Resolver Offset Calibration Using d-q Current Deceleration Data
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Solution Overview
Problem
Existing methods for calibrating resolvers in electrical machines are inadequate, leading to decreased performance and control accuracy due to insufficient calibration of resolver positions, which can result in misalignments caused by both speed-independent and speed-dependent phenomena.
Innovation Solution
A computer system that controls the speed of an electrical machine to pre-set positive and negative speed values, short circuits it, and determines d,q currents and angular velocity during deceleration to calculate both constant and speed-dependent resolver offsets, allowing for accurate calibration and alignment of the resolver position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional resolver calibration methods are used, then the calibration process is simple, but the measurement precision of resolver position is insufficient due to speed-independent and speed-dependent misalignments
Solution Approach 1:
The patent changes the operating parameters of the electrical machine during calibration by controlling it to rotate at multiple different speeds (including zero speed, low speed, and high speed). By measuring d-q currents at these different speed parameters and analyzing their relationships, the method determines both speed-independent and speed-dependent resolver offsets, thereby improving position accuracy through parameter variation.
Solution Approach 2:
The patent replaces traditional mechanical alignment methods with an electrical measurement and calculation approach. Instead of mechanically adjusting the resolver to achieve alignment, the method uses electrical measurements of d-q currents at different speeds and computationally determines the offsets, substituting mechanical adjustment with electrical sensing and mathematical processing.
2Measurement precision
If resolver calibration is performed at multiple speeds to address speed-dependent misalignments, then the measurement precision improves, but the loss of time increases due to multiple measurement steps
Solution Approach 1:
The patent performs preliminary measurements of d-q currents at multiple different speeds during the calibration process. By collecting all necessary measurement data in advance at various operating speeds before finalizing the offset determination, the method enables comprehensive offset calculation without requiring iterative measurements during operation, thus reducing overall calibration time while maintaining precision.
Solution Approach 2:
The patent maintains continuous rotation of the electrical machine throughout the calibration process, measuring d-q currents continuously at different speeds without stopping the rotor. This continuous measurement approach allows for efficient data collection across the speed range, eliminating idle time between measurements and maintaining productive action throughout the calibration procedure.
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 method enables precise calibration of the resolver, addressing both speed-independent and speed-dependent misalignments, thereby improving the control and efficiency of electrical machines, especially in vehicle applications by ensuring accurate rotor position determination.
Implementation Method 1
A resolver operates by converting the mechanical motion of the shaft into an electrical signal that is indicative of the position and speed of the electrical machine
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A computer system (100) is provided. The computer system comprises processing circuitry (160, 402) configured to: for each one of a pre-set positive speed value (ωref) and a pre-set negative speed value (-ωref): controlling the speed of an electrical machine (10) to the pre-set speed value (ωref, - ωref), short circuiting the electrical machine (10), and determining d,q currents (id, iq) and angular velocity (ω) of a rotor (14) of the electrical machine (10) during deceleration from the pre-set speed value (ωref, -ωref), and wherein the processing circuitry (160, 402) is further configured to: determining a resolver offset (θoff, kω) based on the determined d, q currents (id, iq) and the determined angular velocity (ω) of the rotor (14).