Hattori M., Yabuno H., Aoshima N.

An underactuated manipulator is defined as a manipulator with fewer actuators than degree of freedom of the system, which, for example, corresponds to the situation that one of actuators of a manipulator breaks down. Because it is especially hard to fix the broken actuator in space, control methods of the underactuated manipulator are generally considered to be employed as emergency control methods in space. However, the past studies on the underactuated manipulator have targeted ground-fixed manipulators although no fixed plane exists and angular momentum of the system is conserved in space. In this paper, a control method of a two-link underactuated manipulator considering the conservation of angular momentum is proposed. The control method utilizes bifurcation phenomena occurring in the free link by the effect of high-frequency excitation, which also makes state feedback of the free joint not necessary. We finally confirm the validity of the theoretical results experimentally.