J.M. Díaz

Fast Ferry Vertical Accelerations Reduction with Active Flaps and T-Foil

Abstract The research deals with the design and use of actuators to improve the seakeeping performances of a fast ferry. The interest of the research is now restricted to heaving and pitching motions, with heading sea. The ship has active control surfaces (flaps and T-foil). The paper presents a control-oriented model of these actuators, in SIMULINK. This model can be easily coupled with a SIMULINK model of the ship, furnishing a simulation environment for control studies. Using this facility, a study of control alternatives (moving the actuators) has been started. We include in the paper first results with conventional PID control, which are useful as reference for comparison purposes.

Identification of the Vertical Plane Motion Model of a High Speed Craft by Model Testing in Irregular Waves

Abstract Experiments in towing tanks are concerned with the determination of the motion transfer functions, which are obtained by testing in irregular waves. For this purpose a model of pitch and heave motions has been developed, and the identified models of the vertical plane motions of a high-speed craft are showed. Linear models are obtained for different sea states and ship speeds. A general low order model is obtained by pole-zero cancellation. So, a full model may be considered for simulation and verification, and a low order model for design. From the lowest order models, a state space model is obtained.

Improving the comfort of a fast ferry

A study was conducted to determine the effectiveness of using controlled flaps and a T-foil to smoothen a ships vertical motion while navigating in head seas. The study comprised two steps: to develop a tool for control design in the form of a computer-based simulation and to use this tool to develop satisfactory controllers. The simulation was based on mathematical models of the ship, the actuators, the waves and the seasickness effect. Since the actuators have limited action, there is a limited margin for improvement based on more sophisticated control strategies. Possible improvements of motion sickness incidence (MSI) are linked to a control strategy that exploits better synchronization with incident waves.

Experimental Study of Controlled Flaps and T-Foil for Comfort Improvement of a Fast Ferry

Abstract Fast ships can suffer important negative effects from vertical accelerations. The sea-sickness of passengers is related, in a cumulative form, to these accelerations. Our research deals with the alleviation of vertical accelerations, using appendages that can move under control to counteract each incident wave: a T-foil near the bow and transom flaps. After a long modelling work, involving experiments in a towing tank institution, the conditions for the study of control design have been established. First experimental confirmations of the efficacy of controlled appendages have been achieved. A well tuned P.D. has been tested, with very promising results. The paper begins with a short recapitulation of the previous research. Next, the paper focus on the experiments with a replica with appendages.

Decreasing of the Motion Sickness Incidence by a Multivariable Classic Control for a High Speed Ferry

Abstract The decreasing of the motion sickness in a high speed ferry produces a greater passengers comfort and safety of the vehicle. The paper presents a comparative study of the decreasing of the motion sickness incidence in a high speed ferry using different multivariable classic controllers (PD, first order filter and second order filter). The tuning of the controllers is made solving a non-linear optimization problem. The tuning method uses first a genetic algorithm and then a classic non-linear optimization algorithm.

Modelling of a High Speed Craft by a Non-Linear Least Squares Method with Constraints

Abstract A non linear least squares method with constraints have been tried. However, the extra complexity associated with non-linear systems, with constrains and no initial information of model structure, means that exhaustive search is not always feasible. In these cases genetic identification strategy can be used to obtain initial values. On the other hand, a trend in the area of system identification is to try to model the system uncertainties to fit the available analysis and design tools of robust control. The method described is applied to obtain the interval model of the vertical dynamic of a high speed craft for different speed, and comparative results obtained with the mathematical model and with a scaled model in a towing tank are showed.

Identification of Multivariable Models of Fast Ferries

This work presents the formal approach for identifying continuous transfer functions of the vertical dynamics of a high-speed ship as a nonlinear optimization problem with linear constraints. The proposed solution is described with a hybrid optimization method (genetic algorithm + nonlinear optimization algorithm with linear constraints from the Matlab toolbox).

QFT VERSUS CLASSICAL GAIN SCHEDULING: STUDY FOR A FAST FERRY

Abstract In this paper a comparative study of two different control strategies is done: Gain scheduling with classic controllers (PD and second order filter) versus QFT. Both of them are used to decrease motion sickness in a high speed ferry produced by the vertical acceleration associated with heave and pitch motion.

Interactive computer-aided control design using quantitative feedback theory: the problem of vertical movement stabilization on a high-speed ferry

In a first approximation, the vertical acceleration associated with pitch motion can be considered as the main cause of motion sickness, which is without a doubt one of the most unpleasant disadvantages of maritime transport. The reduction of motion sickness can be stated as a monovariable regulation problem of a highly perturbed system. This work presents the design of a monovariable robust controller with quantitative feedback theory (QFT) for reducing the vertical movement on a high-speed ferry. The different stages of QFT methodology have been done with the help of the software tool QFTIT (Quantitative Feedback Theory Interactive Tool). This is a free software tool that is characterized by its ease of use and interactive nature. The designed regulator is validated experimentally in sea behaviour trials with a scaled down replica 1/25 the size of a high-speed ferry. The designed regulator is also compared with a gain-scheduling scheme using a proportional and derivative controller (PD).

Utilidad de las pruebas rapidas de deteccion antigenica en el diagnostico de la nueva gripe A (H1N1) en ninos

INTRODUCTION Accuracy of rapid BD Directigen(®) EZ Flu A+B diagnostic test against Influenza A (H1N1) Virus in children. METHODS A descriptive retrospective study was performed. One hundred and forty children underwent the rapid influenza test and the RT-PCR against Influenza A (H1N1) Virus. RESULTS The sensitivity was 70.4% (95% CI: 58.9-79.7), specificity 100 % (95% CI: 94.7-100), NPV 76.6% (95% CI: 66.9-84,2) and PPV 100% (95% CI: 92.8-100). CONCLUSION This test showed high sensitivity and specificity, very similar to the seasonal influenza, in children.