Decentralized control of rigid robots driven by current-fed induction motors

The problem of controlling a rigid manipulator driven by induction motors to follow a desired trajectory using the decentralized control technique is considered in the paper. Parameter uncertainties of the rigid robot are considered. First, a PI controller is used to force an induction motor to work in the current-command mode, then based on a fourth-order reduced model of induction motors, a current controller is proposed using only local measurements of each link (link position, velocity and stator currents of the induction motor). The rotor flux is estimated through a closed-loop observer. Provided that the flux observer is properly initialized, this controller is singularity-free and guarantees the uniform ultimate stability of the closed-loop system. Simulations are presented to illustrate the performance of this controller