Resolver Offset Calibration Using Short-Circuit Motor Deceleration
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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, particularly in heavy-duty vehicles, where precise speed and torque control are critical for efficiency and longevity.
Innovation Solution
A computer system that controls the speed of an electrical machine to pre-set 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 improved control by subtracting the offset from the estimated 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
Solution Approach 1:
The patent performs preliminary calibration actions by controlling the electrical machine to specific pre-set speed values (positive and negative) and short-circuiting the machine before measuring d,q currents. This preliminary setup ensures that the resolver is calibrated under controlled conditions that account for both speed-independent and speed-dependent offsets, thereby improving measurement precision while maintaining a systematic calibration process.
Solution Approach 2:
The patent changes operational parameters by varying the speed of the electrical machine to pre-set positive and negative speed values during calibration. By measuring d,q currents at different speed conditions and calculating the resolver offset based on these varying parameters, the method achieves comprehensive calibration that accounts for speed-dependent effects, thereby improving resolver position accuracy.
2Manufacturing precision
If resolver calibration is performed at multiple speed values, then the control accuracy of electrical machine is improved, but the calibration time increases
Solution Approach 1:
The patent employs periodic action by controlling the electrical machine to operate at pre-set positive and negative speed values in a systematic sequence during calibration. This periodic measurement approach at different speed points allows comprehensive determination of resolver offsets while maintaining an efficient calibration workflow, balancing improved control accuracy with reasonable calibration time.
Solution Approach 2:
The patent uses feedback by measuring d,q currents at different speed values and using these measurements to calculate the resolver offset. The calculated offset is then used to correct the resolver position, creating a feedback loop that improves control accuracy. This systematic feedback approach ensures that calibration is performed efficiently with minimal time loss while achieving high precision.
3Ease of operation
If short-circuiting method is used for calibration, then the measurement of d,q currents is simplified, but the operational complexity of the system increases
Solution Approach 1:
The patent extracts the calibration measurement process from normal operational conditions by implementing a dedicated short-circuiting mode. During calibration, the electrical machine is short-circuited to isolate the measurement process from load variations and other operational complexities. This extraction simplifies d,q current measurement while the short-circuit control logic is managed as a separate calibration function, maintaining overall system manageability.
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, resulting in improved control and efficiency of electrical machines, particularly in vehicle applications, by accurately determining resolver offsets and enhancing the performance and longevity of electrical machines.
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
Implementation Method 2
When the rotor rotates as the electrical machine is running, voltages will be induced in the stator coils that are proportional to the sine and cosine of the angle between the rotor and stator coils of the resolver
Data Source
AI summary
A computer system is provided. The computer system comprises processing circuitry configured to: for each one of a pre-set positive speed value and a pre-set negative speed value: controlling the speed of an electrical machine to the pre-set speed value, short circuiting the electrical machine, and determining d,q currents and angular velocity of a rotor of the electrical machine during deceleration from the pre-set speed value, and wherein the processing circuitry is further configured to: determining a resolver offset based on the determined d, q currents and the determined angular velocity of the rotor.