Encoder Duty-Cycle Switching for Stable Motor Speed Calculation
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Solution Overview
Problem
Conventional motor rotation speed detection methods in power conversion devices either fix on full or half cycle measurements, leading to instability and increased steps for selection, which can result in incorrect speed detection and system instability due to duty cycle deviations from 50%, causing potential damage and increased load on connected machines.
Innovation Solution
A speed calculation device that automatically switches between full cycle and half cycle measurements based on the duty cycle of the encoder signal, allowing for stable and fine time axis resolution without the need for device replacement or parameter resetting, ensuring accurate motor speed detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the half cycle measurement method is used to improve time axis detection resolution, then detection frequency is improved, but measurement accuracy deteriorates when duty cycle deviates from 50%
Solution Approach 1:
The patent applies dynamics by making the measurement method selectable rather than fixed. The system can dynamically switch between half-cycle measurement (for high resolution when duty is 50%) and full-cycle measurement (for reliability when duty deviates), allowing the measurement approach to adapt to actual operating conditions and maintain both resolution and accuracy.
Solution Approach 2:
The patent changes the measurement parameter (cycle length) based on duty cycle conditions. When duty cycle is within a prescribed range of 50±0.5%, half-cycle measurement is used for high resolution. When duty cycle exceeds this range, full-cycle measurement is used to ensure accurate speed detection, thus optimizing both resolution and reliability through parameter adjustment.
2Reliability
If the full cycle measurement method is used to ensure measurement stability, then measurement reliability is improved, but time axis detection resolution deteriorates
Solution Approach 1:
The system dynamically selects the measurement cycle length based on duty cycle conditions. Instead of always using full-cycle measurement which provides stability but lower resolution, the system switches to half-cycle measurement when duty is within 50±0.5%, thereby achieving both stability and high time axis detection resolution simultaneously.
Solution Approach 2:
The measurement parameter (cycle length) is changed based on operating conditions. The system uses full-cycle measurement for stability when duty deviates from 50%, and switches to half-cycle measurement for higher resolution when duty is within the prescribed range, thus optimizing both reliability and precision through conditional parameter adjustment.
3Measurement precision
If parameter resetting is performed to select detection method, then measurement accuracy is improved, but system complexity and setup time increase
Solution Approach 1:
The system performs self-service by automatically determining the appropriate measurement method based on actual encoder signal duty cycle. Instead of requiring users to manually reset parameters or configure settings, the system autonomously selects between half-cycle and full-cycle measurement based on whether duty is within 50±0.5%, eliminating complex setup steps while maintaining accuracy.
Solution Approach 2:
The system uses feedback from the actual encoder signal duty cycle to automatically adjust the measurement method. By continuously monitoring duty cycle and switching between measurement approaches based on this feedback, the system achieves accurate speed detection without requiring manual parameter configuration or user intervention, thereby reducing setup complexity.
4Device complexity
If the detection method is fixed to one approach, then device complexity is reduced, but adaptability to different duty cycle conditions deteriorates
Solution Approach 1:
The system applies dynamics by making the detection method flexible rather than fixed. Instead of configuring the device for one specific measurement approach, the system dynamically adapts between half-cycle and full-cycle measurement based on actual duty cycle conditions, maintaining low complexity while achieving high adaptability to different operating scenarios.
Solution Approach 2:
The detection device achieves universality by incorporating both half-cycle and full-cycle measurement capabilities within a single system. The device can function in either mode depending on duty cycle conditions, eliminating the need for separate configurations or device replacements and providing adaptability across different duty cycle scenarios without increasing complexity.
Data Source
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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%.