Research on water level control teaching system ba

Research on water level control teaching system based on Configuration Control Technology (2)

2 basic functions of water level control system

2.1 basic functions of this control system

(1) this system detects the water level and temperature of two water tanks, and controls the water level of the water tank at the given value. The given value of water level can be manually input on the main drawing. The system has two control functions: manual and automatic

(2) the system has production process display, temperature and upper and lower liquid level indication. The main picture can display three analog parameters in real time, namely, the temperature of the lower tank, the liquid level of the upper tank and the liquid level of the lower tank

(3) the digital quantities that can be displayed in real time in this system mainly include: lower tank inlet valve, lower tank drain valve, circulating pump valve, upper filling drain valve, circulating pump, group 1 heater, group 2 heater, group 3 heater, lower liquid level lower limit switch, lower liquid level upper limit switch and upper liquid level upper limit switch, etc

(4) the system can indicate the alarm status of all parameters in real time, and can be silenced manually

(5) the system can realize manual/automatic switching. During the commissioning of the water level control system, turn to the manual state for early commissioning. When the system has the conditions for automatic control, turn to the automatic control state to realize automatic control

2.2 main screen of water level control system operation

main screen of water level control system operation can display the water level and temperature of the water tank and the working state of each valve in real time. Through the operation of the picture, the monitoring and remote control of the working parameters of the water level control system can be realized. Figure 2 shows the running state of the water level control system

(1) water tank temperature. The temperature value of the lower water tank is indicated in real time. When the temperature value is higher than the alarm set value, the "alarm window" will automatically pop up; When the temperature value is higher than the set value, the lower tank inlet valve and the lower tank drain valve are opened to discharge the heat, then the sample will bear the tensile force in multiple directions, water is poured into cold water to cool down, and one or two groups of heaters are turned off at the same time; When the temperature value is lower than a certain value, turn on the heater and continue heating. Red indicates that the heater is on and blue indicates that the heater is off

(2) pressure in the tank. It indicates the pressure value in the water tank in real time. When the pressure value is higher than the alarm set value, the "alarm window" will automatically pop up

(3) liquid level in the tank. It indicates the liquid level value in the water tank in real time. When the liquid level value is lower than the alarm set value, it will automatically jump out of the "alarm window"; When the liquid level value is in different stages, the inlet valve and drain valve are in different working states. Red represents closed and green represents open. The liquid level of the water tank can be changed through the switch of the valve

(4) operation status indication. During automatic operation, the switch of the valve is controlled by the water level and the temperature of the water tank; When it is operated manually, the valve can be opened and closed through the switch on the drawing

(5) through the historical curve and real-time curve buttons on the main drawing, you can directly enter the historical curve drawing and real-time curve drawing for data analysis

2.3 definition of variables

define the variables used by the system (variables in Table 1) through the data dictionary in the database, as shown in Figure 3, so as to realize the number eight exchange between the upper computer and PLC and PCL818L module

2.4 trend curve

data analysis they are forming a fire companion relationship analysis is an essential function of a perfect control software. Curve is one of the ways to realize data analysis, which is intuitive and easy to compare. The system designs real-time trend curve and historical curve to analyze the data collection on site

the shape of the trend curve is similar to the coordinate paper. The X axis represents time, and the Y axis needs patience and persistence to represent variable values. It is mainly used to observe the change trend of variables. In the trend curve, engineers can specify the time interval, the numerical range of data, the network resolution, the number of time coordinates, the number of numerical coordinates, and the color attribute of the "pen" that draws the curve

when the software is running, the real-time trend curve can be automatically scrolled to quickly reflect the changes of variables with time. The diachronic trend curve does not scroll automatically, and generally works together with the function buttons to complete the viewing of historical data

real time trend is used to display the changes of data in real time. When drawing and running, the trend curve object is automatically updated by the system. The data will enter from the right side of the trend, and the trend will move from right to left. The real-time trend curve of the system is shown in Figure 4

when the historical curve is drawn and running, it does not update automatically, so it is necessary and difficult to adjust the PID parameters to the ideal value. The historical trend curve should be controlled through the command language combined with the button, mainly by changing the field of the variable of the historical trend curve, or using the function related to the historical trend curve. The historical trend curve of this system is shown in Figure 5

3 conclusion

the test and operation results of the system show that the system can record the operation of the water tank in real time, and automatically transmit the data to the system through the network. The system is user-friendly and easy to use, realizing the real-time monitoring and automatic control of the water level control system. Through the study of this system, students can master the development method of automatic control system, preliminarily understand the working state of industrial site, enhance students' practical operation ability, and increase students' ability to analyze and solve problems through the debugging of the system