Compensating non-linear effects in a MIMO system with unobservable and uncontrollable modes

In this paper we propose an architecture to deal with non-linear effects like saturation that can severly limit the performance of an adaptive optics (AO) system while preserving good performance in both point-spread function (PSF) output and piston management. An AO system uses a wave-front sensor as input device and a deformable mirror (DM) as output device. Since both the input and output devices have several degrees of freedom, this is a MIMO system. We consider the case of MACAO (for multi-application curvature adaptive optics) which has a wave-front sensor with 60 channels and a DM with 60 actuators.