Vision-based Autonomous Landing Control for Unmanned Helicopters

This paper presents the design of a complete control system for the autonomous landing of unmanned flybarless helicopters on known stationary visual landmarks. A state estimator based on the complementary filters notion, estimates the position, translational velocity and attitude vectors of the vehicle by fusing data acquired from the on–board camera and an Inertial Measurement Unit. A vision-aided nonlinear model predictive controller is designed for the landing motion of the helicopter, assuming that the on–board camera is rigidly (i.e., no additional Degrees of Freedom (DOF)) attached on the vehicle. Although the under–actuated character of the helicopter dynamics introduces counter–goals for minimizing the error between the vehicle and the landmark, the proposed control scheme guarantees, via hard nonlinear constraints, that the landmark will always be kept inside the camera field of view during the landing procedure. In order to simplify the derived algorithm without violating the robustness of the proposed controller, we reformulate the translational helicopter dynamics in order to reduce the number of the unknown model parameters to a minimum. Moreover, a parameter/disturbance observer is designed for estimating simultaneously the vehicle’s unknown dynamic parameters as well as the induced disturbances. The efficacy of the proposed landing scheme is evaluated via a set of experimental and simulation results, using a small–scale flybarless helicopter.     

基于模型预测控制的直升机轨迹跟踪控制

针对直升机在实际任务中对轨迹精确控制的实际需求,提出基于模型预测控制(model predictive control,MPC)的直升机轨迹跟踪算法.轨迹控制的整体方案采用分层的架构:底层对直升机的速度以及姿态进行调节,顶层通过实施MPC算法对底层的姿态和速度指令进行调度,以期实现直升机轨迹的精确控制.通过分段MPC方...     

A Review on Fault Diagnosis and Fault Tolerant Control Methods for Single-rotor Aerial Vehicles

Faults or failures are inevitable to occur and their prompt detection and isolation are essential for the dependability of various systems and for avoiding damages to the system itself, persons and the environment. Therefore, the safety of helicopter platforms have attracted the attention of many researchers in the past two decades. In order to deal with these problems, this paper presents an overview of the recent development and current researches in the field of fault diagnosis, including analytical/model-based, signal processing-based and knowledge-based techniques, and also passive/active fault- tolerant control approaches. Among various helicopters, single-rotor aerial vehicles, i.e. manned helicopters, unmanned helicopters, two and three degree-of-freedom unmanned helicopter experimental platforms, are considered for providing an overall picture of the fault diagnosis and fault-tolerant control approaches based on the review of journal articles in last two decades, conference articles in last several years and some books.     

基于MDARM和VxWorks的小型无人机执行器故障检测方法

由于目前在小型无人机执行器故障诊断中存在着智能化程度较低,容易受到人为因素干扰,从而出现故障漏检等问题,难以满足小型无人机对飞行安全的要求;为此,提出一种基于多维数据关联规则挖掘(multidimensional data association rules mining,MDARM)和VxWorks操作系统的小型无人机执行器故障诊断方法,通过建立执行器内部传感器测量的温度、压力、流速、力矩等相关变量的历史数据库,并对这些数据进行预处理,以避免带来噪声污染,并利用可测量参数与不可测量参数之间的关联性,建立故障诊断知识库,避免了诊断过程中的人为因素干扰,实现小型无人机执行器故障的精准测量;实验结果证明,这种方法能够有效地提高故障准确率64.7％,对小型无人机执行器的智能诊提供有效指导,应用前景广阔.     

Actuator Fault Detection and Isolation for a Network of Unmanned Vehicles

This technical note investigates development, design and analysis of actuator fault detection and isolation (FDI) filters for a network of unmanned vehicles. It is shown that actuator fault signatures in a network of unmanned vehicles are dependent and the network can be considered as an over-actuated system. An isolability index mu is defined for a family of fault signatures and a new structured residual set is developed that is selectively capable of properly detecting and isolating mu multiple faults in linear systems with dependent fault signatures, such as over-actuated systems. Our proposed algorithm is then applied to the actuator FDI problem in a network of unmanned vehicles configured according to centralized, decentralized and semi-decentralized architectures. A comparative analysis in terms of the capabilities and limitations of these architectures is performed. Simulation results presented for the formation flight of multiple satellites demonstrate the effectiveness of our proposed FDI algorithm.     

基于故障检测的无人直升机作动器重构控制

提高直升机电传飞控系统的可靠性是保证无人直升机智能化的霞要方面,文中针对单旋翼加尾桨构型无人直升机的作动器故障,研究了倾斜器故障重构控制方法,重点提出了作动器的故障检测方法,运用模型的故障诊断技术,设计了基于倾斜器故障重构控制的无人直升机作动器故障时的重构控制策略,经过试飞证明此方法为作动器故障时的直升机安全飞行提供了一种可行方案,达到了设计目的.     

Advances in Modeling and Control of Tethered Unmanned Helicopters to Enhance Hovering Performance

The hovering capabilities of unmanned helicopters can be seriously affected by wind. One possible solution for improving hovering performance under such circumstances is the use of a tethered setup that takes advantage of the tension exerted on the cable that links the helicopter to the ground. This paper presents a more elaborate strategy for helicopter control in this augmented setup, that extends previous work on the subject by the authors. Particularly, a combination of classical PID control laws, together with model inversion blocks, constitutes the basis of the new controller. Additionally, feed-forward action for counteracting rotational couplings is also taken into account. The resulting nonlinear control structure considers also a viscoelastic model of the tether which accurately reproduce the behavior of real ropes. Several simulations under artificially generated wind influences are presented to endorse the validity of the new proposed controller.     

具有连续增益故障离散系统保性能可靠控制

针对不确定离散线性系统,采用连续增益故障模型,提出了考虑执行器故障的保性能可靠控制问题。通过对具有执行器故障不确定离散线性系统的分析,利用LMI分别给出了保性能标准控制器、保性能可靠控制器存在的充分条件及设计方法。根据凸优化理论．最优保性能标准控制器和最优保性能可靠控制器的设计方法转化为一个线性凸优化算法。在仿真数例中,不仅验证所提出方法的可行性;而且比较了最优保性能标准控制与最优保性能可靠控制。通过比较可以看出,当发生故障时,最优保性能标准系统将失去原有的性能和稳定性;最优保性能可靠系统仍将保持原有的性能。     

Disturbance Observer-Based Safe Tracking Control for Unmanned Helicopters With Partial State Constraints and Disturbances

In this paper, a disturbance observer-based safe tracking control scheme is proposed for a medium-scale unmanned helicopter with rotor flapping dynamics in the presence of partial state constraints and unknown external disturbances. A safety protection algorithm is proposed to keep the constrained states within the given safe-set. A second-order disturbance observer technique is utilized to estimate the external disturbances. It is shown that the desired tracking performance of the controlled un...     

Fault Diagnosis and Fault Tolerant Control for Manipulator with Actuator Multiplicative Fault

In this paper, a new fault diagnosis and fault tolerant control algorithm for manipulators with actuator multiplicative fault is proposed. The dynamic model of the manipulator with disturbance is taken as the research object. When faults occur in the actuator, a nonlinear observer based on radial basis function (RBF) neural network is used to estimate the fault information. After the fault information is obtained, an adaptive back-stepping sliding mode controller is used to control the manipulator to reach the desired trajectory. At last, an illustrated example is given to demonstrate the efficiency of the proposed algorithm, and satisfactory results have been obtained.

     

小型无人直升机悬停状态自适应模糊PID控制器设计

小型遥控直升机在实际应用中主要是完成航拍,为了实现小型直升机水平姿态的自动平衡,将其升级为无人直升机.针对小型直升机的降阶模型,提出了一种便于单片机实现的、针对悬停作业时小型无人直升机自适应模糊PID控制器的设计方法,能对PID参数进行动态整定,实现无人直升机悬停状态时水平姿态的平衡,仿真实验表明,自适应模糊PID控制器的动态性能好、稳态精度高、鲁棒性较强,宜适用于小型无人直升机的增稳控制.     

基于Oracle数据库的直升机故障诊断系统设计与实现

本文介绍一个面向直升机故障检测与维修的Oracle数据库应用系统。首先,概述了系统的设计原则以及系统的功能与总体框架;其次,论述数据库的结构及建立数据库的方法,并对访问数据库的方式作了说明;再次,详细讲述该系统的搜索策略以及智能学习和扩充功能,并简要介绍系统的安全特性;最后,给出了应用该系统的一个典型实例。     

基于事件触发的执行器饱和NCS容错控制

针对具有网络时延和执行器部分故障的网络化控制系统,考虑系统模型可能具有的参数不确定性以及未知扰动,研究执行器饱和时的稳定性问题。对网络时延提出离散事件触发机制,执行器部分故障采用故障矩阵方式,饱和项采取线性凸包法,由此推证出了闭环系统模型。构造Lyapunov 泛函,得出闭环系统在吸引域内达到稳定的充分必要条件,由此得到相应控制器的设计方法。利用仿真证明上述对系统的处理确实可以使系统达到渐近稳定,而事件触发机制也确实可以减少数据量的传输。     

带有稀疏执行器故障的事件触发网络化系统容错控制

针对一类具有事件触发信息传输机制的网络化控制系统,对系统故障执行器个数进行稀疏约束,研究系统在有限个执行器失效情况下的指数稳定及控制器设计问题。将系统故障执行器个数的约束转化为对控制器增益矩阵行的势约束,利用混合整数方法来解决这类稀疏约束的容错控制问题。在此基础上,利用Lyapunov泛函方法,得出闭环系统在有限个执行器失效情况下系统呈指数稳定的充分条件以及具有行稀疏约束的控制器设计方法。最后,通过一个飞行控制系统的数值仿真实例验证所提控制方法的可行性和有效性。     

控制系统执行机构故障的检测与诊断

评述了近年来执行机构故障检测与诊断的主要研究成果和发展现状,并给出了各种诊断方法的典型应用,对各种诊断方法的优缺点进行了比较,最后指出了该领域有待进一步研究的若干问题和发展趋势.     

基于模型跟随的直升机飞行控制与仿真

研究直升飞机飞行控制优化问题,由于控制系统为多变量、非线性系统,造成稳定性和实时性较差。为使直升机飞行品质满足ADS-33性能要求,提出采用模型跟随控制方法为基本结构,结合鲁棒特征结构配置对直升机飞行控制系统进行设计。首先根据ADS-33的性能指标设计理想模型,然后利用模型跟随控制方法构造整个控制系统的框架结构,并采用线性系统的鲁棒特征结构配置对控制器的参数进行设计,并对控制结果进行仿真,结果表明直升机飞行品质达到ADS-33性能指标要求。     

大气扰动下无人机纵向控制律设计研究

针对飞行控制系统设计中的大气扰动抑制问题进行了研究;讨论了Dryden紊流频域模型及时域对应的成形滤波器,建立了大气扰动下飞机纵向运动的小扰动方程;基于H∞控制理论,应用线性矩阵不等式(LMI)方法设计了鲁棒飞行控制系统;以某无人机纵向通道为例,选取全飞行包线内多个特征状态点,对设计的控制器进行仿真实验;仿真结果表明,所设计的控制器具有满意的干扰抑制能力和良好的鲁棒性及动态品质。     

Vision-Based Landing of Light Weight Unmanned Helicopters on a Smart Landing Platform

This paper presents a simple and efficient solution to vision guided autonomous landing of a light-weight (<150 Kg) unmanned helicopter on a smart landing platform, called ISLANDS??Intelligent Self-Leveling and Nodal Docking System. The advantage of ISLANDS is that it may allow the helicopter upon docking to recharge its batteries or refuel, thus, indirectly increasing endurance and flight range. In order for the helicopter to dock with ISLANDS, an on-board ??vision module?? coupled with the helicopter attitude controller is developed. This ??vision module?? detects the location and orientation of ISLANDS and feeds back information to the helicopter attitude controller, which commands the helicopter to descent onto the landing platform at a desired orientation and speed. The Scale Invariant Feature Transform (SIFT) is used for automatic detection of the landing platform based on images captured by a single camera mounted on the helicopter. The detected SIFT features are used to estimate the 3-D orientation of the platform relative to the helicopter using Homography and RANSAC techniques. The focus of this paper is on the vision-guided landing technique in a predefined orientation and not on controller details, which may be found in Shim et al. (1998).     

Control and Limitations of Navigating a Tail Rotor/Actuator Failed Unmanned Helicopter

According to Federal Aviation Administration (FAA) statistics on mechanical failures, tail rotor failure is the third highest cause of fatal accidents in helicopters. Tail rotor failure represents a serious hazard to personnel and mission objectives and can create high fiscal loss. This is especially true for unmanned helicopters, which cannot be equipped with the fail-safes standard on manned counterparts. This work provides an overview of how a helicopter can be controlled after a tail rotor failure and its applicability to both manned and unmanned vehicles. This work specifically details some of the limitations of this type of software failure control.