Research On Elimination Of Thermal Deformation Of Membrane Reflector With Boundary Actuation

With the rapid development of space exploration, communication and earthobservation technology, demands for optical mirrors with large field of vision becomeincreasingly urgent. With rigid materials as the substrate, traditional large aperturereflectors are unable to meet the launch vehicle size requirement limited by their largemass and volume properties. Therefore, scientists are focusing on thin-film opticaltechnology now. With poor stiffness and large flexibility, the surface accuracy ofmembrane structures can be easily interfered. So precise shape control of in-orbitmembrane reflector becomes the focus in space technology area. Thermal disturbanceplays an important role in space membrane’s wrinkling. Thus active control forcesare essential in reducing membrane shape error.Considering of the Von-Karman geometrical nonlinearity, the equilibriumequations for membrane reflector are firstly presented based on Hamilton’s Principleand Love’s thin shell theory. As a simplification for equilibrium equations, thenonlinear mathematical model for the circular membrane in a symmetricaltemperature field is obtained. Movable clamped and integral boundary tensioning areconsidered as boundary condition in this model respectively.An FE model for membrane reflector under thermal load is developed inABAQUS. Thermal deformation of membrane in typical temperature fields isinvestigated. By contrasting the FEM deformation analysis with mathematicalmodeling solutions, it is demonstrated that the theoretical model is capable ofpredicting the amplitude of membrane surface deformation. The simulation result alsoindicates the effectiveness of boundary active control strategy on improvingmembrane surface accuracy with different temperature distributions.Based on their shape memory effect, SMA wires are used as boundary actuatorsto improve the membrane accuracy. A series of actuator properties are tested and aprecise control strategy for SMA wire is adopted, which could effectively decreasethe membrane wrinkle induced by thermal disturbance.For research of membrane deformation in thermal environment, detectionplatform for membrane thermal defelection is built. Data fitting of experimentalresults are compared with the FEM simulation and theoretical solutions. Thusvalidatiy of the theoretical model and feasibility of SMA boundary actuation areverified.