Electric Machine Drive Control With Fixed Sensor Offset Timing
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Solution Overview
Problem
Small electric machines with high efficiency requirements face significant performance issues due to tolerances in the alignment of position sensors relative to the rotor, leading to misalignment and reduced power output.
Innovation Solution
A control system that uses a fixed position-sensor offset to correct control signals generated by a drive controller, ensuring better synchronization of phase excitation with the rotor position, even at varying speeds, thereby simplifying calculations and optimizing performance across a range of operating speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a position sensor is used to determine rotor position for phase excitation synchronization, then the electric machine can generate power, but tolerance in the alignment of the position sensor relative to the rotor causes phase difference between detected and actual rotor positions, reducing power and efficiency
Solution Approach 1:
The patent applies parameter changes by introducing a compensatable time offset parameter that adjusts the phase excitation timing relative to the position sensor signal. This offset compensates for the fixed misalignment between the sensor and rotor, allowing the system to achieve accurate synchronization despite manufacturing tolerances in sensor alignment.
2Manufacturing precision
If the circumference of the rotor is made large to reduce the impact of sensor misalignment, then the phase difference becomes negligible, but the size of the electric machine increases
Solution Approach 1:
Instead of increasing rotor size to reduce the relative impact of misalignment, the patent changes the timing parameter by introducing a compensatable offset. This offset adjusts the phase excitation timing to account for the fixed misalignment, achieving accurate synchronization without increasing the rotor circumference.
3Measurement precision
If speed-dependent time correction is applied to compensate for sensor misalignment, then accurate synchronization is achieved, but the calculations performed by the drive controller become complex and require more instructions per electrical half-cycle
Solution Approach 1:
The patent applies preliminary action by pre-determining a fixed time offset value that compensates for sensor misalignment. This offset is established in advance and applied as a simple correction to the position sensor signal, eliminating the need for complex real-time calculations during operation and reducing the computational burden on the drive controller.
4Device complexity
If a fixed position-sensor offset is used to simplify controller calculations, then the number of instructions per electrical half-cycle is reduced, but the system must be optimized for a specific speed within the operating range
Solution Approach 1:
The patent uses preliminary action by pre-calculating a fixed offset value that provides accurate compensation across the operating speed range. This pre-determined offset simplifies real-time controller operations while maintaining adaptability, as the offset value is established beforehand to account for the fixed sensor misalignment regardless of speed variations.
Data Source
AI summary
A control system for an electric machine, the control system including a position sensor and a drive controller. The drive controller generates one or more control signals for exciting a winding of the electric machine in response to edges of a signal output by the position sensor. The times at which the control signals are generated by the drive controller are corrected by a position-sensor offset that is fixed over an operating speed range of the electric machine.