This paper aims at designing a full-order non-fragile H∞ fuzzy filter for the Takagi–Sugeno (T–S) systems with state and disturbance dependent noise and multiple fading measurements. The Lth-order Rice fading model is utilized to describe multipath fading. A sufficient condition is derived to guarantee the filtering error system is exponentially mean-square stable with a prespecified H∞ performance. Then, the filter parameters are obtained by solving the linear matrix inequalities(LMIs). Finally, two illustrative examples are exploited to demonstrate the effectiveness of the proposed method.

•An adaptive sigmoid function-based sliding-mode observer (SMO) is proposed.•Limitations of a generally used phase-locked loop (PLL) are elaborated.•A tangent function-based PLL structure is proposed to extract rotor position.This paper proposes a position estimation strategy for the sensorless control of permanent-magnet synchronous motors (PMSMs) based on an improved sliding-mode observer (SMO) and a tangent function-based phase-locked loop (PLL) structure. The improved SMO adopts a rotor speed-related adaptive feedback gain, and is able to derive a flux model-based estimator that contains rotor position and speed direction information. To extract accurate rotor position from the proposed SMO and reduce position estimation errors in both forward and reverse rotation of the PMSM, a tangent function-based PLL structure is established. The proposed SMO together with the PLL structure realises a solution to position and speed estimation for sensorless PMSM drives. Compared with the conventional back electromotive force (EMF)-based position estimator, the proposed position estimation strategy has advantages of simple design and robust estimation performance at a wider speed range. Effectiveness of the proposed method has been validated with simulations on virtual platform.

Highlights•A novel robust adaptive sliding mode control is developed for trajectory tracking of underactuated vehicles.•The approach can reduce the chattering problem.•Adaptive estimation of the upper bound of disturbances is utilized to deal with the environment disturbances.•It is a practical design for marine engineering.Environmental disturbances and systematical uncertainties are the main obstacles for ship motion control. This paper devotes to enhancing the control system robustness of underactuated surface ships with model uncertainties and environmental disturbances. A novel nonlinear robust adaptive scheme with sliding mode control is proposed for underactuated ships to track the desired path generated by the logical virtual ship in the presence of unknown plant parameters and environmental disturbances. Compared with the existing results, the proposed controller is designed based on the combination of PI sliding mode control and the upper bound estimation of disturbances. With the proposed design, the control scheme could not only obtain a better performance of the control system, the continuous scheme also reduce the chattering of system by a special construction of the sliding manifolds. Numerical simulations are given to demonstrate the effectiveness of the proposed method.

•The waypoints-based path-following mission is achieved for merits of the proposed DVS guidance.•The DVS obstacles avoidance guidance is practical and critical for implementing the existing algorithm.•The developed robust neural controller is with the finite-time uniformly bounded (FTUB) stability.•The proposed algorithm requires less knowledge of the plant and is with the burden-some superiority.In this note, one focuses on the waypoints-based path-following control of underactuated surface ships with the mechanism of multi-static or slow time-varying obstacles avoidance. In the scheme, an improved dynamical virtual ship (DVS) principle is initially developed to programme the real-time attitude guidance for the underactuated ship in marine practice, providing a smooth transition of heading angle and velocity based on the principle of proximity. The scheduler is applied in the path-following and obstacles avoidance missions. Furthermore, to ensure the effectiveness of the obstacles avoidance manoeuvering, a practical robust neural control is proposed by fusion of neural networks and the robust neural damping technique. It requires less (or no) information of the system parameters and structure, and only four adaptive parameters require to be updated online. These designs would facilitate the implementation of the algorithm in the practical engineering. Considerable efforts are made to obtain the semi-global finite-time uniformly bounded (SGFTUB) stability by employing the Lyapunov theory. The comparative experiments have been presented to verify the effectiveness of the proposed scheme.

•An accurate tracking control scheme is proposed for an MV with complex unknowns.•Complex unknowns including system dynamics and disturbances are exactly observed.•Accurate position and velocity tracking can be achieved under harsh environment.•A purely model-free control approach is achieved with zero-error tracking accuracy.In this paper, a finite-time observer based accurate tracking control (FO-ATC) scheme is addressed for trajectory tracking of a marine vehicle (MV) with complex unknowns including unmodeled dynamics and disturbances. Main contributions are as follows: (1) An accurate tracking control (ATC) scheme is first proposed for a nominal MV tracking system with known dynamics, such that global finite-time stability of can be ensured to achieve fast convergence and precise tracking performance; (2) To exactly attenuate external disturbances, a finite-time disturbance observer (DO) is incorporated into the ATC framework, and establishes the DO-based ATC (DO-ATC) scheme which therefore produces strong disturbance rejection in addition to accurate trajectory tracking; (3) Aiming to precisely identify completely unknown dynamics together with external disturbances, simultaneously, a finite-time unknown observer (UO) is further created within the ATC approach, and thereby contributing to the UO-based ATC (UO-ATC) scheme which eventually achieves accurate trajectory tracking of an MV with fully unknown dynamics under harsh marine environment. Simulation studies and comprehensive comparisons are exhaustively provided to demonstrate the effectiveness and superiority of the proposed ATC schemes.

This paper addresses the feedback stabilization problem for Markov jump linear systems with quantized control input. A simple but powerful input controller for eliminating the input quantization in Markov jump linear systems is used. The proposed mode-dependent input controller comprises two parts: the linear part and the nonlinear part, where the linear part determines the fundamental characteristics of the systems, and the nonlinear part eliminates the effect of the input quantization. The stability is analyzed in detail for both the discrete-time and continuous-time Markov jump linear systems with input quantization. The sufficient conditions and the specific mode-dependent input controller to guarantee the stability of the systems are obtained. Numerical examples are given to illustrate the effectiveness of the results.

This work discusses the issue of input load disturbance rejection (ILDR) for open-loop nonminimum phase (NMP) plants. A novel analytical solution is proposed on the basis of the internal model control (IMC) theory. Differing from other methods, the proposed design is conducted to optimize the ILDR criterion. Optimization of the input disturbance response of the controller is performed under the constraints on robustness. When the input load disturbance is taken into consideration, the proposed controller performs better disturbance rejection capability in terms of 2-norm than most explored IMC-based controllers derived from the conventional criterion. Typical NMP processes are systematically analyzed. Numerical examples are given to illustrate the effectiveness of the novel solution. The quantitative performance specifications and robust stability can be obtained by monotonously tuning the single parameter. Results show that the proposed solution makes the proposed method yield the expected dynamic responses.

In this paper, a two-degree-of-freedom (TDOF) controller is designed for an ill-conditioned process based on the H2 decoupling control method. The ill-conditioned process considered stems from the benchmark problem formulated in the IEEE Conference on Decision and Control (CDC). The goal of this paper is to show that lower order controllers can be reached with respect to the given plant and the corresponding design specifications. The orders of the designed TDOF controllers are 2 and 1, respectively, which is much lower than the previously developed methods. The additional benefit is that the new design procedure is simpler than the developed methods as well. In the proposed design procedure, no weight function needs to be chosen and the controller is given in an analytical form. Simulation shows that the designed controllers satisfy all design specifications of the CDC problem.

This communication addresses the set-point robust proportional-integrative-derivative (PID) tuning for stable first order plus time delay systems from a general min−max model matching formulation. As opposed to some recent optimization-based numerical procedures, the derivation is carried out analytically, and it is based on a Smith-type inverse response configuration. Within the considered context, several choices result in a standard PID. This work investigates the simplest one, leading to a PID controller solely depending on a single design parameter. This contrasts with other analytical approaches resulting in more involved tuning. Attending to common performance/robustness indicators, the free parameter is finally fixed to provide an automatic tuning solely dependent on the model information. Toward this transition, dimensional analysis proves fruitful and allows us to establish that the proposed tuning rule is very robust for lead-dominant plants in the presence of parametric uncertainty. Lastly, simulation examples show that the suggested compensator yields very good results.

Highlights•An extended updated gain observer is designed for a class of MIMO nonlinear systems with noise.•The proposed observer makes a tradeoff between reconstruction speed and noise attenuation.•The observer has the ability of performance recovery.•The observer performance is illustrated by various examples in marine control.In this paper, the state estimation problem of a class of multi-input-multi-output nonlinear systems with measurement noise is studied. We develop an extended updated-gain high gain observer to make a tradeoff between reconstruction speed and measurement noise attenuation. The designed observer, whose gains are driven by nonlinear functions of the available output estimation errors, has the ability to reconstruct system states quickly and reduce the effect of measurement noise. We establish that, if there exists a state feedback law exponentially stabilizing the system with respect to an invariant set, the estimations and estimation errors are bounded. Besides, the trajectories of state- and output-feedback (based on the proposed observer) are sufficiently close, namely performance recovery. The observer performance is illustrated by various examples in marine control, including a case of transformation into the predefined structure.

This paper investigates the observer-based consensus tracking problem of multi-agent systems with one-sided Lipschitz nonlinearity. The agent dynamics considered here covers a broad family of nonlinear systems, and includes the well-known Lipschitz system as a special case. To achieve consensus tracking for such multi-agent systems, two types of observer-based protocols named the continuous protocol and the intermittent protocol are proposed. Furthermore, several multi-step design algorithms are presented to select the observer gains and the controller parameters of the proposed protocols. It is shown that the established sufficient criteria can not only ensure the observer error to approach to zero, but also realize the consensus tracking of multi-agent systems. The obtained results are illustrated by two simulation examples.

Highlights•The concept of guaranteed cost is introduced to incorporate with sampled-data control.•A novel equivalent system is constructed for consensus and consensus energy analyses.•A refined time-dependent Lyapunov functional is applied to LTI multi-agent systems.•LMI-based protocol design method is given with computational complexity considered.•Suboptimal protocol design and sampling interval enlargement problems are discussed.To investigate the energy consumption involved in a sampled-data consensus process, the problem of guaranteed cost consensus for sampled-data linear multi-agent systems is considered. By using an input delay approach, an equivalent system is constructed to convert the guaranteed cost consensus problem to a guaranteed cost stabilization problem. A sufficient condition for guaranteed cost consensus is given in terms of linear matrix inequalities (LMIs), based on a refined time-dependent Lyapunov functional analysis. Reduced-order protocol design methodologies are proposed, with further discussions on determining sub-optimal protocol gain and enlarging allowable sampling interval bound made as a complement. Simulation results illustrate the effectiveness of the theoretical results.

This article presents an H∞ design that alleviates some difficulties with standard Internal Model Control (IMC), while still obeying the same spirit of simplicity. The controller derivation is carried out analytically based on a weighted sensitivity formulation. The corresponding frequency weight, chosen systematically, involves two tuning parameters with clear meaning in terms of common design specifications: one adjusts the robustness/performance trade-off as in the IMC procedure; the other one balances the servo and regulatory performance. For illustration purposes, the method is applied to analytical tuning of PI compensators. Due to its simplicity and effectiveness, the presented methodology is also suitable for teaching purposes.

Highlights•Multi-input multi-output block diagram in frequency domain is introduced to describe the consensus tracking of multi-agent systems.•Consensus tracking condition imposed on the controller is given.•Analytical controller is designed for the consensus of homogeneous multi-agent systems with input time delays to improve the H2 performance index.•Simple quantitatively tuning way is developed to trade off the nominal performance and robustness.An analytical H2 controller design approach of homogeneous multi-agent systems with time delays is presented to improve consensus performance. Firstly, a closed-loop multi-input multi-output framework in frequency domain is introduced, and a consensus tracking condition is given. Secondly, the decomposition method is utilized to simplify the analysis of internal stability and H2 performance index of the whole system to a set of independent optimization problems. Finally, the H2 optimal controller can be computed from all the stabilizing controllers. The contributions of the new approach are that the design procedure is conducted analytically for arbitrary delayed multi-agent systems, and a simple quantitative tuning way is developed to trade off the nominal performance and robustness. The simulation examples show the effectiveness of the proposed control strategy.

This article presents an H∞ design that alleviates some difficulties with standard Internal Model Control (IMC), while still obeying the same spirit of simplicity. The controller derivation is carried out analytically based on a weighted sensitivity formulation. The corresponding frequency weight, chosen systematically, involves two tuning parameters with clear meaning in terms of common design specifications: one adjusts the robustness/performance trade-off as in the IMC procedure; the other one balances the servo and regulatory performance. For illustration purposes, the method is applied to analytical tuning of PI compensators. Due to its simplicity and effectiveness, the presented methodology is also suitable for teaching purposes.

The work of Yassen [M.T. Yassen, Chaos control of chaotic dynamical systems using backstepping design, Chaos Soliton Fract. 27 (2006) 537–548] which mainly investigated the stabilization problem for a class of chaotic systems without the parameters perturbation. This paper is concerned with stabilization problem for a class of parameters perturbation chaotic systems via both backstepping design method and adaptive technique. The proposed controllers can guarantee that the parameters perturbation systems will be stabilized at a fixed bounded point. Furthermore, the paper also proposes controllers to stabilize the uncertain chaotic system at equilibrium point with only backstepping design method. Finally, numerical simulations are given to illustrate the effectiveness of the proposed controllers.

Based on the Lyapunov stability theory and LMI technique, a new sufficient criterion, formulated in the LMI form, is established in this paper for chaos robust synchronization by linear-state-feedback approach for a class of uncertain chaotic systems with different parameters perturbation and different external disturbances on both master system and slave system. The new sufficient criterion can guarantee that the slave system will robustly synchronize to the master system at an exponential convergence rate. Meanwhile, we also provide a criterion to find out proper feedback gain matrix K that is still a pending problem in literature [H. Zhang, X.K. Ma, Synchronization of uncertain chaotic systems with parameters perturbation via active control, Chaos, Solitons and Fractals 21 (2004) 39–47]. Finally, the effectiveness of the two criteria proposed herein is verified and illustrated by the chaotic Murali–Lakshmanan–Chua system and Lorenz systems, respectively.

•Modified HK model is proposed for grouped population.•Open-minded agent may even diversify the final opinions.•The relative size of the largest cluster varies along concave-parabola-like curve.•The tipping point of the curve of relative size occurs at about po=pm.Continuous opinion dynamics in a group-based population with heterogeneous bounded confidences is considered in this paper. A slightly modified Hegselmann–Krause model is proposed, and agents are classified into three categories: open-minded-, moderate-minded-, and closed-minded-agents, while the whole population is divided into three subgroups accordingly. We study how agents of each category and the population size can affect opinion dynamics. It is observed that the number of final opinion clusters is dominated by the closed-minded agents; open-minded agents cannot contribute to forming opinion consensus and the existence of open-minded agents may diversify the final opinions instead; for the fixed population size and proportion of closed-minded agents, the relative size of the largest final opinion cluster varies along concave-parabola-like curve as the proportion of open-minded agents increases, and there is a tipping point when the number of open-minded agents is almost equal to that of moderate-minded agents; for the fixed proportion of the three categories in the population, as the population size becomes larger, the number of final opinion clusters will reach a plateau. Some of the results are different from the previous studies.

•A modified naming game with memory loss is proposed.•The strength of memory loss has little effect on the maximum number of different words.•The maximum number of different words grows almost linearly with population size and coincides with each other under different strength of memory loss.In this paper, we study the dynamics of naming game where individuals are under the influence of memory loss. An extended naming game incorporating memory loss is proposed. Different from the existing naming game models, the individual in the proposed model would forget some words with a probability in his memory during interaction and keep his conveyed word unchanged until he reaches a local agreement. We analyze the dynamics of the proposed model through extensive and comprehensive simulations, where four typical networks with different configuration are employed. The influence of memory loss as well as the population size on the performance of the proposed model is investigated. The simulation results show that (i) the stronger memory loss, the larger convergence time; (ii) as the strength of memory loss becomes stronger, maximum number of total words will decrease, while the maximum number of different words among the population remains almost unchanged; (iii) the maximum number of different words increases linearly with the increase of the population size and coincides with each other under different strength of memory loss. The findings in the proposed model may give an insight to understand better the influence of memory loss on the transient dynamics of language evolution and opinion formation over networks.

•Three exponentially convergent robust controllers are proposed for the trajectory tracking of AUVs in the presence of dynamic uncertainties and time-varying external disturbances.•The filtered, position and velocity tracking errors for the three proposed controllers are exponentially convergent with specific analytic expressions.•The analytic expressions of the filtered, position and velocity tracking errors illustrate how the transient responses of these tracking errors can be modified by adjusting the control parameters.•The three proposed controllers provide faster response speed than the existing RISE-based controller for AUV in the presence of sufficiently smooth bounded external disturbances.•The three proposed controllers are still applicable in the presence of nonsmooth bounded external disturbances as opposite to the existing RISE-based controller for AUV.This paper deals with the trajectory tracking problem of autonomous underwater vehicles (AUVs) in the presence of dynamic uncertainties and time-varying external disturbances. Three exponentially convergent robust controllers, namely, the min-max type controller, the saturation type controller and the smooth transition type controller are proposed to drive an AUV to track a predefined trajectory. It is shown that the filtered tracking errors, position tracking errors and velocity tracking errors for the three proposed controllers are exponentially convergent. Moreover, all the above tracking errors for the three proposed controllers can be shaped by specific analytic expressions and such expressions illustrate how the transient responses of the above tracking errors can be modified by adjusting the control parameters. The characteristics of the three proposed controllers are summarized and demonstrated with numerical simulations. Theoretical comparison analysis and comparative simulations with the existing RISE-based controller of AUV are presented to show the effectiveness of the three proposed exponentially convergent robust controllers.