Analysis and improvement of the main control PLC s

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Analysis and improvement of PLC system for aluminum foil slitting machine

1400 vertical (thick) aluminum foil slitting machine is the first vertical high-speed thick foil slitting machine designed and manufactured by Liaoning Machinery Research Institute by introducing foreign advanced technology. The thickness range of the cut aluminum foil is 0.07~0.4mm; Incoming width 700~1300mm; The maximum production speed is 600m/min; The annual design production capacity is 12000 tons. Compared with the horizontal unit, its unloading mode, tool rest adjustment (when the finished product size is changed), process waste edge treatment, etc. have been greatly improved, greatly reducing the labor intensity of the production personnel, and improving the convenience and operability of the equipment

however, the main control system has some problems, such as unfriendly operation interface and unstable operation (such as frequent communication system failure, operating system crash, and some process parameters can not be modified and changed), which have seriously affected the normal operation of the unit. Therefore, it is necessary to improve and adjust the main control system by comprehensively analyzing various problems in production and formulating relevant countermeasures

1 main control system composition and communication mode

the main electrical control system of the unit is mainly composed of upper computer, lower computer, s programmable controller, DC drive and AC drive. The control schematic diagram of the system is shown in figure 1


1.1. The upper computer is located in the field console. The hardware platform is IBM compatible PC, the software platform is windons NT, and the upper monitoring work control software is mcgs3.2. Its main functions include:

parameter setting

setting contents include: incoming material width, thickness, uncoiling, inner coiling, outer coiling tension, inching, crawling, running speed values, and the selection of inner and outer coiling, Cutter head diameter, etc

data display

the display contents include: the current main operation status of the train, the actual speed value of the train operation, the actual tension value of uncoiling, internal coiling and external coiling due to deformation of the test piece due to torsion, the current coil diameter value of uncoiler, internal coiling and external coiling, and the current date and time

user management

this part mainly includes user login and logout, as well as modifying and managing user passwords and permissions

1.2 the lower computer is located in the control cabinet, the hardware platform is Advantech industrial computer and (PLC) switch value and analog input/output board, the software platform is msdos6.2, and the application software is compiled in basic language. Its main functions include:

1) receiving coil diameter detection signals of uncoiling, inner coiling and outer coiling

2) receiving field tension signals of uncoiling and inner coiling

3) calculating various inertia and compensation

4) providing tension reference signals for uncoiling, inner coiling and outer coiling

5) providing speed reference signals for uncoiling, central roll, shear shaft, inner coiling and outer coiling

1.3 Siemens s programmable controller, It consists of the master station of cpudp and its switching value I/O module in the control cabinet and the expansion station of et200 and switching value I/O module in the field console. Its main functions include:

1) receiving various command signals sent by operators and equipment detection devices on site

2) logical operation and interlock protection of the unit

3) logical control of DC transmission (such as enabling, operation stop, emergency stop, etc.)

4) logical control of AC 6 kg/sq. cm transmission using air pressure source

5) logical control of various hydraulic Logic control of pneumatic system

1.4 DC drive system is composed of DCS500 full digital DC governor and DC motor of ABB company. This series of governors has excellent performance, large power range and high reliability, and is suitable for power supply and control of DC motor

the main function of the system is to accurately control the tension and speed of uncoiler, central roll, cutter shaft, inner coiler and outer coiler according to the tension and speed benchmarks transmitted by the lower computer, so as to make the end face of the product neat (less than ± 0.5mm) and the internal and external tightness consistent

1.5 the AC drive system consists of a set of AC frequency conversion system ACS600 and a set of slip clutch governor system. This part is mainly used for the traction and winding collection of process waste edges. The information exchange between the working speed and the train speed components is mainly realized through the following paths

1) PROFIBUS field bus is adopted between PLC master station (cpudp) and expansion station, which is mainly used to transmit operation signals and field detection signals

2) RS232 serial communication between upper and lower computers is mainly used to transmit operation setting parameters and relevant display parameters of the train

3) direct electrical connection is adopted between the lower computer and the DC drive system (dod500) to transmit analog signals of tension and speed reference

4) direct electrical connection is adopted between the lower computer and the PLC master station (cpudp), so that the master control PLC can transmit the unit start, stop, emergency stop and other switching signals to the lower computer for the control of DC drive tension and speed reference by the lower computer

2 analysis on the causes of unstable operation of the main control system

after the unit was put into operation, the production operators on the one hand reflected that the operation interface (man-machine interface) was not friendly enough, on the other hand, the main control system was very unstable, and problems and failures often occurred, which affected the normal operation of production, mainly in the following aspects

1) since there is no communication channel between the upper computer and PLC, and the information transmitted by the direct electrical connection between the lower computer and the main control PLC (cpudp) is very limited (only several signals such as start, stop and emergency stop), the configuration interface of the upper computer cannot display a large number of fault diagnosis information, making it very difficult to deal with the fault

2) the upper computer is located at the site, and the environment is poor. This equipment is an electronic universal testing machine made by Shandong Sida high tech Testing Technology Co., Ltd. for the production of Metro doors for rail transit departments. The Windows NT system is frequently restarted and crashed due to unexpected electrical interference and abnormal temperature rise, resulting in repeated production interruptions

3) serial communication is adopted between the upper and lower computers. Due to the long distance, a non-standard conversion card is added. However, the conversion card is greatly affected by the environment, which often makes the communication out of step and causes the communication interruption, causing the unit out of control. It has the ability from design to manufacturing and processing

4) the application program in the lower computer is written and compiled in basic language, which makes it very inconvenient to adjust the parameters when the process conditions change, and the expansion and adjustment of the system functions are also greatly limited

5) at the beginning of coiling diameter measurement, the grating ruler was used. Due to environmental conditions, the accuracy was very poor. Later, it was changed to measure the number of turns of coiling shaft and indirectly calculate the coil diameter value. However, when the coil diameter of finished products was large, the error also increased with

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