四旋翼飞行器的轨迹跟踪抗干扰控制

针对四旋翼飞行器轨迹跟踪问题中系统存在模型不确定和易受到外界扰动的情况,提出了基于切换函数的扩张状态观测器设计方法来对系统中的扰动进行估计,并将估计值与滑模控制器的设计相结合,实现了对系统中非匹配不确定性和匹配不确定性的抑制且实现了系统跟踪误差的一致最终有界.首先,根据变量间的耦合关系将飞行器系统模型分解为两个子系统模型,设计扩张状态观测器对子系统中的非匹配不确定性进行估计,并将估计值作为变量加入到切换函数的设计中;进而基于切换函数设计扩张状态观测器以估计经切换函数重构系统中的扰动,并在控制器中对扰动进行补偿.最后通过李雅普诺夫理论证明了控制系统的稳定性.通过仿真验证了本文提出的方法能够有效实现飞行器轨迹跟踪控制且能够抑止传统滑模控制的抖振现象.     

非匹配扰动干扰下的无人直升机轨迹跟踪控制

针对小型无人直升机在飞行过程中容易受到非匹配扰动影响的特点,本文设计了一种基于新型滑模控制方法的轨迹跟踪控制器.首先,建立了无人直升机系统的非线性数学模型,并对该模型进行近似反馈线性化处理,同时将模型分为位置和偏航两个子系统;然后,利用扩展扰动观测器对复合扰动以及非匹配扰动的各阶导数的估计值,设计新型时变滑模面,得到滑模控制律,并给出了控制系统的稳定性分析;最后,仿真结果验证了控制方法的有效性和优越性.该新型滑模控制方法的优越性主要体现在:对非匹配扰动具有较强的鲁棒性,以及能有效地抑制抖振现象.     

Trajectory Tracking Control for Quadrotor Robot Subject to Payload Variation and Wind Gust Disturbance

This work proposes a hierarchical nonlinear control scheme for quadrotor to track 3D trajectory subject to payload variation and fast time-varying wind gust disturbance. In terms of dynamics model, the 6 DOF dynamics model with parametric and nonparametric uncertainties is built up. Wind gust and propeller momentum drag model are implemented to quantify the wind impact (force and moment disturbances) on quadrotor. In terms of control design, adaptive robust controller is developed for dynamic subsystem to deal with moment disturbance and estimate the system parameters. Global sliding mode controller is implemented for kinematic subsystem to generate adequate desired attitude angles for tracking the planned 3D trajectory. Simulations and experiments under various conditions are carried out for verification, and the results indicate the effectiveness, adaptiveness and robustness of the control strategy.     

四旋翼无人机不匹配扰动抗干扰控制

针对四旋翼无人机存在的不匹配干扰和执行器故障等现象,提出了一种基于有限时间观测器的飞行控制方案。从无人机的运动学模型出发,构建了受执行器故障和不匹配干扰影响的控制模型。将干扰观测器与非奇异终端滑模控制 (NTSMC) 方法相结合,以实现复合抗干扰和容错控制器设计。首先,设计了两个非线性有限时间扰动观测器来估计不匹配扰动和执行器故障,有限时间观测器使得估计误差在有限时间内收敛到零。其次,将观测器与NTSMC控制方法结合,以在有限的时间内实现跟踪,并有效地减少抖振。最后,从理论和仿真验证了控制方法的有效性和所期望的控制性能。     

四旋翼无人飞行器的轨迹跟踪与滑模事件驱动控制

四旋翼飞行器作为一个典型的欠驱动的系统,具有强耦合、非线性等特性.针对飞行器外部干扰、和通信资源受限条件下的轨迹跟踪控制问题,进行滑模事件驱动控制方法的研究.首先,分析动力学特性,通过时间尺度分解方法将系统解耦成位置子系统和姿态子系统.其次,将位置子系统转化为严格反馈形式,设计反步滑模控制器,实现位置轨迹稳定跟踪;针对姿态子系统存在时变有界扰动及通信受限,设计滑模事件驱动控制律,在抑制干扰的同时实现对虚拟姿态跟踪指令的跟踪.根据Lyapunov分析方法证明了所设计控制器的稳定性,并通过理论分析证明闭环控制系统不会出现Zeno现象.最后,仿真结果验证了滑模事件驱动控制律在存在外部扰动和通信受限时四旋翼无人飞行器轨迹跟踪的鲁棒性.     

Robust Backstepping Control Based on Integral Sliding Modes for Tracking of Quadrotors

Modern non-inertial robots are usually underactuated, such as fix or rotary wing Unmanned Aerial Vehicles (UAVs), underwater or nautical robots, to name a few. Those systems are subject to complex aerodynamic or hydrodynamic forces which make the dynamic model more difficult, and typically are subject to bounded smooth time-varying disturbances. In these systems, it is preferred a formal control approach whose closed-loop system can predict an acceptable performance since deviations may produce instability and may lead to catastrophic results. Backstepping provides an intuitive solution since it solves underactuation iteratively through slaving the actuated subsystem so as to provide a virtual controller in order to stabilize the underactuated subsystem. However it requires a full knowledge of the plant and derivatives of the state, which it is prone to instability for any uncertainty; and although robust sliding mode has been proposed, discontinuities may be harmful for air- or water-borne nonlinear plants. In this paper, a novel robust backstepping-based controller that induces integral sliding modes is proposed for the Newton–Euler underactuated dynamic model of a quadrotor subject to smooth bounded disturbances, including wind gust and sideslip aerodynamics, as well as dissipative drag in position and orientation dynamics. The chattering-free sliding mode compensates for persistent or intermittent, and possible unmatched state dependant disturbances with reduced information of the dynamic model. Representative simulations are presented and discussed.     

非匹配不确定高阶非线性系统递阶Terminal滑模控制

对于高阶非线性系统,首先采用改进的高阶滑模微分器作为间接干扰观测器,获得前n-1个子系统中的非匹配复合干扰的估计值,证明了估计误差可任意小. 为避免代数环,设计了三种方案获得最后一个子系统中非匹配复合干扰的估计值,并证明了估计误差有界. 在此基础上设计递阶Terminal滑模控制器,证明了控制器参数非奇异及结构非奇异,并给出所需条件. 最后,证明了系统稳定,跟踪误差可任意小. 近空间飞行器姿态控制仿真验证了本文结论.     

输出误差约束下四旋翼无人机预定性能反步控制

针对外界干扰和输出误差约束条件下的四旋翼无人机的跟踪控制问题,提出预定性能反步跟踪控制策略.首先,将四旋翼无人机动力学模型转换为带有外界干扰的严反馈形式;然后,利用反步法设计控制器,通过引入障碍Lyapunov函数保证跟踪误差的预定性能,设计干扰观测器对外界干扰进行估计,并通过滤波器估计姿态子系统中部分虚拟控制输入的导数;通过稳定性分析说明所设计的控制器可以保证跟踪误差的有界稳定性,且跟踪误差一直处于预设边界内;最后,通过仿真验证所设计控制策略的有效性.     

基于模糊不确定观测器的四旋翼飞行器自适应动态面轨迹跟踪控制

针对具有未知外界扰动和系统不确定性的四旋翼飞行器,提出了一种基于模糊不确定观测器（Fuzzy uncertainty observer,FUO）的自适应动态面轨迹跟踪控制方法.通过将四旋翼飞行器系统分解为位置、姿态角和角速率三个动态子系统,使得各子系统虚拟控制器能够充分考虑欠驱动约束;采用一阶低通滤波器重构虚拟控制信号及其一阶导数,实现四旋翼跟踪控制设计的迭代解耦;设计了一种模糊不确定观测器,用以估计和补偿未知外界扰动与系统不确定性,从而确保闭环系统的稳定性和跟踪误差与其他系统信号的一致有界性.仿真研究验证了所提出的控制方法的有效性和优越性.     

Fast terminal sliding mode tracking control of hypersonic vehicles based on non-homogeneous disturbance observer

The tracking control problem of hypersonic vehicles is studied and analyzed in this paper using terminal sliding mode control method (TSMC) and non-homogeneous disturbance observer(NHDO) considering parametric uncertainty and external disturbances. Non-singular terminal sliding mode controller is provided based on NHDO. The key idea is that the NHDO is adopted to estimate the aerodynamic uncertainties and external disturbances simultaneously, which can enhance the robustness of the system and lower the gain of the switch controller. Rigorous stability analysis for the closed-loop system is given via Lyapunov stability theory, which proves that the system states are always bounded even during the estimation process when the estimation error is not zero. The sliding manifold can be reached in finite time and the tracking errors can converge to zero asymptotically. Numerical simulations are conducted with the longitudinal nonlinear dynamic model of hypersonic vehicles to verify the effectiveness and robustness of the designed controller.     

Immersion and Invariance-based Sliding Mode Attitude Control of Tilt Tri-rotor UAV in Helicopter Mode

In this paper, we propose an immersion and invariance-based sliding mode controller for a tilt tri-rotor unmanned aerial vehicle subjects to parameter perturbation, unmodeled dynamics, and external disturbances. The control scheme is divided into three parts, including the disturbance observer, the attitude controller, and the control allocation. Firstly, to alleviate the chattering and improve the robustness for attitude control, the observer using immersion and invariance theory is developed to estimate the disturbance. Note that the observer can relax the requirement of disturbance upper bound and guarantee the convergence of the estimation error. Secondly, to improve the dynamic response capability, a sliding mode attitude controller with an adaptive switch function is designed based on the disturbance observer. Thirdly, a hierarchical control allocation algorithm is proposed. The performance improvement is illustrated by comparing with other sliding mode controllers. Simulations and flight experiments are conducted to verify the effectiveness and applicability of the proposed control scheme.

     

基于滑模观测器和广义观测器的故障估计方法

针对受未知干扰影响的一类非线性系统,提出一种基于滑模观测器和广义观测器的执行器故障和传感器故障估计方法.首先通过线性变换将原系统解耦为两个降阶的子系统,其中一个子系统受执行器故障和干扰的影响,另一个含有传感器故障和干扰,进一步将后一个子系统转化为广义系统.对两类子系统分别设计滑模观测器和广义观测器,给出估计误差一致最终有界的条件,得到系统状态和未知干扰的估计值.然后,利用等效输出控制原理重构执行器故障,引入干扰补偿保证重构算法的鲁棒性,再根据广义观测器的结果获得传感器故障的估计值.最后,通过计算机仿真验证了本文方法的有效性.     

基于扩张状态观测器的 连铸结晶器振动位移系统自适应滑模控制

针对伺服电机驱动的连铸结晶器振动位移系统中存在时变负载转矩、参数不确定性等问题,本文提出了一种基于扩张状态观测器(extended state observer, ESO)的自适应非奇异终端滑模(nonsingular terminal sliding mode,NTSM)控制方法.首先,设计ESO对系统存在的综合扰动和不可测状态进行估计.然后,采用分层设计的方法,分别对位移跟踪子系统和电流环子系统设计基于ESO的自适应NTSM控制器和滑模控制器.为削弱ESO估计误差对跟踪精度的影响,在NTSM控制器中引入了自适应增益.可以证明,所设计的控制器能够保证闭环系统所有信号有界,系统状态可渐近收敛到原点附近的小邻域内.最后,仿真结果验证了所提出控制方法的有效性.     

Design of decentralised adaptive sliding mode controllers for large-scale systems with mismatched perturbations

Based on the Lyapunov stability theorem, a methodology for designing a decentralised adaptive sliding mode control scheme is proposed in this paper. This scheme is implemented for a class of large-scale systems with both matched and mismatched perturbations. The perturbations and the interconnection terms are assumed to be norm bounded under certain mild conditions. The decentralised sliding surfaces with adaptive mechanisms embedded are specially designed for each subsystem, so that when each subsystem enters the sliding mode, the mismatched perturbations and the effects of interconnections can be effectively overcome and achieve asymptotic stability. The decentralised controller with embedded adaptive mechanisms is capable of driving the controlled state trajectories into the designated sliding surface in finite time. This is also achieved without the knowledge of upper bounds of the perturbations except those of the uncertainties in the input channels. A numerical example is included to demonstrate the feasibility of the proposed control scheme.     

Output Feedback Control of a Quadrotor UAV Using Neural Networks

In this paper, a new nonlinear controller for a quadrotor unmanned aerial vehicle (UAV) is proposed using neural networks (NNs) and output feedback. The assumption on the availability of UAV dynamics is not always practical, especially in an outdoor environment. Therefore, in this work, an NN is introduced to learn the complete dynamics of the UAV online, including uncertain nonlinear terms like aerodynamic friction and blade flapping. Although a quadrotor UAV is underactuated, a novel NN virtual control input scheme is proposed which allows all six degrees of freedom (DOF) of the UAV to be controlled using only four control inputs. Furthermore, an NN observer is introduced to estimate the translational and angular velocities of the UAV, and an output feedback control law is developed in which only the position and the attitude of the UAV are considered measurable. It is shown using Lyapunov theory that the position, orientation, and velocity tracking errors, the virtual control and observer estimation errors, and the NN weight estimation errors for each NN are all semiglobally uniformly ultimately bounded (SGUUB) in the presence of bounded disturbances and NN functional reconstruction errors while simultaneously relaxing the separation principle. The effectiveness of proposed output feedback control scheme is then demonstrated in the presence of unknown nonlinear dynamics and disturbances, and simulation results are included to demonstrate the theoretical conjecture.      

Robust adaptive quasi-sliding mode controller for discrete-time systems

In this paper, a discrete robust quasi-sliding mode adaptive controller is presented for the system with model uncertainties, unmodeled dynamics and bounded disturbances. The proposed method is adaptive control in conjunction with a sliding mode based controller design. The bounded motion of the state around the sliding surface and the stability of the global system in the sense that all signals remain bounded are guaranteed. In the proposed adaptive algorithms, the dead-zone method is employed even though the upper and lower bounds of the disturbances are unknown. Simulation results have shown the effectiveness of the proposed algorithms.     

带有执行器故障的多水面船固定时间分布式滑模协同控制

针对未知环境干扰、未知执行器故障等多水面船协同控制问题,提出一种带有执行器故障的多水面船固定时间分布式滑模协同控制方法,可保证协同控制系统的全局固定时间的稳定性.首先,设计一种固定时间干扰观测器,用于估计集总扰动(包括未知环境扰动和未知执行器故障);其次,引入固定时间非奇异快速终端滑模面,可有效地消除系统的奇异性,改善系统的抖振;然后,提出一种基于固定时间非奇异快速终端滑模面和固定时间干扰观测器的分布式容错控制器,使得收敛时间上界与系统初始状态无关;最后,通过仿真实验验证所提出控制律的有效性.     

Reduced-order Generalized Proportional Integral Observer Based Continuous Dynamic Sliding Mode Control for Magnetic Levitation System with Time-varying Disturbances

In order to reduce the influence of time-varying disturbances for magnetic levitation system, we propose a reduced-order generalized proportional integral observer (RGPIO) based continuous dynamic sliding mode control scheme for magnetic levitation system in this paper. Unlike the popular extended state observer (ESO), it could deal with constant or slowing varying disturbances from theoretical point of view, the reduced-order generalized proportional integral observer (RGPIO) is designed to estimate the time-varying disturbances and system states, then the dynamic sliding mode surface is developed and deduce a continuous sliding mode controller (CSMC) for magnetic levitation system. Compared with ESO based continuous sliding mode controller, the proposed method not only ensures the position tracking accuracy, but also obtain better time-varying disturbance reject ability. Simulation and experimental results are also given to verify the effectiveness.

     

Dynamic modelling and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances

In this paper, both the closed-form dynamics and adaptive robust tracking control of a space robot with two-link flexible manipulators under unknown disturbances are developed. The dynamic model of the system is described with assumed modes approach and Lagrangian method. The flexible manipulators are represented as Euler–Bernoulli beams. Based on singular perturbation technique, the displacements/joint angles and flexible modes are modelled as slow and fast variables, respectively. A sliding mode control is designed for trajectories tracking of the slow subsystem under unknown but bounded disturbances, and an adaptive sliding mode control is derived for slow subsystem under unknown slowly time-varying disturbances. An optimal linear quadratic regulator method is proposed for the fast subsystem to damp out the vibrations of the flexible manipulators. Theoretical analysis validates the stability of the proposed composite controller. Numerical simulation results demonstrate the performance of the closed-loop flexible space robot system.     

Multivariable sliding mode backstepping controller design for quadrotor UAV based on disturbance observer

This paper deals with the tracking control problem of quadrotor unmanned aerial vehicles (QUAVs) with external disturbances. First, because the QUAV model contains two non-integrity constraints, the dynamic model of the QUAV is decomposed into two subsystems which are independently controlled, so as to reduce controller design complexity. Secondly, the nonlinear disturbance observer (DOB) technique is integrated into a backstepping control method to design the controller for the first subsystem, in which a DOB is applied to estimate the lumped uncertainty. Based on the double power reaching law and the DOB, a multivariable sliding mode control (MSMC) scheme is developed for the second subsystem. Thirdly, based on Lyapunov theory, the closed-loop system is proved to be asymptotically stable. Finally, our comparative simulation results demonstrate that the presented control scheme behaves better in terms of tracking performance than the adaptive backstepping control (ABC) approach.