Integrated optimization design of mirror semi-active support system based on Warping Harness
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摘要:
基于半主动光学技术的半主动支撑,通过力矩促动器(Warping Harness, WH)弹簧叶片将校正力转换为校正力矩,对由重力、温度等误差源引入的镜面低阶像差进行校正。针对利用传统经验设计反射镜时存在的设计缺陷,提出一种反射镜支撑系统优化设计新方法,即结合结构尺寸优化和经验设计的镜面支撑系统综合设计优化方法,并建立一套基于WH 的半主动镜面支撑系统。首先,按照经验公式设计了支撑系统初始结构;设计了一款L形镂空式WH弹簧叶片,并对其开展了非线性分析及疲劳分析,确定叶片厚度为2 mm、寿命为1.2×106次。然后,通过优化镜面支撑点位置、三角板柔节位置、支撑系统柔性件关键尺寸参数,将光轴竖直及水平状态下镜面RMS值由119 nm和106 nm分别降至13.3 nm和4.8 nm;1 °C温差状态下镜面面形差由2.8 nm降至1.9 nm;一阶谐振频率由80 Hz提升至130 Hz。最后,采用提出的方法对半主动支撑系统的校正能力进行验证。结果表明:本套半主动支撑系统对镜面离焦、初级像散、初级慧差、初级球差的校正率最高可达99%,且校正后各像差幅值均小于1 nm;室温自重状态下对镜面面形RMS值校正率最高可达46.5%;温升10°C情况下的校正率为31.28%。
Abstract:The semi-active support is based on the semi-active optical technology, and the correction force is converted into a correction torque through a Warping Harness(WH) spring blade to correct the mirror low-order aberration introduced by error sources such as gravity and temperature. Aiming at the defects of traditional empirical design of mirrors, a new optimal design method for a mirror support system is proposed, that is, a comprehensive design optimization method of mirror support system based on structural size optimization combined with empirical design, and a set of semi-active mirror support systems based on WH is established. Firstly, the initial structure of the support system is designed according to the empirical formula; an L-shaped hollow WH spring blade is designed, and the nonlinear analysis and fatigue analysis are carried out to determine that the blade thickness is 2 mm and the service life is 1.2×106 times. Then, the RMS value of the mirror surface in the vertical and horizontal states of the optical axis was reduced from 119 nm and 106 nm to 13.3 nm and 4.8 nm by optimizing the position of the mirror support point, the position of the triangular plate flexure joint, and the key dimension parameters of the support system’s flexible parts; under the state of 1 °C temperature difference, the specular aberration is reduced from 2.8 nm to 1.9 nm; the first-order resonance frequency is increased from 80 Hz to 130 Hz. Finally, this method is used to verify the correction ability of the semi-active support system. The results show that the correction rate of the semi-active support system for mirror defocus, primary astigmatism, primary coma and primary spherical aberration can reach up to 99%. The amplitude of each aberration is less than 1 nm; the correction rate of the RMS value of the mirror’s surface shape can reach up to 46.5% under it′s own weight state at room temperature, and the correction rate is 31.28%.
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Key words:
- support system /
- integration optimization /
- semi-active optics /
- Warping Harness /
- low-order aberrations
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表 1 镜面参数
Table 1. Primary mirror parameters
参数 指标 口径d/mm 500.00 焦距f/mm 6000.00 密度(g/cm-3) 2.53 弹性模量GPa 91.00 泊松比 0.24 热膨胀系数(10−6/K) 0.05 表 2 各柔性件截面积计算结果
Table 2. Calculation results of the cross-sectional area of each flexible part
类别 F/N L/mm Amin/mm2 轴向柔性杆 12 48 0.0014 三角板柔节 50 28 0.0011 侧向柔性杆 58 42 0.0020 表 3 支撑点位置优化结果
Table 3. Optimization results of the support point position
项目 参数 R1/mm 68.3 R0/mm 206.5 PV/nm 52.7 RMS/nm 12.0 表 4 支撑柔性件结构尺寸最优解
Table 4. The optimal solution for the structural size of the supporting flexible parts
项目 参数 H/mm 2.9 Rz/mm 1.4 Rc/mm 0.5 RMSx/nm 4.8 RMSz/nm 13.3 RMSt/nm 1.9 表 5 柔性杆轴及侧向解耦结果
Table 5. Flexible rod axis and lateral decoupling results
项目 参数 R轴/mm 1.4 R侧/mm 0.50 S轴轴/mm 0.00030 S轴侧/mm 0.067 S侧/mm 0.014 满足耦合 满足 表 6 30 °C时镜面面形校正前后对比
Table 6. Comparison of mirror surface shapes before and after correction at 30°C
Temp_30°C Before/nm After/nm correct RMS 19.2 13.2 31.28% Power −13.8 −0.382 97.23% Astig0° −0.588 −0.0783 86.68% Astig90° 0.0998 0.0680 31.86% Coma0° −0.0211 −0.0268 −27.01% Coma90° −0.00346 −0.0466 −1246.82% Primary spherical −2.43 −0.981 59.63% Trefoil0° −12.8 −12.4 3.13% Trefoil90° −1.43 −3.45 −141.26% 表 7 镜室组件前四阶谐振频率
Table 7. The first four-order resonance frequencies of the mirror chamber assembly
阶数 1 2 3 4 频率/Hz 130.5 132.7 199.7 203.3 -
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