Float glass production line cold end roller way transmission system

Abstract

The invention discloses a cold end roller way conveying system for a float glass production line, and relates to the technical field of conveying for float glass production. A direct drive roller with a built-in permanent magnet synchronous servo motor is adopted, and an EtherCAT distributed bus is connected with a high-speed PLC, a servo driver and a multi-sensor array. PLC operation model predictive control is carried out, a speed-position closed loop, a torque-tension closed loop, a temperature compensation closed loop and a vibration suppression closed loop are built, and stable transmission with the linear speed of 80 m.min <-1 > and the one-ton-level heavy load under the condition of 150-450 DEG C is achieved. A ceramic-PFA coating and a heat-resisting alloy material remarkably prolong the service life of the roller, and self-calibration, differential pulling distance and buffering logic ensure that cutting and stacking are free of impact. Compared with a traditional centralized shaft system, the occupied area is reduced, the outage rate is reduced, and the productivity is doubled.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission for float glass production, and specifically to a cold-end roller table transmission system for a float glass production line. Background Art

[0002] In existing intelligent heat treatment production lines, the cold-end roller table transmission devices for float glass usually still adopt a centralized long main shaft or a chain / belt drive structure: one or a few motors distribute power to more than a dozen rollers through universal shafts, sprockets or synchronous belts. Due to the long power chain, large transmission clearance and poor synchronism between rollers, slipping, torsional vibration and speed drift are likely to occur at high linear speeds. Traditional rollers mostly have a carbon steel body with an ordinary chromium plating layer on the outside, and their heat resistance and anti-adhesion ability are limited. When facing thick and large glass plates with residual temperature from the outlet of the heat treatment furnace, coating cracking, glass scratching and dust adhesion are likely to occur. Most control levels use single-loop variable frequency speed regulation or simple PID, lacking multi-dimensional real-time feedback on speed, torque, temperature and vibration, resulting in problems such as unstable pulling distance during cutting, lag in stacking rhythm coordination, and cumulative resonance damage. To suppress faults, the production line often has to reduce speed, and the overall efficiency is difficult to exceed 40m·min -1 ; at the same time, the frame is long, occupies a large area, and maintenance depends on manual fastening and lubrication, and line shutdown for maintenance is frequent, seriously restricting the large-scale and low-cost production of high-end float glass. Summary of the Invention

[0003] To overcome the above defects of the existing technology, the present invention provides the following technical solution: A cold-end roller table transmission system for a float glass production line, including a number of directly driven rollers arranged in parallel. Inside each directly driven roller, a permanent magnet synchronous servo motor, a high-temperature planetary reducer and a digital encoder are integrally arranged coaxially; a ceramic-PFA composite anti-adhesion coating is provided on the surface of the directly driven roller; the directly driven roller is connected to the EtherCAT bus through a quick-plug electrical interface to form a distributed drive network; it also includes a high-speed PLC, a number of servo drivers and multi-sensor nodes. The PLC communicates with the servo drivers and sensor nodes through the EtherCAT high-speed field bus; the PLC runs a model predictive control algorithm and constructs a speed-position closed loop, a torque-tension closed loop, a temperature compensation closed loop and a vibration suppression closed loop, and comprehensively controls the rotation speed and phase of each directly driven roller to achieve high-speed, heavy-load and compact transmission of float glass in an environment of 150°C - 450°C.

[0004] Preferably, the hardness of the ceramic-PFA composite coating is ≥8H, the thickness is 80 - 150μm, and the friction coefficient is ≤0.05.

[0005] Preferably, the current loop bandwidth of the servo driver is ≥2kHz, and the position loop bandwidth is ≥500Hz.

[0006] Preferably, the multi-sensor node includes an optoelectronic opposed sensor, a laser ranging sensor, an infrared temperature sensor, and a three-axis vibration sensor. Each sensor node is connected to the PLC through an EtherCAT-I / O module, and the communication cycle is ≤1 ms;

[0007] The quadratic programming solver with a rolling optimization step size of 10 - 20 ms and a prediction time domain of 100 - 200 ms is adopted in the model predictive control algorithm built in the PLC.

[0008] Preferably, when the system starts up, the PLC executes an automatic zero calibration process, including rotating the direct drive roller at a low speed and recording the zero bias of the encoder, and calibrating the thresholds of each optoelectronic opposed sensor through a standard calibration plate.

[0009] Preferably, it further includes a compact rack with a length of 1.2 m. The cross beam also serves as a servo driver, a heat dissipation channel, and a cable tray. A transparent heat-resistant protective cover is provided outside the rack.

[0010] Preferably, when the PLC receives the cutting completion signal, it controls the direct drive rollers in the pre-cut section and the post-cut section to speed up and slow down respectively through the section differential speed algorithm to form a glass plate spacing of 150 - 250 mm.

[0011] Preferably, when the busy signal of the stacking manipulator is set, the PLC automatically reduces the linear speed of the last section direct drive roller to ≤0.2 m·s -1 and maintains the linear speed of the front section direct drive roller ≥0.8 m·s -1 to form a buffer zone of 2 - 3 m.

[0012] Preferably, when the vibration sensor monitors that the resonance amplitudes of the 1st - 3rd order structures exceed the threshold, the PLC adjusts the phase difference between adjacent direct drive rollers by 2° - 5° through phase perturbation to suppress vibration.

[0013] 10. A closed-loop control method for the cold-end roller conveyor system of a float glass production line, comprising the following steps: S1. Power-on self-calibration, where the PLC controls all direct drive rollers to rotate at low speed idly and collects encoder data to calibrate the zero point; S2. Refresh the threshold of the photoelectric opposed sensor through a standard calibration plate, and record the baseline values of the temperature sensor and the vibration sensor at the same time; S3. After the glass plate enters, the PLC calculates the optimal speed command sequence within the future prediction time domain based on the model predictive control algorithm, and issues it to each servo driver through the EtherCAT network; S4. Real-time collect multi-dimensional feedback quantities such as speed, position, torque, temperature, vibration, etc., respectively construct speed-position, torque-tension, temperature compensation, and vibration suppression closed loops and superimpose and correct the aforementioned speed commands; S5. When a cutting, stacking or fault signal is detected, the PLC calls a preset working condition sub-module, dynamically adjusts the speed curves of the direct drive rollers in each section, and performs rolling optimization through the model predictive control algorithm to achieve shock-free switching; S6. During no-load or production gaps, the PLC re-evaluates the model parameters with a recursive algorithm and performs online adaptive update of the system.

[0014] Preferably, the PLC is built-in with a model predictive control MPC unit, which takes the mathematical model of the glass plate movement as the prediction object and rolls and optimizes the speed sequence for the next N sampling periods.

[0015] Speed-position closed loop: Taking the optoelectronic / laser composite speed measurement as the main feedback, and correcting the roller speed in each area in real time;

[0016] Torque-tension closed loop: Taking the motor current and the glass-roller contact pressure as the feedback to balance the traction force;

[0017] Temperature compensation closed loop: Dynamically adjust the MPC model parameters according to the glass and ambient temperatures;

[0018] Vibration active suppression closed loop: Taking the vibration sensor signal as the feedback, and fine-tuning the phase difference between adjacent rollers in real time to counteract resonance.

[0019] The present invention has the following beneficial effects compared with the prior art: (1) The present invention adopts distributed direct drive rollers and an EtherCAT millisecond-level network, and realizes full-line virtual spindle synchronization under the support of the model predictive control algorithm. The no-load linear speed can reach 100 m·min -1 , and the full-load stability is 80 m·min -1 . Compared with the traditional 40 m·min -1The speed bottleneck is broken through, the single-line production capacity release is doubled, the rhythm from cutting to stacking is shortened by more than 30%, truly meeting the high-speed sheet output requirements of ultra-large float glass furnaces, and supporting more variety switches in the same workshop without building additional cold ends; (2) The direct drive rollers of the present invention adopt 17-4PH stainless steel cores, ceramic-PFA composite coatings and high-temperature planetary reducers. The torque margin of a single roller is increased by 40%. When the weight of a single sheet is one ton, there is no sagging or slipping; the coating hardness is ≥8H and the friction coefficient is ≤0.05, and it can operate in the hot end residual temperature range of 150–450°C for a long time without cracking or adhesion. Compared with traditional carbon steel chromium-plated rollers that are prone to failure after 300°C, the roll change and maintenance cycle of the equipment is extended, significantly reducing the downtime frequency and spare part costs; (3) The quadruple closed-loop real-time coupling of speed-position, torque-tension, temperature compensation and vibration suppression in the present invention collects and adjusts the roller speed and phase every 0.5 ms; within 0.8 s after cutting is completed, a spacing of 150–250 mm can be formed through section differential speed, and the dynamic error is ≤±1 mm; the resonance amplitude can be attenuated by more than 50% within 6 s after the vibration sensor is triggered. The multi-dimensional active control enables the ultra-thin large-size glass to be transported at high speed without jumping, scratching or hidden cracks, and the finished product rate is improved; (4) The shaftless drive and 1.2 m frame modular design of the present invention integrate the driver, heat dissipation and wiring, reducing the frame length by more than 30%; the quick plug-and-play electrical interface and hot pluggable roller design shorten the roller replacement time; the self-calibration and multi-sensor redundant mutual inspection change the regular inspection from daily to weekly, reducing the annual maintenance man-hours and greatly increasing the output value per unit area; (5) The start-up self-inspection - recursive self-calibration mechanism of the present invention completes the zero-point drift compensation in a short time; faults such as sensor failure and driver overheating trigger zone speed reduction or bypass transfer through the rule library and threshold judgment, and the degraded operation without production interruption can be realized; the emergency stop braking - data backtracking - fault self-diagnosis link ensures that all rollers are stopped and key parameters are latched within a short time, providing an accurate basis for retrospective analysis afterwards and reducing the annual average fault downtime rate of the whole line. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic process flow diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0022] The present invention provides a cold-end roller conveyor system for a float glass production line, which includes a number of directly-driven rollers arranged in parallel. Inside each directly-driven roller, a permanent magnet synchronous servo motor, a high-temperature planetary reducer, and a digital encoder are integrally arranged coaxially; a ceramic-PFA composite anti-adhesion coating is provided on the surface of the directly-driven roller; the directly-driven roller is connected to the EtherCAT bus through a quick-plug electrical interface to form a distributed drive network; it also includes a high-speed PLC, a number of servo drivers, and multi-sensor nodes. The PLC communicates with the servo drivers and sensor nodes through the EtherCAT high-speed fieldbus; the PLC runs a model predictive control algorithm and constructs a speed-position closed loop, a torque-tension closed loop, a temperature compensation closed loop, and a vibration suppression closed loop to comprehensively control the rotation speed and phase of each directly-driven roller, so as to achieve high-speed, heavy-load, and compact transmission of float glass in an environment of 150°C - 450°C.

[0023] The hardness of the ceramic-PFA composite coating is ≥8H, the thickness is 80 - 150μm, and the friction coefficient is ≤0.05. The current loop bandwidth of the servo driver is ≥2kHz, and the position loop bandwidth is ≥500Hz. The multi-sensor nodes include photoelectric opposed sensors, laser ranging sensors, infrared temperature sensors, and three-axis vibration sensors. Each sensor node is connected to the PLC through an EtherCAT-I / O module, and the communication cycle is ≤1ms; the model predictive control algorithm built in the PLC uses a quadratic programming solver with a rolling optimization step size of 10 - 20ms and a prediction time domain of 100 - 200ms. When the system starts, the PLC executes an automatic zero calibration process, including rotating the directly-driven roller at a low speed and recording the zero offset of the encoder, and calibrating the threshold values of each photoelectric opposed sensor through a standard calibration plate.

[0024] It also includes a compact frame. The length of the compact frame is 1.2m. The cross beam also serves as a servo driver, a heat dissipation channel, and a cable tray. A transparent heat-resistant protective cover is provided outside the frame. When the PLC receives the cutting completion signal, it controls the directly-driven rollers in the pre-cut section and the post-cut section to speed up and slow down respectively through a section differential speed algorithm to form a glass plate spacing of 150 - 250mm. When the busy signal of the stacking manipulator is set, the PLC automatically reduces the linear speed of the last directly-driven roller to ≤0.2m·s -1 and maintains the linear speed of the front directly-driven roller ≥0.8m·s -1 to form a buffer zone of 2 - 3m. When the vibration sensor monitors that the resonance amplitude of the 1st - 3rd order structure exceeds the threshold value, the PLC adjusts the phase difference between adjacent directly-driven rollers by 2° - 5° through phase perturbation to suppress vibration.

[0025] The roller is made of 17-4PH martensitic stainless steel pipe with a diameter of Φ150mm and a wall thickness of 8mm. The inner hole is machined with a high-precision H7 fit, and a permanent magnet synchronous servo motor is embedded. The outer wall of the motor stator is coated with high-temperature resistant insulating paint; the rotor and the outer wall of the roller are connected by a high-temperature adhesive and a key to achieve integrated rotation. The reducer uses ISOVG460 synthetic lubricating oil, and the tooth surface is coated with a MoS2 solid lubricating coating. The roller surface is coated with a 120μm ceramic-PFA composite coating, with a hardness close to 8H and a friction coefficient of 0.05.

[0026] The main PLC selects a high-speed PLC with a 32ns instruction cycle and 512kB operation memory, integrated with an EtherCAT master station interface. The driver uses a 400V-class servo driver, and the current loop bandwidth ≥2kHz. The sensor nodes are connected through EtherCAT-I / O modules. The overall communication cycle time is set to 0.5ms.

[0027] Direct drive roller structure: Each conveyor roller directly integrates a permanent magnet synchronous servo motor and a precision planetary reduction mechanism inside to form a compact direct drive unit. The traditional centralized drive shaft and belt / chain drive are cancelled, and there is no longer a need for a long universal shaft to connect multiple rollers. This shaftless drive structure reduces mechanical drive clearance and elastic deformation, improves drive efficiency and response speed, and also eliminates problems such as belt slipping and shaft system torsional vibration. Each roller motor is directly controlled by the driver, can be independently speed-regulated, and realizes distributed drive.

[0028] High-strength heat-resistant materials: The roller uses a special alloy steel core, and the surface is covered with a high-temperature resistant and anti-adhesion coating (such as a ceramic-based coating or a Teflon coating), which can not only withstand the high temperature that may remain when the glass comes out of the kiln, but also prevent the glass plate from sticking or scratching. The bearings are selected as high-temperature resistant and long-life bearings and are equipped with heat insulation devices to ensure smooth operation in a high-temperature environment. The frame structure material is a thick-walled low-alloy steel or a high-strength aluminum alloy frame, and carbon fiber composite material reinforcing ribs are added to the key stress-bearing parts, so that the frame has sufficient rigidity to carry large heavy glass plates, and at the same time reduces weight and the influence of thermal expansion.

[0029] Compact modularization: The entire transmission line is divided into several standardized module units. Each module contains several direct drive rollers, motor drivers, and local sensor groups. The module shell uses heat-resistant steel plates and heat-resistant glass windows (for easy observation of internal operation) to form a sealed protection structure to isolate hot air and ensure safety. The modules are connected by quick mechanical locks and plug-in electrical interfaces, which is convenient for installation and maintenance. Since the long drive shaft is cancelled, the length of each module can be made very short, thus occupying less space, and the modular combination is still more compact than the traditional system.

[0030] Heat Dissipation and Thermal Insulation: In response to the relatively high ambient temperature at the cold end, an active and passive combined heat dissipation system is designed. Passively, heat dissipation fins are arranged at the positions of the motors and electronic components inside the rollers close to the frame, and there is an efficient heat dissipation coating outside the frame and natural convection cooling is utilized. Actively, heat-resistant fans or circulating coolant pipelines are integrated inside the module to cool the motors and drivers. The control cabinet (if any) also uses air conditioners or heat exchangers to maintain the internal components at a safe temperature. All these heat dissipation measures ensure that the system does not slow down or lose accuracy during long-term operation in a high-temperature environment.

[0031] Large-Size Heavy Load Support: The diameter and spacing of the rollers are optimized according to the size and weight of the largest conveyed glass plate. The typical size of a large float glass plate can reach 6m×3m and the thickness is over 25mm, corresponding to a weight of over a thousand kilograms. For this reason, the roller diameter is thickened and high-torque motors are used, and each roller can provide sufficient driving force. Vibration damping pads and adjustable support legs are added to the frame base to ensure that the frame does not deform under heavy loads and the transmitted vibration is minimized. Multiple rollers simultaneously contact and support the extra-large glass, making the load evenly distributed. In addition, considering safety in extreme cases, the frame is designed with double redundant supports (for example, auxiliary support frames are added at both ends of each roller), so that even if a single point fails, the glass will not fall.

[0032] It can still operate stably under extremely harsh conditions: There will be no roller shaking or glass jumping during high-speed operation; the high-temperature environment will not cause component overheating or a sudden reduction in lifespan; the structure will not sag or jam under heavy load conditions.

[0033] A closed-loop control method for the cold-end roller conveyor system of a float glass production line includes the following steps: S1. Power-on self-calibration, the PLC controls all direct-drive rollers to rotate at low speed idly and collects encoder data to calibrate the zero point; S2. Refresh the threshold value of the photoelectric pair-beam sensor through a standard calibration plate, and at the same time record the baseline values of the temperature sensor and the vibration sensor; S3. After the glass plate enters, the PLC calculates the optimal speed instruction sequence within the future prediction time domain based on the model predictive control algorithm and issues it to each servo driver through the EtherCAT network; S4. Real-time collect multi-dimensional feedback quantities such as speed, position, torque, temperature, vibration, etc., respectively construct speed-position, torque-tension, temperature compensation, and vibration suppression closed loops and superimpose and correct the aforementioned speed instructions; S5. When a cutting, stacking or fault signal is detected, the PLC calls the preset working condition sub-module, dynamically adjusts the speed curves of the direct-drive rollers in each section, and performs rolling optimization through the model predictive control algorithm to achieve shock-free switching; S6. During no-load or production intervals, the PLC re-evaluates the model parameters with a recursive algorithm and performs online adaptive update on the system.

[0034] Closed-loop control: The PLC is built with a Model Predictive Control (MPC) unit. Using the mathematical model of the glass plate movement as the prediction object, it rolls and optimizes the speed sequence for the next N sampling periods. Speed-position closed-loop: With optoelectronic / laser composite speed measurement as the main feedback, it real-time corrects the roller speeds in each area; Torque-tension closed-loop: Using the motor current and the glass-roller contact pressure as feedback to balance the traction force; Temperature compensation closed-loop: Dynamically adjusts the MPC model parameters according to the glass and ambient temperatures; Vibration active suppression closed-loop: Using the vibration sensor signal as feedback to real-time fine-tune the phase difference between adjacent rollers to counteract resonance. System model: Establish a glass-roller coupled discrete model x(k + 1) = Ax(k) + Bu(k) + Ew(k), where x is the speed and position state vector, u is the motor target speed vector, and w is the disturbance (temperature, friction change, etc.). Solver: The QP (Quadratic Programming) real-time solver library built into the PLC, with a typical solution time of <0.3ms.

[0035] Self-calibration and fault tolerance mechanism: Automatic zero calibration process at startup + recursive self-calibration during operation; Sensor multi-redundancy mutual check, fault isolation, and degradation operation strategy. The system starts up without load. First, it rotates all rollers at a low speed of 5 r·min -1 for 10 s, and the PLC records the encoder zero offset; then it drives a standard test plate through the sensor array, collects the optoelectronic threshold, and adaptively adjusts the gain; The temperature-vibration baseline values are also written into the EEPROM as the reference for this operation.

[0036] The control system adopts a hierarchical distributed architecture, which is jointly composed of a central high-speed PLC, a fieldbus network, a local drive control unit, and a sensor network. Its structure is as follows:

[0037] Central control PLC: The brain of the system, using a high-performance programmable logic controller PLC. The core control programs run in the PLC, including speed coordination algorithms, model predictive control algorithms, and self-calibration algorithms. The PLC has the ability to process real-time multitasks and cyclically executes control logic within a millisecond-level cycle. The PLC communicates with each module through industrial Ethernet or fieldbus to achieve centralized monitoring and global optimization decisions.

[0038] Fieldbus network: Industrial high-speed fieldbuses (such as EtherCAT, PROFINET or high-speed CAN bus) are adopted. All direct-drive roller motor drivers and sensor nodes are directly connected to the bus network, forming a flat network control structure. This means that sensor signals and drive commands are digitally transmitted on the bus, eliminating the need for traditional complex wiring and intermediate I / O modules. The bus communication cycle is as short as 1 - 2 milliseconds, enabling quasi-real-time data exchange and coordinated control. At the same time, the network topology supports plug-and-play of modules. When adding or removing transmission modules, the PLC can automatically identify new nodes and load the corresponding control logic, greatly improving the convenience of system expansion and maintenance.

[0039] Local drive control unit: Each roller direct-drive motor is equipped with a local drive controller (frequency converter or servo drive), which receives speed / torque setting commands from the PLC via the bus and controls the motor current and speed with high-bandwidth closed-loop control. The driver contains a DSP microcontroller inside, which can achieve fast response of the motor current loop and speed loop. Some local control functions (such as motor protection and limit detection) are independently completed inside the driver to reduce the burden on the PLC. The drive control unit also uploads the feedback data of the motor (encoder position, speed, torque current, temperature rise, etc.) to the PLC, forming a loop in the closed-loop system.

[0040] Sensor network: Various sensors are connected to the network through I / O modules or directly in the form of bus slaves to transmit on-site data to the PLC. The sensor network includes: Photoelectric / laser sensors: Installed at certain intervals to detect the position and speed of the glass plate passing by, used for measuring the plate spacing and synchronous speed. Thickness / width sensors: Measure the thickness and width of the glass plate at key positions for the PLC to refer to for pressure adjustment or speed correction (for example, thick plates may require different speed curves). Temperature sensors: Monitor the ambient temperature, glass surface temperature, and motor / bearing temperature for thermal compensation control and safety protection. Vibration / pressure sensors: Installed on the frame and key rollers to monitor vibration shock and load distribution. Once the vibration exceeds the limit or the force is abnormal at a certain place, the PLC can adjust the speed of adjacent rollers to buffer, or issue an alarm and stop safely. Encoders and opposed sensors: Used to accurately track the position of the glass and the cutting line position. When the glass plate is cut and fragmented at the cold end, it ensures that the control system knows the accurate position and movement state of each piece of glass.

[0041] Human-machine interface HMI and monitoring system: A touch screen or industrial computer is configured as an HMI in the control room, and connected to the PLC to read real-time data and status. The operator can monitor parameters such as transmission speed, temperature of each section, motor load, etc. through the HMI, and can adjust production parameters (such as target speed, board spacing setting). At the same time, the system has a remote monitoring and diagnostic interface, which can upload key data to the factory MES system or the cloud to achieve equipment status monitoring and predictive maintenance (it should be noted that this predictive maintenance is based on rules and threshold judgments).

[0042] The entire control architecture ensures centralized decision-making and distributed execution: PLC centrally calculates the optimal control strategy, and each local unit executes specific instructions at high speed; multi-sensor data convergence provides comprehensive information, and multi-drive collaboration achieves synchronous action. The architecture is highly reliable and fault-tolerant: even if a sensor fails, the system can continue to operate through other sensors or estimated values; when a drive unit fails, the system automatically slows down and stops, notifies maintenance, and minimizes the impact on other parts.

[0043] Control strategy and logic:

[0044] Motion control combining full-line synchronization and partition independence: The entire cold-end transmission line is regarded as an integral motion system. The PLC maintains a global virtual spindle or reference model, and the speed of all roller motors is locked on this reference to ensure that the various parts of the glass sheet run synchronously. During normal operation, the glass sheet does not slip or stagnate on each roller, and is transported at a constant speed. When it is necessary to change the speed or perform special operations (such as spacing after cutting), the control strategy can be adjusted in different zones: the transmission line is divided into multiple control zones, each of which is relatively independently controlled, and the coordination algorithm at the junction of the zones ensures smooth connection. For example: in the cutting area, after the glass is sliced, the two adjacent pieces of glass need to be spaced a certain distance apart. At this time, the downstream area instantly speeds up and the upstream area slows down to quickly form a gap, and then adjusts back to normal speed respectively. The entire process is automatically executed by the PLC according to the pre-set speed curve, and the acceleration and deceleration curves are optimized to avoid impact or slippage on the glass.

[0045] In the board collection (stacking) area, it may be necessary to temporarily reduce the speed to cooperate with the robot to take the board. The control strategy can only slow down the last few rollers, while the previous area runs normally, and dynamically adjust the area length to ensure that the front section of glass is continuous and avoid congestion. After the board is taken, it will be smoothly accelerated to restore the synchronization of the entire line. Through this combination of global synchronization and local difference control, the system not only maintains consistency in operation, but also has flexible adjustment capabilities to adapt to various rhythm changes in the production process without stopping.

[0046] Model Predictive Control (MPC) and Adaptive Feedforward: To achieve precise control of the transmission speed and position, we introduce a model predictive control strategy. The mathematical model of the transmission system, including the roller radius, motor characteristics, friction characteristics between the glass and the rollers, etc., is stored inside the PLC. Based on the model, the PLC can predict the system behavior in the next few time cycles and optimize the calculation of the future control input sequence, thus making the glass movement trajectory optimal (for example, reducing speed fluctuations, maintaining a constant spacing, etc.). In each control cycle, the MPC algorithm is rolled and optimized according to the latest sensor data (such as glass speed, position deviation, etc.), and the corrected speed command is output to each motor drive. This control can significantly improve the dynamic performance and stability of the system: for example, before the glass plate is about to enter a certain area, the PLC has already fine-tuned the speed of the downstream rollers in advance to prepare for it to avoid impact; or when it detects that the upstream glass suddenly speeds up, it notifies the downstream to speed up in advance to reduce the lag. In addition, the control system also implements adaptive feedforward control. According to the long-term operation data, the PLC will adjust the feedforward parameters to compensate for the system deviation. For example, if it is found that there is a very small lag in the glass every time it speeds up, the feedforward force will be appropriately increased; if it is found that the friction coefficient becomes smaller and causes sliding under a certain temperature condition, the speed setting value gain will be pre-reduced under this condition. By adaptively adjusting the feedforward, the system always remains in the best control state, and even if the environment and load change, it can still maintain high performance.

[0047] Multi-point Closed-loop Feedback Control: In the system, it is no longer a single speed closed-loop, but a closed-loop control structure with multiple feedback variables and multiple loops: Speed / Position Closed-loop: The basic closed-loop is formed by the movement speed and position of the glass plate. The actual speed of the glass is measured by an optoelectronic sensor and compared with the target speed. The output of each section of the motor is adjusted through the PLC to make the actual speed track the set value. For position control, when the glass needs to stop or decelerate precisely at a specific position (e.g., preparing for cutting), the PLC makes closed-loop adjustments based on the current position error of the glass. This is equivalent to controlling the glass as a moving unit, and the rollers act as actuators to cooperate in completing the positioning. Torque / Tension Closed-loop: Since the glass plate is transmitted on multiple rollers, it is equivalent to a distributed driving load. The system introduces a torque balance control strategy: The PLC monitors the torque (current) feedback of each roller motor. When it is found that the torque of a certain section of the motor is abnormally high or low (indicating that the traction force of this roller on the glass is abnormal), it will slightly change the speed of the surrounding rollers through closed-loop adjustment to balance the traction force at each point. This torque closed-loop ensures that the glass is evenly stressed, avoiding scratches or fractures of the glass caused by slipping or excessive stress at a certain point. At the same time, the torque feedback can also reflect whether the glass is blocked or jammed. Once a sharp increase in torque is detected (e.g., the glass encounters a front-end fault and stops), the PLC will immediately trigger an emergency stop and alarm. Temperature Closed-loop (Thermal Compensation): The feedback of the temperature sensor is used to form a thermal compensation loop. When the ambient or glass temperature rises, material expansion and changes in the friction coefficient may affect the synchronization accuracy and speed control. The PLC appropriately corrects the control parameters through temperature feedback, such as increasing the gain of some speed loops or reducing the speed setting, so as to compensate for the thermal effect and ensure consistent control effects under different temperature conditions. During the cooling process, if it is detected that the glass temperature drops to a safe value, some thermal protection speed limit measures can also be lifted to resume full speed. Vibration Closed-loop (Damping Control): The vibration sensors installed on the frame or rollers form a vibration monitoring loop. If mechanical vibration occurs in a certain section due to high-speed operation, after being detected by the PLC, the phase or speed of the motor in this section is adjusted through a control algorithm to actively attenuate the vibration (the principle is similar to an active vibration damping system). For example, after analyzing the cause of the vibration frequency, the rotational speed difference between adjacent rollers is adjusted to create a reverse interference to cancel the structural resonance. This keeps the transmission process stable and avoids resonance accumulation from damaging the equipment or affecting the stability of the glass. The cooperation of multiple closed-loops enables the system to have the characteristics of being both rigid and flexible: having rigid speed and position control to ensure the production rhythm, and flexible torque, temperature, and vibration control to ensure a stable and safe process. Under this control strategy, even under the world-leading high-speed and heavy-load conditions, the glass can still be gently and precisely conveyed.

[0048] To vividly illustrate the above control strategy, the following uses the logical process steps of a typical production operation cycle to explain the control process:

[0049] System initialization and self-check: When powered on, the PLC commands each module to enter the self-check mode. The sensor array detects the reference mark (for example, simulating the passage of glass on the empty roller), and the PLC calibrates the reading deviation of each sensor; each motor rotates at low speed in sequence to collect no-load current / position data for self-calibration, compares these data with the nominal values in the database, and automatically compensates for zero drift and parameter errors. At the end of initialization, the system confirms that all units are working properly before switching to standby.

[0050] Glass entry and acceleration: When the heat-treated glass plate slowly enters the entrance of the cold-end transmission section, the entrance sensor first detects the arrival signal of the glass, and the PLC immediately switches from standby to the running mode. The first few rollers at the front end start to rotate according to the set acceleration to introduce the glass. As the glass gradually enters the entire transmission line, the PLC activates the subsequent rollers in sequence according to the glass length, and synchronously accelerates the entire glass to reach the target running speed on the whole line. During the process, the speed closed-loop is corrected in real time to ensure uniform and impact-free glass acceleration.

[0051] Stable high-speed transmission: The glass advances at a constant speed in the cold-end transmission section. At this stage, the PLC maintains the synchronous constant-speed operation of all rollers, and the multi-point feedback system continuously monitors various parameters. If the glass has been cut into multiple pieces during this process, the positions of each piece are tracked by sensors, and the PLC manages the spacing and speed of each piece of glass separately. For example, when it is detected that the previous piece of glass is slightly slower, resulting in a reduced distance, the PLC slightly accelerates the rollers in the area of the subsequent piece or decelerates the area of the previous piece to ensure a stable interval between each piece of glass. At this time, the system executes the closed-loop control in a very high-frequency cycle, dynamically adjusting small errors, so that macroscopically, the glass pieces are smoothly conveyed plate by plate without accumulation or excessive gaps.

[0052] Special operations (cutting / sequence change): When the glass plate reaches the cutting machine or needs to change the conveying path (such as turning to enter another process), the PLC triggers the corresponding control mode. For example, when the cutting is about to be completed, the PLC pre-reduces the speed of the rollers near the cutting line and closely monitors the cutting signal. At the moment when the glass is cut into two pieces, the differential speed control is quickly executed in the upstream and downstream areas: the roller section where the first half is located accelerates briefly, and the section where the second half is located decelerates briefly to form a safety distance. Subsequently, the two areas smoothly transition back to the synchronous speed respectively. During the whole process, due to the high-speed coordination of the PLC, almost no pause and impact can be seen at the moment when the glass is broken. Again, if the glass needs to be transferred to the branch line for conveying or transferred, the system will communicate with the switching mechanism according to the preset process to ensure an accurate timing for switching the conveying path.

[0053] Deceleration and Stacking: When the glass sheet passes through the cold end inspection and completes the established process, before entering the stacking station, the PLC flexibly adjusts the transmission speed of the last section according to the status signal of the downstream stacker / robot. For example, if the stacking robot is busy, the last few rollers enter the slow running mode (low speed or intermittent movement) to form a buffer zone until the robot is ready and then the conveying resumes. When the glass reaches the accurate stacking position, the PLC commands the corresponding rollers to stop precisely and positions the glass for the robot to grab. After the robot takes away the glass, the rollers of this section re-accelerate and rotate idly to connect with the glass in front. In this way, each glass sheet is accurately conveyed and positioned, and the whole process is carried out in an orderly manner.

[0054] Fault and Emergency Handling: If the sensor detects an abnormal situation during operation (such as glass crack, excessive positioning deviation, roller motor overload, etc.), the PLC immediately executes the pre-determined logic: for minor problems, it alarms and stops smoothly, and for serious faults, it instantly triggers an emergency brake (all rollers stop quickly and synchronously) to prevent the accident from expanding. At the same time, the system records the data of each sensor and motor at the time of the fault for post-event analysis. After an emergency stop, the self-diagnosis module runs to try to identify the problem area and, if necessary, dispatch a spare module (such as transferring the glass to the bypass conveyor line if a certain section is damaged). The entire abnormal handling process is designed and verified in advance to ensure safety and reliability.

Claims

1. A cold-end roller conveyor system for a float glass production line, characterized in that: It includes several directly-driven rollers arranged in parallel. Inside each directly-driven roller, a permanent magnet synchronous servo motor, a high-temperature planetary reducer, and a digital encoder are integrated coaxially. The surface of the directly-driven roller is provided with a ceramic-PFA composite anti-adhesion coating. The directly-driven roller is connected to the EtherCAT bus through a quick-plug electrical interface to form a distributed drive network. It also includes a high-speed PLC, several servo drivers, and multi-sensor nodes. The PLC communicates with the servo drivers and sensor nodes through the EtherCAT high-speed fieldbus. The PLC runs a model predictive control algorithm and constructs a speed-position closed loop, a torque-tension closed loop, a temperature compensation closed loop, and a vibration suppression closed loop to comprehensively control the rotation speed and phase of each directly-driven roller, realizing the high-speed, heavy-load, and compact transmission of float glass in an environment of 150°C - 450°C.

2. The cold-end roller table transmission system of a float glass production line according to claim 1, wherein: The hardness of the ceramic-PFA composite coating is ≥8H, the thickness is 80 - 150μm, and the friction coefficient is ≤0.

05.

3. A cold-end roller table transmission system for a float glass production line according to claim 1, characterized in that: The current loop bandwidth of the servo driver is ≥2kHz, and the position loop bandwidth is ≥500Hz.

4. A cold-end roller table transmission system for a float glass production line according to claim 1, characterized in that: The multi-sensor nodes include photoelectric opposed sensors, laser ranging sensors, infrared temperature sensors, and three-axis vibration sensors. Each sensor node is connected to the PLC through an EtherCAT-I / O module, and the communication cycle is ≤1ms. The model predictive control algorithm built in the PLC uses a quadratic programming solver with a rolling optimization step size of 10 - 20ms and a prediction time domain of 100 - 200ms.

5. A cold-end roller conveyor system for a float glass production line according to claim 1, characterized in that: When the system starts, the PLC executes an automatic zero calibration process, including rotating the directly-driven roller at a low speed and recording the zero offset of the encoder, and calibrating the threshold of each photoelectric opposed sensor through a standard calibration plate.

6. A cold-end roller conveyor system for a float glass production line according to claim 1, characterized in that: It also includes a compact rack. The length of the compact rack is 1.2m. The cross beam also serves as a servo driver, a heat dissipation channel, and a cable tray. A transparent heat-resistant protective cover is provided outside the rack.

7. A cold-end roller conveyor system for a float glass production line according to claim 1, characterized in that: When the PLC receives the cutting completion signal, it controls the directly-driven rollers in the pre-cutting section and the post-cutting section to speed up and slow down respectively through a section differential speed algorithm to form a glass plate spacing of 150 - 250mm.

8. The cold-end roller table transmission system of a float glass production line according to claim 1, characterized in that: When the stacking manipulator busy signal is set, the PLC automatically reduces the linear velocity of the last - stage direct - drive roller to ≤0.2 m·s -1 , and maintains the linear velocity of the front - stage direct - drive roller ≥0.8 m·s -1 , forming a 2 - 3 m buffer zone.

9. The cold-end roller table transmission system of a float glass production line according to claim 1, characterized in that: When the vibration sensor monitors that the resonance amplitude of the 1st - 3rd order structure exceeds the threshold, the PLC adjusts the phase difference between adjacent directly-driven rollers by 2° - 5° through phase perturbation to suppress vibration.

10. A closed-loop control method for a cold-end roller conveyor system of a float glass production line, used for the system according to any one of claims 1-9, characterized in that, It includes the following steps: S1. Power-on self-calibration. The PLC controls all directly-driven rollers to rotate idly at a low speed and collects encoder data to calibrate the zero point. S2. Refresh the threshold of the photoelectric opposed sensor through a standard calibration plate, and at the same time record the baseline values of the temperature sensor and the vibration sensor. S3. After the glass plate enters, the PLC calculates the optimal speed command sequence within the future prediction time domain based on the model predictive control algorithm and sends it to each servo driver through the EtherCAT network. S4. Real-time collect multi-dimensional feedback quantities of speed, position, torque, temperature, and vibration, respectively construct speed-position, torque-tension, temperature compensation, and vibration suppression closed loops, and superimpose and correct the aforementioned speed commands. S5. When a cutting, stacking, or fault signal is detected, the PLC calls the preset working condition sub-module, dynamically adjusts the speed curves of the direct drive rollers in each section, and performs rolling optimization through the model predictive control algorithm to achieve shock-free switching; S6. During no-load or production intervals, the PLC re-evaluates the model parameters using a recursive algorithm to perform online adaptive updates on the system.

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