The control of a spacecraft equipped with a six-degree-of-freedom robot manipulator is studied in this paper. The objective is to rendezvous and synchronize with a satellite to facilitate inspection, servicing or de-orbiting. The space manipulator dynamics model with global parameterization on the configuration manifold is derived and used for designing asymptotically-stable control laws, so that they are valid globally in the configuration manifold. The control system consists of a sliding-mode rendezvous controller as well as a geometric attitude synchronization and a model-based servo control for the robot manipulator. The gains of the sliding-mode controller dictate a user-defined upper-bound on the thrust force. The attitude synchronization controller, concurrently with the rendezvous controller, is capable of micro-orbiting the space manipulator around spinning or tumbling satellites. It is observed through the simulations that the controller consumes limited amount of propellant, and it is feasible to use it for either a re-fueling (larger mass) or a de-orbiting (smaller mass) space manipulator.

In this brief, we design Lyapunov-based control laws to achieve two multi-objective tasks for a network of open-loop unstable, nonholonomic mobile inverted pendulum (MIP) robots, using a connected undirected graph for inter-agent communication. Using the first protocol, translationally invariant formations are achieved along with the synchronization of attitudes and heading velocities to desired values. Using the second protocol, the robots move into a formation and asymptotically track a trajectory. The control laws are based on the kinematic model of the mobile robot, and control torques for the MIPs are extracted using a two-loop control architecture. Both the protocols guarantee boundedness of the linear heading velocity, which is necessary for the stability of the two-loop control architecture. The proposed control laws are experimentally validated on indigenously built MIP robots.

The concurrent control of spacecraft equipped with one-axis unilateral thruster and three-axis attitude actuator is considered in this paper. The proposed control law utilizes attitude control channels along with the single thrust force concurrently, for three-dimensional trajectory tracking and rendezvous with a target object. The concurrent controller also achieves orbital transfer to low Earth orbits with long range separation. To demonstrate the orbit transfer capabilities of the concurrent controller, a smooth elliptical orbit transfer trajectory for co-planar circular orbits is designed. The velocity change and energy consumption of the designed orbit transfer trajectory is observed to be equivalent to that of Hohmann transfer.