Wrinkling Deformation Characteristics And Control Method Of Tensioned Planar Membrane Structure

Membrane has the advantages of light weight,small collection size,low cost and easy folding.It is widely used in fields of satellite large array antenna,solar sail,space solar power station and so on.However,thin membrane has negligible bending stiffness,which easily results in wrinkles when they are subjected to a compressive load.Wrinkles will not only reduce surface precision,but noticeably change in-plane stress field distribution,which become the main factor affecting the performance and dynamic characteristics of membrane structures.Therefore,it is important to accurately describe wrinkles and to analyze the dynamic characteristics of membrane structures.Besides,minimization of wrinkles and inhibition of membrane vibration,have important significance to the design and application of large space membrane structures.Static analysis and dynamic analysis of tensioned planar membrane structures are performed in this thesis,the main works and achievements can be described as follows: 1.The concept of wrinkle wave is proposed,and wrinkle-wave model for membrane structures is built,which can describe fluctuation state of all points on the surface of membrane,fit out wrinkling shape,and reveal the formation and expansion mechanism of wrinkles.The wrinkling amplitude,wavelength and wave number can be obtained quickly with the proposed model,in addition,this model is applicable to various loading cases even number polygonal membrane structures and can overcome the difficult of convergence or non-convergence during FEA calculation.For a square membrane structure,the deformation root mean square(Drms)difference between wrinkle-wave model analytical results and experimental results is about 0.022 mm,while the Drms difference between finite element analysis(FEA)results and experimental results is about 0.18 mm,which show that,wrinkle-wave model analytical results are in better agreement with the experimental results than those obtained using the FEA method.2.Curved edges structures are introduced,for single arc-edge regular polygonal membrane structures,a new stress field model for estimation of the in-plane stress is proposed,and the optimal trimming level is derived;For multiple arc-edge membrane structures,the wrinkling radius is determined with the method of the finite elemental analysis,and the optimal trimming level is predicted through the optimization algorithm,ensure that there are no wrinkles appear inside the effective region with the smallest total area of the membrane structure.Both simulation results and experimental results show that,under the same loads,the unwrinkled area is larger with the proposed method in this thesis than that with the method in the existed literature,the surface precision of membrane structures is improved.3.Dynamic analysis is performed while wrinkle shape is regarded as the new equilibrium state,then dynamic characteristics of membrane structure with wrinkles are studied.On this basis,the equilibrium position is determined with the help of wrinkle-wave model,the inherent vibration mode based space vector is derived using the modal superposition method,dynamic model of wrinkled membrane structure under different loads has been built.According to the contribution of each mode to vibration deformation,the order of the dynamic model is reduced,thus the control-oriented dynamic model of membrane structure is established.The results show that,the dimension reduction model can express the vibration characteristics of wrinkled membrane structure,and the complexity of the model is reduced on the premise of ensuring analysis accuracy,which lays a theoretical foundation for the design of controller.4.In order to ensure the stability of membrane structure,an in-plane active vibration control strategy is presented,vibration is suppressed effectively through adjusting the boundary displacement loads to change the inherent vibration characteristics of membrane structure without attaching extra bimorph actuators on the surface of membrane.On this foundation,a model reference adaptive controller act as a feedforward compensation controller meeting the optimal performance index is introduced to improve the anti-disturbance capability of system,and combining with a PID controller,a multi-model switching PID-MRAC system is designed.The results show that,under the initial disturbance,the vibration duration with the proposed method is reduced to 2.96 s compared to 12.37 s without control,moreover,it is shortened by about 39.7% compared to that with traditional PID control method,and it is shortened by about 15.9% compared to that with the out-plane control method by attaching actuators on membrane in the existed literature.