Continuous and Periodic Event-Triggered Sliding-Mode Control for Path Following of Underactuated Surface Vehicles.

This article develops continuous and periodic event-triggered sliding-mode control (SMC) algorithms for path following of underactuated surface vehicles (USVs). Based on the SMC technology, a continuous path-following control law is designed. The upper bounds of quasi-sliding modes for path following of USVs are established for the first time. Subsequently, both continuous and periodic event-triggered mechanisms are considered and added into the proposed continuous SMC scheme. It is demonstrated that with appropriate selecting of control parameters, the use of hyperbolic tangent functions does not affect the boundary layer of quasi-sliding mode caused by event-triggered mechanisms. The proposed continuous and periodic event-triggered SMC strategies can make the sliding variables reach the quasi-sliding modes and stay in there. Moreover, energy consumption can be reduced. Stability analysis shows that the USV can follow a reference path by using the designed method. The simulation results show the effectiveness of the proposed control methods.

Disturbance observer-based prescribed performance super-twisting sliding mode control for autonomous surface vessels.

This paper proposes a disturbance observer-based prescribed performance super-twisting sliding mode control (DOB PPSTSMC) for trajectory tracking of the autonomous surface vessels (ASVs) subject to unknown external disturbances and modeling errors. Both unknown external disturbances and system modeling errors are approximated by the disturbance observer, thus eliminating most of the effect caused by lumped disturbances in the control performance. Based on this, a prescribed performance super-twisting sliding mode controller is explored to further suppress the residual error of disturbance compensation. Prescribed performance constraints are considered in the coming up with the super-twisting sliding mode controller, so that ASVs not only achieve effective tracking of time-varying desired trajectories, but also improve the transient performance of the control system. In addition, the controller is continuous and chatter-free, which has greater practical value. The excellence of the control project design is highlighted through the simulation and comparison results.

Leader-following consensus for multi-agent systems subject to cyber attacks: Dynamic event-triggered control.

This paper addresses the event-triggered consensus problem for multi-agent systems (MASs) under cyber attacks in the leader-following framework. Via introducing a recoverable cyber attack and dynamic event-triggered mechanism (DEM), the centralized and distributed event-triggered controllers are co-designed. Meanwhile, some dynamic triggering criteria are given to ensure the MASs can achieve consensus. The DEM contains time-varying dynamic parameters, which can extend the interevent time interval to avoid Zeno phenomenon. The simulation results verify the effectiveness of the proposed scheme.

H∞ finite-time composite anti-disturbance switching control for switched systems.

The paper centers on the H∞ finite-time (FT) composite anti-disturbance switching control (ADSC) issue for switched systems (SSs) suffered from multiple disturbances, the unavailable modeled disturbance and the available un-modeled disturbance. The aim is to arrive at the multiple disturbance suppression in FT. A switching estimator is firstly constructed to observe the modeled disturbance combined with the unavailable system state. A switching controller and a switching law are then co-established to restrain the multiple disturbances in the SSs. A condition is attained to ensure that the H∞ FT composite ADSC issue for the SSs is solvable, even the issue is not solvable for subsystems. A verification example is served to text the reasonability of the developed theory.

Fixed-Time Observer Based Prescribed-Time Containment Control of Unmanned Underwater Vehicles with Faults and Uncertainties.

The problem of prescribed-time containment control of unmanned underwater vehicles (UUVs) with faults and uncertainties is considered. Different from both regular finite-time control and fixed-time control, the proposed prescribed-time control strategy is built upon a novel coordinate transformation function and the block decomposition technique, resulting in the followers being able to move into the convex hull spanned by the leaders in prespecifiable convergence time. Moreover, intermediate variables and the control input terms are also shown to remain uniformly bounded at the prescribed-time. To reduce the magnitude of the bounds, a novel fixed-time observer for the fault is proposed. Two numerical examples are provided to verify the effectiveness of the proposed prescribed-time control strategy.

Fixed-time output feedback trajectory tracking control of marine surface vessels subject to unknown external disturbances and uncertainties.

This paper proposes a novel fixed-time output feedback control scheme for trajectory tracking of marine surface vessels (MSVs) subject to unknown external disturbances and uncertainties. A fixed-time extended state observer (FESO) is proposed to estimate unknown lumped disturbances and unmeasured velocities, and the observation errors will converge to zero in fixed time. Based on the estimated values, a novel fixed-time trajectory tracking controller is designed for an MSV to track a time-varying reference trajectory by the extension of an adding a power integrator (API), and the tracking errors can converge to zero in fixed time as well. Additionally, the convergence time of the controller and the FESO is independent of initial state values. Finally, simulation results and comparisons illustrate the superiority of the proposed control scheme.