Electric Power Steering Control With Torque-Adaptive Friction Compensation
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Solution Overview
Problem
Existing electric power steering systems face challenges in balancing subtle steering feel and good steering angle tracking performance when steering assist control and steering angle control operate simultaneously.
Innovation Solution
A control device for electric power steering systems that includes a steering torque detection unit, first and second steering control value calculation units, a mixing unit, and a drive unit to generate steering force, with disturbance compensation torque setting to balance steering assist and angle control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If steering assist control and steering angle control operate simultaneously, then steering angle tracking performance is improved, but steering feel becomes less subtle
Solution Approach 1:
The patent changes the parameter of disturbance compensation torque based on steering torque magnitude. When steering torque is large, larger friction component is compensated; when steering torque is small, smaller friction component is compensated. This dynamic parameter adjustment resolves the contradiction by adapting the compensation level to operating conditions, maintaining both tracking performance and subtle steering feel.
2Measurement precision
If disturbance compensation torque with larger friction component is applied, then steering angle tracking performance is improved, but steering feel becomes heavier
Solution Approach 1:
The patent makes the disturbance compensation torque dynamic by adjusting the friction component based on steering torque magnitude. The system transitions from static compensation to dynamic compensation where the friction component varies with operating conditions, resolving the contradiction between tracking performance and steering feel.
Solution Approach 2:
The patent changes the friction component parameter of disturbance compensation torque based on steering torque magnitude. This parameter adaptation allows the system to optimize both tracking performance and steering feel by selecting appropriate compensation levels for different operating conditions.
Data Source
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Figure 2
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AI summary
In a mode where steering assist control and steering angle control for causing the actual steering angle to follow a target steering angle operate simultaneously, a subtle steering feel when a driver steers the vehicle and good steering angle tracking performance are both achieved. A control device for an electric power steering device includes a first steering control value calculation unit (40) configured to calculate a first steering control value based on the steering torque, and a second steering control value calculation unit (41, 42) configured to calculate a second steering control value for causing the actual steering angle to follow the target steering angle, and generates steering force based on the sum of the first steering control value and the second steering control value. The second steering control value calculation unit (41, 42) calculates the second steering control value based on an angular deviation of the actual steering angle relative to the target steering angle and a disturbance compensation torque, and sets the disturbance compensation torque including a larger friction component when the steering torque is larger than when it is smaller. (Fig. 2)