A singularity-free position tracking controller for induction motors: theory and experiments

In this paper, we present a voltage input controller for a single-link robot manipulator actuated by induction motor. The control is designed to compensate for the nonlinear dynamics associated with the mechanical subsystem and the electrical subsystems while only requiring measurements of rotor position, rotor velocity, and stator winding currents. Specifically, through the use of nonlinear observers for rotor flux and an observed integrator backstepping approach, we obtain semi-global uniform ultimately bounded position (SGUUB) tracking. The result is semi-global in the sense that a control parameter must be made sufficiently large relative to the electromechanical initial conditions in order to guarantee that control singularities are avoided. Experimental results are then presented to illustrate the performance of the proposed approach applied to a one-link robot.