An elbow planar manipulator driven by induction motors using sliding mode control for current loop

The control of a planar elbow manipulator driven by a squirrel-cage induction motor using sliding mode control (SMC) is presented in this paper. The modeling of the manipulator mechanical coupling as a load applied to the induction motor shaft is developed. This has direct influence on both dq currents, which are chosen as the sliding manifold instead of controlling both mechanical and electrical parts as individual processes like most industrial manipulators do. Conventional proportional-integral (PI) controllers are used for each loop, implying easy design procedure and implementation with low computational effort. The system can then be implemented by using a digital signal processor (DSP) and applied in industrial environments. Simulation and experimental results on a real manipulator are shown to validate the proposed control scheme. The results show that there is low steady-state error for the manipulator position.