Research Of Multi-motor Control Based On PLC And Frequency Converter

With the rapid development of the automatic control theory, the networks of the industrial control and the technology of the computer, communication network and so on, On the occasions in the industrial, a single motor control can no longer meet the needs of the actual production process, more and more occasions, the need for simultaneous control of multiple motors is existed, the problem of the multi-motor control has become an important element of the development and research in control industry.In this paper, on the basis of the describing VVVF technology-related knowledge, and functional analysis of the PLC, based on full consideration of the cost, maintenance reliability and many other factors, a multi-motor control system program is proposed,it is constitute of a machine from the PC, Siemens PLC, frequency conversion devices,and asynchronous motor etc. We have the overall design of the control system, and have a key analysis for the principle and characteristics of multi-motor synchronous control, identify synchronous control program, propose a control strategy for multi-motor synchronous based on fuzzy PID compensator, and give the design method of fuzzy PID compensator. Using the USS protocol based on the RS485 interface to carry out the serial communication of the PLC and frequency converter,and discussing the USS agreement how to control the inverter and procedures for the design. Through the USS protocol, S7-200PLC could read and set the inverter parameters in real-time. It also details the serial port communication conditions between Host Computer and the type of Siemens S7-200 PLC as well as the use of high-level language to compile the principle of communication interface between PLC and the PC machine. The use of PLC-free-port communication could achieve the serial data transmission between PC and Host Computer ,the inverter's information will send to the upper machine in real-time through S7-200, achieving the real-time communications between the computer and PLC. By the use of PLC's own logic of operation and data processing capability to enable a design of monitoring system, and ultimately carry out the devices' real-time monitoring of the working conditions which is connected to the PLC. The paper by inverter control to achieve the purpose of motor control,and to achieve the surveillance of the motor running state.The system can monitor the inverter's operating parameters on-line and remote control, and can effectively reduce the system's wiring and the number of cables and improve the system's anti-jamming capability, the automation level of the system and operation reliability.