Electric Power Steering Torque Ripple Suppression via Oversampling
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Solution Overview
Problem
Conventional electric power steering devices using motors generate torque ripples due to electrical or mechanical factors, leading to abnormal noise and degraded steering feel, and existing control techniques are insufficient to meet the recent requirement of suppressing torque ripples to levels below 0.01 Nm.
Innovation Solution
A control device that includes an oversampling code extender for processing steering torque signals, a base assist controller to calculate assist torque, and a quantization noise reduction compensator using FIR filters to reduce torque ripples by enhancing signal resolution and compensating for motor loss torque, thereby improving steering feel and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional notch filter control is used to reduce torque ripple, then some torque ripple suppression is achieved, but the suppression level is insufficient to meet the requirement of below 0.01 Nm
Solution Approach 1:
The patent applies parameter changes by implementing oversampling processing that increases the sampling frequency of the steering torque signal, and by changing the control parameters through moving average processing with weighting. This allows the system to achieve torque ripple suppression below 0.01 Nm by processing signals at higher resolution and applying weighted averaging to smooth out ripple components while maintaining responsiveness.
2Measurement precision
If oversampling processing is performed on steering torque signal, then signal resolution is enhanced and torque ripple is reduced, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by performing oversampling processing on the steering torque signal before it is used for control decisions. By pre-processing the signal with multiple samples and moving average weighting, the system prepares a high-resolution, smoothed torque value in advance, which reduces the need for complex real-time processing during critical control moments.
Solution Approach 2:
The patent uses moving average processing with weighting as an intermediary mechanism between the raw oversampled signal and the final control output. This intermediary process smooths the signal and reduces high-frequency noise and ripple components, effectively decoupling the complexity of oversampling from the control algorithm while preserving measurement precision.
3Object-affected harmful factors
If moving average processing with weighting is applied to oversampled signal, then torque ripple is further reduced to below 0.01 Nm, but control response time may be delayed
Solution Approach 1:
The patent applies dynamics by using weighted moving average processing where recent samples are given higher weights and older samples lower weights. This dynamic weighting scheme allows the filter to respond more quickly to changes in steering torque while still smoothing out ripple components, achieving torque ripple reduction below 0.01 Nm without excessive delay in control response.
Data Source
AI summary
A control device obtains a post-code extension steering torque by performing moving average processing of weighting an oversampling signal obtained by oversampling processing, obtains a base assist torque based on the post-code extension steering torque signal, acquires a base assist torque signal that decreases the base assist torque as a vehicle speed increases, performs stabilization processing on the base assist torque signal to obtain an assist torque signal according to the assist torque of an electric power steering device.