Discrete-time modeling and input-output linearization of current-fed induction motors for torque and stator flux decoupled control

In this paper an exact discrete-time model of the induction motor in a current-fed mode, including stator flux components is derived and validated. The equations of the motor are written in a frame aligned with the rotor electrical position, which results in a linear, time-invariant system. Based on the derived exact discrete-time representation of the motor dynamics, an input-output linearizing control law is designed for decoupled torque and stator flux control. The applied design technique led to a non-trivial, still useful, definition of the electromagnetic output of the motor. Simulation results are presented showing that the aimed performance is obtained, that is, no coupling exists between the outputs, and the initial design problem of controlling a nonlinear interacting TITO system is reduced to a problem of controlling two linear and decoupled SISO systems with simple dynamics.