改进非线性干扰观测器的机械臂自适应反演滑模控制

针对传统滑模和传统干扰观测器在机械臂关节位置跟踪中存在的控制输入抖振、需要测量加速度项、应用模型受限等问题,提出一种改进非线性干扰观测器的机械臂自适应反演滑模控制算法。首先,设计改进的非线性干扰观测器进行在线测试,在滑模控制律中加入干扰估计值对可观测的干扰进行补偿;然后选择合适的设计参数,使观测误差指数型收敛;其次,引入反演自适应控制律,对不可观测的干扰进行估计,进一步改善控制系统的跟踪性能;最后,利用李雅普诺夫函数验证了闭环系统的渐近稳定性,并将其应用于机械臂关节位置跟踪。实验结果表明,与传统滑模算法比较,所提控制算法不但加快了系统的响应速度,而且能有效地削弱系统抖振、避免测量加速度项并扩大应用模型使用范围。     

Anti‐disturbance control for nonlinear system via adaptive disturbance observer

This paper addresses the problems of disturbance estimation and anti‐disturbance control for nonlinear system with exogenous disturbance, which is generated from an unknown exogenous system. The state observer and the adaptive disturbance observer are designed, simultaneously. Compared with the existing methods, which assumed that the exogenous system parameter matrix was known, our disturbance observer is more applicable in practice. Utilizing the estimation information, an observer‐based dynamic output feedback controller is designed, which avoids the influence of output disturbance on the closed‐loop system, and contains a disturbance compensation term to compensate the input disturbance. Finally, simulations are provided to demonstrate the effectiveness of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.     

A novel fixed-time sliding mode control for nonlinear manipulator systems based on adaptive disturbance observer

Considering that in the trajectory tracking control of a nonlinear robotic manipulator system, the control effect is easily limited by the initial state of the system, and the system has modeling error, unknown disturbance, and friction in the actual control, to overcome the above problems, a fixed-time sliding mode control (SMC) strategy based on adaptive disturbance observer (ADO) is developed in this paper. Firstly, feedforward compensation of the system is achieved by developing an ADO to accurately estimate the compound disturbances in the system. Second, a new fixed-time sliding mode (SM) surface is presented to overcome the singularity issue and accelerate the error convergence. In addition, to enhance the performance of the reaching phase, a variable exponential power reaching law (VEPRL) is developed, which can effectively adjust the convergence rate. Through rigorous theoretical analysis, it is shown that the system state can be stabilized at a fixed time, and an upper bound on the convergence time is also given. Finally, the effectiveness of the control method is verified by comparing it with different control schemes in simulation.     

Nonlinear disturbance observer-based control for multi-input multi-output nonlinear systems subject to mismatching condition

For a multi-input multi-output (MIMO) nonlinear system, the existing disturbance observer-based control (DOBC) only provides solutions to those whose disturbance relative degree (DRD) is higher than or equal to its input relative degree. By designing a novel disturbance compensation gain matrix, a generalised nonlinear DOBC method is proposed in this article to solve the disturbance attenuation problem of the MIMO nonlinear system with arbitrary DRD. It is shown that the disturbances are able to be removed from the output channels by the proposed method with appropriately chosen control parameters. The property of nominal performance recovery, which is the major merit of the DOBCs, is retained with the proposed method. The feasibility and effectiveness of the proposed method are demonstrated by simulation studies of both the numerical and application examples.     

An adaptive disturbance rejection control scheme for multivariable nonlinear systems

An adaptive disturbance rejection control scheme is developed for uncertain multi-input multi-output nonlinear systems in the presence of unmatched input disturbances. The nominal output rejection scheme is first developed, for which the relative degree characterisation of the control and disturbance system models from multivariable nonlinear systems is specified as a key design condition for this disturbance output rejection design. The adaptive disturbance rejection control design is then completed by deriving an error model in terms of parameter errors and tracking error, and constructing adaptive parameter-updated laws and adaptive parameter projection algorithms. All closed-loop signals are guaranteed to be bounded and the plant output tracks a given reference output asymptotically despite the uncertainties of system and disturbance parameters. The developed adaptive disturbance rejection scheme is applied to turbulence compensation for aircraft fight control. Simulation results from a benchmark aircraft model verify the desired system performance.     

Robust adaptive backstepping control for a class of uncertain nonlinear systems based on disturbance observers

In this paper, a novel robust adaptive control scheme for a class of uncertain nonlinear systems is proposed using disturbance observer and backstepping method.Firstly, a disturbance observer is developed using radial basis function(RBF) neural network.The parameter updated law of the RBF neural network is given for monitoring subsystem disturbance well.The robust adaptive control scheme is then presented with backstepping method based on the designed disturbance observer.Semiglobal uniform ultimate bounded...     

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 disturbanceobserver based control (DOBC) design. Some critical points raised in the development of the methods have been reviewed anddiscussed which are still relevant for many researchers or practitioners who are interested in this method. The review is followedby 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 couldreduce 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 triggerfurther research and interests in the development of DOBC and related methods, and building up more understanding betweenthis group of control methods with comparable ones (particularly control methods with integral action).     

A new adaptive control for periodic tracking/disturbance rejection

This paper proposes a new adaptive feedforward cancellation (AFC) control that achieves periodic tracking and/or periodic disturbance rejection. The new control design is a direct scheme in the sense that it adaptively updates the desired control without estimating the unknown disturbance. The proposed new control has several advantages. First, its adaptation gain can be arbitrarily chosen without upsetting the system stability. Second, it can be applied to not only minimum‐phase systems, but also non‐minimum phase systems. Finally, it is shown that the proposed AFC control is independent of where the disturbance enters the system. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Composite antidisturbance control for nonlinear systems via nonlinear disturbance observer and dissipative control

This paper investigates the design problem of composite antidisturbance control for a class of nonlinear systems with multiple disturbances. First, a novel nonlinear disturbance observer‐based control scheme is constructed to estimate and compensate the disturbance modeled by the nonlinear exosystem. Then, by combining the dissipative control theory, a linear matrix inequality‐based design method of composite antidisturbance control is developed such that the augmented system is exponentially stable in the absence of unmodeled disturbances, and is dissipative in the presence of unmodeled disturbances. In this case, the original closed‐loop system is exponentially stable in the presence of modeled disturbances. Subsequently, two special cases of composite antidisturbance control are derived with H_∞ performance and passivity, respectively. Finally, the proposed method is applied to control A4D aircraft to show its effectiveness.     

不确定非线性系统的直接自适应神经网络控制

为解决一类带干扰的不确定非线性系统中存在的两类未知项——未知函数和外界干扰,采用了直接自适应神经网络控制方法设计控制器。控制器设计中利用径向基函数神经网络良好的逼近性来近似未知函数,利用非线性衰减项来抑制干扰。所用方法结构简单、算法简洁,在一定条件下稳定性和收敛性能定性地得到保证。最后,仿真结果证明了该方法是正确的。     

Intelligent adaptive observer-based optimal control of overhead transmission line de-icing robot manipulator

In cold season, wet snow ice accretion on overhead transmission lines increases wind load effects which in turn increases line tension. This increased line tension causes undesirable effects in power systems. This paper discusses the design of an observer-based boundary sliding mode control (BSMC) for 3 DOF overhead transmission line de-icing robot manipulator (OTDIRM). A robust radial basis functional neural network (RBFNN) observer-based neural network (NN) controller is developed for the motion control of OTDIRM, which is a combination of BSMC, NN approximation and adaptation law. The RBFNN-based adaptive observer is designed to estimate the positions and velocities. The weights of both NN observer and NN approximator are tuned off-line using particle swarm optimization. Using Lyapunov analysis the closed loop tracking error was verified for a 3 DOF OTDIRM. Finally, the robustness of the proposed neural network-based adaptive observer boundary sliding mode control (NNAOBSMC) was verified against the input disturbances and uncertainties.     

Disturbance observer-based fixed-time prescribed performance tracking control for robotic manipulator

ABSTRACT

This paper investigates the fixed-time prescribed performance tracking control for the n-DOF uncertain manipulator. First, a novel Barrier Lyapunov Function (BLF) is proposed to guarantee the prescribed performance for the manipulator tracking error. Then, we introduce a disturbance observer to estimate the system uncertainty and disturbance accurately in a predefined time. Next, a composite controller based on the nonsingular fast integral terminal sliding mode is constructed. It is strictly proved that the closed-loop system is stable in fixed-time, which is independent of the initial conditions. Moreover, both transient and steady-state performances of the outputs can be preserved. Finally, numerical simulations and experimental studies are presented to demonstrate the effectiveness of the proposed methods.     

一类非仿射非线性离散系统的改进无模型自适应控制

针对一类更广泛的非仿射非线性离散系统,提出一种改进的无模型自适应控制算法。该算法基于非参数动态线性化方法,运用观测器的思想,实现带有扰动系统的实时动态线性化,进而将无模型自适应控制方法的应用推广到更广泛的非仿射非线性离散系统。同时,对推广后的改进无模型自适应控制方法进行理论上的证明,并通过仿真实例验证了所提出的改进无模型自适应控制方法的可行性和有效性。     

基于观测器的受扰非线性系统近似最优跟踪控制

研究一类受扰非线性系统的最优输出跟踪控制问题.给出了有限时域最优输出跟踪控制律的近似设计算法.首先将求解受扰非线性系统最优跟踪控制问题转换为求解状态向量与伴随向量耦合的非线性两点边值问题,然后利用逐次逼近方法构造序列将其转化为求解两个解耦的线性微分方程序列问题.通过迭代求解伴随向量的序列,可得到由解析的线性前馈-反馈控制部分和伴随向量的极限形式的非线性补偿部分组成的最优输出跟踪控制律.利用参考输入降维观测器和扰动降维观测器,解决了前馈控制的物理可实现问题.最后仿真结果表明了该方法的有效性.     

Model‐free adaptive formation control for unknown multiinput‐multioutput nonlinear heterogeneous discrete‐time multiagent systems with bounded disturbance

Based on the model‐free adaptive control, the distributed formation control problem is investigated for a class of unknown heterogeneous nonlinear discrete‐time multiagent systems with bounded disturbance. Two equivalent data models to the unknown multiagent systems are established through the dynamic linearization technique considering the circumstances with measurable and unmeasurable disturbances. Based on the obtained data models, two distributed controllers are designed with only using the input/output and disturbance data of the neighbor agents system. The tracking error of the closed‐loop system driven by the proposed controllers is shown to be bounded by the contraction mapping principle and inductive methods. An example illustrates the effectiveness of the proposed two distributed controllers.     

基于观测器的不确定非线性系统的自适应鲁棒模糊控制

针对单输入单输出不确定非线性系统提出了一种自适应鲁棒模糊控制算法.该算法通过设计观测器来估计系统的状态向量,因此不要求假设系统的状态向量是可测的.在这个算法中,主要的假设为最优逼近参数向量与标称参数向量之差的范数和逼近误差的界限是未知的.通过只对未知界限估计的调节,该算法减轻了在线计算量并且提高了系统的鲁棒性.所设计的自适应鲁棒模糊控制算法保证了闭环系统的所有信号是一致有界的并且跟踪误差估计收敛到一个小的零邻域内.仿真例子证实了所提方法的可行性.     

基于L2干扰抑制的水下机器人三维航迹跟踪控制

为实现自治水下机器人(AUV)的三维航迹跟踪控制,考虑了非线性水动力阻尼对AUV系统的影响和外界海流干扰作用,提出了基于L2干扰抑制的鲁棒神经网络控制方法.该方法基于李雅普诺夫稳定性理论,设计神经网络控制器补偿非线性水动力阻尼和外界的海流干扰,再将神经网络的估计误差当做AUV系统的外部干扰用L2干扰抑制控制器予以消除.最后针对某AUV进行了螺旋线三维下潜跟踪控制仿真实验,结果表明设计的控制器可以较好地克服时变非线性水动力阻尼对系统的影响,并对外界海流干扰有较好的抑制作用,可以实现AUV三维航迹的精确跟踪.     

Composite hierarchical anti‐disturbance control for nonlinear systems with DOBC and fuzzy control

Anti‐disturbance control and estimation problem is introduced for a class of nonlinear system subject to disturbances. The adaptive disturbance observers are constructed separately from the controller design to estimate the disturbance with partial known information. By integrating disturbance‐observer‐based control with fuzzy control, a novel type of composite hierarchical anti‐disturbance control scheme is presented for a class of nonlinear system with unknown nonlinear dynamics. Simulations for a flight control system are given to demonstrate the effectiveness of the results compared with the previous schemes.Copyright © 2012 John Wiley & Sons, Ltd.     

Adaptive fuzzy tracking control for a class of uncertain MIMO nonlinear systems using disturbance observer

In this paper,the adaptive fuzzy tracking control is proposed for a class of multi-input and multioutput(MIMO)nonlinear systems in the presence of system uncertainties,unknown non-symmetric input saturation and external disturbances.Fuzzy logic systems(FLS)are used to approximate the system uncertainty of MIMO nonlinear systems.Then,the compound disturbance containing the approximation error and the timevarying external disturbance that cannot be directly measured are estimated via a disturbance observer.By appropriately choosing the gain matrix,the disturbance observer can approximate the compound disturbance well and the estimate error converges to a compact set.This control strategy is further extended to develop adaptive fuzzy tracking control for MIMO nonlinear systems by coping with practical issues in engineering applications,in particular unknown non-symmetric input saturation and control singularity.Within this setting,the disturbance observer technique is combined with the FLS approximation technique to compensate for the efects of unknown input saturation and control singularity.Lyapunov approach based analysis shows that semi-global uniform boundedness of the closed-loop signals is guaranteed under the proposed tracking control techniques.Numerical simulation results are presented to illustrate the efectiveness of the proposed tracking control schemes.     

基于NDO的ROV变深自适应终端滑模控制器设计

针对ROV的深度控制问题, 提出基于非线性干扰观测器的自适应终端滑模控制方法. 详细叙述了控制器的设计过程, 并利用Lyapunov 稳定性判据, 验证了存在模型参数不确定性和外干扰时, 系统的全局渐近稳定性和跟踪误差的收敛性. 仿真实验表明, 所提出的控制器不仅能够很好地估计并克服外干扰和模型不确定性等因素, 具有很好的鲁棒性能, 而且还可以实现在任意规定时刻变深运动的快速收敛.