用于微小型飞行器姿态估计的四元数扩展卡尔曼滤波算法

针对MEMS陀螺、加速度计、磁强计组合的姿态确定系统,笔者设计了用于微小型飞行器姿态估计的四元数扩展卡尔曼滤波算法．取姿态误差四元数和陀螺随机漂移构建滤波状态向量,通过误差四元数微分方程和陀螺随机误差模型建立了卡尔曼滤波状态方程;采用改进的高斯-牛顿算法将传感器观测量转化为四元数,通过与利用陀螺信息估计的四元数相乘,得到姿态误差四元数作为卡尔曼滤波量测值,显著减小了机动加速度对姿态估计的影响．仿真实验显示：四元数静态估计误差小于0．22％,在动态情况下,四元教估计值能够较好地跟踪真实值的变化,表明该滤波算法能够有效提高姿态估计的精度．     

Huber-based unscented filtering and its application to vision-based relative navigation

A new algorithm called Huber-based unscented filtering (UF) is derived and applied to estimate the precise relative position, velocity and attitude of two unmanned aerial vehicles in the formation flight. The relative states are estimated using line-of-sight measurements between the vehicles along with acceleration and angular rate measurements of the follower. By making use of the Huber technique to modify the measurement update equations of standard UF, the new filtering could exhibit robustness with respect to deviations from the commonly assumed Gaussian error probability, for which the standard unscented filtering would exhibit severe degradation in estimation accuracy. Furthermore, contrast to standard extended Kalman filtering, more accurate estimation and faster convergence could be achieved from inaccurate initial conditions. During filter design, the global attitude parameterisation is given by a quaternion, whereas a generalised three-dimensional attitude representation is used to define the local attitude error. A multiplicative quaternion-error approach is used to guarantee that quaternion normalisation is maintained in the filter. Simulation results are shown to compare the performance of the new filter with standard UF and standard extended Kalman filtering for non-Gaussian case.     

基于MEMS惯性传感器的微型姿态测量系统

提出了一种基于低成本MEMS惯性传感器的微型姿态测量系统,包括MEMS速率陀螺、MEMS磁强计、单轴MEMS加速度传感器.重点研究了基于扩展Kalman滤波（EKF）的姿态估计创新算法,通过速率陀螺更新误差状态四元数计算姿态角,并通过飞行方向的加速度传感器和三轴磁强计来补偿陀螺漂移和姿态角误差,利用扩展卡尔曼滤波方程消除瞬时干扰,实现高动态姿态测量.系统的仿真和高动态实验表明,姿态测量动态精度低于5°,静态精度低于0.7°.     

等效旋转矢量法在旋转弹姿态解算中的应用

作为捷联惯导的核心问题,姿态更新算法的选择至关重要.针对旋转弹的姿态测试问题,在四元数增量算法的基础上利用等效旋转矢量法对姿态进行优化,给出了姿态解算的数学模型.仿真结果显示,该算法对不可交换误差的抑制效果明显,同时,在一定程度上减小了累积误差,提高了导航精度.     

Design of X-type unmanned quadrotor based on STM32北大核心CSCD

For the flight attitude control of unmanned quadrotor, there still exist some issues on accurate measurement, calculation and output. To acquire a stable flight attitude control, an X-type unmanned quadrotor was designed based on STM32 microprocessor. Dual processors, dual gyroscopes and dual accelerometers were integrated into the hardware architecture. Real time flight attitude information was collected. Quaternion complementary filter algorithm and cascade PID control algorithm were adopted in attitude calculation and output. The experiment results showed that the structure of dual gyroscopes and dual accelerometers had higher measurement accuracy under little angle disturbance, and the attitude angle got a smaller output error with appropriate parameter settings of cascade PID. The results demonstrate that dual sensors can perform stronger noise immunity in attitude measurement, and the designed X-type unmanned quadrotor has good flying performance and can achieve the purpose of flight attitude stability control, which provides guidance for further study on flight control system.     

基于STM32的X型四旋翼无人机设计

针对四旋翼无人机飞行姿态测量易受干扰、姿态解算和姿态控制输出误差大等问题,以飞行姿态稳定控制为目标,设计了一种基于STM32系列微控制器的X型四旋翼无人机。采用以双处理器、双陀螺仪和双加速度计为主的硬件架构,实时采集无人机飞行姿态信息,并结合基于四元数的互补滤波算法和串级PID控制算法对姿态信息分别进行解算和控制输出。实验结果显示:小角度扰动下,双陀螺仪和双加速度计姿态测量精度高,合理设置双环PID参数后,姿态角输出误差小。结果表明:双传感器硬件架构在姿态测量中的抗干扰性更强,设计的X型四旋翼无人机飞行性能较好,达到飞行姿态稳定控制的目的。研究结果对后续飞行控制系统的深入研究具有一定的指导作用。     

光纤陀螺姿态系统信号处理方案

光纤陀螺输出信号中存在较大的高频噪声，这降低了光纤陀螺姿态系统的解算精度。为此对信号进行多重积分，求取一个计算周期内载体姿态变化的旋转矢量表达式，从而得到一种新的信号处理方法，并讨论了其工程实现方案。仿真表明，与传统四元数算法比较，该方法在解算系统姿态的同时，能够较好地平滑噪声的影响。     

Study of Visual Information Acquisition Technology based on AGV Robot

Visual information acquisition is an important component of the AGV robot. The system adopts STM32F4 embedded application of the ARM Cortex-M4 kernel as the main control module,using shift algorithm to finish on a specific color piece of target tracking. For multi-sensor fusion of three methods,quaternion method is used to correct the attitude,the stability of AGV robot visual information acquisition and image clarity are improved.     

Research on Steward Dynamic Platform Simulation Numerical Algorithm

In order to achieve attitude control of the six degrees of freedom steward dynamic platform,as well as the real time simulation cockpit attitude,Washout Filtering method was adopted in this paper as the simulation algorithm to derive Washout Filter high-pass, low-pass filter transfer functions into a differential equation algorithm and longitudinal acceleration tilt strategy,pitching strategies etc. Experimental examples are used to verify correctness of the algorithm.     

四元数矩阵的对角化及其算法

四元数矩阵的对角化在四元数力学等四元数应用学科的理论研究和数值计算中起到重要的作用。本文通过引入友向量的方法,进一步研究了四元数矩阵的对角化问题,构造性地给出了四元数矩阵对角化的实用算法。     

基于四元数离散傅里叶变换的全息数字水印算法

目的结合四元数和全息技术的优势,将数字水印技术应用在彩色图像中,以提高水印算法的抗攻击能力。方法将四元数离散傅里叶变换和加密傅里叶全息技术应用到数字水印算法。首先对一幅彩色图像进行数据类型的转换,表示成四元数矩阵,然后对其进行四元数离散傅里叶变换,最后基于人眼视觉特性将水印信息加密后利用重复计算选取合适的嵌入强度后嵌入变换得到的频域矩阵中,实现信息隐藏。结果算法能够将彩色图像作为一个整体进行处理,有较好的不可见性。与此同时,提高了四元数域水印对于裁切攻击的抵抗能力。结论该算法在保证水印不可见性的同时能够抵抗一定程度的攻击,满足数字防伪以及版权保护的需要。     

基于四元数矩阵奇异值分解的彩色图像分解

讨论了四元数矩阵的奇异值分解（QSVD）,四元数矩阵的奇异值仍是正实数,但两个酉矩阵是含有四元数的四元数矩阵。给出通过四元数矩阵的等价实矩阵求解QSVD的有效算法。最后应用QSVD进行彩色图像分解,并给出了在Fruits、Baboon等图像上的实验结果。QSVD使许多基于SVD的图像处理方法可以推广到彩色图像处理上而不用再将彩色图像分解成三个通道图像进行处理。     

基于MEMS的分散式低阶AHPRS系统设计

设计一种基于MEMS陀螺、加速度计、磁强计以及GPS模块姿态航向位置参考系统(AHPRS).首先,姿态航向参考系统主要由姿态估计卡尔曼滤波器与补偿卡尔曼滤波器构成,通过补偿滤波器周期修正姿态估计滤波器,从而弥补了由于机体的刚体运动而导致姿态角的估计误差;其次,采用分散式卡尔曼滤波器的设计思路,以估计的误差姿态角作为导航系统卡尔曼滤波器的输入量,有效降低了导航滤波方程的阶次,减小了对姿态解算计算机的性能要求;最后,通过仿真与飞行试验验证该AHPRS有效地克服了动态环境下对系统姿态估计偏差大的缺点,提高了系统的姿态航向与速度位置估计精度.     

Fusion of MRI and CT images using guided image filter and image statistics

In medical imaging using different modalities such as MRI and CT, complementary information of a targeted organ will be captured. All the necessary information from these two modalities has to be integrated into a single image for better diagnosis and treatment of a patient. Image fusion is a process of combining useful or complementary information from multiple images into a single image. In this article, we present a new weighted average fusion algorithm to fuse MRI and CT images of a brain based on guided image filter and the image statistics. The proposed algorithm is as follows: detail layers are extracted from each source image by using guided image filter. Weights corresponding to each source image are calculated from the detail layers with help of image statistics. Then a weighted average fusion strategy is implemented to integrate source image information into a single image. Fusion performance is assessed both qualitatively and quantitatively. Proposed method is compared with the traditional and recent image fusion methods. Results showed that our algorithm yields superior performance.     

抗打印扫描彩色图像水印算法

目的设计一种适用于彩色打印扫描图像的鲁棒性盲水印算法。方法结合四元数傅里叶变换及离散小波变换的优点,提出了一种双变换域全息水印算法。利用四元数傅里叶变换及离散小波变换,将全息水印信息分散嵌入到彩色宿主图像3个色彩分量的低频小波系数区域,而不引起大的图像失真,同时,算法实现了盲提取。结果算法满足不可见性要求,同时打印扫描实验证明,该算法具有抵抗打印扫描攻击的能力。结论结合四元数傅里叶变换及离散小波变换的双变换域水印算法,保留了2种变换域在处理彩色图像中的优点,在应用于打印扫描彩色图像时,效果比现有算法更好。     

四元数分形的生成与研究

为实现三维分形,应用四元数作为迭代变量生成四维Julia集。在介绍了如何实现三维显示以及迭代方法选择之后,详细说明了生成四元数分形的具体过程,并给出图形实例。因为改进了逃逸时间算法的判别标准,因此,目标集合是边界点集。最后通过观察与分析,总结了四元数Julia集的某些特征,比较了它与复平面Julia集异同点,说明了两者之间的联系。     

Color edge detection using multiscale quaternion convolution

This article presents a novel color edge detection algorithm based on quaternion convolution. A set of multiscale quaternion masks are presented, and the filtered results are multiplied at adjacent scales using dot product to enhance the edge structures while diluting noise. Experimental results show that the proposed method is efficient and robust for color images. © 2010 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 20, 354–358, 2010     

Complementary filter design for testing of IS-95 code divisionmultiple access wireless communication systems

In this paper, a simple design of a complementary filter is presented for performance measurement of an IS-95 code division multiple access wireless communication system (1995). The complementary filter is required to meet the design requirements, which are specified in IS-97 document (1994). The purpose of employing the complementary filter in test equipment is to remove intersymbol interference introduced by the base station transmit-filter and the transmit-phase equalizer. Five window functions, which do not affect the desirable response at the proper sampling times, are applied to the desirable output. The output of a window Is set to be the output of the complementary filter. Then, the complementary filter is obtained by taking a deconvolution of the output response of the window with the impulse response resulted by cascading the base station transmit-filter and the transmit-equalizer. It is found that the output of the complementary filter with the Kaiser window function meets all requirements specified in IS-97. In addition, it is observed that the Kaiser window has the smallest number of the filter coefficients among all windows considered in this paper. Therefore, the complementary filter with the Kaiser window is recommended for implementation of the IS-95 system measurement     

基于MIMU/GPS/EC的联邦卡尔曼滤波器设计

针对组合导航系统高精度、高容错性、高可靠性的实际应用要求,提出了基于MIMU/GPS/电子罗盘的组合导航方案,设计并实现了位置、速度、姿态分别组合的无重置式联邦滤波器,各子滤波器相互独立工作,无反馈重置带来的相互影响,保证了系统最高的容错性能和较高的精度.仿真试验结果表明,所设计的基于MIMU/GPS/电子罗盘的联邦滤波算法能够有效抑制纯惯导的误差发散问题,具有计算量小、容错性高、精度高等特点,有着广阔的应用前景.     

Complementary Kalman Filter as a Baseline Vector Estimator for GPS-Based Attitude Determination

The Global Positioning System (GPS) offers the interferometer for attitude determination by processing the carrier phase observables. By using carrier phase observables, the relative positioning is obtained in centimeter level. GPS interferometry has been firstly used in precise static relative positioning, and thereafter in kinematic positioning. The carrier phase differential GPS based on interferometer principles can solve for the antenna baseline vector, defined as the vector between the antenna designated master and one of the slave antennas, connected to a rigid body. Determining the unknown baseline vectors between the antennas sits at the heart of GPS-based attitude determination. The conventional solution of the baseline vectors based on least-squares approach is inherently noisy, which results in the noisy attitude solutions. In this article, the complementary Kalman filter (CKF) is employed for solving the baseline vector in the attitude determination mechanism to improve the performance, where the receiversatellite double differenced observable was utilized as the measurement. By using the carrier phase observables, the relative positioning is obtained in centimeter level. Employing the CKF provides several advantages, such as accuracy improvement, reliability enhancement, and real-time assurance. Simulation results based on the conventional method where the least-squares approach is involved, and the proposed method where the CKF is involved are compared and discussed.