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.     

行星着陆大气进入段自适应滑模抗扰控制方法

针对行星探测器着陆过程可能存在的干扰影响着陆精度问题，提出了一种抗干扰控制方法。首先建立行星探测器着陆控制模型，利用非线性干扰观测器实现对系统外部干扰的估计；在此基础上提出一种自适应滑模控制律，使得系统状态快速收敛到平衡点附近。最后，将该方法应用于火星着陆场景进行仿真。结果表明，提出的自适应滑模控制方法能够在未知扰动存在的情况下，有效实现行星探测器安全着陆，提高着陆任务的成功率。     

Convex optimization of asteroid landing trajectories driven by solar radiation pressure

High-area/mass ratio landers driven by Solar Radiation Pressure (SRP) have potential applications for future asteroid landing missions. This paper develops a new convex optimization-based method for planning trajectories driven by SRP. A Minimum Landing Error (MLE) control problem is formulated to enable planning SRP-controlled trajectories with different flight times. It is transformed into Second Order Cone Programming (SOCP) successfully by a series of different convexification technologies. A trust region constraint and a modified MLE objective function are used to guarantee the convergence performance of the optimization algorithm. Thereafter, the SRP-driven trajectory optimal control problem is converted equivalently into a sequence of convex optimal control problems that can be solved effectively. A set of numerical simulation results has verified the effectiveness and feasibility of the proposed optimization method.     

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。     

气动力与推力矢量控制近距击顶弹道研究

针对某型反坦克导弹从顶部攻击近距离目标存在的空气动力控制不足的问题,探讨了在导弹初始飞行段采用推力矢量控制的可行性,并对有推力矢量控制的近距击顶飞行弹道进行了分析研究,最,通过计算机数字仿真,进行了弹道飞行仿真计算。结果表明,所提方法改善了导弹飞行弹道特性,提出了导弹机动性能和对近距离目标攻击的效果,并有利于减少最小射程。     

翼伞系统分段归航轨迹的优化设计

如何有效利用翼伞系统自身的可操作性来规划归航轨迹 ,一直是研究人员关心的问题。近来 ,分段设计的方法以其计算简单、轨迹可知和工程实用的特点而备受关注。从六自由度动力学建模和仿真入手 ,分析了翼伞系统飞行的基本特性 ,在此基础上进一步简化了模型。然后详细介绍了一种分段优化设计翼伞轨迹的思想和各阶段的特点 ,仿真试验结果表明此方法是可行的。     

某系列运载火箭多射向发射姿态控制方案研究

介绍了某系列运载火箭实现多射向发射的几种方案 ,比较了它们的优缺点。重点对转动平台和由箭载计算机实现的两种方案从姿态控制系统角度进行了阐述     

弹道学在运载火箭总体设计中的实践与展望

简要介绍了运载火箭弹道学的主要研究内容,从弹道设计的基本方法出发,着重分析了弹道设计对于运载火箭总体设计的重要影响。在回顾我国运载火箭弹道学发展历史的同时,对我国运载火箭弹道学的特点进行了系统总结。最后结合后续我国运载火箭发展的技术需求,对弹道学的未来发展进行展望,提出了若干重点研究方向。     

基于高斯伪谱法的吸气式高超声速飞行器爬升弹道优化研究

吸气式高超声速飞行器爬升弹道设计是其总体设计的一个重要问题。这里提出一种基于高斯伪谱法的弹道优化方法,用于解决该问题。以末端弹道倾角为性能指标,飞行攻角为设计变量,建立了飞行器纵平面弹道优化模型。通过高斯伪谱法对状态变量和控制变量进行离散,将最优控制问题转化为非线性规划问题,再利用序列二次规划算法对其进一步求解。仿真结果表明,该方法收敛域大,对初值不敏感,设计精度高,是吸气式高超声速飞行器方案弹道优化的重要方法。