Robust Backstepping Sensorless Speed Control of PMSM Using Cascaded Sliding Mode and High Gain Observers

In this work we implement a Sensorless speed control for three phase Permanent Magnet Synchronous Motor (PMSM) using the Backstepping Control. Only stator currents and voltages are used for feedback to design a non linear control algorithm which tracks the speed of PMSM with parametric uncertainties and under varying load. A continuous sliding mode observer (SMO) based on sigmoid function is used for rotor position estimation in cascade with an extended high gain observer (EHGO) for robust speed estimation that reduces chattering phenomenon and improve accuracy. This removes the requirement of filter and phase delay compensation. For control of speed, current tracking backstepping controllers are designed which show excellent tracking of reference speed and are prone to parametric uncertainties. Finally the simulation results validate the performance of the proposed controller and observers.

I. Introduction

Permanent Magnet Synchronous Motor (PMSM) offers several advantages over other motors such as high torque to inertia ratio, excellent serviceability and durability, high efficiency and absence of external excitation and rotor windings. Due to these advantages these motors are being used extensively in control systems, home appliances printers, tape drives, cranes and elevators. The control of such motors become highly complex due to above mentioned advantages. Tracking problem of a Permanent Magnet Synchronous Motor (PMSM) which includes speed and position requires the information of rotor shaft position and speed in order to control stator current vector and achieve high performance drive. Due to high cost involved in machine drive because of rotational transducers and shaft sensors used for measuring position and speed of the motor, Sensorless control of (Non-Salient-pole surface) Permanent Magnet Synchronous Motor (PMSM) has gained attention of the electric drive community.