Study on Trajectory Planning of Dual-arm Space Robot Keeping the Base Stabilized

Aiming at the case that the base is required to be stabilized by a balance arm when a dual-arm space robotic system is performing on-orbit missions, we propose coordinated trajectory planning methods of two typical applications — keeping the base centroid fixed (approximately; the same below), and keeping the base attitude and centroid position fixed synchronously. Firstly, the concept of “system centroid equivalent manipulator” is presented, and its kinematic model is derived. Based on the resolution of the position-level kinematic equation, the trajectory of the balance arm for stabilizing the base centroid is planned. Secondly, by combining with the control of a reaction flywheel, the base attitude and centroid can be kept fixed at the same time. The desired angular speed of the flywheel is determined according to the angular momentum conservation law. Finally, a multi-body dynamic model of a dual-arm space robotic system is developed and simulation study is carried out. The proposed methods can overcome the singularity problem which is un-avoidable for previous approaches based on differential kinematics. Furthermore, there are not special requirements on the mass properties and installation position of the balance arm. Simulation results have verified the proposed methods.