Method for sensorless current profiling in a switched reluctance machine

A method for sensorless current profiling of a switched-reluctance motor (SRM) to reduce acoustic noise and torque ripple, the method comprising the steps of:

• a) providing a sensorless switched-reluctance motor control system comprising a switched-reluctance motor having at least one stator pole and at least one rotor pole, a phase inverter controlled by a processor, a load, a converter and a software control module at the processor;
• b) estimating a time-based rotor position estimate at every commutation utilizing a time-based interpolation module at the processor;
• c) determining a series of polynomial coefficients [P0 . . . Pn] for describing a current waveform shape I(θ);
• d) determining a current waveform shape that optimizes a motor performance objective function;
• e) determining an optimum rise point at a turn-on time of the current waveform;
• f) determining torque required to maintain the operating speed of the motor;
• g) setting a target magnitude M for a programmable dwell angle to scale the current waveform as required to produce torque required to maintain a given speed according to the equation
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• h) setting a reference current Iref at each time step in the dwell angle in accordance with the waveform shape and the time-based position estimate and scaled by the target magnitude.

An apparatus for sensorless profiling of a current waveform in a switched-reluctance motor (SRM), comprising:

• a switched-reluctance motor having at least one stator pole and at least one rotor pole;
• a phase inverter controlled by a processor and connected to the switched-reluctance motor to provide power supply to the SRM, the processor having a software control module and a time-based interpolation estimation module;
• a load connected to the switched-reluctance motor via an inline torque meter;
• and
• a converter connected to the load;
• whereby the time-based interpolation module estimates a position of the rotor and the software control module at the processor determines the shape of the current waveform to produce a torque required to maintain the motor operating speed and thereby reduce acoustic noise, torque ripple and increase efficiency utilizing a non-constant current profile.