Underactuated Unmanned Surface Vehicle Research Articles

Adaptive Sliding Mode Trajectory Tracking Control for Unmanned Surface Vehicle with Modeling Uncertainties and Input Saturation

In the presence of modeling uncertainties and input saturation, this paper proposes a practical adaptive sliding mode control scheme for an underactuated unmanned surface vehicle (USV) using neural network, auxiliary dynamic system, sliding mode control and backstepping technique. First, the radial basis function neural network with minimum learning parameter method (MLP) is constructed to online approximate the uncertain system dynamics, which uses single parameter instead of all weights online learning, leading to a reduction in the computational burdens. Then a hyperbolic tangent function is adopted to reduce the chattering phenomenon due to the sliding mode surface. Meanwhile, the auxiliary dynamic system and the adaptive technology are employed to handle input saturation and unknown disturbances, respectively. In addition, a neural shunting model is introduced to eliminate the “explosion of complexity” problem caused by the backstepping method for virtual control derivation. The stability of the closed-loop system is guaranteed by the Lyapunov stability theory. Finally, simulations are provided to validate the effectiveness of the proposed control scheme.

A hybrid coordination controller for speed and heading control of underactuated unmanned surface vehicles system

The speed and heading control problem of an underactuated unmanned surface vehicle (USV) has been studied in this paper. The thrust system consists of two propellers which are driven by two electric-powered motors. A hybrid coordination control strategy based on signal and energy method is proposed. The energy controller uses the Port-Controlled Hamiltonian (PCH) control approach, and the signal controller uses the Lyapunov's direct method and backstepping approach. The design of coordination control strategy is used to adjust the strength of the signal controller and energy controller. Simulation results confirm the validity and stability of control algorithm, and the results show that the proposed algorithm can quickly track signals with energy optimization.

A new guidance law for trajectory tracking of an underactuated unmanned surface vehicle with parameter perturbations

This paper proposes a novel trajectory tracking controller for an underactuated unmanned surface vessel (USV) with multiple uncertainties and input constraints. Unlike previous dynamic surface control (DSC) methods that utilize a first-order filter to obtain derivatives and avoid “explosion of complexity”, we introduce nonlinear tracking differentiators (NTDs) that achieve satisfactory differential performance and fast tracking response and control the vessel to converge to the pseudo-yaw angle and surge. First, a new guidance law for yaw angle and surge is constructed. Second, inner and outer disturbances caused by uncertainties can be observed by reduced-order extended state observers. With the new guidance law, the design process of the controller is simplified and easy to implement. The simulation results show the trajectory tracking error can be stabilized to a certain extent under the parameter perturbations and other uncertainties, which verified the effectiveness of the proposed algorithm.

Filtered Extended State Observer Based Line-of-Sight Guidance for Path Following of Unmanned Surface Vehicles With Unknown Dynamics and Disturbances

This paper investigates the path following problem for an underactuated unmanned surface vehicle (USV) in the presence of ocean currents, model uncertainties and input saturation. Firstly, a novel filtered extended state observer (FESO) based line-of-sight (LOS) guidance law is proposed. The FESO is employed to estimate the time-varying sideslip angle caused by ocean, wind and wave disturbances, which is incorporated into the proposed LOS guidance scheme. Then the path following control system is developed to keep the USV moving on the desired path by combining adaptive fuzzy technique with sliding mode method, where adaptive fuzzy technique is applied to deal with model uncertainties. Besides, an auxiliary system is designed to solve the issue of actuator saturation. By using Lyapunov's stability theory, the closed-loop system is shown to be semiglobally uniformly ultimately bounded (SGUUB). Lastly, the comparison simulation results demonstrate the correctness and effectiveness of the proposed scheme.

Joint Communication and Control for Small Underactuated USV Based on Mobile Computing Technology

To satisfy the requirement of the future ocean communication and maritime transportation, in this paper, an integrated space-air-ground-sea communication control system based on mobile computing technology is proposed to rescue a water container. Specifically, unmanned surface vehicle (USV), as a flexible and lightweight intelligent device deployment integration platform, is the main tool to move towards the water container. However, how to sense the real-time navigation status information of the USV, integrate the information, and eventually distribute it to the ground control center, is still a difficult point for us. To successfully rescue the water container, three aspects of research are needed: information collection of the USV, information fusion, and data distribution to the ground control center. For the information collection part, we mainly use nine-axis, ultrasonic, global positioning system (GPS), and ultra wide band (UWB) sensors to complete the information collection for the USV. For the information fusion part, we set up a computational model to solve it. The USV computational model in previous works is mainly based on large ships, ignoring the modeling of wind, wave, and current for small underactuated USV. We use the classical Nomoto model, combined with the actual any slight wind, wave, and current forces on the USV, and finally combined with the proportion integration differentiation (PID) algorithm to model the USV. For the data distribution to the ground control center part, we have set up a communication protocol for the USV so that it can communicate normally. In addition, we wrote a Browser/Server (B/S) architecture to enable the ground control center to communicate with the host computer. Finally, our proposed control and communication schemes are carried out on actual USV. The real experiments show that the proposed schemes can reduce the ship surge and satisfy the ship navigation.

State recovery and disturbance estimation of unmanned surface vehicles based on nonlinear extended state observers

This paper investigates the state recovery and disturbance estimation of unmanned surface vehicles in the presence of unknown disturbances as well as unmeasured surge, sway, and yaw velocities. The disturbances come from the internal parametric model uncertainties, unknown hydrodynamics, and external disturbances due to wind, waves and ocean currents. At first, a nonlinear extended state observer is developed for not only recovering the unmeasured velocities, but also estimating the disturbances. By using simultaneous Lyapunov inequalities, the observer error dynamics is proven to be input-to-state stable. Then, a finite-time convergent nonlinear extended state observer is proposed to estimate the unknown velocities and disturbances, and the finite-time input-to-state stability of the observer error dynamics is established based on a homogeneous Lyapunov function. By using the proposed nonlinear extended state observers, both velocity and disturbance information can be reconstructed from the position-heading measurement by using global positioning system and gyrocompass only. Simulation results are provided to validate the efficacy of the proposed state recovery and disturbance estimation method for both fully-actuated and under-actuated unmanned surface vehicles.

Adaptive Trajectory Tracking Control for Underactuated Unmanned Surface Vehicle Subject to Unknown Dynamics and Time-Varing Disturbances

This paper proposes an adaptive trajectory tracking control strategy for underactuated unmanned surface vehicles subject to unknown dynamics and time-varing external disturbances. In short, the goal of this paper is to provide a control strategy that allows an underactuated unmanned surface vehicle to track a time dependent trajectory. First, a first-order sliding surface is introduced into the design of surge control law to converge to surge tracking error, and then a second-order sliding surface is hired to design yaw control law to deal with sway motion tracking error. Meanwhile, neural network minimum learning parameter method, which has a smaller amount of computation than a multilayer neural network, is employed to preserve the control law robustness against unknown dynamics and time-varing disturbances induced by wind, waves and ocean currents. Furthermore, much effort is made to obtain uniform ultimate bounded stability for the closed-loop control system. Finally, the numerical simulation experiments of straight line and circle trajectory tracking have been given to prove the correctness and feasibility of the proposed control strategy.

Formation Control for Water-Jet USV Based on Bio-Inspired Method

The formation control problem for underactuated unmanned surface vehicles (USVs) is addressed by a distributed strategy based on virtual leader strategy. The control system takes account of disturbance induced by external environment. With the coordinate transformation, the advantage of the proposed scheme is that the control point can be any point of the ship instead of the center of gravity. By introducing bio-inspired model, the formation control problem is addressed with backstepping method. This avoids complicated computation, simplifies the control law, and smoothes the input signals. The system uniform ultimate boundness is proven by Lyapunov stability theory with Young inequality. Simulation results are presented to verify the effectiveness and robust of the proposed controller.

Fuzzy-Based Optimal Adaptive Line-of-Sight Path Following for Underactuated Unmanned Surface Vehicle with Uncertainties and Time-Varying Disturbances

This paper investigates the path following control problem for an underactuated unmanned surface vehicle (USV) in the presence of dynamical uncertainties and time-varying external disturbances. Based on fuzzy optimization algorithm, an improved adaptive line-of-sight (ALOS) guidance law is proposed, which is suitable for straight-line and curve paths. On the basis of guidance information provided by LOS, a three-degree-of-freedom (DOF) dynamic model of an underactuated USV has been used to design a practical path following controller. The controller is designed by combining backstepping method, neural shunting model, neural network minimum parameter learning method, and Nussbaum function. Neural shunting model is used to solve the problem of “explosion of complexity,” which is an inherent illness of backstepping algorithm. Meanwhile, a simpler neural network minimum parameter learning method than multilayer neural network is employed to identify the uncertainties and time-varying external disturbances. In particular, Nussbaum function is introduced into the controller design to solve the problem of unknown control gain coefficient. And much effort is made to obtain the stability for the closed-loop control system, using the Lyapunov stability theory. Simulation experiments demonstrate the effectiveness and reliability of the improved LOS guidance algorithm and the path following controller.

Dynamic Analysis and Motion Control of an Underactuated Unmanned Surface Vehicle (WL-II)

AbstractAn unmanned surface vehicle (USV) is a promising maritime motion platform used to accomplish hundreds of different tasks. This paper presents a design, improved dynamic modeling, and motion control of an underactuated USV, called WL-II. The detailed structure and component of WL-II are studied first. Then based on WL-II's structure, kinematic and dynamic models are built considering wind as well as sea waves; thus, a nonlinear dynamics model is deduced in the form of a state equation. The hardware and software systems of WL-II are introduced for its control mechanism. Then, the adaptive sliding mode control (SMC) algorithm for WL-II's motion is examined. The simulation and experimental results validate the superior performance of the proposed algorithm for WL-II's heading control to the regular SMC method. In this paper, improved dynamics, which consider more parameters (wind and sea waves), are proposed and reasonably simplified for computation. The adaptive SMC is used to control WL-II's motion to improve control precision and reduce response time.

Saturated coordinated control of multiple underactuated unmanned surface vehicles over a closed curve

This paper presents a design method for saturated coordinated control of multiple underactuated unmanned surface vehicles (USVs) on a closed curve,holding a symmetric formation pattern. Each vehicle is subject tounknown sideslip, uncertain vehicle kinetics, and limited control torques.First, the course angle and surge velocity are considered as immediate signals to stabilize the along-track and cross-track path following errors. In the vehicle kinematics, a reduced-order extended state observer is utilized to compensate for the effect of the unknown sideslip. Next, a bounded neural network control law is constructed at the kinetic level with the aid of the a saturated function, a projection operator, and a dynamic surface design method. Finally, a parameter cyclic pursuit approach is presented to guarantee that the vehicles are evenly spaced over the closed curve for achieving a symmetric formation pattern. The input-to-state stability of the closed-loop system is analyzedvia cascade theory. Comparative studies are given to show the effectiveness of the proposed method.

A task-based hierarchical control strategy for autonomous motion of an unmanned surface vehicle swarm

In this paper, a hierarchical control framework with relevant algorithms is proposed to achieve autonomous navigation for an underactuated unmanned surface vehicle (USV) swarm. In order to implement automatic target tracking, obstacle avoidance and avoid collisions between group members, the control framework is divided into three layers based on task assignments: flocking strategy design, motion planning and control input design. The flocking strategy design transmits some basic orders to swarm members. Motion planning applies the potential function method and then improves it; thus, the issue of autonomous control is transformed into one of designing the velocity vector. In the last layer, the control inputs (surge force and yaw moment) are designed using the sliding mode method, and the problem of underactuation is handled synchronously. The proposed closed-loop controller is shown to be semi-asymptotically stable by applying Lyapunov stability theory, and the effectiveness of the proposed methodology is demonstrated via numeric simulations of a homogeneous USV swarm.

Trajectory tracking control for underactuated unmanned surface vehicles with dynamic uncertainties

The trajectory tracking control problem for underactuated unmanned surface vehicles (USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Serret-Frenet frame based on path following control for underactuated unmanned surface vehicles with dynamic uncertainties

The path following problem for an underactuated unmanned surface vehicle (USV) in the Serret-Frenet frame is addressed. The control system takes account of the uncertain influence induced by model perturbation, external disturbance, etc. By introducing the Serret-Frenet frame and global coordinate transformation, the control problem of underactuated system (a nonlinear system with single-input and ternate-output) is transformed into the control problem of actuated system (a single-input and single-output nonlinear system), which simplifies the controller design. A backstepping adaptive sliding mode controller (BADSMC) is proposed based on backstepping design technique, adaptive method and theory of dynamic slide model control (DSMC). Then, it is proven that the state of closed loop system is globally stabilized to the desired configuration with the proposed controller. Simulation results are presented to illustrate the effectiveness of the proposed controller.

Design of Strait-Line Tracking Controller of Under-Actuated USV Based on Back-Stepping Method and Feedback Compensation

Unmanned surface vehicle (USV) system has been one of main research directions in mobile robotics because it can be used in many situations. However, high performance path following control, especially straight line tracking control, has been one of the difficult problems in autonomous control of USV system. In this paper, we propose a new straight line path following control algorithm by combining yaw angle feedback and back-stepping technique and show its closed loop stability. The most absorbing advantage of the proposed controller is that it not only reserve the good performance of back-stepping controller but also bring much faster convergent rate, which is very important in real applications. The simulation results with respect to a training ship model have shown the feasibility and validity of the proposed method.

A Virtual Target-Based Underway Docking Procedure for Unmanned Surface Vehicles

AbstractThis paper considers the topic of safely docking a small unmanned surface vehicle (USV) with a larger mother ship moving in transit at sea. The proposed underway docking procedure is divided into two distinct phases to ensure a controlled and collision-free operation. Specifically, a safety circle is defined around the mother ship together with a virtual target point that can move along its circumference. During the whole procedure, the mother ship passively moves forward in a straight line while the USV actively tracks the target point using constant bearing guidance. In the first docking phase, the target is positioned at the projection of the USV position onto the safety circle surrounding the mother ship. When the USV has matched its position and velocity with the projected target point, the second phase is initiated by the target point starting to move along the safety circle until its bearing matches up with that of the desired docking point. Subsequently, the target point starts reducing its distance from the safety distance until it becomes equal to that of the docking point such that docking is finally achieved. The suggested underway docking procedure represents a simple and intuitive method which is easy to implement and tune. Its performance is illustrated through a computer simulation with an underactuated USV docking with a mother ship in transit.

Path-following algorithms and experiments for an unmanned surface vehicle

This paper addresses the problem of path following in two-dimensional space for underactuated unmanned surface vehicles (USVs), defining a set of guidance laws at the kinematic level. The proposed ...

Path Following Guidance Control with Bounded Control Effort: Application to the Charlie Unmanned Surface Vehicle

This paper addresses the problem of motion control in two-dimensional space for under-actuated unmanned surface vehicles. A guidance motion control law that guarantees bounded velocity commands is derived at the kinematics level. The main difference with respect to the other approaches known in the literature is to be found in the definition of the error variables to be driven to zero. Besides a brief explanation of the proposed approach to solve the guidance problem for under-actuated systems, numerical and experimental results carried out with the Charlie USV are reported.

Straight-Line Target Tracking for Unmanned Surface Vehicles

This paper considers the subject of straight-line target tracking for unmanned surface vehicles (USVs). Target-tracking represents motion control scenarios where no information about the target behavior is known in advance, i.e., the path that the target traverses is not defined apriori. Specifically, this work presents the design of a motion control system which enables an underactuated USV to track a target that moves in a straight line at high speed. The motion control system employs a guidance principle originally developed for interceptor missiles, as well as a novel velocity controller inspired by maneuverability and agility concepts found in fighter aircraft literature. The performance of the suggested design is illustrated through full-scale USV experiments in the Trondheimsfjord.