A method for moving a fork truck robot

Abstract

The application provides a moving method of a forklift robot, a local path closest to a global path is selected as an optimal path; thus, a trajectory of the optimal path is consistent with a trajectory of the global path, the optimal path has good smoothness, and interference on another global path is avoided when the moving robot moves along the optimal path; thus, the moving robot does not interfere with another moving robot moving between different initial nodes and different target nodes.

Description

Technical Field

[0001] The present invention relates to the technical field of path planning, and in particular to a moving method of a forklift robot. Background Art

[0002] Mobile robots are intelligently controlled devices that move to perform various tasks. With the continuous development of artificial intelligence, mobile robots are gradually being able to replace humans in some tasks. Compared to humans, robots have the advantage of being able to work longer and more efficiently. Mobile robots, especially service robots such as sweeping robots and delivery robots, are becoming increasingly common in daily life.

[0003] For example, a patent document with application number 202211581793.1 in China and publication date of February 24, 2023 discloses a global movement method for a mobile robot. In the process of approaching the initial node to the target node, the node with the smallest cost value is searched, and then the mobile robot moves before the node with the smallest cost value; the moving distance of the mobile robot is short and the moving time is short; at the same time, for known obstacles, the cost values ​​of nodes other than the obstacle nodes are calculated; the mobile robot avoids the obstacle nodes during movement to avoid known obstacles; for newly appearing obstacles, a local path is planned in the process of the mobile robot approaching the newly appearing obstacles to avoid unknown obstacles.

[0004] In this movement method, when avoiding a newly appeared obstacle, the mobile robot deviates from the set trajectory to avoid the obstacle, and then plans the shortest path between the current node and the end point of the path after avoiding the obstacle. When planning the path, the speed of the mobile robot and the deviation angle of the mobile robot are not taken into account to determine the optimal local path, which makes the walking path of the mobile robot poorly smooth. At the same time, it is easy to cause interference with mobile robots on other paths. Summary of the Invention

[0005] The present invention provides a movement method for a forklift robot, which is close to the global path when planning a local path and has good smoothness; at the same time, it avoids interference with forklift robots on other paths. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. 1 Flowchart of the present invention.

[0007] Fig. 2 Schematic diagram of a forklift robot approaching the next node on the local path.

[0008] Fig. 3 Schematic diagram of a forklift robot approaching the target node. DETAILED DESCRIPTION

[0009] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0010] like Figs. 1-3 As shown; A method for moving a forklift robot, comprising the following steps:

[0011] S1. Generate global path 1 between the initial node and the target node.

[0012] S2. Generate one or more local paths 2 on the global path 1.

[0013] S3. Evaluate the speed of different local paths 2 using a speed evaluation function.

[0014] The speed evaluation function is:

[0015] Cost(v,w) =100 +[delta_cost(v,w)* a]+ [dis_angle(v,w)*β]+ [dis_angle(v,w)*traj.xv *γ]+[ (diff_delta / 2)* vel(v,w)*δ]+[ dis_goal(v,w)*η];

[0016] a is the preset steering wheel angle deviation constant of the forklift robot; β is the angle error constant of the forklift robot; γ is the deceleration constant; δ is the acceleration constant; η is the target following error constant;

[0017] delta_cost(v,w) is the cost of the deviation between the optimal steering wheel angle and the current vehicle body angle; dis_angle(v,w) is the cost of the deviation between the optimal vehicle body angle and the current vehicle body angle; traj.xv is the linear velocity when tracing the path; diff_delta is the cost of the deviation between the optimal steering wheel angle and the current steering wheel angle; dis_goal(v,w) is the target node evaluation function; vel(v,w) is the velocity evaluation function; dis_goal(v,w) is the penalty cost for exceeding the end point.

[0018] S4. Select the local path with the lowest evaluation score as the optimal path.

[0019] S5. The forklift robot moves along the optimal path toward the target node.

[0020] S6. When the forklift robot moves along the optimal path toward the target node, determine whether the node with the shortest distance to the mobile robot on the global path 1 is the target node 11 when the mobile robot is at the end node K of the local path; if not, dis_goal(v, ω) is 0; if so, dis_goal(v, ω)=L*cosθL ; L is the distance between the local path end node K and the target node 11; θ L is the angle between the line connecting the local path end node and the target node relative to the direction of the preferred path line. When the local path end node is inconsistent with the target node, it means that the target node is in front of the local path end node, and it does not interfere with the movement of the mobile robot to the local path end node. When the local path end node is consistent with the target node, if the mobile robot moves in front of the local path end node, it will cause the mobile robot to overtake the target node, thus passing L and θ. L The distance LA that the mobile robot exceeds the target node is calculated so that the mobile robot can return to the target node accurately.

[0021] In S3, delta_cost(v,w) is calculated by the following formula;

[0022] delta_cost(v,w)=θ bw -θ t .

[0023] θ bw =arctan[(2θ p -θ t ) / (θ pr -θ r )].

[0024] θ bw is the optimal steering angle of the steering wheel; θ p is the angle of entering the next node p on the local path; θ t is the navigation angle of the mobile robot at time t; θ r is the current navigation angle of the mobile robot; θ pr The angle between the next node p on the local path and the current coordinates of the mobile robot is calculated. The average of the delta_cost(v,w) values ​​at different times is used as the cost of the deviation between the optimal steering wheel angle and the current vehicle body angle. By calculating the average value, the optimal steering wheel overshoot angle is accurately calculated.

[0025] dis_angle(v,w) is calculated by the following formula;

[0026] dis_angle(v,w)=|θ p -θ t |.

[0027] θ p =arctan[(y p -y t ) / (x p -x t )].

[0028] y p is the y coordinate of the next node p; t is the y coordinate of the mobile robot at time t; x p is the x coordinate of the next node p; x t is the x-coordinate of the mobile robot at time t; this coordinate is obtained by the positioning system. The average of the dis_angle(v,w) values ​​at different times is used as the cost value for the deviation between the optimal and current vehicle orientation angles. By calculating the average value, the cost value for the deviation between the optimal and current vehicle orientation angles is highly accurate.

[0029] diff_delta is calculated by the following formula; diff_delta=θ bw -θ w； θ w is the current steering wheel heading angle.

[0030] S1 also includes the preset moving speed range, maximum acceleration and maximum deceleration speed of the forklift robot.

[0031] Moving speed range v1={(v,w) | v∈[v min ,v max ],w∈[w min ,w max The maximum and minimum speed ranges of the forklift robot are preset and can be adjusted according to different usage scenarios to meet different usage needs.

[0032] Maximum acceleration v c is the current linear velocity of the forklift robot, w c is the current angular velocity of the forklift robot; is the maximum linear speed of the forklift robot; is the minimum linear speed of the forklift robot; is the maximum angular velocity of the forklift robot; is the maximum angular velocity of the forklift robot.

[0033] Maximum deceleration dist(v,w) is the shortest distance between the forklift robot and the obstacle.

[0034] The working principle of the present invention is as follows: a forklift-type robot is a forklift-type robot, and a local path closest to the global path is selected as the optimal path; in this way, the trajectory of the optimal path is aligned with the trajectory of the global path, and the optimal path has good smoothness, thereby avoiding interference with another global path when the forklift-type robot moves along the optimal path; in this way, a forklift-type robot will not interfere with a forklift-type robot moving between another different initial node and a different target node.

Claims

1. A method for moving a forklift robot, characterized in that: The following steps are involved: S1, generate a global path between the initial node and the target node; S2. Generate one or more local paths on the global path; S3, evaluating the speed of different local paths through the speed evaluation function; The speed evaluation function is: Cost(v,w) =100 +[delta_cost(v,w)* a]+ [dis_angle(v,w)*β]+ [dis_angle(v,w)*traj.xv *γ]+[ (diff_delta / 2)* vel(v,w)*δ]+[ dis_goal(v,w)*η]; a is the preset steering wheel angle deviation constant of the forklift robot; β is the angular error constant of the mobile robot; γ is the deceleration constant; δ is the acceleration constant; η is the target following error constant; delta_cost(v,w) is the cost of the deviation between the optimal steering wheel angle and the current vehicle body angle; dis_angle(v,w) is the cost of the deviation between the optimal vehicle body angle and the current vehicle body angle; traj.xv is the linear velocity during the path tracking; diff_delta is the cost of the deviation between the optimal steering wheel angle and the current steering wheel angle; dis_goal(v,w) is the target node evaluation function; vel(v,w) is the velocity evaluation function; dis_goal(v,w) is the penalty cost for exceeding the end point; S4, select the local path with the lowest evaluation score as the optimal path; S5. The mobile robot moves along the optimal path toward the target node.

2. The method for moving a forklift robot according to claim 1, wherein: delta_cost(v,w) is calculated by the following formula; delta_cost(v,w)= θ bw -θ t ; i bw =arctan[(2θ p -θ t ) / (θ pr -θ r )]; θ bw is the optimal heading angle of the steering wheel; θ p is the angle of entering the next node p on the local path; θ t is the navigation angle of the mobile robot at time t; θ r is the current navigation angle of the mobile robot; θ pr is the angle between the next node p in the local path and the current coordinates of the mobile robot; the average value of delta_cost(v,w) at different times is used as the cost value of the deviation between the optimal steering wheel orientation angle and the current orientation angle of the vehicle body.

3. The method for moving a forklift robot according to claim 2, wherein: dis_angle(v,w) is calculated by the following formula; dis_angle(v,w)=|θ p -θ t |; θ p =arctan[(and p -and t ) / (x p -x t )]; y p is the y coordinate of the next node p; t is the y coordinate of the mobile robot at time t; x p is the x coordinate of the next node p; x t is the x-coordinate of the mobile robot at time t.

4. The method for moving a forklift robot according to claim 3, wherein: diff_delta is calculated by the following formula; diff_delta=θ bw -θ w； θ w is the current steering wheel heading angle.

5. The method for moving a forklift robot according to claim 4, wherein: S5 is followed by S6, which determines whether the node with the shortest distance to the mobile robot on the global path is the target node when the mobile robot is at the end node of the local path; if not, dis_goal(v, ω) is 0; if so, dis_goal(v, ω)=L*cosθ L ; L is the distance between the local path end node and the target node; θ L It is the angle between the line connecting the end node of the local path and the target node relative to the direction of the preferred path line.

6. A method for moving a forklift robot according to claim 5, characterized in that: S1 also includes the preset mobile robot's moving speed range; v1={(v,w) | v∈[v min ,v max ],w∈[w min ,w max ]},v min is the minimum linear velocity, v max is the maximum linear velocity, w min is the minimum angular velocity, w max is the maximum angular velocity.

7. The method for moving a forklift robot according to claim 6, wherein: S1 also includes the maximum acceleration of the preset mobile robot; v c is the current linear velocity of the mobile robot, is the current angular velocity of the mobile robot; is the maximum linear velocity of the mobile robot; is the minimum linear velocity of the mobile robot; is the maximum angular velocity of the mobile robot; is the maximum angular velocity of the mobile robot.

8. The method for moving a forklift robot according to claim 7, wherein: S1 also includes the maximum deceleration of the preset mobile robot; dist(v,w) is the shortest distance between the mobile robot and the obstacle.

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