Sensorless Position Measurement for Permanent Magnet Machines
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Solution Overview
Problem
Existing sensorless position measurement systems for permanent magnet machines rely on analog to digital converters and position sensors, leading to errors due to non-actual phase voltage measurements and increased system size.
Innovation Solution
A sensorless position measurement system utilizing an inverter, preprocessing circuit, and microcontroller with a capture modulator, which converts line-to-line PWM signals into reconstructed phase PWM signals to determine the angular position of the permanent magnet machine without a position sensor, eliminating the need for analog to digital converters and reducing system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor (rotary encoder) is used to determine angular position, then measurement precision is improved, but device complexity and system size increase
Solution Approach 1:
The patent extracts and eliminates the position sensor (rotary encoder) from the system by developing a sensorless position measurement method. The angular position is determined through signal processing of PWM signals and back electromotive force evaluation, removing the need for external position sensing components while maintaining measurement capability.
Solution Approach 2:
The system uses its own internal PWM signals and electrical characteristics to determine angular position without external sensors. The microcontroller processes the PWM signals generated during normal operation and evaluates back electromotive force to calculate rotor position, making the system self-sufficient for position measurement.
2Measurement precision
If an analog to digital converter is used to convert phase voltage, then measurement capability is improved, but device complexity increases
Solution Approach 1:
The patent removes the analog to digital converter from the system architecture. Instead of converting analog phase voltage signals, the system directly processes digital PWM signals from the inverter and uses microcontroller-based algorithms to evaluate back electromotive force and determine angular position, eliminating the need for ADC hardware.
Solution Approach 2:
The patent replaces the hardware-based ADC conversion process with a software-based signal processing approach. The microcontroller uses digital signal processing algorithms to evaluate the PWM signals and calculate angular position through mathematical computation of back electromotive force, substituting physical conversion hardware with computational methods.
3Measurement precision
If actual phase voltage measurement is implemented, then measurement precision is improved, but device complexity and circuit requirements increase
Solution Approach 1:
The patent creates a virtual representation of the phase voltage through PWM signal processing. Instead of measuring actual analog voltage, the system reconstructs the voltage information from the digital PWM waveforms and uses this copied signal representation to evaluate back electromotive force and determine position, avoiding complex voltage measurement circuits.
Data Source
AI summary
The sensorless position measurement system for the permanent magnet machine utilizes the preprocessing circuit to couple with the inverter for obtaining the line-to-line PWM signal supplied to the permanent magnet machine. The preprocessing circuit converts negative PWM pulses of the line-to-line PWM signal into positive PWM pulses for obtaining the converted line-to-line PWM signal. The function of the preprocessing is achieved by the differential circuit and the polarity correction circuit. The converted line-to-line PWM signal is a digital signal and captured by the capture modulator. The preprocessing circuit is substituted for the analog to digital converter. The microcontroller determines the angular position of the permanent magnet machine based on the converted line-to-line PWM signal. Overall, the sensorless position measurement system for a permanent magnet machine does not need a position sensor to determine the angular position of the permanent magnet machine, thereby reducing the size of the system.