Ship Course Research Articles

A case study: The review of the Los Angeles Bureau of Jewish Education

A solution is proposed to handle complex water boundaries based on the panelled moving patch method, in which the moving patch on the seabed is dynamically meshed by an optimized version of the paving algorithm and smoothed by a hybrid smoother. Using this approach, two typical hydrodynamic interaction scenarios with the non-even seabed are studied, and numerical results are obtained for a variety of values of the relative ship course as well as of characteristics of the seabed.

An Experimental Study on Ship Handling in Waves

This study is aiming at quantitative evaluation of crew's judgement for ship handling in waves.This paper, as the first report of the study, explains the outline of the onboard monitoring equipment named Ship Motion Analyzing Computer System (SMACS) developed by the authors, being capable for recording simultaneously ship motion responses in waves, encounter waves and the reasons for ship's course and/or speed changes.Some of the data obtained from three patrol boats of Maritime Safety Agency of Japan with SMACS are also shown in the paper.

Full-scale Experiment on Computer Aided Navigation System for Safety

Notorious for its ravaging climate in winter, the North Pacific is feared among seafarers as theldevil's water. In the past 10 years, it ran havoc with many large vessels and took many lives and much property.So, the Japanese Ministry of Transport has conducted a research project for five years since 1982 to clarify the effect of wave force on hull and develop Computer Aided Navigation System for Safety (CAN). This is 'a kind of shipboard instrumentation system for the sensing of incident waves, ship motions and structural responses and prediction of response changes to be expected when ship's course or speed is altered.This system was installed on a container ship “Japan Alliance” operating in the North Pacific service and checked its functions and performance. During the experiment, from 1986. 11 to 1987. 1, significant full-scale data on ship motions, vertical accelerations, bending moments etc. were obtained. Report here is a presentation of the experimental results on the Computer Aided Navigation System for Safety.

The Usefulness of Response Monitoring for Estimation of Bow

During the 1970's, the Maritime Administration, as part of its Exploratory Research Program, supported the development of shipboard instrumentation systems for the sensing of ship motions and structural responses and the prediction of response changes to be expected when a ship's course or speed is altered. Two systems were installed, one on the SS LASH Italia operating in the Atlantic/Mediterranean service and the other on the USNS Furman operating in trans-Pacific service. These systems were operated for several years during which time significant data were obtained on midship bending, bow accelerations, bow side frame stresses and rolling. Filtering allowed identification of slamming and green water events. SNAME Panel HS-2 (Impact Loads and Responses), long in need of full-scale data on heavy-weather transient loadings of the hull, wished to determine whether these data, collected for other purposes, could be useful for predicting the frequency and magnitude of loads on the bow flare structure due to slamming and green water events. This paper presents the results of the investigation that was carried out and suggests some implications regarding the establishment of criteria for bow structure design in regard to loadings of this type.

内海航行援助システムの試作

The present paper reported on the development of the prototype coastal navigation support system, using personal computer (TEAC, PS-80) which recently became popular. The system has been constructed for the purpose of load reduction in chart works (ship positioning), so navigator will be released from chart works to keep more careful look out for safe ship operations. The system has the following functions; (1) The system indicates target name, bearing and distance on the CRT display. (2) The informations of ship course and speed are given by gyrocompass and electromagnetic log through A/D converter or by keyboard. (3) The system calculates the ship position from more than two target bearings. (4) The system indicates observed position and dead reckoning position with time on the CRT display. (5) The system indicates name, bearing and distance of next course changing point on the CRT display. (6) Using X-Y ploter, the ship positions are drawn on chart.

航走出会い波浪による波浪方向スペクトルの推定

The directional wave spectrum is estimated here with a ship encounter frequency spectrum and an original frequency spectrum which is measured at a stationary ship. The frequency spectra of ship encounter waves are different from the spectra of the same original waves depending on the ship's course. This is the reason why the frequencies of each directional component waves are deformed in accordance with encounter angle. So, the direc-tional information of each component waves can be extracted inversely from the relation between corresponding frequency of an original wave and an encounter wave by applying the multivariable constrained method of optimization technique. Some considerable conditions to raise the accuracy of the estimation are also described here.

航空機観測による湾内船舶の交通流解析

MSS (Multi Spectra Scanner) data and aerial photograph of sea surface which are observed with a plane contain many informations of marine traffic flow. Analyzing these data, statistical properties of marine traffic in broad area are extracted with less hours working and expenses than the data of traditional marine traffic observation with radar and eye-measurement. That properties are following, (1) average number of ships per square kilometer of each devided area, (2) distribution of ship's course of each devided area, (3) average number of track crossing (collision danger index) of each devided area, (4) distribution of crossing angle, and etc. Although acuracy of MSS data is lower than the aerial photograph data, there is a special merit that those data will be obtained even in night.

レーダ・アスペクタの研究-II

A Radar Aspector which is a equipment to instantly identify aspect angle of another ship concerned was reported before. It could be greatly advantageous for navigators to avoid collision. In this paper, the new type of the Radar Aspector is described. This equipment can provide of manoeuvring information such as course, speed and another information. The equipment utilizes interval time of digitally encoded pulse of radar. For example, each group of intervals corresponds to specific meanings such as ship's course, speed and so on as the following table. [Table] If a ship receives following sequence of pulse interval from another ship's radar, 1, 001μs, 1, 010μs, 1, 023μs, 1, 006μs and 1, 034μs, these are decoded as course 103゜and speed of 24K't. The theory, the fabrication and the results of experiment are reported in this paper.

Statistical Identification of Ship's Course Keeping Motion and Optimal Control

In the former paper, the authors proposed an entirely new autopilot system using a stochastic autoregressive model. According to the model fitting procedure, we could design flexibly an optimal controller under an appropriate evaluation function.In this paper, the experimental results that an on-line direct digital control using the model fitting procedure was applied to an actual ship are reported. For the sake of it, in chapter 2 and 3, the theory proposed in the former paper is outlined. In chapter 4, the hard and software developed for the realization of the on-line controlling of the ship are introduced. In subsequent chapters, the plan and the method of the actual sea tests are described and the results of the on-line direct digital controlling of the actual ship's course keeping motion are scrutinized.The new concept used in this paper for identification of system through the autoregressive model, the AIC (Akaike's Information Criterion) proposed by Dr. Akaike is discussed briefly in Appendix.

Sea state and navigation

Weather Routing is a technique of optimizing the entire route depending on the estimated weather and sea states. But, the estimation can not always be perfect, that the local optimization will also be necessary and of worth.This paper is an approach from the latter aspect to the problem of planning ship's course, and the author desires that design work and operation of ship will become tied more closely by applying the proposal made in the paper.

Using a Hand-held Calculator for Ship's Position Comparison

The author's personal experiences under operational conditions have been with the CBM (Commodore Business Machines) S.R. 4148R, which has proved quite adequate for position comparisons in a surface warship fitted with a Magnavox satellite navigation system primarily used as a DR recorder. It is fed with ship's course and speed, corrections to the positions found being up-dated from satellite passes. Occasionally the criteria for up-dating from a satellite pass are not met and the system may run on DR for several hours without up-dates. Since the system is unable to compensate automatically for tidal or current drift and set or for leeway, the accuracy of the DR will deteriorate with age. The possibility of component malfunction, albeit temporary, may also contribute to DR error. In such conditions a series of astronomical observations is made; the calculator is capable of finding the average of such a series if required.

橋脚周りの風の乱れが接航する船の保針におよぼす影響について

Aerodynamic data of yawing moment and swaying force of ship in wind passing through by the pier of the bridge spanning over the ship's passage were obtained by the wind tunnel with water tank test. Substituting these data in the equations of motion of ship as the external disturbance, the course deviation and the transverse movement of ship were computed with respect to the ship's course and the relative position of the pier. The ship's trajectories are shown in Figs from 8-1 to 8-8 as the parameters of the ship's course, wind direction and configulation of the pier respectively. Results indicate that the minimum clearance of the ship's course to the pier face will be generally required a distance of the ship's length for passing over in safety. Moreover, it is reasonably required for reducing the sheer flow of wind around the pier by improving the sectional configulation from the viewpoint of pier construction to decrease the wind effect on the steering bias of ship.

Statistical Identification of Ship's Course Keeping Motion and Optimal Control

In this paper, the ship's course keeping motion is represented by an Auto Regressive model (A. R. model) in the time series analysis and it is shown that the Akaike's FPE method is effective to the determination of the order of the model. This method is immediately applied to the estimation of spectra of some ship's motions and we designed one optimal controller using the Dynamic Programming.According to our digital simulation, our controller shows some remarkable characteristics and in particular, through a smoother and a lower rudder motion than the manual or the present auto-pilot steering, ship's motions (especially Yawing and Rolling) are considerably reduced. This last point is expected to contribute to the development of the Direct Digital Control.

Some Numerical Results on Wave Resistance of a Point Dipole

The distribution of singularities (that is, source, sink, and dipole) representing a ship's hull has played an important role in the study of wave resistance in naval hydrodynamics. Based on the theoretical wave resistance formula from linearized free-surface theory, six different wave resistance expressions in terms of three wave components along a longitudinal cut parallel to the ship's course are presented. To demonstrate the numerical accuracy of these wave resistance expressions, the analysis has been applied to the theoretical wave profiles generated by a submerged point dipole, and the results are compared with the known theoretical value.

On The Steady Turning of Towed Ships System

We have discussed the course stability of towed ships system in the Journal of the Society of Naval Architects of West Japan No. 42, 43, 44 and 46. In this paper, the auther theoretically and experimentally deals with the steady turning of the towed ships system in still water by the parameters-a ship's course stability criterion, towing points, length of towing rope, number of ships, rudder angle and rudder area ratio of the tugboat, and size of ships. The results are as follows :(1) During the region of short towing rope, the last towed ship has a larger radius than the tugboat, then by the increase of the towing rope's length, the last towed ship gradually tends to turn with the smaller circle and eventually when the towed rope length is over the critical rope's length qcun, the system falls into irregullar motion, and this is identified, and qualitatively agrees with the experimental results.(2) The steady turning of the system by steered the rudder of the tugboat is only possible when the towing rope's length is under qcun L and which is given by the equation (6).(3) The larger the rudder angle and the rudder area ratio of the tugboat are the smaller the radius of steady turning of the towed ships system are.(4) If the rudder angle and rudder area ratio of the tugboat are constant, a) the radius of steady turning decreases, when the number of towed ship increases, b) the radius of steady turning becomes larger, when the towing rope's length increases, and the fore and aft-towing points are apart from the centre of gravity of the towed ship, except the last towed ship.

A proposal of a method to specify the permissible region of instability in the steering characteristics of ships

The way to specify the permissible region of instability of ships is proposed from the viewpoint that ships should be controllable for any human operator without difficulty. In the case of the steering of the ship (course keeping), where the motions of ships are small, we can approach that problem with a linear equation. The importance of the time constant T, as well as the proportionality coefficient K, is stressed. Assuming a very simple human operator model, which can be followed by any human operator, the permissible region is specified as a combination of T and K.

The Time Optimal Control Law to Alter Ship's Course and its Manual Steering Experiments

At first, the time optimal control law to alter ship's course is reported. The dynamics of the ship's turning motion is assumed to be expressed by the following differential equations, ψ=ω, Tω+ω=Kδ, δ=Au, |δ|≤D, |u| ≤1Secondly, the completeness of the control law is examined by a digital computer simulation. A computer time to determine a momentary control to be applied to the system is less than 5 msec, therefore, the control law can be used in a feedback system.Then, manual steering experiments are performed to alter ship's course in a minimum time using T and K obtained from zig-zag maneuvering tests. The parameters are confirmed to be correct enough for being used in a feedback steering system.

On the Improvement of Ship's Manoeuvrability by means of a New Automatic Control System based on the Time Optimal Steering for Turning of Ships

In order to manoeuvre a gigantic ship easily, some devices such as auto-pilots and yaw rate indicators have been equipped on board to keep and/or alter ship's course. Also, for the abovementioned purpose, there are some studies concerned with a time optimal control to alter ship's course [1, 2, 4] and an improvement of ship's manoeuvrability by means of a subsidary automatic device [5, 10].This paper deals with a subsidary automatic control system which is a kind of the time optimal steering for ship's steady turning. The proposed control system has a yaw rate input instead of a rudder angle which is given by helmsman through a steering wheel, and has a feed back loop of yaw rate and can improve the quick responsibility of a ship to almost maximum degree without destroying turning ability. It is, therefore, expected that the helmsman can control easily and quickly even for a ship whose course stability is unstable.In this paper, the required time to set the ship's turning steady by the automatic control system is compared with the times by the time optimal steering and the ordinary steering by using of the digital computer simulation of ship's manoeuvre.

A Study on Wave Bending Moment of Ships from Results of Statistical Analysis of Records in Logbooks

The long-term statistical distribution of maximum values of wave bending moment of a ship is affected by the sea state conditions during voyages throughout her life. Authors analyzed statistically the following records in logbooks of five ships, ship speed, ship course, wind velocity, wind direction, and wave height.From the analysis, it was found that the probability of changing course of ship to avoid heavy storms during her voyages had less effects on statistical distribution of wind velocity than that of wave height. And the relation between wind velocity and wave height observed on a ship was affected by the service condition, speed, and seakeeping quality of the ship. Generally the ratio of the wave height to the wind velocity derived from long-term observation on a ship which had more chance of being caught by heavy storms judging from her service condition etc., was greater than that was derived from the observation on another ship which has less chance.The long-term distributions of wave bending moment of a ship in several sea state conditions derived from our analysis were compared with that of the same ship in the North Atlantic Ocean. From the comparison, it was showed that the probability of escaping from the severe wave conditions of some ships had large affection on the distributions. Examining the relation between the extreme value of wave bending moment expected to be exceeded with the probability of 10-8 or near order and sea state condition, it was found that the extreme value was ruled by only the probability of encounter of one or at most several severe wave conditions in a given long-term sea state condition. An approximate method of estimating the extreme value in a given long-term. sea condition was suggested from the fact.

船の最短時間変針操舵法(逐次高次化法)

船の最短時間変針操舵法(逐次高次化法)