Design Of Four-blade Slit Control System Of China Spallation Neutron Source High Pressure Spectrometer

The main function of the four-blade slit system,as an important component of the high-pressure spectrometer,is to regulate the size of the neutron beam passing through the slit.If the precision of the four-blade slit is low,the area of the neutron beam irradiated to the experimental sample will be too large or too small,which will affect the overall performance of the high-pressure spectrometer.In this paper,we design a four-blade slit system for high-pressure spectrometer by studying the transmission and control of the four-blade slit in the context of the slit of the spectrometer that has been put into use.First,according to the function and performance requirements of the four-blade slit,the overall scheme of the four-blade slit control system is designed,and the control mode of both local touch screen control and remote EPICS control is determined,and the control system mode of closed-loop feedback system as the main operation mode and open-loop feedback system as the backup operation mode is determined.Comparing the transmission scheme of two commonly used feed drive systems,the linear stepper motor was finally selected as the transmission member by combining the size,structure and cost factors.Then,the hardware design of the control system is realized according to the working principle and structure of the four-blade slit system.Analysis and calculation of linear stepper motor as the core component of the feed drive system,finite element verification after the selection;analysis and comparison of absolute and incremental two kinds of scale,select the absolute scale can simplify the control;according to the selected control system hardware,combined with its role to complete the hardware layout design and compact control cabinet design,according to the designed control system structure to complete the wiring design of the control system is completed according to the designed control system structure.Then,the software function of the four-blade slit control system is analyzed,and the main program design of the control system is completed.Design the slit opening algorithm for precise positioning of the slit opening.The blade clash detection algorithm is designed for the case that the four-blade slit may collide with the boron carbide plate during operation.To facilitate the local and remote use of the four-blade slit by the experimenter,a human-machine interface and an EPICS-based remote control system are designed respectively.Finally,the assembly and commissioning of the four-blade slit system was completed according to the designed installation procedure.The NC axis position loop PID parameters of the motor were adjusted to make the motor precisely positioned and run smoothly.The performance parameters of the closed-loop control system and openloop control system of the four-blade slit are tested and analyzed through experiments,and the results show that the four-blade slit system of the high voltage spectrometer designed in this paper meets its technical performance index requirements.