EP1409388A1 - Method for controlling a web accumulator and web accumulator for storing sheetlike objects - Google Patents

Abstract

The invention relates to a method for controlling a storage roller (10) for storing sheet-type objects (34), in particular bank notes, between the wound layers of a belt-type film (36), the latter being wound and unwound between a film drum (12), which is driven by a first motor (16) and comprises a film reservoir roll, and a winding drum (14), which is driven by a second motor (18) and stores the sheet-type objects. According to the invention, the tension of the film is adjusted to a predetermined set value.

Description

 Method for controlling a roll store and roll store for storing sheet-shaped objects

The invention relates to a method for controlling a roll storage device for storing sheet-shaped objects, in particular banknotes, between the winding layers of a band-shaped film which are between a film drum driven by a first motor and comprising a film supply roll and a winding current driven by a second motor and storing the sheet-shaped articles - Mel is spooled back and forth.

Roll storage is often used in ATMs because it enables the same banknotes to be stored and dispensed in a simple manner. When filling or storing, the incoming banknotes are wound one after the other onto the winding drum between the winding layers. The speed of the winding drum can be adapted, for example, depending on the banknotes counted. When the banknotes are dispensed or dispensed, they are unwound again from the winding drum according to the "last in, first out" principle, the film running onto the film drum.

So that the rewinding and rewinding of the film does not lead to the film running out of an existing lateral guide, the film must be kept under tension to avoid loop formation.

A tensile stress in the film that is as uniform as possible can be achieved, for example, by a friction brake acting in both directions. Friction brakes have the disadvantage, however, that they have high changes in the friction torque, especially after have longer breaks in operation or due to temperature changes during longer operation. In order to compensate for this, ie to always ensure a safe operating state, comparatively high friction torques must be set, which in turn lead to corresponding wear on the entire mechanics, so that frequent maintenance and adjustment of the friction torque is required. In addition, there is a correspondingly high loss of energy.

The invention has for its object to provide a method of the type mentioned in which, while avoiding the disadvantages mentioned above, a loop formation of the film can be reliably avoided and an energy-saving operation of the roll memory can be ensured.

This object is achieved in that the tension of the film is regulated to a predetermined target value.

By regulating the film tension or film tensile force to a predetermined low value, for example 10 Newtons, a longer life of the film can be guaranteed. Frequently observed stretching processes, which occur in particular at the edges of the plastic films and lead to tears at the film edges or due to the uneven elongation of the film, cause the film to run off its track, can be completely eliminated in this way. As a result of the fact that a low value for the film tension can be specified and maintained, drive motors with lower outputs can be used, as a result of which the energy consumption of the roll store is reduced. The lower stress on the film enables a reduction in the fo Line thickness, so that with the same installation space for the roll storage, this has a higher storage capacity.

The actual value of the film tension must be recorded for the control. This can be done by directly measuring the film tension, for example by using strain gauges. However, the actual value of the film tension can also be calculated indirectly from the determined power consumption of the first motor and the current radius and moment of inertia of the film drum.

As explained above, roller stores are generally used in higher-level devices, for example money processing devices, such as in automatic cash safes or in money recycling systems. This means that the roll store must be able to store and output banknotes at a speed corresponding to the processing speed of the banknotes in the higher-level device. For this purpose, it is expedient if the peripheral speed of the winding drum can be regulated to a predetermined target value. By regulating the peripheral speed, the storage and output speed of the roll memory can be flexibly adapted to changes in the higher-level system. In addition, such a regulation can reduce the distances between the sheets or banknotes to be stored to a minimum. This in turn leads to a higher storage capacity of the roll memory.

With the simultaneous regulation of the circumferential speed of the winding drum and the film tension by controlling the motors for the film drum and the winding drum, a system with a multi-size control is obtained. The Torques of both motors act both on the winding drum speed and on the film tension or tensile force of the film, on the one hand a predetermined winding speed is to be achieved, and on the other hand, by appropriately controlling both motors, the film-dispensing drum is braked slightly in relation to the film-receiving drum, to stretch the film between the drums. This means that the moment of the motor of the film drum also affects the peripheral speed of the winding drum via the film tension that is actually to be influenced. Conversely, only the circumferential speed of the latter should primarily be regulated by the torque of the motor of the winding drum, but this also has an effect on the film tension. In order to be able to handle such multivariable control practically, the physically coupled control loops for the film tension and the peripheral speed of the winding drum are mathematically decoupled by a mathematical filter network, after which, based on the actual values determined for the film tension and the peripheral speed of the winding drum, the speed of the Foil drum and the specified system parameters, the control signals for the first and the second motor can be calculated.

The invention further relates to a roller store for carrying out the method described above according to claims 8 to 16.

Further features and advantages of the invention result from the following description, which in connection with the accompanying drawings explains the invention with reference to an exemplary embodiment. Show it: Figures 1-3 each a schematic representation of a

Role memory to explain how it works,

FIG. 4 shows a schematic illustration of the essential elements of the roll memory according to the invention and their connection to a control device,

FIG. 5 shows a simplified physical block diagram of the controlled system of the roller store shown in FIG. 4 without the motors,

Figure 6 is a mathematical block diagram of the roll memory and

Figure 7 is a mathematical block diagram of the roll memory with decoupling filter.

1 comprises a housing 10 in which a film drum, generally designated 12, and a winding drum, designated 14, are rotatably mounted about axes 16 and 18, which are parallel to one another. The film drum 12 has a drum core 20, onto which a band-shaped, plastic film 22 can be wound to form a winding 24, the minimum and maximum diameters of the film winding 24 being indicated in FIG. 1. The film 22 runs from the film drum 12 via stationary deflection rollers 26 and a movable deflection roller 28 to the winding drum 14, where it runs onto a drum core 30 of the winding drum 14 and forms a storage winding 32. The movable deflection roller 28 is in each case by means not shown on the deflection catch the winding drum 14 held. The positions of the movable deflection roller 28 with a minimum radius and maximum radius of the winding drum 14 are also indicated in FIG. 1.

For the insertion of sheet-like objects, for example banknotes 34 into the gap between the circumferential surface of the winding drum 14 and the movable deflection roller 28, and thus between two winding layers of the film 22 running onto the winding drum 14, a transport link 36 is used which, like the movable deflection roller 28, is adjustable is.

If the film drum 12 and the winding drum 14 are rotated counterclockwise according to FIG. 2, so that the film 22 runs onto the winding drum 14 in the direction indicated by the arrows in FIG. 2, banknotes 34 are wrapped in the winding 32, i.e. stored in the roll memory. On the other hand, if the drums 12 and 14 are driven clockwise in the manner shown in FIG. 3, the film 22 runs from the winding drum 14 onto the film drum 12, the banknotes 34 emerging from the gap between the surface of the winding drum 14 and the movable one Deflection pulley 28 issued, ie be saved. The function of a roll memory described so far is known per se.

Fig. 4 shows the essential elements of the roll memory and their link to a control and regulating device. The elements corresponding to the illustration in FIGS. 1 to 3 are also provided with the same reference numerals. The drum core 20 of the film drum 12 is connected to a shaft 38 which carries a belt gear 40. This is coupled to the drive pinion 44 of an electric motor 46 via a toothed belt 42.

In the same way, the drum core 30 of the winding drum 14 is connected to a shaft 48 which carries a belt gear 50. This is connected via a toothed belt 52 to the drive pinion 54 of a second electric motor 56.

Each of the electric motors 46 and 56 is equipped with an encoder 58 and 60, e.g. coupled to an incremental decoder, the output signal of which is fed to a control device 62. The control device 62 receives a further input signal from a strain gauge 64, which is used to measure the actual value of the film tension, the current film tension also being able to be determined in another way, as was explained above.

On the basis of the speed information determined by the encoders 58 and 60 and the actual value of the film tension, the specified target values for the film tension and the peripheral speed of the winding drum 14 and the specified system parameters, the control device 62 then determines control signals for the motors 46 and 56 in order to drive them in such a way that the predetermined target values for the film tension and the peripheral speed of the winding drum 14 are observed.

The block diagram according to FIG. 5 shows the coupling between the manipulated variables and the controlled variables of the system. The formula symbols in FIG. 5 denote the following quantities:

MG, MF = moments of motors 56, 46 Vg, Vf = peripheral speeds of the drums 14, 12

F = film tension

d, c = damping and spring constant of the film

JG, JF = moments of inertia of the drums 14, 12

rc, rF = current radii of the drums 14, 12

The control variables are the film tension F and the peripheral speed v _{g of} the winding drum 14. The control variables are the motor torques MF and MG. The torque MF of the film drum motor 12 also acts on the speed VG of the winding drum via the film tension F that is actually to be influenced. The torque MG of the winding drum motor 56 should primarily only regulate the peripheral speed VG of the winding drum 14. But here, too, there is an effect on the film tension, since this should be generated by a difference in the peripheral speeds of the film drum 12 and the winding drum 14.

The coupling between the manipulated and controlled variables is represented by the mathematical block diagram according to FIG. 6. Gi (s) denotes the transfer functions that describe the dynamic behavior of the system. The arrows show the coupling paths between the manipulated variables MF, MG and the controlled variables F, v _g .

In order to be able to handle such a multivariable control practically and to determine the required controllers, the coupling between MG and F or MF and v _{g must be} eliminated. This can be done mathematically through a filter network according to FIG. 7. This filter network includes over structural functions Vι (s), which are to be determined in such a way that the following system of equations is satisfied:

VI (S) -GΪ (S) = V ₃ (s) -G «(s)

Va (ß) -Gι (s) = V «(s) -Ga (s)

If the above equations are met, the undesired coupling paths in the system are eliminated by the upstream filter network, so that only the motor torque MG is coupled to the peripheral speed v _g and the motor torque MF to the film tension F. This has created two control loops that can be designed independently of one another.

When designing the control system, in addition to the coupling of the system sizes described above, it should be noted that winding and unwinding the film also changes the radii of the drums and the associated moments of inertia. The changing radii and moments of inertia result in a non-linear system behavior. The change in the radii can be approximately described by an Archimedean spiral:

^ Foal drum ~ ^ drum core ^" ^ ^" vPo ^"■" ψ)

Explanation of the formula symbols:

rFoiie rommei = current radius of the drum with foil

r o meikem = radius of the drum without foil, d. H . radius

of the drum core

a = thickness of the film φo = starting angle of the drum

φ = current angular position of the drum

The angular position φ of the drums can be determined by measuring and integrating the angular velocity of the motors 46 and 56.

The moment of inertia of the film is determined using the radii previously determined and the material properties of the film 22:

/ ₌ ι _{0 π} ( _f _ \ film 2 H film ^u film "'V film drum' drum core)

Explanation of the formula symbols:

bFoiie = width of the film

pFoiie = density of the film

The respective film roll 24, 32 is regarded as a hollow cylinder which is placed on the respective drum core 20 or 30. The moments of inertia of the drum cores 20, 30 are constants and are determined from the design data.

In order to take into account the influence of the bank notes to be stored on the radius and the moment of inertia of the winding drum 14, a simple model was developed which describes the bank notes as a "paper layer" between the film layers. A density is calculated for the paper layer, which takes into account the distances between the banknotes set by the regulation.

Since the rate of change of the radii and thus the moments of inertia at a required maximum drum speed v _g of 1.2 m / s is relatively low, the temporal change in the route parameters can be compensated for by simple linear transfer functions with changing coefficients.

For the control of the film tension and the peripheral speed v _{g of} the winding drum 14, control concepts known from the literature, such as, for example, cascade controls or state controls with an observer, can be used. Regardless of the respective direction of rotation, the motor 56 then only sets the desired winding speed v _g on the winding drum 14. The film drum motor 56, on the other hand, is solely responsible for maintaining the desired film tension F.

Shares of an incremental encoder 58 in the film drum motor 46 can also be used as a simple pulse generator or counter, which is incremented or decremented with each full rotation of the film drum 12, since the moment of inertia of the film drum 12 changes only relatively little with each rotation and therefore for control purposes of the entire system, the determination of the film drum speed is not absolutely necessary.

In the exemplary embodiment shown, a strain gauge 64 is used to measure the film tension. However, the actual value of the film tension can also be determined indirectly by measuring the current in the motor 46 and by calculating the radius and the moment of inertia of the film drum 12.

Claims

claims 1. A method for controlling a roller store for storing sheet-shaped objects, in particular banknotes between the winding layers of a band-shaped film (22) which are between a film drum (12) driven by a first motor (46), a film supply roll (24) and one of one second motor (56) driven, the sheet-shaped objects (34) storing winding drum (14) back and forth, characterized in that the tension of the film (22) is regulated to a predetermined target value. 2. The method according to claim 1, characterized in that the actual value of the film tension is measured directly. 3. The method according to claim 1, characterized in that the actual value of the film tension is calculated from the determined power consumption of the first motor (46) and the current radius and moment of inertia of the film drum (12). 4. The method according to any one of claims 1 to 3, characterized in that the peripheral speed (v _g ) of the winding drum (14) is regulated to a predetermined target value. 5. The method according to claim 4, characterized in that the speed of the second motor (56) is measured by means of an encoder (60) and from this the actual value of the peripheral speed (v _g ) of the winding drum (14) and its angular position is calculated. 6. The method according to any one of claims 1 to 6, characterized in that the speed of the film drum (12) is measured. 7. The method according to any one of claims 4 to 6, characterized in that the physically coupled control loops for the film tension (F) and for the peripheral speed (v _g ) of the winding drum (14) are decoupled by a mathematical filter network and that on the Based on the determined actual values for the film tension (F) and the peripheral speed (v _g ) of the winding drum (14), the speed of the film drum (12) and the specified system parameters, the control signals for the first and the second motor ( 46, 56) can be calculated. 8. Roll storage for storing sheet-shaped objects, in particular banknotes (34), comprising a film drum (12) which can be driven by a first motor (46) with a supply roll (24) of a band-shaped film (22), one which can be driven by a second motor (56) Wrapping drum (14), the film (22) being able to be rewound between the film drum (12) and the winding drum (14), means (36) for feeding sheet-like objects (34) between the winding layers of the film (22 ) when winding the same on the winding drum (14) or for removing the sheet-like objects (34) when unwinding the film (22) from the winding drum (14) and a control device (62) for controlling the first and second motor (46 , 56), characterized in that the control device (62) for regulating the tension of the film (22) between the two drums (12, 14) is designed to a predetermined target value. 9. Roll storage according to claim 8, characterized in that the control device (62) for regulating the peripheral speed (v _g ) of the winding drum (14) is formed to a predetermined target value. 10. Roll storage according to claim 8 or 9, characterized by a device (64) for measuring the actual value of the film tension (F). 11. Roll storage according to claim 10, characterized in that the device for measuring the actual value of the film tension (F) is a strain gauge (64). 12. Roll storage according to claim 8 or 9, characterized by means for detecting the power consumption of the first motor (46) and means (62) for calculating the actual value of the film tension (F) from the detected data and the current radius and moment of inertia the film drum (12). 13. Roller storage according to one of claims 8 to 12, characterized in that the second motor (46) Encoder (60) is assigned. 14. Roller storage according to one of claims 8 to 13, characterized in that the first motor (56) is assigned an encoder (58). 15. Roll storage according to one of claims 8 to 13, characterized in that the film drum (12) is assigned a tachometer. 16. Roll memory according to one of claims 9 to 15, characterized in that the control device (62) contains a program-controlled computer which It is grammed that it calculates the function values of the resulting transfer functions, which correspond to the two control loops decoupled by a mathematical filter network, from the determined current and the specified data, and from this the control signals for the first and the second motor (46, 56 ) determined.