Sensorless Motor Control via Counter-EMF Harmonic Extraction
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Solution Overview
Problem
Existing sensor-less motor control methods for permanent magnet motors face issues with phase lag and error in rotational position estimation due to harmonic components in counter-electromotive voltage, leading to decreased responsiveness and stability, and require costly measurement setups or struggle with distinguishing between harmonic components from distortion and velocity/load variations.
Innovation Solution
A motor control apparatus that includes a counter-electromotive voltage determination unit, a position determination unit, a velocity determination unit, and a correction unit with harmonic extraction and error reduction capabilities, which extracts and corrects harmonic components in the estimated velocity to improve position and velocity estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low-pass filter is used to remove harmonic components from counter-electromotive voltage, then the error in estimated position is reduced, but phase lag occurs causing lag in rotational position and velocity estimation
Solution Approach 1:
The patent extracts only the fundamental wave component from the counter-electromotive voltage using a specific calculation method that separates it from harmonic components, rather than using a low-pass filter that removes all high-frequency content. This extraction approach eliminates phase lag while maintaining position estimation accuracy.
Solution Approach 2:
The patent changes the parameter extraction method from frequency-domain filtering to a calculation-based approach that computes fundamental wave components directly from voltage and current measurements, thereby avoiding the phase shift introduced by filters while improving measurement precision.
2Measurement precision
If a high-pass filter is used to extract harmonic components for position correction, then some error is reduced, but phase shift occurs causing additional error in rotational position estimation
Solution Approach 1:
The patent uses feedback by calculating the fundamental wave component of counter-electromotive voltage and comparing it with actual measurements to derive accurate position and velocity information, continuously correcting estimation errors without introducing phase shift.
Solution Approach 2:
The patent replaces the mechanical filtering approach (high-pass filter) with a computational method that calculates fundamental wave components through mathematical operations on voltage and current signals, eliminating phase shift while extracting necessary harmonic information.
3Device complexity
If sensor-less method is used to estimate rotational position without position sensor, then cost and size are reduced, but error occurs due to harmonic components in counter-electromotive voltage
Solution Approach 1:
The patent changes the parameter extraction methodology by calculating fundamental wave components from counter-electromotive voltage and current measurements using specific mathematical relationships, thereby eliminating harmonic component errors while maintaining sensor-less operation.
Solution Approach 2:
The patent creates a virtual model of the motor's electrical characteristics by calculating equivalent counter-electromotive voltage and fundamental wave components from measured currents and voltages, using this copied information to accurately estimate position without physical sensors.
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 reduces errors in rotational position and velocity estimation, enhancing the responsiveness and stability of the control loop while eliminating the need for costly measurement setups and improving the distinction between harmonic components, thereby reducing rotational misalignment, vibration, and noise.
Implementation Method 1
counter-electromotive voltages generated in the windings of the motor are determined according to the magnetization distribution of the permanent magnets in the rotor
Data Source
AI summary
A motor control apparatus includes: a unit configured to determine a counter-electromotive voltage in a winding of a motor; a unit configured to determine a rotational position of a rotor of the motor based on the counter-electromotive voltage; a unit configured to determine a first velocity of the rotor, based on change in the rotational position; a correction unit configured to obtain a second velocity by correcting the first velocity based on a harmonic component included in the first velocity; and a driving unit configured to drive the motor based on the second velocity and the rotational position. The correction unit includes a unit configured to obtain the second velocity by reducing error in the first velocity that occurs due to the harmonic component.