Rotor Position Estimation Using Magnetic Field Waveform Analysis
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Solution Overview
Problem
Existing methods for estimating the rotation position of a motor rotor without a position sensor face challenges in accurately determining the rotor angle when it is less than one rotation, leading to estimation failures.
Innovation Solution
A position estimation device and method that acquire detection values of magnetic field strength at multiple locations, select sections based on these values, calculate feature amounts of the magnetic field waveform, and determine the rotor position by matching learned magnitude relationships with calculated ones, even at angles less than one rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor such as an optical encoder is used to estimate the rotation position of the rotor, then the measurement precision of the rotor angle is improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the position sensing function from a dedicated position sensor and implements it through magnetic field detection using existing motor components. The magnetic field detection device utilizes the motor's own magnetic field structure, eliminating the need for separate optical encoders or other position sensors, thereby reducing device complexity while maintaining measurement capability
Solution Approach 2:
The motor system uses its own magnetic field generation capability to perform position measurement. The magnetic field detection device leverages the motor's inherent magnetic field structure and operation to detect rotor position, making the system self-sufficient without requiring external position sensing components
2Device complexity
If magnetic field detection is used to estimate rotor position without a position sensor, then the device complexity is reduced, but the reliability of position estimation deteriorates in the range where rotor angle is less than one rotation
Solution Approach 1:
The patent segments the magnetic field detection range into multiple predetermined sections, each corresponding to a specific pole pair number range. By dividing the detection space into discrete sections and identifying which section the current measurement falls into, the system can reliably determine rotor position even for angles less than one rotation, overcoming the limitation of conventional single-range detection methods
Solution Approach 2:
The patent introduces a new dimension of analysis by using the magnitude relationship among multiple feature amounts (first, second, and third feature amounts) to determine rotor position. Instead of relying on a single measurement parameter, the system evaluates the relative magnitudes of multiple feature amounts derived from different magnetic field detection points, enabling reliable position estimation in the sub-rotation range
3Ease of operation
If conventional position estimation methods are used without section selection, then the ease of operation is maintained, but the measurement precision deteriorates for rotor angles less than one rotation
Solution Approach 1:
The patent performs preliminary classification of the detection range into multiple sections before actual position determination. By pre-defining sections corresponding to different pole pair number ranges and determining which section applies first, the system simplifies the subsequent position calculation while ensuring high precision for all rotor angles including those less than one rotation
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 estimation of the rotor position even at zero degrees, improving reliability and robustness against sensor aging and environmental changes.
Implementation Method 1
acquire detection values of a magnetic field strength at three or more places of the rotor
Data Source
AI summary
A position estimation device acquires detection values of magnetic field strength at three or more locations of a rotor in a range where a rotor angle is less than one rotation. A section is selected based on a detection value of the magnetic field strength from predetermined sections for a pole pair number of the rotor. A feature amount calculator is provided to calculate feature amounts of a waveform of the magnetic field strength based on a combination of the detection values of the magnetic field strength according to the section selected. An estimator is provided to determine, for each segment associated with the section selected, whether or not a magnitude relationship of the feature amounts learned in advance coincides with a magnitude relationship of the feature amounts calculated, and estimating, as a rotation position of the rotor, the pole pair number associated with the segment having the same magnitude relationship.