Aspherical mirror stress loading mechanism and error distribution method thereof

Abstract

The application relates to the technical field of light machine 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 the aspherical mirror. The driving system comprises a servo motor, a shaft coupling and a roller screw. One end of the roller screw is connected with the output end of the servo motor through the shaft coupling, and the other end of the roller screw is connected with the input end of the flexible lever. The aspherical mirror stress loading mechanism has good versatility for various large, medium and small aspherical mirrors and is not limited by the size of a mirror blank and space. Through the error distribution method of the aspherical mirror stress loading mechanism, the precision requirements of the servo motor, the shaft coupling and the roller screw can be quickly distributed in the design stage, so that the performance and stability of the whole system are ensured.

Description

Technical Field

[0001] This invention relates to the field of optomechanical structure technology, and in particular to an aspherical mirror stress loading mechanism and its error distribution method. Background Technology

[0002] Large modular telescopes and low-Earth orbit giant constellation optical payloads urgently require a leap in production capacity in the field of aspherical optical processing. However, the current limited manufacturing capacity and high manufacturing costs stand in stark contrast to the demand for these massive applications of aspherical surfaces.

[0003] Commonly used aspherical surface processing techniques include traditional manual grinding and polishing, computer-controlled optical surface shaping, small grinding head processing, stress disk polishing, magnetorheological polishing, and ion beam polishing. These methods can meet the low-frequency surface shape error requirements of aspherical mirrors, but they are less effective at suppressing mid- / high-frequency surface shape errors, and are also inefficient and costly. The development needs of large modular telescopes have driven the emergence of prestressed processing technology. This technology greatly contributed to the successful development of the Keck telescope and is playing an important role in the development of the TMT telescope (30-meter telescope) and the E-ELT telescope (European Extremely Large Telescope).

[0004] The concept of prestressed machining is to transform complex machining techniques into controlling the surface shape of the mirror blank, converting aspherical machining into spherical machining methods, and obtaining the desired aspherical surface after stress unloading. Prestressed machining is of great significance for improving the machining efficiency of mirrors, suppressing high-frequency errors in mirror surfaces, and promoting the engineering application of aspherical surfaces.

[0005] Existing prestressed loading mechanisms have drawbacks such as poor interchangeability, poor versatility, and low shape control accuracy. They also have the problem of a small dynamic range of stress control loading (adjustment stroke / accuracy ratio), making them unsuitable for various short focal length aspherical surfaces required by compact optical systems. Summary of the Invention

[0006] In view of this, the present invention aims to provide an aspherical mirror stress loading mechanism and its error allocation method, which achieves the loading of aspherical stress through a drive system and a flexible lever. Simultaneously, the error allocation method is obtained by calculating the displacement errors of the servo motor, coupling, and ball screw in the drive system.

[0007] To achieve the above objectives, the technical solution created by this invention is as follows: an aspherical mirror stress loading mechanism includes a drive system and a flexible lever. The input end of the flexible lever is connected to the output end of the drive system, and the output end of the flexible lever is connected to the aspherical mirror. The actuator includes an output shaft and a drive system. The drive system includes a servo motor, a coupling, and a ball screw. The ball screw is connected to the output end of the servo motor through the coupling, and the nut of the ball screw is connected to the output shaft.

[0008] Furthermore, the flexible lever includes a crossbeam and a flexible rod that are perpendicular to each other. One end of the crossbeam is connected to the aspherical mirror. A roller screw is connected to the crossbeam near the other end. The flexible rod is set on the crossbeam and near the aspherical mirror. A flexible hinge is set on the flexible rod near the crossbeam, and a fixing hole is provided on the flexible rod away from the crossbeam.

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

[0010] An error allocation method for an aspherical mirror stress loading mechanism is provided to analyze the servo motor displacement error, coupling displacement error, and roller screw displacement error of the drive system in the aforementioned aspherical mirror stress loading mechanism. The specific steps are as follows:

[0011] S1: Set the displacement error of the drive system to... When the ball screw rotates one revolution, the displacement at the end of the output shaft is calculated.

[0012] S2: Based on the displacement at 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 ball screw are calculated respectively.

[0013] S3: Based on the displacement error of the servo motor, the displacement error of the coupling, and the displacement error of the ball screw, combined with the principle of random error, the total displacement error of the drive system is obtained.

[0014] S4: Based on the proportions of the servo motor, coupling, and ball screw in the total error of the drive system, the displacement error inequalities of the servo motor, coupling, and ball screw are obtained respectively.

[0015] Furthermore, in step S1, the displacement y at the end of the roller screw is:

[0016] (1.1);

[0017] in, For the lead of the roller screw, This refers to the number of revolutions of the servo motor. The transmission efficiency of the coupling.

[0018] Furthermore, in step S2, the servo motor displacement error is obtained by combining equation (1.1). Formulas, coupling displacement error Formula and roller screw displacement error The formulas are as follows:

[0019] (1.2);

[0020] (1.3);

[0021] (1.4);

[0022] in, This refers to the angular error of the servo motor. This refers to the rotational efficiency deviation of the coupling; This refers to the lead error of the roller screw.

[0023] Furthermore, in step S3, based on the three formulas (1.2), (1.3), and (1.4) combined with the principle of random error, the total displacement error of the driving system is obtained. for:

[0024] (1.5);

[0025] Based on the error distribution requirements, the inequality is obtained as follows:

[0026] (1.6).

[0027] Furthermore, in step S4, the proportions of the servo motor, coupling, and ball screw in the total error of the drive system are respectively... , , , , , All three values ​​are non-zero, and (1.7);

[0028] Equation (1.6) is then transformed into:

[0029] (1.8);

[0030] Further results were obtained:

[0031] (1.9).

[0032] Furthermore, based on the corresponding relationships between the servo motor displacement error, coupling displacement error, and roller screw displacement error, the following inequality is obtained:

[0033] (1.10);

[0034] (1.11);

[0035] (1.12).

[0036] Furthermore, the angular accuracy of the servo motor is obtained according to formulas (1.2) and (1.10). for:

[0037] (1.13);

[0038] The transmission efficiency deviation of the coupling is obtained from formulas (1.3) and (1.11). for:

[0039] (1.14);

[0040] The lead error of the roller screw is obtained from formulas (1.4) and (1.12). for:

[0041] (1.15).

[0042] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0043] 1) The flexible design of the flexible lever and flexible hinge makes the driving force at the input end of the aspherical mirror stress loading mechanism more adjustable, which can reduce the displacement accuracy requirements of the driving system.

[0044] 2) The design of the flexible hinge allows the flexible lever to deform under stress, thereby absorbing and dispersing stress, and improving the stability and durability of the aspherical mirror stress loading mechanism.

[0045] 3) During the processing of aspherical mirrors, multiple aspherical mirror stress loading mechanisms are usually evenly distributed around the periphery of the aspherical mirror. The flexible levers in the aspherical mirror stress loading mechanism utilize the principle of reduction to improve the manufacturing efficiency and precision of the aspherical mirror.

[0046] 4) The aspherical mirror stress loading mechanism 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 aspherical mirrors.

[0047] 5) By adopting the error distribution method of the aspherical mirror stress loading mechanism, the accuracy requirements of the servo motor, coupling and ball screw can be accurately matched in the design stage, thereby ensuring the performance and stability of the entire system. Attached Figure Description

[0048] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0049] Figure 1 This is a schematic diagram of the aspherical mirror stress loading mechanism provided in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the structure of a flexible lever provided according to an embodiment of the present invention.

[0051] The reference numerals in the attached figures include: 1, actuator; 11, servo motor; 12, coupling; 13, ball screw; 2, flexible lever; 21, crossbeam; 22, flexible rod; 23, connecting hole; 24, mounting hole; 25, flexible hinge; 26, fixing hole. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0055] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0056] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0057] like Figure 1 As shown in the figure, an aspherical mirror stress loading mechanism provided by this embodiment of the invention includes an actuator 1 and a flexible lever 2. 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 aspherical mirror. The actuator 1 includes an output shaft and a drive system. The drive system includes a servo motor 11, a coupling 12, and a ball screw 13. The ball screw 13 is connected to the output end of the servo motor 11 through the coupling 12, and the lead screw nut of the ball screw 13 is connected to the output shaft. The servo motor 11 drives the lead screw of the ball screw 13 to rotate, causing the lead screw nut of the ball screw 13 to move up and down along the lead screw, thereby driving the output shaft to move and realizing the movement of the flexible lever 2.

[0058] The roller screw 13 is a type of screw characterized by using rollers as rolling elements instead of traditional balls. This design allows the roller screw 13 to have a larger contact surface and force-bearing surface during transmission, thereby improving transmission efficiency and load-bearing capacity.

[0059] The flexible lever 2 includes a crossbeam 21 and a flexible rod 22 that are perpendicular to each other. A mounting hole 24 is provided at one end of the crossbeam 21 for connection to an aspherical mirror. The end of the crossbeam 21 connected to the aspherical mirror serves as the output end of the flexible lever 2, used to transmit the stress of the aspherical mirror stress loading mechanism to the aspherical mirror. A connecting hole 23 is provided on the crossbeam 21 near the other end. A roller screw 13 is connected to the crossbeam 21 through the connecting hole 23, serving as the input end of the flexible lever 2 and transmitting the driving force of the aspherical mirror stress loading mechanism to the flexible lever 2. The flexible rod 22 is mounted on the crossbeam 21 and close to the aspherical mirror. A flexible hinge 25 is provided on the flexible rod 22 near the crossbeam 21, and a fixing hole 26 is provided on the flexible rod 22 away from the crossbeam 21. Through the fixing hole 26, the flexible rod 22 can be fixed in the desired position using bolts, pins, or other fasteners. The flexible hinge 25 is a double-arc flexible hinge.

[0060] The flexible lever 2 incorporates the flexible hinge 25, which allows for a wider range of adjustable driving force at the input end of the aspherical mirror stress loading mechanism, reducing the displacement accuracy requirements of the actuator 1. The flexible hinge 25 design enables the flexible lever 2 to deform under stress, thereby absorbing and dispersing stress, and improving the stability and durability of the aspherical mirror stress loading mechanism.

[0061] During the processing of aspherical mirrors, multiple aspherical mirror stress loading mechanisms are usually evenly distributed around the aspherical mirror. The flexible lever 2 in the aspherical mirror stress loading mechanism improves the loading accuracy of the aspherical mirror by utilizing the lever error reduction principle.

[0062] An error allocation method for an aspherical mirror stress loading mechanism is provided to analyze the displacement errors of the servo motor 11, coupling 12, and roller screw 13 in the drive system of the aforementioned aspherical mirror stress loading mechanism. The specific steps are as follows:

[0063] S1: Set the drive system error to... When the ball screw 13 rotates one revolution, the displacement of the end of the output shaft of the actuator 1 is calculated.

[0064] The displacement y at the end of the output shaft is:

[0065] (1.1);

[0066] in, For the lead of roller screw 13, For the number of rotations of servo motor 11, The transmission efficiency of coupling 12.

[0067] S2: Based on the displacement of the end of the ball screw 13, the displacement errors of the servo motor 11, coupling 12, and ball screw 13 are calculated respectively.

[0068] Taking the partial derivative of formula (1.1), we obtain the error of servo motor 11. Coupling 12 error And roller screw 13 error The formulas are as follows:

[0069] (1.2);

[0070] (1.3);

[0071] (1.4);

[0072] in, This refers to the angle error of servo motor 11; This is the difference between the actual transmission efficiency and the theoretical transmission efficiency of coupling 12 (i.e., the rotational efficiency deviation of coupling 12). This represents the lead error of the roller screw 13.

[0073] S3: Based on the displacement error of servo motor 11, displacement error of coupling 12, and displacement error of roller screw 13, combined with the principle of random error, the total displacement error of the drive system is obtained.

[0074] Based on the three error formulas (1.2), (1.3), and (1.4) and the principle of random error, the total error of the driving system is obtained. for:

[0075] (1.5);

[0076] Based on the error distribution requirement (i.e., the total error of the drive system must be less than or equal to the error of the drive system), the inequality is obtained:

[0077] (1.6).

[0078] S4: Based on the proportions of servo motor 11, coupling 12, and ball screw 13 in the total error of the drive system, the displacement error inequalities of servo motor 11, coupling 12, and ball screw 13 are obtained respectively.

[0079] The proportions of servo motor 11, coupling 12, and ball screw 13 in the total error of the drive system are respectively , , , , , All three values ​​are non-zero; and (1.7);

[0080] Equation (1.6) is then transformed into:

[0081] (1.8);

[0082] Further results were obtained:

[0083] (1.9).

[0084] Furthermore, based on the corresponding relationship between the displacement errors of the servo motor 11, the coupling 12, and the ball screw 13, the following inequality is obtained:

[0085] (1.10);

[0086] (1.11);

[0087] (1.12).

[0088] Furthermore, the angular accuracy of the servo motor 11 is obtained according to formulas (1.2) and (1.10). for:

[0089] (1.13);

[0090] The transmission efficiency deviation of coupling 12 is obtained according to formulas (1.3) and (1.11). for:

[0091] (1.14);

[0092] The lead error of the roller screw 13 is obtained according to formulas (1.4) and (1.12). for:

[0093] (1.15).

[0094] The error allocation method of the aspherical mirror stress loading mechanism provided by the present invention will be described below with reference to a specific embodiment. The driving system error... The parameters are set to 10µm, the lead of the ball 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. Based on experience, the error coefficients of the servo motor 11, coupling 12, and ball screw 13 are respectively set to... , and ,Will , , Substituting into formulas (1.13), (1.14), and (1.15), the angular accuracy of servo motor 11 is obtained. The transmission efficiency deviation of coupling 12 Lead error of roller screw 13 They are respectively:

[0095] (1.16);

[0096] (1.17);

[0097] (1.18);

[0098] Where r is the unit of number of revolutions.

[0099] Converting the number of revolutions in formulas (1.16) and (1.17) into angles yields:

[0100] ,

[0101] .

[0102] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A stress loading mechanism for an aspherical mirror, characterized in that, The device includes an actuator and a flexible lever. 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 drive system. The drive system includes a servo motor, a coupling, and a ball screw. The ball screw is connected to the output end of the servo motor via the coupling, and the nut of the ball screw is connected to the output shaft. The flexible lever includes a crossbeam and a flexible rod that are perpendicular to each other. One end of the crossbeam is connected to the aspherical mirror. A ball screw is connected to the crossbeam near the other end of the crossbeam. The flexible rod is disposed on the crossbeam and near the aspherical mirror. A flexible hinge is disposed on the flexible rod near the crossbeam, and a fixing hole is provided on the flexible rod away from the crossbeam.

2. The aspherical mirror stress loading mechanism according to claim 1, characterized in that, The flexible hinge is a double-arc flexible hinge.

3. An error allocation method for an aspherical mirror stress loading mechanism, used to analyze the servo motor displacement error, coupling displacement error, and roller screw displacement error of the drive system in the aspherical mirror stress loading mechanism according to any one of claims 1-2, characterized in that, The specific steps are as follows: S1: Set the displacement error of the drive system as... When the ball screw rotates one revolution, the displacement of the end of the output shaft is calculated. S2: Based on 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 ball screw are calculated respectively. S3: Based on the displacement error of the servo motor, the displacement error of the coupling, and the displacement error of the ball screw, combined with the principle of random error, the total displacement error of the drive system is obtained; S4: Based on the proportions of the servo motor, the coupling, and the ball screw in the total error of the drive system, the displacement error inequalities of the servo motor, the coupling, and the ball screw are obtained respectively.

4. The error allocation method for the aspherical mirror stress loading mechanism according to claim 3, characterized in that, In step S1, the displacement y at the end of the output shaft is: （1.1）； in, For the lead of the roller screw, This refers to the number of revolutions of the servo motor. The transmission efficiency of the coupling.

5. The error allocation method for the aspherical mirror stress loading mechanism according to claim 4, characterized in that, In step S2, the partial derivative of formula (1.1) is taken to obtain the displacement error of the servo motor. Formula, the displacement error of the coupling Formula and the roller screw displacement error The formulas are as follows: （1.2）； （1.3）； （1.4）； in, This refers to the angular error of the servo motor. This refers to the rotational efficiency deviation of the coupling; This refers to the lead error of the roller screw.

6. The error allocation method for the aspherical mirror stress loading mechanism according to claim 5, characterized in that, In step S3, based on the three formulas (1.2), (1.3), and (1.4) combined with the principle of random error, the total displacement error of the driving system is obtained. for: （1.5）； Based on the error distribution requirements, the inequality is obtained as follows: （1.6）。 7. The error allocation method for the aspherical mirror stress loading mechanism according to claim 6, characterized in that, In step S4, the proportions of the servo motor, the coupling, and the ball 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 （1.8）; Further results were obtained: （1.9）。 8. The error allocation method for the aspherical mirror stress loading mechanism according to claim 7, characterized in that, Based on the corresponding relationship between the servo motor displacement error, the coupling displacement error, and the ball screw displacement error, the following inequality is obtained: （1.10）； （1.11）； （1.12）。 9. The error allocation method for the aspherical mirror stress loading mechanism according to claim 8, characterized in that, The angular accuracy of the servo motor is obtained according to formulas (1.2) and (1.10). for: （1.13）； The transmission efficiency deviation of the coupling is obtained according to formulas (1.3) and (1.11). for: （1.14）； The lead error of the roller screw is obtained according to formulas (1.4) and (1.12). for: （1.15）。

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