Active shape control of membrane structures using spin-synchronous vibrations

A novel approach for shape control of membrane structures is presented. The shape control is accomplished by exciting a spinning membrane. The membrane forms a shape consisting of several vibration modes, depending on the input frequency, and the wave surface stands still when its frequency is synchronized with the spin; that is, the wave propagation and the spin cancel each other, resulting in a static wave surface in the inertial frame. This paper describes the general theory of the static wave-based shape control. The mathematical model of membrane vibration, classification of control input, and the control system for exciting a static wave are summarized. The proposed method is demonstrated through a ground experiment. A 1 m large polyimide film is rotated and is vibrated in a vacuum chamber, and the output shape is measured using a real-time depth sensor. The nonlinear dynamics of membrane deformation under both the ground and space environments is simulated using a numerical method, showing the validity and effectiveness of the shape control method.