深空探测航天器姿态的自抗扰控制

本文针对一种带有挠性附件和液体晃动的深空探测航天器姿态控制问题,提出了自抗扰控制律.该控制律可以自主、有效地抑制挠性附件弹性振动和液体晃动对姿态角运动的耦合作用以及处理大范围的扰动和系统不确定性.基于四元数生成角速度跟踪指令,把控制问题由姿态角控制转化为角速度控制.通过设计扩张状态观测器实时估计并补偿角速度通道总扰动并结合角速度偏差反馈,使得角速度快速跟踪指令,进而实现控制目标.仿真结果验证了控制律的有效性和鲁棒性.     

航天器姿态输出反馈抗干扰跟踪控制

针对采用四元数描述的航天器姿态运动模型研究输出反馈抗干扰跟踪控制问题.首先在姿态运动模型的基础上,结合四元数的性质设计扩张状态观测器(extended state observer,ESO)来估计角速度和干扰力矩,从理论上保证了ESO中的四元数状态满足范数约束,并证明了观测误差的收敛性;进一步利用互连和阻尼分配无源控制(interconnection and damping assignment passivity-based control,IDA--PBC)理论设计控制律,通过姿态和角速度误差状态变换以及引入误差积分项,使得期望的姿态和角速度误差,以及积分项误差运动方程中均出现阻尼项,提高了系统的抗干扰性能,最后利用Laypunov函数证明了闭环系统一致最终有界稳定.仿真结果验证了所设计ESO和IDA--PBC控制律的有效性.     

无人驾驶飞行器姿态的非线性扰动抑制控制

本文研究了无人驾驶飞行器(unmanned aerial vehicle,UAV)的姿态跟踪控制问题.针对在飞行器姿态跟踪时存在的系统模型不确定性和外界扰动,提出了一种基于四元数的姿态跟踪控制方法,基于UAV的姿态误差模型分别设计系统的观测器和控制器.首先,以四元数为姿态参数建立系统的非线性误差模型;在此基础之上,设计一种非线性干扰观测器(nonlinear disturbance observer,NDOB)用以在线估计误差模型中的复合扰动,并在控制输入端进行相应的补偿.然后通过设计非线性广义预测控制律设镇定误差系统,实现姿态跟踪.最后基于频域理论分析了非线性干扰观测器的扰动抑制性能.仿真与实验结果表明本文提出的方法在系统存在复合扰动的情况下能使系统姿态有效的跟踪期望值.     

基于四元数的航天器姿态非线性控制器

针对由四元数描述的航天器姿态控制系统进行了非线性反馈控制器设计.首先,得到一类含角速度测量的反馈控制律.该控制律不仅可以保证闭环系统是全局渐近稳定的,而且保证了2个期望的平衡位置都是稳定的.然后,利用基于四元数的滤波器取代角速度测量,得到一类无需角速度测量的反馈控制律.该控制律同样保证了闭环系统的全局渐近稳定性和2个稳定的期望平衡位置.值得注意的是,2个稳定的期望平衡位置,将促使由任意初始姿态出发的轨迹都就近收敛至任意期望平衡位置.最后,数值仿真展示了所得反馈控制律的优势.     

基于旋转矩阵描述的航天器无角速度测量姿态跟踪无源控制

利用系统无源性和旋转矩阵性质研究无角速度测量下的姿态跟踪控制问题. 为了避免姿态参数的奇异性和模糊性, 提出基于三维特殊正交群(SO(3)) 的控制策略. 首先利用旋转矩阵建立姿态跟踪误差方程, 然后分析了系统的内在无源性, 从而揭示了闭环系统的稳定性. 当角速度无法获得时, 利用新的无源滤波提出一种无角速度测量控制律, 并给出了严格的Lyapunov 稳定性分析. 最后, 通过数值仿真验证了所提出的控制方法的有效性.

     

小卫星编队飞行姿态协同控制及仿真

针对具体的对地定向三星编队成像高度计的姿态协同控制问题,基于四元素方法进行了姿态控制系统设计和数字仿真研究.首先定义了坐标系及姿态误差变量.接着设计了一种非线性姿态跟踪控制器,并运用Lyapunov稳定性理论证明了该控制律的全局稳定性.最后通过基于Matlab的数值仿真和基于STK的可视化,进一步验证了该控制律的稳定性和有效性.数值仿真结果表明利用这种方法可以保证编队中的从星时刻跟踪目标姿态.也就是能够实现合成孔径干涉测量的任务目标.     

基于动态滑模控制的挠性航天器姿态控制

本文采用滑动模态控制方法对挠性航天器设计了姿态镇定控制律.首先,建立了挠性航天器的数学模型.其中,挠性航天器的运动学方程采用姿态四元数描述.然后,通过引入动态切换函数,设计挠性航天器的动态滑模姿态控制律.该控制律能对滑模姿态控制律中由符号函数项引起的抖振进行抑制.采用Lyapunov方法证明了所设计的动态滑模姿态控制律能使闭环航天器姿态系统稳定.最后,通过数值仿真例子验证了所提出方法的有效性.     

小型无人直升机姿态非线性鲁棒控制设计

本文针对小型无人直升机的姿态控制问题,通过系统参数辨识,获得了较为准确的无人直升机姿态动力学模型.并根据无人直升机的动态特性,设计了基于神经网络前馈与滑模控制的非线性鲁棒姿态控制律,该控制律对直升机模型的先验知识要求较低.利用基于Lyapunov的分析方法证明,设计的控制律能够实现对无人直升机姿态角的半全局指数收敛镇定控制,并能确保闭环系统的稳定性.基于姿态飞行控制实验平台的实时飞行控制实验结果表明,提出的控制设计取得了很好的姿态控制效果,并对系统不确定性和外界风扰动具有较好的鲁棒性.     

受扰挠性卫星全局稳定姿态跟踪控制

挠性卫星的姿态跟踪控制要求同时考虑卫星本体姿态跟踪和挠性附件振动对姿态跟踪影响。本文针对存在常值扰动和正弦扰动情况时的挠性卫星姿态跟踪控制问题，考虑目标姿态角速度可以时变的一般情形，设计了基于误差四元数的姿态跟踪控制律，并利用Barbalat引理证明了系统的全局稳定性。数学仿真结果表明该控制律能使闭环控制系统的姿态跟踪全局渐近稳定，从而有效消除常值干扰和正弦干扰，保证卫星本体跟踪精度。     

重力梯度卫星大角度姿态机动的变结构控制

针对重力梯度稳定小卫星的大角度姿态机动问题,采用四元数来描述卫星的姿态,通过选择一类滑动流形,设计了变结构控制律,得到了在大角度姿态机动中卫星的姿态角、姿态角速度以及三个反作用飞轮转速的变化规律.理论分析和数值仿真都表明了该控制律具有渐近稳定性和鲁棒性.     

Finite‐time angular velocity observers for rigid‐body attitude tracking with bounded inputs

The attitude tracking of a rigid body without angular velocity measurements is addressed. A continuous angular velocity observer with fractional power functions is proposed to estimate the angular velocity via quaternion attitude information. The fractional power gains can be properly tuned according to a homogeneous method such that the estimation error system is uniformly almost globally finite‐time stable, irrespective of control inputs. To achieve output feedback attitude tracking control, a quaternion‐based nonlinear proportional‐derivative controller using full‐state feedback is designed first, yielding uniformly almost globally finite‐time stable of the attitude tracking system as well as bounded control torques a priori. It is then shown that the certainty equivalent combination of the observer and nonlinear proportional‐derivative controller ensures finite‐time convergence of the attitude tracking error for almost all initial conditions. The proposed methods not only avoid high‐gain injection, as opposed to the semi‐global results, but also overcome the unwinding problem associated with some quaternion‐based observers and/or controllers. Numerical simulations are presented to verify the effectiveness of the proposed methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Output feedback control for attitude tracking

In this paper the problem of attitude tracking control for a rigid spacecraft is addressed. It is assumed that only attitude measurements are available, and thus spacecraft's angular velocity has to be properly estimated. Two alternative schemes are proposed in which the unit quaternion is adopted to represent the orientation. In the first scheme, a second-order model-based observer is adopted to estimate the angular velocity used in the control law. In the second scheme, an estimate of the angular velocity error is obtained through a lead filter. Sufficient conditions ensuring local exponential stability of the two controllers are derived via Lyapunov analysis.     

四旋翼飞行器自适应动态面轨迹跟踪控制

针对具有未知外界扰动和系统不确定性集总未知非线性的四旋翼飞行器,提出了一种采用自适应不确定性补偿器的自适应动态面轨迹跟踪方法.通过将四旋翼飞行器系统分解为位置、欧拉角和角速率3个动态子系统,使各子系统虚拟控制器设计能充分考虑欠驱动约束;结合动态面控制技术,通过采用一阶低通滤波器,避免对虚拟控制信号求导;进而设计自适应不确定性补偿器,处理未知外界扰动和系统不确定性,最终确保闭环控制系统的稳定性、跟踪误差一致最终有界和系统所有状态信号有界.仿真研究和实验结果验证了本文提出控制方法的有效性和优越性.     

Attitude control without angular velocity measurement: a passivityapproach

It is well known that the linear feedback of the quaternion of the attitude error and the angular velocity globally stabilizes the attitude of a rigid body. In this note, we show that the angular velocity feedback can be replaced by a nonlinear filter of the quaternion, thus removing the need for direct angular velocity measurement. In contrast to other approaches, this design exploits the inherent passivity of the system; a model-based observer reconstructing the velocity is not needed. An application of the proposed scheme is illustrated for the robot control problem. Simulation results are included to illustrate the theoretical results     

干扰环境下的挠性航天器姿态跟踪控制

挠性航天器在姿态机动过程会受环境干扰力矩的作用,研究有扰情况下挠性航天器的姿态跟踪控制问题.首先,设计了干扰观测器在线估计频率已知的外部干扰信号,然后,基于干扰观测器设计了非线性反馈姿态跟踪控制器以跟踪目标姿态,并且该控制器只需要误差四元数和角速度的反馈信息.其次,采用Lyapunov方程和Barbalat引理证明了控...     

Global set stabilization of the spacecraft attitude control problem based on quaternion

In this paper, we develop a global set stabilization method for the attitude control problem of spacecraft system based on quaternion. The control law that uses both optimal control and finite‐time control techniques can globally stabilize the attitude of spacecraft system to a set of equilibria. First, for the kinematic subsystem, we design a virtual optimal angular velocity. To obtain the global minimum of the performance index, this optimal angular velocity is only discontinuous in initial values. It can be regarded as a combination of open loop control and closed loop control. Then for the dynamic subsystem, we design a finite‐time control law that can force the angular velocity to track the virtual optimal angular velocity. It is proved that the closed loop system satisfies global set stability in the absence of disturbances. In the presence of disturbances, the system trajectory will converge to a neighborhood of the equilibrium set. Rigorous analysis shows that by introducing finite‐time control techniques, the closed loop system possesses a better disturbance rejection property. The control method is more natural and energy‐efficient. The effectiveness of the proposed method is demonstrated by simulation results. Copyright © 2009 John Wiley & Sons, Ltd.     

Attitude Synchronization of a Group of Spacecraft Without Velocity Measurements

We consider the coordinated attitude control problem for a group of spacecraft, without velocity measurements. Our approach is based on the introduction of auxiliary dynamical systems (playing the role of velocity observers in a certain sense) to generate the individual and relative damping terms in the absence of the actual angular velocities and relative angular velocities. Our main focus, in this technical note, is to address the following two problems: 1) Design a velocity-free attitude tracking and synchronization control scheme, that allows the team members to align their attitudes and track a time-varying reference trajectory (simultaneously). 2) Design a velocity-free synchronization control scheme, in the case where no reference attitude is specified, and all spacecraft are required to reach a consensus by aligning their attitudes with the same final time-varying attitude. In this work, one important and novel feature (besides the non-requirement of the angular velocity measurements), consists in the fact that the control torques are naturally bounded and the designer can arbitrarily assign the desired bounds on the control torques, a priori, through the control gains, regardless of the angular velocities. Throughout this technical note, the communication flow between spacecraft is assumed to be undirected. Simulation results of a scenario of four spacecraft are provided to show the effectiveness of the proposed control schemes.