Dynamics modelling and path optimization for the on-orbit assembly of large flexible structures using a multi-arm robot

Abstract

This paper presents a comprehensive methodology for modeling an on-orbit assembly mission scenario of a large flexible structure using a multi-arm robot. This methodology accounts for significant changes in inertia and flexibility throughout the mission, addressing the problem of coupling dynamics between the robot and the evolving flexible structure during the assembly phase. A three-legged walking robot is responsible for building the structure, with its primary goal being to walk stably on the flexible structure while picking up, carrying and assembling substructure components. To accurately capture the dynamics and interactions of all subsystems in the assembly scenario, various linear fractional representations (LFR) are developed, considering the changing geometrical configuration of the multi-arm robot, the varying flexible dynamics and uncertainties. A path optimization algorithm is proposed for the multi-arm robot, capable of selecting trajectories based on various cost functions related to different performance and stability metrics. The obtained results demonstrate the effectiveness of the proposed modeling methodology and path optimization algorithm.

Figures (17)

• Figure 1: Three different illustrations of the on-orbit assembly mission scenario being studied: 1 the green robotic arm is attached to the initial and sole assembled tile, while the yellow robotic arm is extending to pick another tile from the tile stack; 2 the multi-arm robot is moving across the structure while transporting the eighth tile for assembly; 3 the final tile from the stack has been picked up by the multi-arm robot, which is now adding it to the rest of the assembled structure.
• Figure 2: (a) TITOP illustration for a generic flexible body $\mathcal{A}_i$. (b) TITOP model $\left[\mathfrak{T}_{P_{i}C_{i}}^{\mathcal{A}_{i}}(\mathrm s)\right]_{\mathcal{R}_{a_i}}$ block-diagram.
• Figure 3: (a) Block-diagram model of the connection between two rigid bodies $\mathcal{B}$ and $\mathcal{A}$. (b) Assembly of the transformation model $\mathbf{R}({\alpha})$.
• Figure 4: Robotic manipulator representation: (a) robotic arm kinematics (Note: for the sake of simplicity, the $\mathbf{x}$-axes are displayed in solid red lines, the $\mathbf{y}$-axes in dashed green lines and the $\mathbf{z}$-axes in dash-dotted blue lines). (b) block-diagram of the parameterized robotic arm written in LFR form. (c) equivalent LFR form of the manipulator.
• Figure 5: 3D representation of an on-orbit assembly mission scenario (Note: for the sake of simplicity, the $\mathbf{x}$-axes are displayed in solid red lines, the $\mathbf{y}$-axes in dashed green lines and the $\mathbf{z}$-axes in dash-dotted blue lines).