| In the helical scan mode of Mobile CT, rotary motion and linear of rotating framemust keep the a certain relationship of position, so the study of the dual motorsynchronization control strategy is very important in the mobile CT helicalsynchronous scanning. The main factors of affecting dual-motor synchronous errorare analyzed in the paper, the cross-coupling controller based on synchronous errorstransfer function is developed on this basis.Firstly, on the basis of uniform sampling of projection data in the Mobile CT, thedemand of t dual-motor position synchronous is analyzed, thereby, a mathematicalmodel of dual-motor synchronization relationship is established. Meanwhile, thesingle-axis tracking system of load characteristics is analyzed, the cascade controlmethod for improving the stability of each motor is taken, and effectively inhibitedsecondary disturbance of speed loop.Secondly, the study focuses on synchronous control of helical movement. Across-coupling synchronous control method is put forward to fulfill the synchronismbetween the rotation motor and horizon motor in helical movement. When comparedwith the conventional cross-coupling system, this new structure not only ensure theaccuracy of the synchronous errors between the two motor, but also availably restrainripple of synchronous errors in the steady-state. By taking this method, the two motorscan keep pace with each other and synchronous accuracy improves a lot.Thirdly, according to the different scanning pitch of Mobile CT carried out thesimulation experiment. The tracking error, relative error, synchronization position andthe cumulative error of synchronous control algorithm were analyzed. The conclusionis that synchronous errors of dual-motor is increased much more by the cross coupledcontroller added on the servo system and meet the requirements of helical scanning of Mobile CT. At the same time, the hardware platform for synchronization control ofdual-motor is designed in this paper. |
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