【作者】 刘海颖；

【导师】 王惠南；

【作者基本信息】 南京航空航天大学 ， 精密仪器及机械， 2008， 博士

【摘要】 微小卫星具有成本低、功能密度高以及研发周期短等一系列优点,成为航天领域的一个重要发展方向,姿态控制系统(ACS)是其核心,一定程度上决定了卫星所能实现的在轨功能。微小卫星的ACS在质量、体积以及功耗等方面有严格限制,本文研究目的是探索并研制满足总体约束和在轨功能要求的高性能ACS。本文以南京航空航天大学“天巡者”微小卫星研制为背景,系统的研究了微小卫星ACS相关理论、方法以及关键技术,主要研究内容和创新性成果如下:(1)在对国内外微小卫星及其ACS研究现状归类分析基础上,通过对“天巡者”微小卫星飞行任务和总体对其ACS要求的分析,提出了具有某种优势且切实可行的ACS方案配置,给出各组成部分的技术指标。建立了完整的微小卫星ACS数学模型,包括卫星运动学、动力学、测量参考、执行结构以及环境干扰等模型,对影响卫星姿态的干扰力矩进行了仿真分析,并采用能量分析法研究了卫星的稳定性。(2)提出了一种新的姿态确定组合滤波方法,融合双矢量姿态确定算法和EKF、UKF等非线性滤波,将高维观测量转化为四元数,使观测方程转化为线性方程,显著的减少了计算量,并提高了滤波精度。以磁强计、太阳敏感器和陀螺组成姿态确定系统,采用直接观测方程,以及q-method和高斯-牛顿算法的预处理观测方程,设计了无陀螺EKF、有陀螺EKF以及无陀螺UKF共9种滤波器,通过详细的仿真分析,表明预处理观测方法具有更好的效果。(3)针对微小卫星初态控制这一关键技术,基于喷气系统设计了速率阻尼、拟PD以及限制姿态反馈等控制律,以适用于大角度姿态捕获,并根据不同的动量轮起旋方式,提出了多种初态控制方案;基于磁力矩器设计了B-dot速率阻尼、能量控制、滑模控制以及限制姿态反馈等磁控制律,提出了B-dot阻尼加动量轮常速起旋、磁控加动量轮姿态捕获的新方法,给出了Y-Thomson初态控制方案。对于所设计的喷气控制和磁控方法进行详细的理论分析和仿真验证,为其工程应用提供了必要的论证。(4)对于微小卫星的长期在轨运行,设计了动量轮俯仰控制和磁卸载控制律。提出了新的磁控章、进动控制律,应用MTS法给出其参数以及时间响应的近似公式,该理论研究及分析对工程设计具有很好的指导价值;设计了动量轮常速旋转的同时进行主动磁控的三轴稳定控制律,不仅避免了动量轮饱和卸载,而且使控制过程操作简捷。(5)研究了喷气系统加偏置动量轮的高精度联合控制方法,设计了LQG控制和Lyapunov控制三轴稳定控制律;针对偏置动量微小卫星姿态机动,设计了Lyapunov控制、滑模控制以及反馈线性化等非线性控制律,用于三轴小机动和俯仰大机动,满足高精度的同时还具有实时性;深入研究了喷气故障情况下的欠驱动控制,提出了一种新的姿态描述方法——(w , z)参数化法,通过两次垂直旋转来表示卫星姿态,设计了欠驱动卫星的稳定控制和再定位控制律,并通过仿真表明其有效性。(6)基于VxWorks实时操作系统进行微小卫星ACS软件设计,提出了采用微内核和软件层次结构的设计思想,完成了多任务调度管理、控制模式管理以及各模式的任务相互通信等设计,仿真实践表明其具有高可靠性、易扩展性等优点,为整个星载软件的实现打下了基础。总之,本文针对“天巡者”微小卫星的功能要求,研究探索一种具有高精度、高可靠性以及高性价比的ACS方案,针对其关键技术提出了解决方法,在理论上、方法上具有多处创新性研究成果,对于满足任务要求和总体约束的高性能微小卫星ACS设计具有较大借鉴意义和应用价值。更多还原

【Abstract】 Micro-satellite is becoming an important direction of spacecraft development due to the advantages such as low cost, high density of functionality and short research developement cycle. The ACS is the most important subsystem that partly defines the function of satellite. Bacause the ACS micro-satellite is under stringent constraints on mass, volume and power, so the purpose of this paper is to design a high performance ACS that satisfied with system constraints and mission demands. Taking the“TXZ”micro-satellite that developing by NUAA an example, the relevant theories, methods and key technologies are studied systematically in this dissertation, and the main content and achievements are as follows:1. Based on the analysis of mission for“TXZ”micro-satellite and its requirements towards ACS, a feasible scheme of the ACS configuration as well as the performance of the sensitive and executive organs are outlined.The integrated mathematical model about ACS for micro-satellite is established, including model of kinematics, dynamic, sensor, actuator and disturbance. The influence of disturbance torque for the attitude control is simulated and analysised, in addition the stabilization of satellite is studied using an energy consideration method.2. A new combined filter for attitude determination is presented which syncretize the two vectors method with EKF or UKF. It reduces high dimension vectors to quaternion, so the nonlinear observation equation is turned into linear that reduce the computational requirement and enhance precision. Using magnetic sensor, sun sensor and gyro, nine filters namely EKF incorporating gyro, EKF or UKF without gyro are developed, that based on direct observation or deal with by q-method and Gauss-Newton method in advance. The simulation result illustrates that indirect method have better effect especially by Gauss-Newton algorithm.3. Aim to the pivotal phase of initial attitude control, the detumbling and the large attitude acquisition controllers using assimilated PD control as well as limited attitude feedback using micro-thrustors are designed. On the other hand the B-dot, energy, sliding mode and limited attitude feedback controllers using magnetic torque are designed. A new method for B-dot detumble and attitude acquisition with the wheel circumgyrate synchronously, as wheel as the initial control scheme using Y-Thomson are proposed. For all the thruster and magnetic contol method, the detailed theoretic and simulating analysis is conducted.4. For normal task phase the pitch axis controller using a momentum wheel and momentum unloading using magnetic torque are developed. A new magnetic controller for nutation and precession damping is given, and its parameters are investigated by MTS method that given preferable instruction for practical application. Moreover with constant wheel the active magnetic controllers are designed for three-axis stabilization, which avoid the momentum satuation and make control process convenient.5. The combined control methods using thrusters plus a momentum wheel are researched. Firstly the LQG and lyapunov control law are designed for stabilization, then three nonlinear controllers of lyapunov, sliding mode and feedback linearization control are designed for large angle maneuver which not only have high precision but alse account for real-time need. The attitude control of underactuated satellite with thruster failure is studied using a new method named (w,z) parametrization. The attitude stabilization and reorientation controllers under actuator failure are designed and validated by simulation tests.6. Based on VxWorks operating system the ACS software designing is carried out. The design philosophy using micro kernel and hierarchical structure method for software system is given. Meanwhile the system schedule of several-tasks, the managing control mode and communication among tasks in every mode are completed for ACS. The simulations indicate that it has the high reliability and extensibility, thereby, can be supported for further develop of micro-satellite.In a word, the ACS for mission demands of“TXZ”satellite is studied deeply and its key technologies are resolved effectivly in this thesis. There are many innovations with great applied value in theory and method which can give reference and instruction in developing the high performance ACS for other micro-satellite.更多还原