IPM Motor Absolute Rotor Position Detection
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Solution Overview
Problem
Existing permanent magnet (PM) motors require external position feedback devices like encoders or resolvers to determine the absolute position of the rotor, which increase space and cost requirements and are prone to electromagnetic noise interference, and sensorless methods only provide electrical angle information, not absolute mechanical position.
Innovation Solution
A PM motor with a multi-phase, multi-slot stator and an asymmetrical rotor configuration allows for absolute angular position detection without external sensors, using asymmetrical pole pairs and winding configurations to differentiate flux magnitudes across segments, enabling the motor drive to determine the absolute mechanical position through interaction with stator windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an external position feedback device (encoder or resolver) is used to determine rotor position, then position detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The motor determines its own rotor position using built-in asymmetries in the permanent magnet configuration and winding arrangements, eliminating the need for external position feedback devices. The motor structure itself provides the reference signals needed for position detection through variations in flux magnitude as the rotor rotates.
Solution Approach 2:
The patent introduces asymmetrical pole pairs with different flux magnitudes and asymmetrical winding configurations in different segments of the motor. These deliberate asymmetries create unique flux patterns that allow the motor drive to determine absolute rotor position without external sensors by detecting which segment produces the highest flux magnitude.
2Measurement precision
If an external position feedback device is used, then position detection capability is improved, but space requirements increase
Solution Approach 1:
The position detection function is merged with the motor structure itself. The asymmetrical permanent magnet configuration and winding arrangements that define the motor's electromagnetic characteristics also serve as the position reference, combining the motor's drive function with its sensing function in a single integrated structure.
Solution Approach 2:
The motor structure provides its own position reference signals through the asymmetrical flux patterns generated by the permanent magnets and windings, eliminating the need for separate external position feedback devices and reducing overall space requirements.
3Device complexity
If sensorless methods with high frequency signal injection are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent uses asymmetrical pole pairs with different flux magnitudes to create segment-specific flux patterns. This asymmetry allows the motor drive to determine which segment is active and calculate absolute rotor position within that segment, providing both sensorless operation and improved position detection accuracy compared to conventional symmetrical motors.
Solution Approach 2:
The patent changes the flux magnitude parameter across different segments by using asymmetrical permanent magnet configurations and varying winding turns. This parameter variation creates detectable differences in flux patterns that enable accurate position determination without external sensors, improving upon conventional sensorless methods.
4Measurement precision
If external position feedback device is used, then position detection is improved, but reliability decreases due to additional failure points
Solution Approach 1:
The motor determines its own position using built-in asymmetries, eliminating external position feedback devices and their associated failure points. The position detection function is self-contained within the motor structure, reducing the number of components that can fail and improving overall system reliability.
Solution Approach 2:
The patent extracts the position reference function from external devices and embeds it within the motor structure itself. By removing external position feedback devices and incorporating position reference capabilities directly into the motor's permanent magnet and winding configuration, the system eliminates additional failure points while maintaining position detection 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
This solution eliminates the need for external position sensors, reduces noise interference, and accurately determines the absolute mechanical position of the rotor within a PM motor, enhancing control precision and reliability.
Implementation Method 1
The magnets are configured such that the magnetic field varies in strength at different locations around the rotor. The magnetic field produced by the permanent magnets interacts with the field generated by a stator current to control rotation of the motor.
Implementation Method 2
PM motors include a set of magnets in the rotor. The magnets are either inserted in slots within the rotor interior permanent magnets) or mounted to the outer surface of the rotor (i.e., surface permanent magnets). The magnets are configured such that the magnetic field varies in strength at different locations around the rotor.
Data Source
AI summary
An IPM motor in which the absolute position of the rotor may be determined is disclosed. The IPM motor includes asymmetries in both the rotor and the stator. The rotor includes an asymmetrical pole configuration for one of the pole pairs in the rotor, and the stator includes a different number of turns for each winding of one phase of the motor. The different number of turns on each winding causes a different magnitude of flux to be generated with each winding. The flux interacts with the asymmetrical pole pair to identify to which winding the asymmetrical pole is proximate. A position sensing routine identifies an angular position with respect to each winding. The position sensing routine, in combination with the flux interaction between the windings and the asymmetrical pole provide an absolute position of the rotor within the IPM motor.