Electric Power Steering Notch Filter Vibration Suppression
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Solution Overview
Problem
Conventional electric power steering apparatuses face challenges in suppressing vibrations and noisy sounds due to steep power spectra generated from the relationship between the calculation periods of the torque and current control systems, which existing filters struggle to attenuate effectively.
Innovation Solution
The electric power steering apparatus employs a specific frequency band removing section with notch filters that attenuate frequency components multiplying by half of the torque control system's calculation frequency, accompanied by a phase delay filter to prevent phase delay, ensuring effective suppression of vibrations and noisy sounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional filters are used to attenuate steep power spectra, then vibration suppression is attempted, but the filters cannot effectively attenuate the specific frequency components and generate phase delay
Solution Approach 1:
The patent changes the parameters of the filter by using a cascade structure of multiple notch filters with specifically designed frequency characteristics. Each notch filter is tuned to attenuate specific frequency components (multiples of half the torque control calculation frequency) while the cascade structure maintains overall phase accuracy, resolving the contradiction between vibration suppression and phase reliability
2Device complexity
If the torque control system uses a longer calculation period than the current control system, then computational load is reduced, but steep power spectra are generated at frequencies multiplying half of the torque control calculation frequency
Solution Approach 1:
The patent extracts and removes the harmful frequency components from the current command value signal using notch filters. By specifically targeting and eliminating the frequency components that are multiples of half the torque control calculation frequency, the system maintains the beneficial longer calculation period while removing the generated vibrations
3Object-affected harmful factors
If existing filtering methods are applied to attenuate power spectra, then some vibration reduction is achieved, but the attenuation is not effective enough and phase delay is introduced
Solution Approach 1:
The patent segments the frequency attenuation task into multiple specialized notch filters, each targeting specific frequency components. This segmentation allows effective attenuation of harmful frequencies while preserving the phase characteristics at other frequencies, maintaining control responsiveness without sacrificing vibration suppression effectiveness
Data Source
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AI summary
[Problem] An object of the present invention is to provide an electric power steering apparatus (including a vector control system) that can exactly suppress vibration, a noisy sound which are generated from power spectra as a vibration source, by attenuating the power spectra which generate from a relationship between calculation periods of a torque control system and a current control system. [Means for solving the problem] The present invention is the electric power steering apparatus that comprises a torque control system to calculate a current command value and a current control system to control a motor current value which passes through a motor based on the current command value: wherein a first calculation period of the torque control system is equal to or longer than a second calculation period of the current control system, wherein the current control system comprises a specific frequency band removing section that attenuates a frequency component which multiplies at least one natural number by an approximate half of a calculation frequency of the torque control system to the current command value, and wherein the specific frequency band removing section comprises notch filters that set an attenuation frequency or comprises the notch filters and a phase delay filter that has a cutoff frequency, which is set to a lower frequency side than a frequency which is attenuated by the notch filters.