The Sensorless Slip-Frequency Vector Control System Based On Flux Observer

Motion control is a comprehensive subject .Modern AC drive is a importantembranchment in the field of motion control .However, it is difficult to rea1izehigh-performance AC drive systems because induction motors are a kind ofstrongly-coupled nonlinear system with many variables and the torque is noteasy to control .With Vector Control technology decoupling and torque controlof AC motOr are solved .The basic idea of Vector control is that three-phasesystem is equiva1ent to two-phase system by coordinate transformation and itrealizes the decoupling between field current and torque current of the stator inorder to control the flux and current respectively,thus induction motor can beconsidered DC motor and high performance is achieved easily .With theprogress of electric and electronic technology and the development ofcomputer,high-integrated special modules and high -precision digital signalprocessor (DSP ) are aPplied to AC drive so that vector control has beendeveloped raPidly.At present the sensorless vector control technology is one major directionof motion control .the conventional vector control system requires speed signaland the signal is acquired by using speed sensors .Obviously the addition ofsensors will result in the degrade of the credibility and adaptability and costincreasing .So many scholars have paid close attention to sensorless vectorcontrol technology .In this technology the key problem is how to estimate thespeed and the flux of the rotor .Using A kind of method based on fiux observerthe speed can be estimated .At the same time the method is modified with thefeedback of torque current .As a result the precision of the speed estimation canbe more improved.In this paper the tendency of motion control is introduced first .Next thebasic vector control principle and coordinate transformations are presented .Themathematic model and the equiva1ent circuit of induction motor are alsoproposed .On the basis of the former theory a dynamic structure of sensorlessvector-controlled system is designed here .A new flux observer and a newmethod of speed estimation are put forward also .And then the model of thecontrol system is established .Following those,the author simulates the dynamic2system using the advanced language C++ and analyzes the result . For the teaching the hardware PWM inverter is designed, including the choice of power module ,filter tache ,auxiliary power supply ,brake unit and protection circuits .In addition data sampling system is contrived with encoder and current/voltage sensors .The control circuit with TMS320F240 for the core is presented at last .The circuit includes memory extension ,D/A converter digital I/O interface and the interface of the serial port .The way of Space Vector PWM realization is briefly introduced in this paper .