Control system for an electric machine
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Solution Overview
Problem
The alignment tolerance of position sensors relative to the rotor in electric machines leads to phase differences between detected and actual rotor positions, compromising power and efficiency, particularly in small or high-efficiency motors.
Innovation Solution
A motor system with a control system that includes a drive controller using a non-volatile memory to store a position-sensor offset, correcting control signals based on this offset to synchronize winding excitation with the rotor position, simplifying calculations and reducing processor requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a position sensor is used to determine rotor position for synchronizing phase excitation, then the power and efficiency of the electric machine are improved, but alignment tolerance between the sensor and rotor causes phase differences that compromise performance
Solution Approach 1:
The patent applies parameter changes by measuring the time difference between position sensor signals and back EMF zero-crossings at different operating speeds, then using these measurements to calculate speed-dependent correction values that adjust the excitation timing parameter dynamically
Solution Approach 2:
The patent implements feedback by using back EMF detection to verify the actual rotor position and comparing it with position sensor readings, then applying correction based on the detected phase difference to improve synchronization accuracy
2Measurement precision
If the circumference of the rotor is increased to reduce the impact of sensor alignment tolerance, then the phase difference caused by misalignment is reduced, but the size of the electric machine increases
Solution Approach 1:
The patent changes the approach from geometric scaling to parametric correction by measuring and applying time-based offset corrections that compensate for misalignment without requiring a larger rotor circumference
3Measurement precision
If speed-dependent correction values are calculated to accurately compensate for sensor misalignment across different speeds, then the synchronization accuracy is improved, but the computational complexity and processor requirements increase
Solution Approach 1:
The patent applies preliminary action by measuring the time differences between position sensor signals and back EMF zero-crossings during an initialization phase, then storing these correction values for direct application during motor operation without real-time calculation
Solution Approach 2:
The patent implements dynamics by providing different levels of correction complexity - from fixed offset values to speed-dependent correction values - allowing the control system to adapt the computational effort to the specific performance requirements
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 approach ensures better synchronization of winding excitation with the rotor position, enhancing the power and efficiency of electric motors by correcting for sensor misalignment, while allowing for the use of simpler and cheaper processors.
Implementation Method 1
the electric machine typically includes a position sensor for determining the position of the rotor
Implementation Method 2
Zero-crossings of back EMF in one of the phase windings is detected via the back EMF detection circuit
Data Source
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AI summary
A control system for a single- phase permanent magnet electric machine, the control system comprising 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.