Space exploration and exploitation depend on the development of on-orbit robotic capabilities for tasks such as servicing of satellites, removing of orbital debris, or construction and maintenance of orbital assets. Manipulation and capture of objects on-orbit are key enablers for these capabilities. This survey addresses fundamental aspects of manipulation and capture, such as the dynamics of space manipulator systems (SMS), i.e., satellites equipped with manipulators, the contact dynamics between manipulator grippers/payloads and targets, and the methods for identifying properties of SMSs and their targets. Also, it presents recent work of sensing pose and system states, of motion planning for capturing a target, and of feedback control methods for SMS during motion or interaction tasks. Finally, the paper reviews major ground testing testbeds for capture operations, and several notable missions and technologies developed for capture of targets on-orbit.

SUMMARY: Free-flying space manipulator systems, in which robotic manipulators are mounted on a free-flying spacecraft, are envisioned for assembling, maintenance, repair, and contingency operations in space. Nevertheless, even for fixed-base systems, control of mechanical manipulators is a challenging task. This is due to strong nonlinearities in the equations of motion, and consequently different algorithms have been suggested to control end-effector motion or force, since the early research in robotic systems. In this paper, first a brief review of basic concepts of various algorithms in controlling robotic manipulators is introduced. Then, specific problems related to application of such systems in space and a microgravity environment is highlighted. Basic issues of kinematics and dynamics modeling of such systems, trajectory planning and control strategies, cooperation of multiple arm space free-flying robots, and finally, experimental studies and technological aspects of such systems with their specific limitations are discussed.

In this paper, the control of free-floating space manipulator systems (FFSMS) with non-zero angular momentum (NZAM), for both motions in the joint and Cartesian space, is studied. Considering NZAM, dynamic models in the joint and Cartesian space are derived. It is shown that the NZAM has a similar result to the effect of gravity in terrestrial fixed base manipulators. Based on these similarities, the application of controllers similar to the ones used for the compensation of gravity in terrestrial fixed base manipulators is proposed here, to compensate the effect of angular momentum. To confirm the asymptotic stability of the closed-loop systems, some structural properties of the dynamic models must be satisfied. It is shown that despite the presence of angular momentum, these structural properties still apply. Thus, the proposed controllers can drive the system in the desired position despite the presence of angular momentum. However, the NZAM imposes constraints on the system workspace, where the end-effector can be driven in the Cartesian space. Limitations are discussed and the application of the proposed controllers is illustrated by examples.

In this paper, a novel model-based impedance controller for a 6-degree-of-freedom (dof) electrohydraulic Stewart platform mechanism is developed. Rigid body and experimentally developed electrohydraulic models, including servovalve, friction and leakage models are employed and described by a set of integrated system equations. Despite the fact that an electrohydraulic servoactuator is not a source of force, as is the case with electric actuators, an impedance controller is developed for the electrohydraulic platform. This controller consists of a feedback and a model-based feedforward loop that compute servovalve currents. An impedance filter modifies the desired trajectory according to a specified behavior. This trajectory is fed to a system model in the controller aiming at a reduction of the effects of the nonlinear hydraulic dynamics. Simulations results compare system response of the developed and of a proportional-derivative (PD) controller for the electrohydraulic platform. Results during interactions with the environment show that the impedance controller is superior to available PD controllers, and that its response is smooth.