Sensorless Motor Control Inductance Calibration
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Solution Overview
Problem
Electric motors face inefficiencies due to angle errors in rotor position estimation, which can significantly lower motor efficiency and increase phase current, especially under varying loads.
Innovation Solution
A computer-implemented method that determines the inductance value resulting in zero angle error for each speed of an electric motor, allowing for accurate synchronization of the rotor and stator, and saves this value in a motor controller's memory for precise operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless algorithms are used to determine rotor position, then device complexity is reduced, but measurement precision deteriorates due to angle errors
Solution Approach 1:
The patent adjusts inductance values as a parameter to compensate for angle errors in sensorless motor control. By varying the inductance parameter based on operating conditions (speed and torque), the system maintains accurate rotor position estimation without requiring additional sensors, thus resolving the contradiction between device complexity and measurement precision.
2Loss of energy
If angle error is reduced through inductance adjustment, then motor efficiency is improved, but device complexity increases due to additional control parameters
Solution Approach 1:
The patent implements dynamic adjustment of inductance values based on real-time operating conditions (speed and torque levels). Rather than using fixed inductance parameters, the system adaptively modifies them to minimize angle errors across varying loads, improving motor efficiency while keeping the control structure manageable through a systematic approach.
3Measurement precision
If inductance values are optimized for each speed, then measurement precision is improved, but productivity decreases due to extended calibration time
Solution Approach 1:
The patent performs inductance value optimization in advance during motor commissioning or setup phase. The optimized inductance values for different speed levels are determined beforehand and stored in memory, so that during normal operation, the motor controller can directly apply these pre-calculated values without real-time computation, thus maintaining high measurement precision while avoiding productivity loss during operation.
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 reduces angle errors, enhancing the correlation between current and torque, enabling motor manufacturers to minimize performance margins while meeting user requirements, thereby improving motor efficiency.
Implementation Method 1
Another way to determine the position of the rotor is to use a sensorless algorithm based on back electromotive force (EMF), inductance, and resistance to predict the position of the rotor.
Implementation Method 2
One way to directly determine the position of the rotor is to use a Hall effect sensor, encoder, or resolver in the motor.
Data Source
AI summary
A system and computer-implemented method for reducing an angle error in an estimated position of a rotor over various loads on an electric motor or type of electric motor. Electrical parameters of an electric motor are measured, a true rotor position is found, and sensorless gains based on the measured parameters are generated, including determining a sensorless angle. Data is gathered at multiple torque levels for at least one speed of the motor, including for each torque level, trying different inductance values, and determining an inductance value that results in an angle error of zero. The angle error is the difference between the true rotor position and the sensorless angle. The inductance value that results in an angle error of zero for each speed may be saved in an electronic memory and used to better control the motor or other motors of the same type.