Research Of The Simulation Testbed Of Spacecraft

In Chinese third lunar exploration program, the return module and the orbital module of the lunar mission spacecraft will separate when orbiting the moon. A testbed on the ground is needed to simulate the separation movement between the return module and the orbital module in zero gravity environment. With this testbed, the reliability of the separating device can be tested and the rule of separating movement can be analysed.After weighing the pros and cons of some zero gravity simulation methods, the scheme of hybrid of flat air bearings and precision self-aligning ball bearing is selected. To gain a balance between the mass and rigid, the multi-objective optimization is conducted. The other structure of the testbed is designed and checked. By mode analysis, the first four natural frequencies and mode shapes are obtained. The structure has good vibration resistance.This dissertation researches the design method of the key point of the structure, the simulating structure of the mass and inertia. Because the equations which describe the mass characteristics have many variable and are non-linear, the traditional symbol derivation method can only get some imaginary solution. The block solving method and the iteration method can gain dimension parameter quickly. The measuring principle of the joint measuring device is deduced and accuracy is analysed.Through fixing a modular, reducing the degree of freedom of the model, 5 DOF dynamics model for testbed on the ground and 6-DOF dynamics model for spacecraft in the space are established. The four/five order-Runge- Kutta method is applied to solve the dynamics differential equations and the numerical solution is obtained. The regulation of the attitude velocity of the modular is analysed. After completed the ADAMS simulation, its result is consistent with the solution of the equation, which demonstrate the dynamics model is effective. This dissertation analyse the effect of the friction disturbance, loss of freedom, different matrix elements associated with the inertia to the process of the separation. Based on the simulation result, the testbed can simulate the separation of the spacecraft effectively.