Study On The Critical Measurement Technology In Three-axis Simulator Used For Satellite Simulation

With the development of the astronautic technology, the requirement for thepointing accuracy of satellites becomes stricter and stricter, three-axis simulator isused to imitate non-friction space environment of satellite and simulate the attitudecontrol system of satellite, so it is of great importance to develop and manufacturethree-axis simulator.This paper is written on the basis of the three-axis simulator being developed.Some method of measuring specifications for the simulator, such as sphericity,imbalance, moment of inertia matrix, friction torque, was put forward in this thesis.Firstly, aiming at the sphericity’s measurement, the latitude circle and thelongitude circle method were designed to measure and separate sphericity from therotary errors, and installing error etc. A small hemisphere was used to simulate theseparating process, and its correctness was proved, and the measurement uncertaintyattained0.3μm.Secondly, with regard to the test of the three-axis simulator’s moment of inertia,the combinatorial method of the gyroscope and the momentum wheel is proposed,the coordinate systems were established. The Euler angular velocity and the angularacceleration which are calculated from the gyroscope’s output, are propagated to thebody coordinate system, theorem of momentum is used to solve the dynamicalproblems of the dynamic equation. The impulse of three-axis momentum round isdesigned, and then the three-axis simulator’s moment of inertia matrix is identified.Thirdly, the balance measurement and adjustment of the simulation platform arestudied, which is divided into three stages, namely the preliminary adjustment stage,the manual adjustment stage and the auto adjustment stage, then the adjustmentaccuracy of all these three stages are analyzed.Lastly, the general friction torque of the simulation platform is tested, and theuncertainty analysis is made for the original measurement methods. Themeasurement method of friction torque coefficient concerned with angular rate is putforward, the simulation platform is controlled to make the positive spin and thenegative spin, the changes of the simulation platform’s angular velocity and angularacceleration are calculated, the least square method is used to identify the interferingmoment of the three-axis simulator, then separated out the eddy current torque, thefriction torque and the air disturbance torque. According to the curves about the angular velocity and angular acceleration when the simulator runs in the differentdirections, then further verifies the correctness of the identification, those curves aresimulated through adding the noise to the gyroscope, the identification precision isverified.