A robust-adaptive linearizing control method for sensorless high precision control of induction motor

Caglar Uyulan

doi:10.1177/0020294019833072

Abstract

Even if there exists remarkable applications of induction machines in variable speed drives and also in speed sensorless control in the low–high speed region, open/closed loop estimators in the literature utilized on induction machine sensorless position control vary regarding to their accuracies, sensitivity, and robustness with respect to the variation of model parameter. The deterioration of dynamic performance depends on the lack of estimation techniques which provide trustable information on the flux or speed/position over a wide speed range. An effective estimator should handle the high number of parameter and model uncertainties inherent to induction machines and also torque ripple, the compensation of which is crucial for a satisfactory decoupling and linearizing control to provide the accuracy and precision requirements of demanding motion control in the field of robotics/unmanned vehicle. In this study, to address all of the above-mentioned problems, robust-adaptive linearizing schemes for the sensorless position control of induction machines based on high-order sliding modes and robust differentiators to improve performance were designed. The control schemes based on direct vector control and direct torque control are capable of torque ripple attenuation taking both space and current harmonics into account. The simulation results comprise both the estimation and sensorless speed control of induction machines over a wide operation range, especially at low and zero speed, all of which are promising and indicate significant superiority over existing solutions in the literature for the high precision, direct-drive, speed/position sensorless control of squirrel-cage induction machines.

Highlights

Since induction machines (IM) have highly nonlinear and coupled fifth-order dynamics under strong parameter and model uncertainties and make it possible to measure only three state variables, linearizing and decoupling control of IMs is a competitive problem in nonlinear control field
Two approaches are taken in the literature: frequency-domain approach based on the injection of hf signals, a major disadvantage being the demand for additional hf signals, sensitive to system parameters, the dynamic delay originated from phaselocked loop (PLL), low signal-to-noise ratio (SNR), and magnetic saturation due to the fundamental field; and time-domain approach, making use of the inverter pulse width modulation (PWM) signals, which provide a high SNR
IMs are widely used in the industry, thanks to their simplicity and high-power supplement, yet are generally not preferred for industrial robotics and high-power motion

Summary

Introduction

Since induction machines (IM) have highly nonlinear and coupled fifth-order dynamics under strong parameter and model uncertainties and make it possible to measure only three state variables, linearizing and decoupling control of IMs is a competitive problem in nonlinear control field. Two approaches are taken in the literature: frequency-domain approach based on the injection of hf signals, a major disadvantage being the demand for additional hf signals, sensitive to system parameters, the dynamic delay originated from PLL, low SNR, and magnetic saturation due to the fundamental field; and time-domain approach, making use of the inverter PWM signals, which provide a high SNR The latter approach is quite effective for the control of IMs (in the very low- and zero-speed region); problems arise due to signal acquisition in the high-speed region—special measures (such as the use of a different model) must be taken when it is aimed to perform velocity control over a wide speed range.

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Conclusion