A classification of techniques for the compensation of time delayed processes. Part 2: Structurally optimised controllers

Following on from Part 1, Part 2 of the paper considers the use of structurally optimised controllers to compensate time delayed processes

Process control for WAAM using computer vision

This study is mainly about the vision system and control algorithm programming for wire arc additive manufacturing (WAAM). Arc additive manufacturing technology is formed by the principle of heat source cladding produced by welders using molten inert gas shielded welding (MIG), tungsten inert gas shielded welding (TIG) and layered plasma welding power supply (PA). It has high deposition efficiency, short manufacturing cycle, low cost, and easy maintenance. Although WAAM has very good uses in various fields, the inability to control the adding process in real time has led to defects in the weld and reduced quality. Therefore, it is necessary to develop the real-time feedback through computer vision and algorithms for WAAM to ensure that the thickness and the width of each layer during the addition process are the same

Disseny i implementació d'una metodologia per a construir sistemes difusos clàssics de forma automàtica a partir de models FIR

En aquest projecte es desenvolupa una nova metodologia que actua com a extensió de la tècnica de FIR. D'una banda construeix de forma automàtica models FIS a partir de models FIR, d'altra banda ofereix la predicció del comportament de sistemes mitjançant un sistema d'inferència híbrid FIR + FISIn this project, a new methodology is developed that acts as an extension of the FIR technique. On one hand, it automatically builds FIS models from FIR models, on the other hand it offers the prediction of the behavior of systems using a FIR + FIS hybrid inference syste

Uma alternativa aos Modelos NEWAVE e DECOMP por meio da Aplicação de Técnicas de Inteligência Artificial.

A estrutura de geração, transmissão e distribuição de energia elétrica no Brasil possui diversas particularidades não encontradas em outras nações. Tais diferenças ocorrem tanto pelas tecnologias utilizadas nas operações, quanto pelas características geográficas do território brasileiro. A determinação dos preços e tarifas da energia no Brasil é uma atividade complexa, e depende de informações fornecidas por agentes distintos. Este trabalho tem como foco o estudo da formação de um determinado preço de energia elétrica no mercado de curto prazo, também conhecido como preço “spot”. O preço “spot” é resultado direto da execução dos modelos matemáticos de planejamento empregados: NEWAVE e DECOMP. Ele representa o custo marginal de operação do sistema elétrico para uma condição de despacho ótimo das usinas geradoras ótima. O processamento do alto volume de dados requeridos por estes modelos é uma tarefa que demanda um tempo elevado, além de conhecimento específico das centenas de variáveis de entrada, o que de certa forma inviabiliza a utilização em cenários onde a tomada de decisão deve ser ágil, como por exemplo, em leilões de energia. O conhecimento prévio de valores que este preço pode assumir é uma informação de grande valor estratégico para vários agentes do setor elétrico brasileiro, destacando-se geradores, distribuidores e comercializadores. Este trabalho propõe uma maneira de se estimar valores futuros do preço “spot” de energia elétrica por meio da análise, utilizando métodos de otimização combinados com redes neurais artificiais

A new approach to securing passwords using a probabilistic neural network based on biometric keystroke dynamics

Passwords are a common means of identifying an individual user on a computer system. However, they are only as secure as the computer user is vigilant in keeping them confidential. This thesis presents new methods for the strengthening of password security by employing the biometric feature of keystroke dynamics. Keystroke dynamics refers to the unique rhythm generated when keys are pressed as a person types on a computer keyboard. The aim is to make the positive identification of a computer user more robust by analysing the way in which a password is typed and not just the content of what is typed. Two new methods for implementing a keystroke dynamic system utilising neural networks are presented. The probabilistic neural network is shown to perform well and be more suited to the application than traditional backpropagation method. An improvement of 6% in the false acceptance and false rejection errors is observed along with a significant decrease in training time. A novel time sequenced method using a cascade forward neural network is demonstrated. This is a totally new approach to the subject of keystroke dynamics and is shown to be a very promising method The problems encountered in the acquisition of keystroke dynamics which, are often ignored in other research in this area, are explored, including timing considerations and keyboard handling. The features inherent in keystroke data are explored and a statistical technique for dealing with the problem of outlier datum is implemented.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Neuro-fuzzy modelling and control of robotic manipulators

The work reported in this thesis aims to design and develop a new neuro-fuzzy control system for robotic manipulators using Machine Learning Techniques, Fuzzy Logic Controllers, and Fuzzy Neural Networks. The main idea is to integrate these intelligent techniques to develop an adaptive position controller for robotic manipulators. This will finally lead to utilising one or two coordinated manipulators to perform upper-limb rehabilitation. The main target is to benefit from these intelligent techniques in a systematic way that leads to an efficient control and coordination system. The suggested control system possesses self-learning features so that it can maintain acceptable performance in the presence of uncertain loads. Simulation and modelling stages were performed using dynamical virtual reality programs to demonstrate the ideas of the control and coordination techniques. The first part of the thesis focuses on the development of neuro-fuzzy models that meet the above requirement of mimicking both kinematics and dynamics behaviour of the manipulator. For this purpose, an initial stage for data collection from the motion of the manipulator along random trajectories was performed. These data were then compacted with the help of inductive learning techniques into two sets of if-then rules that form approximation for both of the inverse kinematics and inverse dynamics of the manipulator. These rules were then used in fuzzy neural networks with differentiation characteristics to achieve online tuning of the network adjustable parameters. The second part of the thesis introduces the proposed adaptive neuro-fuzzy joint-based controller. To achieve this target, a feedback Fuzzy-Proportional-Integral-Derivative incremental controller was developed. This controller was then applied as a joint servo-controller for each robot link in addition to the main neuro-fuzzy feedforward controller used to compensate for the dynamics interactions between robot links. A feedback error learning scheme was applied to tune the feedforward neuro-fuzzy controller online using the error back-propagation algorithm. The third part of the thesis presents a neuro-fuzzy Cartesian internal model control system for robotic manipulators. The neuro-fuzzy inverse kinematics model of the manipulator was used in addition to the joint-based controller proposed and the forward mathematical model of the manipulator in an adaptive internal model controller structure. Feedback-error learning scheme was extended to tune both of the joint-based neuro-fuzzy controller and the neuro-fuzzy internal model controller online. The fourth part of the thesis suggests a simple fuzzy hysteresis coordination scheme for two position-controlled robot manipulators. The coordination scheme is based on maintaining certain kinematic relationships between the two manipulators using reference motion synchronisation without explicitly involving the hybrid position/force control or modifying the existing controller structure for either of the manipulators. The key to the success of the new method is to ensure that each manipulator is capable of tracking its own desired trajectory using its own position controller, while synchronizing its motion with the other manipulator motion so that the differential position error between the two manipulators is reduced to zero or kept within acceptable limits. A simplified test-bench emulating upper-limb rehabilitation was used to test the proposed coordination technique experimentally