Encoder and method for determining rotational relative position between two components, and robot having such encoder

Abstract

The invention relates to an encoder and a method for determining a rotational position of a first component relative to a second component, the second component being rotatable relative to the first component, the encoder comprising: a first read head designed to be arranged on the second component; and a drive unit having a drive element which can be driven in rotation with respect to the first part, is fastened to at least the first disk and is designed to be arranged on the first part, the first disk having at least one circumferential first track on an end face facing the first read head, and the drive element having at least one circumferential second track on an end face facing the second read head. The first magnetic disk has a first track having a plurality of magnetic regions, which are formed one after the other in the circumferential direction of the first magnetic disk and which have alternating magnetization directions, the first read head is designed to detect at least a first periodic pulse sequence by measuring the magnetization direction along the first track when at least the first disk is rotated relative to the first component, the respective detected periodic pulse sequence being comparable to a reference pulse sequence of the same periodicity. To determine at least a first phase difference between the respective detected periodic pulse sequence and the reference pulse sequence and to determine a rotational position of the first component relative to the second component based on the at least first phase difference. The invention also relates to a robot.

Description

Technical Field

[0001] The invention relates to an encoder for determining the rotational position of a first component relative to a second component. In addition, the invention relates to a method for determining the rotational position of a first component relative to a second component using such an encoder. The invention also relates to a robot having such an encoder. Background Art

[0002] Encoders, especially angle encoders, are an important component of many mechatronic products. The term "encoder" is understood as a rotation sensor. One of the main applications is robotics, where the motion state of the robot or robot arm must be known at all times in order to effectively control the robot. In particular, encoders operatively arranged at the output of an actuator can significantly improve the accuracy of the robot, since the encoder measures the real angle that is not affected by the elasticity or other effects of the actuator. However, in order to be able to measure even very small angular changes, the slowly rotating output of the transmission requires very high-resolution encoders. In robotics and other applications, high accuracy and high resolution of angle measuring devices are advantageous, since accurate knowledge of the motion state directly determines the accuracy and repeatability of tool point movements, which are important performance characteristics of the robot arm. The physical resolution of the angle encoder is limited by the size of the structures that can be created on the sensor and the resolution for effectively detecting these structures, which is limited by, for example, the wavelength of light.

[0003] For example, DE 10 2016 202 792 A1 discloses a robot joint, which includes: a robot component; a drive gear rotatably mounted on the robot component and an output gear rotatably mounted on the robot component; a transmission device that connects the drive gear to the output gear to transmit a driving torque; and a motor that drives the drive gear and has a motor shaft, which is connected to the drive gear via a drive connection to introduce a driving torque. A safety clutch is provided and designed to disconnect the drive connection between the motor shaft and the output gear when a predetermined limit torque is exceeded, and to restore the drive connection between the motor shaft and the output gear when it drops below a predetermined limit torque. In addition, a sensor device is provided and designed to detect the rotational angle position of the output gear. In order to be able to determine the exact position and rotational direction of the joint itself even when the robot is externally moved in a passive manner or when the transmission system slips, an output side position measurement that can be performed simply or redundantly is used. In order to perform a simple position measurement, an encoding disc can be connected to the output pulley. In the case of double measurement, another encoding disc must also be arranged on the intermediate pulley set. During rotation, the line on the encoding disc can be detected by a sensor. Summary of the invention

[0004] The object of the present invention is to specify an encoder with an increased resolution. According to a first aspect of the invention, this object is achieved by an encoder having the features of claim 1. Furthermore, according to a second aspect of the invention, this object is achieved by a method for determining a rotational position of a first component relative to a second component having the features of claim 7. Furthermore, according to a third aspect of the invention, this object is achieved by a robot having the features of claim 10. Preferred or advantageous embodiments of the invention are apparent from the dependent claims, the following description and the drawings.

[0005] According to a first aspect of the present invention, an encoder for determining a rotational position of a first component relative to a second component according to the present invention, the second component being rotatable relative to the first component, the encoder comprising: at least one first read head, which is designed to be arranged on the second component; and a drive unit, which has a drive element, which is drivable in a rotational manner relative to the first component and is fastened to at least one first disk and is designed to be arranged on the first component, wherein at least the first disk has at least one circumferential first track on an end surface facing the first read head, the first track having a plurality of magnetic regions, the plurality of magnetic regions being formed one after another in a circumferential direction of the first disk and the plurality of magnetic regions having alternating magnetization directions, and the first read head is designed to detect at least a first periodic pulse sequence by measuring the magnetization direction along the first track during rotation of at least the first disk relative to the first component, and the corresponding detected periodic pulse sequence can be compared with a reference pulse sequence having the same periodicity to determine at least a first phase difference between the corresponding detected periodic pulse sequence and the reference pulse sequence and determine the rotational position of the first component relative to the second component based on the at least first phase difference.

[0006] In this context, encoders or rotation sensors are understood to be rotation angle sensors, angle encoders or even angle position sensors. Typical applications of rotation sensors in vehicles include steering angle sensors and wear-free rotary switches. Further applications in robotics include angle sensors for determining the position and direction of rotation of robot arm segments of a robot arm that are coupled to one another via joints.

[0007] The first component and the second component are connected to each other in an articulated manner, and in particular, the second component can rotate relative to the first component. A drive is provided, which generates the drive power and transmits the drive power to the second component, for example via a pre-transmission device, to set a rotational relative position between the components. For this purpose, the drive is supported on the first component so that the second component can rotate relative to the first component. Preferably, the first component and the second component are each designed as an axis. The two components are preferably arranged concentrically.

[0008] The drive unit is preferably a spindle drive, wherein the drive element is preferably a spindle arranged on the first component and arranged to be relatively rotatable. Preferably, the first component is arranged coaxially with respect to the spindle. At least the first magnetic disk is fastened to the spindle. The spindle can be driven together with at least the first magnetic disk in a manner that rotates relative to the first component at a constant rotation speed. A rotation speed of 4000 to 15,000 revolutions per minute can be achieved. At the end face, the first magnetic disk has a first track, which has a plurality of magnetic areas or magnetized areas, which are arranged one after another in the circumferential direction of the disk, each magnetic area being magnetized or formatted to have a specific magnetization direction.

[0009] The respective disk is a magnetically rotatable device having at least one track on its end face facing the respective read head. The respective track is preferably circular, i.e. completely circumferential on the end face of the respective disk. The first track of the first disk is preferably arranged in the region of at least the outer diameter of the first disk. The further outwardly the track is arranged on the respective disk in the radial direction, the larger the diameter of the respective track and the greater the number of magnetic regions, and accordingly the greater the amount of data that can be stored or encoded on the track. It is conceivable to store more than 20 million bits of data on such a track, which corresponds to a physical resolution of more than 24 bits. Each of the more than 20 million bits is assigned to one of the magnetic regions. In other words, each magnetic region forms a bit by its magnetization direction. The greater the number of bits or magnetic regions, the more precisely the angle that can be measured when the second component rotates relative to the first component. At least the first read head is designed to read a bit pattern of more than 24 bits from the track on the disk at a respective disk rotation speed of at least 4000 revolutions per minute. Thus, the first read head interacts with the magnetic regions forming the track on the first disk.

[0010] Each bit is encoded by magnetizing a magnetic region in a specific magnetization direction along the corresponding track on the corresponding disk. A change in magnetization direction usually means "1", and the same magnetization direction of two consecutive magnetic regions is decoded as "0". At least the first track is preferably completely preformatted with "1". In other words, two magnetic regions that are adjacent in the track direction never have the same magnetization direction. Therefore, the magnetization direction changes in each consecutive magnetic region. This achieves the highest possible angular resolution of the rotation sensor. In this sense, the magnetic regions of the corresponding track have alternating magnetization directions in the circumferential direction of the disk.

[0011] Typically, the tracks are encoded in the longitudinal direction. Longitudinal direction means that the magnetization directions of the magnetic regions are each oriented in the tangential direction of the respective disk. Alternatively, the magnetic regions can be encoded in perpendicular recording, which increases the data density or the number of bits in the circumferential direction. In perpendicular recording, the magnetization directions of the magnetic regions are each oriented axially with respect to the axis of rotation of the respective disk.

[0012] The respective track preferably contains special guiding structures so that the respective read head can reliably follow the track without getting lost.The respective read head floats above the respective magnetic disk on a cushion of air or helium created by the rotating magnetic disk.

[0013] The corresponding tracks on the disk are understood to be data tracks. It is conceivable that a plurality of data tracks are formed on the end face of the corresponding disk facing the read head. For example, a track with a lower resolution can be formed radially inside the first track. Each track can be assigned a read head, wherein the tracks are read simultaneously during a rotation of the corresponding disk. This enables the absolute adjustment angle between the first component and the second component to be determined. Thus, an absolute angle encoder can be realized in this way.

[0014] The first disk is connected to the first component via a drive element, preferably via a spindle of a spindle drive. The first component may be a first robot arm segment, which may be connected to the second robot arm segment in an articulated manner. The drive element drives the respective disk at a constant speed, and the speed generates an air cushion or a helium cushion between the respective disk and the read head. When the respective disk rotates, the respective read head floats on the air cushion or the helium cushion. At least the first read head is fastened to the second component. After the respective disk reaches its operating speed, the respective read head starts to follow the track on the end face of the rotatable device. The second component may be a housing or a second robot arm segment.

[0015] The respective read head is preferably pivotably arranged on the second component. The respective read head can be pivoted between at least one rest position and at least one operating position. The pivoting arrangement is advantageous because the respective read head can be pivoted into the respective operating position only when the respective disk has reached its operating speed. In addition, the respective read head can better follow the respective track, which does not have to be designed to be exactly circular or concentric.

[0016] The respective read head receives the voltage signal by reading the respective data track while sliding or floating along at least the first track on the rotating disk and measuring the respective magnetic field of the magnetic region. The second component is not adjusted relative to the first component. The signal is understood to be a periodic pulse train.

[0017] Subsequently, a reference signal or reference pulse sequence is generated and compared with the periodic pulse sequence. The reference pulse sequence may be a synthetic reference signal, which may be generated by a processor unit, also referred to as a CPU, or by a signal generator. The reference signal is similar to the periodic pulse sequence measured by the corresponding read head in a static state. In particular, the reference pulse sequence has exactly the same frequency, i.e. the same periodicity.

[0018] In an exemplary embodiment, the reference pulse sequence may be provided by or by the processor unit. The processor unit may include a synthetic signal generator, or receive the reference signal from a separate synthetic signal generator. Thus, the reference pulse sequence is a synthetic reference pulse sequence. Therefore, the synthetic reference pulse sequence is not measured, but generated and provided in a computer-aided manner, and the encoding of the corresponding track is known and used to generate the reference pulse sequence.

[0019] Alternatively, the reference pulse sequence may be provided by or by a signal generator comprising: a second magnetic disk which is also fastened to a drive element of a drive unit; and a second read head which is designed to be arranged on the first component, the second magnetic disk having at least one circumferential second track on an end surface facing the second read head, the second track having a plurality of magnetic regions which are formed one after another in the circumferential direction of the second magnetic disk and have alternating magnetization directions, the second track on the second magnetic disk being designed to be identical to the first track on the first magnetic disk. Therefore, the reference signal is not a composite signal but is generated by the second magnetic disk which is mounted on the same drive element as the first magnetic disk and has the same division, i.e., magnetic regions, and format, i.e., changes in magnetization directions, as the first magnetic disk. The reference signal is a voltage measured by the second read head on the first component which rotates at exactly the same speed as the first magnetic disk.

[0020] The periodic pulse train detected by at least a first respective read head is compared with a reference pulse train having the same periodicity to determine at least a first phase difference between the respective detected periodic pulse train and the reference pulse train. This can be done by a Fourier transform or a cross correlation of the signals. Based on at least the first phase difference, the rotational position of the first component relative to the second component can be determined. If the first component is fixed relative to the second component, the phase difference remains constant. In this sense, if the second component is fixed relative to the first component, the first phase difference can be determined.

[0021] When the first component rotates relative to the second component or the second component rotates relative to the first component, the phase difference changes. Depending on the resolution with which this phase difference can be resolved, this increases the overall resolution of the encoder proposed here. For example, if the phase difference can be resolved in 64 steps, an overall resolution of 30 bits or 90 nanoseconds can be obtained. This significantly exceeds the resolution of currently known encoders. In this sense, additional phase differences can be determined or additional phase differences can be determined when the second component rotates relative to the first component. In other words, changes in the phase difference are tracked.

[0022] The total angular difference between the components that can rotate relative to each other can be calculated by counting the zero crossings of the corresponding phase difference (taking into account the direction / sign) and multiplying it by the magnitude of the magnetic angle range. Finally, the actual phase difference can also be multiplied by the magnitude of the magnetic angle range and added.

[0023] According to a second aspect of the present invention, a method for determining a rotational position of a first component relative to a second component is provided, which method can be performed with the aid of an encoder according to the first aspect of the present invention, wherein during rotation of at least a first disk relative to the first component, at least a first periodic pulse sequence is detected by measuring a magnetization direction along a first track with the aid of a first reading head, and the corresponding detected periodic pulse sequence is compared with a reference pulse sequence having the same periodicity to determine at least a first phase difference between the corresponding detected periodic pulse sequence and the reference pulse sequence and the rotational position of the first component relative to the second component is determined based on the at least first phase difference.

[0024] According to a third aspect of the invention, a robot comprises a first robot arm segment and a second robot arm segment operatively connected to the first robot arm segment via a joint, wherein an encoder according to the first aspect of the invention is operatively arranged in the joint. The joint is a robot joint connecting at least two segments of the robot arm. In addition to the encoder, at least one actuator and / or sensor system is arranged in the robot joint to move the robot arm or to detect the current position of the robot arm in space and / or the load on the robot arm.

[0025] The above definitions and descriptions of the technical effects, advantages and advantageous embodiments of the corresponding encoder according to the first aspect of the present invention also apply, with necessary modifications, to the method according to the second aspect of the present invention and the robot according to the third aspect of the present invention, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further measures for improving the invention are described below using the figures together with the description of two exemplary embodiments of the invention, wherein identical or similar elements are marked with the same reference numerals. In the drawings:

[0027] Figure 1 shows a highly schematic diagram of a robot arm of a robot according to the present invention;

[0028] Figure 2 shows a schematic longitudinal sectional view for illustrating the structure of an encoder according to the present invention according to a first embodiment;

[0029] Figure 3 Shown according to Figure 2 A highly schematic diagram of a first disk of an encoder according to the invention.

[0030] Figure 4 A method for illustrating a first track having a plurality of magnetic regions and a periodic pulse sequence measured by a first read head based on the magnetization directions of the magnetic regions is shown. Figure 3 a highly schematic representation of a first disk;

[0031] Figure 5 The measured basis for illustrating the phase difference determination is shown. Figure 4 A schematic representation of a periodic pulse sequence and a reference pulse sequence; and

[0032] Figure 6 A schematic longitudinal sectional view for illustrating the structure of an encoder according to the present invention is shown according to a second embodiment. DETAILED DESCRIPTION

[0033] Figure 1 In a highly schematic and simplified manner, only partially shown here, a robot arm of a robot 16 is shown. In the present example, the robot arm has a first robot arm segment 24 and a second robot arm segment 25 which are connected to each other in an articulated manner via a joint 26. For example, a transmission system is arranged and supported on the first robot arm segment 24, which comprises a drive (not shown here), the driving power of which can be transmitted to the second robot arm segment 25 via a transmission stage (also not shown here). The transmission system is understood to be an actuator of the robot arm. The first component 2 described below can be an output element operatively connected to the second component 3, for example an output shaft of a transmission stage, while the second component 3 can be directly fastened to the second robot arm segment 25 or can be the second robot arm segment 25 itself.

[0034] In the joint 26 between the two robot arm segments 24, 25, a Figure 2The encoder 1 is designed to determine the rotational position of a first component 2 relative to a second component 3, which can rotate relative to the first component. The encoder 1 in this example comprises: a first reading head 4; and a drive unit 5 designed as a spindle drive, which has a drive element 6 that can be driven in a rotational manner relative to the first component 2. The drive element 6 of the drive unit 5 is here a spindle, which is arranged on the first component 2 and can rotate relative to the first component at a constant rotational speed of at least 4000 revolutions per minute. The first magnetic disk 7 is fastened to the spindle and can rotate correspondingly at the same rotational speed. The first reading head 4 is arranged on the second component 3 so as to be pivotable from a parking position into an operating position and from an operating position into a parking position.

[0035] The first magnetic disk 7 has at least one circumferential first track 9 on the end surface 8 facing the first reading head 4, and the first track has a plurality of magnetic regions 10 uniformly formed one after another in the circumferential direction of the first magnetic disk 7. Figure 3 Here it can be clearly seen that the tracks 9 are formed in the region of the outer diameter 17 of the first magnetic disk 7 in order to achieve the highest possible number of magnetic regions 10 .

[0036] The magnetic area 10 is preformatted, such as Figure 4 As shown. The magnetic regions have alternating magnetization directions 11, 12 in the longitudinal direction of the track 9 and in the circumferential direction of the first disk 7. In other words, the magnetization directions 11, 12 change in each consecutive magnetic region 10. Each magnetic region 10 corresponds to a bit. The bits are encoded by magnetizing the magnetic regions 10 along the track 9 on the first disk. This Figure 4 The portion of track 9 in FIG. 1 is illustrated by arrows pointing left and right.

[0037] After the spindle with the first disk 7 reaches the desired operating speed, the first read head 4 can be pivoted from the parked position into an operating position, wherein the first read head 4 can follow the first track 9 to measure the magnetic field of the magnetic region 10 to form a first periodic pulse sequence 13 from the magnetic field. In this context, Figure 4Below the track 9 is shown a first periodic pulse sequence 13 which is detected by a first read head 4 which detects the magnetic field of the magnetic regions 10 and in particular the changes in the magnetization directions 11, 12. Here, the magnetic regions 10 are encoded in the longitudinal direction of the track 9. A change in the magnetization direction 11 or 12 generally means a "1", and the same magnetization direction of two consecutive magnetic regions 10 is then decoded as a "0". Since the track 9 is preformatted so that the magnetization direction 11, 12 changes in each consecutive magnetic region 10, the value "1" is output for each subsequent magnetic region or each subsequent bit. Therefore, the first read head 4 is designed to detect the first periodic pulse sequence 13 by measuring the magnetization directions 11, 12 along the first track 9 when at least the first disk 7 rotates relative to the first component 2. This occurs statically, i.e. when the first component 2 and the second component 3 are not rotating relative to each other or when the components 2, 3 are stationary.

[0038] In addition to the first periodic pulse sequence 13, a synthetic reference pulse sequence 14 is generated in this case and compared with the periodic pulse sequence 13. The reference pulse sequence is thus a synthetic reference signal generated by a processor unit (not shown here) or a signal generator (also not shown here). This reference signal is similar to the first periodic pulse sequence 13 measured by the first reading head 4 in a static state. In particular, the reference pulse sequence 14 has exactly the same frequency as the first periodic pulse sequence 13, i.e. the same periodicity.

[0039] By comparing the detected first periodic pulse sequence 13 with the reference pulse sequence 14, a phase difference 15 between the detected periodic pulse sequence 13 and the reference pulse sequence 14 is determined. Figure 5 1 is shown by way of example. When the frequency of the periodic pulse sequence 13 and the frequency of the reference pulse sequence 14 are identical, a phase difference 15 between the pulse sequences can be calculated, based on which conclusions can be drawn about the rotational position of the first component 2 relative to the second component 3. The phase difference 15 here is the distance between the amplitude 27 of the periodic pulse sequence 13 and the corresponding amplitude 28 of the reference pulse sequence. The phase difference 15 is shown as a double arrow with a base and two tips.

[0040] When the second component 3 is adjusted, in particular rotated, relative to the first component 2, the phase difference 15 changes. The phase difference 15 thus becomes larger or smaller. Thus, a first phase difference 15 is determined when the second component 3 is fixed relative to the first component 2, and a further phase difference is determined when the second component 3 is rotated relative to the first component 2.

[0041] The total angle difference is calculated by counting the zero crossings of the phase difference 15 (taking into account the direction / sign) and multiplying by the magnitude of the magnetic angle range. The actual phase difference 15 is multiplied by the magnitude of the magnetic angle range and added.

[0042] In accordance with Figure 6 In an alternative embodiment, a real reference pulse sequence can be determined instead of a synthetic reference pulse sequence. For this purpose, a signal generator 19 is provided, which comprises a second disk 20 and a second reading head 21, which second disk is also fastened to the drive element 6 of the drive unit 5. The second disk 20 is fastened to the spindle or the drive element 6 together with the first disk 7 so that they always rotate at the same rotational speed. In the present example, the disks 7, 20 are arranged axially spaced apart from each other. However, the disks can also abut against each other.

[0043] The second magnetic disk 20 has at least one circumferential second track 9 on the end surface 22 facing the second reading head 21, the second track having a plurality of magnetic regions 10 formed one after another in the circumferential direction of the second magnetic disk 20 and having alternating magnetization directions 11, 12. The second track 9 on the second magnetic disk 20 is designed to be identical to the first track 9 on the first magnetic disk 7 to enable a reference signal to be compared with a signal measured by the first reading head 4. In other cases, the encoder 1 is used in accordance with Figures 2 to 5 The foregoing contents regarding the first magnetic disk 7 are similarly applicable to the second magnetic disk 20. The foregoing contents regarding the first pickup head 4 are similarly applicable to the second pickup head 21. Furthermore, the foregoing contents regarding the first track 9 are similarly applicable to the second track 9. Therefore, Figures 3 to 5 Similarly applies to Figure 6 A second exemplary embodiment of the present invention.

[0044] By operatively arranging the encoder 1 at the output of the transmission stage, the accuracy of the robot 16 can be significantly improved, since the true angle between the two components 2 , 3 can be measured which is not affected by elasticity or other effects of the transmission train.

[0045] Reference numerals list

[0046] 1 Encoder

[0047] 2 First part

[0048] 3 Second component

[0049] 4 First reading head

[0050] 5 Drivers

[0051] 6. Driving components

[0052] 7 First Disk

[0053] 8 End surface of the first disk

[0054] 9 First Track

[0055] 10 Magnetic Area

[0056] 11 First magnetization direction

[0057] 12 Second magnetization direction

[0058] 13 The first periodic pulse sequence

[0059] 14 Reference pulse sequence

[0060] 15 First phase difference

[0061] 16 Robot

[0062] 17 Outer diameter of the first disk

[0063] 18 Processor Units

[0064] 19 Signal Generator

[0065] 20 Second Disk

[0066] 21 Second reading head

[0067] 22 End surface of the second disk

[0068] 9 Second Track

[0069] 24 First robot arm section

[0070] 25 Second robot arm segment

[0071] 26 Joint

[0072] 27 Amplitude of periodic pulse train

[0073] 28 Amplitude of the reference pulse train

Claims

1. An encoder (1) for determining the rotational position of a first component (2) relative to a second component (3), the second component being rotatable relative to the first component, the encoder comprising: at least one first reading head (4) designed to be arranged on the second component (3); and a drive unit (5) comprising a drive element (6) which can be driven in a rotational manner relative to the first component (2) and is fastened to at least one first magnetic disk (7) and is designed to be arranged on the first component (2), wherein the at least first magnetic disk (7) has at least one circumferential first track (9) on an end surface (8) facing the first reading head (4), the first track having a plurality of magnetic regions (10), the plurality of magnetic regions being formed one after another in the circumferential direction of the first magnetic disk (7) and the plurality of magnetic regions having alternating magnetization directions (11, 12), and the first reading head (4) is designed to detect at least a first periodic pulse sequence (13) by measuring the magnetization direction (11, 12) along the first track (9) during the rotation of the at least first disk (7) relative to the first component (2), and the corresponding detected periodic pulse sequence (13) can be compared with a reference pulse sequence (14) with the same periodicity to determine at least a first phase difference (15) between the corresponding detected periodic pulse sequence (13) and the reference pulse sequence (14) and to determine the rotational position of the first component (2) relative to the second component (3) based on the at least first phase difference (15).

2. The encoder (1) according to claim 1, It is characterized in that The first phase difference (15) can be determined when the second component (3) is fixed relative to the first component (2).

3. The encoder (1) according to claim 1 or claim 1, It is characterized in that When the second component (3) is rotated relative to the first component (2), a further phase difference can be determined.

4. Encoder (1) according to any one of the preceding claims, It is characterized in that The at least first magnetic disk (7) is designed to be circular, and the first track (9) is arranged in the region of an outer diameter (17) of the first magnetic disk (7).

5. Encoder (1) according to any one of the preceding claims, It is characterized in that The reference pulse sequence (14) can be provided by a processor unit (18).

6. The encoder (1) according to any one of claims 1 to 4, It is characterized in that The reference pulse sequence (14) can be provided by a signal generator (19), the signal generator comprising: a second magnetic disk (20), which is also fastened to the drive element (6) of the drive unit (5); and a second reading head (21), which is designed to be arranged on the first component (2), the second magnetic disk (20) comprising at least one circumferential second track (9) on an end face (22) facing the second reading head (21), the second track having a plurality of magnetic regions (10), the plurality of magnetic regions being formed one after another in the circumferential direction of the second magnetic disk (20) and the plurality of magnetic regions having alternating magnetization directions (11, 12), The second track (9) on the second magnetic disk (20) is designed to be identical to the first track (9) on the first magnetic disk (7).

7. A method for determining the rotational position of a first component (2) relative to a second component (3) by means of an encoder (1), the encoder comprising: at least one first reading head (4) designed to be arranged on the second component (3); and a drive unit (5) comprising a drive element (6) which can be driven in a rotational manner relative to the first component (2) and is fastened to at least one first magnetic disk (7) and is designed to be arranged on the first component (2), wherein the at least first magnetic disk (7) has at least one circumferential first track (9) on an end surface (8) facing the first reading head (4), the first track having a plurality of magnetic regions (10), the plurality of magnetic regions being formed one after another in the circumferential direction of the first magnetic disk (7) and the plurality of magnetic regions having alternating magnetization directions (11, 12), and the first reading head (4) having at least one circumferential first track (9). The fetch head (4) is used to detect at least a first periodic pulse sequence (13) by measuring the magnetization direction (11, 12) along the first track (9) during the rotation of the at least first magnetic disk (7) relative to the first component (2), and the corresponding detected periodic pulse sequence (13) is compared with a reference pulse sequence (14) having the same periodicity to determine at least a first phase difference (15) between the corresponding detected periodic pulse sequence (13) and the reference pulse sequence (14) and determine the rotational position of the first component (2) relative to the second component (3) based on the at least first phase difference (15).

8. The method according to claim 7, It is characterized in that The reference pulse sequence (14) is provided by a processor unit (18).

9. The method according to claim 7, It is characterized in that The reference pulse sequence (14) is provided by a signal generator (19), which comprises: a second magnetic disk (20), which is also fastened to the drive element (6) of the drive unit (5); and a second reading head (21), which is designed to be arranged on the first component (2), wherein the second magnetic disk (20) has at least one circumferential second track (9) on an end surface (22) facing the second reading head (21), the second track having a plurality of magnetic regions (10), the plurality of magnetic regions being formed one after another in the circumferential direction of the second magnetic disk (20) and the plurality of magnetic regions having alternating magnetization directions (11, 12), and the second track (9) on the second magnetic disk (20) is designed to be identical to the first track (9) on the first magnetic disk (7).

10. A robot (16) comprising a first robot arm segment (24) and a second robot arm segment (25) operatively connected to the first robot arm segment via a joint (26), wherein: An encoder (1) according to any one of the preceding claims is operatively arranged in the joint (26).

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