Device comprising a heating device for a particle and a blowing machine for producing a preheated particle to a container, control circuit for such a device, and method for controlling the transmission of a container

Abstract

A control loop for an apparatus comprising a heating device, a blow molding machine, a first measuring device and a second measuring device, the control loop comprising: a superordinate control loop having: a first comparator that determines a first control difference between a set light transmittance and an actual light transmittance; and a first controller that outputs a first adjustment of a process parameter of a station of the blow molding machine as a first output variable according to the first control difference as a first input variable, and controls the process parameter of the station of the blow molding machine corresponding to the first adjustment. The first controller outputs the set temperature of the heated parison as a second output variable according to the first control difference as an input variable; a subordinate control loop having: a second comparator that determines a second control difference between the set temperature and the actual temperature; and a second controller that outputs a second adjustment of the heating characteristics of the heating device as a third output variable according to the second control difference as a second input variable, and controls the heating characteristics of the oven in accordance with the second adjustment.

Description

Technical Field

[0001] The invention relates to a control circuit for a device comprising a heating device for preforms and a blow-molding machine for forming preheated preforms into containers, a device comprising a heating device for preforms and a blow-molding machine for forming preheated preforms into containers, and a method for controlling the light transmittance of a container according to the independent claims. Background Art

[0002] It is known that the light transmittance value of the PET container after stretch blow molding is controlled using a control loop which establishes a direct link between the heating parameters of the oven for heating the parison and the stretch blow molding parameters of the stretch blow molding machine (as set variables) and the light transmittance value of the PET container after stretch blow molding (as controlled variable). In general, the control is always carried out in a steady-state machine state, i.e. the control intervention is performed after the measured light transmittance value has reached a stable characteristic. Summary of the invention

[0003] Purpose

[0004] The object of the present invention is to provide a control circuit for a device comprising a heating device for preforms and a blow-molding machine for forming preheated preforms into containers, a device comprising a heating device for preforms and a blow-molding machine for forming preheated preforms into containers, and a method for controlling the light transmittance of containers, which make it possible to take into account the unstable characteristics of the temperature and light transmittance values ​​of the preforms when they leave the oven.

[0005] Solution

[0006] This object is achieved by a control circuit for an apparatus comprising a heating device for parisons and a blow-molding machine for forming preheated parisons into containers, an apparatus comprising a heating device for parisons and a blow-molding machine for forming preheated parisons into containers, and a method for controlling the light transmittance of a container according to the independent claims. Further embodiments are disclosed in the dependent claims.

[0007] The control circuit for a device according to the invention (the device comprising a heating device for a preform, such as a PET preform, a blow molding machine for forming a container, such as a PET container, from the preheated preform, a first measuring device for determining the actual temperature of the heated preform and a second measuring device for determining the actual light transmittance of the container) has, for controlling the light transmittance of the container:

[0008] - A superior control loop, the superior control loop having:

[0009] a first comparator designed to determine a first control difference between a set light transmittance and an actual light transmittance,

[0010] a first controller, which is designed to output a first adjustment of a process parameter of a station of the blow molding machine, such as a pre-blowing time of a station of the blow molding machine, as a first output variable, as a function of a first control difference as a first input variable for the system, and to control the process parameter of the station of the blow molding machine corresponding to the first adjustment, wherein the first controller is further designed to output a set temperature of the heated parison as a second output variable, as a function of the first control difference as an input variable,

[0011] - A lower level control loop, the lower level control loop having:

[0012] a second comparator designed to determine a second control difference between the setpoint temperature of the heated preform and the actual temperature of the heated preform,

[0013] a second controller designed to output a second adjustment of the heating characteristic of the heating device as a third output variable according to the second control difference as a second input variable for the system, and to control the heating characteristic of the oven corresponding to the second adjustment.

[0014] The system may be a system for forming a preform, such as a PET preform, into a container, and the system may include a heating device for the preform and a blow molding machine (or a stretch blow molding machine) for forming the preheated preform into a container.

[0015] The control loop makes it possible to control even before the actual transmittance has reached a stable behavior. Unstable behaviors of the actual transmittance and the actual temperature (or, for example, the actual temperature gradient (if the actual temperature comprises a plurality of actual transmittance values, which can be determined at different positions of the container, wherein, for example, the different positions are arranged along the longitudinal axis of the container)) shortly after a control intervention or during the startup phase can be incorporated into the control.

[0016] For example, when the heating device is changed, it may be necessary to replace or adjust the lower control loop. The upper control loop can remain unchanged through the generally applicable concept of controlling the light transmittance of the container.

[0017] The set transmittance may include a plurality of set transmittance values ​​for different positions of the container, and the actual transmittance may include a plurality of actual transmittance values, which may be determined at different positions of the container. For example, the different positions may be arranged along the longitudinal axis of the container. Therefore, determining the first control difference by means of the first comparator may include: the first control difference includes a plurality of control difference values, which may be determined from the plurality of set transmittance values ​​and the plurality of actual transmittance values, respectively.

[0018] The set temperature may include a plurality of set temperature values ​​for different positions of the parison, and the actual temperature may include a plurality of actual temperature values, which may be determined at different positions of the parison. For example, the different positions may be arranged perpendicular to the longitudinal axis of the container at different heights on the surface of the parison, or the different positions may be arranged along the circumference of the container. Therefore, determining the second control difference by means of the second comparator may include: the second control difference includes a plurality of control difference values, which may be determined correspondingly from the plurality of set temperatures and the plurality of actual temperatures.

[0019] The process parameters may be the pre-blowing time, the intermediate blowing time, the main blowing time of a station of the blow molding machine, the stretching time, the pre-blowing pressure, the intermediate blowing pressure, the main blowing pressure and / or the stretching speed of a stretch rod of a blow molding machine or a stretch blow molding machine.

[0020] The first controller may include an experimental model of the device for steady state. In general, containers, such as PET containers, may leave the blow molding machine at a rate of one per 1 / 100 second. Therefore, the first controller can work so fast that direct learning of artificial intelligence is feasible. No physical model needs to be provided in the first controller. The parameters of the experimental model can be determined within the framework of an experimental design, for example within the framework of a statistical experimental plan, DoE (English: Design of Experiment).

[0021] The experimental model can be designed to simulate the light transmittance at different heights of the container, depending on the process parameters and the temperature gradient of the temperature of the heated parison and / or the corresponding characteristics of the stations. Each station can have different characteristics. For example, the valves at the corresponding stations can be opened and closed in different ways (tolerance).

[0022] The experimental model can also be further designed to individually simulate the light transmittance of each station of the blow molding machine after the heating process.

[0023] The second controller may include a system model which may be designed to simulate the time dynamics of the heating process after the second adjustment. Since the system characteristics of the heating process change slowly compared to the required sampling rate of the second controller, the second controller should also be able to handle unstable states of the heating process. A preform, such as a PET preform, may pass through the heating device, for example, in 30 seconds. The reaction time of the heating device to the second adjustment may be, for example, 2 minutes.

[0024] The system model may take into account at least one of the following:

[0025] - Type of heating device,

[0026] - the geometrical design of the heating chamber of the heating device,

[0027] - the geometry of the parison,

[0028] - material properties of the components located in the heating chamber, such as absorptivity, reflectivity and / or emissivity, thermal conductivity and / or density, humidity of the plastic,

[0029] - parameters that can be measured online, for example by means of infrared absorbance sensors,

[0030] - time-varying and / or constant heating parameter values,

[0031] - the initial temperature gradient of the parison at the inlet of the heating device,

[0032] - Free and / or forced convection in the heating chamber.

[0033] The system model can be designed to calculate the heat flux and convection generated on the surface of the parison at each simulation time. These heat flux and convection can be introduced into the numerical explicit solution of the heat conduction equation of the parison, for example, as boundary conditions.

[0034] The system model can be designed to divide the parison wall volume into a plurality of volume elements. For example, for these volume elements, uniformity of material properties and temperature applies. Discretization of the parison wall volume into volume elements makes it possible to efficiently calculate the resulting volume element temperatures by numerically explicit solution of the matrix-represented heat transfer equation.

[0035] The system model can be designed to be used during operation of the second controller and to simulate online the temperature gradients inside the wall of the parison at different heights.

[0036] The lower control loop can be designed to take into account the temperature in the wall interior as an actual value in conjunction with the actual temperature of the heated parison. Since the actual temperature on the container surface can be determined, the overall heating of the parison can be taken into account in conjunction with the temperature in the wall interior. This can be related to the resulting actual light transmittance of the container. It can be advantageous to incorporate this influence into the control system.

[0037] A reinforcement learning agent, model-based control, MPC control or an algorithm can be provided for the upper and / or lower control loops, which calculates the optimal control intervention by performing an online optimization on a plurality of sampling points, which can be related to the light transmittance of the container or the temperature of the heated preform, with the support of a reinforcement learning agent.

[0038] The control circuit can be designed to assign the actual light transmittance of the container determined by means of the second measuring device to the corresponding station. This allows individual control of the individual stations.

[0039] A device is further provided, which comprises a heating device for a preform, such as a PET preform, a blow molding machine for forming a container, such as a PET container, from the preheated preform, a first measuring device for determining the actual temperature of the preheated preform and a second measuring device for determining the actual light transmittance of the container and a control loop as described above or further below.

[0040] The heating device may include an infrared oven or a microwave oven or a laser oven.

[0041] The infrared oven may include heating plates in a plurality of lamp zones, wherein the heating plates may be designed to be controllable by a control loop. For example, the heating plates may be designed to be individually controllable by a control loop.

[0042] In the microwave oven, the position of the sliding element and / or the generator power can be designed to be controllable by a control loop. For example, the sliding element and / or the generator power can be designed to be controllable individually by a control loop.

[0043] The first measuring device may be arranged at the outlet of the heating device and include a pyrometer and / or a thermal imager which may be designed to measure actual temperature values ​​of the surface of the heated preform at different heights and / or in the circumferential direction.

[0044] The second measuring device may be designed to measure actual light transmittance values ​​of the container at different heights and / or circumferential directions.

[0045] There is further provided a method of controlling the light transmittance of a container, such as a PET container, using an apparatus as described above or further below, wherein the method comprises:

[0046] - determining the actual temperature of the heated preform, for example a PET preform, by means of a first measuring device,

[0047] - determining the actual light transmittance of the container produced from the heated preform by means of a second measuring device,

[0048] - determining a first control difference between a set light transmittance and an actual light transmittance by means of a first comparator,

[0049] - outputting, by means of a first controller, as a first output variable, a first adjustment of a process parameter of a station of the blow molding machine, for example a pre-blowing time of a station of the blow molding machine, as a first output variable, and controlling the process parameter of the station of the blow molding machine corresponding to the first adjustment, and outputting, as a second output variable, a setpoint temperature of the heated parisons, as a first control difference as an input variable,

[0050] - determining a second control difference between the setpoint temperature of the heated preform and the actual temperature of the heated preform by means of a second comparator,

[0051] - outputting, by means of the second controller, a second adjustment of the heating characteristic of the heating device as a third output variable as a function of the second control difference as a second input variable, and controlling the heating characteristic of the oven in accordance with the second adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For better understanding and explanation, the accompanying drawings exemplarily show various aspects and / or embodiments of the present invention. Among them:

[0053] Figure 1 A control loop for controlling the light transmittance of a container, such as a PET container, is shown. DETAILED DESCRIPTION

[0054] Figure 1 A control loop 1 for controlling the light transmittance of a container, such as a PET container, is shown. A system 16 for forming a container from a parison, such as a PET parison, comprises a heating device for the parison and a blow moulding machine (or stretch blow moulding machine) for producing the container from the preheated parison.

[0055] The control loop 1 comprises a superordinate control loop having a first comparator 4 which is designed to determine a first control difference 5 between a set light transmittance 2 and an actual light transmittance 3. The actual light transmittance of the container is determined by means of a second measuring device 9. The set light transmittance 2 may comprise a plurality of set light transmittance values ​​at different positions of the container, and the actual light transmittance 3 may comprise a plurality of actual light transmittance values ​​which may be determined at different positions of the container. For example, the different positions may be arranged along the longitudinal axis of the container.

[0056] The first controller 6 of the upper control loop is designed to output a first adjustment 7 of a process parameter of a station of the blow molding machine as a first output variable according to the first control difference 5 as a first input variable. The process parameter can be a pre-blowing time, an intermediate blowing time, a main blowing time of a station of the blow molding machine, a stretching time of a stretching process of a stretch rod of a blow molding machine or a stretch blow molding machine, a pre-blowing pressure, an intermediate blowing pressure, a main blowing pressure and / or a stretching speed. A plurality of process parameters of a station of the blow molding machine can also be controlled by the first controller 6, such as the plurality of process parameters mentioned above. The first controller 6 is further designed to control the process parameters of the station of the blow molding machine corresponding to the first adjustment 7.

[0057] In addition, the first controller 6 is further designed to output a set temperature 8 of the heated parison as a second output variable according to the first control difference 5 as an input variable. The set temperature 8 may include a plurality of set temperature values ​​at different positions of the parison.

[0058] Furthermore, the control loop 1 comprises a subordinate control loop having a second comparator 11, which is designed to determine a second control difference 12 between the setpoint temperature 8 of the heated preform and the actual temperature 10 of the heated preform. The actual temperature of the heated preform is determined by means of a first measuring device 15. The actual temperature 10 can comprise a plurality of actual temperature values, which can be determined at different positions of the preform mentioned with respect to the setpoint temperature. For example, the different positions can be arranged perpendicular to the longitudinal axis of the container at different heights on the surface of the preform. For example, the actual temperature (and also the actual temperature at different positions of the preform) can be determined using a pyrometer and / or a thermal imager.

[0059] The lower control loop further comprises a second controller 13 which is designed to output a second adjustment 14 of the heating characteristic of the heating device as a third output variable according to the second control difference 12 as a second input variable, and to control the heating characteristic of the oven corresponding to the second adjustment 14 .

Claims

1. A control loop (1) for a device comprising a heating device for preforms, such as PET preforms, a blow molding machine for forming containers, such as PET containers, from the preheated preforms, a first measuring device (15) for determining the actual temperature of the heated preforms and a second measuring device (9) for determining the actual light transmittance of the containers, wherein the control loop (1) comprises, for controlling the light transmittance of the containers: - A superior control loop, the superior control loop having: a first comparator (4) designed to determine a first control difference (5) between a set light transmittance (2) and an actual light transmittance (3), - a first controller (6) which is designed to output, as a first output variable, a process parameter of a station of the blow molding machine, such as a first adjustment (7) of a pre-blowing time of the station of the blow molding machine, based on the first control difference (5) as a first input variable for a system (16), and to control the process parameter of the station of the blow molding machine corresponding to the first adjustment (7), wherein the first controller (6) is further designed to output, as a second output variable, a set temperature (8) of the heated parison based on the first control difference (5) as an input variable, - a lower level control loop, the lower level control loop having: a second comparator (11) designed to determine a second control difference (12) between the setpoint temperature (8) of the heated preform and the actual temperature (10) of the heated preform, a second controller (13) designed to output a second adjustment (14) of the heating characteristic of the heating device as a third output variable based on the second control difference (12) as a second input variable for the system (16), and to control the heating characteristic of the oven corresponding to the second adjustment (14).

2. A control loop according to claim 1, wherein the set transmittance (2) comprises a plurality of set transmittance values ​​for different positions of the container, and wherein the actual transmittance (3) comprises a plurality of actual transmittance values, which are determined at the different positions of the container, wherein, for example, the different positions are arranged along the longitudinal axis of the container.

3. A control loop according to claim 1 or 2, wherein the set temperature (8) includes a plurality of set temperature values ​​for different positions of the preform, and wherein the actual temperature (10) includes a plurality of actual temperature values, which are determined at the different positions of the preform, wherein, for example, the different positions are arranged perpendicular to the longitudinal axis of the container at different heights on the surface of the preform.

4. The control loop according to claim 1 , wherein the first controller ( 6 ) comprises an experimental model of the device for the steady state, wherein, for example, the experimental model is designed to simulate the light transmittance at different heights of the container depending on the process parameters and the temperature gradient of the temperature of the heated parison and / or the corresponding characteristics of the station, For example, the experimental model is further designed to individually simulate the light transmittance of each station of the blow molding machine after the heating process.

5. The control loop according to one of claims 1 to 4, wherein the second controller (13) comprises a system model which is designed to simulate the temporal dynamics of the heating process after the second adjustment.

6. The control loop of claim 5, wherein the system model takes into account at least one of the following: - the type of heating device, - the geometrical design of the heating chamber of the heating device, - the geometry of the parison, - material properties of the components located in the heating chamber, such as absorptivity, reflectivity and / or emissivity, thermal conductivity and / or density, humidity of the plastic, - parameters that can be measured online, for example by means of infrared absorbance sensors, - time-varying and / or constant heating parameter values, - an initial temperature gradient of the parison at the inlet of the heating device, - Free and / or forced convection in the heating chamber.

7. A control loop according to claim 5 or 6, wherein the system model is designed to calculate the heat flux and the convection generated on the surface of the parison at each simulation time, wherein the heat flux and the convection are introduced into the numerical explicit solution of the heat conduction equation of the parison, for example as boundary conditions.

8. The control loop according to claim 5 , wherein the system model is designed to divide the parison wall volume into a plurality of volume elements, wherein for example the homogeneity of the material properties and the temperature applies to the volume elements, wherein, for example, the system model is designed to be used during operation of the second controller (13) and to simulate online the temperature gradients inside the wall of the parison at different heights, For example, the subordinate control circuit is designed to take into account the temperature in the interior of the wall as actual value in conjunction with the actual temperature (10) of the heated preform.

9. A control loop according to one of claims 1 to 8, wherein a reinforcement learning agent, a model-based control, an MPC control or an algorithm is provided for the upper control loop and / or the lower control loop, the algorithm calculating the optimal control intervention by performing an online optimization of a plurality of sampling points and / or with the support of a reinforcement learning agent, wherein the sampling points are related to the light transmittance of the container or the temperature of the heated preform.

10. The control loop according to one of claims 1 to 9, further designed to assign the actual light transmittance of the container determined by means of the second measuring device (9) to the respective station.

11. A device comprising a heating device for preforms, such as PET preforms, a blow-molding machine for forming containers, such as PET containers, from the preheated preforms, a first measuring device (15) for determining the actual temperature (10) of the preheated preforms and a second measuring device (9) for determining the actual light transmittance (3) of the containers, It is characterized in that The device comprises a control loop (1) according to one of claims 1 to 10.

12. The device according to claim 11, wherein the heating device comprises an infrared oven, a microwave oven or a laser oven, For example, the infrared oven comprises a heating plate in a plurality of lamp zones, wherein the heating plate is designed to be controllable by the control circuit (1), wherein for example, the heating plate is designed to be controllable individually by the control circuit (1), or In this case, for example in a microwave oven, the position of a sliding element and / or the generator power are designed to be controllable by the control circuit (1), wherein for example the sliding element and / or the generator power are designed to be controllable individually by the control circuit (1).

13. An apparatus according to claim 11 or 12, wherein the first measuring device (15) is arranged at the outlet of the heating device and comprises a pyrometer and / or a thermal imager, which is designed to measure the actual temperature value (10) of the surface of the heated preform at different heights and / or in the circumferential direction.

14. The device according to one of claims 11 to 13, wherein the second measuring device (9) is designed to measure actual light transmittance values ​​(3) of the container at different heights and / or in the circumferential direction.

15. A method for controlling the light transmittance of a container, such as a PET container, using a device according to one of claims 11 to 14, wherein the method comprises: - determining the actual temperature (10) of the heated preform, for example a PET preform, by means of the first measuring device (15), - determining the actual light transmittance (3) of the container produced from the heated preform by means of the second measuring device (9), - determining a first control difference (5) between a set light transmittance (2) and the actual light transmittance (3) by means of the first comparator (4), - outputting, by means of the first controller (6), a first adjustment (7) of a process parameter of a station of the blow molding machine, for example a pre-blowing time of the station of the blow molding machine, as a first output variable, and controlling the process parameter of the station of the blow molding machine corresponding to the first adjustment (7), and outputting, as a second output variable, a set temperature (8) of the heated parison, as a function of the first control difference (5) as an input variable for a system (16), - determining a second control difference (12) between the setpoint temperature (8) of the heated preform and the actual temperature (10) of the heated preform by means of the second comparator (11), - outputting, by means of the second controller (13), a second adjustment (14) of the heating characteristic of the heating device as a third output variable according to the second control difference (12) as a second input variable for a system (16), and controlling the heating characteristic of the oven corresponding to the second adjustment (14).

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