Analysis Design And Experimental Study For Vertical Docking Test Platform

Spacecraft docking technology is one of the most complicated techniques ofon-orbit service. There is an urgent need to solve the problem for further spacedevelopment of our country. In order to guarantee the high success rate and highreliability of spacecraft docking, a lot of ground docking simulation tests must tobe done. Docking tests are based mainly on impact dynamics and study thesuccess of docking state. The docking tests of motion simulator evaluate theperformance quality of docking mechanism and are closely related to the successof the docking mission.In order to truly represent the relative motion of the small dockingmechanisms, the high demands are raised for the dynamic performance, controlperformance and movement precision of six degrees of freedom docking testsystem. Movement error of the test system will affect the attitude angle error ofdocking mechanism directly. The dynamic analysis and motion accuracy analysisis required for test system, and a complete set of control demonstration system isneeds to be established.Based on the functional requirements of docking test system and thestructure characteristics of the "three claw type" docking mechanism, thecomposition and function principle of test system are introduced. The functionframe of each subsystem is built. According to the design principles of motionplatform and six degrees of freedom motion implementation principle, thestructure design framework of the active and passive motion simulation platformare introduced. The test process and the performance index of the system areintroduced combined with the overall framework.In order to analyze the attitude errors of the vertical docking test platform ofsmall satellite, the static error and kinematic error of test platform are taken intoaccount. The working principle of test system and coordinates of actuator are introduced. The model of friction torque on the joints and torque on the dockingmechanism are built. Dynamics equation of actuator is built by Lagrangeequation and Nielsen equation. Under the condition of24different angle groups,the calculation of dynamic equation is completed by usingMATLAB/SIMULINK platform, and the actual angles of actuator are obtained.The error model of the attitude angle of docking mechanism was establishedunder the influence of motion error and the static error of actuator. The influenceextent from the error sources on different attitude angle error are discussed byanalyzing the calculation results. The methods for reducing the error arepresented in view of the main error sources.According to the control function requirements of the system, overallscheme of the control system of test bed is presented. Based on two phasemeasurement principle, the connection electric circuit of grating ruler isolationmodule and programmable controller are introduced. The power supply circuit ofthe control system is designed and six-dimensional force sensor is selected.Finally, the experimental study is carried on the overall test system. The resultshows that test bed can meet the test requirement of the docking mechanism.