64 research outputs found

    On semi-active inerters for improving machining productivity

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    The inerter is a mechanical element, synthesised in 2002 as an analogue to the electrical capacitor. Originally used in Formula 1 racing as the `J-damper', its potential has since been explored in other vehicles, as well as for vibration control of civil structures. In very recent years, some study has been given to the design and control of semi-active inerters. Such devices would be capable of varying their inertance in response to a control signal. To date, no study has been made of the semi-active inerter in the context of machining chatter. This undesirable form of vibration, leading to poor surface finish on machined parts, is a major issue in machining. The growing requirements of high speed machining of lightweight, flexible parts mean that the need to develop new strategies to tackle chatter will only increase. This thesis seeks to fill this gap in the literature. As a feasibility study, two chatter suppression strategies are developed using a simplified single degree of freedom chatter model. Both strategies assume the existence of an ideal semi-active inerter placed between the vibrating element and ground, allowing the natural frequency to be adjusted on-line. The first of these strategies, discrete inertance variation, is analogous to an existing lobe seeking strategy conducted by changing the spindle speed. It is shown that, with relatively modest ranges of inertance, this is an achievable strategy for high speed machining. The second strategy relies on cyclically adjusting the natural frequency to disrupt self-excited vibration. It is found that the amplitude of this variation is the important characteristic, rather than the ratio of the frequency of inertance variation to the tooth passing frequency. In both cases, the need to be able to rapidly control inertance is noted. The design needs of a semi-active helical inerter are considered, with magnetorheological fluid providing the semi-active control. Three different layouts are studied using quasi-static models. The bypass valve type layout is selected as the most promising for future study. The design of the valve is considered and a new optimisation scheme is developed which better suits the need of the bypass valve than previous schemes. The inerter model is extended into a quasi-dynamic model, which allows the varying inertance to be considered. This model would be key for developing any practical control scheme. Prototype inerters were designed and tested. Initially an oil-based designed is built, followed by a design using magnetorheological fluid. The prototype was tested using a servo-hydraulic actuator, with the goal of validating the models developed in the previous chapter. Unfortunately, trapped air in both systems led to these results being inconclusive in both cases. The use of magnetorheological fluid for flow directional control in this way is unusual at this scale and this work is important for any future researchers who wish to work with the fluid in this way. With this in mind, the issues encountered with the experimental rig are further analysed. Improvements to the design and filling method are proposed. Some more substantial design changes are also presented. Finally, some focus is given to the practical issues of implementing semi-active inerters in machining. The need to miniaturise the design to fit into modern machine tools is highlighted. Two areas in which this would be less of an issue -- fixturing and robotic machining -- are discussed. Notably, key challenges for robotic machining include the number and placement of the inerters, and whether new strategies would be needed to tackle mode-coupling chatter

    Evolutionary Algorithms in Engineering Design Optimization

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    Evolutionary algorithms (EAs) are population-based global optimizers, which, due to their characteristics, have allowed us to solve, in a straightforward way, many real world optimization problems in the last three decades, particularly in engineering fields. Their main advantages are the following: they do not require any requisite to the objective/fitness evaluation function (continuity, derivability, convexity, etc.); they are not limited by the appearance of discrete and/or mixed variables or by the requirement of uncertainty quantification in the search. Moreover, they can deal with more than one objective function simultaneously through the use of evolutionary multi-objective optimization algorithms. This set of advantages, and the continuously increased computing capability of modern computers, has enhanced their application in research and industry. From the application point of view, in this Special Issue, all engineering fields are welcomed, such as aerospace and aeronautical, biomedical, civil, chemical and materials science, electronic and telecommunications, energy and electrical, manufacturing, logistics and transportation, mechanical, naval architecture, reliability, robotics, structural, etc. Within the EA field, the integration of innovative and improvement aspects in the algorithms for solving real world engineering design problems, in the abovementioned application fields, are welcomed and encouraged, such as the following: parallel EAs, surrogate modelling, hybridization with other optimization techniques, multi-objective and many-objective optimization, etc

    Industrial Applications: New Solutions for the New Era

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    This book reprints articles from the Special Issue "Industrial Applications: New Solutions for the New Age" published online in the open-access journal Machines (ISSN 2075-1702). This book consists of twelve published articles. This special edition belongs to the "Mechatronic and Intelligent Machines" section

    The 15th International CDIO Conference: Proceedings – Full Papers

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    We discuss a conceptual thesis structure model and visual tool for enhancing the writing process in the context of an engineering Master’s thesis. Our model is based on visualizing the thesis as a series of funnels that adjust the writing focus to the desired scope in each individual chapter. At the end of the thesis, the focus is widened back into the original topic area with a reflection on how the solutions proposed in the thesis have impacted or potentially will impact the field. Using our model gives students the opportunity to write a good Master’s thesis in various engineering disciplines. In our experience, the Focus Funnel approach has been very useful and effective, resulting in an overall improvement in the quality of engineering Master’s theses in our degree program.</p

    Formal Specification and Verification for Automated Production Systems

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    Complex industrial control software often drives safety- and mission-critical systems, like automated production plants or control units embedded into devices in automotive systems. Such controllers have in common that they are reactive systems, i.e., that they periodically read sensor stimuli and cyclically execute the same program to produce actuator signals. The correctness of software for automated production is rarely verified using formal techniques. Although, due to the Industrial Revolution 4.0 (IR4.0), the impact and importance of software have become an important role in industrial automation. What is used instead in industrial practice today is testing and simulation, where individual test cases are used to validate an automated production system. Three reasons why formal methods are not popular are: (a) It is difficult to adequately formulate the desired temporal properties. (b) There is a lack of specification languages for reactive systems that are both sufficiently expressive and comprehensible for practitioners. (c) Due to the lack of an environment model the obtained results are imprecise. Nonetheless, formal methods for automated production systems are well studied academically---mainly on the verification of safety properties via model checking. In this doctoral thesis we present the concept of (1) generalized test tables (GTTs), a new specification language for functional properties, and their extension (2) relational test tables (RTTs) for relational properties. The concept includes the syntactical notion, designed for the intuition of engineers, and the semantics, which are based on game theory. We use RTTs for a novel confidential property on reactive systems, the provably forgetting of information. Moreover, for regression verification, an important relational property, we are able to achieve performance improvements by (3) creating a decomposing rule which splits large proofs into small sub-task. We implemented the verification procedures and evaluated them against realistic case studies, e.g., the Pick-and-Place-Unit from the Technical University of Munich. The presented contribution follows the idea of lowering the obstacle of verifying the dependability of reactive systems in general, and automated production systems in particular for the engineer either by introducing a new specification language (GTTs), by exploiting existing programs for the specification (RTTs, regression verification), or by improving the verification performance

    Advances in Robotics, Automation and Control

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    The book presents an excellent overview of the recent developments in the different areas of Robotics, Automation and Control. Through its 24 chapters, this book presents topics related to control and robot design; it also introduces new mathematical tools and techniques devoted to improve the system modeling and control. An important point is the use of rational agents and heuristic techniques to cope with the computational complexity required for controlling complex systems. Through this book, we also find navigation and vision algorithms, automatic handwritten comprehension and speech recognition systems that will be included in the next generation of productive systems developed by man

    Best available techniques (BAT) reference document on surface treatment using organic solvents including preservation of wood and wood products with chemicals: Industrial Emissions Directive 2010/75/EU (Integrated Pollution Prevention and Control)

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    The Best Available Techniques (BAT) Reference Document (BREF) on Surface Treatment using Organic Solvents including Preservation of Wood and Wood Products with Chemicals is part of a series of documents presenting the results of an exchange of information between EU Member States, the industries concerned, non-governmental organisations promoting environmental protection, and the Commission, to draw up, review and – where necessary – update BAT reference documents as required by Article 13(1) of Directive 2010/75/EU on Industrial Emissions (the Directive). This document is published by the European Commission pursuant to Article 13(6) of the Directive. The BREF on Surface Treatment Using Organic Solvents including Preservation of Wood and Wood Products with Chemicals covers the surface treatment of substances, objects or products using organic solvents as well as the preservation of wood and wood products using chemicals as specified in Sections 6.7 and 6.10 of Annex I to Directive 2010/75/EU respectively. Important issues for the implementation of Directive 2010/75/EU in the surface treatment using organic solvents (STS) and the wood preservation with chemicals (WPC) sectors are emissions to air and water as well as energy and water consumption. Chapter 1 provides general information on the STS sector and on the main environmental issues associated with their use. Chapters 2 to 14 give the applied processes, current emission and consumption levels, techniques to consider in the determination of BAT for the STS sectors that are covered by these chapters. Chapter 15 provides general information, applied processes, current emission and consumption levels, techniques to consider in the determination of BAT for the wood preservation sector. Chapter 16 provides thumbnail descriptions of additional STS sectors, for which a data collection via questionnaires has not been carried out. General techniques to consider in the determination of BAT (i.e. those techniques to consider that are widely applied in the STS sector) are reported in Chapter 17. Chapter 18 presents the BAT conclusions as defined in Article 3(12) of the Directive, both general and sector-specific. Chapter 19 provides the emerging techniques for the STS and WPC sectors. Concluding remarks and recommendations for future work are presented in Chapter 20.JRC.B.5-Circular Economy and Industrial Leadershi

    Executing Strategic Product Planning - A Subject-Oriented Analysis and New Referential Process Model for IT-Tool Support and Agile Execution of Strategic Product Planning

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    The origin of this research was the failed attempt or rather the impossibility of creating a working and effective information system to support the processes of Strategic Product Planning, based on existing process descriptions for that domain. This work explores the origins of the according problems. As is discovered, the problems do not originate in error containing models or simple programming failures. Rather, as is explored, the origin of the encountered problems lies in fundament
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