Motor Speed Calculation Using Duty-Cycle Adaptive Encoder Timing
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Solution Overview
Problem
Conventional motor rotation speed detection methods in power conversion devices either fix on full cycle or half cycle measurement, leading to instability and increased steps for parameter resetting, and are prone to errors due to duty cycle deviations, causing system instability and potential damage.
Innovation Solution
A speed calculation device and power conversion device that automatically switch between full cycle and half cycle measurements based on the duty cycle of encoder signals, ensuring stable operation and maintaining fine time axis resolution without requiring device replacement or parameter resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the half cycle measurement method is used to achieve fine time axis detection resolution, then the detection frequency is improved, but the motor speed detection becomes unstable when the duty cycle deviates from 50%
Solution Approach 1:
The patent dynamically switches between half cycle measurement mode and full cycle measurement mode based on the detected duty cycle of the encoder signal. When the duty cycle is within a predetermined range (close to 50%), the system uses half cycle measurement for high resolution. When the duty cycle deviates from the range, the system switches to full cycle measurement to ensure stable speed detection, thus adaptively adjusting the measurement method to maintain both precision and reliability.
2Reliability
If the full cycle measurement method is used to ensure stable speed detection, then the reliability is improved, but the time axis detection resolution deteriorates
Solution Approach 1:
The system dynamically adjusts the measurement method by monitoring the duty cycle of the encoder signal. When the duty cycle is within a predetermined range indicating stable signal conditions, the system switches from full cycle measurement to half cycle measurement, thereby improving time axis detection resolution while maintaining reliability. This dynamic adjustment allows the system to optimize measurement precision without sacrificing stability.
3Adaptability or versatility
If the user selects the measurement method by parameter setting before start of use, then the adaptability is improved, but the number of steps for installation and commissioning increases
Solution Approach 1:
The patent implements automatic determination of the measurement method by the power conversion device itself. The control unit automatically detects the duty cycle of the encoder signal and selects the appropriate measurement method (half cycle or full cycle) without requiring user intervention or parameter setting. This self-service approach maintains adaptability to different operating conditions while significantly reducing the complexity of installation and commissioning procedures.
4Measurement precision
If the duty cycle deviates from 50% due to aging change of transmission path, then the measurement accuracy deteriorates, but the fixing method or selection method cannot prevent system stop
Solution Approach 1:
The patent incorporates a feedback mechanism where the control unit continuously monitors the duty cycle of the encoder signal during operation. When the duty cycle deviates from the predetermined range due to aging or other factors, the system automatically switches from half cycle measurement to full cycle measurement, ensuring continuous accurate speed detection and preventing system stoppage. This feedback-based adaptation maintains measurement accuracy and system reliability throughout the device's operational life.
Data Source
AI summary
The purpose of the present invention is to provide a speed detection method for maintaining a fine time axis resolution and a power conversion device that uses the method. This power conversion device comprises an inverter for converting DC voltage into AC voltage and supplying the same to a motor, a motor speed calculation unit for calculating the speed of the motor from output pulses obtained from an encoder connected to the motor, and a control unit for receiving the motor speed from the motor speed calculation unit and controlling the inverter. In the power conversion device, the motor speed calculation unit measures the duty cycle of the output pulses, calculates the speed using the half cycles of the output pulses if the duty cycle is within a prescribed range from 50%, and calculates the speed using the full cycles of the output pulses if the duty ratio is outside of the prescribed range from 50%.