Passivity-based variable structure control of two-link underactuated robot

We present a method for position control of planar two-links robots with a passive rotational last joint. This underactuated mechanical system, which is subject to nonholonomic second-order constraints, are controlled to gain a desired position by the dynamic coupling. This objective is achieved in the absence of gravity. Most controllers based on the precise dynamic or kinematic equations aren´t practical because we can´t get the exact data of the systems. We proposed a passivity-based variable structure controller (PBVSC) to provide the robot robustness to the parameter uncertainty.