International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 3

Number 3

September 2009

327

1 INTRODUCTION

Forming of a model of environment is one of major

tasks of the control systems. This model must ade-

quately reflect an environment, to provide the high

level of understanding of situations and serve as a

substantial auxiliary mean at the search of decisions.

Choosing one such model of environment for differ-

ent situations of vessels interaction is difficult, be-

cause belonging of elements of environment and

properties of operating ship to the categories «sub-

stantial», «unimportant» changes in them. It is also

difficult to get the universal method of decision for

preventing collisions. It is better to determine the

environment model and methods of decisions as it

applies to different situations. Then the choice of

strategies of conduct will be simpler, and they −

more precise. Therefore the local problem of devel-

opment mode for presentation situation of vessels in-

teraction and choosing an effective B-manoeuvre for

collision avoidance and passing at a safe distance of

targets was set.

2 FORBIDDEN DOMAIN FOR B-MANOEUVRE

FORMING

It is accepted, that the alterations of course of oper-

ating ship are instantaneous. At such condition a B-

manoeuvre looks like shown on a Figure 1, where K

− planned course of operating ship; θ − angle of it

alteration; Y − lateral distance from initial line of

way to the operating ship at the end of deviation; S −

length of deviation segment; C

и C

− points of

course alteration. Course for deviation to starboard

(K+θ) is designated K

, to port (K-θ) − as K

. An an-

gle θ for collisions avoidance can undertake from

to 150

, and for returning to the initial line of

way after passing vessels − from 10

to 45

Figure 1. Parameters of B-manoeuvre

Current positions of operating ship and scanned

vessel (target) is shown below on Figure 2 by points

C and Z. Taking into account presents of navigation-

al hazards and necessity to determine only dander

targets within navigable area the zone of manoeu-

vres and motion (ZMM) of operating ship is set

(maximum allowable track margin for current leg).

It is determined by width (Y

, Y

) of starboard

and port lanes for shifting of operating ship at B-

manoeuvres.

Beginning of lane of possible shifting to star-

board forms a segment CQ on the course K

=K+θ

The Display Mode for Choosing the Manoeuvre

for Collision Avoidance

L. Vagushchenko & A. Vagushchenko

Odessa National Maritime Academy, Odessa, Ukraine

ABSTRACT: The display mode is intended for facilitation of building strategies for collision avoidance by

so-called B-manoeuvres. It can be used in ECDIS, ARPA and the simulator systems. B-manoeuvre includes

the segment of deviation at a certain angle from the initial course and at the end of it the segment parallel to

the initial way’s line (planned route). The offered mode is based on the use of forbidden domains for B-

manoeuvres. These domains allow choosing parameters and beginning moment of B-manoeuvre for collision

avoidance with one or a few vessels. The account of presence of navigation hazards at the choice of B-

manoeuvre is produced by setting the borders of maximum lateral shifting from planned route. The offered

mode enables visual drafting of strategies for collision avoidance with vessels by successive B-manoeuvres. It

is possible to use this mode as basis of computer search of strategies for collisions avoidance with a few tar-

gets.

328

(Fig. 2), where θ

= set alteration of initial course

for B-manoeuvres to starboard. The butt end seg-

ment of port lane is directed parallel a course K

=K-

(θ

= set alteration of initial course to port). The

values of θ

and θ

can be both identical and differ-

ent. The current position C of operating ship is con-

sidered as the appointed element of both lanes.

Figure 2. Principle of construction of forbidden domain

Principle of construction of forbidden domain

(FD) is characterized in starboard lane on a Figure 2

(Vagushchenko, A.L. 2008), where

K, V = planned course and speed of operating

ship;

, V

= course and speed of target;

K΄ и V΄, K΄

и V΄

= course and speed of operat-

ing ship in relation to a target at true courses K, K

of operating ship;

= safe limit of distance between ships;

, A

= points of turn from a course K to the

course K

for passing a target at distance D

;

, B

= points of returning from a course K

the former course K for passing a target at distance

;

mnpqer = forbidden domain;

O, A

, B

= the FD center and points of turn from

a course K to the course K

and returning from a

course K

to the former course K for CPA=0;

A΄

, A΄

and B΄

, B΄

= points on the lines

of relative motion of operating ship, proper to the

points A

, A

and B

, B

;

- interval of lateral deviations from the

planned way which provide close-quarters situation

with a target at B-manoeuvres.

Distances S

and S

(J=0, 1, 2) from a current

place C of operating ship to the points A

, A

and

, B

are determined on intervals of time t

and t

for arrival in these points. These intervals

are calculated by values of S΄

and S΄

(CA΄

, CA΄

CA΄

and CB΄

, CB΄

) and V΄, V΄

V/St

AJAJ

′′

SBJBJ

V/St

′′

AJAJ

tVS ⋅=

BJBJ

tVS ⋅=

3 USE THE DISPLAY MODE FOR CHOOSING

MANOEUVRES FOR COLLISION

AVOIDANCE

The category of targets is determined on the loca-

tion FD in relation to the ZMM borders (Fig. 3). If a

target by transponder AIS reported the way points of

the route or informed about the set manoeuvre, then

an operating ship gets FD of this target taking into

account accepted information (target 5, Fig. 3). The

probability of possible maneuvering of danger or ob-

stacle vessels can be determined by the expert sys-

tem (not presented in this paper). In this case the

mode of situation can be added with the second FD

for this target, proper to possible new course (target

1, Fig. 3). These two FD of target 1 allow forming

the incorporated forbidden domain taking into ac-

count a possible manoeuvre of target.

Fig. 3. Situation presentation scheme

The B-manoeuvre for collision avoidance is de-

termined visually on the reflection situation on the

screen. The B-manoeuvre is set by pointing the cur-

sor, for example, on point C

. The trajectory of fu-

ture motion of operating ship would not cross the

forbidden domains. Point C

marked the end of B-

manoeuvre, after which a dangerous ship can be

considered finally passed. By a criterion for the

choice of B-manoeuvre it is possible to take mini-

mum distance of shifting (Y) from the planned line

on condition that the degree of risk of collision with

all targets will not exceed the legitimate value at the

point C

and manoeuvre will not conflict with

329

ColRegs.

The next action is then planned. Depending on

the circumstances one of three actions of operating

vessel gets out after the first B-manoeuvre: motion

along a new line parallel to the planned line (Fig.

4,a); returning on the planned line by B-manoeuvre

(Fig. 4,b); proceeding by the course to next way

point (Fig. 4,c). The borders of ZMM can be cor-

rected accordingly, if necessary.

Figure 4. Variants of conduct after the first B-manoeuvre

After this the point C

is undertaken as ap-

pointted element for new ZMM. In this ZMM for-

bidden domains are determined on the prognosis of

motion of operating ship and targets. Similar to find-

ing the first manoeuvre, the second and the follow-

ing ones are planned, if necessary. The point C

de-

termines ZMM until operating ship will not come to

this point, whereupon the current position of operat-

ing ship becomes the appointed element of this zone.

While searching B-manoeuvres at the beginning

by default the values θ

and θ

are undertaken as the

best from point of providing as noticeable a ma-

noeuvre and prevention of losses of underway time

(θ≈35

). When returning to the former line after de-

viation (Fig. 4,b), the value θ can be taken less.

If it appears that at the chosen values of parame-

ters θ

, θ

, D

a safe manoeuvre does not exist, it is

searched with other values -values of parameters θ

at the search are increased, and a value of pa-

rameter D

is decrease till the least allows value.

4 CONCLUSION

The offered mode for situations presentation simpli-

fies the choice of manoeuvres by a course change for

collision avoidance with a few vessels in open sea

and in the confined waters. Advantages of this mode

are:

− immobility of the domains in relation to ground,

that allows to define manoeuvres for collision

avoidance with mobile objects as with immobile;

− simplicity of account of navigation hazards by

setting the borders of lateral shifting from

planned way;

− possibility to form a strategy for collisions avoid-

ance with a few targets by successive B-

manoeuvres;

− possibility to use this mode as basis of computer

search of strategies for collision avoidance in any

situations.

REFERENCES

Vagushchenko, A.L. 2008. Perfection of methods for operative

correction of ship’s route. The candidate’s thesis on special

field of study 05.22.13 – Navigation and traffic control.

Odessa national maritime academy, Odessa.