Path tracking control of a manipulator with passive joints

A method is proposed of path tracking control of a manipulator with passive joints, i.e. having no actuators. A desired path is geometrically specified in operational space. The position of the manipulator is controlled to follow the desired path. In this method, a path coordinate system based on the desired path is defined in operational space. The path coordinates consist of a component parallel to the desired path and components normal to the desired path. The equation of motion of the manipulator is described in terms of the path coordinates. The acceleration of the components normal to the desired path is controlled according to the feedback based on tracking errors by using the dynamic coupling among the components. This in turn keeps the manipulator on the desired path. Results of path tracking experiments using a two-degree-of-freedom manipulator with a passive joint are presented