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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Development of a Closed-loop for Measuring and Stimulating Peripheral Nervous System / Utveckling av en sluten slinga för mätning och stimulering av det perifera nervsystemet

Roy Hierro, Diego Ignacio January 2022 (has links)
Bioelectronic medicine is an emerging discipline being a intersection of neu- roscience, immunology and electrical engineering. Chronic inflammation is linked to disorders such as diabetes, rheumatoid arthritis, asthma, atheroscle- rosis, obesity and inflammatory bowel disease. Chronic inflammatory diseases have been recognized as the most significant cause of death in the world today, with more than 50% of all deaths being attributable to inflammation-related diseases. To find specific parameters for the stimulation of the vagus nerve would be a major advancement in the field, since it will help restore the vagal tone optimally. A systematic review has been made to understand and explore the tissue damage, stimulation sites, FDA approved parameters and the safety and efficacy in vagus nerve stimulation (VNS). A control closed- loop system was developed based on the needs of the field and a human clinical trial protocol was proposed.    The control close-loop system is able to receive feedback from a continuous real-time measurement of the pressure of the peripheral blood flow and send a VNS based on a heart rate (HR) settled threshold. The stimulation is delivered with previously settled parameters such as, pulse width, output current, duty cycle and frequency and helps observe if the nerve has been correctly targeted or not. From the results, it becomes clear that the connection of the devices has been correctly accomplished and that the HR reduction is being measured by the control close-loop which would stimulate again when the HR threshold is surpassed. Based on the concept of this control close-loop a human protocol has been proposed to test if the hypothesis that patients have their best inflammatory response with different output current rather than all having one best performing one and that non-healthy patients will lower their HR baseline after VNS treatment showing the increase of vagus nerve activity. This report adds value on the creation of a new control close-loop device between the MouseOx and Intan devices. Controlling the stimulation parameters in VNS can be a powerful technique that will increase patient specificity and will help non respondents to different drug treatments to have a more effective alternative. The HR is a simple biomarker to detect VNS bioactivity but lots of further research on non-invasive devices and software limitations are still needed to be overcome to have clear guidance in the field. The proposal of a new human clinical trial that might give a clear and feasible solution to either find an efficient stimulation setting or the assurance of the real need for an interactive control close-loop system that would tailor the stimulation parameters for each specific patient is presented. / Bioelektronisk medicin är en framväxande disciplin som är en skärningspunkt mellan neurovetenskap, immunologi och elektroteknik. Kronisk inflamma- tion är kopplad till sjukdomar som diabetes, reumatoid artrit, astma, åder- förkalkning, fetma och inflammatoriska tarmsjukdomar som är den vanligaste dödsorsaken i världen idag. Att hitta specifika parametrar för stimulering av vagusnerven skulle vara ett stort framsteg på området, eftersom det hjälper till att återställa vagustonen optimalt. En systematisk översyn har gjorts för att förstå och utforska vävnadsskadan, stimuleringsställena, FDA-godkända parametrar och säkerheten och effekten i VNS. Ett kontrollsystem med slutet kretslopp utvecklades baserat på fältets behov och ett protokoll för kliniska prövningar för människor föreslogs. Kontrollsystemet kan ta emot feedback från en kontinuerlig realtidsmätning av trycket i det perifera blodflödet och skicka en VNS baserat på en HR-bestämd tröskel. Stimuleringen levereras med tidigare inställda parametrar såsom pulsbredd, utström, arbetscykel och frekvens. Av resultaten blir det tydligt att anslutningen av enheterna har åstadkommits korrekt och att HR-reduktionen mäts av kontrollens slutslinga som skulle stimulera igen när HR-tröskeln överskrids. Baserat på konceptet med denna kontroll close-loop har ett mänskligt protokoll föreslagits för att testa om hypotesen att patienter har sitt bästa inflammatoriska svar med olika utström snarare än att alla har en bäst presterande och att icke-friska patienter kommer att sänka sin HR baslinje efter VNS-behandling som visar ökningen av vagusnervens aktivitet. Den här rapporten ger ett mervärde när det gäller skapandet av en ny kontrollenhet mellan MouseOx- och Intan-enheterna. Att kontrollera stimuleringsparametrarna i VNS kan vara en kraftfull teknik som kommer att öka patientspecificiteten och som hjälper icke-respondenter till olika läkemedelsbehandlingar att få ett mer effektivt alternativ. HR är en enkel biomarkör för att upptäcka VNS-bioaktivitet, men massor av ytterli- gare forskning om icke-invasiva enheter och mjukvarubegränsningar behövs fortfarande för att få en tydlig vägledning på området. Förslaget om en ny klinisk prövning på människa som kan ge en tydlig och genomförbar lösning för att antingen hitta effektiva stimuleringsmiljöer eller försäkran om det verkliga behovet av ett interaktivt kontrollsystem med nära slinga som skulle skräddarsy stimuleringsparametrarna för varje specifik patient presenteras.
2

Active control of hydrodynamic slug flow

Inyiama, Fidelis Chidozie 04 1900 (has links)
Multiphase flow is associated with concurrent flow of more than one phase (gas-liquid, liquid-solid, or gas-liquid-solid) in a conduit. The simultaneous flow of these phases in a flow line, may initiate a slug flow in the pipeline. Hydrodynamic slug flow is an alternate or irregular flow with surges of liquid slug and gas pocket. This occurs when the velocity difference between the gas flow rate and liquid flow rate is high enough resulting in an unstable hydrodynamic behaviour usually caused by the Kelvin-Helmholtz instability. Active feedback control technology, though found effective for the control of severe slugs, has not been studied for hydrodynamic slug mitigation in the literature. This work extends active feedback control application for mitigating hydrodynamic slug problem to enhance oil production and recovery. Active feedback Proportional-Integral (PI) control strategy based on measurement of pressure at the riser base as controlled variable with topside choking as manipulated variable was investigated through Olga simulation in this project. A control system that uses the topside choke valve to keep the pressure at the riser base at or below the average pressure in the riser slug cycle has been implemented. This has been found to prevent liquid accumulation or blockage of the flow line. OLGA (olga is a commercial software widely tested and used in oil and gas industries) has been used to assess the capability of active feedback control strategy for hydrodynamic slug control and has been found to give useful results and most interestingly the increase in oil production and recovery. The riser slugging was suppressed and the choke valve opening was improved from 5% to 12.65% using riser base pressure as controlled variable and topside choke valve as the manipulated variable for the manual choking when compared to the automatic choking in a stabilised operation, representing an improvement of 7.65% in the valve opening. Secondly, implementing active control at open-loop condition reduced the riser base pressure from 15.3881bara to 13.4016bara.
3

MPC adaptativo - multimodelos para controle de sistemas não-lineares. / MPC adaptive - multimodels for control of nonlinear systems.

Paula, Neander Alessandro da Silva 14 April 2009 (has links)
Durante a operação de um controlador MPC, a planta pode ir para outro ponto de operação principalmente pela decisão operacional ou pela presença de perturbações medidas/não-medidas. Assim, o modelo do controlador deve ser adaptado para a nova condição de operação favorecendo o controle sob as novas condições. Desta forma, as condições ótimas de controle podem ser alcançadas com a maior quantidade de modelos identificados e com um controlador adaptativo que seja capaz de selecionar o melhor modelo. Neste trabalho é apresentada uma metodologia de controle adaptativo com identificação on-line do melhor modelo o qual pertence a um conjunto previamente levantado. A metodologia proposta considera um controlador em duas camadas e a excitação do processo através de um sinal GBN na camada de otimização com o controlador em malha fechada. Está sendo considerada a validação deste controlador adaptativo através da comparação dos resultados com duas diferentes técnicas Controlador MMPC e Identificação ARX, para a comprovação dos bons resultados desta metodologia. / During the operation of a MPC, the plant can change the operation point mainly due to management decision or due to the presence of measured or unmeasured disturbances. Thus, the model of the controller must be adapted to improve the control in the new operation conditions. In such a way, a better control policy can be achieved if a large number of models are identified at the possible operation points and it is available an adaptive controller that is capable of selecting the best model. In this work is presented a methodology of adaptive control with on-line identification of the most adequate model which belongs to a set of models previously obtained. The proposed methodology considers a two-layer controller and process excitation by a GBN signal in the LP optimization layer with the controller in closed loop mode. It is also presented the adaptive controller validation by comparing the proposed approach with two different techniques - MMPC and ARX Identification, to confirm the good results with this new methodology to the adaptive controller.
4

MPC adaptativo - multimodelos para controle de sistemas não-lineares. / MPC adaptive - multimodels for control of nonlinear systems.

Neander Alessandro da Silva Paula 14 April 2009 (has links)
Durante a operação de um controlador MPC, a planta pode ir para outro ponto de operação principalmente pela decisão operacional ou pela presença de perturbações medidas/não-medidas. Assim, o modelo do controlador deve ser adaptado para a nova condição de operação favorecendo o controle sob as novas condições. Desta forma, as condições ótimas de controle podem ser alcançadas com a maior quantidade de modelos identificados e com um controlador adaptativo que seja capaz de selecionar o melhor modelo. Neste trabalho é apresentada uma metodologia de controle adaptativo com identificação on-line do melhor modelo o qual pertence a um conjunto previamente levantado. A metodologia proposta considera um controlador em duas camadas e a excitação do processo através de um sinal GBN na camada de otimização com o controlador em malha fechada. Está sendo considerada a validação deste controlador adaptativo através da comparação dos resultados com duas diferentes técnicas Controlador MMPC e Identificação ARX, para a comprovação dos bons resultados desta metodologia. / During the operation of a MPC, the plant can change the operation point mainly due to management decision or due to the presence of measured or unmeasured disturbances. Thus, the model of the controller must be adapted to improve the control in the new operation conditions. In such a way, a better control policy can be achieved if a large number of models are identified at the possible operation points and it is available an adaptive controller that is capable of selecting the best model. In this work is presented a methodology of adaptive control with on-line identification of the most adequate model which belongs to a set of models previously obtained. The proposed methodology considers a two-layer controller and process excitation by a GBN signal in the LP optimization layer with the controller in closed loop mode. It is also presented the adaptive controller validation by comparing the proposed approach with two different techniques - MMPC and ARX Identification, to confirm the good results with this new methodology to the adaptive controller.
5

Efekt cueingu v otevřených a zavřených smyčkách na chůzi u pacientů s Parkinsonovou nemocí. / Effect of open and closed loop cueing on gait function in Parkinson disease.

Almathami, Saad Hassan January 2021 (has links)
The objective of this study is to evaluate the effectiveness of opened and closed loop cueing intervention on Parkinson disease patients gait function focusing on the temporal and spatial parameters of gait and to define the most effective cueing approach for different gait parameters and finally to examine the closed loop feedback system for regular usage in regular physiotherapy clinics or patients own homes. A 37 clinical trial including 1014 patients were investigated to reach an answer for this review questions. Results reveled that both open and closed cueing intervention has a positive effect on gait spatial, temporal gait parameters and capable to reduce the number of freezes in Parkinson diseases patients. Auditory cueing strategies had a superior effect on patient speed of gait with higher rhythm of cues and better overall gait function during dual tasking. Visual cues showed better effect on stride length and stride frequency. The close loop feedback system of cues still built on complex machinery segments which make it difficult to be used as regular intervention in physiotherapy clinics and patients own homes. As an overall cueing intervention found to be significantly effective as locomotive therapeutic approach on gait functionality, but each intervention procedure and methodology...

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