Application of Profibus in turbocharger production line

1 Introduction

Fieldbus is the embodiment of the development of information technology and network technology in the control field, and is one of the hot spots in the development of automation technology. It has been widely used because of its characteristics of digitalization, openness, decentralization and adaptability to the field environment. At present, the main ones that have gradually matured and have an impact on the process of industrial automation are PROFIBUS, HART, LONWORKS, FF, etc. Among them, PROFIBUS bus is one of the most popular fieldbus technologies, and its products are widely used in automation fields such as industry, electricity, energy, and transportation. PROFIBUS is a national industrial fieldbus protocol standard formulated by Germany in the early 1990s, codenamed DIN19245. It is an international open fieldbus standard, namely the EN50170 European fieldbus standard. This standard provides the best protection for the investment of suppliers and users and ensures the independence of suppliers. PROFIBUS specifically specifies the technical and functional characteristics of the serial fieldbus, which can enable distributed digital controllers from the bottom of the field to the workshop and networking. PROFIBUS is divided into master devices (master stations) and slave devices (slave stations). The master station determines the data communication on the bus. When the master station gets the control right of the bus, it can actively send information without external request. The slave station is a peripheral device, and typical slave stations include: input/output devices, valves, drivers and measuring transmitters. They do not have the control right of the bus, and only confirm the received information or send information to it when the master station issues a request.

2 Solution Analysis

The turbocharger is actually an air compressor that increases the intake volume by compressing the exhaust gas into the air. When the engine speed increases, the exhaust gas discharge speed and the turbine speed also increase synchronously, and the impeller compresses more air into the cylinder. The increase in air pressure and density can burn more fuel. The corresponding increase in fuel volume and adjustment of the engine speed can increase the engine output power. Since the turbocharger is installed on the intake and exhaust manifold of the engine, it is in a high temperature, high pressure and high speed working condition. Its working environment is very harsh and the working requirements are relatively harsh, so the assembly technology of the turbocharger is very high. Among them, the error requirements of the parameters of the compressor end clearance, turbine end clearance, axial clearance, overall dynamic balance, whole machine leak detection and bleed valve opening pressure and displacement are controlled within a dozen or even a few silk. For example, it is difficult to achieve the accuracy requirements with traditional electrical instruments, and the anti-interference ability is poor; and workers are required to manually record and judge whether it is within the error range, which will greatly reduce work efficiency. This is where Profibus fieldbus comes in handy. Profibus forms a network of underlying detection equipment to achieve multi-point digital communication, and forms a network with the host computer to provide data support for the host computer; the host computer downloads the error range as the process parameter of each station to each station, and puts the data into the designated database for various queries and technical analysis. The following is the assembly line data acquisition system of a turbocharger factory.

3 System Structure

According to the on-site conditions, we use Siemens S7-400 to undertake signal acquisition work, and according to the scattered characteristics of the signal locations to be collected on site, we use the remote I/O, namely DP technology, in Siemens Profibus fieldbus. The signals of each sensor are connected to the Profibus substation nearby, which can minimize the on-site wiring work, and because the wiring distance is short, it can reduce the signal attenuation and the impact of various interferences on the signal.

The backbone network of the system uses Profibus network. There are three protocol modes of Profibus fieldbus network, namely FMS, DP and PA. We use DP mode this time. The DP network structure is a master-slave structure. A DP network can contain a master station and up to 126 slave stations. The network transmission distance can reach 1000 meters without using a repeater. The transmission rate is optional from 9.6Kbit/S to 12Mbit/S. When the network transmission rate reaches 12Mbit/S, the maximum transmission distance is 100 meters.

3.1 System network selection

Considering the information exchange between the host computer and the host computer, the host computer and the main PLC, and the main PLC and the slave PLC, the entire network system consists of three layers:

Management network (MIS): using TCP/IP-based Ethernet, the connection between the host computer and the host computer.

MPI network: using a communication processing card to connect the main PLC and the host computer.

DP network: This is the lowest network, connecting the scattered data acquisition sites, that is, the connection between the main PLC and the slave PLC and the touch screen.

Topology: The server on site is the bridge between Ethernet and industrial control network, and it is connected to Ethernet through a 3COM switch.

Figure 1 System network structure diagram

The network structure of the entire monitoring system is shown in Figure 1.

3.2 Host computer

HP ML350 server and Advantech industrial computer are used as host computers. The server is connected to CPU412-2 through the CP5613 communication card, so that the PC and the field bus are connected to form a complete control network system that can complete configuration, operation, operation and other functions. The HP server monitoring software uses SIEMENS company WINCC software, which can realize the issuance and termination of production tasks, store production data in the specified database, offline processing and equipment fault clearing. Advantech industrial computer adopts self-developed production management system, which mainly completes product list, product process, work order and work order process customization, and completes the issuance of production task instructions, downloads the work order process to the TP270 touch screen, and can query production data and generate corresponding reports, Execel.

3.3 SIMATIC S7 master station

As a DP master station, the CPU is located in the control center. This system uses CPU412-2 modular PLC, which integrates PROFIBUS-DP field bus interface device and has powerful processing ability (with a speed of 0.3ms to process 1024 statements). According to the program content, read the input and output of all I/O modules on the bus and read the barcode with more than 4 bytes in CP340 and put it in the corresponding DB block.

3.4 Slave (Slave A, B)

Slave A includes 2 EM277 with CPU226 and 1 IM153-2 with CP340. CPU226 mainly completes the collection of production data and monitors the operation of special machine detection equipment; CP340 reads barcodes from barcode guns.

Slave B includes 12 Siemens TP270-10 touch screens. A friendly human-machine interaction interface is configured for data collection, data storage, offline processing and fault message, so as to reduce the soft faults of operators as much as possible and report communication faults to operators in time.

4 Software Configuration

STEP7 Configuration: Network configuration is divided into two parts: software configuration and hardware configuration. The software part uses STEP7 programming software to configure the S7-400 CPU412-2DP, including communication rate, number of substations and station address. When the software configuration is completed, the corresponding address of each connected monitoring signal in the CPU will be automatically generated. The hardware configuration mainly sets the address dial switch on the interface module IM153-2 of the ET200M substation to the same as the software setting. Because CP340 is used as a slave station to read the barcode of the barcode gun, CP340 must select the ASCII protocol, and the parameters such as the start and end bits and parity check of this protocol must be set, and the driver program must be downloaded to CP340. The hardware configuration is shown in Figure 2.

Figure 2 Hardware Configuration

In most applications, WinCC and PROTOOL are used as monitoring systems for the production process, completing data recording and generating historical curves, configuring monitoring interfaces, generating alarm information, etc., but do not participate in the management of the production process and data processing. But in fact, in addition to caring about real-time information in the production process, enterprises also hope to store this information organically to play a greater role in future product traceability and product development. This project just reflects this point.

WinCC configuration: This is one of the keys to the entire system. All human-computer interaction information in this system is processed by WinCC, including: the issuance of production tasks, the issuance of process parameters, the end of production tasks, data storage, offline and data coverage, etc., which are closely related to the entire production process. The variable record that comes with WinCC can periodically record the real-time data of each tag and store these data in their respective tag data tables. The data tables corresponding to each tag are relatively independent; while the project requires that all data related to a product be stored in a product data table, and only the data of the measurement point is required. Obviously, the variable record function cannot meet this requirement. But the global script provided by WinCC provides us with the tools to achieve this. By writing action scripts to directly communicate with the product database, a set of related data can be stored in the product data table. The scripts in the action module are executed regularly, and each script has its own timer. If the clock timer is used as the timer to trigger the script, the data in the database will always be the current data, not the data of the detection point. Here we use a variable timer to simulate a button click event, that is, using a binary variable, executing the script when the variable changes and on the rising edge (variable = 1), and resetting the variable at the end of the script; the setting of this variable is scattered on each touch screen. The flow chart of the action program for storing collected data is shown in Figure 3.

Figure 3 Flowchart of the save action

PROTOOL configuration: Touch screen TP270-10 is the human-machine interface that directly interacts with the operator. All instructions are sent by the touch screen, and it is connected to the DP network through the DP interface. Considering the complexity of data storage, the human-machine interface is divided into five interfaces: storage interface, tray confirmation interface, overlay interface, offline processing interface and communication fault display interface. Deposit interface: The main interface displays the pallet number and the operation being performed in a high-brightness manner, mainly including information such as production tasks, process parameters, detection status, detection data and detection results, as well as the sending of instructions such as deposit and offline; Pallet confirmation interface: There are 30 pallet numbers in the deposit interface. In order to prevent operators from misselecting pallets under long-term fatigue work, which leads to the loss of product information of other superchargers and incomplete product information of their own products, the pallet confirmation interface is very important; Overwrite interface: Affected by the product structure, the same product may have inconsistent data detected at different relative positions in the same station, resulting in repeated data storage - overwrite; Offline processing interface: When the data detected by the special machine detection equipment is unqualified, the product will be offline processed and the corresponding records in the database will be deleted; Communication fault interface: Displays the communication status of each data collection point after power-on. When there is a communication fault, the touch screen will notify the operator in the form of a system message. The main interface of the whole machine leakage station is shown in Figure 4.

Figure 4 Leakage of the whole machine

LED display system: connected to the data server through the serial port, and counts product output in four real-time statistical ways, including: this month's statistics, this week's statistics, today's statistics and work order statistics; at the same time, the display information can be customized.

5 System Features

* Through open interconnection, it realizes fully integrated automation (TIA) from the production execution system (MES) and enterprise resource planning (ERP), and is open to IT (OPC, ActivX, COM/DCOM, ODBC/SQL, API)

* Visualization on a multi-functional platform (protool/pro)

* Modularization makes the system forward-looking and scalable

* Step-by-step intelligent I/O

* Unified integrated database, easy to maintain and backup data

* Based on centralized operation and monitoring of the entire production process.

6 Conclusion

The system has been running stably and reliably on site for half a year, greatly improving labor productivity and effectively solving many problems in production, such as reducing sudden failures in the production process, shortening production preparation time and repair time, and reducing the labor intensity of workers. At the same time, it provides scientific data basis for the research and development work of R&D staff, creating considerable economic and social benefits for the factory. The system is not only suitable for such supercharger production lines, but also for other occasions where equipment is dispersed and equipment and production data need to be collected.