1,720,990 research outputs found
Mixed H2/Hinfty Control: The Discrete-Time Case
No full textA stochastic H∞ and a mixed, stochastic, H2 /H∞ control problem for discrete-time systems are considered and solved. Conditions for existence of a solution are derived, based on the solvability of an equivalent minimax problem. In this framework, it is possible to consider at the same time both stochastic and deterministic disturbances highlighting their mutual effects. The controller can be designed by solving a system of three coupled Riccati equations. Such equations display how the H2-type minimization problem and the H∞ - type constraint influence each other
A Passivity-Based Bilateral Teleoperation Architecture using Distributed Nonlinear Model Predictive Control
No full textBilateral teleoperation systems allow the telepresence of an operator while working remotely. Such ability becomes crucial when dealing with critical environments like space, nuclear plants, rescue, and surgery. The main properties of a teleoperation system are the stability and the transparency which, in general, are in contrast and they cannot be fully achieved at the same time. In this paper, we will present a novel model predictive controller that implements a passivity-based bilateral teleoperation algorithm. Our solution mitigatesthe chattering issue arising when resorting to the energy tank(or reservoir) mechanism by forcing the passivity as a hard constraint on the system evolution
Robotic surgery: formal verification of plans
No full textIn this paper we discuss the introduction of formal methods for the verification of properties of control systems designed for autonomous robotic systems
Improving Rigid 3-D Calibration for Robotic Surgery
Full text linkAutonomy is the next frontier of research in robotic surgery and its aim is to improve the quality of surgical procedures in the next future. One fundamental requirement for autonomy is advanced perception capability through vision sensors. In this article, we propose a novel calibration technique for a surgical scenario with a da Vinci Research Kit (dVRK) robot. Camera and robotic arms calibration are necessary to precise position and emulate expert surgeon. The novel calibration technique is tailored for RGB-D cameras. Different tests performed on relevant use cases prove that we significantly improve precision and accuracy with respect to state of the art solutions for similar devices on a surgical-size setups. Moreover, our calibration method can be easily extended to standard surgical endoscope used in real surgical scenario
Stochastic port--Hamiltonian systems
Full text linkIn the present work we formally extend the theory of port-Hamiltonian systems
to include random perturbations. In particular, suitably choosing the space of
flow and effort variables we will show how several elements coming from
possibly different physical domains can be interconnected in order to describe
a dynamic system perturbed by general continuous semimartingale. Relevant
enough, the noise does not enter into the system solely as an external random
perturbation, since each port is itself intrinsically stochastic. Coherently to
the classical deterministic setting, we will show how such an approach extends
existing literature of stochastic Hamiltonian systems on pseudo-Poisson and
pre-symplectic manifolds. Moreover, we will prove that a power-preserving
interconnection of stochastic port-Hamiltonian systems is a stochastic
port-Hamiltonian system as well
Human-Robot Interfaces in Autonomous Surgical Robots
No full textThis chapter addresses a very complex problem that can be expressed in a very simple form: is it possible to automate surgery? We believe that, if a solution can ever be approached, it would lie in the intersection of robotics, automation, and cognition, since factors such as experience, knowledge, and intuition are as important as mechanism design and control algorithms in successful surgery. The feasibility of a solution to this problem was analyzed during the European project Intelligent Robotic Surgery (I-SUR), a project of the Seventh Framework Programme during the period 2011 to 2014. In this project, we developed general methods for cognitive surgical robots capable of combining sensing, dexterity, and cognitive capabilities to carry out autonomously simple surgical actions, such as puncturing and suturing. To narrow further the scope of this research, we addressed the well-known surgical area of kidney interventions, whose variability and uncertainty are limited, but still representative of general situations and requiring strong cognitive capabilities to ensure the correct execution of the surgery. We examined the reasoning aspects of these domains, the control capabilities needed to carry out these surgical actions, and we integrated them into a robotic test bed performing autonomous surgical actions on anatomically correct phantoms
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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