Alfredo Liverani

A CAD-augmented reality integrated environment for assembly sequence check and interactive validation

An integrated environment based on CAD assembly software and on an Augmented Reality wearable system is used to improve the overall integration between engineering design and real prototypes manufacturing. The environment following called – Personal Active Assistant (PAA) – exploits a CAD tool connection to remarkably improve object recognition, best assembly sequence optimization, and operator instructions generation. PAA is real-time and wirelessly linked to a remote server or designer workstation where project geometric database is stored. The PAA head-mounted camera is also able to acquire the human-driven assembly sequence and check the efficiency and correctness via object recognition: an incremental sub-assembly detection algorithm has been developed in order to achieve complex dataset monitoring. On the other hand, the Augmented Reality-based assembly evaluation tool allows engineers to interact directly with the assembly operator while manipulating the real and virtual prototype components. Information from the assembly planner can be displayed, directly superimposed, on the real scene by using a see-through head-mounted display. Thus the new combined software and hardware equipment may be considered a step ahead in the support of true concurrent engineering and remote collaboration, strongly improving this latter through a better heterogeneous task integration. Several tests have been performed also to achieve personnel training and warehouse part seeking.

A fast interactive reverse-engineering system

A new method of reverse engineering for fast, simple and interactive acquisition and reconstruction of a virtual three-dimensional (3D) model is presented. We propose an active stereo acquisition system, which makes use of two infrared cameras and a wireless active-pen device, supported by a reconstruction method based on subdivision surfaces. In the 3D interactive hand sketching process the user draws and refines the 3D style-curves, which characterize the shape to be constructed, by simply dragging the active-pen device; then the system automatically produces a low-resolution mesh that is naturally refined through subdivision surfaces. Several examples demonstrate the ability of the proposed advanced design methodology to produce complex 3D geometric models by the interactive and iterative process that provides the user with a real-time visual feedback on the ongoing work.

Towards interactive finite element analysis of shell structures in virtual reality

A first step towards a semi-immersive virtual reality (VR) interface for finite element analysis (FEA) is presented in this paper. During recent years, user interfaces of FEA solvers have matured from character-based command-line driven implementations into easy-to-use graphical user interfaces (GUIs). This new generation of GUIs provides access to intuitive and productive tools for the management and analysis of structural problems. Many pre- and post-processors have been implemented targeting the simplification of the man-machine interface in order to increase the ease of use and provide better visual analysis of FEA solver results. Nevertheless, none of these packages provides a real 3D-enabled interface. The main objective of this project is to join state-of-the-art visualization technology, VR devices, and FEA solvers into the integrated development environment VRFEA.

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.

CAD-CAM integration for 3D Hybrid Manufacturing

Hybrid Manufacturing (HM) is oriented to combine the advantages of additive manufacturing, such as few limits in shape reproduction, good customization of parts, distributive production, minimization of production costs and minimization of waste materials, with the advantages of subtractive manufacturing, in terms of finishing properties and accuracy of dimensional tolerances. In this context, our research group presents a design technique that aims to data processing that switches between additive and subtractive procedures, to the costs and time of product-manufacturing optimization. The component prototyping may be performed combining different stages (addiction, gross milling, fine milling, deposition…) with different parameters and head/nozzles and is able to work with different materials either in addictive, either in milling. The present paper is dedicated to introduce different strategies, or in other terms, different combinations of machining features (addictive or deductive) and different materials to complete a prototype model or mold. The optimization/analysis piece of software is fully integrated in classic CAD/CAM environment for better supporting the design and engineering processes.

Mobile tracking system and optical tracking integration for mobile mixed reality

Augmented Reality AR technology is becoming more available for everyday applications, providing advanced information about the observed objects. In this paper we present a system combining optical tracking and augmented reality with applications in local large areas. We use two different tracking technologies for positioning objects: the infrared marker-based motion capture system OptiTrack and the Vuforia software platform, which enables augmented reality app across the real world environment. We present a robust solution for communication between a client mobile platform and a server that computes all global tracking data. This technology has high potential for end users and can be of great benefit.

From spline to Class-A curves through multi-scale analysis filtering

This paper reports the work on a novel wavelet-based multi-scale filtering application used to generate very smooth subset of profiles known as Class-A curves. The multi-scale representation, based on B-spline wavelets, allows to split a spline curves in terms of a coarser least-square approximation and details coefficients. It raises that non-Class-A curves are determined by geometric imperfections strongly connected to the details coefficients. The extraction and manipulation of details with multi-scale filtering allows to select and evaluate geometric imperfections. Finally, an efficient algorithm devoted to improve a given non-Class-A profile to a Class-A curve has been implemented and tested with several examples in order to check and visualize the results.

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.