Autonomous Surface Craft: prototypes and basic research issues. Massimo Caccia Abstract— An overview of the prototypes of Autonomous Surface Craft (ASC) developed in the last years is presented in this paper, together with a discussion of main research issues, design trends and technological developments. Index Terms— marine robotics, autonomous vehicles. I. I NTRODUCTION This paper will present an overview of the prototypes of autonomous surface craft (ASC) that have been devel- oped, basically for research and military purposes, in the last decade. The fundamental research issues related to the development of ASC and their relationships with unmanned underwater vehicles (UUVs) technology will be discussed. In section II the basic characteristics of the developed, to the author’s knowledge, ASC prototypes will be examined focusing on: • the family of autonomous vessels developed at MIT, consisting of the fishing trawler-like vehicle ARTEMIS, the catamarans ACES (Autonomous Coastal Explo- ration System) and AutoCat [1][2], and the kayak SCOUT (Surface Craft for Oceanographic and Undersea Testing) [3]; • the autonomous vessels developed in Europe such as the Measuring Dolphin of the University of Rostock (Germany) [4], the catamaran Delfim [5] and the boat Caravela [6] developed by the DSOR lab of Lisbon IST- ISR, the autonomous catamarans Charlie of CNR-ISSIA Genova (Italy) [7], and Springer, under development at the University of Plymouth (UK) [8]; • the unmanned surface vessels developed for military purposes such as the testbed of the SSC San Diego [9], the QinetiQ Ltd SWIMS systems [10], and the Israeli Protector USV. Basic research issues will be examined in section III, starting from the definition and identification of practical ASC dy- namics models, going to advanced methodologies for control, guidance and mission control. Fundamental legal issues for large scale civil applications of ASC technology will be introduced too. The different proposed solutions from the point of view of mechanical design, propulsion, power supply and steering systems, will be examined and discussed in section IV. At- tention will be paid to the sinergies between the activities of research and development on UUVs and AUVs on the basis of the experience of MIT AUV lab, where research activities on ASC and AUVs (Odyssey class vehicles) converged at the beginning of the new millennium [11], of IST-ISR DSOR M. Caccia is with CNR-ISSIA, Via De Marini 6, 16149 Genova, Italy , max@ge.issia.cnr.it lab, where the Delfim ASC was conceived to support the operations of the Infante AUV, and of CNR-ISSIA Genova (former CNR-IAN), where a family of ROVs for robotic research and marine science applications [12] had already been developed. In particular, the benefits deriving from a common software infrastructure, control architecture and mission controller will be outlined. II. PROTOTYPES A. ASC for education and civil applications in USA A program for the development of autonomous surface craft has been carried out at MIT Sea Grant College Pro- gram from 1993 to 2000. The goal was to develop a light autonomous surface vessel to be used as a tool for educational purposes, as a precision survey platform and as a communication and navigation link to an AUV. The first developed test platform was ARTEMIS [1], a 1.37 long scale replica of a fishing trawler, originally used for model basin testing, equipped with an electric motor and servo actuated rudder. The vessel, although too small for coastal and open ocean applications, demonstrated the feasibility of automatic heading control and DGPS-based way-point navigation, as well as the possibility of operating autonomously collecting hydrographic data. In particular, the installation of a radio modem allowed human supervisory control of the ASC. In order to increase the ASC size, endurance and sea keeping performances, a kayak platform was considered, converting a 3m long kayak hull to an ASC and testing it in the Charles River. The resulting design was robust enough for severe sea states, but was not stable enough in roll for the collection of bathymetric data [2]. Thus, a catamaran shape, able to provide enhanced roll stability, greater payload, and redun- dancy in hull floatation, was selected for ACES (Autonomous Coastal exploration System, developed in 1996-97 [1]. The vessel, constituted by two commercial hulls linked by a main mechanical steel structure, provided by a quick release mechanism for facilitating transport, was equipped with a 3.3 Hp gasoline engine for propulsion, batteries for electrical power for computers, navigation and control system, and a generator for battery recharging. Engine throttle and rudder were actuated by stepper motors. Performances achieved in radio controlled tests were satisfactory, except for the tendency to pitch up at high speed and lack of feedback sensor in the rudder system. Nevertheless developing a reliable starter and gear actuator for the gasoline outboard motor was considered too complex for reliable autonomous operations [2]. A modified version of the catamaran, characterised by a