Design Of Ground Adaptive Gravity Compensation System For Large-Scale Deployable Space Mechanism Based On Suspended Air Cushion

As space missions increase and space requirements increase,space costs also increase.Whether the spacecraft can operate normally in space is the key to the launch mission.Therefore,the spacecraft need to conduct multiple low-gravity simulation experiments on the ground.The method of using high-pressure gas to create a gas film and using gas buoyancy to offset the gravity of a spacecraft to simulate a low-gravity environment is called air flotation.The key to the air flotation method is the formation of the air film.The air bearing can form a stable air film,but a corresponding marble platform is required.The air flotation platform is built and tested before the experiment.Since the flatness error of the marble platform is very small,the low gravity simulation can be successfully completed without excessive control during the deployment process.However,as the size of the spacecraft increases,the air floatation platform also increases,and the disadvantages of excessive manufacturing costs and long preparation times have also become the main factors restricting its use.Therefore,how to form a film on the ordinary epoxy self-leveling ground and design a simple and fast air-floating gravity compensation device has important engineering application value for the low-gravity simulation test of large-scale deployable structures in space.Aiming at the problem of air-floating gravity compensation for ordinary epoxy self-leveling ground,this paper establishes a dynamic model of a large-scale deployable mechanism in space based on the floating coordinate system method,designs a gravity compensation device based on a suspended air cushion,and selects components.The suspension air cushion is designed and analyzed.The fuzzy PID constant force control strategy is designed,and the force position separation multi-point coordinated compensation control strategy is proposed and verified by simulation.The control software is designed and the air-floating gravity compensation experimental platform is built,which verifies the effectiveness of the air-floating gravity compensation system designed in this paper.The main research contents are as follows:(1)Design and analysis of gravity compensation device based on suspended air cushionIn order to design an air-floating gravity compensation system that can perform low-gravity simulation on ordinary epoxy self-leveling ground,a dynamic model of antenna plate deployment is established based on the floating coordinate system method,and the compensation device scheme is designed and divided based on the design index requirements.The mechanical subsystem and the control subsystem are two parts,and the key components are analyzed and selected.Since the suspended air cushion forms a film on the ordinary ground,its parameters are designed and the interference factors are analyzed.(2)Design of control law of suspended air-cushion gravity compensation systemAiming at the control of system nonlinearity,environmental uncertainty and time-varying nature,a fuzzy PID constant force control strategy is designed.Through fuzzy control,PID real-time parameters are changed to adapt to the current working conditions,and a mixed force position control strategy is designed,based on the antenna plate offset The situation carries on the force control and the position control switch.Aiming at the coordination problem under multi-point control,a force-position separation control strategy is designed,and the offset control is assumed by the outer compensation point.A simulation model is built to compare the control effects of fuzzy PID and classic PID under interference forces,and verify the effectiveness of the control strategy designed in this paper.(3)Construction and verification of air floating gravity compensation systemAccording to the functional requirements of the adjustment process and the subsequent analysis,the control software is designed,the interface operation is realized,and the fuzzy PID algorithm is realized using C++.An experimental platform for the air-floating gravity compensation system was built,and the position control and force control experiments of the single-point,single-plate,and two-plate gravity compensation device system were carried out to verify the effectiveness of the fuzzy PID constant force control and the applicability of the force-position separation control And the feasibility of multi-point coordinated control strategy.In this paper,an air-floating gravity compensation system based on suspended air cushions is designed,which can perform gravity compensation on ordinary epoxy self-leveling ground,and provides a certain theoretical basis and application guidance for the low gravity simulation of large-scale space deployable mechanisms in the future.