Abstract: A model order reduction (MOR) technique for linear dynamic systems is extended to allow the integration of nonlinear components. The main purpose is to build numerical model of complex systems as support of the design process leading to the exploitation of meta-structures. The selected method is applied to a soil-structure interaction case study.
Abstract: The use of Shape Memory Alloys in dampers devices able to reduce the wind, rain or traffic induced oscillations in stayed cables is well represented in the literature. An analysis realized on standard cables at existing facilities shows the reliable efficiency of the SMA wire in damping oscillations. Such studies also provide tools to build the SMA dampers and to account for the effects of the external temperature in the SMA. The particular study reported in this paper focuses on a critical discussion on the relation between the wire diameter and macroscopic behavior and external temperature effects. The damping requires the absorption of the mechanical energy and its conversion to heat via the action of hysteresis cycles. The study was realized on wires of different diameters. In particular, the study centers on wires of diameter 0.2, 0.5 and 2.46 mm. The flat cycles showed by the thin wires (i.e., diameter 0.2 and 0.5 mm) and the non-classical S-shaped cycles of wires of diameter 2.46 mm establish clear differences of the response under external summer-winter temperature actions. Depending of the room temperature and SMA composition, a complete flat transformation in thin wires requires stresses, in general, near 300-400 MPa. A complete transformation for an S-shaped cycle need stresses as higher as 600 MPa. The analysis of the behavior of these wires under the action of warm temperatures in summer and cold temperatures in winter, suggests that thin wires lose their pseudo-elastic state in winter. The S-shaped permits positive working in extended temperature domain and a supplementary investigation establishes that S-shaped can be increased by strain aging. The hysteretic behavior in S-shaped permits practical working under external temperatures as applications in bridges require. From a fundamental point of view, the flat cycles are coherent with the classical treatment of the SMA as a first order phase transition but the S-shaped can be considered associated to an anomaly in heat capacity.
Abstract: In recent years, vibration damping strategies based on semi-active management of strain energy have attracted a large interest and were proven highly effective. However, most of published research considers simple one degree of freedom systems or study the same basic example (the first vibration mode of a cantilever beam) with the same control strategy. This contribution focuses on truss-frame nodes with controllable moment-bearing ability. It proposes and tests an approach that allows the control strategy to be extended to more complex structures and vibration patterns.
Abstract: The author has developed many kinds of robotic fishes based on elastic oscillating fin propulsion system from 1989. The presentation describes past, present, and future robotic fish technologies, and applications of robotic fish technologies to various fields. Firstly, the history of the developed life-like robotic fish, such as sea bream in 1995, coelacanth in 1997, carp in 2000, shark ray in 2004 etc. is mentioned. The developed robotic fishes are basically propelled by vertical tail fin and operated by servo motors. Secondly, the life-like robotic dolphin was newly developed in 2013. The author developed tethered whale robot with horizontal tail fin propelled by hydraulic actuator in 1990s, however, the robotic dolphin is untethered and higher length, that is more than 1m, and has characteristic of fast cruising and higher maneuverability with horizontal tail fin propelled by servo motors. Thirdly, new application fields of robotic fish technologies, such as medical forceps and extractors, space robots which went to International Space Station and swam in the space, and current power plant using oscillating fin propulsion system for new offshore sustainable energy are described. Finally, robotic fish technologies for the next generation underwater vehicle are summarized.
Abstract: The unmanned aerial vehicle (UAV) is a light weight flight system that can carry sensors and cameras for data collection. Tremendous excitement surrounds the use of UAVs because they can be deployed easily and rapidly for data collection; they also can be programmed to execute missions with high degrees of autonomy. For these reasons, UAVs hold promise in accelerating the collection of data in geophysical explorations. In this study, a UAV platform is explored for the collection of data from geophones deployed to measure the vibrations of a concrete slab foundation. The UAV is designed to drop a weight as a controlled energy source. Both the energy and location of the impulsive load are adjustable by the flight parameters of the UAV. The study adopts a time-domain analysis for source localization using the dense array of geophones
Abstract: Shape memory alloys (SMA) provide common solid state actuators with reliable and unique characteristics. Their special behavior is based on a reversible phase transformation and can provide high power density, induced strain and block force which render them indispensable for use in morphing structures that require large shape changes while space and weight restrictions are imposed. Yet, their implementation into morphing structures faces challenges related to their complex multi-disciplinary behavior, their interaction with the passive structural components, geometrical nonlinearity due to large shape changes, the lack of experimental data, and above all, the lack of modelling tools which can robustly simulate the complex thermomechanical behavior and make feasible their design. We briefly review the material characterization process, the developed modelling tools which can simulate the complex thermomechanical response of morphing structures with SMA actuators which can undergo large shape changes under severe geometric nonlinearity, and the testing of prototype morphing components. The design and validation of two morphing structural concepts for curvature control are presented. A morphing strip capable to deform towards a single target shape is initially presented. Subsequently, a morphing airfoil concept implementing an articulated mechanism capable to achieve multiple target shapes for aerodynamic load control is presented. The challenging task to continuously adapt the structural shape to time varying demands, dictates the use of antagonistic actuator configurations to maximize and control the range of morphing. The previously mentioned morphing airfoil configuration is used to alleviate the aerodynamic fatigue loads in wind turbine blades and aircraft wings.
Abstract: A vision-based fuzzy controller for a quadrotor is proposed in this paper to realize ground target tracking. Due to the under-actuated property of quadrotors as well as the coupled dynamics in the image plane, it is challenging to design an image-based visual servoing controller for the quadrotor. Since the fuzzy control does not require an accurate model, a fuzzy-based approach is presented to solve the image-based tracking problem. Fuzzy controller takes image moments as inputs and its outputs are used to control the position of quadrotor in a form of tilt angles and vertical velocity adjustment. The proposed approach is verified by experiment.
Abstract: Aircraft morphing with regard to UAVs has recently gained incredible momentum; however, only a limited amount of research has been conducted on its effect on tailless aircraft. This is partly due to aerodynamic compromises such as directional instabilities that arise in the absence of a vertical stabilizer. Yet birds readily adapt to adverse flight conditions without vertical stabilizers and are unhindered with respect to stability and maneuvering due to their smooth continuous shape change and rapid muscle response. This research, motivated by the discrepancy between manmade and natural flight designs, investigates the aerodynamic effects of a smart morphing horizontal tail exhibiting bending-twisting coupling for yaw control on a bio-inspired aircraft. The structural response due to actuation was determined using Abaqus and coupled with a Reynolds-averaged-Navier-Stokes turbulence model for a low-Reynolds-number fluid analysis of the deformed shape. The morphing tail was simulated as piezoelectric Macro Fiber Composites with oriented PZT rods. Directional moment and stability derivative are presented to gain insight into the effect of the morphing horizontal tail on yaw control.
Abstract: This contribution reviews the challenges in adaptive self-protection of structures. A proper semi-active control strategy can significantly increase structural ability to absorb impact-type loads and damp the resulting vibrations. Discussed systems constitute a new class of smart structures capable of a real-time identification of loads and vibration patterns, followed by a low-cost optimum absorption of the energy by structural adaptation. Given the always surging quest for safety, such systems have a great potential for practical applications (in landing gears, road barriers, space structures, etc.). Compared to passive systems, their better performance can be attributed to the paradigm of self-adaptivity, which is ubiquitous in nature, but still sparsely applied in structural engineering. Being in the early stages of development, their ultimate success depends on a concerted effort in facing a number of challenges. This contribution discusses some of the important problems, including these of a conceptual, technological, methodological and software engineering nature.
Abstract: GALILEO together with EGNOS will provide more robust positioning capability enhancing the adoption of satellite technologies in services where signal continuity and integrity are required, such as those related to Public Regulated Service (PRS) and Safety of Life (SOL) applications. This will have an impact on various sectors and applications, including emergency and disaster management, Search and Rescue Service (SAR) tasks and location-based services (LBS) supporting responders in mission critical operations. In this scenario, in November 2013, the SPARTACUS project started to design, realize and test in simulated and real world scenarios GALILEO-ready tracking solutions that can be deployed in operative missions for enhancing Location Awareness in emergency management and crisis operations. SPARTACUS developed new EU-specific services to ensure precise positioning and timing capabilities to three application areas: 1) tracking, tracing and localization of critical transport assets in case of major failure of existing networks; 2) tracking the flow of relief support goods from the sending side to the receiving/end place; 3) supporting coordination of first responders in disaster management operations, ensuring their safety. By its Consortium, SPARTACUS innovations include hardware adaptations, algorithms for precision improvement, dead reckoning functionalities, location awareness, and ad-hoc independent communication networks.