Attitude guidance and tracking for spacecraft with two reaction wheels

This paper addresses the guidance and tracking problem for a rigid-spacecraft using two reaction wheels (RWs). The guidance problem is formulated as an optimal control problem on the special orthogonal group SO(3). The optimal motion is solved analytically as a function of time and is used to reduce the original guidance problem to one of computing the minimum of a nonlinear function. A tracking control using two RWs is developed that extends previous singular quaternion stabilisation controls to tracking controls on the rotation group. The controller is proved to locally asymptotically track the generated reference motions using Lyapunov's direct method. Simulations of a 3U CubeSat demonstrate that this tracking control is robust to initial rotation errors and angular velocity errors in the controlled axis. For initial angular velocity errors in the uncontrolled axis and under significant disturbances the control fails to track. However, the singular tracking control is combined with a nano-magnetic torquer which simply damps the angular velocity in the uncontrolled axis and is shown to provide a practical control method for tracking in the presence of disturbances and initial condition errors.     

Adaptive control of rigid body satellite

The minimal controller synthesis （MCS） is an extension of the hyperstable model reference adaptive control algorithm. The aim of minimal controller synthesis is to achieve excellent closed-loop control despite the presence of plant parameter variations, external disturbances, dynamic coupling within the plant and plant nonlinearities. The minimal controller synthesis algorithm was successfully applied to the problem of decentralized adaptive schemes. The decentralized minimal controller synthesis adaptive control strategy for controlling the attitude of a rigid body satellite is adopted in this paper. A model reference adaptive control strategy which uses one single three-axis slew is proposed for the purpose of controlling the attitude of a rigid body satellite. The simulation results are excellent and show that the controlled system is robust against disturbances.     

两轮自平衡机器人控制系统的设计

针对自行设计的两轮自平衡机器人Opyanbot建立了动力学模型,应用最优控制和两轮差动等控制方法设计了控制器,提出了针对两轮自平衡机器人平衡和行进的新策略。为了提高两轮自平衡机器人的控制效果,利用基于DSP数字电路的全数字智能伺服驱动单元IPM100分别精确控制左右轮电机,并利用上位机实时控制机器人的运动状态,提高了控制精度、可靠度和集成度,得到了很好的控制效果。     

基于Bang-Bang原理的时间最优控制问题求解

时间最优控制是工程实践中经常遇到的一类最优控制问题。对于较简单的时间最优控制问题可以应用古典变分法和庞特里雅金最大值原理进行分析求解。但在实际问题中,能求得解析解的仅是少数。因此,有必要寻求一种能够有效求解时间最优控制问题的数值方法。在分析时间最优控制问题已有求解方法优缺点的基础上,提出基于Bang—Bang原理和参数最优化方法（遗传算法-单纯形法）相结合求解一类仿射系统的时间最优控制问题的方法。对线性阻尼振子问题进行了数值仿真,结果表明该方法效果良好。     

三轴稳定挠性卫星姿态机动时变滑模变结构和主动振动控制

针对带有控制受限的挠性卫星的姿态机动和振动控制问题, 给出了一类仅利用输出信息的变结构控制和 基于智能材料的主动振动控制技术相结合的复合控制方法. 首先给出变结构姿态控制器的设计来完成卫星姿态机动, 并给出一种切换机制以实现挠性卫星快速姿态机动; 其次, 采用分布式压电元件作为作动器, 设计了应变速率反馈补偿器以增加挠性结构的阻尼, 使其振动能够很快衰减. 最后, 将本文提出的方法应用于三轴稳定挠性卫星的姿态机动控制, 仿真结果表明: 在推力器的控制受限条件下, 完成姿态机动的同时, 有效地抑制挠性附件的振动.     

Chaotic satellite attitude control by adaptive approach

In this article, chaos control of satellite attitude motion is considered. Adaptive control based on dynamic compensation is utilised to suppress the chaotic behaviour. Control approaches with three control inputs and with only one control input are proposed. Since the adaptive control employed is based on dynamic compensation, faithful model of the system is of no necessity. Sinusoidal disturbance and parameter uncertainties are considered to evaluate the robustness of the closed-loop system. Both of the approaches are confirmed by theoretical and numerical results.     

移动机器人的时间最优编队

针对移动机器人的最速编队问题,结合路径规划和任务分解,提出一种分派问题的新解法和时间最优的编队策略。该策略充分考虑了障碍物环境约束和各机器人运动时的相互影响,通过将系统整体路径规划的复杂问题分解为独立路径规划问题和冲突协调问题来分别求解,降低了计算的复杂性,并能了快编队。     

带有干扰的挠性卫星非线性姿态输出反馈控制

针对挠性卫星在飞行过程中存在参数不确定性、干扰（常值扰动和正弦扰动）及挠性附件的振动控制问题,提出了一类基于输出反馈控制系统的鲁棒设计方法,该设计仅利用姿态四元数输出信息,而无需角速度、挠性变形位移及其速率测量信息;同时,在控制中又引入积分环节用于减小常值干扰引起的稳态误差,并且控制器参数的选者并不依赖于系统参数,基于Lyapunov理论证明了所设计的控制器保证了姿态的稳定和模态振动的衰减;最后,将该方法应用于挠性卫星的姿态机动控制,仿真结果表明该控制器不仅对参数不确定性具有很好的鲁棒性,而且能够有效消除常值干扰和正弦干扰的影响,在完成姿态机动控制的同时,能够抑制挠性附件的结构振动,具有良好的过渡过程品质．     

三轴稳定卫星姿态控制周期的仿真研究

针对三轴稳定卫星的姿态控制系统,在离散事件仿真器OMNeT 的基础上,建立了以陀螺、星敏感器为敏感器,以反作用飞轮为执行机构的三轴稳定卫星的闭环控制系统.对于卫星姿态控制系统中控制周期的选取作了初步的分析,最后采用双矢量定姿算法和PID控制算法,设定多种控制周期,对该卫星在对地定向模式下的控制精度进行了仿真,仿真结果清楚的显示了控制周期对姿态控制精度的影响.     

小卫星软件共用平台设计

以小卫星共用平台相配套,以面向对象的程序设计方法（OOP）为基础,提出软件共用平台的设计。利用OOP的封装性、继承性和多态性,设计小卫星软件的基本类库,介绍各个基本类的具体设计思想。最后给出由基本类库生成星载机软件系统的实例。实践表明,软件共用平台对小卫星研制是行之有效的技术。     

针铁矿法沉铁过程双层结构优化控制

针铁矿沉铁过程是锌冶炼过程中一个非常重要的环节,其中最重要的是控制氧气添加量,因此本文提出一种针铁矿沉铁过程双层结构优化控制方法.上层定义氧气利用率衡量理论消耗量与实际添加量的差别,以过程氧气利用率最高为目标优化设定级联反应器出口二价铁离子浓度下降梯度,下层以过程氧气消耗最少和出口离子浓度与上层设定值误差最小为优化目标,过程动态模型和工艺条件为约束,求解构造的非线性优化控制问题得到各反应器最优氧气添加速率.为减少不确定性干扰对系统的影响,采用一种模型参数自适应校正的方法对模型参数进行校正保证优化控制器的性能.最后根据过程离子浓度采样值计算过程实际氧气利用率作为上层优化参数重更新反应器出口二价铁离子浓度最优设定值.由于下层优化问题约束多且约束多呈非线性,采用Legendre伪谱法求解下层优化问题.仿真结果表明,所提出的双层结构优化控制方法能实现过程准确控制,减少过程氧气消耗.     

反步自适应滑模变结构的小卫星姿态鲁棒容错控制

针对小卫星在轨运行中存在输入饱和、干扰力矩与执行器故障的姿态跟踪控制问题,提出了一种反步自适应滑模变结构鲁棒容错控制方法。该方法将反步控制和滑模控制相结合,利用自适应算法估计执行器有效因子最小值和干扰上界,避免了对故障的检测与隔离,实现了输入饱和、干扰和故障对系统稳定性影响的抑制。基于Lyapunov方法从理论上证明了闭环系统的稳定性;将该方法用于小卫星的状态跟踪控制,仿真结果表明该控制器能有效处理姿态控制时输入饱和受限的约束,对部分失效和偏差型故障具有较强的容错能力,并具有一定鲁棒性。     

基于飞轮的偏置动量卫星周期干扰补偿方法

为了提高偏置动量卫星姿态控制精度,针对三轴稳定偏置动量卫星滚动/偏航回路周期干扰力矩补偿问题,提出了一种基于反作用飞轮的滚动/偏航回路周期干扰力矩补偿方案.采用频率分离法,分析了周期干扰力矩对卫星滚动/偏航回路姿态控制精度的影响.设计了周期干扰力矩的飞轮补偿方案,该干扰力矩补偿方案由安装在卫星滚动/偏航轴上的反作用飞轮实现.仿真结果表明,所设计的飞轮补偿方案提高了滚动/偏航轴的控制精度,从而验证了飞轮补偿方案的可行性和有效性.     

A basic attitude instability of spacecraft with imperfect momentum wheels

On a few occasions, spacecraft with momentum wheels have exhibited an undesired, and at first unexplained, attitude wobble. The present paper suggests a possible cause and also suggests that with the present trend in momentum wheel design using magnetic wheel bearings, the problem may get worse.A momentum wheel in practice will run in bearings which comply to the loads placed on them, to a very tiny extent. The compliance will be reduced to zero by the bearing reaction forces precessing the wheel back to its undeflected position. However, in doing so the combination of the very small compliance angle with the angular velocity of the spacecraft will cause an energy flow which will enhance the nutation of the spacecraft which caused the deflection in the first place.     

基于神经网络观测器的卫星姿态控制系统陀螺故障诊断

针对基于解析模型的卫星姿态控制系统陀螺故障诊断方法存在设计复杂、参数求解困难的问题,提出一种基于神经网络观测器的陀螺故障诊断方法。由系统内的冗余关系导出故障诊断逻辑,实现对陀螺故障的检测和隔离;同时利用先验模型知识和神经网络的非线性建模特性对陀螺故障进行估计。仿真结果表明,该方法能够实现对陀螺故障的检测、隔离和估计。     

3 种伪谱最优控制方法的积分形式及统一性证明

为了进一步提高伪谱最优控制方法的计算精度, 削弱微分形式伪谱法对状态变量近似误差的放大幅度, 研究基于积分形式的伪谱最优控制方法. 依次给出3 种伪谱法的积分伪谱离散形式, 证明当Lagrange 多项式对状态变量的近似误差等于零时, Gauss 伪谱法和Radau 伪谱法的积分形式与微分形式是等价的, 而Legendre 伪谱法的积分形式与微分形式是不等价的, 并分析了其不等价的原因.

     

挠性卫星姿态非线性局部镇定控制

本文针对挠性卫星姿态机动和振动抑制问题,给出一种基于多项式平方和(sum of squares,SOS)的非线性局部镇定控制方法.根据姿态系统结构特征,在此基础上,采用SOS结合S-procedure理论,得出相应的非线性局部可镇定条件.该条件可借助有效凸优化工具进行检验,当优化问题可解时,可构造非线性姿态控制器的解析解.最后,将文中方法应用于某型挠性卫星姿态控制.仿真结果表明,在实现大角度姿态快速机动的同时,有效抑制了挠性附件振动.     

Successive Chebyshev pseudospectral convex optimization method for nonlinear optimal control problems

This article aims at proposing a successive Chebyshev pseudospectral convex optimization method for solving general nonlinear optimal control problems (OCPs). First, Chebyshev pseudospectral discrete scheme is used to discretize a general nonlinear OCP. At the same time, a convex subproblem is formulated by using the first-order Taylor expansion to convexify the discretized nonlinear dynamic constraints. Second, a trust-region penalty term is added to the performance index of the subproblem, and a successive convex optimization algorithm is proposed to solve the subproblem iteratively. Noted that the trust-region penalty parameters can be adjusted according to the linearization error in iterative process, which improves convergence rate. Third, the Karush–Kuhn–Tucker conditions of the subproblem are derived, and furthermore, a proof is given to show that the algorithm will iteratively converge to the subproblem. Additionally, the global convergence of the algorithm is analyzed and proved, which is based on three key lemmas. Finally, the orbit transfer problem of spacecraft is used to test the performance of the proposed method. The simulation results demonstrate the optimal control is bang-bang form, which is consistent with the result of theoretical proof. Also, the algorithm is of efficiency, fast convergence rate, and high accuracy. Therefore, the proposed method provides a new approach for solving nonlinear OCPs online and has great potential in engineering practice.     

Two‐Layer Terminal Sliding Mode Attitude Control of Satellites Equipped with Reaction Wheels

This paper addresses the global stability and robust attitude tracking problem of a near polar orbit satellite subject to unknown disturbances and uncertainties. It is assumed that the satellite is fully actuated by a set of reaction wheels (RW) as control actuators because of their relative simplicity, versatility and high accuracy. The terminal sliding mode control (TSMC) approach is utilized in a two‐level architecture to achieve control objectives. In the lower layer a detumbling‐like controller is designed which guarantees the finite‐time detumbling and tracking of the desired angular velocities and based on this result a robust attitude tracking controller is designed in the upper layer to achieve 3‐axis attitude tracking in the presence of unknown disturbances and bounded uncertainties. Robust stability and tracking properties of designed controllers are proved using the Lyapunov theory. Finally, a set of numerical simulation results are provided to illustrate the effectiveness and performance of the proposed control method.     

车型机器人的时间最优轨迹

基于几何最优控制理论, 本文提出了一种新的几何推理方法, 这种方法能够有效地推导出车型机器人给定两点间的时间最优轨迹类型的充分集合. 同时也为此类非线性问题提供了一种新的思路. 首先根据旁氏极大值原理和李代数推导出切换函数的结构特性, 根据这种结构特性建立一个切换坐标系并引入一个新的向量, 该向量在此坐标系中的旋转轨迹与时间最优轨迹具有一一对应关系. 进而得到一个结论: 如果该向量的始末旋转位置和方向一致, 那么将唯一的确定一条最优轨迹. 这是第一次得到一个能够直接应用于计算一条精确的最优轨迹的结论.