An impact angle constraint integral sliding mode guidance law for maneuvering targets interception

An integral sliding mode guidance law(ISMGL)combined with the advantages of the integral sliding mode control(SMC)method is designed to address maneuvering target interception problems with impact angle constraints.The relative motion equation of the missile and the target considering the impact angle constraint is established in the longitudinal plane,and an integral sliding mode surface is constructed.The proposed guidance law resolves the existence of a steady-state error problem in the traditional SMC.Such a guidance law ensures that the missile hits the target with an ideal impact angle in finite time and the missile is kept highly robust throughout the interception process.By adopting the dynamic surface control method,the ISMGL is designed considering the impact angle constraints and the autopilot dynamic characteristics.According to the Lyapunov stability theorem,all states of the closed-loop system are finally proven to be uniformly bounded.Simulation results are compared with the general sliding mode guidance law and the trajectory shaping guidance law,and the findings verify the effectiveness and superiority of the ISMGL.

Robust detection algorithm with triple constraints for cooperative target based on spectral residual

The accurate detection of cooperative targets plays a key and foundational role in unmanned aerial vehicle (UAV) landing autonomously. The standard method based on fixed threshold is too susceptible to both illumination variations and interference. To overcome issues above, a robust detection algorithm with triple constraints for cooperative targets based on spectral residual (TCSR) is proposed. Firstly, by designing an asymmetric cooperative target, which comprises red background, green H and triangle target, the captured original image is converted into a Lab color space, whose saliency map is yielded by constructing the spectral residual. Then, the triple constraints are developed according to the prior knowledge of the cooperative target. Finally, the salient region in saliency map is considered as the cooperative target, and it meets the triple constraints. Experimental results in complex environments show that the proposed TCSR outperforms the standard methods in higher detection accuracy and lower false alarm rate.

Biased retro-proportional navigation law for interception of high-speed targets with angular constraint

A new guidance law, called biased retro proportional navigation(BRPN), is proposed. The guidance law is designed to intercept high-speed targets with angular constraint, which can be used for ballistic target interception. BRPN guidance law is defined, and the exact time-varying bias for a required impact angle is derived. Furthermore, the simulation results(trajectory, variation of navigation ratio, capture region, etc) are compared with those of biased proportional navigation(BPN), proportional navigation and retro-proportional navigation. The results show that,at the cost of a higher intercept time, BRPN demands lower terminal lateral acceleration and has larger capture region compared to BPN.

A Novel Generalized Nonholonomy Criteria and Physical Interpretation of Holonomic/Nonholonomic Constraints of a Free-Flying Space Robot with/without Interaction with a Flying Target Satellite

This paper presents a new nonholonomy criteria and reveals the physical interpretation of holonomoic and nonholonomic constraints acting on a free-flying space robot with or without interaction with a free Flying/Floating target object. The analysis in this paper interprets the physical interpretation behind such constraints, and clarifies geometric and kinematic conditions that generate such constraints. Moreover, a new criterion of finding the holonomy/nonholonomy of constraints impose on a free-flying space robot with or without interaction with a floating object is presented as well. The proposed criteria are applicable in case of zero or non-zero initial momentum conditions. Such nonholonomy criteria are proposed by utilizing the concept of orthogonal projection matrices and singular value decomposition (SVD). Using this methodology will also enable us to verify online whether the constraints are violated in case of real-time applications and to take a correction action or switch the controllers. This criterion is still yet valid even the interaction with floating object is lost. Applications of the proposed criteria can be dedicated to in-orbit servicing robotic satellite to capture malfunctioned spacecrafts and satellites, docking space of NASA and Russian shuttles with International Space Station (ISA), building in-orbit stations, space rescue missions and asteroids dust sampling. Finally, simulation results are presented to demonstrate the effectiveness of the proposed criterion.

Influence of local environmental target constraints on enterprise OFDI

By collecting the environmental target constraints in the annual government work report of prefecture-level cities,this paper studies its impact on local enterprises’OFDI.The main conclusions are as follows:(1)Both direct and indirect constraints have a significant positive impact on enterprises’OFDI,and the degree of direct constraints is stronger than that of indirect constraints.(2)Environmental target constraints of local governments will affect corporate OFDI behavior by affecting production costs,local economic development level and local openness,and(3)There are regional heterogeneity and investment type heterogeneity in the impact of environmental goal constraints on corporate OFDI.The suggestions are as follows:government departments can appropriately strengthen the constraint intensity of environmental targets and formulate specific restraint rules for industries with different levels of pollution,so as to effectively make use of the technology spillover effects brought about by OFDI to promote the upgrading of domestic industrial structure.When making OFDI,enterprises should clarify the investment motivation,strengthen corporate social responsibility,and make use of technology spillover effect to promote the upgrading and development of home country industry while being beneficial to their own development.

Constrained auxiliary particle filtering for bearings-only maneuvering target tracking

To track the nonlinear,non-Gaussian bearings-only maneuvering target accurately online,the constrained auxiliary particle filtering(CAPF)algorithm is presented.To restrict the samples into the feasible area,the soft measurement constraints are implemented into the update routine via the1 regularization.Meanwhile,to enhance the sampling diversity and efficiency,the target kinetic features and the latest observations are involved into the evolution.To take advantage of the past and the current measurement information simultaneously,the sub-optimal importance distribution is constructed as a Gaussian mixture consisting of the original and modified priors with the fuzzy weighted factors.As a result,the corresponding weights are more evenly distributed,and the posterior distribution of interest is approximated well with a heavier tailor.Simulation results demonstrate the validity and superiority of the CAPF algorithm in terms of efficiency and robustness.

Sequential quadratic programming-based non-cooperative target distributed hybrid processing optimization method

The distributed hybrid processing optimization problem of non-cooperative targets is an important research direction for future networked air-defense and anti-missile firepower systems. In this paper, the air-defense anti-missile targets defense problem is abstracted as a nonconvex constrained combinatorial optimization problem with the optimization objective of maximizing the degree of contribution of the processing scheme to non-cooperative targets, and the constraints mainly consider geographical conditions and anti-missile equipment resources. The grid discretization concept is used to partition the defense area into network nodes, and the overall defense strategy scheme is described as a nonlinear programming problem to solve the minimum defense cost within the maximum defense capability of the defense system network. In the solution of the minimum defense cost problem, the processing scheme, equipment coverage capability, constraints and node cost requirements are characterized, then a nonlinear mathematical model of the non-cooperative target distributed hybrid processing optimization problem is established, and a local optimal solution based on the sequential quadratic programming algorithm is constructed, and the optimal firepower processing scheme is given by using the sequential quadratic programming method containing non-convex quadratic equations and inequality constraints. Finally, the effectiveness of the proposed method is verified by simulation examples.

Efficient tracker based on sparse coding with Euclidean local structure-based constraint

Abstract:Sparse coding(SC)based visual tracking(l1-tracker)is gaining increasing attention,and many related algorithms are developed.In these algorithms,each candidate region is sparsely represented as a set of target templates.However,the structure connecting these candidate regions is usually ignored.Lu proposed an NLSSC-tracker with non-local self-similarity sparse coding to address this issue,which has a high computational cost.In this study,we propose an Euclidean local-structure constraint based sparse coding tracker with a smoothed Euclidean local structure.With this tracker,the optimization procedure is transformed to a small-scale l1-optimization problem,significantly reducing the computational cost.Extensive experimental results on visual tracking demonstrate the eectiveness and efficiency of the proposed algorithm.

Structural constraints and its countermeasures to contiguous poor areas with particular difficulties: An case study on southern Shaanxi immigration project

Immigration relocation of the poor in rural areas is an effective targeted measure to help people out of poverty in the new normal. The structural constraints lie in the heavy pressure of land resources and environmental carrying capacity, high cost of immigration settlement and delayed counterpart funds, insufficient industrial support and difficulty in living-making. To realize the goal of targeted poverty alleviation, it demands determination and capability from the policy designer, as well the social basis. The effect imposed by the structural constraints to implementation of such policy should be paid adequate attention by public sectors. It is supposed to change the guiding direction of the policy timely and to relieve financial burden of immigration settlement and resource environmental bearing capacity through mechanism of joint efforts from internal and more external support.

土地出让市场化对城市碳排放绩效的影响研究--基于城市面板数据的检验分析

文章基于2011—2022年中国地级市的面板数据,测算地级市土地出让市场化水平与地级市碳排放绩效,采用空间面板模型、工具变量法及调节效应模型等实证方法,检验了土地出让市场化对城市碳排放绩效的影响及其内在机制。研究发现:土地出让市场化与城市碳排放绩效之间呈显著的“U”型非线性关系,且通过系列稳健性检验与内生性处理后,该结论依然成立;作用机制检验表明,资源配置与产业结构升级在土地出让市场化对城市碳排放绩效的作用机制中发挥中介作用;调节效应检验表明,双重目标约束在土地出让市场化与碳排放绩效关系中发挥显著调节作用。研究结论有助于深入理解土地出让市场化对城市碳排放绩效的影响效果和内在机理,为推进土地出让市场化发展、提升城市碳排放绩效和优化目标约束提供有益借鉴。

稀疏约束与时间一致的背景感知相关滤波目标跟踪

背景感知滤波算法通过循环移位采集真实负样本,有效解决了边界效应.但在复杂场景例如遮挡、快速移动、背景干扰等,其较大的采样区域导致过多背景在杂波干扰,从而影响跟踪效果.针对这一问题,本文首先提取灰度HOG特征与颜色CN特征来提高目标外观模型,在基准目标函数基础上引入L1稀疏正则约束形成弹性网络以自适应筛选关键特征,增强滤波器在复杂背景下的判别能力.同时针对BACF在跟踪过程中目标快速变化,本文引入时间正则项提高滤波器抑制畸变的能力.最后,本文提出了一种独立的尺度滤波器算法,准确提供目标尺度大小.实验仿真结果表明,在公开数据集OTB-2013和OTB-2015上,本文算法较基准算法有很大提升,能够较好应对不同复杂场景下的跟踪难题.

改进RRT算法的全向机器人路径规划

针对快速扩展随机树(RRT)算法在进行全局路径规划时生成路径时间长,长度长,在采样时缺乏目标导引性。所以改进了一种目标偏向采样策略,通过引入由初始点,终点,障碍物和随机点构成的虚拟力场,促使随机采样导向目标点。对于障碍物远近的影响,设定障碍物影响的阈值,引入了自适应系数λ,在扩展步长方面,加入了角度约束,根据偏向目标点角度,选择不同的扩展步长。引入冗余节点剔除策略,缩短路径长度,最后加入贪心策略,减少不必要采样节点的个数。首先,在MATLAB2018a仿真进行实验对比,其次在实际环境中进行实验。实验结果显示,在路径搜索时间,拐点数量以及路径距离等均有明显的提高。

“双碳”视阈下绿色金融发展影响碳排放的内在机制研究

加快绿色金融发展是我国新发展阶段促进发展方式绿色转型和实现“双碳”目标的战略要求。基于空间Durbin模型和GMM动态分析方法,利用我国2006—2021年30个省(区、市)的面板数据,对绿色金融发展与省际碳排放效果之间的内在关系进行实证研究。研究发现:绿色金融发展能够显著减少区域碳排放,相关结论经过稳健性检验后依然成立;低碳技术创新和融资约束作为中介变量,共同构成了绿色金融发展影响碳排放的传导路径。进一步分析表明,绿色金融发展对碳排放有明显的空间溢出效应,并在我国不同经济发展水平的地区存在区域异质性。研究结论可为新时代我国构建绿色金融发展体系、制定促进“双碳”战略目标实现的相关政策提供支撑。

一种应用于大尺寸测量系统的坐标系自动标定方法

针对现有方法在标定过程中过于繁琐的问题,提出了一种应用于大尺寸测量系统的坐标系全自动标定方法。该方法通过固定两个在测量单元局部坐标系已知坐标的测量节点作为标记靶,测量单元之间相互测量彼此的标记靶获得标记靶上的测量点在不同坐标系下的坐标值,利用这些坐标值建立三维几何约束,从而自动标定不同坐标系之间的坐标转换关系。借助于精密激光定位系统平台进行实验验证,结果表明,所提方法可以实现测量单元局部坐标系之间的自动标定,降低了坐标系标定过程中的人工成本。在距离测量单元布站区域约2 m,大小为5 000 mm×5 000 mm×500 mm的测量空间中长度测量的精度在0.46 mm/m以内,测试点三维坐标测量的标准偏差在0.026 mm以内,可以满足绝大部分工业测量的需求。该方法极大的提高了系统的标定效率,有望为具有自动标定功能的大尺寸测量设备的产品化提供新的理论基础。

环境目标约束对地方政府清洁生产型行业土地出让的影响

土地资源配置对产业发展具有重要的引导和支撑作用,优化配置工业用地对中国实现发展方式绿色转型发挥着重要的基础性作用。该研究从环境政策与地方领导干部政绩考核相结合的视角,以2007—2020年中国280个地级市的面板数据作为研究样本,分别采用固定效应模型、工具变量法、中介效应模型实证检验了环境目标约束对地方政府清洁生产型行业土地出让的影响及其作用机制,并进一步采用调节效应模型分析了地方政府面临的经济增长压力和财政压力所发挥的调节作用。研究结果表明:①环境目标约束能够显著促进地方政府增加清洁生产型行业土地出让,该结果在经过内生性处理和多种稳健性检验后依然成立。从土地供应政策、产业结构和领导干部特征差异性视角来看,分别在土地供给充裕、工业主导、在任市长非本地来源、在任市长年龄≤55岁的城市,环境目标约束对地方政府增加清洁生产型行业土地出让的促进作用显著。②机制分析发现,环境目标约束会促使地方政府通过提升环境规制强度、加大环境治理监管力度等途径增加清洁生产型行业土地出让。③进一步研究发现,地方政府面临的经济增长压力会削弱环境目标约束对其清洁生产型行业土地出让的促进作用,而财政压力则与环境目标约束的促进作用具有协同作用。以上结论表明中央实施的环境目标“硬约束”政策已促使地方政府在工业用地出让时向绿色产业偏向性配置,为中国实现环境污染治理和资源优化配置的“双赢”提供了重要的现实证据。

针对机动目标的三维领从协同制导律

针对多飞行器协同拦截机动目标的实际需求,提出一种三维领从时空协同制导律。在视线方向上,基于齐次度理论和固定时间稳定理论设计一种领从协同制导律,确保从飞行器与领飞行器的相对距离和相对速度在固定时间内趋于一致,并且给出一致性误差收敛时间的上界,实现多飞行器的同时刻拦截。在视线法向上为实现以特定的碰撞角度拦截目标,设计一种固定时间收敛的非奇异终端滑模制导律,实现攻击角度的固定时间收敛,并避免了制导指令奇异引起的控制饱和问题。考虑到目标的机动对制导系统产生的不利影响,引入固定时间扰动观测器对目标加速度进行前馈补偿。运用李雅普诺夫稳定性理论来证明系统的固定时间稳定特性。通过仿真实验验证所设计制导律可以有效控制多飞行器在领从框架下同时打击机动目标,并以期望的终端角度攻击目标。

基于多光谱融合的三维视觉重建系统

为了解决目标三维重建时杂散点干扰、数据空洞等问题,提高三维视觉重建效果,提出了基于偏振多光谱融合的三维视觉重建算法。搭建了双目激光扫描与偏振多光谱成像系统,利用本融合算法将多光谱映射的特征区域作为目标三维点云在该截面的二维边界,完成了点云滤波。测试了高斯采样与极值采样方式的解算精度,映射位置与实际位置的偏差均值分别为0.59 mm与0.93 mm。采用4种偏振片的叠加降噪处理后,背景区域噪声强度均值由49.5降低为13.4。对包含两个局部曲率不同的目标特征进行测试发现,优化后,超过80%的测试点的误差优于3.05μm,平均偏差为1.49μm,目标三维视觉重建效果得到了改善。

双基地SAR动目标图像相位误差分析和二维稀疏重聚焦处理

双基地合成孔径雷达(Synthetic Aperture Radar,SAR)系统中,数据采集空间几何关系复杂,动目标回波距离徙动严重,重建图像中往往存在几何失真和散焦现象,需要进一步补偿运动相位误差。为此,分析并推导了双基地动目标极坐标格式图像的二维相位误差谱。根据相位误差模型建立字典,约束动目标回波谱在字典上的投影系数,进而实现杂波和动目标能量的分离和重聚焦成像。点目标仿真验证了算法的有效性。

增长目标约束如何影响数字基础设施建设?

在对增长目标约束和数字基础设施建设(简称“数字基建”)二者关系进行分析的基础上,利用2006—2020年282个地级以上城市的面板数据实证检验增长目标约束如何影响数字基础设施建设,结果发现:(1)增长目标约束将通过政府关注效应和资金支持效应促进数字基建,软约束可以显著促进数字基建,但硬约束则相反。(2)增长目标约束对于数字基建的影响受到市场化水平和人力资本水平的影响。市场化水平越低(人力资本水平越高),增长目标约束对于数字基建的促进作用越强。(3)异质性分析表明,与东部地区相比,增长目标约束对于中西部地区城市的数字基建水平的促进效果更强。同时,增长目标约束对于数字基础设施建设的促进作用仅在2012年后成立,且负向的社会绩效反馈差距比正反馈对数字基建的提升作用更大。以上结论有助于理解政府在数字基建中承担的角色,为更好促进数字基建高质量发展提供了政策启示。

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.