In-Situ Shape Measurement of Flexible Structures

Researchers

Thibaud Talon
Luke Chen
Sergio Pellegrino

Description

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Many advanced spacecraft concepts feature large planar surfaces for applications including solar sailing, communications and sensing, and space solar power. In each case, system performance deteriorates in the presence of unknown deformations and vibrations due to structural flexibility. For example, structural deformations change a solar sail’s thrust vector and induce phase differences between the antennas in large-scale phased arrays. As a result, shape estimation is imperative for maximizing the performance of these systems.

Typical shape estimation schemes for flexible structures are based on optical systems and include techniques like laser scanning, interferometry, photogrammetry, and digital image correlation. For in-situ measurements of flexible spacecraft, this requires placing the optical measurement system at a sufficient distance to image the entire structure. Due to these limitations, our research adopts a different approach. Instead of imaging the entire structure, small sensors capable of locally measuring deformations are distributed across the surface of the structure. Algorithms are then used to synthesize these local deformation measurements into an estimate of the global deformed shape.

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Recent research has focused on the development of algorithms for both quasi-static and dynamic shape measurements of flexible structures, along with the design and test of suitable sensors for these in-situ measurements. The shape reconstruction methodology relies on distributed angle measurements across the structure. These distributed angle measurements are captured from quad photodiode-based light sensors developed in-house. Our algorithms combine these measurements with a finite element model of the structure, along with some geometric assumptions, to accurately reconstruct the structure’s deformed shape. Quasi-static shape reconstruction algorithms have been demonstrated on a 1-meter scale experiment, and Kalman filter-based dynamic shape reconstruction algorithms have been tested in numerical experiments on large-scale flexible spacecraft.

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Publications:

  • Talon, T., Chen, L.C., and Pellegrino, S. (2021). Shape reconstruction of planar flexible spacecraft structures using distributed sun sensors. Acta Astronautica 180: 328-339.

  • Talon, T. and Pellegrino, S. (2018). Shape measurement of large structures in space: experiments. 2018 IEEE International Workshop on Metrology for AeroSpace. Rome, June 20-22, 2018.

  • Talon, T., and Pellegrino, S. (2017). In-space shape measurement of large planar structures. SciTech 2017. Grapevine (TX), AIAA.