Electromagnetic rail launch is a technology that uses precisely controlled magnetic forces to accelerate the armature to a very high speed. The distribution characteristics of magnetic fields are closely related to the launch performance, and one of the physical effects that have an important impact on the magnetic field distribution is the velocity skin effect. However, the traditional numerical algorithms based on finite difference, finite element and finite volume methods are difficult to perform fast calculation of velocity skin effect in real-time simulation and digital twin scenarios of electromagnetic rail launch. Therefore, a fast calculation method based on deep operator network (DeepONet) is proposed in this paper, which can accurately and efficiently solve the velocity skin effect of electromagnetic rail launch.
DeepONet, as a powerful deep learning model that can learn nonlinear operators based on the general approximation theorem of operators, has been proven to have better generalization ability in solving calculus problems than other neural network architectures. DeepONet consists of two subnetworks, one with functions as inputs in the form of discrete points for encoding input functions on a fixed number of sensors, called Branch Net, and another for encoding domains of output functions, called Trunk Net.
In order to verify the performance of DeepONet-based method, this paper solves the magnetic field distribution of electromagnetic rail launch under different velocity and current conditions. Firstly, the magnetic induction intensity in the rail region is obtained based on the traditional finite element method, and the training data set is constructed accordingly. Then, a non-stacked DeepONet is constructed, including branch network and trunk network, which are used to encode the variable parameters and space-time coordinates, respectively. The magnetic induction intensity data of armature and rail are then fed into DeepONet for training. Finally, the results obtained by finite element method and DeepONet are compared under different conditions of velocity and current to verify the effectiveness of DeepONet-based method. The experimental results show that, the relative L2 error between the DeepONet-based method and the finite element method is 0.43% within the training conditions, and 0.74% outside the training conditions, and the average prediction time reaches 0.865s.
The following conclusions can be drawn: (1) Compared with the finite element method, the proposed DeepONet-based method introduces branch and trunk networks to decouple the electromagnetic launch parameters and the space-time computational domain, which can obtain the magnetic field distribution in the electromagnetic rail launch with higher computational efficiency. It does not need to redo finite element calculation for each electromagnetic launch condition. (2) In the transient calculation, the DeepONet-based method realizes the effective simulation of electromagnetic rail launch by introducing time variable into the branch network. The average prediction time in the transient model is 0.87 seconds, which is equivalent to the steady-state model, indicating that even with an increase in problem complexity, the inference efficiency of the DeepONet-based method is still relatively high. (3) The sensitivity analysis shows that network size has a significant impact on the performance of the DeepONet-based method, and the optimal network size for branch and trunk networks may not be the same. Although increasing the network size within a certain range can improve the learning ability of the model and reduce learning errors, overfitting is also prone to occur. Therefore, a reasonable selection of network structure and scale is crucial for the practical application of the DeepONet-based method.
魏蓉, 陈锦培, 仲林林. 基于深度算子网络的电磁轨道发射速度趋肤效应的快速计算方法[J]. 电工技术学报, 0, (): 2492927-2492927.
Wei Rong, Chen Jinpei, Zhong Linlin. A Fast Computational Method for Velocity Skin Effect of Electromagnetic Rail Launch Based on Deep Operator Network. Transactions of China Electrotechnical Society, 0, (): 2492927-2492927.
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