Steering Assist Torque Control via Lateral Position Command
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Solution Overview
Problem
Lane keeping systems in autonomous mode often provide excessive steering assist torque, leading to objectionable variations in lateral acceleration and increased handwheel movement, which can disengage drivers and compromise vehicle stability.
Innovation Solution
A steering system that includes a lateral position module and a torque command module, determining assist torque based on the vehicle's lateral position command, near field heading angle, and curvature of the lane, to provide a more nuanced and controlled steering assist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the lane keeping system provides excessive steering assist torque in autonomous mode, then the vehicle can maintain lane position automatically, but this creates objectionable variations in lateral acceleration and increased handwheel movement
Solution Approach 1:
The system dynamically adjusts the torque assist command based on the driver's handwheel activity. When handwheel activity exceeds a threshold, the system reduces or suspends torque assist to prevent excessive handwheel movement and lateral acceleration variations. This dynamic adaptation allows the system to maintain autonomous lane keeping while responding to driver inputs in real-time.
Solution Approach 2:
The system continuously monitors handwheel activity and uses this feedback to modulate the torque assist command. By measuring the driver's steering inputs and adjusting the assist torque accordingly, the system creates a closed-loop control that prevents harmful lateral acceleration variations while maintaining automated lane positioning.
2Manufacturing precision
If the lane keeping system provides excessive steering assist torque, then lane position maintenance is improved, but driver engagement in the driving process may be reduced
Solution Approach 1:
The system dynamically adapts its level of intervention based on driver behavior. When the driver exhibits normal handwheel activity, the system provides minimal torque assist to maintain lane position. When handwheel activity becomes excessive, the system reduces assist torque, thereby encouraging the driver to take more active control and remain engaged in the driving process.
Solution Approach 2:
The system changes the torque assist parameter based on detected handwheel activity levels. By monitoring steering inputs and adjusting the assist torque parameter in response, the system maintains precision lane positioning while adapting to driver engagement levels, ensuring the driver remains appropriately involved in the driving task.
3Reliability
If the system uses lateral acceleration for controlling torque assist in autonomous mode, then lane keeping functionality is enhanced, but handwheel movement increases beyond typical driver input
Solution Approach 1:
The system uses feedback from handwheel activity sensors to modulate the torque assist command. By continuously monitoring the driver's steering inputs and adjusting the assist torque in real-time, the system maintains reliable lane keeping functionality while preventing excessive handwheel movement that would occur with fixed high-gain torque assist based solely on lateral acceleration.
Solution Approach 2:
The system dynamically changes the torque assist parameter based on detected handwheel activity. When handwheel movement is within normal ranges, the system allows higher torque assist for responsive lane keeping. When handwheel movement becomes excessive, the system reduces the torque assist parameter, thereby maintaining lane keeping reliability while limiting abnormal handwheel movement.
Data Source
AI summary
A steering system providing an assist torque to a handwheel is provided, and includes a lateral position module and a torque command module. The lateral position module determines a lateral position command based on a curvature of a lane and a near field heading angle. The torque command module determines the torque assist based on the lateral position command.