Experimental characterization for active flatness control of membrane structures

Maintenance of membrane structures geometry is crucial for them to be utilized in some space missions, including membrane antennae being developed at the Canadian Space Agency. In the harsh space environment, thermal loading and mechanical loading both can cause the distortion of membrane surfaces. Their effects on surface distortion will interact with each other. In order to properly design active control system, the interaction needs to be well characterized. An experimental setup is designed for this purpose. A square membrane is subjected to mechanical loading provided by corner tension forces and thermal loading provided by a ceramic heater. Surface profile of the membrane is measured using a photogrammetry system, which is based the out-of-plane sensitivity. In cases of symmetric thermal loading and asymmetric thermal loading, different mechanical loading cases are evaluated in terms of mitigating surface distortions. Some results are compared and explained using numerical results. Finally, the controllability of membrane structures is discussed using the results from these experiments. The conclusion has been applied to a larger membrane with multiple shape memory alloy actuators designed at the Canadian Space Agency.