1,721,831 research outputs found
Parameter Identification of a Model Scale Ship Drive Train
No full textSimulation models of the ship propulsion system play an increasingly important role, for instance in controller design and condition monitoring. However, creation of such simulation models requires significant time and effort. In this paper, the application of deterministic identification techniques on a DC-electric ship drive train is explored as an alternative for data-driven identification techniques that require extensive measured data sets collected over long periods of ship operation. First, a nonlinear and a linear simulation model that represent the dynamic behavior of the propulsion plant are developed, and the main parameters to be identified are defined. Then, a set of experiments on a model scale boat in the bollard pull condition are conducted using an ad hoc experimental setup and data acquisition system. Subsequently, various types of identification techniques are applied, aiming to determine the unknown model parameters. Eventually, a comparison is made between experimental and simulated results, using the different sets of the estimated parameters. The value of the demonstrated approaches lies in the fast determination of unknown system parameters. These parameters can be used in simulation models, which in turn can be used for various purposes such as system controller development and tuning. Furthermore, periodic determination of system parameters can support condition monitoring to detect faults or degradation of the system. The latter point directly deals with the condition-based maintenance issue; in fact, monitoring the propulsion plant parameters over time could allow for better management (and timing) of maintenance. Although the developed ideas are far from ready to be used on the full-scale, the authors believe that the methodologies are promising enough to be developed further towards a full-scale application.Ship Design, Production and Operation
Unmanned Surface Vehicle Chase a Moving Target Remotely Controlled
No full textShortly, it is expected to have hybrid marine scenarios in which manned and unmanned vehicles navigate in the same environment. The study of the interactions between autonomous and human-controlled vessels becomes essential to improve and make the control systems more resilient. For such a reason, this paper shows a simulation architecture to test the effectiveness of a guidance law in a target tracking scenario for surface navigation. The guidance logic is based on the idea of reaching and following a target when the future motion is unknown and only the instantaneous position and speed are available. The adopted guidance law can handle both the chasing and the following phases minimising the time needed to reach the chased vehicles. The actuators’ set-point generation is ensured by speed and heading controls, properly developed for this aim. A cyber-physical testing scenario has been developed and can run in real-time. Both target and interceptor dynamics are based on detailed mathematical models in which the parameters have been validated by dedicated tank experiments. An operator remotely controls the target through a human-machine interface and tries to leave behind the autonomously controlled interceptor to make the simulation’s results more realistic. At the end of the paper, the results are reported for investigation and the conclusions are drawn
CHEMICAL ARTS AND RELIGION IN ANTIQUITY. AN INTRODUCTION
Full text linkIntroduction to the special issue dedicated to chemical arts and religion in Antiquit
Interaction between COLREG-compliant collision avoidance systems in a multiple MASS scenario
No full textThe transportation systems are heading towards increasing autonomy in all domains, and the maritime field makes no exception. The International Maritime Organization has been working on releasing a regulatory framework for Maritime Autonomous Surface Ships (MASS) to keep pace with the technological developments in the field. Autonomous shipping forces the researcher and the designers to face a wide range of scientific challenges, such as
navigation decision support systems, collision avoidance algorithms, path planning, navigation and control, sensor data processing and fusion, remote control, and communication, with the final intent of achieving a fully integrated and autonomous worldwide maritime transportation system, where a human-less collaborative conflict resolution could potentially retire the COLREGs. However, the maritime sector will first face a transition period where traditional
ships will share the seas and interact with heterogeneous MASS with various autonomous capabilities featuring different and probably incompatible communication protocols. In such a scenario, the COLREGs will still play a primary role in helping the collision avoidance systems resolve conflicts and limiting the degrees of freedom. This paper aims to study the interaction among multiple vessels with autonomous collision avoidance capabilities operating in a close
navigation scenario. The ships operate according to a COLREG-compliant collision avoidance algorithm. The paper relies on numerical simulation to systematically investigate different scenarios in which autonomous vessels operate and interact in the presence of fixed obstacles. Results are presented and critically discussed
A collision avoidance algorithm for ship guidance applications
No full textThe paper presents a collision avoidance algorithm for ship open sea navigation, based on an ad hoc modified version of the Rapidly-exploring Random Tree (RRT*) algorithm. The proposed approach is designed to act as the high level layer of the navigation control structure for an autonomous ship. Collision and grounding still represent the primary source of sea accidents, thus an automatic system able to detect static and moving obstacles and plan an evasive route could significantly improve safety during navigation, especially in crowded areas. Focusing on the maritime field, a review of the scientific literature dealing with collision avoidance is presented, showing potential benefits and weaknesses of the different approaches. Among the several methods, details about the RRT and RRT* algorithms are given. The ship path planning problem is introduced and discussed, formulating suitable cost functions and taking into account both topological and kinematic constraints. The algorithm is able to manage multiple moving obstacles with variable speed and course. Eventually, a time-domain ship simulator is used to test the effectiveness of the proposed algorithm over a number of realistic operation scenarios. The obtained results are presented and critically discussed
A design framework for combined marine propulsion control systems: From conceptualisation to sea trials validation
No full textThe ship's dynamic performance (acceleration, turning ability, crash stop) strongly depends on both the propulsion system and its control. The steady-state performance analysis of propulsion systems has shown that onboard energy usage benefits from the employment of simulation techniques. Besides, these techniques provide significant advantages in designing the control logic of sophisticated and complex systems. The present work summarizes the research activities conducted to develop suitable simulation framework for the propulsion systems of naval vessels. Theoretical and mathematical models have thus been developed in this paper to simulate the propulsion of ships. Model-scale experiments and full-scale trials have been used to increase the fidelity of the models. The research outcome is a conceptual framework and a fully validated parametric software representing the vessel's dynamic behaviour and propulsion system in steady-state and abrupt manoeuvres. Thanks to this simulation framework, the propulsion control system could be designed, validated, and calibrated before its installation on board, reducing the commissioning time and minimising the propulsion control system's onboard calibration during the acceptance sea trials
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