Gabriele Bruzzone

Basic navigation, guidance and control of an Unmanned Surface Vehicle

This paper discusses the navigation, guidance and control (NGC) system of an Unmanned Surface Vehicle (USV) through extended at sea trials carried out with the prototype autonomous catamaran Charlie. In particular, experiments demonstrate the effectiveness, both for precision and power consumption, of extended Kalman filter and simple PID guidance and control laws to perform basic control tasks such as auto-heading, auto-speed and straight line following with a USV equipped only with GPS and compass.

Sampling sea surfaces with SESAMO: an autonomous craft for the study of sea-air interactions

This paper presents the system design, sea trials and Antartic exploitation of the SESAMO platform. The SESAMO (sea surface autonomous modular unit) prototype robot was especially designed to collect data and samples for the study of the sea-air interface. At sea, operations showed that a relatively simple robot could satisfactorily work in a natural, outdoor environment, dramatically facilitating the job of the human operator. To achieve high quality sampling of the surface microlayer, however, requires a large amount of time, leading to significant demands on logistics resources, mainly in terms of operating time of the support vessel.

Variable-configuration UUVs for marine science applications

In this article, after a brief overview of trends in underwater unmanned vehicle (UUV) design and applications, results in developing an automatic guidance and control system for Romeo are presented. Attention is focused on the design, development, and testing in the operating conditions of a bottom and ice-canopy following system and on the development of methodologies for the at-field identification of the vehicle dynamics in order to guarantee high motion-control performance, even in the presence of variations in the vehicle configuration. In particular, the system performance in the proximity of the coast, where there is only a very shallow column of free water between the ice-pack and the sea-bed, is discussed.

Fast in-field identification of unmanned marine vehicles

To design high-level control structures efficiently, reasonable mathematical model parameters of the vessel have to be known. Because sensors and equipment mounted onboard marine vessels can change during a mission, it is important to have an identification procedure that will be easily implementable and time preserving and result in model parameters accurate enough to perform controller design. This paper introduces one such method, which is based on self-oscillations (IS-O). The described methodology can be used to identify single-degree-of-freedom nonlinear model parameters of underwater and surface marine vessels. Extensive experiments have been carried out on the VideoRay remotely operated vehicle and Charlie unmanned surface vehicle to prove that the method gives consistent results. A comparison with the least-squares identification and thorough validation tests have been performed, proving the quality of the obtained parameters. The proposed method can also be used to make conclusions on the model that describes the dynamics of the vessel. The paper also includes results of autopilot design in which the controllers are tuned according to the proposed method based on self-oscillations, proving the applicability of the proposed method.

A Practical Approach to Modeling and Identification of Small Autonomous Surface Craft

This paper discusses the theoretical model of an autonomous surface craft (ASC) with respect to the performance of basic sensors usually available onboard small and relatively low- cost vessels. The aim is to define a practical model and the corresponding identification procedure for simulation, guidance, and control of this class of vehicles. The work is supported by the extended at-sea trials carried out with the autonomous catamaran prototype Charlie2005.

Integral Line-of-Sight Guidance and Control of Underactuated Marine Vehicles: Theory, Simulations, and Experiments

This paper presents an extensive analysis of the integral line-of-sight (ILOS) guidance method for path-following tasks of underactuated marine vehicles, operating on and below the sea surface. It is shown that due to the embedded integral action, the guidance law makes the vessels follow straight lines by compensating for the drift effect of environmental disturbances, such as currents, wind, and waves. The ILOS guidance is first applied to a 2-D model of surface vessels that includes the underactauted sway dynamics of the vehicle as well as disturbances in the form of constant irrotational ocean currents and constant dynamic, attitude dependent, and forces. The actuated dynamics are not considered at this point. A Lyapunov closed-loop analysis yields explicit bounds on the guidance law gains to guarantee uniform global asymptotic stability (UGAS) and uniform local exponential stability (ULES). The complete kinematic and dynamic closed-loop system of the 3-D ILOS guidance law is analyzed in the following and hence extending the analysis to underactuated autonomous underwater vehicles (AUVs) for the 3-D straight-line path-following applications in the presence of constant irrotational ocean currents. The actuated surge, pitch, and yaw dynamics are included in the analysis where the closed-loop system forms a cascade, and the properties of UGAS and ULES are shown. The 3-D ILOS control system is a generalization of the 2-D ILOS guidance. Finally, results from simulations and experiments are presented to validate and illustrate the theoretical results, where the 2-D ILOS guidance is applied to the cooperative autonomous robotics towing system vehicle and light AUV.

Guidance of Unmanned Surface Vehicles: Experiments in Vehicle Following

Virtual target-based path-following techniques are extended to execute the task of vehicle following in the case of unmanned surface vehicles (USVs). Indeed, vehicle following is reduced to the problem of tracking a virtual target moving at a desired range from a master vessel, while separating the spatial and temporal constraints, giving priority to the former one. The proposed approach is validated experimentally in a harbor area with the help of the prototype USVs ALANIS and Charlie, developed by Consiglio Nazionale delle Ricerche-Istituto di Studi sui Sistemi Intelligenti per lAutomazione (CNR-ISSIA).

Line following guidance control: Application to the Charlie unmanned surface vehicle

A line following guidance solution for underactuated marine systems is presented. The approach differs from other ones known in the literature in the definition of the error variables to be stabilized to zero. The proposed guidance technique has been applied to the Charlie USV (Unmanned Surface Vehicle), developed by CNR-ISSIA Autonomous robotic systems and control group, and experimental results are presented.

Marine vehicles' line following controller tuning through self-oscillation experiments

This paper demonstrates the use of self-oscillation identification experiments for tuning line following controllers for marine vehicles. Two approaches are described: first, when the controller output is yaw rate and second when controller output is reference heading. In the first case, low level controller is yaw rate while in the second it is heading controller. The identification by use of self-oscillations (IS-O) has been applied to identify the steering equation (for the case of the first controller) and it was used to identify the heading closed loop (for the case of the second controller). The second controller has been tested on different inner loop structures in order to prove the functionality of the method. The IS-O method has been chosen because of its simplicity and applicability in the field (effects of external disturbances are minimized). The methodology was applied to autonomous catamaran Charlie. The results are presented in the paper and demonstrate that the proposed method for identification as well as the developed algorithms give satisfactory performance. All algorithms and results presented here are a result of a joint work of researchers at the Consiglio Nazionale delle Ricerche, Genova and the University of Zagreb.

Guidance of unmanned underwater vehicles: experimental results

This paper addresses the problem of guidance of unmanned underwater vehicles (UUVs). In the framework of a two layered hierarchical architecture decoupling the system dynamics and kinematics, two guidance laws for approaching a target with the desired orientation and following an environmental feature have been designed with Lyapunov-based techniques. Suitable acoustic-based estimators of the corresponding operational variables have been designed and integrated with the guidance and control system. Experimental results of pool trials of a prototype UUV executing free-space maneuvering and wall-following tasks are reported and discussed.