Abstract
Sensorless electric drives use measurements of electrical quantities to estimate rotor position and speed. Measurement errors deteriorate the estimation accuracy, thus additional means are necessary to remove high-frequency components from estimated signals. This paper proposes to use an Angle Tracking Observer (ATO) for reducing noise in rotor position estimates, which is related to random errors in the measurements. A simplified, universal structure of ATO has been designed for this purpose. Based on simulations, the gains of ATO algorithm have been selected for optimal balance between error components related to the measurement noise and to the filtering lag. Additionally, implementation issues have been discussed and laboratory validation has been carried out in the paper. The designed ATO is applicable to any sensorless drive and enables drive controller to substantially improve rotor estimation accuracy using very low computing overhead.DOI: http://dx.doi.org/10.5755/j01.eie.22.5.16341
Highlights
Sensorless control of electric drives, which replaces position and speed sensor with an estimation algorithm, is intensively researched [1], [2]
Numerous observers have been proposed, which complement motor model with various methods of correcting its state variables according to measured voltages and currents [3]
In observers no additional means are required to filter the estimates, because the balance between good dynamic properties of the state variables and the sensitivity to measurement noise can be controlled by adjusting gains in the feedback matrix
Summary
Sensorless control of electric drives, which replaces position and speed sensor with an estimation algorithm, is intensively researched [1], [2]. Most sensorless drives estimate position and speed using model-based approach. In contrast to the model-based sensorless approach, there are estimation algorithms which identify selected motor parameters, e.g. stator inductances, whose values are directly related to rotor position [4]. Low-pass filtering is typically used before applying estimated position to drive control algorithm [5], [6]. Selected parameter-based estimators are dedicated to medium and high rotor speeds In such case, specific means of noise reduction are required to condition the signal of estimated position. A mathematical model of electric drive is presented, and later used for pre-selecting ATO gains and evaluating filtering effectiveness, as described in Sections V and VI.
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