Dynamic Surface and Active Disturbance Rejection Control for Path Following of an Underactuated UUV

This paper addresses the problem of accurate path following control for an underactuated unmanned underwater vehicle (UUV) in the horizontal plane. For an underactuated UUV, the line-of-sight (LOS) guidance method is adopted to map 2D reference trajectory into a desired orientation, and through the tracking of heading to achieve path following, where the sideslip is introduced to modify the desired orientation. In this paper, we propose a method called dynamic surface and active disturbance rejection control (DS-ADRC) to solve the path following control problem. This controller can effectively avoid the phenomenon of explosion of terms in the conventional backstepping method, reduce the dependence on the UUV controller mathematical model, and enhance the antijamming ability. Simulation is carried out to verify the effectiveness of the proposed control method for an underactuated UUV. The results show that, even for this controller with disturbance, the cross-track error of UUV is gradually converged to zero and has some certain robustness

Underwater Robots Part I: Current Systems and Problem Pose

International audienceThis paper constitutes the first part of a general overview of underwater robotics. The second part is titled: Underwater Robots Part II: existing solutions and open issues

State relativity and speed-allocated line-of-sight course control for path-following of underwater vehicles

Path-following is a primary task for most marine, air or space crafts, especially during autonomous operations. Research on autonomous underwater vehicles (AUV) has received large interests in the last few decades with research incentives emerging from the safe, cost-effective and practical solutions provided by their applications such as search and rescue, inspection and monitoring of pipe-lines ans sub-sea structures. This thesis presents a novel guidance system based on the popular line-of-sight (LOS) guidance law for path-following (PF) of underwater vehicles (UVs) subject to environmental disturbances. Mathematical modeling and dynamics of (UVs) is presented first. This is followed by a comprehensive literature review on guidance-based path-following control of marine vehicles, which includes revised definitions of the track-errors and more detailed illustrations of the general PF problem. A number of advances on relative equations of motion are made, which include an improved understanding of the fluid FLOW frame and expression of its motion states, an analytic method of modeling the signs of forces and moments and the proofs of passivity and boundedness of relative UV systems in 3-D. The revision in the relative equations of motion include the concept of state relativity, which is an improved understanding of relativity of motion states expressed in reference frames and is also useful in incorporating environmental disturbances. In addition, the concept of drift rate is introduced along with a revision on the angles of motion in 3-D. A switching mechanism was developed to overcome a drawback of a LOS guidance law, and the linear and nonlinear stability results of the LOS guidance laws have been provided, where distinctions are made between straight and curved PF cases. The guidance system employs the unique formulation and solution of the speed allocation problem of allocating a desired speed vector into x and y components, and the course control that employs the slip angle for desired heading for disturbance rejection. The guidance system and particularly the general course control problem has been extended to 3-D with the new definition of vertical-slip angle. The overall guidance system employing the revised relative system model, course control and speed allocation has performed well during path-following under strong ocean current and/or wave disturbances and measurement noises in both 2-D and 3-D scenarios. In 2-D and 3-D 4 degrees-of-freedom models (DOF), the common sway-underactuated and fully actuated cases are considered, and in 3-D 5-DOF model, sway and heave underactuated and fully actuated cases are considered. Stability results of the LOS guidance laws include the semi-global exponential stability (SGES) of the switching LOS guidance and enclosure-based LOS guidance for straight and curved paths, and SGES of the loolahead-based LOS guidance laws for curved paths. Feedback sliding mode and PID controllers are applied during PF providing a comparison between them, and simulations are carried out in MatLab

Underwater Vehicles

For the latest twenty to thirty years, a significant number of AUVs has been created for the solving of wide spectrum of scientific and applied tasks of ocean development and research. For the short time period the AUVs have shown the efficiency at performance of complex search and inspection works and opened a number of new important applications. Initially the information about AUVs had mainly review-advertising character but now more attention is paid to practical achievements, problems and systems technologies. AUVs are losing their prototype status and have become a fully operational, reliable and effective tool and modern multi-purpose AUVs represent the new class of underwater robotic objects with inherent tasks and practical applications, particular features of technology, systems structure and functional properties

Energy Based Control System Designs for Underactuated Robot Fish Propulsion

In nature through millions of years of evolution fish and cetaceans have developed fast efficient and highly manoeuvrable methods of marine propulsion. A recent explosion in demand for sub sea robotics, for conducting tasks such as sub sea exploration and survey has left developers desiring to capture some of the novel mechanisms evolved by fish and cetaceans to increase the efficiency of speed and manoeuvrability of sub sea robots. Research has revealed that interactions with vortices and other unsteady fluid effects play a significant role in the efficiency of fish and cetaceans. However attempts to duplicate this with robotic fish have been limited by the difficulty of predicting or sensing such uncertain fluid effects. This study aims to develop a gait generation method for a robotic fish with a degree of passivity which could allow the body to dynamically interact with and potentially synchronise with vortices within the flow without the need to actually sense them. In this study this is achieved through the development of a novel energy based gait generation tactic, where the gait of the robotic fish is determined through regulation of the state energy rather than absolute state position. Rather than treating fluid interactions as undesirable disturbances and `fighting' them to maintain a rigid geometric defined gait, energy based control allows the disturbances to the system generated by vortices in the surrounding flow to contribute to the energy of the system and hence the dynamic motion. Three different energy controllers are presented within this thesis, a deadbeat energy controller equivalent to an analytically optimised model predictive controller, a $H_\infty$ disturbance rejecting controller with a novel gradient decent optimisation and finally a error feedback controller with a novel alternative error metric. The controllers were tested on a robotic fish simulation platform developed within this project. The simulation platform consisted of the solution of a series of ordinary differential equations for solid body dynamics coupled with a finite element incompressible fluid dynamic simulation of the surrounding flow. results demonstrated the effectiveness of the energy based control approach and illustrate the importance of choice of controller in performance

Recursive parameter identification for second-order K-T equations of marine robot in horizontal motion

890-896In this paper, a dedicated recursive least squares algorithm combining forgetting and weighted factors (FW-RLS) is proposed to identify parameters for the second-order K-T equation of marine robot in horizontal motion. First, the Abkowitz model in horizontal motion is converted into an equivalent second-order K-T equation to reduce the number of identification parameters. Second, a dedicated FW-RLS algorithm based on the equivalent second-order K-T equation is proposed. Finally, the superiority of the FW-RLS algorithm is verified by comparative numerical simulations, which show the FW-RLS algorithm has the online identification capability, higher identification accuracy, and faster convergence rate compared with the traditional batch least squares metho

Recursive parameter identification for second-order K-T equations of marine robot in horizontal motion

In this paper, a dedicated recursive least squares algorithm combining forgetting and weighted factors (FW-RLS) is proposed to identify parameters for the second-order K-T equation of marine robot in horizontal motion. First, the Abkowitz model in horizontal motion is converted into an equivalent second-order K-T equation to reduce the number of identification parameters. Second, a dedicated FW-RLS algorithm based on the equivalent second-order K-T equation is proposed. Finally, the superiority of the FW-RLS algorithm is verified by comparative numerical simulations, which show the FW-RLS algorithm has the online identification capability, higher identification accuracy, and faster convergence rate compared with the traditional batch least squares method

Recursive parameter identification for second-order K-T equations of marine robot in horizontal motion

In this paper, a dedicated recursive least squares algorithm combining forgetting and weighted factors (FW-RLS) is proposed to identify parameters for the second-order K-T equation of marine robot in horizontal motion. First, the Abkowitz model in horizontal motion is converted into an equivalent second-order K-T equation to reduce the number of identification parameters. Second, a dedicated FW-RLS algorithm based on the equivalent second-order K-T equation is proposed. Finally, the superiority of the FW-RLS algorithm is verified by comparative numerical simulations, which show the FW-RLS algorithm has the online identification capability, higher identification accuracy, and faster convergence rate compared with the traditional batch least squares method