Closed loop interferometry: innovative proposals for optical phase detection by using modern control approaches
Carregando...
Data
2022-02-04
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Neste trabalho apresentamos um sistema de controle não linear aplicado ao interferômetro óptico de dois feixes, operando com abordagem de alto ganho (compensação total de fase interferométrica), a fim de converter a curva característica interferométrica para uma característica linear e eliminar algoritmos complexos para demodulação óptica de fase (que pode envolver métodos de desdobramento de fase). O destaque deste trabalho é o uso do filtro ressonante dentro do controlador, é uma nova proposta que reúne duas poderosas ferramentas do controle não linear: o filtro ressonante e a estrutura variável. A estrutura variável provou ser uma ferramenta importante, eficiente e robusta o suficiente para estabilizar o interferômetro. Além disso, a estrutura do filtro permite trabalhar com um ganho consideravelmente menor ao trabalhar em ressonância, quando comparado a trabalhos anteriores. O sistema de controle foi testado no interferômetro de quadratura em malha aberta utilizando um interferômetro de realimentação virtual controlado, que dá equivalência da realimentação física. Este método de implementação foi escolhido devido à necessidade de maior taxa de amostragem e para evitar um maior atraso. O sistema proposto também foi estudado alterando a entrada do controlador (com e sem chaveamento, a estrutura da variável, e mudando a função de chaveamento de uma função de sinal para uma função sigmoide). Após o teste experimental, um atuador flextensional piezoelétrico foi avaliado sob todas as variações do sistema proposto, e então comparado sob a mesma medida ao método arco tangente clássico e a discrepância entre os métodos na faixa de 1.000 Hz foi menor que 5%, assim o sistema desenvolvido é validado para medições de fase óptica.
In this work we present a nonlinear control system applied to the two beam optical interferometer, operating with high gain approach (full compensation of interferometric phase), in order to convert the interferometric characteristic curve to a linear characteristic and eliminate complex algorithms for optical phase demodulation (which can involve phase unwrapping methods). The highlight of this work is the use of resonant filter within the controller, is a new proposal that brings together two powerful tools of the nonlinear control: the resonant filter and variable structure. The variable structure has been proved to be an important tool as well as efficient and robust enough to stabilize the interferometer. Also, the structure of the filter allows working with a considerable smaller gain when working in resonance, when compared to previous works. The controlling system was tested on the quadrature interferometer in open loop using a virtual feedback interferometer controlled, which gives equivalence of the physical feedback. This method of implementation was chosen due the need of higher sampling rate and to avoid a greater delay. The system proposed was also studied by changing the controller input (with and without switching, the variable structure, and changing the switching from a sign function to a sigmoidal one). After the experimental test, a piezoelectric flextensional actuator was evaluated under all the variations of the system proposed, and then compared under the same measurement to the arc tangent classical method and the discrepancy between methods in a range of 1,000 Hz was less than 5%, thereby the system developed is validated for measurements of optical phase.
In this work we present a nonlinear control system applied to the two beam optical interferometer, operating with high gain approach (full compensation of interferometric phase), in order to convert the interferometric characteristic curve to a linear characteristic and eliminate complex algorithms for optical phase demodulation (which can involve phase unwrapping methods). The highlight of this work is the use of resonant filter within the controller, is a new proposal that brings together two powerful tools of the nonlinear control: the resonant filter and variable structure. The variable structure has been proved to be an important tool as well as efficient and robust enough to stabilize the interferometer. Also, the structure of the filter allows working with a considerable smaller gain when working in resonance, when compared to previous works. The controlling system was tested on the quadrature interferometer in open loop using a virtual feedback interferometer controlled, which gives equivalence of the physical feedback. This method of implementation was chosen due the need of higher sampling rate and to avoid a greater delay. The system proposed was also studied by changing the controller input (with and without switching, the variable structure, and changing the switching from a sign function to a sigmoidal one). After the experimental test, a piezoelectric flextensional actuator was evaluated under all the variations of the system proposed, and then compared under the same measurement to the arc tangent classical method and the discrepancy between methods in a range of 1,000 Hz was less than 5%, thereby the system developed is validated for measurements of optical phase.
Descrição
Palavras-chave
Optical interferometry, High gain approach, Resonant filter, Nonlinear control, Interferometria ótica, Alto ganho, Filtro ressonante, Controle não linear