Research On Micro-Vibration Environment Simulation And Pointing Stability Technology Of The Space Optical Payload Based On Six-DOF Parallel Mechanism

Micro-vibration has the characteristics of small amplitude and wide frequency distribution.If the micro-vibration is transmitted to the space optical payload,it will result in unstable pointing and not working normally.Therefore,it is necessary to research the pointing stability technique for optically sensitive payloads.One of the methods to improve the pointing stability is vibration isolation.In order to verify the vibration isolation performance of the isolator,a large number of ground experiments are carried out.However,many factors make it impossible for the real disturbance sources to be widely used in ground experiments.Therefore,the micro-vibration environment simulation technology of the space optical payload is one of the key technologies to develop space optical payloads.The six-degree-of-freedom parallel platform has advantages of strong bearing capacity and high positioning accuracy.Its six-degree-of-freedom motion capability provides a solution for the research of micro-vibration environment simulation technology and pointing stability technology.Therefore,in this paper,the research on micro-vibration environment simulation and pointing stability technology of the space optical payload based on six-DOF parallel mechanism is developed.In order to provide micro-vibration environment for the space optical payload,a micro-vibration environment simulation platform based on Gough-Stewart configuration is developed.There are two ways to simulate micro-vibration environment of the simulation platform: one is to output multi-dimensional vibration from the upper platform,and the other is to output multi-dimensional disturbance forces and moments between the lower platform and the mounting surface.Aiming at the way to simulate the multi-dimensional vibration,combined with the Newton-Euler formula and the Lagrange equation,the dynamic equations of the six-dimensional acceleration outputting from the upper platform are established.And the iterative control strategy of the acceleration transfer function is studied.The accuracy of the dynamic model and the control strategy are verified used the prototype.The experimental results show that the micro-vibration environment simulation platform can be used to simulate multi-dimensional vibration.Aiming at the way to simulate multi-dimensional disturbance,the dynamic relationship between the excitation forces and the multi-dimensional disturbance forces and moments is established.The iterative control strategy for multi-dimensional disturbance is then studied.Finally,the experiment verifies the validity of the way to simulate multi-dimensional disturbance.Facing the research requirements of pointing stability technology,two generations of the parallel platform combined vibration-isolation with pointing based on Gough-Stewart configuration are studied.The platform integrates the pointing performance and the vibration isolation performance,which reduces the launching cost,saves space and improves the success rate of space missions.The first generation parallel platform moves the leg mass down to the base platform,and the hinges are designed at the same end of the leg.The design of legs improves the bending frequency of the leg.Based on the Kane equation,the complete dynamic equation of the first generation parallel platform under the basic excitation is establishe.And the validity of the dynamic equation is verified by the co-simulation technique.Compared with the structure of the first generation parallel platform,the second generation parallel platform improved the hinge structure.Then,the rotation angles and elastic torsional moments of the flexible hinges are added to the previous dynamic model.Finally,the improved dynamic model is verified by co-simulation.The two generations of the parallel platform combined vibration-isolation with pointing use electromagnetic drivers to ensure response speed and control accuracy.However,the stroke of electromagnetic drivers is small which makes it impossible to achieve large angle adjustment.In order to ensure that the parallel pointing platform can combine large-angle adjustment and pointing stability,and aiming at the characteristics that the optical axis of the space optical payload is sensitive to rotation and insensitive to translation,a novel parallel coarse and fine pointing-stability platform based on generalized Stewart configuration is studied.Due to the particularity of the platform structure and the particularity of the movement mode,the modeling is divided into two parts: kinematic modeling in the coarse adjustment stage and dynamic modeling in the fine adjustment stage.In the coarse adjustment stage,combined with the forward and inverse kinematics functions of the parallel mechanism and the Newton-Raphson numerical iterative method,the kinematics model of the parallel platform is established.Then,the accuracy of the kinematics model is verified by virtual prototype technology.In the fine adjustment stage,combined with the Newton-Eulerian formula and the Lagrangian equation,the dynamic equations of the parallel platform are established.And the accuracy of the dynamic model is verified by the co-simulation technique.The simulation results show that the parallel coarse and fine pointing-stability platform can complete large-angle pointing on the basis of pointing stability.