Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instabili...Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instability,occur frequently in both experimental and operational data.This infrequency causes events to be overlooked by existing prediction models,which lack the precision to accurately predict inclination attitudes in amphibious vehicles.To address this gap in predicting attitudes near extreme inclination points,this study introduces a novel loss function,termed generalized extreme value loss.Subsequently,a deep learning model for improved waterborne attitude prediction,termed iInformer,was developed using a Transformer-based approach.During the embedding phase,a text prototype is created based on the vehicle’s operation log data is constructed to help the model better understand the vehicle’s operating environment.Data segmentation techniques are used to highlight local data variation features.Furthermore,to mitigate issues related to poor convergence and slow training speeds caused by the extreme value loss function,a teacher forcing mechanism is integrated into the model,enhancing its convergence capabilities.Experimental results validate the effectiveness of the proposed method,demonstrating its ability to handle data imbalance challenges.Specifically,the model achieves over a 60%improvement in root mean square error under extreme value conditions,with significant improvements observed across additional metrics.展开更多
Nonlinear amphibious vehicle rolling under regular waves and wind load is analyzed by a single degree of freedom system.Considering nonlinear damping and restoring moments,a nonlinear rolling dynamical equation of amp...Nonlinear amphibious vehicle rolling under regular waves and wind load is analyzed by a single degree of freedom system.Considering nonlinear damping and restoring moments,a nonlinear rolling dynamical equation of amphibious vehicle is established.The Hamiltonian function of the nonlinear rolling dynamical equation of amphibious vehicle indicate when subjected to joint action of periodic wave excitation and crosswind,the nonlinear rolling system degenerates into being asymmetric.The threshold value of excited moment of wave and wind is analyzed by the Melnikov method.Finally,the nonlinear rolling motion response and phase portrait were simulated by four order Runge-Kutta method at different excited moment parameters.展开更多
Path planning of amphibious vehicles on military topographic maps is a hot research topic in the field of amphibious tactical training simulation.According to the dynamic characteristics and maneuvering destination re...Path planning of amphibious vehicles on military topographic maps is a hot research topic in the field of amphibious tactical training simulation.According to the dynamic characteristics and maneuvering destination requirements of amphibious vehicles,a three-dimensional simulation model of amphibious vehicles is designed,and a straight-line driving and steering dynamic model is constructed.The optimal maneuvering destination and constraint conditions under the condition of unconnected graph are put forward,and the problems of simulation and maneuvering path planning of amphibious vehicles on unconnected graph are solved by the theory of region partition and shortest path of graph.Compared with Dijkstra algorithm and heuristic algorithm A~*,the experimental results show that the algorithm designed in this paper has superior applicability and time performance.展开更多
The ever-expanding frontier of applications demands that mobile vehicles navigate challenging,complex,and rugged terrains,as well as diverse environments.In this paper,we presented the novel design of an autonomous am...The ever-expanding frontier of applications demands that mobile vehicles navigate challenging,complex,and rugged terrains,as well as diverse environments.In this paper,we presented the novel design of an autonomous amphibious vehicle,driven by Archimedean screw mechanisms.Hydrodynamic simulations were conducted to analyze the propulsive characteristics of screw mechanisms in water.Particularly,an innovative screw-propeller integrated structure was proposed.At a rotation speed of 1000 rpm,the generated thrust of the integrated structure increased by 50% compared with the original screw,indicating a significant improvement in propulsion performance.Simultaneously,we analyzed its contact with the terrain by using the discrete element method.The process was simulated through a co-simulation involving multi-body dynamics,which presented an analytical method for investigating vehicle-terrain contact mechanics.Finally,a series of performance and field experiments were carried out.The vehicle successfully traversed various terrains including sandy,gravel,and grass roads,overcoming a 5 cm high obstacle.Furthermore,it autonomously executed offshore and landing movements,and showcased excellent amphibious trafficability at the coast.Overall,our research provides valuable insights into the development of autonomous screw-driven vehicles,offering a wide range of application prospects.展开更多
When the amphibious vehicle navigates in water,the angle of the anti-wave plate and the position of the center of gravity greatly influence the navigation characteristics.In the relevant research on reducing the navig...When the amphibious vehicle navigates in water,the angle of the anti-wave plate and the position of the center of gravity greatly influence the navigation characteristics.In the relevant research on reducing the navigation resistance of amphibious vehicles by adjusting the angle of the anti-wave plate,there is a lack of scientific selection of parameters and reasonable research of simulation results by using mathematical methods,and the influence of the center of gravity position on navigation characteristics is not considered at the same time.To study the influence of the combinations of the angle of the anti-wave plate and the position of the center of gravity on the resistance reduction characteristics,a numerical calculation model of the amphibious unmanned vehicle was established by using the theory of computational fluid dynamics,and the experimental data verified the correctness of the numerical model.Based on this numerical model,the navigation characteristics of the amphibious unmanned vehicle were studied when the center of gravity was located at different positions,and the orthogonal experimental design method was used to optimize the parameters of the angle of the anti-wave plate and the position of the center of gravity.The results show that through the parameter optimization analysis based on the orthogonal experimental method,the combination of the optimal angle of the anti-wave plate and the position of the center of gravity is obtained.And the numerical simulation result of resistance is consistent with the predicted optimal solution.Compared with the maximum navigational resistance,the parameter optimization reduces the navigational resistance of the amphibious unmanned vehicle by 24%.展开更多
基金Supported by the National Defense Basic Scientific Research Program of China.
文摘Amphibious vehicles are more prone to attitude instability compared to ships,making it crucial to develop effective methods for monitoring instability risks.However,large inclination events,which can lead to instability,occur frequently in both experimental and operational data.This infrequency causes events to be overlooked by existing prediction models,which lack the precision to accurately predict inclination attitudes in amphibious vehicles.To address this gap in predicting attitudes near extreme inclination points,this study introduces a novel loss function,termed generalized extreme value loss.Subsequently,a deep learning model for improved waterborne attitude prediction,termed iInformer,was developed using a Transformer-based approach.During the embedding phase,a text prototype is created based on the vehicle’s operation log data is constructed to help the model better understand the vehicle’s operating environment.Data segmentation techniques are used to highlight local data variation features.Furthermore,to mitigate issues related to poor convergence and slow training speeds caused by the extreme value loss function,a teacher forcing mechanism is integrated into the model,enhancing its convergence capabilities.Experimental results validate the effectiveness of the proposed method,demonstrating its ability to handle data imbalance challenges.Specifically,the model achieves over a 60%improvement in root mean square error under extreme value conditions,with significant improvements observed across additional metrics.
基金The Pre-research Project of the General Armament DepartmentThe Science Fund of North University of China(No.20130105)
文摘Nonlinear amphibious vehicle rolling under regular waves and wind load is analyzed by a single degree of freedom system.Considering nonlinear damping and restoring moments,a nonlinear rolling dynamical equation of amphibious vehicle is established.The Hamiltonian function of the nonlinear rolling dynamical equation of amphibious vehicle indicate when subjected to joint action of periodic wave excitation and crosswind,the nonlinear rolling system degenerates into being asymmetric.The threshold value of excited moment of wave and wind is analyzed by the Melnikov method.Finally,the nonlinear rolling motion response and phase portrait were simulated by four order Runge-Kutta method at different excited moment parameters.
基金Supported by the National Natural Science Foundation of China(61401496)。
文摘Path planning of amphibious vehicles on military topographic maps is a hot research topic in the field of amphibious tactical training simulation.According to the dynamic characteristics and maneuvering destination requirements of amphibious vehicles,a three-dimensional simulation model of amphibious vehicles is designed,and a straight-line driving and steering dynamic model is constructed.The optimal maneuvering destination and constraint conditions under the condition of unconnected graph are put forward,and the problems of simulation and maneuvering path planning of amphibious vehicles on unconnected graph are solved by the theory of region partition and shortest path of graph.Compared with Dijkstra algorithm and heuristic algorithm A~*,the experimental results show that the algorithm designed in this paper has superior applicability and time performance.
基金supported by the National Natural Science Foundation of China(52071131)the Marine Science and Technology Innovation Project of Jiangsu Province(HY2018-15)the National Key Research and Development Program of China(2022YFC2806002,2021YFC2801604,and 2022YFB4703401).
文摘The ever-expanding frontier of applications demands that mobile vehicles navigate challenging,complex,and rugged terrains,as well as diverse environments.In this paper,we presented the novel design of an autonomous amphibious vehicle,driven by Archimedean screw mechanisms.Hydrodynamic simulations were conducted to analyze the propulsive characteristics of screw mechanisms in water.Particularly,an innovative screw-propeller integrated structure was proposed.At a rotation speed of 1000 rpm,the generated thrust of the integrated structure increased by 50% compared with the original screw,indicating a significant improvement in propulsion performance.Simultaneously,we analyzed its contact with the terrain by using the discrete element method.The process was simulated through a co-simulation involving multi-body dynamics,which presented an analytical method for investigating vehicle-terrain contact mechanics.Finally,a series of performance and field experiments were carried out.The vehicle successfully traversed various terrains including sandy,gravel,and grass roads,overcoming a 5 cm high obstacle.Furthermore,it autonomously executed offshore and landing movements,and showcased excellent amphibious trafficability at the coast.Overall,our research provides valuable insights into the development of autonomous screw-driven vehicles,offering a wide range of application prospects.
基金supported by the National Natural Science Foundation of China(52174154).
文摘When the amphibious vehicle navigates in water,the angle of the anti-wave plate and the position of the center of gravity greatly influence the navigation characteristics.In the relevant research on reducing the navigation resistance of amphibious vehicles by adjusting the angle of the anti-wave plate,there is a lack of scientific selection of parameters and reasonable research of simulation results by using mathematical methods,and the influence of the center of gravity position on navigation characteristics is not considered at the same time.To study the influence of the combinations of the angle of the anti-wave plate and the position of the center of gravity on the resistance reduction characteristics,a numerical calculation model of the amphibious unmanned vehicle was established by using the theory of computational fluid dynamics,and the experimental data verified the correctness of the numerical model.Based on this numerical model,the navigation characteristics of the amphibious unmanned vehicle were studied when the center of gravity was located at different positions,and the orthogonal experimental design method was used to optimize the parameters of the angle of the anti-wave plate and the position of the center of gravity.The results show that through the parameter optimization analysis based on the orthogonal experimental method,the combination of the optimal angle of the anti-wave plate and the position of the center of gravity is obtained.And the numerical simulation result of resistance is consistent with the predicted optimal solution.Compared with the maximum navigational resistance,the parameter optimization reduces the navigational resistance of the amphibious unmanned vehicle by 24%.
