| Space simulator is the main mean to simulate the quality characteristics of spacecraft and predict the performance of space work,the ground physical simulation of spacecraft is very important for the success rate and reliability of high efficiency operation of spacecraft.The space simulator simulates the real spacecraft completely from the aspect of structure and mass characteristics,measures the moment of inertia of the space simulator and analyzes the dynamic characteristics,which is of great significance for guiding the design and test of the spacecraft.By simulating the microgravity environment of space on the ground,the mass characteristic of the space simulator is close to that of the real spacecraft.In the measurement of the moment of inertia of the space simulator,since the space simulator has been installed on the performance platform to realize its microgravity working conditions,the moment of inertia can only be measured online,and the moment of inertia can be measured by the periodic method.In the process of measurement,the total inertia of the three axes can be decoupled from each other.The measuring device is the key to measure the moment of inertia of the space simulator and ensure the micro-amplitude periodic vibration of the space simulator.In this paper,the space simulator body is taken as the research object,and the high precision on-line measurement of the moment of inertia of the space simulator is carried out.The aim is to further guide the design and development of spacecraft by measuring its moment of inertia and comparing it with the real spacecraft.The main research contents of this paper are as follows:(1)The kinematics and dynamics equations of the space simulator are established.An analysis of the realization of six degrees of freedom microgravity in space simulator is carried out,the existing structure is analyzed by finite element method to ensure the uniformity of the mass characteristics of the space simulator and spacecraft.By analyzing the friction force of each degree of freedom and matching the mass inertia configuration of the space simulator,the dynamic uniformity between the space simulator and the spacecraft is guaranteed.(2)By studying the existing methods of inertia measurement,a method of inertia measurement suitable for space simulator is proposed and a measurement scheme device is designed.The structure of the measurement scheme is modeled in 3D and the mechanism in the measurement scheme is further optimized by ANSYS.In the measuring device,vibration unit,limit mechanism,distance measuring unit,swing period measuring unit and standard mass block are designed respectively.(3)The mathematical modeling and simulation of the space simulator were carried out to analyze the influence of air resistance and restoring force of the electronic spring on the measurement of the total inertia of the space simulator during the measurement of the total inertia,and Hilbert’s method was used to solve the rotary inertia of the space simulator.The vibration signal of the space simulator is analyzed and processed.The method of empirical mode decomposition and variational mode decomposition is adopted to judge the vibration signal and eliminate the endpoint effect generated in the vibration signal.The influence of these two main factors on the measurement of the total inertia of the space simulator is analyzed.(4)The method of measuring moment of inertia is experimented,and the error factors affecting the accuracy of measuring moment of inertia are studied.During the experiment,coordinate transformation is carried out,and the measured vibration data are transformed into the same coordinate system of the measuring platform for calculation.Then air resistance error compensation and non-linear restoring force error compensation are carried out by least square fitting.The influence of photoelectric sensor on the moment of inertia is studied,and the error compensation analysis is carried out.The obtained moment of inertia data are compared with the design standard values. |
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