1,720,971 research outputs found
A Tutorial on Geometric Control Theory of Linear Systems
No full textThis paper reviews in a condensed form the main
tools and results of the geometric approach developed in the
last forty years. Because of the vastness of the subject, this
tutorial does not pretend to be exhaustive, and more emphasis
will be given to selected topics and to the related computational
tools. The authors hope their effort to provide a unified view of
geometric control theory may be profitable to awake renewed
interest in this research field
A Robust Uncalibrated Visual Compass Algorithm from Paracatadioptric Line Images
No full textDue to their wide panoramic field of view, paracatadioptric cameras are becoming ubiquitous in many robotic applications. A challenging problem consists in using these vision sensors as a visual compass, that is to exploit the image data solely to provide an estimate of their rotational motion when mounted on a mobile/humanoid robot. Existing visual compass algorithms are difficult to implement in real scenarios since they assume known camera calibration parameters and known geometry of image features (e.g. correspondence between points or parallelism among between lines). In this paper we present a new multi-view property for paracatadioptric cameras called disparity-circles constraint and we use it to design a visual compass algorithm to estimate the z−axis camera rotation angle. The proposed algorithm only uses the image projection of 3-D parallel lines and is suitable for real-time implementation. Those 3-D lines that are parallel are shown to be automatically detectable via a RANSAC implementation of the algorithm. Real-data experiments conducted with a paracatadioptric camera mounted on a mobile robotic platform prove the robustness of the proposed approach
KUKA Control Toolbox
No full textThis article presents an open-source MATLAB toolbox for the motion control of KUKA robot manipulators. The KUKA Control Toolbox (KCT) is a collection of MATLAB functions developed at the Univer sity of Siena. The toolbox, which is compatible with all 6 degrees of freedom (DoF) small and low-payload KUKA robots that use the Eth.RSIXML, runs on a remote computer connected with the KUKA controller via transmission control Protocol/Internet Protocol (TCP/IP). KCT includes more than 40 functions, spanning operations such as forward and inverse kine matics computation, point-to-point joint and Cartesian control, trajectory gen eration, graphical display, three-dimensional (3-D) animation and diagnostics. Applicative examples show the flexibility of KCT and its easy interfacing with other toolboxes and external devices
A Geometric Solution to the Cheap Spectral Factorization Problem
No full textThe paper studies the cheap spectral factorization
problem in the state space from a strictly geometric viewpoint.
A new solution based on the geometric properties of the related
Hamiltonian system is proposed and the connection between
the H2-optimal model following and the spectral factorization
problems is pointed out. A numerical example illustrates the
theory and shows the effectiveness of the proposed solution
On a class of hierarchical formations of unicycles and their internal dynamics
Full text linkThis paper studies a class of hierarchical formations for an ordered set of n+1 unicycle robots: the first robot plays the role of the leader and the formation is induced through a constraint function F, so that the position and orientation of the i-th robot depends only on the pose of the preceding ones. We study the dynamics of the formation with respect to the leaders reference frame by introducing the concept of reduced internal dynamics, we characterize its equilibria and provide sufficient conditions for their existence. The discovered theoretical results are applied to the case in which the constraint F induces a formation where the i-th robot follows a convex combination of the positions of the previous i-1 vehicles. In this case, we prove in this case that if the curvature of the leaders trajectory is sufficiently small, the positions and orientations of the robots, relative to the leaders reference frame, are confined in a precise polyhedral region
H2-Pseudo Optimal Model Following: A Geometric Approach
Full text linkThe paper proposes a very straightforward change of the general layout of the geometric approach to the feedforward and feedback model following problems for nonminimum-phase systems. The design technique relies on the replacement of the output matrix of the controlled system with an equally dimensioned matrix ensuring H2-optimality in the standard disturbance decoupling problem, while maintaining the relative degree and the steady-state gain of the original system. The new matrix is derived by applying the standard geometric approach tools to the Hamiltonian system instead of the original plant
Decentralized optimal control of a car platoon with guaranteed string stability
No full textAbstract — This paper presents new decentralized optimal strategies for Cooperative Adaptive Cruise Control (CACC) of a car platoon under string-stability constraints. Two related scenarios are explored in the article: in the first one, a linearquadratic regulator in the presence of measurable disturbances is synthesized, and the string-stability of the platoon is enforced over the controller’s feedback and feedforward gains. In the second scenario, H2- andH∞-performance criteria, respectively accounting for the desired group behavior and the stringstability of the platoon, are simultaneously achieved using the recently-proposed compensator blending method. An analytical study of the impact of actuation/communication delays and uncertain model parameters on the stability of the multi-vehicle system, is also conducted. The theory is illustrated via numerical simulations. I
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
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