INTRODUCTION
Nowaday, several applications conceming control of a 3-
phase induction motor, I.M., based on the modern control
techniques have been established [l] - [SI. Yet there are
many tasks require precise control schemes.The necessity to
perform zero steady state tracking error, robust control with
acceptable transient response and simple control law are the
greatest demand in any application of the modem control
theory. However, in the previous work [5],which depends
on the indirect field-oriented control, for instance, the slip
frequency control method offers the advantage of nondetection of rotor flux. This method uses the stator current
in the feedforward control loop to estimate the rotor flux.
The adverse phenomena which is caused due to the
parameter variations ofthe I.M. in this work is cured by the
proposed control technique .This technique includes the new
error system with nominal reference values which are the
rotor angular velocity and the optimal two - components of
the rotor flux linkage current. The preview feedforward steps
of the desired reference values are introduced in the control
law to improve the transient response, [7] .The filedoriented control system is constructed by deriving a state
equation on a synchronously rotating reference frame, that
means selecting a fixed reference frame in the rotor flux
linkage side. The filed oriented control is achieved by
adjusting the magnitude and the angular frequency ofthe
rotor flux linkage simultaneously. The three-input variables
of the proposed controlled system are the stator angular
frequency, the stator flux current component which is
proportional to the rotor flux linkage, and the torque current I
component which is perpendicular to the stator flux current.
While the three-output variables are the rotational angular
velocity and the two-components of the rotor flux linkage ~
current. The synthsized control system comprises speed 1
control ,field orientation control and constant flux control . 1
The design procedrual of the optimal regulator technique '
with preview feedforward steps and the error system based
on the vector method of the I.M. are investigated in this
paper.