Turning trajectory planning method for automatic driving

Abstract

The invention discloses a turning track planning method for automatic driving. The method comprises the following steps: S1, obtaining a global path according to a current position and a target point of a vehicle; s2, taking a path point closest to real-time positioning of the vehicle in the global path as a starting point, and obtaining a local forward global path and a local backward global path forwards and backwards; s3, generating a local frenet path in the forward direction and a local frenet path in the backward direction; s4, walking according to the local frenet path in the advancing direction, triggering a reversing mechanism, and calculating the local frenet path in the reversing direction; and S5, reversing according to the local frenet path in the reversing direction. The invention provides a track planning method which is different from an existing track planning method for setting a fixed backing route through parameter configuration, the motion fluency of the vehicle is improved, and the problem that the vehicle is caught in a forward and backward endless loop due to excessive dependence on parameters is avoided.

Description

Technical Field

[0001] The present invention relates to the field of autonomous driving technology, and in particular to a turning trajectory planning method for autonomous driving that conforms to vehicle kinematics and has an obstacle detection function during driving. Background Art

[0002] Steering planning for vehicles is one of the core of vehicle autonomous driving. It determines how the vehicle can turn safely and efficiently in a complex traffic environment and ensure the accuracy and stability of vehicle driving. In the field, the turning path is generally planned directly based on the "vehicle's own turning radius" and "the turning channel width required by the vehicle" calculated by the vehicle information, and the wheels are controlled to perform turning operations according to the planned turning path. When the vehicle's own turning radius is greater than the turning radius of the curve, the vehicle will cause a large lateral deviation when turning under normal trajectory planning and control. If it continues to drive, it will have a large deviation from the lane line and cannot pass through the curve smoothly. At this time, it may be necessary to control the vehicle to reverse to adjust the vehicle position. For the planning method of the reversing trajectory in this control part, the general technology in the field is to set a fixed reversing route through the curve through parameter configuration. The usual method is to let the vehicle retreat at a fixed angle and a fixed distance at a specified position to reverse. However, this method has poor generalization, and no dynamic local path planning is performed. In addition, the vehicle will trigger the reversing behavior after the forward operation, thus falling into a loop. Summary of the invention

[0003] The present invention provides a turning trajectory planning method for automatic driving, which is used to solve the technical problems mentioned in the background technology.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is: A turning trajectory planning method for autonomous driving comprises the following steps: S1. Searching for a global path in a map coordinate system in a global road network according to the current position of the vehicle and the target point, wherein the global path includes all path points from the current position of the vehicle to the target point and a number of path points that are searched in a direction in which the vehicle is reversing; S2. Find the path point closest to the vehicle in the global path according to the real-time positioning of the vehicle, take the path point as the starting point, and take several path points forward as the local forward global path; S3, generating a local frenet path in the forward direction according to the real-time positioning of the vehicle and the local forward global path; S4, controlling the vehicle to move along the local frenet path in the forward direction. During the process, when it is detected that the turning radius of the vehicle is greater than the turning radius of the curve, determining whether the lateral deviation of the vehicle exceeds the set threshold. If it does not exceed, the vehicle continues to move forward. If it exceeds, the reversing mechanism is triggered; S5. Calculate the local frenet path in the reversing direction according to the preset reversing mechanism, control the vehicle to reverse according to the local frenet path in the reversing direction, and after reversing until the set conditions are met, control the vehicle to continue moving forward according to the methods of S1 to S4.

[0005] As a further preferred embodiment of the above technical solution, in S5, the method for calculating the local Frenet path in the reversing direction according to the preset reversing mechanism includes: The path points of the local forward global path in the map coordinate system are converted to the base_link coordinate system, and the left or right turn of the vehicle is determined in the base_link coordinate system, and the coordinates of the path points are adjusted and transformed according to the judgment of the turning direction, and the adjusted and transformed base_link coordinate points are reconverted 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 reversing direction is formed according to the local backward global path.

[0006] As a further preferred embodiment of the above technical solution, the method for judging whether the vehicle is turning left or right in the base_link coordinate system includes: in the base_link coordinate system, calculating the average value of the y coordinates of the path points; if the average value of the y coordinates of the path points is greater than 0, it is judged that the vehicle is making a left turn; if the average value of the y coordinates of the path points is less than 0, it is judged that the vehicle is making a right turn.

[0007] As a further optimization of the above technical solution, the adjustment and transformation of the coordinates of the path point according to the judgment of the turning direction specifically means: if the vehicle is making a left turn, the y coordinate of the path point is subtracted by a set threshold value; if the vehicle is making a right turn, the y coordinate of the path point is increased by a set threshold value.

[0008] As a further preferred embodiment of the above technical solution, in S4, the set threshold is 0.5~1m.

[0009] 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 to 50 path points that continue to extend the search in the reversing direction of the vehicle. If the number of path points that can be extended to search is less than 30, the maximum value that can be extended to search is taken.

[0010] As a further optimization of the above technical solution, in S2, taking a number of path points forward specifically refers to taking 30 to 50 path points forward as local forward global paths respectively. If the number of path points that can be taken forward is less than 30, the maximum value that can be taken is taken.

[0011] As a further preferred embodiment of the above technical solution, the spacing between adjacent path points is 40~60cm.

[0012] The present invention has the following beneficial effects: The present invention provides a method for planning a turning trajectory in automatic driving that is different from the existing method of setting a fixed reversing route through parameter configuration. A local reversing path is dynamically generated according to the current position and orientation of the vehicle to perform reversing, thereby improving the smoothness of the vehicle's movement when reversing, being more in line with vehicle kinematics, and avoiding the adverse effects caused by over-reliance on parameters. The processed reversing trajectory will be more consistent with the ideal turning route, and the vehicle will adjust the direction of the front of the vehicle after each reversing, so that the vehicle will not fall into an endless loop of moving forward and backward, and the turning radius of the curve is increased in disguise.

[0013] The present invention will be further described in detail below with reference to specific implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a global path and vehicle positioning of a turning trajectory planning method for autonomous driving in Example 1; Figure 2 A schematic diagram of a local forward path and a global path of the turning trajectory planning method for autonomous driving in Example 1; Figure 3 A schematic diagram of a reversing trajectory after being planned by the turning trajectory planning method for autonomous driving according to Example 1; Figure 4 Schematic diagram of the reversing trajectory planned for the conventional method. DETAILED DESCRIPTION

[0015] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0016] Embodiment 1: A turning trajectory planning method for autonomous driving in this embodiment includes the following steps: S1 searches for a global path in the map coordinate system based on the vehicle's current position (in this embodiment, the vehicle's position and positioning are obtained based on RTK positioning technology) and the target point in the global road network (the spacing between adjacent path points in the global road network is 40 cm). The global path includes all path points from the vehicle's current position to the target point and 30 path points that are extended backward (i.e., in the direction of vehicle reversing). The extension method can be extended according to the curvature of the global path or by interpolation between two points. S2. Find the path point closest to the vehicle in the global path according to the real-time positioning of the vehicle. Take this path point as the starting point, and take 30 path points forward and backward as the local forward global path and the local backward global path, respectively. Figure 1 and Figure 2 As shown, Figure 1 The middle red mark is the vehicle location, the sky blue mark is the point on the global road network closest to the vehicle location, the yellow mark is the target point on the global road network, and the dark blue mark represents a segment of the global path; Figure 2 The white matrix boxes in the middle represent vehicles, the white dots represent the global path, the green dots covering the white global path are the local forward paths, and the green road segments on both sides of the local forward paths are the road boundaries; S3, generating a local frenet path in the forward direction and a 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; S4, control the vehicle to move along 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 offset of the vehicle gradually increases (i.e., the offset value between the vehicle position and the center line of the curve). When it exceeds the set threshold (0.5m), the reversing mechanism is triggered, and the local Frenet path in the reversing direction is calculated according to the turning direction and the threshold. The turning direction is determined as follows: if the average value of the y coordinates of the path points is greater than 0, it is determined that the vehicle is making a left turn, and if the average value of the y coordinates of the path points is less than 0, it is determined that the vehicle is making a right turn. The method of the local frenet path in the reverse direction is as follows: the path points of the local forward global path in the map coordinate system are converted to the base_link coordinate system, the average value of the y coordinates of the path points is calculated, the turning direction of the vehicle is determined according to the average value, and the y coordinates of the path points are adjusted and transformed according to the turning direction and the threshold (in this embodiment, if the vehicle is making a right turn, 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 subtracted by the threshold value 0.5), the adjusted and transformed base_link coordinate points are reconverted to the path points in the map coordinate system, the path points form a new local backward global path, and the local frenet path in the reverse direction is formed according to the new local backward global path; S5, control the vehicle to reverse according to the local frenet path in the reverse direction. The actual path of the vehicle turning in this embodiment is as follows: Figure 3 As shown in the figure, the actual path using the conventional method (parameter setting fixed turning path) is as follows Figure 4 As shown, Figure 3 and Figure 4The middle blue is the reversing path, and the green is the forward trajectory and the road boundary line. It can be seen that when the present embodiment controls the vehicle to reverse, the reversing trajectory converges better with the reference line; when reversing reaches the set condition, the reversing is stopped (for example, the lateral deviation, the vehicle heading angle, and the angle difference between the heading angles of the nearest matching point in the local global path meet the set thresholds), and the vehicle moves forward again according to the S1-S3 method.

[0017] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

[0018] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A turning trajectory planning method for autonomous driving, characterized in that: The following steps are involved: S1. Searching for a global path in a map coordinate system in a global road network according to the current position of the vehicle and the target point, wherein the global path includes all path points from the current position of the vehicle to the target point and a number of path points that are searched in a direction in which the vehicle is reversing; S2. Find the path point closest to the vehicle in the global path according to the real-time positioning of the vehicle, take the path point as the starting point, and take several path points forward as the local forward global path; S3, generating a local frenet path in the forward direction according to the real-time positioning of the vehicle and the local forward global path; S4, controlling the vehicle to move along the local frenet path in the forward direction. During the process, when it is detected that the turning radius of the vehicle is greater than the turning radius of the curve, determining whether the lateral deviation of the vehicle exceeds the set threshold. If it does not exceed, the vehicle continues to move forward. If it exceeds, the reversing mechanism is triggered; S5. Calculate the local frenet path in the reversing direction according to the preset reversing mechanism, control the vehicle to reverse according to the local frenet path in the reversing direction, and after reversing until the set conditions are met, control the vehicle to continue moving forward according to the methods of S1 to S4.

2. The turning trajectory planning method for automatic driving according to claim 1, characterized in that: In the S5, the method for calculating the local frenet path in the reversing direction according to the preset reversing mechanism includes: converting the path points of the local forward global path in the map coordinate system to the base_link coordinate system, judging whether the vehicle turns left or right in the base_link coordinate system, and adjusting and transforming the coordinates of the path points according to the judgment of the turning direction, and reconverting the adjusted and transformed base_link coordinate points into path points in the map coordinate system, the path points form a local backward global path, and forming a local frenet path in the reversing direction according to the local backward global path.

3. The turning trajectory planning method for automatic driving according to claim 2, characterized in that: The method for judging whether a vehicle is turning left or right in a base_link coordinate system comprises: in the base_link coordinate system, calculating the average value of the y coordinates of the path points, and judging that the vehicle is turning left if the average value of the y coordinates of the path points is greater than 0, and judging that the vehicle is turning right if the average value of the y coordinates of the path points is less than 0.

4. The turning trajectory planning method for automatic driving according to claim 3, characterized in that: The adjustment and transformation of the coordinates of the path point according to the judgment of the turning direction specifically means: if the vehicle is making a left turn, the y coordinate of the path point is subtracted by a set threshold value; if the vehicle is making a right turn, the y coordinate of the path point is increased by a set threshold value.

5. The turning trajectory planning method for automatic driving according to claim 4, characterized in that: The set threshold is 0.5~1m.

6. The turning trajectory planning method for autonomous driving according to any one of claims 1 to 5, characterized in that: In S1, the global path includes all path points from the current position of the vehicle to the target point and 30 to 50 path points that continue to be searched in the reverse direction of the vehicle. If the number of path points that can be searched is less than 30, the maximum value that can be searched is taken.

7. The turning trajectory planning method for autonomous driving according to any one of claims 1 to 5, characterized in that: In S2, taking a number of path points forward specifically refers to taking 30 to 50 path points forward as local forward global paths respectively. If the number of path points that can be taken forward is less than 30, the maximum value that can be taken is taken.

8. The turning trajectory planning method for autonomous driving according to any one of claims 1 to 4, characterized in that: The distance between adjacent path points is 40-60 cm.

Images