Motor Driving Device Torque Ripple Compensation
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Solution Overview
Problem
Magnetization variations in three-phase motors lead to torque ripple, noise, and vibration due to mismatches in the phase and amplitude of back electromotive force among phases, which existing sine-wave drive systems fail to adequately address.
Innovation Solution
A motor driving device with an inverter, current control loop, back EMF phase detector, and torque correction unit that applies three-phase sine wave drive voltages using PWM signals, detects phase and amplitude variations, and corrects the drive current indication values to match the back electromotive force phases, reducing torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If three-phase sine wave drive voltages with 120-degree phase difference are applied to the motor, then the motor can be driven with high efficiency, but torque ripple occurs due to magnetization variations among phases
Solution Approach 1:
The patent changes the drive voltage parameters by calculating optimal phase and amplitude for each phase based on detected back EMF characteristics. The drive voltage phase and amplitude are adjusted individually for each phase to match the actual back EMF phase and amplitude, compensating for magnetization variations and eliminating torque ripple while maintaining high efficiency operation
Solution Approach 2:
The patent implements a feedback mechanism where the back EMF phase and amplitude of each phase are detected in real-time, and this detection information is used to calculate and adjust the drive voltage parameters. The current detection unit detects drive current, the back EMF phase detection unit detects back EMF phase, and this feedback loop enables dynamic adjustment of drive voltages to maintain optimal performance despite magnetization variations
2Use of energy by moving object
If the phase of drive voltage is adjusted to match back electromotive force phase for high efficiency, then motor efficiency improves, but manufacturing variations cause phase mismatches and torque ripple
Solution Approach 1:
The motor driving device performs self-adjustment by automatically detecting the actual back EMF phase and amplitude of each phase and using this information to calculate the optimal drive voltage parameters. The system compensates for its own manufacturing variations without requiring external calibration or manual adjustment, adapting to each motor's specific characteristics
Solution Approach 2:
The patent dynamically changes the drive voltage parameters (phase and amplitude) based on detected back EMF characteristics. By calculating optimal parameters that account for manufacturing variations in magnetization, the system maintains high efficiency while compensating for production tolerances
3Object-generated harmful factors
If torque correction is applied to reduce torque ripple, then noise and vibration decrease, but drive complexity increases
Solution Approach 1:
The control unit performs multiple functions: it detects back EMF phase, calculates optimal drive voltage parameters, generates PWM signals, and applies torque correction all within a single integrated unit. This multi-functionality reduces the need for separate dedicated components for each control function, managing complexity while achieving torque ripple reduction
Solution Approach 2:
The patent uses calculated drive voltage parameters as an intermediary to translate back EMF detection information into corrected drive signals. The correction coefficient calculated by the control unit acts as an intermediary that modifies the drive voltage to compensate for magnetization variations, reducing torque ripple through mathematical correction rather than mechanical adjustment
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
The solution effectively reduces torque ripple, achieving low noise and vibration in three-phase motors by aligning drive current phases with back electromotive force phases and adjusting current amplitudes to match amplitude variations, thereby improving motor efficiency and reducing manufacturing complexity.
Implementation Method 1
The inverter applies drive voltages serving as three-phase sine waves to the drive terminals of the three-phase motor using a PWM signal
Implementation Method 2
The back EMF phase detector detects the phase of a back electromotive force of each phase in the motor
Implementation Method 3
The torque correction unit calculates a first torque correction coefficient of a periodic function based on the phase variations in the three phases of the back electromotive force, and corrects the current indication value superimposing the first torque correction coefficient on the current indication value
Data Source
AI summary
A motor driving device and a motor system that can reduce a torque ripple of a motor are provided. The current control loop detects a drive current of the motor, detects an error between the detected value of the drive current and a current indication value as a target value of the drive current, and determines the duty of the PWM signal reflecting the error concerned. The back EMF phase detector detects the phase of a back electromotive force of each phase in the motor. The torque correction unit calculates a first torque correction coefficient of a periodic function based on the phase variations in the three phases of the back electromotive force, and corrects the current indication value superimposing the first torque correction coefficient on the current indication value.