[Abstract] The on-site air conditioning substation is connected to the OP3 operation panel to monitor the on-site equipment. The main station is equipped with a TP270 touch screen to monitor, alarm, and display real-time trends of all air conditioning and exhaust fan systems. The main station and the host computer in the central control room communicate via industrial Ethernet. The host computer uses Siemens' dedicated monitoring software WINCC for monitoring and data archiving. The software configuration of OP3 and TP270, the software settings for network communication, the control program, and the design of the WINCC monitoring software are all described in detail in this paper.
Keywords: Air conditioning subsystem of painting plant, touch screen, WINCC
1. System Hardware Configuration Implementation
Because the factory's air conditioning system is designed as a constant air volume (CAV) full air conditioning system, based on our past project experience and careful calculations, we have differentiated the selection of automatic control system equipment for each area to adapt to changes in building function and equipment requirements during the project. This chapter uses the hardware configuration of the S1 air conditioning unit and AC1 exhaust fan unit as an example to introduce the system hardware setup.
1.1S1 Air Conditioning Unit Hardware Configuration
Based on the electrical schematic diagram and control system requirements of the S1 air conditioning unit, we have analyzed and summarized the hardware configuration of the control system. For simplicity and clarity, we have drawn Table 1, which shows the system hardware configuration of each part.
Table 1 Hardware Configuration of S1 Air Conditioning Unit
The S1 station control cabinet is equipped with a touchscreen OP3 located in the center of the front panel for monitoring the S1 air conditioning unit. The internal equipment of the S1 station control cabinet includes:
I. Voltage Regulator and UPS: Due to the harsh environment and the presence of many high-power inductive loads such as fans and pumps, power fluctuations are likely to occur. In addition, the system requires an uninterruptible power supply. Therefore, a voltage regulator and UPS are required.
II. PLC Unit
1. CPU module
The SIMATIC S7-300 series CPU313C was selected. It features an MPI interface, suitable for medium-to-large-scale I/O configuration and for establishing distributed I/O structures, making it ideal for interconnecting with remote substations. It has 64KB of program memory, 2048 bit memory, 64 counters, and 128 timers with a timing range of 10ms to 9990s.
The CPU313C has a total I/O address space of 1024/1024 bytes, of which 128/128 bytes are process-mapped I/O. It has a total of 8192 digital I/O channels, of which 1024 are centralized I/O channels. It has a total of 512 analog I/O channels, of which 256 I/O channels are centralized (128 O). Each system can be expanded with 32 modules, each integrating a backplane bus.
2. Power Module (PM)
One PS307-5A power module is selected to power both the SIMATIC S7-300 CPU and the expansion modules. The S7-300 requires 24V DC power; the PS307 power module converts 120/230V AC voltage to 24V DC operating voltage. The power module is mounted on a DIN rail, close to the left side of the CPU. It is connected to the CPU using a power connector. The front panel of the module features a power output indicator LED, a line voltage selection switch (120/230V), and a 24V DC ON/OFF switch.
3. Digital Signal Module (DI/DO)
The SIMATIC S7-300 digital input/output modules can transmit status and control signals to the PLC's CPU. Digital I/O modules offer the following performance and advantages:
1) Compact design: The robust plastic housing includes green LEDs to indicate the signal status of the input/output terminals; the connectors are protected by a front cover with a label area.
2) Simple assembly: The module is mounted on a DIN standard guide rail and connected to adjacent modules via a bus connector.
3) Convenient wiring for users: The module is wired via a plug-in front connector. The first insertion...
When the connector is in use, a coding element engages with it, ensuring that the connector can only be inserted into modules of the same type. When changing modules, the wiring configuration of the previous connector can be maintained for use with new modules of the same type.
4) Optimized integration: Modules that can be combined in any way allow the number of input/output points to be matched with the task. 5) Flexible process connectivity: The S7-300 can be connected to processes through various digital actuators and sensors.
4. Analog Signal Module (AI/AO)
The S7-300's analog input/output modules are used to connect analog actuators and sensors without additional amplifiers to perform more complex tasks involving analog processes. The analog input modules convert analog signals during the expansion process into digital signals for internal processing by the S7-300. External devices connected to them include voltage and current sensors, thermocouples, resistors, and resistance thermometers. Their performance and advantages are similar to digital input/output modules. Furthermore, they offer significant technological advantages; their diverse I/O ranges and high resolution allow connection to a wide variety of analog sensors and actuators.
Its characteristics include:
1) The resolution is adjustable from 9 to 15 bits plus the sign bit (for different conversion times).
2) Various measurement ranges: The basic current/voltage measurement range is mechanically set by the range card; fine-tuning is set by the STEP7 "hardware configuration" function in the programming device;
3) Interrupt capability: This module transmits diagnostic and over-limit interrupts to the CPU of the programmable controller;
4) Diagnosis: This module transmits a large amount of diagnostic information to the CPU.
5. PROFIBUS bus communication module CP342-5
The CP342-5 communication processor is designed for use with SIMATIC S7-300/C7-300 PLC systems, enabling the connection of S7-300/C7-300 systems to PROFIBUS fieldbus systems.
1) The latest version of CP342-5 can provide the following communication services:
It can be used as a master or slave station in a PROFIBUS-DP network for network communication, but it should be noted that it cannot be used as both a network master and slave station at the same time.
To communicate with S7 or with the programmer/operator panel:
– The programmer can upload or download the configuration or diagnostics of function modules via CP342-5;
- It can complete the communication interface function between the controller and the operation panel;
It can perform the following types of communication with S5 series products:
–FDL connection;
– Two types of connections in the free layer (SDA, SDN);
- Broadcast function;
– Multi-point transmission function.
2) Communication capabilities of the latest version of CP342-5:
The communication area for the master station is 2160 bytes; the communication area for the slave station is 240 bytes.
3) Configuration settings for CP342-5
Configuring CP342-5 requires STEP7 software, version V5.1 or higher. If FDL is used...
Connectivity and diagnostic functions require the installation of the optional PROFIBUSNCM software package.
6. S1 Station Optional Components:
1) CPU module S7-313C, model: 6ES7313-5BE01-0AB0. This CPU integrates two modules: one is DI24/DO16, and the other is AI5/AO2. The digital DI address is I124.0～I126.0, the DO address is Q124.0～Q125.0, the analog AI address is 752～761, and the AO address is 752～755.
2) The output module is an 8-point SM322 module with relay output, model number 6ES7322-1HF01-0AA0, address Q12.0～Q12.7.
3) Two SM334 4-input/2-output analog modules, model number 6ES7334-0CE01-0AA0, address range AI256～263, AO256～259.
4) One 4-channel analog output module SM332, model number 6ES7332-5HD01-0AB0, with output channel addresses of 288 to 295.
5) Bus connection module CP342-5, model 6GK7342-5DA02-0XE0, provides a PROFIBUS-DP interface for connection to CPU modules or other PROFIBUS interface devices. The PROFIBUS network address is 1.
6) SITOP power supply module
It is a DC power supply module with an input of AC220V and an output of DC24V. SITOP supplies power to field transmitters.
7) One PS307-5A power supply module
Provides power to the CPU and expansion modules.
1.2 Hardware Configuration of AC1 Exhaust Fan Unit
1.2.1 System Hardware Configuration Table
1.2.2 AC1 Station Control Cabinet Optional Components
1. Control cabinet: Dimensions 2000×800×600.
2. Power supply module: PS307-2A.
3. CPU module: S7-315-2DP, model number 6ES7315-2AG10-0AB0, PROFIBUS network address is 6.
4. Two digital input modules: SM321, model number 6ES7321-1BH02-0AA0, address I0.0～I1.7, I4.0～I5.7.
5. Two digital output modules: SM322, with relay output, addresses Q8.0～Q8.7, Q12.0～Q12.7.
6. One Ethernet communication module: CP343-1, model number 6GK7343-1EX20-0XE0, IP address 172.31.96.94, subnet mask 255.255.255.0. Industrial Ethernet does not use a router.
2 System Software Design
With the maturation and widespread application of automation technology in industrial control, more and more industrial enterprises are adopting computer management and production guidance. A computer monitoring system consists of two parts: a lower-level system and a higher-level system. The lower-level system typically uses a PLC or intelligent monitoring instrument as the data acquisition and processing center, while the higher-level system is usually developed independently using higher-level monitoring configuration software as a platform. Compared to the computer higher-level system, the lower-level monitoring system has developed into a relatively mature technology, and its functions are often limited by the PLC or intelligent monitoring instrument used. However, with the rapid development of system software, programming tools, and other third-party applications, there are increasingly more ways to implement a computer higher-level monitoring system. For a computer higher-level monitoring system, a fast development cycle, a user-friendly interface, and support for third-party applications to achieve powerful management functions are essential qualities of excellent higher-level configuration software. Among the numerous supervisory control and data acquisition (SCADA) software options, many imported software programs struggle with Chinese interface localization, artificially increasing the difficulty of on-site operation. Some have weak computational capabilities, requiring all or most of the data needed by the supervisory control system to be generated by the subordinate computer, increasing the burden on the PLC and often making ladder diagram programming complex and difficult to maintain. Others have weak network capabilities, requiring data exchange between control substations to be achieved through a local area network, resulting in poor data transmission security. Still others do not support third-party applications but instead embed programming tools from the supervisory control and data acquisition software vendors, requiring system developers to read extensively before programming, significantly extending the development cycle.
We use STEP7, developed by Siemens, for programming; WinCC, jointly developed by Siemens and Microsoft, for supervisory control and data acquisition (SCADA); and ProTools, Siemens' graphical interface design and configuration software. All of these software programs have successfully resolved Chinese localization issues and offer excellent compatibility and openness. The software emphasizes user-friendly design, and Siemens provides detailed documentation, making it quick and convenient for users.
2.1 Programming of Air Conditioning Units and Exhaust Fans
The program design adopts the idea of modular design, first dividing the entire program into several functional blocks, and placing each functional block into a FC to complete a specific control function. This makes it easier to debug and maintain the system.
1. The hardware configuration is shown in Figure 1 below:
2. Program Block Design
The main program flowchart is shown in Figure 2:
3. Program Block Description
Initialize function block OB100
Insert OB100 into the STEP7 project, put the initialization program into OB100, and the PLC system will automatically call OB100 once after power-on.
The initialization procedure includes: in automatic mode, setting the frequency conversion values of the fan and spray pump to 50Hz, setting the opening of the air supply valve to 100%, setting the opening of the fresh air valve to 0%, and setting the opening of the hot water valve to 0; in manual mode, setting the frequency conversion values of the fan and spray pump to 0, setting the opening of the air supply valve to 100%, and setting the opening of the hot water valve to 0.
Analog input data conversion and display function block FC41
This function block performs scalar conversion of analog input data and processes the data according to the data format requirements in OP3, then transmits the data to the corresponding data area so that the data can be displayed on OP3.
The sensors on site convert the actual analog values into 0-10V signals, while the AI (12-bit) module converts these signals into an internal code number (0-27648) through an A/D converter. The port number read by the PLC is only an internal code value, which requires programming to convert this internal code number into an actual value and send it to the operation panel for display.
The formula is as follows:
First, the data collected from the AI template in PIW754 is converted into actual values and placed into MD36 using a custom "AI-FACT" module. At this time, the data type in MD36 is real. Since OP3 can only display decimal numbers and the number of decimal places is 1 (defined by the user), MD36 is multiplied by 10. Then, the data type is converted into a double-integer decimal number.
FC46 control program module for wind turbine equipment
This function block completes the local and remote start/stop logic control of the air conditioning fan inverter, spray pump, circulating pump, fresh air valve, supply air valve, and return air valve. The spray pump control flowchart is shown in Figure 4:
The control flowchart for the air conditioning fan is shown in Figure 5:
Analog output data conversion and corresponding device control block FC45
When controlling valves or frequency converters, analog outputs are required. These values need to be converted into output values of 0-27648 according to the channel requirements. This function block performs some conversions in the program. Automatic and manual modes require assigning analog output values from different data areas. In addition, limit processing is performed on various devices. The minimum opening degree of the hot water valve is limited to 2%, and the frequency conversion value of the spray pump and fan cannot be less than 25Hz. The parameters of each device are initialized when switching between automatic and manual modes.
FC47 Alarm Processing Module
The function of this block is to detect signals from key components in real time according to the requirements of the air conditioning process, and generate an alarm signal output when the signal exceeds the range.
l Control algorithm processing module FC48
This functional block controls the equipment using a specific algorithm to meet the system's requirements for air supply temperature and humidity. The specific algorithm is explained in detail in Chapter 8, "Control Strategy Research".
Network communication program module FC49
This function block is used to program network communication tasks, which will be explained in detail in the later chapter on network communication.
System delay
To reduce the CPU load, it is unnecessary to perform data conversion processing on the acquired signals in every program scan cycle. The function of this block is to generate different periodic timing signals and process the acquired analog signals once every 150ms.
2.2 TP270 Touchscreen Software Design
TP-270 Introduction: The TP270 touch panel is based on the new standard Microsoft Windows CE operating system. Leveraging the flexibility of the PC world, it combines the robustness and speed of a dedicated hardware solution.
The TP270 panel offers a wide range of products, giving users the opportunity to choose the unit best suited to their specific needs. All units offer the following advantages:
• High configuration efficiency; configuration can be simulated on a configuration computer (no PLC required).
• The process can be clearly displayed and easily operated through a Windows-based user interface.
• A large number of predefined screen objects are available for selection during configuration, and screen objects (such as moving objects) can be used dynamically.
• Recipes and data records can be easily and quickly processed in the recipe screen and recipe view.
• Vector graphics can be created using SIMATIC ProToolCS configuration software without the need for an external graphics editor.
• When downloading data, it can automatically switch to download mode and transmit data via MPI, PROFIBUS/DP, USB, and Ethernet, or via serial download and TeleService.
• It can be connected to SIMATIC5/DP, SIMATIC7 and SIMATIC505 PLCs from other manufacturers via standard connections.
In addition to typical HMI applications (visualized using SIMATIC ProTool), the multi-function panel also supports processes such as diagnostics. The operating unit allows for graphical display of operating status, current process data, and faults related to connected PLCs, facilitating convenient monitoring and operation of associated machinery or systems. High protection (IP65 front) and the elimination of hard drives and fans ensure the unit is suitable for direct field use on various machines in rudimentary industrial environments.
The main monitoring screen of the TP270 is shown in Figure 6. The entire monitoring system is divided into 8 parts. Pressing each button will enter the corresponding screen.
Figure 7 shows the display screen for the S1-S4 air supply fans. The screen displays the operating status of each device in the S1-S4 air conditioning units. A red light indicates the motor is stopped, and a green light indicates the motor is running. A red light also indicates a motor malfunction, and a green light indicates no malfunction. Double-clicking the #1 operating light will bring up a configuration window. In this window, you can set the different colors of the lights to correspond to the internal variables of the PLCs they are connected to. Set red to the 0 value of the #1 operating variable, and green to the 1 value. The configuration method for other indicator lights is similar.
The air conditioning group control screen is shown in Figure 8. The screen displays the manual and automatic status of each unit. It also shows the start/stop controls for spray pumps S1-S5. There are four buttons at the top. To operate, touch the blue part of the button; pressing the button turns the red indicator light on the button green, and releasing it turns it red again. Pressing the start button for S-1-S-4 and the corresponding fan sequence will start S-1, S-2, S-3, S-4, P1, P2, P3, P4, P5, P6, P10, P11, P13, P14, P15, P16, P17, P18, P19, P20, S-7, and S-8 in sequence, taking approximately 2 minutes. Pressing the stop button for S1-S4 and the corresponding fan sequence will shut down the equipment in the reverse direction. Pressing the start button for S-5 and the corresponding fan sequence will start S-5, P7, and P9 in sequence; pressing the stop button for S-5 and the corresponding fan sequence will shut down the equipment in the reverse direction.
When S1 to S4 and related fans start normally, the air conditioning system status will display "Good"; otherwise, it will display "Bad". The screen also displays a micro-positive pressure value and allows you to set the micro-positive pressure value, with a setting range of 0-100 Pa. To set the micro-positive pressure, touch the area for the set value. A digital panel will pop up; press the corresponding number and then press the confirmation button to complete the setting. Pressing the micro-positive pressure adjustment button will initiate automatic micro-positive pressure control of the air conditioning unit. The button will change from red to green to indicate that adjustment has started; pressing it again will turn the button red to indicate that adjustment has stopped.
The user login button is used to bring up the operation password screen. Only after entering the password can you perform a valid operation. The system will automatically log out after 5 minutes. The login password and automatic logout time can be set in the ProTool software.
2.3 Development of WinCC software for the supervisory control system
In this system, WinCC mainly performs real-time monitoring of the entire production line, including the group start-up and stop control of the air conditioning and exhaust system, the collection of various system operating parameters, the display of equipment fault status, alarm records, data summary of each production equipment, report generation, timed printing, and operator operation records.
The supervisory control system consists of 5 parts:
1. The system monitoring screen is the core part of the supervisory control and data acquisition (SCADA) system, mainly including an overview of the entire production line, air conditioning unit screens, and exhaust fan unit screens. Each monitoring screen displays various equipment arranged according to the process flow, allowing operators to monitor various process parameters and equipment operating status.
2. The data archiving screen mainly displays the data collected by the field instruments in the form of tables and curves. It has the functions of printing real-time and historical curves and querying historical data. The time period of historical data can be freely selected within three months.
3. The report printing screen can print historical and online data reports and curves in a unified format, and alarm information can be printed online.
4. The alarm screen can provide information on the last 1,000 alarms, including alarm time, fault location, and some fault causes.
5. In this system, alarm information bars, operation permission information, and change buttons are integrated into every operating interface, ensuring that operators do not miss any important information while operating on any screen. Operation permissions can be set according to different operator identities, and personal passwords can be changed while online. Engineers should have the highest level of access.
Start/Stop Button Configuration Instructions:
Remote control of the equipment is also achieved by connecting buttons with tags. First, create a group start tag all_start in WINCC and connect it to the start position in the master PLC. In the button's properties, select "Release Left Mouse Button" in "Events" and compile the C action as follows to control the start and stop of the equipment.
#include "apdefap.h"
void OnLButtonUp(char* lpszPictureName, char* lpszObjectName, char* lpszPropertyName, UINT nFlags, int x, int y)
{SetTagBit("all_start",1);
SetTagBit("all_start ",0);
END
}
3. Conclusion
This article focuses on the software and hardware design process of the air conditioning monitoring subsystem in the painting plant. It introduces the hardware configuration and programming of the air conditioning unit and the exhaust fan unit respectively. In accordance with the requirements of visual monitoring, the touch screen monitoring software and the control room monitoring software were designed and developed, which achieved the requirements of highly automated monitoring and management.
and Xiaohu
