阅读说明：本技术 极低温低热耗散精密压电陶瓷旋转台 (Accurate piezoceramics revolving stage of utmost point low heat dissipation ) 是由 程光磊 王浩远 蔡方煦 黄成园 杜江峰 于 2020-11-16 设计创作，主要内容包括：一种低热耗散压电陶瓷旋转台,包括机械放大结构、驱动装置、角度传感系统和总控系统,其中：机械放大结构,包括两组互相垂直放置的全同子结构,相对的两个子结构组成一组,两组子结构通过静摩擦力交替搓动转轴,避免滑动摩擦,从而降低旋转产生的热耗散；角度传感系统,包括由探测电极、输入电极、接地电极和输出电极构成的电容阻抗传感器,所述角度传感系统用于无热耗散高精度测量旋转角度,传递信号给控制系统以实现闭环控制；总控制系统,包括用于测量电容传感器信号的测量系统、用于控制压电陶瓷堆电激励的压电陶瓷控制系统和作为总控制系统的输入和输出的计算机。(The utility model provides a low heat dissipation piezoceramics revolving stage, includes mechanical amplification structure, drive arrangement, angle sensing system and overall control system, wherein: the mechanical amplification structure comprises two groups of identical substructures which are vertically arranged, the two opposite substructures form one group, the two groups of substructures rub the rotating shaft alternately through static friction force to avoid sliding friction, and therefore heat dissipation generated by rotation is reduced; the angle sensing system comprises a capacitive impedance sensor consisting of a detection electrode, an input electrode, a grounding electrode and an output electrode, is used for measuring a rotating angle without heat dissipation and with high precision, and transmits a signal to the control system to realize closed-loop control; and the master control system comprises a measuring system for measuring signals of the capacitance sensor, a piezoelectric ceramic control system for controlling the electric excitation of the piezoelectric ceramic stack and a computer which is used as the input and the output of the master control system.)

1. The utility model provides a low heat dissipation piezoceramics revolving stage which characterized in that, includes mechanical amplification structure, drive arrangement, angle sensing system and overall control system, wherein:

the mechanical amplification structure comprises two groups of identical substructures which are vertically arranged, the two opposite substructures form one group, the two groups of substructures rub the rotating shaft alternately through static friction force to avoid sliding friction, and therefore heat dissipation generated by rotation is reduced;

the angle sensing system comprises a capacitive impedance sensor consisting of a detection electrode, an input electrode, a grounding electrode and an output electrode, is used for measuring a rotating angle without heat dissipation and with high precision, and transmits a signal to the control system to realize closed-loop control;

and the master control system comprises a measuring system for measuring signals of the capacitance sensor, a piezoelectric ceramic control system for controlling the electric excitation of the piezoelectric ceramic stack and a computer which is used as the input and the output of the master control system.

2. The piezoceramic rotary table according to claim 1, wherein the holomorphic substructure comprises a frame consisting of a radial amplifying structure located near the outer ring for providing radial deformation, a tangential amplifying structure located near the inner ring for providing tangential drive, a spring plate connecting the inner ring tangential amplifying structure and the mechanical amplifying structure, a piezoceramic stack mounted in the amplifying structure as a source of deformation and power, and a pre-stress plate for providing pre-stress.

3. The piezo-ceramic rotary stage of claim 2, wherein the free end of the radial amplifying structure is connected to the tangential amplifying structure.

4. The piezo-ceramic rotary table according to claim 2, wherein the radial amplifying structure comprises two sets of flexible hinges and two sets of lever amplifying structures respectively connected to the flexible hinges, wherein the flexible hinges are fixed on two end faces of the piezo-ceramic stack in the extension direction, and the angle between the lever amplifying structures and the end faces of the piezo-ceramic stack is pi/2 + theta, where theta determines the mechanical amplification factor.

5. The piezo-ceramic rotary table of claim 3, wherein the two sets of flexible hinges of the radial amplifying structure are twisted in opposite directions, and the free end of the lever amplifying structure of one set is fixed, so that the displacement of the lever amplifying structure of the other set is I/theta times of the deformation of the piezo-ceramic.

6. The piezo-ceramic rotary table according to claim 2, wherein the tangential amplifying structure comprises two sets of flexible hinges, two sets of lever amplifying structures and a transmission frame respectively connected with the flexible hinges; the flexible hinges are fixed on two end faces of the piezoelectric ceramics in the extension direction.

7. The piezo-ceramic rotary table of claim 6, wherein the two sets of flexible hinges of the tangential amplifying structure have the same twisting direction, and the free ends of the lever amplifying structure are displaced in the same direction by 1/2 θ times of the displacement of the piezo-ceramic.

8. The turntable of claim 6, wherein the transmission frame is located inside the tangential amplification structure and connected to the free ends of the two sets of lever amplification structures, and the transmission frame is embedded with alumina sheets for friction transmission with the rotation shaft.

9. The piezo-ceramic rotary stage according to claim 2, wherein the spring plate is located on the outer frame leading from the outer flexible hinge of the tangential amplifying structure and connected to the mechanical amplifying structure, and the spring plate is used for improving the self-compensation effect of the system rigidity and thermal deformation.

10. The piezo-ceramic rotary table according to claim 1, wherein the material of the piezo-ceramic rotary table is tungsten-copper alloy; the mechanical amplification structure is formed by processing a tungsten-copper alloy through a wire cutting slow wire walking process.

Technical Field

The invention relates to the technical field of precise rotation control and extremely low temperature measurement, in particular to an extremely low temperature low heat dissipation precise piezoelectric ceramic rotating table.

Background

The precision piezoelectric ceramic rotary table is widely applied to precision measurement systems such as an electrical transport measurement system, an optical metrology system and the like for precisely rotating a sample or an experimental device. The piezoelectric ceramic displacement platform is limited by the fact that the deformation of piezoelectric ceramic is small, and various large-stroke displacement platforms generally need to form a mechanical amplification structure by a flexible hinge and a lever amplification structure and are realized by matching with the alternate action of a plurality of groups of piezoelectric ceramic stacks. The action modes of the piezoelectric ceramics mainly comprise inertia drive, inchworm drive, walking drive and the like.

The basic principle of inertia driving is that piezoelectric ceramic stacks are deformed through electric excitation, driven parts such as a displacement table top or a rotating shaft and the like move towards a target direction by utilizing static friction force, then the piezoelectric ceramic is quickly restored to an initial state through reverse electric excitation, the driven parts are basically not influenced by reverse restoring action of the piezoelectric ceramic stacks due to inertia effect, and large-stroke displacement of the displacement table can be realized through repeating the process.

The principle of inchworm driving is that the guide rods are sequentially fastened on two sides of the guide rods through the piezoelectric ceramic tubes, and then the guide rods and the piezoelectric ceramic tubes are pushed to move through deformation of a group of piezoelectric ceramic tubes, so that stepping is realized, and large-stroke displacement is realized.

The walking drive utilizes the piezoelectric ceramic stack which can simultaneously carry out extension deformation and tangential deformation, or bonds the tangential deformation piezoelectric ceramic stack on the piezoelectric ceramic stack which then extends deformation. The piezoelectric ceramic stacks on the two sides of the guide rod are alternately paired to compress the guide rod and then tangentially deform to enable the guide rod to move towards the target direction.

The prior art discloses a rotating structure which utilizes a friction plate to drive a displacement table fixed by a bearing, namely an inertia driving displacement table, and the inertia driving has the defects of low motion precision, incapability of being used for sub-nanometer precise driving control and incapability of avoiding heat generated by sliding friction. For the extremely low temperature obtaining device, the refrigeration power of the extremely low temperature obtaining device is only hundreds of microwatts generally at the temperature of 100mK, and the extremely low temperature obtaining device is easily suppressed by the heating power generated by the sliding friction, so that the system can reach the target working temperature after the displacement table acts for a long time; the inchworm drive can have higher drive precision, but the sliding friction can not be avoided as the inertia drive; the walking drive can realize the friction drive without sliding, but to extremely low temperature system, the deformation volume of piezoceramics itself receives expend with heat and contract with cold effect to influence and can reduce by a wide margin, and only the drive efficiency through piezoceramics self deformation is very low to the walking drive is higher to being responsible for flexible piezoceramics heap machining precision requirement, easily receives the temperature variation influence.

Through utilizing the mechanical amplification structure can improve the action efficiency of displacement platform, but can reduce the bulk rigidity and the displacement resolution ratio of structure, mechanical structure itself thermal deformation size of overall structure under the extremely low temperature environment can reach and compare with piezoceramics heap self deformation moreover for normal drive need adopt under the extremely low temperature with the normal atmospheric temperature different structural dimension or calibration volume, use comparatively loaded down with trivial details. The low structural rigidity can lead to the displacement platform resonant frequency to reduce, leads to the displacement platform easily with environmental mechanical vibration noise coupling, is unfavorable for the precision drive.

The positioning sensing device of the piezoelectric displacement table usually uses a carbon film resistor, the self structure of the carbon film resistor can cause sliding friction, and resistance heat can be directly generated when the carbon film resistor is electrified during measurement, so that great negative effects can be generated on a refrigerating device.

Disclosure of Invention

Accordingly, the present invention is directed to a very low temperature, low heat dissipation precision piezo-ceramic rotary table, which is designed to solve at least one of the above problems.

In order to achieve the above object, as an aspect of the present invention, there is provided a low heat dissipation piezoelectric ceramic rotary table comprising a mechanical amplifying structure, a driving device, an angle sensing system and a general control system, wherein:

the mechanical amplification structure comprises two groups of identical substructures which are vertically arranged, the two opposite substructures form one group, the two groups of substructures rub the rotating shaft alternately through static friction force to avoid sliding friction, and therefore heat dissipation generated by rotation is reduced;

the angle sensing system comprises a capacitive impedance sensor consisting of a detection electrode, an input electrode, a grounding electrode and an output electrode, is used for measuring a rotating angle without heat dissipation and with high precision, and transmits a signal to the control system to realize closed-loop control;

and the master control system comprises a measuring system for measuring signals of the capacitance sensor, a piezoelectric ceramic control system for controlling the electric excitation of the piezoelectric ceramic stack and a computer which is used as the input and the output of the master control system.

The holomorphic substructure comprises a radial amplification structure which is positioned close to an outer ring and used for providing radial deformation, a tangential amplification structure which is positioned close to an inner ring and used for providing tangential driving, a spring piece which is connected with the inner ring tangential amplification structure and a mechanical amplification structure frame, a piezoelectric ceramic stack which is arranged in the amplification structure and used as a deformation and power source, and a pre-tightening piece which is used for providing pre-stress.

Wherein the free end of the radial amplification structure is connected with the tangential amplification structure.

The radial amplification structure comprises two groups of flexible hinges and two groups of lever amplification structures respectively connected with the flexible hinges, wherein the flexible hinges are fixed on two end faces of the piezoelectric ceramic stack in the extension direction, the included angle between the lever amplification structures and the end faces of the piezoelectric ceramic stack is pi/2 + theta, and the theta determines the mechanical amplification factor.

The two groups of flexible hinges of the radial amplification structure are opposite in torsion direction, the free end of one group of the lever amplification structure is fixed, and therefore the displacement of the other group of the lever amplification structure is 1/theta times of the deformation of the piezoelectric ceramic.

The tangential amplifying structure comprises two groups of flexible hinges, two groups of lever amplifying structures and a transmission frame, wherein the two groups of lever amplifying structures are respectively connected with the flexible hinges; the flexible hinges are fixed on two end faces of the piezoelectric ceramics in the extension direction.

The torsion directions of the two groups of flexible hinges of the tangential amplifying structure are the same, the free ends of the lever amplifying structure displace towards the same direction, and the displacement is 1/2 theta times of the displacement of the piezoelectric ceramic.

The transmission frame is positioned on the inner side of the tangential amplification structure and connected with the free ends of the two groups of lever amplification structures, and an aluminum oxide sheet is embedded on the transmission frame and used for performing friction transmission with the rotating shaft.

The spring piece is positioned on an outer frame which is led out by a flexible hinge on the outer side of the tangential amplifying structure and is connected to the mechanical amplifying structure, and the spring piece is used for improving the system rigidity and the self-compensation effect of thermal deformation.

The piezoelectric ceramic rotating platform is made of tungsten-copper alloy; the mechanical amplification structure is formed by processing a tungsten-copper alloy through a wire cutting slow wire walking process.

Based on the technical scheme, compared with the prior art, the ultralow-temperature low-heat-dissipation precise piezoelectric ceramic rotary table disclosed by the invention has at least one or part of the following beneficial effects:

1. the precision piezoelectric ceramic servo rotating table for the low-heat-dissipation extremely-low-temperature ultrahigh vacuum has a mechanical amplification design on a mechanical structure and has better driving efficiency; the sliding friction is avoided in the driving mode, the bearing-free driving is realized, the overall heat dissipation power of the rotating platform is obviously reduced, and the pressure on refrigeration when the rotating platform is used in extremely-low-temperature equipment is obviously reduced. At a driving frequency of 1Hz, the heat dissipation power of the entire rotary table is only about 12 μ W, and the driving speed can reach 10 μm/s. The mechanical amplification design of revolving stage itself has temperature self-compensating characteristic, and the drive characteristic of revolving stage receives extremely low temperature environment influence less for the revolving stage can be stable from room temperature to extremely low temperature normal work within a definite time of temperature, has avoided performance loss and the debugging difficulty that is caused by thermal deformation. The tungsten-copper alloy material used by the rotary table and the mechanical amplification structure of the rotary table are designed carefully, the lowest resonance frequency of the tungsten-copper alloy material is above 1300Hz, and the coupling with environmental mechanical vibration noise can be effectively avoided.

2. Hair brushThe proposed capacitive impedance sensor has a heat dissipation power below 1 μ W and a power of 6.3 × 10^-7The measuring precision of rad can reach 5-355 degrees in the angle measuring range, and the measuring requirements of high precision and large stroke can be met. The design of the capacitance impedance sensor avoids sliding friction between components, and meanwhile, the capacitance impedance can be easily made to be large, so that resistance heat is small, if the electrodes are made of the same metal material, the capacitance impedance of all the electrodes changes synchronously along with temperature, and the capacitance impedance sensor can be well suitable for working environments with large-range temperature changes.

Drawings

FIG. 1 is an exploded view of a rotary table assembly according to an embodiment of the present invention;

FIG. 2 is a mechanical enlarged view and a detail enlarged view of the rotary table according to the embodiment of the present invention;

FIG. 3 is a schematic diagram of a capacitive impedance sensor according to an embodiment of the present invention;

FIG. 4 is an equivalent circuit diagram of a capacitive impedance sensor of an embodiment of the present invention;

FIG. 5 is a schematic diagram of the output levels of a capacitive impedance sensor in accordance with an embodiment of the present invention;

FIG. 6 is a schematic diagram of an excitation voltage sequence for a piezoceramic stack of an embodiment of the invention;

fig. 7 is a schematic diagram of the basic principle of the hinge enlarging structure of the embodiment of the present invention.

In the above drawings, the reference numerals have the following meanings:

1. a table top; 2. an upper cover; 3. detecting an electrode plate; 4. fixing the electrode plate;

5. a base; 6. a mechanical amplification structure; 7. a piezoelectric ceramic stack driving the radial amplification structure;

8. driving a piezoelectric ceramic stack of the tangential amplification structure; 9. aluminum oxide flakes;

10. a tangential amplifying structure; 11. a radial amplification structure; 12. a spring plate;

13. a rotating shaft; 14. an output electrode; 15. a detection electrode; 16. a ground electrode;

17. an input electrode; 18. cross section of the rotating shaft.

Detailed Description

The invention discloses a low-heat-dissipation large-stroke precise piezoelectric ceramic servo rotating table, which is a piezoelectric ceramic rotating table with low heat dissipation, precise angle sensing, high-resolution closed-loop control and thermal deformation self-compensation, and belongs to the field of precise rotation control and the field of extremely low temperature measurement. The device is mainly suitable for the accurate rotation of samples and experimental devices required by the precise measurement experiment in the extremely low temperature environment with high heat dissipation requirements.

The invention designs the precise piezoelectric ceramic rotating platform which has no sliding friction, no resistance heat, self-compensation of thermal deformation, higher driving efficiency and higher system rigidity, and is used for precise measurement experiments in extremely low temperature environments.

Specifically, the invention discloses a low-heat dissipation piezoelectric ceramic rotary table, which comprises a mechanical amplification structure, a driving device, an angle sensing system and a general control system, wherein:

the mechanical amplification structure comprises two groups of identical substructures which are vertically arranged, the two opposite substructures form one group, the two groups of substructures rub the rotating shaft alternately through static friction force to avoid sliding friction, and therefore heat dissipation generated by rotation is reduced;

the angle sensing system comprises a capacitive impedance sensor consisting of a detection electrode, an input electrode, a grounding electrode and an output electrode, is used for measuring a rotating angle without heat dissipation and with high precision, and transmits a signal to the control system to realize closed-loop control;

and the master control system comprises a measuring system for measuring signals of the capacitance sensor, a piezoelectric ceramic control system for controlling the electric excitation of the piezoelectric ceramic stack and a computer which is used as the input and the output of the master control system.

The low dissipation mainly comes from three points:

1) avoid sliding friction heating. The invention adopts four (two groups) of substructures, alternately rubs the rotating shaft, and only has static friction force (no work and no heat).

2) The substructure is enlarged. The required voltage is lower for driving the same distance, and therefore the amount of heat generated by the piezoelectric ceramic is smaller, as compared with a structure without mechanical amplification.

3) An angular capacitive sensor is employed with no heat dissipation (compared to resistive sensors in popular commercial rotary tables, etc.).

The holomorphic substructure comprises a radial amplification structure which is positioned close to an outer ring and used for providing radial deformation, a tangential amplification structure which is positioned close to an inner ring and used for providing tangential driving, a spring piece which is connected with the inner ring tangential amplification structure and a mechanical amplification structure frame, a piezoelectric ceramic stack which is arranged in the amplification structure and used as a deformation and power source, and a pre-tightening piece which is used for providing pre-stress.

Wherein the free end of the radial amplification structure is connected with the tangential amplification structure.

The radial amplification structure comprises two groups of flexible hinges and two groups of lever amplification structures respectively connected with the flexible hinges, wherein the flexible hinges are fixed on two end faces of the piezoelectric ceramic stack in the extension direction, the included angle between the lever amplification structures and the end faces of the piezoelectric ceramic stack is pi/2 + theta, and the theta determines the mechanical amplification factor.

The two groups of flexible hinges of the radial amplification structure are opposite in torsion direction, the free end of one group of the lever amplification structure is fixed, and therefore the displacement of the other group of the lever amplification structure is 1/theta times of the deformation of the piezoelectric ceramic.

The tangential amplifying structure comprises two groups of flexible hinges, two groups of lever amplifying structures and a transmission frame, wherein the two groups of lever amplifying structures are respectively connected with the flexible hinges; the flexible hinges are fixed on two end faces of the piezoelectric ceramics in the extension direction.

The torsion directions of the two groups of flexible hinges of the tangential amplifying structure are the same, the free ends of the lever amplifying structure displace towards the same direction, and the displacement is 1/2 theta times of the displacement of the piezoelectric ceramic.

The transmission frame is positioned on the inner side of the tangential amplification structure and connected with the free ends of the two groups of lever amplification structures, and an aluminum oxide sheet is embedded on the transmission frame and used for performing friction transmission with the rotating shaft.

The spring piece is positioned on an outer frame which is led out by a flexible hinge on the outer side of the tangential amplifying structure and is connected to the mechanical amplifying structure, and the spring piece is used for improving the system rigidity and the self-compensation effect of thermal deformation.

The piezoelectric ceramic rotating platform is made of tungsten-copper alloy; the mechanical amplification structure is formed by processing a tungsten-copper alloy through a wire cutting slow wire walking process.

The invention provides a servo piezoelectric ceramic rotary table without sliding friction transmission and capacitance impedance sensor, which is mainly characterized by comprising an integrated mechanical amplification structure, a driving device which is arranged in the integrated mechanical amplification structure and is composed of four groups of piezoelectric ceramics pre-tightened by a pre-tightening sheet, an angle sensing system which is composed of a detection electrode arranged on a rotating shaft, a fixed input electrode, a grounding electrode and an output electrode, and a master control system which is composed of an external measurement system and a piezoelectric ceramic control system.

The mechanical amplification structure of the rotary table comprises 4 groups of identical substructures which are vertically arranged with each other, and each substructure comprises: the device comprises a radial amplification structure which is positioned close to an outer ring and is responsible for providing radial deformation, a tangential amplification structure which is positioned close to an inner ring and is responsible for providing tangential driving, a spring piece which is connected with the inner ring tangential amplification structure and a mechanical amplification structure frame, a piezoelectric ceramic stack which is arranged in the amplification structure and is used as a deformation and power source, a pre-tightening piece which is used for providing pre-stress, and an aluminum oxide sheet which is used for twisting a rotating shaft.

The radial amplifying structure is composed of two groups of flexible hinges and a lever amplifying structure connected with the flexible hinges. The flexible hinges are fixed on two end faces of the piezoelectric ceramic stack in the extension direction, when the piezoelectric ceramic is contracted, the flexible hinges are twisted outwards, and the other free end of the lever amplification structure is expanded outwards. The included angle between the lever structure and the end face of the piezoelectric ceramic stack is pi/2 + theta, wherein theta is a small angle. Ideally, when the hinge is everted, the angle of the hinge increases by a small amount delta, and the free end of the lever amplification structure is radially displaced by a small distance, which is about 1/2 theta times the total contraction of the piezoelectric ceramic by the expansion of the trigonometric function. In the invention, the two groups of flexible hinges have opposite twisting directions, and the free ends of the lever amplifying structures of one group are fixed, so that the I/theta times of the deformation of the piezoelectric ceramics is obtained under the ideal displacement of the lever amplifying structures of the other group. The free end of the radial amplification structure is connected with the tangential amplification structure.

The tangential amplifying structure consists of two groups of flexible hinges, a lever amplifying structure connected with the flexible hinges and a transmission frame. The flexible hinge is fixed to an end surface of the piezoelectric ceramic in the extension direction, which is the same as the radial amplification structure, and the flexible hinge has the same torsion direction, which is different from the radial amplification structure. When the piezoelectric ceramic deforms, the free end of the lever amplifying structure displaces towards the same direction, and the displacement is 1/2 theta times of the displacement of the piezoelectric ceramic under the ideal condition. The transmission frame is positioned on the inner side of the tangential amplifying structure and connected with the free ends of the two groups of lever amplifying structures, and an aluminum oxide sheet is embedded on the transmission frame and used for performing friction transmission with the rotating shaft.

Each sub-amplifying structure is provided with two spring pieces which are led out from the flexible hinge at the outer side of the tangential amplifying structure and are connected to the outer frame of the mechanical amplifying structure. The function of the self-compensating material is to improve the self-compensating effect of system rigidity and thermal deformation. The mechanical amplifying structure is formed by processing a tungsten-copper alloy by a wire cutting slow wire moving process.

The material of the rotary table is made of tungsten-copper alloy, wherein tungsten is one of the metals with the smallest thermal expansion coefficient and the largest Young modulus in all metal simple substances, but the tungsten-copper alloy is difficult to machine, and the tungsten-copper alloy is used for enabling the material to be easier to machine besides basically retaining the characteristics of tungsten. In addition, the tungsten-copper alloy is not superconductive under the condition of extremely low temperature, and the physical properties of the material can be kept stable.

The structure of the capacitive impedance sensor comprises: a sensing electrode rotating with the shaft, a fixed output, an input electrode and a ground electrode, and a metal casing surrounding the sensor.

Basic principle of capacitive sensor: the input electrode is connected with several kilohertz alternating current with several volts level, and the grounding electrode is connected withThe ground line, the input electrode and the ground electrode are not connected and are only separated by a small distance, and the detection electrode is positioned above the two electrodes by a short distance. When the projection of the detection electrode is superposed with the input electrode and the grounding electrode, the input electrode and the grounding electrode respectively form parallel plate capacitors with the detection electrode, and the impedance of the capacitors is in direct proportion to the superposed area of the projection. Let the capacitance between the input electrode and the detecting electrode be C_iThe capacitance between the detecting electrode and the grounding electrode is C_gThus, it can be seen that the level at the probe electrode is proportional to C_i/(C_i+ Cg). Therefore, in the invention, the projection overlapping area between the detection electrode and the input electrode linearly increases along with the rotation of the rotating shaft, and the projection overlapping area between the detection electrode and the grounding electrode linearly decreases along with the rotation of the rotating shaft, so that the level on the detection electrode linearly changes along with the rotation of the rotating shaft. In order to avoid directly leading wires on the detection electrodes, an output electrode is designed on the same plane of the input electrode, and a measuring circuit with large input impedance is used for measuring the input electrode and the output electrode. The projection overlapping area of the output electrode and the detection electrode does not change along with the rotation of the rotating shaft, so that the level on the output electrode is also in direct proportion when the rotating shaft rotates, namely the level also changes linearly along with the rotation of the rotating shaft.

The control system of the rotating platform comprises a measuring system for measuring signals of the capacitance sensor, a piezoelectric ceramic control system for controlling the electric excitation of the piezoelectric ceramic stack, and a computer which is used as the input and the output of the master control system. The computer receives manual instructions, drives the rotating platform through the piezoelectric ceramic control system, and simultaneously reads signals of the capacitance sensor through the measuring system and feeds the signals back to the piezoelectric ceramic control system to form a closed-loop servo system.

In order that the objects, technical solutions and advantages of the present invention will become more apparent, the present invention will be further described in detail with reference to the accompanying drawings in conjunction with the following specific embodiments.

As shown in figure 1, the low-heat-dissipation extremely-low-temperature ultrahigh-vacuum precision piezoelectric ceramic servo rotary table consists of a rotating shaft, a table top 1 mechanical amplification structure 6, a capacitance impedance sensor, an aluminum oxide sheet, a pre-tightening sheet and piezoelectric ceramics.

The capacitive impedance sensor comprises a base 5, a fixed electrode plate 4, a detection electrode plate 3 and an upper cover 2.

As shown in fig. 2, it is a mechanical enlarged structural view and a detail enlarged view of the rotary table; the mechanical amplification structure comprises 4 groups of self-amplification structures which are arranged in the same structure at equal intervals, and comprises a radial amplification structure 11 and a driving piezoelectric ceramic stack 7 thereof, a tangential amplification structure 10 and a driving piezoelectric ceramic stack 8 thereof, a spring piece 12, an aluminum oxide sheet 9 and a pre-tightening sheet (hidden in the figure).

The rotating shaft of the rotating platform and the table top 1 are preferably made of W/Cu with the weight ratio of 80: 20. The table-board is provided with a plurality of M3 threaded holes, and the diameter of the rotating shaft is preferably 5 mm. The length of the rotation axis extends from the capacitive sensor upper cover 2 up to the bottom surface of the mechanical amplification structure 6.

The mechanical amplifying structure is preferably 40mm multiplied by 3.5mm in size, is preferably made of W/Cu alloy with the weight ratio of 80: 20, and is processed by wire cutting slow-moving wires. And blind holes with the size of 3.2mm are machined at four corners of the mechanical amplification structure for fixing.

The piezoelectric ceramic stacks 7 and 8 are preferably 9mm long and 3.5mm wide and thick.

The included angle of the hinge structure of the radial amplifying structure 11 is preferably 97.5 DEG

The angle of the hinge structure of the tangential amplifying structure 10 is preferably 94 degrees

The thickness of the spring piece 12 is preferably 0.2mm, and the included angle between the spring piece and the tangential amplifying structure 10 is preferably 0.2mm

The length of the piezoelectric ceramic mounting position of the amplifying structures 11 and 10 is preferably 9.5mm, and the amplifying structures are pre-tensioned by inserting a pre-tensioning sheet between the mechanical amplifying structure and the piezoelectric ceramic stack.

The tangential amplifying structure 10 is embedded with an alumina sheet 9 and is contacted with the rotating shaft 13. The thickness of the aluminum oxide sheet is slightly larger than the distance between the tangential amplifying structure 10 and the rotating shaft 13, and the aluminum oxide sheet is fully pre-tightened to contact with the rotating shaft 13.

The capacitance sensor base 5 is made of oxygen-free copper preferably, the shape and outline of the capacitance sensor base are the same as those of the mechanical amplification structure 6, and blind holes of 3.2mm are machined at the same positions at four corners of the capacitance sensor base, so that the capacitance sensor base can be arranged on the upper side of the mechanical amplification structure. A5.5 mm hole is formed in the center of the rotating platform base 5, a circular groove with the inner diameter of 165mm is machined in the platform surface, and 4 positioning convex angles are distributed on the inner side of the groove at equal intervals. The depth of the groove is 0.5 mm.

The fixed electrode plate 4 is formed by defining the size of an electrode by a sapphire substrate through ultraviolet lithography, then plating gold for 200nm through an electron beam evaporation process, and then removing glue. And then, defining the size of a 5.5mm diameter preformed hole with the center as a rotating shaft to pass through and a positioning notch with four corners matched with the convex angle in the circle center groove of the rotating table base 5 by using one-time ultraviolet lithography, and then etching by a wet method to obtain the rotary table. And finally removing the glue.

The capacitive impedance sensor upper cover 2 is made of oxygen-free copper preferably, the shape outline of the capacitive impedance sensor upper cover is the same as that of the base 5, blind holes of 3.2mm are formed in the positions with the same four corners, a hole of 5.5mm in diameter is formed in the center of the upper cover, the lower side surface of the upper cover is provided with a circular groove of 165.2mm in inner diameter and 0.7mm in depth of 1mm in thickness, and the circular groove is matched with the circular groove of the base 5, so that the capacitive impedance sensor upper cover can surround electrodes of the capacitive sensor and shield external electromagnetic.

Electrode dimensions of the fixed electrode and the specific principle of the capacitive sensor:

the operation of the capacitive sensor is schematically shown in fig. 3. Wherein 17 is an input electrode, 16 is a ground electrode, and 14 is an output electrode, which are all prepared on the fixed electrode plate 4. 18 is the cross section of the shaft. And 15, a detecting electrode, which is prepared on the detecting electrode plate 3 to rotate together with the rotating shaft.

The detection electrode 15 and the input electrode 17, the detection electrode 15 and the grounding electrode 16, and the detection electrode and the output electrode 14 respectively form a plate capacitor, and an equivalent circuit of the whole capacitive impedance sensor is shown in fig. 4.

It has been pointed out above that if the level on the detection electrode 15 is to be made linearly variable with angular rotation, the area is to be made linearly variable, while the area is not. To achieve this, the inner boundary of the input electrode 17 is a circle of 6mm diameter, and the outer boundary satisfies the equationThe outer boundary of the ground electrode is a circular arc with a diameter of 120mm and a central angle of 355 DEG, and the inner boundary is radially distant from the outer boundary of the input electrode by 2And mu m. The detection electrode is in a sector shape with the radius of 80mm and the central angle of 3 degrees. Assuming that the current detecting electrode has been rotated by an angle of alpha, the overlapping area of the area projection of the detecting electrode and the input electrode is 24.5 alpha +2.281 (mm) as can be seen from simple calculus²) That is, the overlapping area is always proportional to the rotation angle, and since the sum of the areas of the input electrode and the ground electrode is a sector, the sum of the overlapping area of the input electrode and the ground electrode is a constant, it can be known that the divided voltage on the detection electrode is proportional to the rotation angle of the detection electrode, and the input impedance of the measurement circuit can be regarded as infinite, it can be known that the level of the output electrode is equal to the upper divided voltage of the detection electrode and is proportional to the rotation angle, so that the linear relationship between the voltage of the output electrode and the rotation angle can be obtained by measuring the voltage of the output electrode, as shown in.

It should be noted that since the width of the detecting electrode itself is not 0, and the electric field at the edge of the detecting electrode cannot be regarded as a uniform electric field, the area in a small range of the two poles of the range of motion of the rotating shaft will not change linearly (dotted line portion of fig. 5), so that the linear output interval of the final capacitive impedance sensor is about 5 ° to 350 °.

The driving method of the rotary table: the 4 groups of sub-amplification structures are divided into two groups A and B according to the opposite direction.

In the initial state, the piezoelectric ceramics of the 4 groups of sub-amplification structures have no deformation, and the 4 groups of sub-amplification structures compress the rotating shaft.

Firstly, the radial amplification structures of the group B shrink under the drive of the piezoelectric ceramics, and the sub amplification structures of the group B are separated from the contact with the rotating shaft.

And secondly, the tangential amplifying structures of the group A drive the rotating shaft tangentially without sliding under the drive of the piezoelectric ceramics.

And thirdly, the radial amplifying structure of the group B cancels the shrinkage state and restores the state of pressing the rotating shaft.

Fourthly, the radial amplifying structures of the group A contract under the drive of the piezoelectric ceramics, and the sub amplifying structures of the group A are separated from the contact with the rotating shaft.

And fifthly, the piezoelectric ceramics of the tangential amplifying structure of the group A cancels deformation, and the tangential amplifying structure of the group A restores an undeformed state. Meanwhile, the tangential amplifying structure of the B group drives the rotating shaft under the driving of the piezoelectric ceramics in a non-sliding way along the tangential direction.

And sixthly, the radial amplifying structure of the group A cancels the shrinkage state and restores the state of pressing the rotating shaft.

And seventhly, the radial amplification structures of the B group contract under the drive of the piezoelectric ceramics, and the sub amplification structures of the B group are separated from the contact with the rotating shaft.

And eighthly, canceling deformation of the piezoelectric ceramics of the tangential amplifying structure of the group B, and recovering the undeformed state of the tangential amplifying structure of the group B. Meanwhile, the tangential amplifying structure of the group A drives the rotating shaft under the drive of the piezoelectric ceramics in a non-sliding manner along the tangential direction.

Note that the eighth step and the second step correspond to the same state of the turntable, and thus the process from the second step (eighth step) to the seventh step is repeated in sum, and continuous rotation can be achieved. The voltage signal sequence of the piezo-ceramic stack corresponding to the second through seventh cyclic motions in the foregoing driving description is shown in fig. 6, where the high voltage average represents the piezo-ceramic deformation, V_AtIs a group A of tangential piezoelectric ceramic driving voltage sequence, V_ArIs a group A of radial piezoelectric ceramic driving voltage sequence, V_BtIs a group B of tangential piezoelectric ceramic driving voltage sequence, V_BrAnd B groups of radial piezoelectric ceramic driving voltage sequences.

Fig. 7 is a schematic diagram showing the radial and tangential amplification substructures, and the working principle is the same. The gray part is piezoelectric ceramic, the length of the gray part can be changed by applying high voltage to generate input displacement of the amplifying structure, and the input displacement is usually 1-10 mu m. The piezoelectric ceramics and the metal sheets with two deformable sides form two triangles, and the change of the length of the piezoelectric ceramics can cause the obtuse vertex of the triangle to move, thereby realizing displacement output. The output is determined by the acute angle theta of the triangle, which determines (when θ is small).

It should be noted that the amplifying circuit of the capacitive impedance sensor and the control system of the piezoelectric ceramic, and the specific type of the piezoelectric ceramic, etc. included in the present invention should be considered as the prior art. The specific structure and operation principle of the technology can be selected by the conventional choice in the field, and the technology is not considered as the invention point of the patent of the invention, and the patent of the invention is not further described.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.