Sensor assembly for a belt drive

Abstract

The invention relates to a belt drive which comprises a first pulley having a first diameter and a second pulley having a second diameter and a belt which is arranged on a lateral surface of the first and the second pulley in each case and is designed to transmit a rotational movement of the first pulley to the second pulley. The belt drive also has a first sensor assembly which is arranged and designed to detect a rotational position of the first pulley, and a second sensor assembly which is arranged and designed to detect a rotational position of the second pulley. The first diameter corresponds to a first integer multiple of a unit of length and the second diameter corresponds to a second integer multiple of the same unit of length, the first and the second integer multiple of the unit of length being coprime.

Description

[0001] Sensor arrangement for a belt drive

[0002] Description

[0003] A sensor arrangement for a belt drive and a method for determining a rotational position of pulleys are described here.

[0004] Electric drives for motor vehicle steering are known, for example, for power steering systems (Electric Power Steering, EPS). In the case of an axis-parallel drive (APA), a so-called "power pack," which comprises a motor unit and a control or regulation unit in the form of an electronic data processing unit (ECU), can be coupled via a belt drive to a ball screw drive (KGT), which converts a rotational movement of the motor unit into a translational movement to influence the toe angle of the vehicle's wheels.

[0005] The belt drive, which connects the "power pack" or motor unit to the ball screw drive, typically has two pulleys and a belt. To improve existing power steering systems, as well as to implement fully electronically assisted steering systems (steer-by-wire, SBW), it is necessary to determine the current or actual toe angle of the wheels influenced by the steering in order to correctly implement a steering movement initiated by the driver of the vehicle through appropriate control or regulation of the motor unit.

[0006] It is fundamentally possible to use inductive, capacitive, magnetic, and / or optical sensors to determine the rotational position of the pulleys of the belt drive that connects the "Power Pack" or the motor unit to the ball screw drive, thereby drawing conclusions about the current toe angle of the wheels affected by the steering. However, optical sensors are uncommon in practice due to contamination of the sensors and pulleys and / or a lack of accuracy. The most precise measurement results can be achieved using inductive sensors.

[0007] However, one problem with detecting the current or actual rotational position of the pulleys is that a specific rotational position of the two pulleys of the belt drive does not necessarily correspond unambiguously to a specific toe angle of the wheels influenced by the steering. Consequently, the actual or current toe angle of the wheels influenced by the steering can only be determined by determining the rotational positions of the pulleys if the detection of the rotational positions of the pulleys is supplemented by sensor detection directly at the wheels or at least by an evaluation of the detection history of the rotational positions of the pulleys.

[0008] The former, on the one hand, involves additional technical effort and thus relativizes the advantages associated with detecting the rotational position of the pulleys for regulating or controlling the steering. The latter requires that the detection history is always available, even when the vehicle starts moving, and that a memory always provides the historical data at the same time as the sensor detection. If the records of past rotational position detections are not available, for example, when the vehicle starts moving, it is not possible to reliably determine the current toe angle of the wheels influenced by the steering based on the rotational position of the pulleys alone. Safe control of the vehicle is therefore not possible in this situation.Furthermore, a tire change, for example, can lead to an interruption and / or falsification of a recorded detection history, which makes it impossible to subsequently reliably determine an actual steering angle based on a detected rotational position of the pulleys of a steering system.

[0009] The technical task is therefore to provide an improved belt drive for a motor vehicle steering system with a sensor system that enables the determination of a rotational position of the belt drive pulleys and their unambiguous assignment to a specific current toe angle of the motor vehicle wheels influenced by the steering, across the entire steering adjustment range. Furthermore, a corresponding method is to be provided that enables the determination of a rotational position of the belt drive pulleys and their unambiguous assignment to a specific current toe angle of the motor vehicle wheels influenced by the steering, across the entire steering adjustment range.

[0010] These objects are achieved by a device according to claim 1 and a method according to the independent method claim. Advantageous embodiments are defined by the further claims.

[0011] The belt drive has at least a first pulley with a first diameter and a second pulley with a second diameter. Furthermore, the belt drive has a belt that is arranged on a respective lateral surface of the first and second pulleys and is configured to transmit a rotational movement of the first pulley to the second pulley. A first sensor arrangement is arranged and configured to detect a rotational position of the first pulley. Furthermore, a second sensor arrangement is arranged and configured to detect a rotational position of the second pulley.

[0012] The first diameter corresponds to a first integer multiple of a unit of length. A unit of length can be, for example, a millimeter, a centimeter, an inch, or another unit of length of any length. In other words, the first pulley has a diameter whose length or magnitude can be specified as the product of a natural number and a selected unit of length, for example, a centimeter, an inch, or another unit of length of any length. In one example, the first pulley can have a diameter of 31 units of length, for example, a diameter of 31 millimeters.

[0013] The second diameter corresponds to a second integer multiple of the same unit length. For example, the second pulley can have a diameter of 97 units of length, for example, a diameter of 97 millimeters.

[0014] The first and second integer multiples of the unit length are distinct and relatively prime. For example, 31 and 97 are distinct natural numbers that are relatively prime, meaning they have no common natural divisor beyond 1.

[0015] In other words, it can be described that the size ratio between the first pulley and the second pulley and / or the length ratio between the first diameter and the second diameter corresponds to a ratio of two different natural numbers to each other, wherein the two different natural numbers have no common natural divisor other than the number 1.

[0016] Optionally, the first integer multiple and / or the second integer multiple can correspond to a prime number or the product of a first and / or second unit of length and a prime number. In other words, the diameter of the first and / or the second pulley can each correspond to a product of any unit of length and a natural number, in particular a prime number. This ensures that the first integer multiple and the second integer multiple of the unit of length can never have a common natural divisor. The first sensor arrangement can comprise a contactless position sensor, in particular a contactless and inductive position sensor. Furthermore, the second sensor arrangement can also comprise a contactless position sensor, in particular a contactless and inductive position sensor.For example, the first and / or second sensor arrangement may include a CIPOS® sensor that determines the rotational position of the first and / or second pulley.

[0017] Alternatively or additionally, the first sensor arrangement and / or the second sensor arrangement may also comprise capacitive, magnetic and / or optical sensors.

[0018] The first and / or second sensor arrangements can each be configured to determine a rotational position or a rotational attitude of a pulley. In other words, the first and / or second sensor arrangements can each determine by how many degrees a pulley has rotated relative to a defined or imaginary zero position or starting position.

[0019] In one variant, the first and / or second sensor arrangements can determine a rotational position of the first and / or second pulley with an accuracy of, for example, 1.2 degrees, whereby this measurement inaccuracy already includes the deviations from a technically ideal rotation of the pulleys caused by the implemented mechanics of the belt drive.

[0020] In one embodiment, at least a portion of the first sensor arrangement can be integrated into the first pulley and / or coupled to the first pulley. Furthermore, at least a portion of the second sensor arrangement can be integrated into the second pulley and / or coupled to the second pulley. For example, conductor loops and / or magnetic elements can be formed as part of the pulleys or coupled or connected to them.

[0021] Furthermore, the belt drive can comprise a data processing device or be assigned to a data processing device and / or connected to it. The data processing device can in particular be an electronic data processing device. In one variant, the data processing device can also be formed entirely or partially by the first and / or second sensor arrangement and / or by a part of the first and / or second sensor arrangement or can be integrated into it. The data processing device can evaluate the detection of the first sensor arrangement and / or the second sensor arrangement, store it and / or make the detections and / or the evaluations accessible to an external technical device, for example an on-board computer. In a further development, the data processing device can be integrated into an on-board computer or formed as part of an on-board computer.

[0022] The data processing device can be configured to unambiguously determine a rotational position or setting position of the belt drive on a setting path of the belt drive comprising several complete rotations of the first and / or the second pulley, based on the detection of the first sensor arrangement and the detection of the second sensor arrangement.

[0023] This is made possible by the relatively prime size or length ratio of the diameters of the first and second pulleys. The length or size of the diameters of the pulleys implies the circumference of the pulleys as well as the gear ratio of the belt drive with the two pulleys.

[0024] For example, if the first pulley has a diameter of 31 length units and the second pulley has a diameter of 97 length units, the belt drive has a gear ratio of 97 / 31 or approximately 3.129 from the first, smaller, pulley to the second, larger pulley. In other words, approximately 3.129 revolutions of the first, smaller, pulley result in one complete revolution of the second, larger, pulley. The inverse results in a gear ratio of 31 / 97 or approximately 0.3196 from the second, larger, pulley to the first, smaller pulley. In other words, approximately 0.3196 revolutions of the second, larger, pulley result in one complete revolution of the first, smaller, pulley.

[0025] However, since the natural numbers 31 and 97 are relatively prime, a specific rotational position or setting position of the belt drive, which is defined by a specific rotational position of the first pulley and a specific rotational position of the second pulley, is repeated only after 97 complete revolutions of the first pulley and 31 complete revolutions of the second pulley.

[0026] Each combination of a specific rotational position of the first pulley and a specific rotational position of the second pulley can thus be uniquely assigned to a specific setting position of the belt drive over a travel path comprising several complete rotations of the first and / or the second pulley. The belt drive described here can be used, for example, for the steering of a motor vehicle. This can, for example, have an axis-parallel arrangement with one of the belt drives described above. The belt drive can transmit a rotational movement from a first pulley arranged on an electric motor to a second pulley arranged on a ball screw drive, wherein the ball screw drive is configured to convert the rotational movement into a translational movement to effect or assist the steering.

[0027] Known belt drives for motor vehicle steering systems have a travel range of approximately 80 to 120 complete revolutions of the motor-side pulley. In other words, approximately 80 to 120 complete revolutions of a pulley mounted on an electric motor can move a motor vehicle steering system from one maximum possible deflection position to the opposite maximum possible deflection position, or at least assist such a movement.

[0028] The number of maximum possible rotations of the belt drive pulleys between the maximum deflection positions defines the travel of the belt drive. If the size ratios of the pulleys are not chosen to be relatively prime to each other, each combination of specific rotational positions of the two pulleys can be assigned to several possible adjustment positions of the belt drive along the travel, and thus to several possible steering angles of the vehicle wheels. Therefore, a clear determination of the current steering angle of the vehicle based solely on the rotational positions of the pulleys determined by the sensor arrangements is not possible.

[0029] However, if the size ratios of the pulleys are selected to be prime to each other and are matched to the length of the travel and / or to the maximum achievable steering angle, each combination of specific rotational positions can be assigned to exactly one setting position of the belt drive, and thus unambiguously to a steering angle of the vehicle wheels.

[0030] In one variant, the travel of the belt drive can be defined by 80 to 120, in particular by 90 to 110, maximum possible complete revolutions of the first pulley in a specific direction of rotation. The second integer multiple of the unit length, which corresponds to the diameter of the second pulley, can be formed by the product of a natural number and the unit length, whereby the natural number can be greater than 80, in particular greater than 90 and / or greater than 100 and / or greater than 120. The first pulley can be coupled to a motor or electric motor, in particular to the rotor of a brushless electric motor. Optionally, a control or regulation of the motor or electric motor can also be based on the detection of the first sensor arrangement. The brushless electric motor can be a permanent magnet synchronous motor (PMSM) or a brushless asynchronous machine.

[0031] One advantage here is that the detection of the first sensor arrangement can serve at least two different purposes: first, determining the setting position of the belt drive along the travel path and / or determining the steering angle of a steering system, and second, regulating or controlling a motor or electric motor coupled to the belt drive. The motor control can, for example, comprise field-oriented control (FOC). This, on the one hand, eliminates a sensor that is already required for regulating or controlling the motor, and, on the other hand, provides additional benefit from the sensor arrangements required for detecting the rotational position of the pulleys.

[0032] Furthermore, the belt drive can comprise a temperature sensor configured to detect a temperature of the belt drive, in particular a temperature of the belt's surroundings. Alternatively or additionally, the belt drive can comprise a temperature estimator configured to estimate a temperature of the belt drive, in particular a temperature of the belt's surroundings, based on a model of the belt drive.

[0033] An advantage here is that based on the detection of the temperature sensor and / or the temperature estimator, a temperature compensation of the belt elasticity of the belt, in particular a first or second order temperature compensation, can be carried out.

[0034] Furthermore, the data processing device can be configured to determine a compression or expansion of the belt based on the detection of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator. Alternatively or additionally, the data processing device can also be configured to determine a force acting on the belt drive, in particular on the belt, based on the detection of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.One advantage here is that the first sensor arrangement and the second sensor arrangement, which can optionally be supplemented by a temperature sensor and / or a temperature estimator, can also cooperate to form a force sensor, for example, a force sensor for the forces acting on the steering of a motor vehicle during driving operation of the motor vehicle. The acting forces can be determined by detecting compression or expansion of the belt and comparing them with predetermined and / or stored reference values.

[0035] In one embodiment, the data processing device is further configured to determine or estimate wear and / or damage to the belt drive, in particular the belt, based on current and / or recorded detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.

[0036] Determining the wear and / or damage can, in particular, comprise a comparison of the detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor with a model of the belt. The model can, in particular, be a virtual model of the belt drive created by the data processing device, in particular an electronic one, which models the technical and physical properties of the belt drive, which are then compared by the data processing device with the actual detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor.

[0037] Furthermore, the data processing device can be configured to determine and / or estimate subcooling and / or icing of the belt drive and / or a device coupled to the belt drive, in particular a ball screw drive, based on current and / or recorded detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.

[0038] Icing, for example icing of the ball screw drive, can occur, for example, when a motor vehicle with the belt drive comes into contact with water at negative ambient temperatures, for example in a car wash. Icing of the belt drive and / or a device coupled to the belt drive can have a significant negative impact on the road safety of the motor vehicle. Similar to wear and / or damage to the belt drive, hypothermia and / or icing of the belt drive and / or a device coupled to the belt drive, in particular a ball screw drive, can be determined by the data processing device by comparing the detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor with a model of the belt.Here, too, the modeling can be, in particular, a virtual model of the belt drive created by the, in particular electronic, data processing device, which models technical-physical properties of the belt drive, which are then compared by the data processing device with the actual detections of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor.

[0039] The belt drive described above can, in particular, be part of an axially parallel arrangement or an axially parallel drive, in particular for the steering of a motor vehicle. The belt drive and / or the axially parallel arrangement or the axially parallel drive with the belt drive can further be part of a motor vehicle, in particular part of the steering of a motor vehicle.

[0040] Optionally, the data processing device can further be configured to issue a warning message to the driver of a motor vehicle and / or to shut down the motor vehicle based on the detection of wear and / or damage and / or supercooling and / or icing of the belt drive, in particular of the belt, and / or with a device coupled to the belt drive, in particular a ball screw drive.

[0041] One advantage of this is that, on the one hand, the driver of the motor vehicle can be informed of any foreseeable need for maintenance of the motor vehicle, for example with a visually and / or acoustically perceptible warning message, and, on the other hand, that the vehicle can also be shut down by the data processing device in the event of a detected dangerous situation.

[0042] A method for determining a rotational position of pulleys of a belt drive comprises the steps:

[0043] - Providing a first pulley having a first diameter;

[0044] - Providing a second pulley having a second diameter;

[0045] - Providing a belt which is arranged on a respective lateral surface of the first and second pulleys and is adapted to transmit a rotational movement of the first pulley to the second pulley;

[0046] - detecting a rotational position of the first pulley with a first sensor arrangement; - detecting a rotational position of the second pulley with a second sensor arrangement; characterized in that the first diameter corresponds to a first integer multiple of a unit length and the second diameter corresponds to a second integer multiple of the same unit length, wherein the first and second integer multiples of the unit length are different from one another and are coprime to one another.

[0047] Furthermore, the method for determining a rotational position of pulleys of a belt drive may comprise the following steps:

[0048] - Providing a data processing device; and

[0049] - Unambiguous determination of a rotational position or setting position of the belt drive on a travel path comprising several complete rotations of the first and / or the second pulley, based on the detection of the first sensor arrangement and the detection of the second sensor arrangement.

[0050] Further features, properties, advantages, and possible modifications of the belt drive will become clear to a person skilled in the art from the following description, which refers to the attached schematic drawing. The dimensions and proportions of the components shown in Figure 1 are expressly not to scale.

[0051] Fig. 1 shows an example of a belt drive 100.

[0052] Figure 1 shows an example of a belt drive 100 with a first pulley 10 and a second pulley 20. The first pulley 10 is rotatably mounted about a first rotation axis XI and the second pulley 20 is rotatably mounted about a second rotation axis X2.

[0053] Furthermore, Figure 1 shows a belt 30 which is arranged on a lateral surface of the first and second pulleys 10, 20 and is designed to transmit a rotational movement of the first pulley 10 to the second pulley 20.

[0054] Furthermore, the pulleys 10, 20, which are expressly not shown to scale, have a size ratio which corresponds to the ratio of two natural numbers that are relatively prime to each other.

[0055] The rotational position of the pulleys 10, 20 is detected by a sensor arrangement, each of which has at least one sensor. The rotational position of the first pulley is detected by a first sensor arrangement (not shown), and the rotational position of the second pulley is detected by a second sensor arrangement (not shown).

[0056] The first and second sensor arrangements are configured to determine a rotational position of the first pulley 10 and the second pulley 20. The first and second sensor arrangements determine by how many degrees the pulleys have each rotated relative to a predefined zero position.

[0057] The sensor arrays each transmit the detected rotational positions of the pulleys 10, 20 to an electronic data processing device (not shown). Based on the two rotational positions of the pulleys 10, 20, the data processing device determines a setting position of the belt drive on a travel path comprising several complete rotations of the first and second pulleys.

[0058] Since the size ratio of the pulleys 10, 20 corresponds to a ratio of two relatively prime natural numbers, a setting position of the belt drive, which comprises several complete rotations of the first pulley and the second pulley, is only repeated after a large number of complete revolutions of the two pulleys. Only after the number of complete revolutions of the smaller pulley about its rotational axis exceeds the value of the larger natural number of the size ratio of the pulleys, can a specific combination of the rotational position of the first pulley 10 with the rotational position of the second pulley 20 no longer be unambiguously assigned to a setting position of the belt drive on the adjustment path comprising several complete rotations of the first and second pulleys.

[0059] In the example shown, the maximum number of revolutions of the two pulleys 10, 20 is limited by external conditions in such a way that each combination of a rotational position of the first pulley 10 with a rotational position of the second pulley 20 can only be assigned to exactly one setting position of the belt drive 100.

[0060] Each combination of a specific rotational position of the first pulley 10 and a specific rotational position of the second pulley 20 can thus be uniquely assigned to a specific setting position of the belt drive 100 over the adjustment path comprising several complete rotations of the first and second pulleys. The belt drive 100 shown can be used, for example, for the steering of a motor vehicle. This can, for example, have an axis-parallel arrangement with one of the belt drives 100 described above. The belt drive 100 can transmit a rotational movement from a pulley arranged on an electric motor to a second pulley arranged on a ball screw drive, wherein the ball screw drive is configured to convert the rotational movement into a translational movement to effect or assist the steering.

[0061] If the belt drive 100 is used for the steering of a motor vehicle as outlined, each rotational position of the pulleys 10, 20 can be uniquely assigned to a position of the steering mechanism and thus to a toe angle of the motor vehicle wheels influenced by the steering. The position of the steering mechanism and / or the toe angle of the motor vehicle wheels influenced by the steering can thus be determined without additional sensors within the steering mechanism and without a rotation history of the pulleys.

[0062] Optionally, the control of the motor coupled to a pulley, in particular an electric motor, can be based on the detection of one of the sensor arrangements that detect the rotational positions of the pulleys. This eliminates the need for additional sensors for an electrically assisted or fully electric steering system. In particular, the motor can be coupled to the first pulley 10 and controlled based on the detection of the first sensor arrangement.

[0063] The variants of the device described above, as well as their design and operating aspects, serve only to better understand the structure, functionality, and properties; they do not limit the disclosure to the subject matter shown in the drawing. The drawing is highly schematic, with key properties and effects shown in some cases significantly enlarged to clarify the functions, operating principles, technical designs, and features.

[0064] The claims do not limit the disclosure and thus the possible combinations of all features described herein. All disclosed features are also explicitly disclosed individually and in combination with all other features.

Claims

Patent claims 1. A belt drive (100) comprising a first pulley (10) with a first diameter (D1); and a second pulley (20) with a second diameter (D2); and a belt (30) arranged on a cylindrical surface of the first and second pulleys, respectively, and configured to transmit a rotary motion from the first pulley (10) to the second pulley (20); a first sensor arrangement configured and configured to detect a rotational position of the first pulley (10); and a second sensor arrangement configured and configured to detect a rotational position of the second pulley (20);characterized in that the first diameter (D1) corresponds to a first integer multiple of a unit length, and the second diameter (D2) corresponds to a second integer multiple of the same unit length, wherein the first and the second integer multiples of the unit length are different from each other and coprime to each other.

2. Belt drive (100) according to claim 1, wherein the first diameter (D1) and / or the second diameter (D2) correspond to a product of the unit length and a prime number.

3. Belt drive (100) according to one of the preceding claims, wherein the first sensor arrangement comprises a contactless sensing position sensor, in particular a contactless and inductive sensing position sensor, and / or the second sensor arrangement comprises a contactless sensing position sensor, in particular a contactless and inductive sensing position sensor.

4. Belt drive (100) according to one of the preceding claims, wherein at least a part of the first sensor arrangement is integrated into the first pulley (10) and / or coupled to the first pulley (10), and / or at least a part of the second sensor arrangement is integrated into the second pulley (20) and / or coupled to the second pulley (20).

5. Belt drive (100) according to one of the preceding claims, further comprising a data processing device which is configured to uniquely determine a rotational position or positioning position of the belt drive (100) on a positioning path comprising several complete rotations of the first (10) and / or the second (20) pulley, based on the detection of the first sensor arrangement and the detection of the second sensor arrangement.

6. Belt drive (100) according to one of the preceding claims, wherein the first pulley (10) is coupled to a motor or electric motor, in particular to the rotor of a brushless electric motor, wherein a control or regulation of the motor or electric motor is based on the detection of the first sensor arrangement.

7. Belt drive (100) according to one of the preceding claims, further comprising a temperature sensor configured to detect a temperature of the belt drive, in particular a temperature of the environment of the belt (30), and / or a temperature estimator configured to estimate a temperature of the belt drive, in particular a temperature of the environment of the belt (30), based on a model of the belt drive.

8. Belt drive (100) according to any one of the preceding claims 5 to 7, wherein the data processing device is further configured to determine a compression or elongation of the belt (30) based on the detection of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator, and / or the data processing device is further configured to determine a force acting on the belt drive (100), in particular on the belt (30), based on the detection of the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.

9. Belt drive (100) according to any one of the preceding claims 5 to 8, wherein the data processing device is further configured to determine or estimate wear and / or damage to the belt drive (100), in particular to the belt (30), based on current and / or recorded readings from the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.

10. Belt drive (100) according to any one of the preceding claims 5 to 9, wherein The data processing device is further configured to determine and / or estimate subcooling and / or icing of the belt drive and / or a device coupled to the belt drive, in particular a ball screw drive, based on current and / or recorded readings from the first sensor arrangement and the second sensor arrangement and / or the temperature sensor and / or the temperature estimator.

11. An axis-parallel drive, with a belt drive according to one of claims 1 to 10.

12. A motor vehicle steering system for a motor vehicle, comprising a belt drive according to any one of claims 1 to 10, and / or an axle-parallel drive according to claim 11.

13. A motor vehicle steering system for a motor vehicle according to claim 12, wherein the data processing device is further configured to issue a warning message to the driver of a motor vehicle and / or to shut down the motor vehicle based on the detection of wear and / or damage and / or subcooling and / or icing of the belt drive (100), in particular the belt (30), and / or with a device coupled to the belt drive, in particular a ball screw drive.

14. A method for determining a rotational position of pulleys of a belt drive (100) comprises the steps: - Providing a first pulley (10) with a first diameter (Dl); - Providing a second pulley (20) with a second diameter (D2); - Providing a belt (30) which is arranged on a cylindrical surface of the first and second pulleys and is designed to transmit a rotary motion from the first pulley (10) to the second pulley (20); - Detecting a rotational position of the first pulley (10) with a first sensor arrangement; - Detecting a rotational position of the second pulley (20) with a second sensor arrangement; characterized in that the first diameter (D1) corresponds to a first integer multiple of a unit of length and the second diameter (D2) corresponds to a second integer multiple of the same unit of length, wherein the first and the second integer multiple of the unit of length are different from each other and coprime to each other.

15. Method according to claim 14, further comprising the steps: - Providing a data processing device; and - Unambiguous determination of a rotational position or positioning position of the belt drive (100) over a positioning path comprising several complete rotations of the first (10) and / or the second (20) pulley, based on the detection of the first sensor arrangement and the detection of the second sensor arrangement.

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