1,721,227 research outputs found
Full-complexity characterization of control-invariant domains for systems with uncertain parameter dependence
No full textThis letter proposes an algorithm to find a robust control invariant (RCI) set of desired complexity and the associated linear, state-feedback control law. The candidate RCI set is restricted to be symmetric around the origin. The algorithm is applicable to rational parameter dependent systems with bounded additive disturbance. The system constraints are framed as simple affine inequalities whereas the invariance condition as a set of sufficient LMI conditions. The proposed iterative algorithm is guaranteed to be recursively feasible and converge to some stationary point
Low-Complexity Explicit MPC Controller for Vehicle Lateral Motion Control
No full textWe consider the problem of controlling the vehicle lateral motion in highway scenarios while guaranteeing safety. We propose a solution consisting of a Low-Complexity Explicit Model Predictive Controller (LC-EMPC), where the lateral deviation from the desired path is hard constrained according to prescribed bounds. The robust satisfaction of such safety constraints can be achieved by imposing the terminal state to enter a Robust Invariant Set (RIS), which is known to result into a potentially high number of additional constraints, thus increasing the computational complexity of the controller. Our controller, instead, relies on recent results on the calculation of low-complexity RIS to significantly reduce the number of constraints in the MPC controller. Simulation results show that the designed controller is able to meet the desired objectives with highly reduced complexity
Computation of low-complexity control-invariant sets for systems with uncertain parameter dependence
No full textThis paper considers the problem of computing a low-complexity robust control-invariant (LC-RCI) set for uncertain systems, along with a static linear state-feedback law. The LC-RCI set, assumed to be symmetric around the origin and described by the same number of affine inequalities as twice the dimension of the state vector, is the result of an iterative procedure, where semi-definite programs (SDPs) are solved at each step. The SDPs are formulated to increase the LC-RCI volume at each step, subject to tractable reformulations of the system constraints as well as the invariance condition (in the form of standard or dilated LMIs), and a new approach to determinant maximization. The two proposed algorithms are applicable to systems with rational parameter dependence, which cannot be handled with the existing similar approaches without introducing additional conservatism
Vehicle Lateral Motion Control with Performance and Safety Guarantees
No full textThis paper explores the use of Model Predictive Control (MPC) techniques to solve vehicle lateral motion control problem on highway scenarios. In particular, the problem of autonomously driving a vehicle along a desired path is formulated, where safety constraints and performance levels must be guaranteed for all possible road curvatures within a con [pact set. Safety constraints are translated into a maximum lateral deviation and orientation error w.r.t. a desired path, while performance requirements are formulated in terms of bounded lateral acceleration and velocity. Preliminary simulation results ahoy that the designed controller is capable of delivering acceptable performance at the cost of limited online computational costs. (C) 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Tree-Structured Polyhedral Invariant Set Calculations
No full textThis letter provides a description of how hierarchical dependencies between inequalities can be exploited in order to efficiently calculate polyhedral approximations of maximal robust positive invariant sets using geometrically motivated methods. Due to the hierarchical dependencies, the calculations of preimage sets and minimal representations can be alleviated. It is also shown that as a byproduct from the calculations of minimal representations, a stopping criterion is obtained, which means that the commonly used subset test is superfluous
A Framework for Vehicle Lateral Motion Control With Guaranteed Tracking and Performance
Full text linkIn this paper, we propose a framework to design a controller for the vehicle lateral dynamics, which guarantees to meet desired safety and performance requirement. Bounded lateral deviation from the reference trajectory is the strict safety requirement considered in this paper.The proposed control design relies on a mild assumption. That is, the trajectory planner generates a trajectory that is piece-wise clothoidal (PWC), with bounded curvature and curvature rate.Closed-loop simulations using a linear quadratic regulator (LQR) and a model predictive control (MPC) controller, developed based on the proposed framework, validates the proposed approach
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
Political uses of the ancient past on social media are predominantly negative and extreme
Full text linkThis study assesses whether references to the ancient past in debates about political issues on social media over-represent negative and extreme views. Using precision-recall, we test the performance of three sentiment analysis methods (VADER, TextBlob and Flair Sentiment) on a corpus of 1,478,483 posts, comments and replies published on Brexit-themed Facebook pages between 2015 and 2017. Drawing on the results of VADER and manual coding, we demonstrate that: 1) texts not containing keywords relating to the Iron Age, Roman and medieval (IARM) past are mostly neutral and 2) texts with IARM keywords express more negative and extreme sentiment than those without keywords. Our findings show that mentions of the ancient past in political discourse on multi-sided issues on social media are likely to indicate the presence of hostile and polarised opinions
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