1,721,020 research outputs found
A dynamic inversion approach to motorcycle trajectory exploration
No full textRecently developed optimization and nonlinear control
strategies are applied to ride a multi-body motorcycle model
along a specified path with an associated velocity profile. The
resulting control scheme is based on three main pillars: a
dynamic inversion procedure to compute the input-state trajectories
corresponding to a desired maneuvering task, an inverse
optimal control heuristic for designing closed loop dynamics,
and a maneuver regulation controller to overcome limitations of
standard trajectory tracking scheme. The controller (virtual rider)
is implemented on a commercial simulation software. Simulation
results are presented
A virtual rider for motorcycles: Maneuver regulation of a multibody vehicle model
Full text linkThis work develops a virtual rider that can be used to
make a multi-body two-wheeled vehicle follow a specified ground
path with a prescribed velocity profile. The virtual rider system
is based on a simplified motorcycle model, the sliding plane motorcycle,
which is composed of a single rigid body with two ground
contact points. This reduced order nonlinear system was presented
in an earlier work, together with a dynamic inversion procedure
for computing a state-control trajectory corresponding to the desired
task. This dynamic inversion procedure is combined in this
work with a maneuver regulation controller to yield a nonlinear
feedback control strategy. A transverse coordinate system that is
consistent with the mechanical symmetries of ground vehicles is
constructed and used in the development of the maneuver regulation
controller. An inverse optimal control strategy, which also
exploits the mechanical symmetries, is developed to shape the dynamic
response of the closed loop system. Numerical results with
the virtual rider driving amulti-body vehicle through a demanding
maneuver with lateral accelerations reaching 1 g are presented
A Virtual Rider for Motorcycles: An Approach Based on Optimal Control and Maneuver Regulation
No full textRecently developed optimization and nonlinear control strategies are applied to drive a multi-body motorcycle model along a specified path with an associated velocity profile. The resulting control scheme is based on three main pillars: a dynamic inversion procedure to compute the input-state trajectories corresponding to a desired maneuvering task, an inverse optimal control heuristic for designing closed loop dynamics, and a maneuver regulation controller to overcome limitations of standard trajectory tracking scheme. The controller (virtual rider) is implemented on a commercial simulation software. Simulation results are presented
Model predictive for path following with motorcycles: application to the development of the pilot model for virtual prototyping
No full textControlling a riderless motorcycle is a challenging problem because the dynamics are nonlinear and non-minimum phase. In this paper, an innovative control strategy is proposed for driving a motorcycle along a given path, tracking a speed profile given as a function of the arc-length of the path. The solution is based on model predictive control. Exploiting the possibility given by MPC to work on trajectories, we invert the cause-effect structure of the problem and act as if the roll angle was an input. We then determine, among a polynomial set of roll angle trajectories, the optimal one in terms of the error at preview distance from the target path. By inverting the dynamics, we compute the steering and longitudinal controls needed to track the computed roll trajectory
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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