高亚声速靶弹拖曳式诱饵系统的拖缆姿态分析

拖缆姿态分析是高亚声速靶弹拖曳诱饵系统结构及布局设计的基础。针对常见的诱饵气动外形,利用旋成体空气动力学理论,分析估算高亚声速环境下拖曳诱饵的气动阻力。采用离散化方法,将柔软拖缆视为由多段刚体连接而成的链状结构,利用力矩平衡原理,由诱饵端起计算缆绳每一离散刚体段的姿态,并逐次向载弹拖缆定位点递推,最终近似计算出整条拖缆姿态。     

多视场星敏感器结构参数标定方法

提出一种基于星间角距不变原理的多视场(FOV)星敏感器结构参数标定方法.这种方法以欧拉角表征多视场星敏感器各个子视场之间的旋转关系,利用识别得到的各个视场星点的坐标信息和赤经赤纬信息,计算出多对星光矢量来建立标定模型和目标函数,然后使用L-M算法优化目标函数并解算出各个子视场之间的结构参数.此方法不需要外部姿态测量仪器辅助,可用于在轨和地面标定.在全天球随机抽取多个姿态生成多视场的仿真星图用于标定,并采用星内角统计偏差作为结构参数标定精度的评价指标.这种方法能够准确求解多视场星敏感器的结构参数.星内角统计偏差的平均值在星点位置噪声标准差为0.1像素的仿真试验中为1.3",在外场观星的实际试验中为6.4".      

Instantaneous BeiDou–GPS attitude determination: A performance analysis

The advent of modernized and new global navigation satellite systems (GNSS) has enhanced the availability of satellite based positioning, navigation, and timing (PNT) solutions. Specifically, it increases redundancy and yields operational back-up or independence in case of failure or unavailability of one system. Among existing GNSS, the Chinese BeiDou system (BDS) is being developed and will consist of geostationary (GEO) satellites, inclined geosynchronous orbit (IGSO) satellites, and medium-Earth-orbit (MEO) satellites. In this contribution, a BeiDou–GPS robustness analysis is carried out for instantaneous, unaided attitude determination.     

Attitude determination of planetary exploration rovers using solar panels characteristics and accelerometer

In this study, we propose a new attitude determination system, which we call Irradiance-based Attitude Determination (IRAD). IRAD employs the characteristics and geometry of solar panels. First, the sun vector is estimated using data from solar panels including current, voltage, temperature, and the normal vectors of each solar panel. Because these values are obtained using internal sensors, it is easy for rovers to provide redundancy for IRAD. The normal vectors are used to apply to various shapes of rovers. Second, using the gravity vector obtained from an accelerometer, the attitude of a rover is estimated using a three-axis attitude determination method. The effectiveness of IRAD is verified through numerical simulations and experiments that show IRAD can estimate all the attitude angles (roll, pitch, and yaw) within a few degrees of accuracy, which is adequate for planetary explorations.     

New one-axis one-sensor magnetic attitude control theoretical and in-flight performance

New one-axis magnetic attitude control is proposed. Only one attitude sensor providing any inertial direction measurements is necessary, magnetometer is not used. The control may be used as a backup capability in case main actuators or some attitude sensors fail. Sun pointing is achievable using only three-axis Sun sensor, so the control may be used to lower the power consumption during battery charging. Asymptotic stability of different equilibria depending on the satellite inertia tensor is summarized. In-flight results from “Chibis-M” microsatellite are provided proving general control performance.     

弹性高超声速飞行器建模及精细姿态控制

为保证超燃冲压发动机的良好进气,需要对高超声速飞行器进行精细姿态控制,但弹性振动问题极大影响其精细姿态控制精度。以高超声速飞行器的纵向通道为例,分析弹性振动问题对飞行控制系统的影响,建立面向控制的弹性高超声速飞行器数学模型,考虑气动参数和模态参数的大范围摄动,采用主动控制策略,基于鲁棒H∞理论和LQR理论设计精细姿态控制系统。大量仿真表明：在考虑测量噪声、舵机非线性、参数大范围摄动的情况下,控制系统能够很好地跟踪刚体攻角,抑制弹性攻角,并保证进气口当地攻角±0.4度的控制精度,满足高超声速飞行器精细姿态控制的要求。     

Attitude Control Considering Variable Input Saturation Limit for a Spacecraft Equipped with Flywheels

A new attitude controller is proposed for spacecraft whose actuator has variable input saturation limit. There are three identical flywheels orthogonally mounted on board. Each rotor is driven by a brushless DC motor (BLDCM). Models of spacecraft attitude dynamics and flywheel rotor driving motor electromechanics are discussed in detail. The controller design is similar to saturation limit linear assignment. An auxiliary parameter and a boundary coefficient are imported into the controller to guarantee system stability and improve control performance. A time-varying and state-dependent flywheel output torque saturation limit model is established. Stability of the closed-loop control system and asymptotic convergence of system states are proved via Lyapunov methods and LaSalle invariance principle. Boundedness of the auxiliary parameter ensures that the control objective can be achieved, while the boundary parameter’s value makes a balance between system control performance and flywheel utilization efficiency. Compared with existing controllers, the newly developed controller with variable torque saturation limit can bring smoother control and faster system response. Numerical simulations validate the effectiveness of the controller.     

轨姿控液体火箭发动机水击仿真模拟

以轨姿控液体火箭发动机为研究对象,根据模块化思想,利用AMESim建立了仿真平台,仿真计算了发动机系统工作中管路的水击压力。结果表明:轨控发动机的工作是引起大水击的主要因素。通过与理论计算和试验数据的对比表明,仿真模型较好地描述了管路水击的生成过程。介绍了减小系统水击量的措施。     

GNSS多频观测对定姿精度的影响分析

针对单历元定姿的精度问题,对多频双差观测模型下的定姿精度进行了理论推导,分析了影响定姿精度的各种因素,并着重研究了GPS和Galileo系统下多频观测值对定姿精度的改善程度。理论分析和仿真实验均表明．相比于单频定姿,多频观测可以显著提高定姿精度。     

一种改进的基于双矢量观测的姿态确定算法

为了提高飞行器姿态确定的精度和姿态矩阵的解算速度,提出了一种改进的双矢量定姿算法.这种算法利用测量系统的方差对两个观测矢量进行加权处理,求得一个新的矢量,以两观测矢量夹角为判断依据选取加权系数;以新矢量为基准矢量,利用双矢量定姿算法求解姿态矩阵,并对求得的姿态矩阵进行修正.仿真结果表明:这种算法所需时间为优化算法的50%,当两个传感器测量误差不同、两矢量为任意夹角时,这种算法比优化的双矢量算法精度高;当两个传感器测量误差相同时,除了两矢量夹角为90°外,这种算法均比优化的双矢量算法精度高.