Nonfragile Robust H

The nonfragile H∞ filtering problem for a kind of Takagi-Sugeno (T-S) fuzzy stochastic system which has a time-varying delay and parameter uncertainties has been studied in this paper. Sufficient conditions for stochastic input-to-state stability (SISS) of the fuzzy stochastic systems are obtained. Attention is focused on the design of a nonfragile H∞ filter such that the filtering error system can tolerate some level of the gain variations in the filter and the H∞ performance level also could be satisfied. By using the SISS result, the approach to design the nonfragile filter is proposed in terms of linear matrix inequalities. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed method

Novel Distance Measure in Fuzzy TOPSIS for Supply Chain Strategy Based Supplier Selection

In today’s highly competitive environment, organizations need to evaluate and select suppliers based on their manufacturing strategy. Identification of supply chain strategy of the organization, determination of decision criteria, and methods of supplier selection are appearing to be the most important components in research area in the field of supply chain management. In this paper, evaluation of suppliers is done based on the balanced scorecard framework using new distance measure in fuzzy TOPSIS by considering the supply chain strategy of the manufacturing organization. To take care of vagueness in decision making, trapezoidal fuzzy number is assumed for pairwise comparisons to determine relative weights of perspectives and criteria of supplier selection. Also, linguistic variables specified in terms of trapezoidal fuzzy number are considered for the payoff values of criteria of the suppliers. These fuzzy numbers satisfied the Jensen based inequality. A detailed application of the proposed methodology is illustrated

Controladores linguísticos Fuzzy

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia MecânicaEste trabalho tem o objetivo de estudar a utilização de controladores linguísticos Fuzzy, analisando o seu desempenho, relativamente ao uso de controladores clássicos do tipo PID. Para a realização deste trabalho foi desenvolvido, como banco de ensaio, um processo de mistura de água fria e água quente, comduas malhas de controlo, uma para controlo do nível através da válvula de controlo daágua fria e outra para controlo da temperatura através da válvula de controlo da água quente, provocando o acoplamento de efeitos entre as duas malhas de controlo, sendo assim um sistema não linear. Foram estudados e implementados vários controladores Fuzzy, com diferentes estratégias de controlo implementadas através de vários conjuntos de regras heurísticas, estabelecendo uma comparação entre eles e relativamente à utilização de controladores clássicos do tipo PID, através da realização de diversos ensaios. O sucesso obtido com o controlo linguístico Fuzzy sugere que é uma alternativa robusta comparativamente ao controlo clássico, quando estamos perante um sistema de comportamento complexo com acoplamento de efeitos. Com as metodologias clássicas de controlo não é possível desacoplar os efeitos hipoteticamente existentes entre malhas de controlo e pretendeu-se com esta dissertação mostrar as vantagens da utilização do controlo linguístico Fuzzy, para este caso, diminuindo ou eliminando o “overshoot”, conseguindo um menor tempo de estabelecimento dos “set point” de uma forma estável e com a diminuição ou eliminação do acoplamento de efeitos. Neste estudo o processo é simulado e controlado utilizando a plataforma computacional LabView.Abstract: This dissertation aims the study of use Fuzzy linguistic controllers, analyzing the performance, regarding the use of the classic PID controllers. For this work was developed, as a test bed, a process of mixing cold and hot water, with two control loops, one for level control through a control valve of cold water and for temperature control through other control valve of hot water, causing the coupling effects between the two control loops, is thus a non-linear system. Were studied and implemented the various Fuzzy controllers, with different control strategies implemented through multiple sets of heuristic rules, establishing a comparison between them and the use of classic PID controllers, by performing several tests. The success achieved with the Fuzzy linguistic controller suggests that is a robust alternative compared with the classical PID control, when we are dealing with a complex behavior system with coupling effects. Withclassical control methods is not possible decouple the effects hypothetically existing between the meshes of control and it was intended with this dissertation show the advantages of the use of Fuzzy linguistic control, in this case, reducing or eliminating the overshoot, achieving a shorter time of establishing a stable set point and decreasing or eliminating the effects of coupling effects. In this study the process is simulated and controlled using the computing platform LabView