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 unmanned helicopter can be achieved with the application of the backstepping approach, dynamic surface control technique, and Lyapunov method. Finally, the availability of the proposed control scheme has been shown by simulation results.

ADAPTIVE NEURAL NETWORK ATTITUDE CONTROL FOR UNMANNED HELICOPTER

Adaptive flight control technology, feedback linearization, model inversion theory are reviewed and the error dynamic characteristics are analyzed, and an adaptive on-line neural network attitude control system is presented. The model inversion is under the hover condition. And the adaptive control law based on the neural network is designed to guarantee the boundedness of tracking error and control signals. Simulation results demonstrate that the nonlinear neural network augmented model inversion can self-adapt to the uncertainty and modeling errors of unmanned helicopters. Results are compared while the parameters of PD controller and robustness items are changed.

Control System Design for an Unmanned Helicopter to Track a Ground Target

Due to potential wide applications,the problem of utilizing an unmanned helicopter to track a ground target has become one of the most active research directions in related areas.However,in most cases,it is possible for a dynamic target to implement evasive actions with strong maneuverability,such as a sudden turn during high-speed movement,to flee from the tracker,which then brings much difficulty for the design of tracking control systems.Currently,most research on this field focuses on utilizing a ground mobile robot to track a high-speed target.Unfortunately,it is very difficult to extend those developed methods to airborne applications due to much more complex dynamices of UAV-target relative motion.This study investiages thoroughly for the problem of using an unmanned helicopter to track a ground target,with particular emphasis on the avoidance of tracking failure caused by the evasive maneuvers of dynamic targets.Specifically,a novel control scheme,which consists of an innovative target tracking controller and a classical flight controller,is proposed for the helicopter-target tracking problem.Wherein,the tracking controller,whose design is the focus of the paper,aims to utilize the motion information of the helicopter and the dynamic target to construct a suitable trajectory for the helicopter,so that when it flies along this trajectory,the relative pose between the helicopter and the dynamic target will be kept consant.When designing the target tracking controller,a novel coordinate transformation is firstly introduced to convert the tracking system into a more compact form convenient for control law design,the desired velocities for the helicopter is then proposed with consideration of the dynamic constraint.The stability of the closed-loop system is finally analyzed by Lyapunov techniques.Based on Matlab/Simulink environment,two groups of simulation are conducted for the helicopter-target tracking control system where the target moves along a linear path and takes a sudden turn during high-speed movement,respectively.As shown by the simulation results,both the distance error and the pointing error are bounded during the tracking process,and they are convergent to zero when the target moves straightly.Moreover,the tracking performance can be adjusted properly to avoid tracking failure due to evasive maneuvers of the target,so as to guarantee superior tracking performance for all kinds of dynamic targets.

Nonlinear Intelligent Flight Control for Quadrotor Unmanned Helicopter

Quadrotor unmanned helicopter is a new popular research platform for unmanned aerial vehicle(UAV),thanks to its simple construction,vertical take-off and landing(VTOL)capability.Here a nonlinear intelligent flight control system is developed for quadrotor unmanned helicopter,including trajectory control loop composed of co-controller and state estimator,and attitude control loop composed of brain emotional learning(BEL)intelligent controller.BEL intelligent controller based on mammalian middle brain is characterized as self-learning capability,model-free and robustness.Simulation results of a small quadrotor unmanned helicopter show that the BEL intelligent controller-based flight control system has faster dynamical responses with higher precision than the traditional controller-based system.

Development of an Autonomous Flight Control System for Small Size Unmanned Helicopter Based on Dynamical Model

It is devoted to the development of an autonomous flight control system for small size unmanned helicopter based on dynamical model. At first, the mathematical model of a small size helicopter is described. After that simple but effective MTCV control algorithm was proposed. The whole flight control algorithm is composed of two parts: orientation controller based on the model for rotation dynamics and a robust position controller for a double integrator. The MTCV block is also used to achieve translation velocity control. To demonstrate the performance of the presented algorithm, simulation results and results achieved in real flight experiments were presented.

Adaptive Backstepping Tracking Control of a 6-DOF Unmanned Helicopter

This paper presents an adaptive backstepping control design for a class of unmanned helicopters with parametric uncertainties. The control objective is to let the helicopter track some pre-defined position and yaw trajectories. In order to facilitate the control design, we divide the helicopter's dynamic model into three subsystems. The proposed controller combines the backstepping method with online parameter update laws to achieve the control objective. The global asymptotical stability (GAS) of the closed-loop system is proved by a Lyapunov based stability analysis. Numerical simulations demonstrate that the controller can achieve good tracking performance in the presence of parametric uncertainties. © 2014 Chinese Association of Automation.

Selection of a non-localized landing region for an unmanned helicopter based on an attention model

A new landing region selection algorithm for an unmanned helicopter is proposed based on an attention model.Different from the original attention model,some properties of the possible safe landing regions（e.g.,depth,regional color and motion features）are included in the selection algorithm.Furthermore,regional color and motion features are fused directly into the saliency map because these features do not have the ＂central-peripheral＂property.Experimental results validate the feasibility and efficiency of this approach.

Angular velocity dynamics identification of small unmanned helicopter using fuzzy model

Attitude identification method for unmanned helicopter based on fuzzy model at hovering is presented. The dynamical attitude model is considered as basis for attitude control and it is very complex. To reduce the complexity of model, nonlinear model of unmanned helicopter with unknown parameters are to be determined by fuzzy system first and then derivative based gradient method is used to identify unknown parameters of model. Gradient method is used due to ability that fuzzy system is not necessarily to be linear in parameters, therefore all fuzzy sets for input and output can be adjusted. The validity of the proposed model was verified using experimental data obtained by the commercially available flight simulator X-Plane. The simulation results showed high accuracy of the modeling method and attitude dynamics data matched well with experimental data.

Robust Anti⁃swing Control for Unmanned Helicopter Slung⁃Load System with Prescribed Performance

A robust anti-swing control method based on the error transformation function is proposed,and the problem is handled for the unmanned helicopter slung-load system(HSLS)deviating from the equilibrium state due to the disturbances in the lifting process.First,the nonlinear model of unmanned HSLS is established.Second,the errors of swing angles are constructed by using the two ideal swing angle values and the actual swing angle values for the unmanned HSLS under flat flight,and the error transformation functions are investigated to guarantee that the errors of swing angles satisfy the prescribed performance.Third,the nonlinear disturbance observers are introduced to estimate the bounded disturbances,and the robust controllers of the unmanned HSLS,the velocity and the attitude subsystems are designed based on the prescribed performance method,the output of disturbance observer and the sliding mode backstepping strategy,respectively.Fourth,the Lyapunov function is developed to prove the stability of the closed-loop system.Finally,the simulation studies are shown to demonstrate the effectiveness of the control strategy.

Rotosonde: Acquiring Vertical Wind Profile of a Tropical Cyclone with Small Unmanned Helicopters

Spinsonde is a chute-free vertical retardation technique specifically developed for fixed-wing unmanned aircraft to acquire accurate measurement of vertical wind speed profile for meteorological applications. Key advantages of spinsonde over the expendable chute-operated dropsondes are the ability to acquire multi-cycle measurement, efficient use of payload capacity and cost-effectiveness. This work proposes the concept of “rotosonde”, which is the spinsonde equivalent for unmanned helicopters. Computer simulations are carried out to evaluate the performance of the rotosonde and results indicate that the measured speed generally correlates with the wind speed to within ±3 km·h﹣1 even for intensities in excess of 180 km·h﹣1. The profound implication of this work is that unmanned helicopters can now be considered for important field of studies such as cyclogenesis given their reliability to operate in gusty wind conditions in remote oceans, particularly during docking and launching from carriers.

Cable-driven legged landing gear for unmanned helicopter:Prototype design,optimization and performance assessment

Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging terrains.This study presents a novel cable-driven legged landing gear(CLG)with differential transmission for unmanned helicopters in complex landing environments.To obtain the preferred configuration of the legged mechanism,a multi-objective optimization framework for the CLG is constructed by concurrently considering terrain adaptability,landing stability and reasonable linkage of internal forces.The non-dominated sorting genetic algorithmⅡis employed to numerically acquire the optimal scale parameters that guide the mechanical design of the CLG.An unmanned helicopter prototype equipped with the devised CLG is developed with key performance assessment.Experimental results show that the devised CLG can provide energy-efficient support over uneven terrains(totally driven torque demand less than 0.1 N m)in quasi-static landing tests,and favorable terrain adaptability(posture fluctuation of the fuselage less than±1°)in unknown slope landing tests.These exhibited merits give the proposed CLG the potential to enhance the landing performance of future aircraft in extreme environments.

Trajectory tracking anti-disturbance control for unmanned aerial helicopter based on disturbance characterization index

This work studies the trajectory tracking control for unmanned aerial helicopter(UAH)system under both matched disturbance and mismatched ones.Initially,to tackle the strong coupling,an input-output feedback linearization method is utilized to simplify the nonlinear UAH system.Secondly,a set of finite-time disturbance observers(FTDOs)are proposed to estimate mismatched disturbances with their successive derivatives,which are utilized to design the feedforward controller via backstepping.Thirdly,as for matched disturbance,by defining the disturbance characterization index(DCI)to determine whether the disturbance is harmful or not for the UAH system,a feedback controller is proposed and a sufficient condition is established to ensure the convergence of the tracking error.Finally,some numerical simulations and comparisons illustrate the validity and advantages of our control scheme.

具有输入输出约束的无人直升机预设性能安全跟踪控制

针对无人直升机姿态与高度系统存在未知外部干扰、输入饱和、姿态与高度约束等问题,本文提出一种具有输入输出约束的预设性能安全跟踪控制方法.首先,针对无人直升机的姿态与高度约束,通过设计一类边界保护算法,构建了新的安全期望跟踪信号.为了保证系统对于安全期望跟踪信号的跟踪性能,将预设性能函数与边界保护算法进行结合,并对跟踪误差进行转换.针对系统的输入饱和现象,使用Sigmoid函数进行逼近;同时,针对饱和函数的逼近误差与未知外部干扰构成的复合干扰,采用参数自适应方法对其上界进行逼近.然后,结合反步控制方法设计了安全跟踪控制器,并通过Lyapunov稳定性理论证明了闭环系统所有信号的收敛性,保证了无人直升机的安全跟踪性能.最终,通过数值仿真验证了所提控制方法的有效性.

基于避障路径规划的无人直升机空地跟踪控制

针对无人直升机(Unmanned Aerial Helicopter,UAH)在空地协同跟踪过程中的避障和控制问题,提出了新型路径避障规划和跟踪控制设计方法。针对不确定性的线性UAH模型,通过对UAH警示范围内二维环境信息进行处理判断,借助摸墙算法(Wall-Following Algorithm)提出合适的避障策略,计算避障路径的行进角度以及能够弥补绕行距离的跟踪速度;将所得避障方法拓展至三维环境中,根据水平和垂直方向上的障碍物信息确定UAH飞行角度,从而减小由避障环节所带来的绕行距离;在上述避障算法的基础上,引入人工神经网络(Approximate Nearest Neighbor,ANN)估计模型不确定项,进而结合前馈补偿与最优控制等技术建立了跟踪控制设计方案。仿真结果表明,所提避障策略和控制算法有效。

基于需求驱动-体系结构建模的无人直升机系统论证评估方法研究

无人直升机系统是“机-站-链”构成的复杂系统,其论证评估涉及需求域、能力域、信息域等多领域,方法涵盖需求分析管理、体系结构建模以及综合评估优化,对其定性与定量论证评估,本质上是一个复杂系统问题。针对无人直升机系统组成复杂、任务领域多样化、涉及作战节点多、信息交联关系复杂等特点,采用传统的系统工程思想、方法和开发工具已难以满足论证的需要,文中提出一种“需求驱动、体系结构建模”的论证评估方法,并给出开发步骤,可为装备发展需求论证、体系结构建模、综合评估提供科学的技术手段支持。

无人直升机标准验证实践研究

标准验证工作在国内外得到了重视和发展,对技术提升和产品实现具有积极意义。本研究结合无人直升机背景,对若干标准开展了应用验证工作,对具体标准的完善和产品的成功起到了支撑作用,为“国家质量基础的共性技术研究与应用”专项的完成提供了助力。形成的验证案例和积累的实践经验对复杂产品伴随全生命周期策划开展标准验证工作具有一定的借鉴意义。

基于谐波观测器的无人直升机复合非线性模型预测控制

针对受到干扰影响的无人直升机轨迹跟踪问题,提出一种基于谐波观测器的复合非线性模型预测控制方案。将无人直升机的轨迹跟踪问题转换为对位置指令和姿态指令的跟踪问题;设计谐波干扰观测器以实现对周期性干扰的估计;结合干扰估计信息,基于非线性模型预测控制算法设计复合非线性模型预测控制器;基于某小型无人机模型,在MATLAB仿真环境下测试了所提方案。仿真结果表明,方案实现了周期性干扰的有效抑制,保证了无人直升机轨迹的高精度跟踪。

复合式高速无人直升机飞行力学建模及操纵策略研究

双螺旋桨复合式高速无人直升机同时具备了直升机和固定翼飞机的优势,是目前高速飞行器的研究热门之一。针对双螺旋桨复合式高速无人直升机进行了飞行力学相关分析和操纵策略研究。首先,以干扰因子的方式构建旋翼对机翼的气动干扰模型,机身模型采用风洞实验数据,然后,建立该直升机的非线性飞行动力学模型。针对操纵冗余问题,提出一种操纵策略,以权重系数来分配操纵通道,通过添加平均螺距杆纵向通道,由螺旋桨平均螺距控制前飞速度。在此基础上进行配平,实现了各个杆操纵量在3个模式间的光滑过渡,从而验证了操纵策略的合理性。

小型无人直升机系统辨识算法研究

获得精确的小型无人直升机动力学模型,是对其准确控制的前提条件。创新性提出的加权退火算法是一种有效的时域辨识算法,它对模拟退火算法进行特别的改进,可较快的收敛得到小型无人直升机高精度动力学模型。同时,上述算法克服了以往辨识对初始点选择敏感的问题,也避免频域辨识算法通常所需的输入通道扫频环节,从而降低实施辨识的工作量和成本。以真实的四点飞行数据为输入,通过搭建的分布式计算平台,计算出小型无人直升机的全状态空间模型(13阶,包含悬停模态和前飞模态),加权退火辨识算法的有效性得到很好验证。

无人直升机自动着舰导引控制设计与仿真验证

通常无人直升机自动着舰导引控制的方法是:导引系统根据探测到的机舰位置信息,结合任务需求,实时生成一条理想飞行轨迹,按照一定的制导律计算得到导引指令发送给飞控系统,经过计算转化得到最终位置、速度、姿态控制指令,控制无人直升机跟踪这一理想轨迹,进而实现无人直升机返航、着舰。该文针对无人直升机自动着舰的特点和需求,将得到的机舰相对位置信息直接发送给无人直升机飞行控制系统,按照设定边界控制条件设计自动着舰流程和相应的控制律,给定无人直升机速度和位置控制指令,实时调整无人直升机飞行姿态,通过多模态的复合控制,最终引导无人直升机完成返航、近舰和着舰全过程,并且通过半物理仿真试验进行验证。