29 research outputs found
Numerical analysis of dynamical systems with codimension two singularities
Páez Chávez JN. Numerical analysis of dynamical systems with codimension two singularities. Bielefeld (Germany): Bielefeld University; 2009
Numerical analysis of a multistable capsule system under the delayed feedback control with a constant delay
The vibro-impact capsule system is a self-propelled mechanism that has
abundant coexisting attractors and moves rectilinearly under periodic
excitation when overcoming environmental resistance. In this paper, we study
the control of coexisting attractors in this system by using a delayed feedback
controller (DFC) with a constant delay. The aim of our control is to steer this
complex system toward an attractor with preferable performance characteristics
among multiple coexisting attractors, e.g., a periodically fast forward
progression. For this purpose, we give an example of a feedback-controlled
transition from a period-3 motion with low progression speed to a period-1
motion with high progression speed at the system parameters where both
responses coexist. The effectiveness of this controller is investigated
numerically by considering its convergence time and the required control energy
input to achieve transition. We combine pseudo-spectral approximation of the
delay, event detection for the discontinuities and path-following
(continuation) techniques for non-smooth delay dynamical systems to carry out
bifurcation analysis. We systematically study the dynamical performance of the
controlled system when varying its control gain and delay time. Our numerical
simulations show the effectiveness of DFC under a wide range of system
parameters. We find that the desired period-1 motion is achievable in a range
of control delays between a period-doubling and a grazing bifurcation.
Therefore, two-parameter continuation of these two bifurcations with respect to
the control delay and control gain is conducted to identify the delay-gain
parameter region where the period-1 motion is stable. The findings of this work
can be used for tuning control parameters in experiments, and similar analysis
can be carried out for other non-smooth dynamical systems with a constant delay
term.Comment: submitted to International Journal of Nonlinear Mechanic
Experimental studies of forward and backward whirls of drill-string
The authors wish to thank BG Group plc for the financial support to this research.Peer reviewedPostprin
Numerical and experimental studies of stick-slip oscillations in drill-strings.
The cyclic nature of the stick-slip phenomenon may cause catastrophic failures in drill-strings or at the very least could lead to the wear of expensive equipment. Therefore, it is important to study the drilling parameters which can lead to stick-slip, in order to develop appropriate control methods for suppression. This paper studies the stick-slip oscillations encountered in drill-strings from both numerical and experimental points of view. The numerical part is carried out based on path-following methods for non-smooth dynamical systems, with a special focus on the multistability in drill-strings. Our analysis shows that, under a certain parameter window, the multistability can be used to steer the response of the drill-strings from a sticking equilibrium or stick-slip oscillation to an equilibrium with constant drill-bit rotation. In addition, a small-scale downhole drilling rig was implemented to conduct a parametric study of the stick-slip phenomenon. The parametric study involves the use of two flexible shafts with varying mechanical properties to observe the effects that would have on stick-slip during operation. Our experimental results demonstrate that varying some of the mechanical properties of the drill-string could in fact control the nature of stick-slip oscillations
Proof-of-concept prototype development of the self-propelled capsule system for pipeline inspection.
This paper studies the prototype development for the self-propelled capsule system which is driven by autogenous vibrations and impacts under external resistance forces. This project aims for proof-of-concept of its locomotion in pipeline environment in order to mitigate the technical complexities and difficulties brought by current pressure-driven pipeline inspection technologies. Non-smooth multibody dynamics is applied to describe the motion of the capsule system, and two non-smooth nonlinearities, friction and impact, are considered in modelling. The prototype of the self-propelled capsule system driven by a push-type solenoid with a periodically excited rod has been designed to verify the modelling approach. The prototype contains a microcontroller, a power supply, and a wireless control module, which has been tested in a clear uPVC pipe via remote control. Various control parameters, e.g. impact stiffness, frequency and amplitude of excitation, are studied experimentally, and finally, the fastest progression of the system is obtained
Estimating the herd immunity threshold by accounting for the hidden asymptomatics using a COVID-19 specific model
A quantitative COVID-19 model that incorporates hidden asymptomatic patients is developed, and an analytic solution in parametric form is given. The model incorporates the impact of lock-down and resulting spatial migration of population due to announcement of lock-down. A method is presented for estimating the model parameters from real-world data, and it is shown that the various phases in the observed epidemiological data are captured well. It is shown that increase of infections slows down and herd immunity is achieved when active symptomatic patients are 10-25% of the population for the four countries we studied. Finally, a method for estimating the number of asymptomatic patients, who have been the key hidden link in the spread of the infections, is presented. © 2020 Kaushal et al
Controlling multistability in a vibro-impact capsule system
This is the final version of the article. Available from Springer Verlag via the DOI in this record.This work concerns the control of multistability in a vibro-impact capsule system driven by a harmonic excitation. The capsule is able to move forward and backward in a rectilinear direction, and the main objective of this work is to control such motion in the presence of multiple coexisting periodic solutions. A position feedback controller is employed in this study, and our numerical investigation demonstrates that the proposed control method gives rise to a dynamical scenario with two coexisting solutions, corresponding to forward and backward progression. Therefore, the motion direction of the system can be controlled by suitably perturbing its initial conditions, without altering the system parameters. To study the robustness of this control method, we apply numerical continuation methods in order to identify a region in the parameter space in which the proposed controller can be applied. For this purpose, we employ the MATLAB-based numerical platform COCO, which supports the continuation and bifurcation detection of periodic orbits of non-smooth dynamical systems.The second author has been supported by a Georg Forster Research Fellowship granted by the Alexander von Humboldt Foundation, Germany. The authors would like to thank Dr. Haibo Jiang for stimulating discussions and comments on this work
Ecos de la academia: Revista de la Facultad de Educación, Ciencia y Tecnología - FECYT Nro 6
Ecos de la academia, Revista de la Facultad de Educación Ciencia y Tecnología es una publicación científica de la Universidad Técnica del Norte, con revisión por pares a doble ciego que publica artículos en idioma español, quichua, portugués e inglés. Se edita con una frecuencia semestral con dos números por año.En ella se divulgan trabajos originales e inéditos generados por los investigadores, docentes y estudiantes de la FECYT, y contribuciones de profesionales de instituciones docentes e investigativas dentro y fuera del país, con calidad, originalidad y relevancia en las áreas de ciencias sociales y tecnología aplicada.Modelos multidimensionales del bienestar en contextos de enseñanza- aprendizaje: una revisión sistemática.
Nuevas tendencias para el área académica de la Publicidad en la zona 1 del Ecuador.
Propuesta de un curso de escritura académica bajo la base de modelos experienciales.
Aproximación al estudio de las emociones.
Seguimiento a egresados y graduados para actualizar el perfil de egreso y profesional.
Impacto de la Gerencia de Calidad en el clima organizacional en Educación Básica.
Comunicación efectiva del gerente educativo orientada al manejo de conflictos en el personal docente.
Meritocracia: Democratización o exclusión en el acceso a la educación superior en Ecuador.
Asertividad y desempeño académico en estudiantes universitarios.
La creatividad en la formación profesional.
Aspectos metodológicos en el proceso de enseñanza- aprendizaje de la gimnasia en estudiantes
de Educación Física.
English Language Learning Interaction through Web 2.0 Technologies.
La sistematización de la práctica educativa y su relación con la metodología de la investigación.
El ozono y la oxigenación hiperbárica: una vía para mejorar la recuperación en lesiones deportivas.
La labor tutorial: Independencia del aprendizaje en el contexto universitario.
Motivación hacia la profesión docente en la Enseñanza Secundaria.
El uso académico de Facebook y WhatsApp en estudiantes universitarios...
La educación superior en Ecuador: situación actual y factores de mejora de la calidad.
El Proyecto de Investigación “Imbabura Étnica”