Comparison of the Performance of Modal Control Schemes for an Adaptive Optics System and Analysis of the Effect of Actuator Limitations

摘要

In this study, modal control with various bases has been experimentally evaluatedon an experimental Adaptive Optics (AO) testbed. In most custom-built adaptiveoptics control problems, spatial resolution and available stroke of the deformablemirror (DM) are assumed to be sufficient for the intended performance. Inpractice, however, there are situations where DMs of limited capability are usedand the control system is desired to make most out of the hardware even in suchsituations. In this paper, the effect of the hardware limitations, such as the spatialresolution of the wavefront sensor and the deformable mirror (DM) on theperformance of the AO system, is investigated and several control techniques areproposed to mitigate the problem. The derivatives of Zernike polynomials do nothave the orthogonal property.A simple approximate orthogonalization techniqueis proposed along with the method to avoid the discrepancy of minimum error inthe sensor output vector space and in the vector space where the control law isapplied. An anti-windup technique is also proposed to reduce the adverse effectby an integral controller when saturation of the DM occurs. Effectiveness of theproposed techniques is demonstrated by experiments on the pseudo real-time AOtestbed.