Parking assist device

Abstract

The present invention provides a parking assist device capable of generating a forward trajectory in which a hitch angle does not exceed a critical angle at which a vehicle can retreat, even if an actual forward / backward switching position exceeds a recommended forward / backward switching position set in advance due to a delay in operation by a passenger. When parking of a tractor (2) and a trailer (3) to be towed by the tractor (2) is assisted in a state where the tractor (2) and the trailer (3) are connected, a parking start position and a parking target position are acquired, and a travel trajectory for parking from the parking start position to the parking target position is generated. The travel trajectory is configured such that, when the tractor (2) travels along the travel trajectory in the forward section, the hitch angle does not exceed a critical angle at which the tractor (2) can retreat even if the tractor (2) is at a position exceeding the recommended advance / retreat switching position.

Description

Technical Field

[0001] This invention relates to a parking assistance device for assisting in parking a vehicle. Background Technology

[0002] Previously, it was known that the driving trajectory during parking was calculated, and the vehicle was guided and controlled in a way that parking was performed according to the calculated driving trajectory, as a parking assistance method. Here, in particular, the driving trajectory when reversing is as follows: temporarily move forward to an appropriate forward / reverse switching position, which is the parking target position that is the parking space or the like, and then switch to reversing at the forward / reverse switching position and reverse back to the parking target position. However, when providing the above parking assistance to a tractor that is towing a towed vehicle (hereinafter referred to as a trailer), it is necessary to consider not only the movement of the tractor but also the movement of the trailer when setting the above driving trajectory.

[0003] For example, Japanese Patent Application Publication No. 2019-87875 discloses a technique for calculating a guide path for guiding a trailer to a parking space in a parking assist system. This method calculates the guide path of the trailer to move to the parking space in a predetermined posture by minimizing the distance from the guide reference point representing the current position of the trailer to the guide target point.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-87875 (paragraph 0042) Figure 5 )

[0005] Here, as described in Patent Document 1 above, the driving trajectory from the point of reversing to the parking space is roughly divided into: a forward range, from the start of parking to the point of switching from forward to reverse to the forward / reverse switching position; and a reverse range, from the forward / reverse switching position to the parking space. Moreover, when providing parking assistance based on the generated driving trajectory, it is also known that there is a type of parking assistance that only automatically performs steering operations, while the accelerator and brake operations are not performed automatically but are performed manually.

[0006] In parking assist systems where accelerator and brake operations are performed manually, the actual forward / reverse switching position may exceed the pre-set position on the device due to the passenger's operational delay. Figure 15 This is an example of a driving trajectory (hereinafter referred to as the forward trajectory) generated during previous parking assistance operations, and a diagram showing the changes in the connection angle (attachment angle) and curvature between the tractor and trailer as they travel along this forward trajectory. Figure 15As shown, the forward trajectory includes: a first forward trajectory, which moves in a first direction away from the target parking position as the turning direction; and a second forward trajectory, which moves in a second direction different from the first direction as the turning direction in order to adjust the engagement angle after the first forward trajectory. Previously, when the forward / reverse switching position was preset, the forward / reverse switching position was set at the target engagement angle on the second forward trajectory. However, if the passenger delays stopping the vehicle, the absolute value of the engagement angle exceeds the target value as the vehicle moves forward. As a result, the engagement angle is too large at the moment of forward / reverse switching, resulting in a situation where reversing is impossible. Summary of the Invention

[0007] The present invention was made to solve the aforementioned problems and aims to provide a parking assist device that can generate a forward trajectory in which the engagement angle does not exceed the critical angle for reversing, even if the actual forward / reverse switching position exceeds the preset forward / reverse switching position due to the passenger's operation delay.

[0008] To achieve the above objectives, the parking assist device of the present invention assists in parking a tractor and a trailer connected to it. It acquires a parking start position and a parking target position. A driving trajectory for parking from the parking start position to the parking target position is generated. The driving trajectory includes: a forward section, where the tractor and trailer move forward along the forward trajectory from the parking start position to adjust the connection angle, i.e., the engagement angle, between the tractor and the trailer; and a reverse section, where the tractor reverses to the parking target position after the forward section. A recommended forward / reverse switching position is set within the forward trajectory. In generating the driving trajectory, the forward trajectory is generated such that, even when the tractor travels along the forward trajectory beyond the recommended forward / reverse switching position, the engagement angle does not exceed a critical angle for reversing.

[0009] In addition, regarding the generation of driving trajectories, the "driving trajectory of the forward section" and the "driving trajectory of the backward section" do not necessarily need to be generated at the same time. Alternatively, the "driving trajectory of the forward section" can be generated first, and after driving in the forward section, the "driving trajectory of the backward section" can be generated to drive in the backward section.

[0010] Additionally, "forward / reverse switching operation" refers to, for example, switching the vehicle from a forward-moving state to a reverse-moving state. Furthermore, the operation of switching the vehicle from a forward-moving state to a reverse-moving state can be manual (operated by the passenger) or automatic.

[0011] According to the parking assist device of the present invention having the described structure, even if the actual forward / backward switching position exceeds the preset recommended forward / backward switching position due to the passenger's operational delay, a forward trajectory with an engagement angle not exceeding the critical angle for reversing can still be generated. As a result, even if the recommended forward / backward switching position is exceeded, parking assist can continue without interruption until parking is completed. Attached Figure Description

[0012] Figure 1 This is a diagram showing the tractor and trailer of this embodiment.

[0013] Figure 2 It is an enlarged view showing the area near the tractor unit of the tractor.

[0014] Figure 3 This diagram illustrates the movement of the tractor and trailer when the trailer ball and coupling are connected.

[0015] Figure 4 This is a block diagram showing the structure of the parking assist device according to this embodiment.

[0016] Figure 5 This is a flowchart of the parking assistance processing procedure in this embodiment.

[0017] Figure 6 It is a diagram showing the overall driving trajectory from the starting position of parking to the target position of parking.

[0018] Figure 7 This diagram illustrates the critical angle of the mounting angle.

[0019] Figure 8 This is a diagram illustrating mode A, which describes the method for generating the driving trajectory within the forward range from the starting position of parking to the target position of parking.

[0020] Figure 9 It is a diagram showing the shift in the driving trajectory and engagement angle of the generated forward section.

[0021] Figure 10 This diagram illustrates the steady state.

[0022] Figure 11 This is a diagram of pattern B illustrating the method for generating the driving trajectory within the forward range from the starting position of parking to the target position of parking.

[0023] Figure 12 This is a diagram illustrating mode C, which describes the method for generating the driving trajectory within the forward range from the starting position of parking to the target position of parking.

[0024] Figure 13This is a diagram representing the candidate positions for switching between forward and backward.

[0025] Figure 14 This diagram illustrates the method for determining the forward / backward switching position from the candidate forward / backward switching positions.

[0026] Figure 15 This diagram illustrates the problems with previous technologies.

[0027] Explanation of reference numerals in the attached figures

[0028] 1: Parking assist device; 2: Tractor; 3: Trailer; 4: Towing device; 5: Trailer ball; 6: Connecting component; 7: Coupling; 9: Rear camera; 15: LCD display; 31: CPU; 32: RAM; 33: ROM; 41: Forward trajectory (trajectory within the forward range); 41A: First forward trajectory; 41B: Second forward trajectory; 42: Reverse trajectory (trajectory within the reverse range). θ: engagement angle; θ: steering angle of the tractor unit Detailed Implementation

[0029] [Explanation of tractor units and trailers]

[0030] Hereinafter, a specific embodiment of the parking assist device of the present invention will be described in detail with reference to the accompanying drawings. First, the tractor 2 equipped with the parking assist device 1 of this embodiment and the towed vehicle 3 towed by the tractor 2 (hereinafter referred to as the trailer) will be described. Figure 1 This is a diagram showing tractor 2 and trailer 3.

[0031] Here, the tractor unit 2 is also referred to as a tractor, configured to tow the trailer 3. The tractor unit 2 can be, for example, a vehicle powered by an internal combustion engine (such as an engine) (internal combustion engine vehicle), a vehicle powered by an electric motor (such as a motor) (electric vehicle, fuel cell vehicle, etc.), or a vehicle powered by both of the above (hybrid vehicle). Furthermore, the vehicle type is not limited, as long as it has the towing device 4 described later; it can be a regular car or a large commercial tractor unit (tractor unit).

[0032] In addition, such as Figure 1 As shown, a towing device 4 (hook) for towing a trailer 3 is protrudingly disposed on the lower part of the center of the rear bumper of the tractor 2, for example in the vehicle width direction. Figure 2 This is a specially enlarged view showing the area near the traction device 4.

[0033] like Figure 2As shown, the towing device 4 is fixed to, for example, the frame of the tractor 2. As an example, the towing device 4 has a trailer ball 5 vertically arranged in the vertical direction (vehicle vertical direction) with a spherical top. The trailer ball 5 and the connector 7 are connected by covering the trailer ball 5 with a connector 7 provided at the top of the connecting member 6 fixed to the trailer 3, thereby connecting the tractor 2 and the trailer 3. However, the shape of the trailer ball 5 and the connector 7 is not limited to... Figure 2 The shape shown can be any shape that can connect the tractor 2 and the trailer 3.

[0034] Furthermore, with the trailer ball 5 and the coupling 7 connected, in conjunction with the movement of the tractor 2, the trailer ball 5 transmits its forward, backward, left, and right movements to the trailer 3 (connecting member 6). Additionally, as... Figure 3 As shown, even when the connector 7 is connected to the trailer ball 5, the angle of the connector 7 relative to the trailer ball 5 can change freely (but with an upper limit), and the trailer 3 can swing (turn) relative to the tractor 2 in the vehicle width direction.

[0035] On the other hand, such as Figure 1 As shown, a rear camera (shooting device) 9 is installed on the wall of the rear compartment of the tractor 2. The rear camera 9 is, for example, a digital camera with built-in CCD, CIS, or other imaging elements. The rear camera 9 is capable of outputting video data (captured image data) at a specified frame rate. The rear camera 9 has a wide-angle lens or a fisheye lens, and its optical axis is set to face obliquely downwards, enabling it to capture images in a horizontal range of, for example, 140° to 220°.

[0036] Furthermore, the area within the field of view of the rear camera 9 includes at least the towing device 4 and the trailer ball 5 located at the rear end of the tractor 2. The image data captured by the rear camera 9 can be used for, for example, to detect the connection status of the tractor 2 and the trailer 3 (e.g., connection angle (hook-off angle), presence or absence of connection, etc.). However, as a unit for detecting the connection status of the tractor 2 and the trailer 3, a sensor provided on the towing device 4 may be used instead of the rear camera 9.

[0037] On the other hand, the trailer 3, also known as the towed vehicle, is towed by the aforementioned tractor 2. Therefore, it is essentially different from the tractor 2, lacking an engine or motor as a drive source. Furthermore, it lacks a steering device (steering system) for changing the direction of the wheels. Examples include camping trailers with internal living space, and light trailers used for loading and transporting vehicles or boats. The trailer 3 has a main body, a plurality of (two in this embodiment) trailer wheels, a connecting member 6, and a coupling 7.

[0038] Here, as Figure 1 As shown, the connecting member 6 is located at the lower part of the center of the main body of the trailer 3 in the vehicle width direction, and is arranged to protrude forward (in the direction of travel) from the front end of the main body.

[0039] In addition, such as Figure 2 As shown, the connector 7 is located at the front end of the connecting member 6 and has a spherical recess that covers the trailer ball 5. Furthermore, by covering the trailer ball 5 with the connector 7, as described above, the trailer 3 and the tractor 2 can be steerably connected (see reference). Figure 3 Furthermore, the length of the connecting member 6 and its height above the ground (i.e., the position of the coupling 7 of the trailer 3) vary depending on the type of trailer 3. However, in this embodiment, the coupling 7 is located at least in a position where it can be connected to the trailer ball 5 of the tractor 2.

[0040] [Description of Parking Assist Device]

[0041] Next, the parking assist device 1 of the tractor unit 2 will be described. The parking assist device 1 is a device used to assist the driver in operating the vehicle when parking in a designated parking space while the tractor unit 2 is connected to the trailer 3. Figure 4 This is a block diagram showing the structure of the parking assist device 1 in this embodiment.

[0042] like Figure 4 As shown, the parking assist device 1 of this embodiment includes: a vehicle information DB21, which records various data related to the tractor 2 and the trailer 3; and a parking assist ECU23, which performs various calculations based on the input information. Furthermore, the parking assist device 1 is connected via a vehicle network such as CAN to an operation unit 14 that receives operations from the tractor 2's occupants, a liquid crystal display 15 that displays to the tractor 2's occupants the driving trajectory for parking in the parking space or other parking assist-related information, and a speaker 16 that outputs voice guidance related to parking assist. Furthermore, the parking assist device 1 is also connected to various sensors such as a rear-view camera 9 installed on the tractor 2, a vehicle control ECU24 that performs various controls on the tractor 2, a vehicle speed sensor 25, a steering sensor 26, and a shift position sensor 27.

[0043] The control unit 14 is located on the instrument panel or steering wheel of the tractor unit 2. It is operated, for example, when switching to the parking assist mode (described later) or inputting various parameters related to the tractor unit 2 and the trailer 3. It has multiple operation switches (not shown) such as various buttons and switches. Furthermore, the parking assist ECU 23 controls the execution of various actions based on the switch signals output by pressing each switch. Additionally, the control unit 14 may also have a touch panel located in front of the LCD display 15. Furthermore, it may also include a microphone and a voice recognition device.

[0044] The LCD display 15 is installed on the instrument panel of the tractor unit 2. When switching to parking assist mode while the tractor unit 2 is connected to the trailer 3, it displays an overhead view of the vehicle's surroundings, an image captured by the rear camera 9, and the driving trajectory for parking. Additionally, when parking is not performed automatically but by the user, it displays operation instructions for the steering mechanism, brake, accelerator, and gear shift positions for driving along the trajectory. Furthermore, the parking assist device 1 of this embodiment is designed for manual operation of the brake, accelerator, and gear shift positions. The LCD display 15 provides guidance for positions where it is recommended to switch from forward to reverse in the direction of travel. Furthermore, the LCD display 15 can also be used as a display in a navigation device.

[0045] Furthermore, based on instructions from the parking assist ECU 23, speaker 16 also outputs voice guidance for parking operations when switching parking assist modes. Additionally, speaker 16 provides guidance at locations where it is recommended to perform forward / reverse switching operations in the aforementioned direction of travel. Moreover, speaker 16 can also be used as a speaker in a navigation system.

[0046] Additionally, the vehicle information DB21 is a storage unit that stores various information related to the tractor 2 and the trailer 3. For example, regarding the tractor 2, it stores the installation position of the trailer ball 5 (height from the ground, left and right position, distance from the rear of the vehicle), total length, width, wheelbase, minimum turning radius, etc. It also stores the distance from the rear axle of the tractor 2 to the connection point between the tractor 2 and the trailer 3 (the position of the trailer ball 5). On the other hand, regarding the trailer 3, it stores the installation position of the coupling 7 (height from the ground, left and right position, distance from the top of the vehicle), total length, width, minimum turning radius, etc. It also stores the distance from the reference point of the trailer 3 to the connection point between the tractor 2 and the trailer 3 (the position of the trailer ball 5) (equivalent to the trailer wheelbase). Furthermore, the reference point of the trailer 3 is also the rotation center of the trailer 3; when the trailer 3 has one axle (two wheels), the axle center is the reference point. On the other hand, when the trailer 3 has two or more axles (four or more wheels), there is a reference point between the foremost and rearmost axles (the position of which varies according to load distribution). The wheelbase of the trailer is one of the parameters indicating the size of the trailer 3. This information can be pre-input by passengers or vehicle manufacturer personnel using the operation unit 14, or it can be automatically input by values ​​detected by the rear camera 9 and various sensors. Furthermore, since the towing trailer 3 is not necessarily fixed, if the trailer 3 being towed changes, the above parameters also need to be changed. The storage medium for the vehicle information DB21 can be, for example, a memory card. Alternatively, it can be stored in the storage area (e.g., RAM or flash memory) within the parking assist ECU 23.

[0047] On the other hand, the parking assist ECU (electronic control unit) 23 is an electronic control unit that performs overall control of the parking assist device 1, and has: a CPU 31 as a computing and control unit; and an internal storage device, such as RAM 32 used as working memory when the CPU 31 performs various calculations and storing trajectory data when the driving trajectory is calculated, and in addition to the control program, it also has a parking assist processing program recorded (see below). Figure 5 The ROM 33 contains a program, and the flash memory 34 stores the program read from the ROM 33. Furthermore, the parking assist ECU 23 performs various functions as processing algorithms. These include functions such as acquiring the parking start position and parking target position, generating a driving trajectory for parking from the parking start position to the parking target position, and setting recommended forward / backward switching positions within the forward trajectory.

[0048] Furthermore, the vehicle control ECU 24 is an electronic control unit that controls the tractor unit 2. The vehicle control ECU 24 is connected to various drive units of the vehicle, such as the steering system, brakes, accelerator, and transmission. In this embodiment, for example, when switching to the parking assist mode (described later), automatic driving assistance for the tractor unit 2 can be implemented by controlling each drive unit. Specifically, when the parking assist mode is executed, the parking assist ECU 23 sends various assistance information related to automatic driving assistance generated by the parking assist device 1 to the vehicle control ECU 24 via CAN. The vehicle control ECU 24 uses the received assistance information to implement automatic driving assistance after driving begins. Examples of assistance information include: a recommended driving trajectory for the tractor unit 2 and the trailer 3, information indicating vehicle speed and steering angle when driving along the trajectory, etc. In addition, in the automatic driving assistance of this embodiment, basically only the steering system is operated automatically, while the accelerator, brakes, and transmission are controlled manually. On the other hand, the aforementioned automatic driving assistance is not mandatory for the tractor unit 2; the tractor unit 2 can also be a vehicle that can only be manually driven, including the operation of the steering system. In this case, when switching to parking assist mode, the operation guidance of the steering device, brake, accelerator, and gear shift positions for driving along the recommended driving trajectory is performed instead of the aforementioned automatic driving assistance.

[0049] In addition, the vehicle speed sensor 25 is composed of active wheel speed sensors installed on the wheels of the tractor 2, which detect the rotational speed of the wheels and output a speed signal. Furthermore, the steering sensor 26 is installed inside the steering system, which detects the steering angle when the steering wheel is turned and outputs a steering angle signal. Moreover, the shift position sensor 27 is built into the shift lever, which detects which of the following shift positions is being held: "P (Park)," "N (Neutral)," "R (Reverse)," "D (Drive)," "2 (2nd gear)," or "L (Low)."

[0050] The parking assist ECU23 can obtain the current speed, driving distance, steering angle, gear shift position, etc. of the tractor 2 based on the output signals from the various sensors mentioned above.

[0051] [Instructions for Parking Assist Procedures]

[0052] Next, based on Figure 5 The parking assist processing procedure executed by the parking assist ECU 23 in the parking assist device 1 having the above structure will be described. Figure 5This is a flowchart of the parking assistance processing procedure of this embodiment. Here, the parking assistance processing procedure is executed after the ACC power supply (accessory power supply) of the tractor 2 is turned on and the driver operation unit 14 of the tractor 2 selects to switch to parking assistance mode. It is a procedure that assists the driver in parking operations when the tractor 2 is connected to the trailer 3. Furthermore, in the following... Figure 5 The program shown in the flowchart is stored in RAM32 and ROM33 of the parking assist ECU23 and is executed by CPU31.

[0053] First, in step (hereinafter referred to as S) 1, the CPU 31 acquires the parking start position and the parking target position. Basically, the current position of the tractor 2 and trailer 3 is used as the parking start position. However, if it is difficult to park from the current position to the parking target position, a different position can be set as the parking start position, and guidance can be provided up to the parking start position. Regarding the parking target position, for example, the desired parking position can be specified from an image of the tractor 2's surroundings displayed on the LCD 15, and the specified position can be used as the parking target position. Alternatively, a camera or sensor can detect the parking space around the tractor 2, and the detected parking space can be used as the parking target position. Furthermore, in the following description, it is assumed that there are no obstacles around the vehicle that would impede its movement.

[0054] Next, in S2, CPU 31 acquires the positions of the tractor 2 and trailer 3 at the parking start position, as well as the connection angle (attachment angle) between the tractor 2 and trailer 3. The connection angle acquired in S2 at the parking start position (i.e., the moment parking assistance begins) is also specifically referred to as the "initial attachment angle." As described above, the current positions of the tractor 2 and trailer 3 are essentially taken as the parking start position; therefore, the current positions of the tractor 2 and trailer 3 and the connection angle are acquired in S2. Furthermore, the initial attachment angle can be determined, for example, from an image captured by the rear camera 9.

[0055] Next, in S3, CPU31 retrieves information related to the tractor 2 and trailer 3 from the vehicle information DB21. Furthermore, the vehicle information DB21 stores various information related to the tractor 2 and trailer 3, particularly regarding the trailer 3, at least the distance from the reference point of the trailer 3 to the connection point between the tractor 2 and trailer 3 (the position of the trailer ball 5) (hereinafter referred to as the trailer wheelbase) is retrieved. In addition, for example, in S3 above, regarding the tractor 2, the distance from the rear axle of the tractor 2 to the connection point between the tractor 2 and trailer 3 (the position of the trailer ball 5) (hereinafter referred to as the connection distance) or the minimum turning radius of the tractor 2 (corresponding to the maximum curvature of the driving trajectory) is retrieved, etc. Furthermore, the processing order of S2 and S3 can also be reversed.

[0056] Next, in S4, CPU31 generates a forward trajectory for tractor 2, starting from the parking position. Here, as... Figure 6 As shown, the driving trajectory when reversing into a parking target position, such as a parking space, has two parts: a forward section, where the vehicle turns and moves forward in a prescribed manner from the parking start position S; and a reverse section, where the vehicle moves backward to the parking target position G after the passenger performs a forward / reverse switching operation in the direction of travel. Hereinafter, the driving trajectory of the forward section will be referred to as the forward trajectory 41, and the driving trajectory of the reverse section will be referred to as the reverse trajectory 42. Furthermore, regarding the driving trajectory when reversing into parking in the parking assist device 1 of this embodiment, the driving trajectory of the tractor 2 is generated for the forward trajectory 41, and the driving trajectory of the trailer 3 is generated for the reverse trajectory 42. However, it is not necessary to generate only the driving trajectory of the tractor 2 for the forward trajectory 41 and only the driving trajectory of the trailer 3 for the reverse trajectory 42; it is also possible to generate the driving trajectories of both the tractor 2 and the trailer 3 for both the forward trajectory 41 and the reverse trajectory 42.

[0057] Then, in S4 above, CPU31 first generates only the forward trajectory 41 within the driving trajectory from the parking start position to the parking target position. On the other hand, the reverse trajectory 42 is generated at the moment when the forward / reverse switching operation is performed, as described later (S13).

[0058] Furthermore, the forward travel interval also includes: a first forward travel interval, which starts from the parking start position obtained in S1 above and travels in a first direction away from the parking target position (if the parking target position is on the right when viewed from the tractor 2, it is a left turn; if the parking target position is on the left, it is a right turn); and a second forward travel interval, which follows the first forward travel interval and travels in a second direction opposite to the first direction. Hereinafter, the forward travel trajectory 41 of the first forward travel interval will be referred to as the first forward travel trajectory 41A, and the forward travel trajectory 41 of the second forward travel interval will be referred to as the second forward travel trajectory 41B. In addition, the first forward travel interval is a travel interval deliberately set away from the parking target position in order to start reversing from a position away from the parking target position (to ensure the turning radius when reversing), and the second forward travel interval is a travel interval for adjusting the engagement angle. In addition, a straight travel interval may also be included before the first forward travel interval or between the first forward travel interval and the second forward travel interval.

[0059] The following is a detailed explanation of the process for generating the forward trajectory 41 of the tractor 2 in S4 described above. Various modes are considered as methods for generating the forward trajectory 41; modes A to C will be used as examples in the following explanation. Furthermore, in any of modes A to C, a common feature is that, when the tractor 2 travels along the forward trajectory 41, a forward trajectory 41 is generated such that the engagement angle will not exceed the critical angle for reversing as long as the tractor 2 travels along the forward trajectory. To form such a forward trajectory 41, for the second forward trajectory 41B, the curvature ultimately maintained is intentionally set to be less than the curvature smaller than the maximum curvature. Furthermore, the maximum curvature refers to the maximum curvature that the tractor 2 can depict, which is determined by the minimum turning radius of the tractor 2.

[0060] Here, when explaining the "critical angle," as mentioned above, the second forward range is the range used for adjusting the engagement angle, such as... Figure 7 As shown, when switching between forward and reverse, the engagement angle is adjusted so that the trailer 3 is oriented toward the parking target position G. Proceed with the driving. However, if the trailer 3 is moving towards the parking target position G, the engagement angle will be... It's not possible at any angle; for backward movement, the hook angle needs to be adjusted. It needs to be within the specified range (the range of reversible engagement angle). That is, since the trailer 3 does not have a steering device, the curvature of the reversing trajectory 42 of the trailer 3 when reversing is mainly based on the connection angle between the tractor 2 and the trailer 3, i.e., the engagement angle. To determine, but if the hook angle is at the moment of forward / backward switching. If the angle is too large, even if the tractor unit 2 wants to reverse, it will be unable to do so. The critical angle represents the engagement angle at which reversing is possible. The upper limit angle varies depending on the vehicle specifications. For example, if the critical angle is set to Z degrees, the engagement angle at the forward / reverse switching position is... The angle is 0 to -Z degrees (a negative engagement angle indicates that the trailer 3 is in the direction of the parking target position). Figure 7 If the angle is counterclockwise, it can begin to reverse and eventually guide the trailer 3 to the parking target position G. Furthermore, if the second forward trajectory 41B is used as the trajectory that ultimately maintains maximum curvature, although it can switch to the stable state described later, the engagement angle will exceed the critical angle during this process.

[0061] [Pattern A]

[0062] First, when describing pattern A, as follows: Figure 8 As shown, the forward trajectory 41 generated by mode A is as follows: Gradually increase the curvature in the first direction (it should be noted that "gradually" means changing the curvature during forward movement, the same below), maintain the maximum curvature for a specified period (the first period) after reaching the maximum curvature, then gradually decrease the curvature until it reaches 0 (i.e., the neutral position), maintain the curvature at 0 for a specified period (the second period), then gradually increase the curvature in the second direction, maintain the maximum curvature for a specified period (the third period), then gradually decrease the curvature until it reaches a specified curvature less than the maximum curvature, and maintain this specified curvature. Furthermore, the first forward movement interval is before the curvature decreases to 0, and the second forward movement interval is after the curvature changes from 0 to a negative value. Additionally, a positive curvature indicates a turn in the first direction, and a negative curvature indicates a turn in the second direction; the absolute value represents the magnitude of the curvature.

[0063] Furthermore, the lengths of the first to third periods can be appropriately changed, for example, by setting the trailer wheelbase of the trailer 3 and the initial engagement angle. Alternatively, the driving trajectory can also exclude the second period, which maintains a curvature of 0. Moreover, the forward trajectory 41 generated by mode A is essentially set to the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1. However, when the distance between the parking start position and the parking target position is too far or too close, for example, a trajectory that first proceeds straight or backwards may be inserted as needed.

[0064] Specifically, the forward trajectory 41 generated by mode A is as follows: by reducing the curvature to a predetermined curvature less than the maximum curvature in the second forward interval and maintaining this predetermined curvature, the engagement angle does not exceed the critical angle. The predetermined curvature maintained in the forward trajectory 41 is called the towing back curvature. Here, the towing back curvature refers to the curvature after subtracting the curvature margin from the maximum curvature, for example, the curvature that does not exceed the maximum curvature even with a large turn. The rate of change of curvature of the second forward trajectory 41B also varies depending on the trailer dimensions such as the trailer wheelbase.

[0065] As a result, the generated forward trajectory 41 is as follows: Figure 9 As shown. Furthermore, Figure 9 This diagram shows an example of the forward trajectory 41 generated by Mode A from above, and also illustrates the shift of the engagement angle relative to the travel distance. Additionally, as a comparative example, an example of a forward trajectory that maintains maximum curvature directly without decreasing to a predetermined curvature in the second forward interval is shown.

[0066] like Figure 9 As shown, the forward trajectory 41 generated by mode A becomes such that as long as the vehicle travels along the forward trajectory 41, the engagement angle will not exceed the critical angle for reversing. As a result, as described later, although a recommended forward / reverse switching position (S9) is set for the forward trajectory 41, even if the passenger's operation is delayed and the forward / reverse switching occurs beyond the recommended position, the engagement angle at the forward / reverse switching position will not exceed the critical angle. Consequently, parking assistance can continue without interruption until parking is complete. Furthermore, in Figure 8 and Figure 9 In this context, it is assumed that the initial orientation and initial engagement angle of the tractor 2 are 0 degrees (90 degrees perpendicular to the parking space, which serves as the parking target).

[0067] The following describes in more detail how the forward trajectory 41 generated by pattern A, in the second forward trajectory 41B, originates from the hook-up angle. At a certain point before exceeding the critical angle (hereinafter referred to as the switching point), the system switches to a "stable state," and from then on, it becomes the trajectory that maintains this stable state. Furthermore, the stable state refers to the state in which the steering center of the tractor 2 and the steering center of the trailer 3 are aligned. More specifically, it refers to the state in order to maintain a stable angle... The vehicle travels while fixed in place and maintaining the relative positional relationship between the tractor 2 and the trailer 3, with the engagement angle... The steering angle θ of the tractor 2 is in a specific relationship. Under stable conditions, as long as the steering angle θ of the tractor 2 does not change during forward movement, the engagement angle... It is in a fixed state. Therefore, as Figure 8As shown, if the forward trajectory 41 of mode A, where the curvature is fixed (fixed curvature means the steering angle θ is also fixed), switches to a stable state, then as long as the critical angle is not exceeded at the moment of switching to the stable state, the stable state will continue to exist thereafter, and the engagement angle will remain constant regardless of how far the tractor 2 moves along the forward trajectory 41. None of them will exceed the critical angle. Furthermore, Figure 10 This is a schematic diagram illustrating the relationship between the tractor unit 2 and the trailer unit 3 in a stable state. (See diagram for example.) Figure 10 As shown, the steering center of tractor 2 ( Figure 10 The intersection of straight lines L1 and L2 becomes the turning center of tractor 2 and the turning center of trailer 3. Figure 10 The intersection of straight lines L2 and L3 (which becomes the turning center of trailer 3) indicates a stable state. Therefore, if it becomes... Figure 10 After the state is fixed, the steering angle θ is then engaged. The trajectory remains fixed during subsequent forward movement. On the other hand, regarding the trajectory of the comparative example that ultimately maintains maximum curvature, although it switches to a stable state, the engagement angle exceeds the critical angle during this process. Therefore, in the stable state, the engagement angle will be fixed at the state exceeding the critical angle.

[0068] Furthermore, in the aforementioned stable state, switching the direction of travel from forward to backward has the advantage of not requiring a stationary turning operation to achieve stability before starting to move backward. Therefore, in this embodiment, a recommended forward / backward switching position is set after switching to the stable state. Figure 8 In the example shown, the recommended forward / backward switching position is set at the moment of switching to a stable state. However, as long as the recommended forward / backward switching position is set at any time after switching to a stable state, there is basically no need for in-place turning operations. However, it is theoretically possible to completely eliminate the need for in-place turning operations; in practice, a small number of in-place turning operations are sometimes required.

[0069] [Pattern B]

[0070] Next, we will explain pattern B, as follows: Figure 11As shown, the forward trajectory 41 generated by mode B is as follows: The curvature gradually increases in the first direction, reaches its maximum curvature, and is maintained at the maximum curvature for a specified period (the first period). Then, the curvature gradually decreases until it reaches 0 (i.e., a neutral position), and is maintained at 0 for a specified period (the second period). Then, the curvature gradually increases in the second direction, reaches its maximum curvature, and is maintained at the maximum curvature for a specified period (the third period). Then, the curvature gradually decreases until it reaches a specified curvature less than the maximum curvature, and is maintained at this specified curvature. Furthermore, the first forward interval is before the curvature reaches 0, and the second forward interval is after the curvature changes from 0 to a negative value. Additionally, a positive curvature indicates a turn in the first direction, and a negative curvature indicates a turn in the second direction; the absolute value represents the magnitude of the curvature.

[0071] Furthermore, the lengths of the first to third periods can be appropriately varied, for example, by setting the trailer wheelbase of the trailer 3 and the initial engagement angle. Alternatively, the driving trajectory can also exclude the second period, which maintains a curvature of 0. Moreover, the forward trajectory 41 generated by mode B is essentially set to the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1. However, when the distance between the parking start position and the parking target position is too far or too close, for example, a trajectory that first proceeds straight or backwards may be inserted as needed.

[0072] Here, the forward trajectory 41 generated by Mode B is as follows: it has essentially the same shape as the forward trajectory 41 generated by Mode A, and like Mode A, it reduces the curvature to a predetermined curvature less than the maximum curvature in the second forward interval, ultimately maintaining this predetermined curvature so that the engagement angle does not exceed the critical angle. However, in Mode B, the generation condition for the forward trajectory 41 is that in the second forward trajectory 41B, the timing of reducing the curvature from the maximum curvature to the predetermined curvature (the curvature that can be pulled back) is the same as the timing of switching to the stable state. That is, the forward trajectory 41 generated by Mode B can be said to be the forward trajectory 41 that can switch to the stable state earliest among the forward trajectories 41 generated by Mode A. Therefore, in Mode B, the timing of switching from the maximum curvature to the predetermined curvature (the length of the third period) is specifically optimized.

[0073] Furthermore, in the forward trajectory 41 generated by Mode B, if the recommended forward / backward switching position is set at the moment of switching to a stable state, the recommended forward / backward switching position can be set at the moment when the turning section ends and the specified curvature is reached, thereby shortening the forward trajectory 41 as much as possible. As a result, the surrounding space required when parking can be reduced.

[0074] [Mode C]

[0075] Finally, let's explain pattern C, as follows: Figure 12 As shown, the forward trajectory 41 generated by pattern C is as follows: The curvature gradually increases in the first direction, reaches its maximum curvature, and is maintained at the maximum curvature for a specified period (the first period). Then, the curvature gradually decreases until it reaches 0 (i.e., a neutral position), and is maintained at 0 for a specified period (the second period). Then, the curvature gradually increases in the second direction until it reaches a specified curvature less than the maximum curvature, and is maintained at that specified curvature. Furthermore, the first forward range is before the curvature reaches 0, and the second forward range is after the curvature changes from 0 to a negative value. Additionally, a positive curvature indicates a turn in the first direction, and a negative curvature indicates a turn in the second direction; the absolute value represents the magnitude of the curvature.

[0076] Furthermore, the lengths of the first and third periods can be appropriately changed, for example, by setting the trailer wheelbase of the trailer 3 and the initial engagement angle. Alternatively, the travel trajectory can also be a second period without maintaining a curvature of 0. Moreover, the forward trajectory 41 generated by mode C is essentially set to the same shape regardless of the positional relationship between the parking start position and the parking target position obtained in S1 above. However, when the distance between the parking start position and the parking target position is too far or too close, for example, a trajectory that first travels straight or backwards may be inserted as needed.

[0077] Specifically, the forward trajectory 41 generated by mode C is as follows: by not increasing the curvature to the maximum curvature in the second forward interval, but maintaining the specified curvature at the moment when it reaches a curvature less than the maximum curvature, the engagement angle does not exceed the critical angle. The specified curvature ultimately maintained in the forward trajectory 41 is the towing back curvature. Here, the towing back curvature refers to the curvature after subtracting the curvature margin from the maximum curvature, for example, the curvature that does not exceed the maximum curvature even when making a large turn. The rate of change of curvature of the second forward trajectory 41B also varies according to the trailer dimensions such as the trailer wheelbase.

[0078] As a result, the forward trajectory 41 generated by pattern C becomes the following forward trajectory 41: [and] Figure 9 Similarly, in Mode A shown below, as long as the vehicle travels along the forward trajectory 41, the engagement angle will not exceed the critical angle for reversing. As shown later, although a recommended forward / reverse switching position is set for the forward trajectory 41, even if the passenger's operation is delayed and the forward / reverse switching occurs after the recommended position, the engagement angle at the forward / reverse switching position will not exceed the critical angle. As a result, parking assistance can continue without interruption until parking is completed.

[0079] Furthermore, regarding the forward trajectory 41 generated by pattern C, similarly to pattern A, in the second forward trajectory 41B, from the hook angle... At a certain switching point before exceeding the critical angle, the system switches to a "stable state," and from then on, it maintains a stable trajectory. However, compared to Mode A, Mode C does not switch to maximum curvature, so adjusting the engagement angle takes time, and the distance to switch to the stable state is longer. On the other hand, it can suppress the control amount of the steering device in the second forward range. That is, with simpler control, it is possible to switch to a stable state where the engagement angle does not exceed the critical angle.

[0080] Furthermore, although any of the modes A through C can generate the forward trajectory 41, the mode used to generate the forward trajectory 41 can be selected by the passenger or automatically by the device. For example, if the passenger selects the mode, the selection is made based on the passenger's operation received in the operation unit 14 while the LCD 15 displays a setting screen related to parking assist. On the other hand, if the device selects the mode, as described above, the space required to draw the parking trajectory varies depending on the mode. Therefore, for example, when parking assist is activated, the space around the vehicle (the space around the tractor 2 and trailer 3 where the tractor 2 and trailer 3 can travel) is detected using cameras and sensors installed in the vehicle, and the mode can be selected based on this space. For example, as described above, mode B can reduce the space required to draw the parking trajectory. In contrast, mode C simplifies control but requires more space. Therefore, it is preferable to select mode C if there is sufficient space around the vehicle, and to select mode B if there is insufficient space.

[0081] In addition, such as Figure 9 As shown, the forward trajectory 41 of the tractor 2 generated in S4 above is a trajectory that moves diagonally forward, composed of multiple spiral curves, arc curves, and straight lines (including non-straight lines). For example, taking the forward trajectory 41 of mode A as an example, it is composed of the following combination: starting from the parking start position S, a first spiral curve that gradually turns the steering device to the left (i.e., the curvature gradually increases) and moves forward; then a first arc curve that maintains the maximum curvature and moves forward; a second spiral curve that gradually returns the steering device to the straight direction (i.e., the curvature gradually decreases) and moves forward; a first straight line that moves forward straight after the steering device returns to the neutral position; a third spiral curve that gradually turns to the right from the neutral position and moves forward; then a second arc curve that maintains the maximum curvature and moves forward; a fourth spiral curve that gradually returns the steering device to the straight direction (i.e., the curvature gradually decreases) and moves forward from the maximum curvature; and a third arc curve that maintains the specified curvature and moves forward after reaching the specified curvature. In addition to circular arcs, straight lines, and spiral curves, the forward trajectory 41 may also include spline curves.

[0082] Then, in S5, CPU31 predicts the shift of the travel trajectory and engagement angle of the trailer 3 as the tractor 2 moves along the forward trajectory 41 generated in S4 above, and obtains the predicted travel trajectory and engagement angle shift as the forward trajectory 43 of the trailer 3 and the shift of the engagement angle during the forward trajectory. In addition, the prediction of the travel trajectory and engagement angle shift of the trailer 3 is based on various information stored in vehicle information DB21 (such as the distance from the rear axle of the tractor 2 to the connection point (position of the trailer ball 5) of the tractor 2 and the wheelbase of the trailer, etc.) and the orientation and initial engagement angle of the trailer 3 obtained in S2 above.

[0083] Next, in S6, CPU31 sets candidate forward / backward switching positions on the forward trajectory 41 of the tractor 2 generated in S4 and the forward trajectory 43 of the trailer 3 estimated in S5, as candidate positions for the tractor 2 and trailer 3 to switch from forward to backward (from forward to backward). Furthermore, within a range after the stable state of switching to the forward trajectory 41, such as... Figure 13 As shown, multiple candidate forward / backward switching positions are set at predetermined distance intervals (e.g., 1m or 50cm intervals) until the end of the forward trajectory. Furthermore, the interval and number of candidate forward / backward switching positions can be appropriately varied. Alternatively, candidate forward / backward switching positions can be set for a range from the start to the end of the forward trajectory. However, even in this case, it is preferable to set the recommended forward / backward switching position at a position after switching to a stable state. As a result, a forward trajectory 41 can be generated that switches to a stable state at least before the tractor 2 reaches the recommended forward / backward switching position.

[0084] Next, in S7, CPU 31 calculates the reversing trajectory of the trailer 3 assuming it starts reversing from each candidate forward / backward switching position set in S6. Furthermore, at the start of reversing, the initial curvature of the trajectory traced by the trailer 3 is determined by the engagement angle at the moment of forward / backward switching. How the curvature changes thereafter is determined by vehicle information of the trailer 3, such as the trailer wheelbase. Therefore, the calculation of the reversing trajectory in S7 specifically uses the estimation result from S5 to obtain the engagement angle at the candidate forward / backward switching position, and uses the obtained engagement angle and vehicle information of the trailer 3 to calculate the trajectory. Furthermore, the reversing trajectory generated in S7 is an ideal reversing trajectory when forward / backward switching and reversing at the candidate forward / backward switching position, which differs from the actual reversing trajectory.

[0085] Then, in S8, CPU31 compares the reversing trajectory calculated in S7 with each candidate forward / reversing switching position, and selects the candidate forward / reversing switching position from the plurality of candidate forward / reversing switching positions whose endpoint of the reversing trajectory is closest to the parking target position. For example Figure 14This example compares the reverse trajectory of trailer 3 as shown in Figure 44. Figure 14 In the example shown, the endpoint of the second reverse trajectory 44 from the right is closest to the parking target position G, so the candidate for the forward / reverse switching position corresponding to this reverse trajectory 44 is selected.

[0086] Next, in S9, CPU31 corrects the direction of the candidate forward / backward switching position selected in S8 towards the end of the reverse trajectory, which approaches the parking target position. Finally, it determines the corrected candidate forward / backward switching position as the recommended forward / backward switching position (hereinafter referred to as the recommended forward / backward switching position). For example, as... Figure 14 As shown, when comparing the reversing trajectory 44 of the trailer 3, if the endpoint of the reversing trajectory 44 selected in S8 is offset to the right relative to the parking target position G, the endpoint of the reversing trajectory 44 can be brought closer to the parking target position G by moving the candidate for reversing position along the forward trajectory toward the parking start position. On the other hand, if the endpoint of the reversing trajectory 44 selected in S8 is offset to the left relative to the parking target position G, the endpoint of the reversing trajectory 44 can be brought closer to the parking target position G by moving the candidate for reversing position along the forward trajectory toward the side away from the parking start position (forward).

[0087] Furthermore, in S5 to S9 above, the recommended forward / backward switching position is determined by comparing the backward trajectory 44 of each candidate forward / backward switching position. However, as mentioned above, the candidate forward / backward switching position is set on the forward trajectory 41 after switching to a stable state. Therefore, regardless of which candidate forward / backward switching position is used, there is essentially no need for a stationary turning operation before reversing. Additionally, in S4 above, a forward trajectory 41 is generated where the engagement angle will not exceed the critical angle for reversing as long as the vehicle travels along the forward trajectory. Therefore, regardless of which candidate forward / backward switching position is used, the engagement angle at the time of the forward / backward switching operation will not exceed the critical angle. In other words, regardless of which candidate forward / backward switching position is used, the trailer 3 can be guided to the parking target position G. Furthermore, there is essentially no need for a stationary turning operation before reversing. Therefore, to minimize the parking trajectory, the candidate forward / backward switching position closest to the parking start position S can be determined as the recommended forward / backward switching position.

[0088] Next, in S10, CPU31 outputs information related to the recommended driving trajectory of the tractor 2 generated in S4 and the recommended forward / backward switching position determined in S9, as information related to the recommended driving trajectory within the forward range from the parking start position to the parking target position, to other ECUs. Furthermore, the forward trajectory 41 and the recommended forward / backward switching position can be displayed on the LCD 15 before starting parking assistance to guide the occupants, or vehicle control can begin after S11 without guidance.

[0089] Subsequently, CPU 31 controls each drive unit based on the forward trajectory 41 output in S10, thereby implementing parking assistance for the tractor 2 (S11). Specifically, CPU 31 sends various assistance information related to autonomous driving assistance, such as driving trajectory, to vehicle control ECU 24 via CAN. Vehicle control ECU 24 then uses the received assistance information to implement autonomous driving assistance. Specifically, the steering device is controlled so that the tractor 2 moves from the parking start position along the forward trajectory 41 generated in S4. Furthermore, in this autonomous driving assistance, only the steering device is operated automatically, while the accelerator, brake, and gear shift positions are operated manually. On the other hand, the implementation of this autonomous driving assistance is not mandatory for the tractor 2, and the tractor 2 can also be a vehicle that can only be driven manually. In this case, guidance for steering device operation along the forward trajectory 41 generated in S4 is provided instead of the aforementioned autonomous driving assistance.

[0090] Furthermore, during the aforementioned parking assistance operation in the tractor unit 2, in order to allow the driver to confirm whether the parking operation can be performed according to the generated driving trajectory, it is preferable to display a status on the LCD screen 15 of the tractor unit 2 that allows comparison of the driving trajectory and the vehicle's current position. Alternatively, based on images of the surroundings captured by cameras installed on the tractor unit 2 and the trailer 3, a top-down view can be generated and displayed on the LCD screen 15 during the switching to parking assistance mode.

[0091] Furthermore, the parking assist described above also provides guidance for the recommended forward / backward switching position determined in S9. For example, the driving trajectory and the vehicle's current position can be displayed on the LCD 15, along with an icon indicating the recommended forward / backward switching position. Moreover, when the vehicle approaches within a specified distance of the recommended forward / backward switching position, voice guidance instructing the vehicle to perform the forward / backward switching can be output.

[0092] Then, in S12, CPU31 determines whether a forward / reverse switching operation has been performed to switch the vehicle from a forward-moving state to a reverse-moving state. Furthermore, since the forward / reverse switching operation needs to be performed manually, CPU31 determines that the operation was performed when, following the aforementioned voice or visual guidance, the passenger operated the brakes to stop the vehicle and changed the gear position to "R". Moreover, in the case of a manual forward / reverse switching operation, the actual position where the operation was performed is not limited to the recommended forward / reverse switching position determined in S9. However, even if the recommended position is exceeded, the engagement angle will not exceed the critical angle for reversing. The recommended position is the ideal position for reversing without waste under the necessary minimum steering control; however, even assuming the operation was performed outside the recommended position, a reversing trajectory to the parking target position can be generated by appropriately adjusting the steering control.

[0093] Then, if it is determined that a forward / backward switching operation has been performed to switch the vehicle from a forward-moving state to a backward-moving state (S12: Yes), proceed to S13. Conversely, if it is determined that no forward / backward switching operation has been performed (S12: No), return to S11.

[0094] In S13, CPU 31 generates a reversing trajectory 42, which is the trajectory from the position where the vehicle actually travels and stops on the travel trajectory of the forward section (hereinafter referred to as the actual forward / reverse switching position) to the parking target position. As described above, in this embodiment, the travel trajectory 42, which is the travel trajectory of the reversing section, is generated for the trailer 3 instead of the tractor 2.

[0095] Here, at the start of the reversing operation, the initial curvature of the trajectory drawn by the trailer 3 is determined by the engagement angle at the actual forward / reverse switching position. Furthermore, how the curvature changes thereafter is determined by vehicle information of the trailer 3, such as the trailer wheelbase. Therefore, the calculation of the reversing trajectory 42 in S13 specifically involves obtaining the engagement angle at the current moment when the forward / reverse switching operation has been performed, and using the obtained engagement angle and vehicle information of the trailer 3. The reversing trajectory 42 of the trailer 3 generated in S13 is essentially a combination of spiral curves, circular arcs, and straight lines. Even if the forward trajectory 41 is the same, the shape of the reversing trajectory 42 changes if the actual forward / reverse switching position changes. Additionally, it may also include spline curves.

[0096] Furthermore, to shorten the total length of the path required for parking, the focus is on maximizing the curvature of the driving trajectory depicted by the trailer 3 as quickly as possible. After reversing begins, the tractor 2 can immediately perform a reverse turn in the opposite direction of the original turn. On the other hand, when approaching the parking target position, the engagement angle between the tractor 2 and the trailer 3 needs to be close to 0 degrees. However, to shorten the total length of the parking path, instead of gradually decreasing the curvature, the curvature is maintained at a high level until the end, and a rapid decrease in curvature at the end is effective. Therefore, a large turn in the turning direction can be performed at the end of the turn. Thus, regarding the reversing trajectory 42 of S13, a driving trajectory including the aforementioned reverse turn and large turn can also be generated.

[0097] Subsequently, CPU 31 controls each drive unit based on the reverse trajectory 42 calculated in S13 to continue implementing parking assistance for the tractor 2 (S14). Specifically, CPU 31 sends various assistance information related to autonomous driving assistance, such as the driving trajectory calculated in S13, to vehicle control ECU 24 via CAN. Then, vehicle control ECU 24 uses the received assistance information to implement autonomous driving assistance. Specifically, the steering device is controlled so that the tractor 2 moves to the parking target position along the reverse trajectory 42 generated in S13. Control for performing these actions is also implemented when performing reverse steering or sharp steering. In addition, when a stationary steering is required, a stationary steering operation is performed before reversing begins.

[0098] Furthermore, the reverse trajectory 42 generated in S13 above is not the trajectory of the tractor 2 but the trajectory of the trailer 3. Therefore, in order to provide driving assistance for the tractor 2 in S14 above, it is necessary to calculate the steering angle of the tractor 2 based on the trajectory of the trailer 3. Thus, the trajectory of the tractor 2 can be calculated first based on the trajectory of the trailer 3, and then the steering angle of the tractor 2 can be calculated. Alternatively, the steering angle of the tractor 2 can be calculated directly from the trajectory of the trailer 3.

[0099] Furthermore, it is not necessary for the tractor unit 2 to be equipped with the aforementioned automatic driving assistance; the tractor unit 2 can also be a vehicle that can only be driven manually. In this case, the aforementioned automatic driving assistance is replaced by operation guidance for the steering device, brake, accelerator, and gear shift positions for driving along the reverse trajectory 42 generated in S13.

[0100] Finally, the above parking assistance procedure ends when parking at the target location is completed. Figure 5 ).

[0101] Furthermore, the method for generating the forward trajectory 41 described in S4 above is one example of the method for determining the forward trajectory 41. As long as the forward driving trajectory involves turning at least in a first direction away from the parking target position, then switching from the first direction to a second direction different from the first direction, and switching to a stable state with the engagement angle not exceeding the critical angle for reversing, the forward trajectory 41 can be generated by any method. Similarly, the method for generating the reverse trajectory 42 described in S13 is the same; as long as a trajectory capable of reversing from the forward / reverse switching position to the parking target position can be generated, the reverse trajectory 42 can be generated by any method.

[0102] As detailed above, according to the parking assist device 1 of this embodiment and the computer program executed by the parking assist device 1, when assisting the parking of the tractor 2 and the trailer 3 (which is towed by the tractor 2) in a connected state, the parking start position and the parking target position are obtained (S1), and a driving trajectory for parking from the parking start position to the parking target position is generated (S4, S13). The driving trajectory includes: a forward section, in which the connection angle, i.e., the engagement angle, of the tractor 2 and the trailer 3 is adjusted by moving forward along the forward trajectory from the parking start position; and a reverse section, in which the vehicle reverses to the parking target position after the forward section. A recommended forward / reverse switching position for performing the forward / reverse switching operation is set in the forward trajectory 41 (S9). In generating the driving trajectory, the forward trajectory 41 is generated such that when the tractor 2 travels along the forward trajectory 41, even if the position exceeds the recommended forward / reverse switching position, the engagement angle does not exceed the critical angle for reversing (S4). Therefore, even if the actual forward / backward switching position exceeds the preset recommended forward / backward switching position due to the passenger's operational delay, a forward trajectory can still be generated with an engagement angle not exceeding the critical angle for reversing. As a result, even if the recommended forward / backward switching position is exceeded, parking assistance can continue without interruption until parking is completed.

[0103] Furthermore, the forward trajectory 41 includes a first forward trajectory 41A that moves in a first direction away from the parking target position as the turning direction, and a second forward trajectory 41B that moves in a second direction different from the first direction after the first forward trajectory 41A as the turning direction. In the generation of the driving trajectory, the following forward trajectory is generated: after increasing the curvature in the second forward trajectory 41B to reach the maximum curvature, the curvature is reduced to a predetermined curvature less than the maximum curvature and maintained at the predetermined curvature, so that the engagement angle does not exceed the critical angle (S4). Therefore, by forming a forward trajectory that makes the final curvature less than the maximum curvature, even if the actual forward / backward switching position exceeds the preset recommended forward / backward switching position due to the passenger's operation delay, a forward trajectory with an engagement angle not exceeding the critical angle of reversibility can be generated.

[0104] Furthermore, the forward trajectory 41 includes a first forward trajectory 41A that moves in a first direction away from the parking target position as the turning direction, and a second forward trajectory 41B that moves in a second direction different from the first direction after the first forward trajectory 41A as the turning direction. In the generation of the driving trajectory, the following forward trajectory is generated: after increasing the curvature in the second forward trajectory 41B to reach a predetermined curvature less than the maximum curvature, the predetermined curvature is maintained, so that the engagement angle does not exceed the critical angle (S4). Therefore, based on the simplified steering device control of the second forward trajectory, even if the actual forward / backward switching position exceeds the preset recommended forward / backward switching position due to the passenger's operation delay, it is possible to generate a forward trajectory with an engagement angle not exceeding the critical angle for reversing.

[0105] Furthermore, in generating the driving trajectory, the following forward trajectory is generated: the tractor 2 travels along the forward trajectory, thereby switching to a stable state where the steering center of the tractor 2 and the steering center of the trailer 3 are aligned, and then maintaining this stable state (S4). Therefore, if the forward / reverse switching is performed after switching to the stable state, no stationary steering operation is required before starting to reverse, or if it is required, it is minimal. Thus, tire wear can be suppressed without increasing the burden on the power steering device.

[0106] [Postscript]

[0107] The following inventions are disclosed in the above embodiments. In the following description, reference numerals used in the drawings are enclosed in parentheses for reference to the names and representations of the corresponding structures in the embodiments. However, the structural components of each invention are not limited to these annotations.

[0108] (Invention A) The parking assist device (1) according to technical solution 2, wherein, In generating the driving trajectory (41), the following forward trajectory (41) is generated: The curvature after decreasing from the maximum curvature reaches the specified curvature at the recommended forward / backward switching position.

[0109] This allows for the shortest possible travel distance. Consequently, it reduces the amount of surrounding space required when parking.

[0110] (Invention B) According to the parking assist device (1) of technical solution 1, wherein, In the generation of the driving trajectory (41), A plurality of candidate forward / backward switching positions are set on the forward trajectory (41). For each of the plurality of candidates for forward / backward switching positions, calculate the backward trajectory assuming a backward movement begins from the candidate for the forward / backward switching position set on the forward trajectory. For each of the plurality of candidate forward / backward switching positions, the calculated backward trajectory is compared, and the candidate forward / backward switching position selected based on the comparison result is set as the recommended forward / backward switching position.

[0111] Therefore, the most recommended point for switching between forward and reverse directions on the forward trajectory can be determined as the recommended forward / reverse switching position. As a result, by switching between forward and reverse directions at the recommended switching position, the vehicle can be parked along an ideal trajectory until the target parking position is reached.

[0112] (Invention C) The parking assist device (1) according to technical solution 2 or 3, wherein, The specified curvature is the curvature obtained by subtracting the curvature margin from the maximum curvature.

[0113] Thus, by maintaining the curvature that matches the size of the trailer being towed, a forward trajectory is generated with an engagement angle not exceeding a critical angle.

[0114] Furthermore, the present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit of the present invention.

[0115] For example, in this embodiment, modes A to C can be used as methods for generating the forward trajectory 41. However, in the second forward trajectory 41B, as long as a trajectory that ultimately maintains a specified curvature (which can pull backward curvature) less than the maximum curvature is generated, the forward trajectory 41 can also be generated using methods other than modes A to C.

[0116] Furthermore, in this embodiment, the parking assist processing program executed by the parking assist ECU 23 configured as the parking assist device 1 ( Figure 5 The processing can be performed by the control unit of the LCD 15, the vehicle control ECU, the control unit of the navigation device, or other in-vehicle devices.

Claims

1. A parking assist device, wherein, With the tractor and the trailer connected, the parking assistance is provided for both the tractor and the trailer. Obtain the starting position and the target position of parking. Generate a driving trajectory for parking from the starting parking position to the target parking position. The driving trajectory includes: a forward section, which moves forward from the parking starting position according to the forward trajectory, thereby adjusting the connection angle, i.e., the coupling angle, between the tractor and the trailer; and a reverse section, which reverses to the parking target position after the forward section. In the forward trajectory, a recommended forward / backward switching position is set for the recommended forward / backward switching operation. In generating the driving trajectory, the following forward trajectory is generated: When the tractor is traveling along the forward trajectory, even if it exceeds the recommended forward / backward switching position, the engagement angle does not exceed the critical angle for reversing.

2. The parking assist device according to claim 1, wherein, The forward trajectory includes: a first forward trajectory, which moves in a first direction away from the parking target position as the turning direction; and a second forward trajectory, which follows the first forward trajectory and moves in a second direction different from the first direction as the turning direction. In generating the driving trajectory, the following forward trajectory is generated: After reaching the maximum curvature by increasing the curvature in the second forward trajectory, the curvature is reduced to a predetermined curvature less than the maximum curvature and maintained at that predetermined curvature, so that the hook angle does not exceed the critical angle.

3. The parking assist device according to claim 1, wherein, The forward trajectory includes: a first forward trajectory, which moves in a first direction away from the parking target position as the turning direction; and a second forward trajectory, which follows the first forward trajectory and moves in a second direction different from the first direction as the turning direction. In generating the driving trajectory, the following forward trajectory is generated: After increasing the curvature in the second forward trajectory to reach a predetermined curvature less than the maximum curvature, the predetermined curvature is maintained, so that the hook angle does not exceed the critical angle.

4. The parking assist device according to any one of claims 1 to 3, wherein, In generating the driving trajectory, the following forward trajectory is generated: The tractor travels along the forward trajectory, switching to a stable state where the steering center of the tractor and the steering center of the trailer are aligned, and then maintaining this stable state.

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