Motor Failure Determination via Back-EMF Voltage Comparison
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Solution Overview
Problem
Existing motor system failure determination methods cannot accurately distinguish between rotor constraint and position sensor failure when there is no variation in the signal value sensed by the position sensor, leading to incorrect failure detection.
Innovation Solution
A failure determination method that sets a current command value to drive the motor, increases the rotational speed of the magnetic field to a reference speed, compares the intensity of the back electromotive force with the applied voltage, and determines the cause of failure based on these comparisons, including initializing current and voltage values to differentiate between position sensor failure and rotor constraint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the position sensor signal value is not varied, then it is determined that the position sensor has failed, but this cannot distinguish between position sensor failure and rotor constraint
Solution Approach 1:
The patent segments the failure determination process into multiple stages: first checking current command values and motor operation status, then comparing back electromotive force intensity with applied voltage magnitude, and finally determining the specific failure cause based on these comparisons. This segmented approach allows differentiation between position sensor failure and rotor constraint by analyzing multiple parameters rather than relying solely on position sensor signal variation.
Solution Approach 2:
The patent introduces back electromotive force comparison as an intermediary diagnostic parameter. By comparing the intensity of back electromotive force with the magnitude of applied voltage, the system obtains additional information that helps distinguish between position sensor failure and rotor constraint, thereby recovering the lost failure cause information.
2Productivity
If current is applied to the stator coil to drive the motor, then the motor should rotate, but the position sensor may not show variation due to rotor constraint or sensor failure
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the relationship between current command values, motor operation status, and back electromotive force. When the motor is driven and current is applied, the system feedbacks information about back electromotive force intensity and compares it with applied voltage, using this feedback to accurately identify whether the lack of position sensor variation is due to rotor constraint or position sensor failure.
Solution Approach 2:
The patent changes the diagnostic parameters from solely relying on position sensor signal variation to including current command value analysis and back electromotive force intensity comparison. By introducing these additional parameters and analyzing their relationships, the system can accurately identify failure causes even when the motor is being driven and current is applied to the stator coil.
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
Precisely determines the cause of motor system failure, reducing incorrect diagnoses and minimizing repair costs by accurately distinguishing between position sensor failure and rotor constraint, thereby improving system stability and efficiency.
Implementation Method 1
comparing an intensity of a back electromotive force, generated when a rotor of the motor is rotated at the preset reference speed, to a magnitude of a voltage applied to apply current in accordance with the set first current command value
Data Source
AI summary
A failure determination method for a motor system includes setting a current value required to initially drive a motor to a first current command value, increasing a rotational speed of a rotating magnetic field of the motor up to a preset reference speed, comparing an intensity of a back electromotive force, generated when a rotor of the motor is rotated at the preset reference speed, to a magnitude of a voltage applied to apply current in accordance with the set first current command value, and determining a cause of a failure of the motor based on the comparison.