Research, Measurement And Control System Based On The The Ican Experimental Platform

The fieldbus as a new technology in the measurements and control fieldmainly is used for data communication and control of the production site. Withthe development of information technology, the control network represented byfieldbus will become an important part in industrial messurement and controlsystem. CAN bus as one of the most promising fieldbus, uses a number of new,unique technology, with high reliability, real-time and flexibility. Meanwhile, ithas many advantages, such as low development costs, implement easyly.Therefore, CAN bus is gradually spreading from the initial automotive sector toother areas, in particular, more and more loved by industrial measurement andcontrol sector.At first, the paper studies the structure and characteristics of the field buscontrol system. Then studies the characteristics and technical specifications ofCAN bus. Through the studies of theoretical knowledge, a measure and controlsystem combined with laboratory iCAN teaching development platform isdesigned, which realizes the communication between the underlying and thehost computer.For the underlying communicaton system, according to the study ofmodular principle of the iCAN experimental platform, the hardware circuit ofanalog input and output nodes and digital input and output nodes is redesignedwith the low-power STC89C52chip,24-bit high-precision AD7710chip and12-bit MAX232chip. On the basis of reliability, it improves the conversionaccuracy and simplifys the circuit design. In addition, the hardware circuit ofCAN-RS232nodes with MAX232chip is designed. At last, the software isdebugged which not only realizes the transmission and receiving of live analogand digitial signals, but also realizes the exchange between CAN data andRS232data, and it ensures the normal communitation between the underlyingand the host computer.For the host computer monitoring and control system, firstly, a mainoperation interface with the functions of data transmition, data receiving, data saving and historical data quering and so on is developed using VB andSQL2000. Secondly, combining with laboratory iCAN teaching developmentplatform, the software is debugged which realizes the functions of the liveanalog and digitial signals' display, control, storage and query.Finally, the iCAN protocol is analyzed and improved. After analyzing thearbitration based on fixed priority of iCAN protocol, the arbitration based ondynamic priority is applied in the iCAN protocol. Then through analyzing andcomparing the theoretical, the result shows the delay of improved protocol isshorter than the previous protocol under the same load.