Autonomous Vehicle Lateral Control with Cascaded Path Tracking
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Solution Overview
Problem
Current systems for lateral control in autonomous vehicle path-tracking face challenges in accurately maintaining vehicle position relative to a path, particularly in managing sideslip angle and yaw rate, which affects the vehicle's ability to follow the path effectively.
Innovation Solution
A lateral control system with a cascaded control structure, comprising an outer loop that calculates the difference between the desired target and current position, and an inner loop that generates and maintains sideslip angle and yaw rate, using these values to adjust the relative yaw angle and lateral distance, and subsequently control the front steering angle, rear steering angle, and wheel torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-loop control system is used for lateral control, then the device complexity is reduced, but the path-tracking precision and stability deteriorate
Solution Approach 1:
The control system is segmented into two distinct control loops: an outer control loop that manages path-tracking precision by calculating desired yaw angle and lateral distance, and an inner control loop that manages stability by controlling sideslip angle and yaw rate. This segmentation allows each loop to specialize in specific control objectives, improving overall path-tracking precision without requiring a completely complex unified system.
Solution Approach 2:
The control architecture implements a nested structure where the inner control loop (managing sideslip angle and yaw rate) is embedded within the outer control loop (managing path-tracking). The inner loop's output feeds into the outer loop's control calculations, creating a hierarchical nested arrangement that achieves high precision and stability while maintaining manageable system complexity through structured organization.
2Speed
If sideslip angle and yaw rate are not properly managed, then the control response speed is improved, but the vehicle stability deteriorates
Solution Approach 1:
The inner control loop performs preliminary action by proactively managing sideslip angle and yaw rate before they can cause instability. By continuously calculating and adjusting these parameters in advance, the system maintains vehicle stability while allowing the outer loop to operate with fast response for path-tracking corrections.
Solution Approach 2:
The control system implements feedback mechanisms where the inner loop continuously monitors sideslip angle and yaw rate, and the outer loop monitors path deviation. This multi-level feedback ensures that stability-critical parameters are constantly adjusted, maintaining vehicle stability while enabling rapid response to path-tracking errors through the outer loop's corrective actions.
Data Source
AI summary
A system for lateral control in-path tracking of an autonomous vehicle includes a lateral controller. The lateral controller controls movement of the autonomous vehicle relative to a path and receives as an input a desired target. An outer control loop of the lateral controller includes a first controller generating an output based on the difference between the desired target and a current position of the autonomous vehicle. An inner control loop of the lateral controller includes a second controller receiving the generated output from the first controller. The inner control loop generates a sideslip angle and a yaw rate, wherein the sideslip angle and the yaw rate are returned to the second controller. The sideslip angle and the yaw rate are used to generate the relative yaw angle and lateral distance, which are returned to the first controller as the current position of the autonomous vehicle.