PATH TRACKING METHOD AND MOBILE ROBOT USING THE SAME

• US 20200133289A1
• Filed: 09/20/2019
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: UBTECH ROBOTICS CORP LTD
• Original Assignee: UBTECH ROBOTICS CORP LTD
• Inventors: Liu, Zhichao, Xiong, Youjun, Zhang, Jian
• Granted Patent: US 11,287,825 B2
• Time in Patent Office: Days
• CPC Class Codes: B25J 9/1666 Avoiding collision or forbidden zones
• CPC Class Codes: G05D 1/0223 involving speed control of the vehicle vehicle fittings for automatically controlling, i.e. preventing speed from exceeding an arbitrarily established velocity or maintaining speed at a particular velocity, as selected by the vehicle operator B60K31/00
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70

Abstract

The present disclosure provides a path tracking method as well as a mobile robot using the same. The method includes: obtaining a preset path and a current position of the mobile device; determining a forward-looking path point corresponding to the current position on the preset path; obtaining a path curvature corresponding to the forward-looking path point; and determining an adjustment velocity of the mobile device at the current position based on the path curvature corresponding to the forward-looking path point. In this manner, the adjustment velocity of the mobile device can be determined based on the curvature of the path, so as to adjust the velocity of the mobile device and improve the stability of path tracking of the mobile device at different path curvatures.

Claims

1. A computer-implemented path tracking method for a mobile device, comprising executing on a processor of the mobile device steps of:

obtaining a preset path and a current position of the mobile device;

determining a forward-looking path point corresponding to the current position on the preset path;

obtaining a path curvature corresponding to the forward-looking path point;

determining an adjustment velocity of the mobile device at the current position based on the path curvature corresponding to the forward-looking path point; and

adjusting a current velocity of the mobile device at the current position according to the adjustment velocity.

2. The method of claim 1, wherein the step of determining the forward-looking path point corresponding to the current position on the preset path comprises:

obtaining a forward-looking distance corresponding to the current position; and

selecting a first path point on the preset path as the forward-looking path point, wherein a distance between the first path point and the current position is the forward-looking distance corresponding to the current position.

3. The method of claim 2, wherein the step of obtaining the forward-looking distance corresponding to the current position comprises:

obtaining a preset forward-looking distance and taking the preset forward-looking distance as the forward-looking distance corresponding to the current position;

or

obtaining an adjustment forward-looking distance corresponding to a previous position of the mobile device and taking the adjustment forward-looking distance corresponding to the previous position as the forward-looking distance corresponding to the current position.

4. The method of claim 1, wherein the step of determining the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to the forward-looking path point comprises:

selecting at least one path point on a section of the preset path at which the forward-looking path point is located; and

calculating the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to each path point.

5. The method of claim 4, wherein the step of selecting the at least one path point on the section at which the forward-looking path point is located comprises:

searching for a second path point corresponding to the current position, wherein the second path point is a vertical point on the preset path corresponding to the current position; and

selecting at least one path point on a section of the preset path between the second path point and the forward-looking path point from the preset path.

6. The method of claim 4, wherein the step of calculating the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to each path point comprises:

calculating the path curvature corresponding to each path point and a first distance corresponding to each path point, wherein the first distance corresponding to the path point is a distance between the path point and a previous path point;

calculating a product of an absolute value of the path curvature corresponding to each path point and the first distance corresponding to the path point, and summing the products of all the path points to obtain a sum of the products;

determining an adjustment coefficient based on the sum of the products; and

calculating the adjustment velocity of the mobile device at the current position based on the adjustment coefficient and a current velocity of the mobile device.

7. The method of claim 6, wherein the step of calculating the path curvature corresponding to each path point comprises:

calculating a difference between the path curvature of each path point and the path curvature of the previous path point to take as the path curvature corresponding to the path point.

8. The method of claim 6, wherein the step of determining the adjustment coefficient based on the sum of the products comprises:

calculating a first ratio of the sum of the products to the forward-looking distance, wherein the forward-looking distance is a distance between the current position of the mobile device and the forward-looking path point; and

determining the adjustment coefficient based on the first ratio.

9. The method of claim 8, wherein the step of determining the adjustment coefficient based on the first ratio comprises:

calculating the adjustment coefficient based on a penalty function formula and the first ratio, wherein the penalty function formula is;

10. The method of claim 6, wherein the current velocity comprises a current line velocity, and the adjustment velocity comprises an adjustment line velocity and an adjustment angular velocity;

the step of calculating the adjustment velocity of the mobile device at the current position based on the adjustment coefficient and the current velocity of the mobile device comprises;

calculating a product of the current linear velocity of the mobile device and the adjustment coefficient to obtain the adjustment linear velocity;

calculating a product of the forward-looking distance and the adjustment coefficient to obtain the adjustment forward-looking distance, wherein the forward-looking distance is a distance between the current position of the mobile device and the forward-looking path point; and

calculating the adjustment angular velocity based on the adjustment linear velocity, the adjustment forward-looking distance, and a deviation angle, wherein the deviation angle is an included angle between a vector direction from the current position of the mobile device to the forward-looking path point and a direction of the current linear velocity of the mobile device.

11. The method of claim 10, wherein the step of calculating the adjustment angular velocity based on the adjustment linear velocity, the adjustment forward-looking distance, and the deviation angle comprises:

calculating a second ratio of the adjustment linear velocity to the adjustment forward-looking distance; and

calculating a product of the sine of the deviation angle and the second ratio to obtain the adjustment angular velocity.

12. A mobile robot, comprising:

a localization equipment;

a memory;

a processor; and

one or more computer programs stored in the memory and executable on the processor, wherein the one or more computer programs comprise;

instructions for obtaining a preset path and a current position of the mobile device, wherein the current position is obtained through the localization equipment;

instructions for determining a forward-looking path point corresponding to the current position on the preset path;

instructions for obtaining a path curvature corresponding to the forward-looking path point;

instructions for determining an adjustment velocity of the mobile device at the current position based on the path curvature corresponding to the forward-looking path point; and

instructions for adjusting a current velocity of the mobile device at the current position according to the adjustment velocity.

13. The mobile robot of claim 12, wherein the instructions for determining the forward-looking path point corresponding to the current position on the preset path comprise:

instructions for obtaining a forward-looking distance corresponding to the current position; and

instructions for selecting a first path point on the preset path as the forward-looking path point, wherein a distance between the first path point and the current position is the forward-looking distance corresponding to the current position.

14. The mobile robot of claim 13, wherein the instructions for obtaining the forward-looking distance corresponding to the current position comprise:

instructions for obtaining a preset forward-looking distance and taking the preset forward-looking distance as the forward-looking distance corresponding to the current position;

or

instructions for obtaining an adjustment forward-looking distance corresponding to a previous position of the mobile device and taking the adjustment forward-looking distance corresponding to the previous position as the forward-looking distance corresponding to the current position.

15. The mobile robot of claim 12, wherein the instructions for determining the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to the forward-looking path point comprise:

instructions for selecting at least one path point on a section of the preset path at which the forward-looking path point is located; and

instructions for calculating the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to each path point.

16. The mobile robot of claim 15, wherein the instructions for selecting the at least one path point on the section at which the forward-looking path point is located comprise:

instructions for searching for a second path point corresponding to the current position, wherein the second path point is a vertical point on the preset path corresponding to the current position; and

instructions for selecting at least one path point on a section of the preset path between the second path point and the forward-looking path point from the preset path.

17. The mobile robot of claim 15, wherein the instructions for calculating the adjustment velocity of the mobile device at the current position based on the path curvature corresponding to each path point comprise:

instructions for calculating the path curvature corresponding to each path point and a first distance corresponding to each path point, wherein the first distance corresponding to the path point is a distance between the path point and a previous path point;

instructions for calculating a product of an absolute value of the path curvature corresponding to each path point and the first distance corresponding to the path point, and summing the products of all the path points to obtain a sum of the products;

instructions for determining an adjustment coefficient based on the sum of the products; and

instructions for calculating the adjustment velocity of the mobile device at the current position based on the adjustment coefficient and a current velocity of the mobile device.

18. The mobile robot of claim 17, wherein the instructions for calculating the path curvature corresponding to each path point comprise:

instructions for calculating a difference between the path curvature of each path point and the path curvature of the previous path point to take as the path curvature corresponding to the path point.

19. The mobile robot of claim 17, wherein the instructions for determining the adjustment coefficient based on the sum of the products comprise:

instructions for calculating a first ratio of the sum of the products to the forward-looking distance, wherein the forward-looking distance is a distance between the current position of the mobile device and the forward-looking path point; and

instructions for determining the adjustment coefficient based on the first ratio.

20. The mobile robot of claim 19, wherein the instructions for determining the adjustment coefficient based on the first ratio comprise:

instructions for calculating the adjustment coefficient based on a penalty function formula and the first ratio, wherein the penalty function formula is;