Robust adaptive steering control for unmanned surface vehicle with unknown control direction and input saturation

A robust adaptive steering control method is proposed to solve the control problem of the unmanned surface vehicle (USV) with uncertainties, unknown control direction, and input saturation. In the controller design process, the adaptive fuzzy system is incorporated into dynamic surface control (DSC) to approximate the uncertainty term induced by external environmental disturbances and model parameters. Then, the Nussbaum function is used to eliminate the requirement for a priori knowledge of the control direction. Besides, to handle the input saturation, the adaptive fuzzy DSC is extended by a second‐order nonlinear filter and antisaturation auxiliary function to compensate for the magnitude and rate saturation of the rudder. All signals of the closed‐loop system are proven to be uniformly ultimately bounded (UUB) by Lyapunov theorem and the Lemma of Nussbaum gain, and the course error can converge to a small neighborhood of zero through choosing design parameters appropriately. Finally, simulation results and comprehensive comparisons are shown for the USV course system, which is demonstrative of the proposed controller's effectiveness and robustness.     

Decentralized prescribed performance adaptive tracking control for Markovian jump uncertain nonlinear systems with input saturation

A decentralized prescribed performance adaptive tracking control problem is investigated for Markovian jump uncertain nonlinear interconnected large‐scale systems. The considered interconnected large‐scale systems contain unknown nonlinear uncertainties, unknown control gains, actuator saturation, and Markovian jump signals, and the Markovian jump subsystems are in the form of triangular structure. First, by defining a novel state transformation with the performance function, the prescribed performance control problem is transformed to stabilization problem. Then, introducing an intermediate control signal into the control design, employing neural network to approximate the unknown composite nonlinear function, and based on the framework of the backstepping control design and adaptive estimation method, a corresponding decentralized prescribed performance adaptive tracking controller is designed. It is proved that all the signals in the closed‐loop system are bounded, and the prescribed tracking performances are guaranteed. A numerical example is provided to illustrate the effectiveness of the proposed control strategy. Copyright © 2016 John Wiley & Sons, Ltd.     

Robustness and performance of a modified adaptive backstepping controller

Recently, a new class of adaptive control schemes based on non-linear design techniques, have been proposed for minimum phase linear time invariant plants. Under certain assumptions on the plant transfer function, these schemes guarantee uniform signal boundedness and good transient and steady-state response for the regulation or tracking error. In this paper we propose a modification that improves the robustness of these schemes with respect to a class of multiplicative uncertainties and input, output disturbances, without loss of performance. This lack of a trade-off between performance and robustness is a result of restricting the multiplicative unmodelled dynamics to be small in both the low- and high-frequency range. It is also shown that parameter convergence and performance improvement is achieved with a dominantly rich reference input. © 1998 John Wiley & Sons, Ltd.     

Adaptive control in the presence of saturation non-linearity

Saturation non-linearities are perhaps the most commonly present type of non-linearities in dynamic systems. It is therefore important for the controller present to function satisfactorily in the presence of input saturation. In this paper we present an adaptive controller which leads to satisfactory performance in the presence of magnitude saturation of the control input. For both continuous time and discrete time plants, the adaptive controller is shown to result in global stability if the plant is open loop stable and minimum phase, and local stability otherwise. Robustness properties of the resulting adaptive controller are established. The performance is verified through experimental results obtained from adaptive control of a precision machine tool axis. © 1997 by John Wiley & Sons, Ltd.     

Fuzzy adaptive two-bits-triggered control for nonlinear uncertain system with input saturation and output constraint

In this work, a fuzzy adaptive two-bits-triggered control is investigated for the nonlinear uncertain systems with input saturation and output constraint. The considered systems are more widespread. Without sufficient transmission resources, how to resolve the constraint issues while guarantee the control performance is difficult and challenging. Then, hyperbolic tangent function and barrier Lyapunov function are integrated with the designed auxiliary system to solve input saturation and output constraint. Meanwhile, faced with the transmission resources limitation, this work both considers the triggering condition and the control signal transmission bits. A two-bits-triggered control is proposed to economize the transmission resources. Furthermore, improved fuzzy logic systems are established to further promote the control performance. It combines with the time-varying approximation error for processing. The boundedness of all the system signals can be proved. Simulation results illustrate the validity of the proposed approach.     

具有输入饱和的不正定关联系统分散控制

针对在实际控制系统中,如果不考虑输入饱和而设计控制器,闭环系统的稳定性无法保证,讨论了具有输入饱和的不确定非线性交联系统的分散控制问题。利用Riccati方程的方法、Lyapunov稳定理论和矩阵理论,研究了一类具有输入饱和的不确定非线性关联大系统的分散鲁棒镇定问题,给出了该类系统可分散鲁棒控制的一个充分条件,并提出了一种分散鲁棒控制器的设计方法。同时,考虑了一类具有输入饱和的不确定非线性相似关联大系统,由于相似系统的结构特点,给出了简洁的分散鲁棒控制条件。     

Reinforcing robustness of adaptive dynamic surface control

Adaptive dynamic surface control (ADSC) design was proposed as an alternative to adaptive backstepping, capable of curing the ‘explosion of complexity’ problem, caused by the repeated differentiations of the so called intermediate control signals. However, as it is clearly demonstrated in this work, ADSC schemes are sensitive to modeling uncertainties and/or additive external disturbances. In fact, it is shown that a uniformly bounded exogenous perturbation of unknown upper bound may easily destabilize the closed‐loop system. Subsequently, a constructive methodology based on the recently developed by the authors prescribed performance control technique, is proposed, which combined with an ADSC design, results in a modified scheme possessing significantly increased robustness properties. Simulation studies illustrate the approach. Copyright © 2012 John Wiley & Sons, Ltd.     

Issues,progress and new results in robust adaptive control

We overview recent progress in the field of robust adaptive control with special emphasis on methodologies that use multiple‐model architectures. We argue that the selection of the number of models, estimators and compensators in such architectures must be based on a precise definition of the robust performance requirements. We illustrate some of the concepts and outstanding issues by presenting a new methodology that blends robust non‐adaptive mixed µ‐synthesis designs and stochastic hypothesis‐testing concepts leading to the so‐called robust multiple model adaptive control (RMMAC) architecture. A numerical example is used to illustrate the RMMAC design methodology, as well as its strengths and potential shortcomings. The later motivated us to develop a variant architecture, denoted as RMMAC/XI, that can be effectively used in highly uncertain exogenous plant disturbance environments. Copyright © 2006 John Wiley & Sons, Ltd.     

Adaptive fault-tolerant tracking control for nonlinear systems with unknown control coefficient and input saturation

In this article, the tracking control problem is investigated for a class of nonlinear systems in the presence of unknown disturbance, input saturation, actuator fault, and unknown control coefficient. A novel disturbance observer-based adaptive fault-tolerant tracking control strategy is proposed with regard to nonlinear systems. Based on the Gaussian error function, the auxiliary dynamic system is designed to offset effects caused by the input saturation. Moreover, the Nussbaum-type function is employed to avert control singularity and deal with the unknown control coefficient. A theoretical analysis indicates that the boundedness of all signals in the closed-loop system can be guaranteed. Finally, two examples with one concerning the dynamic point-the-bit rotary steerable drilling tool system are given to confirm the validity of the method.     

XRB-220自适应母线保护装置

介绍了最新研制的新型XRB-220型自适应母线保护装置的硬件组成、保护原理及功能。该装置采用新的硬件平台,采用两级32位DSP芯片及高精度A/D转换器,运算速度快,精度高;采用一种新的相量滤波器的设计方法在故障不同时刻形成不同的数据窗长度,保证了装置的自适应性;母线主保护采用复式比率差动保护,CT饱和识别采用时差法和谐波法相结合;辅助功能有母联充电保护、母联死区及失灵保护、断路器失灵保护、母线的运行方式自动识别以及隔离开关切换的正确性校验、CT和PT断线检测。保护装置还具有完善的事件报文处理及录波打印功能。     

Mapping filtered forwarding‐based robust adaptive control for uncertain nonlinear systems with input constraint

This work develops a robust adaptive control algorithm for uncertain nonlinear systems with parametric uncertainties and external disturbances satisfying an extended matching condition. This control method is implemented in the framework of a mapping filtered forwarding‐based technique. As an attractive alternative of the adaptive backstepping method, this bottom‐up strategy forms a virtual controller and a parameter updated law at each step of the design, where Lyapunov functions and the prior knowledge of system parameters are not required. The boundedness of all signals is guaranteed by using Barbalat's lemma. According to immersion relationship, a compliant behavior of systems behaves accordingly to the lower‐order target dynamics. Furthermore, input constraints are handled by estimating a saturated scaling. A spring, mass, and damper system is used to demonstrate the controller performances via simulation results.     

Indirect model reference adaptive control with dynamic adjustment of parameters

The paper discusses in detail a new method for indirect model reference adaptive control (MRAC) of linear time-invariant continuous-time plants with unknown parameters. The method involves not only dynamic adjustment of plant parameter estimates but also those of the controller parameters. Hence the overall system can be described by a set of non-linear differential equations as in the case of direct control. Many of the difficulties encountered in the conventional indirect approach, where an algebraic equation is solved to determine the control parameters, are consequently bypassed in this method. The proof of stability of the equilibrium state of the overall system is found to be different from that used in direct control. Using Lyapunov's theory, it is first shown that the parameter errors between the parameter estimates of the identifier and the true parameters of the plant, as well as those between the actual parameters of the controller and their desired values, are bounded. Following this, using growth rates of signals in the adaptive loop as well as order arguments, it is shown that the error equations are globally uniformly stable and that the tracking (control) error tends to zero asymptotically. This in turn establishes the fact that both direct and indirect model reference adaptive schemes require the same amount of prior information to achieve stable adaptive control.     

Adaptive saturation compensation for strict-feedback systems with unknown control coefficient and input saturation

This work presents an adaptive saturation compensation scheme for the strict-feedback uncertain systems with unknown control coefficient and input saturation. An adaptive saturation dynamic filter that does not require the a priori information of the completely unknown control coefficient is incorporated to correct position errors online to reduce the saturation effect. A Nussbaum-type function is employed to handle the unknown control coefficient and avoid the control singularity. The adaptive command-filtered backstepping is employed to derive the adaptive controller. The repeated differential operations of stabilizing functions required in the traditional backstepping are obviated due to command filters. It is analyzed that the designed adaptive controller achieves the system output tracking and the closed-loop uniform ultimate stability. A simulation example is provided to validate the scheme.     

The robust adaptive control of chaotic systems with unknown parameters and external disturbance via a scalar input

This paper investigates the control of chaotic systems in the presence of unknown parameters, model uncertainties, and external disturbance. We first discuss the control of a class of chaotic systems and then investigate the control of general chaotic systems. Based on the adaptive control scheme, some novel criteria are proposed via a backstepping‐like procedure. As an example, the control of the Zhang hyperchaotic system is investigated via a single input. Some numerical simulations are given to demonstrate the robustness and efficiency of the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd.     

Fictitious reference iterative tuning considering input saturation

This letter presents a simple control method that can alleviate the influence of input saturation by the so‐called fictitious reference iterative tuning and anti‐windup proportional–integral–derivative (PID) control architecture. The effectiveness of the presented method is demonstrated through experiments with a DC motor control system. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Multiple‐model adaptive robust dynamic surface control with estimator resetting

A multiple‐model adaptive robust dynamic surface control with estimator resetting is investigated for a class of semi‐strict feedback nonlinear systems in this paper. The transient performance is mainly considered. The multiple models are composed of fixed models, one adaptive model, and one identification model that can be obtained when the persistent exciting condition is satisfied. The transient performance of the final tracking system can be improved significantly by designing proper switching mechanism during the parameter tuning procedure. The semi‐globally uniformly ultimately bounded stability of the closed‐loop system can be easily achieved because of the framework of adaptive robust dynamic surface control. Numerical examples are provided to demonstrate the effectiveness of the proposed multiple‐model controller. Copyright © 2014 John Wiley & Sons, Ltd.     

Tracking control for nonlinear time-delay multiagent systems with input saturation

In this paper, the tracking control problem for a class of nonlinear time-delay multiagent systems with input saturation is considered. The nonlinear dynamics are dominated by strict-feedback form and satisfy Lipschitz conditions with constant gains. First, it indicated that the tracking control problem is equivalent to a general bound problem of high-dimensional multivariable systems. Second, an ingenious state transformation is utilized to change the bound problem into the parameter design problem. Third, by the static gain control technique and the hyperbolic tangent function, both state feedback and output feedback controllers are built such that all signals of the closed-loop systems are globally bounded, and the tracking errors between the followers and the leader can converge to a small neighborhood around the origin by appropriately selecting parameters. Finally, an example is shown to verify the feasibility of our results.     

Experimental evaluation of combined model reference adaptive controller in a pH regulation process

An experimental evaluation of the combined model reference adaptive control (CMRAC) is presented in this paper. This adaptive control scheme was used to control a relatively complex process like the pH of a solution in a tank reactor at laboratory level. For comparison purposes, some very well‐known control strategies were also implemented, which include PID control and standard model reference adaptive control (MRAC). Tracking and regulation capabilities of the control strategies studied were analysed and compared. Experimental results indicate that CMRAC behaves as well as the standard MRAC and a very well‐tuned PID for a specific and known operating point. Advantages of the adaptive controllers are shown when the operating point changes. Copyright © 2002 John Wiley & Sons, Ltd.     

Robust multiple model adaptive control (RMMAC): a case study

We evaluate the performance of the robust multiple model adaptive control (RMMAC) methodology by considering a mass–spring–dashpot (MSD) system subject to high-frequency disturbances that strongly excite all its lightly damped oscillatory modes. The results demonstrate the superior performance of the RMMAC and its variant RMMAC/XI architecture for a much more difficult adaptive control problem than that designed and analysed in Reference (Int. J. Adaptive Control Signal Processing, in press). Copyright © 2006 John Wiley & Sons, Ltd.     

Decentralized adaptive terminal sliding mode control design for nonlinear connected system in the presence of external disturbance

In this article, a decentralized adaptive integral terminal sliding mode control is presented for a class of nonlinear connected systems. It is assumed that the system is also confronted by unknown disturbances, while the interconnections between subsystems are assumed unknown. An integral terminal sliding surface for each subsystem is locally considered to guarantee the stability of the closed-loop system, and to increase the convergence speed during a tracking task. The unknown interconnections between subsystems are estimated using adaptive rules. An appropriate Lyapunov candidate is chosen to perform global stability analysis. In this regard, design parameters are chosen such that the closed-loop stability is ensured. Performance of the proposed method for a mechanical connected system, including two chaotic subsystems, is shown through simulations.