Electric Power Steering Restoring Force Control
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Solution Overview
Problem
Electric power steering systems in vehicles experience increased internal friction at low temperatures, leading to a false steering sensation due to the additional restoring force used to compensate for this friction, which affects the driver's experience.
Innovation Solution
An electric power steering system that reduces the additional restoring force based on the detected steering direction and manual torque, using a temperature-dependent and manual torque-dependent characteristic curve to minimize interference with the driver's steering sensation while compensating for internal friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional restoring force is provided to compensate for increased internal friction at low temperatures, then the steering system can return to neutral position, but the driver experiences false steering sensation
Solution Approach 1:
The control unit dynamically adjusts the additional restoring force based on detected steering direction and manual torque. When steering direction changes or manual torque increases, the additional restoring force is reduced or deactivated, creating a dynamic response that adapts to driver intent while maintaining the ability to return to neutral position when needed
Solution Approach 2:
The system continuously monitors steering direction and manual torque through sensors, using this feedback to modulate the additional restoring force in real-time. This feedback mechanism ensures the system responds appropriately to driver actions while maintaining reliable return-to-neutral functionality when no steering input is detected
2Ease of operation
If additional restoring force is reduced based on steering direction and manual torque, then steering sensation is improved, but internal friction compensation may be insufficient
Solution Approach 1:
The system dynamically modulates the additional restoring force based on real-time detection of steering direction and manual torque magnitude. When manual torque is low or steering direction changes, the full compensation is applied; when manual torque increases indicating active steering, the compensation is reduced to prevent interference with driver intent
Solution Approach 2:
The control unit changes the parameter of additional restoring force magnitude based on detected conditions. By adjusting this parameter according to steering direction and manual torque thresholds, the system optimizes both steering sensation and friction compensation effectiveness across different operating conditions
Data Source
AI summary
A method for operating an electric power steering system of a motor vehicle, wherein a steering wheel angle is specified by a steering handle as a measurement for a desired wheel steering angle for at least one steerable wheel of the motor vehicle, wherein an electric servo drive having an electric motor provides steering assistance, and wherein an additional restoring force is provided to compensate for increased internal friction in the power steering system based upon temperature, wherein the additional restoring force is reduced based upon a desired steering direction that is detected at the steering handle. Also disclosed is an associated electric power steering system, an associated computer program, and an associated control unit.