least the brakes, accelerator, and shift position are operated manually, and the liquid crystal display 15 provides guidance at a position where it is recommended to perform a reversing operation from forward to reverse. Note that the liquid crystal display 15 may also be used for the navigation system.

[0025] Furthermore, speaker 16 outputs voice guidance and other information to guide the parking operation when transitioning to parking assistance mode, based on instructions from the parking assistance ECU 23. In addition, speaker 16 is used to provide guidance at positions where it is recommended to perform the aforementioned maneuver of changing direction from forward to reverse. Speaker 16 may also be used in conjunction with the speaker used in the navigation system.

[0026] Furthermore, the vehicle information DB21 is a storage means that stores various information about the towing vehicle 2 and the trailer 3. For example, for the towing vehicle 2, the installation position of the hitch ball 5 (height from the ground, position in the left and right directions, distance from the rear end of the vehicle), overall length, vehicle width, wheelbase, minimum turning radius, etc. are stored. The distance from the rear axle of the towing vehicle 2 to the connection point between the towing vehicle 2 and the trailer 3 (position of the hitch ball 5) is also stored. On the other hand, for the trailer 3, the installation position of the coupler 7 (height from the ground, position in the left and right directions, distance from the front end of the vehicle), overall length, vehicle width, minimum turning radius, etc. are stored. The distance from the reference point of the trailer 3 to the connection point between the towing vehicle 2 and the trailer 3 (position of the hitch ball 5) (corresponding to the trailer wheelbase) is also stored. Note that the reference point of the trailer 3 is also the center of rotation of the trailer 3, and if the trailer 3 has one axle (two wheels), the axle center becomes the reference point. On the other hand, if the trailer 3 has two or more axles (four or more wheels), a reference point exists between the foremost axle and the rearmost axle (its position varies depending on the load distribution). The size of the trailer wheelbase is one of the parameters that represent the size of the trailer 3. This information may be entered in advance by the occupants or personnel from the vehicle manufacturer using the control unit 14, or it may be automatically entered using values ​​detected by the rear camera 9 or various sensors. Note that the towed trailer 3 is not necessarily fixed, so if the trailer 3 to be towed changes, the above parameters must also be changed. A memory card can be used as the storage medium for the vehicle information DB 21. Alternatively, it may be stored in the storage area of ​​the parking assistance ECU 23 (for example, RAM or flash memory).

[0027] On the other hand, the parking assistance ECU (Electronic Control Unit) 23 is an electronic control unit that controls the entire parking assistance device 1, and is equipped with an internal storage device such as a CPU 31 as a calculation device and control device, a RAM 32 which is used as working memory when the CPU 31 performs various calculations and stores trajectory data when the driving trajectory is calculated, a ROM 33 which stores control programs as well as the parking assistance processing program (see Figure 5) described later, and a flash memory 34 which stores programs read from the ROM 33. The parking assistance ECU 23 executes various functions as a processing algorithm. For example, it has functions to acquire the parking start position and the parking target position, a function to generate a driving trajectory for parking from the parking start position to the parking target position, and a function to set a recommended turning position where it is recommended to perform a turning maneuver in the forward trajectory.

[0028] Furthermore, the vehicle control ECU 24 is an electronic control unit that controls the towing vehicle 2. The vehicle control ECU 24 is also connected to various drive units of the vehicle, such as the steering, brakes, accelerator, and transmission. In this embodiment, for example, when transitioning to the parking assistance mode, which assists in parking into a parking space as described later, it is possible to perform automatic driving assistance for the towing vehicle 2 by controlling each drive unit. Specifically, when the parking assistance mode is executed, the parking assistance ECU 23 transmits various support information related to automatic driving assistance generated by the parking assistance device 1 to the vehicle control ECU 24 via CAN. The vehicle control ECU 24 then uses the received support information to perform automatic driving assistance after the start of driving. Support information includes, for example, the recommended driving trajectory for the towing vehicle 2 and trailer 3, and information indicating the vehicle speed and steering angle when driving according to the driving trajectory. In this embodiment, the automatic driving assistance basically only automates the steering operation, and the control of the accelerator, brakes, and transmission is performed manually. On the other hand, the installation of the above automatic driving assistance in the towing vehicle 2 is not mandatory, and the towing vehicle 2 may be a vehicle that can only be driven manually, including steering operation. In that case, when transitioning to parking assist mode, the system will provide steering guidance, brake, accelerator, and shift position guidance to help the vehicle follow the recommended driving path instead of the above-mentioned automatic driving assistance.

[0029] Furthermore, the vehicle speed sensor 25 consists of an active wheel speed sensor attached to the wheel of the towing vehicle 2, which detects the rotational speed of the wheel and outputs a speed signal. The steering sensor 26 is installed inside the steering device and detects the steering angle when the steering wheel is turned, which outputs a steering angle signal. In addition, the shift position sensor 27 is built into the shift lever and detects whether the shift position is "P (parking)", "N (neutral)", "R (reverse)", "D (drive)", "2 (2nd gear)", or "L (low)".

[0030] The parking assist ECU23 can acquire the current vehicle speed, mileage, steering angle, shift position, etc. of the towing vehicle 2 based on the output signals from the various sensors mentioned above.

[0031] [Explanation of the parking assistance processing program] Next, the parking assistance processing program executed by the parking assistance ECU 23 in the parking assistance device 1 having the above configuration will be explained with reference to Figure 5. Figure 5 is a flowchart of the parking assistance processing program according to this embodiment. Here, the parking assistance processing program is executed after the ACC power supply (accessory power supply) of the towing vehicle 2 is turned ON and the driver of the towing vehicle 2 operates the operation unit 14 to select the transition to parking assistance mode. This program assists the driver in parking when the towing vehicle 2 is parked with the trailer 3 attached. The program shown in the flowchart in Figure 5 below is stored in the RAM 32 and ROM 33 of the parking assistance ECU 23 and is executed by the CPU 31.

[0032] First, in step 1 (hereinafter abbreviated as S), the CPU 31 acquires the parking start position and the parking target position. Basically, the current positions of the towing vehicle 2 and trailer 3 become the parking start position, but if it is difficult to park from the current position to the parking target position, the parking start position may be set to a different position and guidance to the parking start position may be provided. On the other hand, for the parking target position, for example, the user may specify the desired parking position from the image of the area around the towing vehicle 2 displayed on the LCD display 15, and the specified position may be set as the parking target position, or the system may detect parking spaces around the towing vehicle 2 using cameras or sensors and set the detected parking spaces as the parking target position. Furthermore, in the following explanation, it is assumed that there are no obstacles around the vehicle that would obstruct its movement.

[0033] Next, in S2, the CPU 31 acquires the orientation of the towing vehicle 2 and trailer 3, and the connection angle (hitch angle) between the towing vehicle 2 and trailer 3 at the parking start position. The connection angle at the parking start position (i.e., the time when parking assistance begins) acquired in S2 is also called the "initial hitch angle". As mentioned above, the current position of the towing vehicle 2 and trailer 3 is basically the parking start position, so in S2, the current orientation and connection angle of the towing vehicle 2 and trailer 3 are acquired. The initial hitch angle can be determined, for example, from the image captured by the rear camera 9.

[0034] Next, in S3, the CPU 31 obtains information about the towing vehicle 2 and the trailer 3 from the vehicle information DB 21. The vehicle information DB 21 stores various information about the towing vehicle 2 and the trailer 3, and in particular, for the trailer 3, at least the distance from the reference point of the trailer 3 to the connection point between the towing vehicle 2 and the trailer 3 (position of the hitch ball 5) (hereinafter referred to as the trailer wheelbase) is obtained. In addition, for example, in S3, information such as the distance from the rear axle of the towing vehicle 2 to the connection point between the towing vehicle 2 and the trailer 3 (position of the hitch ball 5) (hereinafter referred to as the connection distance) and the minimum turning radius of the towing vehicle 2 (corresponding to the maximum curvature of the travel trajectory) is also obtained. Note that the processing order of S2 and S3 may be reversed.

[0035] Next, in S4, the CPU 31 generates a forward trajectory for the towing vehicle 2, moving forward from the parking start position. In particular, when performing reverse parking towards a parking target position such as a parking space, the trajectory has a forward section in which the vehicle moves forward while turning in a predetermined manner from the parking start position S, as shown in Figure 6, and a reverse section in which the vehicle reverses to the parking target position G after the occupants perform a reversing operation to change the direction of travel from forward to reverse. Hereinafter, the trajectory in the forward section will be referred to as the forward trajectory 41, and the trajectory in the reverse section will be referred to as the reverse trajectory 42. In this embodiment, when performing reverse parking, the forward trajectory 41 generates the trajectory of the towing vehicle 2, and the reverse trajectory 42 generates the trajectory of the trailer 3. However, it is not necessarily required to generate only the trajectory of the towing vehicle 2 for the forward trajectory 41 and only the trajectory of the trailer 3 for the reverse trajectory 42; the trajectories of both the towing vehicle 2 and the trailer 3 may be generated for both the forward trajectory 41 and the reverse trajectory 42.

[0036] Then, in S4, the CPU 31 first generates only the forward trajectory 41 of the travel trajectory from the parking start position to the parking target position. On the other hand, the reverse trajectory 42 is generated when the turning operation is performed, as will be described later (S13).

[0037] Furthermore, the forward section includes a first forward section in which the vehicle moves forward with a first direction that moves away from the parking target position from the parking start position acquired in S1 (left turn if the parking target position is to the right as viewed from the towing vehicle 2, and right turn if the parking target position is to the left), and a second forward section in which the vehicle moves forward with a second direction that is opposite to the first direction as the turning direction, after the first forward section. Hereinafter, the forward trajectory 41 in the first forward section will be referred to as the first forward trajectory 41A, and the forward trajectory 41 in the second forward section will be referred to as the second forward trajectory 41B. Note that the first forward section is a section in which the vehicle deliberately moves away from the parking target position in order to start reversing at a position away from the parking target position (to secure the turning radius when reversing), and the second forward section is a section in which the vehicle moves to adjust the hitch angle. Furthermore, a section of straight travel may be included before the first forward section, or between the first forward section and the second forward section.

[0038] The following describes in detail the process of generating the forward trajectory 41 of the towing vehicle 2 in S4. Although various patterns are possible for generating the forward trajectory 41, three patterns, A to C, will be used as examples below. In all of patterns A to C, the common point is that when the towing vehicle 2 travels along the forward trajectory 41, the generated forward trajectory 41 does not exceed the limit angle at which the hitch angle can reverse, as long as the vehicle travels along the forward trajectory. To achieve such a forward trajectory 41, the curvature ultimately maintained for the second forward trajectory 41B is deliberately set to be smaller than the maximum curvature. The maximum curvature is the maximum curvature that the towing vehicle 2 can trace, and is determined by the minimum turning radius of the towing vehicle 2.

[0039] To explain the "limit angle," as mentioned earlier, the second forward section is a section for adjusting the hitch angle. As shown in Figure 7, the hitch angle φ is adjusted so that the trailer 3 faces the parking target position G when the maneuver is performed. However, the hitch angle φ cannot be within any range as long as the trailer 3 is facing the parking target position G. In order to reverse, the hitch angle φ must be within a predetermined range (reverse-possible hitch angle range). In other words, since the trailer 3 does not have a steering device, the curvature of the reverse trajectory 42 of the trailer 3 when reversing is mainly determined by the hitch angle φ, which is the connection angle between the towing vehicle 2 and the trailer 3. However, if the hitch angle φ at the time of the maneuver is too large, the towing vehicle 2 will not be able to reverse even if it tries to. The limit angle indicates the upper limit angle of the hitch angle φ that allows for reverse movement, and it varies depending on the vehicle specifications. For example, if the limit angle is Z degrees, then if the hitch angle φ at the turning point is 0 to -Z degrees (a negative hitch angle indicates the angle at which the trailer 3 is in the direction of the parking target position (counterclockwise direction in Figure 7)), then reverse movement can begin, and it becomes possible to guide the trailer 3 to the parking target position G. Furthermore, if the second forward trajectory 41B is ultimately set to maintain the maximum curvature, it is possible to transition to the steady state described later, but in the process, the hitch angle will exceed the limit angle.

[0040] [Pattern A] First, let's explain Pattern A. As shown in Figure 8, the forward trajectory 41 generated by Pattern A is a trajectory in which the curvature is gradually increased in the first direction (where "gradually" means changing the curvature while moving forward, the same applies hereafter) until it reaches the maximum curvature, and then the maximum curvature is maintained for a predetermined period (first period). After that, the curvature is gradually decreased until it reaches curvature 0 (i.e., the neutral position), and then the state of curvature 0 is maintained for a predetermined period (second period). After that, the curvature is gradually increased in the second direction until it reaches the maximum curvature, and then the maximum curvature is maintained for a predetermined period (third period). After that, the curvature is gradually decreased to a predetermined curvature smaller than the maximum curvature, and the trajectory maintains that predetermined curvature. The first forward section is until the curvature becomes 0, and the second forward section is after the curvature changes from 0 to a negative value. A positive curvature value indicates that it is turning in the first direction, and a negative curvature value indicates that it is turning in the second direction, with the absolute value indicating the magnitude of the curvature. Furthermore, the lengths of the first to third periods described above can be changed as appropriate, and can be set, for example, by the trailer wheelbase of trailer 3 or the initial hitch angle. Also, the second period, in which the curvature remains at 0, may be excluded from the trajectory. The forward trajectory 41 generated by pattern A will basically have the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1. However, if the distance between the parking start position and the parking target position is far or too close, additional trajectories such as an initial straight or reverse trajectory may be inserted as needed. In particular, the forward track 41 generated by pattern A is a forward track 41 that reduces its curvature to a predetermined curvature smaller than the maximum curvature in the second forward section and maintains that predetermined curvature so that the hitch angle does not exceed the limit angle. The predetermined curvature that is ultimately maintained in the forward track 41 is the towable reverse curvature. Here, the towable reverse curvature is the curvature obtained by subtracting the curvature margin from the maximum curvature, and is the curvature that does not exceed the maximum curvature even when a turning maneuver is performed. The rate of change of curvature of the second forward track 41B also changes depending on the trailer size, such as the trailer wheelbase. As a result, the generated forward trajectory 41 is as shown in Figure 9. Figure 9 is a top-down view of an example of the forward trajectory 41 generated by pattern A, and also shows the change in hitch angle with respect to the distance traveled. As a comparative example, an example of a forward trajectory in which the maximum curvature is maintained without being reduced to a predetermined curvature in the second forward section is also shown. As shown in Figure 9, the forward trajectory 41 generated by pattern A is such that, as long as the vehicle travels along the forward trajectory 41, the hitch angle will not exceed the limit angle at which reverse movement is possible. As a result, a recommended turning position is set relative to the forward trajectory 41 (S9), as described later. Even if the driver's operation is delayed and the vehicle turns past the recommended turning position, the hitch angle will not exceed the limit angle at the turning position. As a result, parking assistance can be continued until parking is completed without interruption. Note that in Figures 8 and 9, the initial orientation and initial hitch angle of the towing vehicle 2 are assumed to be 0 degrees (90 degrees perpendicular to the target parking space). To explain in more detail below, the forward trajectory 41 generated by pattern A transitions to a "steady state" at a certain point (hereinafter referred to as the transition timing) before the hitch angle φ exceeds the limit angle in the second forward trajectory 41B, and thereafter maintains the steady state. The steady state is defined as the state in which the pivot center of the towing vehicle 2 and the pivot center of the trailer 3 coincide. More specifically, in order to achieve travel with the hitch angle φ fixed and the relative positional relationship between the towing vehicle 2 and the trailer 3 maintained, the hitch angle φ and the steering angle θ of the towing vehicle 2 have a specific relationship. In the steady state, the hitch angle φ remains fixed unless the steering angle θ of the towing vehicle 2 is moved while moving forward. Therefore, as shown in Figure 8, if the forward trajectory 41 of pattern A transitions to a steady state with a fixed curvature (which means the steering angle θ is also fixed), then if the limit angle is not exceeded at the time of transition to the steady state, the steady state will continue thereafter, and no matter how far the towing vehicle 2 moves according to the forward trajectory 41, the hitch angle φ will not exceed the limit angle. Figure 10 schematically shows the relationship between the towing vehicle 2 and the trailer 3 in a steady state. As shown in Figure 10, the steady state is indicated when the pivot center of the towing vehicle 2 (the intersection of lines L1 and L2 in Figure 10 is the pivot center of the towing vehicle 2) and the pivot center of the trailer 3 (the intersection of lines L2 and L3 in Figure 10 is the pivot center of the trailer 3) coincide. Therefore, if the steering angle θ is fixed after reaching the state shown in Figure 10, the hitch angle φ will remain fixed while moving forward. On the other hand, for the forward trajectory of the comparative example that ultimately maintains the maximum curvature, although it transitions to a steady state, the hitch angle exceeds the limit angle during the process, so in the steady state it becomes fixed at a hitch angle that exceeds the limit angle. Furthermore, if the vehicle changes direction from forward to reverse while in the steady state described above, there is the advantage that it is not necessary to perform a stationary steering maneuver to bring it to a steady state before starting to reverse. Therefore, in this embodiment, the recommended turning position is set after transitioning to a steady state. In the example shown in Figure 8, the recommended turning position is set at the transition timing to a steady state, but regardless of when the recommended turning position is set after transitioning to a steady state, stationary steering is basically unnecessary. However, the idea that stationary steering is completely unnecessary is theoretical, and in reality, a small amount of stationary steering may be required in some cases.

[0041] [Pattern B] Next, let's explain Pattern B. As shown in Figure 11, the forward trajectory 41 generated by Pattern B is a trajectory in which the curvature is gradually increased in the first direction until it reaches the maximum curvature, and then the maximum curvature is maintained for a predetermined period (first period). After that, the curvature is gradually decreased until it reaches curvature 0 (i.e., the neutral position), and then the state of curvature 0 is maintained for a predetermined period (second period). After that, the curvature is gradually increased in the second direction until it reaches the maximum curvature, and then the maximum curvature is maintained for a predetermined period (third period). After that, the curvature is gradually decreased until it reaches a predetermined curvature smaller than the maximum curvature, and that predetermined curvature is maintained. The first forward section is until the curvature becomes 0, and the second forward section is after the curvature changes from 0 to a negative value. A positive curvature value indicates that it is turning in the first direction, and a negative curvature value indicates that it is turning in the second direction. The absolute value indicates the magnitude of the curvature. The lengths of the first to third periods described above can be changed as appropriate, for example, by the trailer wheelbase of trailer 3 or the initial hitch angle. The second period, in which the curvature remains at zero, may be excluded from the trajectory. The forward trajectory 41 generated by pattern B will basically have the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1. However, if the distance between the parking start position and the parking target position is far or too close, additional trajectories such as an initial straight or reverse trajectory may be inserted as needed. Here, the forward trajectory 41 generated by pattern B has basically the same shape as the forward trajectory 41 generated by pattern A, and like pattern A, the forward trajectory 41 is designed so that the hitch angle does not exceed the limit angle by reducing the curvature to a predetermined curvature smaller than the maximum curvature in the second forward section and finally maintaining that predetermined curvature. However, in pattern B, the forward trajectory 41 is generated under the condition that the timing at which the curvature is reduced from the maximum curvature to reach the predetermined curvature (curvature at which traction can be reversed) in the second forward trajectory 41B is the same as the timing at which it transitions to a steady state. In other words, the forward trajectory 41 generated by pattern B is the forward trajectory 41 that can transition to a steady state the fastest among the forward trajectories 41 generated by pattern A. For this reason, in pattern B, the timing of the transition from the maximum curvature to the predetermined curvature (length of the third period) is particularly optimized. Furthermore, by setting the recommended turning point at the transition timing when the forward trajectory 41 generated by pattern B transitions to a steady state, it is possible to set the recommended turning point at the timing when the clothoid section ends and a predetermined curvature is reached, making it possible to shorten the forward trajectory 41 as much as possible. As a result, the surrounding space required when parking can also be reduced.

[0042] [Pattern C] Finally, regarding pattern C, as shown in Figure 12, the forward trajectory 41 generated by pattern C is a trajectory in which the curvature is gradually increased in the first direction until it reaches the maximum curvature, which is then maintained for a predetermined period (first period), after which the curvature is gradually decreased until it reaches curvature 0 (i.e., the neutral position), after which the state of curvature 0 is maintained for a predetermined period (second period), and after which the curvature is gradually increased in the second direction until it reaches a predetermined curvature smaller than the maximum curvature, and after which the predetermined curvature is maintained. The first forward section is until the curvature becomes 0, and the second forward section is after the curvature changes from 0 to a negative value. A positive curvature value indicates that it is turning in the first direction, and a negative curvature value indicates that it is turning in the second direction, with the absolute value indicating the magnitude of the curvature. Furthermore, the lengths of the first and third periods described above can be changed as appropriate, and can be set, for example, by the trailer wheelbase of trailer 3 or the initial hitch angle. The second period, in which the curvature remains at 0, may also be omitted from the trajectory. The forward trajectory 41 generated by pattern C will basically have the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1. However, if the distance between the parking start position and the parking target position is far or too close, additional trajectories, such as an initial straight or reverse trajectory, may be inserted as needed. In particular, the forward track 41 generated by pattern C is a forward track 41 that, in the second forward section, does not increase the curvature to the maximum curvature, but rather reaches a predetermined curvature smaller than the maximum curvature and maintains that predetermined curvature, thereby preventing the hitch angle from exceeding the limit angle. The predetermined curvature that is ultimately maintained in the forward track 41 is the towable reverse curvature. Here, the towable reverse curvature is the curvature obtained by subtracting the curvature margin from the maximum curvature, and is, for example, a curvature that does not exceed the maximum curvature even when an increasing turning operation is performed. The rate of change of curvature of the second forward track 41B also changes depending on the trailer size, such as the trailer wheelbase. As a result, the forward trajectory 41 generated by pattern C is such that, as long as the vehicle travels along the forward trajectory 41, the hitch angle does not exceed the limit angle at which reverse movement is possible, similar to pattern A shown in Figure 9. As described later, a recommended turning position is set for the forward trajectory 41, but even if the driver's operation is delayed and the vehicle turns over past the recommended turning position, the hitch angle will not exceed the limit angle at the turning position. As a result, parking assistance can be performed continuously until parking is completed without interruption. Furthermore, the forward trajectory 41 generated by pattern C, like pattern A, transitions to a "steady state" at a certain transition point before the hitch angle φ exceeds the limit angle in the second forward trajectory 41B, and maintains that steady state thereafter. However, compared to pattern A, pattern C takes longer to adjust the hitch angle because it does not transition to the maximum curvature, and the distance to transition to the steady state is longer. On the other hand, it becomes possible to reduce the amount of steering control in the second forward section. In other words, it becomes possible to transition to a steady state where the hitch angle does not exceed the limit angle with simpler control.

[0043] Furthermore, while it is possible to generate the forward trajectory 41 using any of the above patterns A to C, the occupant may choose which pattern to use to generate the forward trajectory 41, or the device may automatically select it. For example, if the occupant makes the selection, the selection is made based on the occupant's input received by the control unit 14 while the setting screen for parking assistance is displayed on the LCD display 15. On the other hand, if the device makes the selection, as mentioned above, the space required to draw the parking trajectory differs depending on the pattern. For example, when starting parking assistance, the device can use cameras and sensors installed on the vehicle to detect the space around the vehicle (the space around the towing vehicle 2 and trailer 3 that the towing vehicle 2 and trailer 3 can travel in) and select a pattern according to that space. For example, as mentioned above, pattern B can reduce the space required to draw the parking trajectory. In contrast, pattern C simplifies control but requires a wider space. Therefore, it is desirable to select pattern C if there is sufficient space around the vehicle, and pattern B if there is not enough space.

[0044] Furthermore, as shown in Figure 9, the forward trajectory 41 of the towing vehicle 2 generated in S4 is a trajectory that moves diagonally forward, with multiple clothoid curves, circular arc curves and straight lines (sometimes there are no straight lines) connected. For example, the forward trajectory 41 of pattern A is a combination of a first clothoid curve that moves from the parking start position S while gradually turning the steering wheel to the left (i.e., while gradually increasing the curvature), a first circular arc curve that moves while maintaining the maximum curvature, a second clothoid curve that moves while gradually returning the steering wheel to the straight direction (i.e., while gradually decreasing the curvature), a first straight line that moves straight after the steering wheel is in the neutral position, a third clothoid curve that moves while gradually turning to the right from the neutral position, a second circular arc curve that moves while maintaining the maximum curvature, a fourth clothoid curve that moves from the maximum curvature while gradually returning the steering wheel to the straight direction (i.e., while gradually decreasing the curvature), and a third circular arc curve that moves while maintaining a predetermined curvature after reaching a predetermined curvature. Furthermore, the forward trajectory 41 may include spline curves in addition to circular arcs, straight lines, and clothoid curves.

[0045] Subsequently, in S5, the CPU 31 predicts the changes in the travel trajectory and hitch angle of the trailer 3 as the towing vehicle 2 moves according to the forward trajectory 41 generated in S4, and acquires the predicted changes in the travel trajectory and hitch angle as the forward trajectory 43 of the trailer 3 and the changes in the hitch angle while traveling along the forward trajectory. The prediction of the changes in the travel trajectory and hitch angle of the trailer 3 is based on various information stored in the vehicle information DB 21 (for example, the distance from the rear axle of the towing vehicle 2 to the connection point between the towing vehicle 2 and the trailer 3 (position of the hitch ball 5), the trailer wheelbase, etc.) and the direction of the trailer 3 and the initial hitch angle acquired in S2.

[0046] Next, in S6, the CPU 31 sets candidate turning positions on the forward track 41 of the towing vehicle 2 generated in S4 and the forward track 43 of the trailer 3 estimated in S5, which are candidate positions where the towing vehicle 2 and trailer 3 will make a U-turn (switch from forward to reverse). Multiple candidate turning positions are set at predetermined distance intervals (for example, 1m intervals or 50cm intervals) up to the end of the forward track, as shown in Figure 13, within the range after the forward track 41 has transitioned to a steady state. The interval and number of candidate turning positions can be changed as appropriate. Alternatively, candidate turning positions may be set for the range from the start to the end of the forward track. However, even in that case, it is desirable to set the recommended turning position at a position after the transition to a steady state. As a result, it becomes possible to generate a forward track 41 that transitions to a steady state before the towing vehicle 2 reaches at least the recommended turning position.

[0047] Next, in S7, the CPU 31 calculates the reverse trajectory of the trailer 3 assuming that reverse movement begins from each of the candidate turning positions set in S6. The initial curvature of the trajectory traced by the trailer 3 at the start of reverse movement is determined by the hitch angle at the time of turning. How the curvature changes thereafter is determined by vehicle information of the trailer 3, such as the trailer wheelbase. Therefore, the calculation of the reverse trajectory in S7 is performed by obtaining the hitch angle at the candidate turning position using the estimation results from S5, and then calculating the trajectory using the obtained hitch angle and vehicle information of the trailer 3. Note that the trajectory generated in S7 is an ideal reverse trajectory when turning around at a candidate turning position and reversing, and differs from the actual reverse trajectory.

[0048] Subsequently, in S8, the CPU 31 compares the reverse trajectories calculated in S7 for each candidate turning position and selects the candidate turning position from among the multiple candidates whose endpoint of the reverse trajectory is closest to the parking target position. For example, Figure 14 shows an example of comparing the reverse trajectories 44 of trailer 3. In the example shown in Figure 14, the endpoint of the second reverse trajectory 44 from the right is closest to the parking target position G, so the candidate turning position corresponding to this reverse trajectory 44 is selected.

[0049] Next, in S9, the CPU 31 corrects the candidate turning position selected in S8 so that the end point of the reverse trajectory moves closer to the parking target position, and finally determines the corrected candidate turning position as the recommended turning position (hereinafter referred to as the recommended turning position). For example, as shown in Figure 14, when comparing the reverse trajectories 44 of the trailer 3, if the end point of the reverse trajectory 44 of the candidate turning position selected in S8 is shifted to the right relative to the parking target position G, it is possible to move the candidate turning position toward the parking start position along the forward trajectory to bring the end point of the reverse trajectory 44 closer to the parking target position G. On the other hand, if the end point of the reverse trajectory 44 of the candidate turning position selected in S8 is shifted to the left relative to the parking target position G, it is possible to move the candidate turning position toward the side away from the parking start position (forward) along the forward trajectory to bring the end point of the reverse trajectory 44 closer to the parking target position G.

[0050] Furthermore, in S5 to S9 above, the recommended turning position is determined by comparing the reverse trajectories 44 for each candidate turning position. However, as mentioned earlier, the candidate turning positions are set relative to the forward trajectory 41 after transitioning to a steady state, so regardless of which candidate turning position is used, the steering operation before starting to reverse is basically unnecessary. Also, in S4 above, as long as the vehicle travels along the forward trajectory, a forward trajectory 41 is generated in which the hitch angle does not exceed the limit angle at which reverse movement is possible. Therefore, regardless of which candidate turning position is used, the hitch angle at the time of the turning operation will not exceed the limit angle. In other words, regardless of which candidate turning position is used, it is possible to guide the trailer 3 to the parking target position G, and since the steering operation before starting to reverse is basically unnecessary, the candidate turning position closest to the parking start position S may be determined as the recommended turning position in order to shorten the parking trajectory as much as possible.

[0051] Next, in S10, the CPU 31 outputs the forward trajectory 41 of the towing vehicle 2 generated in S4 and the recommended turning position determined in S9 to other ECUs as information regarding the recommended travel trajectory for the forward section of the travel trajectory from the parking start position to the parking target position. Note that the forward trajectory 41 and the recommended turning position may be displayed on the LCD display 15 to guide the occupants before starting parking assistance, or vehicle control from S11 onwards may be started without providing guidance.

[0052] Subsequently, the CPU 31 performs parking assistance for the towing vehicle 2 by controlling each drive unit based on the forward trajectory 41 output in S10 (S11). Specifically, the CPU 31 transmits various support information related to automatic driving assistance, such as the driving trajectory, to the vehicle control ECU 24 via CAN. The vehicle control ECU 24 then performs automatic driving assistance using the received support information. Specifically, it controls the steering so that the towing vehicle 2 moves from the parking start position along the forward trajectory 41 generated in S4. In this automatic driving assistance, only the steering operation is automated, and the operation of the accelerator, brake, and shift position is performed manually. On the other hand, the installation of the above automatic driving assistance is not mandatory for the towing vehicle 2, and the towing vehicle 2 may be a vehicle that can only be driven manually. In that case, instead of the above automatic driving assistance, steering operation guidance is provided to drive along the forward trajectory 41 generated in S4.

[0053] Furthermore, while the towing vehicle 2 is performing the above-mentioned parking assistance, it is desirable to display the driving trajectory and the vehicle's current position on the LCD display 15 of the towing vehicle 2 in a way that allows the driver to confirm whether or not the parking operation is being performed according to the generated driving trajectory. In addition, an overhead view image may be generated based on the surrounding images captured by cameras installed on the towing vehicle 2 and the trailer 3, and this overhead view image may be displayed on the LCD display 15 during the transition to parking assistance mode.

[0054] Furthermore, the parking assistance also provides guidance on the recommended turning position determined in S9. For example, the LCD display 15 may display an icon indicating the recommended turning position along with the driving trajectory and the vehicle's current position. In addition, voice guidance may be output to instruct the vehicle to turn when it approaches the recommended turning position within a predetermined distance.

[0055] Subsequently, in S12, the CPU 31 determines whether a reversing operation has been performed to switch the vehicle from a forward-moving state to a reverse-moving state. Since the reversing operation must be performed manually, the CPU 31 determines that a reversing operation has been performed when the occupant stops the vehicle by operating the brakes according to the voice guidance or screen guidance and changes the shift position to "R". In the case of manual reversing operations, the actual position where the reversing operation is performed is not necessarily the same as the recommended reversing position determined in S9. However, even if the position exceeds the recommended reversing position, the hitch angle will not exceed the limit angle at which reverse movement is possible. The recommended reversing position is the ideal position for efficient reverse movement with the minimum necessary steering control, but even if the reversing operation is performed at a position other than the recommended reversing position, it is possible to generate a reverse trajectory to the parking target position by appropriately adding and modifying the steering control.

[0056] If it is determined that a reversing operation has been performed to switch the vehicle from a forward-moving state to a reverse-moving state (S12: YES), the process proceeds to S13. Conversely, if it is determined that no reversing operation has been performed (S12: NO), the process returns to S11.

[0057] In S13, the CPU 31 generates a reverse track 42 that moves the vehicle backward from the position where it actually traveled along the forward track and stopped (hereinafter referred to as the actual turning position) to the parking target position. As mentioned above, in this embodiment, the reverse track 42, which is the travel track in the reverse section, is generated for the trailer 3, not the towing vehicle 2.

[0058] Here, the initial curvature of the trajectory traced by trailer 3 at the start of reverse movement is determined by the hitch angle at the actual turning position. Furthermore, how the curvature changes thereafter is determined by vehicle information of trailer 3, such as the trailer wheelbase. Therefore, the calculation of the reverse trajectory 42 in S13 is performed by obtaining the hitch angle at the moment the turning operation is performed, and using the obtained hitch angle and vehicle information of trailer 3. The reverse trajectory 42 of trailer 3 generated in S13 is basically a combination of clothoid curves, circular arc curves, and straight lines, and even if the forward trajectory 41 is the same, the shape of the reverse trajectory 42 will change if the actual turning position changes. Spline curves may also be included.

[0059] Furthermore, in order to shorten the overall length of the parking route, it is important to increase the curvature of the trajectory traced by the trailer 3 as quickly as possible. Immediately after starting to reverse, the towing vehicle 2 may perform a reverse steering maneuver, deliberately steering in the opposite direction to the original turning direction. On the other hand, when approaching the parking target position, it is necessary to bring the hitch angle of the towing vehicle 2 and the trailer 3 closer to 0 degrees. However, in order to shorten the overall length of the parking route, it is effective to maintain a state where the curvature is as large as possible until the end, rather than gradually decreasing the curvature, and then quickly decreasing the curvature at the end. Therefore, an additional steering maneuver may be performed at the end of the turn to increase the steering in the turning direction. Accordingly, the reverse trajectory 42 in S13 may be generated as a trajectory in which the above-mentioned reverse steering maneuver or additional steering maneuver is performed.

[0060] Subsequently, the CPU 31 continues to provide parking assistance for the towing vehicle 2 by controlling each drive unit based on the reverse trajectory 42 calculated in S13 (S14). Specifically, the CPU 31 transmits various support information related to automatic driving assistance, such as the driving trajectory calculated in S13, to the vehicle control ECU 24 via CAN. The vehicle control ECU 24 then uses the received support information to provide automatic driving assistance. Specifically, it controls the steering so that the towing vehicle 2 moves to the parking target position along the reverse trajectory 42 generated in S13. If the above reverse steering or steering adjustment operation is required, it also controls the operation to perform these operations. Furthermore, if stationary steering is necessary, it performs stationary steering before starting to reverse.

[0061] Furthermore, since the reverse track 42 generated in S13 is the track of the trailer 3 and not the towing vehicle 2, in order to provide driving assistance for the towing vehicle 2 in S14, it is necessary to calculate the steering angle of the towing vehicle 2 from the travel track of the trailer 3. Therefore, the travel track of the towing vehicle 2 may be calculated first from the travel track of the trailer 3, and then the steering angle of the towing vehicle 2 may be calculated, or the steering angle of the towing vehicle 2 may be calculated directly from the travel track of the trailer 3.

[0062] Furthermore, the installation of the above-mentioned automatic driving assistance is not mandatory for the towing vehicle 2, and the towing vehicle 2 may be a vehicle that can only be driven manually. In that case, instead of the above-mentioned automatic driving assistance, guidance will be provided for steering operations, braking, acceleration, and shift position operations to drive along the reverse trajectory 42 generated in S13.

[0063] Finally, the parking assistance program (Figure 5) terminates when the vehicle is parked in the target parking position.

[0064] Furthermore, the method for generating the forward trajectory 41 described in S4 is merely one example of a method for determining the forward trajectory 41. Any method can be used to generate the forward trajectory 41, as long as it is a trajectory in which the vehicle turns in at least one direction away from the parking target position, then switches from the first direction to a second direction different from the first direction, and transitions to a steady state without the hitch angle exceeding the limit angle at which reverse movement is possible. Similarly, the method for generating the reverse trajectory 42 described in S13 is also acceptable; any method can be used to generate the reverse trajectory 42, as long as it is a trajectory that allows the vehicle to reverse from the turning position to the parking target position.

[0065] As described in detail above, according to the parking assistance device 1 and the computer program executed by the parking assistance device 1 according to this embodiment, when assisting the parking of the towing vehicle 2 and the trailer 3 to be towed by the towing vehicle 2 while the towing vehicle 2 and the trailer 3 are connected, the system acquires the parking start position and the parking target position (S1), and generates a driving trajectory for parking from the parking start position to the parking target position (S4, S13). The driving trajectory includes a forward section in which the towing vehicle 2 and trailer 3 are adjusted by moving forward along the forward trajectory from the parking start position to adjust the hitch angle, which is the connection angle between the towing vehicle 2 and the trailer 3, and a reverse section in which the vehicle reverses to the parking target position after the forward section. A recommended turning position is set in the forward trajectory 41 where it is recommended to perform a turning maneuver (S9). In generating the driving trajectory, when the towing vehicle 2 travels along the forward trajectory 41, a forward trajectory 41 is generated in which the hitch angle does not exceed the limit angle at which it is possible to reverse, even after passing the recommended turning position (S4). Therefore, even if the driver's operation is delayed and the actual turning position exceeds the preset recommended turning position, it is possible to generate a forward trajectory in which the hitch angle does not exceed the limit angle at which it is possible to reverse. As a result, even if the recommended turning position is exceeded, parking assistance can be continued until parking is completed without interruption. Furthermore, the forward trajectory 41 includes a first forward trajectory 41A which moves forward with a first direction that separates it from the parking target position as the turning direction, and a second forward trajectory 41B which moves forward after the first forward trajectory 41A with a second direction different from the first direction as the turning direction. In generating the travel trajectory, the curvature is increased in the second forward trajectory 41B until it reaches the maximum curvature, and then the curvature is reduced to a predetermined curvature smaller than the maximum curvature and maintained at that predetermined curvature, thereby generating a forward trajectory in which the hitch angle does not exceed the limit angle for reversing. By making the final curvature smaller than the maximum curvature, it is possible to generate a forward trajectory in which the hitch angle does not exceed the limit angle for reversing, even if the occupant's operation is delayed and the actual turning position exceeds the preset recommended turning position. Furthermore, the forward trajectory 41 includes a first forward trajectory 41A which moves forward with a first direction that separates it from the parking target position as the turning direction, and a second forward trajectory 41B which moves forward after the first forward trajectory 41A with a second direction different from the first direction as the turning direction. In generating the travel trajectory, the curvature is increased in the second forward trajectory 41B until it reaches a predetermined curvature smaller than the maximum curvature, and then that predetermined curvature is maintained, thereby generating a forward trajectory in which the hitch angle does not exceed the limit angle for reversing. This simplifies steering control in the second forward trajectory, and even if the occupant's operation is delayed and the actual turning position exceeds the preset recommended turning position, it is possible to generate a forward trajectory in which the hitch angle does not exceed the limit angle for reversing. Furthermore, in generating the travel trajectory, the towing vehicle 2 travels along the forward trajectory, transitioning to a steady state where the turning center of the towing vehicle 2 and the turning center of the trailer 3 coincide, and then generating a forward trajectory that maintains this steady state (S4). Therefore, if a counter-turn is performed after transitioning to the steady state, stationary steering before starting to reverse becomes unnecessary, or if it is performed, it can be done to a very small extent. Consequently, it is possible to reduce tire wear without increasing the load on the power steering.

[0066] [Note] The embodiments described above also disclose the following inventions. In the following description, the names and expressions of corresponding components in the embodiments, as well as the reference numerals used in the drawings, are indicated in parentheses for reference. However, the components of each invention are not limited to these indications.

[0067] (Invention A) In generating the aforementioned track (41), The parking assist device (1) according to claim 2, which generates the forward trajectory (41) in which a curvature reduced from the maximum curvature reaches the predetermined curvature at the recommended turning position.

[0068] This makes it possible to shorten the forward trajectory as much as possible. As a result, the surrounding space required when parking can also be reduced.

[0069] (Invention B) In generating the aforementioned track (41), Multiple candidate turning points are set on the forward trajectory (41), Assuming that the reverse movement begins from one of the candidate reversing positions set on the forward trajectory, the reverse trajectory is calculated for each of the multiple candidate positions. Parking assistance device (1) according to claim 1, wherein the calculated reverse trajectory is compared for each of the plurality of candidates, and the candidate for the turning position selected based on the comparison result is set as the recommended turning position.

[0070] This allows for the identification of the most recommended point for making a U-turn on the forward trajectory as the recommended U-turn position. As a result, by making a U-turn at the recommended U-turn position, it becomes possible to park to the parking target position along an ideal trajectory.

[0071] (Invention C) The parking assist device (1) according to claim 2 or 3, wherein the predetermined curvature is the curvature obtained by subtracting the curvature margin from the maximum curvature.

[0072] According to this, by maintaining a curvature that matches the size of the trailer being towed, it becomes possible to generate a forward trajectory in which the hitch angle does not exceed the limit angle.

[0073] It should be noted that the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention. For example, in this embodiment, patterns A to C are given as methods for generating the forward track 41, but if it is possible to generate a track in the second forward track 41B that ultimately maintains a predetermined curvature (curvature that allows traction to reverse) that is smaller than the maximum curvature, the forward track 41 may be generated by a method other than patterns A to C.

[0074] Furthermore, in this embodiment, the parking assistance processing program (Figure 5) is executed by the parking assistance ECU 23 of the parking assistance device 1, but the execution entity can be changed as appropriate. For example, the execution may be performed by the control unit of the liquid crystal display 15, the vehicle control ECU, the control unit of the navigation device, or other in-vehicle devices. [Explanation of Symbols]

[0075] 1...Parking assist device, 2...Towing vehicle, 3...Trailer, 4...Towing device, 5...Hitch ball, 6...Coupling member, 7...Coupler, 9...Rear camera, 15...LCD display, 31...CPU, 32...RAM, 33...ROM, 41...Forward track (travel track in the forward section), 41A...First forward track, 41B...Second forward track, 42...Reverse track (travel track in the reverse section), φ...Hitch angle, θ...Steering angle of the towing vehicle

Claims

1. A parking assistance device that assists in parking a towing vehicle and a trailer when the towing vehicle and the trailer to be towed by the towing vehicle are connected, The parking start position and parking target position are obtained. A driving trajectory is generated for parking from the aforementioned parking start position to the aforementioned parking target position. The aforementioned travel trajectory includes a forward section in which the vehicle moves forward from the parking start position according to the forward trajectory to adjust the hitch angle, which is the connection angle between the towing vehicle and the trailer, and a reverse section in which the vehicle moves backward to the parking target position after the forward section. A recommended turning position is set where a turning maneuver is recommended in the aforementioned forward trajectory. In generating the aforementioned track, A parking assist device that generates a forward trajectory in which, when the towing vehicle travels along the forward trajectory, the hitch angle does not exceed the limit angle at which reverse movement is possible, even after passing the recommended turning position.

2. The forward trajectory includes a first forward trajectory that moves forward with a first direction that separates it from the parking target position as the turning direction, and a second forward trajectory that moves forward after the first forward trajectory with a second direction different from the first direction as the turning direction. In generating the aforementioned track, The parking assist device according to claim 1, which generates a forward trajectory in which the hitch angle does not exceed the limit angle by increasing the curvature in the second forward trajectory until it reaches the maximum curvature, and then decreasing the curvature to a predetermined curvature smaller than the maximum curvature and maintaining that predetermined curvature.

3. The forward trajectory includes a first forward trajectory that moves forward with a first direction that separates it from the parking target position as the turning direction, and a second forward trajectory that moves forward after the first forward trajectory with a second direction different from the first direction as the turning direction. In generating the aforementioned track, The parking assist device according to claim 1, which generates a forward trajectory in which the hitch angle does not exceed the limit angle by increasing the curvature in the second forward trajectory to reach a predetermined curvature smaller than the maximum curvature and then maintaining that predetermined curvature.

4. In generating the aforementioned track, The parking assistance device according to any one of claims 1 to 3, wherein the towing vehicle travels along the forward trajectory, transitioning to a steady state in which the turning center of the towing vehicle and the turning center of the trailer coincide, and thereafter generating the forward trajectory that maintains the steady state.

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