A displacement feedback control system and method for an in-plane two-dimensional positioning platform

Abstract

The present invention discloses a displacement feedback control system and method for an in-plane two-dimensional positioning platform. The first and second comb tooth units each include two identical and symmetrically arranged comb tooth groups. The in-plane two-dimensional positioning platform also includes a first reference capacitor and a second reference capacitor. The displacement feedback control system uses one comb tooth group in the first or second comb tooth unit as a driving end and the other comb tooth group as a sensing end. After applying a driving voltage signal to the driving end, a current signal at the sensing end and a reference current signal of the corresponding first reference capacitor or second reference capacitor are obtained. A current variation is obtained based on the current signal and the reference current signal. The actual displacement generated by the sensing end is then calculated based on the current variation. The driving voltage signal is then updated based on a deviation signal between the actual displacement and the expected displacement. The present invention achieves high-precision positioning without adding a displacement sensing structure.

Description

Technical Field

[0001] The present invention relates to the technical field of precision positioning systems, and in particular to a displacement feedback control system and method for an in-plane two-dimensional positioning platform. Background Art

[0002] Precision positioning systems have always played a vital role in modern industrial production and scientific research, and are widely used in fields such as semiconductor technology and ultra-precision machining. To meet the demands of small-scale displacement (tens of microns) and high-precision positioning (nanometer level), micro-positioning platforms based on MEMS (Microelectromechanical Systems) technology, such as scanning probe microscopes (SPMs), are playing an increasingly important role.

[0003] Currently, the mainstream drive method for micro-positioning systems generally uses piezoelectric drive, but piezoelectric drive has disadvantages such as displacement attenuation and motion hysteresis at low temperatures. Electrostatic drive, on the other hand, has the advantages of no low-temperature displacement attenuation, no motion hysteresis, and fast response. It can meet the performance requirements of mainstream positioning systems and is widely used in MEMS in-plane two-dimensional positioning systems. Current electrostatically driven two-dimensional positioning platforms face the following major challenges: (i) achieving large displacement ranges in both two directions; (ii) low-crosstalk motion in the X and Y directions; and (iii) high-precision positioning.

[0004] Based on previous research, a low-crosstalk, in-plane, two-dimensional positioning platform based on electrostatic drive has been proposed. This approach considers both the decoupling of the motion mechanism and the decoupling of the drive voltage. By designing the interconnected structure between the inner and outer frames, the entire motion platform achieves decoupling in the X and Y directions. Furthermore, by adding insulating gaps between the device layers of the inner and outer frames, the drive electrodes in different directions are electrically isolated, thus achieving low-crosstalk motion and a large displacement range for the in-plane, two-dimensional electrostatically driven platform. However, achieving high-precision positioning on this basis remains a pressing challenge.

[0005] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention proposes a displacement feedback control system and method for an in-plane two-dimensional positioning platform, which realizes high-precision positioning function without adding a displacement sensing structure.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, the present invention discloses a displacement feedback control system of an in-plane two-dimensional positioning platform, wherein the in-plane two-dimensional positioning platform includes an outer frame, an inner frame, a displacement platform, a first elastic unit, a second elastic unit, a first comb tooth unit and a second comb tooth unit, wherein the outer frame supports the inner frame through the first elastic unit so that the outer frame can drive the inner frame along a first direction, and the inner frame supports the displacement platform through the second elastic unit so that the inner frame can drive the displacement platform along a second direction, the fixed comb tooth portion of the first comb tooth unit is fixedly connected to the outer frame, the movable comb tooth portion of the first comb tooth unit is fixedly connected to the inner frame, the fixed comb tooth portion of the second comb tooth unit is fixedly connected to the inner frame, and the movable comb tooth portion of the second comb tooth unit is fixedly connected to the displacement platform, and the first direction and the second direction are perpendicular to each other; the first comb tooth unit and the second comb tooth unit respectively include two The in-plane two-dimensional positioning platform further comprises a first reference capacitor and a second reference capacitor, the capacitance of the first reference capacitor is equal to the initial capacitance between any group of comb tooth groups in the first comb tooth unit, and the capacitance of the second reference capacitor is equal to the initial capacitance between any group of comb tooth groups in the second comb tooth unit. The displacement feedback control system uses one group of comb tooth groups in the first comb tooth unit or the second comb tooth unit as the driving end and the other group of comb tooth groups as the sensing end. After applying a driving voltage signal to the driving end, the current signal of the sensing end and the corresponding reference current signal of the first reference capacitor or the second reference capacitor are obtained, and the current change is obtained according to the current signal and the reference current signal, and then the actual displacement generated by the sensing end is calculated according to the current change, and the driving voltage signal is updated according to the deviation signal between the actual displacement and the expected displacement.

[0009] Preferably, the displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module, the output end of the driving voltage amplifier is connected to one group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, the input end of the sensing circuit is simultaneously connected to the output electrode of the first reference capacitor and another group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end, the output end of the sensing circuit is connected to the input end of the phase-locked amplifier, the input end of the phase-locked amplifier is also connected to the ground electrode, the output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier.

[0010] Preferably, the displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module, the output end of the driving voltage amplifier is connected to one group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, the input end of the sensing circuit is simultaneously connected to the output electrode of the second reference capacitor and another group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end, the output end of the sensing circuit is connected to the input end of the phase-locked amplifier, the input end of the phase-locked amplifier is also connected to the ground electrode, the output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier.

[0011] Preferably, the displacement feedback control system further includes an FPGA platform, the FPGA platform is connected to the feedback control module, and the output end of the FPGA platform is connected to the ground electrode for outputting a radio frequency signal to the ground electrode.

[0012] Preferably, the feedback control module is specifically a PID control system.

[0013] In the second aspect, the present invention discloses a displacement feedback control method for an in-plane two-dimensional positioning platform, which uses the displacement feedback control system described in the first aspect to control the in-plane two-dimensional positioning platform, including the following steps: using one group of comb tooth groups in the first comb tooth unit or the second comb tooth unit as the driving end, and the other group of comb tooth groups as the sensing end, applying a driving voltage signal to the driving end to obtain a current signal of the sensing end and a reference current signal of the corresponding first reference capacitor or the second reference capacitor, obtaining a current change based on the current signal and the reference current signal, and then calculating the actual displacement generated by the sensing end based on the current change, and then updating the driving voltage signal based on the deviation signal between the actual displacement and the expected displacement.

[0014] Preferably, the displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module, the output end of the driving voltage amplifier is connected to one group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, the input end of the sensing circuit is simultaneously connected to the output electrode of the first reference capacitor and another group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end, the output end of the sensing circuit is connected to the input end of the phase-locked amplifier, the input end of the phase-locked amplifier is also connected to the ground electrode, the output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier; the displacement feedback control method includes the following steps:

[0015] A1: the driving voltage amplifier applies a driving voltage signal to one of the comb tooth groups in the first comb tooth unit as the driving end;

[0016] A2: the sensing circuit performs a subtraction of the reference current signal corresponding to the first reference capacitor sensed and the current signal of the comb teeth group of the other comb teeth group in the first comb teeth unit serving as the sensing end, amplifies the difference proportionally to obtain an amplified signal, and then sends the amplified signal to the lock-in amplifier;

[0017] A3: The lock-in amplifier obtains an interference-free voltage signal according to the amplified signal, receives a reference signal from the ground electrode, and then simultaneously sends the interference-free voltage signal and the reference signal to the feedback control module;

[0018] A4: The feedback control module obtains the actual displacement of any group of comb teeth in the first comb tooth unit based on the interference-free voltage signal and the reference signal, and compares whether there is a deviation between the actual displacement and the expected displacement. If so, the deviation signal between the actual displacement and the expected displacement is used to update the driving voltage signal, and the updated driving voltage signal is sent to the driving voltage amplifier, and the process returns to step A1.

[0019] Preferably, the displacement feedback control method further comprises: applying a radio frequency signal V to the ground electrode pp , where the RF signal V pp =V pp =A0sin(ωt), where A0 is the amplitude of the applied radio frequency, ω is the radio frequency angular frequency, and t is the time constant; the reference current signal i corresponding to the first reference capacitor sensed by the sensing circuit in step A2 is 11 For: i 11 =A0ωC1cosωt, where C1 is the capacitance value of the first reference capacitor; the current signal i of another comb tooth group in the first comb tooth unit sensed by the sensing circuit is 12 For: i 12 =A0ω(C1+ΔC1)cosωt, where ΔC1 is the capacitance change between the moving comb teeth and the fixed comb teeth of any comb tooth group in the first comb tooth unit; in step A4, the feedback control module calculates the capacitance change and displacement according to the corresponding relationship between capacitance change and displacement, ΔC1=2N a ε0h a Δx / g is used to calculate the actual displacement Δx of any comb tooth group in the first comb tooth unit, where N a is the number of teeth pairs of any comb tooth group in the first comb tooth unit, ε0 is the dielectric constant of air, h a is the comb teeth thickness, and g is the comb teeth gap.

[0020] Preferably, the displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module, the output end of the driving voltage amplifier is connected to one group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, the input end of the sensing circuit is simultaneously connected to the output electrode of the second reference capacitor and the other group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end, the output end of the sensing circuit is connected to the input end of the phase-locked amplifier, the input end of the phase-locked amplifier is also connected to the ground electrode, the output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier; the displacement feedback control method includes the following steps:

[0021] B1: the driving voltage amplifier applies a driving voltage signal to one of the comb tooth groups in the second comb tooth unit as the driving end;

[0022] B2: the sensing circuit performs a subtraction of the reference current signal corresponding to the second reference capacitor sensed and the current signal of the other comb tooth group in the second comb tooth unit serving as the sensing end, amplifies the difference proportionally to obtain an amplified signal, and then sends the amplified signal to the lock-in amplifier;

[0023] B3: the lock-in amplifier obtains an interference-free voltage signal according to the amplified signal, receives a reference signal from the ground electrode, and then simultaneously sends the interference-free voltage signal and the reference signal to the feedback control module;

[0024] B4: The feedback control module obtains the actual displacement of any group of comb teeth in the second comb tooth unit based on the interference-free voltage signal and the reference signal, and uses the deviation signal between the actual displacement and the expected displacement to update the driving voltage signal, and sends the updated driving voltage signal to the driving voltage amplifier, and returns to step B1.

[0025] Preferably, the displacement feedback control method further comprises: applying a radio frequency signal V to the ground electrode pp , where the RF signal V pp =V pp =A0sin(ωt), where A0 is the amplitude of the applied radio frequency, ω is the radio frequency angular frequency, and t is the time constant; the reference current signal i corresponding to the second reference capacitor sensed by the sensing circuit in step B2 21 For: i 21 =A0ωC2cosωt, where C2 is the capacitance value of the second reference capacitor; the current signal i of another comb tooth group in the second comb tooth unit sensed by the sensing circuit is 22For: i 22 =A0ω(C2+ΔC2)cosωt, where ΔC2 is the capacitance change between the moving comb teeth and the fixed comb teeth of any comb tooth group in the second comb tooth unit; in step B4, the feedback control module calculates the capacitance change and displacement according to the corresponding relationship between capacitance change and displacement, ΔC2=2N a ε0h a Δy / g is used to calculate the actual displacement Δy of any comb tooth group in the second comb tooth unit, where N a is the number of teeth pairs of any comb tooth group in the first comb tooth unit, ε0 is the dielectric constant of air, h a is the comb teeth thickness, and g is the comb teeth gap.

[0026] Furthermore, a radio frequency signal V is applied to the ground electrode via the FPGA platform. pp .

[0027] Compared with the prior art, the beneficial effect of the present invention lies in: the displacement feedback control system of the in-plane two-dimensional positioning platform based on the electrostatic drive method proposed in the present invention, on the basis of the non-coupled motion structure, uses two groups of identical and symmetrical comb tooth groups in the first comb tooth unit or the second comb tooth unit, one comb tooth group as the driving end and the other comb tooth group as the sensing end, and sets corresponding reference capacitors, and further utilizes the consistency of the displacement generated by the driving end and the sensing end. Without adding a displacement sensing structure, the platform displacement feedback control link can be realized, thereby further improving the positioning accuracy of the platform.

[0028] Furthermore, the reference current signal corresponding to the phase-locked amplifier and the reference capacitor is used to filter out interference signals; the detected current change is converted into a voltage change and then into a capacitance change through a sensing circuit, and the displacement generated by the sensing end is calculated using the capacitance change; the displacement generated by the driving end can be accurately obtained by detecting the displacement of the sensing end, and the detected displacement is fed back through a feedback control module; the entire structure moves independently in two mutually perpendicular directions (for example, X and Y directions) without interfering with each other, with one end driving and the other end sensing, and only four driving electrodes are used to achieve precise positioning, with a simple structure.

[0029] In a further solution, radio frequency signals are used as the sensing signal source of the sensor, effectively avoiding the influence of the sensor's own electric potential energy on the actuator driving performance; furthermore, the entire feedback control system is based on the FPGA platform, enabling the two-dimensional electrostatic drive platform to achieve rapid response and precise control in the ±X and ±Y directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural diagram of the in-plane two-dimensional positioning platform;

[0031] Figures 2a to 2d Schematic diagram of a displacement feedback control system of an in-plane two-dimensional positioning platform according to a preferred embodiment of the present invention;

[0032] Figure 3a and Figure 3b It is the flow chart of the displacement feedback control system;

[0033] Figure 4 It is the displacement feedback control FPGA platform of the inner two-dimensional positioning platform of the preferred embodiment of the present invention;

[0034] Figure 5 This is a diagram showing the displacement drive positioning effect in the +X-axis direction under different drive voltages. DETAILED DESCRIPTION

[0035] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope of the present invention and its application.

[0036] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for both fixing and circuit / signal communication.

[0037] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of such features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0039] Under normal circumstances, to achieve high-precision positioning function, it is necessary to respectively build-in displacement sensors in different driving directions to further construct a closed-loop feedback control system. It should be noted that, in the current structural design, further building-in displacement sensor structure, such as adding four displacement sensors in the four directions of +X, -X, +Y, and -Y, will make the overall structure of the in-plane two-dimensional positioning platform extremely complicated, and will easily cause the problem of electrical crosstalk between multiple electrodes. Therefore, how to achieve closed-loop feedback control of displacement without increasing the complexity of the structure will be the key to improving the high-precision positioning function of the electrostatically driven two-dimensional platform. This application utilizes the symmetrical distribution characteristics of the in-plane comb teeth (+X and -X, +Y and -Y) of the electrostatically driven MEMS in-plane two-dimensional positioning platform, and proposes a novel new strategy of complementary driving and sensing without additionally adding the displacement sensor structure, which can efficiently achieve high-precision positioning function.

[0040] like Figure 1 As shown, it is a structural schematic diagram of an electrostatically driven in-plane two-dimensional positioning platform 100, wherein the in-plane two-dimensional positioning platform 100 includes an outer frame 10, an inner frame 20, a translation stage 30, a first elastic unit, a second elastic unit, a first comb tooth unit and a second comb tooth unit, wherein the outer frame 10 supports the inner frame 20 through the first elastic unit so that the outer frame 10 can drive the inner frame 20 along the first direction, and the inner frame 20 supports the translation stage 30 through the second elastic unit so that the inner frame 20 can drive the translation stage 30 along the second direction, the fixed comb tooth portion of the first comb tooth unit is fixedly connected to the outer frame 10, the movable comb tooth portion of the first comb tooth unit is fixedly connected to the inner frame 20, the fixed comb tooth portion of the second comb tooth unit is fixedly connected to the inner frame 20, and the movable comb tooth portion of the second comb tooth unit is fixedly connected to the translation stage 30; in this embodiment, the first direction is the X-axis direction, and the second direction is the Y-axis direction, that is, the first direction and the second direction are perpendicular to each other.

[0041] The first comb tooth unit includes a first comb tooth group 41 and a third comb tooth group 43. The first comb tooth group 41 and the third comb tooth group 43 are identical and symmetrically arranged. Specifically, the fixed comb tooth portions of the first comb tooth group 41 and the third comb tooth group 43 are respectively fixedly connected to the inner walls of the two side edges of the outer frame 10 arranged along the Y-axis direction, the movable comb tooth portion of the first comb tooth group 41 is fixedly connected to the side wall of the inner frame 20 opposite to the fixed comb tooth portion of the first comb tooth group 41, and the movable comb tooth portion of the third comb tooth group 43 is fixedly connected to the side wall of the inner frame 20 opposite to the fixed comb tooth portion of the third comb tooth group 43. The second comb tooth unit includes a second comb tooth group 42 and a fourth comb tooth group 44. The second comb tooth group 42 and the fourth comb tooth group 44 are identical and symmetrically arranged. Specifically, the fixed comb tooth portions of the second comb tooth group 42 and the fourth comb tooth group 44 are respectively fixedly connected to the inner walls of the two side edges of the inner frame 20 arranged along the X-axis direction, the movable comb tooth portion of the second comb tooth group 42 is fixedly connected to the side wall of the displacement stage 30 opposite to the fixed comb tooth portion of the second comb tooth group 42, and the movable comb tooth portion of the fourth comb tooth group 44 is fixedly connected to the side wall of the displacement stage 30 opposite to the fixed comb tooth portion of the fourth comb tooth group 44.

[0042] The first elastic unit includes two first elastic elements 51, each of which includes four first flexible rods arranged along the Y-axis. The outer ends of the four first flexible rods are connected by a plurality of first connecting members. The inner ends of some of the first flexible rods are connected to the outer frame 10, while the inner ends of other first flexible rods are connected to the inner frame 20. In this embodiment, the inner ends of the first flexible rods on both sides are connected to the outer frame 10, while the inner ends of the first flexible rods in the middle are connected to the inner frame 20. The second elastic unit includes a second elastic element 52, which includes four second flexible rods arranged along the X-axis. The inner ends of the four second flexible rods are connected by a plurality of second connecting members. The outer ends of some of the second flexible rods are connected to the inner frame 20, while the outer ends of other second flexible rods are connected to the translation stage 30. In this embodiment, the outer ends of the second flexible rods in the middle are connected to the inner frame 20, while the outer ends of the second flexible rods on both sides are connected to the translation stage 30.

[0043] The electrostatic comb-driven, low-crosstalk, in-plane, two-dimensional positioning platform of this embodiment is based on a silicon-on-insulator (SOI) material structure. The SOI material comprises a device layer (silicon), a sacrificial layer (silicon dioxide), and a substrate layer (silicon), totaling three layers. The outer frame 10 is composed of the device layer, the sacrificial layer, and the substrate layer. The inner frame 20 is primarily composed of the device layer, which also includes portions of the sacrificial layer and the substrate layer. The translation stage 30 is also composed of the device layer. The first drive electrode 61, the second drive electrode 62, the third drive electrode 63, the fourth drive electrode 64, and the two ground electrodes 65 are all disposed on the device layer of the outer frame 10. A first insulating gap 101 is provided on the device layers of the outer and inner frames 10 and 20 to electrically insulate the first drive electrode 61, the second drive electrode 62, the third drive electrode 63, the fourth drive electrode 64, and the two ground electrodes 65. Part of the sacrificial layer and the substrate layer of the inner frame 20 are disposed below the corresponding locations of the device layer where the first insulating gap 101 is provided. In this embodiment, the first insulating gap 101 is 20 to 30 μm in size. Furthermore, a second insulating gap 201 is provided in the sacrificial layer of the outer frame 10 and the inner frame 20. The second insulating gap 201 corresponds to the position of the first insulating gap 101 and is slightly larger than the first insulating gap 101. A third insulating gap is provided in the substrate layer of the outer frame 10 and the inner frame 20. The third insulating gap is located near the first insulating gap, for example, at a distance of 200 to 400 μm from the first insulating gap. In this embodiment, the third insulating gap is 20 to 30 μm in size.

[0044] The driving voltage applied to the first drive electrode 61, the second drive electrode 62, the third drive electrode 63, and the fourth drive electrode 64 causes the movable comb teeth of the corresponding first comb tooth group 41, the second comb tooth group 42, the third comb tooth group 43, and the fourth comb tooth group 44 to move in the ±X and ±Y directions, respectively, toward the fixed comb tooth group. In other words, when the required driving voltage is applied between a drive electrode and the ground electrode within the in-plane two-dimensional positioning platform, the corresponding comb tooth generates an electrostatic force, which acts on the support spring, resulting in a corresponding displacement. The translation stage 30 can be driven along the Y-axis by the inner frame 20, and the translation stage 30 and the inner frame 20 can be driven together along the X-axis by the outer frame 10. This structural design ensures that the movement of the translation stage 30 in the X- and Y-axis directions is decoupled.

[0045] The preferred embodiment of the present invention is based on the above-mentioned electrostatic comb-driven low-crosstalk motion in-plane two-dimensional positioning platform, and adds two reference capacitors to further propose a displacement feedback control system and method. Among them, the two reference capacitors are respectively a first reference capacitor 71 and a second reference capacitor 72 added on the outer frame 10. Correspondingly, the ±X direction reference electrodes 66 corresponding to the first reference capacitor 71 and the ±Y direction reference electrodes 67 corresponding to the second reference capacitor 72 are correspondingly set on the device layer of the outer frame 10. In this embodiment, the first reference capacitor 71 and the second reference capacitor 72 respectively adopt a comb-shaped structure. In other embodiments, parallel plate structures can also be used. The in-plane two-dimensional positioning platform is a structural design based on silicon on insulator (SOI) material, adopting an outer frame-in-frame interconnection (frame-in-frame) structure, comprising an external fixed frame (referred to as the outer frame), an internal movable frame (referred to as the inner frame), and a displacement stage. Among them, the outer frame 10 supports the inner frame 20 through two support springs (two first elastic elements 51), and the inner frame 20 supports the displacement stage 30 through a support spring (a second elastic element 52). The outer frame 10 includes fixed comb tooth portions of the first comb tooth group 41 and the third comb tooth group 43, which respectively drive the inner frame 20 along the ±X axis directions. The outer frame 10 also includes a first reference capacitor 71 and a second reference capacitor 72. The capacitance value of the first reference capacitor 71 is equal to the initial capacitance value of the first comb tooth group 41 or the initial capacitance value of the third comb tooth group 43 in the ±X direction (the initial capacitance value of the first comb tooth group 41 is equal to the initial capacitance value of the third comb tooth group 43). The capacitance value of the second reference capacitor 72 is equal to the initial capacitance value of the second comb tooth group 42 or the initial capacitance value of the fourth comb tooth group 44 in the ±Y direction (the initial capacitance value of the second comb tooth group 42 is equal to the initial capacitance value of the fourth comb tooth group 44). The inner frame 20 includes fixed comb tooth portions of the second comb tooth group 42 and the fourth comb tooth group 44, which respectively drive the translation stage 30 along the ±Y axis directions. Because the corresponding drive electrodes (first drive electrode 61, second drive electrode 62, third drive electrode 63, fourth drive electrode 64) and ground electrode 65 of the first, second, third, and fourth comb tooth groups 41, 42, 43, and 44 are uniformly distributed within the outer frame 10, insulating gaps 101 and 201 are required within the device layers of the outer and inner frames 10 and 20 to electrically insulate the drive electrodes. This structural design enables the translation stage 30 to achieve decoupling of its motion mechanism and drive voltage along the X and Y directions.

[0046] The displacement feedback control system of the in-plane two-dimensional positioning platform proposed in the preferred embodiment of the present invention utilizes the symmetrical distribution characteristics of the comb structure of the in-plane two-dimensional positioning platform in the four directions of +X, -X, +Y, and -Y, and can well realize the displacement sensing function in the four directions, such as Figures 2a to 2d shown.

[0047] like Figure 2a As shown, the first comb tooth group 41 serves as a driving end, and the third comb tooth group 43 serves as a sensing end. The displacement feedback control system includes a sensing circuit 200, a lock-in amplifier 300, a driving voltage amplifier 400, a feedback control module 500, and an FPGA platform 600. The output end of the driving voltage amplifier 400 is connected to the first driving electrode 61 corresponding to the first comb tooth group 41, and the input end of the sensing circuit 200 is simultaneously connected to the output electrode (±X direction reference electrode 66) of the first reference capacitor 71 and the third driving electrode 63 corresponding to the third comb tooth group 43. The output end of the sensing circuit 200 is connected to the input end of the lock-in amplifier 300, and the input end of the lock-in amplifier 300 is also connected to the ground electrode 65. The output end of the lock-in amplifier 300 is connected to the input end of the feedback control module 500, and the output end of the feedback control module 500 is connected to the input end of the driving voltage amplifier 400. The FPGA platform 600 is connected to the feedback control module 500, and the output end of the FPGA platform 600 is connected to the ground electrode 65 for outputting a radio frequency signal to the ground electrode 65.

[0048] When moving in the -X axis direction, Figure 2aWhen a drive voltage signal 701 is applied to the first drive electrode 61 of the first comb tooth group 41, the moving comb teeth of the first comb tooth group 41, along with the entire inner frame 20 structure, move in the -X direction. At this time, the movable comb teeth of the third comb tooth group 43 also move in the -X direction, causing the capacitance of the capacitor of the third comb tooth group 43 to change. The displacement of the third comb tooth group 43 and the first comb tooth group 41 are identical. Therefore, the third comb tooth group 43 can be used as a displacement sensor for the first comb tooth group 41. By detecting the capacitance change of the third comb tooth group 43, the displacement of the third comb tooth group 43 can be determined. Since the entire inner frame 20 is integral, the displacement of the third comb tooth group 43 is equal to that of the first comb tooth group 41. A radio frequency signal 702 is applied to the ground electrode 65, and the output electrode (±X-direction reference electrode 66) of the first reference capacitor 71 (the capacitance of the first reference capacitor 71 is equal to the initial capacitance between the first comb tooth group 41 in the X direction and also equal to the initial capacitance between the third comb tooth group 43) obtains a reference current signal 703. This reference current signal 703 serves as a reference signal and does not change with changes in the drive voltage. After the drive voltage signal 701 is applied, the changed current can be detected at the electrode output end corresponding to the third comb tooth group 43 (the third drive electrode 63). The sensing circuit 200 is used to subtract the reference current signal 703 from the sensed current signal 704 after the drive voltage is applied and proportionally amplified. The amplified signal is then transmitted to the lock-in amplifier 300 to obtain a voltage signal without interference (the radio frequency signal 702 is also transmitted to the lock-in amplifier 300 as a reference signal 705). Since this voltage signal is proportional to the displacement, the actual displacement can also be obtained. A determination is made as to whether there is a deviation between the actual displacement and the expected displacement. If so, a new drive voltage signal 701 is generated based on the PID control system and the drive voltage amplifier using the deviation signal. If no deviation exists, updating the drive voltage signal 701 is stopped. By continuously updating the drive voltage, the displacement of the first comb tooth group 41 reaches the expected displacement. The entire system can be controlled based on the FPGA platform 600.

[0049] like Figure 2bAs shown, the second comb tooth group 42 serves as a driving end and the fourth comb tooth group 44 serves as a sensing end. The displacement feedback control system includes a sensing circuit 200, a lock-in amplifier 300, a driving voltage amplifier 400, a feedback control module 500 and an FPGA platform 600, wherein the output end of the driving voltage amplifier 400 is connected to the second driving electrode 62 corresponding to the second comb tooth group 42, the input end of the sensing circuit 200 is simultaneously connected to the output electrode of the second reference capacitor 71 (±Y direction reference electrode 67) and the fourth driving electrode 64 corresponding to the fourth comb tooth group 44, the output end of the sensing circuit 200 is connected to the input end of the lock-in amplifier 300, the input end of the lock-in amplifier 300 is also connected to the ground electrode 65, the output end of the lock-in amplifier 300 is connected to the input end of the feedback control module 500, the output end of the feedback control module 500 is connected to the input end of the driving voltage amplifier 400, the FPGA platform 600 is connected to the feedback control module 500, and the output end of the FPGA platform 600 is connected to the ground electrode 65 for outputting a radio frequency signal to the ground electrode 65.

[0050] Similarly, when moving in the +Y axis direction, Figure 2bWhen a driving voltage signal 701 is applied to the second drive electrode 62 of the second comb tooth group 42, the movable comb teeth of the fourth comb tooth group 44, along with the entire inner frame 20 structure, move in the +Y direction. At this time, the movable comb teeth of the fourth comb tooth group 44 move synchronously in the +Y direction, causing the capacitance of the capacitor of the fourth comb tooth group 44 to change. Therefore, the fourth comb tooth group 44 can be used as a displacement sensor for the second comb tooth group 42. By detecting the capacitance change of the fourth comb tooth group 44, the displacement of the second comb tooth group 42 can be determined. When a radio frequency signal 702 is applied to the ground electrode 65, a reference current signal 703 is generated at the output electrode (±Y direction reference electrode 67) of the second reference capacitor 72 (the capacitance of the second reference capacitor 72 is equal to the initial capacitance between the second comb tooth group 42 and the fourth comb tooth group 44 in the Y direction). This reference current signal 703 serves as a reference signal. After the driving voltage signal 701 is applied, the changed current can be detected at the electrode output end (fourth drive electrode 64) corresponding to the fourth comb tooth group 44. The sensing circuit 200 is utilized to make a difference between the reference current signal 703 and the sensing current signal 704 after applying the driving voltage and proportionally amplify the difference, and then transmit the amplified signal to the lock-in amplifier 300 to obtain a voltage signal without interference (the radio frequency signal 702 is also transmitted to the lock-in amplifier 300 as a reference signal 705). Since the voltage signal is proportional to the displacement, the actual displacement can also be obtained. It is determined whether there is a deviation between the actual displacement and the expected displacement. If there is a deviation, the deviation signal of the actual displacement and the expected displacement is utilized to obtain a new driving voltage signal 701 based on the PID control system and the voltage amplifier. If there is no deviation, the updating of the driving voltage signal 701 is stopped. By continuously updating the driving voltage, the displacement of the second comb tooth group 42 reaches the expected displacement. Among them, the entire system can be controlled based on the FPGA platform 600.

[0051] like Figure 2cAs shown, the third comb tooth group 43 serves as a driving end, and the first comb tooth group 41 serves as a sensing end. The displacement feedback control system includes a sensing circuit 200, a lock-in amplifier 300, a driving voltage amplifier 400, a feedback control module 500, and an FPGA platform 600. The output end of the driving voltage amplifier 400 is connected to the third driving electrode 63 corresponding to the third comb tooth group 43, the input end of the sensing circuit 200 is simultaneously connected to the output electrode (±X direction reference electrode 66) of the first reference capacitor 71 and the first driving electrode 61 corresponding to the first comb tooth group 41, the output end of the sensing circuit 200 is connected to the input end of the lock-in amplifier 300, and the input end of the lock-in amplifier 300 is also connected to the ground electrode 65, the output end of the lock-in amplifier 300 is connected to the input end of the feedback control module 500, the output end of the feedback control module 500 is connected to the input end of the driving voltage amplifier 400, the FPGA platform 600 is connected to the feedback control module 500, and the output end of the FPGA platform 600 is connected to the ground electrode 65 for outputting a radio frequency signal to the ground electrode 65.

[0052] Similarly, when moving in the +X axis direction, Figure 2cAs shown, when a driving voltage signal 701 is applied to the third driving electrode 63 of the third comb tooth group 43, the moving comb teeth of the third comb tooth group 43, along with the entire inner frame 20 structure, move in the +X direction. At this time, the movable comb teeth of the first comb tooth group 41 simultaneously move in the +X direction, causing the capacitance of the capacitor of the first comb tooth group 41 to change. Therefore, the first comb tooth group 41 can be used as a displacement sensor for the third comb tooth group 43. By detecting the capacitance change of the first comb tooth group 41, the displacement of the third comb tooth group 43 can be calculated. Since the entire inner frame 20 is integral, the displacement of the first comb tooth group 41 is equal to the displacement of the third comb tooth group 43. A radio frequency signal 702 is applied to the ground electrode 65, and the output electrode (±X-direction reference electrode 66) of the first reference capacitor 71 (the capacitance of the first reference capacitor 71 is equal to the initial capacitance between the first comb tooth group 41 in the X direction and also equal to the initial capacitance between the third comb tooth group 43) obtains a reference current signal 703. This reference current signal 703 serves as a reference signal and does not change with changes in the driving voltage. After the driving voltage signal 701 is applied, the changed current can be detected at the electrode output end corresponding to the first comb tooth group 41 (the first driving electrode 61). The sensing circuit 200 is used to subtract the reference current signal 703 from the sensing current signal 704 after the driving voltage is applied and proportionally amplified. The amplified signal is then transmitted to the lock-in amplifier 300 to obtain a voltage signal without interference (the radio frequency signal 702 is also transmitted to the lock-in amplifier 300 as a reference signal 705). Since this voltage signal is proportional to the displacement, the actual displacement can also be obtained. A determination is made as to whether there is a deviation between the actual displacement and the expected displacement. If so, a new drive voltage signal 701 is generated based on the PID control system and the drive voltage amplifier using the deviation signal. If no deviation exists, updating the drive voltage signal 701 is stopped. By continuously updating the drive voltage, the displacement of the third comb tooth group 43 reaches the expected displacement. The entire system can be controlled based on the FPGA platform 600.

[0053] like Figure 2dAs shown, the fourth comb tooth group 44 serves as a driving end and the second comb tooth group 42 serves as a sensing end. The displacement feedback control system includes a sensing circuit 200, a lock-in amplifier 300, a driving voltage amplifier 400, a feedback control module 500 and an FPGA platform 600, wherein the output end of the driving voltage amplifier 400 is connected to the fourth driving electrode 64 corresponding to the fourth comb tooth group 44, the input end of the sensing circuit 200 is simultaneously connected to the output electrode of the second reference capacitor 71 (±Y direction reference electrode 67) and the second driving electrode 62 corresponding to the second comb tooth group 42, the output end of the sensing circuit 200 is connected to the input end of the lock-in amplifier 300, the input end of the lock-in amplifier 300 is also connected to the ground electrode 65, the output end of the lock-in amplifier 300 is connected to the input end of the feedback control module 500, the output end of the feedback control module 500 is connected to the input end of the driving voltage amplifier 400, the FPGA platform 600 is connected to the feedback control module 500, and the output end of the FPGA platform 600 is connected to the ground electrode 65 for outputting a radio frequency signal to the ground electrode 65.

[0054] Similarly, when moving in the -Y axis direction, Figure 2dAs shown, when a driving voltage signal 701 is applied to the fourth drive electrode 64 of the fourth comb tooth group 44, the moving comb teeth of the fourth comb tooth group 44, along with the entire center disk, move in the -Y direction. At this time, the movable comb teeth of the second comb tooth group 42 simultaneously move in the -Y direction, causing the capacitance of the capacitor of the second comb tooth group 42 to change. Therefore, the second comb tooth group 42 can be used as a displacement sensor for the fourth comb tooth group 44. By detecting the capacitance change of the second comb tooth group 42, the displacement of the fourth comb tooth group 44 can be determined. When a radio frequency signal 702 is applied to the ground electrode 65, a reference current signal 703 is generated at the output electrode (±Y direction reference electrode 67) of the second reference capacitor 72 (the capacitance of the second reference capacitor 72 is equal to the initial capacitance between the second comb tooth group 42 in the Y direction and the initial capacitance between the fourth comb tooth group 44). This reference current signal 703 serves as a reference signal. After the driving voltage signal 701 is applied, the changed current can be detected at the electrode output end (second drive electrode 62) corresponding to the second comb tooth group 42. The sensing circuit 200 is utilized to make a difference between the reference current signal 703 and the sensing current signal 704 after applying the driving voltage and proportionally amplify the difference, and then transmit the amplified signal to the lock-in amplifier 300 to obtain a voltage signal without interference (the radio frequency signal 702 is also transmitted to the lock-in amplifier 300 as a reference signal 705). Since the voltage signal is proportional to the displacement, the actual displacement can also be obtained. It is determined whether there is a deviation between the actual displacement and the expected displacement. If there is a deviation, the deviation signal of the actual displacement and the expected displacement is utilized to obtain a new driving voltage signal 701 based on the PID control system and the voltage amplifier. If there is no deviation, the updating of the driving voltage signal 701 is stopped. By continuously updating the driving voltage, the displacement of the fourth comb tooth group 44 reaches the expected displacement. Among them, the entire system can be controlled based on the FPGA platform 600.

[0055] In summary, when the first comb tooth group 41, the second comb tooth group 42, the third comb tooth group 43, and the fourth comb tooth group 44 act as driving units to generate displacement, the third comb tooth group 43, the fourth comb tooth group 44, the first comb tooth group 41, and the second comb tooth group 42 act as displacement sensors to sense displacement. Figures 2a to 2d It can be seen from the displacement feedback control system shown that the drive and sensing of the in-plane two-dimensional positioning platform can complement each other. The use of radio frequency signals as the sensing signal source of the sensor can effectively avoid the influence of the sensor's own electric potential energy on the driver's driving performance.

[0056] Based on an electrostatically driven two-dimensional positioning platform, the displacement feedback control system and method provided by the preferred embodiment of the present invention utilizes the complementary nature of the drive and sensor terminals, enabling convenient displacement sensing without the need for additional structures, and achieving higher-precision positioning using the control system. This solution leverages the symmetry of the overall structure, with one end sensing and the other driving, and the displacement of the drive end is calculated by the sensing circuit at the sensing end. Furthermore, by using radio frequency signals and sensing circuits to convert current changes at the sensing end into displacement changes, feedback control is achieved using PID.

[0057] by Figure 2a As an example, a radio frequency signal V is applied to the ground electrode of the in-plane two-dimensional positioning platform. pp =A0sin(ωt) (where A0 is the amplitude of the applied radio frequency, ω is the radio frequency angular frequency, and t is the time constant). The current signal i can be detected at the fixed comb electrode end of the third comb group 43. 11 =A0ωC1cosωt(where i 11 is the initial current without applying a driving voltage, and C1 is the initial capacitance value of the first reference capacitor 71). When a driving voltage is applied to the first comb tooth group 41 to cause the entire internal frame to move along the -X direction, the capacitance value of the capacitor of the third comb tooth group 43 changes by ΔC1, causing the current signal at the fixed comb tooth electrode end of the third comb tooth group 43 to change accordingly; at this time, the current signal at the end of the third comb tooth group 43 is i 12 =A0ω(C1+ΔC1)cosωt. Then, the current signal can be further converted into a voltage signal through the sensing circuit 200, and the phase-locked amplifier 300 is used to output the sensed displacement signal, thereby realizing the corresponding relationship between the motion displacement and the sensed voltage value. Here, the capacitance change ΔC1 between the moving comb teeth and the fixed comb teeth has a one-to-one correspondence with the displacement Δx of the moving comb teeth. According to ΔC1=2N a ε0h a Δx / g(where, N a is the number of teeth in the third comb tooth group 43, ε0 is the dielectric constant of air, h a is the comb tooth thickness, g is the comb tooth gap) the displacement of the third comb tooth group 43 can be obtained. Similarly, Figure 2c The driving and sensing complementary structure principle shown is the same as Figure 2a , I will not go into details here.

[0058] by Figure 2b As an example, a radio frequency signal V is applied to the ground electrode of the in-plane two-dimensional positioning platform. pp =A0sin(ωt) (where A0 is the amplitude of the applied radio frequency, ω is the radio frequency angular frequency, and t is the time constant). The current signal i can be detected at the fixed comb electrode end of the fourth comb group 44. 21=A0ωC2cosωt(where i 21 is the initial current without applying a driving voltage, and C2 is the initial capacitance value of the second reference capacitor 72. When a driving voltage is applied to the second comb tooth group 42 to cause the entire internal frame to move in the +Y direction, the capacitance value of the capacitor of the fourth comb tooth group 44 changes by ΔC2, causing the current signal at the fixed comb tooth electrode end of the fourth comb tooth group 44 to change accordingly; at this time, the current signal at the end of the fourth comb tooth group 44 is i 22 =A0ω(C2+ΔC2)cosωt. Then, the current signal can be further converted into a voltage signal through the sensing circuit 200, and the phase-locked amplifier 300 is used to output the sensed displacement signal, thereby realizing the corresponding relationship between the motion displacement and the sensed voltage value. Here, the capacitance change ΔC2 between the moving comb teeth and the fixed comb teeth has a one-to-one correspondence with the displacement Δy of the moving comb teeth. According to ΔC2=2N a ε0h a Δy / g(where N a is the number of teeth in the fourth comb tooth group 44, ε0 is the dielectric constant of air, h a is the comb tooth thickness, g is the comb tooth gap) the displacement of the fourth comb tooth group 44 can be obtained. Similarly, Figure 2d The driving and sensing complementary structure principle shown is the same as Figure 2b , I will not go into details here.

[0059] Figure 3a and Figure 3b This is a flow chart of the feedback control system of the in-plane two-dimensional positioning platform, which is further explained based on the control principle of the entire system. Where r is the expected displacement, that is, a given expected value, K1 is the electrostatic driving force F and the square of the driving voltage V 2 K2 is the proportional factor of the current change Δi at the sensing end and the displacement change Δx (or Δy). When the system gives the required displacement of the comb teeth, PID control can be used to reasonably adjust the parameters K of the three parts of proportional control, integral control, and differential control. p , K i , K d , and the required electrostatic driving force F is obtained. According to the principle of virtual work, when the driving voltage is applied to the driving electrode, the physical work done to make the comb teeth produce a very small displacement Δx (or Δy) is equal to the electric field energy U obtained by the capacitance between the comb teeth, and FΔx=Δx(dU / dx) (or FΔy=Δy(dU / dy); combined with the capacitance formula between the comb teeth C=2N a ε0h a (x+Δx) / g (or C=2N a ε0h a (y+Δy) / g) to obtain the relationship between driving force and driving voltage F=N a ε0ha V 2 / g(where N a is the comb teeth logarithm, ε0 is the dielectric constant of air, h a For the comb thickness, g is the comb gap, and V is the driving voltage). The driving force signal is directly proportional to the driving voltage square, so that the driving voltage required to be applied on the driving electrode can be obtained. This driving voltage is applied to the driving electrode of the XY two-dimensional platform, and a sensing current is obtained from the sensing end. By comparing with the initial current (i.e. the current output by the corresponding direction reference capacitor), the variation of the current is obtained. The variation of the capacitance is obtained by the proportional relationship between the variation of the current and the variation of the capacitance, and then the actual displacement is obtained by the proportional relationship between the variation of the capacitance and the variation of the displacement. By sensing the actual displacement and comparing it with the expected displacement, the PID control system is utilized to eliminate the error between the expected displacement and the actual displacement based on deviation, and the precise positioning of the in-plane two-dimensional positioning platform can be finally achieved. Figure 3a 、 Figure 3b They are the displacement feedback control flow charts in the X and Y directions respectively.

[0060] Further construct a feedback control system based on the FPGA platform, use FPGA to control the system, so that the in-plane two-dimensional positioning platform can achieve fast response and precise control in the ±X and ±Y directions. Figure 4 As shown, the +X and -X, and +Y and -Y drive units of the in-plane two-dimensional positioning platform achieve sensing through complementary modes, enabling precise switching between the drive and sensing functions of the drive units. By applying an RF signal to the displacement sensor, the output displacement signal is sensed by the sensing circuit and phase-locked by the phase-locked amplifier. It then enters the feedback control system for comparison, and the compared feedback signal is applied to the drive unit via the drive voltage amplifier. Specifically, the +X-axis driver / sensor corresponds to: the third comb group 43 is the +X-axis driver, and the first comb group 41 is the +X-axis sensor; the -X-axis driver / sensor corresponds to: the first comb group 41 is the -X-axis driver, and the third comb group 43 is the -X-axis sensor; the +Y-axis driver / sensor corresponds to: the second comb group 42 is the +Y-axis driver, and the fourth comb group 44 is the +Y-axis sensor; and the -Y-axis driver / sensor corresponds to: the fourth comb group 44 is the -Y-axis driver, and the second comb group 42 is the -Y-axis sensor.

[0061] Figure 5 The diagram below shows the positioning accuracy of the +X axis displacement under different driving voltages. Figure 5As can be seen in the figure, after introducing the displacement feedback control system of the preferred embodiment of the present invention, the displacement output through feedback is closer to the theoretical expected value, achieving higher positioning accuracy. Therefore, the displacement feedback control system based on this in-plane two-dimensional positioning platform can well achieve high-precision positioning without adding additional displacement sensor structures.

[0062] Through the displacement feedback control system and method provided in the preferred embodiments of the present invention, for the in-plane two-dimensional positioning platform driven by electrostatic comb teeth, precise positioning of the entire platform can be achieved even without using an FPGA platform; in other embodiments, the in-plane two-dimensional positioning platform can also be designed with a porous structure on the outer frame to reduce the mass of the entire mechanism, and the displacement stage can also be designed with some special structures to meet different functional requirements.

[0063] The background section of the present invention may contain background information about the problem or environment of the present invention rather than describing prior art by others. Therefore, the inclusion of content in the background section is not an admission by the applicant that the prior art is available.

[0064] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features from different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of the appended claims.

Claims

1. A displacement feedback control system for an in-plane two-dimensional positioning platform, the in-plane two-dimensional positioning platform comprising an outer frame, an inner frame, a displacement platform, a first elastic unit, a second elastic unit, a first comb unit, and a second comb unit, wherein the outer frame supports the inner frame via the first elastic unit so that the outer frame can drive the inner frame along a first direction, and the inner frame supports the displacement platform via the second elastic unit so that the inner frame can drive the displacement platform along a second direction, the fixed comb portion of the first comb unit is fixedly connected to the outer frame, the movable comb portion of the first comb unit is fixedly connected to the inner frame, the fixed comb portion of the second comb unit is fixedly connected to the inner frame, and the movable comb portion of the second comb unit is fixedly connected to the displacement platform, and the first direction and the second direction are perpendicular to each other; characterized in that: The first comb tooth unit and the second comb tooth unit respectively include two groups of identical and symmetrically arranged comb tooth groups, and the in-plane two-dimensional positioning platform also includes a first reference capacitor and a second reference capacitor. The capacitance of the first reference capacitor is equal to the initial capacitance between any group of comb tooth groups in the first comb tooth unit, and the capacitance of the second reference capacitor is equal to the initial capacitance between any group of comb tooth groups in the second comb tooth unit. The displacement feedback control system uses one group of comb tooth groups in the first comb tooth unit or the second comb tooth unit as a driving end and the other group of comb tooth groups as a sensing end. After applying a driving voltage signal to the driving end, a current signal of the sensing end and a reference current signal of the corresponding first reference capacitor or the second reference capacitor are obtained, and a current change is obtained based on the current signal and the reference current signal. Then, an actual displacement generated by the sensing end is calculated based on the current change, and the driving voltage signal is updated based on a deviation signal between the actual displacement and the expected displacement. The step of calculating the actual displacement generated by the sensing end according to the current variation includes: The sensing circuit senses a reference current signal corresponding to the first reference capacitor and a current signal of another comb tooth group in the first comb tooth unit as the sensing end, and amplifies the difference proportionally to obtain an amplified signal, and then sends the amplified signal to the phase-locked amplifier; the phase-locked amplifier obtains an interference-free voltage signal based on the amplified signal, and receives a reference signal of the ground electrode, and then simultaneously sends the interference-free voltage signal and the reference signal to the feedback control module; the feedback control module obtains the actual displacement of any comb tooth group in the first comb tooth unit based on the interference-free voltage signal and the reference signal; specifically, a radio frequency signal V is applied to the ground electrode of the in-plane two-dimensional positioning platform. pp =A0sin(ωt), where A0 is the amplitude of the applied radio frequency, ω is the radio frequency angular frequency, and t is the time constant; the reference current signal i corresponding to the first reference capacitor sensed by the sensing circuit is 11 For: i 11 =A0ωC1cosωt, where C1 is the capacitance value of the first reference capacitor; the current signal i of another comb tooth group in the first comb tooth unit sensed by the sensing circuit is 12 For: i 12 =A0ω(C1+ΔC1)cosωt, where ΔC1 is the capacitance change between the moving comb teeth and the fixed comb teeth of any comb tooth group in the first comb tooth unit; the current signal is converted into a voltage signal by the sensing circuit, and the phase-locked amplifier is used to phase-lock and output the sensing displacement signal to realize the corresponding relationship between the motion displacement and the sensing voltage value; specifically, the feedback control module is based on the corresponding relationship between the capacitance change and the displacement, ΔC1=2N a ε0h a Δx / g is used to calculate the actual displacement Δx of any comb tooth group in the first comb tooth unit, where N a is the number of teeth pairs of any comb tooth group in the first comb tooth unit, ε0 is the dielectric constant of air, h a is the comb teeth thickness, and g is the comb teeth gap.

2. The displacement feedback control system according to claim 1, characterized in that: The displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module. The output end of the driving voltage amplifier is connected to one group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, and the input end of the sensing circuit is simultaneously connected to the output electrode of the first reference capacitor and the other group of the first comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end. The output end of the sensing circuit is connected to the input end of the phase-locked amplifier, and the input end of the phase-locked amplifier is also connected to the ground electrode. The output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier.

3. The displacement feedback control system according to claim 1, characterized in that: The displacement feedback control system includes a sensing circuit, a phase-locked amplifier, a driving voltage amplifier and a feedback control module. The output end of the driving voltage amplifier is connected to one group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the driving end, and the input end of the sensing circuit is simultaneously connected to the output electrode of the second reference capacitor and the other group of the second comb tooth units as the driving electrode corresponding to the comb tooth group of the sensing end. The output end of the sensing circuit is connected to the input end of the phase-locked amplifier, and the input end of the phase-locked amplifier is also connected to the ground electrode. The output end of the phase-locked amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier.

4. The displacement feedback control system according to claim 2 or 3, characterized in that: It also includes an FPGA platform, which is connected to the feedback control module, and an output end of the FPGA platform is connected to the ground electrode for outputting a radio frequency signal to the ground electrode.

5. The displacement feedback control system according to claim 4, characterized in that: The feedback control module is specifically a PID control system.

6. A displacement feedback control method for an in-plane two-dimensional positioning platform, characterized in that: The displacement feedback control system according to claim 1 is used to control the in-plane two-dimensional positioning platform.

7. The displacement feedback control method according to claim 6, characterized in that: The displacement feedback control system includes a sensing circuit, a lock-in amplifier, a driving voltage amplifier, and a feedback control module. The output end of the driving voltage amplifier is connected to the driving electrodes corresponding to the comb group of one group of the first comb tooth units as the driving end, and the input end of the sensing circuit is simultaneously connected to the output electrode of the first reference capacitor and the driving electrodes corresponding to the comb group of another group of the first comb tooth units as the sensing end. The output end of the sensing circuit is connected to the input end of the lock-in amplifier, and the input end of the lock-in amplifier is also connected to the ground electrode. The output end of the lock-in amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier. The displacement feedback control method includes the following steps: A1: the driving voltage amplifier applies a driving voltage signal to one of the comb tooth groups in the first comb tooth unit as the driving end; A2: the sensing circuit performs a subtraction of the reference current signal corresponding to the first reference capacitor sensed and the current signal of the comb teeth group of the other comb teeth group in the first comb teeth unit serving as the sensing end, amplifies the difference proportionally to obtain an amplified signal, and then sends the amplified signal to the lock-in amplifier; A3: The lock-in amplifier obtains an interference-free voltage signal according to the amplified signal, receives a reference signal from the ground electrode, and then simultaneously sends the interference-free voltage signal and the reference signal to the feedback control module; A4: The feedback control module obtains the actual displacement of any group of comb teeth in the first comb tooth unit based on the interference-free voltage signal and the reference signal, and compares whether there is a deviation between the actual displacement and the expected displacement. If so, the deviation signal between the actual displacement and the expected displacement is used to update the driving voltage signal, and the updated driving voltage signal is sent to the driving voltage amplifier, and the process returns to step A1.

8. The displacement feedback control method according to claim 7, characterized in that: Also includes: Apply a radio frequency signal V to the ground electrode pp , where the RF signal V pp =V pp =A0sin(ωt), where A0 is the amplitude of the applied RF, ω is the RF angular frequency, and t is the time constant; The reference current signal i corresponding to the first reference capacitor sensed by the sensing circuit in step A2 is 11 For: i 11 =A0ωC1cosωt, where C1 is the capacitance value of the first reference capacitor; the current signal i of another comb tooth group in the first comb tooth unit sensed by the sensing circuit is 12 For: i 12 =A0ω(C1+ΔC1)cosωt, where ΔC1 is the capacitance change between the moving comb teeth and the fixed comb teeth of any comb tooth group in the first comb tooth unit; In step A4, the feedback control module calculates the capacitance change and displacement according to the corresponding relationship ΔC1=2N. a ε0h a Δx / g is used to calculate the actual displacement Δx of any comb tooth group in the first comb tooth unit, where N a is the number of teeth pairs of any comb tooth group in the first comb tooth unit, ε0 is the dielectric constant of air, h a is the comb teeth thickness, and g is the comb teeth gap.

9. The displacement feedback control method according to claim 6, characterized in that: The displacement feedback control system includes a sensing circuit, a lock-in amplifier, a driving voltage amplifier, and a feedback control module. The output end of the driving voltage amplifier is connected to the driving electrodes corresponding to the comb group of the driving end in one group of the second comb tooth units, and the input end of the sensing circuit is simultaneously connected to the output electrode of the second reference capacitor and the driving electrodes corresponding to the comb group of the sensing end in another group of the second comb tooth units. The output end of the sensing circuit is connected to the input end of the lock-in amplifier, and the input end of the lock-in amplifier is also connected to the ground electrode. The output end of the lock-in amplifier is connected to the input end of the feedback control module, and the output end of the feedback control module is connected to the input end of the driving voltage amplifier. The displacement feedback control method includes the following steps: B1: the driving voltage amplifier applies a driving voltage signal to one of the comb tooth groups in the second comb tooth unit as the driving end; B2: the sensing circuit performs a subtraction of the reference current signal corresponding to the second reference capacitor sensed and the current signal of the other comb tooth group in the second comb tooth unit serving as the sensing end, amplifies the difference proportionally to obtain an amplified signal, and then sends the amplified signal to the lock-in amplifier; B3: the lock-in amplifier obtains an interference-free voltage signal according to the amplified signal, receives a reference signal from the ground electrode, and then simultaneously sends the interference-free voltage signal and the reference signal to the feedback control module; B4: The feedback control module obtains the actual displacement of any group of comb teeth in the second comb tooth unit based on the interference-free voltage signal and the reference signal, and uses the deviation signal between the actual displacement and the expected displacement to update the driving voltage signal, and sends the updated driving voltage signal to the driving voltage amplifier, and returns to step B1.

10. The displacement feedback control method according to claim 9, characterized in that: Also includes: Apply a radio frequency signal V to the ground electrode pp , where the RF signal V pp =V pp =A0sin(ωt), where A0 is the amplitude of the applied RF, ω is the RF angular frequency, and t is the time constant; The reference current signal i corresponding to the second reference capacitor sensed by the sensing circuit in step B2 is 21 For: i 21 =A0ωC2cosωt, where C2 is the capacitance value of the second reference capacitor; the current signal i of another comb tooth group in the second comb tooth unit sensed by the sensing circuit is 22 For: i 22 =A0ω(C2+ΔC2)cosωt, where ΔC2 is the capacitance change between the moving comb teeth and the fixed comb teeth of any comb tooth group in the second comb tooth unit; In step B4, the feedback control module calculates the capacitance change and displacement according to the corresponding relationship ΔC2=2N. a ε0h a Δy / g is used to calculate the actual displacement Δy of any comb tooth group in the second comb tooth unit, where N a is the number of teeth pairs of any comb tooth group in the first comb tooth unit, ε0 is the dielectric constant of air, h a is the comb teeth thickness, and g is the comb teeth gap.

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