PD-Impedance Combined Control Strategy for Capture Operations Using a 3-DOF Space Manipulator with a Compliant End-Effector

Abstract

The contact force/torque between the end-effector of the space manipulator and the target spacecraft will reduce the efficiency and safety of the capture task. A capture strategy using PD-impedance combined control algorithm is proposed to achieve compliant contact between the chaser and target spacecraft. In order to absorb the impact energy, a spring-damper system is designed at the end-effector, and the corresponding dynamics model is established by Lagrange’s equation. Then a PD-impedance control algorithm based on steady-state force tracking error is proposed. Using this method, a compliant contact between the chaser and target spacecraft is realized while considering the dynamic coupling of the system. Finally, the general equation of the reference trajectory of the manipulator end-effector is derived according to the relative velocity and impact direction. The performance of the proposed capture strategy is studied by a co-simulation of MSC Adams and MATLAB Simulink in this paper. The results show that the contact plane at the end-effector of the manipulator can decelerate and detumble the target spacecraft. Besides, the contact force, relative velocity, and angular velocity all decrease to zero gradually, and the final stable state can be maintained for a prescribed time interval.

Impedance Control Using Selected Compliant Prismatic Joint in a Free-Floating Space Manipulator

“…Impedance control [4][5][6][7][8]11,22,31] is a paradigm which aims to achieve desired characteristics of the interaction between the robot and its environment. It draws from the long-recognized analogies between electrical and mechanical building blocks of dynamic systems and became an important toolbox for modeling robotics interacting with environments and humans, cooperative robotics, exoskeletons, etcetera.…”

“…We then discuss the limitations and possibilities of such architecture in a practical setting. A similar architecture, i.e., using a prismatic stage at the end effector, was also proposed for a space manipulator, though one with a controlled base (non-free-floating) [22], and not with a focus on simplification, but rather on introducing an additional layer of interaction between the robot pose control and impedance control. Our earlier work considered a two-dimensional simulation case of a robot with a prismatic compliant stage at the end effector focusing on disturbance to the base of the satellite [23], whereas this work expands it to a three-dimensional case.…”