Measuring device
By introducing additional resistors and conversion units into the rotation angle measurement device, adjusting the signal of the magnetoresistive sensor unit, the problem of signal failure caused by staggering or twisting of the magnetoresistive sensor unit relative to the Weigen sensor is solved, and the effect of accurately determining the rotation direction at low consumption is achieved.
Patent Information
- Application Number
- CN202280101274.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-26
- Publication Date
- 2025-05-30
AI Technical Summary
In the rotation angle measuring device, the staggered or torsional arrangement of the magnetoresistive sensor unit relative to the Wiegand sensor causes the sensor signal to be almost zero in some cases and the rotation direction cannot be determined reliably, especially in extreme cases, the signal compresses, twists and moves, resulting in difficult to determine the rotation direction.
By introducing additional resistor and conversion units into the measuring device, the sensor signal of the magnetoresistive sensor unit is adjusted so that it always has a clear positive or negative sensor value in the case of voltage pulses of the Wiegand sensor, so that the direction of motion of the object can be determined reliably.
Reliable evaluation of sensor signals at low cost is achieved, ensuring accurate direction of rotation or translation of moving objects, avoiding the problem of signal failure in extreme cases.
Smart Images
Figure CN120077245A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a measuring device having: an object rotatable or translatable about a rotation axis; and a measuring system for detecting the movement of the object, the measuring system including an exciter unit that is torsionally connected to the object and has at least one permanent magnet exciter magnet; a Weigand sensor that interacts with the magnetic field of the exciter magnet; and a magnetoresistive sensor unit that interacts with the magnetic field of the exciter magnet and is arranged offset and / or torsionally relative to the Weigand sensor, wherein the magnetoresistive sensor unit has a voltage divider having a first terminal and a second terminal for feeding the voltage divider, at least one magnetoresistive element, and a measuring point. Background Art
[0002] Such a measuring device is used in the form of a rotational angle measuring device to detect the rotational movement of an object, i.e., a shaft rotating about a rotation axis, where the rotational angle measuring system is often also referred to as an angle measuring device, a rotational angle sensor, or a rotary encoder. Such a rotational angle measuring device is particularly used for controlling and monitoring electric motors, especially servo motors, in machines, installations, or vehicles. For example, such a rotational angle measuring device is disclosed in WO 2020 / 015834A1, where the rotational angle measuring device has a shaft rotating about a rotation axis, the shaft having four exciter magnets fastened thereto, a Weigand sensor, and another sensor for determining the rotation direction of the shaft. The exciter magnets are fastened to a plate-shaped carrier element fixedly connected to the rotating shaft and rotate along a circular track. The Weigand sensor and the other sensor are jointly arranged at a rigidly arranged carrier element. The other sensor is arranged offset relative to the Weigand sensor and is configured as a Hall sensor. DE 102012 008 888A1 also discloses a rotational angle measuring device having a Weigand sensor and another sensor, where the other sensor is configured as a magnetoresistive sensor. The rotational angle measuring device has a bipolar exciter magnet that is arranged at the end side of the rotating shaft and rotates together with the shaft about the rotation axis. In the embodiment of DE 10 2012008 888A1, the two sensors are arranged flush, i.e., not offset and not torsionally relative to each other.
[0003] During the operation of a rotational angle measuring device, voltage pulses of a Wiegand sensor and sensor signals of a magnetoresistive sensor unit are generally evaluated in a control unit. To determine the rotational direction of a rotating shaft, at rotational positions where voltage pulses of the Wiegand sensor with corresponding polarities are respectively realized, the sensor signals of the magnetoresistive sensor unit are compared with zero, that is, it is determined whether the sensor signals have negative sensor values or positive sensor values. For example, it can be defined that: when the voltage pulse of the Wiegand sensor has a positive polarity and the sensor value of the magnetoresistive sensor unit is positive, and when the voltage pulse of the Wiegand sensor has a negative polarity and the sensor value of the magnetoresistive sensor unit is negative, the shaft rotates in a first rotational direction, for example, clockwise. Otherwise, when there is a voltage pulse of the Wiegand sensor with a positive polarity and a negative sensor value of the magnetoresistive sensor unit, and when there is a voltage pulse of the Wiegand sensor with a negative polarity and a positive sensor value of the magnetoresistive sensor unit, the shaft rotates in a second rotational direction, that is, counterclockwise. In a measuring device for an object with translatory movement, the voltage pulses of the Wiegand sensor and the sensor signals of the magnetoresistive sensor unit are also evaluated in the control unit, and the movement direction of the object with translatory movement is determined by the principle described according to the rotating shaft.
[0004] In the case where the magnetoresistive sensor unit is arranged offset or twisted relative to the Wiegand sensor, the sensor signals of the magnetoresistive sensor unit are compressed, distorted, and / or shifted such that the following problem occurs: the sensor signals of the magnetoresistive sensor unit are almost zero in one direction or the rotational direction in the region of the voltage pulses of the Wiegand sensor. When this happens, it is no longer possible to reliably determine whether the sensor signals of the magnetoresistive sensor unit have negative sensor values or positive sensor values. In extreme cases, the sensor signals of the magnetoresistive sensor unit can be compressed, distorted, and / or shifted such that when the shaft rotates, two voltage pulses caused by the Wiegand sensor when rotating along different rotational directions exist in the same region with the same polarity, that is, both exist with the same polarity in the negative region or the positive region, and are only distinguished according to the rotational direction. Thus, the rotational direction of the rotating shaft can no longer be determined in the above-mentioned simple manner at the one position or at the multiple positions. Then, the rotational direction, that is, signal evaluation, can only be determined by means of significantly more costly methods. A corresponding problem also exists in the case of an object with translatory movement. Summary of the Invention
[0005] Therefore, the object of the present invention is to provide a measuring device having an offset and / or twisted arrangement of a magnetoresistive sensor unit relative to a Wiegand sensor, by means of which signal evaluation of the sensor can be achieved with relatively low cost.
[0006] This object is achieved by a measuring device having the features of claim 1.
[0007] The measuring device according to the invention comprises an exciter unit having at least one exciter magnet for generating an exciter magnetic field. In a measuring device configured as a rotational angle measuring device, a permanent-magnet exciter magnet is usually arranged at a rotatable shaft such that an alternating exciter magnetic field is generated by the rotational movement of the shaft. However, alternatively, the exciter magnet can also be arranged at an object movable translationally, for example, moving linearly back and forth. In any case, an alternating exciter magnetic field is generated by the movement of the permanent-magnet exciter magnet, i.e., an exciter magnetic field in which the polarity continuously reverses, i.e., the (effective) direction of the field lines changes continuously over time.
[0008] The measuring device according to the invention comprises a Weigand sensor which usually has a pulse line (also called a Weigand line) and a coil arrangement radially surrounding the pulse line. Once a specific trigger field strength is exceeded, the magnetization direction of the pulse line suddenly flips under the action of an external magnetic field. Here, the Weigand line maintains its magnetic polarity until a specific point and flips to the opposite polarity when subjected to a reversed external magnetic field. Thereby, a short voltage pulse with a defined electrical energy is generated in the coil arrangement.
[0009] Furthermore, the measuring device according to the invention comprises a magnetoresistive sensor unit, preferably a TMR sensor or a GMR sensor, and is used to continuously detect the magnetic field of the exciter magnet. The magnetoresistive sensor is based on the magnetoresistive effect, where the resistance of a material changes by applying an external magnetic field. The change in resistance is used to measure the external magnetic field.
[0010] The magnetoresistive sensor unit comprises a voltage divider having a first terminal and a second terminal for feeding the voltage divider, at least one magnetoresistive element, and a measurement point. The sensor signal is derived from the measured value at the measurement point.
[0011] According to the invention, an electrical additional resistance is electrically connected to the measurement point, where the additional resistance can be selectively electrically connected via a conversion unit to a third terminal having a third voltage level or to a fourth terminal having a fourth voltage level, and where the conversion unit is electrically connected to the Weigand sensor, and the voltage pulses of the Weigand sensor are evaluated and implemented such that the conversion between the third terminal and the fourth terminal is achieved according to the polarity of the voltage pulses of the Weigand sensor.
[0012] By means of an additional resistor, the sensor signal of the magnetoresistive sensor unit can be moved in a defined manner such that the sensor signal has either a positive or a negative sensor value in the case of a voltage pulse of the Wiegand sensor, so that the direction of an object, for example the direction of rotation of a shaft, can be determined reliably and with little effort. The additional resistor is a bipolar, passive electrical component and implements an ohmic resistance in electrical and electronic circuits.
[0013] By means of a switching unit, i.e. by selectively connecting the additional resistor to a third terminal or a fourth terminal, the curve of the sensor signal can be moved either in one direction or in the other direction. Preferably, the third terminal is electrically connected to the first terminal and the fourth terminal is electrically connected to the second terminal, so that a switching is achieved between the first terminal and the second terminal by means of the switching unit.
[0014] By manipulating the switching unit according to the polarity of the voltage pulse of the Wiegand sensor, it can be ensured that in the movement region, i.e. in the rotational angle region in which the voltage pulses of the Wiegand sensor are present with the same polarity in the case of rotation of the shaft, the sensor signals of the magnetoresistive sensor unit have opposite polarities to one another. Based on this, the direction of movement of the object can be determined, since the voltage pulses of the Wiegand sensor with the same polarity can be distinguished from one another.
[0015] In a preferred embodiment, a first voltage divider and a second voltage divider are provided, which together form a bridge circuit having two bridge legs connected in parallel, where each bridge leg has two magnetoresistive elements connected in series and a measuring point arranged between the two magnetoresistive elements, and one of the two measuring points is electrically connected to the additional resistor. The sensor signal is derived from the calculation of the measured values at the two measuring points. In this case, the measurement signal is, for example, fed to a comparator and the sensor signal is calculated.
[0016] Alternatively, only a single voltage divider is provided, which has a magnetoresistive element and a resistor with a fixed resistance value, where the magnetoresistive element and the resistor are connected in series. The measuring point is arranged between the magnetoresistive element and the resistor.
[0017] In a preferred embodiment, the voltage pulses caused by the Wiegand sensor at a first position along a first direction of a rotating or translating object and the voltage pulses caused by the Wiegand sensor at a second position along a second direction opposite to the first direction of the rotating or translating object have the same polarity, where the sensor signal of the magnetoresistive sensor unit has a negative value at the first position and a positive value at the second position. In this case, for example, a comparator electrically connected to the two measuring points of the bridge circuit outputs the sensor signal of the magnetoresistive sensor unit, where it is evaluated whether the sensor signal has a positive or a negative sensor value.
[0018] Alternatively, the voltage pulses induced in the first direction of the object moving in a rotational or translational motion by the Wiegand sensor at the first position and the voltage pulses induced in the second direction opposite to the first direction of the object moving in a rotational or translational motion by the Wiegand sensor at the second position have the same polarity, where at the first position, the measured value at the measurement point is greater than a predefined voltage value, and at the second position, the measured value at the measurement point is less than the predefined voltage value. The predefined voltage value is, for example, 50% of the supply voltage present at the first terminal. In this case, only the value at the measurement point is compared with the predefined voltage value. Contrary to the first variant, instead of observing the sensor signal, the value at the measurement point of the voltage divider is observed.
[0019] These two alternatives are used to distinguish the direction in the case where the voltage pulses of the Wiegand sensor have the same polarity. On the one hand, the sensor signal of the magnetoresistive sensor unit is compared with zero, that is, it is determined whether the sensor signal has a negative sensor value or a positive sensor value. On the other hand, the measured value at the measurement point is compared with a predefined voltage value. In both cases, defined and different values are obtained according to the direction of the object moving in a rotational or translational motion in the case where multiple voltage pulses of the Wiegand sensor have the same polarity. Description of the Drawings
[0020] The measuring device will be described below with reference to the drawings, where
[0021] Figure 1 An embodiment of the measuring device according to the invention is shown in cross-section,
[0022] Figure 2 showing Figure 1 a schematic diagram of the bridge circuit and the conversion unit of the measuring device in
[0023] Figure 3 showing Figure 1 the curve of the sensor signals of the Wiegand sensor and the magnetoresistive sensor unit of the measuring device in
[0024] Figure 4 showing Figure 1 a schematic diagram of the voltage divider and the conversion unit of the measuring device in Detailed Description of the Invention
[0025] Figure 1The measuring device 8 configured as a rotational angle measuring device is shown. The measuring device has a shaft 12 forming the object of rotation and a measuring system 10 configured as a rotational angle measuring system for detecting the rotational movement of the shaft 12. The shaft 12 is a hollow shaft in the present embodiment, which extends substantially in the axial direction and is driven by a drive motor 14 having a static motor housing 16. The measuring system 10 includes a rotor unit 18, a stator unit 20, and a magnetic shielding device 22.
[0026] The rotor unit 18 has a rotor printed circuit board 24, which radially surrounds the shaft 12 and is directly fastened to the shaft 12. Thus, the rotor unit 18 is torsionally connected to the shaft 12. On the rotor printed circuit board 24, an exciter unit 25 is provided, which has four exciter magnets 26 evenly distributed along the circumference of the rotor printed circuit board 24. The exciter magnets rotate along a circular track when the shaft 12 rotates. Only two of the four exciter magnets are shown in Figure 1 this figure.
[0027] The stator unit 20 has a stator printed circuit board 32, which radially surrounds the shaft 12. On the stator printed circuit board 32, a sensor device 34 is provided, which has a Weigand sensor 36, an integrated circuit with an evaluation unit, and a magnetoresistive sensor unit 40. The integrated circuit also includes a control logic and an energy management device not shown in detail. The control logic and the energy management device enable the energy-autonomous operation of the sensor device 34 via the electrical energy obtained by the Weigand sensor 36. In addition, the evaluation unit is connected in terms of signal technology to a non-volatile data memory not shown in detail, and the evaluation unit stores and reads the rotation-count values in the data memory.
[0028] The sensor device 34 is radially positioned such that the Weigand sensor 36 and the magnetoresistive sensor unit 40 detect the magnetic field of the exciter magnet 26 when the shaft 12 rotates. The exciter magnet rotates with the shaft 12 and thus passes by the Weigand sensor 36 and the magnetoresistive sensor unit 40.
[0029] The Weigand sensor 36 has a Weigand wire 42 and a coil device 44 that radially surrounds the Weigand wire. Once a specific trigger field strength is exceeded, the magnetization direction of the Weigand wire 42 suddenly flips under the action of an external magnetic field. Here, the Weigand wire 42 maintains its magnetic polarity until a specific point and flips to the opposite polarity when subjected to a reversed external magnetic field. Thereby, a short voltage pulse with a defined electrical energy is generated in the coil device 44. The polarity of the voltage pulse of the coil device 44 is related to the direction to which the Weigand wire 42 flips.
[0030] The magnetoresistive sensor unit 40 is arranged offset in the circumferential direction so as to be arranged in correspondence with the angular offset torsionally with respect to the Wiegand sensor 36 and is based on the magnetoresistive effect, wherein the resistance of the material is changed by applying an external magnetic field. The change in resistance is used to measure the external magnetic field. As shown in Figure 2 As shown, the magnetoresistive sensor unit 40 includes two voltage dividers 46, 48 forming a bridge circuit 50, a first terminal 52 and a second terminal 54, a supply voltage being applied to the first terminal and being grounded at the second terminal for feeding the bridge circuit 50. The bridge circuit 50 includes two bridge branches 56, 58 connected in parallel, each of the bridge branches 56, 58 having two magnetoresistive elements 60, 62, 64, 66 connected in series and measurement points 70, 72 respectively arranged between the two magnetoresistive elements 60, 62, 64, 66. The measurement points 70, 72 are electrically connected to a comparator, wherein the measured values of the two measurement points 70, 72 are calculated as the sensor signal of the magnetoresistive sensor unit.
[0031] According to the invention, an additional resistor 82 is electrically connected to one of the two measurement points 70. In addition, the additional resistor 82 is electrically connected to a conversion unit 84 by means of which the additional resistor 82 can be selectively electrically connected to a third terminal 86 or a fourth terminal 88. In the present case, the third terminal 86 is electrically connected to the first terminal 52, while the fourth terminal 88 is electrically connected to the second terminal 54, such that there is a supply voltage at the third terminal 86 and a ground at the fourth terminal 88. Thereby, the additional resistor 82 is either connected in parallel to one magnetoresistive element 60 of the first bridge branch 56 or connected in parallel to the other magnetoresistive element 62 of the first bridge branch 56. The conversion unit 84 is electrically connected to the Wiegand sensor 36, wherein the conversion of the conversion unit 84 is effected in accordance with the polarity of the voltage pulses of the coil device 44.
[0032] In Figure 3 a diagram showing a plurality of plotted curves of the sensor signal of the magnetoresistive sensor unit 40 and a diagram showing a plotted curve of the voltage pulses of the Wiegand sensor 36 are shown. The solid line shows the curve of the sensor signal of the magnetoresistive sensor unit 40 without the additional resistor 82. The dash-dotted line shows the curve of the sensor signal of the magnetoresistive sensor unit 40 in the case of a parallel circuit of the additional resistor 82 with the magnetoresistive element 60, i.e. when the additional resistor 82 is connected to the first terminal 52. The dashed line shows the curve of the sensor signal of the magnetoresistive sensor unit 40 in the case of a parallel circuit of the additional resistor 82 with the magnetoresistive element 62, i.e. when the additional resistor 82 is connected to the second terminal 54.
[0033] As already explained above, when the additional resistor 82 is connected to the second terminal 54, i.e., in the case of the positive polarity of the voltage pulse of the Wiegand sensor 36, the initial sensor signal, i.e., observed in the Y direction without the additional resistor 82, moves downward, and the sensor value of the sensor signal at the rotational position of the corresponding voltage pulse of the Wiegand sensor 36 is evaluated according to the downward moving dashed line. In contrast, when the additional resistor 82 is connected to the first terminal 52, i.e., in the case of the negative polarity of the voltage pulse of the Wiegand sensor 36, the initial sensor signal moves upward when observed in the Y direction, and the sensor value of the sensor signal at the rotational position of the corresponding voltage pulse of the Wiegand sensor 36 is evaluated according to the upward moving dash-dotted line.
[0034] With this design, there is a one-to-one correlation of the rotational direction in each case of the voltage pulse, where when rotating in the first rotational direction, there is a positive sensor value of the sensor signal when the voltage pulse has a positive polarity, and there is a negative sensor value of the sensor signal when the voltage pulse has a negative polarity. In contrast, when rotating in the second rotational direction opposite to the first rotational direction, there is a negative sensor value of the sensor signal when the voltage pulse has a positive polarity, and there is a positive sensor value of the sensor signal when the voltage pulse has a negative polarity. Thus, the rotational direction of the shaft can be determined in each case of the voltage pulse of the Wiegand sensor.
[0035] In Figure 4 In another embodiment shown in, the magnetoresistive sensor unit 40 only includes a voltage divider 46, which has a single magnetoresistive element 60 and a resistor 90 with a fixed resistance value. The magnetoresistive element 60 and the resistor 90 are connected in series, and a measurement point 70 is provided therebetween. The measurement point 70 is electrically connected to the additional resistor 82. As in the embodiment described above, the additional resistor 82 is electrically connected to the conversion unit 84. To determine the rotational direction, the measured value at the measurement point 70 is compared with a predefined voltage value Vref, and the rotational direction is inferred based on whether the measured value is greater than or less than the predefined voltage value Vref. In the same way, in the embodiment regarding Figure 2 , it is also possible to compare the measured value at one of the two measurement points 70, 72 with the predefined voltage value Vref instead of comparing the two measurement points 70, 72, and thereby infer the rotational direction of the shaft 12.
Claims
1. A measuring device, the measuring device having: an object (12) rotatable or translatable about a rotational axis and a measuring system (10) for detecting the movement of the object, the measuring system (10) comprising: an exciter unit (25), the exciter unit being torsionally connected to the object (12) and having at least one permanent magnetic exciter magnet (26), a Wiedemann sensor (36), the Wiedemann sensor interacting with the magnetic field of the exciter magnet (26), a magnetoresistive sensor unit (40), the magnetoresistive sensor unit interacting with the magnetic field of the exciter magnet (26) and being arranged offset and / or torsionally relative to the Wiedemann sensor (36), wherein the magnetoresistive sensor unit (40) has at least one voltage divider (46, 48), the voltage divider having a first terminal (52) and a second terminal (54) for feeding the voltage divider (46, 48, 90), at least one magnetoresistive element (60, 62, 64, 66) and measuring points (70, 72), characterized in that an additional resistor (82) is electrically connected to the measuring points (70, 72), wherein the additional resistor (82) can be selectively electrically connected to a third terminal (86) or to a fourth terminal (88) via a switching unit (84), and wherein the switching unit (84) is electrically connected to the Wiedemann sensor (36), the voltage pulses of the Wiedemann sensor (36) being evaluated and implemented such that the switching between the third terminal (86) and the fourth terminal (88) is effected in accordance with the polarity of the voltage pulses of the Wiedemann sensor (36).
2. The measuring device according to claim 1, wherein the third terminal (86) is electrically connected to the first terminal (52), and the fourth terminal (88) is electrically connected to the second terminal (54).
3. The measuring device according to claim 1 or 2, wherein a first voltage divider (46) and a second voltage divider (48) are provided, the first voltage divider and the second voltage divider together forming a bridge circuit (50) having two bridge branches (56, 58) connected in parallel, wherein each bridge branch (56, 58) has two magnetoresistive elements (60, 62, 64, 66) connected in series and a measuring point (70, 72) arranged between the two magnetoresistive elements (60, 62, 64, 66), and wherein one of the two measuring points (70, 72) is electrically connected to the additional resistor (82).
4. The measuring device according to claim 1 or 2, wherein the voltage divider (46) has the magnetoresistive element (60) and a resistor (90) with a fixed resistance value, the magnetoresistive element and the resistor being connected in series, and wherein a measuring point is arranged between the magnetoresistive element (60) and the resistor (90).
5. The measuring device according to any one of the above claims, wherein The voltage pulses induced in the first direction of the object (12) moving in a rotational or translational motion by the Wiegand sensor (36) at the first position and the voltage pulses induced in the second direction of the object (12) moving in a rotational or translational motion by the Wiegand sensor (36) at the second position, which is opposite to the first direction, have the same polarity, wherein the sensor signal of the magnetoresistive sensor unit (40) has a negative value at the first position and a positive value at the second position.
6. The measuring device according to any one of claims 1 to 4, wherein The voltage pulses induced in the first direction of the object (12) moving in a rotational or translational motion by the Wiegand sensor (36) at the first position and the voltage pulses induced in the second direction of the object (12) moving in a rotational or translational motion by the Wiegand sensor (36) at the second position, which is opposite to the first direction, have the same polarity, wherein at the first position, the measured value of the measurement point (70) is greater than a predefined voltage value (Vref), and at the second position, the measured value of the measurement point (70) is less than the predefined voltage value (Vref).
7. The measuring device according to any one of the above claims, wherein the magnetoresistive sensor unit (40) is a TMR sensor or a GMR sensor.
Citation Information
Patent Citations
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