CN102416590A - A flexible limit support device and installation method for a large-diameter light-weight reflector - Google Patents

Abstract

The invention discloses a flexible limiting and supporting device for a heavy-caliber light reflector and an installation method, and the device mainly comprises: the device comprises a floating supporting structure, a flexible supporting structure, a gear transmission mechanism and a pressure sensing device. The specific supporting method mainly comprises the following steps: based on the deformation theory of the thin circular plate, the position, the caliber and the bearing reaction force borne by the flexible limiting supporting disc of the large-caliber light reflecting mirror surface under the action of gravity and the pressure of the grinding disc are optimized and analyzed; placing the workpiece on a Whiffletree structure model transition support plate, and positioning the workpiece; rotating the worm gear transmission mechanism to lift the flexible supporting disk; and based on the support reaction force calculated by finite elements, the position of each support disc is positioned in real time by utilizing the pressure sensing device. The invention has good error correction effect, inhibits the influence of external thermal gradient change, and can meet the processing, detection and application processes of the active grinding disc of the large-caliber light reflector.

Description

A flexible limit support device and installation method for a large-diameter light-weight reflector

technical field

The present invention relates to the technical field of light mirror support devices, in particular to a flexible limit support device and method for a large-diameter light mirror. The support device and method can be applied to the active polishing process and detection process of large-diameter grinding discs. In the implementation and application stage, the support device and method can reduce the negative effects of external force load, inertial load and thermal load, thereby ensuring the imaging quality of the optical system.

Background technique

With the continuous improvement of performance requirements of modern optical systems, the quality requirements of optical components are also continuously improved. In order to improve the imaging quality of the optical system and reduce the cost, modern optical parts are developing towards the trend of aspheric surface, large relative aperture and high light weight. However, during use, the lightweight mirror is easily affected by external forces, such as space microgravity, inertial load, vibration, assembly error stress, airflow, temperature load, etc., which affect the imaging quality of the optical system. Therefore, it is necessary to use a The flexible support isolation device isolates the influence of mechanical and thermal effects on the optical system in the support system, ensuring that the mirror and its support structure have good dynamic structural performance and thermal stability.

The processing methods of large-diameter lightweight mirrors mainly include CCOS small grinding head technology, magnetorheological (MRF) technology, ion beam (IBF) technology, and stress disk polishing CCAL technology. However, CCOS polishing technology is likely to cause medium and high frequency errors on the surface of the workpiece, which affects the imaging quality of the optical system. Moreover, it is difficult to ensure the consistency of the removal function during the processing of large-diameter optical components; while MRF and IBF are expensive and have low removal volume. Applied to the nanometer precision improvement stage of the processing process. CCAL polishing technology is based on the theory of elastic thin plates, using an aluminum plate with a diameter of 1/6-1/3 under the action of external variable torque, the thin plate produces high-order curved surface deformation to match the surface of the aspheric primary mirror, and completes the high-precision polishing of the primary mirror. It has the advantages of high removal efficiency and suppression of medium and high frequencies.

At present, the support models for large-aperture lightweight mirrors are mainly the Whiffletree floating support structure model and the Grubb rocking plate support structure model. The Whiffletree support model can balance the external load on the workpiece interface by adjusting the floating of the support disc, so that the force on the mirror surface is more uniform, especially in the polishing process of the large-diameter grinding disc and the active grinding disc. The Whiffletree support model is to select support points on the base support surface, expand the support points to double support surfaces through the principle of leverage balance, and set a dynamic support plate on each support surface. The selected support points of the support model are relatively independent, and each group of support surfaces extended on the support points constitutes a dynamic balance. The Grubb support model is to expand the support points into multi-point supports through a rigid floating bracket on each statically definite support point, and then act on the main mirror. The multi-point supports acting on the mirror obey the rules of static balance. The positioning accuracy of the Whiffletree and Grubb support models on the workpiece support surface is guaranteed by the three-point levelness of the support plate, so the force on the support surface of the workpiece is easily balanced during the application process. However, the final support force of the Whiffletree and Grubb support models is reflected in the rigid support rods, which cannot eliminate the local deformation caused by thermal-structural deformation, vibration load, and airflow changes caused by external temperature changes.

References: "Jerry E. Nelson, Jacob Lubliner, Terry S. Mast, Telescope mirror supports: plate deflections on point supports [J]. Advanced Technology Optical Telescopes, SPIE, 1982(332), 212-228" discloses the Theory and Vukobratovich's "grid effect" formula, those skilled in the art can easily calculate the support point and the position of the support point ring of the large-diameter lightweight mirror based on the above theory and related formulas.

The flexible limit support combines the flexible support method with the rigid support method. The flexible support device is a combination of flexible springs, whose purpose is to balance the pressure of the polishing grinding head, eliminate vibration errors and suppress mirror deformation caused by external loads; the rigid support is designed to limit the position of large-diameter lightweight mirrors during polishing and application stages and protection. During the polishing process of the active grinding disc, due to the heavy weight of the active grinding disc, when the grinding disc is at the edge of the workpiece (the size of the edge of the workpiece exposed by the grinding disc is less than 1/3 of the size of the grinding disc), it will cause the workpiece to have a micron-level inclination. At this time, it can be used at the same time The three-point rigid support acts on the workpiece support surface at the same time, so as to eliminate the slight inclination during the polishing process of the workpiece. The three-point limit support reduces the initial inclination from 3.4 microns to 0.96 microns when the edge of the large-caliber lightweight mirror is polished. It is far lower than the positioning accuracy of the Z-axis of the polishing machine, and the mirror deformation under this support method is recoverable. After simulation analysis, using the flexible limit support model, the flexible support device can support 80% of the gravity of the workpiece and the grinding disc, the equivalent stress of the support surface changes relatively low, and the maximum principal stress meets the ultimate stress requirements of the workpiece, which greatly improves the resistance of the workpiece to the outside world Vibration, atmospheric turbulence changes, thermal load deformation capability.

Contents of the invention

The object of the present invention is to design a flexible position-limiting support device that can be applied to large-diameter grinding disc processing and implementation. The advantages of excessive stress and the improvement of the optical system to resist the influence of external loads during the implementation and application process to improve the quality of optical imaging. Therefore, a flexible limiting device with simple and compact structure, low cost, simple control, high integration, convenient operation, and high-precision polishing of large-diameter, high-weight and light-weight mirrors and optical system installation is provided.

The purpose of the present invention is achieved by the following technical solutions:

A flexible position-limiting support device for a large-diameter lightweight reflector, which includes a floating support structure, a flexible support structure, a gear transmission mechanism, and a pressure sensing device; wherein:

The floating support structure adopts the Whiffletree model, which is a transitional support structure model, and its purpose is to initially position the workpiece; the floating support structure includes a base, a central column, a lever support frame, a lever, and a ball , tripod, floating positioning column, floating support plate, cylindrical pin; wherein the lever support frame, lever, ball, and tripod form a floating lever balance model;

The flexible support structure includes a support column, a base, a flexible support plate, a side support frame, a limit support hole, a flexible support column and a combined spring model; the base is fixed on three support columns;

The pressure sensing device includes a pressure sensor, a signal converter and a pressure output display, and its purpose is to monitor the force that each flexible support structure model produces on the lightweight mirror; the signal converter includes a signal amplification circuit and an A/ D conversion circuit, the output is the elastic action force of each flexible support plate on the workpiece.

Further, the connection mode of the floating positioning column and the floating support plate is a ball joint connection.

Further, the surfaces at both ends of the lever are hemispherical concave surfaces, and the connection mode with the tripod is a ball-joint universal joint connection.

Further, the combined spring model includes a mounting frame and a combined spring, the mounting frame is fixedly matched with the lifting column, and the flexible support structure has the functions of suppressing vibration and resisting thermal load interference.

Furthermore, the lifting model supported by the Whiffletree model adopts a worm gear transmission mechanism, and the lifting model of the flexible support plate and the limit support plate adopts a bevel gear transmission mechanism; the worm gear transmission mechanism can be applied to heavy loads and has a self-locking function; The bevel gear transmission mechanism has high transmission ratio and good positioning accuracy.

Further, the driving gear of the worm gear transmission mechanism is a worm, the driven gear is a worm gear, and the adjusting gear is a central column; the driving gear of the bevel gear transmission mechanism is a bevel gear, the driven gear is a bevel gear, and the adjusting gear is a lifting column; The driven worm gear and the driven bevel gear are direction-changing gears, the left end of the driven worm gear is a worm gear, and the right end is a spur gear; the outer end of the driven bevel gear is a bevel gear, and the inner ring is a threaded hole.

Further, the worm and gear transmission mechanism is fixed inside the base through bearings, and the lever balance model is installed above the base. The lifting method of the floating support model is to drive the worm wheel by rotating the worm, and the spur gear at the right end of the worm wheel cooperates with the spur gear of the center column to achieve The base lifts.

Furthermore, the bevel gear transmission mechanism is fixed inside the base through bearings, and the lifting column passes through the limit support hole to cooperate with the driven bevel gear. The flexible and limit-supported lifting method rotates the active bevel gear to drive the bevel gear, and The lifting of the lifting column is realized by the inner thread of the bevel gear.

Further, the pressure sensor is a patch-type pressure sensor, and the resolution of the patch-type pressure sensor is 0.1 mV and outputs an analog signal.

According to the above-mentioned installation method of a flexible limit support device for a large-diameter light-weight reflector, the steps of the installation method are as follows:

The first step: Based on the thin plate deformation theory and Vukobratovich's "grid effect" formula, roughly calculate the support point and the position of the support point ring of the large-diameter lightweight mirror;

The second step: use finite element analysis software to analyze the flexibility of the low-precision deformation of the large-diameter light-weight mirror surface under the action of gravity and the pressure of the grinding disc, the diameter and position of the limit support disc, and the support reaction force on the support surface;

Step 3: Place the pressure sensor on the flexible support plate, and output the sensor voltage output signal to the pressure output display through the signal amplification circuit and the A/D conversion circuit;

Step 4: Place a metal plate with the same quality as the workpiece on the flexible limit support structure model, adjust the active bevel gear according to the force calculated in the first step, and roughly adjust the position of each flexible limit support plate Position and undo the tablet;

Step 5: Adjust the hand wheel and worm, lift the Whiffletree support platform, place the workpiece on the Whiffletree floating support model of the installation platform, and position the workpiece; slowly lower the Whiffletree support platform, and realize the transition of the bottom surface support of the workpiece from the Whiffletree floating support to the flexible limit. bit support;

Step 6: Adjust each flexible limit support plate by rotating the active bevel gear, and precisely position each flexible limit support plate through the pressure sensor number obtained by the feedback of the pressure sensor device.

Compared with prior art, the advantage of the present invention is:

1. The supporting capacity of the large-caliber lightweight mirror flexible limit support device of the present invention to the optical system is mainly reflected in the flexible support structure, which improves the anti-vibration capacity of the support structure and the ability to resist external load deformation;

2. Compared with the floating support and swing support, the reduction of the flexible limit support greatly reduces the maximum principal stress of the workpiece and eliminates the stress concentration in the application process;

3. Flexible limit support During the polishing process of the active grinding disc, the gravitational load of the grinding disc fully acts on the flexible support model, the polishing surface of the grinding disc is completely attached to the mirror surface, and the force on the polishing area is more uniform;

4. The support force of the floating support model or the swing support model to the workpiece varies with the distance from the position of the polishing disc to the center of the mirror, while the support force of each support disc of the flexible support model to the workpiece is almost the same, and the force on the support surface is uniform.

Description of drawings

Fig. 1 is a schematic diagram of a flexible limit support structure model;

Fig. 2 is a schematic diagram of a floating support structure model;

Fig. 3 is a schematic diagram of a lever balance device model;

Fig. 4 is a schematic diagram of a combined spring model;

Fig. 5 is a schematic diagram of a worm gear transmission model;

Figure 6 is a schematic diagram of a bevel gear transmission

7 is a schematic diagram of a pressure sensing display device;

Figure 8 is a schematic diagram of the position of the flexible limit support of the lightweight mirror with a diameter of Φ1.8m;

Fig. 9 is a position optimization analysis diagram of the limit support plate;

Figure 10 is the optimization analysis of the caliber of the limit support plate;

Figure 11 shows the mirror surface deformation when the edge of the active grinding disc is polished based on the flexible limit support condition;

Figure 12 shows the force distribution of the support plate under the floating structure model, flexible support model, and flexible limit support model.

Labels in the figure: 101, base; 102, central column; 103, lever support frame; 104, lever; 105, ball; 106, tripod; 107, floating positioning column; 108, floating support plate; 109, cylindrical pin; 201, support column; 202, base; 203, flexible support plate; 204, side support frame; 205, limit support hole; 206, installation frame; 207, combined spring; 208, flexible support; 301, worm; Driven worm gear; 303, bearing; 304, lifting column; 305, driving bevel gear; 306, driven bevel gear; 401, pressure sensor; 402, signal amplification circuit; 403, A/D conversion circuit; 404, pressure output display ;

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, the present invention is further explained:

As shown in Figures 1, 2, and 3, the floating support structure of the device of the present invention adopts the Whiffletree model, which is a transitional support structure model, and its purpose is to initially position the workpiece. The floating support structure mainly includes a base 101, a central column 102, a lever support frame 103, a lever 104, a ball 105, a tripod 106, a floating positioning column 107, a floating support plate 108, and a cylindrical pin 109. Wherein lever support frame 103, lever 104, ball 105, tripod 106 constitute floating lever balance model;

As shown in FIG. 3 , the surfaces at both ends of the lever 104 are hemispherical concave surfaces, and the connection mode with the tripod 106 is a ball joint connection;

As shown in Figures 1 and 4, the flexible support structure mainly includes a support column 201, a base 202, a flexible support plate 203, a side support frame 204, a limit support hole 205, a flexible support column 208, a mounting frame 206 and a combined spring 207; The base 202 is fixed on the three supporting columns 201; the mounting frame 206 is fixedly matched with the lifting column 304;

As shown in Figures 1, 2, 5, and 6, the driving gear of the worm gear transmission mechanism is the worm 301, the driven gear is the worm gear 302, and the adjusting gear is the central column 102; the driving gear of the bevel gear transmission mechanism is the bevel gear 305, and the driven gear is The gear is a bevel gear 306, and the adjusting gear is a lifting column 304; wherein the worm gear 302 and the driven bevel gear 306 are direction-changing gears, the left end of the worm gear 302 is a worm gear, and the right end is a spur gear; the outer end of the driven bevel gear 306 is a bevel gear, and the inner The ring is a threaded hole. The worm gear transmission mechanism is fixed inside the base 101 through the bearing 303. The lever balance model is installed above the base. The lifting mode of the floating support model is to drive the worm wheel 302 by rotating the worm 301, and the spur gear at the right end of the gear 302 is directly connected to the center column 102. Teeth cooperate to realize base 101 lifting. The bevel gear transmission mechanism is fixed inside the base 202 through bearings. The lifting column 304 passes through the limit support hole 205 and cooperates with the transmission bevel gear 306. The flexible and limit support lifting method drives the bevel gear 306 by rotating the active bevel gear 305. , and realize the lifting of the lifting column 304 by the internal thread of the bevel gear 306;

As shown in Figure 7, the pressure sensing device includes a patch pressure sensor 401, a signal amplification circuit 402, an A/D conversion circuit 403, and a pressure output display 404, and the signal amplification circuit 402 and the A/D conversion circuit 403 form a signal converter , the purpose of which is to monitor the force generated by each flexible support structure model on the lightweight mirror, and to position the active bevel gear 305 according to the measurement data;

This implementation example combines a highly lightweight hyperboloid lightweight mirror with a diameter of 1.8m for simulation. The material of the lightweight mirror is fused silica, the workpiece weight is 408.68Kg, and the weight is (80.3%). The weight is 20kg. Figure 8 is a distribution diagram of the positions and diameters of 18 flexible support plates and 3-point limit support plates obtained after optimization based on the thin plate theoretical model. Through finite element simulation analysis, using the Whiffletree model, the force of each support plate of the inner and outer rings varies with the radius of the ring, the support reaction force of each support surface of the outer ring is 225.217N, and the support force of each support surface of the inner ring is 225.217N. The reaction force is 217.743N; while in the flexible support structure model, the force of the 18 support plates on the workpiece is 222.73N. Therefore, the flexible support has the advantage of eliminating the stress concentration on the support surface;

Figure 9 is an optimization analysis of the position of the three-point rigid limit support plate based on the flexible support model;

Figure 10 is an optimization analysis of the diameter of the three-point rigid limit support plate based on the flexible support model;

Figure 11 shows the mirror surface deformation obtained based on the analysis of the flexible limit support model when the grinding disc is polished at the edge of the workpiece, PV (peak-to-valley value) 964.4nm, RMS (root mean square value) 215.0nm;

Figure 12 compares and analyzes the force of a 1.8m-diameter high-weight hyperboloid lightweight mirror supported by three models of Whiffletree floating support, flexible support and flexible limit support. The support force of the outer ring position (A7-A18) of the Whiffletree model is greater than the support force of the inner ring position (A1-A6), and the force of the support plate is affected by the polishing position of the grinding disc; the force distribution of the flexible support model is uniform at 18 points, and The force of the support disc on the workpiece is basically not affected by the position of the grinding disc, but when the edge of the grinding disc is polished, the support surface will have a micron-scale inclination; the flexible limit support combines the advantages of the former two, and A1-A18 is a flexible support feature. The distribution is even, and the force of the support disc on the workpiece is basically not affected by the position of the grinding disc. A19-A21 are limit supports, which can limit the protection of the workpiece and reduce the inclination of the workpiece during the polishing process.

The parts not described in detail in the present invention belong to the well-known technology in the art.

Claims (10)

1. the flexible spacing bracing or strutting arrangement of an aperture lightweight speculum, it is characterized in that: this device comprises unsteady supporting construction, flexible support structure, gear drive and pressure sensor device; Wherein:

Said unsteady supporting construction, it adopts the Whiffletree model, and this model is a kind of supporting construction model of transition, its objective is workpiece is carried out initial alignment; Said unsteady supporting construction comprises base (101), newel (102), lever bracing frame (103), lever (104), ball (105), tripod (106), the reference column (107) that floats, supporting disk (108), straight pin (109) float; Wherein lever bracing frame (103), lever (104), ball (105), tripod (106) constitute the floating lever rod balance model;

Said flexible support structure comprises support column (201), pedestal (202), flexible support dish (203), side bracing frame (204), spacing supported hole (205), flexible support post (208) and combined type spring model; Pedestal (202) is fixed on three support columns (201);

Said pressure sensor device comprises pressure sensor (401), signal adapter and pressure Output Display Unit (404), its objective is each flexible support structure model is monitored the active force that the lightweight mirror produces; Signal adapter comprises signal amplification circuit (402) and A/D change-over circuit (403), is output as the elastic acting force of each flexible support dish to workpiece.

2. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1 is characterized in that: the connected mode of the reference column (107) that floats, the supporting disk (108) that floats is that ball head universal connects.

3. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1, it is characterized in that: lever (104) two end surfaces are the hemisphere concave surface, are that ball head universal is connected with the connected mode of tripod (106).

4. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1; It is characterized in that: the combined type spring model comprises installing rack (206), cluster spring (207); Installing rack (206) and lifting column (304) secure fit; Flexible support structure has the vibration of inhibition, the function that the opposing thermal force is disturbed.

5. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1; It is characterized in that: the up-down model that the Whiffletree model supports adopts Worm and worm-wheel gearing, and the up-down model of flexible support dish and spacing supporting disk adopts the bevel gear transmission mechanism; Worm and worm-wheel gearing can be applicable to big mass loading, and has auto-lock function; And bevel gear transmission mechanism gearratio is high, and positioning accuracy is good.

6. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 5, it is characterized in that: the driving gear of Worm and worm-wheel gearing is that worm screw (301), driven gear are that worm gear (302), adjusting gear are newel (102); Bevel gear transmission mechanism driving gear is that bevel gear (305), driven gear are that bevel gear (306), adjusting gear are lifting column (304); Wherein driven worm gear (302), driven bevel pinion (306) are change gear, and driven worm gear (302) left end is that worm gear, right-hand member are spur gear; Driven bevel pinion (306) outer end is that bevel gear, interior ring are screwed hole.

7. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 5; It is characterized in that: Worm and worm-wheel gearing is fixed in base (101) inside through bearing (303); The lever balance model is installed on the pedestal top; The up-down mode of unsteady bolster model drives worm gear (302) for through rotary worm (301), and cooperates realization base (101) up-down with newel (102) straight-tooth by worm gear (302) right-hand member spur gear.

8. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 5; It is characterized in that: the bevel gear transmission mechanism passes through bearing fixing in pedestal (202) inside; Lifting column (304) passes spacing supported hole (205) and cooperates with driven bevel pinion (306); Rotation driving bevel gear (305) is passed through in up-down mode position flexible and spacing support, drives bevel gear (306), and realizes the up-down of lifting column (304) by the internal thread of bevel gear (306).

9. the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1, it is characterized in that: pressure sensor (401) is SMD pressure sensor, the voltage output analog signal that this SMD pressure sensor resolving power is 0.1mV.

10. the installation method of the flexible spacing bracing or strutting arrangement of a kind of aperture lightweight speculum according to claim 1, it is characterized in that: said installation method step is following:

The first step:, roughly extrapolate the strong point and the strong point endless belt position of aperture lightweight mirror based on thin plate Deformation Theory and Vukobratovich " grid effect " formula;

Second step: adopt finite element analysis software, analyze under gravity and the effect of mill pressure, optimize flexibility, spacing supporting disk bore, position and the suffered support reaction of supporting surface of analyzing the low precision distortion of aperture lightweight mirror surface;

The 3rd step: pressure sensor (401) is placed on the flexible support dish (203), and sensor voltage is exported signal gaging pressure is outputed in the pressure Output Display Unit (404) through signal amplification circuit (402) and A/D change-over circuit (403);

The 4th step: will place with the metal plate of workpiece equal quality on the flexible spacing supporting construction model; Active force to calculating to the first step is regulated driving bevel gear (305); Roughly the position to each flexible spacing supporting disk positions, and cancels flat board;

The 5th step: adjusting handle worm screw (301), promote the Whiffletree support platform, workpiece is placed on the unsteady bolster model of Whiffletree of mounting platform, workpiece is positioned; Slowly reduce the Whiffletree support platform, the realization workpiece bottom supports by Whiffletree is unsteady and supports excessively to flexible spacing support;

The 6th step: through rotation driving bevel gear (305), regulate each flexible spacing supporting disk (203), and each flexible spacing supporting disk is accurately located through the pressure sensor numeral that the pressure sensor device feedback obtains.

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