【作者】 李冬；

【导师】 樊明武；

【作者基本信息】 华中科技大学 ， 电工理论与新技术， 2008， 硕士

【摘要】 正电子发射断层成像(PET)是目前分子水平上医学研究的最先进手段,对于肿瘤的早发现、早治疗有着极大优势,因而不断被国内各大医院引进。回旋加速器作为提供PET所需放射性同位素的主要生产设备目前基本依赖进口,为此加快开发具有自主知识产权的紧凑型低能回旋加速器具有十分现实的意义。加速器控制系统的研究是开发自主型加速器系统的一个重要组成部分,因为控制系统的好坏直接关系到加速器能否安全、稳定运行。本文针对紧凑型低能回旋加速器的特殊要求,详细分析了系统的每个组成部分,提出了控制系统总体结构,阐述了其设计思想。初步设计了一次和二次水冷系统的模型,并针对二次水冷系统的数学模型提出了两种建模方法。在此基础之上,介绍了大林和smith预估控制算法,并对一阶大滞后惯性系统进行了控制器的设计,得到了仿真图形。然后,参考MINItrace回旋加速器真空系统设计了符合课题需要的真空系统模型,列出了系统运行流程,并采用Simulink和Stateflow组件对真空系统的运行逻辑进行了仿真。最后,介绍了高频系统的组成,并重点分析了高频功率源的结构和原理,提出了采用DDS芯片AD9850输出的混频信号作为系统的频率源的设计思想。功率源驱动级采用MOSFET晶体管功率放大模块,末级采用高频电子四极管。四极管采用阴地电路,工作在甲乙类。高频功率源采用压控可变衰减器进行幅度调制,以PID作为闭环控制算法,并通过Ziegler-Nichols继电反馈辨识法对PID参数进行整定。更多还原

【Abstract】 PET (Positron Emission Tomography) is the most advanced technique of nuclear medicine presently. It has been introduced by many domestic hospitals due to the predominance in detecting of incipient tumors. As the primary isotope generator, most cyclotrons in our country depend on import. So it is significant to develop the compact low energy cyclotron of independent intellectual property rights. The research of the control system is an important step in cyclotron system design, which is related to the safety and stabilization of the cyclotron.In this thesis, the overall structure of the distributed control system is established firstly according to specific requirement of the compact low energy cyclotron. Then some design thought is proposed basing on the comprehensive analysis of the system constitution. The elementary system model of the primary cooling and secondary cooling is built in the foundation of cooling system research. For the secondary cooling, this thesis puts forward two mathematic modeling methods. After educing the mathematic model, a special controller for the time-delay system is designed using Dahlin Algorithm and Smith Predictor and simulated to get the ideal result. In addition, the vacuum system model is also designed with reference to the vacuum system of MINItrace cyclotron. The running logical process has been simulated by Simulink and Stateflow.Finally, the structure of RF System has been established. The method of picking-up a desired aliased signal of DDS output is accepted in the design of RF Power Generator. A device of AD9850 is used to generate RF signal in the system, and the amplitude modulation of system is achieved by a voltage variable attenuator. The amplifier based on tetrode is selected to get the output power of 10kW.Amplifier operates in a grounded cathode configuration. The PID-control strategy has been accepted in control system ,and the relay method has been used to do the measurement .Controller has a built-in Auto-tuning function which allows the PID parameters to be determined automatically using the Ziegler-Nichols method.更多还原