B1 cigarette packaging unit based on PLC and fieldbus technology

Introduction
At present, the main model B1 cigarette packaging unit in most cigarette factories in China is a high-speed soft pack packaging unit introduced from the German company Smolmen in the 1980s and 1990s. However, due to the long-term operation of the cigarette packaging unit, the electronic control components gradually aged and failed, and the failure rate was very high. In recent years, the defects of the BI unit's electrical control system have become increasingly prominent; the logic components are aging; the machine cannot be automatically shut down when a fault occurs; the layout of the control circuit board is complex, there is no relevant component manufacturer in China, and spare parts are difficult and expensive. At the same time, the BI unit also has problems such as backward control methods and inconvenient maintenance due to English display.
The modified BI unit is an electrical control system with PLC and industrial control computer as the core. PLC completes all data acquisition and real-time control, and completes the entire operation process such as startup, shutdown, process control, and detection. As the host computer, the industrial control computer has a good human-machine interface, while adding statistical reports and reserved network management functions, and providing technical support for remote data acquisition, thereby completely solving the problems existing in the BI unit's electrical control system.

2 Hardware composition of the electronic control system of the BI packaging unit
The BI packaging unit consists of five parts: NF unloading machine, BE packaging machine, RC small package transparent machine, PHZ large strip machine and NK large strip transparent machine, as shown in Figure 1.

The modified electronic control system is composed of 4 independent parts, namely BE, RC, NF, and FHZ/HK, and each part is controlled and displayed separately. The BE packaging machine is the host, and the other parts are slaves. The information exchange function is added between the parts to realize the overall control of the B1 unit, and the phase control adopts an absolute value encoder to make the B1 unit work in a coordinated manner.

3 Renovation Design Plan
3.1 Overall Renovation Block Diagram
The control systems of the original BI unit's main engine BE, RC, and FHZ/NK are not in the same control cabinet, and each part exchanges equipment operation information through switch quantities. The main action of the BE unit is completed by mechanical devices, and the common characteristics of each part are that there are many detection signals and few actuators. In view of this feature, the BI unit is renovated as a whole, and its renovation block diagram is shown in Figure 2.

3.2 BI host transformation
The controller uses the cost-effective S7-400 PLC, which is a high-performance large-scale PLC control system produced by Siemens, with the characteristics of high speed, stability, reliability and openness. The software is powerful, object-oriented, intuitive user interface and easy to use. The new design only retains a very small number of relays, and the control logic is implemented by PLC. The extra space after removing the relays is used to place the PLC sub-sites, which mainly include communication, input and output and special function modules. The transformation of the BI host is mainly to transform its angle feedback system, control system and speed control transmission system. Figure 3 is the structure diagram of the BI host control system.

3.2.1 Modification of angle feedback device
An absolute encoder is used to replace the incremental encoder of the original machine. Compared with the incremental encoder, the absolute encoder outputs the angle value in real time, and there is no need to calculate the current angle of the equipment by pulse counting. Even if the equipment is powered off, the angle value before the power failure can be immediately known after the power is restored, and it can be put into production immediately without re-finding the zero pulse.
3.2.2 Modification of main drive
In view of the high reliability of the current AC frequency conversion technology, the original system DC motor, DC speed regulator and intelligent follow-up unit can be cancelled, and the main engine speed control can be realized by using AC motor plus frequency converter. At the same time, the characteristics of the improved model BO machine of the BI host are adopted, and a manual speed potentiometer is added to its console to facilitate the operation and maintenance personnel to debug and maintain the equipment.
3.2.3 Modification of auxiliary drive system
In addition to the main drive system, the BI host also has 5 auxiliary drive devices such as the feed conveyor belt, the lower flue motor, the box skin rubber roller, the sealing rubber roller and the export conveyor belt. All the DC motors of these auxiliary drives have been changed to ordinary AC speed regulating motors, and all of them are controlled by Siemens 420 frequency converters.
3.2.4 Renovation of the temperature control system
The heating temperature of the drying turret of the BI host needs to be adjusted (although the original machine has an oil heater, it is generally not used because the lubricating oil will never freeze when the equipment is working in the wrapping workshop). The original machine temperature control system consists of a Pt100 thermal resistor, a TEMPMOD A176/A177 conversion board, a temperature measurement board SMC-MAX (A30), an A/D conversion board SMC-02B (A24), a solid-state relay, and a heater. The modified temperature control system is based on retaining the thermal resistor and heater of the original machine, canceling the module TEMPMOD A176/A177 that converts the thermal resistor to 4~20 mA, and directly introducing the thermal resistor line into the control cabinet and connecting it to the analog module of the Siemens PLC. The temperature control is implemented by soft PID, and the PID function block of the Siemens PLC controls the heater temperature.
3.2.5 Transformation of human-machine interface
LCD touch screen technology is used to replace the old CRT display and keyboard input, which greatly reduces the weight of the unit, reduces the size, improves the display quality, and adds new functions such as parameter setting, production and consumption analysis, and fault information alarm positioning. The monitoring function is set with a full Chinese menu to realize the operation status display, vehicle speed display, parameter setting, fault indication, shift record, etc.; a password function is set to prevent irrelevant personnel from changing parameters. The maintenance password can be authorized to the machine maintenance personnel.

3.2.6 Modification of cigarette detector
The B1 photoelectric small packet cigarette detector of type ZN0228-B1 was selected to replace the original small packet cigarette detector. The cigarette detector is a new digital detection mode, which consists of three parts: empty detection probe, missing detection probe and controller. There is no need to change the original host. You only need to replace the original missing and empty detection head with a new detection head, and connect the output line of the controller to the corresponding terminal of the B1 host. Without changing any control circuit and mechanical device of the original host, the sensitivity of missing and empty can be adjusted intuitively and conveniently.
3.3 Fieldbus and network connection
INTERBUS is an industrial fieldbus provided by Phoenix Company of Germany, which complies with the IEC61158 international standard bus. It is now widely used in the automotive industry, tobacco industry, warehousing and transmission technology, paper industry, packaging industry, food industry and other fields. The independent diagnostic program provides detailed fault information (fault address, fault type and fault history), and the diagnostic register provides the user program with tools to process fault information. The 3-line 16-segment LCD display of the control board is intuitive and eye-catching. Figure 4 shows the communication between the control system of unit B1 and the management level computer via Ethernet.

S7-400, S7-300 and ILC200IB controllers are installed in BE control cabinet, RC control cabinet and FHZ/NK control cabinet respectively. S7PLC is equipped with power supply, CPU, interrupt, PID and other modules. INTERBUS bus adapter control board is installed on the PLC baseboard to handle data exchange between PLC and process I/O devices. A large number of I/O modules and unit operation panels are installed on site and connected to PLC through INTERBUS bus.

4 Conclusion
The unit has been running for one year after the transformation. It runs well, has stable performance and low failure rate. The average effective operation rate of the equipment is 83.7%, which is 13% higher than the original 70%. The transformation effect is obvious. The upper computer interface is completely Chinese, which is convenient for fault inspection and troubleshooting. The newly designed electronic control system uses common components, which reduces costs. It greatly saves maintenance costs. The system provides technical support for the network management and remote data acquisition of the workshop, and has strong expansion functions.