Semi-active and active control of vibrations via shape morphing

• Applicant: Arka Prabhata Reksowardojo, Ph.D.
• Subject Area: Applied Mechanics, Statics and Dynamics ; Structural Engineering, Building Informatics and Construction Operation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547150077

Load-bearing structures are usually engineered to meet strength and deformation requirements under extreme and thus infrequently occurring loads. This means that load-carrying capacity is generally underutilized for a significant majority of the lifespan. Adaptive structures incorporate sensors and actuators that enable the modification of geometry and internal forces. This integration allows adaptive structures to achieve optimal responses in terms of strength and deformation criteria across a wide range of service conditions, rather than just one extreme condition with a long return period. Vibration control has gained some level of acceptance in the context of load-bearing civil structures, driven by the general trend towards lightweight and ultra-slender constructions with less inherent damping and lower eigenfrequencies. However, the widespread adoption of active control systems that rely on the application of response-dependent direct control forces remained inhibited by the high operational energy requirements, as well as reliability issues in countering high-amplitude, high-velocity pulse-like disturbances (e.g., seismic and vehicular excitations) common in load-bearing civil structures. The objective of this project is to showcase the potential of semi-active and active vibration control strategies based on shape morphing. The application will focus on discrete, non-continuous structures (e.g., trusses, frames, cable-strut systems). These structures will be designed to reconfigure via controlled deformations into target shapes that eliminate resonant conditions. Through shape optimization, target shapes will be obtained to ensure a sufficient gap between the eigenfrequencies of the structure and the dominant frequency component of the excitation. This approach is considered a semi-active control since actuation efforts are only required during shape reconfigurations. To assess the operational energy requirements of the proposed semi-active control strategy, it will be benchmarked against state-of-the-art strategies based on state-feedback controllers. Also within the scope of the investigation is an active control strategy that combines shape morphing with a conventional state-feedback controller. To account for nonlinearities stemming from shape reconfiguration, a gain scheduling approach involving linear parameter-varying (LPV) systems will be adopted. A small-scale prototype of a shape-morphing bridge will be built and tested to validate the feasibility of the proposed control strategies.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professorin Ann C. Sychterz, Ph.D.