WO2023124339A1

WO2023124339A1 - Path planning method, motion control method and computer program product

Info

Publication number: WO2023124339A1
Application number: PCT/CN2022/123040
Authority: WO
Inventors: 赵安; 赵雨辰; 邸兴超; 边铁栋; 吴锦河; 王润柱
Original assignee: 灵动科技（北京）有限公司
Priority date: 2021-12-29
Filing date: 2022-09-30
Publication date: 2023-07-06
Also published as: CN116414116A

Abstract

Provided are a path planning method for a mobile robot. The method comprises the following steps: acquiring a starting point pose and a starting point curvature τ₀ at a starting point A, and an ending point pose and an ending point curvature τ₁ at an ending point B; determining a point C₁ and a point C₃; determining a point C₂ on a line segment C₁C₃; determining a first path and a second path, both of which are three-order Bezier curves that meet the following constraints: a mobile robot satisfying the starting point pose and the starting point curvature τ₀ at the starting point A according to the first path, the mobile robot satisfying the ending point pose and the ending point curvature τ₁ at the ending point B according to the second path, and according to the first path and the second path, the mobile robot having a linear velocity direction at the point C₂ the same as a vector (A) and having a curvature of 0; and taking a path formed by splicing the first path and the second path as a planned path or a part of the planned path. Provided are a corresponding motion control method for a mobile robot, and a corresponding computer program product. By means of the present invention, a motion path of a mobile robot can be optimized.

Description

Path planning method, motion control method and computer program product

technical field

The present invention relates to the field of mobile robots, especially the field of motion control of mobile robots, and in particular to a path planning method for mobile robots, a corresponding motion control method for mobile robots and corresponding computer program products.

Background technique

With the rapid economic growth and rising labor costs, mobile robots are more and more widely used in various industrial and domestic environments. For example, mobile robots such as automated guided vehicles (AGVs), autonomous mobile robots (AMRs), and forklifts are one of the key equipment in modern logistics systems. Mobile robots can move and dock to target locations according to path planning and job requirements to complete tasks such as material handling and delivery. Path planning is the key in the motion control of mobile robots.

During the working process of the mobile robot, it may be required to reach a specific position in a specific direction. However, in existing trajectory planning algorithms, this is often not achieved accurately, or must be achieved by pre-stopping the mobile robot or pre-orienting the mobile robot.

Especially in work scenarios where mobile robots need to be parked and docked, such as when mobile robots need to dock with charging piles, production lines or shelves, docking tasks often require mobile robots to be parked in a specific pose. The known parking path planning methods have problems such as sudden curvature changes, inaccurate poses, complex calculations, and specific requirements for the poses of the starting point of the path. For example, there is known a parking path planning algorithm using Dubins curves for path planning, wherein the planned path consists of three sections: an arc, a straight line and another arc, or three arcs with alternating directions. The curvature of the planned path is not necessarily continuous, which is not conducive to the accurate docking of the mobile wheel robot.

There are still many deficiencies in the prior art in terms of path planning and motion control for mobile robots.

Contents of the invention

The object of the present invention is to provide an improved path planning method and corresponding motion control method for a mobile robot, to overcome at least one deficiency of the prior art.

According to a first aspect of the present invention, a path planning method for a mobile robot is provided, wherein the path planning method includes the following steps:

S11: Obtain the starting pose and starting curvature τ ₀ of the mobile robot at the starting point A and the ending pose and ending curvature τ ₁ at the ending point B;

S12: Determine point C ₁ and point C ₃ such that the vector

The direction of is the same as the direction of the mobile robot at the starting point A, and the vector

The direction of is the same as that of the mobile robot at the end point B;

S13: Determine point C ₂ on line segment C ₁ C ₃ ;

S14: Determine the first path with the starting point A as the starting point and the point _C2 as the ending point, and determine the second path with the point _C2 as the starting point and the ending point B as the ending point, wherein the first path and the second path are third-order Bezier curves satisfying the following constraints:

According to the first path, the mobile robot satisfies the starting pose and starting curvature τ ₀ at the starting point A,

According to the second path, the mobile robot satisfies the end pose and end curvature τ ₁ at the end point B, and

According to the first path and the second path, the linear velocity direction and vector of the mobile robot at point _C2

are the same and have a curvature of 0; and

S15: The path formed by concatenating the first path and the second path is used as a planned path or a part of the planned path for the mobile robot.

In an exemplary embodiment, in step S12, point C ₁ and point C ₃ are determined in the following manner: point M is determined such that the vector

The direction of is the same as that of the mobile robot at the end point B; and the point C ₁ is determined on the line segment AM, and the point C ₃ is determined on the line segment MB.

In an exemplary embodiment, in step S13 , a point on the line segment C ₁ C ₃ that can minimize the maximum absolute value of the curvature of the first path and the second path is selected as point C ₂ .

In an exemplary embodiment, in step S13, the midpoint of the line segment C ₁ C ₃ is selected as the point C ₂ .

In an exemplary embodiment, in steps S12 and S13, the point C ₁ , the point C ₃ and the point C ₂ are determined in such a way that the maximum absolute value of the curvature of the first path and the second path is minimized.

In an exemplary embodiment, the first path is a curve represented by:

in,

In turn represent the coordinates of the four control points of the Bezier curve and are determined by:

is the coordinates of the starting point A,

is the coordinates of point _C2 ,

vector

The direction of is the same as that of the mobile robot at the starting point A,

vector

The direction and vector of

in the same direction,

Substitute s=0 into

Among them, P′ _p1x (s), P′ _p1y (s), P″ _p1x (s), P″ _p1y (s), are respectively

The first-order abscissa, ordinate and second-order derivative of the abscissa, ordinate, and

Substitute s=1 into

middle;

and / or,

The second path is a curve represented by:

in,

is the coordinates of point _C2 ,

is the coordinates of the end point B;

vector

The direction and vector of

in the same direction;

vector

The direction of is the same as that of the mobile robot at the end point B;

Substitute s=0 into

Among them, P′ _p2x (s), P′ _p2y (s), P″ _p2x (s), P″ _p2y (s), are respectively

The first-order abscissa, ordinate and second-order abscissa, ordinate of the derivative; and

Substitute s=1 into

middle.

In an exemplary embodiment, the planned path is a planned path for the mobile robot to move to the target parking point T and park at the target parking point T with a desired parking posture, wherein the starting point A is the parking The starting point of the planned path, the ending pose and the ending curvature _τ1 are determined according to the desired parking pose.

In an exemplary embodiment, the end point B is the end point of the planned parking path, the end point pose is determined to be the same as the expected berthing pose, and the end point curvature τ ₁ =0.

In an exemplary embodiment, the end point B is a point different from said target berthing point T, wherein:

The direction of the mobile robot at the end point B is the same as the direction of the mobile robot at the target parking point T;

The direction and vector of the mobile robot at the end point B

in the same direction;

In step S15 , the path formed by concatenating the first path, the second path and the line segment BT is used as a parking planning path for moving the mobile robot to the target parking point T.

In an exemplary embodiment, the mobile robot is a differential robot.

According to a second aspect of the present invention, a motion control method for a mobile robot is provided, wherein the motion control method includes the following steps:

S21: Obtain a global path for the mobile robot;

S22: Select a first point on the global path and a second point that is closer to the end point of the global path than the first point, with the first point as the starting point A and the second point as the end point B, and execute according to the present invention A path planning method to obtain a planned path for a mobile robot;

S23: Replace the section from the first point to the second point in the global path with the planned path; and

S24: Control the mobile robot to move according to the replaced global path.

In an exemplary embodiment, when the planned path is a parking planning path for moving the mobile robot to the target parking point T and parking at the target parking point T with a desired parking posture, in the global Determine the first point on the route located in the predetermined berthing area corresponding to the target berthing point T as the starting point A, the predetermined berthing area is a position that is pre-defined for the target berthing point T and covers the position of the target berthing point T Area.

In an exemplary embodiment, the pose and/or curvature of the mobile robot at the starting point A is correspondingly the same as the pose and/or curvature of the mobile robot at the first point on the global path.

According to a third aspect of the present invention, a motion control method for a mobile robot is provided, wherein the motion control method includes the following steps:

S31: Obtain a global path for the mobile robot, and control the mobile robot to move according to the global path;

S32: Take the current position of the mobile robot as the starting point A, determine a third point on the global path that is closer to the termination point of the global path than the current position as the end point B, and execute the path planning method according to the present invention to obtain planning paths for mobile robots;

S33: Replace the section from the current position of the mobile robot to the third point in the global path with the planned path; and

S34: Control the mobile robot to move according to the replaced global path.

In an exemplary embodiment, when the planned path is a parking planning path for moving the mobile robot to the target parking point T and parking at the target parking point T with a desired parking posture, when the mobile robot moves Step S32 is executed after arriving in the predetermined berthing area corresponding to the target berthing point T, the predetermined berthing area is an area defined in advance for the position of the target berthing point T and covering the position of the target berthing point T.

In an exemplary embodiment, the pose and/or curvature of the mobile robot at the starting point A is correspondingly the same as the pose and/or curvature of the mobile robot at the current location.

According to a fourth aspect of the present invention there is provided a computer program product comprising computer program instructions, wherein when said computer program instructions are executed by one or more processors, said processors are capable of performing The inventive path planning method or the motion control method according to the invention.

The positive effect of the present invention is that: the path spliced by the first path and the second path is conducive to enabling the mobile robot to reach a specific position in a specific direction, and there is no special pose requirement for the starting point of the planned path, and it is relatively smooth, and has a continuous curvature. This makes the generated planned trajectories particularly advantageous for mobile robot locomotion and docking. In addition, the above-mentioned constraints on the first path and the second path are not only beneficial to obtain a smooth and continuous curvature path, but also facilitate the determination of the first path and the second path in a simple manner without complicated calculations.

Description of drawings

Hereinafter, the principles, features and advantages of the present invention can be better understood by describing the present invention in more detail with reference to the accompanying drawings. The attached drawings include:

Fig. 1 schematically shows that a path planning method is used to generate a planned path for a mobile robot in an exemplary embodiment of the present invention;

Fig. 2 schematically shows a flow chart of a path planning method for a mobile robot according to an exemplary embodiment of the present invention;

Fig. 3 schematically shows that a path planning method is used to generate a planned path for a mobile robot in an exemplary embodiment of the present invention;

4A and 4B schematically illustrate a planned path and its curvature generated by a path planning method according to an exemplary embodiment of the present invention;

5A and 5B schematically illustrate a planned path and its curvature generated by a path planning method according to an exemplary embodiment of the present invention;

Fig. 6 schematically shows a flow chart of a motion control method for a mobile robot according to an exemplary embodiment of the present invention;

FIG. 7 schematically shows a global path obtained by using a motion control method according to an exemplary embodiment of the present invention; and

Fig. 8 schematically shows a flowchart of a motion control method for a mobile robot according to an exemplary embodiment of the present invention.

Detailed ways

In order to make the technical problems, technical solutions and beneficial technical effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, rather than to limit the protection scope of the present invention.

The present invention is applicable to mobile robots, which can be any robots capable of autonomous space movement, such as AGV, AMR and so on. The mobile robot can be used to perform various tasks, such as a storage robot, a cleaning robot, a family escort robot, a welcome robot, and the like.

It should be understood that, in this article, the expression "first", "second" and so on are used for descriptive purposes only, and should not be interpreted as indicating or implying relative importance, nor should they be interpreted as implying that the indicated technical features quantity. Features defined as "first" and "second" may expressly or implicitly indicate that at least one of these features is included.

A path planning method for a mobile robot 1 according to an exemplary embodiment of the present invention will be described below in conjunction with Fig. 1 and Fig. 2 . Fig. 1 schematically shows a planned path generated by a path planning method for a mobile robot 1 in an exemplary embodiment according to the present invention.

In this embodiment, the mobile robot 1 is, for example, a differential robot, that is, the mobile robot 1 includes a differential wheel motion system. Alternatively, the mobile robot 1 may also be other types of robots, such as a single steering wheel robot or a double steering wheel robot. Correspondingly, the mobile robot 1 can include, for example, a dual steering wheel kinematic system.

The mobile robot 1 includes, for example, a communication device for communicating with other devices, such as a dispatch control system. The mobile robot 1 may also include sensors such as cameras, radars and the like. The mobile robot 1 can acquire required information through the sensors, such as the current position of the mobile robot 1 or its surrounding environment and the like.

The mobile robot 1 further includes, for example, a controller. The controller is used to move the components of the robot 1 , including for example the differential wheel kinematic system, sensors, communication means and the like. The controller can also receive working status or detection data of corresponding components, such as sensors, through communication lines, so as to monitor or control the operation of the mobile robot 1 .

During the working process of the mobile robot 1, it may be necessary to park in a specific pose, that is, park in a specific target parking point in a specific direction (attitude). For example, the mobile robot 1 may need to stop at a certain position in a desired berthing posture to wait for an operator's operation or to dock with other equipment. FIG. 1 exemplarily shows that the mobile robot 1 needs to move to a target docking point adjacent to the charging pile 2 in order to dock with the charging pile 2 for charging.

In order for the mobile robot 1 to reach a specific position with a specific pose, a path planning method according to the mobile robot 1 can be performed. Fig. 2 schematically shows a flowchart of a path planning method for a mobile robot 1 according to an exemplary embodiment of the present invention.

As shown in Figure 2, the path planning method may include the following steps:

S11: Obtain the starting pose and starting curvature τ ₀ of the mobile robot 1 at the starting point A and the ending pose and ending curvature τ ₁ at the ending point B;

S12: Determine point C ₁ and point C ₃ such that the vector

The direction of is the same as that of mobile robot 1 at the starting point A, and the vector

The direction of is the same as that of mobile robot 1 at the end point B;

S13: Determine point C ₂ on line segment C ₁ C ₃ ;

S14: Determine the first path 3 with the starting point A as the starting point and the point _C2 as the ending point, and determine the second path 4 with the point _C2 as the starting point and the ending point B as the ending point, wherein the first path 3 and The second path 4 is a third-order Bezier curve satisfying the following constraints:

According to the first path 3, mobile robot 1 satisfies the starting pose and starting curvature τ ₀ at the starting point A,

According to the second path 4, the mobile robot 1 satisfies the end pose and end curvature τ ₁ at the end point B, and

According to the first path 3 and the second path 4, the linear velocity direction and vector of the mobile robot 1 at point _C2

are the same and have a curvature of 0; and

S15: The path formed by splicing the first path 3 and the second path 4 is used as a planned path or a part of the planned path for the mobile robot 1 .

The resulting planned path is beneficial for the mobile robot 1 to reach a specific location in a specific direction, and there is no special pose requirement for the starting point of the planned path. That is, arbitrary directions and arbitrary curvatures can be used as starting points as desired. In particular, the path spliced by two third-order Bezier curves can make the parking planning path smoother. The above-mentioned constraints on the first path 3 and the second path 4 are beneficial to make the curvature of the generated planned path smooth and have continuous curvature. This makes changes in the speed and acceleration of the mobile robot 1 more gradual. For a differential robot, such a parking planning path with continuous curvature can be adapted particularly advantageously to the motion characteristics of the differential robot. The above-mentioned constraints on the first path 3 and the second path 4 also facilitate the determination of the first path 3 and the second path 4 in a simple manner without complex calculations.

It should be understood that the pose of the mobile robot 1 at a certain point includes the position and orientation of the mobile robot 1 . In the Cartesian coordinate system, the pose of the mobile robot 1 can be expressed as (x, y, θ), for example, where x and y represent the horizontal and vertical coordinates of the mobile robot 1 respectively, and θ represents the direction of the mobile robot 1 . The mobile robot 1 can move forward or backward, so the direction of the mobile robot 1 at the starting point A can correspond to the "front" or "rear" direction of the mobile robot 1 . For the mobile robot 1 implemented as a differential robot, the direction of the mobile robot 1 at the starting point A is the motion direction of the mobile robot 1 at the starting point A.

In the embodiment shown in FIG. 1 , the planned path is a planned path for moving the mobile robot 1 to the target berthing point T and parked at the target berthing point T with a desired berthing posture, wherein the starting point A is The start point, end point pose and end point curvature _τ1 of the parking planning path are determined according to the desired berthing pose. Correspondingly, the path planning method can be regarded as a parking path planning method for the mobile robot 1, which aims to plan a moving path for the mobile robot 1 to park at a specific target parking point in a specific direction . The desired parking pose can be determined by the parking task of the mobile robot 1 . For example, for the mobile robot 1 that needs to be docked with the charging pile 2 , the desired parking pose can be determined according to the position and direction of the charging pile 2 and the docking direction required by the charging pile 2 .

Correspondingly, the obtained parking planning path can enable the mobile robot 1 to start the parking planning path in any direction and any curvature, without making the mobile robot 1 stop first at the beginning of the parking planning path, and without making the mobile robot 1 stop at the beginning of the parking planning path. to adjust to a specific direction. Moreover, it is beneficial to make the parking planning path have continuous curvature. This makes changes in the speed and acceleration of the mobile robot 1 more gradual. Such a parking planning path with continuous curvature is particularly advantageous for differential robots. In addition, the path formed by splicing two third-order Bezier curves will make the parking planning path smoother.

Here, in particular, the path formed by splicing the first path 3 and the second path 4 is used as a planned parking path for the mobile robot 1 . In other words, the starting point A is the starting point of the parking planning path, and the ending point B is the ending point of the parking planning path for the mobile robot 1 , ie, the target parking point T. In the case that the end point B is the end point of the parking planning path, the end point pose is determined to be the same as the desired berthing pose, and the end point curvature τ ₁ =0.

In step S11, for example, the start pose and curvature τ ₀ of the mobile robot 1 at the start point A and the end pose and curvature τ ₁ at the end point B of the path can be obtained from other devices through a communication device. For example, the start pose and curvature τ ₀ of the mobile robot 1 at the start point A and the end pose and curvature τ ₁ at the end point B of the path can also be acquired by sensors.

In this embodiment, points C ₁ and C ₃ are determined in step S12, for example, in the following manner: first, point M is determined such that the vector

The direction of is the same as that of the mobile robot 1 at the end point B; then, a point C ₁ is determined on the line segment AM, and a point C ₃ is determined on the line segment MB. In this way, at least the first path 3 and the second path 4 can be ensured to be within the range of the triangle AMB, which is conducive to generating a smoother planned berthing path.

Optionally, select the midpoint of the line segment AM as the point C ₁ ; and/or select the midpoint of the line segment MB as the point C ₃ . In the case that points _C1 and _C3 are midpoints of line segment AM and line _segment MB respectively, it can be further ensured that the first path 3 and the second path 4 are within the lower part of the triangle AMB, ie the trapezoid _AC1C3B .

In step S13, for example, the midpoint of the line segment C ₁ C ₃ may be selected as the point C ₂ . As a result, the first path 3 and the second path 4 with less curvature can be generated in a simple manner.

After determining the point _C2 , the first path 3 and the second path 4 may be determined in step S14.

For example, the first path 3 can be represented by the following formula:

in,

In turn represent the coordinates of the four control points of the Bezier curve, which can be determined by:

is the coordinates of the starting point A,

is the coordinate of point C ₂ ;

vector

The direction of is the same as that of mobile robot 1 at the starting point A;

vector

The direction and vector of

in the same direction;

Substitute s=0 into

Substitute s=1 into

middle.

Similarly, the second path 4 can be represented by the following formula:

in,

is the coordinates of point _C2 ,

is the coordinates of the end point B;

vector

The direction and vector of

in the same direction;

vector

The direction of is the same as that of mobile robot 1 at the end point B;

Substitute s=0 into

Substitute s=1 into

middle.

As mentioned above, in the path planning method according to the present invention _, after determining the starting point A, the ending point B and the point _C2 , it can be determined as The control points of the first path 3 and the second path 4 of the third-order Bezier curve. This process does not require complex calculations.

Then, the path formed by splicing the first path 3 and the second path 4 may be used as a parking planning path or a part of the parking planning path for moving the mobile robot 1 to the target parking point. Apparently, the first path 3 and the second path 4 themselves have continuous curvature, and the spliced path formed by the first path 3 and the second path 4 also has a continuous curvature at the splicing point C ₂ .

Fig. 3 schematically shows the use of a path planning method to generate a planned path in an exemplary embodiment of the present invention.

As shown in FIG. 3 , the mobile robot 1 needs to move to a target parking point T adjacent to the charging pile 2 in order to dock with the charging pile 2 for charging. In the route planning method, the end point B may not coincide with the target berthing point T of the berthing planning route. In this case, the orientation of the mobile robot 1 at the end point B can be set to be the same as the vector

in the same direction. In addition, the direction of the mobile robot 1 at the end point B and the direction of the mobile robot at the target parking point T can be made the same. Then, similar to the process described above with reference to FIGS. 1 and 2 , the first path 3 and the second path 4 are generated. The difference is that, in step S15 , the path formed by concatenating the first path 3 , the second path 4 and the line segment BT is used as a parking planning path for moving the mobile robot 1 to the target parking point.

Fig. 4A and Fig. 4B schematically show a planned path and its curvature generated by a path planning method according to an exemplary embodiment of the present invention.

As shown in FIG. 4A , the planned path is spliced by the first path 3 and the second path 4 . Points C ₁ and C ₃ can be determined according to the poses of the mobile robot 1 at the starting point A and the ending point B. Alternatively, the points _C1 and _C3 may be set to be separated from the start point A and the end point B by a predetermined distance, respectively. For example, point _C1 is separated from the starting point A by a predetermined first distance, such as 0.4m, and point _C3 is separated from the end point B by a predetermined second distance, such as 0.7m.

After determining points C ₁ and C ₃ , point C ₂ can be determined on line segment C ₁ C ₃ . In FIG. 4A , point C ₂ is determined to be the first quarter point on line segment C ₁ C ₃ . therefore,

As mentioned above, after the point _C2 is determined, the first path 3 and the second path 4 can be further determined. FIG. 4B shows the curvature of the planned path spliced by the first path 3 and the second path 4 . As shown in Figure 4B, the maximum absolute value of the curvature of the resulting planned path will exceed 10.

Fig. 5A and Fig. 5B schematically show a planned path and its curvature generated by using the path planning method according to an exemplary embodiment of the present invention. The difference between this embodiment and the embodiment shown in FIGS. 4A and 4B is that the position of the point C ₂ on the line segment C ₁ C ₃ is different.

As shown _in FIG. 5A, point _C2 is determined as the midpoint of line segment _C1C3 . therefore,

FIG. 5B shows the curvature of the planned path spliced by the first path 3 and the second path 4 shown in FIG. 5A . As shown in FIG. 5B , the maximum absolute value of the curvature of the resulting planned path will be less than 10.

It can be seen that different positions of the point C ₂ on the line segment C ₁ C ₃ will result in different curvatures of the generated first path 3 and the second path 4 . Determining the midpoint of the line segment C ₁ C ₃ as the point C ₂ is beneficial to obtain the first path 3 and the second path 4 with smaller maximum absolute values of curvature.

In an exemplary embodiment according to the present invention, in step S13, a point on the line segment C ₁ C ₃ that can minimize the maximum absolute value of the curvature of the first path 3 and the second path 4 can be selected as point C ₂ . For example, the line segment C ₁ C ₃ can be equally divided into n parts (n is an integer greater than 2), and the first path 3 and the second path 4 generated under the condition that each equalization point is taken as point C ₂ can be compared The maximum absolute value of the curvature, and then the point C 2 that can obtain the maximum absolute value of the minimum curvature of the first path 3 and the second path 4 is taken as _{the final point C 2} _. Alternatively, points on the line segment C ₁ C ₃ may also be selected with a predetermined resolution, for example, one point is selected at intervals of 0.1 m on the line segment C ₁ C ₃ . Then compare the maximum absolute value of the curvature of the first path 3 and the second path 4 generated under the situation of using these points as point C ₂ , and will be able to obtain the minimum value of the curvature of the first path 3 and the second path 4 The point C ₂ with the largest absolute value is taken as the final point C ₂ . Those skilled in the art should understand that other ways can also be used to select a point on the line segment C ₁ C ₃ that can minimize the maximum absolute value of the curvature of the first path 3 and the second path 4 as the point C ₂ .

In an exemplary embodiment according to the present invention, in steps S12 and S13, the points C ₁ , C ₃ and Point _C2 . Similar to the above description about point _C2 , those skilled in the art should understand that point _C1 can be determined in a manner that minimizes the maximum absolute value of the curvature of the first path 3 and the second path 4 in various ways , point C ₃ and point C ₂ . For example, with the minimum maximum absolute value of the curvature of the first path 3 and the second path 4 as the optimization objective, the positions of point C ₁ , point C ₃ , and point C ₂ are determined using an optimization algorithm.

Fig. 6 schematically shows a flowchart of a motion control method for a mobile robot 1 according to an exemplary embodiment of the present invention. Fig. 7 schematically shows a replaced global path 5 obtained by using a motion control method according to an exemplary embodiment of the present invention. The motion control method includes the following steps:

S21: Obtain a global path 5 for the mobile robot 1 (only partially shown in FIG. 7);

S22: Select a first point on the global path 5 and a second point closer to the end point of the global path 5 than the first point, with the first point as the starting point A and the second point as the end point B, and execute according to The path planning method of the present invention is used to obtain a planned path for the mobile robot 1;

S23: Replace the segment (indicated by a dotted line) from the first point to the second point in the global path 5 with the planned path; and

S24: Control the mobile robot 1 to move according to the replaced global path 5 .

The original global route 5 can be obtained by using any applicable known method, for example, it can be planned by the A-star algorithm. When planning the original global path 5, various factors may need to be considered, such as obstacle avoidance, shortest time, etc. The resulting global path 5 may not meet the pose requirements of the target parking point. For example, the mobile robot 1 moving according to the original global path 5 may not be able to park at the target parking point in an accurate direction, resulting in the inability of the mobile robot 1 to accurately dock with the charging pile 2, or causing the mobile robot 1 to have to carry out charging after reaching the target parking point. Additional pose adjustments. Utilizing the motion control method according to the present invention is beneficial for the mobile robot 1 to accurately park at a specific pose. In addition, the features and advantages described above for the path planning method are also correspondingly applicable to the motion control method.

The motion control method can be carried out, for example, by means of a controller of the mobile robot 1 . In step S21, the original global path 5 for the mobile robot 1 can be planned, for example by means of a controller. Optionally, in step S21, the global path 5 for the mobile robot 1 may also be obtained from other equipment, such as a dispatch control system, by means of a communication device.

Optionally, when the planned path is a parking planning path for moving the mobile robot 1 to the target parking point T and parking at the target parking point T with a desired parking posture, on the global path 5 Determining as the starting point A the first point located in the predetermined berthing area corresponding to the target berthing point T, the predetermined berthing area is an area pre-defined for the position of the target berthing point T and covering the position of the target berthing point T . For example, a dedicated charging area 6 can be set for the mobile robot 1 working in the warehouse, at least one charging pile 2 is arranged in the charging area 6, and the mobile robot 1 that needs to be charged can move to a specific charging position in the charging area 6 to Dock with charging pile 2 to charge. Usually, the charging area 6 is a flat barrier-free area, that is, no equipment unrelated to charging is arranged in the charging area 6 , so that the mobile robot 1 can move relatively freely in the charging area 6 without encountering obstacles. In this case, a parking area can be predetermined for the charging location for the mobile robot 1 , which is set, for example, as the entire charging area 6 . Delimiting the parking area in advance and selecting the starting point A in the predetermined parking area can make the mobile robot 1 move along a smoother parking planning path after entering the parking area. When the mobile robot 1 needs to be charged and enters the parking area, it can start to move according to the parking planning path.

The pose and/or curvature of the mobile robot 1 at the starting point A may be correspondingly the same as the pose and/or curvature of the mobile robot 1 at the first point on the global path 5 . Thus, the planned parking path can be smoothly embedded into the original global path 5 , so that the mobile robot 1 does not need to stop at the beginning of the planned parking path, and does not need to adjust to a specific direction at the beginning of the planned parking path.

Fig. 8 schematically shows a flowchart of a motion control method for a mobile robot 1 according to an exemplary embodiment of the present invention. The motion control method includes the following steps:

S31: Obtain a global path 5 for the mobile robot 1, and control the mobile robot 1 to move according to the global path 5;

S32: Taking the current position of the mobile robot 1 as the starting point A, determining a third point on the global path 5 that is closer to the termination point of the global path 5 than the current position as the end point B, and executing the path planning method according to the present invention , to obtain the planned path for the mobile robot 1;

S33: Replace the section from the current position of the mobile robot 1 to the third point in the global path 5 with the planned path; and

S34: Control the mobile robot 1 to move according to the replaced global path 5 .

Optionally, in the case that the planned path is a parking planning path for moving the mobile robot 1 to the target parking point T and parking at the target parking point T with a desired parking posture, when the mobile robot 1 moves to the target parking point T Step S32 starts to be executed after being within the predetermined parking area corresponding to the target parking point T. The predetermined parking area is an area defined in advance for the location of the target parking point T and covers the location of the target parking point T.

The pose and/or curvature of the mobile robot 1 at the starting point A may be correspondingly the same as the pose and/or curvature of the mobile robot 1 at the current location.

The motion control method according to the present invention has corresponding features and similar principles to the path planning method according to the present invention. The features and advantages described above for the path planning method also apply correspondingly for the motion control method.

In addition, the present invention also relates to a computer program product comprising computer program instructions which, when executed by one or more processors, enable said processors to perform the path planning method or motion control method.

In the present invention, the computer program product can be stored in a computer-readable storage medium. The computer-readable storage medium may include, for example, high-speed random access memory, and may also include non-volatile memory, such as a hard disk, internal memory, plug-in hard disk, smart memory card, secure digital card, flash memory card, at least one magnetic disk storage device, Flash memory devices, or other volatile solid-state storage devices. The processor may be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and the like. A general-purpose processor may be a microprocessor or any conventional processor or the like.

While specific embodiments of the invention have been described in detail, these have been presented for purposes of illustration only and should not be construed as limiting the scope of the invention. Various alternatives, changes and modifications can be devised without departing from the spirit and scope of the invention.

Claims

A path planning method for a mobile robot (1), wherein the path planning method comprises the following steps:

S11: Obtain the starting pose and starting curvature τ 0 of the mobile robot (1) at the starting point A and the ending pose and ending curvature τ 1 at the ending point B;

S12: Determine point C 1 and point C 3 such that the vector
The direction of is the same as that of the mobile robot (1) at the starting point A, and the vector
The direction of is the same as the direction of the mobile robot (1) at the end point B;

S13: Determine point C 2 on line segment C 1 C 3 ;

S14: Determine the first path (3) with the starting point A as the starting point and the point C2 as the ending point, and determine the second path (4) with the point C2 as the starting point and the ending point B as the ending point, wherein the first The first path (3) and the second path (4) are third-order Bezier curves satisfying the following constraints:

According to the first path (3), the mobile robot (1) satisfies the starting pose and starting curvature τ 0 at the starting point A,

According to the second path (4), the mobile robot (1) satisfies the end pose and end curvature τ 1 at the end point B, and

According to the first path (3) and the second path (4), the linear velocity direction and vector of the mobile robot (1) at point C2
are the same and have a curvature of 0; and

S15: The path formed by splicing the first path (3) and the second path (4) is used as a planned path or a part of the planned path for the mobile robot (1).
The path planning method according to claim 1, wherein,

In step S12, points C1 and C3 are determined in the following manner:

Determine the point M such that the vector
The direction of is the same as the direction of the mobile robot (1) at the starting point A, and the vector
The direction of is the same as the direction of the mobile robot (1) at the end point B; and

Determine point C 1 on line segment AM and point C 3 on line segment MB.
The path planning method according to claim 1 or 2, wherein,

In step S13 , a point on the line segment C 1 C 3 that can minimize the maximum absolute value of the curvature of the first path ( 3 ) and the second path ( 4 ) is selected as point C 2 .
The path planning method according to claim 1 or 2, wherein,

In step S13, the midpoint of the line segment C 1 C 3 is selected as point C 2 .
The path planning method according to claim 1, wherein,

In steps S12 and S13, points C 1 , C 3 and C 2 are determined in such a way that the maximum absolute value of the curvature of the first path ( 3 ) and the second path ( 4 ) is minimized.
The path planning method according to any one of claims 1-5, wherein,

The first path (3) is a curve represented by:

in,
In turn represent the coordinates of the four control points of the Bezier curve and are determined by:

is the coordinates of the starting point A,
is the coordinates of point C2 ,

vector
The direction of is the same as that of the mobile robot (1) at the starting point A,

vector
The direction and vector of
in the same direction,

Substitute s=0 into
Among them, P′ p1x (s), P′ p1y (s), P″ p1x (s), P″ p1y (s), are respectively
The first-order abscissa, ordinate and second-order derivative of the abscissa, ordinate, and

Substitute s=1 into
middle;

and / or,

The second path (4) is a curve represented by:

in,
In turn represent the coordinates of the four control points of the Bezier curve and are determined by:

is the coordinates of point C2 ,
is the coordinates of the end point B;

vector
The direction and vector of
in the same direction;

vector
The direction of is the same as the direction of the mobile robot (1) at the end point B;

Substitute s=0 into
Among them, P′ p2x (s), P′ p2y (s), P″ p2x (s), P″ p2y (s), are respectively
The first-order abscissa, ordinate and second-order abscissa, ordinate of the derivative; and

Substitute s=1 into
middle.
The path planning method according to any one of claims 1-6, wherein,

The planned path is a planned parking path for the mobile robot (1) to move to the target parking point T and park at the target parking point T with a desired parking posture, wherein the starting point A is the starting point of the parking planning path , the terminal pose and the terminal curvature τ 1 are determined according to the desired parking pose.
The path planning method according to claim 7, wherein,

The end point B is the end point of the planned parking path, the end point pose is determined to be the same as the expected berthing pose, and the end point curvature τ 1 =0.
The path planning method according to claim 7, wherein,

End point B is a point different from said target berthing point T, wherein,

The direction of the mobile robot (1) at the end point B is the same as the direction of the mobile robot (1) at the target parking point T;

The direction and vector of the mobile robot (1) at the end point B
in the same direction;

In step S15, the path formed by splicing the first path (3), the second path (4) and the line segment BT is used as a parking planning path for moving the mobile robot (1) to the target parking point T.
The path planning method according to any one of claims 1-9, wherein,

The mobile robot (1) is a differential speed robot.
A motion control method for a mobile robot (1), wherein the motion control method comprises the following steps:

S21: Obtain the global path (5) for the mobile robot (1);

S22: Select a first point on the global path (5) and a second point closer to the termination point of the global path (5) than the first point, with the first point as the starting point A and the second point as the end point B, execute the path planning method according to any one of claims 1-10, to obtain the planned path for the mobile robot (1);

S23: Replace the section from the first point to the second point in the global path (5) with the planned path; and

S24: Control the mobile robot (1) to move according to the replaced global path (5).
The motion control method according to claim 11, wherein,

In the case where the planned path is a parking planning path for moving the mobile robot (1) to the target parking point T and parking at the target parking point T with a desired parking posture, on the global path (5) Determining as the starting point A the first point located in the predetermined berthing area corresponding to the target berthing point T, the predetermined berthing area is an area pre-defined for the position of the target berthing point T and covering the position of the target berthing point T .
The motion control method according to claim 11 or 12, wherein,

The pose and/or curvature of the mobile robot (1) at the starting point A is correspondingly the same as the pose and/or curvature of the mobile robot (1) at the first point on the global path (5).
A motion control method for a mobile robot (1), wherein the motion control method comprises the following steps:

S31: Obtain a global path (5) for the mobile robot (1), and control the mobile robot (1) to move according to the global path (5);

S32: Taking the current position of the mobile robot (1) as the starting point A, determine a third point on the global path (5) that is closer to the end point of the global path (5) than the current position as the end point B, and execute according to The path planning method according to any one of claims 1-10, to obtain a planned path for the mobile robot (1);

S33: replacing the section from the current position of the mobile robot (1) to the third point in the global path (5) with the planned path; and

S34: Control the mobile robot (1) to move according to the replaced global path (5).
The motion control method according to claim 14, wherein,

In the case that the planned path is a parking planning path for moving the mobile robot (1) to the target parking point T and parking at the target parking point T with a desired parking posture, when the mobile robot (1) moves to the target parking point T Step S32 starts to be executed after being within the predetermined parking area corresponding to the target parking point T. The predetermined parking area is an area defined in advance for the location of the target parking point T and covers the location of the target parking point T.
The motion control method according to claim 14 or 15, wherein,

The pose and/or curvature of the mobile robot (1) at the starting point A is correspondingly the same as the pose and/or curvature of the mobile robot (1) at the current position.
A computer program product, in particular a computer readable storage medium, comprising computer program instructions, wherein, when said computer program instructions are executed by one or more processors, said processors are capable of performing the - The path planning method according to any one of claims 10 or the motion control method according to any one of claims 11-26.