http://www.ifac-papersonline.net/ en Copyright 07:59 PM Wednesday 22, 2012 IFAC-PapersOnline http://www.ifacpapersonline.com 07:59 PM Wednesday 22, 2012 07:59 PM Wednesday 22, 2012 ET webmaster@ifac-papersonline.net webmaster@ifac-papersonline.net http://www.ifac-papersonline.net/Detailed/44903.html 04:00 PM Wednesday 31, 1969 This paper addresses a filtering problem that arises in the design of dynamic positioning systems for ships subjected to the influence of sea waves. Its key contribution is the use of a multiple model adaptive wave filter that relies on measurements of the ship’s position and heading only. To this effect, a bank of Kalman filters is designed for a finite number of parameter values, each corresponding to a different peak frequency of the assumed wave spectrum model. Tools from multiple model adaptive estimation (MMAE) theory are exploited to blend the information provided by the different observers, yielding position and velocity estimates of the ship. These estimates are then be used in an appropriately designed feedback control law. Simulations illustrate the efficacy of the MMAE techniques proposed. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44955.html 04:00 PM Wednesday 31, 1969 The article compares the performance of Feature Correlation and Phase Correlation algorithms for the motion estimation of an underwater vehicle. While feature correlation relies on the extraction and matching of features templates, Phase Correlation is a featureless approach, relying instead on the overall properties of the image. Three versions of Feature Correlation algorithm and two different implementations of the Phase Correlation algorithm are compared, on data collected by the HCMR Thetis submersible during the Nautilos Project in 2004; since the mission focused on different research priorities, the recordings are suboptimal regarding sea bottom mosaicking, featuring motion blurs, roll sweeps, geometric distortions and optical axis non-perpendicular to the bottom. The results show the effectiveness of feature correlation in dealing with blurred images, while in terms of computational time, both implementations of the phase correlation algorithm outperform any of the feature correlation algorithms by a large margin. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44979.html 04:00 PM Wednesday 31, 1969 The purpose of this work is the development of a guidance and control system for the vehicle-following task, extendable to rigid formation maintenance, in the case of more than two vehicle within the framework. The novelty of a guidance system development based on a sliding mode control approach is described and validated by a number of experimental tests carried out with two Unmanned Surface Vehicles (USVs) during at-sea trials, and simulative tests extended to vehicle formation control. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44937.html 04:00 PM Wednesday 31, 1969 This paper considers the problem of speed control for vehicles maneuvering along planar paths. Maneuverability constraints are taken into account when determining a purposefully commanded forward speed which prevents a given vehicle from derailing when traversing a given path. A lookahead system is first developed to collect relevant path curvature information ahead of the vehicle. This system is able to maintain a constant along-path distance in front of the current vehicle location, even for paths that are not arc-length parameterized. A speed assignment algorithm is subsequently developed which employs both the lookahead system information and known vehicle maneuverability constraints to yield feasible speed commands. Finally, the behavior of the proposed speed control system is illustrated through simulations which also demonstrate its improved performance compared to using constant speed. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44989.html 04:00 PM Wednesday 31, 1969 Wave energy converters (WECs) based on oscillating bodies or oscillating water columns would earn huge benefits from a time-domain control on a wave by wave basis. Such a control would allow efficient energy extraction over a wider range of frequencies than what could possibly be achieved when no real-time control is adopted, thus increasing the economical attractiveness of the WECs. Almost every control strategy that showed some potential, however, suffers from the problem that future knowledge of the incident wave elevation, or wave excitation force, is required. In this paper a general control framework for oscillating WECs is presented and a methodology to understand and quantify the wave excitation force prediction requirements, along with the achievable prediction accuracy, is discussed. The two features are compared against each other and linked to the dynamic characteristics of a device. Along with the qualitative discussion, the methodology is applied to some heaving cylinders when reactive control and linear passive control are applied, under different sea conditions. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44983.html 04:00 PM Wednesday 31, 1969 In this paper we present our work and results in the framework of obstacle avoiding for marine vehicle teams by means of trajectory planning. Based on a team of maritime systems, such as Autonomous Underwater Vehicles (AUVs) or Autonomous Surface Vehicles (ASVs), which are intended to perform a preplanned mission in a given formation topology, methods for trajectory planning are investigated which guarantee for both obstacle-free paths and formation preservation. The proposed solution contains advanced graph search and trajectory smoothing to generate executable path for the vehicles. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44947.html 04:00 PM Wednesday 31, 1969 The progress of the standardising process in Integrated Navigation Systems and Integrated Bridge Systems established by the IMO enhanced the harmonising of the electronically devices. The information overflow reduction is one of the expected results. The more of installed bridge sub systems allows the displaying of additional navigational information by the HMI. In consequence the process adequate information selection is an essential and necessary task in ship bridge automation. The following paper describes a data fusion oriented approach for information handling on integrated ship bridge systems using agents. A JDL data fusion model was used for the ship navigational data handling. First experiments supported by data from a Voyage Data Recorder, extern knowledge data bases and various defined information layers will be discussed. The goal of the investigation was the information relevance evaluation in the navigational process current circumstances. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44913.html 04:00 PM Wednesday 31, 1969 Underwater vehicles present difficult control-system design problems due to their nonlinear dynamics, uncertain models, and the presence of disturbances that are difficult to measure or estimate. In this paper, one approach has been carried out for controlling voltage supplied to two horizontal propellers of an underwater vehicle with the objective of controlling the following variables, the yaw angle, the yaw rate and the sway speed. The design is based on the recursive procedure of the multivariable backstepping. The designed algorithm jointly with a simple optimization procedure, that minimizes the energy consumption, is capable of handling these problems with effectiveness. This method, as opposite to the input-feedback linearization, deals directly with nonlinearities and is highly robust to imprecise models. Simulation results are reported to demonstrate the effectiveness of the proposed approaches with an improvement on the precision manoeuvring. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44949.html 04:00 PM Wednesday 31, 1969 Based on the positional data of other inland vessels which is available through the fusion of radar object tracking and AIS (Automatic Identification System) a model-based prediction of their kinematic states is presented. Information about the river shape is fed into the prediction model according to the type of vessel and its navigational situation. Together with the future states of our own vessel, which are known because it is automatically steared along a guiding line, ranges of encounter are calculated. Furthermore, a path planning algorithm based on nonlinear dynamic optimization is presented that is capable of calculating collision-free paths in real-time that account for the vessel's constrained dynamics. Practical results of the discussed automatic collision detection and avoidance module as part of an integrated navigation system for inland vessels are shown concluding the contribution. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44889.html 04:00 PM Wednesday 31, 1969 Prediction tools are very helpful and already in use on ships for a long time, beginning with trail modes in ARPA radars up to curved headline overlay in ECDIS. However, up to now the simplification of these predictions allows restricted use only based either on estimated future courses & tracks or on the simple integration of the current ship motion not including the immediate response on changes of rudder and engine. New concepts for the use of fast time simulation on board were developed at Maritime Simulation Centre Warnemunde MSCW in research projects funded by the German Federal Ministry of Education and Research together with industrial partners. A prediction tool was developed to simulate the ships motion with complex dynamic models in fast time and to display the ships track immediately for the intended or actual rudder or engine manoeuvre. These simulations allow for an unmatched monitoring of Shiphandling processes to follow the underlying manoeuvring concept: - During the manoeuvring process the manoeuvres can be constantly displayed together with the actual ship motion and the predicted future track. This future track is based on input from the ships actual sensors i.e. via the Voyage Data Recorder and furthermore from diagnosis tools analysing the status of the manoeuvring facilities and providing information in case of failures, e.g. reduced engine power or larger rudder response time due to malfunctions of the equipment. - The standard manoeuvres for collision avoidance using the maximum manoeuvring capabilities for e.g. stopping and turning can be updated by fast time simulation taking into consideration the current ships and environmental conditions to be used in collision avoidance displays. Within this paper investigations into the feasibility and user acceptance of the new concept and layout of navigation display will be introduced and selected results of simulation studies will be discussed testing the influence on manoeuvre performance dependent on different kind of prediction functions. This Dynamic Prediction Display is intended be used on board of real ships but is also a effective tool for training in ship handling simulators because the trainee can immediately see the result of the http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44857.html 04:00 PM Wednesday 31, 1969 http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44865.html 04:00 PM Wednesday 31, 1969 The pursuit equations in two-dimensional space are examined, and then parametrised in terms of relative velocity and initial range. Several inferences about the behaviour of these equations are drawn. The burst speed of several fish species are tabulated, along with several types of Autonomous Underwater Vehicle. An example pursuit calculation is described. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44953.html 04:00 PM Wednesday 31, 1969 This paper focuses on a study of the sequential action execution module for a collision avoidance system in ocean navigation. The overall decision-action process of collision avoidance consists on a Fuzzy logic based parallel decision making module and those decisions are formulated into collision avoidance actions by a Bayesian network based sequential action execution module. The presented collision avoidance system is capable of making multiple sequential actions to avoid complicated collision situations involving multiple vessels in ocean navigation while still respecting the COLREGs rules and regulations. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44861.html 04:00 PM Wednesday 31, 1969 Certification of all type of underwater vehicles and working machines is performed to increase reliability and safety of single components and complete systems. Base for certification are the rules for Underwater Technology developed by Germanischer Lloyd. Certification of components and machines are usually performed in scheduled phases, starting with examination of drawings and documents, followed by surveillance of construction and finalized by functional testing and several trials witnessed by GL’s surveyors. Technical reliability and safety can be achieved by competent maintenance and periodical surveys. Certification can be extended to systems, where certified component’s interaction, often of high complexity, has to be considered in particular. Here again, reliability and safety is gained and maintained by repeated testing of components and the complete system during operational life. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44987.html 04:00 PM Wednesday 31, 1969 This paper concerns the interplay between the physical geometry of a wave energy converter (WEC) and the control strategy adopted for the converter, with the ultimate aim of optimising the energy output of the device. An energy-based performance function is employed and we attempt to perform numerical optimisation of a heaving buoy employing a latching control strategy. We allow both draught and radius of the axisymmetric buoy to be adjusted using a numerical optimisation. A linear time-domain hydrodynamic program is used in order to simulate the device motion, while the optimization problem is solved by means of a simplex method. Results show the difference in the frequency response of an optimal buoy for a particular sea-state designed with and without knowledge of the control system. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44887.html 04:00 PM Wednesday 31, 1969 This paper presents the application of a statistical method for model structure selection of lift-drag and viscous damping components in ship manoeuvring models. The damping model is posed as a family of linear stochastic models, which is postulated based on previous work in the literature. Then a nested test of hypothesis problem is considered. The testing reduces to a recursive comparison of two competing models, for which optimal tests in the Neyman sense exist. The method yields a preferred model structure and its initial parameter estimates. Alternatively, the method can give a reduced set of likely models. Using simulated data we study how the selection method performs when there is both uncorrelated and correlated noise in the measurements. The first case is related to instrumentation noise, whereas the second case is related to spurious wave-induced motion often present during sea trials. We then consider the model structure selection of a modern high-speed trimaran ferry from full scale trial data. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44893.html 04:00 PM Wednesday 31, 1969 The paper describes the first steps of the development of an autonomous surface ship for sea demining. The objective is to substitute humans in a dangerous humanitarian task. The research has three main phases. The first one is to develop at laboratory scale the infrastructure for the final system. The second is devoted to medium scale tests in open air scenarios. The third phase is real scale operation. This paper refers to the first phase, in which a ‘universal control unit’ is being developed for autonomous navigation control. Software modules are also under development for on-board control with self-localization, and for area scanning trajectory generation and then tracking. The vehicle uses a towed fish. Both the towing cable and the fish generate electric and magnetic fields, to cause mine detonation by field influence. This study is made both with simulations and with scale experiments. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44897.html 04:00 PM Wednesday 31, 1969 This work introduces the Pirajuba vehicle, an autonomous underwater vehicle that has been developed at the University of Sao Paulo. The paper describes its main systems, emphasizing hardware and software control architectures. The embedded system is low cost and based on off-the-shelf components, and on free and largely known software tools, like C language, and GNU compiler. Results of preliminary tests in a swimming pool are also presented, demonstrating the real-time operation of the AUV. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44935.html 04:00 PM Wednesday 31, 1969 The methods presented in this paper were designed to improve the performance of a control scheme for the automatic track-keeping of inland vessels. The performance of this control scheme heavily depends on the underlying models as it employs model inversion for the calculation of feedforward input signals and reference trajectories for feedback control. However, vessels on rivers are subject to model uncertainties as well as disturbances, such as cross currents or wind. Therefore an estimation scheme was designed for the estimation of disturbances and their integration into the model inversion procedure. Simulation results show the usefulness of the presented methods for various disturbances and model uncertainties. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44871.html 04:00 PM Wednesday 31, 1969 Parametric roll is a dangerous resonance phenomenon for ships caused by time-varying restoring forces. The resulting large roll oscillations may endanger the ship’s safety and possibly lead to capsizing. The susceptibility of container ships to parametric roll resonance has caused considerable research activities in the development of control and operational strategies to avoid large roll motions. In this paper, a novel approach to the active control of ships experiencing parametric roll resonance is presented. The methodology of extremum seeking control is used to iteratively determine the set-point for the wave encounter frequency in order to avoid the conditions for the onset and build-up of parametric roll. The desired trajectory for the wave encounter frequency is tracked by mapping it to the ship speed and heading angle by a control allocation, formulated as a constrained optimization problem, and consequently by implementing speed and heading controllers. The combined variation of the speed and heading angle is shown to efficiently drive the ship out of the parametric roll resonance region. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44981.html 04:00 PM Wednesday 31, 1969 A fleet of unmanned marine vehicles moving together in a prescribed pattern forms a robotic system for cooperative tasks. The problem is to control several marine vehicles such that, after transients, they form a required formation and move along a desired trajectory. The capability to accomplish the mission even in case of fault, is a fundamental requirement for these kind of vehicles. A completely decentralized nonlinear predictive control integrated with a fault tolerant strategy is here proposed for allowing safe cooperation. Based both on the local information and the acquired one through a LAN, each marine vehicle selects the desired formation to keep and plans its future actions. The proposed solution can be applied to different classes of unmanned marine vehicles. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44951.html 04:00 PM Wednesday 31, 1969 This paper focuses on a Fuzzy-logic based parallel decision formulation that aims to improve the safety of marine vessels by avoiding collision situations in ocean navigation. The collision avoidance of the Target vessel with respect to the vessel domain of the Own vessel has been analyzed and input and output Fuzzy Membership Functions are derived in this study. The If-Then rule based decision making process and the integrated novel Fuzzy Inference System are formulated and implemented on MATLAB software platform. Simulations are presented regarding several collision avoidance situations. Furthermore, the decision rules are formulated in accordance with the International Maritime Organization Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) and expert knowledge in navigation, to avoid conflict that might occur during the ocean navigation. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44943.html 04:00 PM Wednesday 31, 1969 This paper presents the main features of a combined diesel or gas ship propulsion system and a control strategy to be applied to its velocity channel. Operating limits, saturations and parameter-dependent delays make the system dynamic behavior highly nonlinear. The main objective is to control the ship velocity by using identification techniques and a combination of Smith predictor with a gain scheduling control method. The aim is to meet the specified time-domain performance with disturbance rejection over the entire operating range. Numerical results clearly show the advantages of using the proposed control technique. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44869.html 04:00 PM Wednesday 31, 1969 This paper describes a procedure that utilizes a series of o®-line algorithms for pre-planning a two-dimensional path for an AUV in a cluttered waterspace. The trajectory is planned as a clothoidal spline or interpolation based on the work of Shin and Singh (1990) between a sequence of objective points. The former are calculated by a method proposed by the authors, based on the traversal of vertices of apriori known obstacles modeled on a concise set of geometrical primitives. The objective points are first sequenced and then extraneous ones are pruned. Finally, the technique of Shin and Singh (1990) and numerical approximation of clothoid parameters is applied to calculating the final path through the obstacle-strewn waterspace. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/44941.html 04:00 PM Wednesday 31, 1969 The paper investigates the digital control of continuous-time processes, where continuous stochastic disturbances act directly on the continuous part of the system, which is typical for motion control of marine vehicles. Instead of zero-order hold, which is normally used, the digital computer and the continuous process are connected by hold elements of arbitrary order. On basis of the parametric transfer function concept, the paper presents a rigorous description of this class of sampled-data system. This description allows to find optimal controllers by using polynomial and numerical methods. For the practically relevant problem, where the disturbances are only known to belong to a certain class, a minimax solution is presented, which guarantees a certain performance for any admissible disturbances. The effect of higher-order hold is briefly discussed on basis of an examples. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif