Event-triggered adaptive sliding mode control for consensus of multiagent systems with unknown disturbances

In this paper, sliding mode controller (SMC) and integral sliding mode controller (ISMC) are designed for a variable speed wind turbine. The main objective of the controller is to optimize the energy captured from the wind at below rated power. To overcome the steady state error, the ISMC is introduced. However, in the presence of large uncertainties, ISMC control approach produces oscillatory phenomenon due to the higher needed gain. To eliminate the tradeoffs between the ISMC tracking performance and the high gain at the control input, we have introduced a new method based on the modification of the output tracking error through the use of the exponential function in order to eliminate the reaching phase. The stability of the proposed ISMC is analyzed by Lyapunov theory and the control action didn't show any chattering. The simulation results of ISMC are presented and the control performance is compared with conventional SMC.

This paper develops a novel integral sliding mode controller (ISMC) for a general type of underwater robots based on multiple-input and multiple-output extended-state-observer (MIMO-ESO). The difficulties associated with the unmeasured velocities, unknown disturbances, and uncertain hydrodynamics of the robot have been successfully solved in the control design. An adaptive MIMO-ESO is designed not only to estimate the unmeasurable linear and angular velocities, but also to estimate the unknown external disturbances. An ISMC is then designed using Lyapunov synthesis, and an adaptive gain update algorithm is introduced to estimate the upper bound of the uncertainties. Rigorous theoretical analysis is performed to show that the proposed control method is able to achieve asymptotical tracking performance for the underwater robot. Experimental studies are also carried out to validate the effectiveness of the proposed control, and to show that the proposed approach performs better than a conventional potential difference (PD) control approach.

This paper addresses the integrated challenge of consensus tracking for second-order nonlinear multi-agent systems (MAS) simultaneously subject to stochastic communication channel fading, actuator faults (both partial loss-of-effectiveness and bias types), and constrained network resources. To tackle this, a synergistic control scheme is proposed that co-designs a fading-resilient event-triggered communication mechanism with a chatter-free adaptive continuous integral sliding mode control (SMC) protocol. The event-triggering condition explicitly incorporates the statistical characteristics of channel fading, enabling efficient bandwidth usage under unreliable links. The proposed continuous SMC, equipped with an adaptive law, eliminates chattering entirely and operates without requiring prior knowledge of fault or disturbance bounds. It is rigorously proven that the tracking errors converge to a bounded region, and Zeno behavior is excluded, ensuring practical implement ability. Numerical simulations validate the effectiveness and superior performance of the proposed method compared to conventional discontinuous SMC and periodic sampling schemes.

ABSTRACTThe control performance of a permanent magnet synchronous motor (PMSM) is significantly deteriorated when faced with unknown disturbances, such as model uncertainties, parameter variations, and external interferences. This paper proposes a model‐free fast integral terminal sliding mode control (MFITSMC) approach based on an extended super‐twisting sliding mode disturbance observer (ESTSMDO), referred to as the ESTSMDO‐based MFITSMC approach. First, a unique ultra‐local model (NULM) of the PMSM is developed that accounts for unknown disturbances. Then, the MFITSMC is formulated by integrating a fast integral terminal sliding mode surface with a switching control law. The speed loop controller is designed using the MFITSMC. The ESTSMDO is meant to precisely estimate unknown disturbances and subsequently input them into the MFITSMC controller. The ESTSMDO‐based MFITSMC approach mitigates chattering and improves the system's robustness to unanticipated disturbances. Finally, the simulation and experimental validation demonstrate that the dynamic response of the PMSM system is markedly enhanced, and the chattering associated with SMC is effectively reduced.

In this paper, a reduced-order observer-based integral sliding mode controller is designed for a class of interconnected descriptor systems. First, the observer matching condition is used to transform the interconnected descriptor system into an interconnected normal system. Based on the canonical form, a reduced-order observer is then designed to estimate the state variables of the interconnected descriptor system. In terms of the measurable output variables and the state variables of the proposed reduced-order observer, a sliding mode control scheme is developed to drive the state trajectories of the system to the sliding surface in a finite time and maintain a sliding motion thereafter. It is shown that at the existence of unknown matched disturbances, the proposed observer-based integral sliding mode control scheme can still ensure the asymptotic stability of the resultant closed-loop system. This is an obvious improvement of the existing observer-based sliding mode control methods in descriptor systems fields. Finally, an example is given to verify the effectiveness of the proposed method.

To achieve precise lateral dynamics control for electric and autonomous vehicles under system model uncertainties and unknown external disturbances, this article introduces a novel barrier function (BF)-based neural network (NN) adaptive integral sliding mode control (ISMC) for multiaxle independent steering vehicles (MISVs). Initially, NNs are designed to approximate the unknown parameters associated with uncertainties in the MISV dynamics model. Subsequently, an adaptive ISMC based on BF is developed to ensure robust vehicle state tracking. Unlike traditional adaptive sliding mode controllers, the proposed approach guarantees rapid convergence of variables within a finite time, even without prior knowledge of the upper bounds of unknown external disturbances, thereby significantly reducing vibration and oscillation phenomena. Finally, the Lyapunov stability theory is applied to rigorously demonstrate that the closed-loop system of the MISV remains stable within finite time. The efficacy of the proposed controller is validated through hardware-in-the-loop (HIL) experiments, with results indicating a reduction in maximum tracking errors for the desired yaw rate and sideslip angle by 8.24% and 40.44%, respectively, compared to the conventional control method.

This article proposes a fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode spacecraft control scheme with consideration of input uncertainties and unknown nonlinearities. First, for the purpose of satisfying the time-varying output constraints and simplifying the computational process, an error transformation function is employed to convert the constrained spacecraft system into an unconstrained one. Second, to ensure superior transient-state performance, an improved sliding manifold integrated with a nonlinear function is designed. Then, for accurately estimating the external disturbances, a fixed-time fuzzy disturbance observer is proposed. Furthermore, the unknown nonlinearities and the input uncertainties are handled by several adaptive laws. The simulation results are presented to verify the superiority and effectiveness of the proposed fixed-time fuzzy disturbance observer–based adaptive integral sliding-mode control scheme.

This paper addresses the robust consensus control problem for the second-order multi-agent system in the presence of unknown lumped disturbances and without velocity measure-ments. A novel robust consensus controller is constructed by combining the improved extended high-gain observer (EHGO) and continuous sliding mode control (SMC) strategy. Specifically, for the unknown velocity and lumped disturbances, the EHGO component can estimate them simultaneously by adjusting a simple dynamic parameter. Then, in light of the singular per-turbation technique, the convergence of the closed-loop error system is demonstrated and robust consensus control is achieved. Finally, a numerical simulation experiment is given to verify the effectiveness of robust consensus control strategy,

This paper presents a fixed-time formation control method for underwater unmanned vehicles (UUVs) based on dual-level homogeneous integral sliding mode control, tackling challenges from unknown disturbances and acoustic communication constraints. A distributed fixed-time observer is first developed to overcome communication limitations, allowing each follower to estimate the leader’s position and velocity within fixed time using its own state and locally available neighbor information. Then, to handle unknown external disturbances, a fixed-time formation controller is designed by combining dual-level homogeneous theory with integral sliding mode control. The proposed controller guarantees that followers converge to the desired formation in fixed time while compensating for disturbances, thus improving system robustness. Simulation results confirm the effectiveness of the method.

In this paper, we propose an adaptive sliding mode-based fault tolerant control for mobile robots. While a mobile robot is tracking a given trajectory, several fault cases may occur, such as sensor model and controller faults, changes in the dynamic equation due to robot body shape or weight changes, and loss of actuator effectiveness. Disturbance signals are caused by the actuator faults and, for various reasons, can be considered the primary issue for the robots. In real-time applications, the Sliding Mode Controller (SMC) is insufficient if the robot parameters are unknown, the robot model is non-linear, and the overall system is subject to disturbances. An adaptive law is used to support the SMC to maintain the sliding surface and solve the problems of unknown system parameters, actuator faults, and disturbances. Besides SMC, the kinematic controller is also used, and its gain values are optimized using a neural network and a kinematic controller. The stability of the overall system is proven by using the Lyapunov theory. Besides actuator faults, the system is disturbed by defining a disturbance signal, which is added to the control signals. To show the effectiveness of the proposed controller, it is compared with traditional SMC and PID.

Sliding mode control unified with the uncertainty and disturbance estimator for dynamically positioned vessels subjected to uncertainties and unknown disturbances

Conventional sliding mode controllers have been successfully applied to control various types systems including the Stewart platform manipulator. But chattering, lack of robustness in the reaching phase and sensitivity to unmatched uncertainty are the basic problems which delayed their practical implementations. To avoid the non robust reaching phase to compensate unmatched uncertainties, integral sliding mode controllers have been proposed but only SISO system examples have been tested. Hence in this paper, MIMO implementation of integral sliding mode controller is tested using a 6 DOF Stewart platform manipulator. The integral sliding mode controller is implemented using MATLAB simulation and the result is compared with PD and conventional sliding mode controller. It was found that the integral sliding mode controller performs better in avoiding uncertainties due to load variation and actuator friction.

SummaryIn this paper, an adaptive integral sliding mode control (ISMC) scheme is developed for a class of uncertain multi‐input and multi‐output nonlinear systems with unknown external disturbance, system uncertainty, and dead‐zone. The research is motivated by the fact that the ISMC scheme against unknown external disturbance and system uncertainty is very important for multi‐input and multi‐output nonlinear systems. The system uncertainty, the unknown external disturbance, and the effect of dead‐zone are integrated as a compounded disturbance, which is well estimated using a sliding mode disturbance observer (SMDO). Then, the adaptive ISMC based on the designed SMDO is presented to guarantee the satisfactory tracking performance in the presence of system uncertainty, external disturbance, and dead‐zone. Finally, the designed adaptive ISMC strategy based on SMDO is applied to the attitude control of the near space vehicle, and simulation results are presented to illustrate the effectiveness of the proposed adaptive ISMC scheme using the SMDO. Copyright © 2016 John Wiley & Sons, Ltd.

This paper presents an improved sliding mode control (SMC) strategy for robotic manipulators by introducing a novel exponential integral-based adaptive gain law, referred to as integral sliding mode control (ISMC). The proposed approach dynamically adjusts the switching gain KKK in real-time, based on the accumulated system error, thereby effectively reducing chattering while preserving system robustness. Unlike many existing methods, the ISMC strategy eliminates the need for state observers or complex estimation techniques, simplifying implementation. Theoretical analysis is provided using Lyapunov stability theory, ensuring global convergence. Simulation results on 2-DOF and 3-DOF robotic arms demonstrate superior tracking accuracy and smoother control signals compared to conventional SMC approaches. This work contributes a lightweight yet effective SMC enhancement with practical benefits for real-world robotic applications.

In real life, almost all systems are nonlinear in nature. The electromagnetic levitation system (EMLS) is one such system that has a wide range of applications due to its frictionless, fast, and affordable technique. Optimal control and sliding mode control (SMC) techniques are often used controllers for EMLS. However, these techniques can achieve the required levitation but lag in having perfect set-point tracking and robustness against uncertainties. To get over these drawbacks, this article proposes the design of unconstrained mismatched uncertainties, constrained mismatched uncertainties, and integral sliding mode control with mismatched uncertainties for the current-controlled-type electromagnetic levitation system (CC-EMLS). The modeled equations of CC-EMLS are transfomed in terms of the mismatched uncertainties, and the required control action is obtained with and without constraints on the control input. The quadratic performance function is suggested for the unconstrained control scheme and is solved using the Hamilton–Jacobi–Bellman (HJB) equation. The non-quadratic cost function is designed for the constrained control method, and the HJB equation is utilized to obtain the solution. Both control schemes provide robustness to the system, but deviations in the set point are observed in tracking the position of the ball when the changes in the payload occur in the system. Therefore, integral sliding mode control with robust–optimal (IOSMC) gain is proposed for the CC-EMLS to overcome the steady-state error in the other two schemes. The stability is proven using the direct method of Lyapunov stability. The essential studies based on the simulation are carried out to showcase the performance of the proposed control schemes. The integral performance indicators are compared for all three proposed control schemes to highlight the efficacy, robustness, and efficiency of the designed controllers.