旋转电动帆推进性能指标分析

电动太阳风帆(简称电动帆,E-sail)是一种新兴的利用太阳风动能产生冲力,实现无工质消耗的空间推进技术.本文考虑由两颗微小卫星通过导线连接构成的电动帆系统,关注传统电动帆推力模型研究中忽略的电动帆姿态对推力的影响,采用旋转电动帆"哑铃"模型假设进行动力学建模.最后,针对日心非开普勒轨道环境开展算例仿真,计入太阳风库仑力摄动的影响,分析电动帆的推进性能指标.仿真结果表明,电动帆推进效率主要由导线长度、导线电势、卫星质量和相对于飞行方向的俯仰角决定.     

太阳帆航天器展开机构柔性动力学建模

研究了大型太阳帆航天器展开机构的柔性动力学建模问题。首先对结合模态综合法和混合坐标法介绍了太阳帆展开机构柔性动力学一般模型建立过程。根据工程需要对展开机构进行模态分析,给出了工程实用的各耦合系数的计算表达式,并计算出各耦合系数。     

电动帆改进推力模型及深空探测性能分析

电动太阳风帆(简称电动帆)是一种利用太阳风动能冲力飞行的新兴无质损飞行器.针对电动帆传统推力模型中忽略了姿态对推力幅值影响的问题,本文推导得出了一种解析形式的改进推力模型,并与最新的多项式拟合改进推力模型进行了对比.对比结果显示两种改进推力模型数值结果很接近,但本文的解析改进推力模型形式更简单.为了重新评估电动帆在深空探测中的性能,以地球至火星的飞行任务为算例,分别采用传统推力模型和解析改进推力模型进行了电动帆轨迹优化仿真.仿真结果显示,在相同特征加速度情况下,采用改进解析推力模型完成任务所需时间,大于采用传统推力模型所用时间.上述现象的原因在于传统推力模型中忽略了姿态改变对推力加速度大小的影响,并高估了电动帆所能产生的最大推进角.     

可重复使用航天器时间协同飞行轨迹优化

针对可重复使用航天器(RLV)时间协同飞行轨迹优化问题,提出了一种基于Radau伪谱法的轨迹优化方法。方法以再入飞行时间可知性、可控性为目标,使用Radau伪谱法对RLV的飞行时间进行预测,进而协调出多RLV的再入协同飞行时间,以此再入飞行时间为终端约束使用Radau伪谱法生成满足协同飞行要求的再入轨迹。仿真结果表明,上述轨迹优化方法可以得到满足时间协同约束、状态约束和控制约束的飞行轨迹,具有较高的稳定性和较快的求解速度。所提方法满足多架RLV时间协同再入飞行的需求,具有很强的实用价值。     

关于PSO方法中粒子运行轨迹的修正

粒子群优化方法（PSO Particle Swarm Optimization）由Kennedy和Eberhart于1995年提出,基于群体智能行为的演化计算方法,并广泛应用于各类优化问题.在一些研究中,对PSO的粒子收敛性及粒子运行轨迹进行了分析,有一定理论价值和指导意义,本文针对一些分析过程中存在的问题进行了讨论,并对相关结论进行了修正.     

Optimal 4-D Aircraft Trajectories in a Contrail-sensitive Environment

Aircraft induced contrails present an important source and a growing concern for climate change in aviation. This paper develops a methodology to determine optimal flight trajectories that minimize the total flying cost in a dynamic, contrail-sensitive environment. The total flying costs consist of costs due to fuel burn, crew, passenger travel time, CO₂ emission, and contrail formation. By constructing a multi-layer hexagonal grid structure to represent the airspace, we formulate the single aircraft trajectory optimization problem as a binary integer program that allows for flight altitude and heading adjustment, and contrail information update. Various cost factors are quantified, in particular the one corresponding to aviation-generated contrails, using the Global Warming Potential concept. Computational analyses show that optimal trajectories depend critically upon the time horizon choice for calculating the CO₂ climate impact. Shifting flights to periods with low contrail effect is not justified, given the limited benefit but potentially large passenger schedule delay cost increase. The analyses are further extended to determining the optimal trajectories for multiple flights using a successive optimization procedure.     

A novel particle swarm optimization algorithm with Levy flight

Particle swarm optimization (PSO) is one of the well-known population-based techniques used in global optimization and many engineering problems. Despite its simplicity and efficiency, the PSO has problems as being trapped in local minima due to premature convergence and weakness of global search capability. To overcome these disadvantages, the PSO is combined with Levy flight in this study. Levy flight is a random walk determining stepsize using Levy distribution. Being used Levy flight, a more efficient search takes place in the search space thanks to the long jumps to be made by the particles. In the proposed method, a limit value is defined for each particle, and if the particles could not improve self-solutions at the end of current iteration, this limit is increased. If the limit value determined is exceeded by a particle, the particle is redistributed in the search space with Levy flight method. To get rid of local minima and improve global search capability are ensured via this distribution in the basic PSO. The performance and accuracy of the proposed method called as Levy flight particle swarm optimization (LFPSO) are examined on well-known unimodal and multimodal benchmark functions. Experimental results show that the LFPSO is clearly seen to be more successful than one of the state-of-the-art PSO (SPSO) and the other PSO variants in terms of solution quality and robustness. The results are also statistically compared, and a significant difference is observed between the SPSO and the LFPSO methods. Furthermore, the results of proposed method are also compared with the results of well-known and recent population-based optimization methods.     

深空探测柔性太阳帆航天器动力学建模与姿态控制

太阳帆利用太阳辐射压力提供太空航行的必要动力,由于具有理论上的无限速度和无需消耗任何燃料等优势,被认为是完成未来深空探测任务的有效技术途径之一.柔性太阳帆航天器的动力学模型包括多体动力学、刚柔耦合动力学和太阳辐射光压模型,复杂的动力学特性导致其姿态控制设计具有很强的挑战性.针对带有控制杆的柔性太阳帆航天器,本文采用拉格朗日方程和有限元法,给出了面向控制的解析式动力学模型.所推导的刚柔耦合动力学模型,刻画了太阳帆航天器的本质动力学特性,即双框架控制杆的短周期运动,姿态与柔性太阳帆的耦合效应,以及在太阳光压恢复力矩下的姿态静稳定性和长周期运动.基于带控制杆的太阳帆航天器的双时间尺度特性,提出了双回路控制结构,用于实现航天器俯仰轴和偏航轴的姿态控制.将内回路设计为PD控制器,用于实现质心位置的调整.将外回路设计为PID控制器,用于阻尼姿态运动,并实现在平衡太阳光压力矩下的姿态保持.从而将柔性太阳帆航天器的复杂姿态控制问题转化为两个低阶子问题,实现了在不同频带上的控制设计.仿真结果验证了动力学建模和姿态控制设计方法的有效性.     

Optimal transition maneuvers for a class of V/STOL aircraft

This paper focuses on the problem of computing optimal transition maneuvers for a particular class of tail-sitter aircraft able to switch their flight configuration from hover to level flight and vice versa. Both minimum-time and minimum-energy optimal transition problems are formulated and solved numerically in order to compute reference maneuvers to be employed by the onboard flight control system to change the current flight condition. In order to guide the numerical computation and to validate its results, in a first stage approximated solutions are obtained as a combination of a finite number of motion primitives corresponding to analytical trajectories of approximated dynamic models. The approximated solution is then employed to generate an initial guess for the numerical computation applied to a more accurate dynamic model. Numerical trajectories computed for a small scale prototype of tail-sitter aircraft are finally presented, showing the effectiveness of the proposed methodology to deal with the complex dynamics governing this kind of systems.     

Flexibility analysis of a tracking control method for air-breathing hypersonic vehicles

This paper studies the flexibility of a tracking control method originally proposed by the authors for air-breathing hypersonic vehicles （AHVs）. The main feature of this method is to design the tracking controller without canceling but using aero-propulsive, as well as elevator-to-lift couplings. By introducing a virtual input, the tracking controller and external reference trajectories are simultaneously obtained by solving a system of linear algebraic equations. This system of linear algebraic equations is always solvable and the solution space of the corresponding homogeneous system is of dimension 3, which leads to much freedom in choosing or defining the free variables. The flexibility is reflected by the fact that the flight requirements of AHVs are involved in the definition of the free variables. Three case studies on different maneuvers, i.e., flight at constant dynamic pressure, flight at variant dynamic pressure and flight with fast climb rate are considered to verify the flexibility of this method. Simulation results show its effectiveness and flexibility.     

飞行航迹再现与三维回放研究

为了便于飞行事后分析,根据民用客机机载数据,本文采用了轨迹积分法重现飞行轨迹并用经纬度转换法进行校正,首次利用几何高度表示飞行轨迹中的高度。为实现在三维场景中进行飞行动态回放研究,设计了三维飞行回放程序,重点设计了飞行轨迹以及姿态的变化在三维场景中的展示。通过程序演示表明:该方法能正确流畅地对飞行进行事后回放演练,有利于观察分析,可用于飞行事后调查与研究。     

Trajectory adjustment for nonprehensile manipulation using latent space of trained sequence-to-sequence model*

When robots are used to manipulate objects in various ways, they often have to consider the dynamic constraint. Machine learning is a good candidate for such complex trajectory planning problems. However, it sometimes does not satisfy the task objectives due to a change in the objective or a lack of guarantee that the objective functions will be satisfied. To overcome this issue, we applied a method of trajectory deformation by using sequence-to-sequence (seq2seq) models. We propose a method of adjusting the generated trajectories, by utilizing the architecture of seq2seq models. The proposed method optimizes the latent variables of the seq2seq models instead of the trajectories to minimize the given objective functions. The verification results show that the use of latent variables can obtain the desired trajectories faster than direct optimization of the trajectories.     

飞机飞行控制多目标优化研究

针对飞行控制系统单目标优化算法与飞行品质要求之间缺乏相关性,且物理意义不明确的缺点,提出了一种基于C*准则的模型参考飞行控制设计多目标优化方法。首先,使用飞行品质建立参考模型,保证所建立的参考模型符合期望飞行品质的要求。然后,通过模型跟随的方法,将飞行品质的要求引入多目标优化中,使得整个优化设计过程物理意义更加明确。最后,使用多目标NSGA-II对某型飞机纵向控制律设计进行数值仿真,结果显示提出的方法可以有效地提高控制器参数整定效率,整定结果满足期望的飞行品质要求。     

Coupled Orbit-attitude Saturated Control for Solar Sail in Earth-Moon 3-body System

This paper aims to investigate a coupled orbit-attitude control strategy for a kind of novel spacecraft, solar sail, to track the given orbit in Earth-Moon 3-Body dynamic environment in presence of the matched and mismatched disturbances, attitude control saturation, orbital modeling error and parametric uncertainties. A cascaded triple-loop control structure is proposed to deal with the strong couplings between the orbit and attitude systems. The inner loop focusing on the orbital effects on attitude dynamics, an adaptive saturation controller is proposed to achieve attitude angular tracking, where the uncertain inertia, unknown matched disturbance and saturated attitude control torque are compensated by combining the unknown knowledge. The middle loop is to handle the orbit effects on attitude kinematics facing the mismatched disturbance. In the outer loop, the effects of attitude system on orbit dynamics are deal with, where an adaptive orbit controller is designed considering the uncertain optical parameter and orbital modeling error. The proposed control structure efficiently simplifies the coupled orbit-attitude control design for solar sail. In contrast to traditional coupled controllers for solar sail, the proposed control laws do not require exact knowledge of parametric uncertainties, disturbances and orbit modeling errors. The combination of unknown information reduces the number of estimated parameters as well. The numerical simulation results demonstrate the effectiveness of the proposed control strategy.

     

Multiobjective optimization–based fault‐tolerant flight control system design

The loss of measurements used for controller scheduling or envelope protection in modern flight control systems due to sensor failures leads to a challenging fault‐tolerant control law design problem. In this article, an approach to design such a robust fault‐tolerant control system, including full envelope protections using multiobjective optimization techniques, is proposed. The generic controller design and controller verification problems are derived and solved using novel multiobjective hybrid genetic optimization algorithms. These algorithms combine the multiobjective genetic search strategy with local, single‐objective optimization to improve convergence speed. The proposed strategies are applied to the design of a fault‐tolerant flight control system for a modern civil aircraft. The results of an industrial controller verification and validation campaign using an industrial benchmark simulator are reported.     

基于Adams的太阳帆展开绳索的建模与仿真

在太阳帆旋转展开过程中,依靠端部系有质量球的对角线绳索的离心力展开方形帆面,绳索与中心毂轮法向方向会产生夹角.利用Adams建模仿真技术成功建立太阳帆展开绳索模型,并对太阳帆绳索展开进行仿真分析,得出绳索与中心毂轮法向的夹角与毂轮相对转速的关系,为太阳帆的结构设计与模拟试验提供参考.     

基于神经网络的飞参数据特征选择方法

针对飞参数据中存在的大量冗余和不相关,提出了一种基于神经网络的飞参数据特征选择方法.为克服传统算法收敛速度慢、易陷入局部极小等缺陷,神经网络的训练采用粒子群优化算法和Levenberg-Marquardt优化算法相结合的方式.神经网络训练结束后,先利用网络权值信息对飞参数据特征的相对重要度进行排序,然后根据重要度次序对飞参数据特征进行选择.实验结果表明该方法能快速有效地删除冗余飞参数据特征,同时提高网络的泛化能力.     

Minimum-time B-spline trajectories with corridor constraints. Application to cinematographic quadrotor flight plans

This paper proposes a novel strategy for completing a flight plan with a quadrotor UAV, in the context of aerial video making. The flight plan includes different types of waypoints to join, while respecting flight corridors and bounds on the derivatives of the position of the quadrotor. To this aim, non-uniform clamped B-splines are used to parameterize the trajectory. The latter is computed in order to minimize its overall duration, while ensuring the validation of the waypoints, satisfying the flight corridors and respecting the maximum magnitude on its derivatives. A receding waypoint horizon is used in order to split the optimization problem into smaller ones, which reduces the computation load when generating pieces of trajectories. The effectiveness of the proposed trajectory generation technique is demonstrated by simulation and through an outdoor flight experiment on a quadrotor.     

基于解析控制律的太阳帆星际转移轨道控制

太阳帆航天器可依靠反射太阳光子提供动力,因此较适用于远距离的星际转移任务.针对太阳帆航天器星际转移轨道控制问题,提出一种新的解析最优控制律,通过设定混合权重对各轨道根数进行联合控制.引入改进春分点轨道根数对解析控制律进行了优化推导,并以水星探测任务为背景进行了相应的仿真分析.仿真结果表明,该控制律计算速度较快,可对各个轨道根数进行联合控制,从而得到满足工程要求的太阳帆航天器星际转移轨道.     

Enhanced parallel cat swarm optimization based on the Taguchi method

In this paper, we present an enhanced parallel cat swarm optimization (EPCSO) method for solving numerical optimization problems. The parallel cat swarm optimization (PCSO) method is an optimization algorithm designed to solve numerical optimization problems under the conditions of a small population size and a few iteration numbers. The Taguchi method is widely used in the industry for optimizing the product and the process conditions. By adopting the Taguchi method into the tracing mode process of the PCSO method, we propose the EPCSO method with better accuracy and less computational time. In this paper, five test functions are used to evaluate the accuracy of the proposed EPCSO method. The experimental results show that the proposed EPCSO method gets higher accuracies than the existing PSO-based methods and requires less computational time than the PCSO method. We also apply the proposed method to solve the aircraft schedule recovery problem. The experimental results show that the proposed EPCSO method can provide the optimum recovered aircraft schedule in a very short time. The proposed EPCSO method gets the same recovery schedule having the same total delay time, the same delayed flight numbers and the same number of long delay flights as the Liu, Chen, and Chou method (2009). The optimal solutions can be found by the proposed EPCSO method in a very short time.