Model updating of a ϕ150 mm mirror including joint parts
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摘要: 针对ϕ150 mm口径反射镜受结合部的非线性因素影响导致结构分析模型精度较差的问题,提出了线性的动力学等效建模与参数修正方法。首先,在实际装配和约束环境下测试并获得了反射镜结构的试验模态参数。然后,根据界面结合部的动力学特征,对反射镜结构按照镜框固定连接模型、镜面螺钉夹持模型以及间隙等效模型进行了等效建模。最后,以试验模态参数为修正目标,采用优化方法对反射镜结构的动力学等效模型进行了参数修正,并采用模型分层和分步修正的思路,依据结合部特征将修正模型细分为两部分,提高模型参数的修正效率。结果表明,参数修正后的固有频率平均误差为1.5%,模态置信度均大于0.8,提升了反射镜结构的动力学模型精度,验证了线性化等效建模方法的正确性。Abstract: For the problem of precision deficiency of the analysis model caused by nonlinear factors of the joint parts in the ϕ150 mm mirror, the equivalent linearized model and the model updating method were presented. First, the experimental modal parameters of the ϕ150 mm mirror within 800 Hz were tested and obtained under the actual assembly and boundary conditions. Then, according to the dynamic characteristics of the interface joints, the equivalent finite element model of the mirror was classified as the connection model of fixed parts, the screw model and the equivalent gap model of the clamping parts, which were modeled by beam elements, rigid elements and spring elements. Finally, taking the measured experimental data including natural frequencies and modal shapes as the objective function, the dynamic model of the ϕ150 mm mirror was corrected by using optimization method. At the same time, the modified model was divided into two parts according to the characteristics of the joints by adopting the idea of hierarchical and step-by-step modification to improve the efficiency of the correction process. The results indicate that the average error of natural frequencies within 800 Hz after model updating is 1.6%, and the minimum value of modal assurance criterion is greater than 0.8, which improves the accuracy of the dynamic model for the reflective mirror. And the equivalent linearized model is also verified.
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Key words:
- mirror /
- dynamic modeling /
- joint part /
- model updating /
- modal
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表 1 初始模型的计算误差
Table 1. Calculation errors of the initial model
order frequency/Hz frequency error/% MAC experimental model initial model 1 147.6 145.2 1.6 0.98 2 185.4 171.2 7.7 0.92 3 343.1 374.1 9.0 0.92 4 657.6 640.2 2.6 0.67 5 734.7 687.1 6.5 0.46 表 2 修正变量的初值与修正结果
Table 2. Initial value and modified results
variable E1 /MPa E2 /MPa R/mm E3 /MPa E4/MPa K1 /(N·mm-1) K2 /(N·mm-1) K3 /(N·mm-1) K4 /(N·mm-1) initial value 100 2×106 14 3×104 1.5×104 1×103 1×104 1×103 1×103 modified value 120 8.2×106 18 2.63×104 8.3×103 800 1.92×104 1.45×103 1×105 表 3 镜框固定连接模型的修正结果
Table 3. Modified results of the fixed connection model
No. frequency/Hz frequency error/% MAC experimental model updated model 1 211.4 217.5 2.9 0.99 2 244.2 249 2.0 0.99 3 562.6 571.4 1.6 0.94 4 751.1 759.2 1.1 0.99 5 1 197.6 1 174.9 1.9 0.87 6 1 688.5 1 636.6 3.1 0.96 7 1 843.2 1 816.9 1.4 0.90 表 4 整体装配模型的模型修正结果
Table 4. Modified results of the assembly model
No frequency error/% MAC 1st step 2nd step 3rd step 1st step 2nd step 3rd step 1 0.06 0.06 0.06 0.98 0.98 0.98 2 7.1 4.1 4.8 0.92 0.92 0.92 3 0.2 0.15 2.4 0.95 0.95 0.95 4 0.09 5.4 0.09 0.75 0.87 0.98 5 4.6 1.5 0.008 0.44 0.81 0.82 -
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