面向小型舰船的固定翼无人机海上回收方法综述

随着现代海战向立体化、多层次的发展,舰/船载无人机着舰技术得到广泛的研究与应用.为研究舰/船载无人机着舰技术的发展现状及其亟需解决的关键技术难题,对目前该领域的文献进行了分析与总结.无人机着舰技术是指无人机借助舰/船及机载导引系统,以飞行控制系统为依托,按照着舰/船流程,通过舰/船及无人机拦阻装备实现满足精度要求的着舰技术.首先,概述了固定翼无人机在小型舰/船上回收技术发展历程,比较分析各种回收技术的优缺点.其次,重点阐述“飞行中制动回收”和“定点高精度回收”方式的关键技术;最后,总结了固定翼无人机小型舰船着陆技术的发展过程中亟需解决的关键技术难题,包括无人机导航系统、控制系统等技术.研究表明,舰/船载无人机着舰技术研究尚未形成成熟的解决方案,仍有许多技术难题亟需解决.本研究为中国固定翼无人机海上回收系统的方案设计提供参考.

自适应交配限制概率的自组织多目标演化算法

为平衡多目标演化算法求解不同优化问题以及求解同一优化问题时不同搜索阶段的勘探与开采能力,并考虑到减小聚类算法辅助演化算法时产生的计算开销,提出了一种基于自适应交配限制概率的自组织多目标演化算法(adaptive mating restriction probability based self-organizing multiobjective evolutionary algorithm,ASMEA).首先,ASMEA在每一代利用自组织映射(self-organizing map,SOM)算法建立了演化种群个体间的邻居关系,基于此关系有利于算子实施恰当的重组操作,并在演化算法后期产生优质解,与此同时,为了节省利用SOM建立当前种群个体之间的邻居关系时引起的计算开销,将SOM与演化算法相融合,交替地进行SOM训练与种群演化.然后,运用交配限制概率控制交配父代来源于SOM发现的邻居种群或者是整个种群,以分别加强开采和勘探.最后,根据采用不同父代来源的重组在过去一定代数产生后代个体的效用,自适应地调整算法的交配限制概率.利用ASMEA和5种具有代表性的多目标演化算法对标准测试题进行求解,求解结果表明:ASMEA在搜索质量、搜索效率以及可视化方面优于其他5种算法,从而验证了ASMEA算法对多目标优化问题具有良好的求解性能.

气管插管患者咳嗽力度评估方法及应用研究进展

咳嗽力度评估对气管插管患者拔管成功与否具有预测作用,咳嗽力度评估工具包括咳嗽峰流速、白卡试验、半定量咳嗽强度评分、膈肌活动度的超声评估及气管插管气囊压力变化评估。临床护士可选择合适的咳嗽力度评估方法预测气管插管患者的拔管结局,为拔管时机的选择提供参考依据。

Fractional order nonsingular terminal sliding mode control for flexible spacecraft attitude tracking

This paper investigates a fractional terminal sliding mode control for flexible spacecraft attitude tracking in the presence of inertia uncertainties and external disturbances. The controller is based on the fractional calculus and nonsingular terminal sliding mode control technique,and it guarantees the convergence of attitude tracking error in finite time rather than in the asymptotic sense. With respect to the controller,a fractional order sliding surface is given,the corresponding control scheme is proposed based on Lyapunov stability theory to guarantee the sliding condition,and the finite time stability of the whole close loop system is also proven. Finally,numerical simulations are presented to illustrate the performance of the proposed scheme.

Three-dimensional guidance law based on adaptive integral sliding mode control

For the terminal guidance problem of missiles intercepting maneuvering targets in the three-dimensional space, the design of guidance laws for non-decoupling three-dimensional engage- ment geometry is studied. Firstly, by introducing a finite time integral sliding mode manifold, a novel guidance law based on the integral sliding mode control is presented with the target acceler- ation as a known bounded external disturbance. Then, an improved adaptive guidance law based on the integral sliding mode control without the information of the upper bound on the target accel- eration is developed, where the upper bound of the target acceleration is estimated online by a designed adaptive law. The both presented guidance laws can make sure that the elevation angular rate of the line-of-sight and the azimuth angular rate of the line-of-sight converge to zero in finite time. In the end, the results of the guidance performance for the proposed guidance laws are pre- sented by numerical simulations. Although the designed guidance laws are developed for the con- stant speed missiles, the simulation results for the time-varying speed missiles are also shown to further confirm the designed guidance laws.

Adaptive finite-time backstepping control for attitude tracking of spacecraft based on rotation matrix

This paper investigates two finite-time controllers for attitude control of spacecraft based on rotation matrix by an adaptive backstepping method. Rotation matrix can overcome the draw- backs of unwinding which makes a spacecraft perform a large-angle maneuver when a small-angle maneuver in the opposite rotational direction is sufficient to achieve the objective, With the use of adaptive control, the first robust finite-time controller is continuous without a chattering phenom- enon. The second robust finite-time controller can compensate external disturbances with unknown bounds. Theoretical analysis shows that both controllers can make a spacecraft following a time-varying reference attitude signal in finite time and guarantee the stability of the overall closed-loop system. Numerical simulations are presented to demonstrate the effectiveness of the proposed control schemes.

Autonomous attitude coordinated control for spacecraft formation with input constraint,model uncertainties, and external disturbances

To synchronize the attitude of a spacecraft formation flying system, three novel autonomous control schemes are proposed to deal with the issue in this paper. The first one is an ideal autonomous attitude coordinated controller, which is applied to address the case with certain models and no disturbance. The second one is a robust adaptive attitude coordinated controller, which aims to tackle the case with external disturbances and model uncertainties. The last one is a filtered robust adaptive attitude coordinated controller, which is used to overcome the case with input con- straint, model uncertainties, and external disturbances. The above three controllers do not need any external tracking signal and only require angular velocity and relative orientation between a spacecraft and its neighbors. Besides, the relative information is represented in the body frame of each spacecraft. The controllers are proved to be able to result in asymptotical stability almost everywhere. Numerical simulation results show that the proposed three approaches are effective for attitude coordination in a spacecraft formation flying system.

Decentralized attitude synchronization tracking control for multiple spacecraft under directed communication topology

This paper studies the attitude synchronization tracking control of spacecraft formation flying with a directed communication topology and presents three different controllers. By introducing a novel error variable associated with rotation matrix, a decentralized attitude synchronization controller, which could obtain almost global asymptotical stability of the closed-loop system, is developed. Then, considering model uncertainties and unknown external disturbances, we propose a robust adaptive attitude synchronization controller by designing adaptive laws to estimate the unknown parameters. After that, the third controller is proposed by extending this method to the case of time-varying communication delays via Lyapunov-Krasovskii analysis. The distinctive feature of this work is to address attitude coordinated control with model uncertainties, unknown disturbances and time-varying delays in a decentralized framework, with a strongly connected directed information flow. It is shown that tracking and synchronization of an arbitrary desired attitude can be achieved when the stability condition is satisfied. Simulation results are provided to demonstrate the effectiveness of the proposed control schemes. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license.

Relative dynamics estimation of non-cooperative spacecraft with unknown orbit elements and inertial tensor

The state estimation for relative motion with respect to non-cooperative spacecraft in ren- dezvous and docking （RVD） is a challenging problem. In this paper, a completely non-cooperative case is considered, which means that both orbit elements and inertial tensor of target spacecraft are unknown. By formulating the equations of relative translational dynamics in the orbital plane of chaser spacecraft, the issue of unknown orbit elements is solved. And for the problem for unknown inertial tensor, we propose a novel robust estimator named interaction cubature Kalman filter （InCKF） to handle it. The novel filter consists of multiple concurrent CKFs interlacing with a max- imum a posteriori （MAP） estimator. The initial estimations provided by the multiple CKFs are used in a Bayesian framework to form description of posteriori probability about inertial tensor and the MAP estimator is applied to giving the optimal estimation. By exploiting special property of spherical-radial （SR） rule, a novel method with respect to approximating the likelihood probability of inertial tensor is presented. In addition, the issue about vision sensor＇s location inconformity with center mass of chaser spacecraft is also considered. The performance of this filter is demonstrated by the estimation problem of RVD at the final phase. And the simulation results show that the perfor- mance of InCKF is better than that of extended Kalman filter （EKF） and the estimation accuracy of oose and attitude is relatively high even in the comoletely non-coooerative case.

Robust Chattering-Free Finite Time Attitude Tracking Control with Input Saturation

This paper addresses the attitude tracking control problem of a rigid spacecraft in the presence of the modeling uncertainty,external disturbance,and saturated control input by designing two robust att计ude tracking controllers.The basic controller is formulated using an integral sliding mode surface which is continuous and provides an asymptotic convergence rate for the closed-loop system.In this case,only the external disturbance with the prior information is considered.Then,to provide a finite time convergence rate and further improve the robustness of the control system under the unknown system uncertainty containing both the modeling uncertainty and external disturbance,a novel integral terminal sliding mode surface(ITSMS)is designed and associated w计h the continuous adaptive control method.Besides,a command filter is utilized to deal with the immeasurability problem within the proposed ITSMS and an auxiliary system to counteract the input saturation problem.Digital simulations are presented to verify the effectiveness of the proposed controllers.