Application of Laguerre based adaptive predictive control to Shape Memory Alloy (SMA) actuators

This paper discusses the use of an existing adaptive predictive controller to control some Shape Memory Alloy (SMA) linear actuators. The model consists in a truncated linear combination of Laguerre filters identified online. The controller stability is studied in details. It is proven that the tracking error is asymptotically stable under some conditions on the modelling error. Moreover, the tracking error converge toward zero for step references, even if the identified model is inaccurate. Experimentalcresults obtained on two different kind of actuator validate the proposed control. They also show that it is robust with regard to input constraints.ANR MAFESM

Laguerre-domain Modeling and Identification of Linear Discrete-time Delay Systems

International audienceA closed-form Laguerre-domain representation of discrete linear time-invariant systems with constant input time delay is derived. It is shown to be useful in a l 2 → l 2 system identification setup (with l 2 denoting square-summables signals) often arising in biomedical applications, where the experimental protocol does not allow for persistent excitation of the system dynamics. The utility of the proposed system representation is demonstrated on a problem of drug kinetics estimation from clinical data

Identificação e controle de processos via desenvolvimentos em séries ortonormais. Parte B: controle preditivo

This paper presents an overview about predictive control schemes based on orthonormal basis function models. Different predictive control schemes based on such models are discussed, namely, linear controllers with terminal (stabilizing) constraints, robust controllers, and non-linear controllers. The discussions comprise a broad bibliographical survey on the subject as well as two case studies involving a simulated dynamic system and a real process.O presente artigo aborda o problema da seleção da estrutura de modelos em algoritmos de controle preditivo para sistemas monovariáveis. Neste sentido, apresenta a utilização de modelos com estrutura dinâmica desenvolvida através de bases de funções ortonormais, como as funções de Laguerre, Kautz ou funções ortonormais generalizadas. Os principais aspectos relacionados com esta classe de modelos no contexto de controladores preditivos lineares com restrições terminais, não lineares e robusto são discutidos e uma revisão bibliográfica é apresentada. O desempenho de malha fechada das estratégias analisadas é ilustrado através de dois casos de estudo envolvendo uma incubadora para recém nascidos e um processo simulado de polimerização isotérmica.322336Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Modelamiento y simulación de un controlador adaptativo por modelo de referencia para un proceso de regulación de pH

En este trabajo se evalúa el comportamiento de un proceso de regulación de pH bajo la acción de un controlador adaptativo por modelo de referencia, tras establecer un pH inicial de 7.0 y utilizar los resultados obtenidos en el trabajo de grado ¿Diagnóstico y simulación de un sistema de control de pH en un reactor de tanque agitado¿, teniendo en cuenta las siguientes variables: ¿ Seis valores para el set point, tres por encima del pH inicial (8.0, 9.0 y 10.0) y tres por debajo del mismo (4.0, 5.0, 6.0). ¿ Cuatro tipos de controladores convencionales para el lazo de regulación interno (P, PI, PD y PID). ¿ Dos métodos de adaptación (Método de optimización del gradiente y método de estabilidad de Lyapunov), con los cuales se encontraron las expresiones para los parámetros ajustables presentes en cada caso. Se utilizaron las aplicaciones GUI y SIMULINK de MATLAB para realizar las simulaciones de los modelos y se obtuvieron los resultados en forma gráfica, lo que permitió comparar el desempeño de los métodos de adaptación según el controlador convencional implementado. Tras realizar todas las simulaciones, se puede concluir que el método de estabilidad de Lyapunov arroja resultados satisfactorios en todos los casos evaluados, mientras que el método de estabilidad del gradiente solo es aplicable cuando se implementan el control proporcional y el proporcional ¿ derivativo en el lazo de regulación convencionalMaestríaMAGISTER EN INGENIERÍA ÉNFASIS EN INGENIERÍA QUÍMIC

Real-time observer model for Kraft wood digester.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.At SAPPI-Tugela a continuous Kraft wood chip digester operates in EMCC mode (extended modified continuous cooking). Chips are initially exposed to a NaOH / Na2S liquor at high temperature in the top section. The chips move downward in plug flow passing circumferential screens used to draw liquor for various circulations. About midway down the spent black liquor is removed and the chips enter the cooler bottom section where some further reaction and washing occurs. Liquor level and chip level are maintained close to each other near the top. Chips require 8-12 hours to pass through the digester, depending on the chip feed rate. The key parameter of interest at the digester exit is the Kappa number, which is a measure of the extent of delignification which has occurred. Different board and paper products require different Kappa number pulp feed. (Final properties such as tensile, tear and bursting strengths will also depend on the way fibres have been modified in the digestion). The objective of this investigation is to predict the Kappa number of the product pulp in real-time, thus facilitating quicker reaction than the present dependence on laboratory analysis permits, possibly even allowing closed-loop control. The extent of delignification depends on liquor strength, temperature and exposure time, with final Kappa number also depending on the properties of the chip feed (wood type and moisture content). Compensation to maintain a steady Kappa number is made difficult by the long and varying residence time, and the fact that any changes apply to the whole profile held up in the digester. A number of static models for Kappa number prediction have been developed by previous workers, but these do not compare well with plant measurements. The collection of data from the Sappi-Tugela reactor, and the pulp quality reports, have been used to determine an efficient model. This step required a considerable data collection exercise, and similar results to the quality reports have been obtained using a simple linear model based on this data. The problem of model error is being reduced by arrangement as a Smith Predictor, in which the model is intermittently corrected by available laboratory analyses. At the same time, an interface was created, in order to synchronise measurement data for the chips presently leaving the reactor. In order to deal with the dead time, each parcel of chips entering the reactor is effectively tracked, and the changes in Kappa number integrated for reaction time under the varying conditions in transit. Knowing the present inventory of the reactor, this model can also be run forward in time as a predictive controller, to determine optimal control actions for maintenance of the target Kappa number

Measuring, modelling and controlling the pH value and the dynamic chemical state

pH value is a challenging quantity to measure, model and control. In fact, pH value is a mere one-dimensional projection of a multi-dimensional quantity called chemical state and measuring, modelling and controlling the chemical state is much more challenging. This thesis contributes to all aspects of pH processes. A new method for measuring the pH value under difficult conditions (pressure and flow variations in thick pulp) is presented. Classical physico-chemical modelling of chemical systems is extended with a concept of population principle which is a new formulation of the "reaction invariant - reaction variant" structure. Self-organising fuzzy controller (SOC) is modified to suit pH-processes better (high frequency noise and oscillations are damped more efficiently). All the methods described above were tested with practical applications that include a pilot neutralisation process, an industrial ammonia scrubber and a paper machine wet end. The new methods showed such a significant improvement that they were installed permanently on the industrial applications.reviewe

Microbiome profiling reveals that Pseudomonas antagonises parasitic nodule colonisation of cheater rhizobia in Lotus

Nitrogen fixation is carried out inside nodules of legumes by symbiotic rhizobia. Rhizobia dominate the nodule microbiome, however, other non-rhizobial bacteria also colonise root nodules. It is not clear whether these less abundant nodule colonisers impact nodule function. In order to investigate the relationship between the nodule microbiome and nodule function as influenced by the soil microbiome, we used a metabarcoding approach to characterise the communities inside Lotus burttii, Lotus japonicus and Lotus corniculatus nodules from plants that were either starved or healthy, resulting from inoculations with different soil suspensions in a closed pot experiment. We found that the nodule microbiome of all tested Lotus species differed according to inoculum, but only that of L. burttii varied with plant health. Using a machine learning algorithm, we found that out of all the non-rhizobial bacteria inside the L. burttii nodules, amplicon sequence variants (ASVs) corresponding to Pseudomonas were the most indicative signatures of healthy plants. Rhizobium ASVs were the most indicative of a starved L. burttii plant nodule. Network analysis revealed that there were exclusively negative significant correlations between Rhizobium and Pseudomonas ASVs and both positive and negative correlations between Pseudomonas and Mesorhizobium ASVs. This was supported by a co-inoculation experiment on L. burttii that revealed fluorescently tagged Pseudomonas could co-colonise nodules formed by Mesorhizobium, but not those formed by Rhizobium. Further evidence for the potential plant benefit of Pseudomonas presence was seen in a co-inoculation with Rhizobium on L. japonicus. The number of ineffective nodules induced by the Rhizobium isolate was reduced when inoculated together with a Pseudomonas nodule isolate. The same reduction in ineffective nodules was not seen in L. burttii. These results support the hypothesis that legume nodule endophytes influence the overall outcome of the root-nodule symbiosis, albeit in a plant host-specific manner. In addition, a novel Mesorhizobium species, Mesorhizobium norwegicum, was physiologically and chemotaxonomically characterised

EFFECTS AND MECHANISMS OF TEMPERATURE AND ANTIMICROBIAL STRESSES ON SALMONELLA ENTERITIDIS RESISTANCE, VIRULENCE AND BIOFILM FORMATION

Ph.DDOCTOR OF PHILOSOPH

A high-speed microscopy approach to single-molecule studies of eukaryote signal transduction

Metabolic processes underlie all forms of life. An organism’s ability to utilise chemical energy to stay alive and eventually reproduce is a central feature of life, regardless of organism length scale. To achieve this, an organism must be adaptable. That is, it must be able to adjust to varying surrounding environmental conditions. Cells must be able to sense this environment, ‘transduce’ the signal and bring about some cell level response. Cells respond to external stimuli by releasing chemical cascades along often intricate signalling pathways which regulate cellular function. In this thesis, I have developed a novel optical microscopy system coupled to microfluidics and image analysis tools to help address challenging biological questions relating to metabolic sensing in eukaryotic life, using Saccharomyces cerevisiæ, as a model system. A set of biophysical tools was developed to monitor signal transduction events in live yeast cells. A bespoke optical microscope was developed that can monitor single living cells and determine their response to controlled variations in environmental nutrient concentration at high sampling speeds comparable to the molecular diffusion time scale in a cells internal environment. High-speed imaging at up to 200 frames per second and exposure times of 4.7 ms can be achieved. An electronic gain of 300x makes the camera system sensitive enough to track diffusion of single or small clusters of fluorescent protein molecules under physiological conditions. A high intensity laser excitation system was developed to deliver the light required to follow single fluorescent proteins in the living cells. A bespoke microfluidics system was built wherein cells can be exposed to rapidly changing extracellular environments and make it possible to follow individual cell responses to changing glucose conditions. Image analysis tools were adapted and developed to facilitate the automated measurement of protein mobility, stoichiometry and copy number, one cell at a time