Adaptive fuzzy neural network control for a space manipulator in the presence of output constraints and input nonlinearities

Space manipulator is considered as one of the most promising technologies for future space activities owing to its important role in various on-orbit serving missions. In this paper, a novel adaptive fuzzy neural network (FNN) control scheme is proposed for the trajectory tracking control of an attitude-controlled free-flying space manipulator in the presence of output constraints and input nonlinearities. The parametric uncertainties and external disturbances are also taken into the consideration. First, a model-based controller is designed by using the barrier Lyapunov function (BLF) to prevent the position tracking errors from violating the predefined output constraints. Then, an adaptive FNN controller is designed by using two FNNs to compensate for the lumped uncertainties and input nonlinearities, respectively. Rigorous theoretical analysis for the semiglobal uniform ultimate boundedness of the whole closed-loop system is provided. The proposed adaptive FNN controller can guarantee the position and velocity tracking errors converge to the small neighborhoods about zero, while ensuring the position tracking errors within the output constraints even in the presence of input nonlinearities. To the best of the authors’ knowledge, there are relatively few existing controllers can achieve such excellent control performance in the same conditions. Numerical simulations illustrate the effectiveness and superiority of the proposed control scheme.     

Constrained adaptive fault-tolerant attitude tracking control of rigid spacecraft

A saturated fault-tolerant attitude tracking controller for disturbed rigid spacecraft is derived using nonlinear state feedback control method. The proposed controller achieves the constraints of control inputs by directly using the bounded function instead of the traditional saturation compensator technique, and the active tolerance to the partial loss of actuator effectiveness is also achieved by directly using the known bounds of the actuator faults in the controller. Specifically, compared with the traditional saturated control methods, a continuously bounded nonlinear function in the proposed controller is used to guarantee that the actuator outputs are smoothly bounded under the prescribed constraints. Based on some properties of the attitude tracking dynamics, the proposed controller can ensure the attitude tracking errors converge to small neighborhoods of zero via stability analysis in the Lyapunov framework. Simulation results are presented to illustrate the effectiveness of the control scheme.     

直-X直升机旋翼动平衡检查调整方法研究

通过对几十架直-X直升机旋翼动平衡检查调整的总结,结合维护手册和实际经验,提出了该型直升机旋翼动平衡检查调整方法,并在实际应用中取得了很好的效果.     

MCMC-Particle-based group tracking of space objects within Bayesian framework

With the intense increase in space objects, especially space debris, it is necessary to efficiently track and catalog the extensive dense clusters of space objects. As the main instrument for low earth orbit (LEO) space surveillance, ground-based radar system is usually limited by its resolution while tracking small space debris with high density. Thus, the obtained measurement information could have been seriously missed, which makes the traditional tracking method inefficient. To address this issue, we conceived the concept of group tracking. For group tracking, the overall tendency of the group objects is expected to be revealed, and the trajectories of individual objects are simultaneously reconstructed explicitly. According to model the interaction between the group center and individual trajectories using the Markov random field (MRF) within Bayesian framework, the objects’ number and individual trajectory can be estimated more accurately in the condition of high miss alarm probability. The Markov chain Monte Carlo (MCMC)-Particle algorithm was utilized for solving the Bayesian integral problem. Furthermore, we introduced the mechanism for describing the behaviors of groups merging and splitting, which can expand the single group tracking algorithm to track variable multiple groups. Finally, simulation of the group tracking of space objects was carried out to validate the efficiency of the proposed method.     

一种天线主面分瓣连接件的设计

设计了一种天线主面分瓣连接件,介绍了该装置的工作原理及工作过程,通过分析、比较,表明该装置动作明确、定位简单准确且夹紧可靠,是一种较好的设计.     

人工鱼群算法在浮标跟踪阶段的使用优化研究

在对人工鱼群算法进行研究的基础上,结合被动浮标对潜跟踪的实际应用,将人工鱼群算法应用于被动浮标对潜跟踪时的投放优化,对算法的应用、相关参数的选择及其对浮标跟踪效果的影响进行了仿真分析,为被动浮标对潜跟踪使用提供了参考.     

月球精确软着陆制导轨迹在轨鲁棒跟踪

为实现在月球表面期望的着陆点进行精确软着陆(PPL),在开环制导规划出的最优标称轨迹基础上,考虑动力下降过程中的干扰和不确定性,对在轨闭环轨迹跟踪制导方法进行研究.针对月球PPL三维球体非线性轨道动力学模型,充分考虑自主制导的鲁棒性、实时性要求,采用动态平面控制技术的思想,解决退步法存在的"计算复杂性膨胀"问题,并证明了闭环系统的稳定性.仿真算例表明,该方法不仅算法简单,过渡过程能够实现快速跟踪,而且能够保证稳态跟踪误差在预先给定的范围之内且可以自由调节.     

星载天线指向精度建模与分析

随着天线定位机构运动日趋复杂以及对定位机构任务要求的不断提高,提高指向精度已成为星载天线机构能力提升的核心。综合考虑卫星姿态控制误差、展开机构误差、双轴驱动机构误差和反射面误差等因素,利用齐次变换矩阵得到天线指向运动学误差等式,从而得到天线指向精度分析的一般方法。以某星载点波束定位机构为例,对各误差源的影响进行了分析,...     

超宽带螺旋天线的小型化设计

介绍一种新型的螺旋结构天线,将平面等角螺旋天线与锥面螺旋天线结合起来,采用渐变式的巴伦平衡馈电。相比传统的平面螺旋天线,针对同样频带宽度的天线设计,这种混合型螺旋天线体积更小。利用Ansoft HFSS电磁场仿真软件对天线进行建模和仿真计算,并结合仿真结果实际制作了该螺旋天线,给出了实测结果,表明天线可以在工程实际中应用。     

激光跟踪仪在全机水平测量的应用

简要介绍了传统飞机全机水平测量方法的优缺点,以及激光跟踪仪系统(Laser Tracker System)测量的基本原理,并对水平测量的可行性进行了讨论。