Shape measurement and control of deployable membrane structures

The shape inaccuracies of inflatable antennas and the potential shape control of the surface of those structures are investigated. Surface shape inaccuracies are due to geometric nonlinear deformation. Correcting the shape of these inflatables focused on the integration of piezopolymer actuators on the membranes. The out-of-plane displacements of a membrane structure were assessed with the shadow moire method. The experimentally measured shape of the structure confirmed the extent of deviation from the ideal optical surface, a paraboloid of revolution. Active control of the shape of the membrane was tested using a piezoelectric material, polyvinylidene fluoride (PVDF). The deformation caused by actuation of the membrane structure was evaluated using electronic speckle pattern interferometry. An analytical solution was developed to verify the extent of shape correction that can be achieved by embedded PVDF actuators. It was confirmed that micron-level shape corrections are possible for future space-based sensors that use inflatable antennae technology.