omni-directional rotational speed and direction sensor

Abstract

The invention relates to a magnetic field sensor (1) which is matched for determining the rotational speed and the direction of rotation of a rotating object which either generates a rotating magnetic field itself or deflects an existing magnetic field accordingly. For this purpose a chip (2) having at least three magnetic field measuring elements (2a, 2b, 2c) is used, which is in the form of a 3D Hall sensor. Such a magnetic field sensor (1) is used, inter alia, in commercial vehicles. The normal direction of the tangential plane of the rotating element defines the z direction. The signals of the sensor elements which are sensitive in the z direction form a difference signal together with the signals of the further sensor elements, respectively. The two difference signals generated have a phase offset from which the direction of rotation can be determined. The output signals generated contain not only information about the direction of rotation but also information about the speed.

Description

Technical Field

[0001] This invention relates to an omnidirectional speed and direction sensor, which is particularly useful in commercial vehicles, especially heavy-duty trucks. Background Technology

[0002] Especially for autonomous driving, a speed sensor is needed to determine the speed and direction of rotation of specific components in a commercial vehicle, such as shafts, gears, or individual vehicle wheels. It is particularly important to measure not only the speed (i.e., rotational velocity) but also the direction of rotation.

[0003] In the prior art, so-called passive sensors are known for this purpose. These passive sensors are fixedly positioned near a rotating object, such as a shaft or gear. In the case of passive sensors, the radial orientation of the sensor is not important for technical reasons.

[0004] In the case of passenger vehicles, active sensors already exist, and in the case of such active sensors, the radial orientation of the sensor is important. Here, the sensor is fastened or fixed in position so that the shaft or rotating component can always be determined with precise rotation direction and speed.

[0005] However, in the case of commercial vehicles, such axial mobility of the active sensor is required due to specific requirements. That is, the sensor must be movable and provide the same measurement results regardless of its position relative to the rotating object.

[0006] In the prior art, for example, patent document EP 3 304 003 B1 is known, which discloses a magnetic field sensor for performing independent velocity and direction measurements.

[0007] Here, the sensor includes first, second, and third magnetic field measuring elements spaced apart from each other. Each magnetic field measuring element outputs a magnetic field signal proportional to the amplitude of the magnetic field associated with the rotating object. Difference pairs of all three measurements are determined, and corresponding difference signals are determined and output as differential channels. A combining element generates a combined signal based on the first, second, and third magnetic field signals. The control circuit then calculates the rotational speed and determines the direction of rotation, and generates a sensor output signal that displays the speed and direction of motion of the rotating object.

[0008] The sensor can be set regardless of the position of the rotating object.

[0009] Here, a Hall sensor is used in particular, which measures the magnetic field from the rotating object at three locations, and thereby the rotational speed and direction of motion can be calculated by the control unit.

[0010] However, the computation of the three differential channels is costly, consuming computation time and storage space. Summary of the Invention

[0011] Therefore, the objective of this invention is to provide an improved magnetic field sensor for determining the rotational direction and rotational speed of a rotating object, in which calculation time can be reduced and accuracy improved.

[0012] This task is accomplished by the magnetic field sensor according to claim 1, the system comprising the magnetic field sensor and the magnetic pole rotor according to any one of claims 10 and 11, and by the method according to claim 13.

[0013] Other advantageous configurations are the subject of the dependent claims.

[0014] The magnetic field sensor according to the invention includes a chip having at least one first, second, and third magnetic field measuring element, each matched to provide a first, second, and third magnetic field signal, the amplitude of which is proportional to a magnetic field originating from a rotating object (or from a permanent magnet and deflected by the motion of the rotating object). The normal vectors of the at least three magnetic field measuring elements are linearly independent of each other. This means that the magnetic field measuring elements are arranged at 90° angles to each other, for example, in a Cartesian coordinate system. A signal detection unit is matched to determine a first difference signal and a second difference signal, wherein the first difference signal is based on the difference between the magnetic field signal of the first magnetic field measuring element and the magnetic field signal of the second magnetic field measuring element, and the second difference signal is based on the difference between the magnetic field signal of the first magnetic field measuring element and the magnetic field signal of the third magnetic field measuring element. The signal detection unit is further matched to calculate and output a combined signal based on the magnetic field signal of the first magnetic field measuring element, the first difference signal, and the second difference signal. Then, an analysis and processing unit is matched to generate an output signal containing the velocity and direction of motion of the rotating object.

[0015] Preferably, the at least three magnetic field measuring elements are Hall sensors. Such sensors are relatively cost-effective compared to other sensors, yet they are highly accurate.

[0016] A Hall sensor consists of a doped semiconductor layer having, for example, four electrodes on its sides. A current is fed through two opposing electrodes, and a so-called Hall voltage is applied to the two electrodes that are subsequently orthogonal to each other. If a magnetic field extending perpendicularly to the layer flows through the Hall sensor, the sensor outputs an output voltage proportional to the magnitude of the vector product of the magnetic flux density and the current. This Hall voltage is caused by the Lorentz force acting on moving charge carriers within the doped semiconductor layer.

[0017] In this configuration, the magnetic field sensor is a 3D Hall sensor, operating with two differential signals. Since changes in magnetic flux in one direction are independent of the orientation of the arrangement—a Hall voltage is always generated regardless of the direction and speed of rotation—direction identification is essentially achieved through phase shift, which is the difference between the minimum and maximum amplitudes of the individual magnetic field measuring elements. Therefore, two differential signals are sufficient for direction identification. The magnetic flux signal can also provide additional diagnostic possibilities, such as determining the thickness of the air gap between the magnetic field sensor and the rotating object. When this is performed in a commercial vehicle, a larger air gap can, for example, indicate that the position of the magnetic field sensor relative to the rotating object has changed over time, thus requiring the driver to visit a repair shop.

[0018] More preferably, vector analysis processing can be performed.

[0019] More preferably, the normal vectors of the three magnetic field measuring elements are arranged to form an angle of approximately 90°, preferably exactly 90°, with each other. With this arrangement, the maximum amplitude of the entire signal can be measured.

[0020] More preferably, there is an additional magnetic field measuring element, which is arranged, for example, at a 45° angle between the three magnetic field measuring elements, which form a 90° angle with each other.

[0021] Preferably, the first magnetic field measuring element is a lateral Hall sensor, and the second and third magnetic field measuring elements are vertical Hall sensors. The vertical Hall sensors are arranged such that they are positioned parallel to the magnetic flux lines and extend parallel to the plane of the chip. Conversely, the two lateral magnetic field measuring elements are perpendicular to the magnetic flux lines and also perpendicular to the chip.

[0022] This, in turn, has the advantage that changes in magnetic flux can be measured independently of this arrangement using a vertical Hall sensor—that is, the magnetic field can always be measured. Specifically, the magnetic field sensor can move away from the rotating object, and still measure with sufficient accuracy. More preferably, the chip is arranged in a plane that is largely parallel, preferably parallel to, the tangential plane of the rotating object. This, in turn, enables one of the measurement signals to be orientation-independent, and accurate measurements can be performed even with a larger gap between the rotating object and the chip.

[0023] More preferably, the chip and at least three magnetic field elements are placed within the housing, and the chip is preferably secured by a bracket. The bracket secures the chip, which has magnetic field measuring elements, firmly within the housing and is thus in a fixed position. Therefore, calibrating the magnetic field sensor once is sufficient, and the sensor can then be used without repeated recalibration.

[0024] The internal space of the housing is preferably at least partially filled with plastic material. This improves the stability of the magnetic field sensor's position within the housing.

[0025] More preferably, a flux blech is provided on the housing to minimize interference signals in the chip area.

[0026] More preferably, the magnetic field sensor has a current interface or a voltage interface, through which a signal can be output, for example, to the control system of a commercial vehicle.

[0027] The magnetic field measuring element is not necessarily a Hall element; it can also be a magnetoresistive element, such as anisotropic magnetoresistive elements, giant magnetoresistive elements, or tunneling magnetoresistive elements.

[0028] More preferably, the analysis and processing unit of the magnetic field sensor is configured to perform temperature compensation on the measurement signals of at least three magnetic field measuring elements.

[0029] Therefore, it is possible to obtain sufficiently accurate signals under different temperatures, and to minimize the temperature dependence or measurement error of rotational speed and rotational speed.

[0030] The system according to the present invention consists of a magnetic field sensor and a magnetic pole rotor, wherein the magnetic pole rotor may be magnetically encoded or magnetically preloaded.

[0031] Magnetic coding here can refer to the arrangement of small permanent magnets on the teeth of a magnetic pole rotor, each of which generates a magnetic field.

[0032] Magnetic preload refers to a magnetic pole rotor made of ferrite material, and a magnetic field is generated by setting permanent magnets on the chip of a magnetic field sensor. The magnetic field is excited by the permanent magnets and deflects according to the position of the magnetic pole rotor. Then, the magnetic field lines extend into one or more teeth of the magnetic pole rotor, but not into the notch, and are then deflected by the rotation of the magnetic pole rotor.

[0033] The magnetic field of the magnetic pole rotor, together with the magnetic field from the magnet on the chip, generates a magnetic field signal, which can then be measured by a magnetic field sensor.

[0034] More preferably, the system includes an additional differential element that is further matched to determine the rotation direction of the magnetic pole rotor. This enables more accurate and safer measurements.

[0035] This additional differential element can also be matched for obtaining and / or compensating for external fields.

[0036] The method according to the present invention for determining the rotational speed and direction of rotation of a rotating object by means of a magnetic field sensor includes the following steps:

[0037] a) Detect the corresponding magnetic field signals of the first magnetic field measuring element, the second magnetic field measuring element, and the third magnetic field measuring element respectively;

[0038] b) Obtain the first difference signal from the difference between the magnetic field signal of the first magnetic field measuring element and the magnetic field signal of the second magnetic field measuring element;

[0039] c) Obtain the second difference signal from the difference between the magnetic field signal of the first magnetic field measuring element and the magnetic field signal of the third magnetic field measuring element;

[0040] d) Calculate the combined signal consisting of the magnetic field signal from the first magnetic field measuring element, the first difference signal, and the second difference signal;

[0041] e) Calculate and output an output signal, the output signal including the speed and direction of motion of the rotating object. Attached Figure Description

[0042] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings.

[0043] Figure 1 The magnetic field sensor 1 and the magnetic pole rotor 20 according to the present invention are shown in three different orientations. Figure 1 Top views and schematic views in 1) to 1c).

[0044] Figure 2 The diagram shows the various magnetic field measuring elements in... Figure 1Typical magnetic field signals in each of the three orientations, where, here, with time, i.e. as the magnetic pole rotor rotates ( Figure 2 Record the changes in the magnetic field signal from a) to 2c).

[0045] Figure 3 The diagram shows the arrangement of the magnetic field sensor according to the invention within the housing. Detailed Implementation

[0046] exist Figure 1 The diagram shows a magnetic field sensor 1 and a magnetic pole rotor 20 according to the present invention. The magnetic field sensor 1 is arranged above the magnetic pole rotor 20 in a top view. The magnetic pole rotor 20 has teeth 21 and notches 22. The magnetic field sensor includes a chip 2 on which three magnetic field measuring elements 2a, 2b, and 2c are arranged. Furthermore, a magnet 2d is arranged on the chip. The magnetic field measuring elements 2a, 2b, and 2c are substantially cuboid in shape, having a large base and relatively small and narrow sides. The first magnetic field measuring element 2a is mounted flat on the chip 2 as a lateral Hall element, with its large base resting flat on the chip 2. Here, the Hall voltage can always be measured when the magnetic pole rotor 20 rotates. The other two magnetic field measuring elements 2b and 2c are vertical magnetic field measuring elements, standing upright on the chip with their small faces and thus arranged perpendicular to the chip. The chip 2 is parallel to the tangential plane of the magnetic pole rotor 20. Figure 1 In b), Figure 1 Chip 2 in component a rotates by 45°, meaning the positions of magnetic field measuring elements 2a, 2b, and 2c also change. Nevertheless, chip 2 remains located in a plane parallel to the tangential plane of the magnetic pole rotor 20. Figure 1 In c), the schematic diagram is rotated 45° again, and here chip 2 is also located in a plane parallel to the tangential plane of magnetic pole rotor 20.

[0047] exist Figure 2 The diagram shows the change in magnetic field strength, that is, the change in the signals of magnetic field measuring elements 2a, 2b, and 2c over time (or in this case, related to the rotation angle) and related to the orientation of chip 2. Figure 2 a) Corresponding to Figure 1 The diagram in a).

[0048] The signal from the second magnetic field measuring element 2b (in) Figure 2 (Drawn as Bx) here has a signal that is greater than that of the first magnetic field measuring element 2a (in Figure 2 The signal from the third magnetic field measuring element 2c (referred to as Bz in the text) and the signal from the third magnetic field measuring element 2c (in the text) Figure 2The amplitude of the signal from the first and third magnetic field measuring elements 2a and 2c is significantly smaller because the magnetic field lines of the magnet 2d deflected by the magnetic pole rotor 20 can only induce a Hall voltage in the second magnetic field measuring element 2b (since the magnetic field lines are not perpendicular to the extension direction of the second magnetic field measuring element 2b). The signals from the first and third magnetic field measuring elements 2a and 2c have larger amplitudes because the magnetic field lines extend perpendicular to the corresponding Hall elements and thus can induce stronger Hall voltages. The two amplitudes of the magnetic field measuring elements 2a and 2c are phase-shifted, which can be explained by the following: the magnetic field changes on these two elements occur in a time-shifted manner because the two elements are spaced apart from each other in the rotation direction of the magnetic pole rotor 20, so the teeth 21 of the magnetic pole rotor pass through the chip 2 in a time-shifted manner—therefore the deflection of the magnetic field lines of the permanent magnet 2d occurs in a phase-shifted manner.

[0049] exist Figure 2 As shown in b), the signals of the magnetic field measuring elements 2b and 2c have similar shapes because the components of the magnetic field created by the permanent magnet 2d and deflected by the rotation of the magnetic pole rotor 20 play a role, respectively, and these components are correspondingly perpendicular to the Hall element and can thus cause a Hall voltage.

[0050] exist Figure 2 c) shows Figure 1 The measurement signals of the sensors in the arrangement shown in c) are illustrated here. The strong swings of the signals from the first and second magnetic field measuring elements 2a and 2b are shown with phase shifts, respectively. This can be explained by the spatial spacing between the first and second magnetic field measuring elements 2a and 2b in the rotational direction. However, a small swing can be seen from the third magnetic field measuring element 2c, because only a very small portion of the magnetic field lines enters perpendicularly to the Hall sensor, thus a strong Hall voltage cannot be generated in the extending direction of the third magnetic field measuring element 2c.

[0051] Based on the signal, not only the rotational speed but also the rotational direction can be determined. In particular, phase shifting allows for the identification of the rotational direction. Two channels are sufficient for direction identification; three channels are not required here. This saves computation time, thus providing results for the calculation of rotational direction and speed more quickly.

[0052] exist Figure 3 The arrangement of chip 2 within housing 5 is shown. Chip 2 is secured to housing 5 by means of bracket 6. The interior space of housing 5 is partially filled with plastic material. This better secures the chip within the housing. The position of housing relative to the magnetic pole rotor is also shown. The air gap L between the magnetic pole rotor 20, which has teeth 21 and notches 22, and housing 5 can vary accordingly. Furthermore, it is indicated that signal detection unit 3, analysis and processing unit 4, and current or voltage interface 7 are located on the chip.

[0053] In addition, a flux guide plate 8 is shown in the area of ​​chip 2, which should keep the magnetic interference field away from chip 2.

[0054] This invention is not limited to the described embodiments. Importantly, there are at least three Hall elements whose normal vectors are linearly independent of each other. However, additional elements, such as additional Hall elements at a 45° angle to the corresponding measuring elements 2a, 2b, and 2c, can be arranged in between. This further improves accuracy.

[0055] This invention relates to a magnetic field sensor 1, which is used to determine the motion of a rotating object, particularly the direction and speed of rotation of the object, which either generates its own rotational magnetic field or deflects an existing magnetic field accordingly. For this purpose, a chip 2 with at least three magnetic field measuring elements 2a, 2b, and 2c is used, preferably a 3D Hall effect sensor. Such a magnetic field sensor 1 is particularly useful in commercial vehicles.

[0056] List of reference numerals

[0057] 1. Magnetic field sensor

[0058] 2 chips

[0059] 2a First magnetic field measuring element

[0060] 2b Second magnetic field measuring element

[0061] 2c Third magnetic field measuring element

[0062] 2D permanent magnet

[0063] 3 Signal Detection Unit

[0064] 4. Analysis and Processing Unit

[0065] 5. Housing

[0066] 6 supports

[0067] 7. Current interface or voltage interface

[0068] 8 Flux Guide Plate

[0069] 20-pole rotor

[0070] 21. Teeth

[0071] 22 gaps

[0072] D1 First Difference Signal

[0073] D2 Second Difference Signal

[0074] KS combined signal

[0075] AS output signal

Claims

1. A magnetic field sensor (1), the magnetic field sensor comprising: The chip (2) has at least one first magnetic field measuring element, a second magnetic field measuring element, and a third magnetic field measuring element (2a, 2b, 2c). The magnetic field measuring elements are respectively matched to output a first magnetic field signal, a second magnetic field signal, and a third magnetic field signal (S1, S2, S3). The amplitudes of the first, second, and third magnetic field signals are proportional to the magnetic field from the rotating object. The directions of the normal vectors of the first, second, and third magnetic field measuring elements (2a, 2b, 2c) are linearly independent of each other. The first magnetic field measuring element (2a) is a lateral Hall sensor, and the second and third magnetic field measuring elements (2b, 2c) are vertical Hall sensors. The normal vectors of the first, second, and third magnetic field measuring elements (2a, 2b, 2c) form a 90° angle with each other. The signal detection unit (3) is matched to determine the first difference signal (D1) and the second difference signal (D2). Wherein, the first difference signal (D1) is based on the difference between the magnetic field signal of the first magnetic field measuring element (2a) and the magnetic field signal of the second magnetic field measuring element (2b). The second difference signal (D2) is based on the difference between the magnetic field signal of the first magnetic field measuring element (2a) and the magnetic field signal of the third magnetic field measuring element (2c). The signal detection unit (3) further matches a combined signal (KS) to determine the magnetic field signal of the first magnetic field measuring element (2a) and the first difference signal (D1) and the second difference signal (D2). Analysis and processing unit (4), the analysis and processing unit is matched to generate an output signal (AS), the output signal containing the speed and direction of motion of the rotating object.

2. The magnetic field sensor (1) according to claim 1, wherein, It is equipped with an additional magnetic field measuring element.

3. The magnetic field sensor (1) according to claim 1 or 2, wherein, The chip (2) is matched for being arranged in a plane that is largely parallel to the tangential plane of the rotating object.

4. The magnetic field sensor (1) according to claim 3, wherein, The chip (2) is matched for being arranged in a plane parallel to the tangential plane of the rotating object.

5. The magnetic field sensor (1) according to any one of claims 1-2 and 4, wherein, A chip (2) having the first magnetic field measuring element, the second magnetic field measuring element and the third magnetic field measuring element (2a, 2b, 2c) is placed in a housing (5).

6. The magnetic field sensor (1) according to claim 5, wherein, The chip (2) can be secured by means of a bracket (6), and / or The internal space of the housing (5) is at least partially filled with plastic material, and / or A flux guide plate (8) is provided to minimize interference signals in the region of the chip (2).

7. The magnetic field sensor (1) according to any one of claims 1-2, 4, 6, wherein the magnetic field sensor further comprises a current interface or a voltage interface (7).

8. The magnetic field sensor (1) according to any one of claims 1-2, 4, and 6, wherein, The analysis and processing unit (4) is matched to perform temperature compensation on the measurement signals of the first magnetic field measuring element, the second magnetic field measuring element and the third magnetic field measuring element (2a, 2b, 2c).

9. A system comprising a magnetic field sensor (1) according to any one of the preceding claims and a magnetic pole rotor (20), the magnetic pole rotor having teeth (21) and notches (22), wherein, The magnetic pole rotor (20) is magnetically encoded.

10. A system comprising a magnetic field sensor (1) according to any one of claims 1 to 4 and a magnetic pole rotor (20), the magnetic pole rotor having teeth (21) and notches (22), wherein, The chip (2) of the magnetic field sensor (1) is magnetically preloaded.

11. The system according to claim 10, wherein, The magnetic field sensor (1) chip (2) is magnetically preloaded by setting a permanent magnet (2d) on the chip (2).

12. The system according to any one of claims 9 to 11, wherein, In addition, a separate differential element is provided, which is matched to determine the rotation direction of the magnetic pole rotor (20).

13. The system according to any one of claims 9 to 11, wherein, In addition, there are additional differential elements, which are matched to obtain and / or compensate for the external field.

14. A method for determining the rotational speed and direction of rotation of a rotating object using a magnetic field sensor (1) according to any one of claims 1 to 8, the method comprising the following steps: a) Detect the corresponding magnetic field signals of the first magnetic field measuring element (2a), the corresponding magnetic field signals of the second magnetic field measuring element (2b), and the corresponding magnetic field signals of the third magnetic field measuring element (2c) respectively (S1, S2, S3). b) Obtain the first difference signal (D1) from the difference between the magnetic field signal of the first magnetic field measuring element (2a) and the magnetic field signal (S1, S2) of the second magnetic field measuring element (2b). c) Obtain the second difference signal (D2) from the difference between the magnetic field signal of the first magnetic field measuring element (2a) and the magnetic field signal (S1, S3) of the third magnetic field measuring element (2c). d) Calculate the combined signal (KS) consisting of the magnetic field signal (S1) of the first magnetic field measuring element (2a), the first difference signal (D1), and the second difference signal (D2); e) Calculate and output an output signal (AS) that includes the speed and direction of motion of the rotating object.

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