Inductive position sensor

Abstract

The invention relates to an inductive position sensor comprising at least one transmitting coil, an absolute position receiving coil pair, a high-resolution position receiving coil pair and an electrically conductive moving target, wherein the absolute position receiving coil pair and the high-resolution receiving coil pair together define a measurement area of the inductive position sensor and in which the moving target can move, wherein the absolute position coil pair has a first sine receiving coil and a first cosine receiving coil, both having one period over the measurement area of the inductive position sensor; wherein the high-resolution position receiving coil pair has a second sine receiving coil and a second cosine receiving coil, both having at least two periods over the measurement area of the inductive position sensor; the absolute position receiving coil pair and the high-resolution position receiving coil pair are arranged in the same area of a printed circuit board of the inductive position sensor.

Description

TECHNICAL FIELD

[0001] The present invention relates to an inductive position sensor comprising at least one transmitter coil, an absolute position receiving coil pair, a high resolution position receiving coil pair, and an electrically conductive moving target. The present invention also relates to the use of such an inductive position sensor. BACKGROUND

[0002] Inductive position sensors are very popular because they are able to resist environmental influences. Especially for through shaft applications, inductive sensors are very attractive because the design flexibility of the coil design easily allows to adapt to e.g. on- and off-axis position sensing applications.

[0003] These benefits are a big advantage for many industrial or automotive applications. But for industrial or robotic applications, often a higher output resolution is required, which is not possible with only one absolute inductive position sensor. Also, some automotive applications require an absolute high resolution sensor, e.g. a steering sensor or a wheel hub traction motor sensor.

[0004] An inductive position sensor setup usually consists of a sensor printed circuit board (PCB) within a housing and an electrically conductive target moving into the proximity of the sensor.

[0005] The sensor PCB comprises a signal conditioning and processing unit, usually an application specific integrated circuit (ASIC), and a sensor coil system connected to the ASIC.

[0006] The sensor coil system consists of one or more transmitter coils and one or more receiver coils.

[0007] Usually, there is one transmitter coil and two receiver coils. The two receiver coils are arranged such that for each 360° mechanical rotation of the target of a rotary position sensor, one receiver coil produces a sine signal and the other receiver coil generates a cosine signal. This configuration provides the absolute position of the target (absolute embodiment). By increasing the number of receiver coil patterns and a suitable target configuration over 360°, the mechanical accuracy and resolution of the measurement per rotation can be improved by generating a number of signal repetitions equal to the number of physical repetitions of the sine and cosine signal repetitions (multi-cycle embodiment). In contrast, by using this approach, the absolute position of the target is lost.

[0008] Usually, a prior art sensor can be realized by using two separate absolute sensors and an incremental sensor and a separate target or by using two separate coil systems next to each other, but this implementation has a rather high space requirement.

[0009] Disadvantages of separate sensors are e.g.: thicker sensor, 2x PCB, 2x target, additional wiring to the evaluation unit (MCU) leads to higher costs. Disadvantages of separate coils next to each other are: size of the PCB (costs), limited opportunity to downsize. SUMMARY

[0010] It is therefore an object of the present application to provide an inductive position sensor which provides absolute and high resolution position data and requires minimal space on the printed circuit board.

[0011] According to the present application, this object is solved by an inductive position sensor comprising at least one transmitting coil, an absolute position receiving coil pair, a high resolution position receiving coil pair and a conductive moving target,

[0012] wherein the absolute position receiving coil pair and the high resolution receiving coil pair together define a measurement area of the inductive position sensor, and the moving target can move within the measurement area,

[0013] wherein the absolute position coil pair has a first sine receiving coil and a first cosine receiving coil, both having one period over the measurement area of the inductive position sensor,

[0014] wherein the high resolution position receiving coil pair has a second sine receiving coil and a second cosine receiving coil, both having at least two periods over the measurement area of the inductive position sensor,

[0015] characterized in that

[0016] the absolute position receiving coil pair and the high resolution position receiving coil pair are arranged within the same area of the printed circuit board of the inductive position sensor.

[0017] The present application describes a new approach to combine a lower resolution absolute sensor with a high resolution incremental sensor. Usually, it is only necessary to use an absolute inductive position sensor in combination with an incremental high resolution position sensor, but this approach requires a lot of space, which is often not available.

[0018] The present application is about an innovative embodiment which includes overlapping an absolute position sensor with a multi-period high resolution sensor to increase mechanical precision and resolution without losing the absolute position. Thus, a high precision, high resolution absolute sensor can be designed.

[0019] The new implementation according to the present application incorporates absolute and high resolution coils at the same PCB area.

[0020] The benefits are e.g.:

[0021] - Implemented in smaller space: 1 x PCB, 1 x target, evaluation unit can be located on same PCB, easier to physically downscale;

[0022] - Can be used for coaxial, through shaft and side shaft applications;

[0023] - Redundancy can be implemented;

[0024] - High robustness against environmental influences;

[0025] - Immunity against stray magnetic fields;

[0026] - Higher output resolution compared to absolute position sensors without high resolution coils.

[0027] According to one variant of the application, the inductive position sensor is a radial position sensor and the measurement region is a 360° circle.

[0028] According to one alternative variant of the application, the inductive sensor is a linear position sensor and the measurement region is a straight line.

[0029] In one preferred variant, the inductive position sensor comprises a signal processing unit for providing signals to the at least one transmitting coil and / or for processing signals of the absolute position receiving coil pair and the high resolution receiving coil pair. The signal processing unit is arranged on the same printed circuit board as the inductive position sensor or is externally connected to the printed circuit board of the inductive position sensor.

[0030] The sensor configuration can be used with different target configurations. The performance of the implementation is largely dependent on the target configuration.

[0031] In an advantageous variant of the application, the electrically conductive target comprises a plurality of segments spaced apart from each other. Preferably, the plurality of segments of the electrically conductive moving target have the same shape and / or pitch.

[0032] According to one preferred variant of the application, the moving target comprises at least one first target element and at least one second target element, wherein the shape of the at least one first target element is different from the shape of the at least one second target element. The at least one first target element and the at least one second target element are preferably arranged on a common substrate, e.g. a printed circuit board. For example, the first target element and / or the second target element comprise a plurality of segments.

[0033] In a particularly preferred variant of the radial inductive position sensor according to the application, the radial area covered by the at least one first target element, in particular the radial area of each segment of the at least one first target element, is constant in the radial direction, i.e. the width of each segment increases constantly from the center to the radial outside.

[0034] According to one variant of the application, the at least one first target element, in particular the plurality of segments of the at least one first target element, covers the entire measurement area of the inductive position sensor or the measurement area of the inductive position sensor which is not covered by the at least one second target element.

[0035] According to one variant of the application, the at least one second target element covers a portion of the measurement area of the inductive position sensor. Preferably, the at least one second target element has a semicircular, full-ring-shaped arc segment, a rectangular or arrowhead shape.

[0036] In a particularly preferred variant of the radial inductive position sensor according to the application, the radial area covered by the at least one second target element varies in the radial direction, i.e. the width of the at least one second target element is constant in the radial direction (rectangular) or varies at a different rate than the radial coverage area (arrowhead).

[0037] According to one variant of the application, the at least one first target element and the at least one second target element are arranged next to each other or at least partially overlap each other.

[0038] In another variant of the application, the at least one first target element and the at least one second target element completely overlap but have different sizes. In particular, one target element is larger than the other target element, such that the larger target element completely covers the smaller target element.

[0039] The application also relates to the use of an inductive position sensor according to the application together with another inductive position sensor according to the application or any other position sensor for calculating further output signals such as torque, diagnostic information or error compensation. BRIEF DESCRIPTION OF DRAWINGS

[0040] The application will be further explained below with reference to the embodiments shown in the drawings. The drawings show:

[0041] Figure 1 is a schematic view of a first embodiment of an inductive position sensor according to the application;

[0042] Figure 2 is a schematic view of a second embodiment of an inductive position sensor according to the application;

[0043] Figure 3 is a first embodiment of a conductive moving target;

[0044] Figure 4 is a second embodiment of a conductive moving target;

[0045] Figure 5 is a third embodiment of a conductive moving target;

[0046] Figure 6 is a fourth embodiment of an electrically conductive moving target;

[0047] Figure 7 is a fifth embodiment of an electrically conductive moving target;

[0048] Figure 8 is a sixth embodiment of an electrically conductive moving target;

[0049] Fig. 9 is a performance comparison of different embodiments of an electrically conductive moving target;

[0050] Figure 10 is an output of an inductive position sensor according to the present application after signal processing; and

[0051] Figure 11 is a schematic diagram of a third embodiment of an inductive position sensor according to the present application. DETAILED DESCRIPTION

[0052] Figure 1 A schematic diagram of a first embodiment of an inductive position sensor 1 according to the present application is shown. The inductive position sensor 1 comprises a transmitting coil 2, an absolute position receiving coil pair 3, 4, a high-resolution receiving coil pair 5, 6 and an electrically conductive moving target 7. The absolute position receiving coil pair 3, 4 and the high-resolution receiving coil pair 5, 6 together define a measurement region of the inductive position sensor 1 and the moving target 7 can move within the measurement region. Figure 1 The first embodiment shown refers to a radial inductive position sensor 1 and the measurement region is a 360° circle.

[0053] The absolute position coil pair 3, 4 has a first sine receiving coil 3 and a first cosine receiving coil 4, both 3, 4 having one period over the measurement region of the inductive position sensor 1.

[0054] The high-resolution position receiving coil pair 5, 6 has a second sine receiving coil 5 and a second cosine receiving coil 6, both 5, 6 having at least two periods over the measurement region of the inductive position sensor 1. According to the present application, the absolute position receiving coil pair 3, 4 and the high-resolution position receiving coil pair 5, 6 are arranged in the same area of a printed circuit board 8 of the inductive position sensor 1. Figure 1 According to the embodiment shown, the second sine receiving coil 5 and the second cosine receiving coil 6 each have 8 periods over the measurement region.

[0055] According to the present application, the absolute position receiving coil pair 3, 4 and the high-resolution position receiving coil pair 5, 6 are arranged in the same area of a printed circuit board 8 of the inductive position sensor 1.

[0056] Figure 1 The inductive position sensor 1 shown further comprises a signal processing unit 9 for providing a signal to the at least one transmitting coil 2 and for processing the signals of the absolute position receiving coil pair 3, 4 and the high-resolution receiving coil pair 5, 6. According to the present application, the signal processing unit 9 is arranged in the same area of the printed circuit board 8 of the inductive position sensor 1 as the absolute position receiving coil pair 3, 4 and the high-resolution position receiving coil pair 5, 6.Figure 1 In the illustrated embodiment, the signal processing unit 9 is externally connected to the printed circuit board 8 of the inductive position sensor 1. In an alternative embodiment of the invention, the signal processing unit 9 and the inductive position sensor 1 are arranged on the same printed circuit board 8. The connections between the signal processing unit 9 and the transmitting coil 2, the absolute position receiving coil pairs 3 and 4, and the high-resolution receiving coil pairs 5 and 6 are numbered the same as the corresponding coils.

[0057] In use Figure 1 During the operation of the inductive position sensor 1 shown, the signal processing unit 9 provides an excitation current to the transmitting coil 2, which creates an electromagnetic field. A conductive moving target 7 is located within the electromagnetic field created by the transmitting coil 2, and thus modifies the electromagnetic field due to the eddy currents induced in the conductive moving target 7. Absolute position receiving coil pairs 3 and 4 and high-resolution receiving coil pairs 5 and 6 can sense changes in the electromagnetic field caused by the conductive moving target 7 and its position. The signals from the absolute position receiving coil pairs 3 and 4 and the high-resolution receiving coil pairs 5 and 6 are used by the signal processing unit 9 to determine the absolute and high-resolution positions of the conductive moving target 7 within the measurement area.

[0058] Figure 2 A schematic diagram of a second embodiment of the inductive position sensor 1 according to the present invention is shown. Figure 2 The second embodiment shown is similar to Figure 1 The difference in the first embodiment shown is that the inductive position sensor includes two transmitting coils 2, and the second sine receiving coil 5 and the second cosine receiving coil 6 each have 32 cycles over the measurement area. Otherwise, the second embodiment corresponds to the first embodiment.

[0059] The high-resolution absolute sensor 1 is implemented with 32-cycle receiving coil pairs 5 and 6, absolute 1x360-degree receiving coil pairs 3 and 4, two separate transmitter coils 2, and a signal processing unit 9 with two inductive position sensor ICs (not shown) that acquire 12-bit signals. The theoretical resolution is 32x12 bits, or 131072 counts or 17 bits.

[0060] As is well known, sensor linearity decreases depending on system configuration and tolerance.

[0061] Figure 2 The implementation of a high-resolution absolute sensor 1 is shown, which has 32-cycle receiving coil pairs 5 and 6, 1x360 absolute receiving coil pairs 3 and 4, and a shared signal processing unit 9.

[0062] Typically, the target must be designed to generate signals for high-resolution receiving coil pairs 5 and 6 and absolute position receiving coil pairs 3 and 4. Accuracy and robustness within tolerance ranges will depend on the target configuration. Below are some implementation examples.

[0063] Figure 3 A first embodiment of the conductive moving target 7 is shown. The conductive moving target 7 includes a plurality of segments 12 spaced apart from each other. The plurality of segments 12 of the conductive moving target 7 have the same shape and spacing. One or more portions of the incremental n-cycle sensor target 7 are removed to generate sufficient signals on the absolute position receiving coil pair 3, 4 in 1 cycle.

[0064] Figure 4 A second embodiment of the conductive moving target 7 is shown. Figure 4 The upper and lower sides of a substrate are shown, one side including a first target element 10 and the other side including a second target element 11, wherein the shape of the first target element 10 differs from the shape of at least one second target element 11. Specifically, the first target element 10 includes a plurality of segments 12 spaced apart from each other. The plurality of segments 12 of the conductive moving target 7 have the same shape and spacing and cover the entire circumference of the circular substrate that constitutes the conductive moving target 7. Therefore, the plurality of segments 12 of the first target element 10 cover the entire measurement area of ​​the inductive position sensor 1. The second target element 11 has a semi-circular shape and is located above the semi-circle of the circular substrate of the conductive moving target 7. Figure 4 When both sides of the same substrate of the same conductive moving target 7 are shown, the first element 10 and the second element 11 of the conductive moving target 7 overlap each other. Therefore, Figure 4 High-resolution segment 12 is shown for n-cycle receiving coil pairs 5 and 6, and stacked target 11 for 1-cycle absolute position receiving coil pairs 3 and 4.

[0065] Figure 5 A third embodiment of the conductive moving target 7 is shown. Figure 5 The third embodiment of the conductive moving target 7 shown is similar to Figure 4 The difference in the second embodiment of the conductive moving target 7 is that the second element 11 has the shape of a full-circumference arc segment, and the second element 11 is arranged on the same side as the first element 10, which includes the segment 12. Furthermore, the first element 10 and the second element 11 of the conductive moving target 7 are arranged adjacent to each other; specifically, the second element 11 is arranged inside the first element 10, and the first element 10 and the second element 11 do not overlap.

[0066] Figure 6 A fourth embodiment of the conductive moving target 7 is shown. Figure 6 The fourth embodiment of the conductive moving target 7 shown is similar to Figure 5The third embodiment of the conductive moving target 7 shown differs in that the second element 11 has a rectangular shape and overlaps the first element 10. In particular, the first element 10 comprising the segments 12 overlaps the second element 11 completely if the gaps between the segments 12 are considered to belong to the first element 10.

[0067] Figure 7 A fifth embodiment of the conductive moving target 7 is shown. Figure 7 The fifth embodiment of the conductive moving target 7 shown differs from the fourth embodiment in that the second element 11 has a more pronounced arrow shape. Figure 6

[0068] Figure 8 A sixth embodiment of the conductive moving target 7 is shown, wherein the second element 11 has a more pronounced arrow shape than the fifth embodiment. Figure 7 The sixth embodiment of the conductive moving target 7 shown differs from the fifth embodiment in that the second element 11 has a more pronounced arrow shape.

[0069] Figure 9a and Figure 9b A comparison of the target configurations is shown for:

[0070] a) Figure 4 The second embodiment of the conductive moving target shown;

[0071] b)The third embodiment of the conductive moving target shown; Figure 5

[0072] c)The fourth embodiment of the conductive moving target shown; Figure 6

[0073] d)The fifth embodiment of the conductive moving target shown, and Figure 7

[0074] e)The sixth embodiment of the conductive moving target shown. Figure 8 The settings of the used comparison are:

[0075] • Speed 1000 rpm

[0076] • Nominal AG 1 mm…1.75 mm

[0077] • X / Y displacement + / - 0.3 mm

[0078] • Tilt + / - 0…0.5 mm

[0079] • Different targets were tested

[0080]

[0081] Figure 9a A performance comparison based on 32X coils is shown. Figure 9b ​​

[0082] There are different signal processing methods to calculate the absolute high resolution angle signal. One possible method is shown below.

[0083] Step 1: Calculate factor = (resolution / high resolution number of periods)

[0084] Step 2: Check actual period

[0085] Actual period = floor(absolute angle / factor)

[0086] Step 3: Calculate high resolution absolute angle

[0087] High resolution absolute = high resolution angle + actual period * resolution

[0088] Step 4: Check for reasonableness and correct period if necessary

[0089] If ((high resolution absolute - high resolution number of periods * low resolution angle)) > threshold -> output = high resolution absolute - resolution

[0090] If ((high resolution absolute - high resolution number of periods * low resolution angle)) < threshold -> output = high resolution absolute + resolution

[0091] Else output = high resolution absolute

[0092] Figure 10 A high resolution output after processing is shown, specifically a 32 period high resolution sensor and signal plots of the processed high resolution absolute sensor.

[0093] By implementing two or more high resolution absolute sensor sets on one PCB, a redundant solution can be generated to achieve higher diagnostic coverage.

[0094] By installing two high resolution absolute sensor sets on each side of a torsion bar, torque can be calculated as the difference between the two sensors.

[0095] Figure 11 A schematic diagram of a third embodiment of an inductive position sensor 1 according to the application is shown. Figure 11 The inductive position sensor 1 shown is a linear position sensor with a straight measurement region along which a conductive target 7 moves. In addition, Figure 11 The third embodiment of the inductive position sensor 1 shown corresponds to Figure 1 The first embodiment of the inductive position sensor 1 shown.

[0096] List of reference signs

[0097] 1 inductive position sensor

[0098] 2 Transmit coil

[0099] 3 Absolute position receiving coil (sine)

[0100] 4 Absolute position receiving coil (cosine)

[0101] 5 High-resolution position receiving coil (sine)

[0102] 6 High-resolution position receiving coil (cosine)

[0103] 7 Electrically conductive moving target

[0104] 8 Printed circuit board (sensor)

[0105] 9 Signal processing unit

[0106] 10 First target element

[0107] 11 Second target element

[0108] 12 Multiple segments (moving target / target element)

Claims

1. An inductive position sensor (1) comprising: at least one transmitting coil (2), an absolute position receiving coil pair (3, 4), a high-resolution position receiving coil pair (5, 6) and an electrically conductive moving target (7), wherein the absolute position receiving coil pair (3, 4) and the high-resolution receiving coil pair (5, 6) together define a measurement region of the inductive position sensor (1), and the moving target (7) is movable in the measurement region, wherein the absolute position coil pair (3, 4) has a first sine receiving coil (3) and a first cosine receiving coil (4), both (3, 4) having one period over the measurement region of the inductive position sensor (1), wherein the high-resolution position receiving coil pair (5, 6) has a second sine receiving coil (5) and a second cosine receiving coil (6), both (5, 6) having at least two periods over the measurement region of the inductive position sensor (1), characterized in that the absolute position receiving coil pair (3, 4) and the high-resolution position receiving coil pair (5, 6) are arranged within the same area of a printed circuit board (8) of the inductive position sensor (1), the electrically conductive moving target (7) comprises at least one first target element (10) and at least one second target element (11) having different sizes, wherein the shape of the at least one first target element (10) is different from the shape of the at least one second target element (11), the at least one first target element (10) covers the complete measurement region of the inductive position sensor (1) and the at least one second target element (11) covers a part of the measurement region of the inductive position sensor (1), the at least one first target element (10) and the at least one second target element (11) partially overlap each other.

2. Inductive position sensor (1) according to claim 1, wherein the inductive position sensor (1) is a radial position sensor and the measurement region is a 360° circle.

3. Inductive position sensor (1) according to claim 1, wherein the inductive position sensor (1) is a linear position sensor and the measurement region is a straight line.

4. Inductive position sensor (1) according to claim 1, further comprising a signal processing unit (9) for providing signals to the at least one transmitting coil (2) and / or for processing signals of the absolute position receiving coil pair (3, 4) and the high-resolution receiving coil pair (5, 6).

5. Inductive position sensor (1) according to claim 4, wherein the signal processing unit (9) is arranged on the same printed circuit board (8) as the inductive position sensor (1) or is externally connected to the printed circuit board (8) of the inductive position sensor (1).

6. Inductive position sensor (1) according to any one of claims 1 to 5, wherein the electrically conductive moving target (7) comprises a plurality of segments (12) spaced apart from each other.

7. Inductive position sensor (1) according to claim 6, wherein the plurality of segments (12) of the electrically conductive moving target (7) have the same shape and / or pitch.

8. Inductive position sensor (1) according to claim 1, wherein the at least one first target element (10) comprises a plurality of segments (12) spaced apart from each other.

9. Inductive position sensor (1) according to claim 1, wherein the at least one second target element (11) has a semi-circular, full-annular arc segment, a rectangular or arrowhead shape.

10. Use of an inductive position sensor, comprising: The use of an inductive position sensor (1) according to any one of claims 1 to 9 together with another inductive position sensor (1) according to any one of claims 1 to 9 or any other position sensor to calculate a further output signal.

11. Use of an inductive position sensor according to claim 10, wherein the further output signal comprises a torque, diagnostic information or an error compensation.

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