Steering Wheel Restoring Torque Adaptation for Straight-Line Stability
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Solution Overview
Problem
Existing electromechanical steering systems face challenges in maintaining precise straight-line stability and intuitive driver feedback, especially under dynamic conditions such as side winds and varying tire pressures, due to asymmetries and traction differences.
Innovation Solution
An adaptive method adjusts the steering wheel return torque based on a restoring function that increases with steering wheel deflection from the straight-ahead position, using an angular offset calculated by a learning algorithm to ensure the torque magnitude remains below a threshold, allowing for symmetrical manual torque buildup and compensation for asymmetries and dynamic disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the steering wheel restoring torque is increased to improve straight-line stability, then the vehicle maintains better straight-ahead driving, but the driver perceives excessive torque and loses intuitive feedback
Solution Approach 1:
The restoring function dynamically adapts its characteristics based on driving conditions. The control device continuously adjusts the restoring torque output by modifying the angular offset value supplied to the restoring function, allowing the system to optimize between stability and driver comfort in real-time depending on detected operating conditions such as vehicle speed, steering angle, and road conditions.
Solution Approach 2:
The system changes the parameter of angular offset value supplied to the restoring function to optimize performance. By adjusting this parameter, the control device modifies the torque characteristics of the restoring function without changing the physical structure, enabling flexible adaptation to different driving scenarios while maintaining both stability and driver comfort.
2Speed
If the power steering motor is actuated with high dynamics to compensate for reaction forces, then steering response is improved, but the system becomes more complex and energy-consuming
Solution Approach 1:
The control device uses feedback from sensors detecting steering wheel angle, vehicle speed, and operating conditions to continuously adjust the power steering motor output. This feedback mechanism enables the system to provide high dynamics when needed while avoiding unnecessary complexity by only activating advanced control features when actually required by the driving situation.
Solution Approach 2:
The system implements dynamic control where the power steering motor actuation characteristics are continuously adjusted based on real-time operating conditions. The control device modifies motor output dynamics adaptively, providing high response when needed while simplifying control in normal conditions, thus balancing performance with system complexity.
3Speed
If the restoring function provides large restoring torques for quick return to center, then steering wheel returns faster to straight-ahead position, but the driver experiences harsh feedback and loss of control intuition
Solution Approach 1:
The restoring function implements different torque characteristics for different steering wheel positions. In the central region around the straight-ahead position, the function provides gentler torque to maintain driver comfort and intuition. In outer regions with larger deflections, the function provides stronger restoring torque to ensure quick return to center, thus creating local quality variations that satisfy both requirements.
Solution Approach 2:
The control device dynamically adjusts the angular offset value supplied to the restoring function based on current steering conditions. This dynamic adjustment allows the system to optimize the balance between return speed and driver comfort in real-time, providing faster return when necessary while maintaining intuitive feedback during normal operation.
Data Source
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AI summary
The invention relates to a method for adjusting a steering wheel restoring torque of an electromechanical steering system, wherein by means of said steering wheel restoring torque a vehicle steering wheel is pushed back to an angular position leading to straight driving. The steering wheel restoring torque is set according to a restoring function, which considers a present steering angular position, wherein the restoring function is designed in such a way that the restoring function specifies restoring torques that increase with increasing deflection of the vehicle steering wheel from the angular position leading to straight travel, the restoring function contains a range leading to the sign change of the restoring torque, wherein said range contains the angular position intended for straight driving, and said range provides for restoring torques that are relatively small in magnitude compared to the maximum restoring torques that can be prompted by the restoring function. An angle value fed to the restoring function is changed by an angle offset value, wherein said angle offset value is adjusted in such a way that the magnitude of the steering wheel restoring torque perceived by the driver during straight driving is below a threshold that can be customized. It is thereby possible to operate an electromechanical steering system in such a way that, for a motor vehicle equipped therewith, advantageous straight-travel behavior results, while the steering wheel restoring characteristics are found to be suitable by the driver. The invention further relates to an electromechanical steering system suitable for performing the method.