Dynamic modeling of liquid-filled free-floating space robot and joint trajectory planning with considering liquid positioning

The free-floating space robot mainly consists of three parts: the main rigid body, the robotic arm and the liquid fuel, where the movements in component parts interact with each other and generate complex coupled dynamic problems. This article establishes an efficient coupled dynamic model of a liquid-filled space robot based on the alternative and iterative algorithm. The moving pulsating ball model (MPBM) is used to describe the dynamic behavior of liquid with large sloshing, while the robotic arm module is modeled using the Newton-Euler method for recursive dynamics. To validate the MPBM, the rigid body motion obtained from the coupled dynamics model is used as the input condition for the Computational Fluid Dynamics (CFD) method. The calculated liquid motion, sloshing force and torque have a high degree of agreement with the simulation results of the equivalent model, thereby verifying the effectiveness of the model proposed in this paper. Finally, based on cosine series basis and Particle Swarm Optimization (PSO) algorithm, the joint trajectory planning problem considering liquid positioning are studied. This method can minimize the deviation of liquid fuel location from the initial position without introducing additional control force and torque after the robotic arm completes the specified action, which is of important significance for liquid management and overall design and dynamics analysis for space robot system in microgravity environments.