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No abstract

This work generalizes the authors' work on highperformance control of induction motors to machines that exhibit significant magnetic saturation. The controller design is based on the standard d d d-q q q model of the induction motor which has been modified to account for the saturation of the iron in the main (magnetic) path of the machine. An input-output linearization controller is used to provide independent (decoupled) control of the speed and flux. With this controller, the flux reference becomes an extra degree of freedom for the designer to help achieve performance objectives. Taking into account saturation along with the voltage and current constraints, the flux reference is chosen to achieve the optimal torque (maximum for acceleration and minimum for deceleration) at any given speed. Experimental results are given to demonstrate the input-output controller's effectiveness in providing the tracking of a given position and speed trajectory while simultaneously tracking the optimal flux reference. The set of experiments are fast point-to-point motion control moves with an inertial load comparing the input-output controller based on the saturated magnetics model with that based on the linear magnetics model.

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In this paper, we consider tbe problem of estimah ing the angular velocity of an induction motor using encoder measurements.-0 methods are compared, In tbe first method, tbe speed is found by calculating the backward differes~ce of tbe position measurem ent and low-pass filtering the result. In the second method, the velocity is estimated using a nonlinear observer constructed using the known dynamic model of the induction motor. Tbe performance of the two methods is evaluated in the context of their use for velocity feedback in a high-performance fieldoriented control law. Experimental results demonstrate that the sped observer leads to a smoother operation of the motor in closed-loop. With the estimator based on differentiation, either tbe delay imposed by the low-pass filter is too large to maintain high bandwidth feedback, or the fluctuations in tbe estimated speed are so large that much more energy ends up being dissipated to achieve the same control task.