Angular Position Detection for PM Motors Using Phase Vectors
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Solution Overview
Problem
Existing permanent magnet motor (PMM) systems face challenges in accurately determining the angular position of the rotor, especially at zero speed, which is crucial for precise control and efficient operation.
Innovation Solution
The development of a motor control system that includes an angular position determination (APD) algorithm, which uses a processor to implement a controller block, a signal generator block, and an estimation block to determine the rotor's angular position by forcing phase vectors to the stator terminals and measuring resulting current or voltage levels, allowing for independent operation in phase coordinates without the need for field-oriented control (FOC).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional position detection methods are used for PM motors, then the system can operate at higher speeds, but accurate position determination at zero speed cannot be achieved
Solution Approach 1:
The patent applies preliminary action by injecting test voltage vectors before normal motor operation to proactively determine rotor position. The controller forces known voltage vectors (such as V1, V2, V3 in a three-phase system) onto the stator windings while the motor is stationary or at low speed, measures the resulting current responses, and calculates the rotor angular position before actual motion begins. This preliminary position determination enables accurate control startup without requiring the motor to be already moving.
2Measurement precision
If field-oriented control (FOC) is implemented for precise control, then control accuracy improves, but system complexity increases
Solution Approach 1:
The patent extracts the position determination function from the complex FOC framework by implementing a standalone angular position determination algorithm that operates independently of field-oriented control. The controller includes a specific angular position determination module that can function without FOC, allowing the system to achieve precise position sensing through direct voltage vector injection and current measurement, thereby reducing overall system complexity while maintaining control accuracy.
3Measurement precision
If voltage or current vectors are applied to determine angular position, then position detection accuracy improves, but the rotor may unintentionally move
Solution Approach 1:
The patent applies partial action by using voltage vectors with magnitudes specifically designed to be sufficient for accurate position detection but insufficient to cause rotor movement. The controller selects voltage vector magnitudes that create measurable current responses for position calculation while remaining below the threshold that would generate enough torque to move the rotor, especially when the motor is stalled or under load. This partial action approach achieves the dual goal of accurate measurement without disturbing the system state.
4Adaptability or versatility
If multiple control frames (α/β, A/B/C) are supported for versatility, then adaptability improves, but control algorithm complexity increases
Solution Approach 1:
The patent implements universality by designing a control system that can operate in multiple reference frames (α/β frame and A/B/C frame) through a unified angular position determination algorithm. The controller is configured to force voltage vectors and measure current responses in a manner that is frame-independent, allowing the same basic algorithm to function across different control frameworks. This multi-functionality enables the system to adapt to various control strategies without requiring separate algorithms for each frame, thereby managing complexity while maintaining versatility.
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 solution enables accurate initial angular position and velocity estimation of the rotor at zero speed, allowing for precise control and efficient operation of PMMs, including the ability to start under full load and automatically determine north-south rotor orientation, with improved control schemes that can operate in various frames such as α/β or A/B/C, enhancing motor control applications.
Implementation Method 1
The alternating current in the stator windings produces a rotating magnetic field which interacts with the magnetic field from the rotor magnets to produce motion
Implementation Method 2
PMMs have permanent magnets located on the rotor and copper windings located on the stator. The alternating current in the stator windings produces a rotating magnetic field which interacts with the magnetic field from the rotor magnets to produce motion
Data Source
AI summary
A method of determining angular position (θ) of a rotor of an N-phase permanent magnet motor (PMM). A processor having an associated stored angular position determination (APD) algorithm is programmed to implement the algorithm to cause an associated motor controller to execute steps including forcing one vector at a time a phase vector set of current or voltage vectors to stator terminals of windings for the N-phases a positive and negative magnitude vector, wherein the vector magnitude is sufficiently small to not move the rotor, and a time duration for the forcing current or voltage vectors is essentially constant. The resulting stator current or voltage levels are measured for each current or voltage vector. An N-dimension current vector or voltage vector is generated from superposition of the resulting stator current levels or resulting stator voltage levels. The N-dimension current vector or voltage vector is used to determine angular position.