High Precision Fixed Time 4-Order S-Curve Trajectory Planning for Multi-Channel Double Crystal Monochromator

Double crystal monochromator (DCM) is the key component of quick-scanning X-ray absorption fine structure (QXAFS) method. It is responsible for the crucial task of monochromitizing hard X-rays emitted from synchrotron radiation facility. A novel multi-channel DCM consisting of two regular hexagon revolvers is discussed in this paper. To compensate the error angles of the crystals introduced by manual assembly accurately and effectively, ensuring the the quality and stability of the spectrum, planning an appropriate motion trajectory of the multi-channel DCM is of great importance. A high precision fixed time vibration-suppressed S-curve trajectory planning method is proposed in this paper. Multi-channel DCM motion analysis, S-curve trajectory planning method, trajectory tracking simulation are discussed in detail. The simulation results on the multi-channel DCM system demonstrate that, the maximum position tracking error is reduced to 5.9 arcsec by proposed S-curve trajectory, which is reduced by 24.46%, 39.16% and 76.63% respectively, compared with conventional 5-order polynomial and B-spline and straight line while the spectrum scanning frequency is 36Hz. The result verifies that the proposed 4-order S-curve trajectory can significantly improve the position tracking accuracy and suppress the vibration of the multi-channel DCM system.