基于鲁棒自适应的无人直升机悬停控制

小型无人直升机凭借良好的机动特性,在军事和民用方面有着广泛的用途。针对小型无人直升机悬停模型,考虑模型参数不确定对无人机控制的影响,提出一种鲁棒自适应控制律,实现无人机控制系统对不确定扰动的抑制。首先,基于无人直升机线性化悬停模型设计滑模面,并结合标称系统控制的反馈增益,获得滑模面的设计参数;在此基础上,利用传统滑模趋近律设计方法设计控制器;为改善系统控制性能,设计基于自适应增益的趋近律,实现系统鲁棒自适应控制。其次,利用Lyapunov稳定理论对所设计的鲁棒自适应控制策略的稳定性进行分析说明。最后,通过与基于指数趋近律以及变速趋近律的两种滑模控制方法仿真对比,验证了所设计的控制方法的有效性和优越性。     

基于有限时间扰动观测器的水厂加矾系统二阶滑模控制

水厂絮凝沉淀过程具有强非线性、不确定性和参数时变等特点,并且原水水质和水量突变等扰动容易对絮凝沉淀过程造成不利影响.本文提出了一种基于有限时间扰动观测器的加矾系统二阶滑模控制设计方法.首先,文章采用带有非光滑项的二阶滑模控制方法设计加矾系统反馈控制;然后,文章设计有限时间扰动观测器对原水水质和水量突变等扰动,以及絮凝沉淀过程强非线性、不确定性和参数时变等导致的模型不匹配进行估计,估计结果作为前馈补偿与反馈控制相结合;最后,理论分析证明了基于有限时间扰动观测器的二阶滑模控制方法的稳定性.仿真结果表明,本文所提出的复合控制方法有效提升了加矾系统的鲁棒性和抗扰动性能.     

小型无人直升机的无模型自适应鲁棒控制设计

本文针对小型无人直升机的姿态控制问题,考虑到现有基于模型的控制方法对系统动力学模型的依赖性,以及未建模动态对系统控制性能的影响,设计了一种新的基于数据驱动的无模型自适应鲁棒控制律.通过基于数据驱动的设计方法,降低了控制器对直升机动力学模型先验知识的依赖,补偿了未建模不确定性的影响.仅利用无人直升机的输入输出数据,即可实现对无人直升机系统的稳定姿态控制.然后本文结合离散滑模控制设计,补偿了未知外界扰动的影响,提高了系统的鲁棒性,并通过理论证明了控制误差的收敛性和闭环系统的稳定性.最后,在本研究组自主开发的无人直升机飞行控制实验平台上,进行了无人机实时控制实验.实验结果表明,本文所提出的控制算法取得了很好的姿态控制效果,并对系统不确定性和外界风扰动具有良好的鲁棒性.     

基于NDOB的匹配/非匹配不确定性系统滑模控制

针对一类n阶匹配与非匹配不确定性和扰动共存的系统,提出了一种新颖的基于非线性干扰观测器的滑模控制方法。将非匹配扰动的估计值融入到滑模面,设计了集成扰动观测的滑模控制。与传统的滑模控制方法相比,该方法在匹配与非匹配不确定性和扰动出现时具有较好的抑制能力,并能有效地抑制切换增益所引起的抖振现象。利用李雅普诺夫理论和输入-输出稳定性概念严格证明了闭环系统的稳定性。最后通过两个仿真实例验证了所提控制方法的有效性。     

小型无人直升机姿态非线性鲁棒控制设计

本文针对小型无人直升机的姿态控制问题,通过系统参数辨识,获得了较为准确的无人直升机姿态动力学模型.并根据无人直升机的动态特性,设计了基于神经网络前馈与滑模控制的非线性鲁棒姿态控制律,该控制律对直升机模型的先验知识要求较低.利用基于Lyapunov的分析方法证明,设计的控制律能够实现对无人直升机姿态角的半全局指数收敛镇定控制,并能确保闭环系统的稳定性.基于姿态飞行控制实验平台的实时飞行控制实验结果表明,提出的控制设计取得了很好的姿态控制效果,并对系统不确定性和外界风扰动具有较好的鲁棒性.     

基于扩张状态观测器的二质量系统非奇异快速终端滑模控制

针对含未知负载信息的二质量伺服系统,提出一种基于有限时间扩张状态观测器的非奇异快速终端滑模控制方法.首先,利用电机侧位置信息设计有限时间扩张状态观测器估计系统的扰动,并将估计值融入到控制器中作为前馈项对系统的未知扰动进行补偿;然后,引入一种新型的滑模趋近律,该趋近律能够避免传统滑模控制中存在的奇异性问题,据此设计非奇异快速终端滑模控制器,保证系统状态在有限时间内收敛到原点,并根据李雅普诺夫稳定性理论分析闭环系统的稳定性;最后,通过仿真和实验验证所提出方法的优越性.结果表明,与传统的PID等控制相比较,所提出的基于扩张状态观测器的有限时间滑模控制方法能够提高系统的跟踪性能,并有效增强二质量伺服系统的抗扰动能力.     

带有非匹配扰动的连铸结晶器振动位移系统自适应反步滑模控制

针对伺服电机驱动的连铸结晶器振动位移系统中存在非匹配的参数不确定性、干扰等问题,提出一种基于非线性扩张状态观测器(ESO)的自适应反步滑模控制方法.首先,基于双曲正切函数和高增益构造ESO对系统中的非匹配扰动进行估计.然后,利用反步法将非匹配扰动视为匹配扰动进行处理, 并在每一步设计自适应积分滑模控制器,以消除非匹配扰动对系统的影响.另外,在反步设计的后两步引入了积分滑模滤波器用于估计前一步虚拟控制律的导数.理论分析表明,所设计的ESO能够保证估计误差收敛到原点附近的小邻域内;所设计的控制器能够保证闭环系统所有信号有界,并且,通过选取适当的参数能够保证系统状态可渐近收敛到原点.最后,通过仿真结果验证了所提出方法的有效性.     

基于扰动和摩擦补偿的柔性机械臂系统非奇异快速终端滑模控制

本文针对系统中存在的关节摩擦、动力学参数不确定性和外部负载干扰等因素引起的柔性机械臂系统控制性能下降的问题,提出了一种基于扰动和摩擦补偿的非奇异快速终端滑模控制方法(NFTSMC-DE-FC).首先,设计扰动估计器(DE)对系统未知动态参数和负载干扰进行估计.然后,针对扰动估计器不能精确估计的关节摩擦力矩进行辨识.最后,利用滑模控制技术设计非奇异快速终端滑模控制器,并将扰动估计值和摩擦力辨识值以前馈的方式进行补偿,实现对柔性机械臂系统给定参考轨迹跟踪的准确性以及对外界扰动的鲁棒性.值得注意的是,与传统只使用扰动估计器的方法相比,本文考虑到了摩擦力等非线性因素的影响,并利用辨识技术对摩擦力进行辨识,提高了控制精度.利用Lyapunov稳定性定理从理论上证明了所设计的控制器可以保证闭环系统的稳定性.实验结果表明,相较于非奇异快速终端滑模控制方法(NFTSMC)和基于扰动估计器的非奇异快速终端滑模控制方法(NFTSMC-DE),所提方法提高了柔性机械臂系统的轨迹跟踪性能.     

适应扰动的无人直升机姿态跟踪控制

无人直升机在实际飞行过程中,会受到阵风等外界因素的干扰,并且模型不确定性也会对控制效果带来不利影响.为应对这些挑战,本文设计了一种基于扩张状态观测器的自抗扰反步控制器.首先,建立了无人直升机姿态动力学模型.随后,引入扩张状态观测器,用以实时观测由外界扰动和模型不确定性组成的总和扰动.观测得到的总和扰动估计值与基于Lyapunov函数的反步法控制器控制算法相结合,用以消除总和扰动的影响,使得无人直升机在各种飞行条件下均能对运动指令进行快速和准确的跟踪.最后,仿真研究和飞行实验验证了该控制律的有效性.与同等条件下的PID控制器相比,该控制律表现出更优的飞行性能.     

一类未知MIMO非线性离散系统的改进自适应准滑模解耦控制

针对一类带有外部扰动的未知MIMO非线性离散系统,提出一种新型自适应准滑模控制算法.该算法基于非参数动态线性化技术,运用高阶滑模控制的思想实现带有扰动系统的二阶准滑模控制.同时,利用扰动解耦技术,在控制器的设计中引入离散扩张状态观测器(DESO)对系统各回路间的耦合以及数据模型的未建模动态进行补偿,以进一步实现多变量系统的解耦,提升控制品质.理论分析和仿真结果说明了所提出方法的有效性和可行性.     

干扰下的无人直升机自适应反步法鲁棒跟踪控制

针对无人直升机干扰下的鲁棒轨迹跟踪问题,设计了一种自适应反步控制方法.鉴于作用在直升机上的干扰是产生跟踪误差的主要原因,该方法的主要思想是寻求一种方法来补偿这种干扰.首先,将未建模动态如外部阵风干扰、配平误差、机身、垂尾、平尾以及其他可忽略的动态产生的力和力矩看成一种组合干扰,从而建立了一个方便反步法控制器设计的简化模型.当设计好反步法控制器后,设计了一个非线性自适应律来估计这种组合干扰,并通过将干扰估计值整合到反步控制器中,使得闭环跟踪系统的鲁棒稳定性得到了保证,即基于李雅普诺夫稳定性理论证明了所设的控制器对于干扰主动阻隔,特别是低频干扰的主动阻隔是有效的.最后,两个仿真研究验证了该方法是优于常规反步法和积分反步法的.     

无人直升机航向自抗扰控制

针对无人直升机系统航向通道扰动大等问题,本文设计了一种自抗扰控制算法来实现其高性能控制.首先分析了航向通道的动态模型,并通过数学变换,将其转化为一类二阶系统;在此基础上,本文设计了适用于无人机航向通道的自抗扰控制策略,它由跟踪微分器、扩展状态观测器、控制器3个环节构成.本文对所设计的自抗扰控制策略进行了仿真和实验测试,并与常见的串级控制方法进行了对比分析.仿真与实验结果表明:这种自抗扰控制策略具有对扰动抑制能力强、控制精度高等优点,其控制性能明显优于常规的串级比例–积分–微分控制方法.     

Novel disturbance-observer-based control for systems with high-order mismatched disturbances

A novel disturbance-observer-based control method is investigated to attenuate the high-order mismatched disturbances. First, a finite-time disturbance observer (FTDO) is proposed to estimate the disturbances as well as the derivatives. By incorporating the outputs of FTDO, the original system is then reconstructed, where the mismatched disturbances are transformed to the matched ones that are compensated by feed-forward algorithm. Moreover, a feedback control law is developed to achieve the stability and tracking performance requirements for the systems. Finally, the proposed composite control method is applied to an unmanned helicopter system. The simulation results demonstrate that the proposed control method exhibits excellent control performance in the presence of high-order matched and mismatched disturbances.     

不确定时滞切换系统的鲁棒滑模控制

该文研究了一类具有非匹配不确定性和非线性扰动的时滞切换系统的滑模控制问题.首先,针对每个子系统设计对应的时滞依赖滑模面,利用驻留时间方法,给出了由滑动模态方程组成的切换系统鲁棒渐近稳定的充分条件;然后设计了滑模控制器,使得闭环系统的状态能够到达滑模面上,产生滑动模态.最后,仿真实例说明所提出方法的有效性.     

Composite Hierarchical Anti-Disturbance Control of a Quadrotor UAV in the Presence of Matched and Mismatched Disturbances

Quadrotor helicopter is an unstable system subject to matched and mismatched disturbances. To stabilize the quadrotor dynamics in the presence of these disturbances, the application of a composite hierarchical anti-disturbance controller, combining a sliding mode controller and a disturbance observer, is presented in this paper. The disturbance observer is used to attenuate the effect of constant and slow time-varying disturbances. Whereas, the sliding mode controller is used to attenuate the effect of fast time-varying disturbances. In addition, sliding mode control attenuates the effect of the disturbance observer estimation errors of the constant and slow time-varying disturbances. In this approach, the upper bounds of the disturbance observer estimation errors are required instead of the disturbances’ upper bounds. The disturbance observer estimation errors are found to be bounded when the disturbance observer dynamics are asymptotically stable and the disturbance derivatives and initial disturbances are bounded. Moreover, due to the highly nonlinear nature of the quadrotor dynamics, the upper bounds of a part of the quadrotor states and disturbance estimates are required. The nonlinear terms in the rotational dynamics are considered as disturbances, part of which is mismatched. This assumption simplifies the control system design by dividing the quadrotor’s model into a position subsystem and a heading subsystem, and designing a controller for each separately. The stability analysis of the closed loop system is carried out using Lyapunov stability arguments. The effectiveness of the developed control scheme is demonstrated in simulations by applying different sources of disturbances such as wind gusts and partial actuator failure.     

Adaptive dynamic programming-based adaptive-gain sliding mode tracking control for fixed-wing unmanned aerial vehicle with disturbances

This article proposes an adaptive dynamic programming-based adaptive-gain sliding mode control (ADP-ASMC) scheme for a fixed-wing unmanned aerial vehicle (UAV) with matched and unmatched disturbances. Starting from the dynamic of fixed-wing UAV, the control-oriented model composed of attitude subsystem and airspeed subsystem is established. According to the different issues in two subsystems, two novel adaptive-gain generalized super-twisting (AGST) algorithms are developed to eliminate the effects of disturbances in two subsystems and make the system trajectories tend to the designed integral sliding manifolds in finite time. Then, based on the expected equivalent sliding-mode dynamics, the modified adaptive dynamic programming approach with actor-critic structure is utilized to generate the nearly optimal control laws and achieve the nearly optimal performance of the sliding-mode dynamics. Furthermore, through the Lyapunov stability theorem, the tracking errors and the weight estimation errors of two neural networks are all uniformly ultimately bounded. Finally, comparative simulations demonstrate the superior performance of the proposed control scheme for the fixed-wing UAV.     

High‐order mismatched disturbance rejection control for small‐scale unmanned helicopter via continuous nonsingular terminal sliding‐mode approach

In this paper, the problem of finite‐time control for small‐scale unmanned helicopter system with high‐order mismatched disturbance is investigated via continuous nonsingular terminal sliding‐mode control approach. The key idea is to design a novel nonlinear dynamic sliding‐mode surface based on finite‐time disturbance observer. Then, the finite‐time convergence and chattering attenuation capability is guaranteed by the continuous nonsingular terminal sliding‐mode control law. Additionally, rigorous finite‐time stability analysis for the closed‐loop helicopter system is given by means of the Lyapunov theory. Finally, some simulation results demonstrate the effectiveness and predominant properties of the proposed control method for the small‐scale unmanned helicopter even in the presence of high‐order mismatched disturbance.     

A HIL Testbed for Initial Controller Gain Tuning of a Small Unmanned Helicopter

A Hardware-In-The-Loop (HIL) testbed design for small unmanned helicopters which provides a safe and low-cost platform to implement control algorithms and tune the control gains in a controlled environment is described. Specifically, it allows for testing the robustness of the controller to external disturbances by emulating the hover condition. A 6-DOF nonlinear mathematical model of the helicopter has been validated in real flight tests. This model is implemented in real-time to estimate the states of the helicopter which are then used to determine the actual control signals on the testbed. Experiments of the longitudinal, lateral and heading control tests are performed. To minimize the structural stress on the fuselage in case of controller failure or a subsystem malfunction, a damping system with a negligible parasitic effect on the dynamics of the helicopter around hover is incorporated. The HIL testbed is capable of testing the helicopter in hover, as well as on any smooth trajectories such as cruise flight, figure-8, etc. Experimentally tuning the controller on the HIL testbed is described and results in a controller which is robust to the external disturbances, and achieves an accuracy of ±2.5 cm in the position control on the longitudinal and lateral trajectory tracking, and ±5 deg accuracy around the yaw axis on the heading trajectory tracking.