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Desenvolvimento de observadores de estado para controlar a suspensão de veículos automóveis
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| 6.27 MB | Adobe PDF |
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Abstract(s)
O observador de estados tem a função de estimar um vetor de estados a partir da saída ou das entradas e saídas de um determinado sistema, evitando eventuais falhas de sensores, baixa fiabilidade e elevado custo económico associados aos mesmos, e também quando é impossível de medir diretamente as variáveis de estado estimadas. Tendo em conta que o sistema a ser observado é uma suspensão automóvel, é impossível medir as perturbações devidas às irregularidades da via de circulação, restando para medida a saída do sistema, a aceleração da massa suspensa e da não suspensa, utilizando acelerómetros. Nesta dissertação é proposta a utilização dum observador de estados assintótico, o qual possui como peculiaridade a ausência da entrada do sistema na estimação do vetor de estados, utilizando somente a saída do sistema em questão, que é a aceleração da massa suspensa, no qual em termos de medição, aumenta-se a facilidade e praticidade consideravelmente. A verificação experimental é realizada em ambiente MATLAB e SIMULINK. São apresentadas simulações tanto do observador assintótico sobre uma suspensão passiva simples quanto sobre uma suspensão passiva mais complexa, tendo em conta a não linearidade da deformação do pneu, assim como do seu coeficiente de amortecimento. Na análise dos resultados, compara-se a estimativa dos estados do sistema original com estados do observador projetado, tanto no sistema mais simples quanto no complexo. O erro é originado da ausência da entrada nas estimativas. Entretanto, os erros obtidos foram consideravelmente baixos. Sendo assim, o uso do observador de estados assintótico em suspensões passivas mostrou realizar boas estimativas e cumprir com o proposto.
The space-state observer or estimator has the function of estimating a state vector from the output or inputs and outputs of a given system, in thi way, avoiding possible sensor failures, low reliability and high costs associated with them, and also when it is impossible to directly measure the estimated state variables. Considering that the system to be observed is an automobile suspension, it is impossible to measure the disturbances due to the irregularities of the roadway. This leaves the output of the system, the acceleration of the suspended and unsuspended mass, to be measured using accelerometers. In this dissertation we propose the use of an asymptotic state observer, which has as peculiarity the absence of the system input in the estimation of the state vector, using only the output of the real system, which is the suspended mass acceleration, which in a matter measurement, increases the ease and practicality considerably. The experimental verification is performed in MATLAB and SIMULINK environment. Simulations of both the asymptotic observer on a simple passive suspension and a more complex passive suspension are presented, taking into account the nonlinearity of the tire deformation as well as its damping coefficient. In the analysis of the results, the estimate of the states of the real system is compared with states of the designed observer on both the simpler and the more complex system. The error is originated from the absence of the input in the estimator. However, the errors obtained were considerably low. Therefore, the use of the asymptotic state observer in passive suspensions has been shown to perform good estimates and to comply with what was proposed.
The space-state observer or estimator has the function of estimating a state vector from the output or inputs and outputs of a given system, in thi way, avoiding possible sensor failures, low reliability and high costs associated with them, and also when it is impossible to directly measure the estimated state variables. Considering that the system to be observed is an automobile suspension, it is impossible to measure the disturbances due to the irregularities of the roadway. This leaves the output of the system, the acceleration of the suspended and unsuspended mass, to be measured using accelerometers. In this dissertation we propose the use of an asymptotic state observer, which has as peculiarity the absence of the system input in the estimation of the state vector, using only the output of the real system, which is the suspended mass acceleration, which in a matter measurement, increases the ease and practicality considerably. The experimental verification is performed in MATLAB and SIMULINK environment. Simulations of both the asymptotic observer on a simple passive suspension and a more complex passive suspension are presented, taking into account the nonlinearity of the tire deformation as well as its damping coefficient. In the analysis of the results, the estimate of the states of the real system is compared with states of the designed observer on both the simpler and the more complex system. The error is originated from the absence of the input in the estimator. However, the errors obtained were considerably low. Therefore, the use of the asymptotic state observer in passive suspensions has been shown to perform good estimates and to comply with what was proposed.
Description
Keywords
Suspensão automóvel Observador de estados