Variable Frequency PWM Wiper Motor Control for EMC Noise Reduction
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Solution Overview
Problem
Current windshield wiper motor control systems in vehicles generate significant electromagnetic compatibility (EMC) noise due to switching at a fixed fundamental frequency, interfering with radio broadcasts and electronic circuit operations.
Innovation Solution
A method and device that dynamically switch the fundamental period and duty cycle of pulse-width modulation pulses between discrete values to minimize EMC noise emission, using an H bridge control system with adjustable frequency and duty cycle to optimize wiper function while reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse-width modulation with fixed fundamental frequency is used to control wiper motor speed, then speed control flexibility is improved, but electromagnetic compatibility noise emission increases
Solution Approach 1:
The patent applies dynamics by making the fundamental frequency variable rather than fixed. The control system dynamically adjusts the fundamental frequency of PWM pulses based on detected radio frequency interference levels, thereby adapting the wiper motor operation to minimize electromagnetic compatibility noise while maintaining speed control flexibility through duty cycle adjustment.
Solution Approach 2:
The patent changes the parameter of fundamental frequency from a fixed value to a variable parameter that can be adjusted in real-time. By modifying the fundamental frequency parameter according to detected interference conditions and adjusting the duty cycle parameter for speed control, the system achieves both speed flexibility and reduced electromagnetic noise emission.
2Device complexity
If fixed fundamental frequency PWM switching is used, then control simplicity is improved, but radio reception quality deteriorates
Solution Approach 1:
The patent implements feedback by detecting radio frequency interference levels and using this information to adjust the fundamental frequency of PWM pulses. The control system continuously monitors the electromagnetic environment and adjusts operating parameters accordingly, creating a closed-loop system that maintains simple control architecture while improving radio reception quality through adaptive frequency selection.
3Adaptability or versatility
If duty cycle adjustment is used to control motor speed, then speed variation range is improved, but electromagnetic noise continuity increases
Solution Approach 1:
The patent applies dynamics by making both the fundamental frequency and duty cycle variable parameters. Instead of using duty cycle adjustment alone which creates continuous noise, the system dynamically varies the fundamental frequency in conjunction with duty cycle adjustment, thereby maintaining the desired speed variation range while disrupting the continuity of electromagnetic noise emission patterns.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces EMC noise levels in radio frequency bands, allowing for flexible programming based on environmental parameters and improving the operation of electronic systems within vehicles.
Implementation Method 1
The windshield wiper motors are powered and controlled in pulse-width modulation mode with a duty cycle of given value
Implementation Method 2
The switching of the wipers over the sectors of the collector and the mechanical switching back and forth of the windshield wiper action generate switching noise
Data Source
AI summary
Method of controlling a motor vehicle windscreen wiper motor, powered and controlled by pulse width modulation (PWM) with duty ratio (T) of determined value, in which the instantaneous fundamental period of the modulated pulses is switched successively between at least two discrete period values (T1, T2), the duty ratio (T) of the pulses (PWM) being substantially established at a determined value for at least one determined duration (Tc) of switching of the modulated pulses. Application to the reduction of the EMC noise level in the radio frequency bands to be protected.