Distributed Measuring And Controling System Based On Embedded Controller

With the rapid development of Fieldbus, industrial Ethernet and embedded controller, distributed measuring and controling system has new ways to solve the problems of distributed control, integration of control systems and enterprise network and other issues. Distributed measuring and controling modules become more and more intelligent and miniaturized in order to meet the requirements of new technology. Embedded controller is used in field measuring and controling modules. It can improve system reliability, and make the whole distributed measuring and controling system become more competitive.CAN BUS is one of the most widely used Fieldbus. It is applied in the fields of process control, textile machinery, robots, sensors and so on. CAN BUS has many advanced characteristics, such as low cost, high reliability, real-time, strong anti-interference ability, which make it prospective. Embedded controller is widely used in consumer electronics, communications, automotives, aerospace, industrial control, instruments, office automation and other fields. Now it has become a common development direction of industrial control, communications and consumer products.The thesis mainly introduces the construction of distributed measuring and controling system. Field measuring and controling modules are the cores that conduct I/O data sampling, information exchanging, control operations, logic control, which realize real-time control function of the whole industrial control. Measuring and controling modules consist of standard signal I/O modules, digital signal I/O modules, thermocouple signal input modules, RTD (Resistance Temperature Detector) signal input modules, impulse signal input modules. These modules are connected with various kinds of the field signals, such as current, voltage, flow, pressure, temperature and so on, and they realize functions of field measuring and controling. Measuring and controling modules sample data from industrial field, then pack it and send it to main module by CAN BUS. Meanwhile these modules receive commands from main module to complete corresponding operations, such as channel configuration, channel rectification, etc. Finally, these modules return confirmation information to communication controller. As a result, distributed measuring and controlling system achieves centralized control.The emphases of the thesis are hardware design and software design of measuring and controling modules. Freescale's 16-bit embedded controller MC9S12D64 with CAN communications controller is used as the microprocessor of these modules. It has plenty of I/O channels and communication interfaces for special use of industrial control.Hardware circuit of measuring and controling modules mainly consists of reset circuit, power circuit, communication circuit, signal conditioning circuit, analog switching circuit, optoelectronic isolation circuit, signal sampling circuit. Software design of modules is mainly about flow chart of main program, communication program of CAN BUS, analog-digital conversion program and algorithms of controlling and measuring.Distributed measuring and controlling system is based on Fieldbus and embedded controller. It can simplify the architecture of industrial control system, enhance the functions of process control, improve system reliability, and reduce production cost.