Information Technology for Designing Rule bases of Fuzzy Systems using Ant Colony Optimization

This paper proposes the universal information technology for designing the rule bases (RB) with the formation of optimal consequents for fuzzy systems (FS) of different types on the basis of ant colony optimization (ACO) techniques. The developed ACO-based information technology allows effectively synthesizing rule bases of various dimensions both for the MISO and MIMO fuzzy systems taking into account the particular features of the RB consequents formation in the conditions of insufficient initial information. In order to study and validate the efficiency of the presented information technology the design of the RB for the adaptive fuzzy control system of the ship steering device is carried out in this work. The computer simulations results show that adaptive control system with developed RB provides achievement of high enough quality indicators of rudder angle control. Thus, application of the proposed ACO-based information technology allows designing effective RB with optimal consequents by means of minor computational costs that, in turn, confirms its high efficiency.

RECURSIVE NEURAL NETWORK MODEL OF CATAMARAN MANOEUVRING

A neural network model to simulate catamaran manoeuvres is proposed as an alternative to the traditional methodology of developing manoeuvring mathematical models. Data obtained in full-scale trials with a real ship are used to train the model. By recording full-scale trials of catamaran manoeuvres it is possible to generate a neural network model which will allow the prediction of the catamaran manoeuvring performance under different conditions. A Recursive Neural Network (RNN) manoeuvring simulation model is proposed and applied to a catamaran in this specific case. Inputs to the simulation are the orders of rudder angle and ship’s speed and also the recursive outputs velocities of sway and yaw. Two types of manoeuvres are simulated: tactical circles and zigzags. The results between the full-scale data and the simulations are compared in order to analyze and determine the accuracy of the RNN. The study is performed for a catamaran operating in the Tagus estuary for passenger transport to and from Lisbon.

Bow and Stern Control Surface’s Effectiveness and Influence on Supercavity

The numerical model of supercavitating flow field was established based on multiphase model, cavitation model, and turbulence model. The model was employed to simulate the supercavitation flow for the supercavitating vehicle with two types of control surfaces: bow rudder and stern rudder. The influence of both control surfaces on the supercavity shape and rudder effectiveness is compared under the different rudder angles (0-12°), and the effectiveness and the influences on supercavities of bow rudder and stern rudder were explored according to the numerical research results. From the research results, the following conclusions can be drawn: (1) the bow rudders have stable rudder effectiveness and available rudder angle, and the bow rudders also have significant influence on supercavities’ shape. (2) By contrast with the bow rudder, stern rudders’ effectiveness is difficult to predict accurately, and the phenomenon of stalling will occur when stern rudders’ rudder angle exceeds 6°; however, there is almost no influence of stern rudders on supercavities. (3) The bow and stern rudders joint control mode must take the influence on supercavities’ shape and the accuracy of control force’s forecasting into account at the same time. The research is helpful to the optimizing of superhigh-speed vehicles and the design of control modes.

Underactuated USV Path Following Mechanism Based on the Cascade Method

The path following control under disturbance was studied for an underactuated unmanned surface vehicle (USV) subject to the rudder angle and velocity constraints. For this reason, a variable look-ahead integral line-of-sight (LOS) guidance law was designed on the basis of the disturbance estimation and compensation, and a cascade path following control system was created following the heading control law based on the model prediction. Firstly, the guidance law was designed using the USV three-degree-of-freedom (DOF) motion model and the LOS method, while the tracking error state was introduced to design the real-time estimation of disturbance observer and compensate for the influence of ocean current. Moreover, the stability of the system was analyzed. Secondly, sufficient attention was paid to the rudder angle and velocity constraints and the influence of system delay and other factors in the process of path following when the heading control law was designed with the USV motion response model and the model predictive control (MPC). The moving horizon optimization strategy was adopted to achieve better dynamic performance, effectively overcome the influence of model and environmental uncertainties, and further prove the stability of the control law. Thirdly, a simulation experiment was carried out to verify the effectiveness and advancement of the proposed algorithm. Fourthly, the “Sturgeon 03” USV was used in the lake test of the proposed control algorithm to prove its feasibility in the engineering practices.

The Prediction of the Performance of a Twisted Rudder

A new design approach using the concept of a twisted rudder to improve rudder performances has been proposed in the current paper. A correction step was introduced to obtain the accurate inflow angles induced by the propeller. Three twisted rudders were designed with different twist angle distributions and were tested both numerically and experimentally to estimate their hydrodynamic characteristics at a relatively high ship speed. The improvement in the twisted rudders compared to a reference flat rudder was assessed in terms of total cavitation amount, drag and lift forces, and moment for each twin rudder. The total amount of surface cavitation on the final optimized twin twisted rudder at a reference design rudder angle decreased by 43% and 34.4% in the experiment and numerical prediction, respectively. The total drag force slightly increased at zero rudder angle than that for the twin flat rudder but decreased at rudder angles higher than 4° and 6° in the experiment and numerical simulation, respectively. In the experimental measurements, the final designed twin twisted rudder gained a 5.5% increase in the total lift force and a 37% decrease in the maximum rudder moment. Regarding these two performances, the numerical results corresponded to an increase of 3% and a decrease of 66.5%, respectively. In final, the present numerical and experimental results of the estimation of the twisted rudder performances showed a good agreement with each other.

Steering drive operation in tracking and positional mode

В статье рассматривается система управления электромеханическим рулевым приводом, работающим в двух режимах: позиционирование угла руля с заданной скоростью перекладки и слежение сигнала управления от системы «Авторулевой». Исследовались суда различной длины. Показано, что качество переходных процессов угла поворота руля судна несущественно зависит от осадки и скорости судна. Коэффициент гибкой обратной связи для режима позиционирования угла поворота руля определяется заданием скорости и требуемого угла перекладки. Вычисление коэффициента гибкой обратной связи осуществляется интерполяционным способом на основе данных полученных решением системы уравнений. В статье также приводится вывод данной системы уравнений. Режим слежения реализуется заданием максимальной скоростью перекладки в той же структурной схеме системы управления. Это приводит к унификации системы управления рулевым приводом. Выведены точность и ограничения по скорости и ускорению угла поворота для следящего режима. Показано, что в режим слежения с учетом ограничений выполняется с высокой точностью, что делает возможным реализацию программного управления рулевым приводом. Предполагается использовать данную систему унифицированного управления в судах с беспилотным управлением. The article considers the control system of an electromechanical steering drive operating in two modes: positioning the steering angle with the required speed of shifting and tracking the control signal from the "Autopilot" system. Ships of various lengths were analyzed. It is shown that the quality of the transients of the ship's rudder angle does not significantly depend on the draft and speed of the ship. The coefficient of flexible feedback for the steering angle positioning mode is determined by setting the speed and the required angle of shifting. The flexible feedback coefficient is calculated using an interpolation method based on the data obtained by solving a system of equations. The article also provides a conclusion of this system of equations. The tracking mode is realized by setting the maximum speed of the shift in the same block diagram of the control system. This results in a unified steering control system. The accuracy and limits on the speed and acceleration of the angle of rotation for the tracking mode are derived. It is shown that the tracking mode, taking into account the limitations, is performed with high accuracy, which makes it possible to realize the program control of the steering drive. It is assumed to use this unified control system in ships with drone control.

EKF-DRNN autopilot for VLCC heading hybrid control

An online Extended Kalman Filter (EKF)-Dynamic Recurrent Neural Network (DRNN) autopilot implementation strategy for Very Large Crude Carrier (VLCC) heading hybrid control with uncertain dynamics is designed in this paper. The autopilot scheme is based on a DRNN control model, which learns VLCC dynamic characteristics, while the VLCC heading control is estimated by the EKF to minimize squared course error. The online EKF-DRNN autopilot provides optimal control on the basis of fuel-saving evaluation criteria using the heading deviation and rudder angle. Therefore, the autopilot output is guaranteed to converge to the desired VLCC trajectory asymptotically. The proposed strategy is evaluated by applying it to VLCC Yuan Kun Yang from COSCO Shipping, and works excellently under different loads, speed and weather conditions. The VLCC heading hybrid controller is also assessed by ‘Z’ manoeuvring and turning test, and the superiority of the online EKF-DRNN autopilot is demonstrated. The remote online monitoring of Yuan Kun Yang’s main navigation data shows that it improved fuel-saving properties despite worsening weather conditions causing increased yawing.