Design of robust controller based on loop-shaping for quick-scanning monochromator

Quick-scanning Double Crystal Monochromator (QDCM) is core equipment of the Quick-scanning X-ray Absorption Fine Structure (QXAFS) experimental method. To realize the sub-second temporal resolution of QXAFS method, QDCM is responsible for achieving a reproducible oscillatory movement of monochromator crystals with a given frequency and amplitude around Bragg angle. A new robust controller design method is proposed for QDCM system. This controller, based on the loop-shaping principle in frequency-domain, considers the effect of nonlinearities and uncertainties in low frequency region and the suppression of vibration mode in high frequency region. The results are shown to demonstrate the feasibility of this method for the QDCM fast-scan seeking.