Design of city water supply network detection and valve intelligent control system

0 Introduction
The urban water supply network is a complex and large-scale pipeline network system, which is the lifeblood of the city. In recent years, with the advancement of technology and the investment of transformation funds, most water supply companies have established water supply data monitoring and control systems (SCADA), realizing the functions of water source and raw water transportation system monitoring, water purification structures and process equipment monitoring, and water supply network pressure measurement, but the valve opening and closing and adjustment must still rely on the operator to go to the site to complete manually. Pipeline network valves are important facilities in the water supply system. They play the role of pipeline network regulation such as transportation, shutoff, adjustment of water supply flow, pressure and change of flow direction. They are important guarantee measures for the smooth transmission and distribution of the water supply system and the emergency repair, maintenance and transformation of the pipeline network. Therefore, as an important equipment in the pipeline network, how to better manage the valve is becoming more and more important for the construction and operation management of the pipeline network.

1 Water supply network monitoring system
Usually, the water supply network monitoring system consists of four parts (as shown in Figure 1): network parameter measurement, valve intelligent control system, network monitoring center, and valve electric actuator. The principle is to remotely collect data on the operation of the network system through sensors, and transmit the signal to the enterprise network control center and valve intelligent control system through wired or wireless means. The valve intelligent control system controls the electric actuator to adjust the valve according to the timely feedback monitoring data transmitted. Among them, the valve intelligent control system is the core part of the control.

2 Pipeline network parameter measurement
The water supply network monitoring point generally requires the measurement of four data channels: pressure, flow, flow velocity, and flow direction. Therefore, it is necessary to configure pressure, flow, flow velocity, and flow direction transmitters on site, and then send parameter signals to the valve intelligent control terminal or the pipeline network monitoring center by wired or wireless means. The main pipeline should be measured in sections, as shown in Figure 2.

The parameter monitoring module of valve V1 is located in front of valve V2, and the parameter monitoring module of valve V2 is located in front of valve V3. And so on, so that the parameter monitoring module can accurately feed back the parameters of the main pipeline L1, L2, ... to the valve intelligent control system and the pipe network monitoring center.

3 Valve intelligent control system
The valve intelligent control system can independently process the transmitted pipe network parameter signals, send execution signals to the valve electric actuator according to the processed results, and upload the parameters to the pipe network monitoring center. The valve intelligent control system can be implemented by computer systems, single-chip microcomputer systems, PLC systems, etc. This paper takes the single-chip microcomputer as the control core and gives a design plan for a certain measurement point.
3.1 Hardware design
The valve intelligent control system mainly includes the main controller CPU, A/D, D/A, 8255A, 6264SRAM, key input circuit, LED display circuit, alarm circuit, clock and reset circuit. Its structure is shown in Figure 3.

The system is based on AT89C52 single-chip microcomputer. With the corresponding sensors, the pressure, flow, flow velocity and flow direction data detected are processed by the transmitter and converted into 0-5 V standard signals, which are sent to ADC0809 chip for A/D conversion. The single-chip microcomputer samples once every 500 ms, and performs median filtering after sampling 5 times. After data conversion, the actual value (engineering quantity) of each parameter is displayed on the LED, and the information is sent to the pipe network monitoring center. At the same time, the detected value is compared with the given value, and the control signal is output according to the comparison result. After conversion by D/A converter, the control voltage is output to drive the valve electric actuator to realize automatic adjustment of the valve.
In order to increase the flexibility of the system, a 4×4 matrix keyboard is designed. The key codes 0-9 are the input digital quantities. Press the "A" key to display the pressure; press the "B" key to display the flow; press the "C" key to display the flow velocity; press the "D" key to display the flow direction; press the "E" key to cancel the alarm; press the "F" key to activate the alarm.
3.2 Software Design
The system application consists of two parts: the main program and the interrupt service program.
3.2.1 Main Program
The main program flowchart is shown in Figure 4. It includes three main links: First, various initializations are implemented, including setting the stack pointer, initializing the 8255A chip, initializing the timer/counter 0, opening interrupts, starting the timer/counter, etc. Second, the display is implemented (displaying various parameters according to the human-computer dialogue function). Third, the keyboard is continuously scanned to determine whether a key is pressed. If no key is pressed, the display is returned; if a key is pressed, the corresponding human-computer dialogue function is implemented according to the key pressed.

3.2.2 Interrupt service program
The interrupt service program mainly includes sampling, data processing, alarm, control algorithm and control value output, all of which are implemented by calling subroutines. The program flowchart is shown in Figure 5.

4 Pipeline network monitoring center
The information processing system of the pipeline network monitoring center can be realized by a computer system. Through different network interfaces such as RS 422/RS 485/Lonworks, the valve terminal is connected to the network. Based on the transmitted pipeline network parameters, the pipeline network monitoring center can record, analyze and process the data through the background monitoring software, display the pipeline network operation status and various required data in real time on the display screen of the control center, and provide solutions. If the data is abnormal, an alarm can be issued to alert the on-duty personnel. The control of the valve electric actuator by the pipeline network monitoring center is higher than that of the valve intelligent control system.

5 Electric actuator for valves
The valves in the electric actuator for valves use solenoid valves. Solenoid valves are industrial equipment controlled by electromagnetics, which are used in industrial control systems to adjust the direction, flow, speed and other parameters of the medium. There is a closed cavity in the solenoid valve, with through holes opened at different positions. Each hole leads to different oil pipes. The valve is in the middle of the cavity, and there are two electromagnets on both sides. The valve body will be attracted to the side where the magnet coil is energized. By controlling the movement of the valve body to block or leak different oil discharge holes, the oil pressure is used to push the piston of the oil steel, which in turn drives the piston rod, and the piston rod drives the mechanical device to move. In this way, the mechanical movement is controlled by controlling the current of the electromagnet. In addition, the valve needs to be equipped with a manual adjustment handle to manually adjust the valve when the system fails.

6 Conclusion
The main purpose of the urban water supply network detection and valve intelligent control system is to solve the data collection, monitoring and automatic control of valve switches of the water supply company at each monitoring point in the water supply pipeline. It is convenient to understand and control the pipeline and valve in a timely and rapid manner, reduce the failure rate and maintenance time, reduce the number of water outages, and improve the service level of the water supply company, thus realizing the informatization and modernization of urban water supply.