Digital repetitive control under varying frequency conditions

Premi extraordinari doctorat curs 2011-2012, àmbit d’Enginyeria IndustrialThe tracking/rejection of periodic signals constitutes a wide field of research in the control theory and applications area and Repetitive Control has proven to be an efficient way to face this topic; however, in some applications the period of the signal to be tracked/rejected changes in time or is uncertain, which causes and important performance degradation in the standard repetitive controller. This thesis presents some contributions to the open topic of repetitive control working under varying frequency conditions. These contributions can be organized as follows: One approach that overcomes the problem of working under time varying frequency conditions is the adaptation of the controller sampling period, nevertheless, the system framework changes from Linear Time Invariant to Linear Time-Varying and the closed-loop stability can be compromised. This work presents two different methodologies aimed at analysing the system stability under these conditions. The first one uses a Linear Matrix Inequality (LMI) gridding approach which provides necessary conditions to accomplish a sufficient condition for the closed-loop Bounded Input Bounded Output stability of the system. The second one applies robust control techniques in order to analyse the stability and yields sufficient stability conditions. Both methodologies yield a frequency variation interval for which the system stability can be assured. Although several approaches exist for the stability analysis of general time-varying sampling period controllers few of them allow an integrated controller design which assures closed-loop stability under such conditions. In this thesis two design methodologies are presented, which assure stability of the repetitive control system working under varying sampling period for a given frequency variation interval: a mu-synthesis technique and a pre-compensation strategy. On a second branch, High Order Repetitive Control (HORC) is mainly used to improve the repetitive control performance robustness under disturbance/reference signals with varying or uncertain frequency. Unlike standard repetitive control, the HORC involves a weighted sum of several signal periods. With a proper selection of the associated weights, this high order function offers a characteristic frequency response in which the high gain peaks located at harmonic frequencies are extended to a wider region around the harmonics. Furthermore, the use of an odd-harmonic internal model will make the system more appropriate for applications where signals have only odd-harmonic components, as in power electronics systems. Thus an Odd-harmonic High Order Repetitive Controller suitable for applications involving odd-harmonic type signals with varying/uncertain frequency is presented. The open loop stability of internal models used in HORC and the one presented here is analysed. Additionally, as a consequence of this analysis, an Anti-Windup (AW) scheme for repetitive control is proposed. This AW proposal is based on the idea of having a small steady state tracking error and fast recovery once the system goes out of saturation. The experimental validation of these proposals has been performed in two different applications: the Roto-magnet plant and the active power filter application. The Roto-magnet plant is an experimental didactic plant used as a tool for analysing and understanding the nature of the periodic disturbances, as well as to study the different control techniques used to tackle this problem. This plant has been adopted as experimental test bench for rotational machines. On the other hand, shunt active power filters have been widely used as a way to overcome power quality problems caused by nonlinear and reactive loads. These power electronics devices are designed with the goal of obtaining a power factor close to 1 and achieving current harmonics and reactive power compensation.Award-winningPostprint (published version

Cinemática inversa de robots industriales

El uso de robots en ambientes industriales, y más precisamente en procesos de manufactura, ha generado toda una línea de investigación y desarrollo en ingeniería. El propósito es el desarrollo de dispositivos encargados del desempeño de operaciones específicas de la función de producción como manejo de materiales, procesamiento de operaciones, ensamble e inspección, realizando labores para las cuales los seres humanos no son aptos, les representa riesgo o dificultad, ejecutando ciclos repetitivos y trabajos de ensamble automatizado en líneas de producción o celdas de manufactura

Integración de dispositivos y redes industriales seriales con redes TCP/IP usando java

La Celda Manufactura Flexible de Experimental (CMFE) del Laboratorio de Mecatrónica de la Universidad Nacional de Colombia se constituye en un proyecto macro que pretende explorar los sistemas modernos de manufactura del entorno industrial. El proyecto de investigación lleva como título “Investigación Experimental en Automatización para Manufactura Flexible”; como parte de su desarrollo, específicamente en cuanto a los estudios adelantados en las áreas de automatización y comunicaciones industriales y la puesta en funcionamiento de la CMFE, en el presente artículo se desarrolla el proceso de implementación de un sistema de integración y comunicación para la celda flexible, empleando redes de área local basadas en el protocolo TCP/IP. En el documento se describen de manera breve los componentes de la celda experimental, con el propósito de enmarcar el problema de investigación; luego se aborda el diseño y estructura final del sistema de integración

Objetos para repensar La heterogeneidad plástica como experiencia estético-artística

Las preguntas surgen a partir de la reflexión al encuentro estético con algunos objetos hechos de manera creativa e ingeniosa en un universo de resignificación y producción alternativa que tiene como regla, la construcción de un objeto, arreglárselas con lo que se tiene a la mano, el reordenar usos, otorgar nuevas funciones, recomponiendo desechos, reincorporando y reestructurando diseños. Mi inquietud por el alcance estético de los objetos resignificados me genera en términos generales, la necesidad de experimentarme en una producción de obra, agregándole a los desechos, otras funcionalidades diferentes a las originales para operar por medio de signos visuales, por lo que pueden significar, darles un orden satisfactorio en la cuidadosa composición de elementos que deben dar origen a un todo integrado, armónico y funcional. Cualidades que tiene estas manifestaciones populares en donde hay una riqueza de heterogeneidad plástica, que no le basta satisfacer una fusión práctica o técnica, sino que también existe en ella un tipo de relación estética visual que logra funcionalmente lo bello y lo útil de quien habla con las cosas y habla por medio de las cosas. Esta investigación-creación aporta en el campo de la investigación en artes a nivel nacional, el análisis y referencia de la estética popular en Colombia y lo que esto puede llegar a futuro a posibilitar, por otra parte, la oportunidad para reflexionar sobre los procesos de creación de obra estético-artística con materiales de desecho.The questions arise from the reflection on the aesthetic encounter with some objects made in a creative and ingenious way in a universe of resignification and alternative production that has as a rule, the construction of an object, making do with what is at hand, rearranging uses, giving new functions, recomposing waste, reincorporating and restructuring designs. My concern for the aesthetic scope of resignified objects generates in general terms, the need to experiment myself in a production of work, adding to the waste, other functionalities different from the original ones to operate through visual signs, for what they can mean, giving them a satisfactory order in the careful composition of elements that should give rise to an integrated, harmonious and functional whole. Qualities that have these popular manifestations where there is a wealth of plastic heterogeneity, which is not enough to satisfy a practical or technical fusion, but there is also in it a kind of visual aesthetic relationship that functionally achieves the beautiful and useful of who speaks with things and speaks through things. This research-creation contributes to the field of research in the arts at the national level, the analysis and reference of popular aesthetics in Colombia and what this can make possible in the future, on the other hand, the opportunity to reflect on the processes of creation of aesthetic artistic work with waste materials.MaestríaMagíster en Estética y CreaciónINDICE Introducción..................................................................................................................................................4 El universo de resignificación como manifestación de la virtualización.....................................................11 El objeto resignificado y la posibilidad de interpretación de la realidad....................................................21 La resignificación de las practicas estético-artísticas hacia lo etnográfico.................................................26 La Exploración.............................................................................................................................................34 La Auto Referencialidad Y La Referencia. ...............................................................................................35 Trayecto I: La Infancia y el Juego simbólico hacia la resignificación...................................................37 Trayecto II: La Televisión.....................................................................................................................48 Trayecto III: Las posibilidades de la internet.......................................................................................59 Trayecto IV: El encuentro estético al caminar....................................................................................65 Referentes Teóricos Y Conceptuales...........................................................................................................74 La prevalencia de la forma impulsó el surgimiento de la idea. ..............................................................75 Referentes Contextuales.............................................................................................................................87 I Crisis. La necesidad te obliga a pensar (Cuba y los embargos Yankis)..................................................88 II Crisis. A la luz de la desesperanza bolivariana (Venezuela )................................................................95 III Crisis. COVID 19. La emergencia sanitaria y económica (Santiago de Cali -1ª parte).......................100 IV crisis. El paso del huracán IOTA – Old Providence and Santa Catalina islands.................................104 V Crisis. Los 12 huevos a 1.800, El grito del florero de Llorente contemporáneo en el estallido social del paro nacional (Santiago de Cali - 2ª parte). ....................................................................................110 Referentes de resignificación popular..................................................................................................123 Experimentación. ......................................................................................................................................127 El lugar de síntesis.................................................................................................................................145 Conclusiones.............................................................................................................................................15

Voltage H8 control of a vanadium redox flow battery

Redox flow batteries are one of the most relevant emerging large-scale energy storage technologies. Developing control methods for them is an open research topic; optimizing their operation is the main objective to be achieved. In this paper, a strategy that is based on regulating the output voltage is proposed. The proposed architecture reduces the number of required sensors. A rigorous design methodology that is based on linear H8 synthesis is introduced. Finally, some simulations are presented in order to analyse the performance of the proposed control system. The results show that the obtained controller guaranties robust stability and performance, thus allowing the battery to operate over a wide range of operating conditions. Attending to the design specifications, the controlled voltage follows the reference with great accuracy and it quickly rejects the effect of sudden current changes.Peer ReviewedPostprint (published version

Power quality improvement through a UPQC and a resonant observer-based mimo control strategy

Performance degradation is, in general, regarded as a power quality problem. One solution to recover grid performance is through the application of a unified power quality conditioner (UPQC). Although these devices are multi-input/multi-output (MIMO) systems, the most common control strategies consist of two decoupled controllers, which neglect the coupling effects and add uncertainty to the system. For this reason, this paper proposes a multivariable resonant observer-based control strategy of a UPQC system. This method includes all significant coupling effects between this system and the grid. This strategy results in a stability-based compensator, which differs from recently proposed strategies that are based on signal calculation and cannot assure closed-loop stability. In addition, this paper introduces a simplified controller tuning strategy based on optimal conventional methods without losing closed-loop performance. It implies that the controller can be easily tuned, despite the complexity of the MIMO dynamic model. The UPQC with the resonant observer is verified on an experimental setup for a single-phase system, obtaining three relevant results for power quality improvement: (1) harmonics compensation tested with a total harmonic distortion limit of 5%; (2) sags and swells mitigation; and (3) power factor correction, achieving a unitary value on the grid side.Peer ReviewedPostprint (published version

Diseño y construcción de un equipo de soldadura por fricción con asistencia láser para la unión de ejes de acero AISI 1045 y aluminio 2017-T4

Welding metal alloys with dissimilar melting points make conventional welding processes unfeasible to be used. On the other hand, friction welding has proven to be a promising technology capable of joining materials, while preventing the temperature from exceeding the melting point. However, obtaining a welded joint with mechanical properties that are similar to the base materials remains a challenge. In the development of this work, a laser-assisted rotary friction welding equipment was designed and manufactured. A 3 HP conventional lathe was used to provide rotary movement, and a hydraulic pressure system that applies axial force through a simple effect cylinder was designed to generate friction to obtain the union between the base materials. In the implemented equipment, joints of AISI 1045 steel and 2017-T6 aluminum shafts were made. The welded joints were metallurgically evaluated, emphasizing on the chemical composition at the weld interface. For microstructure characterization, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and glow discharge optical emission spectrometry (GDOES) were used to measure the initial composition of the welded materials. The results obtained show an adequate joint between the base materials, denoting the usefulness of the equipment manufactured for the union of dissimilar materials.La soldadura de materiales disímiles hace que los procesos de soldadura convencional no sean factibles de ser utilizados. La soldadura por fricción, por otro lado, ha demostrado ser una tecnología prometedora capaz de unir materiales sin que la temperatura supere su punto de fusión. Sin embargo, la obtención de las propiedades mecánicas de la junta soldada con características similares a los materiales base sigue siendo un desafío. En el desarrollo de este trabajo se diseñó y fabricó un equipo de soldadura por fricción rotatoria con asistencia láser. Para proporcionar el movimiento rotatorio se empleó un torno convencional de 3 HP de potencia y para generar fricción se diseñó un sistema hidráulico de presión el cual aplica fuerza axial mediante un cilindro de simple efecto para obtener la unión entre los materiales base. En el equipo implementado se realizaron uniones de ejes de acero AISI 1045 con aluminio 2017-T6; las uniones soldadas se evaluaron metalúrgicamente, haciendo hincapié en la composición química en la interfaz de la soldadura. Para la caracterización de la microestructura se empleó microscopía electrónica de barrido (SEM), espectroscopía de dispersión de energía (EDS) y espectrometría de emisión óptica de descarga luminiscente (GDOES) para medir la composición inicial de los materiales que se soldaron. Los resultados obtenidos muestran una adecuada unión entre los materiales base, denotando la utilidad del equipo fabricado para la unión de materiales disimiles

Adaptive Compensation Strategy For The Tracking/Rejection of Signals with Time-Varying Frequency in Digital Repetitive Control Systems

Digital repetitive control is a technique which al- lows to track periodic references and/or reject peri- odic disturbances. Repetitive controllers are usually de- signed assuming a fixed frequency for the signals to be tracked/rejected, its main drawback being a dramatic per- formance decay when this frequency varies. A usual ap- proach to overcome the problem consists of an adap- tive change of the sampling time according to the refer- ence/disturbance period variation. However, this sam- pling period adaptation implies parametric changes af- fecting the closed-loop system behavior, that may compro- mise the system stability. This article presents a design strategy which allows to compensate for the parametric changes caused by sampling period adjustment. Stabil- ity of the digital repetitive controller working under time- varying sampling period is analyzed. Theoretical devel- opments are illustrated with experimental results.Peer ReviewedPostprint (published version

Non-uniform sampling in digital repetitive control systems: An LMI stability analysis

Digital repetitive control is a technique which allows to track periodic references and/or reject periodic disturbances. Repetitive controllers are usually designed assuming a fixed frequency for the signals to be tracked/rejected, its main drawback being a dramatic performance decay when this frequency varies. A usual approach to overcome the problem consists of an adaptive change of the sampling time according to the reference/disturbance period variation. This report presents a stability analysis of a digital repetitive controller working under time-varying sampling period by means of an LMI gridding approach. Theoretical developments are illustrated with experimental results