Position Control System of a Two Degree of Freedom Manipulator with a Passive Joint

Hirohiko Arai and Susumu Tachi

IEEE Transactions on Industrial Electronics, Vol.38, No.1, pp.15-20, 1991.


The authors propose a method of controlling the position of a manipulator with passive joints which have holding brakes instead of actuators. In this method, the coupling characteristics of manipulator dynamics are used, and no additional mechanisms are required. In this paper, the effectiveness of the method is verified by experiments using a prototype manipulator. The prototype is a two degree of freedom, horizontally articulated manipulator. The first axis is an active joint and the second axis is a passive joint. While the brake of the passive joint is released, the passive joint is indirectly controlled by the motion of the active joint, through the use of dynamic coupling. While the brake is engaged, the active joint is controlled. By combining these two control modes, total position of the manipulator is controlled. The experiments show that the precise positioning of the passive joint is feasible by use of the proposed method.