Sensorless Rotor Position Offset Correction for Resolver Misalignment
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Solution Overview
Problem
Existing control systems for electrical machines in vehicle propulsion systems face challenges in accurately determining the rotor position relative to the stator, especially due to manufacturing variations and installation alignment issues, affecting energy efficiency and torque production.
Innovation Solution
A sensorless motor control system estimates the rotor position during powertrain start-up, compares it to the measured resolver angle, and applies a correcting offset to the resolver signal for precise feedback and control, reducing the need for precise initial alignment of the resolver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is used to measure rotor position, then measurement precision is improved, but installation alignment difficulty increases
Solution Approach 1:
The control system automatically determines the offset between the resolver reference position and the actual rotor position during operation. The system uses sensorless rotor position information combined with resolver position information to calculate and store an offset value, eliminating the need for manual alignment adjustments during installation.
Solution Approach 2:
The system changes the parameter of rotor position measurement by introducing an offset correction. The control system calculates the offset between the resolver-measured position and the actual rotor position, then applies this offset to future position measurements to compensate for installation misalignment.
2Measurement precision
If tight machine tolerances and multiple position sensing devices are used, then rotor position measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The system merges the resolver position sensing with sensorless control techniques. By combining the resolver's absolute position information with the sensorless controller's rotor position estimation, the system achieves high measurement accuracy without requiring multiple separate position sensing devices.
Solution Approach 2:
The control system uses feedback from both the resolver and sensorless rotor position information to calculate an offset value. This offset is then applied to correct future position measurements, creating a self-correcting system that maintains high accuracy without additional sensors.
3Ease of manufacture
If resolver installation alignment is made less critical, then ease of manufacture is improved, but measurement precision may deteriorate
Solution Approach 1:
The control system automatically compensates for installation misalignment by determining the offset between the resolver reference position and actual rotor position during operation. This self-correction mechanism allows flexible installation while maintaining measurement precision.
Solution Approach 2:
The system accounts for the asymmetric error introduced by resolver misalignment by calculating a specific offset value. Rather than requiring symmetric perfect alignment, the system measures and compensates for the actual misalignment angle, allowing asymmetric installation while maintaining accuracy.
Data Source
AI summary
A control system and method to determine position of a rotor relative to a stator for a synchronous multipole electrical machine is presented, including one for application on a fuel/electric hybrid powertrain for a vehicle. The machine includes a stator, a rotor, and a rotor position sensing mechanism. The control system controls the electrical machine, in conjunction with an electrical storage device and an inverter, using algorithms and calibrations which derive a rotor position based upon a sensorless position sensing technique, and determine an offset from a sensed rotor position. Electrical output from the inverter to the machine is controlled based the offset, which is stored non-volatile memory. A rotor position is derived based upon a sensorless position sensing technique during initial machine operation after startup of the machine, and includes operation in a torque-generative mode and in an electrical energy-generative mode.