ALTERNATIVE ASSESSMENT OF WEATHER CRITERION FOR SHIPS WITH LARGE BREADTH AND DRAUGHT RATIOS BY A MODEL EXPERIMENT: A CASE STUDY ON AN INDONESIAN RO-RO FERRY

The weather criterion is one of stability criteria to verify ability of a ships to withstand the combined effects of severe wind and rolling criteria in dead ship condition. An overestimated roll angle is obtained when the weather criterion is applied to ships with breadth and draught ratios larger than 3.50 and ratios between vertical centre of gravity and draught larger than 1.50. This paper discusses the assessment of weather criterion for an Indonesian ro-ro ferry by model experiments. The drift test is performed in four wave steepnesses with wave frequencies near the roll natural frequency. The maximum roll amplitude is used to calculate the effective wave slope coefficient correponding to the wave steepness, with Bertin’s coefficient obtained by the roll decay test. The damping factors correspond to the breadth and draught ratio as well as the bilge keel contribution are determined using the formula of weather criterion with the roll angle obtained by the Japanese formula with a correction factor of 0.70 due to the irregularity of waves. The obtained effective wave slope coefficient and the damping factors due to breadth and draught ratio and the bilge keel are smaller than those used in the weather criterion.

ASYMMETRICAL WATER IMPACT OF TWO-DIMENSIONAL WEDGES WITH ROLL ANGLE WITH MULTI-MATERIAL EULERIAN FORMULATION

A hydrodynamic study on the asymmetrical water impact of two-dimensional wedges with roll angle is presented. The slam induced loads on the wedges entering calm water with both vertical and horizontal velocities are predicted based on the explicit finite element method. The effects of the horizontal impact velocity and the roll angle are investigated through the predicted results of pressure distribution, pressure variation during the water entry and total impact force, which are also compared with analytical formulations and other numerical calculations. The present method gives reasonable predictions, compared to the numerical and analytical results.

Intelligent Detection Method for Roll Stability of Unmanned Vehicle based on Fuzzy Control

When the unmanned vehicle is disturbed by the outside world or carries out dangerous actions such as steering and continuous lane changing, the yaw stability of the unmanned vehicle decreases and the dangerous situation such as rollover is easy to occur. In this paper, the intelligent detection method for roll stability of unmanned vehicles based on fuzzy control is studied. The roll control system of the unmanned vehicle based on a double-layer control strategy is designed. The roll stability of the unmanned vehicle is controlled by an upper-layer fuzzy controller and lower-layer differential braking control. The dynamic model and tire model are built in MATLAB/Simulink to restore the running characteristics of unmanned vehicles. Based on the operation characteristics, the roll stability of the unmanned vehicle’s roll control system based on fuzzy control is tested from three aspects: steady-state response, roll stability and dynamic stability coefficient. The experimental results show that the transverse load’s transfer rate of the proposed method is reduced by more than 0.2% compared with the contrast method, the yaw angular velocity, centroid’s roll angle and roll angle measured under the two working conditions are closer to the actual values, which shows that the method has better control effect and detection accuracy.

Mathematical model for determining the roll angle of a fishing vessel when purse seine sampling

Лов рыбы с применением кошельковых неводов является наиболее распространенным в мире после тралового лова. Процессы кошелькования невода, выборки улова могут существенно влиять на остойчивость рыболовного судна (сейнера). В данной работе рассматривается влияние на угол крена силы, действующие со стороны орудия лова. Приведен алгоритм расчета, учитывающий координаты точки приложения силы натяжения троса, идущего к орудию лова, углы наклона троса, величину силы. Составлены расчетные зависимости для процессов крена, получены выражения для угла наклона корпуса судна. Приведены примеры расчетов. В частности, рассмотрено изменение угла крена от тягового усилия, высоты подъема канифас-блока для промыслового судна. Проведенные расчеты свидетельствуют о достаточной для инженерных расчетов точности и возможности использовать приведенный алгоритм при оценочных расчетах на различных стадиях проектирования. Важно учитывать возможность одновременного наложения ветровых нагрузок, действия волн на корпус судна. В этих случаях крен и дифферент будут возрастать. Поэтому спецификой промысловых судов является необходимость учета поведения судна при проведении промысловых операций. Fishing with the use of purse seines is the most common in the world after trawl fishing. The processes of pursing and seine sampling can significantly affect the stability of a fishing vessel (seiner). In this paper, the influence of forces acting from the fishing gear on the roll angle is considered. The calculation algorithm is given, taking into account the coordinates of the point of application of the tension force of the cable going to the fishing gear, the angles of inclination of the cable, the magnitude of the force. Calculated dependences for roll processes are compiled, expressions for the angle of inclination of the vessel's hull are obtained. Examples of calculations are given. In particular, the change in the roll angle from the traction force, the lifting height of the snatch–block for a fishing vessel is considered. The calculations carried out indicate sufficient accuracy for engineering calculations and the possibility of using the above algorithm for evaluation calculations at various stages of design. It is important to take into account the possibility of simultaneous imposition of wind loads, the action of waves on the hull of the vessel. In these cases, the roll and trim will increase. Therefore, the specifics of fishing vessels is the need to take into account the behavior of the vessel during fishing operations.

METHOD FOR DETERMINING TIPPING STABILITY OF A LARGE-LOADED VEHICLE IN CURVED MOVEMENT

The overturning of the vehicle corresponds to such a rise of the propeller above the support-ing surface, at which the roll angle of the frame reaches a limiting value and its further movement in the direction of roll under the action of gravity and inertia becomes irreversible. The main criteria for the stability of vehicles (V) against overturning are the characteristics of its geometric parame-ters and the location of the center of mass, relative to the propeller, which determine the boundaries of its static stability.

Modeling and Analysis of the Kinetic Influence of Liquid Sloshing Characteristics on High-Clearance Sprayers

To research the influence of liquid sloshing on the driving stability of high-clearance sprayers, this paper builds an equivalent liquid sloshing mechanical model and obtains the stochastic acceleration excitation of the rectangular spray tank using the Adams kinetic model, thus obtaining the relationship between the impact force, moment, and the stochastic acceleration using Fluent numerical simulation analysis. This paper makes further calculations with MATLAB/Simulink system models, and the result from comparing these two calculations shows that the equivalent strategy proposed in this paper has a better consistency. Based on the consideration of the acting forces of the additional moment due to lateral movement of the center of mass of the liquid and the dynamic pressure due to liquid sloshing in the tank, this paper builds a mathematical model of the sprayer and researches the influence of the filling ratio and vehicle velocity on the vehicle stability through stochastic acceleration excitation. The results show that, in the case of different speeds, the liquid sloshing has a small influence on the overall roll angle; in the case of different filling ratios, the liquid sloshing has a big influence on the overall roll angle, the slip angle of the center of mass, and the yaw angular velocity; the filling ratio k = 0.85 and the speed u = 1 m/s−2 m/s are safe operation parameters of the sprayer. This research provides reference solutions for the stability control and optimization problems of the high-clearance sprayer and semitrailer.

Vehicle rollover warning system based on TTR method with Inertial Measurement

This paper presents a theoretical and experimental study conducted on the rollover warning of wheeled off-road operating vehicles. The time to rollover (TTR) warning algorithm was studied with real-time vehicle roll angle and roll angle velocity as the input variables, and lateral load transfer ratio (LTR) was used as the rollover determination index. Subsequently, a vehicle dynamics model was built using CarSim software, and a warning algorithm was established in the MATLAB/Simulink environment. The rollover joint simulation in CarSim and MATLAB/Simulink was conducted under typical working conditions. Finally, combined with inertial measurements, a rollover warning system was independently developed. In addition, the rollover warning system was installed on a light forest firefighting truck to verify the feasibility of the system via a real vehicle experiment, and the law of vehicle rollover motion was also studied. The serpentine experiment and steady-state rotation experiment were conducted. The experimental results showed that at identical front-wheel steering angles, the roll angle and lateral acceleration increased with an increase in the vehicle speed. Furthermore, for identical vehicle speeds, the roll angle and lateral acceleration of the vehicle increased with an increase in the front-wheel steering angle. The dangerous vehicle speed was 50 km/h in the serpentine condition and 40 km/h in the steady-state rotation condition. The risk trend and alarm signal obtained by the rollover warning system were consistent with the actual situation. Thus, this can assist drivers in judging the rollover risk and effectively improve the active safety of special vehicles. Furthermore, it also provides a reference for further research on active rollover control technology of special vehicles.

Establishing the Method to Predict the Limited Roll Angle of the Vehicle Based on the Basic Dimensions

The roll angle of the vehicle φ is a characteristic parameter for the vehicle's instability. This value appears when the vehicle steers. If the vehicle’s body is tilted, the value of the vertical force at the wheels Fzij will also change. When the value of Fzij reaches zero, the wheel will be lifted off the road, the rollover phenomenon can occur. At this time, the roll angle of the vehicle will reach the maximum value φmax. Previous researches have often used only the vehicle dynamics model to determine the limits of this phenomenon. However, the calculation and simulation process are quite complicated. Therefore, this research has proposed a novel method that can calculate the limit of the rollover phenomenon more easily. In this research, the Rollover State Function (RSF) was established to calculate the limited roll angle of the vehicle. According to the content of the paper, this function depends only on the basic dimensions of the vehicle such as the height of center of the gravity, the track width, etc. Besides, it has relatively high accuracy, even when the vehicle's mass changes, its difference is not large. Therefore, the results of the paper can be applied to later studies to predict the rollover phenomenon.