BLDC Motor Stall Detection Using Electric Angle Thresholds
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Solution Overview
Problem
Existing sensorless stall detection methods for BLDC motors are unreliable at low operating speeds, and they require additional sensors, which increase costs.
Innovation Solution
A method and device for detecting stall in a BLDC motor by applying a voltage or current vector and measuring the electric angle between the applied and resulting vectors, indicating a stall if the absolute value of the electric angle crosses a threshold value calculated as arctan2(ωL, R) plus or minus a predefined margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positional sensor (e.g. Hall sensor) is used for determining rotor position, then stall detection reliability is improved, but device cost increases
Solution Approach 1:
The patent extracts the stall detection function from the mechanical sensor domain and implements it through electrical measurements. By analyzing the electric angle between voltage and current vectors in the motor phases, the system achieves sensorless stall detection, removing the need for physical position sensors while maintaining detection capability.
Solution Approach 2:
The patent replaces the mechanical/physical sensor-based detection system with an electrical field-based measurement system. Instead of using Hall sensors to physically detect rotor position, the system uses electrical angle calculations from voltage and current measurements to infer rotor state and detect stalls.
2Device complexity
If sensorless BEMF-based methods are used for stall detection, then device complexity is reduced, but measurement precision deteriorates at low speeds
Solution Approach 1:
The patent changes the measurement parameters from BEMF voltage (which is speed-dependent) to electrical angle between voltage and current vectors. This parameter transformation enables accurate stall detection across the entire speed range including low speeds, because the electrical angle relationship remains valid regardless of motor speed.
Solution Approach 2:
The patent implements a dynamic threshold comparison where the electric angle is continuously monitored and compared against a threshold value. The system adapts to varying operating conditions by continuously calculating the electrical angle from instantaneous voltage and current measurements, enabling reliable stall detection during acceleration, deceleration, and steady-state operation.
Data Source
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AI summary
The invention relates to stall detection of a BL DC motor comprising one or more motor phases for each motor phase a phase inductance L, and a phase resistance R. A driver (213, 230) is configured for driving (110) the BLDC motor (220) by applying a voltage or a current vector to one or more motor phases of the BLDC motor (220) with a rotation speed ω of the voltage vector or the current vector; a detector (212) is configured for obtaining (120) an electric angle between the applied voltage vector and a resulting current vector or between the applied current vector and a resulting voltage vector; a processing device (211) is configured for determining a stall of the rotor if the absolute value of the electric angle or a filtered version thereof crosses a stall threshold value wherein the stall threshold value is arctan2(ωL, R) plus or minus a predefined margin.