Autonomous Vehicle Steering Angle Limits for High-Speed Stability
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Solution Overview
Problem
Existing systems for autonomous and semi-autonomous vehicles fail to dynamically determine appropriate steering angle limits, leading to potentially unsafe maneuvers at highway speeds due to errors in sensor input analysis, which can result in unexpected or aggressive vehicle movements.
Innovation Solution
A vehicle management system that determines a steering wheel angle limit based on maximum lateral acceleration and current conditions, such as weather, road conditions, and vehicle dynamics, to cap or limit steering angles and prevent unsafe maneuvers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the autonomous vehicle control system generates steering commands based on sensor input analysis, then the vehicle can autonomously navigate and respond to environmental hazards, but errors in sensor input analysis can lead to excessively large steering angles and unsafe maneuvers
Solution Approach 1:
A steering angle limit determination module is introduced as an intermediary component between the autonomous vehicle control system and the steering actuator. This module dynamically determines safe steering angle limits based on vehicle speed, lateral acceleration, and road conditions, then compares the generated steering commands against these limits. When a command exceeds the limit, it is adjusted or rejected, preventing unsafe maneuvers while preserving autonomous navigation functionality.
Solution Approach 2:
The system implements a feedback mechanism where the actual steering angle and vehicle state (speed, lateral acceleration) are continuously monitored and fed back to the steering angle limit determination module. This feedback loop allows the system to dynamically adjust steering angle limits in real-time based on current operating conditions, ensuring that autonomous steering commands remain within safe boundaries while adapting to changing environmental factors.
2Speed
If the vehicle allows large steering angles for rapid response to hazards, then collision avoidance capability is improved, but vehicle stability and passenger comfort deteriorate due to excessive lateral acceleration
Solution Approach 1:
The steering angle limit is not a fixed value but a dynamic parameter that adjusts in real-time based on vehicle speed, lateral acceleration, and road conditions. At lower speeds, higher steering angles are permitted for rapid response to hazards. As speed increases, the system dynamically reduces the maximum allowable steering angle to maintain vehicle stability and prevent excessive lateral acceleration, thereby adapting the vehicle's response characteristics to current operating conditions.
Solution Approach 2:
The system changes the parameter of steering angle limit based on vehicle operating conditions. By monitoring vehicle speed and lateral acceleration, the system adjusts the maximum steering angle parameter dynamically - allowing larger angles when safe and responsive action is needed at lower speeds, while constraining the angle parameter at higher speeds to maintain stability and comfort. This parameter adaptation resolves the contradiction between rapid response capability and vehicle stability.
3Reliability
If the system dynamically adjusts steering angle limits based on vehicle conditions, then safety is improved, but system complexity increases due to additional control modules and calculations
Solution Approach 1:
The steering angle limit determination module performs multiple functions: it calculates safe steering angle limits based on vehicle speed and lateral acceleration, compares generated steering commands against these limits, adjusts excessive commands, and prevents unsafe maneuvers. By consolidating these safety-critical functions into a single multi-functional module, the system improves reliability without proportionally increasing complexity, as the module leverages existing sensor data and control architecture.
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
Various embodiments may include methods of limiting a steering command angle during operation of a vehicle. Various embodiments may include determining a speed of the vehicle, applying the determined speed to a dynamic model of the autonomous vehicle to determine a steering wheel command angle limit. Embodiments may further include determining whether a received or commanded steering command angle exceeds the steering wheel command angle limit and altering the steering command angle to an angle no greater than the maximum steering command angle if the received/commanded steering command angle exceeds the steering wheel command angle limit.