ACTIVE DAMPING OF SPACE STRUCTURES BY CONTACT PRESSURE CONTROL IN JOINTS

Lightweight flexible structures; e.g., for large deployable space syst ems, often consist of truss structures. Microslip and macroslip in the joint contact surfaces are the dominating dissipation mechanisms, whe n compared to material damping and environmental damping, if no additi onal damping measures are applied. So far only control of operational modes by actuators in the truss element is realized. This paper aims t o control the nonlinear transfer behavior of joints by adapting the co ntact pressure. This is achieved by piezoelectric elements in bolted c onnections. Active joint description by ordinary differential equation s (ODE) with internal variables, based on experimental data, is implem ented in the hybrid multibody system (MBS) of the assembled truss stru cture. The structural response is decomposed into large rigid body mot ion and superimposed small elastic deformations. The equations of moti on are linearized by a perturbation technique based on the splitting o f low frequency and high frequency modal contents. The flexibility of the MBS is treated by superposition of structural modes calculated by the finite element method (FEM), in the sense of a Ritz approximation. Simulation of free, as well as forced, vibrations of the structure wi th active joints in a closed control loop underline the gain of dampin g performance compared to the associated passive system.