Sensor unit and method for determining a rotation of at least one shaft and a tube in which the shaft is arranged

Abstract

ES presents a sensor unit (137) for determining the rotation of at least one shaft (105) and a tube (110) in which the shaft (105) is movably arranged. The sensor unit (137) comprises a sensor carrier unit (135) in which a first magnetic field sensor (140) is arranged between a second magnetic field sensor (145) and a third magnetic field sensor (150). Furthermore, the sensor unit (137) comprises an evaluation unit (160) configured to determine the rotation using a signal (170) each from the second (145) and the third (150) magnetic field sensor.

Description

[0001] The approach presented here provides a sensor unit and a method for determining a rotation of at least one shaft and a tube in which the shaft is arranged, according to the main claims.

[0002] In specific application scenarios, shafts are used in an axle unit that are arranged coaxially within a tube and can rotate within this tube. In this case, it is often necessary to detect a rotation, or a degree or angle of twist, of the tube and shaft in order to derive parameters that can subsequently be used for control purposes, for example. A particularly advantageous method is contactless sensing of the relevant twist parameters of the shaft and tube, which can be achieved particularly effectively using a magnet or a magnetic field sensor.However, it should be noted that the use of such magnetic field sensors can be problematic, especially when these sensors are mounted on printed circuit boards that also accommodate larger heat sinks for integrated circuits. These heat sinks may protrude into the area between the corresponding magnets and the evaluating magnetic field sensors due to limited installation space. In this case, a magnetic field could be shielded from the magnetic field sensors by corresponding metallic walls or elements, thus making sufficiently precise measurement of the rotation of the shaft and tube impossible.

[0003] Against this background, the present approach provides a sensor unit for determining a rotation of at least one shaft and a tube in which the shaft is movably arranged, wherein the sensor unit has the following features: - a sensor carrier unit in which a first magnetic field sensor is arranged between a second magnetic field sensor and a third magnetic field sensor; and - an evaluation unit configured to determine the rotation using a signal from each of the second and third magnetic field sensors.

[0004] A tube can be understood as a hollow element in which the shaft is movably arranged. A sensor carrier unit can be understood as an element such as a circuit board on which the three magnetic field sensors are arranged or fastened. A magnetic field sensor can generally be understood as a sensor that is capable of qualitatively and quantitatively detecting an existing magnetic field. The magnetic field sensor can be specially designed to also detect a direction of the magnetic field and map it accordingly in a signal. Specifically, the first magnetic field sensor is arranged between the second and third magnetic field sensors. An evaluation unit can be understood as a unit that is capable of processing sensor signals and thereby determining a parameter or a size of the rotation of at least one shaft and the tube from the sensor signals.A relative rotation between the shaft and the pipe can also be determined.

[0005] The approach presented here is based on the finding that by evaluating the signals from the second and third magnetic field sensors, between which the first magnetic field sensor is located, a significant improvement in the determination of the rotation or a magnitude of this rotation is possible. This makes it possible to exploit the fact that by evaluating parameters recorded at two different positions on the sensor carrier unit, the precision of the determination of the rotation is significantly greater than if only one parameter were used to determine the rotation, which was only determined at one position on the sensor carrier unit. At the same time, such a design of the sensor unit requires only minimal additional effort due to the use of a third magnetic field sensor, which can, however, usually be added to the magnetic field sensors already installed on the sensor carrier unit in a technically very simple and cost-effective manner.

[0006] A particularly favorable embodiment of the approach proposed here is one in which the first magnetic field sensor is arranged on the sensor carrier unit on a straight line through the second and third magnetic field sensors. Alternatively or additionally, the evaluation unit can be designed to further determine the rotation of the shaft and / or the tube using a signal from the first magnetic field sensor. Such an embodiment offers the advantage that the second and third magnetic field sensors are very far apart and can therefore provide measured variables from positions that are far apart from each other. In this way, a further increase in the precision of determining the degree of rotation can be achieved. By using the data from the first magnetic field sensor, a significant improvement in the precision of determining the degree of rotation can also be achieved.

[0007] According to a favorable embodiment of the approach proposed here, the first magnetic field sensor can also be arranged on the sensor carrier unit such that it has a substantially equal distance from the second and third magnetic field sensors. Such an embodiment of the approach proposed here offers the advantage of a uniform arrangement of the magnetic field sensors on the sensor carrier unit and generally simplifies the numerical or circuit-based evaluation of the signals from the magnetic field sensors without the use of complex formula calculations.

[0008] The approach presented here can be implemented particularly easily from a technical perspective if the first, second, and / or third magnetic field sensor is designed as a Hall sensor and / or an XMR sensor and / or if the first, second, and / or third magnetic field sensor is arranged on a common printed circuit board. Such an embodiment offers the advantage of cost-effective production of the sensor carrier unit.

[0009] Another advantageous embodiment of the approach proposed here is one in which the first, second, and / or third magnetic field sensor is configured to each detect a portion of a magnetic field in at least two spatial directions, in particular in a direction tangential to the shaft and / or the tube and / or in a direction axial to the shaft and / or the tube. Such an embodiment offers the advantage of being able to perform a very precise determination of the rotation of the shaft and the tube by providing a partial signal from the respective magnetic field sensors that was recorded in different spatial directions.

[0010] Determining the magnitude of the rotation of the shaft and / or the pipe is particularly simple from a technical perspective if, according to one embodiment of the approach proposed here, the rotation of the shaft and / or the pipe is determined using a sum of the signal components of the magnetic fields detected by the second and third magnetic field sensors, which are recorded in a same spatial direction, in particular the axial spatial direction. Alternatively or additionally, the rotation of the shaft and / or the pipe can also be determined using a difference between the signal components of the magnetic fields detected by the second and third magnetic field sensors, which are recorded in a same spatial direction, in particular the tangential spatial direction. By using simple formulaic relationships between different signal components in the respective spatial directions, a very precise determination of the rotation can thus be achieved.

[0011] The approach presented here can be implemented particularly efficiently in an axis unit with the following features: - a sensor unit according to a variant presented here; and - a shaft movably mounted in the tube, with a first magnet arranged on an end face of the shaft opposite the first magnetic field sensor, and a second magnet arranged on an end face of the tube opposite the second and third magnetic field sensors. Signals from the magnetic field sensors can be delivered for evaluation in the sensor unit.

[0012] By means of such an embodiment, the interaction of the shaft with the pipe including the respective magnets and the sensor unit allows a very precise determination of the degree of rotation of the shaft and the pipe.

[0013] A magnetic field can also be impressed on the magnetic field sensors if the first magnet and / or the second magnet is designed as a ring magnet.

[0014] In particular, according to one embodiment, the second magnet can have a larger number of poles than the first magnet. Specifically, the second magnet can have an even number of poles. Such an embodiment advantageously enables the second magnet with the plurality of poles to impart a magnetic field that varies greatly when structurally superimposed on the magnetic field of the first magnet, so that by detecting this variation, a very precise determination of the degree of rotation of the shaft and tube can be achieved.

[0015] To achieve the most precise determination of the degree of rotation of the tube and the shaft, according to a further embodiment, the shaft can be rotatable within the tube within a predefined angular range, in particular wherein the angular range comprises a maximum of 90 degrees. Such an embodiment offers the advantage of being able to compensate to a certain extent for the loss of determinability of the absolute position, especially when using a second magnet with a plurality of poles. By specifying the predefined angular range, an error in determining the absolute position of the tube and the shaft during rotation can be largely compensated.

[0016] Furthermore, an embodiment of the approach proposed here is advantageous as a method for determining a rotation of at least one shaft and a tube in which the shaft is arranged, wherein the method is carried out using a sensor unit according to a variant presented here and comprises the following steps: - Reading one signal each from the second and third magnetic field sensors; and - Evaluate the signal from the second and third magnetic field sensors to determine the rotation of the shaft and tube.

[0017] Such an embodiment also allows the above-mentioned advantages to be realized quickly and efficiently.

[0018] The approach presented here further provides a device or evaluation unit configured to perform, control, or implement the steps of a variant of a method presented here in corresponding devices. This embodiment of the invention in the form of a device or evaluation unit also allows the problem underlying the invention to be solved quickly and efficiently.

[0019] For this purpose, the device or evaluation unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading sensor signals from the sensor or for outputting data or control signals to the actuator, and / or at least one communication interface for reading or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, or the like, wherein the memory unit can be a flash memory or a magnetic storage unit.The communication interface can be designed to read in or output data wirelessly and / or wired, wherein a communication interface that can read in or output wired data can read this data, for example, electrically or optically from a corresponding data transmission line or output it to a corresponding data transmission line.

[0020] In this case, a device or evaluation unit can be understood as an electrical device that processes sensor signals and outputs control and / or data signals depending on them. The device or evaluation unit can have an interface that can be implemented in hardware and / or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the device. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

[0021] Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and / or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer, an evaluation unit or a device.

[0022] Advantageous embodiments of the approach presented here are explained in more detail in the following description. It shows the Fig. 1 is a schematic representation of an embodiment of an axle unit comprising a shaft rotatably arranged within a tube; Fig. 2 shows part of a further embodiment of an axle unit in which the second magnet is designed as a ring magnet; Fig. 3 a diagram showing the change in the field strength curve when the shaft and the tube rotate; Fig. 4 is another diagram showing the change in a field strength curve of specific magnetic field strength values ​​during the rotation of the shaft and the tube; and Fig. 5 a flowchart of a method for determining a rotation of at least one shaft and one tube.

[0023] In the following description of advantageous embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

[0024] Fig. 1 shows a schematic representation of an embodiment of an axle unit 100, which comprises a shaft 105 rotatably arranged within a tube 110. A first magnet 120 is arranged on an end face 115 of the shaft 105, whereas a second magnet 130 is arranged on the end face 125 of the tube 110. The first magnet 115 and the second magnet 130 are each designed as two-pole magnets. Furthermore, a sensor carrier unit 135 of a sensor unit 137 is arranged opposite the magnets 120 and 130. The sensor unit 137 has a first magnetic field sensor 140 positioned between a second magnetic field sensor 145 and a third magnetic field sensor 150.

[0025] For example, the first magnetic field sensor 140, the second magnetic field sensor 145, and the third magnetic field sensor are designed as XMR- or Hall-based sensors and are arranged or aligned in a straight line 155 on a printed circuit board 1578 and positioned, for example, at the same distance from one another. The sensor carrier unit 135 further comprises an evaluation unit 160, which itself comprises a read-in interface 165 for reading in a signal 170 from one of the magnetic field sensors 140, 145, or 150. Furthermore, the evaluation unit 160 comprises a determination unit 170, in which, using the signals 170 from the magnetic field sensors 140, 145, and 150, specifically the second and third magnetic field sensors 145 and 150, a value 175 is determined that represents a rotation of the shaft 105 and the tube 110.

[0026] The Fig. The variant illustrated in Figure 1 as an exemplary embodiment of the axle unit 100 can, for example, be used in any machine in which a rotation of the shaft 105 and the tube 110 is relevant. For example, the shaft 105 can represent a steering column of a vehicle that is rotated in a mount formed by the tube 110. In this case, the rotation of the shaft 105 and the tube 110 can be used as a control signal for a drive-by-wire steering system. However, it is also conceivable that the axle unit 100 is part of another technical device in which a movement or rotation of the shaft 105 and the tube 110 is to be detected.

[0027] As from the Fig. 1, the first magnet 120 is arranged on the shaft 105 opposite the first magnetic field sensor 140, with both the shaft 105, the first magnet 120 and the first magnetic field sensor 140 lying on a rotation axis 180 of the shaft 105. The second magnet 125 is designed as a ring magnet, so that it is arranged opposite the second magnetic field sensor 145 and the third magnetic field sensor 150. If the shaft 105 and the tube 110 or even the shaft 105 are rotated relative to the tube 110, the magnetic field generated by the first magnet 115 is superimposed on the magnetic field generated by the second magnet 120, resulting in a change in the entire magnetic field in the area of ​​the magnetic field sensors 140, 145 and 150.Due to the particularly favorable arrangement of the first, second and third magnetic field sensors 140, 145 and 150, wherein the second magnetic field sensor 145 and the third magnetic field sensor 150 form the outer magnetic field sensors surrounding the first magnetic field sensor 140, a significant improvement in the precision in determining the rotation of the shaft 105 and the tube 110 can now be achieved compared to sensor arrangements in which only two magnetic field sensors are used opposite the first and second magnets.

[0028] The problem of interference from metallic components described above could, in principle, also be solved by using a magnetic sensor to measure the position of shaft 105 and an inductive sensor to measure the position of shaft 110. However, inductive sensors have the disadvantage that they require much more space on the circuit board (up to a factor of 10), which may be limited. In the ERC (electric roll control) system for which the present approach was designed, an inductive sensor cannot be used because, for example, a thin aluminum wall (0.5 mm thick) belonging to a heat sink may be located between the magnets 120 and 130 and the sensors 140 and 145. While this results in only a slight phase shift at high speeds for magnetic sensors, inductive sensors are completely blind and cannot measure through this aluminum wall.When using two magnetic sensors, a set of gears could also be considered to increase the spatial separation between the two target magnets. However, this would significantly increase costs and could lead to backlash issues in the gear system.

[0029] To solve this problem, the approach presented here proposes to measure the independent rotation of two coaxial objects (ie, a smaller shaft 105 rotates inside a larger hollow shaft or tube 110).

[0030] It is quite difficult to implement these two measurements with two target magnets 120 and 130 and two magnetic sensors 140 and 145, designed, for example, as XMR- or Hall-based sensors, on a circuit board such as the circuit carrier 135, although this is sometimes attempted. The reason for this problem is that the fields of the two target magnets interfere with both sensors. Therefore, the first sensor 140, which should only measure the field of the first magnet 120 of the inner shaft 105, will also measure the field of the second magnet 130 of the outer shaft or tube 110, and vice versa. Therefore, the sensor signals cannot be assigned separately to the individual magnets, and thus, it is not possible to determine the angular position of the shaft 105 relative to the tube.

[0031] In order to significantly reduce crosstalk between the two sensor signals, it is now proposed to introduce a third sensor 150, which is positioned opposite the hollow shaft or tube 110 and, for example, is mounted exactly 180° opposite the already existing second sensor 145 and placed at the same radius or distance from the first sensor 140. The second and third sensors 145 and 150 are selected so that they can measure the magnetic field in the x-direction (i.e. tangential) and in the z-direction (i.e. axial), i.e. they can detect individual components of the magnetic field acting on these sensors 145 and 150 in different spatial directions. Due to the symmetry of the two-pole magnetization, for example, both sensors 145, 150 measure the same field in the tangential (x-) direction and the opposite field in the axial (z-) direction.

[0032] Fig. Figure 2 shows part of a further embodiment of an axle unit 100 in which the second magnet 130 is now designed as a ring magnet, in which a multi-pole ring with advantageously an even number of pole pairs (2, 4 or more) is used, whereby the behavior with respect to the sensors 145 and 150 is reversed. Fig. In Figure 2, a twelve-pole double magnet is shown as the second magnet 130. The two magnetic field sensors in question, i.e., the second and third magnetic field sensors 145 and 150, respectively, measure the opposite field in the tangential direction and the same field in the axial direction generated by the multipole ring. t: Replacing the multipole ring as the second magnet 130 results in a loss of information, as the field no longer carries absolute angular information over 360°, but instead repeats over one revolution with the number of pole pairs. This may be acceptable for the application if, for example, the rotation of the outer shaft is limited to a certain angular range. If this is not the case, a processing unit connected to sensors 140, 145, 150 can track the absolute position by counting the polarity changes.

[0033] Fig. 3 shows a diagram 300 illustrating the change in a field strength curve during the rotation of the shaft and the tube, with the distance of the rotation in mm plotted on the abscissa and the magnetic field strength plotted on the ordinate. It should be noted that the value on the abscissa corresponds to a full rotation, i.e., 360 degrees. A first graph 310 depicts a tangential field component, and a second graph 320 depicts an axial field component, which was measured by the second magnetic field sensor 145 over a full rotation, assuming synchronized rotation of both magnets 120 and 130, respectively. However, the synchronous rotation in my example is only for illustration purposes. For the correct functioning of the approach proposed here, it is irrelevant how the magnets rotate relative to each other.

[0034] The large crosstalk of the magnetic field of the inner or first magnet 120, also called dipole DP, can be seen, which significantly modulates the field of the second magnet 130.

[0035] In accordance with the symmetric behavior described above, the following terms are defined: BMP,axial=B202,axial+B202',axial BMP,tangential:=B202,tangential−B202',tangential BDP,axial:=B202,axial−B202',axial BDP,tangential:=B202,tangential+B202',tangential

[0036] Fig. Figure 4 shows another diagram 400 illustrating the change in a field strength curve from specific magnetic field strength values ​​during the rotation of the shaft and the tube, with an angle plotted on the abscissa and a magnetic field strength plotted on the ordinate. Diagram 400 depicts the above-described relationships between magnetic field strength values ​​corresponding to the designations 401, 402, 403, and 404, which were recorded in different spatial directions. In this representation of diagram 400, the terms are plotted over a full revolution for both magnets 120 and 130, respectively.

[0037] Curves 403' and 404' represent the situation in which the first (inner) magnet 120 (DP) is rotated by 27° relative to the other situation. The corresponding curves 401' and 402' cannot be considered separately, as these terms are identical to the designations 401 and 402, since they are now independent of the angular position of the first magnet 120. The mechanical angle α Rohr that of the pipe 110 can now be determined using the following equation: αSTube=1npole pairseatan2(BMP,tangential;BMP,axial) where the variable n_pole_pairs describes the number of pole pairs (12 in this example). Since the magnet 130 is designed as a multipole ring, the above equation describes the angle of the outer shaft, i.e., the tube 110. Structurally, it is also possible to connect the magnets in such a way that the outer magnet ring is connected to the inner shaft 105 and the inner magnet is connected to the outer shaft, i.e., the tube 110.

[0038] The change from a two-pole ring as the second magnet 130 to a multi-pole ring as the second magnet 130 also results in the effect that its field disappears identically at the sensor 140 due to the change in symmetry. Therefore, the field signatures of both magnets 120, 130 are decoupled and can be measured separately: the dipole magnet or first magnet 120 of the inner shaft 105 with the chip or first magnetic field sensor 140, and the multipole ring as the second magnet 130 with the combined signals from the sensor chip or the second magnetic field sensor 145 and the third magnetic field sensor 150.

[0039] In reality, the decoupling will not function perfectly due to assembly tolerances and different sensitivities of the sensor chips or magnetic field sensors 145 and 150, respectively. Therefore, the magnetization of the first magnet 120 can be axially bipolar or surface magnetized rather than diametrically. With the latter two magnetization types, the stray field is already significantly reduced, but not so much that the variant described above is unnecessary.

[0040] It is also possible to use a multi-pole ring as the first magnet 120 for the inner shaft 105. For this purpose, for example, a magnet holder is constructed for the ring as the first magnet 120, which is connected to the inner shaft 105 through a bore of the other, second magnet 130, which is connected to the hollow shaft 110.

[0041] Fig.5 shows a flowchart of a method 500 for determining a rotation of at least one shaft and a tube in which the shaft is arranged, wherein the method 500 is carried out using a sensor unit according to a variant presented here and wherein the method 500 has a step 510 of reading in a signal from each of the second and the third magnetic field sensors and a step 520 of evaluating the signal from the second and the third magnetic field sensors in order to determine the rotation of the shaft and the tube. Reference symbol 100 axle unit 105 Wave 110 tube, hollow shaft 115 Front side of the shaft 120 first magnet 125 Front side of the pipe 130 second magnet 135 Sensor carrier unit 137 Sensor unit 140 first magnetic field sensor 145 second magnetic field sensor 150 third magnetic field sensor 155 Straight 157 circuit board 160 evaluation unit 165 Reading interface 170 Determination unit 175 Signal 180 axis of rotation of the shaft 300 diagram 310 graph, curve 320 graph, curve 400 diagram 401, 402, 403, 404, 403', 404' Graphs of connections of partial magnetic field strengths in different spatial directions 500 Method for determining a rotation of at least one shaft and one pipe 510 Step of reading 520 Step of evaluation

Claims

[1] Sensor unit (137) for determining a rotation of at least one shaft (105) and a tube (110) in which the shaft (105) is movably arranged, the sensor unit (135) having the following features: - a sensor carrier unit (135) in which a first magnetic field sensor (140) is arranged between a second magnetic field sensor (145) and a third magnetic field sensor (150); and - an evaluation unit (160) which is designed to determine the rotation using a signal (170) from each of the second (145) and the third (150) magnetic field sensors. [2] Sensor unit (137) according to claim 1, characterized bythat the first magnetic field sensor (140) is arranged on the sensor carrier unit (135) on a straight line (155) through the second (145) and third (150) magnetic field sensor and / or wherein the evaluation unit (160) is designed to determine the rotation of the shaft (105) and / or the tube (110) further using a signal (170) of the first magnetic field sensor (140). [3] Sensor unit (137) according to claim 1 or 2, characterized by that the first magnetic field sensor (140) is arranged on the sensor carrier unit (137) such that it has a substantially equal distance from the second (145) and the third (150) magnetic field sensor. [4] Sensor unit (137) according to one of the preceding claims, characterized bythat the first (140), second (145) and / or third (150) magnetic field sensor is designed as a Hall sensor and / or an XMR sensor and / or that the first, second (145) and / or third (150) magnetic field sensor are arranged on a printed circuit board (157). [5] Sensor unit (137) according to one of the preceding claims, characterized by that the first (140), second (145) and / or third (150) magnetic field sensors are designed to each detect a portion of a magnetic field in at least two spatial directions (x, z), in particular in a direction tangential to the shaft (105) and / or the tube (110) and / or in a direction axial to the shaft (105) and / or the tube (110). [6] Sensor unit (137) according to claim 5, characterized byin that the evaluation unit (160) is designed to determine the rotation of the shaft (105) and / or the tube (110) using a sum of the signal components of the magnetic fields detected by the second (145) and third (150) magnetic field sensors, which signal components are detected in a same spatial direction, in particular the axial spatial direction, and / or to determine the rotation of the shaft (105) and / or the tube (110) using a difference of the signal components of the magnetic fields detected by the second (145) and third (150) magnetic field sensors, which signal components are detected in a same spatial direction, in particular the tangential spatial direction. [7] Axle unit (100) having the following features; - a sensor unit (137) according to one of claims 1 to 6; and - a shaft (105) which is movably arranged in the tube (110), wherein a first magnet (120) is arranged on an end face (115) of the shaft (105) opposite the first magnetic field sensor (140) and a second magnet (130) is arranged on an end face (125) of the tube (110) opposite the second (145) and third (150) magnetic field sensors. [8] Axle unit (100) according to claim 7, characterized by that the first magnet (120) and / or the second magnet (130) is designed as a ring magnet. [9] Axle unit (100) according to claim 7 or 8, characterized by that the second magnet (130) has a larger number of poles than the first magnet (120). [10] Axle unit (100) according to claims 7 to 9, characterized by that the shaft (105) is rotatable in the tube (110) within a predefined angular range, in particular wherein the angular range comprises at most 90 degrees. [11] Method (500) for determining a rotation of at least one shaft (105) and a tube (110) in which the shaft (105) is arranged, the method (500) being carried out using a sensor unit (137) according to one of claims 1 to 6 and comprising the following steps: - reading (510) one signal (170) each from the second (145) and the third (150) magnetic field sensor; and - Evaluating (520) the signal (170) of the second (145) and the third (150) magnetic field sensor to determine the rotation of the shaft (105) and the tube (110). [12] Computer program configured to execute and / or control the steps (510, 520) of the method (500) according to any one of the preceding claims. [13] A machine-readable storage medium on which the computer program according to claim 12 is stored. [14] Evaluation unit (160) which is designed to carry out, control and / or implement the steps (510, 520) of a method (500) according to claim 11 in corresponding devices.

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