EXPERIMENTS ON QUASI-STATIC AND DYNAMIC CONTROL OF A PVDF LAMINATED MEMBRANE-LIKE MIRROR

Due to their merits of low areal density, in-orbit deploying and low manufacturing cost properties, membrane-like deformable mirrors meet the ultra-lightweight and large aperture demand of space optical mirror systems well. Membrane-like mirrors has therefore become a hot spot in the field of space science research now. Surface of these in-orbit membrane-like structures are susceptible to external environment variation on account of their low stiffness and high flexibility properties. Once excited by external excitations, the membrane vibration endures and this would not only degrade its performance, but also lead to system or structural failures. So dynamic vibration control of the membrane-like mirror is indispensable. When the orbiting mirror passes from Earth's shadow into sunlight, the surface temperature of the mirror changes and this will render membrane thermal distortion. Hence, quasi-static surface error adjustment of the mirror is also requisite. In this paper, a 0.2m diameter scaled-down Kapton membrane-like mirror is taken as the experiment subject. Polyvinylidene Fluoride (PVDF) patches are laminated on the non-reflective side of the mirror as in-plane actuators. High precision laser displacement sensors are used to measure the surface deviation of the mirror. A modal vibration control system based on the positive position feedback (PPF) algorithm and a quasi-static surface control system based on the proportional error feedback algorithm are established respectively. Several mirror control experiments are performed and the results indicate that the methods proposed could suppress the membrane vibration and alleviate the membrane thermal deformation effectively.