Aspheric mirror stress loading mechanism and error distribution method thereof

Abstract

The invention relates to the technical field of optical-mechanical structures, in particular to an aspherical mirror stress loading mechanism and an error distribution method thereof.The aspherical mirror stress loading mechanism comprises a driving system and a flexible lever, the input end of the flexible lever is connected with the output end of the driving system, and the output end of the flexible lever is connected with an aspherical mirror; the driving system comprises a servo motor, a coupler and a roller screw, one end of the roller screw is connected with the output end of the servo motor through the coupler, and the other end of the roller screw is connected with the input end of the flexible lever. The aspheric mirror stress loading mechanism has the advantages that the aspheric mirror stress loading mechanism is not limited by the size of a mirror blank and according to space, and the aspheric mirror stress loading mechanism has good universality for various large, medium and small aspheric surfaces. By adopting the error distribution method of the aspherical mirror stress loading mechanism, the precision requirements of the servo motor, the coupler and the roller screw can be quickly distributed in the design stage, so that the performance and the stability of the whole system are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of optical-mechanical structures, and in particular to an aspherical mirror stress loading mechanism and an error distribution method thereof. Background Art

[0002] Large-scale spliced ​​telescopes and low-orbit giant constellation optical payloads urgently need a leap in production capacity in the field of aspheric optical processing. However, the current limited manufacturing capabilities and expensive manufacturing costs form a sharp contrast with these massive application demands of aspheric surfaces.

[0003] Commonly used aspheric surface processing technologies include traditional manual grinding and polishing, computer-controlled optical surface forming, small grinding head processing, stress disk polishing, magnetorheological polishing, ion beam polishing, etc. These methods can meet the low-frequency surface error requirements of aspheric reflectors, but the suppression effect of medium / high frequency surface errors is poor, and the processing efficiency is low and the cost is high. The demand for the development of large spliced ​​telescopes has promoted the emergence of prestressed processing technology, which has greatly contributed to the successful development of the Keck telescope and is playing an important role in the development of the TMT telescope (Thirty Meter Telescope) and the E-ELT telescope (European Extremely Large Telescope).

[0004] The idea of ​​prestressed processing is to transform the complex processing technology adjustment into the control of the surface shape of the mirror blank to be processed, transform the aspheric processing into the spherical processing method for processing, and obtain the required aspheric surface after stress unloading. Prestressed processing is of great significance to improving the processing efficiency of reflectors, suppressing the high-frequency errors of mirrors, and promoting the engineering application of aspheric surfaces.

[0005] The existing prestressed loading mechanism has the disadvantages of poor interchangeability, poor versatility, low shape control accuracy, etc., and the dynamic range of stress shape control loading (adjustment stroke / accuracy ratio) is too small, which makes it impossible to be used for various short-focus aspheric surfaces required for compact optical systems. Summary of the invention

[0006] In view of this, the invention aims to provide a stress loading mechanism for an aspherical mirror and an error distribution method thereof, which realizes the loading of stress on the aspherical surface through a driving system and a flexible lever. At the same time, the error distribution method is obtained by calculating the displacement error of the servo motor, the coupling displacement error and the roller screw displacement error in the driving system.

[0007] To achieve the above-mentioned purpose, the technical solution created by the present invention is implemented as follows: a stress loading mechanism for an aspheric mirror, comprising a driving system and a flexible lever, the input end of the flexible lever is connected to the output end of the driving system, and the output end of the flexible lever is connected to the aspheric mirror; the actuator comprises an output shaft and a driving system; the driving system comprises a servo motor, a coupling and a roller screw, the roller screw is connected to the output end of the servo motor through a coupling, and the nut of the roller screw is connected to the output shaft.

[0008] Furthermore, the flexible lever includes a crossbeam and a flexible rod which are perpendicular to each other, one end of the crossbeam is connected to the aspheric mirror; a roller screw is connected to the crossbeam near the other end of the crossbeam; the flexible rod is arranged on the crossbeam and close to the aspheric mirror; a flexible hinge is arranged at a position of the flexible rod close to the crossbeam, and a fixing hole is arranged at a position of the flexible rod away from the crossbeam.

[0009] Furthermore, the flexible hinge is a double arc flexible hinge.

[0010] An error allocation method for a stress loading mechanism of an aspherical mirror is used to analyze the displacement error of a servo motor, a coupling and a roller screw of a driving system in the stress loading mechanism of an aspherical mirror. The specific steps are as follows: S1: Set the displacement error of the drive system to ; When the roller screw rotates one circle, the displacement of the end of the output shaft is calculated.

[0011] S2: According to the displacement of the end of the output shaft, the servo motor displacement error, coupling displacement error, and roller screw displacement error are obtained by calculation.

[0012] S3: Based on the servo motor displacement error, coupling displacement error and roller screw displacement error combined with the principle of random error, the total displacement error of the drive system is obtained.

[0013] S4: According to the proportion of servo motor, coupling and roller screw in the total error of the drive system, the servo motor displacement error inequality, coupling displacement error inequality and roller screw displacement error inequality are obtained respectively.

[0014] Furthermore, in step S1, the displacement y of the end of the roller screw is: (1.1); in, is the lead of the roller screw, is the number of revolutions of the servo motor, is the transmission efficiency of the coupling.

[0015] Furthermore, in step S2, combined with equation (1.1), the servo motor displacement error is obtained Formula, coupling displacement error Formula and roller screw displacement error The formulas are: (1.2); (1.3); (1.4); in, is the angular error of the servo motor; is the rotation efficiency deviation of the coupling; is the lead error of the roller screw.

[0016] Furthermore, in step S3, according to formulas (1.2), (1.3), and (1.4) combined with the principle of random error, the total displacement error of the drive system is obtained: for: (1.5); According to the error distribution requirements, we get the inequality: (1.6).

[0017] Further, in step S4, the proportions of the servo motor, coupling and roller screw in the total error of the drive system are respectively , , , , , All three values ​​are non-zero, and (1.7); Then equation (1.6) is transformed into: (1.8); Further we get: (1.9).

[0018] Furthermore, according to the corresponding relationship between the servo motor displacement error, coupling displacement error, and roller screw displacement error, the inequality is obtained: (1.10); (1.11); (1.12).

[0019] Furthermore, according to formulas (1.2) and (1.10), the angular accuracy of the servo motor is obtained: for: (1.13); According to formulas (1.3) and (1.11), the transmission efficiency deviation of the coupling is obtained: for: (1.14); According to formulas (1.4) and (1.12), the lead error of the roller screw is for: (1.15).

[0020] Compared with the prior art, the invention can achieve the following beneficial effects: 1) The flexible design of the flexible hinge introduced into the flexible lever makes the adjustable range of the driving force at the input end of the aspheric mirror stress loading mechanism wider, which can reduce the displacement accuracy requirements of the driving system.

[0021] 2) The design of the flexible hinge enables the flexible lever to produce a certain deformation when subjected to force, thereby absorbing and dispersing stress, improving the stability and durability of the aspheric mirror stress loading mechanism.

[0022] 3) When processing aspheric mirrors, a plurality of aspheric mirror stress loading mechanisms are usually evenly distributed around the aspheric mirror. The flexible lever in the aspheric mirror stress loading mechanism utilizes the shrinkage principle to improve the manufacturing efficiency and precision of the aspheric mirror.

[0023] 4) The stress loading mechanism of the aspheric mirror of the present invention is not limited by the size and space of the mirror blank, and has good versatility for various large, medium and small aspheric surfaces.

[0024] 5) By adopting the error distribution method of the aspherical mirror stress loading mechanism, the accuracy requirements of the servo motor, coupling and roller screw can be accurately matched in the design stage, thereby ensuring the performance and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings: Figure 1 is a structural schematic diagram of an aspheric mirror stress loading mechanism provided according to an embodiment of the present invention; Figure 2 is a schematic diagram of the structure of a flexible lever provided according to an embodiment of the present invention.

[0026] The reference numerals include: 1, actuator; 11, servo motor; 12, coupling; 13, roller screw; 2, flexible lever; 21, beam; 22, flexible rod; 23, connecting hole; 24, mounting hole; 25, flexible hinge; 26, fixing hole. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0028] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0030] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0031] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0032] like Figure 1As shown, an aspheric mirror stress loading mechanism provided by an embodiment of the present invention includes an actuator 1 and a flexible lever 2, wherein the input end of the flexible lever 2 is connected to the output shaft of the actuator 1, and the output end of the flexible lever 2 is connected to the aspheric mirror. The actuator 1 includes an output shaft and a driving system, wherein the driving system includes a servo motor 11, a coupling 12, and a roller screw 13, wherein the roller screw 13 is connected to the output end of the servo motor 11 through the coupling 12, and the nut of the roller screw 13 is connected to the output shaft. The servo motor 11 drives the screw of the roller screw 13 to rotate, so that the nut of the roller screw 13 moves up and down along the screw, thereby driving the output shaft to move, thereby realizing the movement of the flexible lever 2.

[0033] The roller screw 13 is a type of screw, which is characterized by using rollers as rolling elements instead of traditional balls. This design enables the roller screw 13 to have a larger contact surface and force-bearing surface during the transmission process, thereby improving the transmission efficiency and load-bearing capacity.

[0034] The flexible lever 2 includes a crossbeam 21 and a flexible rod 22 which are perpendicular to each other. A mounting hole 24 is provided at one end of the crossbeam 21 for connecting with the aspheric mirror. The end of the crossbeam 21 connected with the aspheric mirror serves as the output end of the flexible lever 2 for transmitting the stress of the aspheric mirror stress loading mechanism to the aspheric mirror. A connecting hole 23 is provided on the crossbeam 21 near the other end of the crossbeam 21. The roller screw 13 is connected to the crossbeam 21 through the connecting hole 23 as the input end of the flexible lever 2 for transmitting the driving force of the aspheric mirror stress loading mechanism to the flexible lever 2. The flexible rod 22 is provided on the crossbeam 21 and close to the aspheric mirror. A flexible hinge 25 is provided at a position of the flexible rod 22 close to the crossbeam 21. A fixing hole 26 is provided at a position of the flexible rod 22 away from the crossbeam 21. Through the fixing hole 26, the flexible rod 22 can be fixed at a desired position using bolts, pins or other fasteners. The flexible hinge 25 is a double arc flexible hinge.

[0035] The flexible design of the flexible hinge 25 introduced into the flexible lever 2 makes the adjustable range of the driving force at the input end of the aspherical mirror stress loading mechanism wider, which can reduce the displacement accuracy requirement of the actuator 1. The design of the flexible hinge 25 enables the flexible lever 2 to produce a certain deformation when subjected to force, thereby absorbing and dispersing stress, and improving the stability and durability of the aspherical mirror stress loading mechanism.

[0036] When processing an aspheric mirror, a plurality of aspheric mirror stress loading mechanisms are usually evenly distributed around the aspheric mirror. The flexible lever 2 in the aspheric mirror stress loading mechanism utilizes the lever error reduction principle to improve the loading accuracy of the aspheric mirror.

[0037] An error allocation method for an aspherical mirror stress loading mechanism is used to analyze the displacement error of the servo motor 11, the displacement error of the coupling 12 and the displacement error of the roller screw 13 of the drive system in the aspherical mirror stress loading mechanism. The specific steps are as follows: S1: Set the drive system error to ; When the roller screw 13 rotates one circle, the displacement of the end of the output shaft of the actuator 1 is calculated.

[0038] The displacement y at the end of the output shaft is: (1.1); in, is the lead of the roller screw 13, is the number of revolutions of the servo motor 11, is the transmission efficiency of the coupling 12.

[0039] S2: According to the displacement of the end of the roller screw 13, the displacement error of the servo motor 11, the displacement error of the coupling 12, and the displacement error of the roller screw 13 are obtained by calculation.

[0040] Taking partial derivative of formula (1.1), we get the servo motor 11 error , coupling 12 error and roller screw 13 error The formulas are: (1.2); (1.3); (1.4); in, is the angle error of the servo motor 11; is the difference between the actual transmission efficiency of the coupling 12 and the theoretical transmission efficiency (i.e., the rotation efficiency deviation of the coupling 12); is the lead error of the roller screw 13.

[0041] S3: According to the displacement error of the servo motor 11, the displacement error of the coupling 12 and the displacement error of the roller screw 13 combined with the principle of random error, the total displacement error of the drive system is obtained.

[0042] According to the three error formulas (1.2), (1.3) and (1.4) combined with the principle of random error, the total error of the drive system is obtained: for: (1.5); According to the error distribution requirement (that is, the total error of the drive system must be less than or equal to the error of the drive system), the inequality is obtained: (1.6).

[0043] S4: According to the proportion of the servo motor 11, the coupling 12 and the roller screw 13 in the total error of the drive system, the displacement error inequality of the servo motor 11, the displacement error inequality of the coupling 12 and the displacement error inequality of the roller screw 13 are obtained respectively.

[0044] The proportions of the servo motor 11, the coupling 12 and the roller screw 13 in the total error of the drive system are , , , , , All three values ​​are non-zero; and (1.7); Then equation (1.6) is transformed into: (1.8); Further we get: (1.9).

[0045] Furthermore, according to the corresponding relationship between the displacement error of the servo motor 11, the displacement error of the coupling 12 and the displacement error of the roller screw 13, the inequality is obtained: (1.10); (1.11); (1.12).

[0046] Furthermore, according to formulas (1.2) and (1.10), the angular accuracy of the servo motor 11 is obtained: for: (1.13); According to formulas (1.3) and (1.11), the transmission efficiency deviation of coupling 12 is obtained: for: (1.14); According to formulas (1.4) and (1.12), the lead error of roller screw 13 is obtained for: (1.15).

[0047] The error distribution method of the aspheric mirror stress loading mechanism provided by the present invention is described below in conjunction with a specific embodiment. is set to 10um, the lead of the roller screw 13 is 2mm, the number of rotations of the servo motor 11 is 1, and the transmission efficiency of the coupling 12 is 1. According to experience, the error coefficient of the servo motor 11, the error coefficient of the coupling 12, and the error coefficient of the roller screw 13 are set to , and ,Will , , Substituting into formulas (1.13), (1.14), and (1.15), we can obtain the angular accuracy of servo motor 11. , Transmission efficiency deviation of coupling 12 and the lead error of the roller screw 13 They are: (1.16); (1.17); (1.18); Where r is the unit of turns.

[0048] Convert the number of turns in formulas (1.16) and (1.17) into angles and we get: , .

[0049] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A stress loading mechanism for an aspherical mirror, characterized in that: It includes an actuator and a flexible lever, wherein the input end of the flexible lever is connected to the output shaft of the actuator, and the output end of the flexible lever is connected to an aspherical mirror; the actuator includes an output shaft and a driving system; the driving system includes a servo motor, a coupling and a roller screw, the roller screw is connected to the output end of the servo motor through a coupling, and the nut of the roller screw is connected to the output shaft.

2. The aspheric mirror stress loading mechanism according to claim 1, characterized in that: The flexible lever includes a crossbeam and a flexible rod which are perpendicular to each other, one end of the crossbeam is connected to the aspheric mirror; the roller screw is connected to the crossbeam near the other end of the crossbeam; the flexible rod is arranged on the crossbeam and close to the aspheric mirror; a flexible hinge is arranged at a position where the flexible rod is close to the crossbeam, and a fixing hole is arranged at a position where the flexible rod is away from the crossbeam.

3. The aspheric mirror stress loading mechanism according to claim 1, characterized in that: The flexible hinge is a double arc flexible hinge.

4. An error allocation method for an aspheric mirror stress loading mechanism, used for analyzing the servo motor displacement error, coupling displacement error and roller screw displacement error of the drive system in the aspheric mirror stress loading mechanism according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: S1: Set the displacement error of the drive system to ; When the roller screw rotates one circle, the displacement of the end of the output shaft is calculated; S2: According to the displacement of the end of the output shaft, the displacement error of the servo motor, the displacement error of the coupling, and the displacement error of the roller screw are obtained by calculation respectively; S3: Obtaining the total displacement error of the drive system according to the displacement error of the servo motor, the displacement error of the coupling and the displacement error of the roller screw in combination with the principle of random error; S4: According to the proportion of the servo motor, the coupling and the roller screw in the total error of the drive system, the servo motor displacement error inequality, the coupling displacement error inequality and the roller screw displacement error inequality are obtained respectively.

5. The error distribution method of the aspheric mirror stress loading mechanism according to claim 4, characterized in that: In step S1, the displacement y of the output shaft end is: （1.1）； in, is the lead of the roller screw, is the number of revolutions of the servo motor, is the transmission efficiency of the coupling.

6. The error distribution method of the aspheric mirror stress loading mechanism according to claim 5, characterized in that: In step S2, the partial derivative of formula (1.1) is obtained to obtain the displacement error of the servo motor: Formula, the coupling displacement error Formula and the roller screw displacement error The formulas are: （1.2）； （1.3）； （1.4）； in, is the angular error of the servo motor; is the rotation efficiency deviation of the coupling; is the lead error of the roller screw.

7. The error distribution method of the aspheric mirror stress loading mechanism according to claim 6, characterized in that: In step S3, according to formulas (1.2), (1.3) and (1.4) combined with the principle of random error, the total displacement error of the drive system is obtained: for: （1.5）； According to the error distribution requirements, we get the inequality: （1.6）。 8. The error distribution method of the aspheric mirror stress loading mechanism according to claim 7, characterized in that: In step S4, the servo motor, the coupling and the roller screw account for the total error of the drive system respectively. , , , , , All three values ​​are non-zero, and (1.7); Then formula (1.6) is transformed into （1.8）; Further we get: （1.9）。 9. The error distribution method of the aspheric mirror stress loading mechanism according to claim 8, characterized in that: According to the corresponding relationship among the servo motor displacement error, the coupling displacement error, and the roller screw displacement error, the inequality is obtained: （1.10）； （1.11）； （1.12）。 10. The error distribution method of the aspheric mirror stress loading mechanism according to claim 9, characterized in that: According to formulas (1.2) and (1.10), the angular accuracy of the servo motor is obtained: for: （1.13）； According to formulas (1.3) and (1.11), the transmission efficiency deviation of the coupling is obtained: for: （1.14）； According to formulas (1.4) and (1.12), the lead error of the roller screw is for: （1.15）。

Images