Motor Drive Controller Rotation Detection via Back-EMF Zero-Crossing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor drive controllers face challenges in determining the rotation state, especially at startup and low rotation speeds, due to insufficient counter-electromotive voltage and complexity in control processes, making it difficult to accurately detect rotation direction under external disturbances.
Innovation Solution
A motor drive controller with a comparison reference voltage generator and a counter-electromotive voltage comparator that compares counter-electromotive voltages across phases to determine rotation state based on zero-cross events, allowing for rapid detection of rotation direction and speed without requiring closed-loop control at startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop control with all-phase opening is executed at startup to detect rotation state, then rotation direction detection accuracy is improved, but control process complexity increases
Solution Approach 1:
The patent extracts the rotation state detection function from the complex closed-loop control process by utilizing the natural counter-electromotive voltage generated during normal operation. Instead of requiring a separate detection mode with all-phase opening, the system continuously monitors counter-electromotive voltage polarity during regular motor operation, thereby achieving rotation direction detection without adding control process complexity.
Solution Approach 2:
The system uses the motor's own counter-electromotive voltage as the detection signal source, eliminating the need for external sensors or special detection circuits. The counter-electromotive voltage, which is naturally generated during motor operation, serves dual purposes: driving the motor and providing rotation state information, thereby simplifying the overall system.
2Speed
If counter-electromotive voltage comparison is used to detect rotation state, then detection speed is improved, but detection reliability deteriorates at low rotation speeds due to insufficient voltage
Solution Approach 1:
The patent changes the detection parameter from voltage magnitude comparison to voltage polarity detection. By monitoring the sign (positive or negative) of the counter-electromotive voltage relative to a reference voltage rather than comparing absolute values, the system achieves reliable rotation state detection even when the counter-electromotive voltage is small at low speeds, while maintaining fast detection response.
3Measurement precision
If monitoring of counter-electromotive voltage change over predetermined period is used for rotation direction detection, then detection accuracy is improved, but startup time increases
Solution Approach 1:
The system performs preliminary detection of rotation state by monitoring counter-electromotive voltage polarity immediately upon startup without waiting for a predetermined period. By using the polarity information available from the first moment the motor generates counter-electromotive voltage, the system determines rotation direction instantly, eliminating the time delay associated with monitoring voltage changes over a predetermined period.
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
Enables quick and accurate determination of rotation state, reducing startup time and simplifying control processes by focusing on polarity changes at zero-cross events between counter-electromotive voltages and a comparison reference voltage, effectively handling external disturbances like wind.
Implementation Method 1
a counter-electromotive voltage comparator (5) that compares the comparison reference voltage with a counter-electromotive voltage of each phase of the motor
Data Source
AI summary
A motor drive controller is for controlling a motor having multiple phases and includes: a comparison reference voltage generator that generates a predetermined constant voltage as a comparison reference voltage; a counter-electromotive voltage comparator that compares the comparison reference voltage with a counter-electromotive voltage of each phase of the motor; and a rotation state detector that detects a rotation state of the motor based on positive/negative polarities of counter-electromotive voltages of other phases with respect to the comparison reference voltage at the time of an occurrence of a zero cross between the counter-electromotive voltage of any one phase and the comparison reference voltage.