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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

Design and Implementation of Voltage Based Human Inspired Feedback Control of a Planar Bipedal Robot AMBER

Pasupuleti, Murali Krishna 2012 August 1900 (has links)
This thesis presents an approach towards experimental realization of underactuated bipedal robotic walking using human data. Human-inspired control theory serves as the foundation for this work. As the name, "human-inspired control," suggests, by using human walking data, certain outputs (termed human outputs) are found which can be represented by simple functions of time (termed canonical walking functions). Then, an optimization problem is used to determine the best fit of the canonical walking function to the human data, which guarantees a physically realizable walking for a specific bipedal robot. The main focus of this work is to construct a control scheme which takes the optimization results as input and delivers human-like walking on the real-world robotic platform - AMBER. To implement the human-inspired control techniques experimentally on a physical bipedal robot AMBER, a simple voltage based control law is presented which utilizes only the human outputs and canonical walking function with parameters obtained from the optimization. Since this controller does not require model inversion, it can be implemented efficiently in software. Moreover, applying this methodology to AMBER, experimentally results in robust and efficient "human-like" robotic walking.
2

Advanced control of a rotary dryer

Yliniemi, L. (Leena) 01 June 1999 (has links)
Abstract Drying, especially rotary drying, is without doubt one of the oldest and most common unit operations in the process industries. Rotary dryers are workhorses which are easy and reliable to operate, but neither energy-efficient nor environmentally friendly. In order to conform better to the requirements of modern society concerning working conditions, safety practices and environmental aspects, the development of control systems can provide opportunities for improving dryer operation and efficiency. Our in depth understanding of rotary drying is poor, because it is a very complex process that includes the movement of solids in addition to thermal drying. Thus even today rotary dryers are controlled partly manually, based on the operator's "eye" and experience, and partly relying on conventional control methods. The control of a rotary dryer is difficult due to the long time delay, which means that accidental variations in the input variables can disturb the process for long periods of time before they are reflected in the output variables. To eliminate such disturbances at an early stage, increasing interest has been shown in more sophisticated control systems such as model-based constructs, fuzzy logic and neural nets in recent years. Although it has proved difficult and time-consuming to develop model-based control systems, due to the complexity of the process, intelligent control methods based on fuzzy logic and neural nets offer attractive solutions for improving dryer control. These methods make it possible to utilize experience, knowledge and historical data, large amounts of which are readily available. The aim of this research was to improve dryer control by developing new hybrid control systems, one consisting of a fuzzy logic controller (FLC) and PI controller and the other of a three-layer neural network (NN) and PI controller. The FLC and NN act as supervisory controllers giving set points for the PI controllers. The performance of each was examined both with simulations and in pilot plant experiments. The pilot plant dryer at the University of Oulu closely resembles a real industrial situation, so that the results are relevant. Evaluation of these results showed that the intelligent hybrid controllers are well suited for the control of a rotary dryer, giving a performance in which disturbances can be eliminated rapidly and operation of the dryer can thereby be improved, with the aim of enhancing its efficiency and environmental friendliness.
3

Control of Rotary Cranes Using Fuzzy Logic and Time-Delayed Position Feedback Control

Al-Mousa, Amjed A. 11 December 2000 (has links)
Rotary Cranes (Tower Cranes) are common industrial structures that are used in building construction, factories, and harbors. These cranes are usually operated manually. With the size of these cranes becoming larger and the motion expected to be faster, the process of controlling them became dicult without using automatic control methods. In general, the movement of cranes has no prescribed path. Cranes have to be run under dierent operating conditions, which makes closed-loop control preferable. In this work, two types of controllers are studied: fuzzy logic and time-delayed position feedback controllers. The fuzzy logic controller is introduced first with the idea of split-horizon; that is, to use some fuzzy engines for tracking position and others for damping load oscillations. Then the time-delayed position feedback method is applied. Finally, an attempt to combine these two controllers into a hybrid controller is introduced. Computer simulations are used to verify the performance of these controllers. An experimental setup was built on which the time-delayed position feedback controller was tested. The results showed good performance. / Master of Science
4

Substructure Synthesis Analysis and Hybrid Control Design for Buildings under Seismic Excitation

Morales Velasco, César A. 18 April 1997 (has links)
We extend the application of the substructure synthesis method to more complex structures, and establish a design methodology for base isolation and active control in a distributed model of a building under seismic excitation. Our objective is to show that passive and active control complement each other in such an advantageous manner for the case at hand, that simple devices for both types of control are sufficient to achieve excellent response characteristics with very low control forces. The Rayleigh-Ritz based substructure synthesis method proved to be highly successful in analyzing a structure more complex than the ones previously analyzed with it. Comparing the responses of the hybridly controlled building and the conventional fixed building under El Centro excitation, we conclude that the stresses are reduced by 99.6 %, the base displacement is reduced by 91.7 % and the required control force to achieve this is 1.1 % of the building weight. / Ph. D.
5

Scheduling for a Large-Scale Production System Based on a Continuous and Timed Petri-Net Model

OKUMA, Shigeru, SUZUKI, Tatsuya, INABA, Akio, KIM, YoungWoo 01 March 2003 (has links)
No description available.
6

Computationally Aware Control of Cyber-Physical Systems: A Hybrid Model Predictive Control Approach

Zhang, Kun January 2015 (has links)
Cyber-Physical Systems (CPS) are systems of collaborating computational elements controlling physical entities via communication. Such systems involve control processes of physical entities and computational processes. The control complexities originated from the physical dynamics and systematic constraints are difficult for traditional control approaches (e.g., PID control) to handle without an exponential increase in design/test etc. costs. Model predictive control (MPC) predicts and produces optimized control inputs based on its predictive model according to a cost function under given constraints. This control scheme has some attractive features for CPSs: it handles constraints systematically, and generates behavior prediction with respective control inputs simultaneously. However, MPC approaches are computationally intensive, and the computation burden generally grows as a predictive model more closely approximates a nonlinear plant (in order to achieve more accurate behavior). The computational burden of predictive methods can be addressed through model reduction at the cost of higher divergence between prediction and actual behavior. This work introduces a metric called uncontrollable divergence, and proposes a mechanism using the metric to select the model to use in the predictive controller (assuming that a set of predictive models are available). The metric reveals the divergence between predicted and true states caused by return time and model mismatch. More precisely, a map of uncontrollable divergence plotted over the state space gives the criterion to judge where a specific model can outperform others. With this metric and the mechanism, this work designs a controller that switches at runtime among a set of predictive controllers in which respective models are deployed. The resulting controller is a hybrid predictive controller. In addition to design and runtime tools, this work also studies stability conditions for hybrid model predictive controllers in two approaches. One is average dwell time based, and it does not rely on the offline computation that studies the system properties. The other one uses a reference Lyapunov function instead of multiple Lyapunov functions derived from multiple predictive controllers. This approach implicitly depends on the offline numerical solutions of certain systematic properties. The term "boundedness" is preferable in this context since it accepts numerical error and approximations. Two examples, vertical takeoff and landing aerial vehicle control and ground vehicle control, are used to demonstrate the approach of hybrid MPC.
7

La commande hybride prédictive d’un convertisseur quatre bras / Predictive Hybrid Control on 3-Phase 4-Wire Power Converters

Rachmildha, Tri Desmana 01 October 2009 (has links)
Dans une large variété d'applications industrielles, il existe une demande croissante pour améliorer la qualité de l'énergie fournie par les systèmes électriques. En plus de la fiabilité et de la disponibilité d'énergie électrique, la qualité de la puissance fournie devient maintenant une question importante. Parmi les causes de la pauvre qualité de puissance, les harmoniques sont considérés comme la raison qui contribue à la majorité de pannes de courant. Beaucoup d'efforts ont été développés pour résoudre le problème des perturbations harmoniques comme, par exemple, installer des dispositifs spéciaux tels que les filtres actifs. Ce travail de thèse traite le développement d’une commande directe de puissance utilisant l'approche prédictive hybride. La commande hybride considère chaque vecteur de tension du convertisseur comme une entité discrète qui sera appliquée pour commander un système linéaire continu. Un critère pour calculer le vecteur optimal de tension à appliquer sera établi à partir d’un modèle prédictif. Le vecteur optimal de tension à appliquer pour chaque période de commutation, et le correspondant temps d'application seront utilisés pour approcher la valeur réelle des variables d'état du système au point de référence désiré. Deux théories de puissance instantanées seront employées, p-q et p-q-r, pour une application de filtre active parallèle de puissance dans un système triphasé de 4 fils. Ces théories instantanées de puissance ont été développées pour être appliquées aux systèmes non équilibrés utilisant les variables de puissance pour obtenir les courants qui devraient être injectés par le filtre actif. Le filtre actif produira la puissance réactive demandée par la charge et compensera la composante d'ondulation de la puissance active de sorte que la source livre seulement la puissance active constante. / In a wide variety of industrial applications, an increasing demand exists to improve the quality of the energy provided by electrical systems. Besides the reliability and availability of electric power, the power quality is now becoming an important issue. Among the causes of the poor power quality, the harmonics are included as the reason which contributes the majority of power failures. Many efforts have been developed to solve the harmonics problem as, for instance, to install special devices such as active filters. This research work deals with the development of direct power control using the hybrid predictive control approach. The hybrid control considers each voltage vector of the converter as a discrete entity which will be applied to control a continuous linear system. One criterion to calculate the optimal voltage vector to apply will be established for the predictive control model. The optimal voltage vector to apply for each switching period, and the corresponding application time will be used to approach the actual value of the state variables of the system to the desired reference point. Two instantaneous power theories will be used, i.e. pq0 and pqr instantaneous power theory for a shunt active power filter application implemented in 3-phase 4-wire system. These instantaneous power theories have been developed to be applied to unbalanced systems using the power variables to obtain the currents that should be injected from active filters. The active filter will produce the required reactive power for the load and compensate the ripple component of active power so that the source only delivers constant active power.
8

RF-MEMS switches for reconfigurable antennas

Spasos, Michail N. January 2011 (has links)
Reconfigurable antennas are attractive for many military and commercial applications where it is required to have a single antenna that can be dynamically reconfigured to transmit or receive on multiple frequency bands and patterns. RF-MEMS is a promising technology that has the potential to revolutionize RF and microwave system implementation for next generation telecommunication applications. Despite the efforts of top industrial and academic labs, commercialization of RFMEMS switches has lagged expectations. These problems are connected with switch design (high actuation voltage, low restoring force, low power handling), packaging (contamination layers) and actuation control (high impact force, wear, fatique). This Thesis focuses on the design and control of a novel ohmic RF-MEMS switch specified for reconfigurable antennas applications. This new switch design focuses on the failure mechanisms restriction, the simplicity in fabrication, the power handling and consumption, as well as controllability. Finally, significant attention has been paid in the switch’s electromagnetic characteristics. Efficient switch control implies increased reliability. Towards this target three novel control modes are presented. 1) Optimization of a tailored pulse under Taguchi’s statistical method, which produces promising results but is also sensitive to fabrication tolerances. 2) Quantification of resistive damping control mode, which produces better results only during the pull-down phase of the switch while it is possible to be implemented successfully in very stiff devices. 3) The “Hybrid” control mode, which includes both aforementioned techniques, offering outstanding switching control, as well as immunity to fabrication tolerances, allowing an ensemble of switches rendering an antenna reconfigurable, to be used. Another issue that has been addressed throughout this work is the design and optimization of a reconfigurable, in pattern and frequency, three element Yagi-Uda antenna. The optimization of the antenna’s dimensions has been accomplished through the implementation of a novel technique based on Taguchi’s method, capable of systematically searching wider areas, named as “Grid-Taguchi” method.
9

Integrated Switching DC-DC Converters with Hybrid Control Schemes

Luo, Feng January 2009 (has links)
In the modern world of technology, highly sophisticated electronic systems pave the way for future's information technology breakthroughs. However, rapid growth on complexity and functions in such systems has also been a harbinger for the power increase. Power management techniques have thus been introduced to mitigate this urgent power crisis. Switching power converters are considered to be the best candidate due to their high efficiency and voltage conversion flexibility. Moreover, switching power converter systems are highly nonlinear, discontinuous in time, and variable. This makes it viable over a wide operating range, under various load and line disturbances. However, only one control scheme cannot optimize the whole system in different scenarios. Hybrid control schemes are thus employed in the power converters to operate jointly and seamlessly for performance optimization during start-up, steady state and dynamic voltage/load transient state.In this dissertation, three switching power converter topologies, along with different hybrid control schemes are studied. First, an integrated switching buck converter with a dual-mode control scheme is proposed. A pulse-train (PT) control, employing a combination of four pulse control patterns, is proposed to achieve optimal regulation performance. Meanwhile, a high-frequency pulse-width modulation (PWM) control is adopted to ensure low output ripples and avoid digital limit cycling. Second, an integrated buck-boost converter with a tri-mode digital control is presented. It employs adaptive step-up/down voltage conversion to enable a wide range of output voltage. This is beneficial to ever-increasing dynamic voltage scaling (DVS) enabled, modern power-efficient VLSI systems. DVS adaptively adjusts the supply voltage and operation frequency according to instantaneous power and performance demand, such that a system is constantly operated at the lowest possible power level without compromising its performance. Third, a digital integrated single-inductor multiple-output (SIMO) converter, tailored for DVS-enabled multicore systems is addressed. With a multi-mode control algorithm, DVS tracking speed and line/load regulation are significantly improved, while the converter still retains low cross regulation.All three integrated CMOS DC-DC converters have been designed and fabricated successfully, demonstrating the techniques proposed in this research. The measurements results illustrate superior line and load regulation performances and dynamic response in all these designs.
10

Desenvolvimento de controladores de forças generalizadas em manipuladores industriais / Development of generalized force controller for industrial robots

André Luís de Aguiar Mirandola 22 September 2006 (has links)
Esta dissertação estuda a otimização da capacidade de interação de manipuladores robôs com o meio externo através do controle das forças e torques envolvidas no contato. Os modelos adotados para as análises levam em consideração a interação entre a extremidade do manipulador e uma superfície. Neste trabalho, são investigadas diferentes metodologias para controle de forças, assim como as vantagens e desvantagens de cada método estudado para comparar e desenvolver um controle adequado das forças de contato. Devido às divergências encontradas na literatura, foram implementadas experimentalmente duas abordagens distintas conhecidas por controle cinestático e controle híbrido. Também, como parte do ambiente experimental, foi desenvolvido um protótipo de um micro manipulador com um grau de liberdade instalado na extremidade do robô. O micro manipulador simplifica a implementação de controle de força ativo, pois trabalha de forma independente do acionamento \"fechado\" dos robôs industriais abordados no trabalho. Assim é possível manter uma força arbitraria desejada no contato com a superfície. O controlador de força se sobrepõe ao controlador de posições convencional do manipulador para produzir o comportamento desejado na interação com o meio externo. / The optimization of a conventional industrial robot manipulator capacity to interact with the surrounding environment is analyzed in this work. The models adopted for the analysis take into account the contact between the robot and an external surface. Different force control approaches are analyzed regarding their implementation advantages and disadvantages. Due to the well known contradictions in the literature experiments were carried out using the kinestatic control and the hybrid control. A micro manipulator with one degree of freedom was developed and installed at the end effector in association with the tool tester. With this system it is possible change the contact force on the surface. The simultaneous coordinate work of the robot position control and the micro manipulator system force control are use to produce a desired behavior in the interaction with the external surface.

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