1,720,966 research outputs found
Developing Advanced Shape Sensing Methodologies for Aerospace Applications
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Shape monitoring of morphing wing structures using the inverse Finite Element Method
Full text linkThis work presents a closed-loop control strategy for morphing wing structures where the feedback originates from monitoring the actual deformed shape of the morphed skin. The approach is based on the inverse Finite Element Method (iFEM), able to reconstruct the displacement field of a structure by minimizing, in a least squares sense, the error between the analytical strains and those experimentally measured in some discrete locations. Once the actual shape has been reconstructed, the actuation loads required to achieve the target shape are computed. The iFEM-based control strategy is assessed numerically on the example problem of a wing segment whose trailing-edge camber is modified via the morphing strategy. Actuation loads are represented by concentrated forces or by a distributed pressure, the effect of aerodynamic loads is taken into account, and strain data are measured on the top and bottom morphing skin. The results show accurate convergence to the target shape, thus demonstrating the potential of the proposed control-loop strategy
Full-field deformation reconstruction of beams using the inverse Finite Element Method: Application to thin-walled structures
Full text linkThis work presents a methodology for the real-time structural deformation reconstruction of solid or thin-walled prismatic beams using discrete strains. Based on the 1D inverse Finite Element Method (iFEM), the approach combines the beam kinematics of Timoshenko theory, strain–displacement relations, and the finite element discretisation framework to reconstruct the full-field deformations of beams with any general cross-section. Although applicable for any general class of beams, the present work investigates its experimental application specifically to conventionally and additively manufactured thin-walled beams discretised using various low and high-order inverse beam elements. The results demonstrate the method’s accuracy and robustness, albeit influenced by the element discretisation scheme and the number of strain sensors used
On the use of the inverse finite element method to enhance knowledge sharing in population-based structural health monitoring
Full text linkEfficient Structural Health Monitoring (SHM) is critical for ensuring safety and improving the operation and maintenance of aerospace structures. This study focusses on advanced shape-sensing methods, such as the inverse Finite Element Method (iFEM), which can estimate the complete displacement field of a structure based on a restricted number of strain measurements, fostering continuous and real-time monitoring. This approach additionally provides valuable insights into the dynamic behaviour of a structure by extracting its Frequency Response Functions (FRFs) and modal properties to perform vibration-based SHM. However, effectively extending SHM to a fleet or population of structures would require a significant amount of data for each one, which may be unavailable or incomplete. A population-based Structural Health Monitoring (PBSHM) strategy can solve data scarcity by sharing knowledge between similar structures via transfer-learning algorithms. In PBSHM, handling data from diverse sources is paramount for achieving accurate results. Therefore, this study integrates iFEM into the PBSHM framework, enhancing knowledge transfer by harmonising fibre-optic strain measurements to vibration-based features and providing reliable source data to inform diagnostics on similar structures. The proposed approach is validated on a population of laboratory-scale steel aircraft subjected to specific operating and damage conditions tested using three different sensor setups
A Multidisciplinary Design Optimisation (MDO) Algorithm for the Automatic Sizing of an Unmanned Lighter-Than-Air Platform
Full text linkThis study aims to present a Multidisciplinary Design Optimisation (MDO) algorithm for the automatic sizing and design of an Unmanned Lighter-Than-Air (LTA) platform, given its mission requirements. The mission in question consists of a territorial mapping, made possible through the implementation of several remote sensing onboard systems. Once assigned the parameters of the mission as inputs, the algorithm, through a process of iterations, returns the optimal sizing of the airship, shows the distribution of all the systems’ masses, and chooses the preferable energy system between the two considered (fuel cells or batteries). Moreover, a sensitivity analysis on the main variables allows to examine how the variation of each of the parameters of the mission affects the distribution of the masses in the airship, and therefore how the optimal design and sizing change. Finally, further studies on the energy systems are presented, to verify the convenience of one option above the other one as a function of the distance from the mission location and the survey area
Shape Sensing of Stiffened Plates Using Inverse FEM Aided by Virtual Strain Measurements
No full textThe inverse problem of structural deformation reconstruction using experimentally measured strains, known as ‘shape sensing’, is a topic with numerous applications in the field of Structural Health Monitoring (SHM). Existing shape sensing methods are influenced by the number and location of in-situ strain sensors used. A dense strainsensor array can produce accurate displacement predictions, whereas a sparse strain-sensor distribution leads to inaccurate predictions and possibly a breakdown of the method. In the latter cases, introducing virtual strain sensors can provide additional input strain data for the shape sensing method. This paper provides experimental validation of this coupled shape-sensing approach, using real and virtual strain data, for the displacement reconstruction of a stiffened aluminium plate instrumented with fibre optic sensors. The inverse Finite Element Method (iFEM) is the shape sensing technique employed, and two strategies are compared for producing virtual strain data: the Smoothing Element Analysis (SEA), and modal expansion. The experimental results presented demonstrate the effectiveness of the two strategies investigated
Shape sensing of plate structures using the inverse Finite Element Method: investigation of efficient strain-sensor patterns
Full text linkMethods for real-time reconstruction of structural displacements using measured strain data is an area of active research due to its potential application for Structural Health Monitoring (SHM) and morphing structure control. The inverse Finite Element Method (iFEM) has been shown to be well suited for the full-field reconstruction of displacements, strains, and stresses of structures instrumented with discrete or continuous strain sensors. In practical applications, where the available number of sensors may be limited, the number and sensor positions constitute the key parameters. Understanding changes in the reconstruction quality with respect to sensor position is generally difficult and is the aim of the present work. This paper attempts to supplement the current iFEM modeling knowledge through a rigorous evaluation of several strain-sensor patterns for shape sensing of a rectangular plate. Line plots along various sections of the plate are used to assess the reconstruction quality near and far away from strain sensors, and the nodal displacements are studied as the sensor density increases. The numerical results clearly demonstrate the effectiveness of the strain sensors distributed along the plate boundary for reconstructing relatively simple displacement patterns, and highlight the potential of cross-diagonal strain-sensor patterns to improve the displacement reconstruction of more complex deformation patterns
An Unmanned Lighter-Than-Air Platform for Large Scale Land Monitoring
Full text linkThe concept and preliminary design of an unmanned lighter-than-air (LTA) platform instrumented with different remote sensing technologies is presented. The aim is to assess the feasibility of using a remotely controlled airship for the land monitoring of medium sized (up to 107 m2) urban or rural areas at relatively low altitudes (below 1000 m) and its potential convenience with respect to other standard remote and in-situ sensing systems. The proposal includes equipment for high-definition visual, thermal, and hyperspectral imaging as well as LiDAR scanning. The data collected from these different sources can be then combined to obtain geo-referenced products such as land use land cover (LULC), soil water content (SWC), land surface temperature (LSC), and leaf area index (LAI) maps, among others. The potential uses for diffuse structural health monitoring over built-up areas are discussed as well. Several mission typologies are considered
Shape Sensing of Plate and Shell Structures Undergoing Large Displacements Using the Inverse Finite Element Method
Full text linkThe inverse Finite Element Method (iFEM) is applied to reconstruct the displacement field of a shell structure which undergoes large deformations using discreet strain measurements as the prescribed data. The iFEM computations are carried out using an incremental procedure where at each load step, the incremental strains are used to evaluate the incremental displacements which in turn update the geometry of the deformed structure. The efficacy of the proposed approach to predict large displacements is examined using two case studies involving a cantilevered wing-shaped plate and a clamped plate. The incremental iFEM procedure is demonstrated to be sufficiently accurate in terms of reproducing the correct nonlinear character of the load-displacement curve even when a reduced number of strain sensors is used. Therefore, this approach may have important implications for real-time monitoring of aerospace structures that undergo large displacements
DESIGN OF A PROTOTYPE UNMANNED LIGHTER-THAN-AIR PLATFORM FOR REMOTE SENSING: CONTROL, ALIMENTATION, AND PROPULSION SYSTEMS
Full text linkThis work presents several aspects related to the design of a new concept for a Remotely Piloted Aircraft System (RPAS), specifically, a Lighter-Than-Air (LTA) platform for the remote sensing of medium-sized rural and urban areas. The airship’s payload is intended to carry an array of sensors ranging from high-definition video cameras to hyperspectral sensors, a thermographic camera, and a LiDAR system, which all require power alimentation during low-speed surveying for fine mapping. Here, a fuel cell design solution, combined with supercapacitors, is proposed. The system is designed to provide energy for both the onboard sensors and the propulsion and thrust vector control system. In this regard, the design and optimization of the propeller blades, using Blade Element Momentum Theory (BEMT), is discussed as well, in a multidisciplinary optimisation fashion. A twin paper describes the other structural aspects of the airship design
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