Use of Modbus RTU, Profibus DP and HTTP Protocol for AC Motor Control

Abstract

This work is part of a project to develop a test stand using a network simulator of ship traffic control and physical models of ship propulsion system components. The lab station is designed to allow control of the engine by three methods. Web-based control, slave-level control as well as master-level control. The components of the lab bench and the various blocks used in the TIA Portal program are described. The article deals with the application of Internet 4.0 to AC motor control. In order to be able to synthesize a laboratory workstation to enable the control capabilities of Internet 4.0, an idea diagram is described. The Profibus DP protocol was used to connect the I/O module to the PLC, which made it possible to control the operation of the motor directly from the module through the PLC connected to the inverter by the Modbus RTU protocol. In order to implement an experimental Internet 4.0 workstation, it was also necessary to add remote control using the HTTP protocol and design a website. All the above-mentioned protocols were briefly discussed and implemented in the TIA Portal environment. Also described is the idea and operation of a program written in the LAD language, which is designed to control an AC motor from three different devices: PLC, I/O module and PC via a web page. In the construction of the program, the MB_COMM_LOAD and MB_MASTER blocks dealing with communication and control with the inverter were used, as well as the WWW block used to communicate the controller with the website. The operation of the software was verified from the level of two devices, the I/O module and the website, including its optimization for the correct operation of the entire system as shown in the graph of the change in the value of the AC motor speed control word. In the final part of the work, an analysis of the suitability and validity of using such a system in industry was carried out.