The authors propose a nonlinear robust control scheme for robotic motion control in Cartesian coordinates. The control input of this scheme consists of nonlinear and linear parts. The nonlinear part decouples and stabilizes robot dynamics in Cartesian coordinates. The linear part utilizes the robust servomechanism theory to suppress effects of modeling error or unknown external disturbance. This scheme was used in the control of a two-joint SCARA-type robot, and simulation results demonstrate that it can achieve fast and precise tracking control in Cartesian coordinates, even in the presence of severe modeling errors.>

The authors propose a nonlinear robust hybrid control scheme for robot motion control. The control input consists of a nonlinear and a linear part. The nonlinear input decouples a robot dynamics and obtains a set of position and force equations in the hand or Cartesian coordinate. The linear part applies the robust servomechanism theory to suppress position or force tracking error due to uncertainties. This nonlinear robust hybrid control scheme is applied to a two-joint SCARA-type robot, and simulation results demonstrated excellent robustness properties and satisfactory hybrid control, even under severe modeling errors.>