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.

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。

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.

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.

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.

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。

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.

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TNESO的PMSLM分数阶自抗扰控制

线性自抗扰控制(LADRC)以结构简单、易于实现且抗干扰能力强的特点在永磁同步直线电机(PMSLM)中得到广泛应用,但电机启动和负载突变会导致LADRC系统中的线性扩张状态观测器(LESO)扰动估计精度下降。为此,提出一种基于时变增益非线性扩张状态观测器(TNESO)的PMSLM分数阶自抗扰控制策略。结合LESO和非线性扰动观测器(NDOB),并根据误差与增益的关系构建动态增益函数,设计新型状态观测器TNESO;在此基础上,以分数阶PDμ控制律代替线性状态误差反馈控制律(LSEF),建立改进型自抗扰速度控制系统,以进一步提高电机控制的实时性和鲁棒性。仿真与实验结果表明:所设计的速度控制系统可以有效减少直线电机启动、负载突变时的观测响应时间,抑制观测初始时刻扰动峰值,从而满足高性能的PMSLM速度控制要求。

基于扩张状态观测器的伺服加载模糊滑模控制

针对电动伺服加载测试台存在的间隙、摩擦等非线性控制问题,以滑模变结构控制(SMC)为主体进行了加载控制器设计。分析伺服加载测试台整体结构,提出一种基于扩张状态扰动观测器(ESO)的模糊滑模控制(FSMC)策略。该策略在使用ESO针对伺服加载系统的外部干扰进行观测的基础上,设计了模糊控制对滑动模态面和滑模趋近律进行自适应调节,提高了系统的动态实时跟随能力和干扰补偿能力,并减小SMC控制器稳定时的抖振现象。仿真结果表明:所设计的基于扩张状态观测器的模糊滑模控制器(FSMC-ESO)对比传统SMC及PID控制具有更好的快速响应性和鲁棒性。

Extended state observer for uncertain lower triangular nonlinear systems subject to stochastic disturbance

The extended state observer （ESO） is the most important part of an emerging control technology known as active disturbance rejection control to this day, aiming at estimating ＂total disturbance＂ from observable measured output. In this paper, we construct a nonlinear ESO for a class of uncertain lower triangular nonlinear systems with stochastic disturbance and show its convergence, where the total disturbance includes internal uncertain nonlinear part and external stochastic disturbance. The numerical experiments are carried out to illustrate effectiveness of the proposed approach.

Development of nonlinear disturbance observer based control and nonlinear PID： A personal note

This paper gives an overview of early development of nonlinear disturbance observer design technique and the disturbance observer based control （DOBC） design. Some critical points raised in the development of the methods have been reviewed and discussed which are still relevant for many researchers or practitioners who are interested in this method. The review is followed by the development of a new type of nonlinear PID controller for a robotic manipulator and its experimental tests. It is shown that, under a number of assumptions, the DOBC consisting of a predictive control method and a nonlinear disturbance observer could reduce to a nonlinear PID with special features. Experimental results show that, compared with the predictive control method, the developed controller significantly improves performance robustness against uncertainty and friction. This paper may trigger further research and interests in the development of DOBC and related methods, and building up more understanding between this group of control methods with comparable ones （particularly control methods with integral action）.

Adaptive Sliding-Mode Tracking Control for an Uncertain Nonlinear SISO Servo System with a Disturbance Observer

An adaptive sliding mode controller with a disturbance observer(ASMC-DO) is proposed for the control of a single-input and single-output(SISO) servo system which has uncertain parameters, nonlinear friction,disturbance and input saturation. It is difficult to choose the suitable value of the parameters. The newly designed adaptive method is used to reduce the effects of system time-varying parameters, such as the moment of inertia and the damp coefficient. The robustness of object is improved. A DO is selected to approximate the compound disturbance and to render the estimate error convergent in finite time. The stability and the convergence of the closed-loop system are proved by using the Lyapunov theory. Experimental results show that the proposed ASMC-DO can better satisfy the influence of variable parameters and external disturbance to the control precision of the SISO servo system than other two controllers. The effectiveness of the proposed controller is showed. The control input stability and robust performances of the input saturation system are enhanced and the chattering is reduced.

基于智能体的电力系统分布式自适应抗干扰控制

针对多机电力系统中不可避免存在非线性、不确定特性和动态干扰等问题,基于径向基神经网络(RBFNN)和非线性干扰观测器(NDO)提出一种分布式自适应抗干扰控制器,以增强多机电力系统的暂态稳定性和鲁棒性。采用RBFNN处理系统中的未知非线性问题,并基于神经网络的输出设计NDO以实现对复合扰动的在线估计;在多智能体框架下为多机电力系统提出一种分布式自适应抗干扰控制策略,实时接收通信网络测量的数据并控制储能装置动作,在外部扰动下实现各电机转速的快速同步与跟踪,并利用Lyapunov稳定性理论证明闭环系统信号的收敛性。仿真实验表明:所提策略有效可行。

具有对称斜装动量轮的再入体动力学分析与姿态鲁棒控制

[目的]针对动量轮再入体姿态控制中存在转矩控制不足的问题进行研究.[方法]提出一种均匀对称斜装的动量轮布局,并利用拉格朗日第二类方程建立动量轮再入体的姿态动力学模型.基于动力学模型设计一种积分滑模综合控制策略,该策略考虑输入饱和对系统的影响,利用非线性扰动观测器对系统的不确定项进行估计.[结果]仿真与再入体模拟实验显示:在同样的控制需求下,本文提出的对称斜装动量轮布局所提供的最大转矩输出相较于传统正交的动量轮布局下降了60%.在引入输入饱和补偿的控制器作用下,控制输入可以更快地脱离饱和状态,再入体在4 s内稳定跟踪期望信号,稳定跟踪误差小于0.07°.[结论]本文提出的对称斜装动量轮布局通过动量轮之间的耦合,提高了动量轮的利用效率.相较于传统滑模控制,本文提出的积分滑模综合控制策略在再入体姿态控制上有抖振低、相对超调量小、鲁棒性高的优点,可有效地对再入体的姿态调整进行精确控制.