An absolute time grating angular displacement sensor based on electric field modulation and a measuring method thereof

Abstract

The application discloses an absolute time-grating angular displacement sensor based on electric field modulation and a measuring method, wherein the upper surface of a stator base is provided with two circles of sensing units arranged uniformly, the sensing units comprise excitation units and induction units arranged alternately; eight sensing units form a pair of poles, and the number of the pairs of poles in the inner and outer circles is different; in all the pairs of poles in the same circle, all the excitation units in the same sequence are connected together to form four excitation unit groups; all the induction units in the same circle are connected to form an induction unit group; the lower surface of a rotor base is provided with modulation unit groups arranged in the inner and outer circles successively, and all the modulation unit groups are composed of modulation units F and modulation units G. The application can realize high-precision absolute angular displacement measurement of the sensor, the signal input and output of the sensor are located on the stator base, the rotor does not need to be provided with a lead wire, the strength of the output signal is not limited by the number of the sensing units, and the structure is simple and the signal transmission efficiency is higher.

Description

Technical Field

[0001] This invention relates to precision angular displacement sensors, specifically to an absolute time-grid angular displacement sensor and measurement method based on electric field modulation, belonging to the field of measurement and sensing technology. Background Technology

[0002] With the rapid development of technology, there are increasingly higher requirements for angular displacement sensors in fields such as precision manufacturing, aerospace, and national defense. Currently, angular displacement sensors are divided into incremental and absolute types. Compared to incremental sensors, absolute angular displacement sensors have advantages such as no need for reset upon power-on, immediate acquisition of absolute angle information, and no cumulative error, gradually becoming the development trend of angular displacement sensors. A currently disclosed patent is an electric field-type time-grid angular displacement sensor (publication number CN103968750A). This sensor uses a high-frequency clock pulse as the measurement reference and utilizes parallel capacitor plates to construct an alternating electric field for precise angle measurement. The sensor outputs signals through wires on the rotor, which is limited by installation constraints, resulting in a complex structure and hindering miniaturization. Its sensing unit is made of metal, limiting its detection range due to manufacturing limitations. The sensor's output signal strength depends on the number of excitation and sensing units, but the mutual cancellation of signals between excitation units leads to low output signal transmission efficiency. The sensor uses an incremental counting method, which results in cumulative error during operation and can only identify the angular displacement within one cycle. The sensor's initial position is uncertain after power-on, and it cannot record the current position after a restart or power failure; a new reference point must be found before it can continue operating. It is also susceptible to environmental influences, generating additional noise or erroneous readings. These issues limit the sensor's application in many situations. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide an absolute time-grid angular displacement sensor and measurement method based on electric field modulation. This invention enables high-precision absolute angular displacement measurement, achieving strong absolute positioning capabilities with a smaller number of sensing units. Furthermore, the signal input and output of this sensor are both located on the stator base, eliminating the need for rotor leads, and the output signal strength is not limited by the number of sensing units. This results in a simple structure and higher signal transmission efficiency.

[0004] The technical solution of this invention is implemented as follows:

[0005] An absolute time-grid angular displacement sensor based on electric field modulation includes a rotor base and a stator base arranged coaxially and parallel to each other with a gap. The upper surface of the stator base has several sensing units arranged uniformly in two concentric rings, inner and outer. All sensing units in the same ring are identical in shape and size. Each sensing unit in both the inner and outer rings includes an excitation unit and a sensing unit, which are arranged alternately. Every eight sensing units form a pole pair. The number of pole pairs on the inner and outer rings are both integers and unequal. In all pole pairs within the same ring, all excitation units in the first sequence are connected together to form excitation unit group A, all excitation units in the second sequence are connected together to form excitation unit group B, all excitation units in the third sequence are connected together to form excitation unit group C, and all excitation units in the fourth sequence are connected together to form excitation unit group D. All sensing units in the same ring are connected together to form a sensing unit group.

[0006] At least a portion of the lower surface of the rotor base is divided into inner and outer rings concentric with the rotor base. The inner ring of the rotor base is uniformly divided into several equal parts, the same number of pole pairs as the inner ring of the stator base, and the outer ring of the rotor base is uniformly divided into several equal parts, the same number of pole pairs as the outer ring of the stator base. Each region corresponds to a modulation unit group, and all modulation units on the same ring are identical in shape and size. All modulation unit groups consist of modulation units F and modulation units G, which are made of different materials. The central angle between the two ends of each modulation unit F is the same as the central angle of the region where the modulation unit F is located. In each region, the modulation unit G occupies the remaining region except for the region occupied by the modulation unit F. When the rotor base and the stator base rotate relative to each other, the modulation units F and G are used to change the dielectric between the capacitors formed by the excitation unit and the induction unit on the same ring of the stator base. The modulation units modulate the signals coupled by the induction unit and the excitation unit to achieve passive sensing measurement of the rotor without the need for leads.

[0007] Furthermore, the sensing unit is a fan-shaped ring concentric with the stator substrate.

[0008] Furthermore, in all modulation units of the same ring, the horizontal plane where all modulation units F / G are located is coplanar with the lower surface of the rotor base, and all modulation units G / F protrude relative to the lower surface of the rotor base.

[0009] Alternatively, in all modulation units of the same ring, the horizontal plane where all modulation units F / G are located is coplanar with the lower surface of the rotor base, and there is a cavity on the lower surface of the rotor base, in which all modulation units G / F are embedded.

[0010] Alternatively, in all modulation units of the same ring, all modulation units F / G protrude relative to the lower surface of the rotor base, and have cavities on the lower surface of the rotor base, with all modulation units G / F embedded in the cavities.

[0011] Furthermore, the relationship between the number of pole pairs N1 of the outer ring and the number of pole pairs N2 of the inner ring of the stator matrix is ​​as follows: N2 = N1 - 1; or N1 and N2 are coprime and N2 ≠ N1 - 1; or N2 = 1, N1 > 1; or N1 = N2 - 1; or N1 and N2 are coprime and N1 ≠ N2 - 1; or N1 = 1, N2 > 1.

[0012] Furthermore, 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 about the horizontal line y=A at its highest point in the interval [0,2π].

[0013] Furthermore, the material of the rotor 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 rotor substrate and protrudes relative to the lower surface of the rotor substrate, the rotor substrate and modulation unit F or modulation unit G are integrally formed.

[0015] This invention also provides an absolute time-grid angular displacement measurement method based on electric field modulation. The method uses the aforementioned absolute time-grid angular displacement sensor based on electric field modulation. During measurement, equal-amplitude sinusoidal excitation signals with phase differences of π / 2 are applied to the four-phase excitation unit groups A, B, C, and D on the outer and inner rings of the stator base, respectively. The induction unit groups on the inner and outer rings of the stator base output induction signals, which are then processed by the circuit and calculated by the program to obtain the angle count values ​​of the inner and outer rings. The angle count values ​​of the inner and outer rings are then subtracted to obtain the unique angle value of the rotor base rotation angle within the whole circumference measurement range.

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

[0017] This invention achieves high-precision absolute angular displacement measurement by arranging different numbers of sensing units on the inner and outer rings of the sensor stator base. The sensor's signal input and output are both located on the stator base, and the output signal strength is not limited by the number of sensing units, resulting in higher signal transmission efficiency. Passive sensing of the rotor is possible, and high-precision positioning can be achieved through a combination of a small number of sensing units on the inner and outer rings. These characteristics give the sensor superior capabilities for absolute measurement applications. Attached Figure Description

[0018] Figure 1This is a three-dimensional structural schematic diagram of Embodiment 1 of the present invention;

[0019] Figure 2 This is a schematic diagram of the stator substrate structure in Embodiment 1 of the present invention;

[0020] Figure 3 This is a schematic diagram of the rotor base structure in Embodiment 1 of the present invention;

[0021] Figure 4 This is a schematic diagram of the sensor absolute angular displacement signal calculation process in Embodiment 1 of the present invention;

[0022] Figure 5 This is a schematic diagram showing the spatial positional correspondence between the sensing unit and the modulation unit in Embodiment 1 of the present invention;

[0023] Figure 6 This is a schematic diagram showing the relationship between the number of poles of the inner and outer rings in Embodiment 2 of the present invention;

[0024] Figure 7 This is a schematic diagram showing the relationship between the number of poles of the inner and outer rings in Embodiment 3 of the present invention;

[0025] Figure 8 This is a schematic diagram showing the relationship between the number of poles of the inner and outer rings in Embodiment 4 of the present invention;

[0026] Figure 9 This is a schematic diagram of the enclosure pattern of the modulation unit F on the rotor substrate in Embodiment 1 of the present invention;

[0027] Figure 10 This is a schematic diagram of the rotor base structure in Embodiment 5 of the present invention;

[0028] Figure 11 This is a schematic diagram of the rotor base structure in Embodiment 6 of the present invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0030] See Figures 1-3This invention discloses an absolute time-grid angular displacement sensor based on electric field modulation, comprising a rotor base 2 and a stator base 1 arranged coaxially and parallel to each other with a gap. The upper surface of the stator base 1 is provided with a plurality of sensing units arranged uniformly in two circumferential rings, inner and outer. All sensing units on the same ring have the same shape and size. The sensing units on both the inner and outer rings include an excitation unit and a sensing unit, and the excitation unit and the sensing unit are arranged alternately in sequence, thereby forming an outer ring excitation unit 1-1-1 and an outer ring sensing unit 1-1-2, as well as an inner ring excitation unit 1-2-1 and an inner ring sensing unit 1-2-2. Every eight sensing units constitute a pole pair. The number of pole pairs on the inner and outer rings are both integers and are not equal. Among all pole pairs in the same ring, 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 ring are connected together to form sensing unit group.

[0031] At least a portion of the lower surface of the rotor base 2 is divided into inner and outer rings concentric with the rotor base. The inner ring of the rotor base 2 is uniformly divided into several equal parts, the same number of pole pairs as the inner ring of the stator base, and the outer ring of the rotor base is uniformly divided into several equal parts, the same number of pole pairs as the outer ring of the stator base. Each equal part of the inner and outer rings contains a modulation unit group; that is, one modulation unit group in the outer and inner rings of the rotor base corresponds sequentially to the spatial position of the central angle between all the sensing units of one pole pair in the outer and inner rings of the stator base. Each modulation unit group consists of a modulation unit F and a modulation unit G, thus forming outer ring modulation unit F2-1-1 and outer ring modulation unit G2-1-2, and inner ring modulation unit F2-2-1 and inner ring modulation unit G2-2-2. All modulation units on the same ring are identical in shape and size. Within the same circle, all modulation units F are made of the same material, and all modulation units G are made of the same material. However, modulation units F and G are made of different materials. The central angle between the two ends of each modulation unit F is the same as the central angle of the region where the modulation unit F is located. In each region, modulation units G occupy the remaining area, except for the area occupied by modulation unit F. Figure 5 This is a schematic diagram showing the spatial correspondence between the sensing unit and the modulation unit of the present invention. When the rotor base rotates relative to the stator base, the modulation unit F and the modulation unit G are used to change the dielectric between the capacitor formed by the excitation unit and the sensing unit on the same ring of the stator base. The modulation unit modulates the signal coupled between the sensing unit and the excitation unit to realize passive sensing measurement of the rotor base without the need for leads.

[0032] From the perspective of the uneven relationship between the lower surface of the modulation unit and the lower surface of the rotor base, the present invention has the following aspects:

[0033] 1. In all modulation units of the same ring, the horizontal plane where all modulation units F / G are located is coplanar with the lower surface of the rotor base, and all modulation units G / F protrude relative to the lower surface of the rotor base.

[0034] 2. In all modulation units of the same ring, the horizontal plane of all modulation units F / G is coplanar with the lower surface of the rotor base, and there is a cavity on the lower surface of the rotor base. All modulation units G / F are embedded in the cavity.

[0035] 3. In all modulation units of the same ring, all modulation units F / G protrude relative to the lower surface of the rotor base and have cavities on the lower surface of the rotor base. All modulation units G / F are embedded in the cavities.

[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 a cavity on the lower surface of the rotor base, without deliberately embedding solid components. The air entering the cavity naturally constitutes the modulation unit G / modulation unit F.

[0037] Preferably, the relationship between the number of pole pairs N1 of the outer ring and the number of pole pairs N2 of the inner ring of the stator substrate is: N2 = N1 - 1; or N1 and N2 are coprime numbers and N2 ≠ N1 - 1; or N2 = 1, N1 > 1. Alternatively, the relationship between the number of pole pairs of the inner and outer rings can be reversed, i.e., N1 = N2 - 1; or N1 and N2 are coprime numbers and N1 ≠ N2 - 1; or N1 = 1, N2 > 1.

[0038] Preferably, the sensing unit (including an excitation unit and an induction unit) is a fan-shaped ring concentric with the stator base. That is, the excitation unit and the induction unit on the same ring of the stator base 1 have the same radial height and the same central angle.

[0039] 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 .

[0040] Preferably, provided that the materials of modulation unit F and modulation unit G are different, the material of the rotor substrate can be 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.

[0041] When the material of modulation unit F or modulation unit G is the same as that of the rotor substrate and protrudes relative to the lower surface of the rotor substrate, the rotor substrate and modulation unit F or modulation unit G are integrally formed.

[0042] During measurement, equal-amplitude, same-frequency sinusoidal excitation signals U, with phase differences of π / 2, are applied to the four-phase excitation unit groups A, B, C, and D on the outer and inner rings of the stator base, respectively. A =U m sinωt,U B =U m sin(ωt+π / 2), U C =U m sin(ωt+π), U D =U m sin(ωt+3π / 2), the induction unit groups on the inner and outer rings of the stator base respectively output induction signals. When the rotor base 2 rotates relative to the stator base 1, the N1 outer ring modulation units F2-1-1 and G2-1-2 set on the outer ring of the rotor base 2 will cause the dielectric between the capacitor formed by the outer ring excitation unit 1-1-1 and the outer ring induction unit 1-1-2 in the outer ring sensing unit of the stator base 1 to change. The outer ring excitation unit 1-1-1 and the outer ring modulation unit are coupled and then coupled to the outer ring induction unit 1-1-2, so that the outer ring induction unit group outputs a precise angular displacement signal U1 related to the rotation angle of the outer ring modulation unit. The displacement value calculated by the precise angular displacement signal U1 output by the outer ring induction unit group is a periodically changing displacement curve within the whole circle measurement range. The N2 inner ring modulation units F2-2-1 and G2-2-2 arranged on the inner ring of the rotor base 2 cause a change in the dielectric between the capacitor formed by the inner ring excitation unit 1-2-1 and the inner ring sensing unit 1-2-2 in the inner ring sensing unit of the stator base 1. The inner ring excitation unit 1-2-1 and the inner ring modulation unit are coupled, and then coupled to the inner ring sensing unit 1-2-2, causing the inner ring sensing unit group to output a coarse angular displacement signal U2 related to the rotation angle of the inner ring modulation unit. The displacement value calculated from the coarse angular displacement signal U2 output by the inner ring sensing unit group is a displacement curve different from the periodic variation of the outer ring over the entire measurement range. The fine angular displacement signal U1 and the coarse angular displacement signal U2 can be expressed as:

[0043] U1=KeU m sin(ωt+K θ1 θ)

[0044] U2=KeU m sin(ωt+K θ2 θ)

[0045] The excitation voltage amplitude U m =27V, frequency f =20kHz, angular frequency ω =2πf =4 × 10 4 π, Ke is the electric field coupling coefficient, K θ1 K is the outer ring angular displacement coefficient.θ2 θ is the inner circle angular displacement coefficient, and θ is the measured angular displacement.

[0046] In Embodiment 1 of this invention, because the number of pole pairs on the outer ring of the stator base is greater than that on the inner ring, its measurement accuracy is higher. Therefore, the signal output by the outer ring sensing unit group is called the fine angular displacement signal U1, and the signal output by the inner ring sensing unit group is called the coarse angular displacement signal U2. In fact, the inner and outer ring sensing units on the stator base and the inner and outer ring modulation units on the rotor base of this invention are combined accordingly to form two independent displacement sensors. By subtracting the outputs of the two sensors, this invention can achieve precise absolute angular displacement positioning.

[0047] like Figure 4 As shown, after the signal acquisition module acquires the signals U1 and U2 output from the outer and inner ring sensing unit groups, the phases of the fine angular displacement signal U1 and the coarse angular displacement signal U2 are respectively compared with the same frequency reference signal U. r Phase comparison is performed by interpolating and counting the phase difference using a high-frequency pulse clock to obtain the precise phase count value for the outer ring and the coarse phase count value for the inner ring. The maximum phase count values ​​for a single cycle of the outer and inner rings are respectively... and Phase count value and The phase count value is zigzag-shaped throughout the measurement range and varies linearly from 0 to 2π within a single pole measurement cycle. and Phase difference after subtraction The rotation angle of the rotor base can be obtained by conversion, which is the only angle value within the whole circumference measurement range.

[0048]

[0049] Example 2: The measurement principle and most of the structure of Example 2 are the same as those of Example 1, except that: Figure 6 As shown, the relationship between the number of pole pairs N1 of the outer ring sensing unit and the number of pole pairs N2 of the inner ring sensing unit on the stator substrate is: N2 = N1 - 1, (N1 = 2, 3, 4...), specifically N1 = 10 and N2 = 9.

[0050] Example 3: The measurement principle and most of the structure of Example 3 are the same as those of Example 1, except that: Figure 7 As shown, the relationship between the number of pole pairs N1 of the outer ring sensing unit and the number of pole pairs N2 of the inner ring sensing unit on the stator substrate is as follows: N1 and N2 are coprime numbers and N2 ≠ N1-1, specifically N1 = 10 and N2 = 3.

[0051] Example 4: The measurement principle and most of the structure of Example 4 are the same as those of Example 1, except that: Figure 8As shown, the relationship between the number of pole pairs N1 of the outer ring sensing unit and the number of pole pairs N2 of the inner ring sensing unit on the stator substrate is: N2 = 1, N1 > 1 and N1 = 10.

[0052] Example 5: The measurement principle and most of the structure of Example 5 are the same as those of Example 1, except that: Figure 10 As shown, the horizontal plane where the modulation unit G is located is coplanar with the surface of the rotor base, while the horizontal plane where the modulation unit F is located is not coplanar with the surface of the rotor base and protrudes relative to the surface of the rotor base.

[0053] Example 6: The measurement principle and most of the structure of Example 6 are the same as those of Example 1, except that: Figure 11 As shown, the horizontal plane where the modulation unit G is located is coplanar with the surface of the rotor base, while the horizontal plane where the modulation unit F is located is not coplanar with the surface of the rotor base and is recessed relative to the surface of the rotor base.

[0054] Example 7: The measurement principle and most of the structure of Example 7 are the same as those of 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 rotor base 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 rotor base 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 rotor base 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 rotor base is the same as that of modulation unit F or modulation unit G.

[0055] Example 8: The measurement principle and most of the structure of Example 8 are the same as those of 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 rotor base is different from that of modulation unit F and modulation unit G: (1) The material constituting modulation unit F is metal, the material constituting modulation unit G is non-metal, and the material of the rotor base is different from that of modulation unit F or modulation unit G; (2) The material constituting modulation unit F is non-metal, the material constituting modulation unit G is metal, and the material of the rotor base is different from that of modulation unit F or modulation unit G; (3) The materials constituting modulation unit F and modulation unit G are two different non-metals, and the material of the rotor base is different from that of modulation unit F or modulation unit G.

[0056] In this invention, the inner ring excitation unit and sensing unit on the stator base form a capacitor structure, as do the outer ring excitation unit and sensing unit. When the rotor is not installed, an excitation signal is applied to the excitation unit, and the sensing unit outputs zero. When the rotor base and stator base are coaxially parallel and directly opposite each other, the inner and outer ring sensing units each generate a non-zero signal. When the rotor base and stator base rotate relative to each other, the modulation units arranged in the inner and outer rings on the rotor base cause changes in the medium between the excitation and sensing units on the inner and outer rings of the stator base, respectively, thus causing the inner and outer ring sensing units to generate an output signal that responds to angular displacement. After the output signals of the inner and outer rings are processed by the circuit and calculated by the program, the precise and coarse angle count values ​​of the inner and outer rings are obtained, respectively. The precise and coarse angle count values ​​are combined and calculated to obtain the absolute angular displacement measurement value of the sensor, thereby achieving absolute positioning.

[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 time-grid angular displacement sensor based on electric field modulation, comprising a rotor base and a stator base arranged coaxially and parallel to each other with a gap, characterized in that: The upper surface of the stator substrate is provided with several sensing units arranged evenly in two concentric rings, inner and outer. All sensing units in the same ring are identical in shape and size. Each sensing unit in both the inner and outer rings includes an excitation unit and a sensing unit, which are arranged alternately. Every eight sensing units constitute a pole pair. The number of pole pairs in the inner and outer rings are both integers and are not equal. Among all pole pairs in the same ring, 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 ring are connected together to form sensing unit group. At least a portion of the lower surface of the rotor base is divided into inner and outer rings concentric with the rotor base. The inner ring of the rotor base is uniformly divided into several equal parts, the same number of pole pairs as the inner ring of the stator base, and the outer ring of the rotor base is uniformly divided into several equal parts, the same number of pole pairs as the outer ring of the stator base. Each region corresponds to a modulation unit group, and all modulation unit groups on the same ring are identical in shape and size. All modulation unit groups consist of modulation units F and modulation units G, which are made of different materials. The central angle between the two ends of each modulation unit F is the same as the central angle of the region where the modulation unit F is located. In each region, the modulation unit G occupies the remaining region except for the region occupied by the modulation unit F. When the rotor base and the stator base rotate relative to each other, the modulation units F and G are used to change the dielectric between the capacitors formed by the excitation unit and the induction unit on the same ring of the stator base. The modulation units modulate the coupled signals of the induction unit and the excitation unit to achieve passive sensing measurement of the rotor without the need for leads.

2. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 1, characterized in that: The sensing unit is a fan-shaped ring concentric with the stator substrate.

3. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 2, characterized in that: In all modulation unit groups of the same ring, the horizontal plane where all modulation units F or G are located is coplanar with the lower surface of the rotor base, and all modulation units G or F protrude relative to the lower surface of the rotor base.

4. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 2, characterized in that: In all modulation unit groups of the same ring, the horizontal plane where all modulation units F or G are located is coplanar with the lower surface of the rotor base, and there is a cavity on the lower surface of the rotor base, in which all modulation units G or F are embedded.

5. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 2, characterized in that: In all modulation unit groups of the same ring, all modulation units F or G protrude relative to the lower surface of the rotor base and have cavities on the lower surface of the rotor base, and all modulation units G or F are embedded in the cavities.

6. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 1, characterized in that: The relationship between the number of pole pairs N1 of the outer ring and the number of pole pairs N2 of the inner ring of the stator matrix is ​​as follows: N2 = N1 - 1; or N1 and N2 are coprime and N2 ≠ N1 - 1; or N2 = 1 and N1 > 1; or N1 = N2 - 1; or N1 and N2 are coprime and N1 ≠ N2 - 1; or N1 = 1 and N2 > 1.

7. The absolute time-grid angular displacement sensor based on electric field modulation 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. The absolute time-grid angular displacement sensor based on electric field modulation according to claim 1, characterized in that: The material of the rotor base 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 time-grid angular displacement sensor based on electric field modulation 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 rotor substrate and protrudes relative to the lower surface of the rotor substrate, the rotor substrate and modulation unit F or modulation unit G are integrally formed.

10. A method for measuring absolute time-grid angular displacement based on electric field modulation, characterized in that: The measurement is performed using an absolute time-grid angular displacement sensor based on electric field modulation as described in any one of claims 1-9. During measurement, equal-amplitude sinusoidal excitation signals with phase differences of π / 2 are applied to the four-phase excitation unit groups A, B, C, and D on the outer and inner rings of the stator base, respectively. The induction unit groups on the inner and outer rings of the stator base output induction signals, which are then processed by the circuit and calculated by the program to obtain the angle count values ​​of the inner and outer rings. The angle count values ​​of the inner and outer rings are then subtracted to obtain the unique angle value of the rotor base rotation angle within the whole circumference measurement range.

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