Papers by Elizabeth Villota
A robust anti-windup design procedure for SISO systems
Http Dx Doi Org 10 1080 00207179 2011 552123, Feb 1, 2011
... IEEE Transactions on Automatic Control , 54: 26972702. ... In essence, by translating the AW... more ... IEEE Transactions on Automatic Control , 54: 26972702. ... In essence, by translating the AW problem into a QFT-style graphical design, for the case of SISO systems, the non-convexity which would impede an LMI-based approach to the problem is largely avoided. ...
Panorama of the Market Demand for Mechanical Engineers in South American Countries
Volume 5: Education and Globalization, 2015
Many educational institutions employ surveys in order to identify what majors to offer or what co... more Many educational institutions employ surveys in order to identify what majors to offer or what competencies to emphasize in their curricula. Different from a survey, we present an analysis of the labor market needs based on data collected from job ads available in the Internet. Tools of natural language processing (NLP) and statistical techniques have been employed to handle the job ads. For Peru, Chile and Colombia, a detailed panorama of the market demand has been depicted: mechanical engineering appears among the top most demanded engineering majors and maintenance is its most frequent technical requirement; management (project, quality and operations) related requirements also rank high, together with a working knowledge of English. By using diverse visualization techniques we can also show the " social network " of a major, where friendship is defined by the amount of job ads shared by any two majors.
La economía peruana ha tenido un gran crecimiento durante la década pasada, debido a los altos pr... more La economía peruana ha tenido un gran crecimiento durante la década pasada, debido a los altos precios de las materias primas que exportamos. Sin embargo, en los últimos meses se ha hecho evidente que, si deseamos tener un crecimiento sostenido, se debe incrementar nuestra productividad. Uno de los pilares para incrementar la productividad es el factor humano; es decir, contar con una fuerza laboral adecuada en cantidad y calidad, acorde a las necesidades de la industria. En ese sentido, el presente trabajo presenta un panorama de la demanda laboral en el rubro de las ingenierías mecánica y eléctrica. Este panorama es el resultado de un análisis del mercado realizado sobre la base de avisos de trabajo disponibles en internet. Decenas de miles de avisos son tratados usando herramientas de procesamiento de lenguaje natural (NLP), en adición a diversas técnicas estadísticas y de visualización. Los resultados permiten afirmar que ambas ramas de ingeniería, mecánica y eléctrica, están entre las 5 más demandadas en el país. Sus correspondientes requerimientos laborales también fueron identificados; en esta parte cabe destacar que conocimientos en el área de mantenimiento se presentan como los más solicitados para ambas ramas. En términos generales, conocimientos de gestión son también muy apreciados por el mercado laboral, así como dominio del idioma inglés. Nuestro estudio constituye un mecanismo transparente basado en datos que podría facilitar el alineamiento de la oferta con la demanda laboral. Este alineamiento es fundamental a la hora de garantizar el crecimiento económico sostenido del país.
The final stage of a satellite project, and notably the most important one, is the satellite'... more The final stage of a satellite project, and notably the most important one, is the satellite's testing. While some of the required tests are relatively easy and inexpensive to perform; others involve sophisticated equipments that are rarely available, or affordable, when dealing with a university project. Tests that validate the attitude determination and control system (ADCS) fit into the latter category; for, the recreation of satellite's environment at open space in a controlled environment is not a trivial matter. Several equipments are mandatory, all of them with prices ranging in the tens of thousands of dollars. The cost and difficulty of owning this type of facility may forbid low funded projects from getting appropriate testing. Nevertheless, at Universidad Nacional de Ingenieria, where the CubeSat project Chasqui I is currently under final testing, a real time hardware in the loop (RT HIL) simulator for ADCS validation has been developed at low cost and ease of imp...
Design principles for robust oscillatory behavior
Systems and Synthetic Biology, 2015
Oscillatory responses are ubiquitous in regulatory networks of living organisms, a fact that has ... more Oscillatory responses are ubiquitous in regulatory networks of living organisms, a fact that has led to extensive efforts to study and replicate the circuits involved. However, to date, design principles that underlie the robustness of natural oscillators are not completely known. Here we study a three-component enzymatic network model in order to determine the topological requirements for robust oscillation. First, by simulating every possible topological arrangement and varying their parameter values, we demonstrate that robust oscillators can be obtained by augmenting the number of both negative feedback loops and positive autoregulations while maintaining an appropriate balance of positive and negative interactions. We then identify network motifs, whose presence in more complex topologies is a necessary condition for obtaining oscillatory responses. Finally, we pinpoint a series of simple architectural patterns that progressively render more robust oscillators. Together, these findings can help in the design of more reliable synthetic biomolecular networks and may also have implications in the understanding of other oscillatory systems.
Influence of parameter values on the oscillation sensitivities of two p53–Mdm2 models
Systems and Synthetic Biology, 2015
Biomolecular networks that present oscillatory behavior are ubiquitous in nature. While some desi... more Biomolecular networks that present oscillatory behavior are ubiquitous in nature. While some design principles for robust oscillations have been identified, it is not well understood how these oscillations are affected when the kinetic parameters are constantly changing or are not precisely known, as often occurs in cellular environments. Many models of diverse complexity level, for systems such as circadian rhythms, cell cycle or the p53 network, have been proposed. Here we assess the influence of hundreds of different parameter sets on the sensitivities of two configurations of a well-known oscillatory system, the p53 core network. We show that, for both models and all parameter sets, the parameter related to the p53 positive feedback, i.e. self-promotion, is the only one that presents sizeable sensitivities on extrema, periods and delay. Moreover, varying the parameter set values to change the dynamical characteristics of the response is more restricted in the simple model, whereas the complex model shows greater tunability. These results highlight the importance of the presence of specific network patterns, in addition to the role of parameter values, when we want to characterize oscillatory biochemical systems.
Proceedings of the 2005, American Control Conference, 2005., 2005
The present study investigates the controlled behavior of a Multidimensional Positional System (M... more The present study investigates the controlled behavior of a Multidimensional Positional System (MPS), under the application of model based control techniques (leadlag, LQR, LQG, LQG-LTR, H∞, µ-synthesis and QFT). The MPS consists of a magnetically levitated system capable of six degree-of-freedom micro and nano positioning using three novel permanent-magnet linear motors. Each motor generates a vertical force for suspension against gravity and a horizontal force for drive. Particular attention is given to the design, analysis and simulation of the control laws that guarantee tracking performance under modeled uncertainties. Closed loop identification is used to derive bounds of the variations in magnitude of the experimental data and mathematical models. Results obtained from numerical simulations are presented and judged with respect to the performance and stability achieved and the work needed to perform the designs. Laboratory experiments indicate partial success in the implementation of the designed control systems. Hence limited experimental results are presented to validate the performance of the control systems.
Hybrid magnetic attitude control system under CubeSat standards
2012 IEEE Aerospace Conference, 2012
In a one-unit (1U) CubeSat satellite, the attitude determination and control system restricts its... more In a one-unit (1U) CubeSat satellite, the attitude determination and control system restricts its allocated mass to be in the range of 150–200 g, and to operate with at most 1 W. Under such tight constraints, effective attitude control system design becomes quite challenging, especially for institutions that have no prior experience in space projects. Novice institutions usually start by designing passive control systems as they are more reliable. They only venture to test active control after attitude determination, satellite's communications, central control and power systems have been tested. Notably, at Universidad Nacional de Ingenieria, within the development of its first CubeSat satellite project Chasqui I, a hybrid magnetic attitude control system has been devised so that active control can be tested with high reliability.
Proceedings of the 45th IEEE Conference on Decision and Control, 2006
This paper considers configurations for antiwindup (AW) control of uncertain systems. Using the B... more This paper considers configurations for antiwindup (AW) control of uncertain systems. Using the Bezout identity and coprime factorizations of the unconstrained controller and the plant, the configurations currently employed for static and dynamic AW control of uncertain systems are related to the general static AW control framework of Kothare et al (1994), and its extension via a Q parameter for dynamic AW controllers. The difference (mismatch) system describing the effect of saturation on the system response is explicitly described using the coprime relations and the Q parameter. This unification of configurations offers insight into the difficulties faced when employing specific AW control configurations and facilitates improved transparency in AW control system design.
Volume 9: Mechanical Systems and Control, Parts A, B, and C, 2007
A robust anti-windup design procedure for SISO systems
International Journal of Control, 2011
... IEEE Transactions on Automatic Control , 54: 26972702. ... In essence, by translating the AW... more ... IEEE Transactions on Automatic Control , 54: 26972702. ... In essence, by translating the AW problem into a QFT-style graphical design, for the case of SISO systems, the non-convexity which would impede an LMI-based approach to the problem is largely avoided. ...
Many educational institutions employ surveys in order to identify what majors to offer or what co... more Many educational institutions employ surveys in order to identify what majors to offer or what competencies to emphasize in their curricula. Different from a survey, we present an analysis of the labor market needs based on data collected from job ads available in the Internet. Tools of natural language processing (NLP) and statistical techniques have been employed to handle the job ads. For Peru, Chile and Colombia, a detailed panorama of the market demand has been depicted: mechanical engineering appears among the top most demanded engineering majors and maintenance is its most frequent technical requirement; management (project, quality and operations) related requirements also rank high, together with a working knowledge of English. By using diverse visualization techniques we can also show the " social network " of a major, where friendship is defined by the amount of job ads shared by any two majors.
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Papers by Elizabeth Villota