Reachable area of an underactuated space manipulator subjected to simple spinning

Manipulators with free links are called underactuated manipulators, and in these systems, the number of actuators is less than the degree of freedom of the manipulator. Motivations of the study on the underactuated manipulators are, for example, to construct back-up strategies in case of actuator failure in extreme missions such as space robots and to realize cost reduction by employing fewer actuators. In this paper, we investigate the reachable area of the tip of a two-link underactuated manipulator whose first link (active link) is equipped through an actuator to a base rotated with a constant angular velocity. We produce pitchfork bifurcations in the free link (second link) by motion with a high-frequency component of the active link and actuate perturbations of the pitchfork bifurcations by changing the configuration of the active link with respect to the direction of the centrifugal force. We investigate the reachable area of the tip of the manipulator under the control by analytical approach and experimentally discuss the validity of the theoretical prediction.