Crone observer - definition and design methodology

CRONE control, robust control methodology based on fractional differentiation, is applied to state observer design. State observation can indeed be viewed as a regulation problem given that the goal of a state observer is to cancel the observation errors in spite of measurement noises, disturbances and plant perturbations. This conclusion has been used recently to define a new class of state observers known in the literature as “dynamic observers” or “input-output observer”. It is based on the observation error dynamic feedback. In this paper, this idea is used to define the CRONE observer design methodology. Performance robustness of the obtained observers versus plant perturbations is analysed. As for CRONE control, fractional differentiation in the definition of an equivalent open loop transfer function permits to reduce the number of parameters to be optimised.