Directional Stability and Control of Ships in Waves

1972 ◽  
Vol 16 (03) ◽  
pp. 205-218
Author(s):  
Haruzo Eda
Keyword(s):  
Automatic Control ◽  
Gain Control ◽  
Small Region ◽  
Wave Crest ◽  
Following Seas ◽  
Directional Stability ◽  
Wave Trough ◽  
Calm Water ◽  
Hull Forms ◽  
And Control

The stability and oscillatory motions of ships (automatically steered and unsteered) in the horizontal plane were examined on a digital computer for the case of regular following seas. Available hydrodynamic data for Series 60 hull forms were used. Analysis of directional stability was made for the case of zero encounter frequency (i.e., the ship runs at high speeds equal to the wave celerity). The ship (which is hydrodynamically stable without automatic control in calm water) is directionally unstable in following seas except for the small region near the ascending node of the waves. Addition of automatic control can give the ship directional stability when it is located on the wave trough, but not when it is located on the wave crest. At relatively high frequency (i.e., at low speeds in following seas), the rudder and control system are almost incapable of reducing oscillatory motion. Violent rudder activity in following seas can be decreased by reducing the yaw-rate-gain control constant and by increasing the rudder-response-time constant.

Analysis of the German Navy Stability Standard BV 1030 With Respect to Operability in Heavy Weather

2014 ◽  
Author(s):  
Stefan Krüger ◽  
Hannes Hatecke ◽  
Andreas Rinke ◽  
Klaus Tammen
Keyword(s):  
Fuel Efficiency ◽  
Wave Crest ◽  
Ship Motions ◽  
Safety Level ◽  
Wave Trough ◽  
Close Cooperation ◽  
Hull Forms ◽  
The Stability ◽  
German Navy ◽  
The University

The stability standard of the German Navy — the BV 1030 — was developed in the mid-sixties of the last century in close cooperation with the German Navy Authorities (now BAIINBw) and the University of Hamburg. Other than the stability standards used for commercial shipping, the BV 1030 is based on righting and heeling lever balances for each individual loading condition of each individual ship. Different types of heeling moments have to be assumed in several combinations and they have to be balanced against the righting levers of the ship. Not only the still water stability curve is subject to this lever balance, but also wave crest and wave trough situations are subject to the stability analysis. The BV 1030 stability standard further requires a minimum stability if the ship is on the wave crest. Since this stability standard is in force, the German Navy never experienced a stability accident. The development of new hull forms with the focus on fuel efficiency has widely brought up new problems in heavy weather, for example the vulnerability for parametric rolling. It was therefore of interest for the German Authorities (BAIIN) whether the existing stability standard has sufficient safety to cover also these phenomena connected to more modern hull forms. Therefore an analysis was carried out in close cooperation between BAIINBw, MARS and TUHH where the operability of several ships of the German Navy was analyzed with numerical sea keeping computations. The nonlinear sea keeping code E4ROLLS was used which allows the computation of time series of the ship motions in irregular, short crested seas. From these computations, operational limits could be derived, or, vice versa, the required stability to guarantee a certain operability. The results showed that the concept of the German BV 1030 stability standard provides a significantly higher safety level compared to IMO standard for commercial ships. The results did also show that for modern hull forms, some adjustments to the existing safety standard were found to be useful to better cope with righting arm fluctuations in longitudinal waves.

Paper 29. Yaw Control in Waves

1972 ◽  
Vol 14 (7) ◽  
pp. 211-228
Author(s):  
H. Eda
Keyword(s):  
Control System ◽  
Automatic Control ◽  
Theoretical Study ◽  
Model Tests ◽  
Low Frequencies ◽  
Following Seas ◽  
Yaw Control ◽  
Hull Forms ◽  
The Stability ◽  
The Waves

Results are given of a recently broadened investigation into the stability of ships in following seas, based on a theoretical study and model tests on Series 60 hull forms. The analysis is derived from perturbations to the steady yaw, sway, surge and automatic control equations. At low frequencies of encounter, corresponding to high ship speeds, it is found that significant destabilizing effects arise from the large surge forces generated by the waves, leading to broaching: stability is greatly improved by appropriate characteristics of the control system. At higher encounter frequencies, typical of lower speed ships, oscillating yaw and sway motions are induced and the rudder has little influence. The study clarifies the influences of wave encounter frequency, encounter angle, control system constants and ship configuration.

Model Studies for an Oceanographic Ship Derived From an Offshore Supply Vessel

1967 ◽  
Vol 4 (04) ◽  
pp. 403-415
Author(s):  
J. R. Paulling ◽  
Maxwell Silverman
Keyword(s):  
Gulf Coast ◽  
Maximum Speed ◽  
Oil Well ◽  
Following Seas ◽  
Model Studies ◽  
Research Ship ◽  
Calm Water ◽  
Hull Forms ◽  
The University ◽  
Offshore Oil

During the last few years, a number of operators of oceanographic research ships have considered the Gulf Coast offshore-oil-well supply vessel type for possible conversion to a research vessel. Such a ship of 155–165 ft length offers a number of attractive features; chiefly, reduced operating costs, and space for mounting portable or interchangeable equipment. The vessel's principal disadvantages reputedly are limited stability and a lack of seakindliness. An investigation of such vessels has recently been conducted by the Scripps Institution of Oceanography and the Department of Naval Architecture of the University of California. Model experiments were conducted to determine the resistance and powering characteristics, the motions in head seas, and rolling in beam seas. The transverse stability was computed for calm water and following seas. Four different hull forms were considered in these studiesa typical 155-ft-long single-chine supply boat;a round-bilge version of the same;a single-chine design developed to overcome several of the suspected deficiencies of Form 1 while still retaining the principal proportions; andan affine variation of Form 1 produced by multiplying transverse dimensions by 0.75 and increasing vertical dimensions by the same amount. It is concluded that the most serious deficiency of the vessel type is the tendency to slam in a head sea. This may limit the maximum speed in head seas. The small saving in resistance exhibited by both the narrower and round-bilge versions is insufficient to justify choosing either of these on this basis alone. In addition, both of these forms roll more severely than the two wide, single-chine forms. Finally, the increased freeboard of the third form results in an ample margin of stability. It is felt, therefore, that Form 3 provides a suitable basis for developing a research ship design.

DEVELOPMENT OF COMPUTERIZED MONITORING AND CONTROL SYSTEM OF THE MOBILE ROBOT’S POSITIONING ON LARGE FERROMAGNETIC SURFACES BASED ON INTELLIGENT TECHNIQUES. COMPLEX OF TASKS OF MONITORING AND AUTOMATIC CONTROL OF MOBILE

2019 ◽  
pp. 37-47
Author(s):  
Yao Yueqin ◽  
Oleksiy Kozlov ◽  
Oleksandr Gerasin ◽  
Galyna Kondratenko
Keyword(s):  
Automatic Control ◽  
Point Of View ◽  
Monitoring And Control ◽  
Large Area ◽  
Monitoring And Control System ◽  
Technical Parameters ◽  
Automatic Control Systems ◽  
Current State ◽  
Computerized Monitoring ◽  
And Control

Analysis and formalization of the monitoring and automatic control tasks of the MR for the movement and execution of various types of technological operations on inclined and vertical ferromagnetic surfaces are obtained. Generalized structure of mobile robotic complex is shown with main subsystems consideration. Critical analysis of the current state of the problem of development of universal structures of mobile robots (MRs) for the various types of technological operations execution and elaborations of computerized systems for monitoring and control of MR movement is done. In particular, wheeled, walked and crawler type MRs with pneumatic, vacuum-propeller, magnetic and magnetically operated clamping devices to grip with vertical and ceiling surfaces are reviewed. The constructive features of the crawler MR with magnetic clamping devices capable of moving along sloping ferromagnetic surfaces are considered. The basic technical parameters of the MR are shown for the further synthesis of computerized monitoring and automatic control systems. Formalization of the tasks of monitoring and control of the MR positioning at the processing of large area ferromagnetic surfaces is considered from the point of view of control theory.

Numerical evaluation of hydrodynamic characteristics of planing hulls by using a hybrid method

2021 ◽  
pp. 147509022199024
Author(s):  
Emre Kahramanoglu ◽  
Silvia Pennino ◽  
Huseyin Yilmaz
Keyword(s):  
Experimental Data ◽  
Hybrid Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Calm Water ◽  
Preliminary Design Stage ◽  
Reduction Function ◽  
Hull Forms ◽  
Good Agreement

The hydrodynamic characteristics of the planing hulls in particular at the planing regime are completely different from the conventional hull forms and the determination of these characteristics is more complicated. In the present study, calm water hydrodynamic characteristics of planing hulls are investigated using a hybrid method. The hybrid method combines the dynamic trim and sinkage from the Zarnick approach with the Savitsky method in order to calculate the total resistance of the planing hull. Since the obtained dynamic trim and sinkage values by using the original Zarnick approach are not in good agreement with experimental data, an improvement is applied to the hybrid method using a reduction function proposed by Garme. The numerical results obtained by the hybrid and improved hybrid method are compared with each other and available experimental data. The results indicate that the improved hybrid method gives better results compared to the hybrid method, especially for the dynamic trim and resistance. Although the results have some discrepancies with experimental data in terms of resistance, trim and sinkage, the improved hybrid method becomes appealing particularly for the preliminary design stage of the planing hulls.

Application of PID in Controllable Pitch Propeller of a Multipurpose Ocean Tug

2013 ◽  
Vol 464 ◽  
pp. 253-257
Author(s):  
Hui Fang Chen
Keyword(s):  
Control System ◽  
Automatic Control ◽  
Automatic Control System ◽  
High Reliability ◽  
Control Process ◽  
Good Control ◽  
Control Performance ◽  
Hardware Configuration ◽  
Design Idea ◽  
And Control

This paper takes the automatic control system of controllable pitch propeller in a multipurpose ocean tug as an example to describe the application of the S7-200 series PLC in the control system of 4500 horse power controllable pitch propeller in detail. The principle of control system is addressed, as well as the hardware configuration, the design idea of the main software and control process. The system shows high reliability, accuracy and good control performance in practical in practical running.

EFFECT OF INITIAL CONTACT LOCATION ON MULTIASPERITY NANOCONTACT: QUASICONTINUUM SIMULATION

NANO ◽  
2014 ◽  
Vol 09 (01) ◽  
pp. 1450004
Author(s):  
WU-GUI JIANG ◽  
SHUANG XU ◽  
ZHENG-WEI WANG
Keyword(s):  
Contact Process ◽  
Copper Substrate ◽  
Wave Crest ◽  
Initial Contact ◽  
Displacement Curve ◽  
Quasicontinuum Method ◽  
Contact Stage ◽  
Wave Trough ◽  
Contact Models ◽  
Microscopic Deformation

Two nanocontact models with different initial contact locations are built to simulate the process of the multiasperity nanocontact for investigating the effect of initial contact location on the nanocontact process by using the quasicontinuum method. The indenter is initially located on the top of the middle wave crest (MWC) of the substrate and the top of the wave trough on the left side (LWT) of the substrate, respectively. The microscopic deformation mechanism, the load–displacement curve and the nanohardness–displacement curve are examined. It is found that the deformation mechanisms in the two multiasperity contact models are different. During the initial contact stage, in the MWC model, the twinning deformation dominates the whole contact process, while in the LMT model many Lomer-Cottrell locks are generated in the copper substrate, which inhibits the occurrence of twinning deformation.

The Isolator of Industrial Automatic Control System Selection and Application

2011 ◽  
Vol 301-303 ◽  
pp. 1714-1718
Author(s):  
Ji Meng Zhang ◽  
Hong Shuo Wang ◽  
Ben De Gan
Keyword(s):  
Control System ◽  
Automatic Control ◽  
Automatic Control System ◽  
Signal Transmission ◽  
Control Process ◽  
Monitoring And Control ◽  
Process Monitoring And Control ◽  
Isolation Device ◽  
System Selection ◽  
And Control

In the automatic control system of industrial field, the production process monitoring and control process is dependent on Mutual coordination of various automation instrument, computer and corresponding actuators. The coordination is accurate or not, the key is signal transmission quality among those agencies. The application and selection of isolation device directly affect signal transmission. This paper discusses the application and choose of industrial site isolator from isolation principle, the principle and choose for isolator, commissioning and parameter selection based on practical application.

The Operation of Cool Edit Pro in Corpus-Based Spoken Language

2013 ◽  
Vol 694-697 ◽  
pp. 2383-2387
Author(s):  
Jie Chen ◽  
Jing Chen
Keyword(s):  
Sound Wave ◽  
Native Speaker ◽  
Spoken Language ◽  
Short Wave ◽  
Wave Crest ◽  
Sharp Wave ◽  
Wave Trough ◽  
Long Wave ◽  
Autonomic Learning ◽  
Language Corpus

Corpus refers to the database of language materials. Cool Edit Pro is a media edit software. This paper explores how to construct spoken language corpus, how to use cool edit pro 2 to make sound wave contrast and give the experimenters an intuitive observation from their own speech waveforms. The key is to offer the obvious waveforms contrast among the sampling waveform of the native speaker, the original and unmodified one of the experimenter and the new waveform of the experimenter after modifications and teachers instructions, which makes the oral autonomic learning more possible and scientific. From long wave or short wave, wave trough or wave crest, smooth wave or sharp wave, the experimenters deviations can be easily identified from the standard during the autonomic practices and efficiently make corrections. Additionally, experimenter also can observe the improvements frequently, which means this experiment more instructive.

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