Maneuvering Angle Rigid Formations With Global Convergence Guarantees

Angle rigid multi-agent formations can simultaneously undergo translational,rotational,and scaling maneuvering,therefore combining the maneuvering capabilities of both distance and bearing rigid formations.However,maneuvering angle rigid formations in 2D or 3D with global convergence guarantees is shown to be a challenging problem in the existing literature even when relative position measurements are available.Motivated by angle-induced linear equations in 2D triangles and 3D tetrahedra,this paper aims to solve this challenging problem in both 2D and3D under a leader-follower framework.For the 2D case where the leaders have constant velocities,by using local relative position and velocity measurements,a formation maneuvering law is designed for the followers governed by double-integrator dynamics.When the leaders have time-varying velocities,a sliding mode formation maneuvering law is proposed by using the same measurements.For the 3D case,to establish an angle-induced linear equation for each tetrahedron,we assume that all the followers'coordinate frames share a common Z direction.Then,a formation maneuvering law is proposed for the followers to globally maneuver Z-weakly angle rigid formations in 3D.The extension to Lagrangian agent dynamics and the construction of the desired rigid formations by using the minimum number of angle constraints are also discussed.Simulation examples are provided to validate the effectiveness of the proposed algorithms.

Experimental Study and 3D CFD Analysis on the Optimization of Throttle Angle for a Convergent Vortex Tube

Seven adjustments of convergent-type Vortex Tube （VT） with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow structures inside the VTs. An experimental setup was designed, and tests were performed on different convergent VT configurations at injection pressures ranging from 0.45 to 0.65 MPa. The angles of the throttle valve were arranged between 30° to 90°, and the numbers of injection nozzles ranged between 2 and 6. Laboratory results indicated that the maximum hot and cold temperature drops ranged from 23.24 to 35 K and from 22.87 to 32.88 K, respectively, at four injection nozzles. Results also showed that temperature drop is a function of hot throttle valve angle with the maximum hot and cold temperature drops depending on the angle applied. We used graphs to demonstrate the changes in the cold and hot temperature drops with respect to hot throttle angle values. These values were interpreted and evaluated to determine the optimum angle, which was 60°. The CFD outputs agreed very well with the laboratory results. The proposed CFD results can help future researchers gain good insights into the complicated separation process taking place inside the VTs.

Confining stress effect on the elastoplastic ground reaction considering the Lode angle dependence

The convergence confinement methods are solutions employed to estimate convergence in circular tunnels. They are mostly based on constitutive equations governed by the Mohr-Coulomb and Hoek-Brown yield criteria. However, the solutions based on these criteria neglect the intermediate principal stress confining effect on the ground reaction estimation. Therefore, in this paper, a Drucker-Prager yield criterion governed solution integrated with the Lode angle parameter is employed. It considers the intermediate principal stress influence and the critical effect of the parameter on failure characterization.Subsequently, it is verified with results attained from numerical simulations which consider an elasticperfectly plastic constitutive law with a non-associative flow rule within FLAC3D. It was drawn from the results that the ground reaction and plastic evolution are influenced by the confining stress.Furthermore, considering a suitable yield criterion leads to realistic convergence and plastic evolution estimation. The circumscribed DP criterion governed solution with Lode angle parameter value(0.8) is considered appropriate for the realistic ground reaction estimation in the three-dimensional(3D) stress state rock mass. It estimates approximately 3.4% of tunnel convergence as compared to the classic solutions(5%) and plastic radius estimated to be approximately 2.45 m compared to 2.84 m.

Three-dimensional impact angle constrained distributed cooperative guidance law for anti-ship missiles

This paper investigates the problem of distributed cooperative guidance law design for multiple anti-ship missiles in the three-dimensional(3-D)space hitting simultaneously the same target with considering the desired terminal impact angle constraint.To address this issue,the problem formulation including 3-D nonlinear mathematical model description,and communication topology are built firstly.Then the consensus variable is constructed using the available information and can reach consensus under the proposed acceleration command along the line-of-sight(LOS)which satisfies the impact time constraint.However,the normal accelerations are designed to guarantee the convergence of the LOS angular rate.Furthermore,consider the terminal impact angle constraints,a nonsingular terminal sliding mode(NTSM)control is introduced,and a finite time convergent control law of normal acceleration is proposed.The convergence of the proposed guidance law is proved by using the second Lyapunov stability method,and numerical simulations are also conducted to verify its effectiveness.The results indicate that the proposed cooperative guidance law can regulate the impact time error and impact angle error in finite time if the connecting time of the communication topology is longer than the required convergent time.

A Hybrid Conjugate Gradient Algorithm for Solving Relative Orientation of Big Rotation Angle Stereo Pair

The fast convergence without initial value dependence is the key to solving large angle relative orientation.Therefore,a hybrid conjugate gradient algorithm is proposed in this paper.The concrete process is:①stochastic hill climbing(SHC)algorithm is used to make a random disturbance to the given initial value of the relative orientation element,and the new value to guarantee the optimization direction is generated.②In local optimization,a super-linear convergent conjugate gradient method is used to replace the steepest descent method in relative orientation to improve its convergence rate.③The global convergence condition is that the calculation error is less than the prescribed limit error.The comparison experiment shows that the method proposed in this paper is independent of the initial value,and has higher accuracy and fewer iterations.

Euclid’s Fifth Postulate and Convergence of Non-Parallel Straight Lines

This paper proves Euclid’s fifth postulate and convergence of straight lines using the formula for the area of trapezoids and assuming straight lines, it derives a general formula for the area of trapezoids involving ratios and we assume that the straight lines determine the nature and area for all the rectilinear figures. Furthermore, this proof is essential in Geometric optics basically in proving and classifying beams of light (wave) that is to mathematically prove the presence of parallel, convergent and divergent beams of light assuming the ray of light is a straight line.

Missile guidance law design based on free-time convergent error dynamics

To solve the finite-time error-tracking problem in mis-sile guidance,this paper presents a unified design approach through error dynamics and free-time convergence theory.The proposed approach is initiated by establishing a desired model for free-time convergent error dynamics,characterized by its independence from initial conditions and guidance parameters,and adjustable convergence time.This foundation facilitates the derivation of specific guidance laws that integrate constraints such as leading angle,impact angle,and impact time.The theoretical framework of this study elucidates the nuances and synergies between the proposed guidance laws and existing methodologies.Empirical evaluations through simulation comparisons underscore the enhanced accuracy and adaptability of the proposed laws.

基于MF和CONVERGE的发动机燃烧参数对NO_(x)排放的优化分析

随着汽车仿真模拟技术的发展,该技术在汽车工业研发和优化中使用越来越普遍。意大利ESTECO公司的多目标优化软件modeFRONTIER与多种软件具有较高的耦合性,也可通过间接接口与新一代热流体分析软件CONVERGE耦合对发动机进行仿真优化。本文在Windows系统中,通过在modeFRONTIER中设定输入和输出变量、输入和输出文件、优化算法策略和目标、软件调用和执行的DOS程序,可进行发动机燃烧参数对氮氧化物(NO_(x))排放的仿真优化分析,得到直观的优化历程图、优化结果图、变量相关性分析图等,以便更好地指导发动机优化实验的进行,提高发动机优化工作的效率。

拦截机动目标的固定时间事件触发协同制导律

针对无向通信拓扑结构下的多枚导弹考虑角度约束同时攻击机动目标的问题,提出一种事件触发控制下的固定时间收敛分布式多弹协同制导律.首先,建立导弹-目标相对运动学模型,在视线坐标系下解耦为沿视线和垂直视线两个方向.其次,在视线切向考虑时间约束,提出一种基于事件触发机制的固定时间收敛协同制导律,保证攻击时间的一致性;在视线法向上考虑空间角度约束,提出一种基于固定时间收敛理论的分布式空间协同制导律,使视线角和视线角速率快速收敛到期望值,以满足脱靶量和终端角度约束;同时,针对目标机动引起的系统扰动,采用固定时间收敛的观测器进行在线估计与补偿.利用Lyapunov理论,证明了所提出协同制导律的稳定性.最后,通过数学仿真,验证了所提出的协同制导律的有效性.

系统收敛时间和攻击角度控制的滑模导引律

针对打击机动目标带攻击角度约束的导引律设计问题,采用滑模控制理论、任意收敛时间控制方法和干扰观测器,设计了一种攻击角度和收敛时间控制的导引律。根据弹目相对运动关系,将目标机动和建模误差等视为干扰,构建了考虑攻击角度约束的制导系统状态方程。分析了任意收敛时间控制方法在干扰情况下的性能,采用滑模控制和干扰观测器对任意收敛时间控制方法进行改进,提升鲁棒性。将该方法用于滑模面和趋近律设计中,采用干扰观测器对系统扰动进行估计,基于滑模控制理论,结合制导控制系统状态方程,推导出了收敛时间和攻击角度可控的滑模导引律。相比有限时间收敛导引律,该导引律的收敛时间和攻击角度可直接设定,无需根据制导参数计算。设置不同的目标机动方式以及不同的攻击角度和收敛时间,进行了多场景的数值仿真。结果表明,所提导引律能够有效实现攻击角度和收敛时间控制,并精确命中目标,同时相比现有导引律其制导性能更佳。

纤维增强注塑熔接线强度预测模型与实验研究

熔接线是影响注塑制品强度的关键因素之一,而目前以汇合角预测熔接线强度的力学模型并没有体现注塑工艺的影响。为了科学定量地认识熔接线区域强度的变化规律,准确预测熔接线力学性能,首先对带扇形孔的制品进行注塑模拟分析,研究了注塑温度、注射速率以及保压压力对熔接线汇合角的影响,结果显示注塑温度、保压压力不是通过改变熔体前沿汇合角来影响熔接线强度。基于此,为全面体现注塑工艺、汇合角对熔接线强度的影响,在现有模型基础上通过引入注塑工艺影响因子重新构造了体现注塑工艺、汇合角对熔接线区域强度影响的预测模型。设计并制造了用于成型扇形孔制品的注射模具,开展了不同工艺条件下30%长玻纤增强聚丙烯扇形孔制品注塑实验,根据实验结果推导出了体现注塑温度和保压压力影响的注塑工艺影响因子数学表达式,利用实验数据拟合确定了模型中的相关参数,并对模型进行了回归分析。结果表明,新构建的强度预测模型可以准确计算不同注塑温度、保压压力下熔接线不同位置的强度。

S弯收扩喷管过膨胀状态下流动分离特性研究

为了研究S弯收扩喷管过膨胀状态下的流动分离特性,数值模拟了不同落压比(NPR)下S弯收扩喷管内的流动特征。结果表明:在落压比为2.0时,喷管内发生非对称分离,出现非对称的双“λ”激波结构,喷流整体向上偏转,上侧出现限制性流动分离RSS,下侧出现自由性流动分离FSS,并产生三维分离涡,喷流出现明显的三维效应。随着落压比从高度过膨胀状态下开始增加,喷管下侧保持FSS不变,喷管上侧RSS逐渐向后移动,直至与外界大气相连,转变为FSS,之后随着落压比增加,上下侧分离结构逐渐对称。推力矢量角随着落压比的增加先增加,后在极小的落压比变化范围内快速降低,直至变为0°,之后保持0°不变。

长大线性工程归化纬度类高斯投影方法研究

对东西向长大线性工程而言,传统高斯投影受带宽影响导致控制距离较短且需要进行频繁的换带计算。为了解决这些问题,提出了一种基于复数归化纬度的斜轴高斯投影理论。首先,对类归化纬度进行了复平面的解析开拓,实现了将椭球面转化为平面的过程。其次,结合类归化纬度线弧长的表达式,推导出了其复数形式的弧长公式。此外,利用复变函数的知识,进一步得到了斜轴高斯投影面的坐标。最后,在实际工程应用中与传统高斯投影方法对比,证明此方法的优越性。

Optimization of magnetic field design for Hall thrusters based on a genetic algorithm

Magnetic field design is essential for the operation of Hall thrusters.This study focuses on utilizing a genetic algorithm to optimize the magnetic field configuration of SPT70.A 2D hybrid PIC-DSMC and channel-wall erosion model are employed to analyze the plume divergence angle and wall erosion rate,while a Farady probe measurement and laser profilometry system are set up to verify the simulation results.The results demonstrate that the genetic algorithm contributes to reducing the divergence angle of the thruster plumes and alleviating the impact of high-energy particles on the discharge channel wall,reducing the erosion by 5.5%and 2.7%,respectively.Further analysis indicates that the change from a divergent magnetic field to a convergent magnetic field,combined with the upstream shift of the ionization region,contributes to the improving the operation of the Hall thruster.

针对三维空间机动目标的预定时间收敛制导律

提出了预定时间视线角(LOS)速率收敛制导律,用于三维场景中的多种交战情况。通过使用这种制导律,视线角速率会在任意预先指定的时间内收敛到0,且收敛时间与初始条件和控制参数无关。此外,收敛时间存在一个确切上界。首先,通过解耦三维(3D)交战模型,设计了一个平面制导律,提出了在二维(2D)场景中的制导指令。然后,通过理论分析证明了制导指令在三维场景中的可行性。最后,仿真验证了制导律的有效性。

全瓷冠预备体轴面聚合度的测量与分析

目的:本研究比较了修复教学医生、修复专科医生、全科医生的前牙、前磨牙、磨牙全瓷冠牙体预备的预备体轴面聚合度。方法:从就诊的患者中筛选符合纳入标准的256个全瓷冠预备体的数据。按照牙位分3组:前牙、前磨牙、磨牙。17名口腔医生按照专业分成三组:修复教学组、修复专科组、全科组。测量预备体近远中及唇舌向的轴面聚合度,以及分析在同组医生中不同组牙位的全瓷冠预备体的轴面聚合度差异以及在同组牙位中不同组医生的全瓷冠预备体轴面聚合度的差异。结果:预备体轴面聚合度最大值在各个医生组中都存在于磨牙组。所有牙位的轴面聚合度均数均大于理论值(小于6°)。全科组的磨牙近远中向轴面聚合度最大(26.11±12.23°),修复专科组的前牙近远中向轴面聚合度最小(6.58±3.83°)。在每组医生中不同组牙位的唇舌向轴面聚合度(FL)及近远中向轴面聚合度(MD)的差异均具有统计学意义(P<0.05),在前磨牙组中不同组医生的预备体轴面聚合度的差异均具有统计学意义(P<0.05)。结论:数字化软件是测量预备体几何形状的有用工具。全瓷冠预备体的轴面聚合度对口腔医生有很高的要求,理论上推荐的值在临床中很少能达到,特别是磨牙。

基于MPSO算法的特定谐波消除技术研究

目的对于级联H桥逆变器的调制,特定谐波消除技术具有开关损耗小,能够消除特定次谐波,变换效率高等优点,但传统粒子群优化算法(Particle Swarm Optimization,PSO)在求解消谐方程组时收敛性差,容易局部最优,提出一种改进的粒子群优化算法(Modified Particle Swarm Optimization,MPSO)。方法该算法用非线性惯性权重取代线性变化的惯性权重,并在非线性惯性权重引入混沌映射以产生随机性更好的随机量,新的惯性权重可权衡粒子的全局搜索和局部搜索能力,使粒子具有后期跳出局部最优的能力;另外,该算法优化了速度和位置的更新机制,以增强算法的收敛速度,并保证粒子在后期仍具有一定种群多样性优势。结果根据级联H桥型逆变器的非线性消谐方程组,在保证输出电压基波的前提下最大化降低目标次谐波,建立适应度函数,将MPSO算法应用于级联H桥型逆变器的SHEPWM,能够在1~1.2的调制度范围内得到优化的开关角,提高收敛精度和求解成功率。通过七电平CHB逆变器仿真平台验证了MPSO算法所求的优化开关角能够有效地消除5次、7次谐波。结论通过使用非线性惯性权重和优化粒子的速度和位置更新机制,可以增加开关角求解成功率,所得解可以有效地消除目标次谐波。

真方位角的计算与程序设计

目前,没有一款软件同时具备高斯投影正、反算及坐标真方位角求取功能。现有软件求取真方位角时,需分别进行高斯投影坐标的换算,计算坐标方位角和子午线收敛角,最后再手动相加求得,计算烦琐、出错率高。本文结合实际用途,编写了真方位角计算软件。本软件可进行多个坐标系下的高斯坐标正、反算,以及对子午线收敛角、坐标方位角、真方位角的一站式计算。

轴对称收敛型电子枪设计方法再讨论

对轴对称收敛型电子枪设计方法进行了整理分析,就阴极半锥角的初始值对迭代综合法的收敛性能所产生的影响进行了讨论,针对低压缩比条件下原来的Vaughan公式失效的问题进行了分析,给出了更为合理的初始值计算公式。采用修正后的公式和迭代综合法对电子枪进行设计,在高压缩比情况下的设计结果与采用原来Vaughan方法的结果完全一致;而对于低压缩比的情况,也得到了合理的设计,从而解决了原来的Vaughan方法在低压缩比情况下失效的问题,扩大了迭代综合法的应用范围。

极区不分带高斯投影的正反解表达式

针对传统高斯投影公式在极区难以应用的问题,通过引入等角余纬度及等量纬度的表达式,推导出严密的复数等角余纬度公式,进而得到严密的极区高斯投影正解表达式;借助符号迭代法及指数函数与三角函数间的关系式,推导出对应的极区高斯投影反解表达式;基于极区高斯投影正解表达式,推导出可用于极区的长度比、子午线收敛角公式;最后,以CGCS2000椭球为例,与实数型幂级数高斯投影公式计算的结果进行对比,验证了本文推导公式的正确性。由于本文推导公式不受带宽限制,且可用于整个极区的表示,对于编制极区地图及极区导航具有重要的参考价值。