【作者】 郭晓倩；

【导师】 吴斌；

【作者基本信息】 北京交通大学 ， 载运工具运用工程， 2010， 硕士

【摘要】 网络控制系统(NCS),又称网络化的控制系统,它通过物理通信网络来实现控制器—执行器和传感器—控制器之间的数据交换,使某一区域内不同地点的设备和用户实现资源共享和协调操作,提高了系统的模块性、可靠性,减少安装和维护费用,在工业上得到了广泛应用。与此同时,网络的引入也带来了时延、数据丢包、资源优化调度等一系列问题,使得对网络控制系统的研究分析日益迫切。本文主要针对网络控制系统中的网络时延问题,在不考虑其他网络影响因素的条件下分析了网络时延对NCS性能的影响,说明随着时延的增大NCS的动态性能和稳定性都降低,因此在NCS的设计过程中不可忽略时延给系统带来的影响。继而讨论了NCS采用PID控制时PID参数稳定域的确定,即先确定Kp的稳定范围,然后寻找给定Kp下K(?)-Kd平面的稳定域,最后通过遍历Kp得到整个PID参数稳定域。该稳定域为NCS智能控制器的设计提供了参数调整范围。PID控制器在各种工业过程控制中显示出很多优点,但其无自适应能力,当网络时延和系统参数发生变化时不能调整控制参数,使系统性能下降。本文在PID控制的基础上引入模糊控制,采用模糊控制器根据系统误差对PID的控制参数进行在线调节,实现了对时延的良好补偿,提高了系统对参数变化的适应性,增强了抗干扰能力。最后,运用TrueTime工具箱建立了NCS仿真平台,模拟实际网络控制系统的运行,对所设计的控制策略进行验证,结果表明设计的模糊PID控制器能够对时延进行有效补偿,使系统输出快速跟踪输入。同时还分析了网络速率和丢包率不同对NCS响应性能的影响,说明了联合网络和控制特性对NCS进行综合设计的重要性。更多还原

【Abstract】 Networked Control System (NCS) which transmits data from controller to actuator and sensor to controller by network has been widely used in industry since it implements resource sharing and co-operation for equipments and users in different areas. It increases the modularity and reliability of system while decreasing costs of installation and maintanance. Meanwhile, the introduction of network to control system makes it quite important to analize NCS because it results in several questions, such as network induced time-delay, data loss, scheduling of resources and so on.Without considering other factors of network, the impact of time-delay on NCS performance is analized which indicates that both dynamic performance and stability of system decreases with increasing time-delay, so that time-delay can’t be ignored while designing a NCS. Then, the method to determine the stability region of PID controllers in NCS with PID control has been studied. Based on this method, the stability region of Kp is firstly found, then the stability region in K(？)-Kλplane can be determined under a fixed Kp, all stability region of (Kp, Ki, Kd) will be obtained by sweeping over Kp.The obtained stability region provides parameter regulating range for intelligent controller design of NCS.The performance of NCS using PID control decreases for PID controller doesn’t have self-adaptive ability to adjust control parameters with variable time-delay and system parameters. A Fuzzy-PID controller has been designed which can adjust PID parameters according to system error so that the impact of time-delay on NCS gets mostly compensated, improving system ability to adapt parameter variation and resist disturbance.Finally, a NCS simulation platform is established by TrueTime toolbox which provides a simulated network environment to verify the validity of signed controllor. The simulation results evidence that Fuzzy-PID controller makes a good compensation to the impact of time-delay on NCS and output can quickly track input signal of system. In addition, the impact of data loss probability and network rate on NCS is also analized to demonstrate the importance of design NCS combining network and control.更多还原