A trajectory control of redundant manipulator with fault joint based on workspace observer

The controller design of a manipulator which has a faulty joint is an important issue for robotic systems operating in hazardous or remote environments. In this paper, the trajectory control for redundant manipulators with free-swinging joints because of unexpected failure is presented. The difficulty of controlling faulty actuators without mechanical brakes because of free movements under the influence of dynamical effects, such as interactive torque, gravity, etc., is well known. Hence the control strategies using joint dynamics models have been developed mainly in past studies. In this paper, the tracking of a trajectory without an exact calculation of such dynamical effects and a braking effect is realized by using a workspace observer. Therefore the calculation of the proposed system is drastically decreased because the workspace observer compensates the disturbance of faulty joints including dynamical effects