Finite element analysis for platform of 3 DOF spacecraft simulator based on the theory of deformable body mechanics

According to the theory of the thin plate and beam bending of elastics mechanics and taking the hypothesis of G.kirchhoff into account, a finite element model of the platform is built. Based on the theory of deformable body mechanics and kinetics, the formulary for the mass-center elastics displacement of the platform caused by deforming was deduced. Depending on the theory of the spacecraft attitude kinetics, the gravity torque vector in the body frame was given as the boundary condition of the finite element model and the formulary for unbalance torque caused by the mass-center displacement was presented. The result and analysis have revealed the essential reason that platform deforming causes unbalance torque is the difference of stiffness of the platform structure in various directions. The unbalance torque cause by the shift between the deformable body mass-center of the platform and the center of rotation is a function of the loading condition and of the elevation angle. It varies with the sine of twice the elevation angle.