This article proposes an event-triggered generalized super-twisting sliding mode disturbance rejection control strategy for permanent magnet synchronous motors (PMSMs), aiming to ensure precise position tracking while efficiently conserving communication resources. A unified event-triggering mechanism facilitates the simultaneous transmission of measurement and actuator signals, effectively implementing feedback-control bidirectional triggering. Furthermore, the entire control strategy is updated based on triggered state information. It incorporates a generalized super-twisting controller characterized by a simple structure and smooth dynamic performance, in addition to a neural network observer and a high-gain observer designed to estimate lumped disturbances and enhance system robustness. The practical stability of the closed-loop system, the boundedness of the signals, and the Zeno-free execution of triggering sequences are rigorously verified. Finally, experimental results on a PMSM validate the superiority of the proposed control approach in terms of transient-state position tracking, steady-state smoothness, communication efficiency, and robustness.

This article explores a novel variable-gain super-twisting observer (VGSTO)-based fixed-time sliding mode control (FTSMC) method for the dc-link voltage control of three-level neutral-point-clamped (NPC) active front-end (AFE) converters. Among the literature review, the super-twisting observer is an attractive solution for disturbance estimation. However, its convergence velocity is limited when the trajectories are far away from the origin. To overcome this drawback, a novel VGSTO is proposed in this work, whose innovation lies in adopting dynamically adapted exponent coefficients in the conventional super-twisting observer; thus, it turns into a linear observer outside a ball around the origin, which increases the convergence rate of conventional super-twisting observer, and the disturbance rejection ability is enhanced significantly. In addition, an FTSMC is designed for the NPC converter and its settling time is independent of the initial states, which breaks through the limitation of the traditional finite-time sliding mode controllers and assures the dynamic performance of the NPC converter. The proposed control scheme is assessed and compared with other representative observer-based sliding mode control methods based on a three-level NPC AFE converter test bench, and the experimental results verify its feasibility and effectiveness.

This article addresses the issue of security in cyber–physical systems (CPSs) in the context of malicious actuator false data injection (FDI) attacks. Building on a stochastic physical dynamics model, the proposed approach distinguishes itself by employing a moving target defense (MTD) strategy to enable proactive protection, which is an aspect rarely addressed in existing related works. The system model is formulated as a family of controllable submodels based on controllability. These controllable submodels are regarded as moving targets. A residual-based attack detector is introduced to justify whether an attack occurs or not. When an alarm is triggered, the current running controllable submodel is switched to another controllable one. Furthermore, an MTD-based security controller is devised to proactively mitigate actuator attacks. Sufficient conditions for the design of security control gains are formulated, using which the CPSs can preserve the mean-square exponential stability with the desired disturbance rejection level. Finally, the effectiveness of the proposed control strategy is demonstrated through a comparative simulation based on a practical physical system.

This paper introduces a fixed-time sliding mode control (FTSMC) scheme that utilizes a fixed-time disturbance observer (FTDOB) for three-level neutral-point-clamped (3L-NPC) converters. Therein, a FTSMC with adaptive exponential coefficient is developed to regulate the dc-link voltage. Compared with existing methods, the proposed approach features a settling time upper bound that is independent of the initial error, which ensures the dynamic performance of the 3L-NPC converters. Furthermore, a FTDOB is employed to estimate external disturbances and act as feedforward compensation of the 3L-NPC converters to enhance its disturbances rejection ability. Finally, a series of simulation results illustrate the advantages of the proposed scheme by compared with several representative methods used in 3L-NPC converters.

In this article, an observer-based prescribed performance speed control method is proposed for permanent magnet synchronous motors. A transformed speed error is introduced and a suitable controller is designed to make it converge to zero, while guaranteeing the original speed error evolves strictly within a prescribed region. The controller is designed based on a backstepping approach. A linear extended state observer is applied to estimate and feed forward the external constant load disturbance to improve robustness. A data-driven radial-basis function neural network is proposed to approximate the nonlinear dynamic caused by parameter uncertainties and periodic-changing disturbance by deploying real-time and historical data. The stability analysis is based on Lyapunov's control theory. Experimental results verify the effectiveness and advantages of the proposed control scheme.

This paper presents a model-free predictive current controller for permanent magnet synchronous motors. The dynamic model of the motor currents is represented using an ultra-local model, where all system parameters, nonlinear terms, and other unmodeled dynamics are encapsulated into two lumped functions. These functions are estimated online using a second-order fixed-time sliding mode observer, allowing for system model estimation without requiring exact knowledge of the system parameters in advance. Subsequently, a predictive controller is designed by taking into consideration the inherent one-step delay. Simulation results are presented to showcase the effectiveness and efficacy of the proposed approach.

In this paper, the fixed-time control problem of DC-DC buck converter systems with mismatched disturbances is investigated. Firstly, the sliding mode fixed-time observers are constructed to estimate the matched and mismatched disturbances of the systems. Secondly, a novel segmented terminal sliding mode control (TSMC) variable considering the mismatched disturbance of the system is designed based on the observations. To improve the tracking performance, a new second-order fixed-time reaching law is proposed. Then, in order to make the DC-DC buck converter systems with mismatched disturbances achieve accurate control in a fixed-time independent of the initial state, a novel fixed-time nonsingular TSMC based on the fixed-time observers is proposed. Finally, comparative experiments are conducted to verify the effectiveness and practicality of the proposed control strategy.

This article develops a new controller design approach to stabilize system states onto the equilibrium at an arbitrarily selected time instant irrespective of the initial system states and parameters. By the stabilization approach, the actual convergence time (not the bound of actual convergence time) is independent of the initial value of system states. This feature differentiates our proposed prescribed-instant stability from conventional fixed, predefined, and prescribed time stability. In this work, we propose the controller design method for the prescribed-instant stability of n -order integrator systems. The proposed control is bounded and can gradually go to zero at an arbitrarily selected time instant, at which the system states reach zero simultaneously. This special stability of the controlled system is analyzed by reduction to absurdity. In simulations, an example of comparison with frequently used prescribed-time control is presented to show the difference. Moreover, the proposed stabilization method is validated by a magnetic suspension system with matched disturbances.

In this paper, the prescribed-instant stability control is proposed and utilized in the leader-follower multiagent system with a directed communication topology. The proposed prescribed-instant stability ensures the settling time is exactly equal to the prescribed time instant. Therefore, the specific time instant at which the system containment is established can be manipulated as per our will. This result is of great significance in some complex multiagent system cooperation tasks. The proof of the main result is demonstrated by the Lyapunov method, Specifically, the settling time is clamped from two sides to the selected time instant. Apart from the theoretical proof, a numerical simulation is also presented to validate the proposed method.

In this paper, a high-order nonlinear disturbance observer-based fractional-order sliding mode control (FOSMC) strategy is proposed for DC/DC buck converters in the presence of mismatched disturbances, ensuring the properties of both stability and dynamic performance. Traditional sliding mode control can deal with matched disturbances while achieving desired closed-loop performance, unfortunately it is particularly sensitive to mismatched disturbances. In the proposed control structure, two nonlinear disturbance observers are constructed to estimate both matched and mismatched disturbances in finite time. Then, the estimated variables are used for the fractional-order sliding mode surface design, where a super twisting sliding mode controller is designed to drive the states of the system to track their desired values. Comparing with the traditional SMC, the proposed method not only reduces the sensitivity of the system to mismatched disturbance, but also improves the transient performance of the system. Simulation and experimental results have comprehensively illustrated the feasibility and effectiveness of the proposed strategy.

This paper presents a tracking control scheme with quantization mechanism for hypersonic flight vehicles (HFVs) with prescribed performance using an interval type-2 fuzzy neural network (IT2FNN). A parameterized tracking error model of the HFV is derived with some considered uncertainties, which are approximated by an IT2FNN. The tracking control of the velocity and altitude of the HFV is designed by using a prescribed performance control technique. It allows that transient characteristics of the tracking errors can be improved and adjusted by some prescribed performance functions. According to an adaptive backstepping control design procedure, novel continuous control laws of the fuel equivalency ratio, canard deflection, and elevator deflection are designed with logarithmic quantization mechanism, for the sake of avoiding inadvertently increasing the effective gains of continuous controllers as well as reducing loads of the communication from controller unit to actuator unit. Besides, the limited tracking errors of the flight path angle and angle-of-attack can be achieved by applying the designed controllers. Finally, the presented tracking controllers with quantization mechanism are validated by comparative simulations.

In this paper, a distributed filtering scheme is presented to deal with the fault detection problem of nonlinear stochastic systems with wireless sensor networks (WSNs). The nonlinear stochastic systems, which are of discrete-time form, are represented by interval type-2 (IT2) Takagi-Sugeno (T-S) fuzzy models. Each sensor of the WSN can receive measurements from itself and its neighboring sensors subject to a deterministic interconnection topology. Independent random variables obeying the Bernoulli distribution are formulated to characterize the randomly occurred packet losses between the WSN and the filter unit. To generate residual signals for evaluation functions of the fault detection mechanism, a novel type of IT2 T-S fuzzy distributed fault detection filter is proposed corresponding to each sensor node. Additionally, a fault reference model is adopted for improving the performance of the fault detection system. A new overall fault detection system is formulated in an IT2 T-S fuzzy model framework. Applying Lyapunov functional approach, we concentrate on the analysis of stability and performance of the resulting fault detection system. New techniques are utilized to handle the decoupling problem in design procedure. The desired parametric matrices of the fuzzy filters are designed subject to a developed criterion, which is a sufficient condition of the robust mean-square asymptotic stability for the overall fault detection system with a disturbance attenuation performance. Finally, a truck-trailer system with a four-node WSN is established for simulation validation. In simulations, the mincx function of the MatLab 2017a in Windows 10 OS is used to optimize the level of the disturbance attenuation performance, and to obtain the filter gains for the established system. By comparing the different time instants when the residual evaluation functions exceed their respective thresholds, simulation results successfully validate the effectiveness and applicability of the presented distributed fault detection scheme.

This paper is concerned with the optimal guaranteed cost sliding-mode control problem for interval type-2 (IT2) Takagi-Sugeno fuzzy systems with time-varying delays and exogenous disturbances. In the presence of the uncertain parameters hidden in membership functions, an adaptive method is presented to handle the time-varying weight coefficients reflecting the change of the uncertain parameters. A new integral sliding surface is presented based on the system output. By designing a novel adaptive sliding-mode controller, system perturbation or modeling error can be compensated, and the reachability of the sliding surface can be guaranteed with the ultimate uniform boundedness of the closed-loop system. Optimal conditions of an H2guaranteed cost function and an H∞performance index are established for the resulting time-delay control system. Finally, an inverted pendulum system represented by the IT2 fuzzy model is applied to illustrate the advantages and effectiveness of the proposed control scheme.

In this paper, a novel adaptive sliding mode controller is designed against the actuator saturation for a PEM fuel cell air-feed system. To deal with the saturation nonlinearity, a diagonal matrix with unknown elements is introduced for adaptive design in terms of sliding mode control strategy. An integral-type sliding mode surface is designed with constrained conditions. The designed SMC law can guarantee the finite-time convergence against the actuator saturation of the plant. The effectiveness of the proposed saturated SMC scheme is validated in the application to air-feed PEM fuel cell systems.

In this paper, the problem of fuzzy filter design is investigated for a class of nonlinear networked systems on the basis of the interval type-2 (IT2) fuzzy set theory. In the design process, two vital factors, intermittent data packet dropouts and quantization, are taken into consideration. The parameter uncertainties are handled effectively by the IT2 membership functions determined by lower and upper membership functions and relative weighting functions. A novel fuzzy filter is designed to guarantee the error system to be stochastically stable with H∞ performance. Moreover, the filter does not need to share the same membership functions and number of fuzzy rules as those of the plant. Finally, illustrative examples are provided to illustrate the effectiveness of the method proposed in this paper.

This paper focuses on the problem of fault detection for Takagi-Sugeno fuzzy systems with time-varying delays via delta operator approach. By designing a filter to generate a residual signal, the fault detection problem addressed in this paper can be converted into a filtering problem. The time-varying delay is approximated by the two-term approximation method. Fuzzy augmented fault detection system is constructed in δ -domain, and a threshold function is given. By applying the scaled small gain theorem and choosing a Lyapunov-Krasovskii functional in δ -domain, a sufficient condition of asymptotic stability with a prescribed H∞ disturbance attenuation level is derived for the proposed fault detection system. Then, a solvability condition for the designed fault detection filter is established, with which the desired filter can be obtained by solving a convex optimization problem. Finally, an example is given to demonstrate the feasibility and effectiveness of the proposed method.

In this paper, the problem of fuzzy control for nonlinear networked control systems with packet dropouts and parameter uncertainties is studied based on the interval type-2 fuzzy-model-based approach. In the control design, the intermittent data loss existing in the closed-loop system is taken into account. The parameter uncertainties can be represented and captured effectively via the membership functions described by lower and upper membership functions and relative weighting functions. A novel fuzzy state-feedback controller is designed to guarantee the resulting closed-loop system to be stochastically stable with an optimal performance. Furthermore, to make the controller design more flexible, the designed controller does not need to share membership functions and amount of fuzzy rules with the model. Some simulation results are provided to demonstrate the effectiveness of the proposed results.

In this paper, the problem of induced L2disturbance attenuation control is investigated for discrete-time Takagi-Sugeno (T-S) fuzzy delta operator systems with time-varying delays and disturbance input via an input-output approach. A model transformation method is utilized to approximate the time-varying delay in T-S fuzzy delta operator systems. By applying the scaled small gain (SSG) theorem and Lyapunov-Krasovskii functional approach, a sufficient condition is established to guarantee that the closed-loop system is asymptotically stable and has an induced L2disturbance attenuation performance. The existence condition of the dynamic output-feedback controller can be solved via convex optimization problems. Finally, simulation results are given to demonstrate the feasibility and effectiveness of the proposed method.