基于自抗扰控制器的CNC雕刻机控制系统轮廓误差控制

针对CNC雕刻机控制系统因时变时延影响轮廓跟踪精度的问题,设计了基于自抗扰控制的单轴轨迹跟踪控制器和基于非线性PID(NLPID)的轮廓误差补偿控制器.首先,针对单轴轨迹跟踪控制,将时变时延引起的不确定性处理成系统总干扰的一部分,设计扩张状态观测器(ESO),对系统内外总干扰和系统状态进行实时估计,并设计误差补偿控制律,实现系统干扰的估计和补偿,得到良好的单轴轨迹跟踪控制性能.然后,根据轮廓误差估计值,设计基于NLPID的轮廓误差补偿控制器,对系统轮廓误差实时补偿,实现了良好的轮廓跟踪控制性能.最后,通过实验验证了所提方法的有效性.     

基于自抗扰控制的直升机航向控制方法

针对直升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的特性,传统的控制方法很难实现良好的性能.提出了一种自抗扰控制器的设计方法,并设计了扩张状态观测器,对参数不确定性和外部干扰进行估计,并实时补偿.与常规控制相比,在保证闭环稳定性的同时,能够应对模型参数的不确定性以及扰动,能够进一步使跟踪误差满足期望精度.并针对实际模型直升机实验平台航向动力学模型,在参数不确定性和主旋翼有扰动情况下,仿真结果验证了该方法的有效性.     

基于ADRC的小型四旋翼姿态控制实现

设计了一个四旋翼飞行系统,提出了一种自抗扰控制方法,解决了该飞行系统的姿态控制问题.将显性互补滤波器与扩张状态观测器相结合,实现了对系统的状态与内外总扰动的实时估计,并在此基础上利用非线性误差反馈控制律对该扰动进行了补偿,消除了内外扰动对系统的影响.最后,分别采用PID与ADRC算法实现四旋翼的姿态控制,对比结果验证了所采用的自抗扰控制方法的有效性和优越性.     

冷轧机压下伺服系统的输出反馈有限时间控制研究

针对冷轧机压下电液伺服系统存在非线性、参数不确定性和负载干扰等特点,提出了基于扩张状态观测器的输出反馈有限时间控制方法.利用扩张状态观测器对系统的状态变量进行观测,解决了电液伺服系统的速度和加速度难以实际测量的难题,并对未知函数及扰动具有鲁棒性.依据有限时间控制理论并结合反步构造法设计了有限时间控制器,并证明了系统的全局稳定性.仿真表明:扩张状态观测器能够快速准确的观测系统的状态;基于扩张状态观测器的有限时间控制方法能使系统快速、准确地跟踪指定位置目标,并具有很强的鲁棒性.     

一类不确定随机非线性系统的采样扩张状态观测器设计与观测误差的收敛性分析

实际系统中普遍存在各种干扰和不确定性因素,并且对控制系统的性能造成负面影响,因此设计对干扰和不确定性具有优异估计性能的观测器显得尤为重要.针对一类具有采样输出的不确定随机非线性系统,设计相应的采样扩张状态观测器用于在线估计不可量测状态和影响系统性能的随机总干扰.所估计的随机总干扰包含系统内部未建模动态、统计特性未知的外部有界噪声干扰以及不确定性因素的非线性耦合作用.在每个采样区间内,设计一个输出预估器用于估计实际输出,相应的输出估计值用于采样扩张状态观测器的设计.证明了所设计的采样扩张状态观测器对不可量测状态和随机总干扰的观测误差的均方收敛性.最后,一个具体仿真实例用于证实理论结果.     

基于扩展状态观测器的Boost变换器控制策略研究

内容针对Boost变换器系统在受到外部扰动时其动态性能不是很理想的问题,提出一种基于扩展状态观测器的Boost变换器控制策略.建立了变换器控制系统的数学模型,通过扩展状态观测器观测负载电流和输入电压变化引起的系统扰动,来估计和补偿输出电压的变化,并引入PD模糊逻辑控制器进一步改善了系统动态性能.该策略不依赖于控制系统数学模型和其具体参数,能精确估计系统的扰动和在线补偿负荷电流和输入电压的变化.进行了仿真和实验验证,结果表明了所提控制策略的有效性.     

自抗扰控制处理边界带有干扰的具有尖端质量的Timoshenko梁方程的稳定性

讨论了边界带有不确定扰动的一维Timoshenko梁方程的边界反馈稳定性.运用的方法主要是自抗扰控制,其主要思想是通过构造常数高增益扩张状态观测器将扰动在线估计并在反馈控制中实时消除.最后通过李雅普诺夫方法证明了闭环系统具有实用稳定性.     

基于扩张状态观测器的轮式移动机器人抗饱和自适应滑模轨迹跟踪控制

针对带有输入饱和约束的轮式移动机器人鲁棒轨迹跟踪问题,文章提出一种抗饱和自适应滑模控制方法.考虑到系统参数摄动和外部扰动等不确定因素对系统控制性能的影响,首先设计非线性扩张状态观测器来估计系统不确定因素,并基于估计值设计抗饱和自适应滑模控制器,消除系统的参数摄动、外部扰动和输入饱和约束对系统控制性能的影响.仿真对比结果验证了文章所提控制方法的优越性和有效性.     

频域内LESO和HGTD的稳定性分析

在频域内提出了线性扩张状态观测器和高增益跟踪微分器的稳定性研究方法.推导出线性扩张状态观测器和高增益跟踪微分器的稳定性条件以及估计精度,可以证明频域内的分析结果与时域内的分析结果一致.根据估计误差计算结果,提出了两种提高估计精度的方法,并通过幅频特性分析和数值仿真验证了两种方法的可行性.     

基于免疫函数的输入死区未知严格反馈非线性系统投影自适应指令滤波反步控制

为解决含有未知项以及输入死区的严格反馈非线性系统跟踪控制问题,提出一种基于免疫函数的投影自适应指令滤波有限时间控制方法.该方法使用免疫函数构造扩张状态观测器对具有输入死区控制系统中的未知项进行逼近,并使用指令滤波解决反步法中微分爆炸问题,建立滤波误差补偿机制降低滤波误差对跟踪精度的影响,同时使用投影算子保证了自适应参数的有界性.与现有文献中基于障碍李雅普诺夫函数的自适应反步约束控制相比较,文章可同时约束系统状态、补偿跟踪误差以及自适应参数在预设的范围内,保证了闭环系统中所有信号有界,结合有限时间控制加快了控制系统的收敛速度.最后仿真结果表明了文章控制方法的有效性.     

Finite-time disturbance observer-based trajectory tracking control for quadrotor unmanned aerial vehicle with obstacle avoidance

This paper investigates the problem of trajectory tracking control for quadrotor unmanned aerial vehicle (UAV) in the presence of dynamic obstacles and external disturbance forces/torques. More specifically, two new sliding mode disturbance observers are firstly designed to estimate the external disturbances, in which the observation errors can converge to zero in finite time. Furthermore, utilizing the observation information, a new sliding mode surface-like variable-based position tracking control scheme and a novel nonsingular terminal sliding mode-based attitude synchronization control scheme are developed to drive the UAV tracking the reference trajectory with obstacle avoiding. Moreover, the tracking errors of the close-loop control system can converge to zero within finite time by the analyses of Lyapunov methodology. Finally, the numerical simulation results are presented to illustrate the effectiveness of the proposed control schemes.     

Adaptive Constrained Control of Unknown Strict Feedback Nonlinear Systems With Dead Zone Input北大核心CSCD

研究了具有死区输入的预设约束未知高阶严格反馈非线性系统的控制问题,提出了一种基于免疫函数的自抗扰预设漏斗约束自适应控制策略。首先,针对系统内部的未知问题,采用免疫函数与扩张状态观测器结合对系统内部未知项进行观测;其次,通过Lyapunov方法与漏斗控制相结合设计控制器,使得跟踪误差能够维持在预先设定的漏斗约束范围内;同时,利用双曲正切函数速率变化快这一特性设计自适应控制律,引入指令滤波器避免反步法中重复求导问题,分析证明了闭环系统所有信号的有界性。仿真实例表明了控制方法的有效性。     

Feedforward Design and Optimality Aspects for the Control of Mechatronic Systems

This paper considers the tracking controller design for a mechatronic handling system. The presented approach is based on Port-Hamiltonian systems and it achieves good tracking as well as good disturbance rejection based on a polynomial approach. A PBC controller stabilizes the trajectory and the feedforward part has to fulfill the given limitations and the time optimality. This approach avoids the solution of a boundary value problem and a real-time integration of the internal dynamics. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Positioning control for a linear actuator with nonlinear friction and input saturation using output‐feedback control

This article deals with the positioning control problem via the output feedback scheme for a linear actuator with nonlinear disturbances. In this study, the proposed controller accounts for not only the nonlinear friction, force ripple, and external disturbance but also the input saturation problem. In detail, the energy consumption for conquering friction and disturbance rejection is estimated and used as compensation based on the hybrid controller including and sliding‐mode‐based adaptive algorithms, which ensures the tracking performance and robustness of electromechanical servo system. Moreover, to confront the input saturation, a saturation observer and an anti‐windup controller are designed. The global robustness of the controller is guaranteed by an output feedback robust law. Theoretically, the designed controller can guarantee a favorable tracking performance in the presence of various disturbance forces and input saturation, which is essential for high accuracy motion plant in industrial application. The simulation results verify the robustness and effectiveness for the motion system with the proposed control strategy under various operation conditions. © 2016 Wiley Periodicals, Inc. Complexity 21: 191–200, 2016     

Model Based Trajectory Control of an Overhead Travelling Crane

Until now, most papers concerning control of overhead travelling cranes have only focussed on position control of the translational degrees of freedom, see for example [1], [3], [4], and [5]. With more advanced robotic applications envisaged, however, there is a demand for both trajectory control in six degrees of freedom and active damping of the weakly damped load oscillations due to the rope suspension [2]. Hence, a model based trajectory control is presented for an overhead travelling crane that has been upgraded with an orientation unit providing three additional axes. Starting from a central multibody model, decentralised design models are derived for each crane axis. By this, couplings between the axes are identified and appear as disturbance inputs in these decentralised design models. Each decentralised axis controller consists of linear state feedback, feedforward control, and observer based disturbance compensation and is derived in symbolic form. This allows for an adaptation of the complete control structure employing the gain scheduling technique with respect to varying system parameters like rope length and load mass. Couplings between the crane axes are compensated by feedforward control, whereas the e.ects of nonlinear friction forces are counteracted by combination of feedforward control and disturbance estimation. Experimental results, taken at a 5 t ‐ bridge crane, show the bene.ts of the proposed control scheme as regards control performance and steady‐state accuracy.     

Nonlinear adaptive output feedback robust control of hydraulic actuators with largely unknown modeling uncertainties

In this paper, a nonlinear adaptive output feedback robust controller is proposed for motion control of hydraulic servo systems in the presence of largely unknown matched and mismatched modeling uncertainties. Different from the existing control technologies, the presented hydraulic closed-loop controller which can deal with strong matched and mismatched parametric uncertainties is synthesized via the backstepping technique. Specially, a nonlinear disturbance observer which can estimate the largely mismatched disturbance is integrated into the design of the linear extended state observer to obtain estimation of unmeasurable system states, uncertain parameters and strong disturbances simultaneously. In addition, the projection-type adaptive law is synthesized into the design of the resulting controller. More importantly, the global stability of the whole closed-loop system is strictly guaranteed by the Lyapunov analysis. Furthermore, the effectiveness and practicability of the presented control strategy have been demonstrated by comparative experiments under different working conditions.     

Optimal Control of Nonlinear Time-Delay Systems with Persistent Disturbances

This paper is concerned with the optimal control of a class of nonlinear time-delay systems affected by external persistent disturbances. A feedforward and feedback optimal control (FFOC) law, consisting of analytical linear feedforward and feedback terms and the limit of a compensation sequence, is obtained by a successive approximation approach (SAA). In order to obtain a physically realizable feedforward control, a disturbance observer is introduced in the exosystem. Simulation results demonstrate the validity of the SAA and the robustness of the FFOC. Communicated by Q. C. Zhao This work was supported by the National Natural Science Foundation of China, Grant 60574023 and the Natural Science Foundation of Qingdao City of China, Grant 05-1-JC-94.     

Iterative learning control for MIMO nonlinear systems with arbitrary relative degree and no states measurement

This article presents a state observer based iterative learning control to solve the trajectory tracking problem of a class of time‐varying Multi‐Input‐Multi‐Output nonlinear systems with arbitrary relative degree. For this purpose, an asymptotically stable observer is derived for the system under consideration. There after, this observer is integrated with the iterative learning controller by replacing the state in the control law with its estimation yielded by the state observer. Hence, the stability of the whole control (nonlinear system plus controller plus observer) is guaranteed. Simulation result on nonlinear system shows that the trajectory tracking error decreases through the iterations. © 2013 Wiley Periodicals, Inc. Complexity 19: 37–45, 2013     

Switched safe tracking control design for unmanned autonomous helicopter with disturbances

In this paper, the switched safe tracking control scheme is investigated for the attitude and altitude system of a medium-scale unmanned autonomous helicopter with output constraints and unknown external disturbances. To keep the attitude angles and altitude within the desired constrained range, an output boundary protection approach is adopted to generate an output constrained trajectory which is piecewise differentiable. The disturbance observer-based control method is employed to handle the unknown external disturbances of the system. Because of the piecewise differentiability of the output constrained trajectory, the closed-loop error system with the safe tracking controller can be seen as a switched system with jump dynamics. The multiple Lyapunov function method is adopted to guarantee the tracking performance with designed average dwell time. Simulation results of an example are provided to illustrate the effectiveness of the proposed control scheme for the unmanned autonomous helicopter system.     

Iterative learning control design of nonlinear multiple time-delay systems

Most available results on iterative learning control address trajectory tracking problem for systems without multiple time-delay. This paper is concerned with iterative learning control design for nonlinear systems with multiple delays, in which external disturbances and output measurement noises are involved. We obtain some new and interesting criteria to guarantee the convergence of the tracking error in the sense of the λ − norm. It will be shown that the convergence of the system outputs to the desired trajectory is ensured in the absence of disturbances and output measurement noises. In the presence of disturbance and measurement noises, we estimate the upper bound of the tracking error. In order to confirm the validity of the present results, numerical simulation is also presented.