(A) study on payload mass adaptation and inverse kinematics in space robot

Abstract

Future robotic manipulator systems(robotic manipulators carried by future spacecraft) will be required to perform complex tasks in space. In particular, the robotic manipulators will play important roles in future space missions such as retrieving, repairing, and servicing satellites in earth orbit. The dynamics of space robotic systems can be written complex and hence their control can be difficult. In this paper some important dynamics and control problems, unique to space robotic systems are discussed. Particular attention is paid to free-floating space robots and only attitude-controlled robotic systems. These manipulators will encounter a number of kinematic, dynamic problems caused by the dynamic coupling between the manipulators and its spacecraft.(the performance of these systems could be severely degraded by dynamic disturbances to the spacecraft caused by manipulator motion). This dynamic coupling also makes it difficult to analyze these systems. This paper reviews an analytical modeling method for space manipulators called the Virtual Manipulator(VM), which has a fixed base in inertial space at a point called a Virtual Ground, and presents a mass adaptation method of the unknown payload using the Virtual Manipulator concept. The Virtual Manipulator is shown to have the potential to be an effective aid for the analysis, design, and development of future space manipulator systems. Free-floating space manipulator systems have dynamic singularities where the spacecraft moves in response to manipulator motions without compensation from its attitude control system. At the dynamic singularities, the manipulator is unable to move its end-effector in some inertial direction, thus dynamic singularities must be considered in the design, planning, and control of free-floating space manipulator systems. The existence and location of dynamic singularities cannot be predicted solely from the manipulator kinematic structure because they are functions of the dynamic...