Adaptive accurate tracking control of HFVs in the presence of dead-zone and hysteresis input nonlinearities

A novel accurate tracking controller is developed for the longitudinal dynamics of Hypersonic Flight Vehicles (HFVs) in the presence of large model uncertainties, external disturbances and actuator nonlinearities. Distinct from the state-of-the-art, besides being continuity, no restrictive conditions have been imposed on the HFVs dynamics. The system uncertainties are skillfully handled by being seen as bounded “disturbance terms”. In addition, by means of back-stepping adaptive technique, the accurate tracking (i.e. tracking errors converge to zero as time approaches infinity) rather than bounded tracking (i.e. tracking errors converge to residual sets) has been achieved. What’s more, the accurate tracking problems for HFVs subject to actuator dead-zone and hysteresis are discussed, respectively. Then, all signals of closed-loop system are verified to be Semi-Global Uniformly Ultimate Boundness (SGUUB). Finally, the efficacy and superiority of the developed control strategy are confirmed by simulation results.     

基于跟踪微分器的高超声速飞行器Backstepping控制

针对存在模型参数不确定和外部干扰的高超声速飞行器（HFV）跟踪控制问题,提出一种基于Backstepping方法的抗饱和非线性控制器。将飞行器纵向动力学模型分为速度子系统和航迹倾角子系统,然后针对每个子系统单独设计控制器。设计跟踪微分器获得信号的一阶导数,用以估计系统中的不确定干扰项和避免"微分项膨胀"问题。控制器设计过程考虑了控制量发生饱和的情况。基于Lyapunov理论证明了闭环系统信号的稳定性。与传统高超声速飞行器Backstepping方法相比,所设计的控制器采用待跟踪状态与理想控制指令之间的实际误差作为反馈量,放宽了对系统干扰项的限制,提高了控制器对控制增益变化的适应性,进而提高了闭环系统的跟踪控制性能。对比仿真结果验证了所设计方法的有效性。     

某支线飞机概念设计阶段机翼气动弹性设计

在飞机的总体方案概念设计阶段,需要对飞机机翼进行气动弹性设计,以避免在后期设计中,因气动弹性问题而对设计方案进行较大更改.以某支线飞机的总体方案论证为背景,研究并归纳该飞机概念设计阶段气动弹性设计与分析的理论基础和计算方法,建立机翼的梁架式模型,初步设计模型刚度与质量分布,并进行机翼的静气动弹性响应与载荷分析、振动特性及颤振特性分析.结果表明:该支线飞机机翼的气动弹性特性合理,符合设计要求.     

具有轨道倾角和最大高度约束的耗尽关机闭路制导

快速响应空间固体运载火箭轨道转移级以最大限度利用能量而非消耗能量为目的进行耗尽关机制导,基于椭圆轨道理论和牛顿迭代法,提出了一种适用于具有轨道、制导多种约束的耗尽关机闭路制导方法,通过实时寻找需要推力方向,充分利用轨道转移级能量,导引上面级进入具有给定轨道倾角和最大高度约束的转移轨道,同时实现耗尽关机.理论推导和数学仿真表明,本文提出的制导方法能在耗尽关机条件下实现对转移轨道的高精度控制.     

Analysis on Potential Conflict Frequency of Intersected Air Routes in Terminal Airspace Design

In order to obtain accurate conflict risks in terminal airspace design, the concept and calculation model of potential conflict frequency for intersected routes are proposed. Conflict frequency is represented by the product of horizontal conflict frequency and vertical conflict probability. The horizontal conflict frequency is derived from the probability density distribution of conflicts in a period of time. Based on the recorded radar trajectory data, the concept and model of ROUTE distance are proposed, and the probability density function of aircraft height at a specified ROUTE distance is deduced by kernel density estimation. Furthermore, vertical conflict probability and its horizontal distribution are achieved. Examples of three intersected arrival and departure route design schemes are studied. Compared with scheme 1, the conflict frequency values of the other two improved schemes decrease to 53 % and 24%, respectively. The results show that the model can quantify potential conflict frequency of intersec ted routes.     

校企一体办学模式下学生职业意识培养研究——以湖南民族职业学院旅游管理专业人才培养为例

面对旅游人才日益明显的供需矛盾和学生职业意识淡薄的现状,高职院校旅游管理专业学生职业意识的培养日益受到重视。依托湖南民族职业学院的光大公司和华夏民族文化风情园,开展校企一体办学模式下以＂双师双能＂的师资建设为龙头,以＂体验式·参与式＂的实践教学体系建设为核心,以融入职业核心能力和企业文化的校本实训教材开发为载体的高职旅游管理专业人才职业意识培养模式的新探索。     

我国通用航空应急管理体系构建

低空空域开放是助力我国通用航空迅速发展的重大战略性举措,同时将对通用航空在作业过程中的应急管理带来挑战。文章给出通用航空突发事件的定义,对引起通用航空突发事件的致灾因素从通用航空器、通用航空作业环境、通用航空服务保障情况做一分析。阐述了通用航空应急管理的定义。最后提出了基于应急管理平台的通用航空应急管理体系。     

Optimization of geosynchronous satellite constellation for independent regional navigation and positioning in Middle East region

Regional Navigation and positioning systems using geosynchronous satellites are emerging for different parts of the world. Optimal constellation geometry achievement for a set of geosynchronous satellites is a key sector in designing of such systems. Genetic algorithm is applied for optimization of constellations with 6 and 7 satellites which is to be used in Middle East region where these systems have been deprived of. Based on the fact that the coverage criterion is not sufficient enough to guarantee a good navigation service, positioning process by the satellite systems is discussed and the performance of the system on the basis of position dilution of precision is collected as the fitness criterion. Placing the satellites in groups to pass over the same ground track is applied as a constraint to the genetic algorithm. By simulation, performance of the best obtained results and GPS are compared in terms of position dilution of precision, visibility and the required epochs (time span) to resolve the ambiguities with a 99% success rate, in this region. Also, capability of the GA for such problems is demonstrated.     

Closed-loop distance-keeping for long-term satellite cluster flight

Cluster flight is a term used for describing multiple satellites that are being held within pre-defined minimum and maximum distances for long time intervals, possibly the entire mission. This technology is required for a myriad of space architectures and missions, including disaggregated space architectures. Whereas the literature is abundant with works on control laws for satellite formation flying, there are only a handful of works on control of cluster flight. The purpose of the current work is to develop a cluster flight control algorithm, which is able to keep the satellites of the cluster within pre-specified minimum and maximum distances, while utilizing small amounts of propellant. The newly developed algorithm relies on the natural inter-satellite distance dynamics. The algorithm incorporates realistic mission constraints, such as constant-magnitude thrust, and is implemented in feedback form, steering the mean elements to judiciously selected reference values. Simulations indicate that a few tens of grams of propellent are sufficient for operating a cluster flight mission in excess of 1 year, using low specific-impulse thrusters.