Build and Multi-datasets Comparison Analysis of LeafSpring Activation Function

针对神经网络中ReLU激活函数存在返回值非负及神经元未激活等问题,提出了一种全新的类ReLU激活函数&mdash;&mdash;LeafSpring. LeafSpring既继承了ReLU的优势,又可以返回负值,通用性更强. LeafSpring函数的推导及函数性质也会被讨论.该激活函数还引入了刚度系数k,可以通过训练主动调节相邻两层的权重系数.为了减少计算量, LeafSpring可以在一定情况下简化为ReLU或Softplus.为了展现LeafSpring激活函数的性能,还将其与ReLU、 Softplus及Sigmoid在4种不同类型的数据集上进行拟合精度对比.对比结果表明, LeafSpring在不同的数据集上均能兼顾拟合精度和收敛速度且在小网格规模可以更快、更准确地拟合复杂非线性函数.</p

一种浮潜陆三栖航行器及其航行方法

本发明涉及航行器，具体地说是一种可以实现水面、水下和地面三栖航行的浮潜陆三栖航行器及其航行方法，航行器主体前后两端的左右两侧分别设有结构相同的水下扇翼推进器，横流风扇安装在航行器主体上，每个水下扇翼推进器中横流风扇可旋转的输出端均连接有转轮，可转动机翼的一端包围在横流风扇可旋转的输出端上，另一端为自由端，可转动机翼通过安装在航行器主体内部的动力源驱动转动；航行器主体前端两侧的水下扇翼推进器的安装方向与后端两侧的水下扇翼推进器的安装方向相对或相同。本发明具有可实现水面、水下和地面三栖航行，且无需变换形态，结构简单，可靠性高，机动性强等特点

Model analysis, design and experiment of a fan-wing underwater vehicle

In order to achieve 5 degrees of freedom (DOFs) movement in an underwater space with only two moving parts, a new kind of unmanned underwater vehicle, Fan-wing Underwater Vehicle (FUV), is proposed. The FUV is driven by two fan-wings which are adapted from the fan-wings for aircraft. The features of the underwater fan-wing are analyzed by 2D computational fluid dynamic (CFD) simulations. In order to analyze the movement of the FUV, a 6-DOF hydrodynamics mathematical model is built. The model is simplified for analyzing two kinds of common conditions movements. According to the simplified model of the ideal straight-line depth-keeping cruise with constant velocity condition, a general procedure to design the FUV is put forward. Some 3D CFD simulations are added to solve the mathematical model in the procedure of the FUV design. Then, according to the design procedure, a control system and a mechanical structure of the FUV are designed. Finally, a real FUV is manufactured, and an underwater test is completed. The experiment shows that the real FUV can achieve 5 DOFs movement in an underwater space, and the results match the design proposes.</p

Theoretical Analysis and Experimental Verification on Thrust of Aquatic-Aerial Amphibious Ducted Fan Propeller

由水空两栖机器人的应用需求出发,从理论计算、仿真以及实验三方面设计了一种涵道风扇推进器.通过理论计算,分析了风扇和电机在2种介质中的工作曲线,提出了风扇推力系数和转矩系数的预估模型.通过选取适当的预估参数,得到了风扇和电机的设计参数.根据理论计算结果,选取了一种较为合适的风扇和电机的组合方式.为了验证理论计算的可靠性,对仅考虑扇叶的理想情况进行了CFD(计算流体动力学)仿真分析.为了研究实际的涵道风扇推进器的工作情况,还对考虑涵道整体表面结构的实际情况进行了CFD仿真分析.最后,对该组合方式的涵道风扇推进器进行了实验,得到了涵道风扇在水下和空气中的实测推力系数分别为1.47×10~(-4)和2.48×10~(-4),实际情况下仿真结果与其的相对误差分别为10.9%和3.6%,接近于实验本身的不确定度;得到的空气中的推力可达55 N以上,水下推力可达245 N以上,均可以满足2种介质中的使用要求

Dual-purpose water-air propulsion sealed motor transmission structure

本发明涉及一种传动结构，具体地说是一种用于水空两用推进的电机密封传动的结构。包括桨、传动轴、非密封环境中的磁力耦合器、非金属隔板、密封环境中的磁力耦合器、主体外壳及电机，其中主体外壳通过非金属隔板分隔成密封腔体和非密封腔体，密封环境中的磁力耦合器和电机容置于主体外壳的密封腔体内，密封环境中的磁力耦合器的一端与电机的输出轴固连、另一端与非金属隔板贴合，传动轴可转动地安装在主体外壳的非密封腔体内，非密封环境中的磁力耦合器与传动轴的一端固定连接、且与非金属隔板贴合，桨与传动轴的另一端固定连接。本发明具有水空两用、结构紧凑、密封效果好、传递扭矩大、维护保养容易且具有过载保护功能等特点

The role studies of fixed-wings in underwater fan-wing thrusters

Fan-wings, as a form of aircraft propulsion, have shown effectiveness for underwater propulsion. The underwater fan-wing thruster (UFT), which is composed of a fixed-wing and a cross-flow fan under the fixed-wing, can generate significate vertical force underwater. Although some experiments and simulations are carried out to analyze the UFT, the role of the fixed-wing to the UFT has not been researched in depth. In this paper, four parameters: the front opening angle, rear opening angle, upper horizontal length, and incoming flow angle are selected for the role study in four aspects, including vertical force, thrust force, torque, and efficiency. Computational fluid dynamics (CFD) simulations in different rotational speeds of the cross-flow fan and incoming flow velocities conditions are carried out for the UFTs with different parameters, which concurred with towing experiments. Self-driving experiments are also carried out for studying the actual cruise performance of the UFT with different parameters. After that, mechanisms of the effects are analyzed on many velocity magnitude cloud maps from CFD simulation. A physical model is utilized to explain some of the unique fluid phenomena. Finally, the role of the fixed-wing is summarized, and some principle on parameter setting is proposed.</p

Underwater Feature Comparison of a Fan-Wing, a Propeller and a Fixed-Wing

Fan-wing thrusters are firstly used on the aircrafts, and then demonstrated underwater. Although the force generation on the underwater fan-wing thruster is demonstrated, the advantages of fan-wing over other propulsors have not been proved. In this paper, a UFT, a vertical placed propeller and a fixed-wing with a high lift to drag ratio is compared in the aspects of underwater propulsion performance. The aspects in study include vertical force, forward drag and efficiency defined. Computational fluid dynamics simulations are carried out in the conditions of different rotational speeds of the moving parts and different cruise velocities. Based on the simulation results, the characteristics of the propulsors are discussed. In the high cruise velocity conditions, the UFT can generate a significant higher vertical force with high efficiency and low forward drag. In the low cruise velocity condition, the propeller performance better on vertical force generation and efficiency. The fixed-wing is the most efficient in all the simulation conditions

Hydrodynamic analyses of an underwater fan-wing thruster in self-driving and towing experiments

Fan-wing thrusters are primarily used for aircraft propulsion, but their potential for underwater applications has also been demonstrated. Although many achievements have been made through experimentation, there still remains much work to be done in mechanism and hydrodynamic analyses, especially for the underwater fan-wing thruster (UFT). In this work, experiments are designed and carried out for a UFT. Both self-driving and towing experiments are conducted with a custom-made experiment device. In the self-driving experiments, vertical force and velocity are measured at different rotational speeds of the cross-flow fan. Then, for studying the hydrodynamic performance, specific towing experiments and computational fluid dynamics (CFD) simulations are carried out. Simulation results are in good agreement with the towing experiment results. On the basis of the CFD simulation results, specific unique characteristics are identified. Finally, a physical model is built and analyzed, and the mechanism and distinctive characteristics are explained by the physical model.</p