Identification of mechanical systems using the Fourier Series method - a time domain method

In this chapter, the Fourier series method for the identification of mechanical systems is presented. The method will initially be developed for systems with only one degree of freedom, and will later be extended to systems with various degrees of freedom. The identification method presented in this dissertation can be summarized in three fundamental steps: 1) Expansion of excitation and response in series of Fourier 2) Integration of movement equations and use of an operational matrix for integration of Fourier series. 3) Parameter estimation by the minimum method squaresDissertação (Mestrado)Neste capitulo, é apresentado o método das séries de Fourier para a identificação de sistemas mecânicos. 0 método será desenvolvido inicialmente para sistemas com apenas um grau de liberdade, sendo posteriormente extendido para sistemas com vários graus de liberdade. □ método de identificação apresentado nesta dissertação pode ser sumarizado em três etapas fundamentais: 1) Expansão da excitação e da resposta em séries de Fourier. 2) Integração das equaçSes do movimento e emprego de uma matriz operacional para integração das séries de Fourier. 3) Estimativa dos parâmetros pelo método dos mínimos quadrado

Faults detection and isolation using reduced-order state observers

Orientador: Robson PederivaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecanicaResumo: Um dos fatores do grande interesse no desenvolvimento de novas técnicas de detecção de falhas é devido ao aumento da demanda da indústria em relação a segurança de seus sistemas, sendo eles supervisionados e monitorados para que as falhas sejam sanadas o mais rápido possível e que os distúrbios em operação normal não causem uma deterioração da performance dos mesmos. Neste trabalho, desenvolveu-se uma metodologia para detecção e localização de falhas em sistemas mecânicos utilizando observadores de estado de ordem reduzida. O método pode reconstruir os estados não medidos ou os valores provenientes de pontos de difícil acesso no sistema. Os parâmetros de interesse sujeitos a falhas são escolhidos, projetando-se um observador global otimizado para análise de todo o sistema considerando possíveis perturbações aleatórias na excitação, na resposta e falhas nos sensores. Projeta-se também observadores robustos a estes parâmetros de interesse, que localizam possíveis falhas ou irregularidades no sistema. Para os componentes que necessitem de um acompanhamento periódico devido às suas grandes solicitações ou falhas constantes, montam-se observadores com um sistema de alarmes que gera uma curva de tendências em um sistema automático para detecção e localização de falhas desenvolvido neste trabalho. Para os sistemas simulados e experimental, fez-se análises da performance transiente e em regime permanente, excitando-se os sistemas com força impulsiva, força senoidal, ruído aleatório, combinações dos mesmos, etc. Os resultados foram bons quando comparados com outros métodos e pôde-se também verificar os resultados através de uma bancada de testesAbstract: The development of new faults detection techniques is necessary because of increasing demands from industries on reliability and safety in mechanical systems. They must be supervised such that occurrence of failures can be accommodated as quickly as possible because they can cause an unacceptable deterioration of the systems performance. In this work, we have developed a methodology to Detect and Isolate Faults in mechanical systems using reduced order state observers. We can monitor unmeasureble variables and the method selects the parameters from components that may fault during the process and constmcts an otimized global observer to analyze alI the system considering random noises in the excitation, in the response and sensor faults. To isolate component failures via robust observation, an automatic system with a bank of detection observers is constmcted, where each observer is only sensitive to one specified component failure while robust to alI other component failures. We have analized the transient and steady-state performance by exciting the system with impulsive force, sinosoidal force, random noise etc. The results were good when we compare them with other methods and we have verified the results through a testing rigDoutoradoMecanica dos Sólidos e Projeto MecanicoDoutor em Engenharia Mecânic

Analise de desempenho de observadores de estado robustos na localizacao de falhas

The state observers can reconstruct and monitor unmeasurable states. A new concept of fault detection and isolation using state observers is presented. The method selects the parameters from components that may fail during the process and constructs optimized robust observers. To isolate component failures via robust observation, a bank of detection observers is organized, in which each observer is only sensitive to one specified component failure while robust to all other component failures. This paper analyzes the performance of transient and steady-state behavior of the state observer

Design of a state observer using decay rate LMI constraints for fault detection in mechanical systems

Nowadays, one of the most important concerns for many companies is to maintain the operation of their systems without sudden equipment break down. Because of this, new techniques for fault detection and location in mechanical systems subject to dynamic loads have been developed. This paper studies of the influence of the decay rate in the design of state observers using LMI for fault detection in mechanical systems. This influence is analyzed by the performance index proposed by Huh and Stein for the condition of a state observer. An example is presented to illustrate the methodology discussed

Fuzzy control embedded in microcontroller and applied to an experimental apparatus using magnetorheological fluid damper

This work focuses on applying fuzzy control embedded in microcontrollers in an experimental apparatus using magnetorheological fluid damper. The non-linear behavior of the magnetorheological dampers associated with the parametric variations on vehicle suspension models corroborate the use of the fuzzy controllers. The fundamental formulation of this controller is discussed and its performance is shown through numeric simulations. An experimental apparatus representing a two degree of freedom system containing a magnetorheological damper is used to identify the main parameters and to evaluate the performance of the closed-loop system with the embedded low-cost microcontroller-based fuzzy controller. © 2013 Brazilian Society for Automatics - SBA

Active modal damping control of a smart truss structure using a self-organizing fuzzy controller

This paper presents design, implementation and experimental results of active vibration control of a truss structure using a pair of piezoelectric ceramic stack actuators. To reduce the vibrations caused by an impulse force, two active strut members are installed along a vertical of the base bay of the truss. The active strut element consists of a piezoelectric ceramic actuator stack, a force transducer and mechanical interfaces. A self-organizing fuzzy controller (SOFC) is designed to suppress vibration of the truss. The SOFC, which uses the input and output history in its fuzzy rules, is designed to maximize modal damping of a constructed truss structure. Experimental results illustrate that the active piezoceramic strut actuators and the SOFC can effectively reduce vibration of the truss.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Identification of structural parameters for active vibration control

The study of algorithms for active vibration control in flexible structures became an area of enormous interest for some researchers due to the innumerable requirements for better performance in mechanical systems, as for instance, aircrafts and aerospace structures. Intelligent systems, constituted for a base structure with sensors and actuators connected, are capable to guarantee the demanded conditions, through the application of diverse types of controllers. For the project of active controllers it is necessary, in general, to know a mathematical model that enable the representation in the space of states, preferential in modal coordinates to permit the truncation of the system and reduction in the order of the controllers. For practical applications of engineering, some mathematical models based in discrete-time systems cannot represent the physical problem, therefore, techniques of identification of system parameters must be used. The techniques of identification of parameters determine the unknown values through the manipulation of the input (disturbance) and output (response) signals of the system. Recently, some methods have been proposed to solve identification problems although, none of them can be considered as being universally appropriate to all the situations. This paper is addressed to an application of linear quadratic regulator controller in a structure where the damping, stiffness and mass matrices were identified through Chebyshev's polynomial functions