• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 48
  • 22
  • 11
  • 4
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 115
  • 86
  • 28
  • 23
  • 20
  • 18
  • 16
  • 14
  • 14
  • 13
  • 13
  • 12
  • 12
  • 12
  • 11
  • 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.

Dinâmica e projeto de controle linear ótimo aplicado no movimento de pregas vocais com rigidez assimétrica /

Alarcão, Sunamita Souza Silva de January 2018 (has links)
Orientador: Fábio Roberto Chavarette / Resumo: A voz é a principal ferramenta de comunicação da espécie humana e a maioria das pessoas dependem dela direta ou indiretamente em sua profissão. Sua produção deve-se ao funcionamento harmônico de sistemas fisiológicos distintos, resumidamente é o resultado da iteração do fluxo de ar vindo dos pulmões, dos tecidos deformáveis das pregas vocais e da onda de pressão acústica. Este trabalho inicialmente mostrará o estudo do comportamento assimétrico das pregas vocais causado por uma diferença entre a rigidez das pregas direita e esquerda. Para isso será utilizado uma modelagem que caracterizou-se como sistema de Van der Pol fortemente acoplado. O objetivo principal deste trabalho é estudar a dinâmica do movimento de pregas vocais com rigidez assimétrica e sincronizar este movimento através do método de controle linear ótimo, mostrando o seu funcionamento com valores distintos da rigidez para cada caso. Assim, o projeto de controle se mostra eficiente produzindo um bom funcionamento das pregas vocais, possibilitando a produção do som mesmo em pregas vocais doentes (assimétricas). / Abstract: The Voice is the main means of communication of human beings, and most people depend directly or indirectly on it in their professions. Its emission is due to the harmonious operation of dierent physiological systems; in sum, it results from the interaction of air coming from the lungs, the deformable tissues of the vocal folds, and an acoustic pressure wave. Initially, this work shall present the asymmetric behavior of the vocal folds caused by a dierence between the stiness value of the right and left folds. To do so, a mathematical model characterized as a strongly coupled Van der Pol system was used. The main objective of this work is to study the dynamics of the movement of vocal folds with asymmetric stiness and synchronize this movement through the optimal linear control method, showing their operation with dierent values of stiness for each case. Therefore, the control design has proven to be ecient, generating a good operation for the vocal folds and rendering possible the emission of sound even in diseased (asymmetric) vocal folds. / Doutor

Combustion Timing Control of Natural Gas HCCI Engines Using Physics-Based Modeling and LQR Controller

Abdelgawad, Marwa 2012 May 1900 (has links)
Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies and low emission levels. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a "fusion" between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making it difficult to control its combustion timing. The aim of this research project is to model and control a natural gas HCCI engine. Since HCCI depends primarily on temperature and chemical composition of the mixture, Exhaust Gas Recirculation (EGR) is used to control ignition timing. In this research, a thermodynamical, physics-based nonlinear model is developed to capture the main features of the HCCI engine. In addition, the Modified Knock Integral Model (MKIM), used to predict ignition timing, is optimized. To validate the nonlinear model, ignition timing under varying conditions using the MKIM approach is shown to be in accordance with data acquired from a model developed using a sophisticated engine simulation program, GT-Power. Most control strategies are based on a linear model, therefore, the nonlinear model is linearized using the perturbation method. The linear model is validated by comparing its performance with the nonlinear model about a suitable operating point. The control of ignition timing can be defined as a regulation process where the goal is to force the nonlinear model to track a desired ignition timing by controlling the EGR ratio. Parameters from the linear model are used to determine the gains of the LQR controller. The performance of the controller is validated by implementing it on the nonlinear model and observing its ability to track the desired timing with 0.5% error within a certain operating range. To increase the operating range of the controller and reduce steady-state error, an integrator is added to the LQR. Finally, it is shown that the LQR controller is able to successfully reject disturbance, parameter variation, as well as noise.

Sampled-Data LQ Optimal Controller for Twin-Buck Converter

Chen, Bo-Hsiung 12 October 2011 (has links)
¡@¡@We consider output voltage regulation of a novel twin-buck switching power converters with so-called zero voltage switching (ZVS) and zero current switching (ZCS). In order to observe the constraints imposed by ZVS and ZCS, it is necessary to adopt the pulse frequency modulation (PFM) technique, which lead to a switching system with aperiodic operating cycles. The control design is based on a sampled data model of the original switching dynamics and a linear quadratic criterion that takes the at-sampling behaviour into account. The applicability of the proposed controller is validated via numerical simulations written in MATLAB and SIMULINK. The controller is realized using Field Programmable Gate Array (FPGA). The experimental results indicate that the feedback system have good transient response and adequate robustness margin against source and load variation, which verify the applicability of the proposed control design approach.

Modeling, Stability Analysis And Control System Design Of A Small-sized Tiltrotor Uav

Cakici, Ferit 01 March 2009 (has links) (PDF)
Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircrafts that can carry cameras, sensors, communications equipment or other payloads. Tiltrotor UAVs provide a unique platform that fulfills the needs for ever-changing mission requirements by combining the desired features / hovering like a helicopter and reaching high forward speeds like an airplane. In this work, the conceptual design and aerodynamical model of a realizable small-sized Tiltrotor UAV is constructed, the linearized state-space models are obtained around the trim points for airplane, helicopter and conversion modes, controllers are designed using Linear Quadratic Regulator (LQR) methods and gain-scheduling is employed to obtain a simulation for the whole flight envelope. The ideas for making a real flying model are established according to simulation results.

Modelling & Control of a 3DOF Helicopter

Bodin, Erik, Stenholm, Fanny January 2015 (has links)
The scope of this report is the development of a mathematical model and a control system for a three degrees of freedom (3DOF) helicopter rig. This 3DOF-system offers a good simplification of a real world tandem helicopter for evaluating performanceof different automatic control principles. A mathematical model of the system is developed using free-body diagrams. This mathematical model is then linearized and a controller is developed by decoupling the system. Due to model imperfections external disturbances and similar effects integral action is added as well as feed-forward compensation to reduce nonlinear effects. After the controller has been decoupled the two different controllers are tuned. The Linear-Quadratic Regulator, described in section 3.6, is used for selectingstate-feedback gains. Due to the highly nonlinear nature of the system an Extended Kalman Filter is developed to estimate unmeasurable states. The model and controller is then implemented on the actual rig and evaluated. The results displayed that the elevation controller had good performance. The travel controller also showed good performance but not as good as the elevation controller. The main goal of this thesis was to develop a controller for the 3DOF helicopter system. The results clearly show that an LQR-controller is able to successfully control a system like this with decent performance characteristics despite the highly nonlinear system.

Modeling, Simulation and Control System Design for Civil Unmanned Aerial Vehicle (UAV)

Bagheri, Shahriar January 2014 (has links)
Unmanned aerial systems have been widely used for variety of civilian applications over the past few years. Some of these applications require accurate guidance and control. Consequently, Unmanned Aerial Vehicle (UAV) guidance and control attracted many researchers in both control theory and aerospace engineering. Flying wings, as a particular type of UAV, are considered to have one of the most efficient aerodynamic structures. It is however difficult to design robust controller for such systems. This is due to the fact that flying wings are highly sensitive to control inputs. The focus of this thesis is on modeling and control design for a UAV system. The platform understudy is a flying wing developed by SmartPlanes Co. located in Skellefteå, Sweden. This UAV is particularly used for topological mapping and aerial photography. The novel approach suggested in this thesis is to use two controllers in sequence. More precisely, Linear Quadratic Regulator (LQR) is suggested to provide robust stability, and Proportional, Integral, Derivative (PID) controller is suggested to provide reference signal regulation. The idea behind this approach is that with LQR in the loop, the system becomes more stable and less sensitive to control signals. Thus, PID controller has an easier task to do, and is only used to provide the required transient response. The closed-loop system containing the developed controller and a UAV non-linear dynamic model was simulated in Simulink. Simulated controller was then tested for stability and robustness with respect to some parametric uncertainty. Obtained results revealed that the LQR successfully managed to provide robust stability, and PID provided reference signal regulation.

Simulation model to evaluate control of balance in humanoid robots

Dadashzadeh, Aidin January 2015 (has links)
This thesis focuses on implementing a program, using Python and the symbolic package SymPy, to evaluate balancing of a humanoid robot modelled as inverted pendulums. The balancing algorithm used to evaluate the program is the feedback controller LQR. The program has successfully implemented a working LQR algorithm together with features such as underactuation and a tilting plane as disturbance. We have shown that the energy is conserved for the falling pendulums and that it is possible to predict the behavior for certain parameter values of the pendulums, thus confirming that the program is working correctly. Furthermore we have shown that a fully-actuated system is more controllable than an under-actuated system, and for each actuator that is removed, the system becomes less controllable. Finally we discuss the program performance where some concern is given toward the seemingly poor execution time of the program. The program has been tested for up to five pendulums with successful results. Most of the results however, are revolving around three pendulum systems.

Optimal cruise control of heavy-haul trains equipped with electronic controlled pneumatic brake systems

Chou, Ming-Shan 24 January 2006 (has links)
In this study a closed-loop cruise controller to minimise the running costs of the heavy-haul train is proposed. The running costs of a heavy-haul train are dependent on its travelling time, maintenance costs and energy consumption during the trip. The Coallink train with the new train technologies, Distributed Power (DP) traction and Electronically Controlled Pneumatic (ECP) brake system, is the centre of the study. A literature study on existing train control, both passenger and heavy-haul trains, is carried out to build up a knowledge base. Many different techniques for train handling were observed, their features in relation to heavy-haul ECP trains are discussed. From these backgrounds, a comprehensive longitudinal train model is proposed and successfully validated with real-life data from Spoornet. In the model, both static and dynamic in-train forces are studied, as well as energy consumption. This is possible by modelling each locomotive and wagon as an individual unit. The equations of motion for the train with coupled units and additional non-linearities, such as traction power limits, are considered. An open-loop controller for maintaining equilibrium velocity is designed. During transient velocity changes, a transient controller for calculating the required additional acceleration and deceleration is designed and validated. Because locomotive traction settings are only available in discrete notches, quantisation conversion from force into notches results in input chattering. In addition, during brake to traction transitions, the locomotives receive a sudden traction demand which results in spikes in in-train forces. To avoid these problems, input filtering is performed for these inputs. Closed-loop controllers based on LQR method, optimised for in-train forces, energy consumption and velocity regulation respectively, are designed and compared. To overcome the communication constraints, a fencing concept is introduced whereby the controller is reconfigured adaptively to the current track topology. Different train configurations in terms of availability of additional control channels for both traction and braking are compared, as well as their effects on dynamic and static in-train force. These configurations are unified, distributed and individual traction and brake controls. The results from these different configurations are compared to recorded train data and given in this study. From the results, it is found that the closed-loop controller optimised for in-train force is able to provide the best overall improvement out of the three controllers. / Dissertation (MEng)--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / Unrestricted

Development of a Stair-Climbing Robot and a Hybrid Stabilization System for Self-Balancing Robots

Robillard, Dominic January 2014 (has links)
Self-balancing robots are unique mobile platforms that stay upright on two wheels using a closed-loop control system. They can turn on the spot using differential steering and have compact form factors that limit their required floor space. However they have major limitations keeping them from being used in real world applications: they cannot stand-up on their own, climb stairs, or overcome obstacles. They can fall easily if hit or going onto a slippery surface because they rely on friction for balancing. The first part of this research proposes a novel design to address the above mentioned issues related to stair-climbing, standing-up, and obstacles. A single revolute joint is added to the centre of a four-wheel drive robot onto which an arm is attached, allowing the robot to successfully climb stairs and stand-up on its own from a single motion. A model and simulation of the balancing and stair-climbing process are derived, and compared against experimental results with a custom robot prototype. The second part, a control system for an inverted pendulum equipped with a gyroscopic mechanism, was investigated for integration into self-balancing robots. It improves disturbance rejection during balance, and keeps equilibrium on slippery surfaces. The model of a gyroscope mounted onto an actuated gimbal was derived and simulated. To prove the concept worked, a custom-built platform showed it is possible for a balancing robot to stay upright with zero traction under the wheels.

Výukový model pro mechatroniku: vývoj modelu a rychlé komunikace pomocí USB / Educating model for mechatronics: model development and fast USB communication

Formánek, Martin January 2020 (has links)
Táto diplomová práca sa zaoberá návrhom a realizáciou výukového modelu pre študentov mechatroniky na vysokej škole. Úvod práce sa zaoberá krátkym uvedením do problematiky používania univerzálnej sériovej zbernice a jej implementáciou pre komunikáciu s mikrokontrolérom. Druhá časť je venovaná hardwaru zariadenia, medzi čo patrí voľba vhodného motoru, návrh vhodných elektronických komponentov, návrh dosiek plošných spojov a taktiež mechanickej konštrukcie celého zariadenia. Nasleduje softwarová časť, popisujúca praktickú realizáciu komunikácie, program v mikrokontroléry, a Toolbox, ktorý umožňuje užívateľovi jednoduchú interakciu s hardwarom a to jak z Matlabu. tak zo Simulinku. Kombinácia navrhnutých hardwarových a softwarových prvkov umožňuje jednoduchú cestu k zlepšeniu vedomostí študentov v oblastiach programovania, riadenia a modelovaní sústav. Pre tieto účely je práca rozšírená o pracovný list, ktorý dopĺňa navrhnuté zariadenie o sadu experimentálnych úloh, zameraných na vybrané mechatronické problémy.

Page generated in 0.0224 seconds