连续小推力条件下星座轨道机动方法研究

基于连续小推力条件下星座轨道机动的动力学特性分析,研究了其入轨的布局置入和离轨机动方法。地球轨道上的大型星座数量巨大,传统的轨迹优化方法较难应用。针对多星入轨的星座布局置入任务,求解了分时序抬轨的相位调整问题,并在轨道抬升过程中,利用轨道倾角偏置补偿升交点赤经漂移。针对星座中卫星的离轨任务,设计了半长轴和偏心率的联合调整方法。在保证卫星快速离轨的同时,能够有效减少燃料的消耗。考虑到连续小推力机动的弧段效应,控制策略需要围绕控制效应的曲线积分进行优化。     

具有相乘非线性的马达速度鲁棒控制

变转速变排量联合控制是一种新型的容积控制,具有效率高和相对快的响应,但由于具有相乘的本质非线性,给控制带来一定的难度.针对变频调速变排量联合控制的泵控马达速度试验系统,建立了系统的数学模型,对存在的本质非线性问题,提出采用精确反馈线性化方法进行线性化处理,并设计了基于积分滑模面的马达速度滑模变结构控制器.由于系统参数多,各个参数是变化的且不易确定,造成常规的滑模变结构控制输出抖振现象严重,为降低输出抖振现象,提出采用自适应模糊滑模控制器进行改进,并对稳定性进行证明.最后对该控制方法的抗干扰性和正弦信号跟踪性进行了仿真试验,仿真结果验证了所设计的控制方法正确性.      

泵阀联合EHA效率设计仿真分析

分析了泵阀联合电动静液作动器(EHA,Electrical Hydraulic Actuator)效率的影响因素,提出了降低油源压力设计值以提高效率的方法.针对泵阀联合EHA的工作特点,在负载相同的条件下,对伺服阀和定量泵的输出流量、损耗流量变化、作动系统整体效率变化进行了分析,并分析了油源压力设计值变化对系统主要性能参数的影响.相对于常规阀控系统设计,在一定范围内降低油源压力设计值的方法可提高液压系统总效率,减少流量损耗引起的功率损耗.系统快速性提高,稳定性增强,抗扰动能力下降,因而系统效率设计要兼顾性能综合进行.以弹性负载为对象的作动系统仿真计算验证了设计方法的可行性.      

Task allocation strategies for cooperative task planning of multi-autonomous satellite constellation

In recent years, the application of imaging satellites has entered a completely new stage, with the new demands such as rapid response to emergency events, observation of large-scale regional targets and multivariate data fusion, the multi-autonomous satellite constellation has been proposed. This paper first designs the structure of multi-autonomous satellite constellation, and a centralized-distributed structure is proposed. This structure could improve the dynamic response capacity of the whole constellation. Then, this paper adds adapted filtering mechanism to single autonomous satellite online scheduling algorithm to enhance its performance. This article also pays more attention on task allocation strategies of the master satellite in constellation, and ten different task allocation strategies based on five dimensions are analyzed by simulation experiments. At last, this paper extracts several characteristic features of the regular observation targets and designs a selector based on support vector machine (SVM). This selector could select an appropriate strategy according to the features of each experiment scenario.     

Tightly combined GPS/Galileo RTK for short and long baselines: Model and performance analysis

To ensure the compatibility and interoperability with modernized GPS, Galileo satellites are capable of broadcasting navigation signals on carrier phase frequencies that overlap with GPS, i.e., GPS/Galileo L1-E1/L5-E5a. Moreover, the GPS/Galileo L2-E5b signals have different frequencies with wavelength differences smaller than 4.2?mm. Such overlapping and narrowly spaced signals between GPS and Galileo bring the opportunity to use the tightly combined double-differenced (DD) model for precise real-time kinematic (RTK) positioning, resulting in improved performance of ambiguity resolution and positioning with respect to the classical standard or loosely combined DD model. In this paper, we focus on the model and performance assessment of tightly combined GPS/Galileo L1-E1/L2-E5b/L5-E5a RTK for short and long baselines. We first investigate the tightly combined GPS/Galileo DD observational model for both short and long baselines with simultaneously considering the GPS/Galileo overlapping and non-overlapping frequencies. Particularly, we introduce a reparameterization approach to solve the rank deficiency that caused by the correlation between the DISB parameters and the DD ionospheric parameters for both overlapping and non-overlapping frequencies. Then we present performance assessment for the tightly combined GPS/Galileo RTK model with real-time estimation of the differential inter-system bias (DISB) parameters for short and long baselines in terms of ratio value, ambiguity dilution of precision (ADOP), ambiguity conditional number, decorrelation number, search count, empirical success rate, time-to-first-fix (TTFF), and positioning accuracy. Results from both static and kinematic experiments demonstrated that compared to the loosely combined model, the tightly combined model can deliver improved performance of ambiguity resolution and precise positioning with different satellite visibility. For the car-driven short baseline experiment with 10° elevation cut-off angle, the tightly combined model can not only significantly increase the ratio value by approximately 27.5% (from 16.0 to 20.4), but also reduce the ambiguity ADOP, the conditional number, and the search count in LAMBDA by approximately 22.2% (from 0.027 to 0.021 cycles), 14.9% (from 199.2 to 169.6), and 25.4% (from 150.1 to 112.0), respectively. Comparable decorrelation number, empirical success rate, and positioning accuracy are also obtained. For the car-driven long baseline experiment, it is also observed that the ambiguity resolution performance in terms of the ratio value, the decorrelation number, the condition number, and the search count are significantly improved by approximately 18.5% (from 2.7 to 3.2), 22.0% (from 0.186 to 0.227), 55.9% (from 937.6 to 413.7), and 10.3% (from 43.8 to 39.3), respectively. Moreover, comparable ADOP, empirical success rate, and positioning accuracy are obtained as well. Additionally, the TTFF can be reduced (from 54.1 to 51.8 epochs with 10° elevation cut-off angle) as well from the results of static experiments.     

基于缓解HoL堵塞的单组播混合调度算法

针对联合输入交叉队列（CICQ）结构的单组播混合调度研究不多,且没有针对性研究头分组（HoL）堵塞问题,提出了以缓解HoL堵塞为目标的一种新的单组播混合调度算法,即单组播低HoL堵塞（MULHB）算法,使交换机尽量逼近work-conserving状态。该算法还充分考虑了单组播之间的差异性,利用权重裁决单组播之间的竞争,避免"饿死"现象发生。同时,还给出了一种新的组播分组入队算法,即动态组播分组入队（DMQ）策略,该策略在不乱序的前提下,允许新到达分组选择合适的队列入队。仿真结果表明,在不同业务下,DMQ-MULHB算法的通过率及平均时延均优于现有主流的单组播混合调度算法,尤其在非均匀业务下,该算法性能接近输出排队（OQ）调度。      

Walker-δ星座星间链路的预算分析与仿真

为确定星间链路其他传输耗损以及合理发射功率,首先,在方位角、俯仰角的变化范围较小,平均距离较小和距离变化范围较小的情况下,给出Walker-δ星座星间链路的建立准则。然后,详细讨论星座星间链路的预算分析和自由空间传输耗损及其他传输耗损,并给出这些传输耗损的参考值或求解公式;特别是提出以数据传输速率的数学期望等于额定数据传输速率为条件来确定合理发射功率的方法,并推导数据传输速率方差的计算公式。最后,在仿真算例中,分析Walker 27/3/1星座中星间链路的方位角、俯仰角和距离的变化范围,讨论不同载波频率和不同数据传输速率对星间链路发射功率的影响,并给出了合理的发射功率。     

月球天梯力学特性研究

月球天梯的构型对其力学特性和质量特性起决定性作用,直接关系到天梯建造材料的选取。目前对月球天梯的研究集中在组合横截面积构型上,未对其他构型天梯的特性展开深入研究。针对这一问题,文章进行了不同构型月球天梯的力学特性研究。建立了月球天梯动力学模型,分别将天梯缆绳线密度和应力作为常值,推导了等横截面积和变横截面积两种新构型月球天梯的动力学方程和质量特性方程,进行了不同构型天梯关键特性参数的计算和对比分析。研究结果表明,变横截面积天梯可将最大应力设计为任意恒定值,降低了对材料极限应力的要求,其总质量小于等横截面积和组合横截面积天梯,为最优构型方案。     

串联式TBCC进气道模态转换模拟器设计及其特性分析

为了实现涡轮基组合循环（TBCC）推进系统平稳模态转换过程的模拟,在前期风洞试验研究的基础上对串联式TBCC进气道模态转换模拟器进行重新设计。采用线性化及非对称的思路对该模拟器进行设计并对其特性展开数值仿真研究。结果表明：该模拟器不仅需要模拟发动机工况改变引起的背压变化,而且能通过流通截面面积线性变化,实现两个通道的流量分配。该装置的特点是能保证模态转换过程中每一点的涡轮/冲压通道的总堵塞比不变,使本文所研究的进气道在总堵塞比保持为65%时进行模态转换,结尾激波基本维持在喉道等直段内且进气道出口马赫数基本维持在0.30,流量系数基本为0.45,涡轮/冲压通道流量呈线性变化,与预期目标一致。     

间冷对燃气轮机燃烧室性能的影响

间冷循环可使燃气轮机功率提高且耗油率降低,但由于间冷的介入,燃烧室的喷油量和容热负荷会大幅增加,这必然导致燃烧室性能的恶化。采用数值模拟的方法,对比研究了在标准工况和间冷后增容工况下燃烧室冷态流场和燃烧性能的差异,并提出组合涡诱导结构以解决间冷给燃烧室带来的问题。结果表明:间冷后压力损失增加了135%,燃烧后高温区偏心严重,燃烧效率、出口温度分布系数等明显降低;使用组合涡诱导控制结构后燃烧效率可提高1.6%,且出口温度分布改善明显。