Steering Wheel Torque Control for Vehicle Yaw Stability
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Solution Overview
Problem
Traditional yaw stability control systems face a conflict between optimally utilizing front axle and rear axle tyre-to-road friction due to reliance on steering-wheel angle as an indicator of driver intent, leading to suboptimal vehicle control, especially in scenarios like aquaplaning, low friction conditions, tyre explosions, and dynamic driving maneuvers.
Innovation Solution
The method involves using steering-wheel torque as an indicator of driver intent, transforming it into a target yaw and/or lateral vehicle state to control actuators like brakes and engine, ensuring optimal front axle friction utilization and effective vehicle yaw rate control through a torque ramp and vehicle state actuator management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steering-wheel angle is used as an indicator of driver intent to calculate target yaw rate, then the control system can maintain directional stability, but the front axle tyre-to-road friction cannot be optimally utilized and rear axle friction utilization becomes suboptimal
Solution Approach 1:
The patent changes the indicator parameter from steering-wheel angle to steering-wheel torque. This parameter change allows the system to detect driver intent more accurately without conflicting with optimal tyre friction utilization, as torque directly reflects the driver's steering effort rather than the mechanical angle which is influenced by pneumatic trail effects
Solution Approach 2:
The patent introduces steering-wheel torque as an intermediary parameter that mediates between driver intent and vehicle control. This intermediary provides a more direct and accurate representation of driver intent compared to steering-wheel angle, enabling better coordination between stability control and friction utilization
2Reliability
If traditional yaw stability control brakes the rear inside wheel to counteract understeer, then vehicle yaw stability is improved, but excessive steering intervention occurs and time delay increases in critical situations
Solution Approach 1:
The patent applies preliminary action by using steering-wheel torque to predict and prevent excessive steering before it occurs. The torque-based detection allows the system to anticipate driver intent and apply appropriate control actions in advance, reducing the need for corrective braking interventions and minimizing response time
Solution Approach 2:
The patent implements feedback by continuously monitoring steering-wheel torque and using it to adjust vehicle control in real-time. This feedback mechanism enables the system to respond more quickly and accurately to driver intent, reducing time delays compared to traditional angle-based systems
3Adaptability or versatility
If steering-wheel angle is used to calculate target yaw rate, then the control system can respond to driver steering input, but it cannot accurately detect driver intent in low friction conditions such as aquaplaning
Solution Approach 1:
The patent changes the measurement parameter from steering-wheel angle to steering-wheel torque. Torque provides more precise information about driver intent because it directly measures the force applied by the driver, which remains meaningful even when road friction conditions change and affect the relationship between steering angle and vehicle response
Data Source
AI summary
A method in controlling a steering assistance actuator in a steering system (100) of a vehicle and one or more controllable vehicle state actuators so that the steering-wheel torque applied by the driver is an indicative for the driver intention and transformed to a target yaw and/or lateral vehicle state to be controlled by one or more vehicle state controllers and actuated by the vehicle state actuators along with the fact that the level of understeer is used to achieve an additional steering-wheel torque in the form of a ramp in the steering-wheel torque as a function of the level of understeer.