Design of Luenberger function observer with disturbance decoupling for matrix second-order linear systems-a parametric approach

A simple method for disturbance decoupling for matrix second-order linear systems is proposed directly in matrix second-order framework via Luenberger function observers based on complete parametric eigenstructure assignment. By introducing the H2 norm of the transfer function from disturbance to estimation error, sufficient and necessary conditions for disturbance decoupling in matrix second-order linear systems are established and are arranged into constraints on the design parameters via Luenberger function observers in terms of the closed-loop eigenvalues and the group of design parameters provided by the eigenstructure assignment approach. Therefore, the disturbance decoupling problem is converted into an eigenstructure assignment problem with extra parameter constraints. A simple example is investigated to show the effect and simplicity of the approach.

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.

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.

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.

Fast Smooth Second-Order Sliding Mode Control with Disturbance Observer for Automatic Shell Magazine

This paper studies practical control design for a novel automatic shell magazine(ASM)with a new fast smooth second-order sliding mode(FSSOSM)control based on disturbance observer.The dynamic model of the ASM with parameter perturbations and nonlinear friction is established.A higher order sliding mode disturbance observer based on super-twisting algorithm is utilized as a robust compensator to estimate the lumped uncertainties.The proposed FSSOSM control is performed to obtain the continuous sliding mode control law and inhibit the chattering phenomenon.The finite time convergence is investigated by utilizing the Lyapunov stability theorem.Three controllers,the traditional sliding mode controller,the proposed FSSOSM controller and a continuous fixed-time second-order sliding mode(CFTSOSM)controller,are compared.Extensive comparative simulation results under three typical working conditions(no-loaded,half-loaded and full-loaded)demonstrate that the proposed control strategy has a high dynamic tracking performance along with a good robustness against model uncertainty.

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。

基于非线性扰动观测器的三相PWM整流器滑模控制

针对交流微电网中三相PWM整流器的运行状态易受负载扰动、滤波电容参数摄动影响的问题,本文提出一种基于非线性扰动观测器的三相PWM整流器滑模控制方法。首先,将负载扰动、滤波电容参数摄动等视为集总扰动,构建电压环非线性模型。其次,设计非线性扰动观测器,实现集总扰动的在线估计。为实现主动抗干扰控制和滑模抖振抑制,将估计的集总扰动引入到滑模面中,得到了一种含有扰动估计的新型滑模面。最后,基于滑模控制理论设计电压外环滑模控制器,并采用Lyapunov稳定性理论对其进行了稳定性证明。动态性能测试结果表明,非线性扰动观测器能够快速、准确地对集总扰动进行估计;与双环PI控制相比,所提控制的过渡过程时间减少了60%,电压跌落量减少了54%;滤波电容参数变化时,所提控制的动态性能保持良好。稳态性能测试结果表明,与传统滑模控制和双环PI控制相比,所提控制的电流总谐波畸变率分别减少了70%和44%,同时滑模抖振得到了有效地抑制。测试结果证明了所提控制方法的强抗负载扰动能力和良好的滤波电容参数鲁棒性。

Sliding Mode Control with Disturbance Observer for a Class of Nonlinear Systems

This paper is concerned with the stabilization problem for a class of nonlinear systems with disturbance. The disturbance model is unknown and the first derivative of disturbance is bounded. Firstly, a general disturbance observer is proposed to estimate disturbance approximatively. Secondly, since the bound of the disturbance observer error is unknown, an adaptive sliding mode controller is designed to guarantee that the state of system asymptotically converges to zero and the unknown bound can be adjusted by an adaptive law. Finally, an example is given to illustrate the effectiveness of the proposed method.