Sensorless Rotor Orientation Using Stator Probe Signals
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Solution Overview
Problem
Some electric motor systems, using commutation angle estimators or phase-locked loops, are unable to distinguish between the electrical angle of a rotor and its opposite, leading to uncertainty in angular position estimation, which can result in incorrect torque direction and increased complexity due to the need for sensors.
Innovation Solution
A system that includes an excitation signal generator, a phase detector, and a probe-signal generator to determine the orientation of the rotor by analyzing the response of the stator windings to a probe signal, allowing for accurate differentiation between the correct and incorrect angular positions without the need for sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If commutation angle estimators or phase-locked loops are used to determine rotor position, then the system can operate without sensors, but the system cannot distinguish between the electrical angle and its opposite (180° error)
Solution Approach 1:
The system performs preliminary action by injecting a probe signal before final commutation decisions are made. This probe signal excites the motor windings and allows the system to measure the back-EMF or current response, which reveals the true rotor orientation. By performing this measurement step beforehand, the system resolves the 180° ambiguity before executing the actual commutation sequence, ensuring correct torque direction without requiring additional sensors.
Solution Approach 2:
The probe signal acts as an intermediary that mediates between the control system and the rotor position. Instead of directly measuring rotor position (which would require sensors), the system uses this intermediate probe signal to indirectly determine the rotor orientation by analyzing the motor's electrical response. This intermediary measurement provides the missing orientation information without adding sensor complexity.
2Device complexity
If the system cannot distinguish between correct and opposite angular positions, then sensorless operation is maintained, but reverse rotation or incorrect torque direction occurs
Solution Approach 1:
The system implements feedback by measuring the electrical response (back-EMF or current) to the injected probe signal and using this information to determine the correct rotor orientation. The feedback loop compares the measured response against expected patterns for different rotor positions, allowing the controller to distinguish between the correct angle and its 180° opposite. This feedback mechanism ensures reliable torque direction while maintaining sensorless operation.
3Measurement precision
If additional sensors are added to resolve angular position ambiguity, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The system replaces the mechanical/sensor-based position detection approach with an electrical measurement approach. Instead of using physical sensors to directly detect rotor position, the system uses electrical probe signals and measures the resulting back-EMF or current responses to infer the rotor orientation. This substitution eliminates the need for additional sensors while achieving the same angular position discrimination capability.
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 accurate determination of the rotor's angular position, reducing the risk of reverse rotation and minimizing disturbances in motor control, while avoiding the complexity and cost of sensor-based systems.
Implementation Method 1
an excitation signal generator to provide an excitation signal to a stator of a motor to induce a response signal
Implementation Method 2
a phase detector to detect a phase difference between the excitation signal and the response signal
Implementation Method 3
a probe-signal generator to provide the probe signal to the stator
Data Source
AI summary
One or more examples relate, generally, to an orientation of a rotor. Some examples relate to an apparatus. The apparatus may include sample-accumulation logic to generate, over a time duration, a value indicative of inductance at least partially responsive to a probe signal provided to a stator of a motor. The apparatus may also include a probe-current discriminator to generate a further value indicative of an orientation of a rotor of the motor at least partially responsive to the generated value. The apparatus may also include update logic to update a process variable of a control loop at least partially responsive to a state of the further value.