Papers by Rodolfo Villamizar
Corrosion
The electrochemical frequency modulation (EFM) is a promising non-destructive technique that uses... more The electrochemical frequency modulation (EFM) is a promising non-destructive technique that uses a small bi-harmonic disturbance signal along with the discrete Fourier transform (DFT) to calculate the corrosion current and Tafel slopes from a set of equations that rely on harmonic components. Significant results have been published mainly on systems exhibiting Tafel behavior. This work presents the use of polynomial approximation as a data analysis alternative for the EFM technique, which has three main advantages over the procedure proposed by the authors of the EFM technique: a) reduction of the estimation error caused by the capacitance effect, b) reduction of the estimation error caused by high harmonic components and c) the reduction of computational complexity. This analysis was tested experimentally using a traditional three-electrode cell with a carbon steel working electrode and a sodium chloride solution as the electrolyte. Finally, the results were compared to linear pol...
Following glucose profiles of T1DM UVA/Padova in silico patients, by using estimated carbohydrate intake in a MPC controller
2020 7th International Conference on Control, Decision and Information Technologies (CoDIT), 2020
In recent years, several closed loop control strategies have been developed in order to maintain ... more In recent years, several closed loop control strategies have been developed in order to maintain a health glucose level in type 1 diabetic mellitus (T1DM) patients. However, a feedback controller itself is unable to define a postprandial (after a food intake) glucose trajectory. Thus, in this paper a new control approach is defined by using two main blocks: a MPC feedback/feed-forward controller and a carbohydrate intake estimator. Then, by estimating moment and amount of intake of carbohydrates, on one hand, such disturbance is compensated and on other one, a healthy subject profile is generated for being followed by the MPC feedback controller. One of the advantages of using a glucose profile in place of a fixed glucose reference is that quantity of infused insulin could be lower and distributed along the time, which could avoid hypoglycemia episodes. Finally, an in-silico validation of the control approach was achieved by using glucose dynamics models provided by the T1DMS UVA/Padova simulator (Accepted by Food & Drug Administration).
The implementation of the dynamic and kinematic models of an underwater remotely operated vehicle... more The implementation of the dynamic and kinematic models of an underwater remotely operated vehicle (VideoRay Pro III) in Matlab/Simulink is presented. The system was built as a closed loop configuration where the inputs are the desired bodyfixed velocities or the inertial-frame position and orientation. The block diagram allows for the observation of the UROV states and thrusts exerted by the propellers. The implementation of the VideoRay Pro III models is the initial phase of a research that seeks to establish the instrumentation and computational architecture for the aided inertial navigation of an UROV.
Simulación de la dinámica de la glucosa y la insulina en pacientes con diabetes mellitus tipo I
Rev. Colomb. de Computación, 2008
La diabetes mellitus tipo I es una enfermedad de salud publica cada vez mas comun entre la gente,... more La diabetes mellitus tipo I es una enfermedad de salud publica cada vez mas comun entre la gente, no necesariamente tiene sus origenes en el paso genetico entre generaciones. Como tal existe un desorden en los niveles normales en la glucosa en la sangre y su tratamiento medico actual mas comun es la aplicacion de insulina al paciente deacuerdo a ciertas relaciones como el peso, la edad, habitos alimenticios entre otros, este ajuste lo realiza el medico casi a prueba y error hasta encontrar el nivel adecuado para cada paciente asi como su frecuencia de aplicacion. Palabras clave: Diabetes Mellitus Tipo I, Dosificacion, Insulina, Subcutanea, modelos de compartimientos.
Carbohydrate Intake Estimation in Type I Diabetic Patients Described by UVA/Padova Model
Journal of Physics: Conference Series, 2017
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licenc... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Reducción Del Modelo De Sorensen Para La Dinámica De La Glucosa Usando Mpca
Proposal of a reduced model to control the glucose dynamic in type I Diabetes Mellitus patient
Robust control law for a friction-based semiactive controller of a two-span bridge
Smart Structures and Materials 2003: Smart Systems and Nondestructive Evaluation for Civil Infrastructures, 2003
abstract This paper addresses the problem of formulating a feedback control law for the semiactiv... more abstract This paper addresses the problem of formulating a feedback control law for the semiactive control of a class of two-span bridge, which is equipped with controllable friction devices at the joints between the columns and the deck. A finite element model is available to represent the essential dynamical features of the bridge. Based on this model, a Lyapunov-based robust semiactive control law is designed, which uses feedback from the nodes where the devices are located. Two sources of uncertainties are considered in the ...
Experimental Verification of a Backstepping Controller for Magnetorheological MR Dampers in Structural Control
Proceedings of the 2005 IEEE International Symposium on, Mediterrean Conference on Control and Automation Intelligent Control, 2005., 2005
Abstract This paper deals with the development and validation of a backstepping controller to eff... more Abstract This paper deals with the development and validation of a backstepping controller to effectively reduce seismic responses of civil engineering buildings due to external disturbances such as earthquakes, heavy loads and strong winds. Semiactive control systems using magnetorheological MR dampers are especially studied by means of simulated and experimental tests. Two control strategies using backstepping control technique were studied. Experimental verification of semiactive controllers was achieved ...
Revista Uis Ingenierias, May 14, 2013
Este artículo presenta una revisión del estado del arte de métodos de medición no invasiva de glu... more Este artículo presenta una revisión del estado del arte de métodos de medición no invasiva de glucosa en el cuerpo mediante diversos tipos de espectroscopia por radiación infrarroja cercana. Primero se presentan algunos conceptos fundamentales relacionados con glucosa y espectroscopia, luego se realiza un resumen de los métodos propuestos y las técnicas, reportados en la literatura, empleadas para: i) la aplicación de la espectroscopia, ii) la simulación de muestras y iii) el análisis de resultados. Finalmente, se relacionan algunas de las propuestas aplicadas in vivo, agrupadas de acuerdo con la región del cuerpo empleada para la toma de las muestras espectrales.
Revista Colombiana de Computación, 2011
En el presente artículo se aplican y ajustan algunas técnicas y metodologías para la detección de... more En el presente artículo se aplican y ajustan algunas técnicas y metodologías para la detección de fallos en una planta de Cracking Catalítico Fluidizado (FCC) modelo UOP, inicialmente se realiza un análisis de confiabilidad que permite definir el nivel de criticidad de cada uno de los equipos e identificar modos de fallo potenciales y su efecto sobre la operación de la planta; con la información entregada por este análisis se establecen casos de estudio, como requerimientos para un sistema de supervisión, detección y clasificación de situaciones anómalas, que pueden llevar al proceso a una condición de fallo. Para estudiar los casos se simulan las condiciones con un modelo de operación de la unidad FCC y se detectan los fallos con una herramienta basada en PCA (Análisis de componentes principales) y Lógica Fuzzy; finalmente se ajusta la herramienta utilizando datos históricos del proceso en presencia del fallo.
Online monitoring systems demand an adequate operation of sensor system used to acquire structura... more Online monitoring systems demand an adequate operation of sensor system used to acquire structural state measurements. If a damaged sensor record is incorporated in the diagnosis algorithm, it could be generate uncertainties and generate unsuitable alarms. Thus, appropriate operation of sensor system is a critical requirement in order to obtain a high reliability for structural damage diagnosis algorithms. In this work a data-driven procedure is studied in order to mitigate the faulty sensor effect in a monitoring system. The studied method takes advantage of piezo-diagnostics approach, where piezoelectric devices are attached to the surface of the monitored structure to produce guided waves. Thus, piezoelectric measurements are analyzed by applying principal component analysis and cross-correlation, in order to detect abnormal behaviors. In this sense, the squared prediction error Q and Hotelling squared statistical indices are used to observe a typical behaviour caused by sensor p...
Control robusto del pH en fotobiorreactores mediante rechazo activo de perturbaciones
En este trabajo se aborda el problema de la regulacion del pH en fotobiorreactores usando el enfo... more En este trabajo se aborda el problema de la regulacion del pH en fotobiorreactores usando el enfoque de control por rechazo activo de perturbaciones. Dicha formulacion se basa en el diseno de observadores GPI para la estimacion en linea de perturbaciones externas y dinamicas no modeladas empleando el concepto de planitud diferencial. Con el fin de validar el rendimiento del controlador propuesto, se utiliza un simulador de un fotobiorreactor tipo Raceway a escala. Los resultados de simulacion demuestran que el algoritmo de control evaluado mejora significativamente la precision de la regulacion del pH, logrando con ello una influencia positiva en la produccion de biomasa.
Torsional Waves for Load Monitoring of Cylindrical Waveguides
This paper is aimed to produce a methodology to monitoring changes in the load condition in the s... more This paper is aimed to produce a methodology to monitoring changes in the load condition in the support based on the understanding of how the mode T(0,1) interacts with simple supports under varying load conditions. An analytical expression of the phase velocity for the fundamental torsional mode T(0,1) propagating in a medium under mechanical stress is derived based on the acoustoelasticity effect. A test bench is implemented to emulate a failure or a change in the loading support conditions. A scheme pitch-catch is adopted taking advantage of an affordable way to produce torsional waves in situ based on the magnetostriction effect
Automatic Tuning of a Pipeline Faults Detection Algorithm
This paper discusses the experimental results obtained by using a principal component analysis ba... more This paper discusses the experimental results obtained by using a principal component analysis based algorithm in joint with Self Organizing Maps (SOM) Neural Networks for detection of damages in pipeline structures. Also, a differential evolutive algorithm is used for tunig the neural network parameters. A pipeline section test structure was instrumented with an active piezoelectric system in order to apply a high known frequency signal and to determine the base-line structural dynamical performance. Several piezoelectric sensors were located along the structure surface and damage features are obtained by processing the time vibrational dynamical response through principal component analysis. Q-statistic and Hotteling T2 indexes obtained from the PCA analysis are used to detect deviations of the current vibrational response respect to the undamaged one. Algorithm validation was achieved by using experimental data, obtained from a carbon steel tubing section, where damages were indu...
Sensors, Apr 19, 2018
In this paper, a support stiffness monitoring scheme based on torsional guided waves for detectin... more In this paper, a support stiffness monitoring scheme based on torsional guided waves for detecting loss of rigidity in a support of cylindrical structures is presented. Poor support performance in cylindrical specimens such as a pipeline setup located in a sloping terrain may produce a risky operation condition in terms of the installation integrity and the possibility of human casualties. The effects of changing the contact forces between support and the waveguide have been investigated by considering variations in the load between them. Fundamental torsional T(0, 1) mode is produced and launched by a magnetostrictive collar in a pitch-catch configuration to study the support effect in the wavepacket propagation. Several scenarios are studied by emulating an abnormal condition in the support of a dedicated test bench. Numerical results revealed T(0, 1) ultrasonic energy leakage in the form of SH 0 bulk waves when a mechanical coupling between the cylindrical waveguide and support is yielded. Experimental results showed that the rate of ultrasonic energy leakage depends on the magnitude of the reaction forces between pipe and support; so different levels of attenuation of T(0, 1) mode will be produced with different mechanical contact conditions. Thus, it is possible to relate a measured attenuation to variations in the supports condition. Results of each scenarios are presented and discussed demonstrating the feasibility and potential of tracking of the amplitude of the T(0, 1) as an indicator of abnormal conditions in simple supports.
Journal of Physics: Conference Series
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licenc... more Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
PCA y lógica fuzzy para la detección de eventos anormales de operación, en una planta de Craqueo Catalítico Fluidizado FCC
En el presente artículo se aplican y ajustan algunas técnicas y metodologías para la detección de... more En el presente artículo se aplican y ajustan algunas técnicas y metodologías para la detección de fallos en una planta de Cracking Catalítico Fluidizado (FCC) modelo UOP, inicialmente se realiza un análisis de confiabilidad que permite definir el nivel de criticidad de cada uno de los equipos e identificar modos de fallo potenciales y su efecto sobre la operación de la planta; con la información entregada por este análisis se establecen casos de estudio, como requerimientos para un sistema de supervisión, detección y clasificación de situaciones anómalas, que pueden llevar al proceso a una condición de fallo. Para estudiar los casos se simulan las condiciones con un modelo de operación de la unidad FCC y se detectan los fallos con una herramienta basada en PCA (Análisis de componentes principales) y lógica fuzzy; finalmente se ajusta la herramienta utilizando datos históricos del proceso en presencia del fallo.
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Papers by Rodolfo Villamizar