Optimal path planning and weighted control of a four-arm robot in on-orbit servicing

TL;DR

This paper develops a trajectory optimization and weighted control method for a four-arm robot performing on-orbit servicing, enabling precise docking and manipulation near spacecraft.

Contribution

It introduces a combined trajectory planning and convex optimization-based control approach for orbital multi-arm robots in on-orbit servicing.

Findings

Successful simulation of docking and manipulation tasks

Effective trajectory planning with timing and force control

Weighted control improves task performance and stability

Abstract

This paper presents a trajectory optimization and control approach for the guidance of an orbital four-arm robot in extravehicular activities. The robot operates near the target spacecraft, enabling its arm's end-effectors to reach the spacecraft's surface. Connections to the target spacecraft can be established by the arms through specific footholds (docking devices). The trajectory optimization allows the robot path planning by computing the docking positions on the target spacecraft surface, along with their timing, the arm trajectories, the six degrees of freedom body motion, and the necessary contact forces during docking. In addition, the paper introduces a controller designed to track the planned trajectories derived from the solution of the nonlinear programming problem. A weighted controller formulated as a convex optimization problem is proposed. The controller is defined as the optimization of an objective function that allows the system to perform a set of tasks simultaneously. Simulation results show the application of the trajectory optimization and control approaches to an on-orbit servicing scenario.