Autonomous surface vehicles (ASVs) are marine vessels capable of performing various marine operations without a crew in a variety of cluttered and hostile water/ocean environments For complex missions, there are increasing needs for deploying a fleet of ASVs instead of a single one to complete difficult tasks Cooperative operations with a fleet of ASVs offer great advantages with enhanced capability and efficacy Despite various application potentials, coordinated motion control of ASVs pose great challenges due to the multiplicity of ASVs, complexity of intravehicle interactions and fleet formation with collision avoidance requirements, and scarcity of communication bandwidths in sea environments Coordinated control of multiple ASVs has received considerable attention in the last decade This article provides an overview of recent advances in coordinated control of multiple ASVs First, some challenging issues and scenarios in motion control of ASVs are presented Next, coordinated control architecture and methods of multiple ASVs are briefly discussed Then, recent results on trajectory-guided, path-guided, and target-guided coordinated control of multiple ASVs are reviewed in detail Finally, several theoretical and technical issues are suggested to direct future investigations including network-based coordination, event-triggered coordination, collision-free coordination, optimization-based coordination, data-driven coordination of ASVs, and task-region-oriented coordination of multiple ASVs and autonomous underwater vehicles

An Overview of Recent Advances in Coordinated Control of Multiple Autonomous Surface Vehicles

In this paper, accurate trajectory tracking problem of a surface vehicle disturbed by complex marine environments is solved by creating a finite-time control (FTC) scheme whereby the nonsingular fast terminal sliding mode (NFTSM) and finite-time disturbance observer (FDO) techniques are deployed. Salient features are as follows. By devising an FDO, complex disturbances arising from marine environments can be exactly identified within a short time, in conjunction with the defined NFTSM manifold, and thereby contributing to exact trajectory tracking. Finite-time disturbance observation is completely decoupled from the nominal FTC scheme, and achieves stronger disturbance rejection and faster transient response, simultaneously. Both disturbance observation and trajectory tracking errors can exactly reach to zero in a finite time. Simulation results and comparisons are comprehensively conducted on CyberShip II and demonstrate remarkable superiority of the FTC scheme.

Accurate Trajectory Tracking of Disturbed Surface Vehicles: A Finite-Time Control Approach

This article addresses the event-triggered dynamic surface control of an underactuated autonomous surface vehicle with unknown kinetics for circumnavigating a dynamic target with unknown velocity. A modular design approach to the event-triggered dynamic surface control is proposed for target enclosing. In the estimator module, an extended state observer is employed for estimating the relative motion between the target and the surface vehicle. A fuzzy system is used for online modeling the unknown vehicle kinetics. In the controller module, an event-triggered dynamic surface control law is constructed by using the estimated relative velocities and vehicle kinetics in the estimator module. In the control law, a triggered mechanism is introduced to reduce the transmission load and the execution rate of actuators. Besides, the control inputs are bounded with the aid of a projection operator and saturated functions. The input-to-state stability of the closed-loop target enclosing system is proven through Lyapunov analysis. Simulation results substantiate the effectiveness of the event-triggered dynamic surface control method for circumnavigating a maneuvering target.

Event-Triggered Dynamic Surface Control of an Underactuated Autonomous Surface Vehicle for Target Enclosing

With the advance of the Internet of Underwater Things, underwater acoustic sensor network (UASN) has been considered as a promising technology for oceanic engineering to explore and exploit marine resources. Due to the time variability, frequency selectivity, and the very limited available bandwidth, underwater acoustic (UWA) channels are generally known as one of the most challenging communication media in use today. The highly dynamic nature of UWA links calls for adaptive, scalable, and efficient routing schemes for UASNs. Depth-based routing has attracted much attention because it can work efficiently without the need for full-dimensional location information of sensors. However, it suffers from the problems of void region and detouring forwarding. To this end, this paper proposes a distance-vector-based opportunistic routing (DVOR) scheme to address these problems. DVOR uses a query mechanism to establish the distance vectors for UWA nodes, which record the smallest hop counts toward the sink. Then, an opportunistic routing is developed to coordinate the packet forwarding based on the distance vectors. DVOR has a low signaling overhead in opportunistic forwarding, as well as the ability to avoid the problems of void region and long detour. Simulation results show that DVOR outperforms the existing routing protocols in terms of packet delivery ratio, energy-efficiency, and average end-to-end delay.

Distance-Vector-Based Opportunistic Routing for Underwater Acoustic Sensor Networks

In this article, in the presence of unknown actuator faults, input saturations, and complete unknowns including both internal dynamics and external disturbances, exact trajectory-tracking problem of a surface vehicle (SV) is solved by creating a finite-time fault estimator based fault-tolerance control (FFE-FTC) scheme. By virtue of input saturations, smoothly saturated controls are separated from input nonlinearities including unknown faults, thereby leaving faults-mixed unknowns be exactly observed by a finite-time fault estimator (FFE). By defining an integral sliding-mode (ISM) manifold and deriving affine controls with unknown gains from smooth saturations, Nussbaum technique is deployed to synthesize a uniformly adaptive finite-time controller working in a large range outside input saturations. Within the close range where saturations are removed, an ISM-based nonsmooth controller with finite-time auxiliary compensation dynamics is devised to finely stick tracking errors to the origin. Intuitively, large- and close-range control actions are triggered by measuring the ISM error, thereby contributing to the entire FFE-FTC scheme, which achieves exact fault-tolerance and unknown rejection under input saturations. Lyapunov and nonsmooth syntheses prove that the closed-loop FFE-FTC system is globally finite-time stable. Simulation results and comparisons on a prototype SV demonstrate remarkable performance in terms of feasibly saturated controls and exact trajectory-tracking, simultaneously.

Finite-Time Fault Estimator Based Fault-Tolerance Control for a Surface Vehicle With Input Saturations

Distributed finite-time fault-tolerant containment control for multiple ocean Bottom Flying node systems with error constraints

The Ocean Bottom Flying Node (OBFN) is a kind of small Autonomous Underwater Vehicle (AUV) used in detection of seabed resources. Based on directed commination topology, this paper investigates the problem of distributed finite-time fault-tolerant containment control for multiple OBFN systems in presence of model uncertainties, external disturbances, and thruster faults. By choosing the nonsingular fast terminal sliding surface and defining the containment error variables, a distributed finite-time containment control method is designed, so as to make the states of the multiple OBFN systems converge to the sliding surface in finite time. The thruster faults, model uncertainties, and external disturbances are considered together and estimated by utilizing Neural Networks (NNs). An adaptive law is designed to compensate the upper bounds of estimation error. Based on the graph theory and matrix theory, it is demonstrated that the follower OBFNs could enter the convex hull formed by the leader OBFNs in finite time through using the Lyapunov approach. Numerical simulation is presented to show the effectiveness of the proposed algorithm.

Distributed finite-time fault-tolerant containment control for multiple ocean bottom flying nodes

A novel adaptive second order sliding mode path following control for a portable AUV

In this paper, a finite-time trajectory tracking control for unmanned surface vessel with error constraints and input saturations is proposed. We take the limited actuator capability into account and employ the hyperbolic tangent function to address the saturation problem, which is converted into the unknown input gains. A tan-type barrier Lyapunov function tackles the error constraints, where error variables remain within the predefined bounds. In addition, the neural networks are utilized for model uncertainties and external disturbances. We present a semi-globally uniformly bounded control method, and develop a finite-time control approach subsequently. Finally, the effectiveness of the proposed strategies is verified by the simulation studies.

Finite-time trajectory tracking control of unmanned surface vessel with error constraints and input saturations

Underwater sensor networks are facing a great challenge in designing a routing protocol with longer network lifetime and higher packet delivery rate under the complex underwater environment. In this paper, we propose an energy-aware and void-avoidable routing protocol (EAVARP). EAVARP includes layering phase and data collection phase. During the layering phase, concentric shells are built around sink node, and sensor nodes are distributed on different shells. Sink node performs hierarchical tasks periodically to ensure the validity and real-time of the topology. It makes EAVARP apply to dynamic network environment. During the data collection phase, data packets are forwarded based on different concentric shells through opportunistic directional forwarding strategy (ODFS), even if there are voids. The ODFS takes into account the remaining energy and data transmission of nodes in the same shell, and avoids cyclic transmission, flooding, and voids. The verification and analysis of simulation results show the effectiveness of our proposed EAVARP in terms of selecting performance matrics in comparison to existing routing protocols.

Hongde Qin

Papers

Distributed finite-time fault-tolerant containment control for multiple ocean Bottom Flying node systems with error constraints

Distributed finite-time fault-tolerant containment control for multiple ocean bottom flying nodes

A novel adaptive second order sliding mode path following control for a portable AUV

Finite-time trajectory tracking control of unmanned surface vessel with error constraints and input saturations

An Energy-Aware and Void-Avoidable Routing Protocol for Underwater Sensor Networks