Modelling and real-time implementation of wireless communication on a typical industrial process

Abstract

Communication amongst field devices, control unit and programming unit in industrial automation networks is essential for bulk production, but largely consists of wired networks that can sometimes be bulky and substantially lack mobility as at times there can arise a need for a field device to be moved either for maintenance purposes or for rearrangement. There was therefore a need for wireless communication and PROFIBUS networks that can provide the minimum movement to field devices or the programing computer. Although wireless communication technology has penetrated the commercial network, it is still inadequately utilised in industrial settings due to electromagnetic induction and other forms of interferences due to industrial machinery. This dissertation introduced wireless communication in a PROFIBUS network where the MPI section was replaced with the wireless link. The PROFIBUS network technology is a hybrid of protocols where the PROFIBUS DP employs RS485 technology with a transmission rate of 45 kbps and above while the PROFIBUS PA employs Manchester Encoded Bus Powered (MBP) technology at a fixed rate of 31.25 kbps. In RS485 technology, data is transmitted as a voltage difference between the two wires while in MBP data is transmitted as transitions in current signal and data and power are transmitted on the same conductors. The PROFIBUS data is also transmitted in the form of telegrams which further puts a strain on any form of intermediate processing and hence the need for high speed processing. In this research task the PROFIBUS PA level transmitter measures the pressure of the fluid in the Blend Chest and sends it to the PLC. The level transmitter was installed and wired to the PROFIBUS DP/PA coupler. The PROFIBUS network, consisting of the PLC, variable speed drives, variable speed pumps, delivery pump and level transmitter, was configured and commissioned for controlling and monitoring from the programing computer. The program for the PLC was written using Siemens Step-7, compiled and downloaded to the PLC. The control and monitoring was done using the variable table. The wireless communication channel was then simulated using Matlab and Simulink. The wireless devices were then integrated into the PROFIBUS network and the MPI cable linking the programing computer and the PLC was then replaced by the wireless channel and the network was controlled and monitored from the programing computer over the wireless channel. On successful completion of this research task the research plant at MUT was controlled and monitored from the programing computer over the wireless channel and the researchers and demonstrators can now access the PLC and the PROFIBUS network using the wireless communication.