A digital twin system for a rotary cutting machine and an implementation method thereof

Abstract

The application discloses a digital twin system for a rotary cutting machine and an implementation method thereof, and comprises a real rotary cutting machine in a physical world, a rotary cutting machine in a digital world and an OPCUA server interconnecting the two, wherein the OPCUA server comprises an OPCUA gateway, and the rotary cutting machine in the digital world and the real rotary cutting machine in the physical world perform bidirectional data transmission through the OPCUA gateway and a communication protocol. The application has the following advantages: the 1:1 virtual rotary cutting machine model in a virtual scene is simulated to cut, three-dimensional visual online monitoring and remote feedback closed-loop operation of the real rotary cutting machine are realized, the intelligent level of the rotary cutting machine is improved, the rotary cutting machine can efficiently cut out single boards with uniform thickness and high quality, the state of the rotary cutting machine can be grasped in real time, problems can be timely warned, and safety accidents can be reduced.

Description

Technical Field

[0001] This invention relates to a digital twin system and its implementation method for veneer lathes, belonging to the field of veneer lathe control technology. Background Technology

[0002] As the main production equipment for wood veneer, the veneer laminating machine functions to process round logs of a certain length and diameter into a continuous veneer strip through a veneer lamination process. This strip is then cut into multiple veneers of the same specifications by manual measurement or automatic guillotine cutting. Currently, veneer laminating machines suffer from problems such as uncontrollable lamination parameters, high testing and development costs, and cumbersome blade adjustment procedures.

[0003] Currently, the non-clamping rotary cutting method mainly utilizes a pressing friction roller (pressure roller) that serves as both a clamping and feeding mechanism, and two main friction rollers (drive rollers) with surface textures that clamp the log and provide friction drive to fix it in place. A rotary cutter contacts the log below the pressure roller, generating a certain cutting force to begin rotary cutting. The drive roller has motors at both ends, and its rotation is controlled by a PLC using frequency conversion speed regulation. The rotary cutter is mounted on a cutter head, which uses a lead screw feed system. Each end of the cutter head has a motor with a reducer. Before rotary cutting, the worker adjusts the cutter installation parameters, including cutter height and clearance. During rotary cutting, the PLC controls the motors at both ends using frequency conversion speed regulation to make the cutter head complete the feeding motion, thus rotary cutting the log into veneer.

[0004] Currently, spindleless veneer lathes generally suffer from the following problems:

[0005] 1. The parameters of the rotary cutting process are uncontrollable. During the rotary cutting process, the feed speed of the blade table and the rotary cutting angle are fixed values ​​and cannot be updated in real time according to the condition of the log.

[0006] 2. The testing and development costs are high. The rotary cutting scheme varies depending on the tree species and the diameter of the logs. If the rotary cutting parameters are confirmed every time, the rotary cutting machine is used for trial cutting, which will not only waste materials, but also increase the wear and tear of the rotary cutting machine. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the above-mentioned shortcomings by providing a digital twin system and its implementation method for veneer laminating machines. In a virtual scene, a 1:1 virtual veneer laminating machine model is used to simulate veneer laminating, realizing three-dimensional visualization online monitoring and remote feedback closed-loop operation of the real veneer laminating machine. This can improve the intelligence level of the veneer laminating machine, enabling it to efficiently veneer laminating high-quality veneers with uniform thickness, and can monitor the status of the veneer laminating machine in real time, providing timely warnings for problems and reducing the occurrence of safety accidents.

[0008] To solve the above technical problems, the present invention adopts the following technical solution:

[0009] A digital twin system for a veneer lathe includes a physical veneer lathe, a digital veneer lathe, and an OPC UA server that interconnects the two. The OPC UA server includes an OPC UA gateway. The digital veneer lathe and the physical veneer lathe transmit data bidirectionally through the OPC UA gateway and a communication protocol.

[0010] The veneer lathe in the physical world consists of a veneer lathe body, a measurement module, and a control system;

[0011] The measurement module includes a set of laser rangefinders, with eight laser rangefinders arranged in a straight line. The outermost laser rangefinder measures the distance to the calibration block next to the rotary cutter, while the remaining laser rangefinders measure the distance to the surface of the log.

[0012] The control system includes lead screw control, roller control, and rotary cutter control;

[0013] The veneer lathe in the digital world refers to the working scene of the veneer lathe and the digital twin system of the veneer lathe under Unity3D on the host computer. The digital twin system of the veneer lathe includes a log reconstruction module, a veneer lathe analysis and motion planning module, a control decision module, and a three-dimensional online monitoring module.

[0014] Furthermore, the log reconstruction module uses laser rangefinder data collected by a real rotary cutting machine to calculate the location of log defects, find the lowest point of the log, remove the defects, and then uses the laser rangefinder data collected again to calculate the radius of the log and generate a log model for subsequent rotary cutting analysis and three-dimensional rotary cutting display.

[0015] The calculation process for the radius of the log is as follows:

[0016] The outermost laser rangefinder measures the distance to the calibration block, denoted as L2. The remaining laser rangefinders measure the distance to the log, denoted as L1. R is the radius of the log, r is the radius of the roller, and h is the distance from the calibration block to the center of the roller. Based on geometric relationships, we can obtain...

[0017] Furthermore, the rotary cutting analysis and motion planning module is based on a feedforward and PID neural network. Its hidden layer consists of proportional, integral, and differential elements, which can perform proportional, integral, and differential operations on the input signal. The output layer neurons can realize the synthesis and output of the control law of the entire network. The screw feed speed is calculated using the log size obtained by the log reconstruction module, the preset rotary cutting plate thickness, and the installation dimensions of the rotary cutting machine. The rotary cutter angle is calculated using the log size obtained by the log reconstruction module.

[0018] Furthermore, the calculation process for the lead screw feed speed is as follows:

[0019] Assume the diameter of both the dual drive rollers and the feed roller is d (mm), and their rotational speed is n0 (r / min); the center distance between A and B is c (mm); the instantaneous diameter of the log to be processed is φ (mm), and its instantaneous rotational speed is n (r / min); the feed speed of the rotary cutter is v. t (mm / min), the thickness of the single-layer rotary cutting is S (mm);

[0020] The log is held in a rotating manner by the dual drive rollers and the feed rollers. The linear velocity of the dual drive rollers and the feed rollers is equal to that of the log, so φ·n=d·n0;

[0021] Let point P be the point of contact between the rotary cutter and the log.

[0022] Differentiate both sides of the above equation with respect to the rotation time t.

[0023] Based on the conservation of mass and density of the log before and after rotary cutting, the rate of change of the cross-sectional area of ​​the veneer, Vc·S, is equal to the rate of change of the cross-sectional area of ​​the log, S'. Therefore, S' φ =v c ·S, of which Therefore, φ' = 2nS;

[0024] Thus, the kinematic equations are obtained.

[0025] Let the lead screw feed rate be u = v t , S d Let w be the preset single-board thickness value and w be the output value of the PIDNN. Based on market experience, the initial value of the connection weight from the input layer to the hidden layer is selected, and then u, the lead screw feed speed, can be obtained through calculation by the hidden layer.

[0026] Furthermore, the calculation process for the rotary cutter angle is as follows:

[0027] Let H be the tool mounting height, α g (∠FAG) is the working rear angle, α z (∠DAG) is the back angle after tool loading, α f (∠DAE) is the additional rear angle, α y (∠EAF) is the clearance angle. The only factor affecting the cutting angle is the working clearance angle α. g , where α z For installation parameters,

[0028] According to geometric relationships, we can obtain: φ is the instantaneous radius of the log, and S is the preset thickness of the rotary-cut board, so the cutting angle is determined only by the blade mounting height.

[0029] Furthermore, the control decision module calculates the motor speed and stepper motor angle based on the lead screw feed speed and cutter angle obtained from the rotary cutting analysis and motion planning module, and matches them according to the switching frequency of the motor servo driver. The results are then fed back to the PLC through the server to control the motor speed and angle.

[0030] Furthermore, the three-dimensional online monitoring module communicates with the PLC through the server to obtain the operating status of each motor and the data of each laser ranging sensor. In Unity3D, the above data is used to perform three-dimensional visualization monitoring of the rotary cutting process through three-dimensional virtual simulation, real-time curve graphs, and tables.

[0031] Furthermore, the OPC UA server includes a communication network consisting of an OPC UA gateway and a router, and an OPC UA perception data model established for the veneer lathe in the physical world and the veneer lathe in the digital world. By standardizing the data format through modeling, multi-source data is mapped to the model structure tree. Based on data integration, the instantiation of the model and data interaction are realized. The OPC UA gateway is connected to the PLC of the veneer lathe in the physical world through the RS485 communication protocol, and the host computer is connected to the OPC UA gateway through a wireless network, enabling Unity3D to remotely communicate with the PLC of the veneer lathe in the physical world, thereby interacting with each laser rangefinder and each motor.

[0032] Furthermore, the process of establishing the OPC UA data awareness model is as follows:

[0033] The process involves identifying the equipment types, parameters, and methods required for modeling, as well as the relationships between equipment, between equipment and parameters, and between equipment and methods. A type model is defined using the UA Modeler software, primarily including defining object type models, variable type models, reference type models, and data type models. These are then merged into a unified type model. The four type models are instantiated, and an instantiation information model is established according to the standard address space method of the OPC UA server. XML is exported using the UA Modeler tool as the data source for the instantiation information. Finally, the information model is converted into code using the tools included with the open62541 and added to the OPC UA Server.

[0034] A method for implementing a digital twin system for a veneer lathe includes the following steps:

[0035] Step S01, System initialization;

[0036] Step S02: Select offline mode. If yes, execute step S03 first, then execute step S04, and return to step S02. If no, execute S05.

[0037] Step S03, set parameters;

[0038] Step S04: Perform rotary cutting simulation;

[0039] Step S05: Control the laser rangefinder to sequentially collect the depth information of the log surface, that is, the distance from the laser rangefinder to the log surface;

[0040] Step S06: The PLC transmits the log surface data to Unity via the OPC UA gateway;

[0041] In step S07, the log reconstruction module uses the log surface depth information to calculate the defect location, find the lowest point on the log surface, and feeds the result back to the PLC to control it to rotary cut the log to the defect location to obtain an effective round log, i.e. a standard cylinder.

[0042] Step S08: After removing defects, collect the surface depth information of the log again to detect whether there are defects on the surface. If there are defects, proceed to S07. Otherwise, use the surface depth information of the log to calculate the radius of the log and generate a log model in Unity for rotary cutting analysis and 3D rotary cutting display.

[0043] Step S09: Calculate the lead screw feed speed and cutter angle by calling the rotary cutting analysis and motion planning module;

[0044] In step S10, the control decision module matches the screw feed speed and rotary cutter angle calculated in step S09 with the switching frequency of the motor servo driver, and transmits the required motor speed and angle to the PLC.

[0045] Step S11: Data exchange with PLC is performed through OPC UA gateway. The data is classified and stored through OPC UA data perception model. Unity then performs 3D visualization based on the information type.

[0046] Step S12: Determine if there is a next work signal. If yes, proceed to step S05; otherwise, proceed to step S02, or terminate directly.

[0047] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0048] 1. Compared with traditional rotary cutting machines, the digital twin system for rotary cutting machines can determine the optimal rotary cutting scheme based on the morphology analysis of the logs being rotary cut, thereby improving the quality of wood board rotary cutting and the utilization rate of wood.

[0049] 2. The aforementioned digital twin system for the veneer laminating machine can communicate with the laser rangefinder of the veneer laminating machine through an OPC UA gateway and display the data in a three-dimensional visual format on the digital world interface of the veneer laminating machine, thereby enabling remote real-time monitoring and control of the veneer laminating machine, reducing factory personnel and improving factory safety.

[0050] 3. The digital twin system of the veneer lathe, equipped with a digital world veneer lathe, can be used offline to allow staff to test or learn the functions of the veneer lathe and improve the training methods for operating the veneer lathe.

[0051] 4. The parameters of the rotary cutting process are controllable. During the rotary cutting process, the feed speed of the blade table and the rotary cutting angle can be updated in real time according to the condition of the log.

[0052] 5. Low testing and development costs, applicable to rotary cutting solutions for logs of different tree species and diameters. Attached Figure Description

[0053] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0054] Figure 1 This is a structural block diagram of the digital twin system for a veneer lathe in this invention;

[0055] Figure 2 This is a flowchart of the data interaction process in this invention;

[0056] Figure 3 This is a flowchart of the implementation method in this invention;

[0057] Figure 4 This is a schematic diagram illustrating the principle of calculating the radius of a round log in this invention.

[0058] Figure 5 This is a schematic diagram of the feedforward and PID neural network principle in this invention;

[0059] Figure 6 A schematic diagram illustrating the establishment of the kinematic equations in this invention;

[0060] Figure 7 This is a schematic diagram of the cutting angle of the rotary cutter in this invention. Detailed Implementation

[0061] Example 1: A digital twin system for a veneer lathe includes a physical veneer lathe, a digital veneer lathe, and an OPC UA server interconnecting the two. The digital veneer lathe and the physical veneer lathe transmit data bidirectionally through an OPC UA gateway and the OPC UA communication protocol.

[0062] The veneer lathe described in the physical world consists of a veneer lathe body, a measurement module, and a control system. The veneer lathe body is an existing veneer lathe, including mechanical components such as dual drive rollers, feed rollers, rotary blades, and lead screw slides. The measurement module includes a set of laser rangefinders. A set of laser rangefinders is installed on the back side of the dual drive rollers. Laser rangefinder No. 1 measures the distance to the calibration block next to the rotary blade, and laser rangefinders No. 2 to No. 8 measure the distance to the surface of the log. Based on the installation dimensions, the surface depth information of the log at the location of laser rangefinders No. 2 to No. 8 can be obtained.

[0063] like Figure 1 As shown, the control system adopts a PLC system control, which includes lead screw control, roller control, and rotary knife control. In the roller control, the two drive rollers are connected by a synchronous belt, and the main drive roller is controlled by a motor. The synchronous belt enables the two drive rollers to rotate at the same speed. The feed roller is controlled by a motor, and the control module keeps the speed of the two drive rollers and the feed roller the same. In the rotary knife control, the rotary knife is controlled by a stepper motor connected to a reducer, ensuring that the rotary knife can change different angles according to different diameter logs.

[0064] The digital world veneer machine refers to the working scene of the veneer machine under Unity3D on the host computer and the digital twin system of the veneer machine. The digital twin system of the veneer machine includes a log reconstruction module, a veneer analysis and motion planning module, a control decision module, and a three-dimensional online monitoring module.

[0065] The log reconstruction module uses laser rangefinder data collected by a real rotary cutting machine to calculate the location of log defects, find the lowest point of the log, remove the defects, and then uses the laser rangefinder data collected again to calculate the radius of the log and generate a log model for subsequent rotary cutting analysis and 3D rotary cutting display.

[0066] The principle of calculating the radius of a log is as follows: Figure 4 As shown:

[0067] Eight laser rangefinders are positioned along a straight line. The outermost laser rangefinder measures the distance from it to the calibration block, denoted as L2. The remaining laser rangefinders measure the distance from them to the log, denoted as L1. R is the radius of the log, r is the radius of the roller, and h is the distance from the calibration block to the center of the roller. Based on geometric relationships, we can obtain...

[0068]

[0069] The rotary cutting analysis and motion planning module is based on a feedforward and PID neural network. Its hidden layers consist of proportional, integral, and differential elements, capable of performing proportional, integral, and differential operations on the input signal. The output layer neurons can synthesize and output the control law of the entire network. Initial values ​​of the PID connection weights are input using market experience, and then the network self-learns to achieve excellent dynamic and static performance in the resulting control system. The screw feed speed is calculated using the log dimensions obtained from the log reconstruction module, the preset rotary cutting plate thickness, and the installation dimensions of the rotary cutting machine. The rotary cutter angle is calculated using the log dimensions obtained from the log reconstruction module, and the system communicates with the PLC in real time to obtain the instantaneous radius of the log, achieving closed-loop operation.

[0070] Assume the diameter of both the dual drive rollers and the feed roller is d (mm), and their rotational speed is n0 (r / min); the center distance between A and B is c (mm); the instantaneous diameter of the log to be processed is φ (mm), and its instantaneous rotational speed is n (r / min); the feed speed of the rotary cutter is v. t (mm / min), the veneer rotary cutting thickness is S (mm), as shown in the diagram. Figure 5 As shown.

[0071] Because the double drive roller and the feed roller clamp the log and rotate, and the linear velocity of the double drive roller and the feed roller is equal to that of the log, φ·n=d·n0.

[0072] Let point P be the point of contact between the rotary cutter and the log.

[0073] Differentiate both sides of the above equation with respect to the rotation time t.

[0074] Based on the conservation of mass and density of the log before and after rotary cutting, the rate of change of the cross-sectional area of ​​the veneer, Vc·S, is equal to the rate of change of the cross-sectional area of ​​the log, S'. Therefore, S' φ =v c ·S, of which Therefore, φ' = 2nS.

[0075] Thus, the kinematic equations are obtained.

[0076] Based on the kinematic equations, a feedforward and PID-based neural network is established, such as... Figure 6 As shown.

[0077] Let the lead screw feed rate be u = v t , S d Let w be the preset single-board thickness value and w be the output value of the PIDNN. Based on market experience, the initial value of the connection weight from the input layer to the hidden layer is selected, and then u, the lead screw feed speed, can be obtained through calculation by the hidden layer.

[0078] Principle of rotary cutter angle calculation:

[0079] Cutting angle diagram as shown Figure 7 As shown, H is the tool mounting height, α g (∠FAG) is the working rear angle, α z (∠DAG) is the back angle after tool loading, α f (∠DAE) is the additional rear angle, α y (∠EAF) is the clearance angle. The only factor affecting the cutting angle is the working clearance angle α. g , where α z For installation parameters,

[0080] According to geometric relationships, we can obtain: φ is the instantaneous radius of the log, and S is the preset thickness of the rotary cutting board. Therefore, the cutting angle is only determined by the blade mounting height. In this invention, the rotary cutter is connected to a stepper motor with a reducer, and the cutting angle can be changed by changing the angle of the stepper motor.

[0081] The control decision module calculates the motor speed and stepper motor angle based on the lead screw feed speed and cutter angle obtained from the rotary cutting analysis and motion planning module, and matches them with the switching frequency of the motor servo driver. The results are then fed back to the PLC through the server to control the motor speed and angle.

[0082] The 3D online monitoring module communicates with the PLC via a server to obtain the operating status of each motor (including speed, rotation angle, status words and fault codes) and data from each laser ranging sensor (including log surface depth information and laser ranging sensor status). In Unity3D, the above data is used to perform 3D visualization monitoring of the veneer cutting process through 3D virtual simulation, real-time curves, tables, etc. The digital twin of the veneer cutting machine can be used offline. After setting the corresponding parameters, the operator can conduct online development, debugging and learning of the veneer cutting machine.

[0083] like Figure 2 As shown, the OPC UA server includes a communication network consisting of an OPC UA gateway and a router, and an OPC UA perception data model established for the veneer machine in the physical world and the veneer machine in the digital world. By standardizing the data format through modeling, multi-source data is mapped to the model structure tree. Based on data integration, the instantiation of the model and data interaction are realized. The OPC UA gateway is connected to the PLC of the veneer machine in the physical world via RS485, and the host computer is connected to the OPC UA gateway via a wireless network, enabling Unity3D to remotely communicate with the PLC of the veneer machine in the physical world, thereby interacting with each laser rangefinder and each motor.

[0084] OPC UA data awareness model establishment process:

[0085] The process involves identifying the equipment types, parameters, and methods required for modeling, as well as the relationships between equipment, between equipment and parameters, and between equipment and methods. Examples include motor number, voltage, torque, speed, pulse count, status words, fault codes, and start / stop commands. The UA Modeler software is used to define type models, primarily including object type models, variable type models, reference type models, and data type models, which are then merged into a unified type model. These four type models are instantiated, and an instantiation information model is created according to the standard address space format of the OPC UA server. XML is exported using the UA Modeler tool to serve as the data source for the instantiation information. Finally, the tools included with the open62541 are used to convert the information model into code and add it to the OPC UA Server.

[0086] like Figure 3 As shown, a method for implementing a digital twin system for a veneer lathe includes the following steps:

[0087] Step S01, System initialization;

[0088] Step S02: Select offline mode. If yes, execute step S03 first, then execute step S04, and return to step S02. If no, execute S05.

[0089] Step S03, set parameters;

[0090] Step S04: Perform rotary cutting simulation;

[0091] Step S05: Control the laser rangefinder to sequentially collect the depth information of the log surface, that is, the distance from the laser rangefinder to the log surface;

[0092] Step S06: The PLC transmits the log surface data to Unity via the OPC UA gateway;

[0093] In step S07, the log reconstruction module uses the log surface depth information to calculate the defect location, find the lowest point on the log surface, and feeds the result back to the PLC to control it to rotary cut the log to the defect location to obtain an effective round log, i.e. a standard cylinder.

[0094] Step S08: After removing defects, collect the surface depth information of the log again to detect whether there are defects on the surface. If there are defects, proceed to S07. Otherwise, use the surface depth information of the log to calculate the radius of the log and generate a log model in Unity for rotary cutting analysis and 3D rotary cutting display.

[0095] Step S09: Calculate the lead screw feed speed and cutter angle by calling the rotary cutting analysis and motion planning module;

[0096] In step S10, the control decision module matches the screw feed speed and rotary cutter angle calculated in step S09 with the switching frequency of the motor servo driver, and transmits the required motor speed and angle to the PLC.

[0097] Step S11: Data exchange is performed with the PLC through the OPC UA gateway. The data is classified and stored by the OPC UA data perception model. Unity performs three-dimensional visualization based on the information type, including rotary cutting simulation animation, real-time curve graphs, tables, etc.

[0098] Step S12: Determine if there is a next work signal. If yes, proceed to step S05; otherwise, proceed to step S02, or terminate directly.

[0099] During system initialization, the PLC controls the rotary cutter to rotate closer to the feed roller to avoid initial contact with the log and prevent obstruction of log surface information extraction. The lead screw slide moves the drive roller and cutter towards the double rollers, waiting for the log to fall between the double drive rollers and the feed roller. After the log falls between the double drive rollers and the feed roller, the motor drives the roller to rotate, and the roller drives the log to rotate. The laser rangefinder extracts the log surface depth information through the gap between the two rollers, and the data is transmitted via the PLC and OPC. The UA gateway uploads data to the host computer. The host computer uses the log reconstruction module to remove defects from the logs, transforming them into standard cylinders and generating a log model in Unity. The rotary cutting analysis and motion planning module uses the model and the instantaneous radius of the logs to analyze and determine the changes in the lead screw feed speed and the rotary cutter angle. The control decision module calculates the motor control parameters based on the changes in the lead screw feed speed and the rotary cutter angle and feeds them back to the PLC via the server. Furthermore, during the actual operation of the rotary cutting machine, the 3D online monitoring module performs real-time visualization and detection of the machine's operating status, including the operating status of each motor and each laser ranging sensor.

[0100] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A digital twin system for a rotary cutting machine, characterized by: The OPC UA server includes a real rotary cutting machine of a physical world, a rotary cutting machine of a digital world and an OPC UA gateway interconnecting the two, and the rotary cutting machine of the physical world and the rotary cutting machine of the digital world perform bidirectional data transmission through the OPC UA gateway and a communication protocol; The physical world rotary cutting machine is composed of a rotary cutting machine main body, a measurement module and a control system; The measurement module includes a set of laser ranging sensors, and eight laser ranging sensors are arranged on a straight line, with the outermost laser ranging sensors measuring the distance to the rotary knife calibration block and the remaining laser ranging sensors measuring the distance to the log surface The control system includes a lead screw control, a roller control and a rotary knife control; The digital world rotary cutting machine refers to a rotary cutting machine working scene and a rotary cutting machine digital twin system under unity3D on an upper computer, and the rotary cutting machine digital twin system includes a log reconstruction module, a rotary cutting analysis and motion planning module, a control decision module and a three-dimensional online monitoring module. The rotary cutting analysis and motion planning module is established based on feedforward and PID neural network, the hidden layer of which is composed of proportional elements, integral elements and differential elements, respectively, and can complete proportional, integral and differential operations on input signals, and the output layer neurons can realize the synthesis and output of the entire network control law, the last log size obtained by the log reconstruction module, the preset rotary cutting plate thickness and the rotary cutting machine installation size are used to calculate the lead screw feed speed, and the last log size obtained by the log reconstruction module is used to calculate the rotary knife angle. The lead screw feed speed calculation process is as follows: The diameters of the double-drive roller and the feed roller are both d, mm, the rotational speed is n0, r / min, the center distance between A and B is c (mm), the instantaneous diameter of the log to be processed is φ (mm), the instantaneous rotational speed is n (r / min), the feed speed of the rotary knife is vt (mm / min), and the rotary cutting thickness of the veneer is S (mm). The double drive roller and the feed roller hold the log to rotate, and the double drive roller and the feed roller have the same linear speed as the log, so ; Let the contact point of the rotary knife and the log be P point, ; simultaneously taking the derivative of both sides of the above equation with respect to the rotation time t, ; According to the mass conservation and density conservation of the logs before and after rotary cutting, the cross-sectional area change rate Vc·S of the veneer is equal to the cross-sectional area change rate S' of the logs, so there is wherein , so ; Instantaneous kinematic equation ; The preset screw feed speed , , Sd is a preset single board thickness value, w is an output value of the PIDNN, and then ; The initial value of the connection weight from the input layer to the hidden layer is selected according to market experience, and then the hidden layer calculation can obtain u, i.e. the lead screw feed speed.

2. A digitally-twin system for a rotary-cut machine as claimed in claim 1, wherein: The log reconstruction module calculates the log defect position using the laser ranging sensor data collected by the real rotary cutting machine, finds the lowest point of the log, and after removing the defects, calculates the log radius using the laser ranging sensor data collected again and generates a log model, which is used for subsequent rotary cutting analysis and three-dimensional rotary cutting display. The log radius calculation process is as follows: The outermost laser ranging sensor measures its distance to the calibration block, denoted as L2, and the rest of the laser ranging sensors measure their distance to the log, denoted as L1. R is the radius of the log, r is the radius of the roller, and h is the distance from the calibration block to the center of the roller. According to the geometric relationship, the following can be obtained .

3. A digitally twinned system for a rotary cutter machine as claimed in claim 1, wherein: The rotary knife angle calculation process is as follows: H is the height of the tool, (∅FAG) is the working clearance angle, (∅DAG) is the tool setting clearance angle, (∅DAE) is the additional clearance angle, (∅EAF) is the movement clearance angle; the only influencing factor of the cutting angle is the working clearance angle wherein is the installation parameter, , ; According to the geometric relationship, we have: , is the instantaneous radius of the log, S is the preset rotary cut plate thickness, so the cutting angle is only determined by the cutter installation height.

4. A digitally twinned system for a rotary cutter machine as claimed in claim 1, wherein: The control decision module calculates the motor speed and step motor angle according to the lead screw feed speed and rotary knife angle obtained by the rotary cutting analysis and motion planning module, and matches the motor servo driver switching frequency, and feeds back to the PLC through the server to control the motor speed and angle.

5. A digitally-twin system for a rotary cutter machine as claimed in claim 1, wherein: The three-dimensional online monitoring module communicates with the PLC through the server to obtain the running state of each motor and the data of each laser ranging sensor, and uses the above data to perform three-dimensional visual monitoring of the rotary cutting process through three-dimensional virtual simulation, real-time curve and table in unity3D.

6. A digitally twinned system for a rotary cutter machine as claimed in claim 1, characterized in that: The OPC UA server includes an OPC UA gateway, a communication network composed of routers and an OPC UA perception data model established for a physical world rotary cutting machine and a digital world rotary cutting machine, through a modeling specification unified data format, multi-source data is mapped to a model structure tree, and on the basis of data integration, instantiation and data interaction of the model are realized, wherein the OPC UA gateway is connected with the PLC of the physical world rotary cutting machine through an RS485 communication protocol, and the upper computer is connected with the OPC UA gateway through a wireless network, so that the unity3D can remotely communicate with the PLC of the physical world rotary cutting machine, thereby interacting with each laser ranging sensor and each motor.

7. A digitally-twin system for a rotary-cut machine as claimed in claim 6, characterized in that: The OPC UA data perception model establishment process comprises the following steps: Confirming the device types required for modeling, the parameters of the devices, the methods possessed by the devices, and the relationships between the devices or between the devices and the parameters and the methods, defining a type model through a UA Modeler software, mainly including defining an object type model, a variable type model, a reference type model and a data type model, then merging into a unified type model, instantiating the four type models, establishing an instantiated information model in accordance with a standard address space mode of the OPC UA server, exporting an XML by using a UA Modeler tool as a data source for realizing the instantiated information, and finally converting the information model into code by using a tool provided by the open62541 and adding the code to the OPC UA Server.

8. A method of implementing a digital twin system for a rotary cutter, the method comprising: The implementation method is applied to the rotary cutting machine-oriented digital twin system as claimed in any one of claims 1-7, and comprises the following steps: Step S01, system initialization; Step S02, whether to select an offline mode, if yes, first execute step S03, then execute step S04, and return to step S02, if no, execute S05; Step S03, setting parameters; Step S04, rotary cutting simulation; Step S05, controlling the laser ranging sensor to sequentially collect the log surface depth information, i.e. the distance from the laser ranging sensor to the log surface; Step S06, the PLC transmits the log surface data to unity through the OPC UA gateway; Step S07, the log reconstruction module calculates the defect position by using the log surface depth information, finds the lowest point of the log surface, feeds back the result to the PLC, controls the log to be rotary cut to the defect position, and obtains an effective log, i.e. a standard cylinder; Step S08, after removing the defect, the log surface depth information is collected again to detect whether there is a defect on the surface, if there is a defect, execute S07, otherwise, calculate the log radius by using the log surface depth information, and generate a log model in unity for rotary cutting analysis and three-dimensional rotary cutting display; Step S09, calculate the screw feed speed and the rotary knife angle by calling the rotary cutting analysis and motion planning module; Step S10, the control decision module matches the screw feed speed and the rotary knife angle calculated in step S09 according to the switching frequency of the motor servo driver, and transmits the required motor speed and angle to the PLC. Step S11, data exchange with PLC through OPC UA gateway, data is classified and stored through OPC UA data perception model, and unity is three-dimensionally visualized according to information type; Step S12, it is judged whether there is next operation signal, if yes, step S05 is executed, if not, step S02 is executed, and the process can also be directly ended.

Images