2. Maestría
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Tesis de la Escuela de Posgrado
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Item Application of derivative-free adaptive control to a nanopositioning machine(Pontificia Universidad Católica del Perú, 2023-05-11) Velasquez Elguera, Mario Sebastian; Perez Zuñiga, Carlos GustavoNanopositioning and nanomeasuring machines are playing an increasingly important role in the evolution of modern technologies in various fields. The Institute of Process Measure ment and Sensor Technology at Ilmenau University of Technology has been researching for more tan one decade high precisión machines. In this direction, the general objective of this master tesis is the development of aderivative-free model reference adaptive control (DFMRAC) algorithm for the vertical axisofa nanopositioning and nanomeasuring machine. Firstly, a nonlinear unknown friction term is included in the adaptation process of a standard model reference adaptive control (MRAC) and the DFMRAC. Then, the MRAC and DFMRAC algorithms are developed theoretically, in which the DFMRAC stability análisis requiresa Lyapunov-Krasovskii functional to prove that the error signal and the weightpa- rameters are uniformly ultimately bounded (UUB). Thanks to this characteristic, the DFMRAC algorithm does not have the problema of the weight drifting parameters, as MRAC does. Overall, the new adaptive controllers have significantly better results and fine-tuning in the machine. Regarding the sine reference experimental tests with afixed amplitude of 1mm and a frequency from 0.25 Hz to 2 Hz, a reduction of the máximum error and root mean square error (RMSE) of about 95% is achieved in comparison to a simple PI state-feed back controller and the previously applied MRAC with an adaptation weight matrix of lower order. Referring to the step reference tests, with a step height of 10mm and different transition times (which are related to the máximum reached velocity from 1mm/s to 5mm/s) the máximum error and the RMSE are reduced approximately by 60% and 75%, respectively. Furthermore, the corresponding extensions to the unknown input matrix case are developed for the adaptive proposals, however it does not significantly improve the experimental results. The new controllers out performed the previous ones with DFMRAC being the best one because it does not have the drifting weight parameters problem and it is easier to implement (no need to implement any projection method). Finally, eventhough, the new adaptive algorithms have extended the size of the weight matrix and added nonlinearities to the computer calculations, the execution time is only increased by around 1 μs.Item Synthesis, characterization and corrosion resistance of electroless Ni-P and Ni-P-SiC coatings: a comparative study(Pontificia Universidad Católica del Perú, 2019-08-06) Camargo León, Magali Karina; Díaz Tang, Isabel; Flores Merino, Santiago EleodoroElectroless Ni-P coatings have been widely used due to their good combination of properties such as hardness, wear resistance and corrosion resistance. The addition of dispersed hard micro-particles into the Ni-P matrix has led to the development of composite coatings. Ni-P composite coatings exhibit an improved hardness and wear resistance properties; however, there is still a disagreement among researches on the corrosion behavior of composite Ni-P coatings. The present investigation involves the synthesis, characterization and a comparative study of the corrosion resistance in NaCl 3,5% of electroless Ni-P and Ni-P-SiC deposits obtained by either prepared or commercial electrolytic nickel/hypophosphite based baths. The characterization of deposits involved studies about morphology by SEM, chemical composition by energy-dispersive X-ray spectroscopy (EDX) and glow discharge optical emission spectroscopy (GDOS), microstructure by X-ray diffraction (XRD) and hardness. All deposits showed an amorphous micro-structure and high phosphorus content (10-14 wt%). Ni-P-SiC deposits showed an increased hardness (802 HV-815 HV) in comparison with Ni-P deposits (469 HV-626 HV). The techniques used to study the corrosion resistance in NaCl 3,5% were linear polarization resistance (LPR), Tafel plots and electrochemical impedance spectroscopy (EIS). These techniques agreed to show the better corrosion resistance of Ni-P-SiC coatings over the Ni-P coatings. This fact can be ascribed to the decrease in the effective metallic area available for corrosion. Ni-P-SiC deposits exhibited higher polarization resistance (Rp) values (103-66 kΩ.cm2) in comparison with Ni-P deposits (46-55 kΩ.cm2). Also, the corrosion current density values of Ni-P-SiC deposits (0,17-0,65 µA/cm2) were lower than Ni-P deposits (0,71-1,08 µA/cm2). Concerning to the mechanism by which the Ni-P and Ni-P-SiC become corroded, EIS experiments demonstrated that the corrosion process involved a charge transfer mechanism in all the cases. Tafel plots also corroborated this mechanism since of all deposits showed a Tafel behavior.Item Síntesis de nanopartículas de óxido de cinc para la detección de huellas dactilares latentes(Pontificia Universidad Católica del Perú, 2017-11-29) Flores Mariños, Betty Mercedes; Guzmán Córdova, Maribel GiovanaEl objetivo principal de este trabajo fue el desarrollo y optimización de un proceso de síntesis de nanopartículas de óxido de cinc para aplicaciones en la detección de huellas dactilares latentes. En efecto, se sintetizó nanopartículas de óxido de cinc por reacción química de precipitación en medio acuoso entre una solución de nitrato de cinc y otra de hidróxido de sodio de concentraciones 0,02 M y 0,4 M respectivamente. Las nanopartículas obtenidas fueron caracterizadas por FT-IR, SEM, EDS, DRX, TEM y PL, este último en un equipo Raman, para verificar su identidad, pureza, tamaño y forma. Los resultados confirmaron la formación de nanopartículas de óxido de cinc de alta pureza, de tamaños promedio entre 17 a 27 nm, cristalinas con un arreglo hexagonal tipo Wurzita y con morfología semiesférica. Para comparar sus propiedades luminiscentes se utilizó dos materiales de comparación, SF y COM, previamente caracterizadas por DRX, SEM, EDS e IR. Los tamaños promedio de cristalito obtenidos por DRX para estas dos muestras fueron de 57 y 105 nm respectivamente. Las nanopartículas sintetizadas y las muestras de comparación mostraron propiedades luminiscentes al ser irradiadas con luz UV de 325 nm. La luz emitida por las muestras fue de 600, 550 y 634 nm para las nanopartículas sintetizadas, las muestras SF y COM respectivamente. De otro lado, al irradiar las muestras con luz de 488 nm, se obtuvieron emisiones de luz de 590, 625 y 590 nm respectivamente. Una vez comprobada las propiedades luminiscentes, se utilizó las nanopartículas para detectar huellas dactilares latentes sobre diversas superficies como acero, aluminio, vidrio, cartulina, plástico y madera. Fue posible realizar satisfactoriamente el revelado de las huellas por medio de la luminiscencia sobre superficies de acero, aluminio, vidrio y cartulina. Sin embargo, el revelado sobre plástico y madera no fue posible debido a la porosidad de la madera y al reflejo de la luz de la lámpara sobre el plástico.Item Preparation of molecular sieves with antimicrobial properties from pillared clays and silver and copper nanoparticles(Pontificia Universidad Católica del Perú, 2017-03-09) Lucero Lucas, Gisella Liliana; Rädlein, Edda; Sun Kuo, María del RosarioAluminum pillared clays (Al–PILC) modified with silver and copper nanoparticles were prepared in order to get a material with antimicrobial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Al-PILC were characterized by X - ray diffraction (XRD), Scanning electron microscopy (SEM) with energy – dispersive X - ray spectroscopy (EDX), the Boehm titration and the nitrogen sorption method. According to these techniques, the pillaring process increased the interlayer distance in 8.7 Å and it corresponds approximately to the size of the Keggin´s ion. The surface area of the natural clay grew from 56 m2/g to 195 m²/g for the Al-PILC after its calcination because new micropores arise. Silver and copper nanoparticles were prepared by a chemical reduction method using D – glucose and ascorbic acid as reductor agents. Silver and copper nanoparticles were analyzed by UV – Visible spectroscopy and SEM – EDX. In addition, the silver concentration in a suspension was determined by atomic absorption spectroscopy. Nanoparticles were spherical and their particle size was between 15 and 33 nm and they were immersed in a starch matrix. Synthesis conditions (frequency and temperature) had an influence on the particle size which increased with higher frequency (80 kHz) and temperature (59°C). Copper nanoparticles were prepared using different volume of ascorbic acid; 1.6 ml produced smaller particles (20 – 86 nm); however, this range of particle size was not reproducible. For that reason, in the microbiological experiments were used commercial copper nanoparticles with a size between 27 nm and 34 nm. Silver al copper nanoparticles were incorporated to Al–PILC by impregnation and the modified clays were characterized by SEM –EDX. From the microbiological experiments, the silver and copper suspensions reduce the number of S. aureus and E. coli alive cells in comparison to the number of alive cells in the sample without modified clay and nanoparticles.