Electric Vehicle Inverter Torque Control for Noise Reduction
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Solution Overview
Problem
Conventional inverter devices for electric vehicles generate noticeable machine noise due to vibrations in gears and couplings when operating at low speeds and low torque, where torque polarity fluctuates between positive and negative.
Innovation Solution
An inverter device with a control unit that includes a limiter unit and a lower-limit generating unit, which limits the torque or current command to a preset value, preventing the torque from becoming too small and thus reducing vibrations and noise by maintaining a minimum torque output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is operated at low speed and low torque, then energy consumption is reduced, but machine noise is generated due to torque polarity fluctuation and gear/coupling vibrations
Solution Approach 1:
The control unit changes the torque command parameter by imposing a lower limit (absolute value threshold) to prevent torque from reaching zero. This parameter modification ensures torque maintains a minimum magnitude, preventing polarity fluctuations that cause gear and coupling vibrations, thereby reducing machine noise while allowing continued operation at low speeds with improved energy efficiency
2Manufacturing precision
If torque control is precisely maintained to match torque command, then motor control performance is improved, but torque fluctuations cause vibrations in connecting members
Solution Approach 1:
The control unit applies preliminary anti-action by preemptively limiting the torque command to prevent it from reaching zero or small values. This anticipatory constraint stops torque polarity fluctuations before they occur, thereby preventing vibrations in gears and couplings while maintaining precise torque control within the safe operating range
Data Source
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AI summary
An inverter device for an electric vehicle includes an inverter circuit 2 that controls an electric motor 3 connected to a wheel 8 via a connecting member and a control unit 20 that controls torque of the electric motor 3. The control unit 20 includes a current control unit 23 that executes control so that a q-axis current command iq* for the electric motor 3 matches a current flowing through the electric motor 3, and a limiter unit 21 that puts limitations so that a magnitude of the q-axis current command iq* does not become equal to or smaller than a preset predetermined value.