Abstract

Autonomous space robots are crucial for performing future in-orbit operations, including
servicing of a spacecraft, assembly of large structures, maintenance of other space assets
and active debris removal. Such orbital missions require servicer spacecraft equipped with
one or more dexterous manipulators. However, unlike its terrestrial counterpart, the base
of the robotic manipulator is not fixed in inertial space; instead, it is mounted on the base�spacecraft, which itself possess both translational and rotational motions. Additionally, the
system will be subjected to extreme environmental perturbations, parametric uncertainties
and system constraints due to the dynamic coupling between the manipulator and the
base-spacecraft. This paper presents the dynamic model of the space robot and a three�stage control algorithm for this highly dynamic non-linear system. In this approach, feed�forward compensation and feed-forward linearization techniques are used to decouple and
linearize the highly non-linear system respectively. This approach allows the use of the
linear Proportional-Integral-Derivative (PID) controller and Linear Quadratic Regulator
(LQR) in the final stages. Moreover, this paper covers a simulation-based trade-off analysis
to determine both proposed linear controllers’ efficacy. This assessment considers precise
trajectory tracking requirements whilst minimizing power consumption and improving
robustness during the close-range operation with the target spacecraft.