New Distributed Fibre Optic 3DSensor with Thermal Self-Compensation System: Design, Research and Field Proof Application inside Geotechnical Structure

Thanks to the dynamic development of advanced building technologies as well as the growing awareness, experience and responsibilities of engineers, structural health monitoring systems (SHM) are increasingly applied in civil engineering and geotechnical applications. This is also facilitated by the construction law and standard requirements, e.g., the observation method for geotechnical structures described in the Eurocode 7. Still, the most common approach is to apply spot sensors in selected points of the structure to validate theoretical models, numerical simulations and support technical assessments by involving statistic and approximation methods. The main limitation of spot sensing is the inability to detect localized damages such as cracks, fractures, sinkholes or shear planes. Thus, such analysis is subject to considerable uncertainty, especially within geotechnical structures, characterized by random mechanical parameters that change with location, but also over time. Another approach is based on distributed fibre optic sensors (DFOS), which are finding a growing acceptance in laboratory and field projects, overcoming limitations of conventional measurements. The design and applications of new DFOS dedicated for 3D displacement sensing are described hereafter in the article. The novelty of the presented solution lies in several features, including design, application, production technology and materials. This article is focused on the operational rules governing DFOS and proving their effectiveness in laboratory and geotechnical field applications.

Compensation system design of disturbing torques for a magnetically suspended sensitive gyroscope with double spherical envelope surfaces

Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. But the high accuracy is sensitive to various disturbing torques acting on the rotor. In order to compensate for the drift errors produced by disturbing torques, this paper proposes a compensation system of Lorentz force magnetic bearings. Based on the geometric construction and running regularity of the compensation system, the analytical expression of the compensation torque has been deduced, and the generation mechanism of the compensation torque is revealed, which laid the foundation for the design of high-precision MSSGs. The common issues caused by disturbing torques can be effectively resolved by the proposed method in gyroscopes with a levitating rotor. To verify the feasibility and superiority of this compensation method, comparative simulations are carried out before and after the disturbing torques were compensated.