Absolute type linear displacement sensor based on electric field self-coupling and measuring method

Abstract

The invention discloses an absolute type linear displacement sensor based on electric field self-coupling and a measuring method, two columns of sensing units are arranged on the lower surface of a movable ruler base body side by side, and each column of sensing units comprises excitation units and induction units which are arranged in a staggered mode; every eight sensing units form an antipode, and in all antipodes in the same column, all excitation units in the same sequence are correspondingly connected so as to form four excitation unit groups. All the sensing units in the same column are connected to form a sensing unit group. Two rows of modulation units are arranged on the upper surface of the sizing base body side by side, and each row of modulation units is formed by arranging a plurality of modulation unit groups; and the numbers of the modulation unit groups in the two columns are different. The modulation unit group is composed of two kinds of modulation units made of different materials. According to the invention, absolute passive signal sensing and high-precision displacement measurement in a wide range can be realized, relatively strong absolute positioning capability of the sensor can be realized by arranging relatively few sensing units, the transmission efficiency of output signals is high, and the measurement stability is good.

Description

Technical Field

[0001] The invention relates to a precision linear displacement sensor, in particular to an absolute linear displacement sensor based on electric field self-coupling and a measuring method, belonging to the technical field of measurement sensing. Background Art

[0002] Absolute sensors have the characteristics of high precision, good stability, and no loss of power-off data. They are widely used in industrial automation, precision measurement and processing of machine tools, and other fields. In recent years, a single-row multi-layer structure-based electric field time-grating linear displacement sensor (publication number CN103822571A) has been developed in China. The sensor uses a high-frequency clock pulse as the measurement reference and uses an alternating electric field constructed by a flat capacitor to directly couple the electric wave signal required for measurement, so it can achieve high-precision displacement measurement within a certain range. However, the sensor is an incremental displacement measurement, and the position information of its power-off position sensor will be lost, and its anti-interference ability is weak, and it is easily affected by the electromagnetic field in the environment, so it cannot be widely used in the industrial field. In addition, the sensor's movable scale and fixed scale need to be wired separately, resulting in an increase in internal resistance when the fixed scale range increases, limiting the measurement range. In addition, the sensor lead installation is complicated, which reduces the reliability of the sensor. At the same time, although the increase in the number of sensing units increases the range, it will also increase the internal resistance, causing the output signal to decay as the range increases, resulting in an increase in the power consumption of the sensor, affecting the signal transmission efficiency. The above problems have led to the limitation of the sensor in application fields such as large-scale measurement. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an absolute linear displacement sensor and a measurement method based on electric field self-coupling. The present invention can realize absolute passive signal sensing and high-precision displacement measurement over a large range. A relatively small number of sensor units can be arranged to achieve a strong absolute positioning capability of the sensor, and the output signal transmission efficiency is high and the measurement stability is good.

[0004] The technical solution of the present invention is achieved in this way:

[0005] An absolute linear displacement sensor based on electric field self-coupling, comprising a movable ruler substrate and a fixed ruler substrate which are arranged in parallel with each other and have a gap, wherein two rows of uniformly arranged sensing units are arranged side by side on the lower surface of the movable ruler substrate along the length direction, and all sensing units in the same row are completely consistent in shape and size; each row of sensing units comprises an excitation unit and a sensing unit, and the excitation unit and the sensing unit are arranged alternately in sequence; every eight sensing units constitute a pole pair, and among all pole pairs in the same row, all the excitation units in the first sequence are connected together to form an A excitation unit group, all the excitation units in the second sequence are connected together to form a B excitation unit group, all the excitation units in the third sequence are connected together to form a C excitation unit group, and all the excitation units in the fourth sequence are connected together to form a D excitation unit group; all the sensing units in the same row are connected together to form a sensing unit group;

[0006] Two columns of modulation units corresponding to the two columns of sensing units on the moving ruler substrate are arranged side by side along the length direction on the upper surface of the fixed-length substrate, and each column of modulation units is composed of a number of identical modulation unit groups arranged end to end; the number of modulation unit groups in the two columns is different; all modulation unit groups are composed of modulation units F and modulation units G, and the modulation units F and modulation units 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 the modulation unit F belongs and is consistent with the length of each pole pair in the corresponding column on the moving ruler substrate; in each modulation unit group, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area of ​​the modulation unit group; when the moving ruler substrate and the fixed-length substrate move relative to each other, the alternating change of the modulation units F and the modulation units G in each column on the fixed-length substrate causes the medium between the adjacent excitation units and the sensing units in the corresponding column on the moving ruler substrate to change, and the sensing unit group in the corresponding column outputs a signal that is linearly related to the displacement.

[0007] Wherein, the sensing unit is rectangular.

[0008] Preferably, in all modulation unit groups in the same column, the horizontal plane where all modulation units F / modulation units G are located is coplanar with the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are protruding relative to the upper surface of the fixed-length substrate.

[0009] Alternatively, in all modulation unit groups in the same column, the horizontal plane where all modulation units F / modulation units G are located is coplanar with the upper surface of the fixed-length substrate, and there is a cavity on the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are embedded in the cavity.

[0010] Alternatively, in all modulation unit groups in the same column, all modulation units F / modulation units G are protruding relative to the upper surface of the fixed-length substrate, the upper surface of the fixed-length substrate has a cavity, and all modulation units G / modulation units F are embedded in the cavity.

[0011] Furthermore, assuming that the number of two columns of modulation unit groups is M1 and M2, the relationship between M1 and M2 is: M2=M1-1; or M1 and M2 are prime numbers to each other and M2≠M1-1; or M2=1, M1>1.

[0012] Preferably, the cross-sectional shape of the modulation unit F is a double cosine shape, which is a fully closed symmetrical shape 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 the modulation unit F or the modulation unit G is the same as that of the fixed-length substrate and is raised relative to the upper surface of the fixed-length substrate, the fixed-length substrate and the modulation unit F or the modulation unit G are integrally formed.

[0015] The present invention also provides an absolute linear displacement measurement method based on electric field self-coupling, which is performed using the aforementioned absolute linear displacement sensor based on electric field self-coupling. During measurement, equal-amplitude and same-frequency sinusoidal excitation signals with phase differences of π / 2 are applied to the four-phase excitation unit groups A, B, C, and D of the two columns of sensor units on the moving ruler substrate respectively. The induction unit groups of the two columns of sensor units on the moving ruler substrate respectively output displacement signals and obtain two columns of linear displacement count values ​​after circuit processing and program solution. The two linear displacement count values ​​are subjected to difference processing to perform absolute position positioning within the measurement range, thereby obtaining a unique displacement value of the sensor within the large-scale displacement measurement range.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention can realize absolute passive signal sensing and high-precision displacement measurement in any large range by simply combining different numbers of modulation units on a fixed-length substrate. A relatively strong absolute positioning capability of the sensor can be achieved by arranging fewer sensing units on a moving-length substrate. The intensity of the input and output signals of the sensor is not affected by the number of sensing units. The leadless design of the stator substrate can realize passive sensing of moving-length signals, and the output signal has high transmission efficiency, good measurement stability, and strong reliability. At the same time, the sensor has low power consumption, simple structure, low manufacturing cost, and is easy to install and maintain. The above characteristics make the sensor have reliable, accurate and efficient measurement capabilities and application prospects in the fields of industrial automation and precision machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the three-dimensional structure of the fixed-size substrate and the movable-size substrate in Example 1.

[0019] Figure 2 This is a schematic diagram of the structure of the moving ruler base in Example 1.

[0020] Figure 3 This is a schematic diagram of the fixed-length base structure of Example 1.

[0021] Figure 4 Schematic diagram of the spatial correspondence between the modulation unit on the fixed-size substrate and the sensing unit on the movable-size substrate in Example 1.

[0022] Figure 5 This is a flow chart of displacement signal processing and solution for absolute positioning of the sensor in Example 1.

[0023] Figure 6 Schematic diagram of the relationship between the number of modulation units in two columns on the fixed-length substrate in Example 2.

[0024] Figure 7 Schematic diagram of the relationship between the number of modulation units in two columns on a fixed-length substrate in Example 3.

[0025] Figure 8 Schematic diagram of the relationship between the number of modulation units in two columns on a fixed-length substrate in Example 4.

[0026] Fig. 9 It is a schematic diagram of a curve of a modulation unit pattern formed on a fixed-length substrate in Example 1.

[0027] Fig.10 This is a schematic diagram of the fixed-length substrate structure of Example 5.

[0028] Fig.11 This is a schematic diagram of the fixed-length substrate structure of Example 6. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1: See Figure 1-Figure 3The present invention discloses an absolute linear displacement sensor based on electric field self-coupling, comprising a movable ruler substrate 1 and a fixed ruler substrate 2 which are arranged in parallel with each other and have a gap therebetween. The lower surface of the movable ruler substrate 1 is provided with two rows of evenly arranged sensing units side by side along the length direction, and all sensing units on the same row are exactly the same in shape and size. Each row of sensing units includes an excitation unit and a sensing unit, and the excitation unit and the sensing unit are alternately arranged in sequence. For the convenience 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 and 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, where the eight sensing units are regarded as a whole, including the eight sensing units themselves and the spacing between the sensing units. The pole pair width is the sum of the widths of the eight sensing units and the spacing between them. Among all the poles in the same column, all the excitation units in the first order are connected together to form an A excitation unit group, all the excitation units in the second order are connected together to form a B excitation unit group, all the excitation units in the third order are connected together to form a C excitation unit group, and all the excitation units in the fourth order are connected together to form a D excitation unit group; all the induction units in the same column are connected together to form an induction unit group.

[0031] The upper surface of the fixed-length substrate 2 is provided with two columns of modulation units corresponding to the two columns of sensing units on the moving-length substrate 1 in parallel along the length direction. Each column of modulation units is composed of a number of identical modulation unit groups arranged end to end, and the number of modulation unit groups in the two columns is different. All modulation unit groups are composed of modulation units F and modulation units G, corresponding to the sensing units, and are respectively referred to as the first column modulation unit F2-1-1 and the first column modulation unit G2-1-2 and the second column modulation unit F2-2-1 and the second column modulation unit G2-2-2. In the same column, 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 modulation units 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 the modulation unit F belongs and is consistent with the length of each pole pair in the corresponding column on the moving-length substrate. Figure 4 This is a schematic diagram of the spatial correspondence between the modulation unit on the fixed-length substrate and the sensing unit on the moving-length substrate in Example 1. In each modulation unit group, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area of ​​the modulation unit group. When the moving-length substrate and the fixed-length substrate move relative to each other, the alternating change of the modulation unit F and the modulation unit G in each column on the fixed-length substrate causes the medium between the adjacent excitation units and sensing units in the corresponding column on the moving-length substrate to change, and the sensing unit group in the corresponding column outputs a signal that is linearly related to the displacement.

[0032] According to the relative position relationship of the modulation unit on the fixed-length substrate, the present invention can have the following three situations:

[0033] 1. In all modulation unit groups in the same column, the horizontal plane where all modulation units F / modulation units G are located is coplanar with the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are raised relative to the upper surface of the fixed-length substrate.

[0034] 2. In all modulation unit groups in the same column, the horizontal plane where all modulation units F / modulation units G are located is coplanar with the upper surface of the fixed-length substrate. There is a cavity on the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are embedded in the cavity.

[0035] 3. In all modulation unit groups in the same column, all modulation units F / modulation units G are protruding relative to the upper surface of the fixed-length substrate, and there is a cavity on the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are embedded in the cavity.

[0036] As an implementation scenario, the modulation unit G / modulation unit F embedded in the cavity can be composed of air. That is, in this case, it is only necessary to open a cavity on the upper surface of the fixed-length substrate, and there is no need to deliberately embed a solid component. The air entering the cavity naturally constitutes the modulation unit G / modulation unit F.

[0037] Furthermore, assuming that the number of two columns of modulation unit groups is M1 and M2, the relationship between M1 and M2 is: M2=M1-1; or M1 and M2 are prime numbers to each other and M2≠M1-1; or M2=1, M1>1.

[0038] Preferably, under the premise that the modulation unit F and the modulation unit G are made of different materials, the material of the fixed-length substrate is the same as that of the modulation unit F, or the same as that of the modulation unit G, or different from the materials of both the modulation unit F and the modulation unit G.

[0039] When the material of the modulation unit F or the modulation unit G is the same as that of the fixed-length substrate and is raised relative to the upper surface of the fixed-length substrate, the fixed-length substrate and the modulation unit F or the modulation unit G are integrally formed.

[0040] As can be seen from the figure, the sensing units (including the excitation units and the induction units) in Example 1 are all rectangular. The lengths of the two rows of rectangles in Example 1 are the same, but the widths are different. In Example 1, the width of each row of sensing units is the same as the spacing between two adjacent sensing units, but can also be different, as long as they are arranged at equal spacings.

[0041] Preferably, the cross-sectional shape of the modulation unit F is a central rotationally symmetrical figure. Specifically, the cross-sectional shape of the modulation unit F is a double cosine shape, which refers to a fully closed symmetrical figure formed by the cosine curve Acos(ωx) symmetrically around the horizontal line y=A at its highest point in the interval [0,2π]. For its specific formation, see Fig. 9 .

[0042] During measurement, four excitation voltage signals U with the same frequency and amplitude and a phase difference of π / 2 are applied to the four excitation unit groups A, B, C, and D in the first and second columns on the movable ruler substrate. 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 movable ruler substrate is parallel to the fixed ruler substrate and moves relative to each other, the first column of modulation units F2-1-1 and the first column of modulation units G2-1-2 on the fixed ruler substrate will cause the dielectric between the capacitors formed by the first column of excitation units and induction units on the movable ruler substrate to change. The first column of excitation units 1-1-1 and the first column of modulation unit groups are coupled and then coupled with the first column of induction units 1-1-2, so that the first column of induction unit groups on the movable ruler substrate outputs a precise displacement signal U1 related to the displacement of the first column of modulation unit groups. The precise displacement signal output by the first column of induction unit groups is a circle in the linear measurement range. The second column of modulation units F2-2-1 and G2-2-2 on the fixed-length substrate will cause the dielectric between the capacitors formed by the second column of excitation units and induction units on the moving ruler substrate to change. The second column of excitation units 1-2-1 and the second column of modulation unit groups are coupled and then coupled with the second column of induction units 1-2-2, so that the second column of induction unit groups on the moving ruler substrate outputs a coarse displacement signal U2 related to the displacement of the second column of modulation unit groups. The coarse displacement signal output by the second column of induction unit groups is a displacement curve with a different periodic change from the first column in the linear measurement range. The precise 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 is 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 a pair of poles in the first and second columns on the moving ruler substrate, 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 vice versa. The more modulation unit groups within the same measuring range, 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 substrate and the two columns of modulation units on the fixed scale substrate 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 linear displacement measurement can be achieved.

[0047] As Figure 5 shown, after the output signals U1 and U2 of the two columns are processed into square waves by the shaping circuit and compared with the reference square wave U r with the same frequency for phase difference comparison, 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 change 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 lies in 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 substrate 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 lies in 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 substrate 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 lies in that: as Figure 8As shown, the absolute positioning relationship between 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-length substrate is: M2=1, M1 is a positive integer greater than 1, and actually M1=16. In this embodiment, the movable ruler substrate needs to be made longer and arranged with more pole pairs. At this time, the movable ruler substrate is fixed, while the fixed-length substrate is made shorter and can move relative to the movable ruler substrate.

[0052] Embodiment 5: The measurement principle and most of the structures of this embodiment are the same as those of embodiment 1, except that: Fig.10 As shown, the modulation units F in the first and second columns on the fixed-length substrate are parallel to the surfaces of the modulation units G but are not in the same plane, and the horizontal plane where the modulation units F are located is raised relative to the surface of the fixed-length substrate.

[0053] Embodiment 6: The measurement principle and most of the structures of this embodiment are the same as those of embodiment 1, except that: Fig.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 units G but are not in the same plane, and the horizontal plane where the modulation units F are located is recessed relative to the surface of the fixed-length substrate.

[0054] Embodiment 7: The measurement principle and most of the structures of this embodiment are the same as those of embodiment 1, except that: Fig.10 and Fig.11 As shown, the modulation unit F and the modulation unit G are made of different materials, and the material of the fixed-length substrate is the same as the material constituting the modulation unit F or the modulation unit G: (1) the material constituting the modulation unit F is metal, the material constituting the modulation unit G is non-metal, and the material of the fixed-length substrate is the same as the material of the modulation unit F or the modulation unit G; (2) the material constituting the modulation unit F is non-metal, the material constituting the modulation unit G is metal, and the material of the fixed-length substrate is the same as the material of the modulation unit F or the modulation unit G; (3) the material constituting the modulation unit F and the material constituting the modulation unit G are two different non-metals, and the material of the fixed-length substrate is the same as the material of the modulation unit F or the modulation unit G.

[0055] Embodiment 8: The measurement principle and most of the structures of this embodiment are the same as those of embodiment 1, except that: Fig.10 and Fig.11As shown, the modulation unit F and the modulation unit G are made of different materials, and the material of the fixed-length substrate is different from the materials constituting the modulation unit F and the modulation unit G: (1) The material constituting the modulation unit F is metal, the material constituting the modulation unit G is non-metal, and the material of the fixed-length substrate is different from the material of the modulation unit F or the modulation unit G; (2) The material constituting the modulation unit F is non-metal, the material constituting the modulation unit G is metal, and the material of the fixed-length substrate is different from the material of the modulation unit F or the modulation unit G; (3) The material constituting the modulation unit F and the material constituting the modulation unit G are two different non-metals, and the material of the fixed-length substrate is different from the material of the modulation unit F or the modulation unit G.

[0056] When the movable scale substrate and the fixed scale substrate are parallel and face each other and move relative to each other, the two columns of modulation units F and modulation units G arranged on the fixed scale substrate will respectively cause the dielectric between the capacitors formed by the excitation units and the sensing units in the first column and the second column to change, and the passive sensing measurement of the fixed scale is realized by modulating the signals coupled between the sensing units and the excitation units. The present invention can realize the absolute positioning of the sensor by arranging two columns of modulation unit groups with different numbers on the fixed scale substrate, and has a strong absolute positioning capability.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the applicant has described the present invention in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that modifications or equivalent substitutions of the technical solution of the present invention without departing from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. An absolute linear displacement sensor based on electric field self-coupling, comprising a movable scale substrate and a fixed scale substrate arranged in parallel with each other with a gap, characterized in that: The lower surface of the movable ruler base body is provided with two rows of evenly arranged sensing units arranged side by side along the length direction, and all sensing units in the same row are completely consistent in shape and size; each row of sensing units includes an excitation unit and a sensing unit, and the excitation unit and the sensing unit are arranged alternately in sequence; every eight sensing units constitute a pole pair, and among all pole pairs in the same row, all the excitation units in the first sequence are connected together to form an A excitation unit group, all the excitation units in the second sequence are connected together to form a B excitation unit group, all the excitation units in the third sequence are connected together to form a C excitation unit group, and all the excitation units in the fourth sequence are connected together to form a D excitation unit group; all the sensing units in the same row are connected together to form a sensing unit group; Two columns of modulation units corresponding to the two columns of sensing units on the moving ruler substrate are arranged side by side along the length direction on the upper surface of the fixed-length substrate, and each column of modulation units is composed of a number of identical modulation unit groups arranged end to end; the number of modulation unit groups in the two columns is different; all modulation unit groups are composed of modulation units F and modulation units G, and the modulation units F and modulation units 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 the modulation unit F belongs and is consistent with the length of each pole pair in the corresponding column on the moving ruler substrate; in each modulation unit group, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area of ​​the modulation unit group; when the moving ruler substrate and the fixed-length substrate move relative to each other, the alternating change of the modulation units F and the modulation units G in each column on the fixed-length substrate causes the medium between the adjacent excitation units and the sensing units in the corresponding column on the moving ruler substrate to change, and 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 / modulation units G are located is coplanar with the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are protruding relative to the upper surface of the fixed-length substrate.

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 / modulation units G are located is coplanar with the upper surface of the fixed-length substrate. There is a cavity on the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are embedded in the cavity.

5. 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, all modulation units F / modulation units G are protruding relative to the upper surface of the fixed-length substrate, and there is a cavity on the upper surface of the fixed-length substrate, and all modulation units G / modulation units F are embedded in the cavity.

6. The absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: Assuming that the number of two columns of modulation unit groups is M1 and M2, the relationship between M1 and M2 is: M2=M1-1; or M1 and M2 are prime numbers and M2≠M1-1; or M2=1, M1>1.

7. The 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 is a fully closed symmetrical shape formed by the cosine curve Acos(ωx) symmetrically about the horizontal line y=A at its highest point in the interval [0,2π].

8. The 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. The absolute linear displacement sensor based on electric field self-coupling according to claim 1, characterized in that: When the material of the modulation unit F or the modulation unit G is the same as that of the fixed-length substrate and is raised relative to the upper surface of the fixed-length substrate, the fixed-length substrate and the modulation unit F or the modulation unit G are integrally formed.

10. An absolute linear displacement measurement method based on electric field self-coupling, characterized in that: An absolute linear displacement sensor based on electric field self-coupling as described in any one of claims 1 to 9 is used. During measurement, equal-amplitude and same-frequency sinusoidal excitation signals with phases differing by π / 2 are applied to the four-phase excitation unit groups A, B, C, and D of the two columns of sensor units on the moving ruler substrate respectively. The induction unit groups of the two columns of sensor units on the moving ruler substrate respectively output displacement signals and obtain two columns of linear displacement count values ​​after circuit processing and program solution. The two linear displacement count values ​​are subjected to difference processing to perform absolute position positioning within the measurement range, thereby obtaining a unique displacement value of the sensor within the large-scale displacement measurement range.

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