The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.F...The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.First,the methodology is introduced with the development of an interior ballistics(IB)lumped parameter code(LPC),integrating an original image processing method for calculating the specific regression of propellant grains that compose the gun propellant.The ONERA CFD code CEDRE,equipped with a Dynamic Mesh Technique(DMT),is then used in conjunction with the developed LPC to build a dedicated methodology to calculate IB.First results obtained on the AGARD gun and 40 mm gun test cases are in a good agreement with the existing literature.CEDRE is also used to calculate inter-mediate ballistics(first milliseconds of free flight of the projectile)with a multispecies and reactive approach either starting from the gun muzzle plane or directly following IB.In the latter case,an inverse problem involving a Latin hypercube sampling method is used to find a gun propellant configuration that allows the projectile to reach a given exit velocity and base pressure when IB ends.The methodology developed in this work makes it possible to study the flame front of the intermediate flash and depressurization that occurs in a base bleed(BB)channel at the gun muzzle.Average pressure variations in the BB channel during depressurization are in good agreement with literature.展开更多
It is a complicated nonlinear controlling problem to conduct a two-dimensional trajectory correction of rockets.By establishing the aerodynamic correction force mathematical model of rockets on nose cone swinging,the ...It is a complicated nonlinear controlling problem to conduct a two-dimensional trajectory correction of rockets.By establishing the aerodynamic correction force mathematical model of rockets on nose cone swinging,the linear control is realized by the dynamic inverse nonlinear controlling theory and the three-time-scale separation method.The control ability and the simulation results are also tested and verified.The results show that the output responses of system track the expected curve well and the error is controlled in a given margin.The maximum correction is about±314 m in the lengthwise direction and±1 212 m in the crosswise direction from the moment of 5 s to the drop-point time when the angle of fire is 55°.Thus,based on the dynamic inverse control of feedback linearization,the trajectory correction capability of nose cone swinging can satisfy the requirements of two-dimensional ballistic correction,and the validity and effectiveness of the method are proved.展开更多
目前,主流的基于点击的交互式分割方法对所有用户点击进行无差异的编码.这样的编码方法意味着用户的交互只能给神经网络提供目标的位置信息,且每次点击的影响力是相同的.然而,不同阶段的点击的影响力是不同的.早期的交互用于目标轮廓的...目前,主流的基于点击的交互式分割方法对所有用户点击进行无差异的编码.这样的编码方法意味着用户的交互只能给神经网络提供目标的位置信息,且每次点击的影响力是相同的.然而,不同阶段的点击的影响力是不同的.早期的交互用于目标轮廓的选择,中后期的交互则偏向于对分割结果的局部细节进行微调.因此,应该适当扩大早期点击的影响力,以便更快地获得目标轮廓,同时削弱中后期点击的影响力,以防止因为超调或歧义而影响交互式分割的收敛性.1)本文提出了一种动态盘码(Dynamic Disk Coding,DDC)算法,该算法将用户的每个点击都编码成一个特定半径的圆盘,以此添加关于点击影响力的先验信息;2)本文提出了一个交互式分割网络DDC-Net,通过交互信息预处理模块加强交互信息,并在分割网络的浅层和深层将交互式信息与语义信息进行混合,缓解交互信息随着网络加深而逐渐衰减的问题;3)本文提出了一种改进的模拟训练策略,使得网络在训练时能够充分学习不同编码半径的点击所具备的不同影响力,从而使得提出的方法兼顾收敛速度和收敛性.通过实验表明,本文提出的使用动态盘码的深度交互式分割方法具有科学性和有效性,相较于基线方法,和分别平均取得3.63%和2.44%的提升.展开更多
Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In ...Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In network-based control systems,error codes induced by noisy channel can significantly decrease the quality of control.To solve this problem,the network-based control system with delay and noisy channel is firstly modeled as an asynchronous dynamic system(ADS).Secondly,conditions of packet with error codes(PEC)loss rate by using M-ary modulation are obtained based on dynamic output feedback scheme.Thirdly,more importantly,the selection principle of M-ary modulation is proposed according to the measured signal-to-noise ratio(SNR)and conditions of PEC loss rate.Finally,system stability is analyzed and controller is designed through Lyapunov function and linear matrix inequality(LMI)scheme,and numerical simulations are made to demonstrate the effectiveness of the proposed scheme.展开更多
基金the French Defense Innovation Agency (AID)the French Procurement Agency for Armament (DGA)ONERA's scientific direction for funding and supporting the present work
文摘The aim of this paper is to simulate and study the early moments of the reactive ballistics of a large caliber projectile fired from a gun,combining 0D and 2D axisymmetric Computational Fluid Dynamics(CFD)approaches.First,the methodology is introduced with the development of an interior ballistics(IB)lumped parameter code(LPC),integrating an original image processing method for calculating the specific regression of propellant grains that compose the gun propellant.The ONERA CFD code CEDRE,equipped with a Dynamic Mesh Technique(DMT),is then used in conjunction with the developed LPC to build a dedicated methodology to calculate IB.First results obtained on the AGARD gun and 40 mm gun test cases are in a good agreement with the existing literature.CEDRE is also used to calculate inter-mediate ballistics(first milliseconds of free flight of the projectile)with a multispecies and reactive approach either starting from the gun muzzle plane or directly following IB.In the latter case,an inverse problem involving a Latin hypercube sampling method is used to find a gun propellant configuration that allows the projectile to reach a given exit velocity and base pressure when IB ends.The methodology developed in this work makes it possible to study the flame front of the intermediate flash and depressurization that occurs in a base bleed(BB)channel at the gun muzzle.Average pressure variations in the BB channel during depressurization are in good agreement with literature.
基金Project(9140A05030109HK01)supported by Equipment Pre-research Foundation,China
文摘It is a complicated nonlinear controlling problem to conduct a two-dimensional trajectory correction of rockets.By establishing the aerodynamic correction force mathematical model of rockets on nose cone swinging,the linear control is realized by the dynamic inverse nonlinear controlling theory and the three-time-scale separation method.The control ability and the simulation results are also tested and verified.The results show that the output responses of system track the expected curve well and the error is controlled in a given margin.The maximum correction is about±314 m in the lengthwise direction and±1 212 m in the crosswise direction from the moment of 5 s to the drop-point time when the angle of fire is 55°.Thus,based on the dynamic inverse control of feedback linearization,the trajectory correction capability of nose cone swinging can satisfy the requirements of two-dimensional ballistic correction,and the validity and effectiveness of the method are proved.
文摘目前,主流的基于点击的交互式分割方法对所有用户点击进行无差异的编码.这样的编码方法意味着用户的交互只能给神经网络提供目标的位置信息,且每次点击的影响力是相同的.然而,不同阶段的点击的影响力是不同的.早期的交互用于目标轮廓的选择,中后期的交互则偏向于对分割结果的局部细节进行微调.因此,应该适当扩大早期点击的影响力,以便更快地获得目标轮廓,同时削弱中后期点击的影响力,以防止因为超调或歧义而影响交互式分割的收敛性.1)本文提出了一种动态盘码(Dynamic Disk Coding,DDC)算法,该算法将用户的每个点击都编码成一个特定半径的圆盘,以此添加关于点击影响力的先验信息;2)本文提出了一个交互式分割网络DDC-Net,通过交互信息预处理模块加强交互信息,并在分割网络的浅层和深层将交互式信息与语义信息进行混合,缓解交互信息随着网络加深而逐渐衰减的问题;3)本文提出了一种改进的模拟训练策略,使得网络在训练时能够充分学习不同编码半径的点击所具备的不同影响力,从而使得提出的方法兼顾收敛速度和收敛性.通过实验表明,本文提出的使用动态盘码的深度交互式分割方法具有科学性和有效性,相较于基线方法,和分别平均取得3.63%和2.44%的提升.
基金Project(61172022) supported by the National Natural Science Foundation of ChinaProject(GDW20151100010) supported by the State Administration of Foreign Experts Affairs of China
文摘Error codes induced by M-ary modulation and modulation selection in network-based control systems are studied.It is the first time the issue of error codes induced by M-ary modulation is addressed in control field.In network-based control systems,error codes induced by noisy channel can significantly decrease the quality of control.To solve this problem,the network-based control system with delay and noisy channel is firstly modeled as an asynchronous dynamic system(ADS).Secondly,conditions of packet with error codes(PEC)loss rate by using M-ary modulation are obtained based on dynamic output feedback scheme.Thirdly,more importantly,the selection principle of M-ary modulation is proposed according to the measured signal-to-noise ratio(SNR)and conditions of PEC loss rate.Finally,system stability is analyzed and controller is designed through Lyapunov function and linear matrix inequality(LMI)scheme,and numerical simulations are made to demonstrate the effectiveness of the proposed scheme.
