Alessandro Ceruti

Airship Research and Development in the Areas of Design, Structures, Dynamics and Energy Systems

Recent years have seen an outpour of revived interest in the use of airships for a number of applications.Present day developments in materials, propulsion, solar panels, and energy storage systems and the need for a more eco-oriented approach to flight are increasing the curiosity in airships, as the series of new projects deployed in recent years show; moreover, the exploitation of the always mounting simulation capabilities in CAD/CAE, CFD and FEA provided by modern computers allow an accurate design useful to optimize and reduce the development time of these vehicles.The purpose of this contribution is to examine the different aspects of airship development with a review of current modeling techniques for airship dynamics and aerodynamics along withconceptual design and optimization techniques, structural design and manufacturingtechnologies and, energy system technologies. A brief history of airships is presented followed by an analysis of conventional and unconventional airships including current projects and conceptual designs.

Tablet-based 3D sketching and curve reverse modelling

This paper describes the development of an innovative hardware and software tool useful to sketch planar shapes in computer aided industrial design and computer aided design systems. The proposed system is based upon a tracked touch screen hand-held by the designer. The whole system is composed by a portable hand-held small touch screen (tablet size), a fixed LCD display and an optical tracking equipment. The touch screen is added by a simple camera for mixed reality optional functionality and its 6° of freedom movements are tracked. A custom software has been implemented for optimal exploitation and 3D sketching. The system acts as a free sketching device, a 3D mouse, as a realtime virtual and physical sketching plane or an external shape remodelling tool. The results obtained confirm the benefits of the virtual tablet in design, modelling and reverse engineering of industrial products.

Augmented Reality to Support On-Field Post-Impact Maintenance Operations on Thin Structures

This paper proposes an augmented reality (AR) strategy in which a Lamb waves based impact detection methodology dynamically interacts with a head portable visualization device allowing the inspector to see the estimated impact position (with its uncertainty) and impact energy directly on the plate-like structure. The impact detection methodology uses a network of piezosensors bonded on the structure to be monitored and a signal processing algorithm (the Warped Frequency Transform) able to compensate for dispersion the acquired waveforms. The compensated waveforms yield to a robust estimation of Lamb waves difference in distance of propagation (DDOP), used to feed hyperbolic algorithms for impact location determination, and allow an estimation of the uncertainty of the impact positioning as well as of the impact energy. The outputs of the impact methodology are passed to a visualization technology that yielding their representation in Augmented Reality (AR) is meant to support the inspector during the on-field inspection/diagnosis as well as the maintenance operations. The inspector, in fact, can see interactively in real time the impact data directly on the surface of the structure. To validate the proposed approach, tests on an aluminum plate are presented. Results confirm the feasibility of the method and its exploitability in maintenance practice.

Multi-Disciplinary Design Optimization of Unconventional Airship Configurations with Heuristic Algorithms

This paper describes the Multi Disciplinary Optimization of an airship with unconventional configuration. The shape of the airship is based upon two semi-ellipsoids, whose axis ratios can be altered for optimization purpose. The parameters to optimize are: volume, ratio between longitudinal and lateral semi-axis, ratio between vertical and lateral semi-axis, percentage of the top surface covered by photovoltaic films, dimension of the tail. The goals of the optimization are: equilibrium between buoyancy and weight, reaching of the design speed, static longitudinal stability of the vehicle. The mathematical model developed to evaluate airship features includes the computation of the ballonet volume, a weight breakdown, the energy storage for night operations, the power system evaluation and stability considerations. Six heuristic optimization strategies have been applied in order to achieve the best solution; some case studies have been developed and the final optimal configurations found by algorithms have been analyzed in order to validate the optimization framework. The approach demonstrate that the heuristic optimization strategies used are good tool for the conceptual design of unconventional airship since this problem requires a multi-disciplinary approach and several parameters including aerodynamics, propulsion, mass breakdown, aerostatics and stability, which are strongly dependent each other, must be jointly considered and addressed at the same time to obtain an optimum and balanced design.

Heuristic optimization of Bezier curves based trajectories for unconventional airships docking

Purpose This paper aims to describe a methodology to optimize the trajectory of unconventional airship performing a high-altitude docking manoeuvre. Design/methodology/approach The trajectories are based upon Bezier curves whose control points positions are optimized through particle swarm optimization algorithm. A minimum energy strategy is implemented by considering the airship physical properties. The paper describes the mathematical model of the airships, the trajectories modelling through Bezier’s curves and the optimization framework. A series of test cases has been developed to evaluate the proposed methodology. Findings Results obtained show that the implemented procedure is able to optimize the airship trajectories and to support their in-flight docking; a strong influence of the wind speed and course on the trajectories planning is highlighted. Research limitations/implications The wind speed considered in these simulations depends only on altitude, and gusts effect has been neglected. Practical implications The proposed model can support the study of unconventional airship trajectories and can be useful to evaluate best in-air docking strategies. Originality/value The paper addresses the problem of trajectory optimization for a class of new air vehicles with an heuristic approach.

Design for Additive Manufacturing Using LSWM: A CAD Tool for the Modelling of Lightweight and Lattice Structures

This paper presents the development of a CAD conceived to support the modelling of lightweight and lattice structures just from the initial stages of the design process. A new environment, called LWSM (acronym of LightWeight Structures Modelling), has been implemented in Python programming language in an open-source CAD software to allow the fast modelling of several sandwich structures or the filling of solid parts with cubic and tetrahedral lattice structures which can be produced by Additive Manufacturing (AM) techniques. Several tests have been carried out to validate the tool, one of which is included in the paper. The design of a bracket component inside LWSM using a traditional dense geometry and a lattice structure is described. The use of Design for Additive Manufacturing (DfAM) functions helps the user in the design of innovative structures which can produced only with AM technologies. A significant change in the shape of the part respect to traditional solutions is noticed after the use of DfAM functions by experimenters: FEM analysis confirms a strong weight reduction.

Use of Augmented Reality in aircraft maintenance operations

This paper illustrates a Human-Machine Interface based on Augmented Reality (AR) conceived to provide to maintenance operators the results of an impact detection methodology. In particular, the implemented tool dynamically interacts with a head portable visualization device allowing the inspector to see the estimated impact position on the structure. The impact detection methodology combines the signals collected by a network of piezosensors bonded on the structure to be monitored. Then a signal processing algorithm is applied to compensate for dispersion the acquired guided waves. The compensated waveforms yield to a robust estimation of guided waves difference in distance of propagation (DDOP), used to feed hyperbolic algorithms for impact location determination. The output of the impact methodology is passed to an AR visualization technology that is meant to support the inspector during the on-field inspection/diagnosis as well as the maintenance operations. The inspector, in fact, can see interactively in real time the impact data directly on the surface of the structure. Here the proposed approach is tested on the engine cowling of a Cessna 150 general aviation airplane. Preliminary results confirm the feasibility of the method and its exploitability in maintenance practice.

Meta-heuristic multidisciplinary design optimization of wind turbine blades obtained from circular pipes

Aim of this paper is to present a methodology useful to optimize the geometry of the blades of a small-size wind turbine which are obtained from a circular pipe: an optimal chord distribution and airfoil sweep can be obtained with a proper cutting path. A strong reduction in manufacturing costs and time can be achieved for blades which are a critical element in wind turbine systems, especially in case of renewable plants in developing countries. An algorithm has been developed to obtain the shape of the blades and wind turbine performances are computed by the Blade-Element Method, due to its low computational simplicity; the XFoil tool has been used to compute the aerodynamic of the blades. Heuristic algorithms have been applied to obtain a feasible design solution assuring the best efficiency of the wind turbine. Also structural considerations are kept into account to provide a feasible configuration able to withstand the forces acting on the rotating blades. Results obtained suggest that an optimal design of such a kind of blades can be obtained thanks to this methodology. The mathematical framework developed for the optimization is efficient and the heuristics algorithms allow the convergence to feasible configurations. The computing time is compatible with a practical application of the method also in industries.

Integrated geometrical and dimensional tolerances stack-up analysis for the design of mechanical assemblies: an application on marine engineering

This paper presents a knowledge based engineering environment methodology to support the designer in the correct setting of geometrical and dimensional tolerances in assemblies of mechanical compon...

Visual Aided Assembly of Scale Models with AR

The study of the methodologies useful to support the assembly of parts is a challenging engineering task which can benefit of the most recent innovations in computer graphics and visualization technologies. This paper presents a proposal for an innovative methodology based on Virtual and Augmented Reality useful to support the components’ assembly. The herein introduced strategy is based upon a four stages procedure: at first the designer conceives the assembly sequence using a CAD system, visualizing the scene wearing an immersive Virtual Reality device. In the second stage, the same sequence is developed by an unexperienced user using the same equipment: the differences between two assembly sequences are recorded and exploited to detect critical points in the assembly sequence and to develop a Knowledge Based System. Finally, a virtual user manual is produced in Augmented Reality. When the final user uses the tool, the position of the object to assemble is detected by tracking the finger position of the user itself. A series of symbols and writings is added to the external scene to help the end-user in the assembly procedure. A test case based on the assembly of a scale model has been developed to evaluate the methodology. After an evaluation process, the procedure seems to be feasible and presents some advantages over the state-of-the-art methodologies proposed by literature.