Manufacturing-sensitive control of high rotor pole switched reluctance motors
A method for controlling switched reluctance machine (SRM) utilizing a SRM control system. The method allows for adaptive pulse positioning over a wide range of speeds and loads. An initial rotor position is provided for the SRM utilizing an initialization mechanism. A pinned point on a phase current waveform is defined during an initial current rise phase of the current waveform. A slope of the current rise is determined as the current waveform reaches the pinned point. The slope is then fed to the commutation module of the SRM control system. An error signal from calculated inductance or current slope is used as an input to a control loop in the SRM control system. The time determining module determines an optimum time signal to fire a next pulse. The optimum time signal is fed to the SRM for turning the plurality of SRM switches to on and off states.
1. A method for controlling a switched reluctance machine (SRM) comprising the steps of:
a) providing an SRM control system having a commutation module;
b) providing an initial rotor position for the SRM utilizing an initialization mechanism;
c) defining a pinned point on a phase current waveform during an initial current rise phase of the current waveform;
d) determining a slope of the current rise as the current waveform reaches the pinned point, the slope being fed to the commutation module;
e) calculating an error signal and providing the error signal as an input to a control loop in the SRM control system; and
f) determining an optimum time to fire a next pulse;
whereby the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.
2. The method of claim 1 wherein the defined pinned point is static with respect to an underlying inductance value of the SRM.
3. The method of claim 1 wherein the pinned position is defined at a point corresponding to a magnitude between 50% and 100% of the steady state current on the initial current rise.
4. The method of claim 1 wherein the SRM control system is designed to utilize the underlying inductance to calculate the error signal from a desired inductance value.
5. The method of claim 1 wherein the SRM control system is designed to utilize the measured current rise over a fixed time period to calculate the error signal from a desired current rise.
6. A method for controlling a switched reluctance machine (SRM) comprising the steps of:
a) providing an SRM control system having a commutation module;
b) providing an initial rotor position for the SRM utilizing an initialization mechanism;
c) defining a pinned point on a phase current waveform during an initial current rise phase of the current waveform, the pinned point being static with respect to an underlying inductance value of the SRM;
d) determining a slope of the current rise as the current waveform reaches the pinned point, the slope being fed to the commutation module;
e) providing a frequency input signal to the commutation module to obtain a digital estimate for shaft speed;
f) calculating a current speed utilizing the slope of the current rise and frequency input signal;
g) generating a commanded current by a regulator unit utilizing a reference speed and the current speed;
h) comparing the commanded current with a measured current by an inner current loop in the SRM control system; and
i) generating pulse width modulation (PWM) signals to create a plurality of commutation angles for turning a plurality of switches of the SRM to on and off states;
whereby the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.
7. The method of claim 6 wherein the pinned position is defined at a point corresponding to a magnitude between 50% and 100% of the steady state current on the initial current rise.
8. The method of claim 6 herein the regulator unit is a proportional-integral unit.
9. A switched reluctance machine (SRM) control system for controlling an SRM comprises:
an initialization module to provide an initial rotor position for the SRM utilizing an initialization mechanism;
a point defining module to define a pinned point on a phase current waveform during an initial current rise phase of the current waveform;
a slope determining module to determine a slope of the current rise as the current waveform reaches the pinned point;
a commutation module to receive the slope of the current rise from the slope determining module and a frequency input signal;
an error calculating module to calculate an error signal that being fed to a control loop in the SRM control system; and
a time determining module to determine an optimum time to fire a next pulse;
whereby the SRM control system enables adaptive pulse positioning over a wide range of speeds and loads.
10. The SRM control system of claim 9 wherein the defined pinned point is static with respect to an underlying inductance value of the SRM.
11. The SRM control system of claim 9 wherein the pinned position is defined at a point corresponding to a magnitude between 50% and 100% of the steady state current on the initial current rise.
12. The SRM control system of claim 9 is designed to utilize the underlying inductance to calculate the error signal from a desired inductance value.
13. The SRM control system of claim 9 is designed to utilize the measured current rise over a fixed time period to calculate the error signal from a desired current rise.
14. The SRM control system of claim 9 wherein the optimum time determined from the time determining module is utilized to turn the plurality of switches of the SRM to on and off states.