Attitude and gyro bias estimation for a VTOL UAV

In this paper, a nonlinear complementary filter (x-estimator) is presented to estimate the attitude of a vertical take off and landing unmanned aerial vehicle (VTOL UAV). The measurements are taken from a low-cost IMU (inertial measurement unit) which consists of 3-axis accelerometers and 3-axis gyroscopes. The gyro bias are estimated online. A second nonlinear complementary filter (z-estimator) which combines 3-axis gyroscope readings with 3-axis magnetometer measurements, is also designed. Based on the proposed estimators, the full orientation matrix R will be retrieved. Note that R evolves on the special orthogonal group SO(3), since it is a transformation matrix between two orthogonal frames. This representation of orientation by the rotation matrix allows to overcome the problem of singularities that appear in local parametrization such as Euler angles. Therefore, both estimators may be used to describe any type of 3D motion. The convergence of the two observers is theoretically and experimentally proven; simulations and experiments are conducted on a real platform in hovering flight conditions.  

Development of an autonomous aerial vehicle: A case study

This paper describes the design, development, and deployment of an unmanned autonomous aerial vehicle developed at the Georgia Institute of Technology during 1990–1991. The approach taken, the system architecture, and the embedded intelligence of the project as conceived by a team of students, faculty, and industrial affiliates is reported. The project focused on engineering a vehicle which performed an intended mission in the time, space, and weight restrictions specified as part of an AUVS 1991 Competition. This paper documents the system and its various components and also provides a discussion of integration issues.The project demonstrated capabilities of existing and new technologies, but also highlighted many serious integration issues, particularly when using prototype components. The project also demonstrated the utility and mutual benefits of academic-industry projects. All members of the team benefited by working on a real and tangible project. Industrial participates gained first hand experience integrating their products with other components and many saw potential for their products and services in new markets.  

小型无人直升机纵横角动态耦合辨识建模

针对小型无人直升机耦合建模问题提出了一种频域解耦辨识建模方法,该方法通过处理针对耦合辨识的实验数据得到指定频域范围内被辨识耦合的频域特性,对频域特性进行拟合从而获得耦合模型.提出了适用于多输入输出(MIMO)系统的频域特性计算方法,定义了一种复合相干函数并证明其能够用于表达在耦合通道辨识中输入输出的相关性.基于该方法,对一种小型无人直升机在悬停状态的纵横角动态耦合模型进行了辨识,并将耦合模型加入到直升机仿真模型中考察其对模型预测精度的影响.模型预测输出与实际输出的比较表明,相较于普通模型,考虑了耦合动态的仿真模型能够更为精确地预测实际输出.  

旋翼空中机器人系统架构及设计

设计并验证了某型旋翼空中机器人的系统架构。整个空中机器人系统由直升机和地面站两部分组成。直升机是空中机器人的主体，可以自主飞行并完成指定任务。地面站用于监控无人直升机的飞行，并实现人机交互等多项功能。此外，地面站还可通过视觉导航系统引导直升机的自主着陆。直升机与地面站之间通过指令数字链路和视频模拟链路进行信息交互和实时通讯。经实际飞行验证，该空中机器人系统具有鲁棒和实时的特点，能实现直升机自主飞行和自主起降功能。  

基于ARM的空中机器人飞行控制系统的设计

提出了一种基于ARM9内核的嵌入式处理器S3C2440的空中机器人飞行控制系统的设计方案,详细介绍了系统的硬件结构组成及基于嵌入式Linux操作系统的飞行控制软件设计,并描述了软件的功能划分和控制策略的实现。该飞行控制系统使空中机器人具备遥控遥测、指令处理、姿态控制飞行和自主导航等功能,成本低、性能高。  

线性光隔PS8741在空中机器人电压监测中的应用

针对某型空中机器人机载电源监测电压存在的温度漂移现象,提出3种温度补偿方案:加入负温度系数热敏电阻、普通光隔线性化、直接采用线性光隔,最终选用高精度线性光隔PS8741;详细给出了PS8741的工作原理及典型应用电路,并对电路进行高低温试验;为便于数据处理,开发了基于MATLAB的图形用户界面(GUI);实验结果表明,利用PS8741测得电压线性度好,抗干扰性强,可有效抑制监测电压随温度漂移,为空中机器人的准确、安全飞行提供有利保障。  

An Experimental Test Bed for Small Unmanned Helicopters

This paper introduces a custom experimental test bed for the evaluation of autonomous flight controllers for unmanned helicopters. The development of controllers for unmanned helicopters is a difficult procedure which involves testing through simulation at first, and then actual experimentation on real vehicles. As simulation cannot accurately represent the exact real flight conditions and the dangers involved in them, the suggested test bed fills the gap between simulation runs and experimental flights. The developed system involves a small helicopter mounted on a flying stand, equipped with a set of sensors for real-time flight monitoring and control. For demonstration purposes, the test bed has been used for design and validation of a fuzzy logic based autopilot, able to perform hovering and altitude control. Experimental results are presented and commented for various test cases.  

Dynamic modeling and nonlinear tracking control of a novel modified quadrotor

In this article, a nonlinear tracking controller is designed based on Lyapunov stability for a novel aerial robot. The proposed 6‐rotor configuration improves stability and payload lifting capacity of the robot compared with conventional quadrotors while avoiding further complexities in the robot dynamics and steering principles. The dynamical model of the robot is derived using Newton‐Euler method. The model represents a nonlinear, coupled, and underactuated system. The proposed control strategy includes 2 main parts: an attitude controller and a position controller. Both the attitude and position controls are Lyapunov‐based nonlinear tracking controllers that guarantee the asymptotic convergence of the states' tracking errors to zero. Simulation results are presented to illustrate appropriate performance of the closed‐loop system in terms of position/attitude tracking even in the presence of wind disturbance.  

Localization of emergency acoustic sources by micro aerial vehicles

For micro aerial vehicles (MAVs) involved in search and rescue missions, the ability to locate the source of a distress sound signal is significantly important and allows fast localization of victims and rescuers during nighttime, through foliage and in dust, fog, and smoke. Most emergency sound sources, such as safety whistles and personal alarms, generate a narrowband signal that is difficult to localize by human listeners or with the common localization methods suitable for broadband sounds. In this paper, we present three methods for MAV‐based emergency sound localization system. The first method involves designing a new emergency source for immediate localization by the MAV using a common localization method. The other two novel methods allow localizing the currently available emergency sources, or other narrowband sounds in general, that are difficult to localize due to the periodicity in the sequence of sound samples. The second method exploits the Doppler shift in the sound frequency, caused due to the motion of the MAV and the dynamics of the MAV to assist with the localization. The third method involves active control of the robot's attitude and fusing acoustic and attitude measurements for achieving accurate and robust estimates. We evaluate our methods in real‐world experiments with real flying robots.  

The AutoSOAR autonomous soaring aircraft part 2: Hardware implementation and flight results

Autonomous soaring has the potential to greatly improve both the range and endurance of small robotic aircraft. This paper describes the results of a test flight campaign to demonstrate an autonomous soaring system that generates a dynamic map of lift sources (thermals) in the environment and uses this map for on‐line flight planning and decision making. The aircraft is based on a commercially available radio‐controlled glider; it is equipped with an autopilot module for low‐level flight control and on‐board computer that hosts all autonomy algorithms. Components of the autonomy algorithm include thermal mapping, explore/exploit decision making, navigation, optimal airspeed computation, thermal centering control, and energy state estimation. A finite state machine manages flight behaviors and switching between behaviors. Flight tests at Aberdeen Proving Ground resulted in 7.8 h flight time with the autonomous soaring system engaged, with three hours spent climbing in thermals. Postflight computation of energy state and frequent observations of groups of birds thermalling with our aircraft indicate that it was effectively exploiting available energy.