Magnetic Pole Position Estimation Using Phase Matching Voltage
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Solution Overview
Problem
Conventional methods for estimating the magnetic pole position of a synchronous motor require significant calculation and are prone to errors due to varying motor parameters, making it difficult to accurately control the motor without a position detector.
Innovation Solution
A method that applies a phase matching voltage with a higher frequency than the instructed voltage, detects the phase matching current, corrects the parameter values to minimize phase difference, and calculates the magnetic pole position using the corrected values, reducing the calculation burden and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional motor model expression with constant parameters is used to estimate magnetic pole position, then the estimation process is simple, but the estimation accuracy deteriorates due to parameter variations
Solution Approach 1:
The patent implements a feedback mechanism where the estimated magnetic pole position is continuously used to generate a phase matching voltage, and the phase difference between this voltage and the actual back-EMF is measured. This phase difference information is fed back to correct the q-axis inductance parameter, creating a closed-loop system that automatically adapts to parameter variations and maintains high estimation accuracy.
Solution Approach 2:
The system uses the motor's own back-EMF signal to correct its parameters. By extracting phase information from the back-EMF and comparing it with the phase matching voltage generated from the estimated position, the system self-corrects the q-axis inductance value without requiring external calibration equipment or complex intervention, enabling the motor to adapt to its own characteristic variations.
2Measurement precision
If two estimated positions are calculated for each cycle to renew q-axis inductance, then the parameter accuracy is improved, but the calculation amount increases
Solution Approach 1:
The patent extracts only the necessary phase information from the back-EMF signal to correct the q-axis inductance parameter, rather than performing complete position estimation calculations twice. By separating the parameter correction function from the full position estimation process and using only the phase difference information, the system achieves accurate parameter renewal with reduced computational burden.
3Measurement precision
If position detector is used to detect magnetic pole position, then the position detection accuracy is high, but the motor downsizing is difficult and connection lines are required
Solution Approach 1:
The patent replaces the mechanical position detector system (encoders, resolvers, or Hall sensors requiring physical mounting and connection lines) with an electrical field-based estimation method. By using the motor's own back-EMF signal and mathematical models to estimate the magnetic pole position, the system eliminates the need for additional mechanical sensing components and their associated connection lines, enabling motor downsizing while maintaining position detection capability.
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
This approach allows for accurate estimation of the magnetic pole position with reduced calculation complexity, enabling prompt and reliable motor control, and simplifying the control unit design.
Implementation Method 1
During the operation of the motor, the motor itself induces a voltage which is changed with the magnetic pole position. Therefore, the magnetic pole position can be estimated from the induced voltage.
Implementation Method 2
applying, to the motor, a phase matching voltage which has a frequency higher than that of the instructed voltage and has a phase matching with the estimated magnetic pole position previously obtained, detecting a phase matching current generated from the phase matching voltage from the motor
Data Source
AI summary
A magnetic pole position in a synchronous motor having salient poles is estimated from an instructed voltage applied to the motor, a current generated from the instructed voltage and parameters. To estimate the position substantially matching with a true magnetic pole position, a phase matching voltage having a phase matching with the estimated magnetic pole position previously obtained is applied to the motor. The phase matching voltage has a harmonic frequency higher than that of the instructed voltage. A phase matching current generated from the phase matching voltage is detected from the motor. A value of at least one of the parameters is corrected such that a difference in phase between the phase matching voltage and the phase matching current substantially becomes zero. An estimated magnetic pole position is calculated from the instructed voltage, the generated current and the parameter having the corrected value.