Electric Power-Steering Control Device Road Surface Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electric power-steering systems fail to provide accurate feedback of road surface reactions to drivers, leading to instability and difficulty in maintaining vehicle convergence, especially when returning to neutral position or at higher speeds, due to interference between base assist and torque modifying operations.
Innovation Solution
An electric power-steering control device that separates the functions of estimating road surface force and generating assist compensation quantities, using a closed-loop system to compute target steering torque based on detected steering torque and motor speed, while minimizing interference between basic assist and compensation processes, and employing frequency band extraction to filter out unpleasant vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the assist steering power is determined based on steering torque to make steering operation lighter, then the steering operation becomes lighter, but it is difficult to provide accurate feedback of road surface reactions to the driver
Solution Approach 1:
The patent segments the control into two independent parts: basic assist quantity based on steering torque for ease of operation, and assist compensation quantity based on motor speed for road surface reaction feedback. This segmentation allows each part to optimize its function without interfering with the other.
Solution Approach 2:
The patent introduces motor speed as an intermediary parameter to estimate road surface reaction force. Instead of directly using steering torque for feedback, the system uses motor speed to infer road surface conditions, which then informs the assist compensation quantity.
2Ease of operation
If the assist torque is generated based on steering torque to suppress required torque on shaft, then the steering operation can be made light, but the convergence of the vehicle cannot be secured when returning to neutral position
Solution Approach 1:
The patent makes the assist compensation quantity dynamic by basing it on motor speed rather than static steering torque. This dynamic adjustment allows the system to adapt to changing conditions during steering operations, providing stability during return-to-center while maintaining lightness during initial steering.
Solution Approach 2:
The patent implements feedback by using motor speed information to generate assist compensation quantity. The motor speed reflects the actual state of the steering system, and this feedback is used to adjust the assist torque to ensure proper convergence behavior.
3Stability of the object's composition
If damping is used to secure convergence by giving resistance when returning steering wheel, then convergence improves, but resistance is also given when turning steering wheel deeply and steering feeling is spoiled
Solution Approach 1:
The patent applies different control characteristics to different phases of steering operation. The assist compensation quantity is specifically designed to provide damping during the return-to-center phase (when motor speed indicates reversing motion) while maintaining light assist during the initial deep steering phase, creating local optimization for each operational phase.
Data Source
AI summary
A base assist section generates a base assist command so that a steering reaction according to a road surface reaction returns to a steering wheel side. A modifying section generates a torque modifying command for modifying the base assist command so that an unstable movement of a vehicle converges appropriately. A sum of the each command becomes a final assist torque command. The base assist section estimates a road surface force based on the self-generated base assist command and a steering torque actually detected. A target steering torque is generated based on the estimated force, and the base assist command is generated based on a deviation of the target steering torque and the steering torque.