1,721,011 research outputs found
Aircraft maneuver regulation: a receding horizon backstepping approach
No full textCoordinated flight is a nonholonomic constraint that implies no sideslip of an aircraft. The equations of motion in coordinated flight are kinematically reducible. This property simplifies the maneuver regulation problem because under such assumption it is possible to write a lateral controller for the transverse dynamics independent of velocity. Assuming coordinated flight, the maneuver regulator consists of a model predictive controller based on the kinematic model. Since, in reality the coordinated flight assumption is seldom satisfied, the kinematic control action is back-stepped into dynamics to compute the actuation of the control surfaces. The proposed control law is tested on a multi-body SW model of an aircraft on various maneuvers, including some aggressive ones
Motion on submanifolds of noninvariant holonomic constraints for a kinematic control system evolving on a matrix Lie group
No full textor a control system on a matrix Lie group with one or more configuration constraints that are not left/right invariant, finding the combinations of (kinematic) control inputs satisfying the motion constraints is not a trivial problem. Two methods, one coordinate-dependent and the other coordinate-free are suggested. The first is based on the Wei-Norman formula; the second on the calculation of the annihilator of the coadjoint action of the constraint one-form at each point of the group manifold. The results are applied to a control system on SE(3) with a holonomic inertial constraint involving the noncommutative part in a nontrivial way. The difference in terms of compactness of the result between the two methods is considerable
Trajectory Manifold Exploration for the PVTOL aircraft
No full textIn this paper, we study the trajectory space of the PVTOL aircraft. We show that, due to the non-minimum phase nature of the system, more aggressive trajectories may be tracked with respect to the simplified differentially flat model. Given bounded C2trajectories of the center of gravity, we show that there exists a bounded roll trajectory which implements them. We compute an approximation of such roll trajectory using a Newton method for nonlinear optimization based on a trajectory tracking projection operator
Motion on constrained submanifolds for a kinematic control system evolving on a matrix Lie group
No full textPath Following of a Rolling Disk Using Throttle Only
No full textIn this paper we address the problem of controlling a disk, rolling on a horizontal plane, using only throttle as control input The disk is supposed to follow an assigned path in the plane. The problem is difficult because of the high order of underactuation and of the instability of the system. The controller is based upon an internal manifold and a receding horizon technique. By using a backstepping control technique the controller tracks a lean angle trajectory. The lean angle reference trajectory is generated at each instant through a receding horizon algorithm and it is such that, if followed, the system tracks the assigned path with a bounded error
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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