Trajectory planning and feedforward control of a tethered robot system

The authors previously (1996) proposed a new type of space robot system, consisting of a spacecraft and a robot attached through a tether to it. This system is called a "tethered robot system." In this paper, we clarify the characteristics of the tethered robot system, and especially focus on position control of the center of mass of the robot. Tether tension is used to control the position, taking into account the gravity gradient and the centrifugal force. The results from the trajectory planning procedure suggest that the shape of the path depends both on the direction to the destination point and the time to accomplish the mission, it does not depend on the distance. From the simulation results with feedforward control it is concluded that accurate path planning is possible only if the destination point is close to the initial point, or if the time to accomplish the mission is long enough.