Sensorless EC Motor Stall Detection by Electric Angle Threshold
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Solution Overview
Problem
Existing methods for detecting stalls in electronically commutated motors, such as BLDC and stepper motors, often require positional sensors, which increase costs, or rely on current spikes and BEMF drops that are less reliable at low speeds and high loads.
Innovation Solution
A sensorless stall detection method that involves driving the motor with a voltage or current vector and measuring the electric angle between the applied and resulting vectors. If the absolute value of this electric angle falls within a range defined by arctan2(ωL, R) plus or minus a predefined margin, a stall is indicated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a positional sensor (e.g., Hall sensor) is used to detect rotor position for stall detection, then reliability of stall detection is improved, but device cost increases
Solution Approach 1:
The patent extracts the stall detection function from the positional sensor system and implements it through electrical measurements (current, voltage, impedance) already present in the motor control system. This removes the need for additional positional sensors while maintaining detection capability through alternative physical quantities.
Solution Approach 2:
The patent uses electrical impedance and current measurements as intermediary parameters to indirectly detect rotor position and stall conditions. Instead of directly measuring position with sensors, the system uses electrical characteristics that change with rotor position and load conditions as mediators to infer stall state.
2Device complexity
If conventional sensorless methods using current spikes or BEMF drops are used, then device complexity is reduced, but measurement precision deteriorates at low speeds and high loads
Solution Approach 1:
The patent changes the detection parameter from relying on dynamic phenomena (current spikes, BEMF drops) to using steady-state electrical impedance characteristics. By measuring impedance magnitude and phase angle at the motor terminals, the system can detect stall conditions through changes in electrical parameters that remain reliable across different operating speeds and load conditions.
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 method allows for reliable stall detection without the need for positional sensors, effective at low speeds and high loads, and can be implemented using a simple comparison of the electric angle with a stall threshold value.
Implementation Method 1
one or more motor phases with ωL an imaginary part, and R a real part of each motor phase
Data Source
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AI summary
The invention relates to stall detection of an electronically commutated 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 electronically commutated motor (220) by applying a voltage or a current vector to one or more motor phases of the electronically commutated 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.