On Trajectory Tracking Model Predictive Control of an Unmanned Quadrotor Helicopter Subject to Aerodynamic Disturbances

In this article a model predictive control (MPC) strategy for the trajectory tracking of an unmanned quadrotor is presented. The quadrotor's dynamics are modeled using a hybrid systems approach and, specifically, a set of piecewise affine (PWA) systems around different operating points of the translational and rotational motions. The proposed control scheme is dual and consists of an integral MPC for the translational motions, followed by an MPC scheme for the tracking of the quadrotor's attitude motions. By the utilization of PWA representations, the controller is computed for a larger part of the quadrotor's flight envelope, which provides more control authority for aggressive maneuvering. The proposed dual control scheme is able to calculate optimal control actions with robustness against atmospheric disturbances (e.g. wind gusts) and with respect to the physical constraints of the quadrotor (e.g. maximum lifting forces or fixed thrust limitations in order to extend flight endurance). Extended simulation studies indicate the efficiency of the MPC scheme, both in trajectory tracking and aerodynamic disturbance attenuation.     

超小型旋翼机系统悬停状态的辨识仿真研究

建立了超小型旋翼机系统的非线性参数化模型. 通过把非线性模型在悬停点线性化,得到用物理参数描述的系统姿态运动的线性模型;基于其离散状态空间模型,采用子空间方法进行线性系统识别．仿真结果表明：子空间方法可以较准确地辨识所推导的超小型旋翼机系统悬停状态的线性物理参数模型,从而能获得系统的一些难以准确计算或测量的主要物理参数．     

无人旋翼机线性自抗扰航向控制

研究无人旋翼机器人在干扰情况下的航向控制问题.无人旋翼机航向动力学包含输入非线性、时变参数和主-尾旋翼之间的强耦合,难以建立精确的数学模型,并且易受外部扰动影响,很难达到良好的控制性能.针对这一问题提出基于线性自抗扰控制(linear adaptive disturbance rejection control,LADRC)的航向控制方法,通过设计扩张线性状态观测器对未知模型和外界干扰进行实时估计并进行在线补偿.以自主研制的无人旋翼机为例,建立其航向动力学方程,把通道间的交叉耦合影响视为不确定扰动,将其与外部干扰作为扩张状态,利用观测器带宽确定观测器增益,设计线性扩张状态观测器来跟踪各阶扩张状态变量,为说明LADRC的有效性,选用PD控制为非线性状态误差反馈控制律实现航向控制.仿真以及试验结果表明在外部扰动或模型结构参数发生变化时控制器仍可获得理想的动态性能,具有很好的适应性和鲁棒性.     

基于自适应遗传算法的小型无人旋翼机系统辨识方法

提出一种基于自适应遗传算法的小型无人旋翼飞行器系统辨识方法.通过机载传感器设备,系统采集小型无人旋翼机的输入信号(舵机的控制信号)和输出信号(飞行器的姿态及速度等信息);经过数据预处理后,利用自适应遗传算法构建小型无人旋翼飞行器高精度动力学模型,并通过仿真和实验对模型的自效性进行验证.实验表明,基于本文提出的动态模型,...     

多飞行机器人吊运系统研究进展及挑战

多飞行机器人吊运系统是指由多个旋翼飞行机器人、吊绳及单个悬挂负载共同构成的具有空中操作能力的一类新型机电系统,具有灵活性强、地域可达性好、运输便捷、载荷能力强等显著优点.多飞行机器人吊运系统应用广泛,但是其建模与控制还存在诸多挑战.旋翼飞行机器人自身是一种复杂的欠驱动非线性系统,随着吊绳和负载的引入,系统的耦合性、欠驱动特性和非线性也会随之增加.为了全面对多飞行机器人吊运系统的研究进行综述,首先介绍了多飞行机器人吊运系统的常见构型,并对比分析了其优缺点;其次,从动力学建模、协调控制、实验三个方面介绍了多飞行机器人吊运系统的研究现状与挑战;最后,凝练了现存的关键科学问题,对其潜在的应用领域和未来的研究工作进行了探讨与展望.     

崎岖地表上的旋翼无人机自主安全降落系统

针对旋翼无人机全自主作业的需求,构建了崎岖地表上的旋翼无人机自主安全降落系统．该系统通过机载实时运算自动分析落区地形,寻找可行落点并实施自动降落．系统以低成本的立体RGB-D相机作为深度传感设备,利用截断符号距离函数（TSDF）对着陆区地形进行实时3维建模,生成低噪的落区地形深度图像,并设计了一种适应起落机构形状的实时精细落点搜索方法,最后使用级联PID（比例－积分－微分）控制器控制无人机实施安全降落．系统基于大疆M100无人机平台实现,定制了仿真器进行算法调试,并最终在实际的崎岖地表上实现了自主安全降落．本文工作可为旋翼无人机紧急降落、物流运输或者灾后搜救提供有效安全的解决方案．     

3自由度旋翼飞行机械臂系统动力学建模与预测控制方法

旋翼飞行机械臂(rotorcraft aerial manipulator,RAM)系统是安装在飞行机器人上的可操作型机械臂,悬停模式下执行准确的空中操作时旋翼无人机与所加机械臂之间存在相对扰动,通过分离机械臂与飞行机器人进行动力学建模并不能有效消除这种扰动.本文基于对相互扰动力学作用的分析建立整体动力学模型,并在悬停飞行模式下将其简化为线性控制参考模型.进而对旋翼系统控制延时所引起的动力学扰动进行补偿,同时设计预测控制器来消除末端执行器的位置和姿态误差.最后,在存在内部和外部扰动的情况下,设定销钉插入操作任务进行控制方法的对比仿真.末端执行器位姿偏差的仿真结果表明了模型结构与控制方法的有效性.     

Scuffing Resistance and Starved Lubrication Behavior in Helicopter Gear Contacts: Dependence on Material,Surface Finish,and Novel Lubricants

A loss of lubrication event within rotorcraft drivetrain components leads to the rapid failure of contacting gear and bearing surfaces, thermal runaway, and catastrophic damage with possible loss of life. This article demonstrates that the scuffing failure of the gear and bearing surfaces can be delayed by varying the properties of the contact materials and residual lubricant in high-speed contacts. A ball-on-disc tribometer is used to simulate loss of lubrication conditions in gears for a variety of material, surface finish, and lubricant combinations to compare relative time to scuffing initiation at high entrainment and sliding velocities (both 16 m/s). Comparisons of material and surface finishing generally show that contacts tend to survive longer without lubricant if the coefficient of friction is relatively low during initial run-in. However, a 9 cSt oil produced longer times to failure than the baseline 5 cSt oil with higher coefficients of friction throughout the experiment. Further measurements showed that silicon nitride and AISI 9310 steel in contact can survive much longer after the lubricant supply is shut off compared to a steel-on-steel contact. The 9 cSt oil, silicon nitride, and superfinished surfaces showed the greatest promise in loss of lubrication technology from these results, with increases of 28, 388, and 1,538%, respectively, over baseline results. Thus, material, surface finish, and novel lubricant selection strategies may allow tailoring of survivability characteristics of aircraft mechanical systems.     

直升机旋翼转速调节器设计研究

文章在对直升机旋翼转速调节系统分析研究的基础上,提出了一种基于集成电路设计旋翼转速调节器的总体设计方案,完成了具体电路设计,采用Multisim仿真工具和具体电路调试验证了模块电路设计的正确性。实际应用表明,旋翼转速调节器功能完备,各项性能指标满足飞机所提出的性能指标要求,可在飞机上推广使用。     

Health monitoring of vibration signatures in rotorcraft wings

We propose to design and to evaluate an on-board intelligent health assessment tool for rotorcraft machines, which is capable of detecting, identifying, and accommodating expected system degradations and unanticipated catastrophic failures in rotorcraft machines under an adverse operating environment. A fuzzy-based neural network paradigm with an on-line learning algorithm is developed to perform expert advising for the ground-based maintenance crew. A hierarchical fault diagnosis architecture is advocated to fulfill the time-critical and on-board needs in different levels of structural integrity over a global operating envelope. The research objective is to experimentally demonstrate the feasibility and flexibility of the proposed health monitoring procedure through numerical simulations of bearing faults in USAF MH-53J PAVELOW helicopter transmissions. The proposed fault detection, identification and accommodation architecture is applicable to various generic rotorcraft machines. The proposed system will greatly reduce the operational and developmental costs and serve as an essential component in an autonomous control system.