AU2019348372A1 - Method for driving a support roller, controller, drive system, conveyor belt device, and computer program product - Google Patents

Abstract

The invention relates to a method for driving a support roller (5) of a belt (3) by means of a motor (7), to a controller (13), to a drive system, to a conveyor belt device (1), and to a computer program product. The method is used to regulate a differential quotient (A) of corresponding changes in the torque (D) of the motor (7) and a slip (S) between the support roller (5) and the belt (3). At least one characteristic (K) is recorded which indicates the torque (D) on the basis of the slip (S). The at least one characteristic (K) is used to determine a target value for the differential quotient (A), and the differential quotient (A) is regulated at the target value.

Description

Description

Method for driving a support roller, controller, drive system,

conveyor belt device and computer program product

The invention relates to a method for driving a support roller

of a belt by means of a motor, to a controller, to a drive

system, to a conveyor belt device and to a computer program

product.

Conveyor belt devices are widely used in the field of mining.

As a rule, conveyor belt devices have a driven belt drum,

wherein the belt drum is driven by an (electric) motor.

The motor must be designed according to the length and

quantity of the bulk material to be transported. Extending an

existing conveyor belt device is technically complex, since

the motor on the belt drum usually has to be replaced by a

more powerful motor.

To protect the belt, it is therefore known to drive additional

support rollers in addition to the belt drum. By driving

additional support rollers, the load on the belt drum motor

and the belt can be reduced. Such a design is disclosed in DE

2012 102 945 Al, for example.

DE 10 2014 107 591 Al discloses a conveyor belt system, in

particular a belt conveyor, which has a plurality of support

roller frames arranged in tandem, each having at least one

support roller rotatably mounted thereon, and an endless

conveyor belt resting on support rollers as an upper run and

guided in a rotating manner below said support rollers as a

lower run. Distributed over the entire length of the conveyor belt system are drivable or driven support rollers disposed in the support roller frames and each transmitting at least some of the conveyor belt drive power to the conveyor belt section running on the respective support roller.

However, controlling the rotational speed of the respective

support roller is problematic, since the rotational speed of

the respective support roller must be matched to the local

belt speed. Such matching is the subject of EP 3 412 604 Al.

Controlling the rotational speeds and/or torques of the

individual support rollers is complex, however.

Disadvantageously, the rotational speeds and/or the torques of

individual drives or drive systems are linked by a slightly

elastic belt.

Accordingly, the object of the invention is to improve the

driving of a belt support roller, in particular of a conveyor

belt device.

This object is achieved by a method as claimed in claim 1. The

object is also achieved by a controller as claimed in claim 9.

In addition, the object is achieved by a drive system as

claimed in claim 10, a computer program as claimed in claim

11, and a conveyor belt device as claimed in claim 12.

Advantageous further developments and embodiments of the

invention are set forth in the respective dependent claims.

Moreover, one aspect of the invention is to improve a support

roller drive in such a way that it can operate independently

in each case of other drives of a conveyor belt device.

In particular, the invention is based on the idea that a conveyor belt device can comprise a plurality of drive systems for a plurality of drive rollers.

A conveyor belt device generally comprises a belt, wherein the belt is tensioned and retained by a plurality of rollers. Some of the rollers are implemented as drive rollers. The drive rollers are each connected to a motor, wherein the drive rollers are provided for driving the belt. A drive roller may be implemented as a support roller or as a belt drum.

The drive rollers are used to transmit a force to the belt. The force is proportional to the torque applied to the drive rollers by the motor.

The conveyor belt device preferably comprises a plurality of drive systems, wherein the respective drive system is designed to drive a drive roller.

The respective drive system advantageously comprises a motor coupled to the respective drive roller. The respective drive system additionally comprises a controller and a power supply for the motor. The power supply is preferably designed as a frequency converter.

The controller advantageously comprises a slip control device and a rotational speed control device. The slip control device advantageously provides a setpoint rotational speed for the rotational speed control device. The rotational speed control device is advantageously incorporated in the power supply for the respective motor.

In order to operate the respective drive unit independently,

the rotational speed of a driven support roller must adapt to

the local belt speed of the conveyor belt device.

In particular, the invention is based on the recognition that

in order to transmit a force from a drive roller to a belt,

there must be a slip between the belt shell surface and the

belt. For a small slip, in particular a slip of less than 1%,

the following applies: a higher slip results in a greater

transfer of force to the belt.

To transmit a force from the drive roller to the belt, a slip

between the drive roller's shell surface and the belt is

advantageous. The slip S is advantageously proportional to the

difference between the tangential speed v_t of the drive

roller and the speed v of the belt. The tangential speed is

the speed of a point on the shell surface of the drive roller.

A possible definition of the slip S is therefore

v-vt S:=V - V

The slip is preferably adjustable according to a predefinable

force, wherein the force from the driven belt drive roller

acts on the belt. Advantageously, the slip is adjustable from

% to 5%, in particular from 0.1% to 1%. The advantageous slip

range depends on the conveyor belt device. However, an

advantageous value range varies according to the design and

mode of operation of a conveyor belt device.

The belt speed is preferably determined using a sensor. The

sensor supplies the belt speed to a controller.

The method for driving a belt support roller, in particular a support roller of a conveyor belt device, by means of a motor comprises the following steps: - acquiring at least one characteristic curve for motor torque as a function of slip between the support roller and the belt for a belt loading assigned to the characteristic curve during test operation of the support roller, - determining a setpoint for a difference quotient of mutually corresponding changes in the torque and slip on the basis of the at least one characteristic curve, - continuously determining actual values of the difference quotient and slip and adjusting the difference quotient to the setpoint value during normal operation of the support roller.

The support roller is used to apply a force to the belt in a direction tangential to the shell surface of the support roller. The support roller is connected to a motor. The motor is connected to a power supply, the power supply being advantageously designed as a frequency converter. The motor provides the torque for transmission of the force by the support roller.

The method according to the invention thus provides control adjustment, not to a motor torque setpoint, but to a setpoint for a difference quotient of mutually corresponding changes in torque and slip. The advantage of this compared to adjustment to a torque setpoint is that the support roller is not accelerated in an uncontrolled manner and that it is possible to react to dynamic changes in the belt / support roller system, e.g. to a change in the loading of the belt. The determination of the setpoint from at least one characteristic curve acquired during test operation advantageously allows control matched to the actual system parameters.

In one embodiment of the method, a control point on a characteristic curve is selected for determining the setpoint for the difference quotient, and a slope of this characteristic curve at the control point is determined as the setpoint for the difference quotient. The control point on a characteristic curve can be selected, for example, as a function of the belt loading. This means that the control adjustment can be matched to the loading of the belt. In addition, a point on a characteristic curve at which the slope of the characteristic curve is positive is preferably selected as the control point. This advantageously prevents control from becoming unstable, since a negative slope indicates slipping of the support roller under the belt.

The rotational speed of the motor is preferably used as the manipulated variable for difference quotient control. This takes into account the fact that a change in the rotational speed of the motor changes the rotational speed of the support roller and thus its tangential speed v t and the slip and therefore the difference quotient.

The slip can be determined from a speed of the belt and a rotational speed of the support roller, e.g. using the sensor for the belt speed and using an encoder to determine the rotational speed of the support roller. The slip is preferably determined from the speed of the belt and the rotational speed of the support roller using a computing unit, wherein the computing unit is assigned to a controller. The slip determined during operation is supplied to a slip control device. The slip control device preferably supplies a setpoint rotational speed to a rotational speed control device. The rotational speed control device is used to control the speed of the motor and thus the rotational speed of the support roller.

The method enables the belt to be driven in a particularly

simple and efficient manner. In particular, the simple motor

rotational speed control allows such a drive to be operated

autonomously.

In the case of low slip, a characteristic curve can show a

linear increase in the force transmitted to the belt. For high

slip, the force transmitted to the belt increases only

slightly or even decreases. If the slip exceeds a critical

value, the shell surface of the support roller merely slides

along the underside of the belt without transmitting any

appreciable force to the belt. Accordingly, there is only

slight friction between the shell surface of the support

roller and the belt. The transmission of force from the

support roller to the belt is limited accordingly.

Preferably, a plurality of characteristic curves are

determined as a function of the belt loading. Depending on the

loading state of the belt, a corresponding characteristic

curve is selected and advantageously supplied to the slip

control device.

The torque is preferably calculated from the motor's

electrical power which is determined e.g. from actual values

of currents and voltages of a frequency converter feeding the

motor.

The difference quotient of mutually corresponding changes in torque and slip is determined for changes in the rotational speed of the motor as the quotient AD/AS of the change AD in torque corresponding to the change in rotational speed and the change AS in slip corresponding to the change in rotational speed.

Instead of the torque, the force can also be used for control purposes. The relationship between the force F and the torque D is given by the radius r of the support roller: D=r-F => F=D/r.

The difference quotient is preferably determined at regular intervals, e.g. every ten minutes or every hour.

The difference quotient is preferably also determined when the belt loading changes.

Difference quotient control via the rotational speed is preferably provided by P-, PI- or PID-control means. Accordingly, the slip control device and/or the rotational speed control device are designed as a P control loop, a PI control loop or a PID control loop.

The loading state of the belt can be determined by a measuring device, e.g. a belt weigher. Depending on the determined loading of the belt, a corresponding characteristic curve can be provided to the slip control device and/or to the rotational speed control device.

In an advantageous embodiment of the invention, a setpoint value for the difference quotient is selected at a slip of 0% to 5%, in particular at a slip of 0.1% to 1%, preferably 0.1% to 0.5%. However, the slip values quoted are dependent on the conveyor belt device.

The slip is advantageously selected in this value range on completion of a start-up phase and subsequently changed by the respective drive.

At the beginning of an operating period, in particular during the start-up phase, a slip is set at which a maximum force can be transmitted to the belt. Such a slip can be set, purely by way of example, in the range around 0.5%. After the belt has reached a largely constant speed, the slip or the rotational speed is varied. The slip or rotational speed is preferably varied at regular intervals.

A tangential approximation of a plurality of areas of the characteristic curve can provide a characteristic curve that is modified at least in some regions. The modified characteristic curve is preferably a characteristic curve that is matched to the current loading of the belt. The tangent or a set of tangents for different slip values is preferably used as a tangential approximation.

In another advantageous embodiment of the invention, the slip is reduced if the difference quotient assumes a negative value.

In the case of a negative difference quotient, an increase in slip results in a reduction in the force transmitted to the belt. Accordingly, it can be assumed that the slip is too high.

Thus, when any such negative increase is detected, the slip is

reduced. In particular, a reduction in the rotational speed of

the motor produces a reduction in slip. Advantageously, when

negative slip is detected, a reduced setpoint rotational speed

is supplied to the speed control device.

Checking for a negative difference quotient advantageously

ensures that the belt is protected.

In another advantageous embodiment of the invention, slip

control takes place only after a start-up phase, in particular

after the belt speed has attained a constant value or a

substantially constant value.

During the start-up phase of the conveyor belt device, the

rotational speed of the respective motor is preferably

increased within a predefinable time to a rotational speed

corresponding approximately to the rotational speed at which

no slip occurs. During the start-up phase, preferably only the

speed of the respective drive is controlled.

Once the speed corresponds approximately to the speed that the

belt is designed to have during regular operation, the slip

control device is preferably activated.

In another advantageous embodiment of the invention, the

characteristic curve is modified based on determining the

difference quotient.

In particular, by regularly determining the difference

quotient, it can advantageously be ascertained whether the

characteristic curve, corresponding to the loading of the

conveyor belt device, is in accordance with the determined

difference quotient.

If it is ascertained that the slope of the characteristic

curve used is at variance with the determined difference

quotient at the respective slip, the characteristic curve is

preferably modified or another characteristic curve is

selected. The new characteristic curve is advantageously

supplied to the slip control device.

Modifying the characteristic curve or replacing the

characteristic curve with another characteristic curve

advantageously enables the control action to be matched to the

respective loading of the belt conveyor.

The start-up phase may be characterized by an increasing belt

speed. The slip control device is preferably activated only

when the rotational speed control device detects just a slight

deviation in the positive and negative direction of the

rotational speed.

A controller according to the invention for a drive, in

particular of a conveyor belt device, comprises

- an input for a measured belt speed,

- a slip control device,

- an interface to a power supply and

- a rotational speed control device,

wherein the controller is designed to carry out a method as

described here.

The controller also optionally comprises an input for an

encoder. Advantageously, the encoder is used to determine the

rotational speed of the motor. The rotational speed of the

motor is supplied to the rotational speed control device.

In addition, the controller optionally comprises an input for

a sensor for determining a loading state of the belt. Such a

sensor can take the form of a belt weigher.

The power supply preferably provides the controller with the

torque to be applied by the motor.

The controller is preferably assigned to a computing unit or

comprises such a computing unit.

The slip control device is preferably used to control the

slip. The rotational speed control device is preferably used

to control the rotational speed.

The slip control loop supplies rotational speed setpoint

values to the rotational speed control device. The rotational

speed setpoint values are determined on the basis of the slip.

The rotational speed control device is preferably assigned to

a power supply of the motor.

The belt speed is preferably determined by means of a sensor,

wherein the sensor advantageously supplies the belt speed to

the slip control device and/or the rotational speed control

device as an actual speed value in each case.

The characteristic curve or the plurality of characteristic

curves are preferably stored in the controller. The respective

characteristic curve is supplied to the slip control loop for

controlling the slip.

The open- or closed-loop control of the rotational speed or

slip is preferably performed autonomously using the controller

described here. Autonomous operation is to be understood as meaning that the controller is only connected to or communicates with the motor assigned thereto, the power supply assigned thereto and with the sensors assigned thereto.

In particular, the drive system is used for a conveyor belt device. The drive system comprises a motor and a support roller, a power supply for the motor, in particular a frequency converter, and a controller as described above.

A sensor for determining the belt speed is preferably assigned to the drive system. The sensor is preferably used to determine the belt speed in the region of the support roller. In this way, the speed of the belt in the vicinity of the respective support roller can be determined. The belt speed is preferably supplied to the controller which is used for open or closed-loop control of the motor connected to the support roller.

Such a drive system can preferably be operated autonomously.

The computer program product is designed to be executed on a computing device, wherein the computer program product is designed to carry out a method as described here.

The computer program product is installed on a computing unit for execution and is preferably stored there. The computing unit is advantageously assigned to the controller. To carry out the method, the computer program product is preferably loaded into the main memory of the computing unit wherein it is executed by a CPU. The method is preferably used to provide rotational speed setpoint values to a motion controller or to a power supply of the motor.

By means of a computer program product as described here, the

method described here can be carried out particularly easily

and with a high degree of speed and accuracy.

The conveyor belt device comprises at least one drive system

according to the foregoing description or at least one

controller as described above.

The conveyor belt device advantageously comprises a plurality

of drive rollers, each of which is assigned to a motor. The

drive rollers are used to drive the belt of the conveyor belt

device.

Accordingly, a conveyor belt device may comprise a plurality

of drive systems. The belt is advantageously driven by the

majority of the drive systems simultaneously.

An existing conveyor belt device can advantageously be

equipped with one or more drive systems as described here. In

this case, the respective drive system is advantageously used

to drive a support roller. Driving one or more support rollers

advantageously enables the load to be taken off the drive

system for a belt drum.

The respective support roller is preferably assigned to a

drive system in each case. The respective support roller is

preferably driven using an autonomous drive system.

The controller preferably comprises a memory, wherein the

memory has constant parameters, such as the radius of the

respective support roller, technical data of the motor or

pretensioning of the belt. In addition, the memory can have dynamic values, such as the belt loading or friction coefficients between the support roller and the belt.

The belt speed is preferably determined by a sensor and the speed is supplied to the plurality of controllers.

The controller preferably comprises a means of inputting values such as technical data of the power supply or of the motor and for the diameter of the shell surface of the support roller.

The characteristic curve can preferably be approximated via a spline curve with slope values, preferably similarly to a Taylor expansion.

The determined setpoint value for the difference quotient preferably changes when the belt loading is changed. Accordingly, adjustment to a new advantageous setpoint value advantageously takes place after a change in the loading.

A drive system as described here can preferably be used autonomously in a conveyor belt device. In addition, in the event of mechanical modifications, the respective drive system can be adapted with little time and effort.

In the event of failure of a drive system, the force required to move the belt can preferably be distributed over the other drive systems. If a drive system fails, a signal is preferably sent to the other drive systems of the conveyor belt device. On receipt of the signal, the respective motor torque and/or the respective slip is preferably increased accordingly.

In summary, the invention relates to a method for driving a support roller of a belt by means of a motor, to a controller, to a drive system, to a conveyor belt device, and to a computer program product. The method is used to control a difference quotient of mutually corresponding changes in the motor torque and slip between the support roller and the belt. For this purpose, at least one characteristic curve is acquired which indicates the torque as a function of the slip. Based on the at least one characteristic curve, a setpoint value for the difference quotient is determined. In addition, the characteristic curve can be matched to a variable loading of the belt.

The invention will now be described and explained in more detail with reference to the accompanying drawings. The embodiments shown in the figures are merely by way of example and in no way limit the scope of the invention.

FIG 1 shows an exemplary drive system,

FIG 2 shows an exemplary method,

FIG 3 shows a characteristic curve and

FIG 4 shows an exemplary controller.

FIG 1 shows an exemplary drive system. The drive system is advantageously part of a conveyor belt device 1. The drive system shown here comprises a motor 7, wherein the motor drives a support roller 5. The support roller 5 acts with its shell surface on an underside of a belt 3. The belt 1 is part of the conveyor belt device 1. The belt 3 is used to transport bulk material 11, wherein the bulk material 11 is loaded on the belt 3.

The motor 7 is supplied with electrical energy by a power

supply 9. The power supply 9 can be designed as a frequency

converter.

A controller 13 is assigned to the power supply 9. The

controller 13 is used to control the rotational speed w and/or

the torque D of the motor 7. A characteristic curve K is

assigned to the controller 13. Based on the characteristic

curve K, a slip S between the shell surface of the support

roller 5 and the underside of the belt 3 is set using the

controller 13. The slip S is selected using the characteristic

curve K.

A sensor 15 is used to determine the speed v of the belt 3.

The sensor 15 determines the speed v of the belt in the region

of the support roller 5.

The support roller 5 is used to drive the belt 3. The support

roller 5 has a tangential speed v t on its shell surface. The

difference between the tangential speed v_t and the speed v of

the belt 1 is proportional to the slip S between the support

roller 5 and the belt 3.

FIG 2 shows an exemplary method. The method is preferably used

to control the rotational speed w of the motor 7. The motor 7

is advantageously used to drive a belt 3 of a conveyor belt

device 1. The method is designed to drive the belt 3 as

protectively as possible.

The method comprises the following steps:

In a first method step V1, the rotational speed w and/or the torque D of the motor 7 is controlled in such a way that a substantially constant slip S or a substantially constant speed v of the belt 3 is set. The first method step V1 can also be referred to as the start-up phase.

In a second, optional method step V2, the slip S is set on the basis of a characteristic curve K determined experimentally during test operation of the support roller 5, wherein the characteristic curve K specifies the torque D of the motor 7 or a force F transmitted to the belt 3 by the support roller 5 as a function of the slip S. A force F to be applied to the belt 3 is preferably predefined. Alternatively or in addition, the force F is determined such that the speed v of the belt 3 remains constant. Advantageously, this force F, when set, results in a constant speed v of the belt 3.

In a third method step V3, the slip S is varied. For varying the slip, the rotational speed w of the motor 7 is increased or decreased, for example, by a small value, e.g. 5% or 1% of the rotational speed w. Consequently, the slip S is increased or decreased by a slip difference AS. In addition, the change AD in the torque D of the motor 7 or the change AF in the force F is determined on the basis of the slip difference AS.

In a fourth method step V4, a difference quotient A=AD/AS or A=AF/AS is determined. For example, the difference quotient A is determined after a change in the loading of the belt 3 with the bulk material 11. In addition, a setpoint value for the difference quotient A is determined on the basis of the characteristic curve K. To determine the setpoint for the difference quotient A, a control point RP on the characteristic curve K (see FIG 4) is selected at which the slope of the characteristic curve K is positive.

In a sixth method step V6, the sign (+ or -) of the difference quotient A is determined.

If the difference quotient A is negative, the rotational speed w of the motor 7 is too high. As illustrated in the characteristic curve K shown in FIG 3, effective transmission of a force F from the support roller 5 to the belt 3 is possible only for a small slip S. Above a critical slip S max, the support roller 5 merely spins and sliding friction effects predominate between the support roller 5 and the belt 3. Accordingly, in the event of a negative difference quotient A, the slip S or the rotational speed w is reduced. The reduction of the slip S or the rotational speed w takes place in a fifth method step V5.

After the reduction of the slip S or reduction of the rotational speed w, the transition to the second method step V2 or to the third method step V3 preferably occurs.

If the difference quotient A is positive, in a seventh method step V7 the difference quotient A is adjusted by changing the rotational speed w to the setpoint determined in the fourth method step V4.

The method shown in FIG 2 allows a plurality of drive systems to be operated independently of one another.

FIG 3 shows a characteristic curve K. The characteristic curve K indicates the relationship between the slip S and the force F or torque D transmitted to the belt. The force F transmitted to the belt 3 is proportional to the torque D provided by the motor 7. The characteristic curve K indicates an essentially linear increase dF/dS for low slip values. For high slip S, there is a fall-off in the force K transmitted to the belt as the slip S increases up to a critical slip S max. At the critical slip S max, a maximum force F-max is transmitted to the belt 3.

The variation Var of the slip S or the rotational speed w of

the motor 7 is indicated by a horizontal section. The slip S

is increased or decreased in such a range.

The increase dF/dS is determined on the basis of the slip

difference and the resulting force difference. The increase

dF/dS is the slope of the slope triangle shown above the

section.

FIG 4 shows an exemplary controller 13. The controller

comprises inputs for the measured speed v of the belt, and

optionally an input for the torque D.

The controller 13 also comprises a slip control device RE2 and

a rotational speed control device RE1. The slip control device

provides the rotational speed control device RE1 with

rotational speed setpoint values w setpoint. The rotational

speed control device RE1 can also be assigned to the power

supply 9 of the motor 7.

In addition, an acquired characteristic curve K is stored. The

characteristic curve is advantageously stored in a memory of a

computing unit RE. The computing unit RE is used to determine

the difference quotient A and the setpoint for the difference

quotient A. The controller preferably incorporates other parameters, such as the diameter of the respective support roller 5, technical data of the motor 7 and an existing tension of the belt 3. The dashed rectangle symbolizes other possible elements of the controller 13, such as an interface, or an interface to an encoder or to the power supply 9.

Claims (12)

Claims

1. A method for driving a support roller (5) of a belt (3) by

means of a motor (7), wherein:

- during test operation of the support roller (5), at least

one characteristic curve (K) for a torque (D) of the motor (7)

as a function of a slip (S) between the support roller (5) and

the belt (3) is acquired for a loading of the belt (3)

assigned to the characteristic curve (K),

- a setpoint value for a difference quotient (A) is determined

from mutually corresponding changes in the torque (D) and the

slip (S) on the basis of the at least one characteristic curve

(K),

- and during normal operation of the support roller (5),

actual values of the difference quotient (A) and of the slip

(S) are continuously determined and the difference quotient

(A) is adjusted to the setpoint value.

2. The method as claimed in claim 1, wherein a control point

(RP) on a characteristic curve (K) is selected to determine

the setpoint value for the difference quotient (A), and a

slope of this characteristic curve (K) at the control point

(RP) is determined as the setpoint value for the difference

quotient (A).

3. The method as claimed in claim 2, wherein the control point

(RP) on a characteristic curve (K) is selected as a function

of a loading of the belt (3).

4. The method as claimed in claim 2 or 3, wherein a point on a

characteristic curve (K) at which the slope of the

characteristic curve (K) is positive is selected as the

control point (RP).

5. The method according to one of the preceding claims,

wherein a rotational speed (w) of the motor (7) is used as a

manipulated variable of the control of the difference quotient

(A).

6. The method as claimed in one of the preceding claims,

wherein the slip (S) is determined from a speed (v) of the

belt (3) and a rotational speed of the support roller (5).

7. The method as claimed in claim 6, wherein the speed (v) of

the belt (3) is measured.

8. The method as claimed in one of the preceding claims,

wherein the torque (D) is determined from an electric power of

the motor (7).

9. A controller (13) for a drive, wherein the controller (13)

comprises

- an input for providing a measured speed (v) of a belt (3),

- a slip control device (RE2),

- an interface for connection to a power supply (9),

- a rotational speed control device (REl),

wherein the controller (13) is designed to carry out a method

as claimed in one of the preceding claims.

10. A drive system, in particular for a conveyor belt device

(1), comprising a motor (7) and a support roller (5), a power

supply (9) for the motor (7), in particular a frequency

converter, and a controller (13) as claimed in claim 9.

11. A computer program product for execution on a computing

unit, wherein the computer program product is designed to

carry out a method as claimed in one of claims 1 to 8.

12. A conveyor belt device (1), comprising at least one drive

system as claimed in claim 10 or a controller (13) as claimed

in claim 9.