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.