Absolute type time grating angular displacement sensor based on electric field modulation and measuring method

Abstract

The invention discloses an absolute time grating angular displacement sensor based on electric field modulation and a measurement method, the upper surface of a stator base body is provided with an inner circle of sensing units and an outer circle of sensing units which are uniformly arranged, and the sensing units comprise excitation units and induction units which are arranged in a staggered manner; every eight sensing units form an antipode, and the numbers of antipodes of the inner ring and the outer ring are different. In all the antipodes in the same circle, all the excitation units in the same sequence are correspondingly connected together, so that four excitation unit groups are formed; all the sensing units in the same circle are connected to form a sensing unit group. The lower surface of the rotor base body is provided with modulation unit groups with inner and outer rings arranged in sequence, and each modulation unit group is composed of a modulation unit F and a modulation unit G. High-precision absolute angular displacement measurement of the sensor can be achieved, signal input and output of the sensor are both located on the stator base body, the rotor does not need a lead, the output signal strength is not limited by the number of sensing units, the structure is simple, and the signal transmission efficiency is higher.

Description

Technical Field

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

[0002] With the rapid development of science and technology, there are increasingly higher requirements for angular displacement sensors in the fields of precision manufacturing, aerospace, national defense and military. At present, angular displacement sensors are divided into two types: incremental and absolute. Compared with incremental sensors, absolute angular displacement sensors have the advantages of no need to reset when turned on, immediate acquisition of absolute angle information and no cumulative error, and gradually become the development trend of angular displacement sensors. At present, the patent that has been disclosed in the technology is an electric field time-grating angular displacement sensor (publication number CN103968750A). This sensor uses high-frequency clock pulses as the measurement reference and uses parallel capacitor plates to construct an alternating electric field for precise angle measurement. The sensor leads out the signal through the wire on the rotor. Due to installation restrictions, the structure is complex and not conducive to miniaturization. Its sensing unit is metal, which is limited by the manufacturing process and has a narrow detection range. The output signal strength of the sensor depends on the number of excitation units and induction units, but the mutual cancellation of signals between its excitation units will result in a low transmission efficiency of the output signal. The sensor adopts an incremental counting method, which will have cumulative errors when working and can only identify the angular displacement within one cycle. The initial position of the sensor after power-on is uncertain, and the current position cannot be recorded after restart or power failure. The reference point must be found again to continue working. It is easily affected by the working environment, generating additional noise or erroneous readings. The above problems limit the application of this sensor in many occasions. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an absolute time-grating angular displacement sensor based on electric field modulation and a measurement method. The present invention can realize high-precision absolute angular displacement measurement of the sensor, and can realize a strong absolute positioning capability of the sensor through the combination of fewer sensing units. At the same time, the signal input and output of the sensor of the present invention are both located on the stator matrix, the rotor does not need leads, and the output signal strength is not limited by the number of sensing units, the structure is simple, and the signal transmission efficiency is higher.

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

[0005] An absolute time-grating angular displacement sensor based on electric field modulation comprises a rotor base and a stator base which are arranged coaxially and in parallel with each other and have a gap, wherein the upper surface of the stator base is provided with a plurality of sensing units which are evenly arranged in the circumferential direction in two inner and outer circles, and all the sensing units on the same circle are completely consistent in shape and size; the sensing units on the inner and outer circles both comprise excitation units and induction units, and the excitation units and induction units are arranged alternately in sequence; every eight sensing units constitute a pole pair, and the number of pole pairs on the inner and outer circles are both integers and unequal; among all pole pairs on the same circle, 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 circle are connected together to form an induction unit group;

[0006] At least part of the lower surface of the rotor base is divided into inner and outer rings concentric with the rotor base, the inner ring on the rotor base is evenly divided into several equal parts with the same number of poles on the inner ring of the stator base, and the outer ring on the rotor base is evenly divided into several equal parts with the same number of poles on the outer ring of the stator base; a modulation unit group is arranged in the area corresponding to each equal part, and all the modulation units on the same ring are completely consistent in shape and size; all the 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, wherein the central angle between the two ends of each modulation unit F is consistent with the central angle corresponding to the area where the modulation unit F is located; in each area, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area; when the rotor base and the stator base rotate relative to each other, the modulation units F and modulation units G are used to change the medium between the capacitors formed by the excitation units and the induction units on the same ring of the stator base, and the passive sensing measurement of the rotor without leads is realized by modulating the signals coupled between the induction unit and the excitation unit through the modulation units.

[0007] Furthermore, the sensing unit is in the shape of a fan ring that is concentric with the stator base.

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

[0009] Alternatively, in all modulation units in the same circle, the horizontal plane where all modulation units F / modulation units 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, and all modulation units G / modulation units F are embedded in the cavity.

[0010] Alternatively, in all modulation units in the same circle, all modulation units F / modulation units G are protruding relative to the surface of the lower body of the rotor base, and there is a cavity on the lower surface of the rotor base, and all modulation units G / modulation units F are embedded in the cavity.

[0011] Furthermore, the relationship between the number of poles N1 of the outer ring of the stator base and the number of poles N2 of the inner ring is: N2=N1-1; or N1 and N2 are prime numbers to each other and N2≠N1-1; or N2=1, N1>1; or N1=N2-1; or N1 and N2 are prime numbers to each other 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 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.

[0014] When the material of the modulation unit F or the modulation unit G is the same as that of the rotor base and is raised relative to the lower surface of the rotor base, the rotor base and the modulation unit F or the modulation unit G are integrally formed.

[0015] The present invention also provides an absolute time-grating angular displacement measurement method based on electric field modulation, which is performed using the aforementioned absolute time-grating angular displacement sensor based on electric field modulation. 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 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 respectively output induction signals and obtain the angle count values ​​of the inner and outer rings after circuit processing and program solution. The angle count values ​​of the inner and outer rings are subjected to difference processing to obtain a unique angle value of the rotation angle of the rotor base within the full-circle measurement range.

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

[0017] The present invention can realize high-precision absolute angular displacement measurement of the sensor by arranging different numbers of sensing units on the inner and outer rings of the sensor stator substrate. The signal input and output of the sensor are both located on the stator substrate, the intensity of the output signal is not limited by the number of sensing units, the signal transmission efficiency is higher, and passive sensing of the rotor can be realized. By combining fewer sensing units in the inner and outer rings, high-precision positioning of the sensor can be achieved. The above characteristics make the sensor have better absolute measurement application capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1Schematic diagram of the three-dimensional structure of Example 1 of the present invention;

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

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

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

[0022] Figure 5 Schematic diagram of the spatial position correspondence between the sensing unit and the modulation unit in Embodiment 1 of the present invention;

[0023] Figure 6 Schematic diagram of the relationship between the number of pole pairs of the inner ring and the outer ring in Example 2 of the present invention;

[0024] Figure 7 Schematic diagram of the relationship between the number of pole pairs of the inner ring and the outer ring in Example 3 of the present invention;

[0025] Figure 8 Schematic diagram of the relationship between the number of pole pairs of the inner ring and the outer ring in Example 4 of the present invention;

[0026] Fig. 9 Schematic diagram of the enclosed pattern of the modulation unit F on the rotor base in Example 1 of the present invention;

[0027] Fig.10 This is a schematic diagram of the rotor base structure in Example 5 of the present invention;

[0028] Fig.11 This is a schematic diagram of the rotor base structure in Example 6 of the present invention. DETAILED DESCRIPTION

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

[0030] See also Figure 1-Figure 3The present invention discloses an absolute time-grating angular displacement sensor based on electric field modulation, comprising a rotor base 2 and a stator base 1 which are coaxially arranged in parallel with each other and have a gap therebetween, wherein the upper surface of the stator base 1 is provided with a plurality of sensing units which are evenly arranged in two inner and outer circles, and all the sensing units on the same circle are exactly the same in shape and size; the sensing units on the inner and outer circles both include excitation units and induction units, and the excitation units and induction units are arranged alternately in sequence, thereby forming an outer circle excitation unit 1-1-1 and an outer circle induction unit 1-1-2 and an inner circle excitation unit 1-2-1 and an inner circle induction unit 1-2-2. Every eight sensing units constitute a pole pair, and the number of pole pairs on the inner circle and the outer circle are both integers and are not equal; among all pole pairs in the same circle, all excitation units in the first order are connected together to form an excitation unit group A, all excitation units in the second order are connected together to form an excitation unit group B, all excitation units in the third order are connected together to form an excitation unit group C, and all excitation units in the fourth order are connected together to form an excitation unit group D; all sensing units in the same circle are connected together to form a sensing unit group.

[0031] At least part of the lower surface of the rotor base 2 is divided into inner and outer rings concentric with the rotor base. The inner ring on the rotor base 2 is evenly divided into several equal parts with the same number of poles as the inner ring of the stator base, and the outer ring on the rotor base is evenly divided into several equal parts with the same number of poles as the outer ring of the stator base. A modulation unit group is provided in the area corresponding to each equal part of the inner and outer rings, that is, a modulation unit group of the outer ring and the inner ring of the rotor base corresponds to the spatial position of the central angle of all the sensing units of a pole of the outer ring and the inner ring of the stator base. Each modulation unit group is composed of a modulation unit F and a modulation unit G, thereby forming an outer ring modulation unit F2-1-1 and an outer ring modulation unit G2-1-2 and an inner ring modulation unit F2-2-1 and an inner ring modulation unit G2-2-2. All modulation units on the same ring are exactly the same in shape and size. In the same circle, 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, wherein the central angle between the two ends of each modulation unit F is consistent with the central angle corresponding to the area where the modulation unit F is located. In each area, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area. Figure 5 The schematic diagram of the spatial position correspondence between the sensing unit and the modulation unit of the present invention. When the rotor base and the stator base rotate relative to each other, the modulation unit F and the modulation unit G are used to change the medium between the capacitors formed by the excitation unit and the induction unit on the same circle of the stator base, and the modulation unit is used to modulate the coupled signal between the induction unit and the excitation unit to realize the passive sensing measurement of the rotor base without leads.

[0032] From the perspective of the concave-convex relationship between the lower surface of the modulation unit and the lower surface of the rotor base, the present invention has the following situations:

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

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

[0035] 3. In all modulation units of the same circle, all modulation units F / modulation units G are protruding relative to the surface of the lower body of the rotor base, and there is a concave cavity on the lower surface of the rotor base, and all modulation units G / modulation units F are embedded in the concave 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 lower surface of the rotor base, 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] Preferably, the relationship between the number of poles N1 of the outer ring of the stator base and the number of poles N2 of the inner ring is: N2=N1-1; or N1 and N2 are prime numbers to each other and N2≠N1-1; or N2=1, N1>1. Or the relationship between the number of poles of the inner and outer rings is reversed, that is, N1=N2-1; or N1 and N2 are prime numbers to each other and N1≠N2-1; or N1=1, N2>1.

[0038] Preferably, the sensing unit (including the excitation unit and the induction unit) is in the shape of a sector ring concentric with the stator base, that is, the excitation unit and the induction unit on the same circle 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 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 .

[0040] Preferably, under the premise that the modulation unit F and the modulation unit G are made of different materials, the material of the rotor base can be 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.

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

[0042] During the measurement, the four-phase excitation unit groups A, B, C, and D on the outer and inner rings of the stator base are respectively applied with equal amplitude and frequency sinusoidal excitation signals U with a phase difference of π / 2. 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 matrix output induction signals respectively. When the rotor matrix 2 and the stator matrix 1 rotate relative to each other, the N1 outer ring modulation units F2-1-1 and outer ring modulation units G2-1-2 set on the outer ring of the rotor matrix 2 will cause the medium between the capacitors 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 matrix 1 to change. The outer ring excitation unit 1-1-1 and the outer ring modulation unit are coupled and then coupled with 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 full cycle measurement range. The N2 inner ring modulation units F2-2-1 and inner ring modulation units G2-2-2 set on the inner ring of the rotor base 2 will cause the dielectric between the capacitors formed by the inner ring excitation unit 1-2-1 and the inner ring induction unit 1-2-2 in the inner ring sensing unit of the stator base 1 to change. The inner ring excitation unit 1-2-1 and the inner ring modulation unit are coupled and then coupled with the inner ring induction unit 1-2-2, so that the inner ring induction unit group outputs a coarse angular displacement signal U2 related to the rotation angle of the inner ring modulation unit. The displacement value calculated by the coarse angular displacement signal U2 output by the inner ring induction unit group is a displacement curve different from the outer ring periodic change within the full cycle measurement range. The precise 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 is the outer ring angular displacement coefficient, Kθ2 is the inner ring angular displacement coefficient, and θ is the measured angular displacement.

[0046] In Example 1 of the present invention, because the number of pole pairs of the outer ring on the stator substrate is greater than the number of pole pairs of the inner ring, the measurement accuracy is higher, so the signal output by the outer ring sensing unit group is called the precise 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 substrate of the present invention and the inner and outer ring modulation units on the rotor substrate are correspondingly combined to form two independent displacement sensors. The present invention makes a difference in the outputs of the two sensors to achieve accurate absolute positioning of angular displacement.

[0047] like Figure 4 As shown in the figure, after the signal acquisition module collects the signals U1 and U2 output by the induction unit group of the outer ring and the inner ring, the phases of the precise angular displacement signal U1 and the coarse angular displacement signal U2 are respectively compared with the same frequency reference signal U r Phase comparison, through the high-frequency pulse clock to interpolate and count the phase difference, respectively, to obtain the outer ring precise measurement phase count value and the inner ring rough measurement phase count value, the maximum phase count value of a single cycle of the outer ring and the inner ring are and Phase count value and The phase count value is a sawtooth shape in the entire measurement range, changing linearly from 0 to 2π in a single pole measurement cycle. and Phase difference after subtraction The unique angle value of the rotation angle of the rotor base within the full-circle measurement range can be obtained by conversion.

[0048]

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

[0050] Embodiment 3: The measurement principle and most of the structure of Embodiment 3 are the same as those of Embodiment 1, except that: Figure 7 As shown, the relationship between the number of poles N1 of the sensor unit pairs on the outer ring and the number of poles N2 of the sensor unit pairs on the inner ring of the stator substrate is: N1 and N2 are prime numbers to each other and N2≠N1-1, specifically N1=10, N2=3.

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

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

[0053] Embodiment 6: The measurement principle and most of the structure of Embodiment 6 are the same as those of Embodiment 1, except that: Fig.11 As shown, the horizontal plane where the modulation unit G is located is coplanar with the surface of the rotor base, and 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] Embodiment 7: The measurement principle and most of the structure of Embodiment 7 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 rotor base 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 rotor base 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 rotor base is the same as the material of the modulation unit F or the modulation unit G; (3) the materials constituting the modulation unit F and the modulation unit G are two different non-metals, and the material of the rotor base 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 structure of Embodiment 8 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 composed of different materials, and the material of the rotor base is different from the materials of 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 rotor base is different from the materials 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 rotor base is different from the materials of the modulation unit F or the modulation unit G; (3) The materials constituting the modulation unit F and the modulation unit G are two different non-metals, and the material of the rotor base is different from the materials of the modulation unit F or the modulation unit G.

[0056] The excitation unit and the induction unit of the inner ring on the stator substrate of the present invention form a capacitor structure, and the excitation unit and the induction unit of the outer ring form a capacitor structure. When the rotor is not installed, an excitation signal is applied to the excitation unit, and the output of the induction unit is zero. When the rotor substrate and the stator substrate are coaxially and parallelly installed, the induction unit of the inner ring and the induction unit of the outer ring will respectively generate a non-zero signal. When the rotor substrate and the stator substrate rotate relative to each other, the modulation units arranged in the inner and outer rings on the rotor substrate will respectively cause the medium between the excitation unit and the induction unit of the inner and outer rings on the stator substrate to change, so that the induction unit of the inner ring and the induction unit of the outer ring respectively generate an output signal that responds to the angular displacement. After the output signals of the inner and outer rings are processed by circuits and solved by programs, the angle count values ​​of the inner and outer rings are respectively obtained. After the angle count values ​​of the fine measurement and the rough measurement are combined and solved, the absolute angular displacement measurement value of the sensor is obtained, thereby achieving absolute positioning.

[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 time-grating 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 matrix is ​​provided with a plurality of sensor units uniformly arranged in the circumferential direction of two inner and outer circles, and all the sensor units on the same circle are exactly the same in shape and size; the sensor units on the inner and outer circles include excitation units and induction units, and the excitation units and induction units are arranged alternately in sequence; every eight sensor units constitute a pole pair, and the number of pole pairs on the inner and outer circles are both integers and unequal; among all pole pairs in the same circle, all the excitation units in the first order are connected together to form an excitation unit group A, all the excitation units in the second order are connected together to form an excitation unit group B, all the excitation units in the third order are connected together to form an excitation unit group C, and all the excitation units in the fourth order are connected together to form an excitation unit group D; all the induction units in the same circle are connected together to form an induction unit group; At least part of the lower surface of the rotor base is divided into inner and outer rings concentric with the rotor base, the inner ring on the rotor base is evenly divided into several equal parts with the same number of poles on the inner ring of the stator base, and the outer ring on the rotor base is evenly divided into several equal parts with the same number of poles on the outer ring of the stator base; a modulation unit group is arranged in the area corresponding to each equal part, and all the modulation units on the same ring are completely consistent in shape and size; all the 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, wherein the central angle between the two ends of each modulation unit F is consistent with the central angle corresponding to the area where the modulation unit F is located; in each area, except for the area occupied by the modulation unit F, the modulation unit G occupies the rest of the area; when the rotor base and the stator base rotate relative to each other, the modulation units F and modulation units G are used to change the medium between the capacitors formed by the excitation units and the induction units on the same ring of the stator base, and the passive sensing measurement of the rotor without leads is realized by modulating the signals coupled between the induction unit and the excitation unit through the modulation units.

2. The absolute time-grating angular displacement sensor based on electric field modulation according to claim 1, characterized in that: The sensor unit is in the shape of a sector ring which is concentric with the stator base.

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

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

5. The absolute time-grating angular displacement sensor based on electric field modulation according to claim 2, characterized in that: In all modulation units in the same circle, all modulation units F / modulation units G are protruding relative to the lower surface of the rotor base, and there is a concave cavity on the lower surface of the rotor base, and all modulation units G / modulation units F are embedded in the concave cavity.

6. The absolute time-grating angular displacement sensor based on electric field modulation according to claim 1, characterized in that: The relationship between the number of poles N1 of the outer ring of the stator base and the number of poles N2 of the inner ring is: N2=N1-1; or N1 and N2 are prime numbers and N2≠N1-1; or N2=1, N1>1; or N1=N2-1; or N1 and N2 are prime numbers and N1≠N2-1; or N1=1, N2>1.

7. The absolute time-grating 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 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 time-grating 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-grating angular displacement sensor based on electric field modulation 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 rotor base and is raised relative to the lower surface of the rotor base, the rotor base and the modulation unit F or the modulation unit G are integrally formed.

10. An absolute time-grating angular displacement measurement method based on electric field modulation, characterized in that: An absolute time-grating angular displacement sensor based on electric field modulation as described in any one of claims 1 to 9 is used for measurement. 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 on the outer ring and inner ring of the stator base respectively. The induction unit groups on the inner and outer rings of the stator base respectively output induction signals and obtain the angle count values ​​of the inner and outer rings after circuit processing and program solution. The angle count values ​​of the inner and outer rings are subjected to difference processing to obtain a unique angle value of the rotation angle of the rotor base within the full-circle measurement range.

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