Abstract
This paper presents a method for shaft position estimation of a synchronous motor with permanent magnets. Zero speed and very low speed range are considered. The method uses the analysis of high-frequency currents induced by the introduction of additional voltage in the control path in the stationary coordinate system associated with the stator. An artificial neural network estimates the sine and cosine values necessary in the Park’s transformation units. This method can achieve satisfactory accuracy in the case of low asymmetry of inductance in the direct and quadrature axes of the coordinate system associated with the rotor. The TensorFlow/Keras package was used for artificial network calculations and the scikit-learn package for preprocessing. Aggregating the outputs of several artificial neural networks provides an opportunity to reduce the resultant estimation error. The use of as few as four networks has enabled the error to be reduced by approximately 20% compared to a single example network.
Highlights
The main achievement presented in this paper is the development of a method for estimating the shaft position at zero speed, using a method based on an analysis shape of the obtained current hodograph
The additional voltage introduced should be low enough while the frequency high enough in order to minimize the amount of additional torque generated and prevent undesirable shaft oscillation. This approach is mainly used in motors with internal magnets (IPMSM), due to the large differences in inductance in the d and q axes, which facilitates the determination of the main axis for an ellipse-shaped hodograph
This paper provides a method for estimating the shaft position for SPMSM drive in the case of a standstill or very low speed operation
Summary
In zero or a very low speed range, the position estimation is performed by generating an additional high frequency voltage test signal (or appropriately shaped pulses) in the stator This forces the flow of high-frequency currents, the instantaneous value of which depends on the instantaneous inductance. The main achievement presented in this paper is the development of a method for estimating the shaft position at zero speed, using a method based on an analysis shape of the obtained current hodograph. This shape does not have to be regular.
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