An automatic driving turning trajectory planning method

Abstract

The application discloses a kind of automatic driving's turning trajectory planning method, comprising: S1, according to the current position of vehicle and target point obtains global path;S2, with the nearest path point in global path of real-time positioning of vehicle as starting point, obtain local forward global path and local backward global path forward and backward;S3, generate the local frenet path of advancing direction and the local frenet path of retreating direction;S4, according to the local frenet path of advancing direction, trigger the mechanism of reversing, calculate the local frenet path of reversing direction;S5, according to the local frenet path of reversing direction, reverse.The application provides a kind of trajectory planning method different from existing fixed reversing route by parameter configuration setting, improves the motion fluency of vehicle, avoids the problem that makes vehicle fall into advancing and retreating dead cycle caused by too much dependence on parameter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automatic driving, and in particular to a turning trajectory planning method for automatic driving in compliance with vehicle kinematics and with obstacle detection function in the driving process. BACKGROUND

[0002] Turning planning for a vehicle is one of the cores of automatic driving of the vehicle, which determines how the vehicle safely and efficiently turns in a complex traffic environment, and guarantees the accuracy and stability of driving of the vehicle. In the field, a turning path is generally planned according to a “turning radius of the vehicle itself” and a “turning channel width required by the vehicle” calculated according to vehicle information, and a wheel is controlled to perform a turning operation according to the planned turning path. When the turning radius of the vehicle itself is greater than the turning radius of a curve, a turning of the vehicle under normal trajectory planning and control will cause a large lateral deviation, and if the vehicle continues to drive, the vehicle will deviate greatly from a lane line and cannot pass through the curve smoothly, in which case the vehicle may need to be controlled to reverse to adjust the position of the vehicle. For the planning method of the reverse trajectory in the control part, a general technology in the field is to set a fixed reverse route to pass through the curve by parameter configuration, and a common method is to let the vehicle retreat a fixed distance at a fixed angle at a specified position to reverse, but this method has poor generalization, and no dynamic local path planning is performed, and the vehicle will trigger the reverse behavior after the forward operation, thereby falling into a cycle. SUMMARY

[0003] The present application provides a turning trajectory planning method for automatic driving to solve the technical problems mentioned in the background.

[0004] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0005] A turning trajectory planning method for automatic driving, comprising the following steps:

[0006] S1. searching for a global path in a map coordinate system according to a current position of a vehicle and a target point in a global road network, the global path comprising all path points from the current position of the vehicle to the target point and a plurality of path points searched in a direction of reverse driving of the vehicle from the path points;

[0007] S2. finding a path point closest to the vehicle in the global path according to real-time positioning of the vehicle, and taking a plurality of path points in front of the path point as a local forward global path;

[0008] S3. generating a local frenet path in a forward direction according to the real-time positioning of the vehicle and the local forward global path;

[0009] S4, control the vehicle to walk according to the local frenet path in the forward direction, and when the turning radius of the vehicle collected in the process is greater than the turning radius of the curve, it is judged whether the lateral deviation of the vehicle exceeds the set threshold value, and if not, the vehicle continues to move forward, and if so, the reverse mechanism is triggered;

[0010] S5, according to the preset reverse mechanism, the local frenet path in the reverse direction is calculated, and the vehicle is controlled to reverse according to the local frenet path in the reverse direction. When the vehicle reverses to meet the set conditions, the vehicle continues to move forward according to the method of S1 to S4.

[0011] As a further preferred embodiment of the above technical solution, in S5, the method of calculating the local frenet path in the reverse direction according to the preset reverse mechanism comprises:

[0012] Convert the path points of the local forward global path in the map coordinate system to the base_link coordinate system, judge whether the vehicle is turning left or right in the base_link coordinate system, and adjust and transform the coordinates of the path points according to the judgment of the turning direction, and convert the base_link coordinate points after adjustment and transformation to the path points in the map coordinate system. The path points form a local backward global path, and a local frenet path in the reverse direction is formed according to the local backward global path.

[0013] As a further preferred embodiment of the above technical solution, the method of judging whether the vehicle is turning left or right in the base_link coordinate system comprises: calculating the average value of the y coordinates of the path points in the base_link coordinate system, and if the average value of the y coordinates of the path points is greater than 0, it is judged that the vehicle is turning left, and if the average value of the y coordinates of the path points is less than 0, it is judged that the vehicle is turning right.

[0014] As a further preferred embodiment of the above technical solution, the adjustment and transformation of the coordinates of the path points according to the judgment of the turning direction specifically means: if the vehicle is turning left, the y coordinate of the path point is reduced by a set threshold value, and if the vehicle is turning right, the y coordinate of the path point is increased by a set threshold value.

[0015] As a further preferred embodiment of the above technical solution, in S4, the set threshold value is 0.5-1m.

[0016] As a further preferred embodiment of the above technical solution, in S1, the global path includes all path points from the current position of the vehicle to the target point and 30-50 path points extended in the reverse direction of the vehicle, and if the number of path points that can be extended is less than 30, the maximum value that can be extended is taken.

[0017] As a further preferred embodiment of the above technical solution, the S2 is characterized in that the number of the path points taken in the front direction is 30-50, and if the number of the path points taken in the front direction is less than 30, the maximum number of the path points taken in the front direction is taken.

[0018] As a further preferred embodiment of the above technical solution, the distance between the adjacent path points is 40-60 cm.

[0019] The present application has the following advantages:

[0020] The present application provides a planning method for the turning trajectory of automatic driving, which is different from the existing method of setting a fixed reversing route through parameter configuration, and generates a local path for reversing according to the current position and orientation of the vehicle, thereby improving the smoothness of the vehicle during reversing, being more consistent with the kinematics of the vehicle, avoiding the adverse effects caused by excessive dependence on parameters, and making the processed reversing trajectory more consistent with the ideal turning route, and adjusting the orientation of the vehicle after each reversing, so that the vehicle does not fall into a dead cycle of advancing and retreating, and the turning radius of the curve is also increased.

[0021] The present application will be further described in detail with reference to the specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a schematic diagram of the global path and vehicle positioning of the turning trajectory planning method of automatic driving according to Embodiment 1;

[0023] Figure 2 FIG. 2 is a schematic diagram of the local forward path and global path of the turning trajectory planning method of automatic driving according to Embodiment 1;

[0024] Figure 3 FIG. 3 is a schematic diagram of the reversing trajectory planned by the turning trajectory planning method of automatic driving according to Embodiment 1;

[0025] Figure 4 FIG. 4 is a schematic diagram of the reversing trajectory planned by the conventional method. DETAILED DESCRIPTION

[0026] The embodiments of the present application will be described in detail below with reference to the accompanying drawings, but the present application can be implemented in various different ways as limited and covered by the claims.

[0027] Embodiment 1:

[0028] The turning trajectory planning method of automatic driving according to the present embodiment includes the following steps:

[0029] S1 searches for a global path in the global road network (the distance between adjacent path points in the global road network is 40 cm) according to the current position of the vehicle (in this embodiment, the position and location of the vehicle are obtained based on RTK positioning technology) and the target point, and the global path includes all path points from the current position of the vehicle to the target point and 30 path points searched by extending the path points backward (i.e. in the reverse direction of the vehicle);

[0030] S2 finds the path point closest to the vehicle in the global path according to the real-time positioning of the vehicle, takes 30 path points forward and backward respectively as the local forward global path and the local backward global path with the path point as the starting point, as shown in Figure 1 and Figure 2 Figure 1 In the figure, the red mark represents the vehicle positioning, the sky blue mark represents the point in the global road network closest to the vehicle positioning, the yellow mark represents the target point on the global road network, and the dark blue mark represents a section of the global path. Figure 2 In the figure, the white matrix box represents the vehicle, the white point represents the global path, the green point overlaid on the white global path is the local forward path, and the green road section on both sides of the local forward path is the road boundary.

[0031] S3 generates the local frenet path in the forward direction and the local frenet path in the backward direction according to the real-time positioning of the vehicle and the local forward global path and the local backward global path.

[0032] S4 controls the vehicle to walk according to the local frenet path in the forward direction, when the turning radius of the vehicle is greater than the turning radius of the curve, the lateral deviation of the vehicle gradually increases (i.e. the deviation value of the vehicle position from the center line of the curve), when it exceeds the set threshold value (0.5 m), the reverse mechanism is triggered, and the local frenet path in the backward direction is calculated according to the turning direction and the threshold value; wherein the judgment method of the turning direction is: if the average value of the y coordinate of the path point is greater than 0, it is judged that the vehicle is making a left turn, and if the average value of the y coordinate of the path point is less than 0, it is judged that the vehicle is making a right turn.

[0033] ​The method of the local frenet path in the reversing direction is: converting the path point of the local forward global path in the map coordinate system into the base_link coordinate system, calculating the average value of the y coordinate of the path point, judging the turning direction of the vehicle according to the average value, and adjusting and transforming the y coordinate of the path point according to the turning direction and the threshold value (in this embodiment, the vehicle is turning right, so the y coordinate of the path point is increased by the threshold value 0.5, and if it is turning left, the y coordinate is reduced by the threshold value 0.5), converting the base_link coordinate point after the adjustment and transformation into the path point in the map coordinate system, the path point forms a new local backward global path, and the local frenet path in the reversing direction is formed according to the new local backward global path;

[0034] S5, control the vehicle to reverse according to the local frenet path in the reversing direction, the actual path of the vehicle turning in this embodiment is as shown in Figure 3 , the actual path using the conventional method (fixed parameter setting turning path) is as shown in Figure 4 , Figure 3 and Figure 4 The blue in the above is the reversing path, and the green is the forward trajectory and the road boundary line. It can be seen that when the vehicle is controlled to reverse in this embodiment, the reversing trajectory is better converged on the reference line; when the vehicle is reversed to the set condition (for example, the parameters such as the lateral deviation, the vehicle orientation angle and the included angle difference of the orientation angle of the nearest matching point in the local global path meet the set threshold value), the vehicle stops reversing, and then proceeds according to the method of S1-S3.

[0035] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiments. Improvements and changes made by those skilled in the art without departing from the technical concept of the present application should also be considered as the protection scope of the present application.

[0036] Although the embodiments of the present application have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present application.

Claims

1. An automatic driving turn trajectory planning method, characterized by, The method comprises the following steps: S1, searching for a global path in a map coordinate system according to a current position of a vehicle and a target point, the global path comprising all path points from the current position of the vehicle to the target point and a plurality of path points searched in a direction opposite to a direction in which the vehicle is moving; S2, finding a path point closest to the vehicle in the global path according to real-time positioning of the vehicle, taking a plurality of path points in front of the path point as a local forward global path; S3, generating a local frenet path in a forward direction according to real-time positioning of the vehicle and the local forward global path; S4, controlling the vehicle to move according to the local frenet path in the forward direction, and when a turning radius of the vehicle is greater than a turning radius of a curve, determining whether a lateral deviation of the vehicle exceeds a preset threshold value, and if not, continuing to move forward, and if so, triggering a reverse mechanism; S5, calculating a local frenet path in a reverse direction according to a preset reverse mechanism, controlling the vehicle to move in the reverse direction according to the local frenet path in the reverse direction, and when a preset condition is met, controlling the vehicle to continue to move forward according to the method of S1 to S4, the method of calculating the local frenet path in the reverse direction according to the preset reverse mechanism comprising: converting the path points of the local forward global path in the map coordinate system into a base_link coordinate system, determining whether the vehicle is turning left or right in the base_link coordinate system, adjusting and transforming the coordinates of the path points according to the determination of the turning direction, converting the base_link coordinate points after the adjustment and transformation into the path points in the map coordinate system again, the path points forming a local backward global path, and forming the local frenet path in the reverse direction according to the local backward global path. 2.The automatic driving turning trajectory planning method of claim 1, wherein, The method of determining whether the vehicle is turning left or right in the base_link coordinate system comprises: calculating an average value of y coordinates of the path points in the base_link coordinate system, and if the average value of the y coordinates of the path points is greater than 0, determining that the vehicle is turning left, and if the average value of the y coordinates of the path points is less than 0, determining that the vehicle is turning right. 3.The automatic driving turning trajectory planning method of claim 2, wherein, The adjustment and transformation of the coordinates of the path points according to the determination of the turning direction specifically means: if the vehicle is turning left, subtracting a preset threshold value from the y coordinates of the path points, and if the vehicle is turning right, adding a preset threshold value to the y coordinates of the path points.

4. The automatic driving turning trajectory planning method according to claim 3, characterized in that, The preset threshold value is 0.5-1 m.

5. The method of claim 1-4, wherein, In S1, the global path comprises all path points from the current position of the vehicle to the target point and 30-50 path points searched in the direction opposite to the direction in which the vehicle is moving, and if the number of the path points that can be searched is less than 30, the maximum number of the path points that can be searched is taken.

6. The method of claim 1-4, wherein, In S2, the plurality of path points taken in front specifically means 30-50 path points taken in front, and if the number of the path points that can be taken in front is less than 30, the maximum number of the path points that can be taken is taken.

7. The method of claim 1-4, wherein, The distance between adjacent path points is 40-60 cm.

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