Electric Power Steering Inertia Compensation
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Solution Overview
Problem
Existing Electric Power Steering (EPS) systems rely on torque loop compensation, which can make the system sensitive to disturbances and affect steering feel due to phase lag and other issues, compromising stability and precision in steering feel, particularly at lower frequencies.
Innovation Solution
A control system for power steering that generates a base torque command without altering the hand wheel torque signal at low frequencies, and includes a module for motor inertia compensation, allowing the system to operate without a notch filter at lower frequencies, thereby improving stability and steering feel by shifting the phase crossover frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a torque compensator (notch filter) is employed in the torque path to ensure system stability, then stability is improved, but steering feel deteriorates due to phase lag and sensitivity to disturbances
Solution Approach 1:
The patent divides the compensation function into two separate modules: a base torque command generator that processes hand wheel torque signal without alteration at low frequencies, and a motor inertia compensation module that handles high-frequency disturbances. This segmentation allows stability compensation without degrading low-frequency steering feel.
Solution Approach 2:
The patent applies different compensation strategies to different frequency ranges: the base torque command generator preserves the hand wheel torque signal at low frequencies (below 10 Hz) to maintain steering feel, while the motor inertia compensation module addresses high-frequency disturbances. This local differentiation of compensation quality resolves the contradiction between stability and steering feel.
2Stability of the object's composition
If a torque compensator is used to achieve stability, then stability is improved, but on-center feel precision deteriorates
Solution Approach 1:
The patent segments the torque compensation function into base torque command generation and motor inertia compensation, where the base torque command generator does not alter the hand wheel torque signal at low frequencies, preserving on-center feel precision while the inertia compensation handles stability.
Solution Approach 2:
The patent performs preliminary compensation by generating the base torque command without alteration before applying motor inertia compensation. This preliminary action preserves the original hand wheel torque signal characteristics at low frequencies, maintaining precise on-center feel while ensuring stability through subsequent inertia compensation.
3Stability of the object's composition
If a torque compensator is applied to ensure stability, then stability is improved, but disturbance rejection deteriorates
Solution Approach 1:
The patent divides the compensation function into base torque command generation and motor inertia compensation modules, where the inertia compensation module specifically addresses disturbance rejection by compensating for motor inertia effects without affecting low-frequency steering signals.
Solution Approach 2:
The patent applies motor inertia compensation specifically to high-frequency disturbance components while preserving low-frequency hand wheel torque signals. This local application of compensation quality improves disturbance rejection without degrading steering feel or on-center precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the stability and steering feel of EPS systems by eliminating the need for a torque compensator at lower frequencies, resulting in improved disturbance rejection and a more precise on-center feel, similar to Hydraulic Power Steering systems.
Implementation Method 1
a second module to generate a motor inertia compensation command based on a motor inertia of a motor of the power steering system
Data Source
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AI summary
A method of controlling a power steering system is provided. The method generates a base torque command based on a hand wheel torque signal without altering the hand wheel torque signal at a range of relatively low frequencies. The method generates a motor inertia compensation command based on a motor inertia of a motor of the power steering system. The method generates an assist torque command based on the base torque command and the motor inertia compensation command. The method operates a motor of the power steering system to generate a torque based on the assist torque command.