A non-linear control of robot manipulators driven by induction motors

We present in this paper a new asymptotically stable scheme for motion control of rigid robots with induction motor drives. The result is established considering a model that includes the electrical and mechanical dynamics of the induction motors, as well as the full rigid body dynamics of robot manipulator. The procedure we win follow consists of four steps. First, we design an inner control loop such that the overall system becomes a cascade connection of two nonlinear subsystems, i.e., the motor electrical dynamics and the robot mechanical system. The outpout of the first subsytem, that is the generated torque, drives the robot dynamics, and the other crosscoupling are removed. Second, the torque required to track the desired joint trajectory is evaluated by passivity approach. Third, we define a desired current behavior which reflects an objective of attaining field orientation. Four, we design a controller that insures the torques generated by the motors asymptotically track the desired torque. Parameters of robot and motors are known. The local stability is obtained for controller with the nonlinear observer of rotor motor currents. Simulation results are presented with a robot SCARA to illustrate the performance of the central law.