System and method for virtual pressure based control of filling machine flow control valves

Abstract

In a method of controlling a flow regulating valve (6) of a filling machine (1) for forming a composite package (2) from a multi-layer composite packaging material and filling the composite package with a pourable product, the position of the regulating valve controlling the flow of product filling the package, the method includes implementing flow feedback control and controlling a flow set point (F SP ) and the inlet flow rate measurement (F IN ) and the inlet flow measurement (F IN ) and flow set point (F SP ) based on the difference between the feedback control contribution (C FB ) and the generated feedback control contribution (C FB ) based on the virtual pressure (P V ), and the flow feedforward control generates a virtual pressure (P V ) and uses the hydrodynamic map to calculate the flow set point (F SP ) and virtual pressure (P V ), the feedforward control contribution (C FF ) at its output, and the feedforward control contribution (C FF ) is a control signal (S c ) to determine

Description

[Technical field]

[0001] The present invention relates to a system and method for controlling a flow control valve in a filling machine for filling composite packages with pourable food products. [Background technology]

[0002] As we all know, many liquid or pourable foods, such as fruit juice, UHT (ultra-high temperature treated) milk, wine, tomato sauce, etc., are distributed and sold in composite packages made of multi-layer composite packaging materials.

[0003] A typical example is the cube-shaped pourable food packaging known as Tetra Brik AsePtiC®, which is made by sealing and folding a laminated strip of packaging material. The packaging material has a multi-layer structure with a base layer of carton and / or paper, covered on both sides with a layer of heat-sealable plastic material, e.g., polyethylene. In the case of aseptic packaging for shelf-stable products, the packaging material includes a layer of oxygen barrier material, e.g., aluminum foil, which overlaps with a layer of heat-sealable plastic material and is covered with another layer of heat-sealable plastic material to form the inner surface of the package that ultimately contacts the food.

[0004] Composite packages of this kind are usually produced in fully automatic filling (also referred to as packaging) plants which at least start with a web of multi-layer composite packaging material (wound from a reel), form the composite package and fill the composite package with a pourable food product.

[0005] A typical packaging plant includes at least a filling machine that forms composite packages from the multi-layer composite packaging material and fills the composite packages with a pourable food product. Additionally, the packaging plant may also include downstream processing equipment that receives the composite packages from the filling machine and performs additional processing on the composite packages. The downstream processing equipment may include, for example, one or more of a buffer unit for temporarily buffering the composite packages; an application unit for applying, for example, straw to the composite packages; and a grouping unit, for example a palletizer unit, for grouping multiple composite packages together in a storage unit (such as a pallet).

[0006] In known filling machines, particularly roll-fed filling machines used for filling liquid or pourable food products into multi-layer composite packages, the liquid food product is fed to tube 4 via pipe 5 and a regulating valve 6 is used to regulate the flow of the liquid food product through pipe 5 to tube 4 and filled into package 2.

[0007] The filling machine comprises a control unit operatively connected to the regulating valve and configured to provide a control signal to the same regulating valve to regulate its opening and closing, thereby regulating the flow of liquid through pipe 5 and into tube 4.

[0008] According to a known solution, the control unit is configured to implement a flow Proportional-Integral-Derivative (PID) module that receives as inputs a flow setpoint and an inlet product flow measurement received from a flow meter sensor, the output of the flow PID module representing a first control corrective action based on the difference between the actual flow measured by the flow meter and the desired flow represented by the flow setpoint.

[0009] The control unit is further configured to implement a flow feedforward (FF) module that receives the flow setpoint as an input and generates at its output a second control corrective action using a hydrodynamic map that maps valve positions with respect to the flow setpoint and pressure values ​​as a function of the flow setpoint and a nominal inlet pressure that has a fixed value by design.

[0010] The outputs of the flow proportional-integral-derivative (PID) module and the flow feedforward module (both indicative of the control position of the regulator valve) are combined in a control unit to generate a control signal for the regulator valve, which is then adjusted as a function of the combined control action.

[0011] European Patent Application No. 21180243, filed on June 18, 2021 in the name of the present applicant, discloses an advantageous and effective solution for controlling a regulating valve.

[0012] According to this solution, the filling machine further comprises a pressure sensor for determining an inlet pressure measurement of the liquid food supplied from the processing line towards the pipe, the pressure sensor being positioned upstream of the regulating valve with respect to the flow direction of the liquid food towards the pipe.

[0013] The inlet pressure measurement is provided to the control unit as a further control parameter, in particular as an input to the flow feedforward module.

[0014] As disclosed in the above-mentioned European Patent Application No. 21180243, the use of the inlet pressure measurements as input to the flow feedforward control module is particularly advantageous because it allows the regulating valve to adjust also based on real-time pressure measurements from the process line, thereby enabling the regulating valve to quickly adapt to pressure changes or fluctuations in the same process line. For example, if a disturbance in the product line causes a drop in pressure in the process line, the regulating valve may be adjusted to compensate for this pressure drop.

[0015] In this regard, FIG. 1 shows exemplary plots associated with a hydrodynamic map implemented in a flow feedforward control module to determine the respective contributions to the controlled position of the flow regulator valve. The graphs plot flow (y-axis) versus valve position (x-axis), with each graph plotting a different pressure value (in the example, P1 through P2). 11 ) is mentioned.

[0016] In particular, for a given flow setpoint, FIG. 1 illustrates the advantage of using the inlet pressure measurement provided by the pressure sensor instead of the nominal inlet pressure value (design value) to determine the position of the flow regulating valve.

[0017] Applicants have realized that, although advantageous, in some situations an alternative solution may be preferable.

[0018] In particular, the installation of pressure sensors along the process line may not be possible for some filling machines, e.g. due to customer constraints, hardware and / or software limitations, or other reasons, such that the control solution disclosed in the above-mentioned European Patent Application No. 21180243 cannot be implemented and the associated advantages cannot be achieved. For example, there may be physical constraints on the machine that make the introduction of pressure sensors physically impractical. Also, certain customers may want to avoid the introduction of pressure sensors for economic reasons, e.g. due to the need for maintenance and / or replacement in case of parts breaking.

[0019] Therefore, there is a need for a solution for controlling flow regulating valves that can improve response to disturbances in the product line while maintaining the current layout of the filling machine (i.e., without installing pressure sensors along the process line). Summary of the Invention [Problem to be solved by the invention]

[0020] It is therefore an object of the present solution to provide an improved system and method for controlling a flow regulating valve, which can at least partially meet the above-mentioned needs.

[0021] According to the present solution, a control method and system are provided as defined in the accompanying claims. [Means for solving the problem]

[0022] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0023] [Figure 1] 3 shows plots of quantities related to the operation of a control unit of a filling machine according to known solutions for controlling a flow regulating valve; [Diagram 2] FIG. 2 is a schematic diagram of a filling machine with a corresponding control unit. [Diagram 3] FIG. 2 is a schematic block diagram of a control device for a filling machine according to a possible embodiment. [Figure 4] 4 shows plots of quantities related to the operation of the control device of FIG. 3; [Diagram 5] FIG. 2 is a schematic block diagram of a control unit of a filling machine according to one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Figure 2 shows as an example a filling machine 1 (sometimes also called a packaging machine) in which the control solution can be implemented. In this example, the filling machine 1 is a roll-fed filling machine used to fill multi-layer composite packages 2 with liquid or pourable food products.

[0025] The multi-layer composite packaging material may comprise at least one layer of fibrous material, such as a paper or paperboard layer, and at least two layers of heat-sealable plastic material, such as polyethylene, sandwiching the layers of fibrous material between each other, with one of the two layers of heat-sealable plastic material defining the inner surface of the composite package 2 that will ultimately contact the pourable food product packaged within the same composite package 2.

[0026] The multi-layer composite packaging material may also include a layer of gas- and light-barrier material, such as an aluminum foil or an ethylene vinyl alcohol (EVOH) film, in particular arranged between one of the layers of heat-sealable plastic material and the layer of fibrous material. Preferably, the multi-layer composite packaging material may include a further layer of heat-sealable plastic material interposed between the layer of gas- and light-barrier material and the layer of fibrous material.

[0027] In particular, the multi-layer composite packaging material is provided in the form of a web and is in particular wound up on a packaging material reel 3 from where it is fed in a web feed direction A through the filling machine 1 .

[0028] The liquid food is fed to the tube 4 via a pipe 5 and a regulating valve 6 is used to regulate the flow of the liquid food through the pipe 5 to the tube 4 and to be filled into the packages 2. In particular, the regulating valve 6 connects the pipe 5 to a processing line 7 arranged to process (in a known manner) the liquid food before packaging (the processing line 7 is also connected to a tank or similar storage element 7').

[0029] The lower end 8 of the tube 4 is fed to a folding device 9 where a transverse seal is made and the tube 4 is folded according to fold lines, also called lines of weakness, and then cut so that a composite package 2 filled with liquid food is formed.

[0030] As shown in FIG. 2, the filling machine 1 further comprises a sterilization device S, such as a hydrogen peroxide bath or an LVEB (Low Voltage Electron Beam) station, to ensure that the web is free of unwanted microorganisms prior to the formation of the tube 4.

[0031] The filling machine 1 further comprises a control unit 10 which (in addition to other functions for managing the operation of the filling machine 1, not shown here) is operatively linked to the regulating valve 6 and supplies the same with a control signal S C to adjust its position and thereby the flow of liquid through pipe 5 into tube 4.

[0032] The control unit 10 may comprise, for example, a programmable logic controller (PLC) or any suitable processing and calculation unit, and transmits the above-mentioned control signal S to the regulating valve 6. C The apparatus is configured to execute a computer program designed to generate

[0033] The filling machine 1 further comprises a flow meter 16 and a level detector 18 .

[0034] Flow meter 16 measures the inlet product flow rate F of the liquid food product fed from processing line 7 to filling machine 1. IN and the level detector 18 determines a product level measurement L of the liquid food being delivered from the pipe 5 to the tube 4 for filling into the packages 2. M Determine.

[0035] Determined product flow rate and level measurements F IN , L M are provided to the control unit 10 as control parameters via wire or wirelessly.

[0036] In particular, the flow meter 16 is positioned upstream of the regulating valve 6 in relation to the flow direction of the liquid food into the filling machine 1, and the level detector 18 is positioned in any suitable manner (e.g., in close proximity to the tube 4) to detect the level of fluid in the tube 4 (e.g., non-contact via electromagnetic measurement).

[0037] In the proposed solution, the filling machine 1 does not need a pressure sensor to determine the inlet pressure measurement of the liquid food delivered from the processing line 7 towards the pipe 5. In other words, the pressure measurement is not a control parameter used by the control unit 10 to adjust the position of the regulating valve 6.

[0038] FIG. 3 is a schematic block diagram of a control unit 10 according to one or more embodiments of the present solution, which receives inlet product flow measurements F from a flow meter 16. IN , and the flow rate setting value F SP is configured to receive

[0039] The control unit 10 includes a flow feedforward (FF) control module 20 and a flow feedback (FB) control module 22, both of which have as their respective inputs a flow setpoint F SP Receive.

[0040] Flow set point F SP indicates the target flow rate of product through the regulating valve 16 from the pipe 5 to the tube 4. The flow rate set point F SP may be determined as a function of one or more of the starting flow percentage, the nominal flow percentage, the machine speed flow percentage, the level set point and / or the product level (measured by the level detector 18).

[0041] The flow feedback control module 22 further receives the inlet product flow measurement F from the flow meter 16. IN Takes as input.

[0042] In one embodiment, the flow feedback control module 22 is implemented by a proportional-integral-derivative (PID) module, which determines the flow set point F SP (representing the desired flow rate) and the inlet product flow rate measurement F measured by flow meter 16 IN (representing the actual flow rate) at its output based on proportional, integral and derivative control actions (in any known manner not described in detail herein) based on the difference between FB In other words, the above difference is the flow set point F SP 3 shows the difference between the expected flow rate, represented by ΔE, and the actual flow rate of the product as measured by the flow meter 16.

[0043] As shown in Figure 3, the flow rate setting F SP and the inlet product flow rate measurement F IN The difference between is performed in a first summing block 23 , the output of which is input to the flow feedback control module 22 .

[0044] According to a particular aspect of the present solution, the flow feedforward control module 20 has as its input the feedback control contribution C generated at the output of the flow feedback control module 22. FB Based on the virtual pressure P V Receive.

[0045] The flow feedforward control module 20 determines the flow set point F SP and virtual pressure P V At its output, a flow set point F is provided using a hydrodynamic map that provides a control position value of the regulating valve 6 based on the value of SP and the above virtual pressure P V Based on this, the feedforward control contribution C is FF Generate.

[0046] In particular, according to one aspect of the present solution, the feedforward control contribution C generated by the flow feedforward control module 20 FF is the control signal S of the flow rate control valve 6 of the filling machine 1. cdirectly defines (in an exclusive and independent manner) and regulates its opening and closing (the position of the valve ranging from a closed position to a fully open position), thereby regulating the flow of liquid food therethrough into pipe 5 and then into tube 4 to form filled packages 12.

[0047] In this regard, Fig. 4 shows the feedforward control contribution C FF 1 shows exemplary graphs of a fluid dynamics map implemented in the flow feedforward control module 20 to determine the controlled valve position (i.e., the position of the regulating valve 6). In particular, the graphs plot controlled valve position (y-axis) versus pressure drop (x-axis), with each graph plotting a different flow set point (in this example, F1 through F2). 14 ) is mentioned.

[0048] In particular, the flow set point F SP Given the value of , the virtual pressure P V Depending on the value of the control signal S, the actual operating point of the regulating valve 6 on the associated graph and the corresponding control position of the same flow regulating valve 6 can be determined. c (Determine).

[0049] In particular, the virtual pressure P V is the feedback control contribution C generated at the output of the flow feedback control module 22 FB and the reference pressure value P ref is determined as a function of

[0050] More specifically, the virtual pressure P V The value of is the reference pressure value P ref and feedback control contribution C FB and is performed in a second summation block 24. For example, the feedback control contribution C FB The unit is the reference pressure value P ref may be the same as

[0051] According to one embodiment, the reference pressure value P refcorresponds to the maximum pressure value that the liquid food product may reach when being fed from the processing line 7 towards the pipe 5 during operation of the filling machine 1. The maximum pressure value may be application specific and / or may vary depending on the application.

[0052] Thus, the operation of the control unit 10 is to control the estimated product pressure (virtual pressure P V ), taking advantage of the direct proportional relationship between the flow rate and pressure fluctuation of the fill fluid product.

[0053] Feedback control contribution C FB is the measured flow rate (measured inlet product flow rate F IN ) to the flow rate set point F SP This same correction (by direct proportionality) is applied to the reference pressure P ref , giving an estimated indication of the filled product pressure, for example at the regulating valve 6, V (thereby avoiding the use of a dedicated pressure sensor to actually measure the product pressure).

[0054] FIG. 5 shows a further embodiment of the control device 10.

[0055] In this embodiment, the control unit 10 may further comprise a level feedback control module 32 implemented by respective proportional-integral-derivative (PID) control modules, which adjusts the product level measurements L received from the level detector 18 according to proportional, integral and derivative control actions (any known method not described in detail here). M (representing the actual product level) and the level set point L SP (representing the desired product level) as the output, based on the difference between SP Further control contribution C SP Generate.

[0056] As shown in Figure 5, the product level measurement L M and the level setting value LSP is carried out in a third summation block 33, which, as its output, represents the input of the level feedback control module 32.

[0057] In this case, the control unit 10 implements a dual PID control loop based on the pressure and level measurements and adjusts the flow rate through the regulating valve 6 with an additional control action based on the product level (to achieve even more stable operation of the filling machine 1).

[0058] Further control contribution C above SP is the actual flow rate set point F provided at the input of the flow feedback control module 22. SP may be represented as:

[0059] In the embodiment shown in FIG. 5, a further control contribution C SP via the first switch 33a, the flow set point F SP and furthermore, the mechanical flow contribution C M . . are selectively provided to a summing block 34 which receives

[0060] In particular, this mechanical flow contribution C M is generated by multiplier block 36, which receives as inputs the machine speed percentage and, selectively, either the nominal flow percentage (via second switch 33b) or the starting flow percentage (via ramp generator 35 and third switch 33c).

[0061] In known methods, the mechanical flow contribution C M is the flow rate set point F at the start of filling machine 1 SP It may represent a contribution to

[0062] The advantages of the discussed solution are clear from the above description.

[0063] In any case, it is emphasized that the improved control actions performed by the control unit 10 make it possible to compensate for instantaneous flow (and pressure) fluctuations and disturbances and provide a more accurate response of the regulating valve 6.

[0064] Thus, a more stable operation of the filling machine 1 is achieved, resulting in more consistent levels and flow of product in the filled packages and reduced product and packaging waste in the event of product line disturbances.

[0065] Advantageously, the above improvements are achieved without requiring additional components along the product processing line. In particular, the virtual pressure P based on the output of the flow feedback control loop V A pressure sensor is not required to provide a measurement of inlet product pressure since the same indication of product pressure is achieved by estimation of

[0066] However, modifications may be made to what is described herein without departing from the scope of protection defined in the appended claims.

[0067] In particular, the solution described is applicable to any packaging or filling machine and for any type of pourable food product.

Claims

1. 1. A method for forming a composite package (2) from a multi-layer composite packaging material and controlling a flow control valve (6) of a filling machine (1) for filling said composite package (2) with a pourable product, said flow control valve (6) controlling the flow of a pourable food product being filled into said composite package (2), comprising: Flow feedback control is implemented, and the flow set point (F ＳＰ ) and the inlet flow rate measurement of the pourable product (F ＩＮ ) and receiving the inlet flow measurement (F ＩＮ ) and the flow rate set point (F ＳＰ ) based on the difference between the feedback control contribution (C ＦＢ ) and A flow rate feedforward control is performed to adjust the flow rate set point (F ＳＰ ) and using a hydrodynamic map that maps the output position of the flow regulating valve (6) against the flow reserve pressure of the pourable product, a feedforward control contribution (C ＦＦ ) and At the output of the flow feedback control module (22), the feedback control contribution (C ＦＢ ) based on the virtual pressure (P Ｖ ) and In the flow rate feedforward control, the virtual pressure (P Ｖ ) and uses the hydrodynamic map to determine the flow rate setpoint (F ＳＰ ) and the virtual pressure (P Ｖ ) based on the feedforward control contribution (C ＦＦ ) as output, A control signal (S) for controlling the operating position of the flow rate adjusting valve (6) ｃ ) is the feedforward control contribution (C ＦＦ ) method.

2. The virtual pressure (P Ｖ ) is an estimated indication of the pressure of the pourable product; The method of claim 1.

3. The feedback control contribution (C) at the output of the flow feedback control module (22) ＦＢ ) and the reference pressure value (P ｒｅｆ ) as a function of the virtual pressure (P Ｖ ) to determine The method of claim 1.

4. The virtual pressure (P Ｖ ) to the reference pressure value (P ｒｅｆ ) and the feedback control contribution (C ＦＢ ) and determine it as the difference The method of claim 3.

5. The reference pressure value (P ｒｅｆ ) corresponds to the maximum pressure value that the pourable product can reach during operation of the filling machine (1), The method of claim 3.

6. The hydrodynamic map is Ｖ ) and the flow rate set point (F ＳＰ ) to provide the operating position of the flow control valve (6), The method of claim 1.

7. The flow rate set point (F ＳＰ ) indicates a target flow rate of product through said flow control valve (6) and is determined as a function of one or more of a starting flow rate percentage, a nominal flow rate percentage, a machine speed flow rate percentage, a level set point, and a product level measured by a level detector (18); The method according to claim 1.

8. The flow rate feedback control is performed by a proportional-integral-derivative (PID) module (22). The method according to claim 1.

9. The product level measurement value (L Ｍ ) and The product level measurement value (L Ｍ ) and the level set point (L ＳＰ ) and the additional control contribution (C ＳＰ ) is determined, The flow rate set point (F ＳＰ ) is the control contribution (C ＳＰ ), which is a function of The method of claim 1.

10. the filling machine (1) is configured to form a tube (4) from the web of multi-layer composite packaging material, and comprises a filling pipe (5) for filling the tube (4) with the pourable product, and the flow control valve (6) is configured to connect the filling pipe (5) to a product processing line (7); The method of claim 1.

11. 1. A control system for controlling a flow regulating valve (6) of a filling machine (1) configured to form a composite package (2) from a multi-layer composite packaging material and fill the composite package (2) with a pourable product, the regulating valve (6) being configured to regulate the flow rate of the product filled into the composite package (2), the control system comprising: A control signal (S) for controlling the operating position of the flow rate adjusting valve (6) Ｃ a control unit (10) configured to determine The control unit (10) is configured to implement the method according to any one of claims 1 to 10. Control system.

12. A filling machine (1) comprising a control system according to claim 11.

13. The packaging machine is configured to form a tube (4) from a web of multi-layer composite packaging material, and is provided with a filling pipe (5) for filling the tube (4) with a filling material; The flow control valve (6) is configured to connect the filling pipe (5) to a product processing line (7).

13. The filling machine of claim 12.

14. a flow meter (16) is arranged upstream of the flow control valve (6) in the direction of flow of the pourable product from the processing line (7) to the filling tube (5); 14. The filling machine of claim 13.

15. A control unit (10) controls the control signal (S ｃ ) does not receive product pressure measurements as a control parameter for determining 13. The filling machine of claim 12.

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