互补滤波算法在四旋翼飞行器姿态解算中的应用

针对四旋翼飞行器飞行过程中的姿态最优估计问题,本着准确、快速的原则,选择了基于陀螺仪、加速度计和电子罗盘的捷联式惯性测量系统.由于这些传感器存在温度漂移和噪声干扰等问题,采用互补滤波算法,通过融合IMU多传感器的数据信号,对测得的姿态数据进行补偿修正,解算出高精度的姿态角.为了验证互补滤波算法的有效性和实用性,通过实际的四旋翼飞行器角度测量系统对互补滤波算法展开研究.结果表明姿态角解算中采用互补滤波算法能够快速、稳定的输出高精度姿态数据,姿态角最大跟踪误差控制在±2°以内,满足四旋翼飞行器飞行控制的要求,成功完成了姿态的最优估计.     

基于混合滤波的四旋翼无人机抗干扰姿态控制系统设计

针对四旋翼无人机抗干扰姿态控制系统抗干扰能力较差,控制性能较差的问题;文章提出基于混合滤波的四旋翼无人机抗干扰姿态控制系统,优化设计了系统的硬件和软件部分;硬件部分设计主控制器,通过发生器输出的PWM波信号控制电速;设计传感器模块,测量姿态角与加速度等数据,采用双陀螺仪和双加速度计结构,避免共振对测量结果产生影响;设计电机驱动模块,选用X2216型无刷直流电机为运行提供较高的转速和响应速度;设计无线数据传输模块,选用3DR无线数据传输模块实时监测姿态信位置信息数据;构建基于混合滤波的四旋翼无人机抗干扰姿态控制系统,对角速度数据、加速度数据等数进行融合改正,再运用互补滤波器对陀螺仪和加速度计进行信号检测和控制调度,得到精确的实时姿态角;采用姿态控制算法和串级PID控制策略,提高对系统的控制力,保证飞行的平稳;实验结果表明,基于混合滤波的四旋翼无人机抗干扰姿态控制系统抗干扰性强、控制能力高以及响应速度快。     

基于不变扩展卡尔曼滤波的无人机姿态估计

为解决四旋翼无人机姿态估计问题，提出了一种不变扩展卡尔曼滤波(Invariant Extended Kalman Filter, InEKF)算法，用于同时估计四旋翼的姿态和惯性测量单元(Inertial Measurement Unit, IMU)的陀螺仪偏差。利用李群理论和不变观测器设计方法，将算法表述为一个连续时间随机非线性滤波器，其状态空间由直积矩阵李群SO(3)×R³给出，SO(3)中的估计值由IMU对重力矢量和地球磁场向量测量值加以修正。为在无人机上实现该算法，将状态和协方差传播方程离散化。最后，所提滤波算法相对于现有算法的性能优势通过仿真实验得到了验证。     

基于视觉的四旋翼无人机自主定位与控制系统

针对GPS(global positioning system)信号缺失环境下无人机(UAV)自主飞行控制问题,设计了一种基于视觉的自主定位与控制方法.首先通过增加特征点提取数量和优化关键帧存储来对传统视觉SLAM(simultaneous localization and mapping)算法进行改进,提高了算法的鲁棒性与通用性.其次,引入光流传感器作为视觉SLAM地图丢失情况下辅助位置信息测量单元,提高无人机飞行控制的安全性,并成功地克服视觉SLAM图像丢失问题和光流法存在的位置漂移问题.然后采用EKF(extended Kalman filter)融合无人机位置和3维加速度信息,得到了较为精确的位置信息,同时提高了信号输出频率.最后,利用上述方法获取的无人机位置信息设计PID(proportion integration differentiation)和RISE(robust integral of the signum of the error)非线性控制器,增加了算法的鲁棒性.为验证该控制策略的有效性,搭建了四旋翼无人机视觉控制系统实验平台.该平台采用嵌入式控制系统架构,使用机载计算机运行所提算法,避免了图像及控制命令在无线传输过程中引起的时间延迟和信号干扰.室外飞行实验表明,此控制方案实现了自主定位与飞行控制功能.     

基于模糊卡尔曼滤波的四旋翼姿态估计方法

针对四旋翼在飞行中因运动加速度及磁场干扰等影响引起的姿态估计误差，提出一种基于动态估计的模糊扩展卡尔曼滤波姿态估计算法。该算法利用传感器数据对运动频率、运动加速度及磁场干扰的大小进行估计，对估计值模糊推理后，使用输出值调整卡尔曼滤波测量噪声方差和梯度下降步长，增加姿态估计算法的动态适应性。为验证所设计算法的估计效果，使用四旋翼仿真模型进行验证。实验结果表明，该算法能够有效地提高四旋翼在高机动、强干扰情况下姿态估计的姿态跟踪精度、动态性能、抗干扰能力。     

采用组合滤波算法的无人机航向测量系统研究

为了解决低成本小型无人机航姿精密测量的问题,设计了一种基于MARG传感器的航向测量系统方案。该系统由MEMS IMU、电子罗盘和STM32F407微处理器组成,采用运算量较小的梯度下降算法和改进型二阶互补滤波算法将具有互补特性的电子罗盘和IMU进行数据组合滤波,并基于四元数进行坐标转换,解算出飞行器航向信息。通过对航向测量系统的实验测试及其在旋翼飞行器上的验证分析,结果表明,在没有外界信息辅助的情况下,该系统较好地解决了噪声干扰与航向测量问题,可以满足小型旋翼无人机对航向信息的要求。     

一种小型无人机高度测量方法的研究与实现

为了满足某小型无人机飞行控制中对高度信号的采集与处理,提出了用无线电高度来确定基准高度,用气压高度来确定相对高度,用起飞点的实测温度进行补偿的设计思想,综合这3种手段来有效消除外界环境对气压高度测量精度的影响。传感器数据融合方面,利用飞行器运动学推算出的高度状态方程以及传感器观测模型,采用Kalm an滤波技术来估计和修正传感器的测量高度。测试结果表明,此方法得到了较准确的高度测量信息,可以满足无人机飞行控制的需求。     

基于IEKF的四旋翼无人机姿态测量方法研究

研究四旋翼无人机在实时飞行时姿态测量的问题.由于四旋翼无人机多采用陀螺仪、加速度计、地磁计(MEMS)传感器测量各姿态,测量值存在偏差,无法直接使用.为解决利用不准确的传感器测量信息获得精确姿态角度的难点,并为了克服常规的扩展卡尔曼算法(EKF)带来的较大滤波偏差,以及四元素法表述复杂等困难,采用了一种改进的迭代EKF(IEKF)算法,利用欧拉角的描述方法,融合MEMS的信息对四旋翼无人机的姿态角度进行测量.实验结果表明,改进方法能准确测量出姿态角,且通过与常规EKF测量效果的比对可以看出,IEKF在测量精度上确有较明显的改善,表明改进方法是有效的,为四旋翼无人机实时调整姿态提供了一种科学手段.     

低成本无人机姿态解算研究

针对小型四旋翼无人机姿态解算数据精度低、缺少余度控制、易发散等问题,提出一种基于GPS、三轴陀螺仪加速度计、三轴磁力计的随机加权自适应滤波算法估计无人机姿态;建立四旋翼无人机姿态旋转矩阵,搭建加速度计和磁力计获取无人机姿态信息的模型,以及采用四元数解算法的陀螺仪定姿解算模型;采用随机加权自适应估计法,依据多元函数求极值定理,在保证总体均方差最小的情况下导出最优随机加权因子,进而解算出姿态角信息,提高四旋翼无人机姿态解算滤波精度与稳定性;仿真与试验结果表明:随机加权自适应滤波与平均值滤波算法相比解算精度更高,输出结果更平稳,且无人机各项预期功能均能正常实现,能够满足四旋翼无人机自主飞行的需要。     

一套完整的基于视觉光流和激光扫描测距的室内无人机导航系统

提出了一套室内四旋翼无人机控制, 导航, 定位和地图构建的完整解决方案. 无人机机载系统包括三个主要传感器, 即惯性测量单元, 下视相机和激光扫描测距仪. 经过处理, 融合这些传感器的测量数据, 无人机能够可靠的估计自己的飞行速度和实时位置, 并且沿着室内的墙壁进行无碰撞飞行. 通过收集一个完整飞行实验的数据, 无人机的飞行路径和在室内的环境也可以被很好地估计出来. 这套系统中的自主导功能不需要任何远程传感信息或脱机计算能力. 这套室内导航方案的性能和可靠性已在实际的飞行实验中被验证.     

Nonlinear robust control of a quadrotor helicopter with finite time convergence

In this paper, the control problem for a quadrotor helicopter which is subjected to modeling uncertainties and unknown external disturbance is investigated. A new nonlinear robust control strategy is proposed. First, a nonlinear complementary filter is developed to fuse the raw data from the onboard barometer and the accelerometer to decrease the negative effects from the noise associated with the low-cost onboard sensors Then the adaptive super-twisting methodology is combined with a backstepping method to formulate the nonlinear robust controller for the quadrotor''s attitude angles and the altitude position. Lyapunov based stability analysis shows that finite time convergence is ensured for the closed-loop operation of the quadrotor''s roll angle, pitch angle, row angle and the altitude position. Real-time flight experimental results, which are performed on a quadrotor flight testbed, are included to demonstrate the good control performance of the proposed control methodology.     

四旋翼飞行器带速度补偿的多回路PID位置跟踪控制

针对四旋翼飞行器的位置跟踪问题,采用ADAMS(automatic dynamic analysis of mechanical system)软件搭建了四旋翼飞行器的非线性数学模型,并将模型导入到Matlab中,采用多回路PID位置控制策略对飞行器的位置跟踪进行控制,并在此基础上提出采用速度PID进行补偿多回路PID的位置跟踪控制策略.仿真结果表明:所设计的速度PID对多回路PID的位置跟踪控制策略进行补偿,对于四旋翼飞行器位置控制具有响应速度快、超调小、鲁棒性强等特点;所采用的联合仿真方法效果直观.     

基于Mahony滤波器和PID控制器的四旋翼飞行器姿态控制

四旋翼飞行器由于其简单的气动布局和复杂的动力学模型在控制领域引起了研究热潮,姿态估计与控制器设计一直是实现四旋翼飞行器稳定飞行的难点。为实现精确的四旋翼飞行器姿态估计,首先分析了IMU传感器示值组成和误差存在的原因,然后在方向余弦矩阵（DCM）和重正交化的基础上,具体给出了Mahony滤波器的实现流程。通过与扩展卡尔曼滤波器对比表明,该算法不仅能保证很高的姿态估计精度,而且计算时间小于扩展卡尔曼滤波器,有助于提高系统姿态估计的实时性。结合Mahony滤波后的姿态信息,采用嵌套PI-PID控制策略设计了控制器。最后,将姿态估计算法和控制算法应用到实验平台上,可以实现四旋翼飞行器悬停和角度跟踪功能。     

基于互补滤波器的四旋翼飞行器姿态解算

针对小型四旋翼飞行器姿态解算这一基本问题,详细分析了姿态解算的过程,提出了其中的难点问题.应用低成本捷联惯性测量单元,设计了一种基于互补滤波器算法的姿态求解器.经过实验验证表明:与目前常用的卡尔曼滤波算法相比,采用互补滤波器算法的求解器能显著降低对处理器速度和精度的要求,有效融合了捷联惯性测量单元的传感器数据,实现了小...     

Inertial-Aided Metric States and Surface Normal Estimation using a Monocular Camera

In this paper, a visual inertial fusion framework is proposed for estimating the metric states of a Micro Aerial Vehicle (MAV) using optic flow (OF) and a homography model. Aided by the attitude estimation from the on-board Inertial Measurement Unit (IMU), the computed homography matrix is reshaped into a vector and directly fed into an Extend Kalman Filter (EKF). The sensor fusion method is able to recover metric distance, speed, acceleration bias and surface normal of the observed plane. We further consider reducing the size of the filter by using only part of the homography matrix as the system observation. Simulation results show that these smaller filters have reduced observability compared with the filter using the complete homography matrix, however it is still possible to estimate the metric states as long as one of the axes is linearly excited. Experiments using real sensory data show that our method is superior to the homography decomposition method for state and slope estimation. The proposed method is also validated in closed-loop flight tests of a quadrotor.     

Adaptive fractional-order nonsingular fast terminal sliding mode formation control of multiple quadrotor UAVs-based distributed estimator

This paper mainly solves two major problems that are unavoidable in leader–follower formation process of quadrotor UAV group: the existence of external uncertainty disturbance and communication limited between quadrotor unmanned aerial vehicle (UAV) group. To solve the problem that only one of the followers in the leader–follower formation can obtain the leader's information, an improved distributed estimator is proposed in this paper, which can accurately estimate the leader's information for each follower. In addition, in order to eliminate the influence of uncertain external disturbance on the performance of quadrotor UAV, an adaptive estimation law is designed based only on velocity and position variables. For the attitude and position subsystem of the quadrotor UAV, a sliding surface with fractional-order term is designed. Which makes the quadrotor UAV tracking error system obtain good robustness at the stage of reaching the sliding surface and fast convergence and accurate tracking performance in the sliding stage. Based on Lyapunov stability theory, the convergence results are analyzed strictly. The results show that the algorithm can make the position distance between leader and followers converge to the desired offset. Simulation results verify the effectiveness and superiority of the control algorithm.     

RANGE–Robust autonomous navigation in GPS‐denied environments

This paper addresses the problem of autonomous navigation of a micro air vehicle (MAV) in GPS‐denied environments. We present experimental validation and analysis for our system that enables a quadrotor helicopter, equipped with a laser range finder sensor, to autonomously explore and map unstructured and unknown environments. The key challenge for enabling GPS‐denied flight of a MAV is that the system must be able to estimate its position and velocity by sensing unknown environmental structure with sufficient accuracy and low enough latency to stably control the vehicle. Our solution overcomes this challenge in the face of MAV payload limitations imposed on sensing, computational, and communication resources. We first analyze the requirements to achieve fully autonomous quadrotor helicopter flight in GPS‐denied areas, highlighting the differences between ground and air robots that make it difficult to use algorithms developed for ground robots. We report on experiments that validate our solutions to key challenges, namely a multilevel sensing and control hierarchy that incorporates a high‐speed laser scan‐matching algorithm, data fusion filter, high‐level simultaneous localization and mapping, and a goal‐directed exploration module. These experiments illustrate the quadrotor helicopter's ability to accurately and autonomously navigate in a number of large‐scale unknown environments, both indoors and in the urban canyon. The system was further validated in the field by our winning entry in the 2009 International Aerial Robotics Competition, which required the quadrotor to autonomously enter a hazardous unknown environment through a window, explore the indoor structure without GPS, and search for a visual target. © 2011 Wiley Periodicals, Inc.     

基于扩张状态观测器的四旋翼无人机快速非奇异终端滑模轨迹跟踪控制

针对受多源干扰影响的四旋翼无人机系统的轨迹跟踪控制问题进行研究,充分考虑位置回路和姿态回路动态特性,提出一种全回路复合快速非奇异终端滑模轨迹跟踪控制方案.首先,通过变换将轨迹跟踪问题转化为位置回路和姿态回路的指令跟踪控制问题;然后,将各通道之间的耦合以及多源干扰影响视作集总干扰,并基于扩张状态观测器对其进行估计;接着,基于干扰估计信息和快速非奇异终端滑模控制算法,分别在位置回路和姿态回路构造复合快速非奇异终端滑模控制器;最后,基于位置回路和姿态回路虚拟控制量解得无人机真实控制量旋翼转速.仿真结果表明,所提出控制方案显著提升了四旋翼无人机轨迹跟踪的响应速度和抗干扰性能.     

基于故障程度的四旋翼无人机容错控制

针对四旋翼无人机执行机构部分失效故障,采用一组线性二次最优控制器,并且设计了可变因子二阶卡尔曼滤波器在线快速估计状态和检测故障。当故障被检测和诊断出来时,通过可变因子二阶卡尔曼滤波器调节,同时切换到相应的线性二次最优控制器使故障影响变小。最后,在Matlab实验平台上对所提方法的可行性和有效性进行仿真验证验证,结果表明四旋翼无人机执行机构在发生部分失效故障时,输出信号能够快速跟踪轨迹,实现了对执行机构部分失效故障的容错控制。