Position Tracking Control of the Induction Motor
in the Presence of Saturation Effects

Abstract

In this paper, we present an adaptive position tracking controller for the full-order model of the induction motor including magnetic saturation effects. Previously neglected in many control strategies, the electrical subsystem model now accounts for the phenomenon of stator/rotor flux saturation. Specifically, the controller utilizes stator and rotor current measurements (in addition to rotor position/rotor velocity measurements) to achieve global asymptotic rotor position tracking despite uncertainty in the stator and rotor resistance parameters. Experimental results are included to illustrate the performance of the proposed controller.

Research Objective:

Our objective is to design a full-state feedback, singularity free controller for the full-order, nonlinear dynamic model of an induction motor, which includes saturaion effects, to obtain rotor position tracking despite parametric uncertainty in the stator and rotor resistance constants. The control algorithm requires measurement of rotor position, rotor velcoity, stator flux and rotor flux. Since flux measurements are hard to obtain, we utilize a numerical algorithm to obtain stator/rotor flux from measurements of stator/rotor currents.

Approach:

We first develop a desired torque trajectory to promote rotor position tracking in the mechanical subsystem. Subsequently, a desired stator flux trajectory and a desired rotor flux trajectory are then designed, despite uncertainty in the stator resistance and rotor resistance parameters, to ensure that: i) the desired torque is delivered to the mechanical subsystem i.e., a proper commutation strategy) , ii) rotor flux tracking is achieved, and iii) control singularities are avoided. The stator voltage control inputs are then designed to promote stator flux tracking. A Lyapunov stability analysis then performed to ensure closed-loop system stability i.e., we show that all plant and control signals are bounded) as well as illustrate the global asymptotic position tracking result.

The Experimental Setup:

An experiment was conducted on a three phase wound induction motor powered by three linear amplifiers (Techron, Model 7570-60) to test the performance of the proposed controller. The rotor position was measured using a 10,240 line shaft-mounted encoder (BEI Inc.). A Backwards Difference strategy was used to obtain the rotor velocity. Three hall effect sensors (Microswitch, Model CSLB1AD) were used to measure the stator phase currents. Two hall effect sensors (Microswitch, Model CSLB1AD) were used to measure the rotor phase currents. A QNX based real time environment developed in-house serves as the user-interface required to implement the control algorithm. The control algorithm is computed on a Pentium processor thus eliminating the need for a separate DSP board. The sampling frequency was selected to be 1300 Hz. The MultiQ board (8 A/D, 8 D/A, and 6 encoder channels) manufactured by Quanser Consulting was used to output the three phase voltages to the induction motor.

The Mechatronics Workstation - Union Camp Laboratory

Some Experimental Results:

Select and click to view some of the experimental plots:



Publication:

For more information concerning this research, please refer to the following publication:

M. Feemster, A. Behal, P. Aquino, and D. M. Dawson, "Tracking Control of the Induction Motor in the Presence of Magnetic Saturation Effects", Proc. of the IEEE Conference on Decision and Control, Phoenix, AZ, pp. 341-346, December 1999.