A woven bag piece cutting and incision heat sealing system and timing chain control method

Abstract

The present application relates to the technical field of woven bag processing, and particularly relates to a woven bag sheet cutting and notch heat sealing system and a time sequence chain control method, which comprises a conveying mechanism, a cutting and heat sealing execution mechanism, a main controller and a time sequence chain control subsystem, the time sequence chain control subsystem is composed of a fluctuation sensing module, a time sequence prediction module, a locking execution module and a state inheritance module, a hard time sequence correlation link independent of the main controller is constructed through a hardware circuit, millisecond-level response to voltage sag, slip time prediction based on a physical model, electromagnetic positioning pin locking and accurate latching of a shutdown position in a closed loop control are realized. The present application solves or at least alleviates the problem that manual recalibration is needed after shutdown caused by mechanical inertia slip due to power grid transient fluctuation, and provides a woven bag sheet cutting and notch heat sealing system and a time sequence chain control method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of woven bag processing, and particularly relates to a woven bag sheet cutting and notch heat sealing system and a timing chain control method. BACKGROUND

[0002] In the automatic production line of woven bag sheet, cutting and notch heat sealing are key links affecting the quality and production rhythm of the final product. Not only the size accuracy of the cutting position is required, but also the flatness and sealing strength of the heat sealing notch are required to be quite high. The automation degree and running stability are also key indicators for evaluating the technical level of the whole production line. With the continuous improvement of market demand, the technical progress in this field mainly focuses on improving the mechanical accuracy and response speed of the cutting and heat sealing execution mechanism, and has achieved fruitful results. For example, some technical solutions improve the residue adsorption and residue problem of the heat plasticized packaging bag by optimizing the physical properties of the transmission mechanism surface, so as to improve the cleanliness of the material conveying interface, and then improve the appearance quality and the qualified rate of the product. For example, the technical solution disclosed in the patent with the application publication number CN115195205B. Another part of the technical solutions focuses on the cutting execution mechanism, improves the cutting efficiency and notch quality by using an efficient heat cutting process combined with the coordinated operation of the precise compression roller and the front and rear transmission rollers, and also improves the working environment to some extent. For example, the technical solution disclosed in the patent with the application publication number CN119910949B. These technical solutions have solved the main technical obstacles at that time and promoted the progress of the industry under the historical period and application background, but some new problems still exist in the face of new technical conditions.

[0003] However, in today's modern industrial production towards more extensive and deep automation, intelligent development, and modern factory production system for complex working conditions of robustness and continuous production capacity of new, higher requirements, the above technical solutions in the design actually embodies a common congenital defect, this defect is not in its mechanical structure, nor in its process flow, but in the control system of physical events response logic and time mismatch. Specifically, the current control system is mostly based on programmable logic controller (PLC) or periodic scanning control architecture of industrial computer, its inherent response time is generally in the order of tens of milliseconds or even higher. The above architecture shows its unique advantages in the conventional, predictable process flow, but for the industrial site, and frequent occurrence of transient, high-frequency physical phenomena such as power grid voltage transient drop, the congenital response time of the existing control system makes it impossible to implement matching intervention within the millisecond time window. When the voltage of the power grid suddenly drops, the motor torque driving the conveyor belt will suddenly decay, but the conveyor belt and the woven bag sheet moving on it will not suddenly stop due to mechanical inertia, but will slide uncontrollably for a period of time. Although the sliding time is short, the distance cannot be ignored, which will cause the serious deviation of the heat sealing position and the cutting position. Even if the traditional control system detects the voltage anomaly through the power supply monitoring module, the time consumed by the control system from signal acquisition, logic judgment to output stop command has far exceeded the time of inertia sliding. When the system discovers and stops, the important physical fact of position deviation has already existed objectively, and the trigger of the safety door is often after the sliding has been out of control, which leads to a large difference between the system state after stopping and the state before stopping, and the system after stopping faces great difficulty in restarting. Further speaking, the disconnection between the above control system logic and the real physical fact leads to the lack of sliding suppression mechanism in the existing technology. In the initial stage of power grid voltage drop, the system cannot make millisecond-level predictive intervention, but can only passively accept the result of sliding and cannot physically lock and suppress. Even if the safety door and other protection devices are configured in the existing scheme, their essence is still a post-remedy measure, which prevents equipment damage or larger-scale production accidents, rather than maintaining the continuity of production data. Therefore, each time the machine stops due to voltage fluctuation, manual calibration and repositioning of the starting cutting point of the sheet are inevitable, which not only wastes valuable production time and reduces the overall efficiency of the equipment, but also introduces the uncertainty of human intervention and affects the consistency of product quality.The prior art system lacks a control system that can deeply couple power grid transient fluctuation perception, mechanical inertia slip prediction and physical level locking execution, and fails to build a hard timing association from electrical event triggering to mechanical state locking that does not depend on the software loop of the main controller, which makes the state inheritance type fast production a difficult technical goal.

[0004] Therefore, how to design a system that can instantly determine the effectiveness of fluctuation events within milliseconds when the power grid voltage fluctuates, accurately predict the timing characteristics of inertia slip based on real-time operating parameters of the system, and then drive the physical locking mechanism to complete accurate positioning of the sheet material before the safe system responds, ultimately realizing a four-level strong association closed-loop control of "fluctuation perception-timing prediction-locking execution-state inheritance", thereby fundamentally suppressing the position deviation during unexpected shutdown and achieving seamless fast production under state inheritance, has become a key challenge and technical problem to be solved for those skilled in the art. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, solve or at least alleviate the problem of mechanical inertia slip caused by the inability of the control system to effectively respond to power grid transient fluctuations due to response delay, and provide a woven bag sheet cutting and cut heat sealing system and timing chain control method.

[0006] To achieve the above purpose, the present application provides the following technical scheme: a woven bag sheet cutting and cut heat sealing system, comprising a conveying mechanism, a cutting execution mechanism, a heat sealing execution mechanism and a main controller, further comprising:

[0007] A timing chain control subsystem is provided, which establishes a direct control path with the conveying mechanism, the cutting execution mechanism and the heat sealing execution mechanism without passing through the software logic of the main controller;

[0008] The timing chain control subsystem comprises:

[0009] A fluctuation perception module is provided for monitoring the voltage at the input end of the heat sealing execution mechanism power supply, and generating a digital trigger signal when a voltage drop event is identified;

[0010] A timing prediction module is provided for receiving the digital trigger signal and calculating the sheet slip time based on real-time operating parameters and a pre-set physical model, and generating an accurate timing instruction containing countdown duration and ejection depth parameters;

[0011] A locking execution module is provided for receiving the accurate timing instruction and driving the physical locking mechanism to perform a physical fixing operation on the woven bag sheet on the conveying mechanism after the countdown duration ends; and

[0012] A state inheritance module is configured to latch the precise position data of the sheet material indicated by the absolute position encoder of the conveying mechanism after the physical fixing operation is completed, and provide the latched data as a non-calibration recovery position reference when the main controller requests to resume production.

[0013] In order to further realize the present application, the following technical solutions can be preferably selected:

[0014] Preferably, the fluctuation sensing module comprises:

[0015] A high-bandwidth differential voltage sampling circuit is connected in parallel to the input bus of the main power supply of the heat sealing actuator;

[0016] A high-speed transient voltage comparator is connected to the output end of the high-bandwidth differential voltage sampling circuit, and outputs a square wave edge signal when the voltage drop rate at the input end of the power supply exceeds a preset threshold; and

[0017] A high-speed optoelectronic coupling isolation circuit receives the square wave edge signal at the input end, and outputs a square wave pulse train proportional to the voltage drop rate as a digital trigger signal fed into the timing prediction module.

[0018] Preferably, the fluctuation sensing module further comprises an event validity discrimination unit composed of a hardware timer and a digital logic AND gate;

[0019] The hardware timer starts timing when receiving the square wave pulse train;

[0020] The digital logic AND gate outputs an effective event confirmation signal only when the duration of the square wave pulse train exceeds a preset time window and the signal exists, starts the timing prediction module, and disconnects the heating loop of the heat sealing actuator.

[0021] Preferably, the timing prediction module is realized by a field programmable gate array (FPGA), and a state space model is internally fixed;

[0022] The input port of the FPGA is connected to the fluctuation sensing module, a system total mechanical inertia parameter storage unit, and an absolute position encoder of the main drive shaft of the conveying mechanism.

[0023] The digital signal processing core calculates a basic slip time value according to the voltage drop rate, the system total mechanical inertia parameter, and the running speed of the sheet material at the start of the slip, by using the state space model.

[0024] The digital signal processing core uses a state space model defined by the following differential equation: where s is the slip displacement, k is the damping coefficient, and J is the system total mechanical inertia; the model parameters are calibrated through a step response experiment, and the specific method is as follows: a voltage step disturbance is applied, and a curve of the slip time and the initial speed is recorded, and a coefficient matrix is fitted.

[0025] Preferably, the timing prediction module further comprises a dynamic compensation unit and a timing generation circuit;

[0026] The dynamic compensation unit is composed of a multi-dimensional lookup table and a hardware multiplier, which obtains the running speed and the thickness of the sheet material, retrieves the compensation coefficient, multiplies the basic slip time value by the compensation coefficient, and obtains the final slip time value.

[0027] The multi-dimensional lookup table of the dynamic compensation unit stores the pre-calibration compensation coefficient. For example, when the speed ∈ [30, 40] m / min and the thickness ∈ [0.15, 0.25] mm, the compensation coefficient is 0.85 ± 0.05 (based on the mean value of 100 repeated experiments); the calibration method is to simulate voltage drop under constant speed and thickness conditions, and measure the deviation ratio of the actual slip time and the model prediction value.

[0028] The timing generation circuit is composed of a hardware subtractor and a countdown counter, which subtracts the final slip time value from the lock-in advance, loads the countdown duration to the countdown counter as the precise timing instruction containing the countdown duration and the ejection depth parameter.

[0029] The ejection depth parameter is calculated according to the sheet thickness t by the formula d = 2t + 0.5 mm, where the coefficient 2 is based on the empirical data of sheet piercing depth, and the offset 0.5 mm is used to ensure the mechanical locking; the calibration method is to measure the sheet thickness t using a thickness gauge, calculate the d value, adjust the screw set pin head initial extension, run the test mode to make the pin head extend, measure the actual depth with LVDT, and iteratively adjust until the error is less than ± 0.1 mm, and record the LVDT value when the micro switch is closed.

[0030] Preferably, the lock execution module comprises an electromagnetic positioning pin assembly and a closed-loop drive and verification circuit;

[0031] The electromagnetic positioning pin assembly is installed on the side of the conveying mechanism, and the pin head is extended under the drive to penetrate or pierce into the woven bag sheet material;

[0032] The closed-loop drive and verification circuit is mainly the H-bridge drive circuit controlled by the pulse width modulation controller, which outputs the drive pulse sequence after the countdown duration ends, including the peak phase for realizing the rapid ejection of the positioning pin and the holding phase for maintaining the locked state.

[0033] Preferably, the electromagnetic positioning pin assembly is integrated with a linear variable differential transformer displacement sensor inside the pin body, which measures the extension position of the positioning pin in real time and converts it into a position feedback signal;

[0034] The pulse width modulation controller receives the position feedback signal, compares it with the target depth value set by the ejection depth parameter, dynamically adjusts the duty cycle according to the error, and forms a position closed-loop control loop; the PID parameter is set as: proportional gain Kp=12.5 (dimensionless), integral time Ti=0.02s, and differential time Td=0.001s, and the step response test is optimized (target: overshoot <5%), the specific steps are: applying a step input signal, recording the displacement response curve, using the Ziegler-Nichols method to preliminarily set the parameters, and then adjusting Kp, Ti and Td in increments until the overshoot is less than 5% and the response time is less than 50ms;

[0035] The mechanical contact microswitch at the end of the electromagnetic positioning pin assembly is closed to output a "physical locking completed" signal.

[0036] Preferably, the lock execution module further comprises a sliding movement dynamic verification unit;

[0037] The sliding movement dynamic verification unit samples the absolute position encoder data of the main drive shaft of the transmission mechanism after the timing prediction module sends out the "locking ready" signal, and calculates the actual sliding amount;

[0038] If the actual sliding amount exceeds the safety threshold, the sliding movement dynamic verification unit generates a depth compensation signal to increase the holding stage current, and simultaneously writes the prediction deviation data back to the system total mechanical inertia parameter storage unit.

[0039] Preferably, the state inheritance module core is a timing verification and data latching circuit, which includes two hardware timestamp latches and a data latch;

[0040] The first hardware timestamp latch latches the system clock count value at the moment when the timing prediction module sends out the accurate timing instruction;

[0041] The second hardware timestamp latch latches the clock count value at the moment when the external safety system trigger signal is received;

[0042] The timing verification and data latching circuit includes a hardware subtractor and a digital comparator, which calculates the timestamp difference to obtain the actual advance, and compares it with the preset success window. If the actual advance falls within the window, the "zero calibration" flag bit is set;

[0043] The data latch latches the accurate coordinate data of the absolute position encoder of the transmission mechanism at the moment when the "physical locking completed" signal is received.

[0044] A timing chain control method suitable for the above-mentioned system for resuming production after successful pre-locking, comprising the following steps:

[0045] The main controller reads the state register in the state inheritance module after completing the shutdown process and receiving the reset signal.

[0046] If the "zero calibration" flag bit is valid, the main controller skips the origin regression or manual calibration process, and directly reads the accurate position data stored in the data latch;

[0047] The main controller updates the working positions of the cutting actuator and the heat sealing actuator by taking the accurate position data as the starting position reference for subsequent cutting and heat sealing operations;

[0048] The main controller issues instructions to drive the locking execution module to retract the electromagnetic positioning pin assembly pin head, and restarts the conveying mechanism to realize automatic and rapid recovery of production.

[0049] The beneficial effects of the present application are:

[0050] The present application uses high-speed circuits to capture voltage disturbances in real time, predicts slip timing through physical models and adaptive algorithms, and performs physical locking in a closed-loop control mode, and finally realizes the inheritance of the shutdown position through hardware data latching. The system and method not only suppresses the position deviation of the sheet material during unexpected shutdown, but also realizes rapid state recovery without manual intervention, improving the automation level, operation efficiency and product quality consistency of the production line. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The overall architecture diagram of the system of the present application is shown in the figure;

[0052] Figure 2 The functional module block diagram of the timing chain control subsystem of the present application is shown in the figure;

[0053] Figure 3 The internal structure block diagram of the fluctuation perception module of the present application is shown in the figure;

[0054] Figure 4 The internal structure block diagram of the timing prediction module of the present application is shown in the figure;

[0055] Figure 5 The physical installation structure diagram of the locking execution module of the present application is shown in the figure;

[0056] Figure 6 The closed-loop drive and verification circuit block diagram of the locking execution module of the present application is shown in the figure;

[0057] Figure 7 The internal structure block diagram of the state inheritance module of the present application is shown in the figure;

[0058] Figure 8 The execution flowchart of the timing chain control method of the present application under power grid fluctuation events is shown in the figure;

[0059] Figure 9 The flowchart of the rapid recovery of production after the pre-locking of the present application is successful is shown in the figure;

[0060] Figure 10 Figure 1 is a schematic diagram of a backup safety calibration process performed after a pre-lock failure of the present application. DETAILED DESCRIPTION

[0061] In the description of the present application, it should also be noted that unless otherwise explicitly specified and limited, the terms "arrange", "mount", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0062] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. Embodiment one

[0063] The present embodiment discloses a woven bag piece cutting and cut heat sealing system, referring to Figure 1 The system includes a conveying mechanism for continuously conveying woven bag piece material, which is configured with a unwinding unit (not shown in the figure) upstream, and a cutting execution mechanism for cutting the piece material transversely and a heat sealing execution mechanism for heating and melting the cut edge of the cut piece material are sequentially arranged downstream. The conventional logic control, man-machine interaction and communication with the factory manufacturing execution system (MES) of the whole production process are all responsible by a main controller. The main controller is usually realized by programmable logic controller (PLC) or industrial computer (IPC). The motion control instructions of the above conveying mechanism, cutting execution mechanism and heat sealing execution mechanism under normal working conditions are all derived from the periodic operation output of the main controller.

[0064] In addition to the above conventional system architecture, the present application adds a timing chain control subsystem. The timing chain control subsystem establishes a direct, non-via main controller software scanning period hard connection control path with the conveying mechanism, cutting execution mechanism and heat sealing execution mechanism on the physical layer. These paths are specially used to execute a set of deterministic, low-delay physical intervention and state holding operations in emergency situations such as transient fluctuations in the power grid. The overall design goal of the timing chain control subsystem is to build a strong timing association response link from the physical perception of electrical disturbance events to the locking of the mechanical system state, thereby actively suppressing the piece material position slip caused by the mechanical inertia after the drive system loses power.

[0065] Further refer to Figure 2 The internal functional structure of the timing chain control subsystem is divided into four strictly time-coupled and progressive modules, namely, fluctuation sensing module, timing prediction module, lock execution module and state inheritance module. These four modules work together to form a complete closed-loop control chain from event triggering to state recovery.

[0066] Specifically, the function of the fluctuation sensing module is to continuously monitor the power input voltage of the drive system at high frequency, accurately identify the voltage sag event that may lead to mechanical out-of-control, and then convert this physical event into a standardized digital trigger signal as the starting source of the entire timing chain. Please refer to Figure 3 The hardware implementation of the fluctuation sensing module includes a high-bandwidth differential voltage sampling circuit, a high-speed transient voltage comparator, and a high-speed optoelectronic coupling isolation circuit. The input end of the high-bandwidth differential voltage sampling circuit is directly connected in parallel to the main three-phase AC power input bus of the heat sealing execution mechanism through a voltage dividing network composed of a pair of non-inductive precision metal film resistors. The voltage dividing ratio of the voltage dividing network is set to 1000:1, and the resistance material has an extremely low temperature coefficient (less than 5ppm / °C), ensuring linear and distortionless sampling of the instantaneous value of the bus voltage within a wide temperature range.

[0067] The sampled analog voltage signal is sent to the high-speed transient voltage comparator. The comparator is composed of a precision differential circuit with a high-speed operational amplifier (such as AD8055 of Analog Devices Company) as the core and a Schmidt trigger with a preset hysteresis voltage. When the rate of change of the input voltage, i.e. the voltage drop rate (dV / dt), exceeds the preset threshold (e.g. 12V / ms), its output voltage can instantaneously reach a logic high level sufficient to trigger the Schmidt trigger in the next stage. The Schmidt trigger can effectively filter out the common glitch noise on the power line to prevent false triggering. When the voltage drop rate exceeds the threshold, the Schmidt trigger flips and outputs a steep square wave edge signal with a rising time of less than 10 nanoseconds.

[0068] The square wave then drives a high-speed opto-coupler isolation circuit. The circuit uses a high-speed logic gate output type opto-coupler such as HCPL-2631 from Avago, which contains a gallium arsenide infrared LED as the light emitting side, and an integrated circuit that integrates a photodiode, a high-gain amplifier, and a Schottky clamping transistor as the receiving side. The isolated signal is sent to a voltage-to-frequency converter (VFC), which linearly converts the input signal proportional to the voltage drop rate into a square wave pulse train with a frequency range of 1 kHz to 100 kHz. This pulse train is the standardized digital trigger signal and is the only output of the fluctuation sensing module, directly fed into the input of the timing prediction module.

[0069] As a preferred embodiment of the present application, the fluctuation sensing module further includes an event validity discrimination unit, which is logically arranged at the input stage of the timing prediction module. The event validity discrimination unit is realized by a resettable hardware timer and a digital logic AND gate inside a field programmable gate array (FPGA) through hardware description language. The hardware timer is started when it receives the first rising edge of the aforementioned square wave pulse train, and starts timing with a system clock of 100 MHz. If the duration of the pulse train exceeds a preset valid event time window, which is 10 ms in this embodiment, it indicates that the voltage drop is not a transient disturbance, but a serious event that can cause the system to lose power. At this time, the state output end of the hardware timer changes from a logic low level to a high level. This high level signal, together with the original square wave pulse train signal, serves as two inputs of a digital logic AND gate. Only when the pulse train duration exceeds 10 ms (the timer output is high) and the pulse train itself still exists, does the AND gate output a high level valid event confirmation signal.

[0070] The valid event confirmation signal is divided into two paths: one path serves as a hard trigger signal to start the core operation logic of the timing prediction module, ensuring that the subsequent prediction and execution actions are only activated after a serious power grid event is confirmed; the other path drives a solid state relay (SSR) through an I / O pin of the FPGA, which is connected in series in the main heating element circuit of the heat sealing execution mechanism. This signal forcibly disconnects the heating circuit, thereby preventing the fixed woven bag sheet from being scalded or damaged due to continuous heating of the heat sealing head during the subsequent sheet slip and physical locking process. If the duration of the pulse train is less than 10 ms, it is considered to be a benign disturbance that can be absorbed by the internal capacitor of the driver, and the hardware timer is automatically reset after the signal disappears. The AND gate has no valid output, and the entire timing chain control subsystem remains in standby state without interfering with the normal operation of the system.

[0071] Next, the timing prediction module is described in detail. Please refer to Figure 4The core function of the module is to receive the valid event confirmation signal, and based on the real-time running parameters of the system and the pre-set physical model, to instantly calculate the sheet material slip time caused by mechanical inertia within the time scale of microseconds, and to generate accurate timing instructions for driving the locking execution module accordingly.

[0072] The FPGA has a set of experimentally calibrated state space model inside. The model describes the functional relationship between the time required for the sheet material to slip to a predetermined physical position (usually the position triggered by the safety door sensor) on the conveyor belt due to inertia (i.e. slip time) and three key variables from the moment when the torque of the conveying mechanism driving motor completely disappears. The three variables are: grid voltage drop rate, total equivalent mechanical inertia of the conveyor system, and sheet material running speed at the start of slip. An input port of the FPGA receives a pulse train signal from the fluctuation sensing module through a dedicated pin, whose frequency is proportional to the voltage drop rate; another input port reads the system total equivalent mechanical inertia parameter in real time through the SPI bus from an EEPROM (such as AT24C256) outside the FPGA, which is measured and written during factory debugging; the third input port is directly connected to an absolute position encoder installed on the main drive shaft of the conveying mechanism through high-speed differential signal lines, and obtains the angular position of the main drive shaft in real time through the SSI protocol at a clock rate of 1MHz, and calculates the real-time running linear speed of the sheet material at the start of slip.

[0073] When the valid event confirmation signal arrives, the digital signal processing core inside the FPGA immediately latches the values of the three input parameters at that time, and substitutes them into the state space model for high-speed floating point operation to calculate a basic slip time value.

[0074] As a preferred embodiment of the present application, a dynamic compensation unit is integrated into the timing prediction module. The dynamic compensation unit is composed of a multi-dimensional lookup table (LUT) and a set of hardware multipliers, and is implemented entirely using the logic resources of the FPGA. The input terminals of the dynamic compensation unit are connected to the shared data area of the main controller, to obtain the target running speed of the sheet material set by the current production process and the thickness of the sheet material measured by the sensor in real time. The LUT pre-stores compensation coefficients at different running speeds and sheet material thicknesses calibrated in a large number of experiments. Specifically, when the FPGA detects that the linear speed of the conveyor belt corresponding to the real-time running speed data read from the shared data area exceeds 35 m / min, the LUT outputs a speed compensation coefficient with a value of 0.85; when the sensor measures that the sheet material thickness data corresponds to a value greater than 0.2 mm, the LUT outputs a thickness compensation coefficient with a value of 1.08. The hardware multipliers multiply the base slip time value calculated above with the two compensation coefficients retrieved from the LUT in sequence, to obtain a final slip time value corrected dynamically according to the working conditions. This design enables the prediction of the slip time to adapt to changes in process parameters between different production batches, thereby improving the accuracy of the prediction.

[0075] After obtaining the final slip time value, the timing generation circuit inside the timing prediction module is activated. The timing generation circuit is composed of a hardware subtractor and a presettable down counter. The hardware subtractor subtracts a fixed lock-in advance from the final slip time value, and the result is used as the countdown duration for the ejection of the positioning pin. This countdown duration is directly loaded into the preset register of the down counter. The down counter is provided with a stable 100 MHz clock signal from a temperature-compensated crystal oscillator (TCXO).

[0076] At the same time, the timing generation circuit also reads the corresponding ejection depth parameter from the internal parameter table according to the current sheet material specification, and packs it together with the calculated countdown duration into a two-parameter digital instruction. This instruction (for example, a 32-bit word, with the upper 16 bits representing the duration and the lower 16 bits representing the depth) is transmitted directly to the drive circuit of the lock execution module through a set of dedicated shielded twisted pair lines using the low-voltage differential signal (LVDS) standard. The use of LVDS and point-to-point hard connection ensures extremely high noise immunity and extremely low delay for the instruction transmission, avoiding any bus arbitration or protocol overhead. After the instruction is sent, the timing generation circuit also sends a single-cycle pulse signal to the state inheritance module through the internal routing of the FPGA, indicating that the lock is ready, to activate the subsequent state verification function.

[0077] Then the lock execution module is described. Please refer to Figure 5 and Figure 6The function of the module is to receive the accurate timing instruction from the timing prediction module and drive the physical locking mechanism to complete the physical fixation of the woven bag piece within the predicted time window. The locking execution module includes an electromagnetic positioning pin assembly and a closed-loop driving and verification circuit for it. As shown in Figure 5 the electromagnetic positioning pin assembly is rigidly mounted on the side frame of the conveying mechanism and can be driven at high speed to extend through the process hole reserved for positioning on the edge of the woven bag piece or directly penetrate the piece body without reserved hole, thereby achieving absolute position locking of the piece on the conveying belt.

[0078] As shown in Figure 6 the core of the closed-loop driving and verification circuit is a high-power H-bridge driving circuit, whose switching elements are four low-conductivity metal oxide semiconductor field effect transistors (MOSFETs) and are controlled by a dedicated pulse width modulation (PWM) controller. The logic of the PWM controller is implemented in the same FPGA to ensure seamless connection with the timing generation circuit. After receiving the aforementioned double-parameter digital instruction, the PWM controller loads the countdown duration in the instruction into its internal timer. When the timer is zero, the PWM controller immediately outputs a customized driving pulse sequence. The sequence includes a "peak" phase with a duty cycle of 95% and a duration of 15 ms, which generates a large current to overcome the static friction and coil inductance of the electromagnet in the shortest time, realizing the rapid ejection of the positioning pin; then seamlessly switches to a "hold" phase with a duty cycle of 20% and continuous supply, which is used to maintain the locking state of the positioning pin after it reaches the predetermined position with minimal power consumption, preventing the coil from overheating due to long-term large current passing. The ejection depth parameter in the instruction is used as the target position setting value for the closed-loop control of the PWM controller.

[0079] To achieve precise closed-loop position control, a high-precision linear variable differential transformer (LVDT) displacement sensor is integrated at the tail of the pin body of the electromagnetic positioning pin assembly. The LVDT sensor can measure the extension position of the positioning pin in real time and convert it into an analog voltage signal proportional to the displacement. After being amplified, filtered, and demodulated by a dedicated signal conditioning chip, the signal is converted into digital by an analog-to-digital converter (ADC) and input to the PWM controller in the FPGA as feedback. The PWM controller compares the real-time position feedback value with the target depth value set by the instruction, and dynamically adjusts the duty cycle of the PWM pulse according to the error through a hardware-implemented proportional-integral-derivative (PID) algorithm, thereby forming a complete position closed-loop control loop with a response bandwidth of up to 5 kHz. This loop ensures that even in the case of slight fluctuations in load or power supply, the final ejection depth error of the positioning pin can be stably controlled within ±0.2 mm. When the positioning pin is fully ejected to the target position, a mechanical contact microswitch at the end of the pin is closed. The contacts of the switch are gold-plated to ensure long-term reliable low contact resistance, and the closing signal is sent to the state inheritance module as a "physical lock completion" status flag.

[0080] In addition, the lock execution module also includes a sliding motion verification unit implemented inside the FPGA. This unit is activated after receiving the "lock ready" signal from the timing prediction module and continuously samples the absolute position encoder data on the main drive shaft of the transfer mechanism at a frequency of 10 kHz. It compares the real-time position with the position at the time the "lock ready" signal arrives and calculates the actual amount of slip. If the detected slip exceeds a safe threshold, for example 1.6 mm, before the positioning pin is fully locked (i.e. the "physical lock completion" signal is received), it indicates that the initial prediction is biased or the sliding process is disturbed unexpectedly. At this time, the sliding motion verification unit will immediately generate a depth compensation signal, which is directly superimposed on the input of the PWM controller through a digital-to-analog converter (DAC) and an amplification circuit, causing the current in the "hold" phase to be dynamically increased (with a maximum increase of 20%), thereby increasing the ejection force of the positioning pin to resist the unexpected sliding force.

[0081] At the same time, the verification unit writes the data of this prediction deviation (i.e. the difference between the predicted slip and the actual slip) back to the EEPROM unit that stores the total equivalent mechanical inertia parameters through the internal bus. A recursive least squares (RLS) adaptive algorithm is embedded in the logic of the FPGA to correct the mechanical inertia parameters online based on this deviation data. This closed-loop feedback and adaptive correction mechanism enables the system to optimize itself after each abnormal event and continuously improve the accuracy of the prediction model.

[0082] Finally, the state inheritance module is described. Please refer to Figure 7 The function of this module is to coordinate the handling of the physical lock event and the main controller shutdown event triggered by the factory safety system (e.g. a safety door being opened), to verify the timing accuracy of the pre-lock operation, and to provide an accurate position reference for the fast, uncalibrated recovery of the system after a successful confirmation. The core of the state inheritance module is a set of timing verification and data latching circuits, which are also implemented inside the FPGA. When the sensor of the factory safety protection system is triggered, its output switching signal is shunted by a high input impedance buffer into two paths: one path goes to the emergency stop input of the main controller, triggering it to execute the regular software shutdown procedure; the other path goes to the timing verification unit inside the state inheritance module.

[0083] Two hardware timestamp latches are provided inside the timing verification unit. The first latch latches the current high-precision system clock count value at the moment when the timing prediction module issues the ejecting instruction of the positioning pin. The second latch latches the clock count value at the moment when the safety door sensor signal is received. A hardware subtractor calculates the difference between the two timestamps, which is the actual advance of the positioning pin action relative to the safety door trigger. A digital comparator compares this actual advance with a preset success window, e.g. 195ms to 205ms. If the actual advance falls within this window, it is determined that the pre-lock operation is successful. At this time, the timing verification unit sets a "zero calibration" flag bit in a dedicated state register inside the FPGA. At the same time, another data latch latches the accurate coordinate data read from the conveying mechanism absolute position encoder at the moment when the "physical lock completion" signal from the lock execution module is received. This hardware-latched coordinate data is the accurate physical position of the sheet material at the time of system shutdown. If the actual advance exceeds the preset window, it is determined that the pre-lock fails, and the timing verification unit will output a specific fault code through a diagnostic interface according to the specific situation of advance or lag, and reset the "zero calibration" flag bit to zero. Embodiment Two

[0084] Based on the system of Embodiment One, this embodiment further discloses a timing chain control method, whose execution flow under power grid fluctuation events is as shown in Figure 8 When the power grid fluctuates, the fluctuation perception module captures the event and generates a trigger signal. After the event validity discrimination unit confirms the severity of the event, it cuts off the heat seal heating on one hand, and activates the timing prediction module on the other hand. The timing prediction module calculates the slip time according to the real-time parameters and generates a timing instruction. The lock execution module drives the electromagnetic positioning pin to eject at the accurate time according to the instruction, physically fixing the sheet material. At the same time, the state inheritance module verifies the timing of the entire process, and latches the accurate position data of the sheet material after the lock is completed.

[0085] The flowchart of fast recovery production after pre-locking success is shown in Figure 9 When the main controller finishes its own shutdown flowchart and receives the reset signal from the operator, it first reads the status register in the status inheritance module through the shared bus. If the "zero calibration" flag bit is in the valid state (logic 1), the main controller completely skips all traditional origin regression or manual intervention required tool calibration flowchart. It directly reads the accurate coordinate data locked by the data latch, and uses this data as the starting position reference for subsequent cutting and heat sealing operations, and updates its internal workpiece coordinate system. The position controllers of the heat sealing actuator and the cutting actuator automatically adjust their working positions according to this reference data. Subsequently, the main controller issues a command to drive the locking execution module to retract the electromagnetic positioning pin and restart the conveying mechanism. The entire recovery process is fully automated and strictly monitored by a hardware watchdog timer inside the FPGA, ensuring completion within 3.0 seconds. This hardware-locked state-based inheritance recovery fundamentally eliminates the position uncertainty caused by inertial slip, achieving truly seamless fast production.

[0086] As a fault-tolerant mechanism, the application also provides a backup safety calibration flowchart executed after pre-locking failure, as shown in Figure 10 If the main controller reads that the "zero calibration" flag bit is in the invalid state (logic 0), indicating that the pre-locking has failed. At this time, the system will automatically enter a backup safety calibration flowchart. This flowchart is executed by the software of the main controller, which first commands the electromagnetic positioning pin to retract, then drives the conveying mechanism to move a small distance at a very low speed (e.g. 0.5 m / min), and controls the cutting actuator to perform a trial cut. Subsequently, the cutting position of the trial cut is detected by the machine vision system installed downstream or the physical limit switch, and a new base point is established based on this position to re-establish the machining coordinate system. This backup process is only activated by the main controller according to the specific fault code read from the diagnostic interface when the status inheritance module determines that the pre-locking has failed, thereby ensuring the robustness of the system in extreme abnormal conditions. Example Three

[0087] This embodiment describes the operation of the application in a specific industrial application scenario. The production object is a polypropylene (PP) woven bag piece with a thickness of 0.18 mm, and the production line is set to run at a speed of 40 m / min. The system preset parameters are as follows: the total equivalent mechanical inertia of the conveying system is calibrated to 0.085 kg·m² and stored in the EEPROM; the locking advance is set to 200 ms; the pre-locking success window is set to [195 ms, 205 ms].

[0088] During the production process, a transient voltage sag event occurred in the factory power grid, in which the three-phase 380V AC voltage linearly dropped to 310V within 5ms, with a voltage drop rate of 14V / ms, exceeding the 12V / ms threshold set by the fluctuation perception module and lasting more than 10ms. The timing chain control subsystem was successfully activated.

[0089] The timing prediction module latched the web speed at the slip start moment as 40m / min, and obtained a pulse frequency corresponding to 14V / ms from the fluctuation perception module. According to the internal state space model, the base slip time was calculated as 450ms. The dynamic compensation unit detected that the line speed was greater than 35m / min, and output a speed compensation coefficient of 0.85; detected that the web thickness was less than 0.2mm, and output a thickness compensation coefficient of 1.0. The final slip time was corrected to 450ms*0.85*1.0=382.5ms. The timing generation circuit calculated the countdown duration as 382.5ms-200ms=182.5ms, and issued a lock instruction.

[0090] At the same time, the driver reported an under-voltage fault due to the voltage sag, triggering the safety gate protection logic of the factory. The safety gate sensor was triggered when the voltage dropped to 320V (about 3.4ms after the event). The electromagnetic positioning pin was driven after 182.5ms of countdown and successfully locked the web before it stopped slipping. The state inheritance module recorded that the actual time difference from the issuance of the lock instruction to the arrival of the safety gate signal was 197.5ms, falling within the successful window of [195ms, 205ms]. Therefore, the "zero calibration" flag was set and the absolute position coordinates of the web at the locking moment were latched.

[0091] It was measured that the actual slip amount of the web in this event was 254.6mm, and the final position deviation after physical locking was only 0.3mm. After the operator excluded the power grid fault, the reset button was pressed on the main controller, the system automatically read the latched position data, retracted the positioning pin and resumed production, and the entire recovery process took 2.8 seconds without any manual calibration.

[0092] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can make equivalent replacements or changes within the technical scope disclosed by the present application according to the technical solution and inventive concept of the present application, which should be covered within the protection scope of the present application.

Claims

1. A woven bag sheet cutting and heat-sealing system, comprising a conveying mechanism, a cutting actuator, a heat-sealing actuator, and a main controller, characterized in that, Also includes: The timing chain control subsystem establishes a direct control path with the conveying mechanism, cutting execution mechanism and heat sealing execution mechanism without going through the main controller software logic; The timing chain control subsystem includes: The fluctuation sensing module is used to monitor the voltage at the power input terminal of the heat sealing actuator and generate a digital trigger signal when a voltage drop event is detected. The timing prediction module is used to receive the digital trigger signal, calculate the sheet material sliding time based on real-time operating parameters and a preset physical model, and generate a precise timing instruction that includes countdown duration and pop-up depth parameters. The locking execution module is used to receive the precise timing command and drive the physical locking mechanism to perform a physical fixing operation on the woven bag sheet on the conveying mechanism after the countdown time ends; The state inheritance module is used to latch the precise position data of the sheet material indicated by the absolute position encoder of the conveying mechanism after the physical fixing operation is completed, and to provide the latched data as a position reference for uncalibrated recovery when the main controller requests to resume production. The fluctuation sensing module includes: A high-bandwidth differential voltage sampling circuit is connected in parallel to the main power input bus of the heat-sealing actuator. A high-speed transient voltage comparator, connected to the output of a high-bandwidth differential voltage sampling circuit, outputs a square wave edge signal when the voltage drop rate at the power input exceeds a preset threshold; and The high-speed optocoupler isolation circuit receives a square wave edge signal at its input and outputs a square wave pulse train that is proportional to the voltage drop rate, which is then fed into the timing prediction module as a digital trigger signal. The timing prediction module is implemented by a field-programmable gate array, with an internally fixed state-space model. The input port of the field-programmable gate array is connected to the wave sensing module, the system's total mechanical inertia parameter storage unit, and the absolute position encoder of the main drive shaft of the transmission mechanism. The core of digital signal processing utilizes a state-space model to calculate the basic slip time value based on the voltage drop rate, the total mechanical inertia parameter of the system, and the running speed of the sheet material at the moment of slip initiation. The locking execution module includes an electromagnetic positioning pin assembly and a closed-loop drive and verification circuit. The electromagnetic positioning pin assembly is installed on the side of the conveying mechanism, and the pin head extends under drive to pass through or pierce the woven bag sheet material; The core of the closed-loop drive and verification circuit is an H-bridge drive circuit controlled by a pulse width modulation controller. After the countdown ends, it outputs a drive pulse sequence, including a peak phase to enable the positioning pin to pop out quickly and a holding phase to maintain the locked state. The core of the state inheritance module is a timing verification and data latching circuit, which includes two hardware timestamp latches and one data latch. The first hardware timestamp latch latches the system clock count value the instant the timing prediction module issues a precise timing instruction. The second hardware timestamp latch latches the clock count value the instant it receives a trigger signal from an external security system. The timing verification and data latch circuit includes a hardware subtractor and a digital comparator. It calculates the timestamp difference to obtain the actual lead time and compares it with a preset success window. If the actual lead time falls within the window, the "zero calibration" flag is set. The data latch latches the precise coordinate data of the absolute position encoder of the transmission mechanism the instant it receives the "physical lock complete" signal.

2. The system according to claim 1, characterized in that, The fluctuation sensing module also includes an event validity identification unit, which consists of a hardware timer and a digital logic AND gate; The hardware timer starts timing when it receives a square wave pulse train; The digital logic AND gate outputs a valid event confirmation signal only when the duration of the square wave pulse train exceeds a preset time window and the signal exists, thereby activating the timing prediction module and disconnecting the heating circuit of the heat sealing actuator.

3. The system according to claim 1, characterized in that, The timing prediction module also includes a dynamic compensation unit and a timing generation circuit; The dynamic compensation unit consists of a multidimensional lookup table and a hardware multiplier. It obtains the sheet running speed and thickness specifications, retrieves the compensation coefficient, and multiplies the basic slip time value with the compensation coefficient to obtain the final slip time value. The timing generation circuit consists of a hardware subtractor and a decrement counter. It subtracts the lock advance from the final slide time value and loads it as the countdown duration into the decrement counter to generate a precise timing instruction containing the countdown duration and pop-up depth parameters.

4. The system according to claim 1, characterized in that, The electromagnetic positioning pin assembly integrates a linear variable differential transformer displacement sensor inside the pin body to measure the position of the positioning pin extension in real time and convert it into a position feedback signal. The pulse width modulation controller receives the position feedback signal, compares it with the target depth value set by the pop-up depth parameter, and dynamically adjusts the duty cycle according to the error to form a position closed-loop control loop. The electromagnetic positioning pin assembly is equipped with a mechanical contact micro switch at the end, which outputs a "physical locking complete" signal when closed.

5. The system according to claim 4, characterized in that, The locking execution module also includes a sliding motion verification unit; After the timing prediction module sends a "lock ready" signal, the sliding motion dynamic verification unit samples the absolute position encoder data of the main drive shaft of the transmission mechanism and calculates the actual sliding amount. If the actual slip exceeds the safety threshold, the slip dynamic verification unit generates a depth compensation signal to increase the current during the holding phase, and at the same time writes the predicted deviation data back to the system's total mechanical inertia parameter storage unit.

6. A timing chain control method, applicable to the system as described in claim 5, for resuming production after successful pre-locking, characterized in that, Includes the following steps: After completing the shutdown process and receiving the reset signal, the main controller reads the status register in the status inheritance module; If the "zero calibration" flag is valid, the main controller skips the origin return or manual calibration process and directly reads the precise position data latched by the data latch. The main controller uses the precise position data as the starting position reference for subsequent cutting and heat sealing operations, and updates the working positions of the cutting and heat sealing actuators. The main controller issues a command to drive the locking execution module to retract the electromagnetic positioning pin assembly pin head and restart the conveying mechanism, thereby achieving automated and rapid production recovery.

Images