Prototype Development And Research On Key Technologies Of The Five Degrees-of-freedom Air Bearing Spacecraft Simulator

Ground air bearing spacecraft simulation system consists of one or more air bearing spacecraft simulators and relevant support instrumentations. Air bearing spacecraft simulator can simulate space activities of satellites and other spacecraft, which is a unique full-physical method during spacecraft research. Compared with mathematical modeling, it is very important to access directly circuit by hardware for verification testing scheme design of spacecraft control system and checking the fea-ture of actual control system. Primitive physical simulation usually executes on a static simulator, however, with the development of space technology, modern small satellite demands high mobility in space and orbital transfer flight, therefore, to pro-vide more degrees of freedom, a dynamic air bearing spacecraft simulator is needed. Foreign universities and research institutes have developed multiple degrees of free-dom air bearing spacecraft simulation system, however, national research especially on more than three degrees of freedom air bearing spacecraft simulation system is very meager, which is out of harmony with rapid development of aerospace in china.Based on analysis of the demand of the 5-dof air bearing spacecraft simulation system and combined practical situation, this paper presents a set of structure scheme design of air bearing spacecraft simulation system, carries out theoretical calculation and test on key part of planar air bearing and spherical air bearing, designs air bear-ing supply circuit, studies the features of cold gas propulsion loop, analyzes mass properties of mechanical structures of the simulator body. On the basis of above work, the first prototype of the 5-dof air bearing spacecraft simulation system is con-structed in china.The prototype which depends on high-pressure gas film formed by three planar air bearings and one spherical air bearing can realize translation and rotary motion in the manner of approximate frictionless and less disturbance, therefore, this simulator can simulate spacecraft orbit maneuver and attitude rotation on ground, which has high practical application value.It is a key problem how to describe motion state of the five degrees of freedom and construct dynamic model. According to the motion situation, this paper defines six coordinate systems, presents the method that orbital motion and attitude motion status of simulator is described respectively by orbital coordinate system origin and Euler angle of attitude platform, and creates kinematics and dynamics model of simu-lator based on spacecraft dynamics principle and analysis on the course of force transfer spherical air bearing, deduces the equation of system state under the envi- ronment that cold gas propulsion device acts as actuator of orbit and attitude, con-cludes and analyzes generation cause and eliminate measure of disturb force and moment, which provides theory basis for late orbit and attitude control.In terms of image recognition, this paper deduces a kind of localization algo-rithms which realize non-contact measurement to position coordinates of simulator by the method of monocular vision device cooperated with existing attitude sensors, and measured data derived from attitude sensor is conducted state estimation based on the theory of EKF. This paper analyzes the feature of open loop motion, studies mass center excursion and the impact from product of inertia and nuzzle thrust. Con-trol method of simulator is designed by the theory of variable structure control, be-cause the motion of the simulator is strong nonlinear and coupling.Based on the prototype, control program under real time operate system of VxWorks and human machine interface program of LabVIEW are developed, and wireless connection and data delivery are realized between simulator and computer on ground, therefore, this prototype can be observed and controlled effectively.The examination of the basic features about bearing capacity, motion freedom and sustainable working time proves that the prototype reaches the expected purpose. The examinations about wingborne, orbital motion, pitch rotation, yaw rotation and fixed-point circumnavigation show that the simulator can be used to simulate orbit and attitude combined motion of spacecraft. Relevant research work is accurate and effective.