基于迁移学习的变可信度气动力建模方法

Variable fidelity aerodynamic modeling method based on transfer learning

  • 摘要: 基于离散数据集建立气动模型是飞行器优化设计的重要环节,但建立完备的高精度数值模拟与风洞试验数据集周期长、成本高。为缩短研制周期、节约设计成本,本文基于有限数据集建立高精度的气动力模型,提出一种基于迁移学习的变可信度气动力建模方法。该方法结合气动数据融合理论与迁移学习方法,设计了基于长短期记忆(Long Short-Term Memory, LSTM)神经网络的回归网络结构,采用预训练微调的参数调优机制进行迁移训练,以获得高可信度气动力模型。首先,以NACA 2414翼型的XFLR软件计算数据(低精度)与风洞试验数据(高精度)为研究对象,利用小量高精度数据对基于大量低精度数据集训练的模型进行迁移学习,形成高保真气动力预测模型。然后,设计了使用1/2至1/10风洞数据量的建模实验,并与未迁移的LSTM神经网络模型和加法标度函数(Additive Scaling Function Based Multi-fidelity Surrogate, AS-MFS)模型进行对比讨论。实验结果表明:在所有数据量下本文提出的迁移学习模型均获得了更高预测精度,阻力和升阻比的预测精度比未迁移的LSTM神经网络模型平均提升了7.22%和8.85%,比AS-MFS模型平均提升了8.66%和4.36%。

     

    Abstract: The establishment of the aerodynamic model based on discrete data sets is an important part of aircraft optimization design. However, it takes a long time and high cost to build a complete and high-precision numerical simulation and wind tunnel test data set. In order to shorten the development cycle and save the design cost, this paper proposes a variable fidelity aerodynamic modeling method based on transfer learning, aiming at establishing high-precision aerodynamic models on limited data sets. This method combines the aerodynamic data fusion theory and transfer learning method, designs a regression network structure based on Long Short-Term Memory (LSTM) neural network, and adopts the parameter tuning mechanism of pre-training and fine-tuning for transfer training, so as to obtain the aerodynamic model with high fidelity. Specifically, taking the XFLR calculation data (low precision) and wind tunnel test data (high precision) of NACA 2414 airfoil as the research object, a high-fidelity aerodynamic prediction model is formed by using a small amount of high-precision data to conduct transfer learning on the pre-trained model of a large number of low-precision data sets. Then, a wind tunnel data modeling experiment with data volume ranging from 1/2 to 1/10 was designed, and it was compared with the unmigrated LSTM model and the Additive Scaling Function Based Multi-fidelity Surrogate (AS-MFS) model. Experimental results show that the proposed method achieves higher prediction accuracy under all data quantities, and the prediction accuracy of the drag and lift-drag ratio is increased by 7.22% and 8.85% on average, respectively, compared with that before migration; compared with AS-MFS, the average improvement is 8.66% and 4.36%, respectively.

     

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