BLDC Commutation Control via Pre-calculated PWM Signals
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Solution Overview
Problem
High-speed miniaturized Brushless Direct Current Motors (BLDCMs) face challenges in timely commutation due to the inability of existing PWM drive signals to control commutation effectively, leading to commutation delay, unevenness, and disappearance of back electromotive force zero-crossing points, affecting efficiency and stability.
Innovation Solution
A commutation control method and device that detects the rotor position in the BLDCM, determines a first drive scheme based on the position, updates the PWM drive signal by adjusting the duty cycle and phase, and controls the motor using the updated signal to ensure timely commutation, utilizing a processor and memory to execute computer programs for implementing these operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PWM drive signals are used to control the three-phase full-bridge circuit, then the control structure remains simple, but the BLDCM cannot perform commutation in time, leading to commutation delay and instability
Solution Approach 1:
The patent applies preliminary action by detecting the rotor position in advance and pre-calculating the required PWM drive signal parameters (duty cycle and phase) before commutation is needed. The controller stores multiple groups of drive signals corresponding to different rotor positions and selects the appropriate pre-calculated signals when commutation is required, ensuring timely and accurate commutation without adding complex real-time computation during the commutation moment.
2Reliability
If the PWM drive signal duty cycle and phase are updated in real-time, then commutation timing accuracy improves, but the computational burden increases
Solution Approach 1:
The controller pre-calculates and stores multiple groups of PWM drive signals, each corresponding to a specific rotor position range. When the rotor position sensor detects a position change, the controller directly selects the pre-calculated drive signal group without performing real-time computation, thus achieving both high commutation precision and fast signal update.
Solution Approach 2:
The patent implements dynamic adaptation by continuously monitoring the rotor position and dynamically switching between different pre-calculated PWM drive signal groups. The duty cycle and phase parameters are dynamically adjusted based on the detected rotor position, ensuring optimal commutation performance throughout the motor's operating range.
3Speed
If high-speed commutation is implemented, then motor speed increases, but commutation becomes uneven and back electromotive force zero-crossing points disappear
Solution Approach 1:
The patent employs feedback by continuously detecting the rotor position using a position sensor and using this feedback information to determine when to switch between different PWM drive signal groups. This closed-loop feedback mechanism ensures that commutation occurs at the correct moments even at high speeds, maintaining commutation uniformity and preserving the detectability of back electromotive force zero-crossing points for sensorless control.
Data Source
AI summary
A commutation control method, a device for a brushless direct current motor, and a storage medium are described. The method includes performing detection on a position of a rotor in a brushless direct current motor. The detection is further configured to be triggered by commutation of the brushless direct current motor. The method includes determining, for the brushless direct current motor, a first drive scheme corresponding to the detected position of the rotor, the first drive scheme indicates a manner in which a three-phase full-bridge circuit of the brushless direct current motor operates; updating a pulse width modulation (PWM) drive signal, the updating is performed on the basis of the first drive scheme; and using the updated PWM drive signal to control the brushless direct current motor to perform commutation.