弹道修正执行机构综述

二维弹道修正弹是一种低成本、高精度的精确打击弹药,修正机构是弹道修正弹上的重要部件,其性能决定了弹丸的弹道修正能力。针对弹道的二维修正需求,介绍了国内外对二维弹道修正弹修正机构的研究状况;列举了应用在二维弹道修正弹上不同类型的修正机构;阐述了不同类型修正机构的工作原理、特点以及各自的局限性。最后,对不同类型修正机构特性进行了比较,给出了相关技术指标,对比了各自的优缺点。阐述了选择和设计执行机构应注意的问题。     

Disturbance observer based model predictive control for accurate atmospheric entry of spacecraft

Facing the complex aerodynamic environment of Mars atmosphere, a composite atmospheric entry trajectory tracking strategy is investigated in this paper. External disturbances, initial states uncertainties and aerodynamic parameters uncertainties are the main problems. The composite strategy is designed to solve these problems and improve the accuracy of Mars atmospheric entry. This strategy includes a model predictive control for optimized trajectory tracking performance, as well as a disturbance observer based feedforward compensation for external disturbances and uncertainties attenuation. 500-run Monte Carlo simulations show that the proposed composite control scheme achieves more precise Mars atmospheric entry (3.8?km parachute deployment point distribution error) than the baseline control scheme (8.4?km) and integral control scheme (5.8?km).     

电长度测量方法探究

从电长度的概念出发，主要介绍了使用网络分析仪来实现电长度测量的三种方法，分别是频域电延迟法、时域反射法和时域传输法；针对三种不同方法分别做了试验。     

预置接触区长度系数的Spirac切齿调整计算方法

基于参考点处瞬时接触椭圆大体决定接触区长度的方法,提出一种切齿调整计算方法.根据奥利康刀倾半展成法(Spirac)切齿原理,建立摆线齿准双曲面齿轮的数学模型,得到了大轮齿面参考点处瞬时接触椭圆参数;在满足参考点位置、压力角和螺旋角的基础上,将刀倾角也作为迭代变量,并将接触区长度系数等于预置值作为新增的迭代条件,迭代求解切齿调整参数.最后以一对摆线齿准双曲面齿轮副为例,对比该方法与Spirac切齿调整计算结果,验证了该方法的准确性,并对不同预置接触区长度系数得到的齿面进行齿面接触分析.结果表明,该方法解决了反复调整刀倾角的问题,并通过精确控制大轮齿面接触区长度系数等于设计值,实现了对大轮齿面接触区长度的预控.     

数控车床长度补偿功能的使用研究

数控车床上坐标指令（G92、G54～G59）与刀具长度补偿功能（Txxyy,调用xx号刀具和yy号刀补）不能同时使用,当调用后者时,前者指定的工件原点自动失去作用,与数控铣床上两者的使用方法不同.数控车床的对刀方法有其特殊性.本文介绍数控车床上对刀操作,长度补偿值的设置方法,说明长度补偿与编程坐标系原点的关系,长度补偿功能的使用技巧.     

关于外测新体制的一些分析与思考

针对外测新体制下数据处理中遇到的一些重要问题进行了较为深入的讨论。认真分析了多站测速系统的严重病态以及样条约束的EMBET算法在目标非平稳段的剩余截断误差等制约弹道处理精度的重要问题,并提出解决问题的思路与方法。     

A multi-aircraft conflict detection and resolution method for 4-dimensional trajectory-based operation

Conflict Detection and Resolution(CDR) is the key to ensure aviation safety based on Trajectory Prediction(TP). Uncertainties that affect aircraft motions cause difficulty in an accurate prediction of the trajectory, especially in the context of four-dimensional(4D) Trajectory-Based Operation(4DTBO), which brings the uncertainty of pilot intent. This study draws on the idea of time geography, and turns the research focus of CDR from TP to an analysis of the aircraft reachable space constrained by 4D waypoint constraints. The concepts of space–time reachability of aircraft and space–time potential conflict space are proposed. A novel pre-CDR scheme for multiple aircraft is established. A key advantage of the scheme is that the uncertainty of pilot intent is accounted for via a Space-Time Prism(STP) for aircraft. Conflict detection is performed by verifying whether the STPs of aircraft intersect or not, and conflict resolution is performed by planning a conflict-free space–time trajectory avoiding intersection. Numerical examples are presented to validate the efficiency of the proposed scheme.     

Backstepping sliding-mode control of stratospheric airships using disturbance-observer

In the presence of unknown disturbances and model parameter uncertainties, this paper develop a nonlinear backstepping sliding-mode controller (BSMC) for trajectory tracking control of a stratospheric airship using a disturbance-observer (DO). Compared with the conventional sliding mode surface (SMS) constructed by a linear combination of the errors, the new SMS manifold is selected as the last back-step error to improve independence of the adjustment of the controller gains. Furthermore, a nonlinear disturbance-observer is designed to process unknown disturbance inputs and improve the BSMC performances. The closed-loop system of trajectory tracking control plant is proved to be globally asymptotically stable by using Lyapunov theory. By comparing with traditional backstepping control and SMC design, the results obtained demonstrate the capacity of the airship to execute a realistic trajectory tracking mission, even in the presence of unknown disturbances, and aerodynamic coefficient uncertainties.     

Contingency target assessment,trajectory design,and analysis for NASA’s NEA scout solar sail mission

The presented study examines contingency target selection and trajectory design for NASA’s Near-Earth Asteroid Scout mission under the assumption of a missed lunar gravity assist. Two previously considered asteroids are selected as potential targets for the given scenario based on favorable orbital characteristics for launch dates ranging from June 27, 2020 through July 26, 2020. Initially, a simplified circular restricted 3-body problem + ideal solar sail model is utilized to survey trajectory options for a month-long launch window. Selected solutions from this data set are then converged in an N-body ephemeris + non-ideal sail model. Results suggest that NEA Scout can still perform asteroid rendezvous mission under the missed lunar gravity assist scenario with new targets, 2019 GF1, 2018 PK21, and 2007 UN12, based on the target launch dates. Further target assessment is carried out for 165 days beyond the current June 27, 2020 launch date.     

用RTR技术确定SRM燃烧室凝相粒子加入边界条件

由于缺乏有效的实验手段, 目前的ＳＲＭ 颗粒轨道模型很不完善, 其中粒子的加入边界条件完全是建立在人为假设的基础上。针对这种情况, 发展了一种以实验为基础的确定凝相粒子加入边界条件的方法, 首先利用ＲＴＲ技术对实验发动机热试车条件下凝相粒子的运动进行实验研究, 通过图象处理技术获得粒子的运动轨迹, 然后采用轨道模型法计算实验条件下凝相粒子的运动轨迹, 通过轨迹反推法给出了粒子加入边界条件。