带太阳帆板航天器姿态最优控制的小波展开法

讨论航天器太阳帆板展开过程中主体姿态的最优控制问题。在控制算法中利用小波分析理论,将离散正交小波函数引入最优控制问题,利用小波展开法替代传统的Ｆｏｕｒｉｅｒ基函数,提出一种基于小分析的最优控制算法。     

航天器太阳阵多体展开的动力学分析

本文研究航天器太阳阵多体系统展开过程的动力学问题.文中引入 Denavit-Hartenberg 座标系及齐次座标变换理论对系统进行描述,应用 Kane 动力学方程建立了太阳阵展开和撞击动力学模型,编制了仿真软件 K-DIDAS,并对带大型太阳阵的航天器进行了多体系统展开动力学分析计算,给出了供工程应用的有关数据和参数.     

航天器挠性梁伸展动力学特性数值分析

利用动量矩定理推导出带挠性伸展梁航天器的姿态动力学方程,推导了梁质量微元的动力学方程.在梁等速伸展的情况下对动力学方程进行变换,通过Runge-Kutta积分法得出了数值解.结果表明:梁等速伸展时,其振动的振幅随其长度的增长而增大;随航天器初始姿态角速率的增大而增大;随伸展速率的增大     

航天器挠性梁伸展动力学特性数值分析

利用动量矩定理推导出带挠性伸展梁航天器的姿态动力学方程,推导了梁质量微元的动力学方程．在梁等速伸展的情况下对动力学方程进行变换,通过Runge-Kutta积分法得出了数值解．结果表明梁等速伸展时,其振动的振幅随其长度的增长而增大;随航天器初始姿态角速率的增大而增大;随伸展速率的增大     

航天器太阳帆板振动抑制的输入整形方法研究

利用输入整形与PD(比例微分)控制相结合的主动振动控制策略,在保证航天器完成三轴姿态机动的同时抑制太阳帆板的振动。首先,基于角动量定律和拉格朗日法建立了带挠性太阳帆板航天器的动力学模型。然后,在动力学模型的基础上,采用PD控制作为航天器三轴姿态机动的控制策略,利用挠性太阳帆板各阶模态的固有频率和阻尼比得到系统的输入整形器,对原始姿态机动的脉冲进行输入整形前馈控制,以抑制太阳帆板各阶模态的振动。仿真结果表明:两种输入整形方法均能抑制太阳帆板的振动,ZV(零残余振动)输入整形器简单且脉冲数量少,输入时间较短,但对于参数摄动以及输入的微小误差比较敏感,抑制振动的效果难以满足零残余振动的标准;ZVD(微分零残余振动)输入整形器脉冲数量较多,具有一定量的延时,但更为高效,鲁棒性强,能够极大地抑制挠性太阳帆板的残余振动,缩短航天器的机动稳定时间,且整个机动过程更加平稳。     

航天器多体系统动力学模型及仿真软件

本文以Newton-Euler方程为基础,应用旋量-矩阵方法推导的多体系统动力学理论模型,开发了相应的仿真软件,然后以单翼航天器太阳阵的展开为例,对多体系统进行了动力学仿真和分析.理论模型和仿真软件都充分考虑了其在航天器动力学分析中的通用性和实用性.     

考虑铰摩擦的柔性太阳阵展开动力学研究

研究了空间漂浮航天器太阳阵展开与锁定过程的刚柔耦合动力学问题. 基于Jourdain 速度变分原理和单项递推组集方法, 建立了太阳阵展开与锁定过程的刚柔耦合多体系统动力学模型,采用虚功率原理推导了铰摩擦对系统动力学方程的贡献. 在以上动力学模型中引入3-D 鬃毛摩擦模型来研究铰链的摩擦特性对太阳阵展开动力学的影响. 所建动力学模型的正确性通过与商业软件ADAMS 和NASTRAN 的联合仿真对比得到了验证,该模型能够有效地预测太阳阵的展开历程以及航天器姿态的动态行为.      

挠性联结双体航天器的稳定性与分岔

研究圆轨道内受万有引力矩作用的挠性联结双体航天器在轨道平面内的姿态运动,讨论其相对轨道坐标系统平衡状态的稳定性与分岔。提出判平衡方程非平凡解存在性的几何方法,并应用Ｌｉａｐｕｎｏｖ直接法、Ｌｉａｐｕｎｏｖ－Ｓｃｈｍｉｄｔ约化方法和奇异性理论导出解析形式的稳定性与分岔的充要条件,从而对系统的全局运动性态作出定性的描述。     

飞轮控制航天器的自适应姿态跟踪

本文讨论飞轮控制航天器的姿态控制问题。由于航天器在运行过程中受各种复杂环境因素的影响，难以确定其动力学参数的准确值，因此姿态控制系统必须具有自适应能力，以适应不可预计的干扰和航天器自身参数的改变。文中基于滑模控制方法提出一种改进的自适应姿态控制规律，适用于有内扰动力短存在的航天器。此控制规律可在不须提供动力学参数的情况下，使飞轮控制航天器跟踪期望的姿态变化规律以实现姿态机动。利用Lyapunov直接方法证明了控制系统的渐近稳定性。对于受随机扰动力短作用的航天器姿态跟踪的时间历程进行了数值仿真，计算结果证实上述方法的有效性。     

万有引力场中带挠性板非轴对称航天器的姿态稳定性

本文讨论由非轴对称主刚体和矩形挠性板组成的航天器在万有引力场中的姿态运动。利用Ｇａｌｅｒｋｉｎ方法对动力学方程离散化，并利用Ｋｅｌｖｉｎ－Ｔａｉｔ－Ｃｈｅｔａｙｅｖ定理判断航天器在轨道坐标系内相对平衡的稳定性。导出适用于任意阶模态的解析形式稳定性充分条件。     

应用遗传算法求解二维扩压器壁面速度最优分布

将遗传算法应用于求解透平机械中的二维扩压器壁面最优化速度分布，该方法可以容易的求解出既满足在扩压器出口流动速度极小又保证壁面边界层不发生分离的最优速度分布。用该方法求取著名的Ｓｔｒａｔｆｏｒｄ实验条件下的二维扩压器最优速度分布，所得结果与该实验吻合良好。     

Optimal Slewing of a Flexible Spacecraft

An optimal slewing program is designed within the class of Euler rotations for a spacecraft with elastic elements. The mathematical model constructed accounts for an arbitrary number of partial modes of elastic vibrations. An optimal reorientation problem is formulated using a nontraditional performance criterion, which minimizes the dynamic overloads of the elastic elements in relative motion. An algorithm for solving the corresponding nonlinear boundary-value problem is developed and implemented in a software package of FORTRAN-programs. A neural network is generated in the space of slew parameters; it may be trained during a preflight period. Known radial basis functions are used to model the process of fast in-flight computation of the optimal reorientation program     

基于遗传算法参数整定的方位保持仪温控系统

遗传算法是一种高效的模拟生物进化过程的全局随机化搜索优化方法，它可直接得到所求解问题的全局最优解。针对方位保持仪，提出了一种分段参数设置与级间控制相结合的三级温控方案，并基于遗传算法对PID控制参数进行了优化整定。同时介绍了整个温控系统的软件实现。大量试验证明该控制策略接近最优，达到了战技指标要求。     

自适应免疫遗传算法

遗传算法(GA)是基于自然遗传规则随机搜索技术的一种进化算法,但是随着实际结构的大型化和复杂化,它往往出现过早收敛的现象。在研究了算法的编码方式、控制参数和算子操作之后,就其全局收敛性的不足,提出动态自适应策略以改进其性能,在基本遗传算子的基础上,采用了免疫遗传算子和保优策略。其中免疫算子可以防止交叉变异中的个体退化,自适应策略则保持了种群的多样性,以此保证遗传算法尽快收敛到全局最优解,称之为自适应免疫遗传算法(AIGA)。随后以经典的十杆桁架结构优化问题作为例子说明算法的优越性,结果表明AIGA在随机结构优化中计算有效、结果可靠。     

Control of Chaotic Motion in a Spinning Spacecraft with a Circumferential Nutational Damper

Control of chaotic vibrations in a simplified model of a spinning spacecraft with a circumferential nutational damper is achieved using two techniques. The control methods are implemented on a realistic spacecraft parameter configuration which has been found to exhibit chaotic instability when a sinusoidally varying torque is applied to the spacecraft for a range of forcing amplitude and frequency. Such a torque, in practice, may arise in the platform of a dual-spin spacecraft under malfunction of the control system or from an unbalanced rotor or from vibrations in appendages. Chaotic instabilities arising from these torques could introduce uncertainties and irregularities into a spacecraft's attitude and consequently could have disastrous affects on its operation. The two control methods, recursive proportional feedback (RPF) and continuous delayed feedback, are recently developed techniques for control of chaotic motion in dynamical systems. Each technique is outlined and the effectiveness of the two strategies in controlling chaotic motion exhibited by the present system is compared and contrasted. Numerical simulations are performed and the results are studied by means of time history, phase space, Poincaré map, Lyapunov characteristic exponents and bifurcation diagrams.     

A Suggestion of Fractional-Order Controller for Flexible Spacecraft Attitude Control

A controller design method for flexible spacecraft attitude control isproposed. The system is first described by partial differential equationwith internal damping. Then the frequency response is analyzed, and thethree basic characteristics of the flexible system, namely, averagefunction, lower bound and upper bound are defined. On this basis, afractional-order controller is proposed, which functions as phasestabilization control for lower frequency and smoothly enters toamplitude stabilization at higher frequency by proper amplitudeattenuation. It is shown that the equivalent damping ratio increases inproportion to the square of frequency.     

Optimal control of stretching process of solar arrays on spacecraft using wavelet expansion method

The optimal attitude control problem of spacecraft during its solar arrays stretching process is discussed in the present paper. By using the theory of wavelet analysis in control algorithm, the discrete orthonormal wavelet function is introduced into the optimal control problem, the method of wavelet expansion is substituted for the classical Fourier basic function. An optimal control algorithm based on wavelet analysis is proposed. The effectiveness of the wavelet expansion approach is shown by numerical simulation. This work is supported by the National Natural Science Foundation of China.     

Minimization of the Wing Airfoil Drag Coefficient Using the Optimal Control Method

The problem of designing a wing airfoil starting from the surface velocity (or pressure) distribution, given in multi-parameter form, is considered. In the diffuser region, the velocity decrease law is determined from the conditions of minimum drag and separationless flow for a given Reynolds number. The case of boundary layer suction for the purpose of improving the aerodynamic characteristics of the airfoil is studied. A solution is obtained using optimal control theory.     

带空间机械臂航天器姿态运动规划的数值算法研究

自由漂浮空间机械臂系统在无外力矩作用时,系统的动量矩守恒而成为非完整系统。利用这一特性本文研究了自由漂浮空间机械臂系统的三维姿态运动规划问题。导出带空间机械臂的航天器三维姿态运动数学模型,将系统的非完整运动规划问题转化为非线性系统最优控制问题,在最优控制中利用小波逼近控制输入规律,提出基于遗传算法的最优控制数值算法。通过数值仿真,表明该方法对带空间机械臂航天器系统的非完整姿态运动规划是有效的。     

Control structure interaction in the nonlinear analysis of flexible mechanical systems

The effect of the control structure interaction on the feedforward control law as well as the dynamics of flexible mechanical systems is examined in this investigation. An inverse dynamics procedure is developed for the analysis of the dynamic motion of interconnected rigid and flexible bodies. This method is used to examine the effect of the elastic deformation on the driving forces in flexible mechanical systems. The driving forces are expressed in terms of the specified motion trajectories and the deformations of the elastic members. The system equations of motion are formulated using Lagrange's equation. A finite element discretization of the flexible bodies is used to define the deformation degrees of freedom. The algebraic constraint equations that describe the motion trajectories and joint constraints between adjacent bodies are adjoined to the system differential equations of motion using the vector of Lagrange multipliers. A unique displacement field is then identified by imposing an appropriate set of reference conditions. The effect of the nonlinear centrifugal and Coriolis forces that depend on the body displacements and velocities are taken into consideration. A direct numerical integration method coupled with a Newton-Raphson algorithm is used to solve the resulting nonlinear differential and algebraic equations of motion. The formulation obtained for the flexible mechanical system is compared with the rigid body dynamic formulation. The effect of the sampling time, number of vibration modes, the viscous damping, and the selection of the constrained modes are examined. The results presented in this numerical study demonstrate that the use of the driving forees obtained using the rigid body analysis can lead to a significant error when these forces are used as the feedforward control law for the flexible mechanical system. The analysis presented in this investigation differs significantly from previously published work in many ways. It includes the effect of the structural flexibility on the centrifugal and Coriolis forces, it accounts for all inertia nonlinearities resulting from the coupling between the rigid body and elastic displacements, it uses a precise definition of the equipollent systems of forces in flexible body dynamics, it demonstrates the use of general purpose multibody computer codes in the feedforward control of flexible mechanical systems, and it demonstrates numerically the effect of the selected set of constrained modes on the feedforward control law.