Electric Power Steering Noise Suppression via Adaptive Filtering
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Solution Overview
Problem
Conventional electric power steering devices require on-off switching of filters to compensate for phase delays, leading to incomplete suppression of torque ripples and noise in steering torque signals across various situations.
Innovation Solution
An electric power steering device with a noise suppression unit that uses a combination of filters, including a low-pass filter and a high-pass filter, to reduce noise in the output shaft rotational angle signal, eliminating the need for filter switching and ensuring consistent noise reduction across situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a smooth filter is used to suppress torque ripple caused by quantization error, then torque ripple suppression is improved, but phase delay occurs in the digital filter process requiring on-off switching
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adjustable based on operating conditions. The controller dynamically switches between different filter processing modes (first filter processing and second filter processing) depending on the steering torque magnitude, allowing the system to adapt to varying operational requirements and eliminate the need for complex on-off switching control.
Solution Approach 2:
The patent changes the filter processing parameters based on the steering torque detection value. When the absolute value of steering torque exceeds a threshold, first filter processing is applied; otherwise, second filter processing is applied. This parameter change approach allows the system to optimize noise suppression while minimizing phase delay effects under different operating conditions.
2Measurement precision
If on-off switching of smooth filter is implemented to compensate phase delay, then phase delay compensation is improved, but noise suppression effectiveness is reduced when filter is off
Solution Approach 1:
The system dynamically selects between two different filter processing approaches based on real-time steering torque conditions. The first filter processing mode provides strong noise suppression when steering torque is significant, while the second filter processing mode minimizes phase delay when steering torque is small, achieving both noise suppression and phase delay compensation without requiring filter on-off switching.
Solution Approach 2:
The patent changes the filter processing parameters based on the steering torque detection value. When the absolute value of steering torque exceeds a threshold, first filter processing is applied for optimal noise suppression; otherwise, second filter processing is applied to minimize phase delay. This parameter adaptation ensures continuous effective noise suppression while compensating for phase delay effects.
3Object-affected harmful factors
If filter processing is applied to reduce noise in output shaft rotational angle signal, then noise reduction is improved, but steering responsiveness may be degraded
Solution Approach 1:
The patent changes the filter processing parameters based on the steering torque detection value. When the absolute value of steering torque exceeds a threshold, first filter processing is applied for optimal noise suppression; otherwise, second filter processing is applied to minimize phase delay and maintain responsiveness. This adaptive approach ensures noise reduction while preserving steering responsiveness across different operating conditions.
Data Source
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AI summary
An electric power steering device is provided to be capable of reducing noises in the steering torque signal, regardless of various situations. For this aim, the electric power steering device (1) includes a torque detector (14) including an input shaft rotational angle detector (15) and an output shaft rotational angle detector (16) configured to respectively detect rotational angles of an input shaft (2a) and an output shaft (2c) coupled by a torsion bar (2b) arranged in a steering system of a vehicle; an electric motor (12) configured to be controlled based on a torque detection value detected by the torque detector (14), and to generate a steering assistance force to be exerted on the output shaft (2c); a motor rotational angle detector (17) configured to detect a motor rotational angle of the electric motor (12); and a noise suppression unit (20a) configured to reduce a noise in a signal of the rotational angle of the output shaft detected by the output shaft rotational angle detector (16), by using the motor rotational angle detected by the motor rotational angle detector (17).