【作者】 周鑫；

【导师】 王春麟；

【作者基本信息】 武汉理工大学 ， 机械电子工程， 2011， 硕士

【摘要】 随着电子技术的不断发展,自动化系统产生了深刻的变革。从微观层面看,自动化系统中的仪器仪表向智能化方向发展；从宏观层面看,自动化系统经历着由分布式控制系统向现场总线控制系统的变化。智能仪表不仅提高了仪表本身的性能,还能与现场总线技术结合改变整个控制系统,因此基于现场总线的智能仪表研究有着重要意义。由于传统的基于4到20mA模拟信号的设备仍然广泛应用,能够兼容模拟和数字通信方式的总线技术有着巨大需求,HART协议就是在此背景下产生的。HART总线技术将数字信号叠加到现有模拟线路上,使得模拟仪表的数字化改造有了可能。我国的自动化系统需要升级模拟仪表的低成本解决方案,因此设计基于HART协议的智能变送器具有迫切的现实意义。本文根据HART协议规范,设计以C8051F410微处理器为核心的智能变送器,利用4到20mA模拟信号传送主变量,FSK信号进行数字通信。C8051F410处理器的低功耗特点在硬件层面上解决了变送器低功耗的问题。数字通信实现了对变送器发送命令进行控制的功能,在此基础上实现了与主设备同步、增益校正、增益计算、测量标定等功能。测量标定功能可以将若干个标定点存入Flash中保存,根据其计算电流输出值可以实现分段化的非线性校正。本文对智能变送器的电源单元、信号单元、通信单元和处理单元的硬件设计做了介绍,着重分析了HART调制解调器与4到20mA电流环的耦合方式；对系统软件的组成也做了介绍,特别是HART命令层功能的实现程序和输出电流的分段化非线性校正程序。此外还一并介绍了调试过程中需要使用到的HART/RS232转换器的硬件和软件设计。更多还原

【Abstract】 With the speed development of electronic technique, automation system is changing profoundly. From the micro perspective, the instrumentation of automation system go to intelligent direction; from the macro perspective, the automation system itself is changing from distributed control system to fieldbus control system. Intelligent instrument continuously improve the performance of itself, while changing the whole control system combined with the fieldbus technology. So the research of intelligent instrument based on fieldbus has important significance.The traditional based on 4 to 20mA analog signal equipment is still widely used, so the fieldbus technology compatible with analog and digital communication mode has huge demand, HART protocol was generated in this background. HART bus technology adds digital signal to the existing analog circuit, it is possible to make analog instrument digitally and intelligently. The automation system in China need the low cost solutions of upgrading analog instrument, so the research of intelligent transmitter based on HART protocol has the urgent practical significance.This paper design the intelligent transmitter in the core of C8051F410 according to the HART protocol standard, using 4-20mA analog signal transmit main variable and achieving digital communication through FSK signal. The low power consumption characteristic in C8051F410 processor solves the problem of transmitter low power consumption in hardware level. Digital communication sends commands to control the transmitter. On this basis, it is possible to achieve synchronization, gain adjustment, gain calculation, measure calibration functions and so on. Measure calibration function could store several standard fixed-point in Flash memory. Through these standard fixed-points, we could calculate the output current to realize the subsection nonlinear correction. This paper also introduces the hardware design of transmitter, consist of power unit, signal unit, communication unit and processing unit, especially the coupling way of HART modem and 4-20mA current loop. System software architecture is also discussed, especially the program realization of HART command layer and the nonlinear correction of output current. In addition, the hardware and software design of the HART/RS232 converter needed for debugging is also recommended.更多还原