Dinis R.,Institute Telecomunicac Oes |
IEEE Transactions on Communications | Year: 2013
In this paper we consider the optimum detection of OFDM (Orthogonal Frequency Division Multiplexing) signals with strong nonlinear distortion effects. It is shown that the optimum performance with strong nonlinear distortion effects is not as bad as one might expect and can even be better than the performance with conventional, linear transmitters. To achieve these excellent performances we should employ receivers able to take advantage of the information associated to transmitted data symbols that is inherent to the nonlinear distortion component, in opposition to traditional OFDM implementations where nonlinear distortion effects are regarded as an undesirable noise-like component. We study the achievable gains of the optimum receiver both analytically and by simulation. Since the complexity of optimum receivers is extremely high when we have nonlinear distortion effects, even for OFDM signals with a small number of subcarriers, we propose several sub-optimum receivers and evaluate their performance. Our sub-optimal receivers allow remarkable performance improvements, being able to reduce significantly the gap between the optimum performance and the performance of typical OFDM receivers. © 1972-2012 IEEE.
Onori M.,KTH Royal Institute of Technology |
Lohse N.,University of Nottingham |
Barata J.,UNINOVA |
Assembly Automation | Year: 2012
Purpose - Current major roadmapping efforts have all clearly underlined that true industrial sustainability will require far higher levels of systems' autonomy and adaptability. In accordance with these recommendations, the Evolvable Assembly Systems (EAS) has aimed at developing such technological solutions and support mechanisms. Since its inception in 2002 as a next generation of production systems, the concept is being further developed and tested to emerge as a production system paradigm. The essence of evolvability resides not only in the ability of system components to adapt to the changing conditions of operation, but also to assist in the evolution of these components in time. Characteristically, Evolvable systems have distributed control, and are composed of intelligent modules with embedded control. To assist the development and life cycle, a methodological framework is being developed. After validating the process-oriented approach (EC FP6 EUPASS project), EAS now tackles its current major challenge (FP7 IDEAS project) in proving that factory responsiveness can be improved using lighter multi-agent technology running on EAS modules (modules with embedded control). The purpose of this paper is to detail the particular developments within the IDEAS project, which include the first self re-configuring system demonstration and a new mechatronic architecture. Design/methodology/approach - The paper covers the development of a plug & produce system for FESTO AG. The work covers the background methodology and details its constituents: control system, architecture, design methodology, and modularity. Specific detail is reserved for the configuration approach which integrates several tools, and the commercially available control boards. The latter have been specifically developed for distributed control applications. Findings - The paper details probably the first self-configuring assembly system at shop-floor level. This is one of the very first industrial plug & produce systems, in which equipment may be added/removed with no programming effort at all. Research limitations/implications - The paper reports the findings and development carried out within the framework of a single project. It also clarifies that the solution is not a general panacea for all the issues within assembly. Practical implications - The implications are quite large as the work proves the validity of an approach that could change our way of designing and building assembly systems. In the words of an industrial partner, this is "a new way of engineering assembly systems". Social implications - Should this approach be used in industry then the implications could be huge. It would, for example, mean that new services are created, whereby assembly system modules are leased to users through a network of depots, rather than bought at a high cost. The system modules also have a far longer lifespan, implying very good ecological solutions. Originality/value - The highly original paper describes what is probably one of the very first projects to show that distributed control at shop-floor level is viable and technologically feasible. © Emerald Group Publishing Limited.
Onori M.,KTH Royal Institute of Technology |
Assembly Automation | Year: 2010
Purpose - This roadmap is primarily concerned with the adaptive assembly technology situation in Europe, a topic of particular interest as assembly is often the final process within manufacturing operations. Being the final set of operations on the product, and being traditionally labour-intensive, assembly has been considerably affected by globalisation. Therefore, unlike most technology roadmaps, this report will not focus solely on particular technologies, but will strive to form a broader perspective on the conditions that may come to influence the opportunities, including political aspects and scientific paradigms. The purpose of this paper is to convey a complete view of the global mechanisms that may come to affect technological breakthroughs, and also present strategies that may better prepare for such a forecast. Design/methodology/approach - The paper describes a technological roadmap. Findings - This paper provides a complete overview of all aspects that may come to affect assembly in Europe within the next 20 years. Originality/value - The paper gives an original Evolvable Ultra Precision Assembly Systems FP6 project result which will be of general interest for strategic R&D. © Emerald Group Publishing Limited [ISSN 0144-5154].
Ortigueira M.D.,UNINOVA |
Coito F.J.V.,UNINOVA |
Trujillo J.J.,University of La Laguna
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2013
A derivative based discrete-time signal processing is presented. Both nabla (forward) and delta (backward) derivatives are studied and generalised including the fractional case. The corresponding exponentials are introduced as eigenfunctions of such derivatives. © 2013 IFAC.
AIP Conference Proceedings | Year: 2012
Starting from the discrete-time nabla (forward) and delta (backward) derivatives we introduce a two-sided derivative valid for any order. Its eigenfunction is the normal discrete exponential. This derivative leads to discrete non causal linear systems. © 2012 American Institute of Physics.
Ribeiro R.A.,UNINOVA |
Falcao A.,UNINOVA |
Mora A.,UNINOVA |
Knowledge-Based Systems | Year: 2014
The main goal of information fusion is to combine heterogeneous information to obtain a single composite of potential comparable alternative solutions that can be classified and ranked. The crux of information fusion, which is a type of data fusion, is threefold: (i) data must be comparable and numerical, using some normalization process; (ii) imprecision in data must be taken into consideration; (iii) an appropriate aggregation function to combine values into a single score must be selected. Recently, computational intelligence concepts and techniques to perform data/information fusion are emerging as suitable tools. Although with a different perspective, another field where much work has also been done for combining heterogeneous information is multi-criteria decision-making. In general, multi-criteria problems are modelled by choosing a set of relevant criteria - usually dealing with heterogeneous data - that have to be aggregated (i.e. fused) to obtain a single rating for each candidate alternative. In this paper we propose an algorithm for data/information fusion, which includes concepts from multi-criteria decision-making and computational intelligence, specifically, fuzzy multi-criteria decision-making and mixture aggregation operators with weighting functions. The application field of interest for this work is safe spacecraft landing with hazard avoidance; hence two existing hazard maps will be used to illustrate the versatility of the algorithm. © 2013 Elsevier B.V. All rights reserved.
Campos A.,UNINOVA |
Neves-Silva R.,New University of Lisbon
Smart Innovation, Systems and Technologies | Year: 2011
Building owners, or investors, and facility managers, or building technical consultants, have the difficult task of maintaining an infrastructure by selecting the most adequate investments. Nowadays, this maintenance means in most countries to update a building to current regulations regarding energy efficiency. The decision to retrofit a building involves several actors and a diverse set of criteria, covering technical, economical, social and financial aspects. This paper presents a novel approach to support investors and technical consultants in selecting the most appropriate energy-efficient retrofit scenario for a building. The proposed approach uses the actual energy consumption of the building to predict energy profiles of introducing new control strategies to increase energy efficiency. Additionally, the approach uses the Analytic Hierarchy Process combined with benefits, opportunities, costs and risks and a sensitivity analysis to support actors in selecting the best scenario to invest. © 2011 Springer-Verlag Berlin Heidelberg.
Ortigueira M.D.,UNINOVA |
Computers and Mathematics with Applications | Year: 2010
The alternative system initial conditions versus the derivative initial conditions is focused in this paper. It is shown that Riemann-Liouville and Caputo initial conditions result from the corresponding derivative and not necessarily from the system at hand. To setup the correct system initialization, a formulation generalizing the integer order approach is presented. This is based on a generalization to the fractional environment of the well known jump formula. The obtained scheme is very general and does not depend on any transform. Besides, it can also be used in the time variant case. The Riemann-Liouville and Caputo initial conditions are interpreted in terms of this general framework and deduced equations where they are correct. © 2009 Elsevier Ltd. All rights reserved.
Pinto A.,New University of Lisbon |
Ribeiro R.A.,Uninova |
Nunes I.L.,New University of Lisbon
Accident Analysis and Prevention | Year: 2012
Quantifying or, more generally, estimating the severity of the possible consequences of occupational accidents is a decisive step in any occupational risk assessment process. Because of the lack of historic information (accident data collection and recording are incipient and insufficient, particularly in construction) and the lack of practical tools in the construction industry, the estimation/quantification of occupational accident severity is a notably arbitrary process rather than a systematic and rigorous assessment. This work proposes several severity functions (based on a safety risk assessment) to represent biomechanical knowledge with the aim of determining the severity level of occupational accidents in the construction industry and, consequently, improving occupational risk assessment quality. We follow a fuzzy approach because it makes it possible to capture and represent imprecise knowledge in a simple and understandable way for users and specialists. © 2011 Elsevier Ltd. All rights reserved.
Jardim-Goncalves R.,UNINOVA |
Automation in Construction | Year: 2010
The Single European Electronic Market (SEEM) is expected to stimulate the take-up of eBusiness in Europe, increasing the competitiveness of SMEs through advanced eBusiness process models and tools, by offering to companies a model for modernizing work organization that allows them to face changing markets with an effective use of Information and Communication Technologies (ICT). However, the Building and Construction industry (B&C) has its ICT fragmented, having in the Building Information Model (BIM) paradigm a vehicle to address this problem. Interfacing with BIM brings another layer of complexity, mostly due to the heterogeneity of the systems and applications that need to interface with it. Thus, the adoption of a cluster of proper services in the Web that can offer in a unique way the functionalities needed for the adoption of BIM, is essential. The implementation of BIM under the Cloud Computing paradigm holds the promise of accelerating the B&C industry to achieve the Single Electronic Market. After presenting the vision for a Single European Electronic Market, and the expectation of the B&C sector to be integrated in a universal information space, this paper proposes the SOA4BIM framework as a cloud of services that enables universal access to the BIM paradigm by any system, application, or end user on the web. © 2009 Elsevier B.V. All rights reserved.