Design of PLC intelligent slave station based on PROFIBUS DP protocol

Abstract ： In industrial control system ,PLC It is a digital operation electronic system specially designed for application in industrial environment , It is to realize industrial automation 、 The basis of IOT control , It has a very broad application prospect .PLC There are many kinds , Various functional modules are also extremely rich , The modules can be easily networked and programmed . stay PLC Application , Lord - The slave mode accounts for a large proportion , The master-slave relationship is based on Profibus-DP、Net Wait for communication . This paper introduces a method based on Profibus-DP Intelligent slave of , Realize set communication 、 A slave station integrating signal conditioning and high-precision speed measurement , It can make up for industrial control occasions PLC The function of the slave station does not match .

 1. What is an intelligent slave station

The master-slave station structure in the control system is a frequently used communication mode . The peripheral equipment that collects and sends input and output information is called （ be called ） From station , It is usually a driver with binary value or analog input and output 、 Valves, etc , It can also be an intelligent slave station , That is, the slave station supports programmability （ belt CPU And memory , Can be programmed to achieve certain functions ）, It is this programmable function that allows the slave station to add some other expandable functions , Thus, it is different from the slave station with single function , So called “ Intelligent slave station ”. Adopt intelligent slave station , Can constitute a digital 、 Intelligent bidirectional 、 Multipoint communication system fieldbus network , Achieve optimal control . at present PLC Most of the slave stations have a single function , Intelligent slave stations often need to be customized .

2. Functions that can be realized by intelligent speed measuring slave station

An industrial control system , It is necessary to monitor the operation status of a key component in the equipment in real time , Realize closed-loop control , Improve equipment processing quality . The control system is based on Profibus-DP Structure of master and slave stations , The main station adopts Siemens PLC. Found in the design process , Lack of high-precision speed measurement slave station .

This problem may arise on many occasions . Many enterprises in our country attach great importance to R & D , Especially in the machinery manufacturing industry , The equipment manufactured has strong performance , It is similar to the world-class products , Even better . The improvement of mechanical equipment performance index and reliability depends on the substantial improvement of measurement and control system . In research and development , There are many demands that can not be met by the existing products in the current market , Because the functions required for R & D , Often very specific , But there are many requirements . The products on the market can only meet one , Not all .

therefore , To achieve the function , Often only “ Put together ”. Build with multiple products to realize .

What are the disadvantages of doing this ？

Low integration , It's bigger . Open the cabinet , It may be necessary for a simple function , Add multiple modules , In addition to occupying the location of multiple modules , Some of the functions of these modules are still idle and wasteful .

  For these customized needs , The advantages of intelligent slave stations have emerged .

Functions to be implemented , No multiple modules at all

For the speed measurement occasions mentioned in this article , The intelligent slave station itself has high speed CPU And special interfaces for sensors , It is a precise speed measuring instrument , The speed measurement slave station can also realize Profibus-DP signal communication , To support STEP Software graphical programming .

The intelligent slave station has done all the speed measurement work , The master station only needs to read data .

The following figure shows the programming interface of botu software for intelligent slave station , It operates like an ordinary slave station , But the functions provided are much more powerful than ordinary slave stations .

 3. Scalability of intelligent slave station

Because the intelligent slave station has built-in high-speed CPU, We can put some measurement and control operations on the slave station , Therefore, the R & D intensity of electrical engineers can be greatly reduced , At the same time, it provides slave products that are highly matched with the demand .

The intelligent slave provides highly reliable Prifibus-DP signal communication , Signal conditioning circuit with sensor , So it can expand many functions .

The function mentioned in this paper is to measure the speed of reciprocating motion with high precision . We can also easily expand it into rotational speed 、 temperature 、 pressure 、 Vibration and other tests or controls .

In a word , Measurement and control is a technical activity . Professional people can be more professional .