Programmable controller (PLC) is a new type of general control equipment, which integrates traditional relay control technology, computer control technology and communication technology, and is specially designed for industrial control. It has a series of advantages such as strong function, universal flexibility, strong reliability, good environmental adaptability, simple organization, convenient use, small size, light weight and low power consumption. In recent years, with the maturity of programmable controllers, more and more devices are controlled by PLC instead of traditional relays, and good economic benefits have been achieved.

Air compressor is one of the four important fixed equipment in mine production. It generates compressed air to drive rock drills, pneumatic rock loaders and other pneumatic tools. Whether it can run safely directly affects the output and benefit of coal mine production. The main factors affecting its safe production are the over-temperature, over-pressure, water cut-off and oil cut-off of air compressor.

With the development of coal mine modernization, the requirement of mine equipment is getting higher and higher, and the construction of intrinsically safe mine has become the core of coal mine production and construction. The reliability, operability, monitorability and maintainability are the most basic requirements for the continuous updating and improvement of mining equipment. The control circuit made of relay is unreliable, easy to maintain and monitor, and can not meet the current requirements. Now there is an urgent need for a controller with high reliability, easy maintenance, easy operation, easy monitoring and low price to replace the circuit composed of relays. With the rapid development of electronic technology, software technology and control technology, programmable controller (PLC) has developed rapidly with high performance and reasonable price. Compared with the control circuit connected by relay, PLC has great advantages. Many mining equipments have chosen PLC instead of more important equipment control. Traditional protection mainly adopts separated instruments, which have poor reliability, low concentration and high cost, and cannot effectively meet the requirements of economy and safety of mine equipment investment.

In this paper, the programmable controller (PLC) is used as the core controller, and the signal parameters needed for control are provided for the PLC through the detection instrument, so as to realize the automatic detection and control of the air compressor. The main parameters monitored are the temperature of high and low pressure cylinders of air compressor, lubricating oil temperature, motor temperature, air bag temperature and outlet water temperature; High and low pressure cylinder pressure, air bag pressure and lubricating oil pressure; High/low pressure, middle/rear cooling water cut-off detection and other parameters.

Second, the control function and control principle

1. Protection control function

(1), motor current and voltage detection.

2. Detection of primary and secondary oil cylinders, oil pressure and airbag pressure.

(3) Detection of primary and secondary exhaust temperature, oil temperature and motor temperature.

(4), motor start delay.

5], motor running without water.

2. Protection control principle

Before starting the main engine, both the water source solenoid valve and the ventilation solenoid valve are open. When the cooling water pressure and flow rate reach the specified value, the air compressor can be started with no load, and after a period of delay, the exhaust solenoid valve will be automatically closed to make the air compressor run normally. Allow low oil pressure to start when starting, and monitor the oil pressure after setting a certain time. When stopping, press the reset button, the solenoid valve deflates, and cut off the main power supply after a delay of 30 seconds. Stop the air compressor and close the water source solenoid valve and the ventilation solenoid valve at the same time. In the insurance state, if one of the above monitoring parameters fails within the set range, an alarm signal will be generated, and at the same time, the exhaust solenoid valve will be opened, and the compressor will run at reduced load. If the fault is delayed for 30 seconds, the automatic machine will not stop.

(1). Control map

1- 1 compressor control distribution diagram

2. Control communication principle

PROFIBUS can realize data transmission between digital and analog input/output, intelligent signal device and process adjustment device, and programmable controller PLC and PC, and disperse I/O channels near actual field equipment. On the one hand, PROFIBUS covers the communication requirements in the sensor/actuator field, on the other hand, it has all the communication network communication functions in the unit-level field. It supports high-speed circulating data communication and meets the requirements of real-time monitoring.

1-2 system control communication diagram

Thirdly, the signal acquisition S7-200 provides a pulse capture function for each local digital input. The pulse capture function allows the PLC to capture pulses with short duration. At the beginning of the scanning cycle, these pulses are not always read by the CPU. When using the pulse capture function to set the input, the state change of the input will be latched and kept until the next scanning cycle. This ensures that pulses with short duration are captured and kept at the S7-200 reading input point.

This design needs to collect the following parameters:

(1), the pressure signal is 1 the pressure of primary cylinder, secondary cylinder, gas storage tank and lubricating oil is 4 o'clock respectively;

(2) The temperature signal is 1 cylinder exhaust temperature, cylinder 2 intake temperature, airbag temperature, oil temperature, motor temperature and cooling water outlet temperature ***6 points;

(3) The power signal is the main motor current 1 point, the power voltage 1 point and ***2 points.

(4) Flow detection has two points: high/low pressure end, two points for intermediate/post-cooling, and four points for * * *.

The total acquisition parameters are 4+6+2+4= 16.

After the above-mentioned parameters are collected, it is first judged whether the relevant parameters are abnormal, and then a dynamic data table is formed for real-time tour display and stored for random query in the future.

Fourth, the system software design

This system is mainly based on protection. According to the requirements of Coal Mine Safety Regulations and the protection principle of air compressor, the design flow of control software is as follows.

Verb (abbreviation of verb) conclusion

The system mainly uses S7-200 as the core controller and PROFIBUS as the communication bridge, and provides detection signals for control through detection elements, thus achieving the purpose of protection and control. In the process of writing this article, I have received strong support from many leaders of Zhangji Mine Electromechanical Department, and I would like to express my sincere thanks! At the same time, I would like to thank the Automation Drive Group of Siemens (China) Co., Ltd. for providing a lot of information.