Holger Korte

Application of NaLA, a fishing net configuration and loading analysis system, to bottom gill nets

The net-shape and loading analysis system (NaLA) was developed to determine fishing net configuration and load in a previous study. The system has since been applied to general gill nets and aquaculture nets, and its validity has been proven through model experiments in tanks. In this study, the system was applied to estimate the dynamic behavior of a bottom gill net for walleye pollock, to test the system’s applicability of the system to gear operations in the field. To obtain in situ data, four bottom gill net operations were performed in February 2004 off the coast of Sawara, Hokkaido, Japan. During operations, vertical displacements of the bottom gill net’s float and sinker lines were measured as representative values of gear behavior, and ocean current direction, and speed at the gear position were observed simultaneously. Then, bottom gill net behavior was simulated using NaLA, incorporating observed environmental conditions and gear specifications. The resulting calculated behavior was compared to measured behavior in terms of the relationship between net height and environmental or setting conditions. Agreement between the calculated and measured net behavior was found. Thus, it is believe that our NaLA calculation model has the potential to simulate the dynamic behavior of bottom gill nets in situ.

AdaNav – a modular control and prototyping concept for vessels with variable gear configurations

Abstract According to their tasks and relations, specialized vessels are equipped with modern steering devices like podded drives or thrusters. Such modern steering concepts substantially increase the manoeuvring capability of the vessels. However, mates are not able to handle those gears efficiently, because the relations between action and reaction are far too complex. Automation is needed to support the steering team. The industrial production of wheelhouse systems within the large spectrum of types of manoeuvring gears and their location on vessel hulls is still a hard problem. Finally, each adaptation for the navigation and track guidance system looks like an individual system production. For an easier prototyping and implementation of different steering concepts in navigation and track guidance systems for vessels, a modular concept has been applied by the University of Rostock, Center for Marine Information Systems (CeMarIS). Supported by the Federal Ministry of Economics and Technology, in the joint project “Adaptive Navigation System for Ships” the control of each device was implemented into a new automation strategy for the guidance process to realize an optimal manoeuvrability in motion. At the end of the project, final tests in the Maritime Simulation Center in Warnemunde (MSCW) have demonstrated the efficiency of the developed modular control concepts.

Parametric Design of Optimal Digital Controllers on the Basis of Global Optimization Algorithms

Abstract The problem of optimal digital controller design is considered for sampled-data systems under typical sector-type restrictions imposed on location of the closed loop poles. The set of admissible characteristic polynomials having a fixed degree is parameterized in terms of a real vector with elements in [0,1]. This idea makes it possible to use a two-level optimization procedure based on global optimization algorithms, which is sometimes more attractive than a local search.

Track Control of a Towed Underwater Sensor Carrier

Abstract The current paper presents a mathematical model allowing the description of the motion of marine towing systems and demonstrates it with the example of a towed underwater sensor carrier. This model is to prove that the principle of distinguishing the total motion of water craft into the three partial, hardly interactive processes of forward, depth and horizontal motion is to be applied to this towing system. Having noticed a lack of proper descriptions of horizontal track control of towed sensor carriers in scientific literature, we will outline the design of the track controller with the help of a classical design method.

Automatic Course Control of Dragging/Towing Vessels

Abstract PID course controllers for common ships with yaw-dynamic stability can be carried out designed with the help of an analysis of the pole-zero-configuration. All poles and zeros are real and negative or zero. In this relation it is rather simple to find out the quantities of the controller parameters by means of the characteristic pole pair. Towing vessels have a more complicated yawing behaviour. They tend to oscillate in their yawing motion. The present paper gives a survey of the change of pole and zero configurations in the complex plane as a consequence of the impact of the towing force. It shows the demands to a controller of towing or dragging ships.

Precise Maneuver Planning for Berth-to-Berth Navigation of Modern Ships

Abstract Modern steering devices for ships lead to an improved control capability and allow independent actions without tugs by mates in use with modern electronics. Within the project AdaNav developed MIMO controller enables DP equivalent functions for ships being able to traverse. The following contribution shows the inclusion of such modern maneuvering quality as computer based assistance system into electronic ship guidance systems like ECDIS. To guarantee fully responsibility of mates the concept bases on introduced planning practice implementing additional waypoints and attributes.

Using a Netting Geometry Simulator to Develop Smart Fishing and Smart Gear

As fishing gear consists mainly of netting and rope, and lacks a definite geometry of its own, external forces acting on the netting and other rigging determine its geometry. The underwater geometries and loads of most fishing gear cannot be grasped in detail. However, the versatile simulation technique that we have developed for fishing gear allows us to understand the physical properties of dynamic fishing gear underwater. This will allow companies to design optimal fishing gear, based on scientific research and avoiding empirical procedures. In addition, it will allow fishermen to evaluate and improve their standard operating techniques, and to develop optimal techniques. The calculation model assumes that the net consists of lumped point masses that are interconnected by mass-less springs. The equations of motion of these point masses can be expressed in a local coordinate system, which simplifies the treatment of the hydrodynamic forces acting on each mass using the inertia transformation algorithm. The computer simulation not only estimates the overall shape of fishing gear but also its mesh geometry, the tension on the netting, and the impact force on the sea bed. This will allow the development of smart gear and smart fishing. Users will be able to develop and operate fishing and aquaculture gear based on a sound understanding of the physical parameters, and design gear that is economical, efficient to operate, and less harmful to the ecosystem. In this paper, we introduce the net geometry simulation system (NaLA) and discuss how to apply the system to developing smart gear and smart fishing.Copyright

INFLUENCE OF SHIP MOTION NONLINEARITIES ON THE COURSE CONTROLLER DESIGN

Abstract Since a ship yard usually provides insufficient data for developing a ship control system, the course and track controller design is based upon a Nomoto model determined with a Clarke estimation of hydrodynamic derivatives. Several ships examined show a poor system performance with a course control derived from these models besides parameter identification problems of adaptive control concepts. Hence, the steering quality of the Mariner class is discussed and linear model parameters are obtained by an interval approximation of Dieudonnes spiral curve in the working range of the rudder. This approach leads to a better controlled nonlinear process.

ASFOSS - Current information system using AIS 1

Abstract The manoeuvring freedom is reduced by use of larger and larger vessels in estuarine waters. Modem steering and propulsion devices only compensate in a conditional manner this disadvantage. Especially unknown adverse conditions of winds and currents give an only hardly solvable task to ship officers. A reasonable support in the decision making can give the appropriation of externally measured surrounding values on board. The developed system ASFOSS transmit the measured data via AIS from the estuary basis to the ship. On board of the ship the data will be presented at an integrated display device like ECDIS, conning or radar.