Electric Power Steering Control for Road Feel and Stability
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Solution Overview
Problem
Conventional electric power steering systems suppress road condition-induced vibrations, preventing drivers from feeling responsive steering feedback, which deteriorates the steering experience.
Innovation Solution
An electric power steering system with a control mechanism that adjusts assist torque components based on steering torque and vehicle speed, allowing drivers to feel road information while maintaining system stability and suppressing unwanted vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If steered angle feedback control is applied to suppress reverse input vibration, then vehicle stability is improved, but steering feel is deteriorated
Solution Approach 1:
The patent applies different feedback control strategies for different speed ranges. At low speeds, steered angle feedback control is weakened or disabled to preserve steering feel, while at high speeds it is activated to suppress vibrations and improve stability. This local differentiation of control characteristics resolves the contradiction between steering feel and vehicle stability.
Solution Approach 2:
The patent dynamically adjusts the feedback control gain based on vehicle speed. The control system transitions from a steering-feel-prioritizing mode at low speeds to a stability-prioritizing mode at high speeds. This dynamic adaptation allows the system to optimize performance for different operating conditions, resolving the contradiction between competing objectives.
2Power
If torque feedback control is applied to maintain optimal steering torque, then steering assistance is improved, but steering feel is deteriorated
Solution Approach 1:
The patent applies partial feedback control by selectively enabling steered angle feedback only when necessary (at high speeds), rather than continuously applying full torque feedback. This partial application of control maintains steering assistance where needed while preserving steering feel during normal driving conditions.
Data Source
AI summary
An electric power steering system includes a motor control device that controls driving of a motor based on an assist command value, the motor applying assist torque to a steering mechanism. The motor control device computes a first assist component based on steering torque and a vehicle speed. The motor control device computes a second assist component based on the steering torque and the first assist component. The motor control device computes the assist command value by adding the second assist component to the first assist component. The motor control device includes a road information compensation portion that adjusts the second assist component contained in the assist command value. A basic assist component computation portion computes the first assist component in accordance with a degree of adjustment of the second assist component.