Temperature-insensitive shape sensor for realtime deformation monitoring of discontinuous spaceborne antenna truss

Space-borne deployable antennas are evolving towards larger aperture and higher precision, aiming to achieve high-resolution detection of weak electromagnetic targets. Random and uncertain structural deformations often occur in such discontinuous structure containing kinematic pairs due to the unstable motion of mechanism caused by kinematic pair clearances and on-orbit environment, which are hard to be theoretically predicted. In this study, Brillouin optical time domain analysis-fiber Bragg gratings optically fused high-resolution shape sensor assisted with a transfer learning-assisted error online prediction model was proposed and demonstrated for space-borne antenna truss monitoring. The shape sensor exhibited highly flexible, temperature/ axial stretching/ axial compression insensitive, and calibration-free characteristics. The shape reconstruction error from discrete curvatures was online predicted from the perspective of transfer learning, which addressed the challenge of reconstruction error varying from geometric shape and reconstruction distance. The overall shape deviation was decreased by 53.4 %. The effectiveness and accuracy of the proposed deformation monitoring method was demonstrated by a dodecagonal circular antenna truss under non-uniform temperature environment, and achieved a measurement accuracy of 94.8 % and 96.0 % for 9.2 m distance under two conditions compared to the applied maximum deformations. The unique displacement transfer characteristics in clearances-containing discontinuous structures were detected for the first time, which will provide a novel means and new sight into kinematic mechanism understanding and closed-loop control of deployable antennas, soft robots and artificial muscles.