Two degree-of-freedom spacecraft attitude controller

Two degree-of-freedom controller is designed together with its governing equations for a spacecraft pitch attitude control. The attitude controller incorporates the Active Force Control (AFC) technique into the conventional Proportional-Derivative (PD) controller based spacecraft pitch attitude loop. The PD-AFC attitude controller is then employed to enhance the attitude pointing of the Combined Energy and Attitude Control System (CEACS). Numerical treatments are performed to validate the effectiveness of AFC, whereby the CEACS attitude performance is analysed from its accuracy point of view. The results show that the PD-AFC attitude control performance is superiorly better than that of the solely conventional PD type.     

基于宽带宽测量的姿态确定方法

针对由飞轮等星上高速旋转部件所引起的高频姿态和指向抖动,提出一种基于磁流体动力学特性的角位移敏感器用于星上高精度宽带宽的微振动测量,以弥补常规姿态测量系统测量频带低,动态范围有限的缺点.介绍以扩展姿态确定带宽为基础的高精度姿态确定方法.给出了以陀螺、星敏及ADS测量信息为基础的宽带宽的姿态确定方法及系统的模型,采用了卡尔曼滤波来确定卫星姿态.仿真分析结果表明存在高频姿态抖动的情况下,宽带宽的姿态确定方法的估计精度优于传统的姿态确定方法,由此验证了宽带宽的姿态确定方法的有效性及精确性.     

ROBUST H∞ DESIGN OF THE ATTITUDE CONTROL/MOMENTUM MANAGEMENT SYSTEM FOR A SPACE STATION

Through input-output decomposition of structured parameter uncertainties of the controlled plant, the robust control problem of space station attitude system with parameter uncertainties is converted to a conventional disturbance rejection H∞ controller design problem, then a full-state feedback H∞ robust controller is formulated, which can be solved using the Glover-Doyle algorithm. The proposed method was applied to the attitude control/momentum management (ACMM) system of a space station, and two kinds of parameter uncertainties which appear most frequently in spacecraft engineering were considered. Simulation results showed efficiency of the given method.     

面向叶片型面的五轴联动柔性数控砂带抛光技术

针对叶片型面抛光,在分析五轴联动数控砂带抛光可行性的基础上,设计并开发了五轴联动柔性数控砂带抛光机。提出了接触轮与叶片型面有效贴合的概念,并通过改善抛光工具、采用柔性抛光技术和控制抛光轴矢量来实现砂带与叶片型面的有效贴合。抛光轴矢量由抛光位点处法矢和接触轮进给矢量计算获得,既实现了砂带与叶片型面的有效贴合,而且满足抛光轮接触压力方向与柔性机构收缩方向基本一致的要求。抛光轨迹规划采用等参数线法,抛光行距根据抛光带宽确定。最后进行抛光实验,结果为精抛后粗糙度达到0.25~0.39μm,抛光前后叶型轮廓度变化0.007mm,抛光去除量在0.010~0.016mm之间,满足图纸要求。通过实验表明,五轴联动数控砂带抛光叶片型面可行,采用本文所述技术能够满足叶片型面抛光要求。     

飞行器自适应ESO姿态控制器设计

飞行器无动力再入过程中,姿态受到气动及不确定干扰影响,控制模型具有强耦合、大范围参数摄动等非线性特征。针对再入飞行器姿态控制问题,结合扩张状态观测器（Extended State Observer,ESO）和自适应控制律,基于奇异摄动理论将非线性姿态控制模型分为快慢两回路,分别设计了飞行器内环和外环自适应姿态控制器,并通过 Lyapunov 稳定性理论证明控制器的稳定性。仿真结果表明,控制系统在强干扰及参数大范围摄动的情况下,具有较强的鲁棒性,能够获取良好的动态品质和跟踪性能。     

一种同步自旋卫星姿态控制优化方法

根据同步自旋卫星姿态的运动规律以及自旋卫星姿态的长期实测数据,建立了姿态变化规律方程,采用最小二乘方法求解姿态变化方程,实现对自旋卫星姿态预测,预测误差小于0.05..针对目前工程应用中姿态保持周期短的问题,结合姿态及轨道倾角变化规律,建立目标姿态选取的约束方程,并利用投影梯度法求解约束方程,寻求姿态保持时间长的姿态控制目标.实际应用结果表明：该方法可以延长姿态控制周期,使自旋卫星姿态保持周期达到1 a.     

空间机械臂视觉测量技术研究

空间机械臂技术是维护空间站、执行指定任务、保障航天员出舱作业的安全等必不可少的关键技术。视觉测量技术则是保证空间机械臂顺利完成空间遥操作任务的前提。基于此前提,首先对空间机械臂视觉测量技术进行了概述,并分别对手眼关系标定、标志器识别以及相对三维位姿测量等关键技术进行了阐述;然后,以加拿大机械臂为例提出了一种基于边缘特征的标志器识别算法,给出了具体的识别流程,并采用一种基于非迭代的相对位姿测量算法实现了位姿求解;最后,针对标志器识别算法和位姿测量算法给出了基于仿真图像的实验结果和机械臂原理样机集成实验结果。最终实验结果表明:提出的空间机械臂视觉测量方法合理可行,满足预期的技术指标要求,具有较强的工程应用价值。     

基于高斯过程的航天器自适应滑模姿态控制

针对存在模型不确定性和外界干扰的刚性航天器,提出了一种基于高斯过程回归(GPR)的新型自适应滑模姿态控制算法。该算法具有自学习能力,在不同的姿态控制任务下都能够实现高精度、强鲁棒和高效率的姿态跟踪。首先,在航天器的四元数标称系统动态模型基础上,应用在线稀疏高斯过程回归(SOGP)方法学习系统的未知动态;其次,结合高斯过程的预测均值设计滑模控制算法,利用高斯过程的预测方差自适应调节控制增益,并应用李雅普诺夫方法严格证明闭环系统的稳定性,保证了航天器姿态跟踪误差的渐进收敛性;最后,通过数值仿真验证了所设计控制器的有效性。结果表明,该自学习控制算法与自适应滑模控制(ASMC)与神经网络自适应控制等算法相比,具有更快的收敛速度、更高的跟踪精度以及更低的控制成本。     

复杂环境下多无人机轨迹姿态协同控制

考虑多无人机在实际飞行过程中的避障需求，在建立面向控制的四旋翼无人机轨迹姿态模型基础上，为克服传统多无人机为每架无人机规划轨迹的不足，研究了基于多无人机中心点的轨迹设计策略。进一步，考虑避障约束，基于半定规划进行迭代区域扩张完成了多无人机的安全飞行区域及队形设计。在此基础上，基于干扰补偿策略为每架无人机设计了协同控制器，最终确保了多无人机在多障碍环境下的安全飞行。     

Tumbling object deorbiting using spaceborne laser engagement – A CubeSat case study

This paper demonstrates active space debris removal using spaceborne laser systems. The laser beam and the surface of the target are discretised into multiple rays and finite elements, respectively, for laser-target interaction modelling, in which the laser ablation process is investigated. A high-fidelity attitude/orbit propagator tool is developed to account for both the linear impulse and angular impulse induced by the laser engagement and other perturbations. The laser system is activated only when three switch criteria are satisfied. In numerical simulations, laser pulses from international space station are generated to deorbit a 3U CubeSat with initially tumbling modes. The results validate the effectiveness of deorbiting tumbling CubeSats using spaceborne laser engagement, with the perigee height lowered by approximately $2.4\mathrm{km}$ in around $30\min$ after $2\mathrm{h}$ propagation. It is also found that the laser engagement becomes more effective for an initially faster rotating object.