Electric Power Steering Inertia Compensation with Frequency Dependent Damping
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Solution Overview
Problem
Existing electric power steering systems face challenges in compensating for motor inertia, particularly at the initial acceleration or deceleration stages, and often result in unexpected outcomes due to inadequate coordination between inertia compensation and frequency-dependent damping algorithms.
Innovation Solution
A control system for electric power steering that includes a control module capable of determining a frequency-dependent damping coefficient and inertia compensation coefficient, using these to calculate filter coefficients for generating a compensation command that actively compensates for motor inertia and frequency-dependent damping, ensuring coordinated response and improved haptic feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter on motor velocity sensor is used to emulate derivative calculation for inertia compensation, then motor inertia can be compensated, but compensation only starts after motor begins moving causing lack of initial compensation
Solution Approach 1:
The patent applies preliminary action by calculating inertia compensation torque before the motor actually moves. The control module computes the compensation torque based on predicted motor acceleration and applies it in advance during the initial acceleration phase, ensuring compensation is active from the very start of movement rather than waiting for motor velocity to be detected.
2Adaptability or versatility
If inertia compensation and frequency dependent damping algorithms are used separately, then each function can be implemented, but unexpected results occur due to lack of coordination between the two
Solution Approach 1:
The patent merges the inertia compensation algorithm and frequency dependent damping algorithm into a unified control framework. The control module simultaneously calculates both compensation torques and combines them into a single coordinated control signal, ensuring that both functions work together harmoniously rather than independently, thereby eliminating unexpected interactions and improving system reliability.
Data Source
AI summary
A control system for an electric power steering system is provided. The system includes a motor and a control module in communication with the motor. The control module provides a compensation command to the motor. The control modules includes a frequency dependent damping module for determining a frequency dependent damping (FDD) coefficient based on a base assist command and a vehicle speed. The control module includes a coefficient module for determining a plurality of filter coefficients. The filter coefficients are based on the FDD coefficient, the vehicle speed, and an inertia compensation coefficient. The control module includes a filter module for determining the compensation command based on the plurality of filter coefficients.