四旋翼飞行器非线性轨迹跟踪控制

针对四旋翼飞行器在复杂飞行条件下速度不可测的轨迹跟踪控制问题,考虑系统存在外界未知干扰和模型参数不确定的情况,提出了一种基于扩张观测器的轨迹跟踪控制方法。该方法设计了积分型反步法跟踪控制器,以降低系统的稳态误差,并引入了状态扩张观测器,来估计系统未知速度信息,同时对干扰和模型参数不确定因素进行实时估计并给予补偿;最后,选取李雅普诺夫函数证明了该控制系统的稳定性。以Quanser公司的Qball2四旋翼飞行器为研究对象和飞行实验平台,对所设计的控制器进行验证。实验结果表明,本文所设计的基于扩张观测器的轨迹跟踪控制器,能够有效地估计轨迹跟踪控制过程中的未知速度信息,解决外界未知干扰和模型参数不确定的问题,增强对环境的适应能力,有效提高了飞行器对未知干扰的鲁棒性和轨迹跟踪控制的精确性。     

Hybrid finite-time trajectory tracking control of a quadrotor

In this paper, accurate trajectory tracking control problem of a quadrotor with unknown dynamics and disturbances is addressed by devising a hybrid finite-time control (HFTC) approach. An adaptive integral sliding mode (AISM) control law is proposed for altitude subsystem of the quadrotor, whereby underactuated characteristics can decoupled. Backstepping technique is further deployed to control the horizontal position subsystem. To exactly attenuate external disturbances, a finite-time disturbance observer (FDO) combining with nonsingular terminal sliding mode (NTSM) control strategy is constructed for attitude subsystem, and thereby achieve finite-time stability. Using the compounded control scheme, trajectory tracking errors can be stabilized rapidly. Simulation results and comprehensive comparisons show that the proposed HFTC scheme has remarkably superior performance.     

Using the Kalman filter in the quadrotor vehicle trajectory tracking system

A problem of control of quadrotor vehicle motion over a trajectory defined implicitly in the coordinate space is considered. The previously proposed system of automated control of quadrotor vehicle flight is supplemented with relations based on an extended Kalman filter for estimating the plant state vector and the systematic error of measurements. The workability of the control system in the presence of the measurement noise is verified by results of modeling and experiments with the AR.Drone quadrotor vehicle.     

无人机机载侦察视频的高效视频码率控制

提出了一种基于缓冲区状态及梯度算子的低延时高效视频码(HEVC)率控制方法,以解决现有的码率控制算法在无人机机载侦察系统中因比特分配不当引起的视频质量较差的问题。首先,利用剩余比特及缓冲区状态预分配帧层目标比特;然后,以视频中每帧各最大编码单元(LCU)的时空复杂度作为权重,预分配各LCU的目标比特;最后,通过R-λ模型获得目标比特下的编码参数,实现视频压缩编码,并完成模型参数更新。实验结果表明:在8 Mbps的带宽下,提出的算法使码率控制误差缩小到HM16.0的2/5,视频中图像质量波动范围降低到HM16.0的1/4以内。提出的方法有效抑制了帧间比特消耗波动,使得缓冲区占用量能在小范围内平稳波动,图像主观质量也得到了改善,更好地满足了机载侦察系统低延时的应用需求。     

A robust approach for trajectory tracking control of a quadrotor with experimental validation

In this paper, a new control scheme for motion control of quadrotors is presented. The proposed model based controller makes use of simple estimations of vehicle parameters. Besides, the controller is developed under properties of the vehicle model. A rigorous analysis is developed to prove that the closed-loop system trajectories are uniformly ultimately bounded. The validity of the proposed control scheme is tested by numerical simulations and experimental results. This validation shows that the proposed controller guarantees that the quadrotor performs tracking of a desired pose (position and orientation) trajectory with good accuracy. The new scheme has been compared with respect to other robust controllers. The results indicate better tracking accuracy for the new scheme.     

折臂式高空作业车轨迹跟踪与控制研究

针对折臂式高空车自动化控制程度较低的问题,以某型号18 m折臂式高空作业车为研究对象,应用机器人学理论,通过建立其运动学模型,实现了作业平台的轨迹跟踪控制,为最终实现折臂式高空车常用工况下的自动控制打下基础.为解决折臂式高空车臂架液压系统控制精度低,控制存在滞后问题,建立了臂架液压系统的数学模型,针对该模型设计自整定模糊PID控制系统,在MATLAB/Simulink环境下,对控制系统进行仿真验证,仿真结果表明,加入自整定模糊PID控制器后,臂架系统的响应速度增加,稳态误差消除,跟随能力加强.     

水下运载器纵向轨迹自适应跟踪控制

针对强非线性、大俯仰角运动的水下运载器纵向运动轨迹跟踪问题提出了一类非线性自适应控制方案.首先,直接采用非线性运动模型,在控制器设计过程中引入饱和函数,通过麦克劳林展开公式避免了俯仰角为小角度的假设限制;其次,考虑到运载器非线性运动模型很难给出精确的数学描述并且实际运载器系统存在模型误差,采用在线自适应方法近似逼近其非线性模型;最后,利用Backstepping方法设计了非线性自适应控制器,并利用Lyapunov理论证明了控制系统的稳定性.半实物仿真结果表明:在考虑测量噪声和参数不确定性的情况下,该算法对给出的3种轨迹的跟踪误差均小于0.5m,俯仰舵偏均小于15°,俯仰力矩均在105 N.m量级.结果验证了本文提出的控制系统鲁棒性强,满足跟踪性能要求.     

Adaptive compensation control for attitude adjustment of quad-rotor unmanned aerial vehicle

A compensation control strategy based on adaptive back-stepping technique is presented to address the problem of attitude adjustment for a quad-rotor unmanned aerial vehicle (QR- UAV) with inertia parameter uncertainties, the limited airflow disturbance and the partial loss of rotation speed effectiveness. In the design process of control system, adaptive estimation technique is introduced into the closed loop system in order to compensate the lumped disturbance term. More specifically, the designed controller utilizes “prescribed performance bounds” method, and therefore guarantees the transient performance of tracking errors, even in the presence of the lumped disturbance. Adaptive compensation algorithms under the proposed closed loop system structure are derived in the sense of Lyapunov stability analysis such that the attitude tracking error converge to a small neighborhood of equilibrium point. Finally, the simulation results demonstrate the effectiveness of the proposed controller.     

Adaptive time-varying formation tracking control of unmanned aerial vehicles with quantized input

This paper considers the adaptive time-varying formation tracking control of unmanned aerial vehicles (UAVs) with quantized input. Uncertainties and nonholonomic constraint are involved in the UAV model. With a novel transformation of the final control signal, a very coarse quantization can be achieved. Adaptive quantized controllers are proposed by employing backstepping technique. It is proved that, with our proposed strategy, all signals of the closed-loop system are globally uniformly bounded, and the formation tracking error converges to an arbitrarily small residual set. Simulation results are given to illustrate the effectiveness of the proposed strategy.     

四旋翼无人机可视化半实物仿真平台研究

四旋翼无人机的飞行控制是当前无人机研究领域的一个热点,目前的控制设计多采用MATLAB/Simulink进行数值仿真验证,仿真环境中较少考虑机载设备的作用.而在无人机原型开发过程中,又多采用现场调试的方法,不易快速更改控制算法及参数.为提高飞行控制算法开发时的效率,设计并实现了一种四旋翼无人机可视化半实物仿真平台.利用MATLAB实时视窗系统搭建了平台的主框架,将四旋翼无人机的惯性导航传感器及电机控制系统融入平台之中.并且利用了开源飞行模拟软件FlightGear,及对虚拟地球仪软件Google Earth的二次开发,为仿真平台增添了无人机位置、姿态以及航迹的三维可视化显示功能.实验结果表明,该平台运行稳定可靠.     

四旋翼飞行器轨迹跟踪控制器的设计与验证

为了解决四旋翼飞行器在外界扰动影响和系统模型参数存在不确定性情况下的精确轨迹跟踪控制问题,设计并验证了一种四旋翼飞行器的非线性轨迹跟踪控制器。首先建立了考虑执行机构特性的四旋翼飞行器数学模型,并将虚拟控制量映射到了实际中对电机的控制;然后通过在反步法轨迹跟踪控制中加入积分项,设计了一种基于积分型反步法的非线性轨迹跟踪控制器,消除模型参数不确定性及外界干扰引起的误差,仿真结果验证了该方法的可行性;最后,利用QBall2四旋翼飞行实验平台,对所设计的非线性轨迹跟踪控制器进行验证,实际飞行实验结果表明了所设计控制器的有效性,提高了实际飞行过程中外界干扰和不确定性下的四旋翼飞行器轨迹跟踪控制的精度。     

Control of flight parameters of a quadrotor vehicle moving over a given trajectory

The problem of control of an autonomous unmanned aerial vehicle with vertical takeoff and landing, which moves over a trajectory specified in the coordinate space, is considered. A method of constructing a system of automatic control of quadrotor vehicle takeoff and flight is proposed. Analytical relations for control actions on four engines that ensure vehicle motion over a prescribed trajectory with desired values of altitude and velocity are derived.     

Adaptive vision-based control of an unmanned aerial vehicle without linear velocity measurements

In this paper, an image-based visual servo controller is designed for an unmanned aerial vehicle. The main objective is to use flow of image features as the velocity cue to compensate for the low quality of linear velocity information obtained from accelerometers. Nonlinear observers are designed to estimate this flow. The proposed controller is bounded, which can help to keep the target points in the field of view of the camera. The main advantages over the previous full dynamic observer-based methods are that, the controller is robust with respect to unknown image depth, and also no yaw information is required. The complete stability analysis is presented and asymptotic convergence of the error signals is guaranteed. Simulation results show the effectiveness of the proposed approach.     

基于改进扩展状态观测器的四旋翼无人机轨迹鲁棒跟踪控制

针对四旋翼无人机在轨迹跟踪过程中会受到内外部扰动、模型误差等不确定性因素的影响,本文提出了一种基于改进型扩展状态观测器的积分滑模控制方案。具体来讲,首先,将四旋翼无人机系统存在的模型误差以及内外部扰动等不确定性因素视作集总干扰,通过借鉴的改进扩展状态观测器对其进行观测;进而,在此基础上,进一步考虑四旋翼无人机系统控制的连续性,基于四旋翼无人机轨迹误差、速度误差、姿态角误差和姿态角速度误差设计积分滑模控制器,分析了系统的稳定性并分别进行了数值仿真和实机实验。结果表明,采用本文算法时,在数值仿真中,各状态跟踪误差不超过1%,跟踪精度最高;在实机实验中,位置跟踪误差总体上能控制在20%以下。因此,本文方法具备有效性和可行性。     

Gesture recognition in the problem of contactless control of an unmanned aerial vehicle

Optoelectronics, Instrumentation and Data Processing - The problem of contactless control of an unmanned aerial vehicle by human gestures is considered. A system of commands is proposed for an...     

超小型旋翼飞行器遥操作仿真模型控制函数的辨识

为了研究采用极大似然法进行飞行参数辨识的效果,利用递推极大似然法对超小型旋翼飞行器遥操作仿真模型控制函数的参数进行了辨识,对极大似然辨识的结果进行了动态性能分析和系统相对稳定性分析,并将其和用传统的最小二乘辨识的结果进行了对比。研究结果不仅验证了仿真控制函数的可用性,而且论证了极大似然法在飞行器参数辨识中的优势。     

Position and attitude tracking control for a quadrotor UAV

A synthesis control method is proposed to perform the position and attitude tracking control of the dynamical model of a small quadrotor unmanned aerial vehicle (UAV), where the dynamical model is underactuated, highly-coupled and nonlinear. Firstly, the dynamical model is divided into a fully actuated subsystem and an underactuated subsystem. Secondly, a controller of the fully actuated subsystem is designed through a novel robust terminal sliding mode control (TSMC) algorithm, which is utilized to guarantee all state variables converge to their desired values in short time, the convergence time is so small that the state variables are acted as time invariants in the underactuated subsystem, and, a controller of the underactuated subsystem is designed via sliding mode control (SMC), in addition, the stabilities of the subsystems are demonstrated by Lyapunov theory, respectively. Lastly, in order to demonstrate the robustness of the proposed control method, the aerodynamic forces and moments and air drag taken as external disturbances are taken into account, the obtained simulation results show that the synthesis control method has good performance in terms of position and attitude tracking when faced with external disturbances.     

Experimental study on cascaded attitude angle control of a multi-rotor unmanned aerial vehicle with the simple internal model control method

This paper proposes a cascaded control structure and a method of practical application for attitude control of a multi-rotor Unmanned aerial vehicle (UAV). The cascade control, which has tighter control capability than a single-loop control, is rarely used in attitude control of a multi-rotor UAV due to the input-output relation, which is no longer simply a set-point to Euler angle response transfer function of a single-loop PID control, but there are multiply measured signals and interactive control loops that increase the complexity of evaluation in conventional way of design. However, it is proposed in this research a method that can optimize a cascade control with a primary and secondary loops and a PID controller for each loop. An investigation of currently available PID-tuning methods lead to selection of the Simple internal model control (SIMC) method, which is based on the Internal model control (IMC) and direct-synthesis method. Through the analysis and experiments, this research proposes a systematic procedure to implement a cascaded attitude controller, which includes the flight test, system identification and SIMC-based PID-tuning. The proposed method was validated successfully from multiple applications where the application to roll axis lead to a PID-PID cascade control, but the application to yaw axis lead to that of PID-PI.

     

An improved model-based predictive control of vehicle trajectory by using nonlinear function

A new model-based predictive control algorithm for vehicle trajectory control is proposed by using vehicle velocity and sideslip angle. Based on the error function combined with vehicle velocity and side slip of a bicycle model, a predictive control method has been proven to be useful on low velocity. Thus, it could be applied for an autonomous vehicle without a driver. Although an autonomous robot is not necessary to be driven with a high velocity, a commercial vehicle has to be driven at high velocity. Thus the previous predictive control formulation is not enough for a commercial driving system. This study is proposed to enhance the capacity of the predictive controller for rather high speed vehicles. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Mr. Jeong-Han Lee is pursuing a Ph.D. degree in Mechanical Engineering at Pusan National University under the supervision of professor Wan-Suk Yoo. His research interests are focused on the area of adaptive control using multibody dynamics. Dr. Wan-Suk Yoo received his Ph.D. degree in 1985 from the University of Iowa. In 1994, he became a full professor at the Pusan National University, and he was selected an ASME fellow. He is serving as a vicepresident of the KSME.     

某小型无人机螺旋桨静强度分析

螺旋桨作为无人机上的重要承载部件,性能直接影响无人机的安全.为研究桌小型无入机螺旋桨使用时的安全性,提出了一种简化的螺旋桨载荷分析方法,应用ANSYS分析软件对螺旋桨进行数值模拟,得到了螺旋桨叶的应力和应变响应.计算结果表明某小型无人机的桨叶静强度满足设计要求.