Four-Wheel Steering Angle Constraints for Speed-Adaptive Stability
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Solution Overview
Problem
Existing four-wheel steering systems for vehicles face complexity in controlling both front and rear wheels for safe and stable operation, particularly in dynamic conditions such as varying speeds and trajectories, which can lead to increased complexity and potential instability.
Innovation Solution
The implementation of a vehicle computing system that dynamically determines steering angle constraints based on vehicle speed, trajectory, and operational domain, using a kinematic vehicle model to generate and apply steering limits for leading and trailing wheels, ensuring reduced sideslip and improved stability through independent control of all four wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If four-wheel steering is implemented to improve maneuverability and stability, then vehicle control performance is improved, but system complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting steering angle limits based on vehicle speed. At different speeds, different steering angle constraints are imposed on front and rear wheels to optimize stability and maneuverability. This resolves the contradiction by using variable parameters (steering angle limits) to improve reliability while managing complexity through speed-based control strategies.
Solution Approach 2:
The patent implements dynamics by transitioning from static steering limits to dynamic steering angle constraints that adapt to vehicle speed. The system continuously adjusts the steering angle limits for front and rear wheels based on real-time speed conditions, enabling the system to improve stability and maneuverability while keeping control complexity manageable through adaptive rather than fixed control parameters.
2Measurement precision
If dynamic steering angle constraints are applied to improve stability and reduce sideslip, then vehicle control precision is improved, but control system complexity increases
Solution Approach 1:
The patent uses parameter changes by implementing speed-dependent steering angle limits. The control system adjusts the maximum allowable steering angles for front and rear wheels based on vehicle speed, providing precise control at different operating conditions. This approach improves measurement precision for steering control while managing complexity by using speed as a straightforward parameter for adjustment.
Solution Approach 2:
The patent applies segmentation by dividing the steering control into separate angle limits for front wheels and rear wheels. Each wheel set has its own steering angle constraints that are independently adjusted based on speed, allowing precise control of each segment while simplifying the overall control logic through modular speed-based thresholds.
3Speed
If four-wheel steering is used to enhance maneuverability at low speeds, then vehicle agility is improved, but control complexity and potential instability increase
Solution Approach 1:
The patent implements dynamics by applying different steering angle constraints at different speed ranges. At low speeds, the system allows larger steering angles for both front and rear wheels to maximize maneuverability and agility. At higher speeds, the constraints are reduced to maintain stability. This dynamic adjustment resolves the contradiction by adapting control parameters to speed conditions.
Solution Approach 2:
The patent applies local quality by imposing specific steering angle limits on front and rear wheels based on local speed conditions. Each wheel set receives tailored steering constraints appropriate for the current speed regime, enabling optimal maneuverability at low speeds while maintaining stability at high speeds, thus resolving the contradiction through localized control adjustments.
Data Source
AI summary
Four-wheel steering of a vehicle, e.g., in which leading wheels and trailing wheels are steered independently of each other, can provide improved maneuverability and stability. Steering angle constraints may be used to limit or prevent saturation of steering by only one set of wheels as well as to reduce sideslip. The steering angle constraints are vehicle independent and applicable across a fleet of different vehicles based on vehicle speed. For instance, the steering angle constraints establish angle limits that dynamically adjust based on vehicle speed to ensure vehicle velocity and acceleration remain within predefined limits as established by autonomous vehicle system design.