Pablo Puerto

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Jade-Hochschule

Technical University of Munich

Luigi Maria Galantucci

Politecnico di Bari

Sabry El-hakim

Lindsay MacDonald

University College London

Armando Albertazzi

Simon Fletcher

University of Huddersfield

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Papers by Pablo Puerto

Analyses of Key Variables to Industrialize a Multi-Camera System to Guide Robotic Arms

Robotics

Robotic arms are widely used in sectors such as automotive or assembly logistics due to their fle... more Robotic arms are widely used in sectors such as automotive or assembly logistics due to their flexibility and cost. Other manufacturing sectors would like to take advantage of this technology, however, higher accuracy is required for their purposes. This paper integrated a multi-camera system to achieve the requirements for milling and drilling tasks in aeronautic parts. A closed-loop framework allows the position of the robot’s end-effector to be corrected with respect to a static reference. This is due to the multi-camera system tracking the position of both elements due to the passive targets on their surface. The challenge is to find an auxiliary system to measure these targets with an uncertainty that allows the desired accuracy to be achieved in high volumes (>3 m3). Firstly, in a reduced scenario, a coordinate measuring machine (CMM), a laser tracker (LT), and portable photogrammetry (PP) have been compared following the guidelines from VDI/VDE 2634-part 1. The conclusions...

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Calibration Procedure of a Multi-Camera System: Process Uncertainty Budget

Sensors

The Automated six Degrees of Freedom (DoF) definition of industrial components has become an adde... more The Automated six Degrees of Freedom (DoF) definition of industrial components has become an added value in production processes as long as the required accuracy is guaranteed. This is where multi-camera systems are finding their niche in the market. These systems provide, among other things, the ease of automating tracking processes without human intervention and knowledge about vision and/or metrology. In addition, the cost of integrating a new sensor into the complete system is negligible compared to other multi-tracker systems. The increase in information from different points of view in multi-camera systems raises the accuracy, based on the premise that the more points of view, the lower the level of uncertainty. This work is devoted to the calibration procedures of multi-camera systems, which is decisive to achieve high performance, with a particular focus on the uncertainty budget. Moreover, an evaluation methodology has been carried out, which is key to determining the level...

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A Study on the Uncertainty of a Laser Triangulator Considering System Covariances

Sensors, 2020

A laser triangulation system, which is composed of a camera and a laser, calculates distances bet... more A laser triangulation system, which is composed of a camera and a laser, calculates distances between objects intersected by the laser plane. Even though there are commercial triangulation systems, developing a new system allows the design to be adapted to the needs, in addition to allowing dimensions or processing times to be optimized; however the disadvantage is that the real accuracy is not known. The aim of the research is to identify and discuss the relevance of the most significant error sources in laser triangulator systems, predicting their error contribution to the final joint measurement accuracy. Two main phases are considered in this study, namely the calibration and measurement processes. The main error sources are identified and characterized throughout both phases, and a synthetic error propagation methodology is proposed to study the measurement accuracy. As a novelty in uncertainty analysis, the present approach encompasses the covariances of correlated system vari...

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A Comparison of Techniques to Measure the Wear Flat Area of Conventional and Superabrasive Grinding Wheels

Journal of Tribology, 2015

Wear of abrasive grains is one of the key issues influencing the grinding process and the resulti... more Wear of abrasive grains is one of the key issues influencing the grinding process and the resulting workpiece quality. Being able to quantify wheel wear in-process allows parameterization of grinding models that can help assuring part surface integrity. However, one of the main problems in measuring wear of abrasive grains is their small size, which makes this task to be not trivial. In this paper, several measuring techniques are compared in order to determine which one offers the best potential to quantify the wear of conventional and superabrasive grinding wheels. The selected techniques include optical macroscopy, optical microscopy, profilometry, and scanning electron microscopy (SEM). Among other results, direct comparisons of the same exact wear flat area measured with different techniques are shown.

Analysis of the behavior of grinding wheels in surface grinding

AIP Conference Proceedings, 2012

ABSTRACT Grinding is a machining process in which metal removal takes place through the action on... more ABSTRACT Grinding is a machining process in which metal removal takes place through the action on the workpiece of hard abrasive particles which are attached to the grinding wheel by a bond. The abrasive grains are sharp and irregular tiny particles with several cutting edges. The material removed from the workpiece has the shape of very small chips. The random nature of the distribution of cutting edges on the surface of the wheel and its changing layout produced by wear, makes it difficult to study the cutting mechanism of abrasive grains. The optimal selection of the grinding wheel, which is the cutting tool in grinding processes, improves some key aspects of the process, such as productivity, roughness, thermal damage, tool-life... The aim of this study is to determine a methodology in order to analyze and compare the performance of different grinding wheels for the same application.

Evolution of Surface Roughness in Grinding and its Relationship with the Dressing Parameters and the Radial Wear

Procedia Engineering, 2013

Grinding is a machining process specially indicated for finishing operations in hard materials, i... more Grinding is a machining process specially indicated for finishing operations in hard materials, in order to obtain low surface roughness (Ra 0.1 m to 2 m) and tight tolerances. The cutting tool is the grinding wheel which is formed by abrasive particles attached in a bond. The wear of these abrasive particles modifies significantly the roughness obtained in the workpiece. In this work, the evolution of part roughness has been continuously monitored as the grinding process progresses and the wheel gets worn. The roughness evolution is then related to different process variables such as the dressing parameters, the grinding conditions, the grinding forces and the radial wear of the wheel.

$The methodology to measure the different variables of the grinding process is explained in the next lines. Fig. 1. Micro-wear mechanisms in abrasive grains: sharp grit, attritious wear, grit fracture and bond fracture [4]$

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Methodology to Evaluate the Performance of Portable Photogrammetry for Large-Volume Metrology

Metrology

The increased relevance of large-volume metrology (LVM) in industrial applications entails certai... more The increased relevance of large-volume metrology (LVM) in industrial applications entails certain challenges: measurements must be cost-efficient and the technologies must be easy to use while ensuring accuracy and reliability. Portable photogrammetry shows great potential to overcome such challenges, but industrial users do not yet rely on its accuracy for large scenarios (3 to 64 m), especially when mass-market cameras are not conceived of as industrial metrology instruments. Furthermore, the measurement results might also depend on the operator’s skills and knowledge of the key process variables. In this work, a methodology was designed so that the measurement uncertainty of portable photogrammetry can be evaluated under controlled conditions for LVM. To do so, PTB’s reference wall, which was designed to assess laser-based methods applied to large volumes, was used as a reference artefact to study the measurement performance under different conditions, enabling an analysis of th...