Motion of a Tethered System Under Attitude Control With Large Deformation, Rotation and Translation

Abstract

In this paper, we discuss about the motion of a system consisting of a very flexible body and rigid bodies at its end under attitude control to the end body. A tethered subsatellite in space is known as an example of this system. We consider two mathematical models for flexible body. First, the flexible body motion in a plane is described by using Finite Element Method formulation. Second, the flexible body in planer motion is described by using Absolute Nodal Coordinate formulation. In this method, it is easy to describe the motion of the flexible body with large deformation, rotation and translation displacement. We can consider interaction between the deflection of the flexible body and the motion of the rigid bodies in these methods. Furthermore we attempt to control the attitude of the end body using a reaction wheel. The flexible body motion is influenced on the motion of the rigid bodies under attitude control of end body. The control technique consists of an attitude control by the reaction wheel and a control by the reaction wheel with the joint torque control to cancel accumulation of angular momentum. First, eigenvalue analysis is carried out where control gain changes. Second, the motion under controlled system is discussed under free vibration. We compared these results. Furthermore we treat large deformation problem. The end of flexible body moves horizontally. As a result, we confirm the interaction between flexible body and rigid body under the attitude control.