This paper investigates a strategy for Takagi-Sugeno fuzzy control applied to
speed control of induction motor. The strategy implements a weighted interpolation
between a set of local controllers previously designed. When changes occur in the
operational conditions of the induction motor, the gains of the control law are adjusted
automatically to maintain satisfactory performance of the control system. For controller
design the fuzzy state space representation of the plant was considered in the form of
an augmented system, including a new state variable which in this case, was selected
as the integral of speed error. This formulation allowed the design of local controllers
with the structure PI, through state feedback with pole placement. As variables of
operation for the switching fuzzy controllers local variables were selected angular
velocity and stator current component responsible for torque electric, expressed in a
frame rotating synchronously with the rotor flux. Then, the stability of Takagi-Sugeno
fuzzy controller designed was assured by the Lyapunov criterion, in the form of
LMIs. The performance of the Takagi-Sugeno fuzzy controller was assessed through
simulation studies and their results compared to the performance of a conventional PI
controller, for regulating the rotor speed. The results obtained in simulation tests show
that employing the proposed strategy makes the system more robust to parametric
variations in the drive system.
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