Electric Motor Noise Reduction Using Rotational Frequency Filtering
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Solution Overview
Problem
Existing methods for noise reduction in electric motors often rely on measuring noise and generating anti-noise, which requires additional sensors and complexity.
Innovation Solution
A method that determines the instantaneous rotational frequency of an electric motor, filters specific frequency components (interference signals) from this signal, and generates a correction signal to reduce the amplitude of these interference signals within the motor control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise measurement sensors (microphone or acceleration sensor) are used to measure generated noise and generate anti-noise correction signals, then noise reduction is achieved through destructive interference, but device complexity increases due to additional sensors and measurement systems
Solution Approach 1:
The patent extracts the noise reduction function from the physical measurement domain and relocates it to the signal processing domain. Instead of using sensors to measure actual noise, the system extracts rotational frequency information from existing rotation signals and generates correction signals based on filtered frequency components, eliminating the need for additional noise measurement sensors
Solution Approach 2:
The patent introduces an intermediary approach by using rotation signals as a mediator between motor operation and noise reduction. Rather than directly measuring noise, the system uses rotation signals to derive frequency information that correlates with noise-generating operations, enabling indirect noise control through the motor control unit
2Object-affected harmful factors
If additional noise measurement sensors are installed to enable active noise cancellation, then noise reduction effectiveness is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent makes the motor control unit multi-functional by enabling it to perform both motor control and noise reduction functions. The existing rotation signal processing infrastructure is leveraged for dual purposes: controlling motor operation and generating noise reduction correction signals, eliminating the need for separate noise measurement sensor systems
Solution Approach 2:
The system achieves self-service noise reduction by using its own operational data (rotation signals) to generate correction signals. The motor control unit independently processes its own rotation signals, filters frequency components, and generates correction signals without requiring external noise measurement sensors or additional measurement infrastructure
3Device complexity
If rotation signals are processed to extract and filter frequency components corresponding to instantaneous rotational frequency multiples, then noise reduction is achieved without additional sensors, but signal processing complexity increases
Solution Approach 1:
The patent applies preliminary filtering to rotation signals to extract frequency components corresponding to multiples of instantaneous rotational frequency before these signals are used for correction signal generation. This preliminary frequency component extraction simplifies the overall processing by pre-identifying the noise-relevant frequency ranges
Solution Approach 2:
The system implements feedback by continuously monitoring rotation signals, dynamically filtering frequency components based on instantaneous rotational frequency, and adjusting correction signals in real-time. This closed-loop feedback mechanism enables adaptive noise reduction that automatically tracks changes in motor operating conditions
Data Source
AI summary
Various embodiments of the teachings herein include a method for noise reduction during operation of an electric motor. The method may include: determining an instantaneous rotational frequency of the electric motor from a signal representing a rotational position and/or a rotational speed of the electric motor; filtering a frequency component from the signal, the frequency component corresponding to the instantaneous rotational frequency of the electric motor multiplied by a specified factor greater than 1 and lying within a specified acoustic frequency range; and generating a correction signal based on the filtered signal and feeding this correction signal into the control loop so an amplitude of the interference signal is reduced.