Siemens air compressor intelligent control system
Air compressor system structure ADT200-190 and IBMPC compatible PC/104CPU module system constitute a high performance data acquisition system, which is characterized by: 8/16 single-ended analog input channels; resolution is 12 bits, conversion time is 20s Or 10s A/D converter; range is applicable to ±5V, ±10V or 0+10V analog input range. Can meet the requirements of multi-parameter acquisition.
(1) Temperature acquisition: There are 2 kinds of range for the temperature signal collected by the system, and the exhaust temperature of the 2nd stage cylinder is above 200°C. JM202I/IL/II with measuring range of -100°C300°C is selected; other temperature measurement range is 0 ° C 70 ° C, the United States DALLAS company's single-line digital temperature sensor DS1820, measuring range of -55 ° C 75 ° C, the signal is a single line and connected together.
(2) Pressure collection: The pressure signals are Class I cylinder pressure (≤0.23MPa), Class II cylinder pressure (≤0.80MPa) and gas tank pressure (≤0.80MPa) of two sets of air compressors. Class I cylinders use two 24PC type pressure sensors with a range of 0100 psi; Class II cylinders and gas storage tanks use four 24PC type pressure sensors with a range of 0250 psi, a working power supply of DC012V, and a full-scale output of approximately 220 mV.
(3) Current and voltage acquisition: Two current sensors are used to measure the current of two main motors, the range is 0100A, and one voltage sensor measures the 3-phase voltage of the total power supply. Level switch: Detects the presence or absence of cooling water and inputs the signal for the switch.
PLC Control System Design The SIMATICS7-200 series from Siemens is a small programmable controller that can be used for simple field control instead of relays. It can also be used in complex automation control systems with extremely powerful communication functions. The S7-200 is highly reliable and can be programmed with ladder diagrams, statement tables and function blocks. Its instructions are powerful, easy to master, and easy to operate. Built-in high-speed counter, high-speed output, PID controller, RS-485 communication / programming interface, PPI communication protocol, MPI communication protocol and free-form communication protocol, I / O terminal block can be easily removed. It can be expanded up to 248 digital point I/O or 35 analog I/O, with up to 26kb of program and data storage space.
The overall implementation scheme of the PLC control system is as follows: From the process and control requirements of the air compressor, it is proposed to use Siemens S7-200 PLC to automatically control the air compressor. From the above I/O port allocation, the air compressor control system requires at least 8 input ports and 16 output ports. Considering the scalability of the CPU, the S7-200 CPU 226 with port 24 in/out is selected here.
The system adopts the master-slave control mode of the upper and lower position machine. The lower position machine adopts Siemens S7-200 series CPU226PLC. CPU226 has two RS485 serial ports, and both serial ports can be used as PPI communication mode or free port communication mode. The PC/104 industrial computer provides an RS485 serial port. The RS485 serial port has only TD and RD2 root data lines, and there is no hardware handshake signal line. Therefore, only the software handshake communication mode can be used. S7-200PLC serial port initialization can be achieved by setting the special flag bit SMB30. The transmitted data is sent directly by sending the command XMT. The S7-200PLC does not receive data instructions. It only provides one receive interrupt. Each time a data is received, an interrupt is generated, and the received data is taken from SMB2.
The software design PC/104 industrial computer software is written in TURBOC language. It mainly consists of sampling and filtering module, communication module, acquisition display module and alarm module. The main block sampling filter module reads the converted data of the A/D converter into the memory of the CPU, and then performs appropriate filtering processing. The working principle of the average filtering method is: in the K sampling values, a maximum value and a minimum value are removed, and then the remaining K-2 sampling values ​​are arithmetically averaged, and the result is used as a filtering value, and K is taken in the program. Generally taken as 10. acquisition display and alarm module, each time a unit status parameter is detected, then scale conversion and display, and finally determine whether the system status parameters are normal, if normal, then the next status parameter is detected, otherwise alarm, Stop and display the corresponding point of failure.
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