PID embedded LQR for autonomous driving vehicles (ADVS)

• US 10,671,070 B2
• Filed: 05/23/2018
• Issued: 06/02/2020
• Est. Priority Date: 05/23/2018
• Status: Active Grant

• Current Assignee: Baidu USA LLC (Baidu Incorporated)
• Original Assignee: Baidu USA LLC (Baidu Incorporated)
• Inventors: Zhu, Fan
• Primary Examiner(s): Cheung, Calvin
• Application Number:
  US15/987,877
• Publication Number:
  US 20190361438A1
• Time in Patent Office: 741 Days
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B60W 2050/0011 Proportional Integral Differential [PID] controller
• CPC Class Codes: B60W 50/0098 Details of control systems ensuring comfort, safety or stability not otherwise provided for
• CPC Class Codes: B60W 60/001 Planning or execution of driving tasks
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence
• CPC Class Codes: G05B 6/02 electric
• CPC Class Codes: G05D 1/0088 characterized by the autonomous decision making process, e.g. artificial intelligence, predefined behaviours using knowledge based models G06N5/00
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287

Abstract

In one embodiment, a system receives a reference trajectory including a reference path in which the ADV is to follow. The system controls the ADV along the reference path using a path tracking algorithm, including: determining a first lateral distance error, determining a second lateral distance error based on the first lateral distance error using a proportional-integral-derivative (PID) control system, where the second lateral distance error compensates for a lateral drift, and generating a steering command based on the second lateral distance error using the path tracking algorithm to control the ADV to minimize a lateral distance error, e.g., a lateral distance between an actual path taken by the ADV and the reference path.

Claims

1. A computer-implemented method for operating an autonomous driving vehicle (ADV), the method comprising:

receiving a reference trajectory including a reference path in which the ADV is to follow; and

controlling the ADV along the reference path using a path tracking control system, including

determining a first lateral distance error;

determining a second lateral distance error based on the first lateral distance error using a proportional-integral-derivative (PID) control system, wherein the second lateral distance error compensates for a lateral drift; and

generating a steering command based on the second lateral distance error using the path tracking control system to control the ADV to minimize a lateral distance between an actual path taken by the ADV and the reference path.

2. The computer-implemented method of claim 1, wherein the path tracking control system is a linear quadratic regulator (LQR) control system.

3. The computer-implemented method of claim 1, further comprising:

determining a lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles; and

generating the steering command based on the second lateral distance error and the second lateral distance error change rate using the path tracking control system to control the ADV to minimize the lateral distance between the actual path taken by the ADV and the reference path.

4. The computer-implemented method of claim 3, wherein determining a second lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles further comprises:

buffering a previously determined second lateral distance error for the previous driving cycle; and

determining the second lateral distance error change rate based on a change of the previous and a current determined second lateral distance errors determined in the previous and current driving cycle respectively.

5. The computer-implemented method of claim 3, further comprising generating a steering angle based on the second lateral distance error and the second lateral distance error change rate, wherein the steering angle is utilized to generate the steering command.

6. The computer-implemented method of claim 5, further comprising determining a heading error based on a difference between a current heading direction of the current driving cycle and an expected heading direction of the previous driving cycle, wherein the steering angle is generated further based on the heading error using the path tracking control system.

7. The computer-implemented method of claim 6, further comprising determining a heading error change rate based on the difference between the current heading direction and the expected heading direction in view of a time duration between the current driving cycle and the previous driving cycle, wherein the steering angle is generated further based on the heading error change rate using the path tracking control system.

8. The computer-implemented method of claim 1, wherein the PID control system determines the second lateral distance error by:

determining a desired lateral distance error;

calculating a difference value based on the desired lateral distance error and the first lateral distance error;

calculating the second lateral distance error based on a proportional, an integral, or a derivative term of the difference value; and

feeding back the second lateral distance error in view of the lateral drift for the PID control system to continuously update the calculation for the difference value in real-time.

9. The computer-implemented method of claim 1, wherein the proportional, the integral, and the derivative coefficients of the PID control system are approximately 1, 0.5, and 0.1 respectively.

10. A non-transitory machine-readable medium having instructions stored therein, which when executed by one or more processors, cause the one or more processors to perform operations, the operations comprising:

receiving a reference trajectory including a reference path in which an autonomous driving vehicle (ADV) is to follow; and

controlling the ADV along the reference path using a path tracking control system, including

determining a first lateral distance error;

determining a second lateral distance error based on the first lateral distance error using a proportional-integral-derivative (PID) control system, wherein the second lateral distance error compensates for a lateral drift; and

generating a steering command based on the second lateral distance error using the path tracking control system to control the ADV to minimize a lateral distance between an actual path taken by the ADV and the reference path.

11. The non-transitory machine-readable medium of claim 10, wherein the path tracking control system is a linear quadratic regulator (LQR) control system.

12. The non-transitory machine-readable medium of claim 10, wherein the operations further comprise:

determining a lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles; and

generating the steering command based on the second lateral distance error and the second lateral distance error change rate using the path tracking control system to control the ADV to minimize the lateral distance between the actual path taken by the ADV and the reference path.

13. The non-transitory machine-readable medium of claim 12, wherein determining a second lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles further comprises:

buffering a previously determined second lateral distance error for the previous driving cycle; and

determining the second lateral distance error change rate based on a change of the previous and a current determined second lateral distance errors determined in the previous and current driving cycles respectively.

14. The non-transitory machine-readable medium of claim 12, wherein the operations further comprise generating a steering angle based on the second lateral distance error and the second lateral distance error change rate, wherein the steering angle is utilized to generate the steering command using the path tracking control system.

15. The non-transitory machine-readable medium of claim 14, wherein the operations further comprise determining a heading error change rate based on a difference between a current heading direction and an expected heading direction in view of a time duration between the current driving cycle and the previous driving cycle, wherein the steering angle is generated further based on the heading error change rate using the path tracking control system.

16. A data processing system, comprising:

one or more processors; and

a memory coupled to the one or more processors to store instructions, which when executed by the one or more processors, cause the one or more processors to perform operations, the operations including

receiving a reference trajectory including a reference path in which an autonomous driving vehicle (ADV) is to follow; and

controlling the ADV along the reference path using a path tracking control system, including

determining a first lateral distance error;

determining a second lateral distance error based on the first lateral distance error using a proportional-integral-derivative (PID) control system, wherein the second lateral distance error compensates for a lateral drift; and

generating a steering command based on the second lateral distance error using the path tracking control system to control the ADV to minimize a lateral distance between an actual path taken by the ADV and the reference path.

17. The system of claim 16, wherein the path tracking control system is a linear quadratic regulator (LQR).

18. The system of claim 16, further comprising:

determining a lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles; and

generating the steering command based on the second lateral distance error and the second lateral distance error change rate using the path tracking control system to control the ADV to minimize the lateral distance between the actual path taken by the ADV and the reference path.

19. The system of claim 18, wherein determining a second lateral distance error change rate based on the determined second lateral distance error for a current and a previous driving cycles further comprises:

buffering a previously determined second lateral distance error for the previous driving cycle; and

determining the second lateral distance error change rate based on a change of the previous and a current determined second lateral distance errors determined in the previous and current driving cycles respectively.

20. The system of claim 18, further comprising generating a steering angle based on the second lateral distance error and the second lateral distance error change rate, wherein the steering angle is utilized to generate the steering command using the path tracking control system.