CN113741463B - Fixed-point and directional parking control method and system for unmanned ground maneuvering platform - Google Patents
Fixed-point and directional parking control method and system for unmanned ground maneuvering platform Download PDFInfo
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Abstract
The application discloses a fixed-point directional parking control method and a system for an unmanned ground maneuvering platform, wherein the method comprises the following steps: s1, acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path; s2, the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned; s3, the vehicle runs according to the generated new path, and the judgment and switching of the reversing working condition are carried out in the running process; s4, returning the vehicle according to the original path of the virtual path, and stopping at a preset end position with a preset course. The application can greatly reduce the position deviation of the actual parking point and the preset target point in space, and can also ensure that the course gesture of the unmanned ground maneuvering platform when parking is in an error allowable range with the preset course gesture deviation.
Description
Technical Field
The application relates to parking control, in particular to a fixed-point directional parking control method and system for an unmanned ground maneuvering platform.
Background
Along with the acceleration of the intelligent age, the unmanned ground maneuvering platform has wider application scenes. For the unmanned logistics distribution vehicle in a low-speed scene, only a target point for driving needs to be set manually, and the unmanned ground maneuvering platform can be planned autonomously and can reach the vicinity of the target point along the planned path. For a general unmanned ground mobile platform, the following problems exist in the process of reaching the vicinity of the end point of a path and judging that the vehicle is stopped, namely:
1. the existing parking criteria are all that whether the vehicle position is in a circular area with a certain error threshold value as a radius by judging whether the vehicle position is in the circular area with a path end point as the center of a circle, and if the vehicle position is in the circular area, parking is judged. Therefore, the unmanned ground maneuvering platform has larger deviation in space position from the actually preset path end point when parking.
2. In most scenes, the unmanned ground maneuvering platform is expected to keep a preset heading gesture when parking, so that convenience is brought to the development of subsequent related works, but the function is difficult to realize by using a traditional method.
Disclosure of Invention
The application aims to overcome the defects of the prior art, and provides a fixed-point directional parking control method and a fixed-point directional parking control system for an unmanned ground maneuvering platform, which can greatly reduce the position deviation of an actual parking point and a preset target point in space, and can also ensure that the course gesture of the unmanned ground maneuvering platform during parking and the preset course gesture deviation are in an error allowable range.
The aim of the application is realized by the following technical scheme: a fixed-point directional parking control method of an unmanned ground maneuvering platform comprises the following steps:
s1, acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path;
s101, acquiring original path information of a navigation plan, wherein the original path information comprises preset path end point coordinates, a heading, an error threshold and environment information of a space around the path end point when parking is scheduled; the environmental information of the surrounding space includes obstacle information and infeasible area information;
s102, generating rays by taking a terminal point as an end point and a preset parking heading as a direction, taking a section of straight line path with the length of 5m, and performing circular area collision detection on the path, namely taking each point on the path as a circle center and taking a collision radius r=1.2m as a circle; if no obstacle information or no feasible area information exists in all the areas of the circumference envelope, the obtained straight line path with the length of 5m is taken as a virtual path through collision detection; otherwise, the collision detection is not passed, and the step S103 is entered;
s103, directly performing linear expansion and failing to pass collision detection, performing arc expansion firstly, and knowing that the maximum value delta exists in the front wheel steering angle according to the vehicle structure max By taking the original path end point as a tangent point and the required parking heading as a tangential direction, sequentially traversing the front wheel rotation angle delta of the vehicle from 5 degrees to 5 degrees as step length, namely sequentially enabling delta to be 1 ＝5°、δ 2 ＝10°、δ 3 ＝15°、δ 4 ＝20°、δ 5 =25°, substitutedObtaining corresponding turning radius valueR i The central angle theta is traversed by a step length of 15 degrees from 30 degrees, and a turning radius R i And an arc central angle theta i Correspondingly generating a section of arc track, taking the end point of the arc as an end point and taking rays along the tangential direction of the end point of the arc, and taking a section of 10m long straight line path from the end point, so as to obtain a section of arc and straight line spliced path; performing collision detection in step S102 on the generated virtual path, if the generated virtual path passes the collision detection, taking the spliced path as the virtual path, and if the generated virtual path does not pass the collision detection, continuing to traverse R i And theta i Searching for a path.
S2, the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
returning several control parameters and path information, including:
end position coordinates (x end ，y end )
Preset heading θ of vehicle at stop 0
If the virtual path includes a circular arc segment, the following parameters need to be returned additionally:
generating a front wheel angle delta corresponding to the arc section path i ，
The end point of the path of the circular arc segment, i.e. the coordinate (x) of the tangent point of the path of the circular arc segment with the path of the straight line segment in the virtual path r ，y r )。
S3, the vehicle runs according to the generated new path, and the judgment and switching of the reversing working condition are carried out in the running process:
s301, judging whether the vehicle reaches a straight line segment part of the virtual path or not according to the relative position relation between the position coordinates of the vehicle and the coordinates of straight line segment path points in the virtual path, if so, entering a step S302, and if not, performing loop judgment according to the step S301;
s302, calculating the deviation e of the heading of the vehicle and the preset heading under the condition that the sampling period t=0.05s 0 Lateral deviation e of position coordinates of center of rear wheel of vehicle from closest point on straight line path 1 Deviation e 0 I.e. heading angle and straightness of the vehicleDeviation value of direction angle of line segment path, transverse deviation e 1 I.e. the deviation value of the position of the central point of the rear wheel of the vehicle and the nearest point of the path in the Y direction under the coordinate system of the vehicle, if the heading is deviated e 0 Less than the error threshold delta 0 Lateral deviation value e 1 Less than the error threshold delta 1 I.e. e 0 ＜Δ 0 &e 1 ＜Δ 1 Step S303 is carried out if the reversing judgment condition is met, otherwise, the monitoring course deviation and the transverse deviation are calculated in a circulating mode;
s303, controlling a vehicle chassis, braking the vehicle to reduce the speed to 0, switching to a reverse gear working condition, and controlling the motor to rotate reversely in the subsequent movement.
S4, returning the vehicle according to the original path of the virtual path, and stopping at a preset end position with a preset course:
s401, judging the type of the virtual path, if the virtual path is a straight path, entering a step S402, and if the virtual path is a spliced path of a circular arc section and a straight line, entering a step S403;
s402, calculating the position coordinates of the center of the rear wheel of the vehicle and the original path end point (x) at the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 If the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, and if the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, otherwise, stopping the vehicle until the vehicle is stopped, and continuously monitoring the distance;
s403, calculating the tangential point (x) of the position coordinates of the center of the rear wheel of the vehicle and the tangent point of the straight line segment path and the circular arc segment path at the sampling period t=0.05s r ，y r ) If the calculated value is less than the error threshold delta 2 If the arc reversing condition is met, the step S404 is entered, otherwise, the vehicle is reversed straight and the distance is monitored;
s404, adjusting the front wheel steering angle to the front wheel steering angle delta of the generated circular arc section path, continuing reversing and calculating the position coordinates of the rear wheel center of the vehicle and the original path end point (x) under the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 And if the vehicle is stopped, stopping the vehicle until the vehicle is stopped, otherwise, continuing reversing the vehicle and monitoring the distance all the time.
A fixed point directional parking control system for an unmanned ground motorized platform, comprising:
the path expansion module is used for acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path; the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
the reversing working condition judging module is used for judging and switching reversing working conditions in the process of the vehicle according to the generated new path;
and the reversing working condition control module is used for enabling the vehicle to return according to the original path of the virtual path and stopping at a preset end position with a preset course.
The beneficial effects of the application are as follows: (1) The application provides a virtual path expansion mode, the original path is expanded to generate a new path, and the unmanned ground maneuvering platform can realize a high-precision fixed-point directional parking function by pre-aiming following and reversing back navigation on the new path.
(2) For the environment with barriers or infeasible areas in space, the application provides a mode of combining arc expansion and linear paths, which can avoid the barriers and infeasible areas in the environment and control the vehicle to realize the high-precision fixed-point directional parking function according to the original path return of the expanded virtual path.
(3) The control system designed by the application creatively provides double constraint of position and course in the reversing judgment module, ensures that the unmanned ground maneuvering platform is flush with the path to the greatest extent when the unmanned ground maneuvering platform runs on the straight line segment of the virtual path, (theoretically, zero-error parking can be realized if percentage coincidence can be realized), and can greatly reduce the position deviation and the angle deviation of reversing back to the end point of the original path.
Drawings
FIG. 1 is a schematic diagram of the Ackerman geometry;
FIG. 2 is a schematic diagram of a pure-pure algorithm;
FIG. 3 is a flow chart of the method of the present application;
FIG. 4 is a schematic diagram of an original path;
FIG. 5 is a schematic view of path expansion for unobstructed areas;
FIG. 6 is a schematic view of path expansion for an obstructed area;
FIG. 7 is a flow chart of a method of path expansion;
FIG. 8 is a flow chart of a method for determining a reverse operating condition;
FIG. 9 is a flow chart of a method of reverse operating mode control;
FIG. 10 is a schematic diagram of the overall design of the system and the control relationship with the on-board control core;
FIG. 11 shows the embodiment of the direct follow (l) in path 1 d ＝1.2m，Δ 2 =0.4m) simulation result diagram;
FIG. 12 is a schematic diagram of simulation results of two following modes in the path 1 of the embodiment;
FIG. 13 is a partial enlarged view of simulation results of two following modes in example path 1;
FIG. 14 is a schematic diagram of the simulation results of two following parking heading in embodiment Path 1;
FIG. 15 is a schematic diagram of the embodiment in path 2 following (l) d ＝1.2m，Δ 2 =0.1m) simulation result diagram;
FIG. 16 is a schematic diagram of simulation results of two following modes in the path 2 of the embodiment;
FIG. 17 is a partial enlarged view of simulation results of two following modes in example path 2;
FIG. 18 is a schematic diagram of the simulation results of two following modes of parking heading in embodiment Path 2.
Detailed Description
The technical solution of the present application will be described in further detail with reference to the accompanying drawings, but the scope of the present application is not limited to the following description.
The application designs a fixed-point directional parking control system which can be applied to a low-speed unmanned ground maneuvering platform, and can greatly reduce the position deviation of an actual parking point and a preset target point in space, and meanwhile, the heading gesture of the unmanned ground maneuvering platform during parking and the preset heading gesture deviation are ensured to be within an error allowable range. The method is beneficial to improving the motion precision of the unmanned ground maneuvering platform and the functional comprehensiveness of the unmanned ground maneuvering system, improves the social production efficiency and the liberation productivity, and has important practical significance and engineering application value;
according to the Ackerman geometry principle (as shown in figure 1), the following kinematic equation is satisfied for the front wheel steering angle under low speed conditions (v < 10 km/h).
Wherein: r is the turning radius of the ground maneuvering platform.
The maximum limit value delta exists in the front wheel steering angle of a vehicle steering based on the Ackerman principle due to the constraint of the mechanical structure of the vehicle max Thus there is a minimum value R for the turning radius min In-situ steering cannot be achieved.
Wherein delta max ＝25°，R min ＝1.7m
According to the traditional pure-pure algorithm, a four-wheel unmanned ground maneuvering platform is simplified into a double-shaft model (bicycle model), and the control scheme of the algorithm is that a fixed pretightening distance l is preset d According to the pretightening distance l d And a vehicle rear wheel center point (g) e ，g n ) Pretightening point (g) x ，g y ) The relative geometrical relationship between them solves for the theoretical value of the front wheel rotation angle, as shown in fig. 2.
From geometrical relationships
Is simultaneously available with (1)
Namely:
wherein: delta (t) is the front wheel steering angle
L is the wheelbase, namely the distance between the front axle and the rear axle of the ground maneuvering platform
(g x ，g y ) Preview point for pure-pure algorithm
l d For pretightening distance, i.e. pretightening point (g x ，g y ) To the centre point (g) e ，g n ) Distance of (2)
Alpha (t) is the included angle between the connecting line of the pretightening point and the central point of the rear wheel of the ground maneuvering platform and the heading of the vehicle
As can be seen from equation (2), when the pre-aiming distance l of the vehicle d Smaller, the front wheel rotation angle δ is larger, and the front wheel rotation angle maximum value δ is larger max =25°. Therefore, when the path end point is near, the traditional pure-pure algorithm always pretightens the end point of the path, and pretightens the distance l d When the theoretical value delta (t) of the vehicle rotation angle obtained by the solution of the formula (2) is smaller than the limit value delta of the front wheel rotation angle max In this case, the vehicle cannot turn according to the predetermined calculated angle δ (t) due to its own structure, resulting in failure of the conventional pure-pure algorithm.
Meanwhile, the existing parking decision strategy is: when the position of the center point of the rear wheel of the unmanned ground maneuvering platform is within a certain range r of the end point of the path 0 And judging that the vehicle is stopped when the vehicle is in the inner state. Such a processing mode is on the one hand within the design error range r 0 When a large amount of optimization work is needed, r 0 Too large will cause too large a position error in parking, r 0 If too small, the vehicle can not always reach the judging condition of parking, and the vehicle turns around the end point. Meanwhile, different parameters r need to be selected for different paths and different vehicle models 0 Thus the algorithm is less efficientThe application range is limited.
In the application, a fixed-point directional parking control scheme is designed, an original path obtained through planning is expanded, a section of virtual path is obtained through path expansion after the end point of the original path, and a new path is obtained by splicing the virtual path and the original path. When the heading gesture and the position deviation of the vehicle meet certain judging conditions, the running working condition of the vehicle is switched to a reversing working condition, and the vehicle returns along the original path of the virtual path, so that the vehicle is ensured to realize fixed-point directional parking at the road end point according to a preset track and heading, and the fixed-point directional parking function of the unmanned ground maneuvering platform is realized, and specifically:
as shown in fig. 3, a fixed-point directional parking control method of an unmanned ground maneuvering platform comprises the following steps:
s1, acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path;
the original path and the preset heading are shown in fig. 4, and the fixed-point directional parking system can ensure that the vehicle parks in a very small error limit near the preset end point and ensure that the deviation between the heading during parking and the preset parking heading is also in an allowable error range.
And (3) performing path expansion on the original path to obtain a section of virtual path, wherein the virtual path and the original path are combined to form a new path, and the end point of the original path is used as a path point in the new path. When the distance from the unmanned ground maneuvering platform to the original path end point is smaller than the pretightening distance l d When the pre-aiming point of the pure-pure algorithm is located on the virtual path. The function of path expansion is to find a feasible virtual path with a relatively short length to join with the original path, and generate a new path.
The design strategy for path expansion is as follows:
1.1 if the space around the end point is unobstructed (the space around is all feasible), the path that is extended is a straight line on a ray. The starting point of the ray is the end point of the original path, the direction of the ray is the heading of the unmanned ground maneuvering platform during the preset parking, and the new path obtained by expansion is shown in fig. 5.
1.2 if there is an obstacle in the space around the end point (when there is an infeasible domain in the surrounding space), the extended virtual path is a path obtained by splicing a section of circular arc and a ray. The starting point of the circular arc line is the end point of the original path, and the circular arc line is tangent with a preset course when the vehicle stops. Presetting the front wheel rotation angle delta 0 (the angle value needs to be optimized) steering to form a section of circular arc track with the central angle theta (the angle value needs to be optimized). The arc path is utilized to avoid the obstacle area (infeasible area), then the end point of the arc is used to make a tangent line, and a section of straight line path is taken from the tangent line, so that an expanded virtual path is obtained as shown in fig. 6.
As shown in fig. 7, a specific method of path expansion is as follows:
s101, acquiring original path information of a navigation plan, wherein the original path information comprises preset path end point coordinates, a heading, an error threshold and environment information of a space around the path end point when parking is scheduled; the environmental information of the surrounding space includes obstacle information and infeasible area information;
s102, generating rays by taking a terminal point as an end point and a preset parking heading as a direction, taking a section of straight line path with the length of 5m, and performing circular area collision detection on the path, namely taking each point on the path as a circle center and taking a collision radius r=1.2m as a circle; if no obstacle information or no feasible area information exists in all the areas of the circumference envelope, the obtained straight line path with the length of 5m is taken as a virtual path through collision detection; otherwise, the collision detection is not passed, and the step S103 is entered;
s103, directly performing linear expansion and failing to pass collision detection, performing arc expansion firstly, and knowing that the maximum value delta exists in the front wheel steering angle according to the vehicle structure max By taking the original path end point as a tangent point and the required parking heading as a tangential direction, sequentially traversing the front wheel rotation angle delta of the vehicle from 5 degrees to 5 degrees as step length, namely sequentially enabling delta to be 1 ＝5°、δ 2 ＝10°、δ 3 ＝15°、δ 4 ＝20°、δ 5 =25°, substitutedObtaining corresponding turning radius value R i The central angle theta is traversed by a step length of 15 degrees from 30 degrees, and a turning radius R i And an arc central angle theta i Correspondingly generating a section of arc track, taking the end point of the arc as an end point and taking rays along the tangential direction of the end point of the arc, and taking a section of 10m long straight line path from the end point, so as to obtain a section of arc and straight line spliced path; performing collision detection in step S102 on the generated virtual path, if the generated virtual path passes the collision detection, taking the spliced path as the virtual path, and if the generated virtual path does not pass the collision detection, continuing to traverse R i And theta i Searching for a path.
S2, the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
returning several control parameters and path information, including:
end position coordinates (x end ，y end )
Preset heading θ of vehicle at stop 0
If the virtual path includes a circular arc segment, the following parameters need to be returned additionally:
generating a front wheel angle delta corresponding to the arc section path i ，
The end point of the path of the circular arc segment, i.e. the coordinate (x) of the tangent point of the path of the circular arc segment with the path of the straight line segment in the virtual path r ，y r )。
S3, the vehicle runs according to the generated new path, and the judgment and switching of the reversing working condition are carried out in the running process:
the function of the reversing working condition judgment is to judge when the operation working condition of the unmanned ground maneuvering platform is switched to the reversing working condition. The determination module is enabled when the vehicle is traveling to a straight line segment portion of the virtual path, when the vehicle coincides with a straight line segment in the virtual path (a lateral position deviation of a closest point on the straight line segment of the virtual path from a center point of a rear wheel of the vehicle is at an error threshold value delta 1 Within the range, course deviation is withinError threshold delta 0 In range), the module judges that the vehicle is effective, realizes the braking of the vehicle and switches to a reversing working condition;
as shown in fig. 8, the method for determining the reverse operation condition is as follows:
s301, judging whether the vehicle reaches a straight line segment part of the virtual path or not according to the relative position relation between the position coordinates of the vehicle and the coordinates of straight line segment path points in the virtual path, if so, entering a step S302, and if not, performing loop judgment according to the step S301;
s302, calculating the deviation e of the heading of the vehicle and the preset heading under the condition that the sampling period t=0.05s 0 Lateral deviation e of position coordinates of center of rear wheel of vehicle from closest point on straight line path 1 Deviation e 0 Namely, the deviation value of the heading angle of the vehicle and the direction angle of the straight-line path, and the lateral deviation e 1 I.e. the deviation value of the position of the central point of the rear wheel of the vehicle and the nearest point of the path in the Y direction under the coordinate system of the vehicle, if the heading is deviated e 0 Less than the error threshold delta 0 Lateral deviation value e 1 Less than the error threshold delta 1 I.e. e 0 ＜Δ 0 &e 1 ＜Δ 1 Step S303 is carried out if the reversing judgment condition is met, otherwise, the monitoring course deviation and the transverse deviation are calculated in a circulating mode;
s303, controlling a vehicle chassis, braking the vehicle to reduce the speed to 0, switching to a reverse gear working condition, and controlling the motor to rotate reversely in the subsequent movement.
S4, returning the vehicle according to the original path of the virtual path, and stopping at a preset end position with a preset course:
the process can be called reverse working condition control, and the function is to enable the vehicle to return according to the original path of the virtual path and stop at a preset end position with a preset course.
When the unmanned ground maneuvering platform is switched to a reversing working condition, the unmanned ground maneuvering platform has small lateral deviation and heading deviation from the straight line segment of the virtual path, and can be approximately considered to coincide with the straight line segment path. And in the straight line section part of the virtual path, reversing directly according to the straight line.
If the whole virtual path is straight, the virtual path reaches the rear wheel of the vehicleEnd point of heart and original path (x end ，y end ) Coincidence (position deviation at a minimum error threshold delta 2 Internal), namely realizing fixed-point directional parking.
If the whole virtual path is formed by splicing a straight line and an arc path, firstly, reversing the straight line until the center of the rear wheel of the vehicle reaches the tangent point (x) r ，y r ) (the positional deviation is at a very small error threshold DeltaA) 2 Inner), the front wheel steering angle is turned to the front wheel steering angle preset value delta of the previously generated path i Reversing is continued until the center of the rear wheel of the vehicle is away from the end point (x end ，y end ) Coincidence (position deviation at a minimum error threshold delta 2 Internal), namely realizing fixed-point directional parking.
As shown in fig. 9, the specific process of the reverse operation mode control is as follows:
s401, judging the type of the virtual path, if the virtual path is a straight path, entering a step S402, and if the virtual path is a spliced path of a circular arc section and a straight line, entering a step S403;
s402, calculating the position coordinates of the center of the rear wheel of the vehicle and the original path end point (x) at the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 If the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, and if the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, otherwise, stopping the vehicle until the vehicle is stopped, and continuously monitoring the distance;
s403, calculating the tangential point (x) of the position coordinates of the center of the rear wheel of the vehicle and the tangent point of the straight line segment path and the circular arc segment path at the sampling period t=0.05s r ，y r ) If the calculated value is less than the error threshold delta 2 If the arc reversing condition is met, the step S404 is entered, otherwise, the vehicle is reversed straight and the distance is monitored;
s404, adjusting the front wheel steering angle to the front wheel steering angle delta of the generated circular arc section path, continuing reversing and calculating the position coordinates of the rear wheel center of the vehicle and the original path end point (x) under the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 And if the vehicle is stopped, stopping the vehicle until the vehicle is stopped, otherwise, continuing reversing the vehicle and monitoring the distance all the time.
As shown in fig. 10, a fixed-point directional parking control system of an unmanned ground mobile platform comprises:
the path expansion module is used for acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path; the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
the reversing working condition judging module is used for judging and switching reversing working conditions in the process of the vehicle according to the generated new path;
and the reversing working condition control module is used for enabling the vehicle to return according to the original path of the virtual path and stopping at a preset end position with a preset course.
In fig. 10, the overall scheme of the system is also presented in relation to the vehicle control core.
In the embodiment of the application, the scheme of the application is further described by a simulation mode:
path 1: (no obstacle in surrounding space)
Direct following path (pretarge distance l) d =1.2m, end stop position deviation Δ 2 The following result when=0.4m) is shown in fig. 11
It can be seen that the error when the vehicle reaches the vicinity of the end point cannot be satisfied less than the stop position deviation Δ 2 Therefore, the vehicle can pass through the end point, the end point is always pre-aimed to do circular motion, and the pure-pure pre-aiming algorithm fails. The conventional direct pretightening method is only carried out by amplifying the stop position deviation delta 2 The vehicle is ensured to be able to stably park at the expense of stopping accuracy.
And adjusting the path following parameters, and using a system to control the following method to follow the same path.
The method directly follows: (pretarget distance l) d =1.2m, end stop position deviation Δ 2 ＝0.6m)
The system control follows: (pretarget distance l) d Heading deviation threshold Δ=1.2m 0 =0.01 rad, lateral deviation threshold Δ 1 =0.01m, terminalDeviation of the dot stop position delta 2 ＝0.02m)
The two path following results are shown in fig. 12, the partial enlarged view near the end position is shown in fig. 13, and the simulation results of the course when the two following modes are stopped are shown in fig. 14;
according to the simulation results, under the environment that the surrounding space is free from obstacles, compared with the result obtained by directly following, the result obtained by controlling the following by using the system designed by the patent has a great degree of improvement on the parking point position accuracy and the parking point course control.
Path 2: (obstacle and infeasible area of surrounding space)
Direct following (pretarget distance i) d =1.2m, end stop position deviation Δ 2 The path following result when=0.1m) is shown in fig. 15;
the error in the vicinity of the vehicle reaching the end point cannot be satisfied less than the stop position deviation Δ 2 Therefore, the vehicle can cross the end point, and the surrounding space has an infeasible area and an obstacle to prevent the vehicle from always pretightening the end point to do circular motion, so that the vehicle is forced to stop in consideration of obstacle avoidance. The traditional direct pre-aiming method also only amplifies the stop position deviation delta 2 Ensuring that the vehicle can stably stop under the condition of sacrificing accuracy;
and adjusting the path following parameters, and using a system to control the following method to follow the same path.
The method directly follows: (pretarget distance l) d =1.2m, end stop position deviation Δ 2 ＝0.2m)
The system control follows: (pretarget distance l) d Heading deviation threshold Δ=1.2m 0 =0.01 rad, lateral deviation threshold Δ 1 =0.01m, end stop position deviation Δ 2 ＝0.04m)
The two path following results are shown in fig. 16, the partial enlarged view near the end position is shown in fig. 17, and the simulation results of the course when the two following modes are stopped are shown in fig. 18; according to the simulation results, in the environment with the obstacle in the surrounding space, the arc expansion mode designed by the system control method avoids the obstacle and the infeasible area, and compared with the result obtained by direct following, the result obtained by the system control method has the advantage that the parking point position accuracy and the parking point course control are improved to a greater extent.
While the foregoing description illustrates and describes the preferred embodiments of the present application, it is to be understood that the application is not limited to the forms disclosed herein, but is not to be construed as limited to other embodiments, and is capable of use in various other combinations, modifications and environments and is capable of changes or modifications within the spirit of the application described herein, either as a result of the foregoing teachings or as a result of the knowledge or skill of the relevant art. And that modifications and variations which do not depart from the spirit and scope of the application are intended to be within the scope of the appended claims.
Claims (5)
1. A fixed-point directional parking control method of an unmanned ground maneuvering platform is characterized by comprising the following steps of: the method comprises the following steps:
s1, acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path;
the step S1 includes:
s101, acquiring original path information of a navigation plan, wherein the original path information comprises preset path end point coordinates, a heading, an error threshold and environment information of a space around the path end point when parking is scheduled; the environmental information of the surrounding space includes obstacle information and infeasible area information;
s102, generating rays by taking a terminal point as an end point and a preset parking heading as a direction, taking a section of straight line path with the length of 5m, and performing circular area collision detection on the path, namely taking each point on the path as a circle center and taking a collision radius r=1.2m as a circle; if no obstacle information or no feasible area information exists in all the areas of the circumference envelope, the obtained straight line path with the length of 5m is taken as a virtual path through collision detection; otherwise, the collision detection is not passed, and the step S103 is entered;
s103, directly performing linear expansion and failing to pass collision detection, performing arc expansion firstly, and enabling the vehicle structure to be capable ofKnowing that there is a maximum delta in the front wheel steering angle max By taking the original path end point as a tangent point and the required parking heading as a tangential direction, sequentially traversing the front wheel rotation angle delta of the vehicle from 5 degrees to 5 degrees as step length, namely sequentially enabling delta to be 1 ＝5°、δ 2 ＝10°、δ 3 ＝15°、δ 4 ＝20°、δ 5 =25°, substitutedObtaining corresponding turning radius value R i The central angle theta is traversed by a step length of 15 degrees from 30 degrees, and a turning radius R i And an arc central angle theta i Correspondingly generating a section of arc track, taking the end point of the arc as an end point and taking rays along the tangential direction of the end point of the arc, and taking a section of 10m long straight line path from the end point, so as to obtain a section of arc and straight line spliced path; performing collision detection in step S102 on the generated virtual path, if the generated virtual path passes the collision detection, taking the spliced path as the virtual path, and if the generated virtual path does not pass the collision detection, continuing to traverse R i And theta i Searching a path;
s2, the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
s3, the vehicle runs according to the generated new path, and the judgment and switching of the reversing working condition are carried out in the running process;
s4, returning the vehicle according to the original path of the virtual path, and stopping at a preset end position with a preset course.
2. The method for controlling fixed-point directional parking of an unmanned ground mobile platform according to claim 1, wherein the method comprises the following steps: in the step S2, the generated virtual path is joined with the original path, and after a new path is obtained, several control parameters and path information are returned, which specifically includes:
end position coordinates (x end ，y end )
Preset heading θ of vehicle at stop 0
If the virtual path includes a circular arc segment, the following parameters need to be returned additionally:
generating a front wheel angle delta corresponding to the arc section path i ，
The end point of the path of the circular arc segment, i.e. the coordinate (x) of the tangent point of the path of the circular arc segment with the path of the straight line segment in the virtual path r ，y r )。
3. The method for controlling fixed-point directional parking of an unmanned ground mobile platform according to claim 1, wherein the method comprises the following steps: the step S3 includes:
s301, judging whether the vehicle reaches a straight line segment part of the virtual path or not according to the relative position relation between the position coordinates of the vehicle and the coordinates of straight line segment path points in the virtual path, if so, entering a step S302, and if not, performing loop judgment according to the step S301;
s302, calculating the deviation e of the heading of the vehicle and the preset heading under the condition that the sampling period t=0.05s 0 Lateral deviation e of position coordinates of center of rear wheel of vehicle from closest point on straight line path 1 Deviation e 0 Namely, the deviation value of the heading angle of the vehicle and the direction angle of the straight-line path, and the lateral deviation e 1 I.e. the deviation value of the position of the central point of the rear wheel of the vehicle and the nearest point of the path in the Y direction under the coordinate system of the vehicle, if the heading is deviated e 0 Less than the error threshold delta 0 Lateral deviation value e 1 Less than the error threshold delta 1 I.e. e 0 ＜Δ 0 &e 1 ＜Δ 1 Step S303 is carried out if the reversing judgment condition is met, otherwise, the monitoring course deviation and the transverse deviation are calculated in a circulating mode;
s303, controlling a vehicle chassis, braking the vehicle to reduce the speed to 0, switching to a reverse gear working condition, and controlling the motor to rotate reversely in the subsequent movement.
4. The method for controlling fixed-point directional parking of an unmanned ground mobile platform according to claim 1, wherein the method comprises the following steps: said step S4 comprises the sub-steps of:
s401, judging the type of the virtual path, if the virtual path is a straight path, entering a step S402, and if the virtual path is a spliced path of a circular arc section and a straight line, entering a step S403;
s402, calculating the position coordinates of the center of the rear wheel of the vehicle and the original path end point (x) at the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 If the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, and if the distance is not equal to the preset distance, stopping the vehicle until the vehicle is stopped, otherwise, stopping the vehicle until the vehicle is stopped, and continuously monitoring the distance;
s403, calculating the tangential point (x) of the position coordinates of the center of the rear wheel of the vehicle and the tangent point of the straight line segment path and the circular arc segment path at the sampling period t=0.05s r ，y r ) If the calculated value is less than the error threshold delta 2 If the arc reversing condition is met, the step S404 is entered, otherwise, the vehicle is reversed straight and the distance is monitored;
s404, adjusting the front wheel steering angle to the front wheel steering angle delta of the generated circular arc section path, continuing reversing and calculating the position coordinates of the rear wheel center of the vehicle and the original path end point (x) under the sampling period t=0.05s end ，y end ) If the calculated value is less than the error threshold delta 2 And if the vehicle is stopped, stopping the vehicle until the vehicle is stopped, otherwise, continuing reversing the vehicle and monitoring the distance all the time.
5. A fixed-point directional parking control system of an unmanned ground maneuvering platform, based on the method of any one of claims 1 to 4, characterized in that: comprising the following steps:
the path expansion module is used for acquiring original path information of navigation planning, and performing path expansion on the original path information to obtain a virtual path; the generated virtual path is jointed with the original path to obtain a new path, and key control parameters and new path information are returned;
the reversing working condition judging module is used for judging and switching reversing working conditions in the process of the vehicle according to the generated new path;
and the reversing working condition control module is used for enabling the vehicle to return according to the original path of the virtual path and stopping at a preset end position with a preset course.
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