An absolute linear displacement sensor based on electric field self-coupling and a measuring method thereof
By setting up interleaved sensing and modulation units on the moving and fixed scale substrates, and combining them with electric field self-coupling technology, absolute passive signal sensing is realized, which solves the problems of limited measurement range and increased power consumption in the existing technology. It achieves high-precision, low-power displacement measurement, which is suitable for industrial automation and precision machining.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING UNIV OF TECH
- Filing Date
- 2024-11-29
- Publication Date
- 2026-06-26
AI Technical Summary
Existing electric field time-grating linear displacement sensors based on single-row multilayer structures lose position information when power is off, have weak anti-interference capabilities, and have complex sensor leads, resulting in limited measurement range and increased power consumption, making them unsuitable for widespread application in industrial fields.
The system employs a moving scale base and a fixed scale base arranged in parallel. The moving scale base has interleaved sensing units, and the fixed scale base has modulation units. Absolute passive signal sensing is achieved through electric field self-coupling, and high-precision displacement measurement is performed using four-phase excitation signals and signal calculation methods.
It achieves absolute high-precision displacement measurement over a large range, with high output signal transmission efficiency, good measurement stability, low power consumption, and simple structure, making it suitable for industrial automation and precision machining.
Smart Images
Figure CN119594837B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to precision linear displacement sensors, specifically to an absolute linear displacement sensor and measurement method based on electric field self-coupling, belonging to the field of measurement and sensing technology. Background Technology
[0002] Absolute sensors are characterized by high precision, good stability, and data retention even when power is off, making them widely used in industrial automation, precision machine tool measurement, and other fields. In recent years, a single-row, multi-layer electric field-type time-grating linear displacement sensor (publication number CN103822571A) has been developed in China. This sensor uses a high-frequency clock pulse as the measurement reference and employs an alternating electric field constructed from parallel-plate capacitors to directly couple the required traveling wave signal, thus achieving high-precision displacement measurement within a certain range. However, this sensor is an incremental displacement measurement; its position information is lost when power is off, and it has weak anti-interference capabilities, making it susceptible to electromagnetic fields in the environment, thus limiting its widespread applicability in industrial applications. Furthermore, the sensor's moving and fixed scales require separate leads, leading to increased internal resistance as the fixed scale range increases, thus limiting the measurement range. The complex wiring installation also reduces sensor reliability. While increasing the number of sensing units increases the range, it also increases internal resistance, causing the output signal to attenuate with increasing range, resulting in increased power consumption and affecting signal transmission efficiency. These issues limit the sensor's application in large-range measurement and other related fields. Summary of the Invention
[0003] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide an absolute linear displacement sensor and measurement method based on electric field self-coupling. This invention can realize absolute passive signal sensing and high-precision displacement measurement over a large range. It can achieve strong absolute positioning capability of the sensor with fewer sensing units, and has high output signal transmission efficiency and good measurement stability.
[0004] The technical solution of this invention is implemented as follows:
[0005] An absolute linear displacement sensor based on electric field self-coupling includes a movable scale base and a fixed scale base arranged parallel to each other with a gap. Two rows of uniformly arranged sensing units are arranged side-by-side along the length of the lower surface of the movable scale base. All sensing units in the same row are identical in shape and size. Each row of sensing units includes an excitation unit and a sensing unit, which are arranged alternately. Every eight sensing units form a pole pair. In the same row, all excitation units in the first position are connected together to form excitation unit group A, all excitation units in the second position are connected together to form excitation unit group B, all excitation units in the third position are connected together to form excitation unit group C, and all excitation units in the fourth position are connected together to form excitation unit group D. All sensing units in the same row are connected together to form a sensing unit group.
[0006] The upper surface of the fixed-scale base has two rows of modulation units arranged side-by-side along its length, corresponding to the two rows of sensing units on the moving-scale base. Each row of modulation units consists of several identical modulation unit groups arranged end-to-end. The number of modulation unit groups in the two rows is different. All modulation unit groups consist of modulation units F and modulation units G, which are made of different materials. The length of each modulation unit F is consistent with the length of the modulation unit group to which it belongs and is consistent with the length of each pole pair in the corresponding column on the moving-scale base. In each modulation unit group, except for the area occupied by modulation unit F, modulation unit G occupies the remaining area of the modulation unit group. When the moving-scale base and the fixed-scale base move relative to each other, the alternating change of each row of modulation units F and modulation units G on the fixed-scale base causes the medium between adjacent excitation units and sensing units in the corresponding column on the moving-scale base to change. The sensing unit group in the corresponding column outputs a signal that is linearly related to the displacement.
[0007] The sensing unit is rectangular.
[0008] Preferably, in all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base, and all modulation units G / F protrude relative to the upper surface of the fixed-length base.
[0009] Alternatively, in all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base, and there is a cavity on the upper surface of the fixed-length base, in which all modulation units G / F are embedded.
[0010] Alternatively, in all modulation unit groups in the same column, all modulation units F / G protrude relative to the upper surface of the fixed-length substrate, and have cavities on the upper surface of the fixed-length substrate, with all modulation units G / F embedded in the cavities.
[0011] Furthermore, let the number of the two modulation unit groups be M1 and M2, then the relationship between M1 and M2 is: M2 = M1 - 1; or M1 and M2 are coprime numbers and M2 ≠ M1 - 1; or M2 = 1 and M1 > 1.
[0012] Preferably, the cross-sectional shape of the modulation unit F is a double cosine shape, which refers to a fully enclosed symmetrical figure formed by the cosine curve Acos(ωx) symmetrically about the horizontal line y=A at its highest point in the interval [0,2π].
[0013] Preferably, the material of the fixed-length substrate is the same as the material of the modulation unit F, or the same as the material of the modulation unit G, or different from the materials of both the modulation unit F and the modulation unit G.
[0014] When the material of modulation unit F or modulation unit G is the same as that of the fixed-length substrate and protrudes relative to the upper surface of the fixed-length substrate, the fixed-length substrate and modulation unit F or modulation unit G are integrally formed.
[0015] This invention also provides an absolute linear displacement measurement method based on electric field self-coupling. The method employs a aforementioned absolute linear displacement sensor based on electric field self-coupling. During measurement, equal-amplitude, same-frequency sinusoidal excitation signals with phase differences of π / 2 are applied to the four-phase excitation unit groups (A, B, C, D) of two rows of sensing units on the moving scale substrate. The sensing unit groups of the two rows of sensing units on the moving scale substrate output displacement signals, which are then processed by circuitry and calculated by a program to obtain the linear displacement count values of the two rows. The difference between the two linear displacement count values is then used to determine the absolute position within the measurement range, thus obtaining the unique displacement value of the sensor within its large displacement measurement range.
[0016] Compared with the prior art, the present invention has the following beneficial effects:
[0017] This invention achieves absolute passive signal sensing and high-precision displacement measurement over any large range by simply combining different numbers of modulation units on the fixed-scale substrate. A smaller number of sensing units on the moving-scale substrate are sufficient to achieve strong absolute positioning capabilities. The strength of the sensor's input and output signals is unaffected by the number of sensing units. The leadless design of the stator substrate enables passive sensing of the moving-scale signal, resulting in high output signal transmission efficiency, good measurement stability, and high reliability. Furthermore, the sensor features low power consumption, simple structure, low manufacturing cost, and ease of installation and maintenance. These characteristics make this sensor a promising candidate for reliable, accurate, and efficient measurement in fields such as industrial automation and precision machining. Attached Figure Description
[0018] Figure 1 This is a three-dimensional structural diagram of the fixed-length base and the moving-length base in Example 1.
[0019] Figure 2 This is a schematic diagram of the moving ruler base structure in Example 1.
[0020] Figure 3 This is a schematic diagram of the fixed-length base structure for Example 1.
[0021] Figure 4 This is a schematic diagram showing the spatial correspondence between the modulation unit on the fixed-length substrate and the sensing unit on the moving-length substrate in Example 1.
[0022] Figure 5 This is a flowchart of displacement signal processing and calculation for sensor absolute positioning in Example 1.
[0023] Figure 6 This is a schematic diagram showing the relationship between the number of two columns of modulation units on the fixed-length substrate in Example 2.
[0024] Figure 7 This is a schematic diagram showing the relationship between the number of two columns of modulation units on the fixed-length substrate in Example 3.
[0025] Figure 8 This is a schematic diagram showing the relationship between the number of two columns of modulation units on the fixed-length substrate in Example 4.
[0026] Figure 9 This is a schematic diagram of the curve forming the modulation unit pattern on the fixed-length substrate of Example 1.
[0027] Figure 10 This is a schematic diagram of the fixed-length substrate structure in Example 5.
[0028] Figure 11 This is a schematic diagram of the fixed-length base structure in Example 6. Detailed Implementation
[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0030] Example 1: See Figures 1-3This invention discloses an absolute linear displacement sensor based on electric field self-coupling, comprising a movable scale base 1 and a fixed scale base 2 arranged parallel to each other with a gap. Two rows of uniformly arranged sensing units are arranged side-by-side along the length of the lower surface of the movable scale base 1, with all sensing units in the same row having identical shape and size. Each row of sensing units includes an excitation unit and a sensing unit, which are arranged alternately. For ease of distinction, they are respectively referred to as the first row of excitation units 1-1-1 and the first row of sensing units 1-1-2, as well as the second row of excitation units 1-2-1 and the second row of sensing units 1-2-2. Every eight sensing units constitute a pole pair. Here, the eight sensing units are considered as a whole, including both the eight sensing units themselves and the spacing between them. The pole pair width is the sum of the widths of the eight sensing units and the spacing between them. In the same column of all pole pairs, all excitation units in the first position are connected together to form excitation unit group A, all excitation units in the second position are connected together to form excitation unit group B, all excitation units in the third position are connected together to form excitation unit group C, and all excitation units in the fourth position are connected together to form excitation unit group D; all sensing units in the same column are connected together to form sensing unit group.
[0031] The upper surface of the fixed-scale base 2 has two rows of modulation units arranged side-by-side along its length, corresponding to the two rows of sensing units on the movable-scale base 1. Each row of modulation units consists of several identical modulation unit groups arranged end-to-end, with a different number of modulation unit groups in each row. All modulation unit groups consist of modulation units F and modulation units G, corresponding to the sensing units, and are respectively referred to as the first row of modulation units F2-1-1 and the first row of modulation units G2-1-2, as well as the second row of modulation units F2-2-1 and the second row of modulation units G2-2-2. Within the same row, all modulation units F are made of the same material, and all modulation units G are made of the same material, but modulation units F and G are made of different materials. The length of each modulation unit F is consistent with the length of the modulation unit group to which it belongs and is consistent with the length of each pole pair in the corresponding column on the movable-scale base. Figure 4 This is a spatial correspondence diagram of the modulation units on the fixed-scale substrate and the sensing units on the moving-scale substrate in Example 1. In each modulation unit group, modulation units G occupy the remaining area of the modulation unit group, except for the area occupied by modulation unit F. When the moving-scale substrate and the fixed-scale substrate move relative to each other, the alternating change of each column of modulation units F and modulation units G on the fixed-scale substrate causes a change in the medium between adjacent excitation units and sensing units in the corresponding column on the moving-scale substrate, and the sensing unit group in the corresponding column outputs a signal that is linearly related to the displacement.
[0032] Based on the relative positional relationship of the modulation unit on the fixed-length substrate, the present invention can be implemented in the following three ways:
[0033] 1. In all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base, and all modulation units G / F protrude relative to the upper surface of the fixed-length base.
[0034] 2. In all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base. There is a cavity on the upper surface of the fixed-length base, and all modulation units G / F are embedded in the cavity.
[0035] 3. In all modulation unit groups in the same column, all modulation units F / G protrude relative to the upper surface of the fixed-length base, and have a cavity on the upper surface of the fixed-length base. All modulation units G / F are embedded in the cavity.
[0036] In one implementation, the modulation unit G / modulation unit F embedded in the cavity can be made of air. In this case, it is only necessary to open the cavity on the upper surface of the fixed-length substrate. There is no need to deliberately embed solid components. The air entering the cavity naturally constitutes the modulation unit G / modulation unit F.
[0037] Furthermore, let the number of the two modulation unit groups be M1 and M2, then the relationship between M1 and M2 is: M2 = M1 - 1; or M1 and M2 are coprime numbers and M2 ≠ M1 - 1; or M2 = 1 and M1 > 1.
[0038] Preferably, provided that the materials of modulation unit F and modulation unit G are different, the material of the fixed-length substrate is the same as the material of modulation unit F, or the same as the material of modulation unit G, or different from the materials of both modulation unit F and modulation unit G.
[0039] When the material of modulation unit F or modulation unit G is the same as that of the fixed-length substrate and protrudes relative to the upper surface of the fixed-length substrate, the fixed-length substrate and modulation unit F or modulation unit G are integrally formed.
[0040] As shown in the figure, the sensing units (including excitation units and sensing units) in Embodiment 1 are all rectangular. The two columns of rectangles in Embodiment 1 have the same length but different widths. In Embodiment 1, the width of each column of sensing units is the same as the spacing between adjacent sensing units; however, they can also be different, as long as they are arranged at equal intervals.
[0041] Preferably, the cross-sectional shape of the modulation unit F is a centrally rotationally symmetric figure. Specifically, the cross-sectional shape of the modulation unit F is a double cosine shape, which refers to a fully closed symmetric figure formed by the cosine curve Acos(ωx) symmetrically about the horizontal line y=A at its highest point in the interval [0,2π]. See [link to details on its formation] for further information. Figure 9 .
[0042] During measurement, four excitation voltage signals U, with the same frequency and equal amplitude, are applied to the four excitation unit groups A, B, C, and D in the first and second columns on the moving scale base, respectively. These signals are sequentially phased by π / 2. A =U m sin(ωt), U B =U m sin(ωt+π / 2), U C =U m sin(ωt+π), U D =U m sin(ωt+3π / 2). When the moving scale base is parallel to and directly opposite the fixed scale base and moves relative to it, the first column of modulation units F2-1-1 and G2-1-2 on the fixed scale base will cause a change in the dielectric between the capacitor formed by the excitation unit and the sensing unit in the first column on the moving scale base. The first column of excitation unit 1-1-1 and the first column of modulation unit group are coupled and then coupled to the first column of sensing unit 1-1-2, so that the first column of sensing unit group on the moving scale base outputs a precise displacement signal U1 related to the displacement of the first column of modulation unit group. The precise displacement signal output by the first column of sensing unit group is one circumference within the linear measurement range. The displacement curve changes periodically; the second column of modulation units F2-2-1 and G2-2-2 on the fixed-scale substrate causes a change in the dielectric between the capacitors formed by the excitation units and sensing units in the second column on the moving-scale substrate. The second column of excitation units 1-2-1 and the second column of modulation units are coupled, and then coupled to the second column of sensing units 1-2-2, causing the second column of sensing units on the moving-scale substrate to output a coarse displacement signal U2 related to the displacement of the second column of modulation units. The coarse displacement signal output by the second column of sensing units, within the linear measurement range, is a displacement curve with a different period than that of the first column. The fine displacement signal U1 and the coarse displacement signal U2 can be expressed as:
[0043] U1 = K e U m sin(ωt+2πx / w1)
[0044] U2 = K e U m sin(ωt+2πx / w2)
[0045] The excitation voltage amplitude U m =26V, frequency f=20kHz, angular frequency ω=2πf=4×10 4 π, K e is the electric field coupling coefficient, w1 and w2 are the widths corresponding to one pole pair in the first and second columns on the moving scale substrate, respectively, and x is the displacement measurement value.
[0046] In the present invention, fine measurement and coarse measurement are relative. The first column can be used as fine measurement and the second column as coarse measurement, or the first column can be used as coarse measurement and the second column as fine measurement. Within the same measuring range, the more modulation unit groups there are, the higher the measurement accuracy of the sensor. In the present invention, the column with more modulation unit groups is used as fine measurement and the other column as coarse measurement. In fact, the two columns of sensing units on the moving scale base and the two columns of modulation units on the fixed scale base are correspondingly combined to form two independent linear displacement sensors. By taking the difference between the displacement values output by the two sensors, accurate absolute measurement of linear displacement can be achieved.
[0047] As Figure 5 shown, after processing the output signals U1 and U2 of the two columns into square waves through a shaping circuit and comparing the phase difference with the reference square wave U r with the same frequency, the maximum phase meter values of a single pair-pole period for the first column and the second column are respectively and The phase meter values and are serrated throughout the measurement range and linearly vary from 0 to 2π within a single measurement period. After taking the difference between the phase meter values and to obtain the phase difference and performing displacement calculation in the FPGA, the absolute displacement measurement value of the sensor within a large measurement range can be obtained.
[0048]
[0049] Embodiment 2: The measurement principle and most of the structures in this embodiment are the same as those in Embodiment 1. The difference is that: as Figure 6 shown, the absolute positioning relationship formed by the number M1 of the modulation unit groups in the first column and the number M2 of the modulation unit groups in the second column on the fixed scale base is: M2 = M1 - 1; specifically, M1 = 16 and M2 = 15.
[0050] Embodiment 3: The measurement principle and most of the structures in this embodiment are the same as those in Embodiment 1. The difference is that: as Figure 7 shown, the absolute positioning relationship formed by the number M1 of the modulation unit groups in the first column and the number M2 of the modulation unit groups in the second column on the fixed scale base is: M1 and M2 are relatively prime and M2 < M1 - 1; specifically, M1 = 16 and M2 = 11.
[0051] Embodiment 4: The measurement principle and most of the structures in this embodiment are the same as those in Embodiment 1. The difference is that: as Figure 8As shown, the absolute positioning relationship between the number of modulation unit groups M1 in the first column and the number of modulation unit groups M2 in the second column on the fixed-length substrate is: M2 = 1, M1 is a positive integer greater than 1, and in practice M1 = 16. In this embodiment, the movable scale substrate needs to be made longer and has more pole pairs. At this time, the movable scale substrate is fixed, while the fixed-length substrate is made shorter and can move relative to the movable scale substrate.
[0052] Example 5: The measurement principle and most of the structure in this example are the same as in Example 1, except that: Figure 10 As shown, the modulation units F in the first and second columns on the fixed-length substrate are parallel to the surface of the modulation unit G but not on the same plane, and the horizontal plane where the modulation unit F is located protrudes relative to the surface of the fixed-length substrate.
[0053] Example 6: The measurement principle and most of the structure in this example are the same as in Example 1, except that: Figure 11 As shown, the modulation units F in the first and second columns on the fixed-length substrate are parallel to the surface of the modulation unit G but not on the same plane, and the horizontal plane where the modulation unit F is located is recessed relative to the surface of the fixed-length substrate.
[0054] Example 7: The measurement principle and most of the structure in this example are the same as in Example 1, except that: Figure 10 and Figure 11 As shown, modulation unit F and modulation unit G are made of different materials, and the material of the fixed-length substrate is the same as that of modulation unit F or modulation unit G: (1) The material of modulation unit F is metal, the material of modulation unit G is non-metal, and the material of the fixed-length substrate is the same as that of modulation unit F or modulation unit G; (2) The material of modulation unit F is non-metal, the material of modulation unit G is metal, and the material of the fixed-length substrate is the same as that of modulation unit F or modulation unit G; (3) The materials of modulation unit F and modulation unit G are two different non-metals, and the material of the fixed-length substrate is the same as that of modulation unit F or modulation unit G.
[0055] Example 8: The measurement principle and most of the structure in this example are the same as in Example 1, except that: Figure 10 and Figure 11As shown, modulation unit F and modulation unit G are made of different materials, and the material of the fixed-length substrate is different from the material of modulation unit F and modulation unit G: (1) The material of modulation unit F is metal, the material of modulation unit G is non-metal, and the material of the fixed-length substrate is different from the material of modulation unit F or modulation unit G; (2) The material of modulation unit F is non-metal, the material of modulation unit G is metal, and the material of the fixed-length substrate is different from the material of modulation unit F or modulation unit G; (3) The materials of modulation unit F and modulation unit G are two different non-metals, and the material of the fixed-length substrate is different from the material of modulation unit F or modulation unit G.
[0056] When the moving scale base and the fixed scale base are parallel and directly opposite each other and move relative to each other, the two columns of modulation units F and G arranged on the fixed scale base will cause changes in the dielectric between the capacitors formed by the excitation units and sensing units in the first and second columns, respectively. Passive sensing measurement of the fixed scale is achieved by modulating the signals coupled between the sensing units and the excitation units. This invention, by arranging two columns of modulation unit groups with different numbers on the fixed scale base, can achieve absolute positioning of the sensor and has strong absolute positioning capability.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the applicant has described the present invention in detail with reference to preferred embodiments, those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.
Claims
1. An absolute linear displacement sensor based on electric field self-coupling, comprising a moving scale base and a fixed scale base arranged parallel to each other with a gap, characterized in that: The lower surface of the moving scale base is provided with two rows of uniformly arranged sensing units side by side along the length direction. All sensing units in the same row are identical in shape and size. Each row of sensing units includes an excitation unit and a sensing unit, which are arranged alternately. Every eight sensing units form a pair of poles. In all pairs of poles in the same row, all excitation units in the first position are connected together to form excitation unit group A, all excitation units in the second position are connected together to form excitation unit group B, all excitation units in the third position are connected together to form excitation unit group C, and all excitation units in the fourth position are connected together to form excitation unit group D. All sensing units in the same row are connected together to form sensing unit group. The upper surface of the fixed-scale base has two rows of modulation units arranged side-by-side along its length, corresponding to the two rows of sensing units on the moving-scale base. Each row of modulation units consists of several identical modulation unit groups arranged end-to-end. The number of modulation unit groups in the two rows is different. All modulation unit groups consist of modulation units F and modulation units G, which are made of different materials. The length of each modulation unit F is consistent with the length of the modulation unit group to which it belongs and is consistent with the length of each pole pair in the corresponding column on the moving-scale base. In each modulation unit group, except for the area occupied by modulation unit F, modulation unit G occupies the remaining area of the modulation unit group. When the moving-scale base and the fixed-scale base move relative to each other, the alternating change of each row of modulation units F and modulation units G on the fixed-scale base causes the medium between adjacent excitation units and sensing units in the corresponding column on the moving-scale base to change. The sensing unit group in the corresponding column outputs a signal that is linearly related to the displacement.
2. The absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: The sensing unit is rectangular.
3. The absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: In all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base, and all modulation units G / F protrude relative to the upper surface of the fixed-length base.
4. The absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: In all modulation unit groups in the same column, the horizontal plane where all modulation units F / G are located is coplanar with the upper surface of the fixed-length base. There is a cavity on the upper surface of the fixed-length base, and all modulation units G / F are embedded in the cavity.
5. An absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: In all modulation unit groups in the same column, all modulation units F / G protrude relative to the upper surface of the fixed-length substrate, and have a cavity on the upper surface of the fixed-length substrate, in which all modulation units G / F are embedded.
6. An absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: Let the number of the two modulation unit groups be M1 and M2. Then the relationship between M1 and M2 is: M2 = M1 - 1; or M1 and M2 are coprime numbers and M2 ≠ M1 - 1; or M2 = 1 and M1 > 1.
7. An absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: The cross-sectional shape of the modulation unit F is a double cosine shape, which refers to the fully enclosed symmetrical figure formed by the cosine curve Acos(ωx) symmetrically about the horizontal line y=A at its highest point in the interval [0,2π].
8. An absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: The material of the fixed-length substrate is the same as the material of the modulation unit F, or the same as the material of the modulation unit G, or different from the materials of both the modulation unit F and the modulation unit G.
9. An absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: When the material of modulation unit F or modulation unit G is the same as that of the fixed-length substrate and protrudes relative to the upper surface of the fixed-length substrate, the fixed-length substrate and modulation unit F or modulation unit G are integrally formed.
10. A method for measuring absolute linear displacement based on electric field self-coupling, characterized in that: The measurement is performed using an absolute linear displacement sensor based on electric field self-coupling as described in any one of claims 1-9. During measurement, a sinusoidal excitation signal with equal amplitude and frequency, with a phase difference of π / 2, is applied to the four-phase excitation unit groups A, B, C, and D of the two rows of sensing units on the moving scale base. The sensing unit groups of the two rows of sensing units on the moving scale base output displacement signals respectively. After circuit processing and program calculation, the linear displacement count values of the two columns are obtained. The difference between the two linear displacement count values is processed to determine the absolute position within the measurement range, thus obtaining the unique displacement value of the sensor within the large displacement measurement range.