Inductance type linear displacement sensor coil
The electrically induced eddy current linear displacement sensor uses uniformly spaced excitation coils and phased reception coils to address non-linear errors, simplifying design and maintaining compactness while ensuring uniform signal reception.
Patent Information
- Application Number
- CN202510517032.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-15
AI Technical Summary
In the existing eddy current linear displacement sensor, the nonlinear error between the excitation coil and the receiving coil leads to an increase in signal error, and the existing compensation methods require complex theoretical calculations and long design cycles.
Multiple groups of excitation sub-coils with the same specification are arranged in parallel along the measured stroke direction. The receiving sub-coil is in a standard sine or cosine shape and is distributed with a preset phase difference. The excitation sub-coil and the receiving sub-coil are non-contact crossed in space, and the excitation current magnitude, phase and frequency are consistent to ensure that the magnetic field and eddy current changes are uniform.
The receiving coil design is simplified, the development cycle is shortened, the product structure is compact, nonlinear compensation is avoided, and signal uniformity and detection sensitivity are improved.
Smart Images
Figure CN120313461A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of sensors, and particularly to an inductive linear displacement sensor coil. Background Art
[0002] According to Faraday's electromagnetic induction principle, when a bulk metal conductor is placed in a changing magnetic field or moves in a magnetic field to cut magnetic force lines, eddy currents in the form of vortices will be generated in the conductor. This current is called eddy current, and the above phenomenon is called the eddy current effect. A sensor made based on the eddy current effect is called an eddy current sensor, also known as an inductive linear displacement sensor.
[0003] The coil structure in the existing eddy current linear displacement sensor is as Figure 1 shown. Its structure and working principle are as follows: Structurally, it consists of an excitation coil 100 printed on a PCB, multiple receiving coils 200, and an additional conductive moving slider 300. The excitation coil 100 generates a high-frequency alternating magnetic field under the excitation of a circuit. This magnetic field generates eddy currents on the moving slider. The moving slider 300 reflects the magnetic field generated by the eddy currents to the multiple receiving coils 200. The multiple receiving coils 200 receive the magnetic field reflected by the moving slider 400 and generate a set of alternating voltage signals. Then, the processor converts this alternating voltage signal into a position signal corresponding to the moving slider 300. In the existing eddy current linear displacement sensor, the winding structure of the excitation coil 100 is as Figure 2 、 Figure 3 and Figure 4 shown: The excitation coil 100 winds back and forth around the outside of the multiple receiving coils 200 for one week. That is to say, multiple turns of the excitation coil 100 are connected in series. All turns of the excitation coil 100 are outside the periphery of all receiving coils 200. The excitation coil 100 and the receiving coils 200 do not cross in the plane of the receiving coils. Multiple turns of series winding can achieve a higher magnetic flux, increase the signal amplitude of the receiving coil 200, and improve the signal-to-noise ratio. The receiving coils 200 are generally designed in an approximate sine or cosine curve shape. Some receiving coils are designed in 2 groups, as Figure 2 、 Figure 4 shown, and some are designed in 3 groups, as Figure 3 shown. However, as Figure 5 shown, the magnetic flux density of the excitation coil 100 in the existing eddy current linear displacement sensor at the left and right extreme positions is larger than that at other positions. This leads to an increase in the non-linear error of the signals at both ends of the receiving coil 200 and an increase in the displacement signal error.
[0004] To solve the problem of "increasing non - linear error", one approach is to generate a uniform magnetic field along the entire length of the internal receiving coil 200, so as to obtain a relatively perfect sine - cosine output signal. The means to achieve this is to keep the excitation coil 100 as far away from the receiving coil 200 as possible. However, this will result in a smaller total measurement stroke, or in order to meet the measurement stroke, the overall length of the product is increased, the cost increases accordingly, and the overall structure becomes larger. Additionally, to solve the problem of "increasing non - linear error" without changing the overall size of the product, a more general approach is as Figure 6 、 Figure 7 and Figure 8 shown: This problem is solved by changing the shapes of the left and right ends of the receiving coil 200. As Figure 6 shown, the two ends of the receiving coil 200 are symmetrically designed, and the enclosed area is smaller compared to the middle. At the same time, the tail shape is also specially designed according to the non - linear problem for error compensation. Figure 7 and Figure 8 are two other methods to solve the problem. Non - linear compensation is done at both ends of the receiving coil 200 respectively. Among them, Figure 8 puts all the non - linear compensation at the left end. That is to say, the receiving coil 200 is not in a standard sine - cosine shape, and non - linear compensation is required at both ends of the receiving coil 200. For the above - mentioned compensation methods, non - linear analysis and theoretical calculations need to be carried out on the shapes of the excitation coil 100 and the receiving coil 200, and corresponding compensation is finally carried out. Finally, iterative optimization design also needs to be carried out according to the simulation results. This design method requires strong theoretical calculation ability and simulation ability, and the corresponding design cycle becomes very long. Summary of the Invention
[0005] The present invention provides an inductive linear displacement sensor coil to solve at least one of the above - mentioned technical problems.
[0006] The technical solution of the present invention to solve the above - mentioned technical problems is as follows: An inductive linear displacement sensor coil includes:
[0007] An excitation coil, including multiple groups of excitation sub - coils with the same specifications, and the multiple groups of excitation sub - coils are arranged in parallel alignment at equal intervals along the measurement stroke direction;
[0008] A receiving coil, including multiple groups of receiving sub - coils with a standard sine shape or a standard cosine shape. The multiple groups of receiving sub - coils are arranged within the excitation range of the excitation coil with a preset phase difference, and each group of receiving sub - coils is symmetrically distributed both in the measurement stroke direction and in the direction perpendicular to the measurement stroke direction. Each group of receiving sub - coils is non - contact and cross - arranged with the multiple groups of excitation sub - coils in space.
[0009] Based on the above - mentioned technical solution, the present invention can also be improved as follows.
[0010] Furthermore, when powered on, the magnitudes, phases, and frequencies of the exciting currents in each group of exciting sub-coils are the same.
[0011] Furthermore, the exciting sub-coil has a rectangular structure, and the wide side of the exciting sub-coil is located in the measurement stroke direction; the specifications include the width and length of the exciting sub-coil.
[0012] Furthermore, the spacing is less than the width of the exciting sub-coil.
[0013] Furthermore, the spacing satisfies that when all the exciting sub-coils are powered on, the eddy current change information received by the receiving coil is uniform everywhere in the measurement stroke direction.
[0014] Furthermore, the exciting sub-coil is a single-turn coil or a multi-turn coil connected in series; and / or, the receiving sub-coil is a single-turn coil or a multi-turn coil connected in series.
[0015] Furthermore, the exciting sub-coils are printed on a printed circuit board to form an exciting circuit board; when the exciting sub-coil is a multi-turn coil connected in series, the exciting circuit board has multiple layers, and the exciting sub-coils printed at the same positions on each layer are connected in series.
[0016] Furthermore, the receiving sub-coils are printed on a printed circuit board to form a receiving circuit board; when the receiving sub-coil is a multi-turn coil connected in series, the receiving circuit board has multiple layers, and the receiving sub-coils printed at the same positions on each layer are connected in series.
[0017] Furthermore, the receiving sub-coil includes a positive receiving sub-coil and a negative receiving sub-coil, the positive receiving sub-coil and the negative receiving sub-coil are connected in series, and are symmetrically distributed in the direction perpendicular to the measurement stroke direction.
[0018] Furthermore, the number of groups of the receiving sub-coils is two or three; when the number of groups of the receiving sub-coils is two, the two groups of receiving sub-coils are arranged within the excitation range of the exciting coil with a 90° phase difference; when the number of groups of the receiving sub-coils is three, the three groups of receiving sub-coils are arranged within the excitation range of the exciting coil with a 120° phase difference.
[0019] The beneficial effects of the present invention are as follows: In a coil of an inductive linear displacement sensor according to the present invention, the exciting coil is composed of multiple groups of exciting sub-coils arranged in parallel alignment at equal intervals along the measurement stroke direction. Therefore, the radial width of the exciting coil is fixed and will not gradually increase. Moreover, the specifications of the multiple groups of exciting sub-coils are the same. After an alternating current is applied to the exciting coil, the magnetic field generated in the measurement stroke direction of the exciting coil is uniform everywhere, so there is no phenomenon that the magnetic field at both ends is stronger than that in the middle. The multiple groups of receiving sub-coils are arranged within the excitation range of the exciting coil with a preset phase difference, and each group of receiving sub-coils is symmetrically distributed both in the measurement stroke direction and perpendicular to the measurement stroke direction. Each group of receiving sub-coils is non-contact and cross-shaped with the multiple groups of exciting sub-coils in space. Therefore, the eddy current change information received by the receiving sub-coils is uniform everywhere in the measurement stroke direction. Furthermore, there is no need to perform non-linear compensation on the receiving sub-coils, which greatly simplifies the design of the receiving coil and shortens the product development cycle. Moreover, the total length of the exciting coil is the same as the length of the receiving coil, which makes the product structure more compact. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 FIG. 6 is a schematic structural principle diagram of a coil of an existing eddy current linear displacement sensor;
[0021] Figure 2 FIG. 10 is a schematic diagram of the first winding structure of a coil of an existing eddy current linear displacement sensor;
[0022] Figure 3 FIG. 14 is a schematic diagram of the second winding structure of a coil of an existing eddy current linear displacement sensor;
[0023] Figure 4 FIG. 18 is a schematic diagram of the third winding structure of a coil of an existing eddy current linear displacement sensor;
[0024] Figure 5 FIG. 22 is a schematic diagram of the magnetic flux density distribution in a coil of an existing eddy current linear displacement sensor;
[0025] Figure 6 FIG. 26 is a schematic diagram of the first compensation structure of the receiving coil in a coil of an existing eddy current linear displacement sensor;
[0026] Figure 7 FIG. 30 is a schematic diagram of the second compensation structure of the receiving coil in a coil of an existing eddy current linear displacement sensor;
[0027] Figure 8 FIG. 34 is a schematic diagram of the third compensation structure of the receiving coil in a coil of an existing eddy current linear displacement sensor;
[0028] Figure 9 FIG. 38 is a schematic diagram of the structure of a coil of an inductive linear displacement sensor according to the present invention;
[0029] Figure 10 This is a schematic diagram of the distribution of the exciting coil in the coil of an inductive linear displacement sensor according to the present invention. Specific embodiments
[0030] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0031] As Figure 9 shown, an inductive linear displacement sensor coil includes:
[0032] The exciting coil includes multiple groups of exciting sub-coils 1 with the same specifications. The multiple groups of exciting sub-coils 1 are arranged in parallel and aligned at equal intervals h along the measurement stroke direction (i.e., the X-axis direction);
[0033] The receiving coil includes multiple groups of receiving sub-coils 2 in the shape of a standard sine shape or a standard cosine shape. The multiple groups of receiving sub-coils 2 are arranged within the excitation range of the exciting coil with a preset phase difference, and each group of receiving sub-coils 2 is symmetrically distributed both in the measurement stroke direction and perpendicular to the measurement stroke direction (i.e., the Y-axis direction). Each group of receiving sub-coils 2 is non-contact and cross-shaped with the multiple groups of exciting sub-coils 1 in space.
[0034] In this embodiment, the exciting sub-coil 1 is of a rectangular structure, and the wide side of the exciting sub-coil 1 is located in the measurement stroke direction; the specifications include the width S and length L of the exciting sub-coil 1. There are two groups of receiving sub-coils 2, namely the first group of receiving sub-coils 21 and the second group of receiving sub-coils 22. The first receiving sub-coil 21 is in a standard sine shape, and the second receiving sub-coil 22 is in a standard cosine shape. The first group of receiving sub-coils 21 and the second group of receiving sub-coils 22 are arranged within the excitation range of the exciting coil with a 90° phase difference; in addition, the first group of receiving sub-coils 21 includes a first positive receiving sub-coil 211 and a first negative receiving sub-coil 212. The first positive receiving sub-coil 211 and the first negative receiving sub-coil 212 are connected in series and are symmetrically distributed perpendicular to the measurement stroke direction; the second group of receiving sub-coils 22 includes a second positive receiving sub-coil 221 and a second negative receiving sub-coil 222. The second positive receiving sub-coil 221 and the second negative receiving sub-coil 222 are connected in series and are symmetrically distributed perpendicular to the measurement stroke direction. The positive receiving sub-coil and the negative receiving sub-coil are connected in series to increase the output signal of the sensor.
[0035] In other embodiments, the number of groups of the receiving sub-coils 2 may also be three; when the number of groups of the receiving sub-coils 2 is three, the three groups of receiving sub-coils 2 are arranged within the excitation range of the excitation coil with a 120° phase difference. When the number of groups of the receiving sub-coils 2 is three, each group of receiving sub-coils 2 may also be composed of a series-connected forward receiving sub-coil and a negative receiving sub-coil.
[0036] In this embodiment, specifically:
[0037] The excitation range of the excitation coil is a rectangular area with a length of D and a width of L formed by all the excitation sub-coils 1. Each group of receiving sub-coils is symmetrically distributed in the horizontal direction (i.e., the X direction) of the excitation coil, and the length of the receiving sub-coil (referring to the overall distribution length of the receiving sub-coil in the X-axis direction, not the wire length of the receiving sub-coil) is less than or equal to the length D of the excitation coil. In the vertical direction (i.e., the Y-axis direction), each group of receiving sub-coils is also symmetrically distributed with respect to the excitation coil, and the height of the detection coil (referring to the overall distribution width of the receiving sub-coil in the Y-axis direction) is less than or equal to the height L of the excitation coil. When energized, the magnitudes, phases, and frequencies of the excitation currents in each group of excitation sub-coils 1 are the same. For multiple groups of excitation sub-coils 1 connected in parallel, their excitation currents need to meet the following two requirements to generate the above-mentioned horizontally uniform magnetic field. The first requirement is that the magnitudes of the excitation currents inside these excitation sub-coils 1 are the same. The second requirement is that the phases of the excitation currents inside these excitation sub-coils 1 are the same. The first requirement can be achieved through the structural form of the excitation sub-coils 1, that is, the length and width of each group of excitation sub-coils 1 are the same, including the wire diameter being the same, so that the resistance values of each group of excitation sub-coils 1 are equal. Through the circuit, the voltages across each group of excitation sub-coils 1 are equal, so the currents flowing through them are equal. The second requirement is achieved through the circuit to make the currents flowing through each group of excitation sub-coils 1 at the same moment. In this way, the magnetic fields generated by each group of excitation sub-coils 1 are uniform throughout the measurement stroke.
[0038] Figure 10 FIG. is a schematic diagram of the distribution of multiple groups of excitation sub-coils in the excitation coil. The excitation coil is composed of multiple groups of excitation sub-coils with the same shape connected in parallel. The solid-circle ports of all the excitation sub-coils are connected together, and the hollow-circle ports of all the excitation sub-coils are connected together. The excitation signal is input through the pads at the solid circle and the hollow circle. After an alternating current is applied to the excitation coil, the magnetic fields generated by each group of excitation sub-coils in the horizontal direction are uniform everywhere.
[0039] The spacing h is less than the width S of the excitation sub-coil to ensure that the magnetic fields generated by each group of excitation sub-coils 1 are consistent in the horizontal direction.
[0040] The spacing h satisfies that when all the exciting sub-coils 1 are energized, the eddy current change information received by the receiving coil is uniform everywhere in the measurement travel direction X. Therefore, when designing the spacing h, it can be adjusted according to the eddy current change information received by the receiving coil, and the spacing when the eddy current change information received by the receiving coil is uniform everywhere in the measurement travel direction X is the final spacing.
[0041] The exciting sub-coil 1 is a single-turn coil or a multi-turn coil connected in series; and / or, the receiving sub-coil 2 is a single-turn coil or a multi-turn coil connected in series. Using a multi-turn coil connected in series for the exciting sub-coil 1 can increase the eddy current density per unit detection area, thereby improving the detection sensitivity. Using a multi-turn coil connected in series for the receiving sub-coil with the same induced voltage direction can also improve the detection sensitivity of the sensor.
[0042] The exciting sub-coil 1 is printed on a printed circuit board to form an exciting circuit board; when the exciting sub-coil 1 is a multi-turn coil connected in series, the exciting circuit board has multiple layers, and the exciting sub-coils 1 printed at the same positions on each layer are connected in series. The receiving sub-coil 2 is printed on a printed circuit board to form a receiving circuit board; when the receiving sub-coil 2 is a multi-turn coil connected in series, the receiving circuit board has multiple layers, and the receiving sub-coils 2 printed at the same positions on each layer are connected in series. In addition, the printed circuit board can be a planar printed circuit board or a flexible printed circuit board.
[0043] For example: exciting sub-coils with corresponding positions and the same shape can be arranged on multiple board layers of the printed circuit board, and the exciting sub-coils at the same position on different layers are connected in series, which can increase the eddy current density per unit detection area, thereby improving the detection sensitivity. The receiving sub-coil can also be arranged in the form of receiving sub-coils with corresponding positions and the same shape on multiple board layers of the same printed circuit board, and the receiving sub-coils on different board layers are connected in series. The receiving sub-coil and the exciting sub-coil can be located on different layers of the same circuit board to ensure that the receiving sub-coil and the exciting sub-coil do not intersect.
[0044] When using the inductive linear displacement sensor composed of the coil structure of the present invention for linear displacement measurement, the sensor can be fixed near the surface to be measured of the conductive test piece to be measured in a certain way, and it is ensured that the horizontal direction of the sensor is consistent with the movement direction of the test piece, and the gap between the sensor plane and the plane to be measured is equal everywhere. An alternating current is applied to the excitation coil, which will induce eddy currents on the conductive test piece to be measured. The magnetic field generated by the eddy currents is superimposed on the magnetic field of the excitation coil, and the receiving coil outputs the position information of the conductive structure to be measured according to the superimposed magnetic field. Specifically, the conductive object to be measured is moved horizontally from the leftmost end to the rightmost end of the sensor. Since the eddy currents are affected by the position of the metal structure, when the metal slider moves with the moving object, the impedance or output signal of each receiving sub-coil reflects the position information in a specific direction. Therefore, by analyzing the impedance changes or output signals of multiple groups of receiving sub-coils, the position of the metal structure can be detected, that is, the change in the impedance of the receiving coil or the form of the change in the amplitude and phase of the output signal reflects the change in the position of the object to be measured, and thus the measurement of displacement can be realized.
[0045] In the coil of an inductive linear displacement sensor of the present invention, the excitation coil is composed of multiple groups of excitation sub-coils arranged in parallel alignment at equal intervals along the measurement stroke direction. Therefore, the radial width of the excitation coil is fixed and will not gradually increase. Moreover, the specifications of multiple groups of excitation sub-coils are the same. After an alternating current is applied to the excitation coil, the magnetic field generated in the measurement stroke direction of the excitation coil is uniform everywhere, so there is no phenomenon that the magnetic field at both ends is stronger than that in the middle. Multiple groups of receiving sub-coils are arranged in the excitation range of the excitation coil with a preset phase difference, and each group of receiving sub-coils is symmetrically distributed both in the measurement stroke direction and perpendicular to the measurement stroke direction. Each group of receiving sub-coils is non-contact and crossed with multiple groups of excitation sub-coils in space. Therefore, the eddy current change information received by the receiving sub-coils is uniform everywhere in the measurement stroke direction, and thus there is no need to perform non-linear compensation on the receiving sub-coils, which greatly simplifies the design of the receiving coil and shortens the product development cycle. Moreover, the total length of the excitation coil is the same as the length of the receiving coil, which makes the product structure more compact.
[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. An inductive linear displacement sensor coil, characterized in that, Comprising: An excitation coil, including multiple groups of excitation sub-coils with the same specifications, and the multiple groups of excitation sub-coils are arranged in parallel alignment at equal intervals along the measurement stroke direction; A receiving coil, including multiple groups of receiving sub-coils with a standard sine shape or a standard cosine shape, the multiple groups of receiving sub-coils are arranged within the excitation range of the excitation coil with a preset phase difference, and each group of receiving sub-coils is symmetrically distributed both in the measurement stroke direction and perpendicular to the measurement stroke direction, and each group of receiving sub-coils is non-contact and crosswise with the multiple groups of excitation sub-coils in space.
2. The inductive linear displacement sensor coil according to claim 1, characterized in that, When powered on, the magnitudes, phases, and frequencies of the excitation currents in each group of excitation sub-coils are the same.
3. The inductive linear displacement sensor coil according to claim 1, wherein, The excitation sub-coil is of a rectangular structure, and the wide side of the excitation sub-coil is located in the measurement stroke direction; the specifications include the width and length of the excitation sub-coil.
4. The inductive linear displacement sensor coil according to claim 3, characterized in that, The interval is less than the width of the excitation sub-coil.
5. The inductive linear displacement sensor coil according to claim 1, wherein The interval satisfies that when all the excitation sub-coils are powered on, the eddy current change information received by the receiving coil is uniform everywhere in the measurement stroke direction.
6. The inductive linear displacement sensor coil according to claim 1, wherein The excitation sub-coil is a single-turn coil or a multi-turn coil connected in series; or / and, the receiving sub-coil is a single-turn coil or a multi-turn coil connected in series.
7. The inductive linear displacement sensor coil according to claim 6, characterized in that, The excitation sub-coils are printed on a printed circuit board to form an excitation circuit board; when the excitation sub-coil is a multi-turn coil connected in series, the excitation circuit board has multiple layers, and the excitation sub-coils printed at the same positions on each layer are connected in series.
8. The inductive linear displacement sensor coil according to claim 6, wherein The receiving sub-coils are printed on a printed circuit board to form a receiving circuit board; when the receiving sub-coil is a multi-turn coil connected in series, the receiving circuit board has multiple layers, and the receiving sub-coils printed at the same positions on each layer are connected in series.
9. The inductive linear displacement sensor coil according to claim 1, wherein The receiving sub-coil includes a positive receiving sub-coil and a negative receiving sub-coil, the positive receiving sub-coil and the negative receiving sub-coil are connected in series, and are symmetrically distributed perpendicular to the measurement stroke direction.
10. The inductive linear displacement sensor coil according to claim 1, wherein The number of groups of the receiving sub-coils is two or three; when the number of groups of the receiving sub-coils is two, the two groups of receiving sub-coils are arranged within the excitation range of the excitation coil with a 90° phase difference; When the number of groups of the receiving sub-coils is three, the three groups of receiving sub-coils are arranged within the excitation range of the excitation coil with a 120° phase difference.