Motor Control Device for Rapid Magnetic Pole Position Estimation
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Solution Overview
Problem
Conventional methods for estimating the magnetic pole position of a motor are time-consuming, leading to delays in motor startup, particularly in applications like electric vehicles, where rapid initialization is critical.
Innovation Solution
A motor control device that applies a voltage with a predetermined frequency to estimate the magnetic pole position using current components from multiple axes, including first, second, third, and fourth axis components, allowing for stable and rapid estimation regardless of the initial magnetic pole position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional high-frequency voltage application method is used for magnetic pole position estimation, then the estimation can be performed without position sensors, but the estimation time is prolonged due to dependency on initial axial error
Solution Approach 1:
The current estimation process is segmented into multiple axis components (first axis, second axis, third axis, fourth axis) rather than relying on a single axis estimation. This segmentation allows parallel processing of multiple current components to converge on the magnetic pole position more rapidly, reducing the time dependency on initial axial error while maintaining estimation accuracy.
Solution Approach 2:
The invention transitions from two-axis current component estimation to four-axis current component estimation by introducing additional orthogonal axis pairs. This dimensional expansion provides more information pathways for position estimation, enabling faster convergence regardless of the initial axial error condition.
2Productivity
If multiple axis current components are used for estimation, then the estimation speed and stability are improved, but the processing complexity increases
Solution Approach 1:
The estimation unit is designed to universally process multiple axis current components using the same fundamental estimation algorithm. By applying a unified processing approach across all four axis components rather than requiring separate specialized processors, the system achieves high estimation speed while controlling processing complexity through methodological consistency.
Data Source
AI summary
To estimate an initial magnetic pole position, estimated control axes corresponding to the d-axis and q-axis are set as the γ-axis and δ-axis, and a with high frequency rotation voltage or alternating voltage on the γδ coordinate system applied to the motor. A high frequency current ih flowing in the motor is then extracted from a detected motor current (armature current) and a direct current component (ihγ×ihδ)DC of a product of the γ-axis and δ-axis components of the high frequency current ih is derived. Alternatively, the γ′-axis component ichγ and the δ′-axis component 66 of the high frequency current ih that are shifted by π/4 in electric angle from the γ-axis and the δ-axis are used to obtain a direct current component of their product (ichγ×ichδ)DC. The magnetic pole position is then estimated by computing the axial error Δθ between the γ-d axes utilizing the direct current components.