System and method for controlling a flow regulating valve in a filling machine

Abstract

A method for controlling a flow regulating valve (6) of a filling machine (1), controlling the flow of pourable food product, envisages: receiving an inlet pressure measurement (P.sub.IN) from a pressure sensor (14); receiving an inlet flow measurement (F.sub.IN) from a flow meter (16); determining a control signal (S.sub.c) for controlling an operating position of the flow regulating valve (6) by combined contributions (C.sub.1, C.sub.2) of a flow feedback control module (22), receiving at its input a flow set point (F.sub.SP) and the inlet flow measurement (F.sub.IN) and generating a first control contribution (C.sub.1) indicative of a difference between the inlet flow measurement and the flow set point; and a flow feed-forward control module (20), receiving at its input the inlet pressure measurement (P.sub.IN) and the flow set point (F.sub.SP) and generating a second control contribution (C.sub.2) as a function of the flow set point and inlet pressure measurement, using pre-stored fluid-dynamic maps, which may be a result of a characterization of the flow regulating valve in a test condition. The flow feed-forward control module uses the fluid dynamics maps in a dynamically adaptive manner, depending on different operating conditions of the filling machine and/or the related pourable food product, thereby adapting to the same different operating conditions and/or the pourable food product.

Claims

1. A method for controlling a flow regulating valve of a filling machine configured to form composite packages from a multilayer composite packaging material and to fill the composite packages with a pourable food product, wherein the regulating valve controls the flow of the pourable food product filling the packages, the method comprising: receiving an inlet pressure measurement of the pourable food product from a pressure sensor; receiving an inlet flow measurement of the pourable food product from a flow meter; determining a control signal for controlling an operating position of the flow regulating valve by combined contributions of: a flow feedback control module, receiving at its input a flow set point and the inlet flow measurement and generating a first control contribution indicative of a difference between the inlet flow measurement and the flow set point; a flow feed-forward control module, receiving at its input the inlet pressure measurement and the flow set point and generating a second control contribution as a function of the flow set point and inlet pressure measurement, using stored fluid-dynamic maps, wherein the flow feed-forward control module is configured to use the stored fluid dynamics maps in a dynamically adaptive manner, depending on different operating conditions of the filling machine and/or the related pourable food product, thereby adapting to said different operating conditions and/or pourable food product.

2. The method according to claim 1, comprising performing a dynamic adaptation procedure to dynamically adapt the stored fluid dynamics maps in the flow feed-forward control module to said different operating conditions of the filling machine and/or pourable food product.

3. The method according to claim 2, wherein the stored fluid dynamics maps represent a relation between the second control contribution to the operating position of the flow regulating valve and the inlet pressure measurement and flow set point; and wherein the dynamic adaptation procedure comprises: determining a position of the flow regulating valve; determining a theoretical pressure value corresponding to the pressure that would be required as an input to the flow feed-forward module in order to match the determined position of the flow regulating valve with the value of the second control contribution generated at its output; obtaining a delta pressure value by computing a difference between the measured inlet product pressure and said theoretical pressure; using said delta pressure value to determine an adjustment associated with the stored fluid dynamic maps used in the flow feed-forward module.

4. The method according to claim 3, comprising adding the computed delta pressure value to the value of the measured inlet product pressure, at the input of the flow feed-forward module.

5. The method according to claim 3, comprising shifting said stored fluid dynamic maps of a shifting quantity, being a function of the delta pressure value, thereby determining dynamically adapted fluid dynamic maps to be used in the flow feed-forward module receiving at the input the inlet pressure measurement.

6. The method according to claim 2, comprising performing the dynamic adaptation procedure when the filling machine starts a new production, implying a different pourable food product and/or different operating conditions of the filling machine.

7. The method according to claim 1, wherein the fluid dynamics maps define a relation between a variable, being a function of product pressure and flow, and the position of the flow regulating valve.

8. The method according to claim 7, wherein the dynamic adaptation procedure further comprises: computing a corresponding value for said variable from the position, by means of the inverse of said relation; and determining the theoretical pressure value from the computed value of said variable, by means of said function.

9. The method according to claim 1, wherein the flow set point is indicative of a target flow of product through the regulating valve, preferably determined as a function of one or more of: a start flow percentage, a nominal flow percentage, a machine speed flow percentage, a level set point and a product level measured by a level detector.

10. The method according to claim 1, wherein the flow feedback control module is implemented by a proportional-integral-derivative, PID, module.

11. The method according to claim 1, wherein the first and second control contributions are combined in a summing block, which generates at the output the control signal for the flow regulating valve, for modulating its operating position and thereby adjusting the flow of the pourable food product passing therethrough.

12. The method according to claim 1, further comprising: receiving a product level measurement from a level detector; determining a control contribution by a proportional-integral-derivative module, based on a difference between the product level measurement and a level set point; and wherein the flow set point is a function of said control contribution.

13. A control system for controlling a flow regulating valve of a filling machine configured to form composite packages from a multilayer composite packaging material and to fill the composite packages with a pourable food product, wherein the regulating valve is configured to control the flow of the pourable food product filling the packages, the control system comprising: a pressure sensor, configured to determine an inlet pressure measurement of the pourable food product; a flow meter, configured to determine an inlet flow measurement of the pourable food product; a control unit configured to determine a control signal for controlling an operating position of the flow regulating valve, wherein the control unit is configured to implement the method according to claim 1.

14. The system according to claim 13, wherein the filling machine is configured to form a tube from a web of the multilayer composite packaging material and comprises a filling pipe for filling the tube with the pourable food product, wherein the regulating valve is configured to couple the filling pipe to a product processing line, and wherein the pressure sensor and the flow meter are arranged upstream of the regulating valve with respect to a direction of flow of said pourable food product from the processing line to the filling pipe.

15. A filling machine, comprising the control system, according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic representation of a known filling machine with a control unit for controlling a corresponding flow regulating valve;

(3) FIG. 2 is a schematic block diagram of the control unit of the filling machine, according to a possible embodiment;

(4) FIGS. 3-5 show plots of quantities related to the operation of the control unit of FIG. 2;

(5) FIG. 6 is a flow chart of operations performed in the control unit of FIG. 2;

(6) FIGS. 7A and 7B are schematic block diagrams of the control unit of the filling machine according to different embodiments; and

(7) FIG. 8 is a schematic block diagram of the control unit of the filling machine according to yet a different embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

(8) FIG. 2 (where elements similar to those discussed above with reference to FIG. 1 are denoted with the same references) shows a schematic block diagram of a control unit 10, for controlling a flow regulating valve 6 in a filling machine 1 (the same filling machine 1 being e.g. arranged and configured as previously disclosed with reference to FIG. 1).

(9) The control unit 10 is configured to receive the above discussed filling control parameters, and in particular: the inlet pressure measurement, P.sub.IN, from the pressure sensor 14; and the inlet product flow measurement, F.sub.IN, from the flow meter 16.

(10) The control unit 10 comprises: a flow feed-forward (FF) control module 20, receiving at its input the inlet pressure measurement P.sub.IN from the pressure sensor 14 and, moreover, a flow set point, F.sub.SP; and a flow feedback control module 22, receiving at its input the same flow set point F.sub.SP and the inlet product flow measurement F.sub.IN from the flow meter 16 (in the example being arranged and operating in parallel to the flow feed-forward control module 20).

(11) The flow set point F.sub.SP is indicative of a target flow of product through the regulating valve 16 and into the pipe 5 towards the tube 4. The flow set point F.sub.SP may be determined as a function of one or more of a start flow percentage, a nominal flow percentage, a machine speed flow percentage, a level set point and/or a product level (as measured by level detector 18).

(12) In a possible embodiment, the flow feedback control module 22 is implemented by a proportional-integral-derivative (PID) module, which generates at its output a first control contribution C.sub.1, based on a difference between the inlet product flow measurement F.sub.IN measured by means of the flow meter 16 (and representing a real flow) and the flow set point F.sub.SP (representing a desired flow), according to proportional, integrative and derivative control actions (in any known manner, here not discussed in detail).

(13) As shown in the same FIG. 2, the above difference between the inlet product flow measurement F.sub.IN and the flow set point F.sub.SP is performed in a summing block 23, whose output represents the input of the flow feedback control module 22.

(14) The flow feed-forward control module 20 generates at its output a second control contribution C.sub.2, as a function of the flow set point F.sub.SP and the inlet pressure measurement P.sub.IN, using the pre-set fluid-dynamic maps, which are a result of characterization of the flow regulating valve 6 in a test condition, as previously discussed.

(15) The first and second control contributions C.sub.1, C.sub.2 are combined (in particular, added) in a summing block 24, which generates at the output the control signal S.sub.c for the flow regulating valve 6 of the filling machine 1, for modulating its position (the position of the valve ranging from a closed position to a fully open position) and thereby adjusting the flow of the liquid food product passing therethrough into the pipe 5 and then into the tube 4 for the formation of the filled packages 12.

(16) FIG. 3 shows exemplary graphs related to the fluid-dynamic maps implemented in the flow feed-forward control module 20 to determine the second control contribution C.sub.2 to the controlled position of the flow regulating valve 6.

(17) In the representation of FIG. 3, these graphs plot the flow (in the y axis) versus the valve position (in the x axis), each graph referring to a different pressure value. In particular, given the value of the inlet pressure measurement P.sub.IN (and thus the corresponding graph) and a flow set point F.sub.SP, the position of the flow regulating valve 6 (representing the above discussed second control contribution C.sub.2 by the feed-forward control module 20) can be found in the same corresponding graph.

(18) FIG. 4 shows a different representation for the same fluid-dynamic maps implemented in the flow feed-forward control module 20, where a combination variable C.sub.d, which is determined as a function of both flow and pressure values, is introduced:

(19) $C_d=\left(F_{\mathrm{IN}},P_{\mathrm{IN}}\right).$

(20) Again, given the values of the inlet pressure measurement P.sub.IN and the flow set point F.sub.SP (and thus a resulting value C.sub.d of the combination variable C.sub.d), the working point, i.e. the position of the flow regulating valve 6 according to the above discussed second control contribution C.sub.2, may be determined in the graph.

(21) As previously discussed, the fluid-dynamic maps stored and implemented in the flow feed-forward control module 20 are pre-determined, e.g. obtained by a characterization of the flow regulating valve 6 (or being set by design). Therefore, the same maps do not take into account different properties of the filling food product, e.g. in terms of its viscosity, and/or different operating conditions of the filling machine 1, e.g. in terms of a high volume/capacity, high pressure drop or high speed.

(22) In this respect, FIG. 5 shows different plots relating to the actual model of the flow regulating valve 6, in case of different products (denoted with P1, P2, P3) and different operating conditions (e.g. a high-speed condition) of the filling machine. It is evident that the predetermined map stored in the flow feed-forward control module 20 may not be ideal in modelling the system in case of different products and/or different operating conditions, so that the position of the flow regulating valve 6 determined by the same flow feed-forward control module 20 may bring the system to a less than ideal initial working point or offset position.

(23) As a consequence, the flow feedback control module 22, implemented by the proportional-integral-derivative (PID) module, has to compensate the offset position with the first control contribution C.sub.1, determining a slower overall response by the control system.

(24) In order to solve this issue, and according to an aspect of the present solution, the flow feed-forward control module 20 is configured to use the fluid dynamics maps in a dynamically adaptive manner, depending on the different operating characteristics of the filling machine 1 (and the related liquid food product), thereby adapting to these different characteristics.

(25) As will be detailed in the following, according to a possible embodiment, the flow feed-forward control module 20 is configured to dynamically adapt the pre-stored fluid dynamics maps to the above different characteristics of the filling machine and related product.

(26) In more details, and with reference to FIG. 6, according to an aspect of the present solution, a dynamic adaptation procedure is implemented in the control unit 10 during an adaptation time interval, e.g. when the filling machine 1 starts a new production (which may imply a different liquid food product and/or different operating parameters and conditions for the same filling machine 1).

(27) In a first step, denoted with 30, the control unit 10 may wait for stabilization of the filling operations.

(28) As shown at step 31, operating signals indicative of the filling machine operation are then acquired for a defined period of time, in particular: the inlet product flow and pressure F.sub.IN, P.sub.IN (provided by the flow meter 16 and, respectively, the pressure sensor 14); the (actual) position of the flow regulating valve 6 (e.g. determined by the position of a corresponding driving servomotor); the value of the second control contribution C.sub.2 generated by the flow feed-forward control module 20.

(29) The control unit 10 then process the received data, as shown at step 32, in order to adapt to the (possibly different) operating conditions of the filling machine 1 and related product; according to a possible embodiment, a dynamically adapted fluid-dynamic map is determined, to be implemented in the flow feed-forward control module 20, in order to adapt to the filling machine behaviour.

(30) In particular, a theoretical pressure value is determined, corresponding to an inlet pressure that would be required as an input to the flow feed-forward module 20 in order to match the (actual) position of the flow regulating valve 6 with the value of the second control contribution C.sub.2 generated at the output of the same flow feed-forward control module 20.

(31) In a possible embodiment, as shown starting from step 33, it is considered that the maps are expressed by means of a matrix, which represents a relation between the above discussed variable C.sub.d and the position of the flow regulating valve 6 (see above FIG. 4), C.sub.d being a function of inlet product pressure and flow.

(32) From the determined position of the flow regulating valve 6, e.g. indirectly measured by means of a corresponding driving servomotor, the correspondent C.sub.d value is therefore computed, by means of the reverse C.sub.d-valve position matrix.

(33) At step 34, from the computed C.sub.d value, as a function of inlet product flow and pressure, the theoretical pressure value is obtained.

(34) As shown at step 35, by computing the difference between the measured inlet product pressure P.sub.IN and this theoretical pressure, a delta pressure (P) value is obtained.

(35) This P value is then used to determine the adjustment associated with the fluid dynamic maps used in the flow feed-forward module 20, in order to adapt to the different operating conditions of the filling machine 1, at step 36.

(36) In more details, as shown at step 36 and as also shown schematically in FIG. 7A, the computed P value can be added to the measured inlet product pressure value P.sub.IN and the sum can be used as the input to the flow feed-forward module 20, in order to identify the correct working point on the pre-stored fluid dynamic maps. This has the effect of actually shifting the standard, pre-stored, fluid dynamic map (and in particular the value of the variable C.sub.d) of a C.sub.d quantity, based on the P value, thereby obtaining the final map, adapted to the actual operating conditions of the filling machine 1 (e.g. to the liquid food product viscosity and/or the machine operating conditions, e.g. the corresponding speed).

(37) As shown at step 36, in a corresponding manner, instead of adding the P value to the input of the flow feed-forward module 20, the control unit 10 may actually compute the shifted or dynamically adapted fluid dynamic maps, as a function of the above C.sub.d quantity (in other words, computing a different, shifted, matrix representing the relation between the variable C.sub.d and the position of the flow regulating valve 6, by means of the above expression (1) considering the sum of the inlet product pressure P.sub.IN and the P value).

(38) As shown schematically in FIG. 7B, this shifted or dynamically adapted fluid dynamic map is then used in the flow feed-forward module 20, receiving in this case at the input the raw inlet product pressure measurement P.sub.IN (as provided by the pressure sensor 14).

(39) As shown at step 38, the control unit 10, after the above discussed determination of the adapted fluid-dynamic map, may start a transition period from the standard, pre-stored, map to the adapted map by means of a pressure ramp (starting from a fixed initial value and arriving to the above discussed sum of the inlet product pressure value P.sub.IN and the P value).

(40) At the end of the transition period, the value of the second control contribution C.sub.2 generated at the output of the flow feed-forward control module 20 will thus substantially match the position required for the flow regulating valve 6 based on the specific filling machine/product system. Therefore, it will be possible to compensate the contribution of the (slower) flow feedback control module 22, with the (faster) flow feed-forward control module 20 representing the main contribution to the determination of the position control signal for the flow regulating valve 6 (thus achieving the desired responsiveness of the control unit 10 to possible pressure disturbances).

(41) The new fluid-dynamic map may be used until the next production stop is requested; when the filling machine 1 is restarted, the adaptation procedure may be performed again.

(42) As shown in FIG. 8, according to a possible embodiment, the control unit 10 may further comprise a level feedback control module 42, implemented by a respective proportional-integral-derivative (PID) module, which generates at its output a control contribution C.sub.SP indicative of the flow set point F.sub.SP, based on a difference between the product level measurement L.sub.M received from the level detector 18 (representing a real product level) and a level set point L.sub.SP (representing a desired product level), according to proportional, integrative and derivative control actions (in any known manner, here not discussed in detail).

(43) As shown in the same FIG. 8, the above difference between the product level measurement L.sub.M and the level set point L.sub.SP is performed in a summing block 43, whose output represents the input of the level feedback control module 42.

(44) The control unit 10 implements in this case a double PID control loop, based on the pressure and level measurements, in order to adjust the flow through the regulating valve 6 with an additional control action based on the product level (so as to achieve an even more stable operation of the filling machine 1).

(45) The control contribution C.sub.SP may represent the actual flow set point F.sub.SP, provided at the input of the flow feedback control module 22.

(46) In the embodiment shown in FIG. 8, the control contribution C.sub.SP is selectively provided, via a first switch 43a, to a summing block 44, which generates at the output the flow set point F.sub.SP and further receives at the input a machine flow contribution CM.

(47) In particular, this machine flow contribution CM is generated by a multiplier block 46, which receives at its inputs: a machine speed percentage; and, selectively, either a nominal flow percentage (via a second switch 43b), or a start flow percentage (via a ramp generator 45 and a third switch 43c).

(48) In a known manner, the machine flow contribution CM represents a contribution to the flow set point F.sub.SP used at the start of the filling machine 1.

(49) The advantages of the discussed solution will be clear from the foregoing description.

(50) In any case, it is underlined again that the improved control action implemented by the control unit 10 allows to achieve a more stable operation of the filling machine 1, with a more stable level of product in the filled packages, reducing waste of product and of the same packages.

(51) The discussed solution allows to promptly adapt to the operating characteristics of the filling machine (and product), e.g. at the start of any new production or at any other suitable time.

(52) In particular, thanks to the adaptation of the fluid dynamic maps to the filling system, the feed forward action determines the main contribution to the position of the flow regulating valve 6, with the PID action load being reduced (thus achieving a faster response to pressure disturbances).

(53) Clearly, changes may be made to what described herein without, however, departing from the scope of protection as defined in the accompanying claims.

(54) In particular, it is underlined that the discussed solution may be applied for any packaging or filling machine and for any kind of pourable food product.