Simulation on Flexible Multibody System with Topology Changes for In-space Assembly

In-space assembly (ISA) has become a potential solution to building large space structures. However, the motion of an ISA system will experience a sudden topology change when two flexible modules are assembled together thus causing the whole system to oscillate. Therefore, understanding the dynamics of an ISA system during and after assembly is of importance. This paper presents a methodology for simulations of ISA system based on the modeling of flexible multibody system with topology changes. The theory of Absolute Nodal Coordinate Formulation (ANCF) is applied to describing the deformation of flexible bodies. Meanwhile, combining the impulse-momentum equations and the constraint equations in velocity level, a linear algebraic equation is obtained to solve the discontinuous velocity changes when different modules are assembled together. In addition, the dynamic model of a typical ISA system made up of hexagon truss modules is established based on Lagrange’s equations of the first kind. Finally, numerical simulations are provided to evaluate the effect of gravity and to investigate a basic assembly procedure. The presented model is verified to be able to accurately describe the assembly procedure and able to capture the oscillations after topology changes. The simulation results are furthermore analyzed to study the dynamic characteristics of the ISA system.