Parking path generation method and device and computer program product

Abstract

The invention relates to a parking path generation method and device and a computer program product, and the method comprises the steps: receiving an initial parking path which comprises at least two paths; acquiring the curvature and the curvature change rate of the starting point or the ending point of each section of path; determining the length of the clothoid corresponding to each section of path according to a preset clothoid end point curvature and the curvature and curvature change rate of the starting point or the end point of each section of path; constructing the clothoid corresponding to each section of path according to the length of the clothoid corresponding to each section of path; and generating a new parking path according to the clothoid corresponding to each section of path and the at least two sections of paths. According to the method and the device, the technical problem that the vehicle has a pivot steering phenomenon when the curvature at the turning point of the parking path obtained according to a geometric method or based on a search method is not zero can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of automatic parking, and in particular to a parking path generation method, device and computer program product. Background Art

[0002] Parking path generation methods are mainly divided into geometric methods and search-based methods. The geometric method mainly relies on parking space information and obstacle information, calculates the arc according to the minimum turning radius of the vehicle, and generates a parking path that avoids obstacles by adding arcs and straight lines; the search-based method calculates a local optimal path for a vehicle by obtaining the parking space and drivable area data identified by the environmental perception link in real time. The calculation methods include hybrid A-star algorithm, RRT algorithm, etc. After the initial parking path is obtained by the geometric method and search method, the initial parking path is smoothed by smoothing methods such as optimization, and the smoothed parking path is given to the control link in the form of trajectory points. The control link uses the smoothed parking path as a reference, and completes the tracking of trajectory points on the parking path through the horizontal and vertical control algorithms to park the vehicle in the parking space.

[0003] However, the curvature of the parking path obtained by the geometric method or the search method is not zero at the turning point of the path. After the parking path is given to the control link in the form of trajectory points, the vehicle may turn on the spot. In order to solve this problem, it is proposed to use clothoid curves to splice and replace part of the original parking path, but this method has problems such as the need to calculate the offset and poor versatility. Moreover, the length of the clothoid curve is generally calculated based on the maximum vehicle speed and the time required for the steering wheel to go from 0 to the maximum angle, or the curve length is set according to empirical values, without considering the curvature of the original trajectory, which will cause a sudden change in curvature and is not conducive to the control link tracking the trajectory points. Summary of the invention

[0004] The purpose of the present application is to propose a parking path generation method and device, and a computer program product, so as to solve the technical problem that when the curvature of a parking path obtained according to a geometric method or a search method is not zero at a turning point of the path, the vehicle turns on the spot.

[0005] To achieve the above objective, according to a first aspect of the present application, a parking path generation method is provided, the method comprising:

[0006] Receiving an initial parking path, wherein the initial parking path includes at least two paths;

[0007] Get the curvature and curvature change rate of the starting point or end point of each path segment;

[0008] Determine the length of the clothoid curve corresponding to each path segment according to the preset curvature of the end point of the clothoid curve and the curvature and curvature change rate of the starting point or the end point of each path segment;

[0009] Constructing a clothoid curve corresponding to each path segment according to the length of the clothoid curve corresponding to each path segment;

[0010] A new parking path is generated according to the clothoid curve corresponding to each path segment and the at least two paths.

[0011] According to a second aspect of the present application, a parking path generation device is provided, the device comprising a module for executing the method described in the first aspect of the present application.

[0012] According to a third aspect of the present application, a parking path generation device is provided, comprising:

[0013] A communication interface, used to communicate with other electronic devices;

[0014] a memory for storing computer program instructions;

[0015] A processor is used to execute the computer program instructions to support the implementation of the method according to the first aspect of the present application according to the parking path generation device.

[0016] According to a fourth aspect of the present application, a computer program product is provided, comprising computer program instructions, wherein the computer program instructions instruct a computer device to perform operations corresponding to the method according to the first aspect of the present application.

[0017] The present application proposes a parking path generation method and device, and a computer program product. The initial parking path is smoothed by introducing a clothoid curve so that the curvature of the end of the final parking path is zero, thereby solving the problem of vehicle turning on the spot. The length of the clothoid curve corresponding to each path segment is determined by the preset curvature of the end of the clothoid curve and the curvature and curvature change rate of the starting point or end point of each path segment. This method can avoid sudden changes in the curvature of the connected clothoid curve and the curvature of the end of the original path, thereby ensuring the curvature continuity of the parking path at the turning point. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a flowchart of a parking path generation method in an embodiment of the present application.

[0020] Figure 2 Schematic diagram of the coordinate system of the clothoid curve in the embodiment of the present application.

[0021] Figure 3Schematic diagram of the splicing of clothoid curves in the embodiment of the present application. DETAILED DESCRIPTION

[0022] The detailed description of the drawings is intended as an illustration of the current embodiment of the present application, and is not intended to represent the only form in which the present application can be implemented. It should be understood that the same or equivalent functions can be accomplished by different embodiments intended to be included in the spirit and scope of the present application.

[0023] See also Figure 1 An embodiment of the present application provides a parking path generation method, the method comprising the following steps:

[0024] Step S10: receiving an initial parking path, wherein the initial parking path includes at least two paths.

[0025] Specifically, during automatic parking, multiple adjustments are often required to park the vehicle into a parking space. In this case, the initial parking path will include at least two paths, and there will be a turning point between the two adjacent paths. For example, if the vehicle needs to be parked in a parking space, the initial parking path may include the first path (turning to avoid obstacles) and the second path (entering a new parking space).

[0026] Step S20, obtaining the curvature and curvature change rate of the starting point or end point of each path segment.

[0027] Specifically, in the above example, the turning point of the two adjacent path segments is the end point of the first path segment and the starting point of the second path segment. Although they are the same point, the curvature and the curvature change rate of the end point of the first path segment and the starting point of the second path segment are different. The curvature and the curvature change rate of the end point of the first path segment should be calculated and determined based on the first path segment, and the curvature and the curvature change rate of the starting point of the second path segment should be calculated and determined based on the second path segment. In other words, a sudden change in curvature will occur at the turning point. If it is not handled, the vehicle will turn on the spot.

[0028] Step S30, determining the length of the clothoid curve corresponding to each path segment according to the preset curvature of the end point of the clothoid curve and the curvature and curvature change rate of the starting point or the end point of each path segment.

[0029] Specifically, in this embodiment, the preset end curvature of the clothoid curve is 0; in the above example, it is necessary to determine the length of the clothoid curve corresponding to the first path segment according to the end curvature of the clothoid curve, the curvature of the end point of the first path segment and the curvature change rate; and determine the length of the clothoid curve corresponding to the second path segment according to the end curvature of the clothoid curve, the curvature of the starting point of the second path segment and the curvature change rate;

[0030] The length of the clothoid curve is calculated as follows:

[0031]

[0032] Where s is the length of the clothoid curve, s_k is the curvature of the end or starting point of the path, e_k is the curvature of the end point of the clothoid curve, and d_k is the rate of change of the curvature of the end or starting point of the path;

[0033] Specifically, the length of the clothoid curve corresponding to each path segment is determined by the preset curvature of the end point of the clothoid curve and the curvature and curvature change rate of the starting point or end point of each path segment. This method can avoid a sudden change in the curvature of the connected clothoid curve and the curvature at the end of the original path, ensure the curvature continuity of the parking path at the turning point, reduce the impact on the vehicle steering system, avoid severe friction between the tires and the ground, and improve the safety and comfort of parking.

[0034] Step S40: constructing a clothoid curve corresponding to each path segment according to the length of the clothoid curve corresponding to each path segment.

[0035] Specifically, a clothoid curve is usually described by a specific mathematical equation. Common types of clothoid curves include Clothoid and Cornu (Euler-Spiral) curves, both of which can provide continuously changing curvatures and are suitable for vehicle path planning. These mathematical equations contain some parameters, such as initial curvature, terminal curvature, curve length, etc. Therefore, based on the known length of the clothoid curve and the curvatures of the starting and end points, these parameters can be solved to obtain the mathematical equation of the clothoid curve.

[0036] Step S50, generating a new parking path according to the clothoid curve corresponding to each path segment and the at least two paths;

[0037] Specifically, after obtaining the clothoid curve corresponding to each path segment, the clothoid curve can be used to smooth the at least two path segments to obtain an optimized new parking path, which can enable the vehicle to achieve smooth and safe steering during parking, while improving parking efficiency and accuracy.

[0038] In some specific embodiments, the step S40 further includes:

[0039] Step S401, obtaining the curvature change rate of the clothoid curve corresponding to each path segment according to the curvature of the starting point or the end point of each path segment, the curvature of the end point of the clothoid curve and the length of the clothoid curve corresponding to each path segment.

[0040] Specifically, the curvature change rate of the clothoid curve is a constant, and its curvature changes linearly with the arc length, which is mathematically defined as:

[0041]

[0042] Among them: k is the curvature, dk is the change in curvature, which can be calculated based on the curvature of the starting point and end point of the clothoid curve. In the above example, the starting point of the clothoid curve corresponding to the first path segment is the end point of the first path segment, and the starting point of the clothoid curve corresponding to the second path segment is the starting point of the second path segment. s is the length of the clothoid curve calculated in step S30, ds is the change in length of the clothoid curve, in fact ds=s, c is the curvature change rate, which is a constant.

[0043] Step S402 , constructing a clothoid curve corresponding to each path segment according to the length and curvature change rate corresponding to each path segment.

[0044] Specifically, for the clothoid curve of each path segment, its length, curvature change rate, starting curvature and end curvature are already known. This information provides sufficient parameters to define the shape of the clothoid curve, so the clothoid curve corresponding to each path segment can be constructed. It should be noted that with the given length, curvature change rate, starting curvature and end curvature as constraints, there may be multiple clothoid curves that meet the constraints, each curve has its own unique shape and transition effect, and which curve to choose depends on the specific application requirements and performance goals. For example, in this embodiment, the constraints can be further added, that is, the clothoid curves corresponding to the two adjacent path segments are as close as possible, so that it is easy to smoothly enter the second path segment from the first path segment.

[0045] In some specific embodiments, determining the length of the clothoid curve corresponding to each path segment according to the preset end point curvature of the clothoid curve and the curvature and curvature change rate of the starting point or end point of each path segment further includes:

[0046] Based on the standard coordinate system, the coordinates and tangent angles of each point on the clothoid curve corresponding to each path segment are obtained according to the length and curvature change rate of the clothoid curve corresponding to each path segment, and the clothoid curve corresponding to each path segment in the standard coordinate system is generated according to the coordinates and tangent angles of each point;

[0047] A coordinate transformation matrix is ​​obtained according to the tangent angle of each point on the clothoid curve corresponding to each path segment, and the clothoid curve corresponding to each path segment in the standard coordinate system is transformed to the non-standard coordinate system according to the coordinate transformation matrix to obtain the clothoid curve corresponding to each path segment in the non-standard coordinate system.

[0048] Specifically, the standard coordinate system indicates that the origin of the rectangular coordinate system is established at a place with a curvature of 0, that is, x0=0, y0=0, s0=0, k0=0, and this is an infinite series. Under the premise of satisfying the above assumptions, the coordinates and tangent angles of any point on the clothoid curve corresponding to each path in the standard coordinate system are obtained according to the following method:

[0049]

[0050]

[0051] Among them, x j is the horizontal coordinate of point j on the clothoid curve, y j is the ordinate of point j on the clothoid curve, s j is the length of the clothoid curve from the starting point to point j, α j is the tangent angle of point j on the clothoid curve, the standard coordinate system is a rectangular coordinate system with a curvature of 0 at the origin, N is a preset value, i∈0~N, and ! is the factorial operation symbol.

[0052] In application, it is impossible to start from the place where the curvature is 0 every time. For example, when connecting two arc curves, the curvature is from one non-zero curvature to another non-zero curvature. At this time, the calculation method of the standard coordinate system is limited. If the origin of the rectangular coordinate system is not established at the place where the curvature is zero (referred to as the non-standard coordinate system), the mathematical processing is very complicated. Therefore, this embodiment first calculates the coordinates and tangent angles of each point of the clothoid curve based on the standard coordinate system, and then converts the calculation results to the non-standard coordinate system. Figure 2 shown.

[0053] In some specific embodiments, obtaining a coordinate transformation matrix according to the tangent angle of each point on the clothoid curve corresponding to each path segment further includes:

[0054] For any point on the clothoid curve corresponding to each path in the standard coordinate system, substitute the tangent angle of the arbitrary point into the following matrix equation A coordinate transformation matrix corresponding to the arbitrary point is obtained, and the coordinates of the arbitrary point in the standard coordinate system are transformed into the non-standard coordinate system according to the coordinate transformation matrix to obtain the coordinates of the arbitrary point in the non-standard coordinate system.

[0055] Specifically, for any point j on the clothoid curve, according to the relationship between the curvature of the clothoid curve and the arc length Calculate the heading angle α of point j in the standard coordinate system XOY j , you can get the coordinate transformation matrix of the non-standard coordinate system xoy and the standard coordinate system XOY corresponding to point j:

[0056]

[0057] Then the transformation relationship between the two coordinate systems about the coordinates of point j is:

[0058]

[0059] Among them, X0 and Y0 are the coordinates of the origin o of the non-standard coordinate system xoy in the XOY coordinate system, X j and Y j is the coordinate of point j in the non-standard coordinate system xoy; j and j is the coordinate of point j in the non-standard coordinate system xoy;

[0060] Conversely, the coordinates in the standard coordinate system XOY are mapped to the non-standard coordinate system xoy as:

[0061]

[0062] The method of this embodiment first calculates the clothoid curve based on the standard coordinate system, and then converts the clothoid curve in the standard coordinate system to the non-standard coordinate system, so that the clothoid curve can be calculated starting from the place where the curvature is non-zero, which increases the use scenarios of the clothoid curve. At the same time, it also simplifies the calculation process of the clothoid curve with non-zero curvature at the starting point, and improves the calculation speed of the program.

[0063] In some specific embodiments, the step S50 further includes:

[0064] Step S501 : splicing the clothoid curves corresponding to each constructed path segment to the starting point or the end point of the corresponding path.

[0065] Specifically, in the above example, after step S50, the first clothoid curve corresponding to the first path segment and the second clothoid curve corresponding to the second path segment can be obtained, and the starting point of the first clothoid curve is spliced ​​to the end point of the first path segment to form a new first path segment, and the starting point of the second clothoid curve is spliced ​​to the starting point of the second path segment to form a new second path segment. During the automatic parking process, the vehicle first travels along the new first path segment, and then adjusts to travel along the new second path segment until it parks in the parking space. Some adjustments may be required between the new first path segment and the new second path segment, but these adjustments are easy to implement because there is no obvious curvature mutation in the adjustment process, and the vehicle will not turn on the spot.

[0066] The method of this embodiment splices a clothoid curve at the turning point of the initial parking path (where the curvature is not zero) to smooth the initial parking path, so that the curvature at the end of the final parking path is zero, solving the problem of vehicle turning on the spot, without replacing the original part of the path, and without calculating the splicing offset, thereby improving the applicability of the smoothing method.

[0067] In some specific embodiments, the step S50 further includes:

[0068] Step S502, obtaining the end point position of the clothoid curve corresponding to each path segment, and generating a straight line corresponding to each path segment according to the end point position;

[0069] Step S503 , splicing the straight lines corresponding to each path segment to the end point of the corresponding clothoid curve.

[0070] Specifically, the method of this embodiment takes into account the control errors in actual situations, and the need to preview a certain distance forward when controlling the selection of tracking points. As a result, even if the curvature of the end point of the spiral curve is 0, the steering wheel still has a certain angle after the vehicle reaches the end point of the curve, which may still cause a certain amount of on-the-spot turning. Therefore, the method of this embodiment adds a straight line at the end point of the spiral curve to adjust the control link.

[0071] For example, Figure 3 As shown in the figure, the planned initial parking path includes the first path p1⌒p2 and the second path p7⌒p8. The dotted rectangular frame is the parking space. p2 and p7 are the turning points of the initial parking path (p2 and p7 are the same point). p2 is the end point of the first path p1⌒p2, and p7 is the starting point of the second path p7⌒p8. For the clothoid curve corresponding to the first path p1⌒p2, the length of the clothoid curve is calculated according to the curvature and curvature change rate of point p2. The clothoid curve in the standard coordinate system is calculated from the length of the clothoid curve and then converted to the non-standard coordinate system. The curve is spliced ​​to point p2 according to the translation and rotation of the coordinate system to form a clothoid curve of p2⌒p3; the straight lines are spliced ​​according to the position of p3 to form a straight line of p3⌒p4. Finally, the first path p1⌒p2 is smoothed to path p1⌒p4, and p4 is the turning point of the first path after smoothing. Similarly, p7⌒p8 can be smoothed to p5⌒p8. Performing the above path smoothing operation at each turning point of the parking path can solve the problem of turning on the spot during parking, improve the parking control effect, and enhance the comfort of the parking process.

[0072] Another embodiment of the present application further provides a parking path generation device, including a module for executing the parking path generation method described in the above embodiment. This device can be a hardware device, a software device, or a combination of hardware and software.

[0073] Another embodiment of the present application also provides another parking path generation device, including:

[0074] A communication interface, used to communicate with other electronic devices;

[0075] a memory for storing computer program instructions;

[0076] The processor is used to execute the computer program instructions to support the parking path generation device to implement the method described in the above embodiment.

[0077] In this embodiment, the memory mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating device, an application required for at least one function, etc., and the data storage area can store related data, etc. In addition, the memory can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, and a flash card (FlashCard), etc., or the memory can also be other volatile solid-state storage devices.

[0078] The processor may be a central processing unit (CPU), or other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor. The processor is the control center of the parking path generation device, and uses various interfaces and lines to connect various parts of the parking path generation device.

[0079] An embodiment of the present application also provides a computer program product, including computer program instructions, wherein the computer program instructions instruct a computer device to perform operations corresponding to the method described in the above embodiment.

[0080] Specifically, the computer program product includes a series of computer program instructions, which can instruct a computer device to execute the parking path generation method described in the present application. These instructions are codes written in a computer program, which define how to perform specific operations. In this embodiment, these instructions are used to execute the parking path generation method of the above embodiment.

[0081] These program instructions are designed to be loaded onto a computer device and instruct the device to perform specific operations, which are the various steps in the parking path generation method described in the above embodiment.

[0082] In this way, the computer program product provides a complete software solution, which can be run on various computer devices to implement the parking path generation method of the above embodiment.

[0083] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A parking path generation method, characterized in that: The method comprises: Receiving an initial parking path, wherein the initial parking path includes at least two paths; Get the curvature and curvature change rate of the starting point or end point of each path segment; Determine the length of the clothoid curve corresponding to each path segment according to the preset curvature of the end point of the clothoid curve and the curvature and curvature change rate of the starting point or the end point of each path segment; Constructing a clothoid curve corresponding to each path segment according to the length of the clothoid curve corresponding to each path segment; A new parking path is generated according to the clothoid curve corresponding to each path segment and the at least two paths.

2. The method according to claim 1, characterized in that The step of constructing the clothoid curve corresponding to each path segment according to the length of the clothoid curve corresponding to each path segment further comprises: Obtaining a curvature change rate of the clothoid curve corresponding to each path segment according to the curvature of the starting point or the end point of each path segment, the curvature of the end point of the clothoid curve, and the length of the clothoid curve corresponding to each path segment; The clothoid curve corresponding to each path segment is constructed according to the length and curvature change rate of each path segment.

3. The method according to claim 2, characterized in that The determining the length of the clothoid curve corresponding to each path segment according to the preset curvature of the end point of the clothoid curve and the curvature and curvature change rate of the starting point or the end point of each path segment further comprises: Based on the standard coordinate system, the coordinates and tangent angles of each point on the clothoid curve corresponding to each path segment are obtained according to the length and curvature change rate of the clothoid curve corresponding to each path segment, and the clothoid curve corresponding to each path segment in the standard coordinate system is generated according to the coordinates and tangent angles of each point; The coordinate conversion matrix is ​​obtained according to the tangent angle of each point on the clothoid curve corresponding to each path segment, and the clothoid curve corresponding to each path segment in the standard coordinate system is converted to the non-standard coordinate system according to the coordinate conversion matrix to obtain the clothoid curve corresponding to each path segment in the non-standard coordinate system.

4. The method according to claim 3, characterized in that The coordinates and tangent angle of any point on the clothoid curve corresponding to each path in the standard coordinate system are obtained as follows: Among them, x j is the horizontal coordinate of point j on the clothoid curve, y j is the ordinate of point j on the clothoid curve, s j is the length of the clothoid curve from the starting point to point j, α j is the tangent angle of point j on the clothoid curve, the origin of the standard coordinate system is a rectangular coordinate system with a curvature of 0, N is a preset value, and i is 0~N.

5. The method according to claim 4, characterized in that The step of obtaining a coordinate transformation matrix according to the tangent angle of each point on the clothoid curve corresponding to each path segment further includes: For any point on the clothoid curve corresponding to each path in the standard coordinate system, substitute the tangent angle of the arbitrary point into the following matrix equation The coordinate transformation matrix corresponding to the arbitrary point is obtained, and the coordinates of the arbitrary point in the standard coordinate system are transformed into the non-standard coordinate system according to the coordinate transformation matrix to obtain the coordinates of the arbitrary point in the non-standard coordinate system; α is the tangent angle.

6. The method according to claim 1, characterized in that The generating a new parking path according to the clothoid curve corresponding to each path segment and the at least two paths further comprises: The clothoid curve corresponding to each constructed path segment is spliced ​​to the starting point or end point of the corresponding path.

7. The method according to claim 6, characterized in that The generating a new parking path according to the clothoid curve corresponding to each path segment and the at least two paths further comprises: Obtaining the end point position of the clothoid curve corresponding to each path segment, and generating a straight line corresponding to each path segment according to the end point position; Connect the straight lines corresponding to each path segment to the end point of the corresponding clothoid curve.

8. A parking path generation device, characterized in that: The device comprises a module for executing the method according to any one of claims 1 to 7.

9. A parking path generation device, characterized in that: include: A communication interface, used to communicate with other electronic devices; a memory for storing computer program instructions; A processor, configured to execute the computer program instructions to enable the apparatus to implement the method according to any one of claims 1 to 7.

10. A computer program product, characterized in that The method comprises computer program instructions, wherein the computer program instructions instruct a computer device to execute operations corresponding to the method according to any one of claims 1 to 7.

Images