【作者】 徐忠锦；

【导师】 张思祥；

【作者基本信息】 河北工业大学 ， 测试计量技术及仪器， 2006， 硕士

【摘要】 现场总线是目前国际上过程控制领域一个热点,通过现场总线数字通信技术可以延伸到现场级仪表,给控制体系带来一场革命。考虑到我国目前传统的基于4～20mA的模拟设备仍然广泛的应用于工业控制,为满足从模拟到全数字的过渡HART协议应运而生。该协议基于Bell202通信标准,在4～20mA的模拟信号上叠加不同的频率信号来传送数字信号。其特点是在现有的模拟信号传输线上实现数字信号通信,属于模拟系统向数字系统转变过程中的过渡产品,由于这项技术属于承前启后的研究,所以,在当前的过渡时期具有较强的市场竞争能力,得到了较快发展。首先,论文对HART协议做了较全面的分析。HART协议采用ISO/OSI简化模型,ISO/OSI分为七个功能层,HART协议只用了第一、二、七层即物理层、数据链路层和应用层。其中物理层规定了信号的传输方式以及信号电平等内容,数据链路层规定了设备类型以及数据传输帧格式,应用层规定了HART协议的各种命令及响应码。其次,论文以HART协议为通信标准,提出了智能变送器系统总体方案设计的方法。并为传统变送器的HART改造作了可行性分析。通过对HART通信协议的掌握,研究和设计了微处理器和传感器系统相结合的智能变送器系统。论文在介绍了HART协议的基础上着重研究了智能变送器的硬件和软件设计,硬件上较为详尽的介绍了智能变送器的各个设计模块——微处理器模块、传感器模块、通信模块和A/D、D/A模块的设计;软件上对系统的软件结构进行了分析和设计,重点介绍了数据链路层和应用层的实现,其中包括测控程序、通信程序的实现;此外,提出了利用数据融合基础解决实际中多参数测试交叉灵敏度问题的方法。最后,通过使用智能压力变送器进行现场通信试验和调试,并对在开发研制过程中硬件和软件调试中所遇到的问题和经验进行了总结。更多还原

【Abstract】 Nowadays,fieldbus technique became very important in the world of process control,through which digital communication is used to fields instruments,this leads to a revolution to control systems.However,4～20mA analog signal instruments alse have a large application in industry,the HART communication protocol—a transitional protocol during transition from analog system to digital system—emerges as the times require.Based on Bell202 communication standards,HART protocol transfer data with different frequency signals and plus with analog signals of 4～20mA.It is characteristic that realizes digital communication in the transmission of analog signals,it has strong competition in this interim period and grows quickly because of this technology belongs to research of link between the preceding and the following.Firstly, in this paper, HART protocol is illustrated, it adopt a predigested mode of OSI/ISO in which have seven functional layers, only three layers have been used in HART protocol.Physical Layer specifies the transmittal manner of signal and voltage of signal, Data Link Layer specifies the device type and format of data transmit, Command Layer specifies all kinds of HART command and reoponse codes.Secondly, being based upon HART protocol,the method of smart transducer design is introduced, meanwhile make a feasibility analyse for HART retrofit of traditional transducer.through master the knowledge of HART protocol,this paper researches the system of smart transducer that it combines MCU with sensor.It importantly researches the hardware and software of smart transducer,the detailed hardware are introduced,including the single-chip microcomputer module,the sensor module,the communication module and A/D、D/A module.Then,the structures of software are analyzed and designed,the completion of Data Link Layer and Command Layer is emphasized,which including the realization of measuring and controlling program、communication program.Furthermore, data fusion is proposed to mitigate the crosstalks between different measured parameters.Finally, make the experiments and debugging through pressure smart transducer, at the same time, the problem and experiences I met in developing hardware and software of smart transducer system are summarized in the last of this paper.更多还原