Luis M. Matey

A large haptic device for aircraft engine maintainability

The virtual reality for maintainability (Revima) VR system supports maintainability simulation in aeronautics. Within this project we have developed and integrated a haptic device, the large haptic interface for aeronautic maintainability (LHIfAM). We use this device to track hand movements and provide force feedback within the large geometric models that describe aircraft engines. The user movements are the same as those that occur when testing physical mock-ups. An integrated haptic device and VR system for testing aircraft engines reduces development costs and avoids the necessity of physical mock-ups formaintainability.

Description of a haptic system for virtual maintainability in aeronautics

This paper describes a haptic system for maintainability simulation in aeronautics, called REVIMA (Virtual Reality for Maintainability). In this project a software-hardware tool is designed and built to realistically simulate assembly-disassembly operations. It also helps to perform accessibility, interference and maintainability analysis by using virtual reality techniques without physical mock-ups. The system gives the user a reliable and realistic response. In order to achieve these requirements, the device has a workspace similar to the size of a turbo-engine. In addition this workspace can be placed in different positions to study ergonomics aspects of the simulated tasks.

PolyJet technology for product prototyping: Tensile strength and surface roughness properties

Design and manufacturing engineers are not fully aware of the different possibilities that PolyJet™ technology offers. The goal of this article is to provide the design and manufacturing engineers with greater knowledge about the final properties of parts printed with PolyJet rapid prototyping technology. This knowledge includes the effect of printing orientation and post-processing on the mechanical and surface properties of printed parts. Eighteen different samples considered all the possible printing orientations and the surface finishing treatments recommended by the manufacturer. These finishing properties include part printing using the matte/glossy option and removal of the support material using water pressure and/or a caustic soda bath. Tensile tests and surface roughness measurements were analysed for the printed samples using the statistical design of experiments in order to determinate the influence of the printing orientation and finishing properties on the results. These tests showed that the part orientation has a significant effect on elastic modulus and fracture stress while there is no statistical significance on ultimate tensile strength. With regard to the finish, none of the tensile test outputs showed significant differences. In terms of roughness, the analysis of variance indicated that position and finish presented statistically significant differences between the means of the three roughness directions. From all these experiences, it is possible to conclude that the glossy finish and the xy printing direction worked very well regarding roughness, whereas the critical load direction of the part should be placed along the x-axis when printing.

Approximation of Optimal Voxel Size for Collision Detection in Maintainability Simulations within Massive Virtual Environments

This paper describes a Collision Method for massive virtual environments composed of millions of triangles. It has been applied in the aeronautics industry for maintainability simulations using virtual aircraft engine mock‐ups. The method performs well and has a good interactive frame rate even when it is used for computing force feedback with haptic devices. Space sorting problems chiefly related to voxel techniques, such as memory requirements and optimal voxel size, have been solved. We use advanced memory structures and hashing techniques. To find the optimal voxel size, several analytical solutions have been proposed and compared. These solutions are based on the performance cost function of the algorithm used. Experiments have been undertaken to verify these analytical solutions.

Path‐planning techniques for the simulation of disassembly tasks

Purpose – This paper aims to develop path‐planning techniques that support a general selective disassembly planner in a virtual reality environment.Design/methodology/approach – The paper presents an automatic selective disassembly planning and two path‐planning techniques that support it. The first one is based on single translations, while the second is based on the generation of a random search tree. The methods used have been adapted and modified from available robotic path‐planning methods for their use in disassembly path planning.Findings – The paper finds that the proposed techniques are applicable to the automatic generation of disassembly sequences.Research limitations/implications – The paper provides an automatic tool that can be integrated in simulation software for the analysis and validation of disassembly operation.Practical implications – Maintenance operations have a great impact in the security and life expectancy of any product. This is especially true for some applications such as aer...

Modeling of Shotcrete Application for Use in a Real‐Time Training Simulator

This article describes how simulators can provide significant advantages for training operators of concrete spraying machinery. These advantages include economic savings, the practical absence of safety risks, and environmental and educational benefits. The main challenge in developing a real-time training simulator for concrete spraying machinery lies in the modeling of shotcrete application. A novel method that models and simulates in real time is presented in this article. The three main factors that influence shotcrete sprayability are adhesion, cohesion, and rebound. Furthermore, the method presented makes it possible to spray onto additional supporting elements, which is a typical shotcrete application. The proposed method considers a wet-mix thick flow spraying process and is based on experiments that were run with a real concrete spraying machine and complemented by expert advice. A method was developed and evaluated in this paper using a user-centered methodology that resulted in realistic shotcrete application modeling that meets the needs for training machinery operators.

Automatic extraction of the topology of 3D electrical mock-ups using a mixed octree-voxel method

This paper presents a method for the automatic identification of wiring routing and electrical topology of large aircraft harnessing mock-ups. This task constitutes one of the initial steps of an enrichment process that seeks to add electrical information to the 3D geometrical representation of the mock-ups in order to perform thermal and electrical simulations with them. The proposed solution uses spatial partition techniques of the scene containing the mock-up, combining both octrees and voxels. This method analyses large mock-ups and offers a good resolution of the wire routing with a low execution time. Results of the implementation are presented and compared with similar algorithms that use alternative partitioning techniques.

Temporal Nearest End-Effectors for Real-Time Full-Body Human Actions Recognition

In this paper we present a novel method called Temporal Nearest End-Effectors (TNEE) to automatically classify full-body human actions captured in real-time. This method uses a simple representation for modeling actions based exclusively on the recent positions of the users end-effectors, i.e. hands, head and feet, relative to the pelvis. With this method, the essential information of full-body movements is retained in a reduced form. The recognition procedure combines the evaluation of the performed poses and the temporal coherence. The performance of TNEE is tested with real motion capture data obtaining satisfactory results for real-time applications.

Towards Adaptive Occlusion Culling Using Camera Coherence

Occlusion culling proves to be useful for the interactive visualization of environments that are not densely occluded. Those which are built up by dense geometric sets like aerospace engines composed of thousands of components and millions of polygons. In first place the convenience of using occlusion culling is studied with a simple scheme. Then improvements are analyzed. The key points to obtain frame rate speed-ups are: a convenient occlusion query scheduling provides the performance required; depth sorting is performed only when camera orientation changes more than a given threshold; coherence reduces the number of occlusion queries posted per frame. It is possible to select the percentage of occlusion queries that will be performed in each frame, from non-conservative schemes up to a conservative one. Furthermore, we propose a small addition to the GPU occlusion queries to perform faster renderings

Collision problem: characteristics for a taxonomy

The collision problem appears within many fields. The specific characteristics that can be identified in different problems lead to the broad set of specialized algorithms that appear in the literature. This paper deals with the first step needed to address the collision problem taxonomy challenge: a survey that compiles and suggests a set of characteristics that could be used to discriminate collision problems, i.e. to generate the taxonomy.