Position Control of a Manipulator with Passive Joints Using Dynamic Coupling

Hirohiko Arai and Susumu Tachi

IEEE Transactions on Robotics and Automation, Vol.7, No.4, pp.528-534, 1991.


This paper describes a method of controlling the position of a manipulator which is composed of active and passive joints. The active joints have actuators and position sensors. The passive joints have holding brakes instead of actuators. While the brakes are released, the passive joints are indirectly controlled by the motion of the active joints using the coupling characteristics of manipulator dynamics. While the brakes are engaged, the passive joints are fixed and the active joints are controlled. The position of the manipulator is controlled by combining these two control modes. This paper describes the basic principle of the control method and the conditions that ensure the controllability of the passive joints. An algorithm for point to point control of the manipulator is also presented. The feasibility of the method is demonstrated by simulation experiments of a manipulator with two degrees of freedom.