Stabilization of Physical Systems via Saturated Controllers With Partial State Measurements

This article provides a constructive passivity-based control (PBC) approach to solve the set-point regulation problem for input-affine continuous nonlinear systems while considering bounded inputs. As customary in PBC, the methodology consists of two steps: energy shaping and damping injection. In terms of applicability, the proposed controllers have two advantages concerning other PBC techniques: 1) the energy shaping is carried out without solving partial differential equations and 2) the damping injection is performed without measuring the passive output. As a result, the proposed methodology is suitable to control a broad range of physical systems, e.g., mechanical, electrical, and electromechanical systems, with saturated control signals. We illustrate the applicability of the technique by designing controllers for systems in different physical domains, where we validate the analytical results via simulations and experiments

Tuning of Passivity-Based Controllers for Mechanical Systems

This article describes several approaches for tuning the parameters of a class of passivity-based controllers for standard nonlinear mechanical systems. In particular, we are interested in tuning controllers that preserve the mechanical system structure in the closed loop. To this end, first, we provide tuning rules for stabilization, i.e., the rate of convergence (exponential stability) and stability margin (input-to-state stability). Then, we provide guidelines to remove the overshoot. In addition, we propose a methodology to tune the gyroscopic-related parameters. We also provide remarks on the damping phenomenon to facilitate the practical implementation of our approaches. We conclude this article with experimental results obtained from applying our tuning rules to a fully actuated and an underactuated mechanical system

Rediscovering Cova de la Sarsa (València, Spain): a Multidisciplinary Approach to One of the Key Early Neolithic Sites in the Western Mediterranean

Cova de la Sarsa (València, Spain) is one of the most important Neolithic impressed ware culture archaeological sites in the Western Mediterranean. It has been widely referenced since it was excavated in the 1920s, due partly to the relatively early excavation and publication of the site, and partly to the qualitative and quantitative importance of its archaeological remains. Unfortunately, as it was an older excavation and lacked present-day rigorous methodological approaches, this important site has been somewhat relegated to the background in the reviews about the Neolithic at the end of the 20th century. However, during the last few years, both the site itself and its archaeological remains have been the object of new studies that hopefully will return the site to the forefront of discussions about the Mediterranean Neolithic. We here present the most relevant results of the research carried out by our group (i.e., pottery study, radiocarbon dating, and isotope analysis), and contextualize them within the dense research history of the cave and the studies carried out by other colleagues with the purpose of revisiting its materials and increasing the knowledge available from the site. Radiocarbon dates on human remains show that the cave was used during prehistoric times as a funerary space longer than expected, and also sporadically afterwards. The characterization of the pottery assemblage concludes that most materials belong to the Early Neolithic. Isotopic analysis portrays an overall similar diet based on terrestrial C3 resources throughout prehistoric times, with a possible varied dietary protein input between individuals during the Early Neolithic

Tunable coupling engineering between superconducting resonators: from sidebands to effective gauge fields

In this work we show that a tunable coupling between microwave resonators can be engineered by means of simple Josephson junctions circuits, such as dc- and rf-SQUIDs. We show that by controlling the time dependence of the coupling it is possible to switch on and off and modulate the cross-talk, boost the interaction towards the ultrastrong regime, as well as to engineer red and blue sideband couplings, nonlinear photon hopping and classical gauge fields. We discuss how these dynamically tunable superconducting circuits enable key applications in the fields of all optical quantum computing, continuous variable quantum information and quantum simulation - all within the reach of state of the art in circuit-QED experiments.Comment: 11 pages, 4 figure

Computing Black Hole entropy in Loop Quantum Gravity from a Conformal Field Theory perspective

Motivated by the analogy proposed by Witten between Chern-Simons and Conformal Field Theories, we explore an alternative way of computing the entropy of a black hole starting from the isolated horizon framework in Loop Quantum Gravity. The consistency of the result opens a window for the interplay between Conformal Field Theory and the description of black holes in Loop Quantum Gravity.Comment: 9 page

Detailed black hole state counting in loop quantum gravity

We give a complete and detailed description of the computation of black hole entropy in loop quantum gravity by employing the most recently introduced number-theoretic and combinatorial methods. The use of these techniques allows us to perform a detailed analysis of the precise structure of the entropy spectrum for small black holes, showing some relevant features that were not discernible in previous computations. The ability to manipulate and understand the spectrum up to the level of detail that we describe in the paper is a crucial step towards obtaining the behavior of entropy in the asymptotic (large horizon area) regime

The role of mobile policies in coalition building : the Barcelona model as coalition magnet in Buenos Aires and Rio de Janeiro (1989-1996)

Research on policy mobility has tended to focus on what moves (e.g. policy models, templates) and who moves them (e.g. consultants, international organizations) with less attention paid to the relational politics of grounding dominant ideas in local policy making. The ‘demand side’ at the end of the mobilization process (e.g. local authorities and policy actors) is usually depicted as passive or as having stable interests. This assumption is problematic as it can reinforce taken for granted power asymmetries in the flow of urban policy ideas, particularly in cases where cities in the Global North are presented as ‘exporting sites’ for a Global South audience of ‘importing sites’. Drawing on the concept of policy ideas as ‘coalition magnets’ from policy studies, this paper demonstrates how local policies are relationally produced by cosmopolitan policy actors on the ‘demand side’ who strategically mobilize circulating ideas as a tool for coalition building. We provide a relational comparative study of Buenos Aires and Rio de Janeiro’s policy processes and urban outcomes in mobilizing the Barcelona model of urban regeneration and strategic planning drawing on evidence from interviews, document analysis, and the biographies of key policy actors. It demonstrates the strategic importance of mobile policies for emerging political actors who employ them as a ‘coalition magnet’ to build support for their governments

Dead-zone compensation via passivity-based control for a class of mechanical systems

This manuscript introduces a passivity-based control methodology for fully-actuated mechanical systems with symmetric or asymmetric dead-zones. To this end, we find a smooth approximation of the inverse of the function that describes such a nonlinearity. Then, we propose an energy and damping injection approach — based on the PI-PBC technique — that compensates for the dead-zone. Moreover, we provide an analysis of the performance of the proposed controller near the equilibrium. We conclude this paper by experimentally validating the results on a two degrees-of-freedom planar manipulator

Physics‐Informed Neural Networks to Model and Control Robots: A Theoretical and Experimental Investigation

This work concerns the application of physics‐informed neural networks to the modeling and control of complex robotic systems. Achieving this goal requires extending physics‐informed neural networks to handle nonconservative effects. These learned models are proposed to combine with model‐based controllers originally developed with first‐principle models in mind. By combining standard and new techniques, precise control performance can be achieved while proving theoretical stability bounds. These validations include real‐world experiments of motion prediction with a soft robot and trajectory tracking with a Franka Emika Panda manipulator.</jats:p

Bridging the gap between policy and science in assessing the health status of marine ecosystems

Human activities, both established and emerging, increasingly affect the provision of marine ecosystem services that deliver societal and economic benefits. Monitoring the status of marine ecosystems and determining how human activities change their capacity to sustain benefits for society requires an evidence-based Integrated Ecosystem Assessment approach that incorporates knowledge of ecosystem functioning and services). Although, there are diverse methods to assess the status of individual ecosystem components, none assesses the health of marine ecosystems holistically, integrating information from multiple ecosystem components. Similarly, while acknowledging the availability of several methods to measure single pressures and assess their impacts, evaluation of cumulative effects of multiple pressures remains scarce. Therefore, an integrative assessment requires us to first understand the response of marine ecosystems to human activities and their pressures and then develop innovative, cost-effective monitoring tools that enable collection of data to assess the health status of large marine areas. Conceptually, combining this knowledge of effective monitoring methods with cost-benefit analyses will help identify appropriate management measures to improve environmental status economically and efficiently. The European project DEVOTES (DEVelopment Of innovative Tools for understanding marine biodiversity and assessing good Environmental Status) specifically addressed t hese topics in order to support policy makers and managers in implementing the European Marine Strategy Framework Directive. Here, we synthesize our main innovative findings, placing these within the context of recent wider research, and identifying gaps and the major future challenges