多目标融合的冗余空间机械臂碰前轨迹优化

面向在轨对接与装配任务,提出了多目标融合的冗余度空间机械臂碰前轨迹优化方法。通过分析任务特点,阐述了空间机械臂碰前的多重任务目标。针对由空间机械臂连续轨迹跟踪、碰撞姿态控制及碰撞冲量幅值优化三个目标组成的第一类任务,通过设置任务优先级融合多目标并采用基于主任务零空间的方法实现对碰前轨迹的优化;而对由空间机械臂点到点规划、碰撞姿态控制及碰撞冲量幅值优化三个目标组成的第二类任务,通过设置任务权重将多目标融合并采用遗传算法对碰前轨迹进行优化。以典型七自由度机械臂为例开展仿真实验,验证了提出的轨迹优化方法的有效性。     

自落式缓冲气囊仿真研究

缓冲气囊被广泛应用于武器装备及物资空投、航天器着陆回收、汽车安全气囊等领域。设计具有优良缓冲性能的气囊系统可以减小物品或乘员所受的冲击力,最大程度上避免了物资的损坏和乘员伤亡。文章以某型空投缓冲系统所用气囊作为研究对象,运用LS-DYNA有限元仿真软件,采用控制体积法对该气囊缓冲过程进行了数值模拟计算,同时,结合工程计算与试验测试,合理确定气囊设计中关键技术状态,获得了带有辅囊的自落式缓冲气囊设计思路与方法,提高了研制品质,节省了研制成本与周期。     

Solving Job-Shop Scheduling Problem Based on Improved Adaptive Particle Swarm Optimization Algorithm

An improved adaptive particle swarm optimization(IAPSO)algorithm is presented for solving the minimum makespan problem of job shop scheduling problem(JSP).Inspired by hormone modulation mechanism,an adaptive hormonal factor(HF),composed of an adaptive local hormonal factor(H l)and an adaptive global hormonal factor(H g),is devised to strengthen the information connection between particles.Using HF,each particle of the swarm can adjust its position self-adaptively to avoid premature phenomena and reach better solution.The computational results validate the effectiveness and stability of the proposed IAPSO,which can not only find optimal or close-to-optimal solutions but also obtain both better and more stability results than the existing particle swarm optimization(PSO)algorithms.     

Simple method for performance evaluation of multistage rockets

Multistage rockets are commonly employed to place spacecraft and satellites in their operational orbits. Performance evaluation of multistage rockets is aimed at defining the maximum payload mass at orbit injection, for specified structural, propulsive, and aerodynamic data of the launch vehicle. This work proposes a simple method for a fast performance evaluation of multistage rockets. The technique at hand is based on three steps: (i) the flight-path angle at each stage separation is guessed, (ii) the spacecraft velocity is maximized at the first and second stage separation, and (iii) for the last stage the thrust direction is obtained through the particle swarm optimization technique, in conjunction with the use of the Euler–Lagrange equations and the Pontryagin minimum principle. The coast duration at the second stage separation is optimized as well. The method at hand is extremely simple and easy-to-implement, but nevertheless it proves to be capable of yielding near-optimal ascending trajectories for a multistage launch vehicle with realistic structural, propulsive, and aerodynamic characteristics. The solutions found with the technique under consideration can be employed either for a rapid evaluation of the multistage rocket performance or as guesses for more refined optimization algorithms.     

Optimal nodal flyby with near-Earth asteroids using electric sail

The aim of this paper is to quantify the performance of an Electric Solar Wind Sail for accomplishing flyby missions toward one of the two orbital nodes of a near-Earth asteroid. Assuming a simplified, two-dimensional mission scenario, a preliminary mission analysis has been conducted involving the whole known population of those asteroids at the beginning of the 2013 year. The analysis of each mission scenario has been performed within an optimal framework, by calculating the minimum-time trajectory required to reach each orbital node of the target asteroid. A considerable amount of simulation data have been collected, using the spacecraft characteristic acceleration as a parameter to quantify the Electric Solar Wind Sail propulsive performance. The minimum time trajectory exhibits a different structure, which may or may not include a solar wind assist maneuver, depending both on the Sun-node distance and the value of the spacecraft characteristic acceleration. Simulations show that over 60% of near-Earth asteroids can be reached with a total mission time less than 100 days, whereas the entire population can be reached in less than 10 months with a spacecraft characteristic acceleration of 1 mm/s².     

可应用于民机空气动力设计中的数值优化方法

目前民机成功设计的一个关键要素即在设计中有效地引入计算流体力学（CFD）的模拟方法和软件,特别是具有设计能力的方法和工具。本文概要地叙述了反设计、基于CFD低可信度和高可信度模型等数值优化方法的发展和应用于民机设计的历史和现状;简单地介绍了即将举行的空气动力优化设计计算系列研讨会;重点讨论了对可应用于民机设计的基于Navier-Stokes方程解算器的OPTIMAS的数值优化方法的要求及其构造方法,并以翼身组合体整流外形和翼身融合体（BWB）外形的算例表明其有效性,说明OPTIMAS可以成为民机日常设计的方法和工具之一。     

Rapid design and optimization of low-thrust rendezvous/interception trajectory for asteroid deflection missions

Asteroid deflection techniques are essential in order to protect the Earth from catastrophic impacts by hazardous asteroids. Rapid design and optimization of low-thrust rendezvous/interception trajectories is considered as one of the key technologies to successfully deflect potentially hazardous asteroids. In this paper, we address a general framework for the rapid design and optimization of low-thrust rendezvous/interception trajectories for future asteroid deflection missions. The design and optimization process includes three closely associated steps. Firstly, shape-based approaches and genetic algorithm (GA) are adopted to perform preliminary design, which provides a reasonable initial guess for subsequent accurate optimization. Secondly, Radau pseudospectral method is utilized to transcribe the low-thrust trajectory optimization problem into a discrete nonlinear programming (NLP) problem. Finally, sequential quadratic programming (SQP) is used to efficiently solve the nonlinear programming problem and obtain the optimal low-thrust rendezvous/interception trajectories. The rapid design and optimization algorithms developed in this paper are validated by three simulation cases with different performance indexes and boundary constraints.     

Stochastic processes for line shapes and intensities

Stochastic processes provide flexible and fast calculations for modeling dynamical interactions between an atom and charged particles. We use a stochastic renewal process for the plasma microfield being the cause of Stark broadening. The accuracy and improvement possibilities of Lyman profiles calculations with a renewal process are analyzed by comparing to ab initio simulations for ion broadening only. Stochastic processes may also be applied to out of equilibrium plasmas. We present our first results for the effect of Langmuir waves on a line broadened by electrons only, and for the changes of atomic populations submitted to strong temperature fluctuations.     

亚声速翼身融合无人机概念外形参数优化

为了兼顾翼身融合（BWB）布局无人机（UAV）的气动、隐身和结构重量要求,应用优化方法研究了某亚声速翼身融合无人机概念方案的外形设计问题。外形优化设计流程包括全机参数化几何外形模型、气动分析、机翼根部弯矩计算、雷达散射截面（RCS）分析、代理模型的建立和外形参数优化计算。选择了三种不同优化目标研究翼身融合无人机外形优化问题：①未配平状态升阻比最大;②配平状态升阻比最大;③配平状态升阻比尽量大和机翼弯矩尽量小。通过优化结果的对比分析,揭示了配平约束和机翼弯矩目标对优化设计结果的影响。研究结果表明：计入配平约束能够有效提高配平升阻比;将配平状态升阻比尽量大和机翼根部弯矩尽量小作为优化目标能够获得合理的优化外形。     

基于SPF/DB工艺的某翼类构件内部结构优化分析

采用SPF/DB工艺成形的翼类构件,内部结构不仅影响其力学性能,同时决定SPF/DB工艺的可行性。翼类构件在应用SPF/DB工艺成形过程中,内部夹层扩散焊接焊缝处形成筋条,从而增强结构强度,因此中间夹层扩散焊接筋条分布决定了成形后构件内部结构。本文利用有限元软件ABAQUS6.8对不同内部结构的某翼类构件进行静力学分析及超塑成形的数值模拟,得到既满足强度要求又有利于SPF/DB工艺要求的内部结构。