In order to avoid the resonance between the two dimensional turntable and the satellite, the modal simulation of the two dimensional turntable is carried out in this paper. And the simulation results are compared with the experimental results, combined with modal experiment, the simulation results before and after optimization are further verified. Firstly, two dimensional turntable as the research object in this paper, and it is modeled with the finite element method, then we use Patran/Nastran to conduct the modal simulation. In the modal simulation process, the bearing can be equivalent to the spring element, and the MPC element is used to instead of the spring element. And we introduce the modeling method of the MPC unit, the fundamental frequency of two dimensional turntable is obtained through modal simulation. At last, the model experiment is verified by hammering method, the frequency response functions in each direction of x, y and z are measured. Simulations and experimental results show: after optimization, the fundamental frequency of the two dimensional turntable is 42 Hz, which is higher than that of the base frequency 25 Hz, illustrating that the optimized structural design of the two dimensional turntable meets the requirements; The natural frequency and the experimental errors of three - dimensional turntable in x, y, z are 5%, which shows that MPC can simulate the bearing accurately, and is suitable for the simulation of two dimensional turntable.
Collimation frame is the key supporting component of Space two-dimensional turntable. Its stiffness characteristics are vital for the performance of turntable. In order to reduce weight and improve rigidity, a lightweight collimation frame is designed. Compared with some commonly used aerospace materials, titanium alloy is chosen as the material of collimation frame for its excellent advantages. Modal analysis of the collimation frame is realized by using finite element analysis software MSC. Patran /Nastran to verify whether the stiffness of frame meet the design requirements. The results of analysis show that the first natural frequency of collimation frame is 169.5Hz, which satisfies the design requirement of stiffness. Then, modal experiment is conducted to verify the correctness of the results obtained from finite element modal analysis. The results of experiment show that simulation and experiment results agree well, which further confirm the correctness of the finite element modal analysis. Therefore, it proves that the selection of material and the design of structure are feasible.