Research On Intelligent Control Of A Kind Of Membrane Structure

Membrane space structures are considered viable among proposed large space structures that will make innovative missions possible,such as: membrane antennas,membrane solar arrays,membrane solar sails,et al.This kind of tension membrane structure have some special dynamical properties,such as,nonlinearity,low stiffness,low damping ratios,low modal frequencies and so on.Due to these properties,the deformation and vibration of these structures are extremely easy excited by space environment disturbance load and spacecraft maneuver disturbance load.The deformation and vibration problem of the membrane structure will significantly degrade the shape accuracy and pointing stability of the spacecraft.Hence,the shape and vibration control for membrane structures is ultra-needed.This dissertation systematically addresses the dynamic modeling,shape control and vibration control problem of membrane structure through the aspects of theoretical analysis,numerical simulation and experimental validation.The main work of this dissertation can be summarized as below:1.The electro-mechanical dynamic model of membrane structures is established,the form finding method and wrinkling analysis method are proposed and the mechanic characteristics of the membrane structures are analyzed.(1)By using the nonlinear finite element theory,the nonlinear element models of beams with internal compression,cables and membranes with internal tension of the tensional membrane structure are deduced,respectively.The electro-mechanical dynamic models of the smart piezoelectric patch actuator and smart piezoelectric rod actuator are proposed,respectively.Finally,the electro-mechanical dynamic model of the membrane structure is carried out.(2)The modified nonlinear force density method(MNFDM)is proposed to solve the form finding problem of the membrane structure,the force density of the cable element is transformed from the stress of the element,and it makes the form finding error more precise and the stress distribution more uniform.The membrane wrinkling analysis method is proposed based on stability theory.The wrinkling development pattern of a square membrane under across corners tension force is studied.(3)The dynamic characteristics of the membrane structure are computed,and the effects of the internal tension of the membrane of its dynamic characteristics are researched.The space environment disturbance load and spacecraft maneuver disturbance load model are proposed,and the membrane structure deformation and vibration response are simulated.The simulation results prove that the large amplitude deformation and vibration of the membrane structure maybe occur in space.2.The smart hybrid optimization shape control method for membrane structure is proposed,and simulation validations are performed.(1)The straightness index and flatness index are proposed as the objective function of the membrane structure frame and membrane structure face shape control problem,respectively.The piezoelectric patch-based structure frame shape control method and the linear actuator-based membrane structure face shape control method are proposed,this method describes the shape control problem as constrained multivariable optimization problem.(2)In order to solve the constrained multivariable optimization problem of the shape control problem,the smart hybrid optimization algorithm which combines the evolution algorithm and local search algorithm together is proposed.The membrane structure frame and membrane structure face shape control simulation are carried out,the simulation results indicate that the shape control methods can improve the shape precision greatly.3.Three kinds of smart fuzzy vibration control methods of membrane structure are proposed,the robustness,adaptability and reliability of the large membrane structure vibration controller are improved.(1)As the vibration amplitude of the membrane structure is hard to predict,the variable universe adaptive fuzzy vibration control(AFC)method is proposed to address this problem.In this method,the fuzzy universe of the controller can turn with the vibration amplitude adaptively.The simulation results determined that this method can keep a good control effect under various excitation conditions.(2)As the rule base of the fuzzy controller is hard to adapt the variation of the structure parameters,the online learning fuzzy vibration control(OLFC)method is proposed to solve this problem.The OLFC can learn the rule base online through reinforcement learning,even when the structure parameters changes.The simulation results determined that this method only needs a little information about the plant to design the reward function,and can gain a good control effect in a short time.(3)As the centralized control has its limitations,the decentralized adaptive fuzzy vibration control(DAFC)method is proposed.The simulation results determined that the decentralized controllers can rapidly suppress the structure vibration even under subsystem failures.4.The large membrane structure shape and vibration control experiment system is established,the dynamic characteristics test experiment,shape and vibration control experiment are carried out.(1)The work piece of large membrane structure with size 8m×2.5m is designed and manufactured;the dynamic characteristics test system based on laser scan measuring instrument,the shape measure system based on double camera photogrammetric instrument are established;the frame shape control device based on piezoelectric stack,the membrane shape control device based on step motor are developed;all these subsystems constituted the large membrane structure shape and vibration control experiment system.(2)The dynamic characteristics test experiment,shape and vibration control experiment are carried out,the experiment results demonstrate that: the relative error of the first four mode frequencies between simulation results and the experiment results are less than 10%,respectively,it demonstrate that the dynamic model established in this paper is correct;the shape measurement accuracy is higher than 1mm,the shape control accuracy of the smart hybrid optimization shape control method is better than 3mm(3?);the proposed smart fuzzy vibration control method can suppress the structure vibration effectively.The above researches could provide a theory foundation for the membrane structure nonlinear dynamic modeling,shape and vibration control investigation,and provide theoretical reference for the design,manufacture and application of the space borne membrane structure.