Interactive control of manufacturing assemblies with Mixed Reality

The aim of this work is an efficien methodology development for a real-time control of human assembling sequences of mechanical components. The method involves a CAD environment, an hardware system, referred to as a PAA (Personal Active Assistant), and a set of Mixed Reality features. The whole scheme is targeted to positively influence the connection between CAD and Mixed Reality in order to proficiently reduce the gap between engineers and manual operators. The system is based on a CAD assembly module and on a Mixed Reality wearable equipment. It can be used to improve several activities in the industrial field, such as operator professional training, optimal assembly sequence seeking or on-field teleconferencing (suitable for remote collaboration or for full exploitation of Concurrent Engineering suggestions during design and set up stages). The main characteristic o PAA is a real-time wireless linkage to a remote servere or designer workstation, where project geometric database is stored. The Mixed Reality wearable equipment consists of an optical see-through display device and a PAA head-mounted camera. The user can freely operate in the mixed environment, while the camera can record the human driven assembly sequence and check the efficiency and correctness via object recognition: an incrementally sub-assembly detection algorithm has been developed in order to achieve complex dataset monitoring. Conversely, designer or assembly planner can exploit the peculiarities of Mixed Reality-based assembly: a straightforward interaction with assembly operator can be obtained by sending vocal advices or by displaying superimposed visual information on the real scene. In the paper a new method for CAD models and Mixed Reality environment integration will be presented and discussed in order to improve and simplify personnel training or warehouse part seeking

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\ub0 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

Design for disassembly (DfD) and augmented reality (AR): Case study applied to a gearbox

open5noToday's market drives companies to change, adapt, and compete. Many consumers are increasingly looking at price, without sacrificing quality. In order to be attractive to the customer, companies must be able to offer the required quality at the lowest possible price. The life cycle of many products has been shortened compared to the past because now technologies are evolving faster. For these reasons, it is important that companies reevaluate all the operations that are carried out within them, to optimize them and eventually adopt new technologies if they offer interesting opportunities. In this discussion, we first study the design for disassembly, a technique that can bring several advantages during the life cycle of a component, offering the possibility of reducing time and cost of disassembling a product, and better reuse of the different materials of which it is composed. Subsequently, augmented reality is discussed, and how this technology is exploited in the world, especially in the industrial sector. During the work, we discuss a case study, with the gearbox being the object of analysis. This allows us to apply the theoretical concepts illustrated in a concrete way, allowing for a better understanding of the topics.openFrizziero L.; Liverani A.; Caligiana G.; Donnici G.; Chinaglia L.Frizziero L.; Liverani A.; Caligiana G.; Donnici G.; Chinaglia L

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 thatnon-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

Fairing with neighbourhood LOD filtering to upgrade interactively B-Spline into Class-A curve

Class-A curves show very appreciable features in terms of smoothness and curvature trend that is commonly perceived as high quality profiles. These curves are commonly sketched by experienced operators, but at the present day no tools are available to transform a B-spline into a Class-A curve. The k-neigh-fast is an improved version of k-neighbours algorithm, described in Amati et al. (Comput Graph 30(3):345\u2013352, 2006), aiming to transform a B-spline non-Class-A slope into a B-spline Class-A curve by manipulating a group of k geometric coefficients. Once the level of detail (LOD) representation of a curve has been computed, the kneigh-fast algorithm, detects those control points representing non-Class-A imperfections. At each LOD, the algorithm individuates the detail coefficient maximizing the internal functional. Then k-neighbours has been modified applying filtering criteria. A control step starts to verify the transformation from a non-Class-A curve into a Class-A shape. This process is repeated until the chosen stopping condition is satisfied. The final shape with improved smoothness and monotonic curvature is achieved through manual procedure. This paper reports results dealing on an improved and faster wavelet-based LOD filtering implementation used to generate very smooth set of profiles that own to Class-A set. The LODs representation allows to divide curves into their coarser least-square approximations and details coefficients. The extraction and manipulation of details with multi-level filtering, allows to determine geometric imperfections. This method has been tested to the smoothing of the hull profile of ships: results are good since the non-A-curve are well converted in smoother lines. A more efficient implementation, based on a flexible LOD representation led to prove many benefits of this techniques; the tests performed exploiting a computer program implementation have demonstrated very good results in most of simulations considered

A spatial tracked touch screen for computer aided sketching

This paper describes the development of an innovative harware and software tool useful to sketch planar shapes in Computer-Aided Industrial Design and Computer Aided Design systems. The whole system is composed by a portable hand-held small touchscreen, a large fixed main screen and an optical tracking equipment. The touch-screen is added by a simple camera for Mixed Reality optional functionality and its 6 degrees of freedom movements are tracked through four groups of Light Emitting Diodes located on back of the monitor. A Nintendo WiiMote with infrared camera is used to acquire Light Emitting Diodes relative positions for real-time tracking. A 6 degrees of freedom Inertial Measurement Unit has been added to improve the stability of the pose estimation: an Extended Kalman Filter provides the data fusion. Furthermore, a custom software has been implemented for optimal exploitation of a such configured hardware and facilitate input and 3D sketching. The physical tablet can be used in three different ways: as a 3D mouse which sets the point of view of the main screen according to its attitude, to set a plane in the main screen so that a 2D sketch can be referenced in the 3D space and as a support device to improve the manual draw of an object by overwriting the image contour. The results obtained confirms the usefulness of the virtual tablet in design, modelling, and reverse engineering of industrial products

General anisotropic doubly-curved shell theory: A differential quadrature solution for free vibrations of shells and panels of revolution with a free-form meridian

The Generalized Differential Quadrature (GDQ) method is applied to study the dynamic behavior of anisotropic doubly-curved shells and panels of revolution with a free-form meridian. The First-order Shear Deformation Theory (FSDT) is used to analyze the above mentioned moderately thick structural elements. In order to include the effect of the initial curvature in the evaluation of the stress resultants three different approaches, specifically Qatu approach, Toorani\u2013Lakis approach and Reissner\u2013Mindlin approach, are considered and compared. An improvement of the Classical Reissner\u2013Mindlin Theory (CRMT) using a different kinematical model is considered. By so doing a generalization of the theory of anisotropic doubly-curved shells and panels of revolution is proposed. Four different anisotropic shell theories, namely General First-order Shear Deformation Theory by Qatu (GFSDTQ), General First-order Shear Deformation Theory by Toorani\u2013Lakis (GFSDTTL), General First-order Shear Deformation Theory by Reissner\u2013Mindlin (GFSDTRM) and Classical Reissner\u2013Mindlin Theory (CRMT), are compared in order to show the differences and the accuracy of these theories. The solution is given in terms of generalized displacement components of points lying on the middle surface of the shell. Simple Rational Be\ub4 zier curves are used to define the meridian curve of the revolution structures. Results are obtained taking the meridian and circumferential coordinates into account, without using the Fourier modal expansion methodology. Furthermore, GDQ results are compared with those obtained by using commercial programs such as Abaqus, Ansys, Nastran, Straus and Pro/Mechanica. Very good agreement is observed