Underactuated spacecraft angular velocity stabilization and three-axis attitude stabilization using two single gimbal control moment gyros

Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros （SGCMGs） as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.

Fuzzy Self-adaptive Proportional Integration Differential Control for Attitude Stabilization of Quadrotor UAV

The technology of attitude control for quadrotor unmanned aerial vehicles(UAVs) is one of the most important UAVs' research areas.In order to achieve a satisfactory operation in quadrotor UAVs having proportional integration differential(PID) controllers,it is necessary to appropriately adjust the controller coefficients which are dependent on dynamic parameters of the quadrotor UAV and any changes in parameters and conditions could affect desired performance of the controller.In this paper,combining with PID control and fuzzy logic control,a kind of fuzzy self-adaptive PID control algorithm for attitude stabilization of the quadrotor UAV was put forward.Firstly,the nonlinear model of six degrees of freedom(6-DOF) for quadrotor UAV is established.Secondly,for obtaining the attitude of quadrotor,attitude data fusion using complementary filtering is applied to improving the measurement accuracy and dynamic performance.Finally,the attitude stabilization control simulation model of the quadrotor UAV is build,and the self-adaptive fuzzy parameter tuning rules for PID attitude controller are given,so as to realize the online self-tuning of the controller parameters.Simulation results show that comparing with the conventional PID controller,this attitude control algorithm of fuzzy self-adaptive PID has a better dynamic response performance.

MODEL OF CENTRIFUGAL EFFECT AND ATTITUDEMANEUVER STABILITY OF A COUPLEDRIGID-FLEXIBLE SYSTEM

The influences of nonlinear centrifugal force to large overall attitude motion of coupled rigid-flexible system was investigated. First the nonlinear model of the coupled rigid-flexible system was deduced from the idea of “centrifugal potential field', and then the dynamic effects of the nonlinear centrifugal force to system attitude motion were analyzed by approximate calculation; At last, the Lyapunov function based on energy norm was selected, in the condition that only the measured values of attitude and attitude speed are available, and it is proved that the PD feedback control law can ensure the attitude stability during large angle maneuver.

Coupled trajectory and attitude stability of displaced orbits

Coupled trajectory and attitude stability of displaced solar orbits is studied by using sailcraft with a kind of two-folding construction with two unequal rectangular plates forming a right angle. Three-dimensional coupled trajectory and attitude equations are developed for the coupled dynamical system, and the results show that all three types of displaced solar orbits widely referenced can be achieved through selecting an appropriate size of the two-folding sail. An anal- ysis of the corresponding linear stability of the trajectory and attitude coupled system is carried out, and both trajectory and attitude linearly stable orbits are found to exist in a small range of parameters, whose non-linear stability is then examined via numerical simulations. Finally, passively stable orbits are found to have weak stability, and such passive means of station-keeping are attractive and useful in practice because of its simplicity.

Misalignment Angle Calculation Accuracy Analysis of Three-Axis Stabilized Geostationary Satellite

The most challenging problem of navigation in three-axis stabilized geostationary satellite is accurate calculation of misalignment angles, deduced by orbit measurement error, attitude measurement error, thermal elastic deformation, time synchronization error, and so on. Before the satellite is launched, the misalignment model must be established and validated. But there were no observation data, which is a non-negligible risk of yielding the greatest returns on investment. On the basis of misalignment modeling using landmarks and stars, which is not available between different organizations and is developed by ourselves, experimental data are constructed to validate the navigation processing flow as well as misalignment calculation accuracy. In the condition of using landmarks, the maximum misalignment calculation errors of roll, pitch, and yaw axis are 2, 2, and 104 micro radians, respectively, without considering the accuracy of image edge detection. While in the condition of using stars, the maximum errors of roll, pitch, and yaw axis are 1, 1, and 3 micro radians, respectively, without considering the accuracy of star center extraction. Results are rather encouraging, which pave the way for high-accuracy image navigation of three-axis stabilized geostationary satellite. The misalignment modeling as well as calculation method has been used in the new generation of geostationary meteorological satellite in China, FY-4 series, the first satellite of which was launched at the end of 2016.

Evaluation of E-sail parameters on central spacecraft attitude stability using a high-fidelity rigid–flexible coupling model

This study examines the impact of electric solar wind sail(E-sail)parameters on the attitude stability of E-sail’s central spacecraft by using a comprehensive rigid–flexible coupling dynamic model.In this model,the nodal position finite element method is used to model the elastic deformation of the tethers through interconnected two-node tensile elements.The attitude dynamics of the central spacecraft is described using a natural coordinate formulation.The rigid–flexible coupling between the central spacecraft and its flexible tethers is established using Lagrange multipliers.Our research reveals the significant influences of parameters such as tether numbers,tether’s electric potential,and solar wind velocity on attitude stability.Specifically,solar wind fluctuations and the distribution of electric potential on the main tethers considerably affect the attitude stability of the spacecraft.For consistent management,the angular velocities of the spacecraft must remain at target values.Moreover,the attitude stability of a spacecraft has a pronounced dependence on the geometrical configuration of the E-sail,with axisymmetric E-sails proving to be more stable.

Finite-time attitude tracking control for spacecraft without angular velocity measurements

The output feedback control for spacecraft attitude tracking system is investigated in this study. It is assumed that angular velocity measurements are not available for feedback control.A technique named adding power integrator(API) is adopted to estimate the pseudo-angular-velocity. Then we design a finite-time attitude control law, which only utilizes the relative attitude information. The stability analyses of the feedback system are proved as well, which shows the attitude tracking errors will converge into a region of zero even the external disturbances exist. The simulation results illustrate the high precision and robust attitude control performance of the proposed control strategy.

Research on the attitude regulation of 3-DOF hover system

Quadrotor helicopter is emerging as a popular platform for unmanned aerial vehicle re- search, due to its simplicity of structure and maintenance as well as the capability of hovering and vertical take-off and landing. The attitude controller is an important feature of quadrotor helicopter since it allows the vehicle to keep balance and perform the desired maneuver. In this paper, nonlin- ear control strategies including active disturbance rejection control （ADRC）, sliding mode control （SMC） and backstepping method are studied and implemented to stabilize the attitude of a 3-DOF hover system. ADRC is an error-driven control law, with extended state observer （ESO） estimating the unmodeled inner dynamics and external disturbance to dynamically compensate their impacts. Meanwhile; both backstepping technique and SMC are developed based on the mathematical model, whose stability is ensured by Lyapunov global stability theorem. Furthermore, the performance of each control algorithm is evaluated by experiments. The results validate effectiveness of the strate- gies for attitude regulation. Finally, the respective characteristics of the three controllers are high- lighted by-comparison, and conclusions are drawn on the basis of the theoretical and experimental a- nalysis.

Attitude control of a rigid spacecraft with one variable-speed control moment gyro

Nonlinear controllability and attitude stabilization are studied for the underactuated nonholonomic dynamics of a rigid spacecraft with one variable-speed control moment gyro （VSCMG）, which supplies only two internal torques. Nonlinear controllability theory is used to show that the dynamics are locally controllable from the equilibrium point and thus can be asymptotically stabilized to the equilibrium point via time-invariant piecewise continuous feedback laws or time-periodic continuous feedback laws. Specifically, when the total angular momentum of the spacecraft-VSCMG system is zero, any orientation can be a controllable equilib- rium attitude. In this case, the attitude stabilization problem is addressed by designing a kinematic stabilizing law, which is implemented through a nonlinear proportional and deriva- tive controller, using the generalized dynamic inverse （GDI） method. The steady-state instability inherent in the GDI con- troller is elegantly avoided by appropriately choosing control gains. In order to obtain the command gimbal rate and wheel acceleration from control torques, a simple steering logic is constructed to accommodate the requirements of attitude sta- bilization and singularity avoidance of the VSCMG. Illustrative numerical examples verify the efficacy of the proposed control strategy.

Attitude Control of an Axi-Symmetric Rigid Body Using Two Controls without Angular Velocity Measurements Paper

This paper considers the problem of controlling the rotational motion of an axi-symmetric rigid body using two independent control torques without angular velocity measurements. The control law which stabilizes asymptotically this motion is obtained only in terms of the orientation parameters. Global asymptotic stability is shown by applying LaSalle invariance principal. Numerical simulation is introduced.

考虑姿态稳定性的智能客车轨迹跟踪控制研究

针对智能客车行驶中遇到突发情况时驾驶员应急激烈操作以及车辆传感器识别误差导致车辆路径规划不合理引起的车辆侧翻,提出一种基于车身姿态稳定性的轨迹跟踪控制策略.根据现有主动防侧倾研究基础推导智能客车目标侧倾角算法,以横向载荷转移率为侧翻指标,采用卡尔曼滤波算法进行车辆参数估计,实现横向载荷转移率预测.根据智能客车横向载荷转移率预测值设计基于差动制动的纵向控制策略、考虑车身侧倾和俯仰运动的垂向控制策略以及轨迹跟踪横向控制策略,最后通过仿真验证上述策略控制效果.结果表明,基于车身姿态稳定性的轨迹跟踪控制策略在车辆行驶遇到突发情况驾驶员激烈操作时能够保证车辆行驶稳定,在智能客车轨迹跟踪过程中能降低车辆侧翻风险.

四旋翼无人机改进自抗扰姿态控制

针对四旋翼无人机姿态控制过程中模型不确定及外部扰动问题,设计了一种自抗扰控制的姿态控制器。将模糊控制方法与传统的自抗扰控制理论相结合,增加了一个集模糊化、模糊推理和清晰化为一体的模糊控制单元,采用改进天牛须算法整定自抗扰控制器参数,提高了参数整定效率。为解决fal函数拐点处不平滑,易产生小幅抖振以及误差较大时系统增益较大等问题,引入了改进的yfal函数替代扩张状态观测器中的fal函数,并对改进后的状态观测器进行了收敛性判断。仿真结果表明,改进后的自抗扰控制器具有更快的响应速度和抗干扰能力。

基于预定义时间的四旋翼滑模控制

针对四旋翼位置环和姿态环的控制问题,使得四旋翼位姿能够在预定时间内稳定,提出一种基于预定义时间滑模控制算法的位姿控制器。该控制器通过对四旋翼位置环和姿态环2个环节的控制,使得四旋翼的位姿能够在预定时间内稳定。理论推导及数值仿真表明:所提算法具有正确性;仿真结果表明:应用所提控制器的四旋翼的位置和姿态能够在预定时间内达到稳定。

仿生扑翼飞行器姿态稳定控制设计与实验

针对扑翼飞行器在飞行过程中姿态调整控制问题,提出了一种快速响应的自动姿态稳定控制方法。利用牛顿定律和动量矩定理建立扑翼飞行器数学模型,结合扑翼飞行器姿态变化工作原理,研究飞行过程中姿态调整控制方案策略。采用串级PID控制算法设计姿态调整内环和外环控制器,以扑翼飞行器欧拉角为输出,对扑翼飞行器姿态调整过程进行了仿真计算以及外场飞行实验。通过对扑翼飞行器姿态角的响应仿真分析及外场飞行实验数据分析,验证了扑翼飞行器数学模型的准确性及姿态控制器的有效性。结果表明:在阶跃信号输入下,姿态角能快速响应并快速趋于稳态,外场飞行中扑翼飞行器俯仰角保持15°,飞行加速度保持1 m/s^(2),可以较好地自动保持姿态稳定。

水下机器人回收装置的动力学分析与实验验证

为提高水下自主航行器(autonomous underwater vehicle,AUV)布放回收过程中的效率和安全性,通过以船舶起重机为基础研究了一种不仅可以通过电机自主调节吊笼的姿态而且能够利用绳索减摇使回收过程更加稳定的AUV水面布放回收装置,建立了船-起重机-吊点-减摇装置-吊笼的三维动力学模型,首先通过Adams搭建虚拟样机进行动力学仿真,得出了当利用电机调节吊笼开口方向时4根绳索的拉力的变化和吊笼的姿态变化,然后利用MATLAB联合仿真采用PID控制策略对其进行了减摇的仿真分析,验证了减摇方案的可行性。在已有的理论基础上搭建了实验样机进行了实验验证。结果表明:在受船舶激励的情况下,横摇的减摇效果达70%;纵摇的减摇效果达60%,电机进行姿态调整时各个绳索的拉力稳定能够完成姿态调整,能够有效地完成布放回收工作。可见当AUV靠近吊笼时依靠姿态调整电机进行姿态调整,能保证AUV进入吊笼;当AUV进入吊笼以后本装置有良好的减摇效果,使回收过程更加稳定。

航天器敏捷机动控制技术发展及展望

对航天器敏捷控制技术的发展现状进行综述,分析了航天器敏捷机动在路径规划、高敏捷高稳定度控制等方面面临的技术挑战;从航天器输入激励方面给出了不同路径规划对姿态敏捷机动性能的影响及适用范围。分析了单级路径跟踪控制、执行机构精准输出控制、多级复合控制等方法对提升航天器敏捷机动高稳定控制性能的技术途径。航天器敏捷机动控制作为一项系统性技术,需要从结构动力学、控制架构、测量与执行部件研制等多方面开展综合分析与设计。针对航天器敏捷机动控制技术发展需求及所面临的挑战,从智能自主控制架构设计、自主决策与协同规划技术、高性能部件研制技术等方面,给出敏捷航天器控制技术的发展建议。

Attitude control of multi-spacecraft systems on SO(3)with stochastic links failure

In this paper,for Multi-Spacecraft System(MSS)with a directed communication topology link and a static virtual leader,a controller is proposed to realize attitude consensus and attitude stabilization with stochastic links failure and actuator saturation.First,an MSS attitude error model suitable for a directed topology link and with a static virtual leader based on SO(3)is derived,which considers that the attitude error on SO(3)cannot be defined based on algebraic subtraction.Then,we design a controller to realize the MSS on SO(3)with attitude consensus and attitude stabilization under stochastic links failure and actuator saturation.Finally,the simulation results of a multi-spacecraft system with stochastic links failure and a static virtual leader spacecraft are demonstrated to illustrate the efficiency of the attitude controller.

机载LiDAR姿态角稳定装置的神经网络逆系统解耦控制研究

机载激光雷达(LiDAR)工作过程中,机载平台姿态角波动会造成激光扫描点云的密度分布不均匀,导致后续数字表面模型重建时精度降低,因此设计了一种推转式姿态角稳定装置,可实现机载平台姿态角波动的实时补偿。设计的姿态角稳定装置具有非线性和强耦合的运动控制特点,为消除其运动耦合关系、提高运动控制精度,基于神经网络逆系统解耦控制策略对姿态角稳定装置进行解耦处理,取得了满意的控制效果。首先,建立了姿态角稳定装置动力学系统的多变量神经网络逆系统模型;其次,采用PID闭环反馈控制器与神经网络逆系统前馈补偿器组合的前馈-反馈复合控制器,实现控制系统的实时解耦,改善动态控制性能;最后,进行了实验验证。结果表明,设计的神经网络逆系统解耦控制方法可有效提高姿态角稳定装置控制精度,并对误差干扰具有优良鲁棒性。

具有输入约束和扰动补偿的四旋翼无人机姿态稳定模型预测控制

为了解决四旋翼无人机飞行过程中的姿态控制问题,考虑受到执行器输入约束和外界未知扰动影响,设计了一种具有输入约束和扰动补偿的四旋翼无人机姿态稳定模型预测控制方法;设计简化的四旋翼无人机姿态动力学模型,降低控制器设计的复杂程度,设计带有输入约束的控制器,模拟饱和输入现象,实现饱和输入下的四旋翼姿态稳定控制;设计风扰观测器,实现对外部未知扰动的估计,有效跟踪外部持续扰动,并由此设计扰动补偿律;围绕代价函数设计带有扰动补偿律的最优控制律,作用于四旋翼姿态系统,实现四旋翼无人机姿态的稳定控制;最后进行数值仿真,设置风扰观测器参数λ_(i)为0.25,预测时域N_(p)为10,控制时域N_(c)为9,仿真测试文章方法与不带观测器的非线性预测控制方法(NMPC),验证文章控制方法的有效性和优越性。

中长周期波浪对斜坡堤扭王字块稳定性影响试验研究

本文针对中长周期波浪对斜坡堤扭王字块在位稳定性的影响开展了物理模拟试验,将高精度惯性姿态传感器与扭王字块固定,通过姿态传感器采集得到波浪作用下扭王字块的角速度时程,定量地分析波浪作用下斜坡堤扭王字块体的在位稳定性,探究了波浪周期和波高对于斜坡堤上扭王字块在位稳定性的影响。研究发现:波浪周期对扭王字块在位稳定性的影响呈非线性关系。随着波浪周期的增大,扭王字块的角速度幅值呈现出先增大、后减小、再增大的趋势。中等周期波浪作用下,静水面附近的扭王字块的变位最显著,而长周期波浪作用下,静水面上一倍波高处的扭王字块的变位最明显。