Solar cell backboard coating line high-precision tension control system

Abstract

According to the high-precision tension control system for the solar cell backboard coating line, high-precision tension control is achieved based on an SINAMICS 120 servo dragging system, a Siemens S7-300 series PLC is adopted as a control core, a PROFIBUS-DP field bus communication network is established, CPU317-2DP serves as a master station, a field remote IO module and a CU320 driving unit serve as slave stations, and the high-precision tension control system for the solar cell backboard coating line achieves high-precision tension control. An industrial personal computer is used as a man-machine interaction medium, normal operation of the whole production line is achieved by setting tension and production speed, tension control is performed in a mode of combining a floating roller and a high-sensitivity tension sensor, a high-precision servo system S120 is used for dragging, high-precision control of tension is achieved, and actual operation of the system shows that the production efficiency is greatly improved. Compared with a traditional tension control system, the system has the advantages of being stable in tension control, high in precision, stable in production speed, friendly in man-machine, capable of achieving non-stop roll changing and capable of completely meeting the requirement for continuous production of the back plate.

Description

Technical Field

[0001] The present application relates to a solar back panel coating line tension control system, and in particular to a solar cell back panel coating line high-precision tension control system, belonging to the technical field of solar back panel tension control. Background Art

[0002] Solar energy is widely developed and utilized as a renewable energy source with huge reserves, cleanness and no pollution. The solar backplane is located on the back of the solar cell module, protecting and supporting the cells. In outdoor environments, it can protect the solar cell module from water vapor erosion, block oxygen to prevent oxidation, withstand high and low temperatures, have good insulation, aging resistance and corrosion resistance, reflect sunlight, improve the conversion efficiency of the module, and has a high infrared emissivity, which can reduce the temperature of the module.

[0003] The solar backsheet coating line is the basic equipment for producing backsheets. The material of the backsheet PET is coated, dried, and compounded on the coating line to form a semi-finished product. The semi-finished product is balanced and dried, cut and sorted to become a finished backsheet and delivered to the solar cell module manufacturer for use. The solar backsheet coating line consists of several parts, such as the unwinding unit, the coating unit, the drying unit, the compounding unit, and the winding unit. In the backsheet coating process, the level of tension control is directly related to the quality of the backsheet product. In the coating process, the fluctuation of tension will lead to uneven coating thickness, and in severe cases, it may cause coating to come off, resulting in serious quality defects, and eventually the entire roll of products will be scrapped. In the winding process, too little tension will cause the winding to bring in air, reduce the friction between the layers, and slide between the layers, resulting in an uneven end face of the winding. If the winding tension is too large, the tension of the outer layer will squeeze the inner layer inward, causing the winding to come out outward, forming a telescope-shaped defect. Therefore, only by achieving stable tension control can qualified backsheet products be produced, which is of great significance to the tension control of the solar backsheet coating line.

[0004] The quality of the photovoltaic power station of solar panels is one of its decisive factors. If the service life of the components does not meet the standards or the photoelectric conversion rate decays too quickly, it will lead to huge subsequent maintenance costs and reduced power generation efficiency, which will have a huge impact on the photovoltaic power station. Since the solar backsheet is installed on the outermost layer of the solar panel and is exposed to the air for a long time, the working environment conditions are relatively harsh. Once the backsheet material fails, the packaging materials and battery silicon wafers inside the component will be directly exposed to the harsh outdoor environment, which will then cause problems such as hydrolysis of the packaging materials, corrosion and delamination of the battery and welding belt, and quickly reduce the power output and service life of the component. In severe cases, it will also cause the insulation failure of the component to cause fire and safety accidents. Therefore, the quality of the solar backsheet is particularly important. In the manufacturing process of the solar backsheet, the coating quality is an important part of the backsheet quality control. Stable tension control is the premise of stable coating. Uneven distribution of tension will cause the coating to have uneven thickness, delamination and stripes and other apparent defects.

[0005] The problems that need to be solved in the tension control of the solar backsheet coating line in the prior art and the key technical difficulties of this application include:

[0006] (1) At present, the tension control level in the backplane coating process is not high. There is a lack of reliable solar backplane coating line processes and equipment. There is a lack of key factor models for tension control in backplane coating. It is impossible to build a tension control plan, accurately adjust the tension, monitor the fluctuation of tension and speed in real time in the host computer, and change rolls without stopping the machine. It is impossible to stabilize the tension control at the same time, which affects the quality of the backplane products. During the coating process, the fluctuation of tension leads to uneven coating thickness. In severe cases, it may cause coating to delaminate, resulting in serious quality problems, and eventually the entire roll of products will be scrapped. During the winding process, too little tension causes the winding to bring in air, reduce the friction between the layers, and slide between the layers, resulting in an uneven end face of the winding. If the winding tension is too large, the tension of the outer layer squeezes the inner layer inward, causing the winding to come out outward, forming a telescope-shaped problem. The existing technology cannot achieve stable tension control, and it is easy to produce unqualified backplane products, which seriously affects the quality of the backplane and even the entire solar cell.

[0007] (2) The prior art lacks an efficient solar cell backplane coating line tension control strategy, a backplane coating line unwinding tension control model, a backplane coating line rewinding tension control model, a backplane coating line tension control model, a backplane coating line tension control model, a tension control influencing factor model, a tension control system architecture, a solar backplane coating line tension control system hardware design and software design, and a host computer configuration design; this results in uneven distribution of coating line tension, resulting in coating thickness unevenness, coating delamination, and streaking, which seriously restricts the solar backplane manufacturing process and reduces the quality of the solar backplane. Since the solar backplane is installed on the outermost layer of the solar module and is exposed to the air for a long time, the working environment conditions are relatively harsh. Once the backplane material fails, the packaging material and battery silicon wafers inside the module will be directly exposed to the harsh outdoor environment, which will cause hydrolysis of the packaging material, corrosion and delamination of the battery and solder strips, and rapidly reduce the power output and service life of the module. In severe cases, it will also cause module insulation failure, causing fire and safety accidents. If the component lifespan does not meet the standards or the photoelectric conversion rate decays too quickly, it will lead to huge subsequent maintenance costs and reduced power generation efficiency, which will have a huge impact on the photovoltaic power station.

[0008] (3) The prior art lacks a servo drag system to achieve high-precision tension control, lacks a field bus communication network, lacks a master station, a field remote IO module and a drive unit as a slave station, and is unable to achieve normal operation of the entire production line by setting tension and production speed. It lacks tension control by combining a floating roller and a high-sensitivity tension sensor, lacks a high-precision servo system S120 as a drag, and is unable to achieve high-precision tension control. The system tension control is unstable and has low precision, the production speed is unstable, and it does not have the function of changing rolls without stopping the machine. It cannot meet the continuous production requirements of the backplane, resulting in cumbersome equipment operation, high error rate and high failure rate. The equipment cannot achieve zero maintenance, and at the same time cannot reduce material loss and increase equipment production capacity, and cannot meet the large-scale high-precision production requirements of solar cell backplane coating lines. Summary of the invention

[0009] This application improves the solar back panel coating line process and equipment, establishes a key factor model for tension control in back panel coating, constructs a tension control scheme, uses a process PID controller based on the Siemens S120 servo system to adjust the tension of the coating line, and monitors the fluctuation of tension and speed in real time in the host computer, uses film storage to achieve non-stop roll change, and stabilizes tension control. After the solar back panel coating line adopts a servo tension control system, the tension is stable and uniform, and the equipment is simple and convenient to operate, with low error rate and low failure rate. The equipment can achieve zero maintenance, and its operation time is shorter, with higher accuracy and stronger adaptability. At the same time, it can reduce material loss, and also improve equipment production capacity at high speeds. At the same time, the servo system using a common DC bus can effectively save energy, and has achieved good results in the actual production process.

[0010] In order to achieve the above technical effects, the technical solutions adopted in this application are as follows:

[0011] The high-precision tension control system of the solar cell backsheet coating line is based on the SINAMICS120 servo drag system to achieve high-precision tension control. The Siemens S7-300 series PLC is used as the control core, and the PROFIBUS-DP fieldbus communication network is established. The CPU317-2DP is used as the master station, the field remote IO module and the CU320 drive unit are used as slave stations, and the industrial computer is used as the human-computer interaction medium. The normal operation of the entire production line is achieved by setting the tension and production speed. The tension is controlled by combining the floating roller and the high-sensitivity tension sensor. The high-precision servo system S120 is used as the drag to achieve high-precision tension control, including:

[0012] 1) Solar cell backplane coating line tension control strategy, including: backplane coating line unwinding tension control model, backplane coating line winding tension control model, backplane coating line tension control model, backplane coating line tension control model, tension control influencing factor model;

[0013] 2) Tension control system architecture;

[0014] 3) Hardware design of solar back panel coating line tension control system;

[0015] 4) Solar back panel coating line tension control system software design, including: tension control STEP7 programming software configuration, coating line tension STEP7 program design, coating line tension S120 hardware configuration, communication between S7-300 and S120;

[0016] 5) Host computer configuration design;

[0017] This application improves the solar backplane coating line process and equipment, establishes a key factor model for tension control in backplane coating, constructs a tension control scheme, uses a process PID controller based on the S120 servo system to adjust the tension of the coating line, and monitors the fluctuations of tension and speed in real time on the host computer, uses film storage to achieve non-stop roll change and stabilize tension control.

[0018] Preferably, the unwinding tension control model of the backsheet coating line: Ts is a tension sensor, Tc is a tension transmitter, T is a transmission control system inverter, M is a transmission motor; Gearbox is a transmission system reducer;

[0019] Calculation method: Set the production line running speed to V, unit m / s, and the diameter of the unwinding substrate to Φ, then the roll diameter calculation formula is:

[0020]

[0021] In the formula, I is the reduction ratio of the gearbox, n is the output speed of the motor, and D is the real-time calculated diameter;

[0022] Under normal circumstances, the roll diameter is accurately calculated using formula 1. The tension control system adjusts the current of the motor to output the required torque, and adjusts the output force of the motor to indirectly adjust the tension on the substrate.

[0023] According to practical experience, the preset tension should be relatively large, and the unwinding force equation is established as follows:

[0024]

[0025] F r is the material die tension, i is the transmission ratio, r is the material roll radius, M e is the resistance torque generated by the AC motor, M f is the viscous friction torque, M0 is the dry friction torque, ω is the angular velocity of the roll, and J is the moment of inertia on the motor shaft;

[0026] The equivalent moment of inertia J of the material roll is composed of the axis moment of inertia J0 and the material moment of inertia J r Composition, the unwinding process, the unwinding diameter gradually decreases with time, J r It is also related to the unwinding radius, J r is a time variable, a function of the roll diameter r, r is a function of time t, J0 is a fixed value, the moment of inertia of the roll changes little in an instant, J w The influence on tension is not calculated, and in the uniform winding process, the viscous friction is considered to be a constant, and the force equation is simplified to:

[0027]

[0028] The unwinding diameter and angular velocity of unwinding are two aspects that interfere with the tension. The unwinding diameter is calculated based on the initial diameter and line speed. Speed ​​and tension influence each other. The production line speed is fixed, while the diameters of winding and unwinding are constantly increasing and decreasing. The control system calculates the corresponding motor angular velocity based on the line speed and diameter to control the tension to be stable.

[0029] Preferably, the backsheet coating line winding tension control model: the control task that needs to be completed in the winding system is to use formula 4 to complete the calculation of the dynamic winding diameter, and use formula 5 to calculate the dynamic radius of the winding:

[0030] VV=ω×rEquation 4

[0031] V×T=ω×r×τEquation 5

[0032] Where: V is the set speed of the entire line, r is the real-time winding diameter, τ is the time during the winding process, ω is the angular velocity of the winding motor. In addition, special matters such as rotational inertia compensation and friction compensation are added to improve the accuracy of speed control and meet the tension control requirements.

[0033] Preferably, the tension control model of the back sheet coating line: the unwinding tension is divided into passive unwinding and active unwinding according to the unwinding actuator, the passive unwinding adopts a magnetic powder clutch or a pneumatic brake, and the active unwinding adopts an AC variable frequency motor or an AC servo motor;

[0034] The floating roller indirect tension detection is adopted. When the tension is stable, the substrate tension and the thrust generated by the low-friction cylinder are balanced, so that the floating roller is in the central position. When the tension is unstable, the balance between the substrate tension and the cylinder force is broken, and the position of the floating roller is offset. Driven by the connecting rod, the position change of the floating roller is detected by the potentiometer and the absolute value encoder. The voltage analog signal of the potentiometer or the Gray code of the encoder is fed back to the PLC, and the PLC then transmits the digitized signal to the CU320 controller. Under the action of the PID controller, the speed of the unwinding shaft is adjusted to keep the floating roller in the middle position at all times, while ensuring the stability of the substrate tension.

[0035] The unwinding tension is set through HMI, and the required pressure of the cylinder is calculated according to Tension (Kgf) = P*AFG, where P is the cylinder input pressure, A is the cross-sectional area of ​​the cylinder piston, F is the friction force of the cylinder itself, and G is the deadweight of the floating wheel;

[0036] The proportional valve detects the output air pressure and compares it with the set air pressure. If it is lower than the set value, the air supply solenoid valve opens, the exhaust solenoid valve closes, and the air source pressure enters. When the detected pressure is equal to the set value, both solenoid valves close and the pressure is maintained. Conversely, if the output air pressure is higher than the set value, the exhaust solenoid valve opens to exhaust and reduce the pressure. The proportional valve outputs a stable air pressure by switching the two solenoid valves.

[0037] Preferably, the tension control system architecture is as follows: in the solar backsheet coating line, there is only one reference speed point. According to the position of the pull-tab device, the tension section of the entire coating line is divided into several areas. The tension division includes the following sections: unwinding section, unwinding storage section, compound section, winding storage section and winding section. The floating wheel + tension sensor is used for tension control in the unwinding and winding process, and tension sensors are set in other sections to detect tension changes.

[0038] The unwinding part adopts constant tension unwinding, and the rewinding part adopts conical rewinding. The position of the floating spoke is fed back to the controller, and the speed adjustment value of the motor is obtained through calculation. The motor speed is controlled by the S120 motor module. The drag motor is equipped with an encoder, which feeds back the actual speed of the motor to the motor module to realize the closed loop of the motor speed loop.

[0039] During the unwinding and winding process, the given speed calculation of the motor requires the reel diameter data. The reel diameter calculation adopts the proximity sensor method. The proximity sensor is installed near the reel. The proximity sensor detects the rotation of the reel. When the initial diameter and the thickness of the coil are known, the thickness is subtracted by 2 times the thickness of the coil for each rotation to obtain the reel diameter.

[0040] Preferably, the solar back panel coating line tension control system hardware design: establish an electrical control system, including the core controller PLC, coating line drag servo motor module, industrial computer and touch screen and other line connections;

[0041] The system hardware includes: upper industrial computer, touch screen, PLC master station, local analog expansion module, remote IO substation, MM440 inverter substation and CU320 servo control module substation:

[0042] Among them, PLC realizes logic control, analog-to-digital conversion, data processing, and communication. The analog expansion module realizes the collection of tension and floating spoke position data, and the air pressure setting of the electric proportional valve. The remote IO is distributed on site to control various buttons and signal indications. CU320 is the controller of the traction system, which controls the motor module to realize speed control. The industrial computer and the on-site touch screen serve as the human-computer interaction interface to realize the input and monitoring of various parameters.

[0043] Preferably, the tension control STEP7 programming software is configured: the coating line tension control system adopts the PROFIBUS-DP bus control network. First, the STEP7 programming software is used to create the network and configure the hardware. After the hardware configuration is completed, programming design is performed. A system that is exactly the same as the actual hardware system is generated in the STEP7 software. The configuration of the hardware part requires the establishment of a project, the configuration of the rack, the configuration of the power module, the selection of the CPU model, the digital input and output module, the analog input and output module, and the creation of the PROFIBUS-DP bus network. The master station and slave station of the network need to be created, and the station address and baud rate information of each station in the network need to be set;

[0044] The on-site operation of the coating line rewinding and unwinding adopts the SMARTI / 0 series intelligent slave station, which is connected to the DP bus by setting the GSD file. The models of the SMARTI / 0 intelligent slave station include 16-point digital input module GPL-D22A / C, 32-point digital input module GPL-D224 / C, transistor 16-point digital output module GPL-TR22A / B / C, and transistor 32-point digital output module GPL-TR24A / B / C.

[0045] After the remote I0 bus settings are completed, you need to continue to configure the driveDP bus. Using the SINAMICSS120 drag system, there are a total of 26 drag points on the entire line. Each CU320 control unit controls up to 6 servos, and a total of 5 CU320s are required. In the hardware directory on the right side of the configuration interface, open the PROFIBUS-DP directory, find the S120CU320 under the SINAMICSS120 subdirectory, drag it to the DRIVEDP bus, and set the bus address. Enter the version number of the CU320 in the pop-up property menu, make detailed settings in the DP slave property interface, and configure the corresponding message for each motor module.

[0046] Preferably, the coating line tension STEP7 program design: for the entire coating line, the tension is pre-established at startup, and the process is as follows: the controller detects faults and alarm signals of the entire line, and it cannot be started if there is an alarm. If the floating wheel is not in the middle position, the reeling and unreeling motor will unwind or retract, tightening the film path and floating back to the middle position. The film storage working position detection relies on the proximity switch, and the working position, super high limit, super low limit, and in-place limit four proximity switches are set. If it is detected that the storage film is not in the working position, the storage film will run to the working position before starting; after the above confirmation is completed, the coating line starts to be linked, and during the linkage process, the tension sensor and the floating wheel detect the tension change, and feedback to the PLC and CU320, and the PID controller output is used to control the motor speed to make the tension stable;

[0047] For the unwinding part, it is composed of a double-station unwinding, a film storage rack and a film standby device. In the continuous production of the backplane, one unwinding station unwinds normally, and the other unwinding station is in standby state. The film head has been fixed on the standby table with tape in advance, and the film storage rack is in a high position. The reserve film path is about 30 meters. When the unwinding station needs to splice the film, the unwinding shaft and the film pulling pressure wheel stop, and the film storage rack takes over the unwinding work and starts unloading. When the joint is connected, the standby unwinding station unwinds normally, and the film storage stops. After a delay, the film storage rack automatically returns to the high working position, and the previous unwinding station is used as a standby station.

[0048] When winding and splicing the film, one of the double-station winding shafts will rewind normally, and the other winding shaft will have tape pre-affixed on its core. The flip frame will be flipped to the appropriate position in advance, and when the unwinding joint reaches the rewinding point, the splicing button will be pressed, the winding shaft and the pull tab will stop rotating, the winding film storage will start to rise, the film storage path will be stored, the substrate will be manually broken and then bonded to the shaft core and smoothed firmly, the splicing button will be pressed again, the film splicing will be completed, the film storage will stop, the winding shaft and the pull tab will restart to start the winding process, and after the tension is stable, the film storage will return to the working position.

[0049] Preferably, the communication between S7-300 and S120: S7-300 and SINAMICSS120 use PROFIBUS-DP communication, PROFIBUS-DP bus performs periodic and non-periodic data communication, S7-300 sends CTW 1 control word and NSETP_B to the servo drive through PROFIBUS periodic communication; at the same time, S7-300 system function blocks SFC58 / SFC59 are used to perform non-periodic data exchange and read or write parameters to the drive;

[0050] PLC controls the servo drive system through messages. The messages are based on the PROFIDRIVER protocol. The PROFIDRIVER protocol predefines the functions of each status word and control word of the received and sent PPO messages. The servo controller receives the control signal through the message, and the various states of the servo controller are also fed back to the PLC through the message. The length of the message reception and transmission cycle is determined by the hardware. The servo system communicates periodically through PROFIBUS-DP to improve accuracy. The controller selects the message: SIEMENS telegram 370PZD 1 / 1;

[0051] Use S7-300's SFC14 and SF15 to read and write SINAMICSS20, use communication to control S120, SF14 reads S120 status, it occupies 7 PZDs, first fill in the hardware address of 5120 in LADDR, where 256 corresponds to hexadecimal W#16#100 and fill in the data block address in RECORD, P#DBXO.0BYTE 14, these addresses are used to allocate the process data PZD value read from SINAMICSS120, RETVAL indicates that the return value is used to display fault information; SFC15 performs a write operation, which sends a command word to the servo controller, fills in the address in the 5120 hardware in LADDER, and fills in the set DB address P#DB 1.DBX0.0 BYTE 24 in RECORD, that is, 24 bytes starting from DB1.DBX0.0, and allocates these addresses to the PZD value written in 5120, RETVAL indicates that the return value is used to display fault information.

[0052] Preferably, the upper computer configuration design: the upper computer directly issues control commands to the PC, which displays the dynamic changes of various signals in real time on the screen, including hydraulic pressure, temperature, and water level. The instructions issued by the upper computer are transmitted to the lower computer, and the lower computer translates the command into the corresponding timing signal to control various equipment to complete the production task;

[0053] The user uses the editor in the configuration software to create a new WINCC project. The WINCC editor saves this information in the CS database. During the system operation, the runtime software calls out these project data information from the configuration library and executes them. The data in the current process is temporarily stored in the RT database, that is, the runtime database.

[0054] Then, WINCC and the automation system communicate with each other through a communication driver or channel. The channel collects the process values ​​of all running system components, reads the process variables from the automation system, and inputs the new change values ​​into the automation system when necessary.

[0055] The archiving system stores the process values ​​in the process archive, and uses the archived process values ​​to display the temporary progress of the process values ​​in the online trend control or online table control; individual process values ​​are monitored through alarm records. Once the set limit value is exceeded, the alarm record generates an alarm message and displays it in the alarm control. The alarm record accepts the operator's confirmation and manages the message. The alarm record saves all messages in the message archive;

[0056] Finally, the reporting system produces documentation of the system process within the preset time according to requirements, accesses process value archives and message archives.

[0057] Compared with the prior art, the innovations and advantages of this application are:

[0058] (1) This application is based on the SINAMICS120 servo drag system to achieve high-precision tension control, uses Siemens S7-300 series PLC as the control core, establishes a PROFIBUS-DP field bus communication network, uses CPU317-2DP as the master station, and the field remote IO module and CU320 drive unit as the slave station. The industrial computer is used as the human-computer interaction medium. The normal operation of the entire production line is achieved by setting the tension and production speed. The tension is controlled by combining a floating roller and a high-sensitivity tension sensor. The high-precision servo system S120 is used as the drag to achieve high-precision tension control. The actual operation of the system shows that compared with the traditional tension control system, the system has stable tension control, high precision, stable production speed, and is human-machine friendly. It has the function of changing rolls without stopping the machine, which fully meets the requirements of continuous production of backplanes.

[0059] (2) The present application designs a tension control strategy for the solar cell backplane coating line, establishes a backplane coating line unwinding tension control model, a backplane coating line winding tension control model, a backplane coating line tension control model, a backplane coating line tension control model, and a tension control influencing factor model; proposes a tension control system architecture; designs the hardware and software design of the solar cell backplane coating line tension control system, including: tension control STEP7 programming software configuration, coating line tension STEP7 program design, coating line tension S120 hardware configuration, and communication between S7-300 and S120; implements the upper computer configuration design, improves the tension control level, and establishes a reliable solar backplane coating line process and equipment. During the coating process, the fluctuation of tension leads to uniform coating thickness, avoiding coating delamination and serious quality defects, and making the winding end surface smooth, thereby achieving stable and efficient tension control, avoiding the production of unqualified backplane products, and promoting the improvement of the quality of the backplane and even the entire solar cell.

[0060] (3) This application improves the solar back panel coating line process and equipment, establishes a key factor model for tension control in back panel coating, constructs a tension control scheme, uses a process PID controller based on the Siemens S120 servo system to adjust the tension of the coating line, and monitors the fluctuation of tension and speed in real time in the host computer, uses film storage to achieve non-stop roll change, and stabilizes tension control. After the solar back panel coating line adopts a servo tension control system, the tension is stable and uniform, and the equipment is simple and convenient to operate, with low error rate and low failure rate. The equipment can achieve zero maintenance, shorter operation time, higher accuracy, and stronger adaptability. At the same time, it can reduce material loss, and also improve equipment production capacity at high speeds. At the same time, the servo system using a common DC bus can effectively save energy, and has achieved good results in the actual production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is the structural diagram of the unwinding tension control system model for the backsheet coating line.

[0062] Figure 2 It is a schematic diagram of the winding taper tension control of the back panel coating line.

[0063] Figure 3 It is a structural diagram of the floating rod for the indirect tension detection of the floating roller.

[0064] Figure 4 It is the control block diagram of the tension of the rewinding and unwinding part.

[0065] Figure 5 It is the hardware structure block diagram of the control system.

[0066] Figure 6 This is the remote IO configuration diagram of the tension control STEP7 programming software.

[0067] Figure 7 It is the complete configuration diagram of the tension control STEP7 programming hardware.

[0068] Figure 8 It is the control flow chart of the production procedure of the backplane coating line.

[0069] Fig. 9 It is the unwinding and splicing flow chart of the tension control of the solar backsheet coating line. DETAILED DESCRIPTION

[0070] The following, in conjunction with the accompanying drawings, further describes the technical solution of the high-precision tension control system of the solar cell backplane coating line provided by the present application, so that those skilled in the art can better understand the present application and implement it.

[0071] On the solar backsheet coating line, tension control is the most important control system. The production process of solar backsheets includes constant tension unwinding, coating, drying, lamination, and finally variable tension winding. The change of tension has a great impact on product quality. When the substrate (raw material for producing solar backsheets) passes through the coating line, if the tension is too small, the backsheet substrate will be offset on the equipment, and may even be separated from the guide wheel, resulting in production failure; if the tension is too large, the material will be stretched and deformed, and the geometric dimensions will change. In more serious cases, the coil will break, resulting in production interruption. If the tension is seriously out of control, it may also pull the guide and damage the equipment; during the winding process, too small tension will cause the winding to be drawn into the air, the friction between the layers will be reduced, and the layers will slide, resulting in uneven winding and bamboo shoot-like defects. Excessive tension will cause wrinkles, bulges, star-shaped end faces and other defects in the winding; during coating, unstable tension control will lead to uneven coating thickness, stripes, de-coating and other defects, which seriously affect the quality of the backsheet. Therefore, a high-precision tension control system is the core control link of the solar backsheet coating line.

[0072] High-precision tension control is achieved based on the SINAMICS120 servo drag system. Siemens S7-300 series PLC is used as the control core, a PROFIBUS-DP fieldbus communication network is established, CPU317-2DP is used as the master station, the field remote IO module and CU320 drive unit are used as slave stations, and an industrial computer is used as the human-computer interaction medium. The normal operation of the entire production line is achieved by setting the tension and production speed. The tension is controlled by combining a floating roller and a high-sensitivity tension sensor. The high-precision servo system S120 is used as the drag to achieve high-precision tension control.

[0073] The actual operation of the system shows that compared with the traditional tension control system, this system has stable tension control, high precision, stable production speed, and is human-machine friendly and has the function of changing rolls without stopping, which can meet the continuous production requirements of backboards.

[0074] 1. Solar cell backsheet coating line tension control strategy

[0075] (I) Backsheet coating line unwinding tension control model

[0076] Unwinding tension control system model Figure 1 shown.

[0077] In the figure: Ts is the tension sensor, Tc is the tension transmitter, T is the transmission control system inverter, and M is the transmission motor;

[0078] Gearbox is the transmission system reduction box;

[0079] Calculation method: Set the production line running speed to V, unit m / s, and the diameter of the unwinding substrate to Φ, then the roll diameter calculation formula is:

[0080]

[0081] In the formula, I is the reduction ratio of the gearbox, n is the output speed of the motor, and D is the real-time calculated diameter;

[0082] Under normal circumstances, the roll diameter can be accurately calculated using Formula 1. However, when the unwinding curl tightness is abnormal, the measured value of the line speed does not match the actual value, and the diameter calculated using Formula 1 will have a deviation. Secondly, the tension control system adjusts the current of the motor to output the required torque, and adjusts the output force of the motor to indirectly adjust the tension on the substrate.

[0083] In actual industrial production, the stress of the unwinding part is relatively complicated, which is related to many factors such as the tension setting value. In order to simplify the model, it is known from practical experience that the preset tension should be relatively large, and the unwinding stress equation is established as follows:

[0084]

[0085] F r is the material die tension, i is the transmission ratio, r is the material roll radius, M e is the resistance torque generated by the AC motor, M f is the viscous friction torque, M0 is the dry friction torque, ω is the angular velocity of the roll, and J is the moment of inertia on the motor shaft;

[0086] The equivalent moment of inertia J of the material roll is composed of the axis moment of inertia J0 and the material moment of inertia J r Composition, the unwinding process, the unwinding diameter gradually decreases with time, J r It is also related to the unwinding radius, J r is a time variable, a function of the roll diameter r, r is a function of time t, J0 is a fixed value, the moment of inertia of the roll changes little in an instant, J w The influence on tension is not calculated, and in the uniform winding process, the viscous friction is considered to be a constant, and the force equation is simplified to:

[0087]

[0088] The unwinding diameter and angular velocity of unwinding are two aspects that interfere with the tension. The unwinding diameter is calculated based on the initial diameter and line speed. Speed ​​and tension influence each other. The production line speed is fixed, while the diameters of winding and unwinding are constantly increasing and decreasing. The control system calculates the corresponding motor angular velocity based on the line speed and diameter to control the tension to be stable.

[0089] (II) Backsheet coating line winding tension control model

[0090] The tension control of the backsheet coating line winding is taper tension control, such as Figure 2 .

[0091] As the winding diameter increases, the tension setting value decreases, and the actual tension value also gradually decreases with the setting value. When the machine needs to be wound, taper control needs to be set. At this time, the tension decreases linearly with the increase of the winding radius, so that the inner layer of the winding film on the winding shaft is wound tightly and the outer layer is wound loosely. The inward extrusion pressure of the outer layer will not damage the inner layer. The larger the taper coefficient, the greater the tension change with the change of the roll diameter. When the taper coefficient is 0, it is a constant tension control mode. In actual production, if the taper control is not ideal, the product will be wound sideways, uneven, loose, etc., which will affect the product quality and appearance.

[0092] The control task that needs to be completed in the system is to use formula 4 to complete the calculation of the dynamic winding diameter, and use formula 5 to calculate the dynamic radius of the winding:

[0093] V=×r Formula 4

[0094] V×τ=ω×r×τEquation 5

[0095] Where: V is the set speed of the entire line, r is the real-time winding diameter, τ is the time during the winding process, ω is the angular velocity of the winding motor (measured by the encoder at the tail of the winding motor). In addition, special matters such as rotational inertia compensation and friction compensation are added to improve the accuracy of speed control and meet the requirements of tension control.

[0096] (III) Backsheet coating line tension control model

[0097] According to the unwinding actuator, the unwinding tension is divided into passive unwinding and active unwinding. Passive unwinding adopts magnetic powder clutch or pneumatic brake, and active unwinding adopts AC variable frequency motor or AC servo motor.

[0098] The floating roller is used for indirect tension detection. The structure of the floating roller is as follows: Figure 3. When the tension is stable, the substrate tension and the thrust generated by the low-friction cylinder are balanced, so that the floating roller is in the central position. When the tension is unstable, the balance between the substrate tension and the cylinder force is broken, and the position of the floating wheel is offset. Driven by the connecting rod, the position change of the floating wheel is detected by the potentiometer and the absolute value encoder. The voltage analog signal of the potentiometer or the Gray code of the encoder is fed back to the PLC, and the PLC then transmits the digitized signal to the CU320 controller. Under the action of the PID controller, the speed of the unwinding shaft is adjusted to keep the floating wheel in the middle position at all times, while ensuring the stability of the substrate tension. Since the floating wheel itself is an energy storage mechanism, it has a buffering effect on the rapid changes in tension and speed. The floating roller system has high requirements for the cylinder, and the friction between the cylinder piston and the cylinder wall should be small. This case uses a low-friction cylinder produced by Fujikura Co., Ltd. of Japan.

[0099] The unwinding tension is set through the HMI, and the required pressure of the cylinder is calculated according to Tension (Kgf) = P*AFG, where P is the cylinder input pressure, A is the cross-sectional area of ​​the cylinder piston, F is the friction force of the cylinder itself, and G is the deadweight of the floating wheel.

[0100] The proportional valve detects the output air pressure and compares it with the set air pressure. If it is lower than the set value, the air supply solenoid valve opens, the exhaust solenoid valve closes, and the air source pressure enters. When the detected pressure is equal to the set value, both solenoid valves close and the pressure is maintained. Conversely, if the output air pressure is higher than the set value, the exhaust solenoid valve opens to exhaust and reduce the pressure. The proportional valve outputs a stable air pressure by switching the two solenoid valves.

[0101] (IV) Model of factors affecting tension control

[0102] In the solar backsheet coating process, if the tension is properly controlled, the coating thickness and appearance can be effectively controlled. However, in the actual production process, there are many interfering factors, which makes the tension control system complicated. A model of factors affecting tension control is established:

[0103] 1) During the reeling and unwinding process, the diameter of the reel changes continuously, and the change in diameter causes the change in tension. If the output torque of the motor remains unchanged and the diameter decreases, the tension will increase. On the contrary, if the diameter increases, the tension will decrease.

[0104] 2) When the machining accuracy and assembly error of the various components of the coating line, the mounting base, the side wall panel, and the guide wheel do not meet the design requirements, the flatness and straightness of the base assembly, the verticality of the wall panel, the parallelism and horizontality of the guide wheel, the roundness of the guide roller, the dynamic and static balance, and the bearing installation accuracy affect the uniformity of the tension;

[0105] 3) The quality of the substrate affects the stability of the tension. The uneven thickness of the substrate leads to bulging, and the linearity of the substrate is not good. When the sheet path is long, it causes serpentine movement. The quality of the substrate is eccentric, resulting in insufficient roundness, and a loose and tight phenomenon during unwinding.

[0106] 4) During the process of automatic film splicing without stopping the coating line, the turning of the turning frame and the switching of the reel and the film storage will produce a large tension change. The higher the running speed of the coating line, the greater the tension fluctuation range;

[0107] 5) During the process of raising and lowering the coating line speed, the asynchrony of each dragging point causes the fluctuation of tension;

[0108] 6) During the drying process, the hot dry air blows on the back plate, causing the sheet path to shake, thus affecting the tension;

[0109] 7) For some materials with a large elastic modulus, the tension setting value is too large, causing the substrate to be stretched, or during the drying process, high temperature causes the substrate to shrink, which causes tension changes.

[0110] Among the above factors, changes in the diameter of the reel, non-stop splicing, and the speed increase and decrease processes have the greatest impact on tension fluctuations.

[0111] 2. Tension control system architecture

[0112] In the solar backplane coating line, there is only one reference speed point. According to the position of the pull-tab device, the tension section of the entire coating line is divided into several areas. The tension division includes the following sections: unwinding section, unwinding storage section, compound section, winding storage section and winding section. Floating wheels + tension sensors are used for tension control in unwinding and winding, and tension sensors are set in other sections to detect tension changes.

[0113] The unwinding part uses constant tension unwinding, and the rewinding part uses conical rewinding. The position of the floating spoke is fed back to the controller, and the speed adjustment value of the motor is calculated. The motor speed is controlled by the S120 motor module. The drag motor has an encoder, which feeds back the actual speed of the motor to the motor module to achieve a closed motor speed loop. The control block diagram of the tension of the unwinding and rewinding part is shown in the figure. Figure 4 .

[0114] During the unwinding and winding process, the given speed calculation of the motor requires the reel diameter data. The reel diameter calculation adopts the proximity sensor method. The proximity sensor is installed near the reel. The proximity sensor detects the rotation of the reel. When the initial diameter and the thickness of the coil are known, the thickness is subtracted by 2 times the thickness of the coil for each rotation to obtain the reel diameter.

[0115] 3. Hardware design of tension control system for solar backsheet coating line

[0116] According to the production process of solar back panel coating line, an electrical control system is established, including core controller PLC, coating line drag servo motor module, industrial computer and touch screen and other line connections.

[0117] The system hardware includes: upper industrial computer, touch screen, PLC master station, local analog expansion module, remote IO substation, MM440 inverter substation and CU320 servo control module substation. Figure 5 It is the hardware structure block diagram of the control system.

[0118] Among them, PLC realizes logic control, analog-to-digital conversion, data processing, and communication. The analog expansion module realizes the collection of tension and floating spoke position data, and the air pressure setting of the electric proportional valve. The remote IO is distributed on site to control various buttons and signal indications. CU320 is the controller of the traction system, which controls the motor module to realize speed control. The industrial computer and the on-site touch screen serve as the human-computer interaction interface to realize the input and monitoring of various parameters.

[0119] 4. Software design of tension control system for solar backsheet coating line

[0120] (I) Tension control STEP7 programming software configuration

[0121] The coating line tension control system adopts PROFIBUS-DP bus control network. First, use STEP7 programming software to create the network and configure the hardware. After the hardware configuration is completed, programming design is carried out. A system that is exactly the same as the actual hardware system is generated in STEP7 software. The configuration of the hardware part requires the establishment of a project, the configuration of the rack, the configuration of the power module, the selection of the CPU model, the digital input and output module, the analog input and output module, and the creation of the PROFIBUS-DP bus network. The master station and slave station of the network need to be created, and the station address and baud rate information of each station in the network need to be set.

[0122] Configuration of the master station: Based on STEP7 programming software, create an empty project, insert the system master station S7-300 station, open the hardware configuration interface, right-click to place the rack, power supply, CPU and input and output modules. The CPU has two bus ports, one MPI / DP is set as the DP port, which is used to connect the remote IO module. The communication rate is generally set to 1.5Mbps. The other port is a pure PROFIBUS-DP port, which is used to communicate with the servo control system. The communication rate is set to 6Mbps;

[0123] Continue to insert other required modules into the rack, SM321, SM322 digital input and output modules, SM331 and SM332 analog input and output modules, and perform I0 addressing.

[0124] After the PROFIBUS-DP bus is established, the DP substation is inserted. The temperature control of the drying oven adopts ET20OM distributed I0. The temperature control slave uses IM153-1 and FM355-2C temperature control modules to complete the collection of the oven temperature and the control of the pneumatic regulating valve, so that the temperature in the drying oven is stable around the set value ±2℃;

[0125] The on-site operation of the coating line rewinding and unwinding adopts the SMARTI / 0 series intelligent slave station, which is connected to the DP bus by setting the GSD file. The SMARTI / 0 intelligent slave station models include 16-point digital input module GPL-D22A / C, 32-point digital input module GPL-D224 / C, transistor 16-point digital output module GPL-TR22A / B / C, and transistor 32-point digital output module GPL-TR24A / B / C. Configuration as follows Figure 6 shown.

[0126] After the remote I0 bus is set up, you need to continue to configure the driveDP bus. Use the SINAMICSS120 drag system, with a total of 26 drag points. Each CU320 control unit can control up to 6 servos, so a total of 5 CU320s are needed. In the hardware directory on the right side of the configuration interface, open the PROFIBUS-DP directory, find the S120CU320 in the SINAMICSS120 subdirectory, drag it to the DRIVEDP bus, and set the bus address. Enter the version number of the CU320 in the pop-up property menu, and make detailed settings in the DP slave property interface. Configure the corresponding message for each motor module. You can choose the standard message provided by Siemens or use a custom message. The screen after the hardware configuration is completed is as follows: Figure 7 .

[0127] (II) STEP7 programming of coating line tension

[0128] For the entire backplane coating line, according to the production process, the procedure flow is as follows Figure 8 shown.

[0129] For the entire coating line, the tension is pre-established at startup. The process is as follows: the controller detects faults and alarm signals of the entire line. If there is an alarm, it cannot be started. If the floating wheel is not in the middle position, the rewinding and unwinding motor will unwind or retract, tightening the film path and floating back to the middle position. The film storage working position detection relies on proximity switches. Four proximity switches are set for the working position, super-high limit, super-low limit, and in-place limit. If it is detected that the film storage is not in the working position, the film storage will run to the working position before starting. After the above confirmation is completed, the coating line starts to be linked. During the linkage process, the tension sensor and the floating wheel detect the tension change and feed it back to the PLC and CU320. The motor speed is controlled by the PID controller output to stabilize the tension.

[0130] The solar back panel coating line is semi-automatic splicing, which realizes non-stop continuous production and ensures the continuity of production. It is also of great benefit to the stability of coating quality. Semi-automatic splicing has the advantages of simple structure, convenient operation, low labor intensity, high splicing efficiency, low failure rate and error rate, and less loss at the end of the film.

[0131] For the unwinding part, it is composed of double-station unwinding, film storage rack and standby device. In the continuous production of backboard, one unwinding station unwinds normally, and the other unwinding station is in standby state. The film head has been fixed on the standby table with tape in advance, and the film storage rack is in a high position. The reserve film path is about 30 meters. When the unwinding station needs to splice the film, the unwinding shaft and the film pulling pressure wheel stop, and the film storage rack takes over the unwinding work and starts unloading. When the joint is connected, the standby unwinding station unwinds normally, and the film storage stops. After a delay, the film storage rack automatically returns to the high working position, and the previous unwinding station is used as a standby station. The splicing process is as follows Fig. 9 .

[0132] When winding and splicing, one of the double-station winding shafts is wound normally, and the other winding shaft core is pre-sticked with tape. The flip frame is flipped to the appropriate position in advance. When the unwinding joint reaches the winding, the splicing button is pressed, the winding shaft and the pull tab stop rotating, the winding storage starts to rise, the storage path, the substrate is manually broken and then bonded to the shaft core and smoothed firmly, the splicing button is pressed again, the splicing is completed, the storage stops, the winding shaft and the pull tab restart to start the winding process, and after the tension is stable, the storage returns to the working position;

[0133] Divide the program into several subroutines. Each subroutine block contains logical instructions for some devices and tasks. The instructions in the organization block determine whether to call the associated control program module. At the same time, similar or related functions are classified and written into general modules. When such programs are needed, they can be called directly. Set the OB organization block, FC function, FB function block, SFC system function and DB data block respectively.

[0134] (III) Coating line tension S120 hardware configuration

[0135] Connect S120 via DP communication card or RS232 serial port, open Starter software, create a new project, and start configuring the drive parameters:

[0136] Step 1: Insert the drive unit;

[0137] Step 2, select the type of CU320 drive;

[0138] Step 3: Select the version number of the device, which should be consistent with the CF card version number;

[0139] Step 4, select the communication method between PC and driver, and set the IP address if there is an Ethernet interface CBE;

[0140] Step 5: Set the DP address of the drive, which is consistent with the DIP switch on the CU320.

[0141] (IV) Communication between S7-300 and S120

[0142] PROFIBUS-DP is used for communication between S7-300 and SINAMICSS120. PROFIBUS-DP bus performs periodic and non-periodic data communication. S7-300 sends CTW 1 control word and NSETP_B (main set value) to the servo drive through PROFIBUS periodic communication. At the same time, S7-300 system function blocks SFC58 / SFC59 are used to perform non-periodic data exchange and read or write parameters to the drive.

[0143] PLC controls the servo drive system through messages. The messages are based on the PROFIDRIVER protocol. The PROFIDRIVER protocol predefines the functions of each status word and control word of the received and sent PPO messages. The servo controller receives the control signal through the message, and the various states of the servo controller are also fed back to the PLC through the message. The length of the message reception and transmission cycle is determined by the hardware. The servo system communicates periodically through PROFIBUS-DP to improve accuracy. The controller selects the message: SIEMENS telegram 370PZD 1 / 1;

[0144] Receive words: status word (ZSTW1), AKTSATZ (position block status), POSZSW (position status word), ZSW2 (status word 2), MELDW (message word), XSIP (actual position value); send words: control word (STW1), control word 2 (STw2), POSSTW (position control word), SAYZANW (position block selection), MDIPOS (MDI position), OVER (percentage), MDIVEL (MDI speed), MDIACC (MDI acceleration), MDIDCC (MDI deceleration), MDIMODE (MDI mode);

[0145] In SIMOTION SCOUT debugging, the message configured in the PLC must be the same as the communication message of the servo axis and controller. After configuration, write the communication program with the servo driver in STEP7. First read the status of the servo through the DRIVER-CLIQ line, and then let the servo execute the command through the control word.

[0146] Use S7-300's SFC14 and SF15 to read and write SINAMICS S20 (read the status in the servo controller and write control commands to the servo controller), use communication to control S120, SF14 reads the S120 status, it occupies 7 PZDs (process data area, used for control and detection), first fill in the hardware address of 5120 in LADDR, 256 corresponds to hexadecimal W#16#100 and fill in the data block (DB) address in RECORD, P#DBXO.0BYTE 14, these addresses are used to allocate the process data PZD value read from SINAMICS S120, RETVAL represents the return value used to display fault information; SFC15 performs a write operation, which is to send a command word to the servo controller, fill in the address in the 5120 hardware in LADDER, and fill in the set DB address P#DB 1.DBX0.0 BYTE in RECORD. 24, that is, 24 bytes starting from DB1.DBX0.0, assign these addresses to the PZD values ​​written in 5120, and RETVAL indicates the return value used to display fault information.

[0147] 5. Host computer configuration design

[0148] The upper computer directly issues control commands to the PC, which displays the dynamic changes of various signals in real time on the screen, including hydraulic pressure, temperature, and water level. The instructions issued by the upper computer are transmitted to the lower computer, which then translates the commands into corresponding timing signals to control various equipment to complete production tasks.

[0149] The user uses the editor in the configuration software to create a new WINCC project. The WINCC editor saves this information in the CS database. During system operation, the operating system software retrieves and executes the project data information from the configuration library. The data in the current process is temporarily stored in the RT database, that is, the operating system database.

[0150] Then WINCC and the automation system rely on communication drivers or channels to complete communication. The channel collects the process values ​​of all running system components, then reads the process variables from the automation system, and inputs the new changed values ​​into the automation system when necessary.

[0151] The archiving system stores the process values ​​in the process archive and uses the required archived process values ​​to display the temporary progress of the process values ​​in the online trend control or online table control;

[0152] A single process value is monitored through an alarm record. Once the set limit value is exceeded, the alarm record generates an alarm message and displays it in the alarm control. The alarm record accepts the operator's confirmation and manages the message. The alarm record saves all messages in the message archive.

[0153] Finally, the reporting system produces documentation of the system process within the preset time according to requirements, accesses process value archives and message archives.

[0154] This application improves the solar backplane coating line process and equipment, establishes a key factor model of tension control in backplane coating, constructs a tension control scheme, and uses a process PID controller based on the Siemens S120 servo system to adjust the tension of the coating line. The tension and speed fluctuations are monitored in real time on the host computer, and the film storage is used to achieve non-stop roll change and stabilize the tension control. After the solar backplane coating line adopts the servo tension control system, the equipment has simple and convenient operation, low error rate and low failure rate, the equipment can achieve zero maintenance, and at the same time can reduce material loss. The equipment capacity is also improved at high speeds. At the same time, the servo system with a common DC bus can effectively save energy and has achieved good results in the actual production process.

Claims

1. High-precision tension control system for solar cell backsheet coating line, characterized in that: Based on SINAMICS120 servo drag system to achieve high-precision tension control, Siemens S7-300 series PLC is used as the control core, PROFIBUS-DP field bus communication network is established, CPU317-2DP is used as the master station, field remote IO module and CU320 drive unit are used as slave stations, industrial computer is used as human-computer interaction medium, and the normal operation of the entire production line is achieved by setting tension and production speed. Tension control is carried out by combining floating roller and high-sensitivity tension sensor, and high-precision servo system S120 is used as drag to achieve high-precision tension control, including: 1) Solar cell backplane coating line tension control strategy, including: backplane coating line unwinding tension control model, backplane coating line winding tension control model, backplane coating line tension control model, backplane coating line tension control model, tension control influencing factor model; 2) Tension control system architecture; 3) Hardware design of solar back panel coating line tension control system; 4) Solar back panel coating line tension control system software design, including: tension control STEP7 programming software configuration, coating line tension STEP7 program design, coating line tension S120 hardware configuration, communication between S7-300 and S120; 5) Host computer configuration design; This application improves the solar backplane coating line process and equipment, establishes a key factor model for tension control in backplane coating, constructs a tension control scheme, uses a process PID controller based on the S120 servo system to adjust the tension of the coating line, and monitors the fluctuations of tension and speed in real time in the host computer, and uses storage to achieve non-stop roll change and stabilize tension control.

2. According to the high-precision tension control system of the solar cell backsheet coating line of claim 1, it is characterized in that: Unwinding tension control model of backsheet coating line: Ts is the tension sensor, Tc is the tension transmitter, T is the transmission control system inverter, M is the transmission motor; Gearbox is the transmission system reducer; Calculation method: Set the production line running speed to V, unit m / s, and the diameter of the unwinding substrate to Φ, then the coil diameter calculation formula is: In the formula, I is the reduction ratio of the gearbox, n is the output speed of the motor, and D is the real-time calculated diameter; Under normal circumstances, the roll diameter is accurately calculated using formula 1. The tension control system adjusts the current of the motor to output the required torque, and adjusts the output force of the motor to indirectly adjust the tension on the substrate. According to practical experience, the preset tension should be relatively large, and the unwinding force equation is established as follows: F r is the tension of the material mold, i is the transmission ratio, r is the radius of the material roll, M e is the resistance torque generated by the AC motor, M f is the viscous friction torque, M0 is the dry friction torque, ω is the angular velocity of the roll, and J is the moment of inertia on the motor shaft; The equivalent moment of inertia J of the material roll is composed of the axis moment of inertia J0 and the material moment of inertia J r Composition, the unwinding process, the unwinding diameter gradually decreases with time, J r It is also related to the unwinding radius, J r is a time variable, a function of the roll diameter r, r is a function of time t, J0 is a fixed value, the moment of inertia of the roll changes little in an instant, J w The influence on tension is not calculated, and in the uniform winding process, the viscous friction is considered to be a constant, and the force equation is simplified to: The unwinding diameter and angular velocity of unwinding are two aspects that interfere with the tension. The unwinding diameter is calculated based on the initial diameter and line speed. Speed ​​and tension influence each other. The production line speed is fixed, while the diameters of winding and unwinding are constantly increasing and decreasing. The control system calculates the corresponding motor angular velocity based on the line speed and diameter to control the tension to be stable.

3. According to the high-precision tension control system of the solar cell backsheet coating line of claim 1, it is characterized in that: Backsheet coating line winding tension control model: The control task that needs to be completed in the system is to use formula 4 to complete the calculation of the dynamic roll diameter, and use formula 5 to calculate the dynamic radius of the winding: V=ω×r Formula 4 V×τ=ω×r×τ Formula 5 Where: V is the set speed of the entire line, r is the real-time winding diameter, τ is the time during the winding process, ω is the angular velocity of the winding motor. In addition, special matters such as rotational inertia compensation and friction compensation are added to improve the accuracy of speed control and meet the tension control requirements.

4. According to the high-precision tension control system of the solar cell backsheet coating line of claim 1, it is characterized in that: Backsheet coating line tension control model: According to the unwinding actuator, the unwinding tension is divided into passive unwinding and active unwinding. Passive unwinding adopts magnetic powder clutch or pneumatic brake, and active unwinding adopts AC variable frequency motor or AC servo motor; The floating roller indirect tension detection is adopted. When the tension is stable, the substrate tension and the thrust generated by the low-friction cylinder are balanced, so that the floating roller is in the central position. When the tension is unstable, the balance between the substrate tension and the cylinder force is broken, and the position of the floating roller is offset. Driven by the connecting rod, the position change of the floating roller is detected by the potentiometer and the absolute value encoder. The voltage analog signal of the potentiometer or the Gray code of the encoder is fed back to the PLC, and the PLC then transmits the digitized signal to the CU320 controller. Under the action of the PID controller, the speed of the unwinding shaft is adjusted to keep the floating roller in the middle position at all times, while ensuring the stability of the substrate tension. The unwinding tension is set through HMI, and the required pressure of the cylinder is calculated according to Tension (Kgf) = P*AFG, where P is the cylinder input pressure, A is the cross-sectional area of ​​the cylinder piston, F is the friction force of the cylinder itself, and G is the deadweight of the floating wheel; The proportional valve detects the output air pressure and compares it with the set air pressure. If it is lower than the set value, the air supply solenoid valve opens, the exhaust solenoid valve closes, and the air source pressure enters. When the detected pressure is equal to the set value, both solenoid valves close and the pressure is maintained. Conversely, if the output air pressure is higher than the set value, the exhaust solenoid valve opens to exhaust and reduce the pressure. The proportional valve outputs a stable air pressure by switching the two solenoid valves.

5. According to the solar cell backsheet coating line high-precision tension control system of claim 1, it is characterized in that: Tension control system architecture: In the solar backsheet coating line, there is only one reference speed point. According to the position of the pull-tab device, the tension section of the entire coating line is divided into several areas. The tension division includes the following sections: unwinding section, unwinding storage section, compound section, winding storage section and winding section. The floating wheel + tension sensor is used for tension control in the unwinding and winding process, and tension sensors are set in other sections to detect tension changes. The unwinding part adopts constant tension unwinding, and the rewinding part adopts conical rewinding. The position of the floating spoke is fed back to the controller, and the speed adjustment value of the motor is obtained through calculation. The motor speed is controlled by the S120 motor module. The drag motor is equipped with an encoder, which feeds back the actual speed of the motor to the motor module to realize the closed loop of the motor speed loop. During the unwinding and winding process, the given speed calculation of the motor requires the reel diameter data. The reel diameter calculation adopts the proximity sensor method. The proximity sensor is installed near the reel. The proximity sensor detects the rotation of the reel. When the initial diameter and the thickness of the coil are known, the thickness is subtracted by 2 times the thickness of the coil for each rotation to obtain the reel diameter.

6. According to the solar cell backsheet coating line high-precision tension control system of claim 1, it is characterized in that: Hardware design of solar back panel coating line tension control system: Establish electrical control system, including core controller PLC, coating line drag servo motor module, industrial computer and touch screen and other line connections; The system hardware includes: upper industrial computer, touch screen, PLC master station, local analog expansion module, remote IO substation, MM440 inverter substation and CU320 servo control module substation: Among them, PLC realizes logic control, analog-to-digital conversion, data processing, and communication. The analog expansion module realizes the collection of tension and floating spoke position data, and the air pressure setting of the electric proportional valve. The remote IO is distributed on site to control various buttons and signal indications. CU320 is the controller of the traction system, which controls the motor module to realize speed control. The industrial computer and the on-site touch screen serve as the human-computer interaction interface to realize the input and monitoring of various parameters.

7. The high-precision tension control system for the solar cell backsheet coating line according to claim 1, characterized in that: Tension control STEP7 programming software configuration: The coating line tension control system adopts PROFIBUS-DP bus control network. First, use STEP7 programming software to create the network and configure the hardware. After the hardware configuration is completed, perform programming design. Generate a system that is exactly the same as the actual hardware system in STEP7 software. The configuration of the hardware part requires the establishment of a project, configuration of the rack, configuration of the power module, selection of the CPU model, digital input and output module, analog input and output module. When creating the PROFIBUS-DP bus network, it is necessary to create the master station and slave station of the network, set the station address and baud rate information of each station in the network; The on-site operation of the coating line rewinding and unwinding adopts the SMARTI / 0 series intelligent slave station, which is connected to the DP bus by setting the GSD file. The models of the SMARTI / 0 intelligent slave station include 16-point digital input module GPL-D22A / C, 32-point digital input module GPL-D224 / C, transistor 16-point digital output module GPL-TR22A / B / C, and transistor 32-point digital output module GPL-TR24A / B / C. After the remote I0 bus settings are completed, you need to continue to configure the driveDP bus. Using the SINAMICSS120 drag system, there are a total of 26 drag points on the entire line. Each CU320 control unit controls up to 6 servos, and a total of 5 CU320s are required. In the hardware directory on the right side of the configuration interface, open the PROFIBUS-DP directory, find the S120CU320 under the SINAMICSS120 subdirectory, drag it to the DRIVEDP bus, and set the bus address. Enter the version number of the CU320 in the pop-up property menu, make detailed settings in the DP slave property interface, and configure the corresponding message for each motor module.

8. The high-precision tension control system for the solar cell backsheet coating line according to claim 1, characterized in that: Coating line tension STEP7 programming: For the entire coating line, the tension is pre-established at startup. The process is as follows: the controller detects faults and alarm signals on the entire line. If there is an alarm, it cannot be started. If the floating wheel is not in the middle position, the rewinding and unwinding motor will unwind or retract, tightening the film path and floating back to the middle position. The film storage working position detection relies on the proximity switch. Set the working position, super high limit, super low limit, and in-place limit four proximity switches. If it is detected that the film storage is not in the working position, the film storage will run to the working position before starting; after the above confirmation is completed, the coating line starts to be linked. During the linkage process, the tension sensor and the floating wheel detect the tension change and feedback to the PLC and CU320. The motor speed is controlled by the PID controller output to make the tension stable; For the unwinding part, it is composed of a double-station unwinding, a film storage rack and a film standby device. In the continuous production of the backplane, one unwinding station unwinds normally, and the other unwinding station is in standby state. The film head has been fixed on the standby table with tape in advance, and the film storage rack is in a high position. The reserve film path is about 30 meters. When the unwinding station needs to splice the film, the unwinding shaft and the film pulling pressure wheel stop, and the film storage rack takes over the unwinding work and starts unloading. When the joint is connected, the standby unwinding station unwinds normally, and the film storage stops. After a delay, the film storage rack automatically returns to the high working position, and the previous unwinding station is used as a standby station. When winding and splicing the film, one of the double-station winding shafts will rewind normally, and the other winding shaft will have tape pre-affixed on its core. The flip frame will be flipped to the appropriate position in advance, and when the unwinding joint reaches the rewinding point, the splicing button will be pressed, the winding shaft and the pull tab will stop rotating, the winding film storage will start to rise, the film storage path will be stored, the substrate will be manually broken and then bonded to the shaft core and smoothed firmly, the splicing button will be pressed again, the film splicing will be completed, the film storage will stop, the winding shaft and the pull tab will restart to start the winding process, and after the tension is stable, the film storage will return to the working position.

9. The high-precision tension control system for the solar cell backsheet coating line according to claim 1, characterized in that: Communication between S7-300 and S120: PROFIBUS-DP is used for communication between S7-300 and SINAMICSS120. PROFIBUS-DP bus is used for periodic and non-periodic data communication. S7-300 sends CTW 1 control word and NSETP_B to the servo drive through PROFIBUS periodic communication. At the same time, S7-300 system function blocks SFC58 / SFC59 are used for non-periodic data exchange to read or write parameters to the drive. PLC controls the servo drive system through messages. The messages are based on the PROFIDRIVER protocol. The PROFIDRIVER protocol predefines the functions of each status word and control word of the received and sent PPO messages. The servo controller receives the control signal through the message, and the various states of the servo controller are also fed back to the PLC through the message. The length of the message reception and transmission cycle is determined by the hardware. The servo system communicates periodically through PROFIBUS-DP to improve accuracy. The controller selects the message: SIEMENS telegram 370PZD 1 / 1; Use S7-300's SFC14 and SF15 to read and write SINAMICS S20, use communication to control S120, SF14 reads S120 status, it occupies 7 PZDs, first fill in the hardware address of 5120 in LADDR, 256 corresponds to hexadecimal W#16#100 and fill in the data block address in RECORD, P#DBXO.0BYTE 14, these addresses are used to allocate the process data PZD value read from SINAMICS S120, RETVAL indicates that the return value is used to display fault information; SFC15 performs a write operation, which sends a command word to the servo controller, fills in the address in the 5120 hardware in LADDER, fills in the set DB address P#DB 1.DBX0.0 BYTE 24 in RECORD, that is, 24 bytes starting from DB1.DBX0.0, and allocates these addresses to the PZD value written in 5120, RETVAL indicates that the return value is used to display fault information.

10. The high-precision tension control system for the solar cell backsheet coating line according to claim 1, characterized in that: Upper computer configuration design: The upper computer directly issues control commands to the PC, which displays the dynamic changes of various signals in real time on the screen, including hydraulic pressure, temperature, and water level. The instructions issued by the upper computer are transmitted to the lower computer, which then translates the commands into corresponding timing signals to control various equipment to complete production tasks; The user uses the editor in the configuration software to create a new WINCC project. The WINCC editor saves this information in the CS database. During the system operation, the runtime software calls out these project data information from the configuration library and executes them. The data in the current process is temporarily stored in the RT database, that is, the runtime database. Then, WINCC and the automation system communicate with each other through a communication driver or channel. The channel collects the process values ​​of all running system components, reads the process variables from the automation system, and inputs the new change values ​​into the automation system when necessary. The archiving system stores the process values ​​in the process archive, and uses the archived process values ​​to display the temporary progress of the process values ​​in the online trend control or online table control; individual process values ​​are monitored through alarm records. Once the set limit value is exceeded, the alarm record generates an alarm message and displays it in the alarm control. The alarm record accepts the operator's confirmation and manages the message. The alarm record saves all messages in the message archive; Finally, the reporting system produces documentation of the system process within the preset time according to requirements, accesses process value archives and message archives.

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