Variable PWM Frequency Control for Electric Motor Noise Masking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing electric motor control methods using pulse width modulation (PWM) generate high-energy, narrow-band noise emissions that are easily perceptible, especially in low ambient noise environments, making them difficult to ignore and causing noise pollution.
Innovation Solution
The method involves detecting ambient noise parameters and varying the pulse width modulation frequency and pulse intervals to adapt the acoustic emission spectrum of the electric motor to match the ambient noise, reducing noise emissions by masking them within the environmental noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pulse width modulation with low frequency is used, then cost is reduced, but noise emissions become perceptible and disturbing
Solution Approach 1:
The patent applies dynamics by making the PWM frequency variable rather than fixed. The control device dynamically adjusts the PWM frequency within a range (e.g., 20-20,000 Hz or higher) based on ambient noise conditions, transforming the static frequency into a dynamic parameter that adapts to environmental conditions, thereby reducing perceptible noise while maintaining cost-effectiveness
Solution Approach 2:
The patent changes the frequency parameter of the PWM signal from a fixed value to a variable range. By modifying the PWM frequency parameter within specific ranges (e.g., shifting from 20-20,000 Hz to 20,000-40,000 Hz or higher), the patent transforms narrow-band noise into broadband noise that is less perceptible, resolving the contradiction between cost and noise emissions
2Object-generated harmful factors
If pulse width modulation frequency is increased to ultrasonic range, then noise becomes inaudible, but EMC requirements become difficult to meet and costs increase
Solution Approach 1:
The patent uses dynamics by implementing variable PWM frequency control that adapts to different operating conditions. Instead of permanently operating at high ultrasonic frequencies (which increase costs and EMC complexity), the system dynamically selects appropriate frequency ranges based on ambient noise levels, achieving noise reduction only when necessary while maintaining cost-effectiveness and EMC compliance during normal operation
Solution Approach 2:
The patent changes the PWM frequency parameter selectively rather than permanently. By adjusting the frequency parameter within specific ranges (e.g., shifting to 20,000-40,000 Hz or higher only when noise reduction is needed), the patent achieves inaudible noise emissions temporarily without incurring the permanent costs and EMC challenges associated with continuous high-frequency operation
3Object-generated harmful factors
If pulse width modulation frequency is increased to ultrasonic range, then noise becomes inaudible, but electromagnetic compatibility requirements become difficult to meet
Solution Approach 1:
The patent applies dynamics by making the PWM frequency adaptive rather than fixed at high ultrasonic values. The control device dynamically adjusts frequency based on ambient noise conditions, achieving noise reduction only when necessary while maintaining electromagnetic compatibility during normal operation, thus resolving the contradiction between noise reduction and EMC reliability
Solution Approach 2:
The patent selectively changes the PWM frequency parameter within specific ranges rather than permanently operating at high frequencies. By shifting frequency to ultrasonic ranges (e.g., 20,000-40,000 Hz or higher) only when noise reduction is needed, the patent achieves inaudible emissions without the persistent electromagnetic compatibility challenges associated with continuous high-frequency operation
4Device complexity
If fixed pulse width modulation frequency is used, then control is simple, but noise emissions are narrow-band and highly perceptible
Solution Approach 1:
The patent applies dynamics by transforming the static PWM frequency into a dynamic parameter that varies within a specified range. The control device modulates the frequency around a central value (e.g., varying between 20-20,000 Hz or 20,000-40,000 Hz), converting narrow-band noise into broadband noise that is less perceptible, thereby resolving the contradiction between control simplicity and noise emissions with minimal added complexity
Data Source
Figure 1
Figure 2A~2B
Figure 3B
AI summary
The method involves recording a parameter, which represents or affects the spectrum of ambient noise of the electric motor, available during the control. The control pulses are generated with a reference pulse width repetition factor and temporally varying pulse widths and pulse distances as a function of the recorded parameter. The electric motor is controlled by the control pulses. An independent claim is included for a device for controlling an electric motor by pulse width modulation.