Robust Sensor-less Control of BLDCM via Block-Pulse Functions Expression

Abstract

This paper examined the robustness of former presented estimation method, that is made under very simple assumption of that, during short period of PWM control both electrical angle and electrical speed of AC servo-motor do not vary. In each PWM periods control input is known, currents is measurable, then position and speed as parameters can be solved.Over 0.06 (p. u.) of speed command estimated position and speed had good accuracy, and smooth sensor-less control was achieved. Under 0.06 (p. u.) of speed command, 6-th harmonics in estimated position became harmful then correction using the Newton's Method is taken. Even these correction effort residues of correction error could not diminished. To reduce the effects of correction error, feed-forward voltage in control inputs are employed and gains of feedback was low downed.On this estimation, machine parameters, armature resistance and reactance are supposed as constant. But they may be change according to temperature rise and magnetic saturation. Moreover they includes some errors. Even these problems under very short PWM interval changes of estimated EMFs are small enough then machine parameters disappear from estimate equation. Then this estimation method is robust from parameter changes.This estimation method stands on estimation of back EMFs. Then it can not apply on zero speed. But experimental result shows a sensor-less start up under proposed estimation method without any other equipment is capable without any auxiliary equipment.