Path planning method and device

Abstract

The invention relates to a path planning method and device, and the method comprises the steps: carrying out the iterative processing from a preset initial position through the following steps: determining a sampling point in a neighborhood of a current path node; under the condition that the course angle of the sampling point indicates that steering is needed, taking the current path node as a starting end point, and adopting a combined curve at least composed of a first clothoid and a second clothoid to carry out path expansion towards the direction of the sampling point to obtain a new path node, determining the combined curve as a path segment between the current path node and the new path node; wherein the first end point of the first clothoid is a current path node, and the instantaneous radius at the second end point of the first clothoid and the instantaneous radius at the first end point of the second clothoid meet the equal condition. Therefore, the control precision can be improved, in-situ steering of the tires is effectively avoided, and abrasion of the tires in the driving process is reduced.

Description

Technical Field

[0001] The present application relates to the field of automatic driving technology, and in particular to a path planning method and device. Background Art

[0002] Driving path planning is an integral part of autonomous driving. In related technologies, there are generally two types of path planning methods: geometric methods and search methods.

[0003] Among them, both the geometric method and the search method use a combination of straight lines and arcs to obtain the driving path. This approach is simple and efficient, and the project implementation is relatively easy. However, this type of method has a sudden change in curvature at the arc-straight line or arc-arc joints, resulting in poor control effect and the possibility of tire turning on the spot. Summary of the Invention

[0004] The present application provides a path planning method and device, which can improve control accuracy, effectively avoid tire turning on the spot, and reduce tire wear during driving.

[0005] In a first aspect, the present application provides a path planning method, comprising:

[0006] Starting from the preset starting position, the iteration process is performed using the following steps until the set iteration stop condition is met:

[0007] Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process;

[0008] In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet an equality condition; and the second endpoint of the second clothoid curve is the new path node;

[0009] After the iteration is completed, the target planning path is determined based on the path segments between multiple path nodes.

[0010] In a second aspect, an embodiment of the present application provides a path planning device, comprising:

[0011] The iteration module is used to start from a preset starting position and perform iterative processing using the following steps until the set iteration stop condition is met:

[0012] Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process;

[0013] In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet an equality condition; and the second endpoint of the second clothoid curve is the new path node;

[0014] The final path determination module is used to determine the target planning path based on the path segments between multiple path nodes after the iteration is completed.

[0015] In a third aspect, an embodiment of the present application provides an electronic device, including:

[0016] Memory for storing computer programs;

[0017] The processor is used to execute the computer program stored in the memory, and when the computer program is executed, the method provided in the embodiment of the present application is implemented.

[0018] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium on which a computer program is stored, characterized in that when the computer program is executed by a processor, the method provided in the embodiment of the present application is implemented.

[0019] The above-mentioned technical solution provided by the embodiment of the present application has the following advantages over the prior art: the method provided by the embodiment of the present application, by taking the current path node as the starting endpoint and adopting a combined curve consisting of at least a first clothoid curve and a second clothoid curve to extend the path toward the sampling point when the heading angle of the sampling point indicates that a turn is required, a new path node is obtained, and the combined curve is determined as the path segment connecting the current path node and the new path node. The path segment between the front and rear path nodes can be planned into a curve with continuous curvature. Specifically, by ensuring that the curvature of the first clothoid curve and the first clothoid curve are continuous at the connection point, it is ensured that the path is planned into a path curve with continuous curvature, thereby improving control accuracy, effectively avoiding tire turning in place, and reducing tire wear during vehicle driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0023] Figure 1 This is a flow chart of a path planning method provided by an embodiment of the present application;

[0024] Figure 2 It is a schematic diagram of a path planning scenario;

[0025] Figure 3 The path planning is performed according to the existing technology, and the relationship between the path curvature k and the path length s is shown;

[0026] Figure 4 is a schematic diagram of a clothoid curve;

[0027] Figure 5 A flow chart of a method provided in an embodiment of the present application for extending a path toward a sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve to obtain a new path node;

[0028] Figure 6A schematic diagram of the final planned path segment;

[0029] Figure 7 A schematic diagram of the final planned path segment;

[0030] Figure 8 A flow chart of a method for determining a second endpoint of a first clothoid curve based on a first arc length of the first clothoid curve provided in an embodiment of the present application;

[0031] Figure 9 A flow chart of a method for determining a second endpoint of a first clothoid curve based on a path sampling length provided in an embodiment of the present application;

[0032] Figure 10 A flowchart of a method for determining the midpoint of a target arc based on the radius of the target arc and the first endpoint of the target arc provided in an embodiment of the present application;

[0033] Figure 11 A graph showing the relationship between the path curvature k and the path length s of a target planning path planned according to the path planning method provided in an embodiment of the present application;

[0034] Figure 12 This is a structural block diagram of a path planning device provided in an embodiment of the present application;

[0035] Figure 13 This is a structural block diagram of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] The disclosure below provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, these are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0038] Figure 1 This is a flow chart of a path planning method provided by an embodiment of the present application. Figure 1 As shown, the method includes the following steps:

[0039] Step 101: Determine a sampling point in the neighborhood of the current path node.

[0040] In the first round of iteration, the current path node is the preset starting position.

[0041] Step 102: When the heading angle of the sampling point indicates that a turn is required, the current path node is used as the starting endpoint, and a combined curve consisting of at least a first clothoid curve and a second clothoid curve is used to extend the path toward the sampling point to obtain a new path node, and the combined curve is determined as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet the equality condition; and the second endpoint of the second clothoid curve is the new path node.

[0042] Step 103: Determine whether the set iteration stop condition is currently met. If so, execute step 104; if not, use the current new path node as the current path node and return to execute step 101.

[0043] Step 104: Determine a target planning path based on the path segments between the multiple path nodes.

[0044] For ease of understanding, the following Figure 2 The scenario shown here provides a unified description of steps 101 to 104. Figure 1 The scenario shown is taken as an example; other scenarios are similar.

[0045] like Figure 2 As shown, the vehicle is first planned to start from point A (i.e., the preset starting position) and travel along the straight path segment AB to point B. The path planning process from point A to point B is the first round of iteration. That is, in the first round of iteration, the preset starting position is used as the current path node, and sampling points are determined within the neighborhood of the current path node. For example, sampling point B is determined within the neighborhood of point A. Since the heading angle of point B is 0°, it means that no turning is required from point A to point B, and the path segment from point A to point B is planned as a straight line.

[0046] In the second round of iteration, point B is used as the current path node. Sampling is performed at point B according to different turning radius and path sampling length to obtain 5 sampling points, namely C1, C2, C3, C4 and C5. Among them, C5 is based on the minimum turning radius R min The center of the circle where the arc BC5 is generated is O1, and the turning radius R corresponding to the four sampling points C1, C2, C3 and C4 is x >R min, x takes values in {1, 2, 3, 4}.

[0047] For the five sampling points C1, C2, C3, C4 and C5, the path planning method provided in the embodiment of the present application is applied to extend the path starting from point B in the direction of each sampling point to obtain a new path node and a path segment between point B and the new path node.

[0048] In the third round of iteration, the new path node determined in the second round of iteration is used as the current path node, and the above process is repeated. Taking point C5 as the current path point, sampling is performed at point C5 according to different turning radii and path sampling lengths, resulting in nine sampling points: D1, D2, D3, D4, D5, D6, D7, D8, and D9. For these nine sampling points, the path planning method provided in the embodiment of the present application is applied, and the path is extended starting from point C5 in the direction of each sampling point to obtain a new path node and the path segment between point C5 and the new path node.

[0049] And so on, until the path planning is completed. Wherein, as an optional implementation, the judgment condition for completing the path planning, that is, the above-set iterative stop condition is: the number of iterations reaches the set number threshold. As another optional implementation, the judgment condition for completing the path planning, that is, the above-set iterative stop condition is: the path node obtained by the current plan and the preset end position meet the equality condition. The equality condition here is, for example, that the distance between the path node obtained by the current plan and the preset end position is less than the set distance threshold, and the embodiments of the present application do not impose any restrictions on this.

[0050] exist Figure 2 In the scenario shown, if a circular arc curve is used to form the path segment between the two path points in the case of turning, the curve of the path curvature k changing with the path length s will be as follows: Figure 3 As shown. Figure 3 It can be seen that the curvature at the connection between the arc curve and the straight line, and between the arcs, has undergone a sudden change, which can easily lead to poor control effect and the tire turning on the spot.

[0051] To address the technical issues of poor control effectiveness and tire pivoting caused by sudden changes in curvature in paths planned using existing technologies, the present application provides a novel path planning method. Specifically, when steering is required, a combined curve consisting of at least a first clothoid curve and a second clothoid curve is used to plan a path segment, wherein the first endpoint of the first clothoid curve is the current path node, such as point B, and the instantaneous radius of the first clothoid curve at the second endpoint is equal to the instantaneous radius of the second clothoid curve at the first endpoint; the second endpoint of the second clothoid curve is a new path node, such as point C5. This allows the path to be planned as a path curve with continuous curvature, thereby improving control accuracy, effectively preventing tire pivoting, and reducing tire wear during driving.

[0052] Among them, the clothoid curve can be referred to Figure 4 The solid line starts at O0 and has a curvature of 0, and is extended to point (x t ,y t ), at which point the vehicle reaches its minimum turning radius R min , the instantaneous center is o t (x ot ,y ot ), at this time, the length of the path traveled is L min The formula of the clothoid curve is:

[0053] A 2 =RL

[0054] Where L is the arc length, R is the turning radius at the arc length L, and A represents the curvature characteristics of the clothoid curve.

[0055] The above-mentioned first endpoint can be the starting point and the corresponding second endpoint can be the end point, or the above-mentioned first endpoint can be the end point and the corresponding second endpoint can be the starting point. For the convenience of calculation, the first endpoint can be considered as the starting point and the second endpoint can be considered as the end point.

[0056] Specifically, for the first circular arc curve, the current path node can be used as the first endpoint of the first clothoid curve, i.e., the starting endpoint. The second endpoint of the first clothoid curve is continuously explored through a calculation method until the second endpoint of the first clothoid curve is determined. After the second endpoint of the first clothoid curve is determined, the first clothoid curve is determined. Thereafter, a symmetry operation is performed on the first clothoid curve to obtain a second clothoid curve symmetrical to the first clothoid curve. The second endpoint of the second clothoid curve can be used as the newly planned path node, and a combined curve consisting of at least the first clothoid curve and the second clothoid curve is determined as the path segment connecting the current path node and the new path node.

[0057] Since the instantaneous radii of the first clothoid curve and the second clothoid curve at the connection point meet the equality condition, the curvature k of the combined curve composed of the first clothoid curve and the second clothoid curve is continuous with the curve length s, and there is no problem of curvature mutation.

[0058] The technical solution provided by the embodiment of the present application is to use a combined curve consisting of at least a first clothoid curve and a second clothoid curve to extend the path toward the sampling point when the heading angle at the sampling point indicates that a turn is required, using the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as the path segment connecting the current path node and the new path node. The path segment between the two previous and next path nodes can be planned into a curve with continuous curvature. Specifically, by ensuring that the curvature of the first clothoid curve and the first clothoid curve are continuous at the connection point, it is ensured that the path is planned into a path curve with continuous curvature, thereby improving control accuracy, effectively avoiding tire turning in place, and reducing tire wear during vehicle driving.

[0059] Figure 5 A flow chart of a method for obtaining a new path node by extending a path toward a sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve provided in an embodiment of the present application. Figure 5 The process shown in Figure 1 Based on the process shown, the following steps are included:

[0060] Step 501: Determine a first arc length of a first clothoid curve and a second arc length of a second clothoid curve.

[0061] pass Figure 1 As can be seen from the description of the illustrated process, a second clothoid curve can be obtained by performing a symmetric operation on the first clothoid curve. Therefore, the first clothoid curve and the second clothoid curve have the same arc length. In other words, the first arc length and the second arc length determined in step 501 are equal. Based on this, once the first arc length of the first clothoid curve is determined, the second arc length of the second clothoid curve is also determined.

[0062] Taking the determination of the first arc length of the first clothoid curve as an example, the first arc length of the first clothoid curve is determined based on the following formula (1):

[0063]

[0064] Where V is the desired vehicle speed, V≤V max , V max The maximum speed allowed. is the desired steering wheel angle, is the maximum steering wheel angle allowed. γ is the steering ratio of the steering wheel angle to the front wheel angle. L bis the wheelbase. ω is the expected steering wheel angular rate, R is the radius of the circle where the sampling point is located, R ≥ R min , R min is the minimum turning radius.

[0065] L is the first arc length of the first clothoid curve, and A represents the curvature characteristics of the clothoid curve.

[0066] Step 502: Compare the sum of the first arc length and the second arc length with the preset path sampling length; if the sum of the first arc length and the second arc length is greater than or equal to the path sampling length, execute step 503; if the sum of the first arc length and the second arc length is less than the path sampling length, execute step 504.

[0067] Step 503: Using a combined curve consisting of the first clothoid curve and the second clothoid curve, the path is extended toward the sampling point to obtain a new path node.

[0068] Step 504: Using a combined curve consisting of the first clothoid curve, the target arc, and the second clothoid curve, the path is extended toward the sampling point to obtain a new path node.

[0069] For ease of understanding, steps 502 to 504 are described in a unified manner below:

[0070] In step 502, the sum of the first arc length of the first clothoid curve and the second arc length of the second clothoid curve (i.e., 2L) is compared with a preset path sampling length. The preset path sampling length represents the maximum length of the path segment between two preceding and succeeding path nodes. If the sum of the first arc length of the first clothoid curve and the second arc length of the second clothoid curve is greater than or equal to the preset path sampling length, this means that the combined curve formed by the first clothoid curve and the second clothoid curve can already meet the path segment length requirement. Therefore, if the sum of the first arc length and the second arc length is found to be greater than or equal to the path sampling length, step 503 is executed. In step 503, the combined curve formed by the first clothoid curve and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node.

[0071] If the sum of the first arc length of the first clothoid curve and the second arc length of the second clothoid curve is less than the preset path sampling length, it means that the path segment between the current path node and the next path node using the combined curve of the first clothoid curve and the second clothoid curve is not enough. Therefore, when it is compared that the sum of the first arc length and the second arc length is less than the path sampling length, step 504 is executed. In step 504, the combined curve composed of the first clothoid curve, the target arc and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node.

[0072] Specifically, as an optional implementation, in step 503, a combined curve consisting of a first clothoid curve and a second clothoid curve is used to extend the path toward the sampling point, and the specific implementation of obtaining a new path node includes: taking the current path node as the first endpoint of the first clothoid curve, and determining the second endpoint of the first clothoid curve based on the first arc length; performing a symmetric operation on the first clothoid curve based on the first connecting line to obtain a second clothoid curve; wherein the first endpoint of the second clothoid curve is the second endpoint of the first clothoid curve, and the second endpoint of the second clothoid curve is the new path node; the first connecting line is the line between the first endpoint of the second clothoid curve and the center of the circle where the sampling point is located.

[0073] Among them, reference Figure 6 For illustration, the clothoid curve p1h is the first clothoid curve, and point p1 is the first endpoint of the first clothoid curve, i.e., the current path node. The clothoid curve hp2 is the second clothoid curve, point h is the first endpoint of the second clothoid curve, and point p2 is the second endpoint of the second clothoid curve, i.e., the new path node. Point O is the center of the circle containing the sampling points, and line oh is the first connecting line.

[0074] As to how to determine the second endpoint of the first clothoid curve based on the first arc length and thus determine the first clothoid curve, the following is described. Figure 8 The process shown is explained and will not be described in detail here.

[0075] As an optional implementation, in step 504, a combined curve consisting of a first clothoid curve, a target arc, and a second clothoid curve is used to extend the path toward the sampling point, and the specific implementation of obtaining a new path node includes: taking the current path node as the first endpoint of the first clothoid curve, and determining the second endpoint of the first clothoid curve based on the path sampling length; taking the second endpoint of the first clothoid curve as the first endpoint of the target arc, determining the radius of the circle where the sampling point is located as the radius of the target arc, and determining the midpoint of the target arc based on the radius of the target arc and the first endpoint of the target arc; performing a symmetric operation on the first clothoid curve and the first arc based on the second connecting line to obtain the second arc and the second clothoid curve; wherein the first arc is the arc between the first endpoint of the target arc and the midpoint of the target arc, and the second arc is the arc between the midpoint of the target arc and the second endpoint of the target arc; the second endpoint of the target arc is the first endpoint of the second clothoid curve, and the second endpoint of the second clothoid curve is the new path node; the second connecting line is the line between the midpoint of the target arc and the center of the circle where the target arc is located.

[0076] Among them, reference Figure 7To illustrate, the clothoid curve p1c1 is the first clothoid curve, point p1 is the first endpoint of the first clothoid curve, i.e., the current path node, and c1 is the second endpoint of the first clothoid curve. Arc c1c2 is the target arc, point c1 is the first endpoint of the target arc, and point c2 is the second endpoint of the target arc. Clothoid curve c2p2 is the second clothoid curve, point c2 is the first endpoint of the second clothoid curve, and point p2 is the second endpoint of the second clothoid curve, i.e., the new path node. Point O is the center of the circle containing the sampling point, h is the midpoint of the target arc, and line Oh is the second connecting line. Arc c1h is the first arc, and arc hc2 is the second arc.

[0077] As for how to determine the second endpoint of the first clothoid curve based on the path sampling length, the following is described. Figure 9 The process shown is explained and will not be described in detail here.

[0078] As for how to determine the midpoint of the target arc based on the radius of the target arc and the first endpoint of the target arc, the following is described. Figure 10 The process shown is explained and will not be described in detail here.

[0079] Figure 5 The process shown determines the first arc length of the first clothoid curve and the second arc length of the second clothoid curve, and compares the sum of the first arc length and the second arc length with a preset path sampling length; when it is found that the sum of the first arc length and the second arc length is greater than or equal to the path sampling length, a combined curve consisting of the first clothoid curve and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node; when it is found that the sum of the first arc length and the second arc length is less than the path sampling length, a combined curve consisting of the first clothoid curve, the target circular arc and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node. This process can be effectively applied to all sampling-based path planning methods that use arc paths of different lengths and radii as sampling samples.

[0080] Figure 8 A flow chart of a method for determining a second endpoint of a first clothoid curve based on a first arc length of the first clothoid curve provided in an embodiment of the present application, Figure 8 The process shown in Figure 5 Based on the process shown, the following steps are included:

[0081] Step 801: Use the current path node as the first endpoint of the first clothoid curve.

[0082] refer to Figure 6 To explain, such as Figure 6 As shown, the current path node p1 serves as the first endpoint of the first clothoid curve.

[0083] Step 802: Using a preset sampling interval length as the current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length.

[0084] As an optional implementation, determining the initial second endpoint of the first clothoid curve based on the current arc length includes: determining the initial second endpoint of the first clothoid curve based on the following formula (2):

[0085]

[0086] Among them, x i 、y i and θ i are the horizontal coordinate, vertical coordinate and heading angle of the i-th initial second endpoint of the first clothoid curve in the coordinate system with the current path node as the vertex. A is the parameter of the first clothoid curve, which can be calculated by the above formula (1). S is the current arc length of the first clothoid curve, s=iΔs, Δs is the preset sampling interval length. i is The values are taken in sequence.

[0087] It can be seen from this that, in the initial case, the preset sampling interval length is used as the current arc length of the first clothoid curve.

[0088] refer to Figure 6 To explain, such as Figure 6 As shown, the other endpoint of the first clothoid curve with the current arc length s is point h, which serves as the initial second endpoint of the first clothoid curve, wherein, as Figure 6 As shown, the first clothoid curve is a solid line curve from point p1 to point h. The coordinates of the initial second endpoint h of the first clothoid curve and the heading angle θ can be calculated using the above formula (2). It should be noted that the second endpoint h of the first clothoid curve has not yet been determined. The introduction of h here is for the convenience of description and understanding. The coordinates of h are not included in the calculation of the above formula.

[0089] Step 803: Modify the current arc length of the first clothoid curve based on the sampling interval length.

[0090] As an optional implementation, changing the current arc length of the first clothoid curve based on the sampling interval length includes: changing the current arc length of the first clothoid curve based on the following formula (3):

[0091] s=iΔs formula (3)

[0092] Step 804: Determine whether the modified current arc length exceeds the first arc length. If not, return to step 802 based on the modified current arc length; if so, execute step 805.

[0093] Step 805: Determine the last initial second endpoint as the second endpoint of the first clothoid curve.

[0094] In step 804, whether the modified current arc length exceeds the first arc length is determined to determine whether path extension toward the sampling point is necessary. If the modified current arc length does not exceed the first arc length, path extension toward the sampling point continues according to step 802. If the modified current arc length exceeds the first arc length, the current path extension process is terminated, and the last initial second endpoint is determined as the second endpoint of the first clothoid curve.

[0095] In addition, according to Figure 1 As described in the embodiment shown, a second clothoid curve can be obtained by performing a symmetric operation on the first clothoid curve based on the first connecting line.

[0096] Figure 8 In the process shown, the second endpoint of the first clothoid curve can be accurately determined by taking the current path node as the first endpoint of the first clothoid curve and continuously exploring the second endpoint of the second clothoid curve through a calculation method.

[0097] Figure 9 A flow chart of a method for determining a second endpoint of a first clothoid curve based on a path sampling length provided in an embodiment of the present application is provided. Figure 9 The process shown in Figure 5 Based on the process shown, the following steps are included:

[0098] Step 901: Use the current path node as the first endpoint of the first clothoid curve.

[0099] refer to Figure 7 To explain, such as Figure 7 As shown, the current path node p1 serves as the first endpoint of the first clothoid curve.

[0100] Step 902: Using a preset sampling interval length as the current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length.

[0101] As an optional implementation, determining the initial second endpoint of the first clothoid curve based on the current arc length includes: determining the initial second endpoint of the first clothoid curve based on the following formula (4):

[0102]

[0103] Among them, x i 、y i and θ iare the horizontal coordinate, vertical coordinate and heading angle of the i-th initial second endpoint of the first clothoid curve in the coordinate system with the current path node as the vertex. A is the parameter of the first clothoid curve, which can be calculated by the above formula (1). S is the current arc length of the first clothoid curve, s=iΔs, Δs is the preset sampling interval length. i is The values are taken in sequence. L s is the preset path sampling length.

[0104] It can be seen from this that, in the initial case, the preset sampling interval length is used as the current arc length of the first clothoid curve.

[0105] refer to Figure 7 To explain, such as Figure 7 As shown, the other endpoint of the first clothoid curve with the current arc length s is point c1, which serves as the initial second endpoint of the first clothoid curve, wherein, as Figure 7 As shown, the first clothoid curve is a solid line curve from point p1 to point c1. The coordinates of the initial second endpoint c1 of the first clothoid curve and the heading angle θ can be calculated using the above formula (3). It should be noted that the second endpoint c1 of the first clothoid curve has not yet been determined. For ease of description and understanding, point c2 is introduced here, and its coordinates are not included in the calculation of the above formula.

[0106] Step 903: Modify the current arc length of the first clothoid curve based on the sampling interval length.

[0107] As an optional implementation, changing the current arc length of the first clothoid curve based on the sampling interval length includes: changing the current arc length of the first clothoid curve based on the following formula (5):

[0108] s=iΔs formula (5)

[0109] Step 904: Determine whether the modified current arc length exceeds half of the path sampling length. If not, return to step 902 based on the modified current arc length; if so, execute step 905.

[0110] Step 905: Determine the last initial second endpoint as the second endpoint of the first clothoid curve

[0111] In step 904, whether the modified current arc length exceeds half the path sampling length is determined to determine whether path extension toward the sampling point is necessary. If the modified current arc length does not exceed half the path sampling length, path extension toward the sampling point continues according to step 902. If the modified current arc length exceeds the first arc length, the current path extension process is terminated, and the last initial second endpoint is determined as the second endpoint of the first clothoid curve.

[0112] Figure 9 In the process shown, the second endpoint of the first clothoid curve can be accurately determined by taking the current path node as the first endpoint of the first clothoid curve and continuously exploring the second endpoint of the second clothoid curve through a calculation method.

[0113] Figure 10 A flowchart of a method for determining the midpoint of a target arc based on the radius of the target arc and the first endpoint of the target arc is provided in an embodiment of the present application. Figure 10 The process shown in Figure 5 Based on the process shown, the following steps are included:

[0114] Step 1001: Determine the maximum semi-center angle of the target arc based on a preset path sampling length, the sum of the first arc length and the second arc length, and the radius of the target arc.

[0115] As an optional implementation, determining the maximum semi-center angle of the target arc based on the preset path sampling length, the sum of the first arc length and the second arc length, and the radius of the target arc includes: determining the maximum semi-center angle of the target arc based on the following formula (6):

[0116]

[0117] Among them, θ max is the maximum semi-center angle of the target arc. R is the radius of the circle where the target arc lies. 2L is the sum of the lengths of the first and second arcs.

[0118] Step 1002: Using a preset arc sampling interval angle as the current center angle of the first arc, and determining an initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc.

[0119] As an optional implementation, determining the initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc includes: determining the initial second endpoint of the first arc based on the following formula (7):

[0120]

[0121] Among them, x j 、y j and θ j are respectively the abscissa, ordinate and heading angle of the i-th initial second endpoint of the first arc in the coordinate system with the current path node as the vertex. and are the horizontal coordinate, vertical coordinate and heading angle of the current path node respectively. R is the radius of the circle where the target arc is located. Δθ is the current center angle of the circle. Δδ is the preset arc sampling interval angle. The values are taken in sequence.

[0122] It can be seen from this that, in the initial case, the preset arc sampling interval angle is used as the current center angle of the first arc.

[0123] refer to Figure 7 To explain, such as Figure 7 As shown, the other endpoint of the first arc length with the current central angle Δθ, that is, the midpoint of the target arc length is point h, which serves as the initial second endpoint of the first arc length, wherein, Figure 7 As shown, the length of the first arc is the solid line from point c1 to point h. The coordinates of the initial second endpoint h of the first arc and the heading angle θ can be calculated using the above formula (5). It should be noted that the second endpoint h of the first arc has not yet been determined. For ease of description and understanding, h is introduced here, and its coordinates are not included in the calculation of the above formula.

[0124] Step 1003: Modify the current center angle of the first arc based on the arc sampling interval angle.

[0125] As an optional implementation, changing the current center angle of the first arc based on the arc sampling interval angle includes: changing the current center angle of the first arc based on Δθ=jΔδ in the above formula (7).

[0126] Step 1004: Determine whether the changed current center angle exceeds the maximum semi-center angle; if so, return to step 1003 based on the changed current center angle; if not, execute step 1005.

[0127] Step 1005: Determine the last initial second endpoint as the midpoint of the target arc.

[0128] In step 1004, whether the changed current central angle exceeds the maximum semi-central angle is determined to determine whether path extension toward the sampling point is necessary. If the changed current central angle does not exceed the maximum semi-central angle, path extension toward the sampling point continues according to step 1002. If the changed current central angle exceeds the maximum semi-central angle, the current path extension process is terminated, and the last initial second endpoint is determined as the second endpoint of the first arc, i.e., the midpoint of the target arc.

[0129] Figure 10 The process shown, by taking the second endpoint of the first spiral curve as the first endpoint of the target arc and continuously exploring the second endpoint of the first arc through a calculation method, can accurately determine the second endpoint of the first arc, that is, accurately determine the midpoint of the target arc.

[0130] exist Figure 10Based on the process shown in FIG, the first clothoid curve and the first arc are symmetrically operated based on the second connecting line to obtain the second arc and the second clothoid curve. Figure 7 For illustration, the clothoid curve p1c1 is the first clothoid curve, point p1 is the first endpoint of the first clothoid curve, also known as the current path node, and c1 is the second endpoint of the first clothoid curve. Arc c1h is the first arc, point O is the center of the circle containing the sampling point, h is the midpoint of the target arc, and line Oh is the second connecting line. Then, a symmetric operation is performed on the first clothoid curve and the first arc based on the second connecting line to obtain the second arc hc2 and the second clothoid curve arc c2p2.

[0131] As an optional implementation, a symmetric operation is performed on the first clothoid curve and the first circular arc based on the second connecting line to obtain a combined curve of the first clothoid curve-the target circular arc-the second clothoid curve, including:

[0132] Select discrete points on the first clothoid curve, symmetric these discrete points based on the symmetry line (i.e., the second connecting line), find the corresponding symmetric points, and connect the symmetric points of the second endpoint of the first clothoid curve, the symmetric points corresponding to these discrete points, and the first endpoint of the second clothoid curve in order to obtain the second clothoid curve. Figure 7 , select discrete points from the first clothoid curve p1c1, symmetricize these discrete points based on the line segment oh to obtain a corresponding series of symmetrical points, connect point C2, a series of symmetrical points corresponding to these discrete points, and point P2 in sequence to obtain the second clothoid curve C2p2.

[0133] Similarly, select discrete points on the first arc, symmetric these discrete points based on the symmetry line (that is, the second connecting line), find the corresponding symmetric points, and connect the midpoint of the target arc, the symmetric points corresponding to these discrete points, and the symmetric points of the first endpoint of the target arc in order to obtain the second arc. Figure 7 , select discrete points on the first arc c1h, symmetric these discrete points based on the line segment oh, and obtain a corresponding series of symmetrical points; connect point h, a series of symmetrical points corresponding to these discrete points, and point c2 in sequence to obtain the second arc hc2.

[0134] Afterwards, refer to Figure 8 The first clothoid curve p1c1, the first circular arc c1h, the second circular arc hc2 and the second clothoid curve c2p2 are combined to obtain the curve p1c1hc2p2, that is, the combined curve of the first clothoid curve-the target circular arc-the second clothoid curve.

[0135] As an optional implementation manner, the second endpoint of the first clothoid curve is determined based on a symmetric point of symmetry of the symmetry line, including:

[0136] The symmetry point is determined based on the following formula (8):

[0137]

[0138] in, and are the horizontal and vertical coordinates of the symmetrical point in the coordinate system with the current path node as the vertex. In the above formula (8), d x d y and l are intermediate quantities in the calculation process, refer to Figure 7 The second endpoint c1 of the first clothoid curve p1c1 is symmetrical to the target symmetry line oh, and the coordinates of the symmetrical point c2 can be calculated using the above formula (8).

[0139] Finally, the coordinates of all points on the path curve planned according to the above method are converted into an absolute coordinate system. As an optional implementation, the coordinate conversion is performed based on the following formula (9):

[0140]

[0141] Where ori(0,0,0) is the origin of the absolute coordinate system, p is the relative coordinate of all points on the path curve planned according to the above method relative to the current path point, p′ is the coordinate of all points on the path curve relative to the origin of the absolute coordinate system, and P = Trans(m,n) is the coordinate transformation method, see the following formula (10).

[0142]

[0143] Figure 11 The relationship curve between the path curvature k and the path length s of the target planning path planned by the path planning method provided in the embodiment of the present application is shown in FIG. Figure 11 It can be seen that by applying the technical solution provided in the embodiments of the present application, the path can be planned into a path curve with continuous curvature, thereby improving control accuracy, effectively avoiding tire turning on the spot, and reducing tire wear during vehicle driving.

[0144] Figure 12 This is a structural block diagram of a path planning device provided in an embodiment of the present application. Figure 12 Shown, including:

[0145] The iteration module 120 is configured to perform iterative processing starting from a preset starting position using the following steps until a set iteration stop condition is met:

[0146] Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process;

[0147] In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet an equality condition; and the second endpoint of the second clothoid curve is the new path node;

[0148] The final path determination module 121 is used to determine the target planned path according to the path segments between multiple path nodes after the iteration is completed.

[0149] In one possible implementation, the iteration module 120 includes:

[0150] an arc length determining unit, configured to determine a first arc length of the first clothoid curve and a second arc length of the second clothoid curve;

[0151] a comparing unit, configured to compare the sum of the first arc length and the second arc length with a preset path sampling length;

[0152] a first path extension unit configured to, when comparing the sum of the first arc length and the second arc length to be greater than or equal to the path sampling length, extend the path toward the sampling point using a combined curve consisting of the first clothoid curve and the second clothoid curve to obtain a new path node;

[0153] The second path extension unit is used to use a combined curve consisting of the first clothoid curve, the target arc and the second clothoid curve to extend the path toward the sampling point to obtain a new path node when it is compared that the sum of the first arc length and the second arc length is less than the path sampling length.

[0154] In a possible implementation manner, the first path extension unit includes:

[0155] a first determining subunit, configured to use the current path node as a first endpoint of a first clothoid curve, and determine a second endpoint of the first clothoid curve based on the first arc length;

[0156] The first symmetry subunit is used to perform a symmetry operation on the first clothoid curve based on the first connecting line to obtain a second clothoid curve; wherein the first endpoint of the second clothoid curve is the second endpoint of the first clothoid curve, and the second endpoint of the second clothoid curve is a new path node; the first connecting line is the line between the first endpoint of the second clothoid curve and the center of the circle where the sampling point is located.

[0157] In a possible implementation manner, the first determining subunit is specifically configured to:

[0158] Using a preset sampling interval length as a current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length;

[0159] modifying a current arc length of the first clothoid curve based on the sampling interval length, and determining whether the modified current arc length exceeds the first arc length;

[0160] If not, then based on the changed current arc length, return to the operation of determining the initial second endpoint of the first convolution curve based on the current arc length, until the changed current arc length exceeds the first arc length, and determine the last initial second endpoint as the second endpoint of the first convolution curve.

[0161] In a possible implementation manner, the second path extension unit includes:

[0162] a second determining subunit, configured to use the current path node as a first endpoint of a first clothoid curve, and determine a second endpoint of the first clothoid curve based on the path sampling length;

[0163] a third determining subunit, configured to use the second endpoint of the first clothoid curve as the first endpoint of a target arc, determine the radius of the circle where the sampling point is located as the radius of the target arc, and determine the midpoint of the target arc based on the radius of the target arc and the first endpoint of the target arc;

[0164] The second symmetry subunit is used to perform a symmetric operation on the first clothoid curve and the first arc based on the second connecting line to obtain the second arc and the second clothoid curve; wherein, the first arc is the arc between the first endpoint of the target arc and the midpoint of the target arc, and the second arc is the arc between the midpoint of the target arc and the second endpoint of the target arc; the second endpoint of the target arc is the first endpoint of the second clothoid curve, and the second endpoint of the second clothoid curve is a new path node; the second connecting line is the line between the midpoint of the target arc and the center of the circle where the target arc is located.

[0165] In a possible implementation manner, the third determining subunit is specifically configured to:

[0166] Determining a maximum semi-center angle of the target arc based on a preset path sampling length, a sum of the first arc length and the second arc length, and a radius of the target arc;

[0167] Using a preset arc sampling interval angle as the current center angle of the first arc, and determining an initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc;

[0168] Modifying the current center angle of the first arc based on the arc sampling interval angle, and determining whether the modified current center angle exceeds the maximum semi-center angle;

[0169] If not, based on the changed current center angle, return to the operation of determining the initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc, until the changed current center angle exceeds the maximum semi-center angle, and the last initial second endpoint is determined as the midpoint of the target arc.

[0170] In a possible implementation manner, the second determining subunit is specifically configured to:

[0171] Using a preset sampling interval length as a current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length;

[0172] modifying a current arc length of the first clothoid curve based on the sampling interval length, and determining whether the modified current arc length exceeds half of the path sampling length;

[0173] If not, then based on the changed current arc length, return to the operation of determining the initial second endpoint of the first spiral curve based on the current arc length, until the changed current arc length exceeds half of the path sampling length, and determine the last initial second endpoint as the second endpoint of the first spiral curve.

[0174] In a possible implementation manner, the first determining subunit is specifically configured to:

[0175] The initial second endpoint of the first clothoid curve is determined based on the following formula:

[0176]

[0177] Among them, x i 、y i and θi are respectively the abscissa, ordinate and heading angle of the initial second endpoint of the first clothoid curve in a coordinate system with the current path node as the vertex;

[0178] Where A is the parameter of the first clothoid curve,

[0179] Where V is the desired driving speed, γ is the steering ratio of the steering wheel angle to the front wheel angle, and L b is the vehicle wheelbase, ω is the maximum angular velocity, R is the radius of the circle where the sampling point is located, L is the first arc length, and S is the current arc length of the first clothoid curve.

[0180] In a possible implementation manner, the third determining subunit is specifically configured to:

[0181] The initial second endpoint of the first arc is determined based on the following formula:

[0182]

[0183] Among them, x j 、y j and θ j are respectively the abscissa, ordinate and heading angle of the initial second endpoint of the first arc in a coordinate system with the current path node as a vertex;

[0184] and are the horizontal coordinate, vertical coordinate and heading angle of the current path node respectively; R is the radius of the circle where the target arc is located, and Δθ is the current center angle.

[0185] like Figure 13 As shown, an embodiment of the present application provides an electronic device, including a processor 111, a communication interface 112, a memory 113 and a communication bus 114, wherein the processor 111, the communication interface 112, and the memory 113 communicate with each other through the communication bus 114.

[0186] Memory 113, for storing computer programs;

[0187] In one embodiment of the present application, the processor 111 is configured to execute a program stored in the memory 113 to implement the path planning method provided by any of the aforementioned method embodiments, including:

[0188] Starting from the preset starting position, the iteration process is performed using the following steps until the set iteration stop condition is met:

[0189] Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process;

[0190] In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius of the first clothoid curve at the second endpoint and the instantaneous radius of the second clothoid curve at the first endpoint meet an equality condition; and the second endpoint of the second clothoid curve is the new path node;

[0191] After the iteration is completed, the target planning path is determined based on the path segments between multiple path nodes.

[0192] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the parking path processing method provided in any of the aforementioned method embodiments are implemented.

[0193] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0194] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a general hardware platform, or of course, by hardware. Based on this understanding, the above technical solution, in essence, or the part that contributes to the relevant technology, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiment.

[0195] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "comprise", "include", "contain" and "have" are inclusive and therefore specify the presence of stated features, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring them to be performed in the specific order described or illustrated, unless the order of execution is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0196] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A path planning method, characterized in that: include: Starting from the preset starting position, the iteration process is performed using the following steps until the set iteration stop condition is met: Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process; In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet an equality condition; and the second endpoint of the second clothoid curve is the new path node; After the iteration is completed, the target planning path is determined based on the path segments between multiple path nodes.

2. The method according to claim 1, characterized in that The method of using a combined curve consisting of at least a first clothoid curve and a second clothoid curve to extend the path toward the sampling point to obtain a new path node includes: determining a first arc length of the first clothoid curve and a second arc length of the second clothoid curve; comparing the sum of the first arc length and the second arc length with a preset path sampling length; When it is found that the sum of the first arc length and the second arc length is greater than or equal to the path sampling length, a combined curve consisting of the first clothoid curve and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node; When it is found that the sum of the first arc length and the second arc length is less than the path sampling length, a combined curve consisting of the first clothoid curve, the target arc and the second clothoid curve is used to extend the path toward the sampling point to obtain a new path node.

3. The method according to claim 2, characterized in that The method of using a combined curve consisting of the first clothoid curve and the second clothoid curve to extend the path toward the sampling point to obtain a new path node includes: Taking the current path node as the first endpoint of a first clothoid curve, and determining the second endpoint of the first clothoid curve based on the first arc length; A symmetric operation is performed on the first clothoid curve based on the first connecting line to obtain a second clothoid curve; wherein the first endpoint of the second clothoid curve is the second endpoint of the first clothoid curve, and the second endpoint of the second clothoid curve is a new path node; and the first connecting line is a line between the first endpoint of the second clothoid curve and the center of the circle where the sampling point is located.

4. The method according to claim 3, characterized in that The determining the second endpoint of the first clothoid curve based on the first arc length includes: Using a preset sampling interval length as a current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length; modifying a current arc length of the first clothoid curve based on the sampling interval length, and determining whether the modified current arc length exceeds the first arc length; If not, then based on the changed current arc length, return to the operation of determining the initial second endpoint of the first convolution curve based on the current arc length, until the changed current arc length exceeds the first arc length, and determine the last initial second endpoint as the second endpoint of the first convolution curve.

5. The method according to claim 2, characterized in that The method of using a combined curve consisting of the first clothoid curve, the target arc, and the second clothoid curve to extend the path toward the sampling point to obtain a new path node includes: Taking the current path node as the first endpoint of a first clothoid curve, and determining the second endpoint of the first clothoid curve based on the path sampling length; Using the second endpoint of the first clothoid curve as the first endpoint of a target arc, determining the radius of the circle where the sampling point is located as the radius of the target arc, and determining the midpoint of the target arc based on the radius of the target arc and the first endpoint of the target arc; The first clothoid curve and the first circular arc are symmetrically operated based on the second connecting line to obtain the second circular arc and the second clothoid curve; wherein, the first circular arc is the circular arc between the first endpoint of the target circular arc and the midpoint of the target circular arc, and the second circular arc is the circular arc between the midpoint of the target circular arc and the second endpoint of the target circular arc; the second endpoint of the target circular arc is the first endpoint of the second clothoid curve, and the second endpoint of the second clothoid curve is a new path node; the second connecting line is the connecting line between the midpoint of the target circular arc and the center of the circle where the target circular arc is located.

6. The method according to claim 5, characterized in that The determining the midpoint of the target arc based on the radius of the target arc and the first endpoint of the target arc includes: Determining a maximum semi-center angle of the target arc based on a preset path sampling length, a sum of the first arc length and the second arc length, and a radius of the target arc; Using a preset arc sampling interval angle as the current center angle of the first arc, and determining an initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc; Modifying the current center angle of the first arc based on the arc sampling interval angle, and determining whether the modified current center angle exceeds the maximum semi-center angle; If not, based on the changed current center angle, return to the operation of determining the initial second endpoint of the first arc based on the current center angle, the first endpoint of the target arc, and the radius of the target arc, until the changed current center angle exceeds the maximum semi-center angle, and the last initial second endpoint is determined as the midpoint of the target arc.

7. The method according to claim 5, characterized in that The determining the second endpoint of the first clothoid curve based on the path sampling length includes: Using a preset sampling interval length as a current arc length of the first clothoid curve, and determining an initial second endpoint of the first clothoid curve based on the current arc length; modifying a current arc length of the first clothoid curve based on the sampling interval length, and determining whether the modified current arc length exceeds half of the path sampling length; If not, then based on the changed current arc length, return to the operation of determining the initial second endpoint of the first spiral curve based on the current arc length, until the changed current arc length exceeds half of the path sampling length, and determine the last initial second endpoint as the second endpoint of the first spiral curve.

8. The method according to claim 4 or 7, characterized in that The determining the initial second endpoint of the first clothoid curve based on the current arc length includes: The initial second endpoint of the first clothoid curve is determined based on the following formula: Among them, x i 、y i and θ i are respectively the abscissa, ordinate and heading angle of the initial second endpoint of the first clothoid curve in a coordinate system with the current path node as a vertex; Where A is the parameter of the first clothoid curve, Where V is the desired driving speed, γ is the steering ratio of the steering wheel angle to the front wheel angle, and L b is the vehicle wheelbase, ω is the maximum angular velocity, R is the radius of the circle where the sampling point is located, L is the first arc length, and S is the current arc length of the first clothoid curve.

9. The method according to claim 6, characterized in that The determining the initial second endpoint of the first arc based on the current central angle, the first endpoint of the target arc, and the radius of the target arc includes: The initial second endpoint of the first arc is determined based on the following formula: Among them, x j 、y j and θ j are respectively the abscissa, ordinate and heading angle of the initial second endpoint of the first arc in a coordinate system with the current path node as a vertex; and are the horizontal coordinate, vertical coordinate and heading angle of the current path node respectively; R is the radius of the circle where the target arc is located, and Δθ is the current center angle.

10. A path planning device, characterized in that: include: The iteration module is used to start from a preset starting position and perform iterative processing using the following steps until the set iteration stop condition is met: Determine a sampling point in the neighborhood of a current path node; wherein, in the first iteration process, the current path node is the starting position, and in non-first iteration processes, the current path node is a new path node obtained in the previous iteration process; In a case where the heading angle of the sampling point indicates that a turn is required, extending the path toward the sampling point using a combined curve consisting of at least a first clothoid curve and a second clothoid curve with the current path node as the starting endpoint to obtain a new path node, and determining the combined curve as a path segment connecting the current path node and the new path node; wherein the first endpoint of the first clothoid curve is the current path node, the instantaneous radius at the second endpoint of the first clothoid curve and the instantaneous radius at the first endpoint of the second clothoid curve meet an equality condition; and the second endpoint of the second clothoid curve is the new path node; The final path determination module is used to determine the target planning path based on the path segments between multiple path nodes after the iteration is completed.

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