Autonomous Vehicle Steering Control With Yaw-Limited Path Tracking
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Solution Overview
Problem
Fully automated agricultural machines lack robust control systems to handle operational anomalies and corrections without operator oversight, requiring more sophisticated navigation to maintain precision and efficiency.
Innovation Solution
A cascading control loop system in autonomous machines that combines an outer loop to determine the set heading using a hyperbolic tangent function and an inner loop to drive the machine, with automatic adjustment of the error slope to prevent excessive yaw rate, allowing the machine to follow a reference path while maintaining stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the error slope parameter is increased to improve path tracking accuracy, then the machine responds more aggressively to correct heading errors, but the yaw rate becomes excessive causing instability and overshooting
Solution Approach 1:
The error slope parameter is transformed from a static fixed value to a dynamic variable that automatically adjusts based on current operating conditions (distance to reference path, current yaw rate). This allows the system to maintain high tracking accuracy when safe while preventing instability when the machine is vulnerable to overshooting
Solution Approach 2:
The system implements feedback by continuously monitoring the current yaw rate and distance to reference path, then using this information to adjust the error slope parameter. The feedback loop ensures that aggressive correction is only applied when the machine can safely handle the resulting yaw changes
2Productivity
If the machine follows the reference path aggressively to improve efficiency, then less time is spent correcting deviations, but the control system becomes unstable due to excessive heading changes
Solution Approach 1:
The adaptive error slope enables the control system to dynamically balance aggressive path following with stability maintenance. By adjusting the error slope in real-time based on machine response capabilities, the system achieves high productivity without sacrificing control reliability
3Device complexity
If a fixed error slope parameter is used to simplify control, then the system is easier to implement, but it cannot adapt to varying distances from the reference path or changing operating conditions
Solution Approach 1:
The control system performs self-adjustment by automatically modifying the error slope parameter based on its own state (current position, current yaw rate). This self-service capability eliminates the need for complex external tuning while maintaining high adaptability to varying operating conditions
Data Source
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AI summary
A mobile machine comprises a chassis, a plurality of ground-engaging elements, actuators for driving movement of the ground-engaging elements and a controller for controlling each of the actuators to cause the mobile machine to follow a reference path. The controller is configured to implement a cascading control loop for controlling movement of the mobile machine, the cascading control loop including an outer loop and an inner loop. The outer loop is configured to determine a set heading for reducing a distance between the mobile machine and the reference path, the set heading being determined using an error slope parameter. The inner loop is configured to drive the actuators so that the mobile machine follows the set heading determined by the outer loop. The controller is configured to automatically adjust the error slope value so that the rate of change of the set heading does not exceed a maximum yaw rate.