Disturbance observer based path tracking control of robot manipulator considering torque saturation

In this paper, a path tracking algorithm is proposed to compensate path deviation due to torque bound. For this, a disturbance observer is applied to each joint of an n degrees of freedom manipulator to obtain a simple equivalent robot dynamics (SERD) being represented as an n independent double integrator system. For an arbitrary trajectory generated for a given path in Cartesian space, whenever the saturation of any actuators is met, the desired acceleration of the nominal trajectory in Cartesian space is modified online by using SERD. Also an integral action with respect to the difference between the nominal and the modified trajectories is utilized in nonsaturated region of actuators to reduce the path error. To verify the effectiveness of the proposed algorithms, numerical simulations and real experiments are performed for two degrees of freedom SCARA type direct-drive arm.