Method to estimate motor speed for stabilized motor control
AssigneeHer Majesty the Queen in right of Canada, as represented by the Minister of National Defence
InventorsDonald R. McGaughey, Mohammed Tarbouchi, Ken Nutt
Life of this patent
Estimating the term…
Abstract
A method to estimate motor speed for extended stabilized rotational control of an induction motor at all speeds including slow speeds. The speed estimator supplies real-time motor control feedback information for a variable speed motor drive controller without a mechanical encoder. The speed estimator is based on an optimized fast orthogonal search algorithm with control of the carrier drive frequency to reduce computation time. The reduced processing time provides for an update rate to the motor controller sufficient to maintain motor stability to near zero the motor rated base speed.
Claims20
A method to estimate the speed of a motor comprising:
- (a) selecting to accept the carrier drive frequency or adding the selected carrier drive frequency;
- (b) sampling the current waveform at the motor;
- (c) selecting candidate frequencies for a sinusoidal candidate signal pair;
- (d) correlating the sampled waveform and candidate functions for all candidate frequencies of interest;
- (e) fitting the candidate signal pair that corresponds to the carrier drive frequency;
- (f) determining the reduction in the mean square error between previously fitted candidate signal pairs plus current test fit candidate signal pair and the original sample signal;
- (g) selecting top candidate signal pairs to fit spectrum model term;
- (h) removing unwanted frequencies from frequencies found;
- and
- (i) comparing spectrum model to motor speed harmonic model for match to establish motor speed estimate.
A method to estimate the speed of a motor comprising:
- (a) selecting to accept the carrier drive frequency or adding the selected carrier drive frequency;
- (b) sampling the current waveform at the motor;
- (c) selecting candidate frequencies for a sinusoidal candidate signal pair;
- (d) correlating the sampled waveform and candidate functions for all candidate frequencies of interest;
- (e) fitting the candidate signal pair that corresponds to the carrier drive frequency;
- (f) searching for possible sub-harmonic frequencies using RTFOS;
- (g) comparing sub-harmonic frequency to a harmonic speed model to identify the frequency search regions;
- (h) searching for frequencies in each region using RTFOS;
- (i) determining frequency pairs;
- (j) selecting frequency pairs most distant to known motor controller harmonics;
- and
- (k) comparing frequency pair to motor speed harmonic model for match to establish motor speed estimate.
Dependencies are inferred from the claim text.