Design and implementation of discrete type 1 and type 2 controllers with residual feedback for modal adaptive optics




Hampton, Peter John

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This thesis deals with the design. implementation and experimental validation of digital controllers for an Adaptive Optics (AO) test bench. The AO model has been modeled using a discrete model and this model was validated using experimental measurements. The controllers developed consist of 1-D parallel controllers, one for each mode of the optical system. Two controllers were designed and analyzed for the system: (i) a Type I controller that exhibits improved bandwidth over standard AO controllers and (ii) a Type 2 controller that is capable of low frequency prediction and can provide exceptionally low following error if the quantization noise sources are sufficiently small. The implementation of the controllers on the AO test bench was considered and the problems arising from the quantization of the output of the controller due to hardware limitations were studied. Controller implementations that improve the performance of the system with respect to stability despite the non-linear effects of the quantizer are provided. The controllers developed were implemented and their performance was evaluated and compared with the results expected from theoretical analysis. The experimental results are very close to the ones expected from the theoretical analysis except when the quantization effects become significant.



adaptive optics, telescopes