Dynamic Surface Control with Nonlinear Disturbance Observer for Uncertain Flight Dynamic System

A new robust control method of a nonlinear flight dynamic system with aerodynamic coefficients and external disturbance has been proposed.The proposed control system is a combination of the dynamic surface control(DSC)and the nonlinear disturbance observer(NDO).DSC technique provides the ability to overcome the″explosion of complexity″problem in backstepping control.NDO is adopted to observe the uncertainties in nonlinear flight dynamic system.It has been proved that the proposed design method can guarantee uniformly ultimately boundedness of all the signals in the closed-loop system by Lyapunov stability theorem.Finally,simulation results show that the proposed controller provides better performance than the traditional nonlinear controller.

Nonsingular Fast Terminal Sliding Mode Control Based on Nonlinear Disturbance Observer for a Quadrotor

Given external disturbances and system uncertainties,a nonsingular fast terminal sliding mode control(NFTSMC)method integrated a nonlinear disturbance observer(NDO)is put forward for quadrotor aircraft.First,a NDO is proposed to estimate the actual values of uncertainties and disturbances.Second,the NFTSM controller based on the reaching law is designed for the attitude subsystem(inner loop),and the control strategy can ensure Euler angles’fast convergence and stability of the attitude subsystem.Moreover,the NFTSMC strategy combined with backstepping is proposed for the position subsystem(outer loop),which can ensure subsystem tracking performance.Finally,comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control(SMC)and the SM integral backstepping control under uncertainties and disturbances.

Adaptive current compensation with nonlinear disturbance observer for single-sided linear induction motor considering dynamic eddy-effect

An adaptive current compensation control for a single-sided linear induction motor(SLIM) with nonlinear disturbance observer was developed. First, to maintain t-axis secondary component flux constant with consideration of the specially dynamic eddy-effect(DEE) of the SLIM, a instantaneously tracing compensation of m-axis current component was analyzed. Second,adaptive current compensation based on Taylor-discretization algorithm was proposed. Third, an effective kind of nonlinear disturbance observer(NDOB) was employed to estimate and compensate the undesired load vibrations, then the robustness of the control system could be guaranteed. Experimental verification of the feasibility of the proposed method for an SLIM control system was performed, and it showed that the proposed adaptive compensation scheme with NDOB could significantly promote speed dynamical response and minimize speed ripple under the conditions of external load coupled vibrations and unavoidable feedback control variables measured errors, i.e., current and speed.

Enhanced adaptive nonlinear extended state observer for pure feedback systems with matched and mismatched disturbances

In this paper, an enhanced adaptive nonlinear extended state observer (EANESO) for single-input single-output pure feedback systems in the presence of external time-varying disturbances is proposed. In this paper, a nonlinear system with matched and mismatched disturbances is considered. The conventional extended state observer (ESO) can only be applied to systems that are in the form of integral chains. Moreover, this method has limitations in the face of mismatched disturbances. In the presence of time-varying disturbances, the traditional ESOs cannot estimate the disturbances accurately. To overcome this limitation, an EANESO is proposed in this paper. The main idea is to design the nonlinear ESO (NESO) to estimate the states of the system and multiple disturbances simultaneously. The observer gains are considered time-varying and adjusted with adaptation laws to improve the estimation accuracy and overcome the peaking phenomenon. Next, the proposed controller is designed based on output feedback to eliminate the effects of multiple disturbances and stabilize the closed-loop system. Subsequently, the stability analysis of the closed-loop system and convergence of the observer error are discussed. Finally, the proposed method is applied to the inverted pendulum system. The simulated results show good performance of the proposed method as compared with a recently published scheme in the related literature.

Active Disturbance Rejection Control for Uncertain Nonlinear Systems With Sporadic Measurements

This paper deals with the problem of active disturbance rejection control(ADRC)design for a class of uncertain nonlinear systems with sporadic measurements.A novel extended state observer(ESO)is designed in a cascade form consisting of a continuous time estimator,a continuous observation error predictor,and a reset compensator.The proposed ESO estimates not only the system state but also the total uncertainty,which may include the effects of the external perturbation,the parametric uncertainty,and the unknown nonlinear dynamics.Such a reset compensator,whose state is reset to zero whenever a new measurement arrives,is used to calibrate the predictor.Due to the cascade structure,the resulting error dynamics system is presented in a non-hybrid form,and accordingly,analyzed in a general sampled-data system framework.Based on the output of the ESO,a continuous ADRC law is then developed.The convergence of the resulting closed-loop system is proved under given conditions.Two numerical simulations demonstrate the effectiveness of the proposed control method.

基于IGWO-MPC和NDO-ISMC级联算法的UUV轨迹跟踪控制器设计

为了解决水下机器人(UUV)在受海流等复杂干扰力影响时的轨迹跟踪问题,设计了一种基于改进灰狼算法的模型预测控制(IGWO-MPC)和基于非线性干扰观测器的积分滑模控制(NDO-ISMC)级联的轨迹跟踪控制器。基于MPC方法设计了运动学控制器,提出利用在GWO算法中引入非线性收敛因子,基于个体经验和权重更新灰狼位置,以及反向学习策略所设计出的IGWO算法,来优化MPC的滚动优化求解过程,使机器人以期望的最优速度对给定位姿进行跟踪。基于IGWO-MPC运动学控制器得到的期望速度指令,设计了NDO-ISMC动力学控制器,该控制器利用NDO对干扰力进行估计,并对ISMC动力学输出控制律进行补偿以抑制扰动对跟踪精度的影响,同时输出扰动条件下机器人能够稳定跟踪上期望速度的控制推力。最后,利用MATLAB进行三维空间环境仿真,验证文章提出的将IGWO-MPC与NDO-ISMC算法级联的轨迹跟踪控制器能够使UUV在复杂水下环境下实现精确且稳定的轨迹跟踪。

改进NDO的板球系统自适应滑模抗扰控制

为解决板球系统因受到外部负载扰动、摩擦力、交叉耦合干扰等不确定性扰动而跟踪精度不高的问题,提出一种基于改进的非线性干扰观测器(NDO)和非线性信息增益滑模控制策略。利用预设性能函数(PPF)对误差的变换技术,将误差限定在规定范围内,建立改进的NDO来估计不确定性扰动。运用精确的估计值来设计滑模控制器,滑模面包含一个修正项,可以降低扰动的影响,从而提高控制精度,并采用非线性信息增益设计自适应切换项增益,降低抖振的影响。最后,仿真表明改进的NDO能有效地估计扰动,改善了动态品质,所提控制方案提高了传统的NDO的控制精度和抗扰能力。

Disturbance observer based actor-critic learning control for uncertain nonlinear systems

This paper investigates the disturbance observer based actor-critic learning control for a class of uncertain nonlinear systems in the presence of unmodeled dynamics and time-varying disturbances.The proposed control algorithm integrates a filter-based design method with actor-critic learning architecture and disturbance observer to circumvent the unmodeled dynamic and the timevarying disturbance.To be specific,the actor network is employed to estimate the unknown system dynamic,the critic network is developed to evaluate the control performance,and the disturbance observer is leveraged to provide efficient estimation of the compounded disturbance which includes the time-varying disturbance and the actor-critic network approximation error.Consequently,highgain feedback is avoided and the improved tracking performance can be expected.Moreover,a composite weight adaptation law for actor network is constructed by utilizing two types of signals,the cost function and the modeling error.Eventually,theoretical analysis demonstrates that the developed controller can guarantee bounded stability.Extensive simulations and experiments on a robot manipulator are implemented to validate the performance of the resulted control strategy.

基于NDO的永磁同步电动机自适应分数阶滑模控制

针对永磁同步电动机(PMSM)驱动的高档数控机床进给系统易受参数变化、外部扰动等不确定性因素影响的问题,设计了一种基于非线性干扰观测器(NDO)的自适应分数阶滑模控制(AFOSMC)方法。建立了含有不确定性的PMSM动态数学模型。将自适应控制与分数阶滑模控制(FOSMC)相结合,抑制了整数阶滑模控制的抖振现象,且能实时调整切换增益,提高了系统的控制精度。然而,外部干扰会对系统产生极大的影响,因此采用NDO实时辨识外部干扰,将观测值作为前馈补偿引入AFOSMC中,以提高控制器的抗干扰能力。实验结果表明,基于NDO的AFOSMC方法有效地削弱了抖振现象,提高了进给系统的跟踪性能和抗扰能力。

A Harmonic Disturbance Suppression Method For Frequency Time-variable Systems

为抑制谐波扰动对控制系统的影响，对频率时变的谐波扰动进行分析，提出两种针对频率时变的谐波扰动的抑制方法：线性反馈方法与基于非线性干扰观测器的方法。线性反馈方法依据于线性矩阵不等式理论，将频率变化的谐波扰动分解为频率固定的谐波扰动与非线性不确定项，采用一般的干扰观测方法对固定频率扰动进行观测，并采用线性反馈方法对非线性不确定项进行抑制。基于非线性干扰观测器的方法直接对谐波扰动进行观测，并采用鲁棒控制器进行干扰补偿。采用李亚普诺夫理论来验证扰动抑制方法的稳定性。将两种扰动抑制方法应用于磁悬浮飞轮电机控制系统，通过仿真与实验结果表明，两种方法具有很好的扰动抑制能力。基于非线性干扰观测器的扰动抑制方法依据扰动的特性设计，具有更好的动态、稳态特性与鲁棒性。

Distributed Cooperative Anti-Disturbance Control for High-Order MIMO Nonlinear Multi-Agent Systems

To solve the synchronization and tracking problems,a cooperative control scheme is proposed for a class of higher-order multi-input and multi-output(MIMO)nonlinear multi-agent systems(MASs)subjected to uncertainties and external disturbances.First,coupled relationships among Laplace matrix,leader-following adjacency matrix and consensus error are analyzed based on undirected graph.Furthermore,nonlinear disturbance observers(NDOs)are designed to estimate compounded disturbances in MASs,and a distributed cooperative anti-disturbance control protocol is proposed for high-order MIMO nonlinear MASs based on the outputs of NDOs and dynamic surface control approach.Finally,the feasibility and effectiveness of the proposed scheme are proven based on Lyapunov stability theory and simulation experiments.

Robust Position Anti-Interference Control for PMSM Servo System With Uncertain Disturbance

Aiming to suppress the influence of uncertain disturbances in the drive control of permanent magnet synchronous machines(PMSM),such as the parameter uncertainties and load disturbance,a robust anti-interference control for the angular position tracking control of a PMSM servo system has been proposed in this paper.During the position tracking,uncertain system disturbances being regarded as a lumped unknown term will be online observed by a nonlinear disturbance observer(NDOB),of which the influence will consequently be counteracted by a robust backstepping compensator(RBC).The asymptotical stability of proposed control scheme is analyzed and designed according to the Lyapunov stability criterion,and its convergence against the system uncertain disturbance is verified on a prototype PMSM servo platform and shows good performance in rotor angular position tracking and anti-interference.

Integral sliding mode control for flexible ball screw drives with matched and mismatched uncertainties and disturbances

The design of servo controllers for flexible ball screw drives with matched and mismatched disturbances and uncertainties is focused to improve the tracking performance and bandwidth of ball screw drives.A two degrees of freedom mass model is established based on the axial vibration characteristics of the transport ball screw,and the controller of an adaptive integral sliding mode is proposed combining the optimal design of state feedback gain matrix K to restrain the vibration and the matched disturbances and uncertainties.Then for the counteraction of the mismatched disturbances and uncertainties,a nonlinear disturbance observer is also developed.The trajectory tracking performance experiments and bandwidth analysis were conducted on experimental setup with the proposed control method.It is proved that the adaptive integral sliding mode controller has a high tracking performance and bandwidth especially for the axial vibration characteristics model of ball screw drives.And the ball screw tracking accuracy also has a considerable improvement with the application of the proposed nonlinear disturbance observer.

Active Disturbance Rejection Control for a Multiple-Flexible-Link Manipulator

The control problem of multiple-flexible-link manipulators( MFLMs) is studied in this paper.The dynamic model of MFLM is derived and separated into two-time scale by utilizing the singular perturbation technique. The active disturbance rejection control( ADRC) is adopted to the slow subsystem to track a desired trajectory. The proposed ADRC structure preshapes the desired trajectory by utilizing the tracking differentiator,estimates the disturbance and internal states with an extended state observer,and guarantees a robust performance by combining a feedback controller with a feedforward term. Two types of feedback controllers are designed,proportional derivative( PD) controller and nonlinear PD( NPD) controller. For the fast subsystem,a fast stabilizing control is designed according to the standard linear quadratic regulator approach. Simulations are performed to evaluate the proposed control scheme.Results show that,compared with the traditional PD controller,the ADRC structure based control scheme has smaller overshot and shorter settling time,suppresses vibration quickly,and is robust to the maneuver speed. In general,the control scheme utilizing ADRC structure and NPD feedback controller shows better performance.

基于改进NDO复合控制在像旋补偿机构的应用

针对扰动会对航空成像系统像旋补偿伺服机构跟踪精度产生影响的问题,提出一种改进型复合控制算法。首先,针对等效扰动,提出一种基于有限时间双曲正弦跟踪微分器(FSTD),用来构造改进非线性干扰观测器(NDO),使系统对参数摄动不敏感且对扰动估计更加精确;其次,为了提升系统的跟踪精度,结合变速趋近律的思想设计新型高阶滑模控制器(N-HSMC),保证系统快速性的同时还能有效削弱抖振;最后,通过仿真对比验证了所提算法的有效性。

基于扰动观测器的PMSM系统自适应反步滑模控制

针对负载转矩波动和系统参数变化的永磁同步电机(PMSM)系统的控制问题,提出了一种带有非线性扰动观测器的自适应反步滑模位置跟踪控制方法。首先,设计了自适应反步滑模控制器,以确保电机位置快速收敛到期望值,并设计了自适应收敛增益,以减小电机位置响应下的大的过冲;其次,设计非线性扰动观测器估计未知扰动,并为自适应反步滑模控制提供前馈补偿,以提高系统的鲁棒性,并减少稳态位置误差。仿真结果表明,该方法可以有效减少过冲,很好地实现了PMSM系统的快速位置跟踪控制,具有良好的抗扰动性能。

基于扰动补偿的磁悬浮转台分数阶滑模控制

针对存在非线性、耦合性和不确定性的磁悬浮转台的高精度运动控制问题,提出一种基于非线性干扰观测器的分数阶滑模控制方法以提高跟踪精度.首先,基于系统电磁力模型和动态解耦方法,构建六自由度磁悬浮转台系统动力学模型;其次,设计非线性干扰观测器,对包含系统误差、六自由度间耦合项和外界干扰的集总扰动进行估计,证明了估计误差有界且可调节到任意小;然后,在离散域提出了一种分数阶滑模面,采用分数幂函数替代传统符号函数来抑制抖振,引入分数阶微积分来减小跟踪误差;最后,设计有限时间收敛的分数阶滑模控制策略,并利用李雅普诺夫稳定性理论证明闭环系统稳定性.实验结果表明:与整数阶滑模控制方法相比,采用所提方法,2个水平自由度和绕竖直方向旋转自由度对三角波的跟踪误差均方根分别减小了12.8%、16.8%和23.7%,最大跟踪误差分别减小9.26%、13.00%和33.20%;跟踪圆形轨迹时,2个水平自由度的跟踪误差均方值分别减小6.39%和12.40%,最大跟踪误差分别减小9.90%和12.10%.

海参捕捞机器人运动控制系统的仿真研究

随着水下机器人技术的发展,海参捕捞机器人将逐渐取代费时费力的人工捕捞作业。但是海参捕捞机器人的运动控制精度一直影响其运动稳定性和捕捞效率,一方面是由于海底的作业环境恶劣多变,机器人的结构功能复杂;另一方面是随着海参的累积,机器人的参数发生改变,原有控制模型的控制精度下降。为提高海参捕捞机器人的运动控制精度,在综合考虑机器人各种载荷的基础上,还考虑了海参对机器人造成的干扰,建立更加全面的机器人动力学模型;并运用模型预测控制理论和非线性干扰观测器对机器人的运动过程进行模拟分析。通过分别模拟机器人的定深下潜、运动姿态保持、路径跟踪和载重上升运动过程,定量分析机器人的运动控制精度,最后构建一个系统全面且精度较高的海参捕捞机器人运动控制系统。

新型矢量推力八旋翼飞行器的设计与控制

飞行器在物理交互场景中应用广泛,但现有的飞行器及装置在面对大矢量推力应用时,往往难以满足结构和控制简单的要求。为解决这一问题,设计了一种结构简单可行的矢量推力八旋翼飞行器,利用倾斜共轴转子和铰链—同步带的结构,只需一个额外的执行器,即可控制所有转子的倾转角度,从而实现矢量推力,可在物理交互场景中提供足够的横向推力。基于此,设计了对应的位姿控制器,采用SO(3)上的几何控制方法设计了全局稳定的位姿控制器,使用非线性扰动观测器对外部力和力矩进行估计并补偿,以提高整个控制系统的鲁棒性。在MATLAB/Simscape中,进行了飞行器的5D轨迹跟踪、倾转悬停和扰动估计的仿真实验,实验结果充分验证了该飞行器设计的可行性和相应控制算法的有效性。