41,918 research outputs found
Chaotic multi-objective optimization based design of fractional order PI{\lambda}D{\mu} controller in AVR system
In this paper, a fractional order (FO) PI{\lambda}D\mu controller is designed
to take care of various contradictory objective functions for an Automatic
Voltage Regulator (AVR) system. An improved evolutionary Non-dominated Sorting
Genetic Algorithm II (NSGA II), which is augmented with a chaotic map for
greater effectiveness, is used for the multi-objective optimization problem.
The Pareto fronts showing the trade-off between different design criteria are
obtained for the PI{\lambda}D\mu and PID controller. A comparative analysis is
done with respect to the standard PID controller to demonstrate the merits and
demerits of the fractional order PI{\lambda}D\mu controller.Comment: 30 pages, 14 figure
Least-square based recursive optimization for distance-based source localization
In this paper we study the problem of driving an agent to an unknown source
whose location is estimated in real-time by a recursive optimization algorithm.
The optimization criterion is subject to a least-square cost function
constructed from the distance measurements to the target combined with the
agent's self-odometry. In this work, two important issues concerning real world
application are directly addressed, which is a discrete-time recursive
algorithm for concurrent control and estimation, and consideration for input
saturation. It is proven that with proper choices of the system's parameters,
stability of all system states, including on-board estimator variables and the
agent-target relative position can be achieved. The convergence of the agent's
position to the target is also investigated via numerical simulation
Two-Stage Transfer Learning for Heterogeneous Robot Detection and 3D Joint Position Estimation in a 2D Camera Image using CNN
Collaborative robots are becoming more common on factory floors as well as
regular environments, however, their safety still is not a fully solved issue.
Collision detection does not always perform as expected and collision avoidance
is still an active research area. Collision avoidance works well for fixed
robot-camera setups, however, if they are shifted around, Eye-to-Hand
calibration becomes invalid making it difficult to accurately run many of the
existing collision avoidance algorithms. We approach the problem by presenting
a stand-alone system capable of detecting the robot and estimating its
position, including individual joints, by using a simple 2D colour image as an
input, where no Eye-to-Hand calibration is needed. As an extension of previous
work, a two-stage transfer learning approach is used to re-train a
multi-objective convolutional neural network (CNN) to allow it to be used with
heterogeneous robot arms. Our method is capable of detecting the robot in
real-time and new robot types can be added by having significantly smaller
training datasets compared to the requirements of a fully trained network. We
present data collection approach, the structure of the multi-objective CNN, the
two-stage transfer learning training and test results by using real robots from
Universal Robots, Kuka, and Franka Emika. Eventually, we analyse possible
application areas of our method together with the possible improvements.Comment: 6+n pages, ICRA 2019 submissio
Vortex Flows in the Solar Chromosphere -- I. Automatic detection method
Solar "magnetic tornadoes" are produced by rotating magnetic field structures
that extend from the upper convection zone and the photosphere to the corona of
the Sun. Recent studies show that such rotating features are an integral part
of atmospheric dynamics and occur on a large range of spatial scales. A
systematic statistical study of magnetic tornadoes is a necessary next step
towards understanding their formation and their role for the mass and energy
transport in the solar atmosphere. For this purpose, we have developed a new
automatic detection method for chromospheric swirls, i.e. the observable
signature of solar tornadoes or, more generally, chromospheric vortex flows and
rotating motions. Unlike the previous studies that relied on visual
inspections, our new method combines a line integral convolution (LIC) imaging
technique and a scalar quantity which represents a vortex flow on a
two-dimensional plane. We have tested two detection algorithms, based on the
enhanced vorticity and vorticity strength quantities, by applying them to 3D
numerical simulations of the solar atmosphere with CO5BOLD. We conclude that
the vorticity strength method is superior compared to the enhanced vorticity
method in all aspects. Applying the method to a numerical simulation of the
solar atmosphere revealed very abundant small-scale, short-lived chromospheric
vortex flows that had not been found by visual inspection before.Comment: 12 pages, 9 figures, accepted for publication in A&
Video Interpolation using Optical Flow and Laplacian Smoothness
Non-rigid video interpolation is a common computer vision task. In this paper
we present an optical flow approach which adopts a Laplacian Cotangent Mesh
constraint to enhance the local smoothness. Similar to Li et al., our approach
adopts a mesh to the image with a resolution up to one vertex per pixel and
uses angle constraints to ensure sensible local deformations between image
pairs. The Laplacian Mesh constraints are expressed wholly inside the optical
flow optimization, and can be applied in a straightforward manner to a wide
range of image tracking and registration problems. We evaluate our approach by
testing on several benchmark datasets, including the Middlebury and Garg et al.
datasets. In addition, we show application of our method for constructing 3D
Morphable Facial Models from dynamic 3D data
Unobtrusive and pervasive video-based eye-gaze tracking
Eye-gaze tracking has long been considered a desktop technology that finds its use inside the traditional office setting, where the operating conditions may be controlled. Nonetheless, recent advancements in mobile technology and a growing interest in capturing natural human behaviour have motivated an emerging interest in tracking eye movements within unconstrained real-life conditions, referred to as pervasive eye-gaze tracking. This critical review focuses on emerging passive and unobtrusive video-based eye-gaze tracking methods in recent literature, with the aim to identify different research avenues that are being followed in response to the challenges of pervasive eye-gaze tracking. Different eye-gaze tracking approaches are discussed in order to bring out their strengths and weaknesses, and to identify any limitations, within the context of pervasive eye-gaze tracking, that have yet to be considered by the computer vision community.peer-reviewe
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