Electric Motor Pulse Phase Shifting for Torsional Vibration Control
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Solution Overview
Problem
Electric motors experience vibrations when pulsed, particularly when the modulation frequency aligns with the natural resonance frequencies of the driven equipment, leading to inefficiencies and potential damage.
Innovation Solution
Phase shifting the modulation frequency between 0 degrees and 180 degrees at a shifting frequency greater than the modulation frequency to reduce or cancel vibrations, allowing for efficient torque delivery without the need for vibration mitigation hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is pulsed at a modulation frequency to reduce duty cycle and increase efficiency, then efficiency is improved, but vibrations are induced in the driven equipment
Solution Approach 1:
The patent applies parameter changes by modifying the phase of the modulation frequency. Specifically, it shifts the phase of the pulse width modulation signal between 0 and 180 degrees to alter the timing characteristics of the pulsed torque delivery. This phase shifting changes the temporal distribution of torque pulses without affecting the overall duty cycle or average torque, thereby reducing vibrations while maintaining efficiency improvements from pulsing operation.
2Use of energy by moving object
If the modulation frequency is near the natural frequency resonance of the vehicle structure, then efficiency gains from pulsing are achieved, but vibrations are amplified
Solution Approach 1:
The patent implements preliminary anti-action by proactively shifting the phase of the modulation frequency before vibrations can be amplified by resonance. The controller detects when the modulation frequency approaches the natural resonance frequency of the driven equipment and applies a phase shift to the PWM signal in advance. This preemptive phase adjustment alters the torque pulse timing to avoid constructive interference with structural resonances, thereby preventing vibration amplification while preserving efficiency benefits.
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 torsional vibrations and maintains efficiency gains from pulsing the electric motor, with a 75% reduction in peak torsional response amplitude compared to unmodified pulsing, ensuring consistent torque delivery and minimizing NVH issues.
Implementation Method 1
Phase shifting the modulation frequency between 0 degrees and 180 degrees to reduce vibrations induced in the driven equipment
Implementation Method 2
pulsing the electric motor at the modulation frequency to deliver a target torque
Data Source
AI summary
A method of controlling an electric motor includes pulsing the electric motor and phase shifting the modulation frequency. Pulsing the electric motor at the modulation frequency propels a vehicle to increase efficiency of the electric motor. Phase shifting the modulation frequency includes phase shifting between 0 degrees and 180 degrees to reduce vibrations induced in the vehicle.