Resolver Signal Calibration for Electrical Machine Load Angle Errors
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Solution Overview
Problem
Existing methods for calibrating resolver offsets in electrical machines, particularly those using delta-sigma analog-to-digital conversion, face challenges due to mechanical resolver offsets and group delays, leading to inaccurate rotor position determination and inefficiencies in control and operation.
Innovation Solution
A computer system is configured to determine both mechanical offset and group delay errors by averaging current load angles at various speed intervals, allowing for precise calibration of resolver signals using available current data and facilitating accurate rotor position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If mechanical resolver offset is calibrated using traditional methods, then offset compensation is simplified, but group delay error remains uncorrected reducing overall accuracy
Solution Approach 1:
The patent merges the calibration of resolver offset with the determination of group delay characteristics into a single integrated process. By performing both calibrations using the same multi-speed measurement procedure and combining the results, the system achieves comprehensive error compensation without significantly increasing device complexity. The offset and group delay are determined together and applied jointly during normal operation.
Solution Approach 2:
The patent creates a universal calibration procedure that simultaneously handles both resolver offset compensation and group delay characterization. The same multi-speed measurement sequence serves multiple functions: determining mechanical offset, characterizing group delay vs. speed relationship, and providing data for both corrections. This multi-functional approach maintains simplicity while achieving high accuracy.
2Loss of time
If resolver offset calibration is performed at a single speed, then calibration time is reduced, but accuracy deteriorates due to speed-dependent group delay variations
Solution Approach 1:
The patent performs preliminary action by conducting comprehensive multi-speed calibration measurements during manufacturing or initial setup. This time-consuming but thorough calibration is done once in advance, creating a lookup table or mathematical model that can be quickly applied during normal operation. The initial time investment yields long-term benefits by enabling accurate compensation across the entire operating speed range without requiring repeated calibrations.
Solution Approach 2:
The patent implements periodic action by measuring resolver signals at multiple discrete speed points during calibration. Rather than continuous measurement, the system samples at specific predetermined speeds, processes this periodic set of measurements to determine offset and group delay characteristics, then uses this compiled data for ongoing operation. This periodic sampling approach balances calibration time with comprehensive accuracy.
Data Source
AI summary
A computer system includes processing circuitry configured to: determine a first average of a measured current load angle of an electrical machine and a first average of a correct current load angle of the electrical machine for a plurality of positive speed values within a positive speed interval, determine a second average of the measured current load angle of the electrical machine and a second average of the correct current load angle of the electrical machine for a plurality of negative speed values within a negative speed interval, determine a resolver offset error of the electrical machine from the first and second average of the measured current load angle, and determine a resolver delay error of the electrical machine from the first and second average of the measured current load angle, from the first and second average of the correct current load angle, and from the rotor speed.