Electric Power Steering Torque Damping Adaptation
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Solution Overview
Problem
Existing electric power assisted steering systems lack the ability to dynamically adjust torque damping based on steering direction, leading to inconsistent steering feel and stability, particularly when moving away from or returning to the center position.
Innovation Solution
An electric power assisted steering system that uses different torque damping functions, each with unique gain terms, for steering movements away from and towards the center position, with a blending mechanism to smoothly transition between these functions, ensuring a more natural and stable steering experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single torque damping function is used for all steering movements, then the system structure is simple, but the steering feel is inconsistent and driver confidence is reduced
Solution Approach 1:
The patent applies the Dynamics principle by making the torque damping function adaptive rather than static. The system dynamically selects between a first torque damping function and a second torque damping function based on the steering wheel's movement direction relative to the center position. This dynamic adaptation ensures consistent and natural steering feel throughout the steering range, resolving the contradiction between steering feel consistency and system simplicity.
Solution Approach 2:
The patent implements Parameter changes by modifying the damping characteristics based on steering conditions. The first torque damping function applies different damping characteristics than the second function, with the transition between them controlled by blending factors. This parameter change approach allows the system to provide optimized damping for both center-seeking and center-holding scenarios, improving steering feel consistency without requiring a completely complex system architecture.
2Stability of the object's composition
If high damping is applied at all steering velocities, then vehicle stability is improved, but steering responsiveness is reduced
Solution Approach 1:
The patent applies the Local quality principle by providing different damping characteristics for different steering scenarios. The first torque damping function is optimized for maintaining vehicle stability during center-seeking movements, while the second torque damping function is optimized for steering responsiveness during center-holding movements. This localized optimization ensures that high damping is applied only where needed for stability, rather than uniformly across all steering conditions.
Solution Approach 2:
The system dynamically adjusts damping levels based on the steering wheel's movement direction and velocity. By using blending factors that vary with steering conditions, the system transitions smoothly between high-damping and low-damping modes, maintaining both vehicle stability and steering responsiveness without the trade-off that would result from applying high damping at all times.
3Ease of operation
If a single torque damping function is used, then the control system is simple, but steering behavior is inconsistent during direction changes
Solution Approach 1:
The patent implements Feedback by continuously monitoring the steering wheel's movement direction and using this information to select the appropriate torque damping function. The blending factor is determined based on feedback from the steering angle and angular velocity sensors, ensuring that the correct damping characteristics are applied during direction changes. This feedback mechanism maintains consistent steering behavior without requiring overly complex control logic.
Solution Approach 2:
The control system dynamically switches between the first and second torque damping functions based on real-time steering conditions. The blending factor provides smooth transitions between functions during direction changes, eliminating the inconsistencies that would occur with a single static function. This dynamic control approach maintains steering behavior consistency while keeping the control system structure manageable.
Data Source
AI summary
An electric power assisted steering system comprises a first part that in use determines the sign of a first signal indicative of the position of a part of the steering, and a second part that in use determines the sign of a second signal indicative of the velocity of a part of the steering. A processing unit that in use determines whether the steering wheel is moving away from a centre position or returning to the centre position from the determined signs of the two signals, and sets a value of a torque damping component using different tunes for when the steering wheel is moving away from the centre and when term and when the steering wheel is returning to the centre. The processing unit may blend the two tunes when it detects a change in the direction of steering corresponding to a return to centre following movement away from centre or movement away from centre following a return to centre.