Method for initializing a rotation angle measurement system using a Wiegand sensor and rotation angle measurement system

Abstract

A method for initializing a rotation angle measurement system (10) and a rotation angle measurement system (10) having a correspondingly configured initialization unit (36) are provided. In the present invention, after the rotation angle measurement system (10) using the Wiegand sensor is installed at a place of use, an initialization AC current (IS) is supplied to a sensor coil (26) that radially surrounds the Wiegand wire (24) for initialization, and the initialization AC current (IS) provides a current direction that switches over time and a current amplitude (ISA) that decreases over time. This ideally completely eliminates or at least greatly reduces the possibility of magnetizing the Wiegand wire (24). This provides a highly reliable rotation angle measurement system (10) using the Wiegand sensor.

Description

[Technical field]

[0001] The present invention relates to a method for initializing a rotation angle measurement system using a Wiegand sensor and a rotation angle measurement system using a Wiegand sensor for detecting the rotational movement of a shaft, the rotation angle measurement system comprising a permanent magnet excitation unit mountable for rotation with the shaft to be detected, and a stationary Wiegand sensor, the stationary Wiegand sensor having a Wiegand wire and a sensor coil radially surrounding the Wiegand wire. [Background technology]

[0002] Rotation angle measuring systems using Wiegand sensors are well known in the prior art and are used in particular for controlling and monitoring electric motors, in particular servomotors, in machines, plants or vehicles. Rotation angle measuring systems are often also called angle measuring devices, rotation angle sensors or rotary encoders.

[0003] The permanent magnet excitation unit is mounted to rotate with the shaft and is configured such that, as the excitation unit rotates, an alternating excitation magnetic field is generated at the location of the Wiegand sensor. The Wiegand wire of the Wiegand sensor is magnetically bistable, and the magnetization direction of the Wiegand wire suddenly reverses under the influence of an excitation magnetic field that is sufficiently strong and opposite to the magnetization direction of the Wiegand wire. This sudden reversal of the magnetization of the Wiegand wire generates a short voltage pulse in a sensor coil that radially surrounds the Wiegand wire. While the excitation unit rotates, the alternating excitation magnetic field generated thereby results in a succession of voltage pulses in the sensor coil of the Wiegand sensor. The frequency of the voltage pulses is directly proportional to the rotation speed of the excitation unit and, therefore, to the rotation speed of the shaft.

[0004] If the Wiegand sensor is exposed to a strong magnetic field, for example during transportation or installation, the Wiegand wire becomes strongly magnetized, and the excitation magnetic field generated by the excitation unit during operation of the rotation angle measuring system may not be sufficient to completely reverse the magnetization of the Wiegand wire. As a result, only a relatively weak voltage pulse is generated in the sensor coil, which cannot be reliably detected by the evaluation unit of the rotation angle measuring system. Furthermore, due to the relatively weak voltage pulse, the energy supply is insufficient, which may lead to malfunctions in the rotation angle measuring system with energetically autonomous Wiegand sensors, in which the electrical energy of the voltage pulse is used to energize the entire rotation angle measuring system. Summary of the Invention [Problem to be solved by the invention]

[0005] Given this background, the challenge is to create a rotation angle measurement system using a highly reliable Wiegand sensor. [Means for solving the problem]

[0006] This problem is solved by a method for initializing a rotation angle measuring system using a Wiegand sensor having the features of claim 1 and by a rotation angle measuring system using a Wiegand sensor having the features of claim 7.

[0007] In the method for initializing the Wiegand sensor-based rotation angle measurement system according to the present invention, the rotation angle measurement system is first mounted at the location of use. In particular, a permanent magnet excitation unit is mounted on the shaft to be detected and rotates with said shaft, and a Wiegand sensor with a Wiegand wire and a sensor coil radially surrounding the Wiegand wire is arranged such that an alternating excitation magnetic field is generated by the excitation unit at the location of the Wiegand sensor during rotation of the excitation unit. The excitation unit is typically mounted directly on the axial end of the shaft during the mounting process. The Wiegand sensor is typically located in a housing and is positioned at the axial end of the shaft that holds the excitation unit during mounting.

[0008] In the present invention, after the rotation angle measurement system is installed at the place of use, an initialization AC current is supplied to the sensor coil radially surrounding the Wiegand wire by an initialization unit of the rotation angle measurement system. The initialization AC current provides a current direction that switches with time and a current amplitude that decreases with time. This generates an initialization magnetic field inside the coil at the position of the Wiegand wire that is parallel to the axial direction of the Wiegand wire, whose direction switches with time and whose amplitude / intensity decreases with time.

[0009] Because Wiegand wires are ferromagnetic, the so-called "elementary magnets" inside the Wiegand wire tend to align with the externally applied magnetic field. Switching the initialization magnetic field results in these elementary magnets being successively "flipped," with the percentage of elementary magnets that flip with each reversal of the initialization magnetic field decreasing as the intensity of the initialization magnetic field decreases. This produces a relatively disordered arrangement of elementary magnets inside the Wiegand wire, so that from a macroscopic perspective, the Wiegand wire has essentially no magnetic polarization, i.e., it is not magnetized.

[0010] Therefore, the method for initializing a rotation angle measurement system using a Wiegand sensor according to the present invention ideally completely eliminates or at least significantly reduces magnetization of the Wiegand wire that may occur due to transportation or installation of the rotation angle measurement system. This allows reliable detection of shaft rotation, since the magnetization of the Wiegand wire during operation can be reliably reversed by the excitation magnetic field generated by the permanent magnet excitation unit. Therefore, the initialization method according to the present invention provides a rotation angle measurement system using a Wiegand sensor with high reliability.

[0011] Preferably, the direction of the initializing alternating current fed to the sensor coil, and therefore the direction of the initializing magnetic field generated thereby, is changed at least 5 times, preferably at least 10 times, more preferably at least 20 times, which allows a reliable reduction in the magnetization of the Wiegand wire.

[0012] In a preferred embodiment of the present invention, the starting current amplitude of the initialization AC current at the start of supplying the initialization AC current to the sensor coil is at least two times, preferably at least three times, the ending current amplitude of the initialization AC current at the end of supplying the initialization AC current to the sensor coil, ensuring a reduction in magnetization of the Wiegand wire.

[0013] Advantageously, before feeding the initialization alternating current, the permanent magnetic excitation unit of the rotation angle measurement system is arranged so that the excitation magnetic field generated by the excitation unit at the position of the Wiegand wire crosses the axial direction of the Wiegand wire, i.e. the magnetic field lines of the excitation magnetic field essentially cross the axial direction of the Wiegand wire. Preferably, the excitation unit is arranged so that the angle between the axial direction of the Wiegand wire and the excitation magnetic field is between 70 degrees and 110 degrees, more preferably between 80 degrees and 100 degrees. As a result, the excitation magnetic field has no excitation magnetic field component parallel to the axial direction of the Wiegand wire or only a relatively small excitation magnetic field component. The excitation magnetic field does not have a significant effect on the reversal of the magnetization of the Wiegand wire. This allows a reliable reversal of the magnetization of the Wiegand wire, thereby allowing a reliable reduction of the magnetization of the Wiegand wire.

[0014] In an alternative advantageous embodiment of the invention, the excitation unit is rotated at a constant rotation frequency while an initialization alternating current is fed, the initialization alternating current being pulsed such that an initialization alternating current pulse is fed to the sensor coil when the excitation magnetic field generated by the excitation unit at the position of the Wiegand wire crosses the axial direction of the Wiegand wire. Preferably, the initialization alternating current pulse is fed to the sensor coil when the angle between the axial direction of the Wiegand wire and the excitation magnetic field is in each case between 70 degrees and 110 degrees, more preferably between 80 degrees and 100 degrees. The excitation magnetic field can be detected using the Wiegand sensor or an additional magnetic field sensor. As mentioned above, the energization of the sensor coil allows a reliable reversal of the magnetization of the Wiegand wire when the excitation magnetic field crosses the axial direction of the Wiegand wire, which allows a reliable reduction of the magnetization of the Wiegand wire. A precise positioning of the excitation unit is not required for the uniform rotation of the excitation unit and for the control of the pulsing of the initialization alternating current.

[0015] In another advantageous embodiment of the invention, the permanent magnet excitation unit is moved so that the parallel component of the excitation magnetic field (which is parallel to the axial direction of the Wiegand wire) generated by the excitation unit at the position of the Wiegand wire while the initialization AC current is applied to the sensor coil and the parallel component of the initialization magnetic field (which is parallel to the axial direction of the Wiegand wire) generated at the position of the Wiegand wire by feeding the initialization AC current to the sensor coil always point in the same direction, i.e. always to a point in the same direction. In this context, the terms "always" and "at all times" should be interpreted such that the parallel components of the excitation magnetic field and the parallel components of the initialization magnetic field point in the same direction during the main time segments of the feeding process, so that the excitation magnetic field "supports" the initialization magnetic field in the reversal of the magnetization of the Wiegand wire. This allows a reliable reduction of the magnetization of the Wiegand wire without requiring a precise positioning of the excitation unit and with relatively low current amplitudes and therefore with relatively low electrical energy.

[0016] The excitation unit is rotated at a constant rotation frequency during the period when the initialization AC current is fed, and the rotation frequency of the excitation unit is preferably directly proportional to the switching frequency of the initialization AC current, where the proportionality factor is equal to the inverse of the number of magnetic poles of the excitation unit, so that the switching frequency of the excitation magnetic field generated at the position of the Wiegand sensor is equal to the switching frequency of the initialization magnetic field generated by feeding the initialization AC current to the sensor coil. This realizes a relatively easy way to move the excitation unit so that the parallel components of the excitation magnetic field and the parallel components of the initialization magnetic field always point in the same direction during the entire period when the initialization AC current is fed, since it is essential that the excitation unit is aligned once in the rotation direction before the start of feeding the initialization AC current.

[0017] In another preferred embodiment of the invention, the excitation unit is rotated alternately clockwise and counterclockwise while supplying the initialization AC current, such that the switching frequency of the rotation direction of the excitation unit is directly proportional to the switching frequency of the initialization AC current, thereby allowing the excitation unit to be moved while supplying the initialization AC current, such that the parallel components of the excitation magnetic field and the parallel components of the initialization magnetic field always point in the same direction, without requiring any significant absolute rotation of the excitation unit and thus of the shaft on which it is mounted.

[0018] More preferably, the excitation unit is rotated such that the rotation angle, which the excitation unit rotates clockwise or counterclockwise, respectively, decreases over time, so that the absolute value of the parallel component of the excitation magnetic field at the extreme value of the initialization alternating current decreases over time, allowing a particularly efficient reduction of the magnetization of the Wiegand wire.

[0019] The rotation angle measurement system using a Wiegand sensor for detecting the rotational movement of a shaft according to the invention comprises a permanent magnet excitation unit which can be mounted to rotate with the shaft to be detected. The excitation unit can be formed of a single permanent magnet body or can have a number of permanent magnets mounted on magnet carriers. The excitation unit is usually rotationally symmetrical and comprises magnetic poles which are evenly distributed around the circumference of the excitation unit. The excitation unit is usually mounted directly on the axial end of the shaft.

[0020] The rotation angle measurement system using a Wiegand sensor for detecting the rotational movement of a shaft according to the present invention comprises a stationary Wiegand sensor with a Wiegand wire and a sensor coil radially surrounding the Wiegand wire. The general design and operation of a Wiegand sensor is known from the prior art. The Wiegand sensor is arranged such that an alternating excitation magnetic field is generated by an excitation unit at the position of the Wiegand sensor when the excitation unit is rotated. The Wiegand sensor is typically arranged in a housing arranged on the axial end of the shaft carrying the excitation unit.

[0021] The present invention further provides an initialization unit configured to feed an initialization alternating current to the sensor coil, the initialization alternating current providing a current direction that switches over time and a current amplitude that decreases over time. The initialization unit is thus configured to generate, at the position of the Wiegand wire, an initialization magnetic field that is parallel to the axial direction of the Wiegand wire, the direction of which switches over time, and the amplitude or strength of which decreases over time. The initialization unit can be configured by a special electric circuit and / or a suitably programmed integrated circuit or microcontroller. The initialization unit can comprise its own current source electrically connected to the sensor coil or can be configured to control a separate current source electrically connected to the sensor coil.

[0022] As described above, the initialization unit provides a reliable rotation angle measurement system using a Wiegand sensor by making it possible to eliminate, or at least significantly reduce, magnetization of the Wiegand wire that may occur due to transportation or installation of the rotation angle measurement system.

[0023] Preferably, the rotation angle measuring system using a Wiegand sensor according to the present invention comprises an evaluation unit with a current source, the evaluation unit being configured to feed a detection current to the sensor coil via the current source in order to detect the magnetization direction of the Wiegand wire. The initialization unit is configured to feed an initialization alternating current to the sensor coil via the current source of the evaluation unit. The evaluation unit can be configured by a special electric circuit and / or a suitably programmed integrated circuit or microcontroller. More preferably, the evaluation unit and the initialization unit are configured in a single integrated circuit. This provides a rotation angle measuring system using a Wiegand sensor with a small size and simple configuration.

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rotation angle measuring system using a Wiegand sensor according to the present invention as well as different embodiments of a method for initializing a rotation angle measuring system using a Wiegand sensor according to the present invention will be described below with reference to the accompanying drawings. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram of a rotation angle measurement system using a Wiegand sensor according to the present invention. [Diagram 2] FIG. 2 shows possible initialization positions of an excitation unit relative to a Wiegand sensor in a first embodiment and a second embodiment of the method for initializing the rotation angle measurement system according to the invention in FIG. [Diagram 3] FIG. 3 shows a schematic diagram of the course of an initialization alternating current that is supplied to the sensor coil of the Wiegand sensor of the rotation angle measuring system of FIG. 1 during the initialization method according to the invention. [Figure 4] FIG. 4 shows a schematic part of the course of the initialization AC current supplied to the sensor coil in a second embodiment of the initialization method according to the invention, as well as the position of the excitation unit relative to the Wiegand sensor when the initialization AC current has an extreme value. [Diagram 5] FIG. 5 is a diagram showing possible starting positions of the excitation unit relative to the Wiegand sensor in the third, fourth and fifth embodiments of the initialization method according to the invention. [Figure 6] FIG. 6 shows a schematic part of the course of the initialization AC current supplied to the sensor coil in the third and fourth embodiments of the initialization method according to the present invention, as well as the position of the excitation unit relative to the Wiegand sensor when the initialization AC current has an extreme value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] 1 shows a rotation angle measurement system 10 using a Wiegand sensor attached to the axial end of a shaft 12. The rotation angle measurement system 10 is attached to the shaft 12 and includes a housing 14 having a housing bottom 16 that radially surrounds the shaft, and a housing cover 18 attached to the housing bottom 16.

[0027] The rotation angle measurement system 10 using a Wiegand sensor further comprises a permanent magnet excitation unit 20 fixedly rotatably attached to the end face of the shaft 12 and arranged concentrically with respect to the shaft 12. In this embodiment, the excitation unit 20 is a radially magnetized disk magnet having a single magnetic north pole N and a single magnetic south pole S. The excitation unit 20 generates an excitation magnetic field EM.

[0028] The rotation angle measurement system 10 using a Wiegand sensor further includes a Wiegand sensor 22 having a Wiegand wire 24 and a sensor coil 26 radially surrounding the Wiegand wire 24. The Wiegand sensor 22 is disposed on a printed circuit board 28 fixed in a housing axially spaced from the excitation unit 20. The Wiegand sensor 22 is disposed such that the Wiegand wire 24 extends perpendicular to the axial direction of the shaft 12 and is disposed concentrically with respect to the excitation unit.

[0029] The rotation angle measuring system 10 using a Wiegand sensor further comprises an integrated circuit 30 constituting an evaluation unit 32 having a current source 34 and an initialization unit 36. The integrated circuit 30 is arranged on the printed circuit board 28 and is electrically connected to the Wiegand sensor 22.

[0030] The evaluation unit 32 is configured to evaluate the voltage pulses generated in the sensor coil 26. The evaluation unit 32 is further configured to feed a detection current from a current source 34 to the sensor coil 26 in order to detect the magnetization orientation of the Wiegand wire 24.

[0031] The initialization unit 36 ​​is configured to supply an initialization alternating current IS having a current direction that switches over time and a current amplitude ISA that decreases over time from a current source 34 of the evaluation unit 32 to the sensor coil 26 to generate an initialization magnetic field IM having a magnetization direction that switches over time and a magnetic field amplitude IMA that decreases over time.

[0032] After being attached to the shaft 12, an initialization unit 36 ​​initializes the rotation angle measurement system 10 using a Wiegand sensor.

[0033] In a first embodiment, to initialize the Wiegand sensor-based rotation angle measurement system 10, the excitation unit 20 is aligned with the Wiegand sensor 22 in one of two configurations as shown diagrammatically in Fig. 2. The excitation unit 20 is thus positioned such that the excitation magnetic field EM is perpendicular to the axial direction of the Wiegand wire 24, i.e. such that the magnetic field lines of the excitation magnetic field EM extend substantially perpendicular to the axial direction of the Wiegand wire 24.

[0034] Subsequently, an initialization alternating current IS is fed to the sensor coil 26 by the initialization unit 36, the fed initialization alternating current IS having a time course as shown diagrammatically in Fig. 3. By feeding the initialization alternating current IS to the sensor coil 26, an initialization magnetic field IM parallel to the axial direction of the Wiegand wire 24, i.e. magnetic field lines substantially parallel to the axial direction of the Wiegand wire 24, are generated. The direction of the initialization magnetic field IM is defined by the current direction of the initialization alternating current IS.

[0035] FIG. 3 specifically shows the schematic course of the initialization alternating current IS over time t and the schematic course of the initialization magnetic field IM generated at the position of the Wiegand wire 24 by feeding the initialization alternating current IS to the sensor coil 26. Since the magnetic field amplitude IMA of the initialization magnetic field IM is substantially directly proportional to the current amplitude ISA of the initialization alternating current IS, the courses of the initialization alternating current IS and the initialization magnetic field IM are represented by a single curve in FIG. 3 for simplification. The current direction of the initialization alternating current IS and the magnetization direction of the initialization magnetic field IM are given by the signs of the initialization alternating current IS and the initialization magnetic field IM, respectively. The initialization alternating current IS is simplified to a rectangular shape. However, the initialization alternating current IS can in principle have any alternating waveform with decreasing amplitude. In particular, the initialization alternating current IS can have a sawtooth or sinusoidal waveform.

[0036] The initialization alternating current IS is given a relatively large starting current amplitude ISA at the beginning of the power supply, so that the initialization magnetic field IM is also given a relatively large starting magnetic field amplitude IMA. The current amplitude ISA of the initialization alternating current IS is continuously decreased with time t so that the initialization alternating current IS supplies a relatively low ending current amplitude ISae at the end of the power supply. As a result, the magnetic field amplitude IMA of the initialization magnetic field IM also decreases with time t to a relatively low ending magnetic field amplitude IMAe.

[0037] Preferably, the starting current amplitude ISAs is at least twice as large as the ending current amplitude ISae, more preferably at least three times as large as the ending current amplitude ISae. Preferably, the current direction of the initialization AC current IS is changed at least 10 times, more preferably at least 20 times, during the power supply.

[0038] In the second embodiment, the excitation unit 20 is rotated at a constant rotation frequency while feeding an initialization alternating current IS, and the excitation magnetic field EM is detected by the Wiegand sensor 22 and / or by an additional magnetic field sensor (not shown). An initialization alternating current pulse ISP is fed to the sensor coil 26 by the initialization unit 36 ​​when the angle between the axial direction of the Wiegand wire and the excitation magnetic field is between 80 degrees and 100 degrees, i.e., when the excitation magnetic field EM substantially crosses the axial direction of the Wiegand wire. Here, the initialization alternating current pulse ISP provides a current direction that switches with time and a current amplitude ISA that decreases with time.

[0039] FIG. 4 shows a part of the course of the initialization AC current IS caused by the rotation of the excitation unit 20, and the direction of the excitation unit 20 on the time axis of the initialization AC current pulse ISP.

[0040] In a third embodiment, at the start of initialization of the rotation angle measurement system 10 using a Wiegand sensor, the excitation unit 20 is aligned with respect to the Wiegand sensor 22 according to one of the two arrangements shown diagrammatically in Fig. 5. The excitation unit 20 is thus arranged such that the excitation magnetic field EM is parallel to the axial direction of the Wiegand wire 24, i.e. such that the magnetic field lines of the excitation magnetic field EM extend substantially parallel to the axial direction of the Wiegand wire 24.

[0041] The starting current direction of the initialization AC current IS at the start of the power supply process is always set so that the parallel component of the excitation magnetic field EM parallel to the axial direction of the Wiegand wire 24 and the parallel component of the initialization magnetic field IM parallel to the axial direction of the Wiegand wire 24 are always oriented in the same direction.

[0042] While supplying the initialization AC current IS, the excitation unit 20 is rotated at a constant rotation frequency, which is half the AC frequency of the initialization AC current IS, i.e., half the frequency at which the current direction of the initialization AC current changes, so that the parallel components of the excitation magnetic field EM and the initialization magnetic field IM are always oriented in the same direction.

[0043] FIG. 6 shows a part of the course of the initialization AC current IS due to the rotation of the excitation unit 20 and the orientation of the excitation unit 20 at the extreme values ​​of the initialization AC current IS.

[0044] 5, the excitation unit 20 is not rotated with a constant rotation frequency relative to the Wiegand sensor 22, but is always rotated alternately by 180 degrees clockwise and 180 degrees counterclockwise. Here, the frequency of switching the rotation direction, i.e., the frequency at which the rotation direction of the excitation unit is reversed, is exactly the same as the frequency of the initialization AC current IS, so that the parallel component of the excitation magnetic field EM and the parallel component of the initialization magnetic field IM always point in the same direction.

[0045] The time course of the initialization AC current IS and the alignment of the excitation unit 20 when the initialization AC current IS is at an extreme value due to the “back and forth rotation” of the excitation unit 20 in the fourth embodiment are substantially identical to those in the third embodiment shown diagrammatically in FIG. 6 .

[0046] In the fifth embodiment, starting from one of the two positions shown diagrammatically in FIG. 5, the excitation unit 20 is always rotated alternately clockwise and counterclockwise relative to the Wiegand sensor 22, and, as in the fourth embodiment, the switching frequency of the rotation direction is exactly the same as the switching frequency of the initialization AC current IS.

[0047] However, unlike the fourth embodiment, the excitation unit in the fifth embodiment is not always rotated back and forth by a constant rotation angle of 180 degrees, but is rotated back and forth by a rotation angle that decreases over time, so that the magnitude of the parallel component of the excitation magnetic field EM at the extreme value of the initialization AC current IS decreases over time. [Explanation of symbols]

[0048] 10 Rotation angle measurement system using Wiegand sensor 12 Shaft 14 Housing 16 Bottom of housing 18 Housing cover 20 Excitation unit 22 Wiegand Sensor 24 Wiegand Wire 26 Sensor coil 28 Printed Circuit Board 30 Integrated Circuits 32 Evaluation Units 34 Current source 36 Initialization Unit EM Excitation Magnetic Field IM initialization magnetic field IMA Initialization magnetic field amplitude IMAs: Initial magnetic field amplitude of the initial magnetic field IMAe Final magnetic field amplitude of the initialization magnetic field IS initialization AC current ISA Initialization AC current amplitude ISAs: starting current amplitude of the initial AC current ISAe End current amplitude of the initial AC current ISP Initialization AC Pulse N magnetic north pole S magnetic south pole

Claims

1. Mounting the rotation angle measurement system (10) at a location of use; After the attaching step, a step of supplying an initialization alternating current (IS) to a sensor coil (26) radially surrounding the Wiegand wire (24), the initialization alternating current (IS) providing a current direction that switches over time and a current amplitude (ISA) that decreases over time.

2. 2. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 1, wherein the current direction of the initialization alternating current (IS) switches at least five times.

3. 3. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 1 or 2, wherein a starting current amplitude (ISAs) of the initialization AC current (IS) at the start of the power supply is at least twice as large as an ending current amplitude (ISAe) of the initialization AC current (IS) at the end of the power supply.

4. Prior to the step of supplying the initialization alternating current (IS), 4. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 1, further comprising the step of positioning the permanent magnet excitation unit (20) such that at the position of the Wiegand wire (24), an excitation magnetic field (EM) generated by the permanent magnet excitation unit (20) crosses the axial direction of the Wiegand wire (24).

5. A method for initializing a rotational angle measurement system (10) using a Wiegand sensor described in any one of claims 1 to 4, wherein a permanent magnet excitation unit (20) is rotated at a constant rotational frequency and the initialization AC current (IS) is pulsed so that an initialization AC current pulse (ISP) is supplied to the sensor coil (26) when an excitation magnetic field (EM) generated by the permanent magnet excitation unit (20) at the position of the Wiegand wire (24) crosses the axial direction of the Wiegand wire (24).

6. 4. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 1, further comprising a step of moving the permanent magnet excitation unit (20) during the step of supplying the initialization alternating current (IS) such that a parallel component of an excitation magnetic field (EM) parallel to the axial direction of the Wiegand wire (24), which is generated by the permanent magnet excitation unit (20) at the position of the Wiegand wire (24), and a parallel component of an initialization magnetic field (IM) parallel to the axial direction of the Wiegand wire (24), which is generated at the position of the Wiegand wire (24) by the step of supplying the initialization alternating current (IS) to the sensor coil (26), always point in the same direction.

7. 7. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 6, wherein the permanent magnet excitation unit (20) rotates at a constant rotation frequency during the step of supplying the initialization alternating current (IS), and the rotation frequency is directly proportional to the alternating frequency of the initialization alternating current (IS).

8. 7. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor according to claim 6, wherein during the step of supplying the initialization alternating current (IS), the permanent magnet excitation unit (20) is rotated alternately clockwise and counterclockwise such that a switching frequency of the rotation direction of the permanent magnet excitation unit is directly proportional to a switching frequency of the initialization alternating current (IS).

9. 9. The method for initializing a rotation angle measurement system (10) using a Wiegand sensor as described in claim 8, wherein the permanent magnet excitation unit (20) is rotated such that the rotation angles by which the permanent magnet excitation unit (20) rotates clockwise and counterclockwise, respectively, decrease over time.

10. A rotation angle measurement system (10) using a Wiegand sensor to detect rotational motion of a shaft, comprising: a permanent magnet excitation unit (20) mountable for rotation with the shaft (12) to be sensed; a stationary Wiegand sensor (22), the stationary Wiegand sensor (22) comprising: Wiegand wire (24); a sensor coil (26) radially surrounding the Wiegand wire (24); The rotation angle measurement system (10) using a Wiegand sensor is provided with an initialization unit (36) configured to supply an initialization alternating current (IS) to the sensor coil (26), the initialization alternating current (IS) providing a current direction that switches over time and a current amplitude (ISA) that decreases over time.

11. 11. The system for measuring a rotation angle using a Wiegand sensor according to claim 10, further comprising an evaluation unit having a current source configured to supply a detection current to the sensor coil via the current source in order to detect the magnetization direction of the Wiegand wire, and an initialization unit configured to supply the initialization AC current to the sensor coil via the current source of the evaluation unit.

12. 12. The rotation angle measurement system (10) using a Wiegand sensor according to claim 11, wherein the evaluation unit (32) and the initialization unit (36) are formed by a single integrated circuit (30).

Images