EP4673797A1

EP4673797A1 - Method for controlling a movable operating member of an automatic machine for producing or packing consumer articles

Info

Publication number: EP4673797A1
Application number: EP24714996.6A
Authority: EP
Inventors: Matteo Degli Esposti; Gabriele Fabbri
Original assignee: GD SpA
Current assignee: GD SpA
Priority date: 2023-03-02
Filing date: 2024-03-01
Publication date: 2026-01-07
Also published as: WO2024180519A1; IT202300003834A1

Abstract

A method for controlling a movable operating member (5) of an automatic machine (1) for producing or packing consumer articles (2); the method comprises the steps of: defining a motion profile (MP) of the movable operating member (5) by which to perform at least oonnee processing oonn the articles (2); controlling in position or velocity, by means of a control unit (6), an electric drive (3) of an electric actuator (4) mechanically connected to the movable operating member (5) to make the movable operating member (5) execute the motion profile (MP); defining an ideal torque profile (ITP) for the movable operating member (5) to be delivered during execution of the motion profile (MP); defining a tolerance interval (I) depending, at least, on the ideal torque profile (ITP); wherein the tolerance interval (I) defines a window of acceptable torque which can be delivered by the electrical drive (3) which follows, instant by instant, the ideal torque profile (ITP); wherein the tolerance interval (I) is variable in width (W) as a function, at least, of the ideal torque profile (ITP).

Description

"METHOD FOR CONTROLLING A MOVABLE OPERATING MEMBER OF AN

AUTOMATIC MACHINE FOR PRODUCING OR PACKING CONSUMER ARTICLES"

CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Application claims priority from Italian Patent Application No . 102023000003834 filed on March 2 , 2023 , the entire disclosure of which is incorporated herein by reference . TECHNICAL FIELD

The present invention relates to a method for controlling a movable operating member of an automatic machine for producing or packing consumer articles .

The present invention has an advantageous , but not exclusive , application in an automatic packaging machine that produces cigarette packets and in the method for controlling it , monitoring its implementations , to which the description that follows will re fer explicitly, but without thus losing its general nature .

PRIOR ART

An automatic packaging machine comprises a plurality of movable operating members that act on the consumer articles ( such as cigarette packets , foodstuf fs , sanitary pads , etc . ) to change the conformation, structure or position . The movable operating members are generally mechanica parts with di f ferent shapes and dimensions , adapted to process the consumer articles and are , in most cases , actuated by means o f electric motors or pneumatic cylinders .

Usually, and increasingly over recent years , these movable operating members are moved/driven by means of electric motors , the control of which provides , often already inside the respective electric drive , a maximum threshold of the torque that can be delivered before it is disabled for safety purposes ( for example , in accordance with the known " safe torque of f" system) . Said threshold is set to disable the torque in the case of entanglements or collisions that require the electric drive to provide a higher torque than the pre-established threshold .

To prevent collisions , recursive control methods are known that report an error and block providing of the torque as a function of the so-called tracking error, i . e . the dif ference between the desired position and the actual position of the movable operating member . When this di f ference exceeds a certain, predefined threshold, an error i s reported and production is halted to avoid potential collisions .

Negative feedback control methods are also known ( such as proportional-integral-derivative control : PID) that are capable of reacting to a possible positive or negative tracking error, with the value tending to be close to zero .

However, these methods are limited in predicting and avoiding collisions , since this is an indirect measurement ( the tracking error ) . In other words , a collision is detected or predicted, since the movable operating member, or the motor that controls it , impeded by a mechanical factor, remains behind with respect to the command given by the drive that controls it , causing an increase in the tracking error up to the point of exceeding the predefined threshold that causes the drive itsel f to stop the motor and disable the torque .

In certain cases , over recent years , various torque sensors or clutch devices , mechanical releases or energy absorbers have been integrated into automatic machines , which intervene in the case of collision in order to reduce the damage .

As an alternative or in addition to them, torque controls are present , which establish a fixed tolerance window, the limit values of which are determined as a function of the maximum and minimum torques to which a movable operating member may be sub j ected .

These systems function best for movable operating members that must move with substantially continuous laws of motion . Furthermore , they perform their function ef ficiently for constant inertia systems .

However, it often happens that an automatic machine for producing or packing consumer articles comprises variable inertia movable operating members . For these systems , setting a fixed window for detecting collisions or impediments to the motion of the movable operating member is inef fective , since , in order to define the limit values of this range , it is clearly necessary to consider the relative torques at the maximum inertia of the movable operating member . Consequently, it may be that a collision occurs at the moment of minimum inertia of the movable operating member and that said collision is not detected by the control system, since the torques in play are , in any case , within the tolerance window established in relation to the maximum inertia of the system .

Failed detection of the collision causes non-intervention of the control system to reduce the damage and therefore an increase in that damage ( in other words , the movable operating member continues to push against the obj ect of the collision, damaging the obj ect or the operating member itsel f ) .

There is therefore a need to improve the collision controls and therefore , in general , control of the movable operating members , in order to detect , and possibly prevent , collisions inside the automatic machine .

Document WO9640558A1 describes a machine driven by a servomotor under the control of a control system that incorporates a diagnostic system for early detection of a need for assistance , thus allowing preventive maintenance to avoid breakdowns on the machine .

DESCRIPTION OF THE INVENTION

The obj ect of the present invention is to provide a method for controlling a movable operating member of an automatic machine for producing or packing consumer articles , which is at least partially free from the problems described here above and, at the same time , is simple and cheap to manufacture .

According to the present invention, a method for controlling a movable operating member of an automatic machine for producing or packing consumer articles is provided in accordance with the independent claims that follow and, preferably, with any one of the claims that are directly or indirectly dependent on the independent claims .

A machine adapted to implement the aforementioned method is provided .

The claims describe preferred embodiments of the present invention and form an integral part of this description .

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the appended drawings , which illustrate several non-limiting embodiments thereof , wherein :

• Figure 1 is a perspective and schematic view of an automatic packing machine for the production of packets ;

• Figure 2 is a schematic view of a block diagram of a possible embodiment of the control method according to the present invention; and

• Figure 3 is an explanatory graph of the torque delivered, of the desired one and of a tolerance interval in a nominal operating condition of an operating member of the automatic machine ;

• Figure 4 is an explanatory graph of the torque delivered, of the desired one and of a tolerance interval in a condition of collision of an operating member of the automatic machine .

PREFERRED EMBODIMENTS OF THE INVENTION

Figure 1 shows an automatic machine 1 for the production of articles of the tobacco industry, in particular an automatic packaging machine 1 for the application of a transparent overwrapping to cigarette packets . The present invention can obviously also be applied to di f ferent machines for producing or packing consumer articles , j ust as cigarettes are .

The automatic machine 1 compri ses a frame 2 onto which a plurality of moving operating members ( such as , for example , pincers , drums , pushers , etc . ) are mounted, which perform production and/or packing operations of consumer articles (which, in the non-limiting embodiment shown in Figure 1 , are cigarette packets 3 ) .

The same reference numbers and reference letters in the figures identi fy the same elements or components with the same function .

In this description, the term " second" component does not imply the presence of a " first" component . Such terms are , in fact , adopted as labels to improve clarity and should not be intended as limiting .

The elements and features illustrated in the di f ferent preferred embodiments , including the drawings , may be combined with each other without deviating from the scope of protection of this application as described below . The automatic machine 1 comprises various elements adapted to perform the processing on the articles ( cigarette packets 2 in the embodiment shown in Figure 1 ) . These elements are generically indicated as movable operating members 5 in the present description .

In particular, the automatic machine 1 comprises one or more electric drives 3 configured to control at least one electric actuator 4 , which is mechanically connected to a respective movable operating member 5 ( also known as last trans feror ) , which performs the processing on the articles ( for example , on the packets 2 ) . The electric actuator 4 is , in fact , electrically connected to the electric drive 3 and is configured to receive torque from the electric drive 3 in order to make the movable operating member 5 perform a motion profile MP .

According to several preferred but non-limiting embodiments , the electric actuators 4 comprise electric motors ( in particular, the brushl ess type ) . According to other embodiments not shown, the actuators 4 also comprise di f ferent types of drives to electric motors ( for example , electrically actuated cylinders , etc . ) .

In several , non-limiting cases , the electric drives 3 are grouped in a dedicated zone of the automatic machine 1 ( for example , a general or dedicated electric panel ) . As an alternative or in addition, several electric drives 3 are arranged at the respective electric actuator 4 . For example , in the case of an electric motor, the respective drive may also be arranged on board the stator of the motor itsel f . In other words , in several non- limiting cases , the electric drives 3 are arranged on board a machine control unit . As an alternative or in addition, several electric drives 3 can be arranged on board the respective electric actuator 4 to which they are connected . The automatic machine 1 also comprises a control unit 6 ( Figure 1 ) , which is configured to control the electric actuators 4 by means of the drives 3 . In other words , the control unit 6 is configured to control the electric drive 3 to command the motion of the movable operating member 5 .

Advantageously but not in a limiting manner, the automatic machine 1 compri ses an interface device 7 ( shown in Figure 1 ) configured to al low an operator 0 to start a training process as described below . In particular, the interface device 7 comprises a screen 8 ; more precisely, the screen 8 is a touchscreen .

According to a further aspect of the present invention, a control method is provided, in particular a method of detection of a collision of a movable operating member 5 of an automatic machine 1 for producing or packing consumer articles 2 .

Advantageously, the automatic machine 1 is configured to perform the method described below . In particular, the control unit 6 is programmed to perform said method .

The method comprises a step of defining the motion profile MP of the movable operating member by which to perform at least one processing on the articles 2 . For example , the motion profile MP may be defined as the position or velocity that the movable operating member 5 or the actuator connected to it must have in order to process , or even only move , a packet 2 .

Once the motion profile MP has been defined, the method comprises the step of controlling, by means of the control unit 6 , the position or velocity of the electric drive 3 of the electric actuator 4 , in order to have the movable operating member perform the first motion profile MP . For example , the control unit 6 sends a position setpoint to the drive 3 , which consequently delivers the torque necessary to maintain at a minimum the tracking error of the member 5 (i.e. the difference between the current position and the one controlled by the drive 3) . Obviously, the same applies for possible control in velocity, rather than in position.

In addition, the method provides for defining an ideal torque profile ITP (shown in Figure 3) for the movable operating member 5, to be delivered during execution of the motion profile MP. Definition of that profile allows considerable speeding up of the motion of the movable operating member 5, which is also controlled with a so-called feedforward torque, to send in advance to the drive 3 the torque values that will be required and to improve the dynamic response of the member 5. In particular, use of a feedforward torque control is particularly advantageous in variable inertia systems.

In particular, the feedforward torque values injected are taken from a specific torque consultation table TT. In detail, the feedforward torque values injected are pre-calculated by means of an inertia table of a known type and not further detailed below. More precisely, the two setpoints, i.e. the desired values (position or velocity and torque) , enter in two different control points. The position setpoint enters into the position loop, and the torque setpoint is sent in feedforward according to known diagrams, which are not further detailed below.

Advantageously, the method also comprises the step of defining the tolerance interval I as a function, at least, of the ideal torque profile ITP. The tolerance interval I defines a window of acceptable torque which can be delivered by the electric drive 3 which follows, instant by instant, the ideal torque profile ITP. In other words, the tolerance interval I defines, in time, a tolerance band B that substantially follows the trend of the ideal torque profile ITP (i.e. that always contains the ideal torque profile ITP within it ) .

Advantageously, the tolerance interval I is variable in width W as a function, at least , of the ideal torque profile ITP . In particular, therefore , the distance between an upper limit UL and a lower limit LL of the tolerance interval I varies as the ideal torque profile ITP varies .

In other words , the width W of the tolerance band B is variable at least as a function of the torque values assumed by the ideal torque profile ITP .

Advantageously but not in a limiting manner, and as shown in the non-limiting embodiment of Figure 3 , the tolerance interval I is defined such that the ideal torque profile ITP is always in the middle of the tolerance interval I itsel f . In other words , instant by instant , the distance between the ideal torque profile ITP and the upper limit UP is equal to the distance between the ideal torque profile ITP and the lower limit LL .

According to several non-limiting preferred embodiments , the control method also comprises the step of controlling, at a first time instant T ' and in feedforward, the electric drive with a desired torque DT in accordance with a point P of the ideal torque profile ITP . The method also provides for detecting, at a second time instant T ' ’ following the first time instant T ' , a torque ET actually delivered by the electric drive 3 in accordance with the previously commanded desired torque DT .

The method also comprises the step of phasing in time the desired torque DT with the torque ET actually delivered, i . e . of determining the di f ference between the instants T ' and T ' ’ and moving in accordance with them a desired torque profile DTP or a torque profile ETP actually delivered, in order to make them concur and be able to compare how delivery of the torque ET actually delivered by the drive 3 to follow the motion profile MP is di f ferent to the desired torque DT .

Once the profiles ETP and DTP are realigned/re-phased, the method provides for checking whether the torque ET actually delivered is within the tolerance interval I at point P of the ideal torque profile TTP .

Advantageously but not in a limiting manner, the method also comprises the step of comparing, after the phasing phase , the desired torque DT with the torque EP actually delivered to obtain the torque error TE . In particular, wherein the step of veri fying is performed on the torque error ( TE ) and/or one of its derivatives . In this manner, it is possible to veri fy whether the torque error TE exceeds the tolerance interval I and to detect a possible collision several instants before with respect to a detection performed by means of a tracking error, as occurs in the prior art . In fact , detection of the torque in the manner described above detects a direct measurement of the opposition to motion of the movable operating member 5 and is detected before it exceeds the tracking error limits (which represents an indirect method, detectable only several cycle times afterwards ) .

In particular, the method also comprises the steps of diagnosing, according to the veri fying step and/or the comparing step, a collision of the movable operating member 5 ; and, consequently, the step of controlling the electric drive 3 , by means of the control unit 6 , in order to stop or disable ( i . e . remove torque from) the electric actuator 4 .

Advantageously but not in a limiting manner, the method also comprises a training step, prior to control of the drive 3 by the control unit 6 , in order to define the tolerance interval I . In particular, the training step is performed by the control unit 6 following an instruction from the operator 0.

In particular, during the training step, the tolerance interval I is defined as a function of the torque error TE , i . e . the di f ference , instant by instant , between the ideal torque profile ITP ( coinciding with the desired torque profile DTP ) and the torque profile ETP' actually delivered by the electric drive 3 to the electric actuator 4 to make the movable operating member 5 perform the motion profile MP during the training step . In particular, the training step comprises the sub-step of controlling, at a time instant , the electric drive 3 with a desired torque DT in accordance with a point P of the ideal torque profile ITP . The training step then comprises the substep of detecting, at a time instant following the previous time instant , the torque ET actually delivered by the electric drive 3 in accordance with the previously commanded desired torque DT . Lastly, the training step compri ses the further sub-steps of phasing in time the desired torque DT with the torque ET actually delivered ( as described above ) ; and comparing, after the phasing phase , the desired torque DT with the torque ET actually delivered to obtain the torque error TE .

Advantageously but not in a limiting manner, the training step is performed at a velocity lower than the nominal production velocity for the movable operating member 5 .

In particular, the torque error TE detected during the training step is used to define the tolerance interval I as follows .

In several , non-limiting cases , as shown in the embodiment of Figure 3 , the tolerance interval I is defined, above and below the ideal torque profile ITP, as the absolute value of at least twice the torque error TE detected during the training step . In particular, Figure 3 shows a torque profile ETP' actually delivered during the training step, which di f fers from the torque profile ETP actually delivered during the production motion of the movable operating member 5 . These ETP and ETP' profiles may be di f ferent for di f ferent reasons , such as di f ferent materials being processed, wear and tear, increase in some friction, lubrication, etc .

According to several non-limiting embodiments , as an alternative or in addition ( as a maximum constraint with respect to what has been stated previously) , the tolerance interval I i s defined as a function of at least one prede fined percentage of the value , instant by instant , of the ideal torque profile TTP . In particular, the tolerance interval I comprises an upper portion UP of the ideal torque profile ITP and a lower portion LP of the ideal torque profile ITP . More in particular, the predefined percentage defines the thickness , or width W, of the upper portion UP and/or both of the lower portion LP . In this manner, for high desired torque DT values , the width W is proportionately higher with respect to lower desired torque DT values .

In certain non-limiting cases , not shown, the tolerance interval I is asymmetric with respect to the ideal torque profile ITP . In particular, the tolerance interval I is defined as a function of a first predefined percentage and a second predefined percentage of the value , instant by instant , of the ideal torque profile ITP ; the first predefined percentage defines the width of the upper portion UP to the ideal torque profile and the second predefined percentage defines the width W of the lower portion LP to the ideal torque profile , the first predefined percentage being di f ferent from the second predefined percentage . In this manner, it is possible to reduce the tolerance interval I and therefore to increase the sensitivity of collision control in situations in which it is possible to predict the dri ft or, in any case , the direction towards which the torque error TE is tending . Advantageously but not in a limiting manner, the first predefined percentage and/or the second predefined percentage is equal to at least 30%, in particular 40%, of the desired torque DT (i.e. point by point of the ideal torque profile ITP) .

Figure 2 shows a schematic view of a block diagram of a part of the control method, in which it is shown that a torque comparator TC (configured to perform the aforementioned comparing step) receives in input the desired torque DT (from the torque table TT) controlled at time T' to the drive 3 and receives the torque ET actually delivered and detected at instant T' ’ as a function of the desired torque DT . The comparator TC re-phases the profile DTP and the profile ETP and determines, instant by instant, the torque error TE (in output from the comparator TC) .

In Figures 3 and 4, the x-axis corresponds with the sampling time t by the control unit 6, whereas the y-axis corresponds with the torque delivered by the drives 3. In particular, the y-axis has values expressed in degrees, where a full circle (360°) corresponds with a machine cycle, whereas the y-axis is expressed in Nm.

In particular, it is clear how in Figure 3, i.e. in the case in which the torque profile ETP is actually within the tolerance interval I (in contrast with what is shown in Figure 4) , the width W of the tolerance band B is higher for high torques, i.e. for high torque errors ET (left side of the graph) with respect to the reduced width of band B for reduced torques (right side of the graph) . In this manner, it is possible to detect, even for variable inertia systems, possible collisions with sufficient sensitivity, without necessarily sacrificing the sensitivity in the reduced inertia phases (right side of the graph) , to the advantage of a correct sensitivity in the high inertia phases (left side of the graph) . Although the invention described here above makes particular reference to an example of a precise embodiment, it is not to be considered as limited to said example of an embodiment, as its scope includes all those variants, changes or simplifications that would be obvious to a person skilled in the art, such as: the addition of further actuators, another type of automatic machine different to a packing machine for the tobacco industry, a different form of the motion profiles, a different order of the method steps, a different number of motors, etc.

The present invention has multiple advantages.

In the first place, it allows detecting of possible collisions by verifying a direct measurement, which can be the torque, rather than an indirect measurement such as the tracking error.

Furthermore, the method described above provides for a point variability of the tolerance interval, thus allowing its width to be varied as a function of the ideal torque profile and therefore of the inertia, in the case of variable inertia mechanisms .

Lastly, the present invention makes it possible to avoid covering the automatic machine in force and/or torque sensors.

Further advantages linked to the procedure according to the present invention relate to the fact that the FID controller is responsible exclusively for the non-modelled part of the torque, i.e. any unexpected variations in inertia, friction and wear and tear .

KEY

1 machine

2 packets 3 electric drives

4 electric actuator

5 movable operating member

6 control unit

7 interface device

8 screen

B tolerance band

DT desired torque

DTP desired torque profile

ET torque actually delivered

ET ' torque actually delivered

ETP torque profile actually delivered

F frame

I tolerance interval

TTP ideal torque profile

LL lower limit

LP lower portion

MP motion profile

0 operator

P point of TTP profile

T ' first time instant

T ' ' second time instant

TC torque comparator

TE torque error

TE ' torque error

TT torque table

UL upper limit

UP upper portion

W width

Claims

1) A method for controlling a movable operating member (5) of an automatic machine (1) for producing or packing consumer articles (2) ; the method comprises the steps of: defining a motion profile (MP) of the movable operating member

(5) by which to perform at least one processing on the articles (2) ; controlling in position or velocity, by means of a control unit

(6) , an electric drive (3) of an electric actuator (4) mechanically connected to the movable operating member (5) to make the movable operating member (5) execute the motion profile (MP) ; defining an ideal torque profile (ITP) for the movable operating member (5) to be delivered during execution of the motion profile (MP) ; defining a tolerance interval (I) depending, at least, on the ideal torque profile (ITP) ; wherein the tolerance interval (I) defines a window of acceptable torque which can be delivered by the electrical drive (3) which follows, instant by instant, the ideal torque profile (ITP) ; the method being characterised in that the tolerance interval (I) is variable in width (W) as a function, at least, of the ideal torque profile (ITP) .

2) The method according to claim 1 and comprising the further steps of: controlling, at a first time instant and as feedforward, the electric drive (3) with a desired torque (DT) in accordance with a point (P) of the ideal torque profile (ITP) ; detecting, at a second time instant following the first time instant, a torque (ET) actually delivered by the electric drive (3) in accordance with the previously commanded desired torque (DT) ; phasing in time the desired torque (DT) with the torque (ET) actually delivered; checking whether the torque (ET) actually delivered is within the tolerance interval (I) at point (P) of the ideal torque profile ( ITP) .

3) The method according to claim 2 and comprising the step of comparing, after the phasing step, the desired torque (DT) with the torque (ET) actually delivered to obtain a torque error (TE) ; wherein the step of verifying is performed on the torque error (TE) and/or one of its derivatives.

4) The method according to claim 2 or 3 and comprising the further steps of: diagnosing, according to the verifying step and/or the comparing step, a collision of the movable operating member (5) ; and controlling the electrical actuator (3) to stop or disable the electrical actuator (4) .

5) The method according to any one of the preceding claims, wherein the tolerance interval (I) is defined such that the ideal torque profile (ITP) is always in the middle of the tolerance interval (I) .

6) The method according to any one of the preceding claims and comprising a training step for defining the tolerance interval (I) ; wherein the tolerance interval (I) is defined as a function of a torque error (TE) , which is a difference, instant by instant, between the ideal torque profile (ITP) and a torque profile (ET) actually delivered by the electric drive (3) to the electric actuator (4) to make the movable operating member (5) perform the motion profile (MP) .

7) The method according to claim 6, wherein the training step comprises the sub-steps of: controlling, at a third time instant, the electrical drive (3) with a desired torque (DT) in accordance with a point (P) of the ideal torque profile (ITP) ; detecting, at a fourth time instant following the third time instant, a torque (ET) actually delivered by the electrical drive (3) in accordance with the previously commanded desired torque (DT) ; phasing in time the desired torque (DT) with the torque (ET) actually delivered; and comparing, after the phasing phase, the desired torque (DT) with the torque (ET) actually delivered to obtain the torque error (TE) .

8) The method according to claim 6 or 7, wherein the tolerance interval (I) is defined, above and below the ideal torque profile (ITP) , as the absolute value of at least twice the torque error (TE) .

9) The method according to any one of the preceding claims, wherein the tolerance interval (I) is defined as a function of at least a predefined percentage of the value, instant by instant, of the ideal torque profile (ITP) ; wherein the tolerance interval (I) comprises an upper portion (UP) of the ideal torque profile (ITP) and a lower portion (LP) of the ideal torque profile (ITP) ; wherein the at least a predefined percentage defines the width of the upper portion (UP) and/or both of the lower portion (LP) .

10) The method according to claim 9, wherein the tolerance interval (I) is defined as a function of a first predefined percentage and a second predefined percentage of the value, instant by instant, of the ideal torque profile (ITP) ; wherein the first predefined percentage defines the width (W) of the upper portion (UP) of the ideal torque profile and the second predefined percentage defines the width (W) of the lower portion (LP) of the ideal torque profile (ITP) , the first predefined percentage being different from the second predefined percentage .

11) The method according to claim 9 or 10, wherein the at least predefined percentage is at least 30%, in particular 40%.

12) An automatic machine (1) for producing consumer articles (2) comprising:

- at least one movable operating member (5) by means of which at least one processing on the articles (2) for consumption is carried out;

- at least one electric drive (3) ;

- at least one electric actuator (4) mechanically connected to the movable operating member (5) and electrically connected to the electric drive (3) ; the electric actuator (4) being configured to receive torque from the electric drive (3) in order to make the movable operating member (5) perform a motion profile (MP) ;

- a control unit (6) being configured to control the electric drive (3) to drive the motion of the moving operator organ (5) ; the automatic machine (1) being characterised in that the control unit (6) is configured to carry out the method according to any one of the preceding claims.