Active Shape Control of Membrane Structures Using Spin-Synchronous Vibrations

A novel approach for shape control of membrane structures is presented to realize their use in three-dimensional and variable configurations. 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 rate; that is, the wave propagation and the spin cancel each other, resulting in a static wave surface in the inertial frame. This idea enables control of continuous membrane structures with large deformation using fewer actuators than conventional methods. This paper describes the general theory of the static wave-based shape control. The mathematical model of membrane vibration, the 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 vibrated in a vacuum chamber, and the output shape is measured using a real-time depth sensor. It is shown that the observed shapes agree with numerical simulation results. An additional simulation that models the Japanese solar sail Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS) demonstrates that the proposed method also works with a practically large-scale membrane in the space environment.