An evolution in ship control

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A R C H I E F Lab. V. Scheepsbouwkunde

Technische Hogeschool

Delft

AN EVOLimOtrtN SHIP CONTROL

By C O M M A N D E R H . E. H . P A I N , D^S.C, R . N . (ret.)

24tk November, 1961

SYNOPSES.—The author presents in a descriptive manner the progress nùide in tke control of ship operations since the early days of direct control of the rudder hy hmd tiller through various stages to the present-day systems using a gyro or transmitting magnetic compass coupled to some form of automatic rudder œntrol. The remarkable improvement in gyro-compass technique embo<äed in the Arma Brown instnment that enables it to be installed in almost any position, in any class

of vessel, is shown integrated with auto-electric steering control. This is désigned

particularly to enable ii tó be incorporated in systems of " centralized " groining of information and control services when required, each tailored to the requirements of owners and type of ship operation.

ITie '* universal " tgrplication of the present system is iUustrated by its use in all types of vessel inclacSng liners, tankers, cargo vessels, cable ships, trawlers and yachts.

TTie need for still further standardization in the design and appUcation of navigation, control tmd skip operating services with the object of dchievJng an increase in éffîciency cmd rediKtion in /nanpower as well as in shipbuilding and operating costs is discussed. It is emphasized that the realisation of these objectives which are directed towards the ultimate goal of fully automatic control must always remain compatible with the maintenance óf tke principle of the economic, safe and timely arrival of a ship at its destination,

Deßrätion

B

EFORiË attempting to discuss the evolution and progress qf sKip

contrpl covering nearly half a century it will be necessary to de&w tb^ use made of the teirn "ship control" In the present context it is held to mean operation^ control sited in the bridge structure,, parti-cularly the basis at^d control of navigation and more generally the efficient passage of a vessel, from departure to destination. To the degree applicable it also includes direct operational control of propulsion machinery.

Introduction

In speaking of ship control it is pertinent to remember that the primary object of all shipborne dévices is to facilitate the execution of the a^njld principle " safe and timely arrival ", a phrase Üiat explains the purpose of everything concemipg a:ship. To arrive anywhere in whatever time, the direction in which to go is a first essential which l^ds naturally to considaation of the compass. The general reliability of the magnetic compass is accepted, and despite its limitations due to teri^tial and local magnetic errors, its use in ships if only as a stand-by will continue for a very long time to come.

It is the purpose of this paper to outline bri^y the background of the prœent-day gyro-compass and the development of the automatic helmsman ; then to discuss how the combination of advanced design in steering engine and steering

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'Sf'' .>•' • ^ P A I N : A N E V O L i m O N I N SHIP C O N T R O L

qo^^ol ^ n make a real coatribution to the streamlining of ship control miethods aóid'^acïiÊve a saving in shipbuilding and ship running costs ; and finally, to refer to present trends and future possibilities.

Until very recently the main datum for steering a ship automatically was the gyro-compass and it still remains the most efficient, although the transmitting magnetic compass can provide a valuable stand-by. It is therefore appropriate to examine in brief the main characteristics of a gyro-compass with particular reference to the latfôt development in this field.

The Oyro'Compass

In principle, evwy gyro-compass consists of a spinning wheel suspended in two &ames or gimbals so that it is free to precess about two axes (gimbal axes) that are nominaUy at right angles to each other and also to the spin axis, l l i e ©Toscope is arranged with its. spin axis approximately horizontal and its outer gimbal axis vertical. In addition, the gyro frame is adjusted so that it is actually or effectively pendulous (or top heavy) about the iniier gimbal axis, i.e., if the spin axis tilts by a small ainount so that it is no longer horizontal, a twque is applied which is proportional to this tilt and in a direction dependent üpOn the direction of tilt.

An essential condition for the operation of a gyro-coir^ass is its dependence on the fact that the earth is rotating and it is only the ïiorii^ntal componei^ts of the earth's rotation that contribute towards its meridiaa-sedcing properties. It is for this reason that it becomes more and more diflacult to achieve acranacy in north-seeking as a gyro-compass approaches h i ^ latitudes.

The method by which the gyro-compass ** finds " the north can be explained qualitatively as follows. Assume that the gyro-compass is bottom heavy so that when it is correctly settled the wheel will appear to be rotating clockwise, viewed from the south side. Assume also that the s^in axis is pointiog slif^tly east of north instead of exactly north, then because of the rotation of the earth the north end of the spin axis'vdll tend to rise, i.e., to follow the direction of the stm. Because of the pendulosi^ Of the inner gimbal the rising tendency will cause a torque to be applied to the wheel aboUt the inner gimbal axis, the direction of this torque being such as to precess the gyroscope about the vertical- or azimuth-gimbal axis back towards the nordi. Conversely, if the north end of the spin axis is pointing west of true north, a simUar but opposite seqùence of changes occurs. It wOl be seen that the combination of pendulosity änd the rotatiisn of the earth leads to the tendency of the spin axis to settle along the meridian.

The errors and pperational limitations of gjnro-compasses arise from distur-bance and perturbations Tx^fa result .in the spin axis* xoovjng out of the plane of the meridian. These disturbances arise &om impofections of the gimbal bearmgs and other sources of random torques about eithsr gimbal axis on the one hsuad and from accelerations in the motion Ofthe carrying vessel on the other.

The history of the development of and improvement in the gyro-compass is Èu-gely die history of various attempts to eliminate these S O I U X Ä S of error. This

is reflected, for example, in comparing Fig. 1, which illustrates an early non-transmitting gyro-compass, with Fig. 2, which ^ w s the remarkable compactness of a n ^ instrument. In the latter case, moreover, not only can it be installed in M i y convenient position in the ship, but latitude and speed corrections can, if desired, be applied continuously and automatically.

Essentially the new gyro-compass consists of two major assemblies within a sihg^ complete structure. One contains tiie meciianical components of the compass itself and the other fhe electronics, controls and r^îeater circuits. The latter embrace the latest printed circuit and transistor technûii^.

It is not intended to elaborate on the theory of gyro-compasses and it is unnecessary to deal in detail with anything other than the actual assembly Of the new instrument which does represent the most revolutionairy feature from the UMir's viewpoint.

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Tke Sensitive Element

Referring to Figs. 3 and 4, the sensitive element is compo^ of the gyro ball, the float tank, which supports the gyro spin rotor, and the pendulum assembly.

Gyro Ban

The gyro ball is a hermetically sealed spherical shell that contains the gyro spin rotor, assembly and two electro-magnets. These electro-magnets form part of a position-sensing device by which the motion of the ball relative to the containers roiind it is detected. The shell of the ball is made up of the ^ r o cases and two hollow hemisphraes (end bells) with their centrra coincident at the centre of the gyro rotor.

Floating Gimbal emd Torsion Wires

The gyro baB is supported by the surrounding fluid at neutrd buoyancy and is located by fine borizontaJ wires ctnmected to a small gimbal nested into a de^ annular groove around the drcumftxence of the gyro ball. The planie of the gimbal is perpendicular to^the spin axis of the gyro rotor. Clearance is provided between Uie gyro ball and the gimbal to permit movement of the ball without gimbal interference.

The horizontal torsion wires are comparable with frictionless be^-ings. However, a measurable angülar off-set tilt [»t\^^^ the gyro ball and the gimbal twists the torsion wires and a torque is produced about the horizontal axis of

the gyro.

The floa,ting gimbal is centred within the float tank by two vertical torsion wires. Similarly, a measurable angular off-set between the gimbal and the tar^

twists these wires and a torque is produced about the vertical axis of the gjro

bail.

Electric current is supplied to the rotor of the gyro ball through the torsion wires, and through four flexible silyer-wire helical coils located concsntrically with the torsion wires.

Float Tank

Referring now to Fig. 4, the float tank contains the gyro ball and floating gimb^. The space between the gyro ball and the tank is âled with a high-densi^ nOn-conductive fluid that holds the gyro ball in a state of neutral buoyancy at the normal operating temperature of the fluid that is arranged to bë well above ambient. Because of this neutre buoyaiù^, the torsion wires do not transmit any forces to the gyro ball when the tank is subjected to accelerations.

The float tïuik is trunnioned to the tilt gimbal by means of pivots on the axis normally in line with the gyro spin axis. Tlw tank is free to swing about thes© pivots between limits of plus of mraus sixty degrees and is made pendulous so that its mean position is truly vertical. Viscous dampmg is introduced between the gyro tank and the tilt gimbal to reduce the swinging of the tank dm to east-west accelerations.

Azimuth and tilt-position Sensing Coils

Two sets of coils are mountoi m the float tank in line witii the gyro spin axis. These are the azimuth and tüt gyro-position sensing coils. T h ^ are placed so that they are opposite the electro-magnets inside tttô gyro ball and can thus sense any magnetic field induced by the electro-magnets inside the gyro ball. A n angular displacement between the gyro spin axis and the tank causes tbe sensing coils to produce a volta^ that is proportional to the displacement.

Because of the intercomiexion between the two sets of pick-o£&, the v o l t a ^ indiwed by any translational d&placemait are cancelled out and no output results. These sensing coils and the electro-magnets are the major cont-ponents of the gyro-position sensing system.

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60 P A I N : A N E V O L U T I O N I N SHIP C O N T R O L

Pendulum Assembly

The pendulum assembly provides the vertical reference for the sensitive element. It is a small Iwrmetically sealed unit mounted directiy on the side of the gyro float tank and senses the tilt of the tank about its east-west axis. It translates the tSt ofthe tank about its nominally east-west axis into aproportional output voltage whidh is intiroduced into the servo loops togetiier with the outputs pf the azimuth and tilt gyro-position sensing coils. Within the case, the unit contams an electro-magnet pick-off device and a penduliim bob. A highly viscous fluid is used to damp the pendulum bob with respect to the case.

Gimbailittg

The sensitive dement is supported by two gimbals whose axes of rotation are màtually perpendicular. These gimbals are driven in azimuth and in tilt by their respective servo-drive assemblies.

Ths tilt gimbal supports the sensitive element by free-swinging pivots. This

gimbal is in turn supported along its east-west axis by the tilt pivot on the azimuth gimbal. Stops are provided to prevent it from rotating through an angle of more than plus or minus sixty degrees with respect to the azimuth gimbal. It is also medhaniqally linked to the azimuth gimlial by a servo-gear tram.

The azimuth gimbal rotates about the vertical axis. Its bearings are supported by the gjro compass chassis, which is in turn fixed io tiie carrying vessel. It is driven about its vertical axis by its own servo motor and gear train. As has been said, whoi the axes of the gyro and the tank are aligned, there is no output from the position-sensing coils. If a bias signal is placed in srai« with the sensing coil m the servo loop the input will be the sum of the pick-oflf signal and the additional bias sign^. A servo motor will then drive until the output ofthe pick-off is exactly equal to the bias signal in magnitude and of opposite polarity. The siun of the two signals is then aîn zero, and the servo is again at a null. Since the pick-off output voltage is proportional to the angular displacement between the baU and the tank, the servo, in re-establishing its null, produces an oêt tetween ball and tank proportional to the Has signal voltage. A displacement between the ball and the tank twists the torsion wires centering the gyro withm the tank. The torque on the gyro is prcîortional to tte amount of displacemem. Thus, a torque may be applied about the vertical axis of the gyrO 1^ inserting a signal into the azimuth servo loop that is pro-portional to the desired toique. Similarly, a torque may be applied to the horizontal axis of the gyro by inserting a signal into thè tilt servo.

The sensitive element pf a directional gyro must be horizontal with respect to the surface of the eardi and corrected for azhnutb drift.

In the new gyro, azimuth drift is eliminated by a horizontal torque as just described so that the presence of tprque bias ih the tilt wire is-compensated for without the need for having fhe sensitive element in a tilted position >yhea it has settied- This has the important advantage that when t^ instrument is used as a directional gyro by switching off tlw pöidulum signal (in very latittides, for example) the gyro will not show a large error drift rate in azimuth due to an uncompensated torqiw bias on the tilt axis. A manually operated speed control introduces a bias voltage into the azimuth servo loop. When set to the speed of die vessel between the range of 0 ^ 0 knots, the gyro automatically remains pointing north.

A further manually operated correction signal corresponding to the latitude of the vessel is applied to the tilt servo motor whidi creates a displacement in tiit between the tank and the gyro axis. The effect of this displacement is to apply a torque to the gyro about its horizontal axis proportional to ttus latitude setiing. The torque produced by tiiis signal is just sufficient to precess the gyro at the same rate as the local vertical component of the earth's rotation.

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To make the gyro nortih-seeking, a part of the pendulum output is added in ^ e s with the gyro tilt pidc-oC As the spin axis starts to tilt, the tilt servo vyill drive the tank in tilt to keep up with the gyro ball. As soon as tiie tank tilts, , the pendulum generates an output, which produces a tilt offset between the ball and tank. This offset vnnds Up the horizontal torsion wires, which apply a horizontal torque to the gyro ball, resulting in azimuth precession. Tlie pendulum output is connected to the tilt servo in such a way that when the north end of the spin axis rises relative to the horizontal it is made tó precess to the west. When it dips, the precession is to the east. In ttiis way the spin axis is made to precess towards the meridian. In addition and to reduce oscillation about the meridian, damping is introduced by adding a portion of the pendulum output to tiie azönutii servo.

That briefly outlines tiie tedinique used in the latest gyro-con:^)ass. In summary, it achieves a radical reduction in size and weight combined with accuracy at least equal to all earlier types. Speed and latitude corrections are manually applied ^ d then automatically compensated. Installation problems are greatly reduced and routine maintenance by ships' staffs ^bmost eliminated. It maintains the advantage of earlira- g>To-compasses in its ability to transmit heading reference to repeaters and recorders, to the direction finding apparatus and to radar (an essential feature of "true motion" equipments) and {lerhaps more iii:4)ortantly, to the automatic helmsman.

Two features are notewOTthy. These arc the built-in ability to accept an automatic speed' correction input from the ship's log when available and the faciUty to incorporate an automatic monitoring device which indicates when the

gyeo suffers a long^terin disturbance, causing it to deviate from its normal

séttling position.

Automatic Steering

When the eariy type of gyro-con4)ass as illustrated in Fig. 1 had been given the added facility of being able tp transmit heading reference to remote positions, it was a natural step to consider using the information so iransimtted as the basis for automaticaUy steering a ship. At first this was achieved by medianically Ihildng a control system to the tdemotor transmitter in the wheelhouse as shown in Fig. 5. From this concept stems the many varieties qf automatic helmsman now available.

It will not be nëcœsary to d ^ ^ all the advantages Of the ability to steer â ship automatically, even if it ware possible to get agreemMit as to precisely what those advantages are. They certainly include a more effident patii through tbe water, the effideiwy inareasing by comparison with the human helmsman as sea conditions deteriorate. They also indude the replacement of the human helmsman or alternatively teaving him free for otlwr ^ties and to a vaiying and arguable degree an increase in speed,, reduction in fuel consumption and lessening of ship war.

tn manual steering the helmsman applies hdm to coirect an observed deviation from the required course. As the ship answers, tiie helm is r c t u n ^ to amic^hq» and then reversed to check the movement. This must result.in a more or less continuous cycle of movement of the controls and the ship's heading generally atout a mean. - In automata steering the same applies but the cycle is more regular because of the greaUa: sensitivity to deviations of the ship's heading from the mean and to faster responsive action in correction. The gyro-compass will sense a very small change in ship's heading and can initiate rapid correctiye measures.

In the • metiiod of automatic steering to be described, the response to a deviation signal from the gyro compass operates through a dirostional control dement or " Brains Unit " and breaker switdies, which in tum control an electric motor (After Power Unit) cormected to and contiolling thé steering engine.

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compass (I) is trarramitted to a follow-up " compass " motor (2) connected by gearing through a differential unit to the contact dnun of the brains unit. As the compass motor turns it changes the positton of the contact drum. The drum is made up of copper segments insulated from one another, while attached to the drum axis is^a bracket cariying two sets of trolley roller contacts (3) which are free to revolve around the drum in such a way lhat they wiD remain at rest in one of two positUsns, port or starboard. The angular distance of either the port or starboard position from the centre can be adjusted by a mamiaÜy operated rudder angle adjustment which thus controls the extent of the initial application of rudder to check ship's head (Fig. 6).

Ihe roller cont^ts are racked together so that the distance between them can be varied by a manually controlled contact .roller or yaw adjustnœnL This controls the sensitivity of the steiering and vrill ensure the most economical use of the rudder (Fig. 6).

Movement of the roller contacts on the drum is governed by a pair of electro magnets (Trolley Coils—4) mounted on each side of the " Y " asseanbly carrying the roller contacts. The bracket holding the comacts has a magnetic pole shoe attached each side of the rotating axis. When the electro magnets become energized by the roller ràntacts making contact with the copper segments of the drum, tiiey attract tiie magnetic pole shoes. Direction of rotation is governed by the movement of the drum. If Âe drum rotates to starboard the port contact segment vfäi make contact with the port trolley contact and so energize the port trblley coils. The whole..contact roller assembly will tiien rotate to starboard an amourit controlled the rudder a n ^ adjustment governing the amount of rudder movement initially applied.

The cyde of operation can be appreciated by referring to' position (2) of the sequence diagram in Fig. 7 which illustiates the position v/ben the drum has been rotated 1^ the repeter signal from the compass opautiog the compass motor. Contact is made between the drum and one trolley rpUer, energizing the appropriate trolley coil to rotate tiie whole contact roller assemWy an amount dependent on the rudder aingle adjustment (position 3).

At the same time, this contact will energize the operatmg coils of one of the breaker switches, allowing the electrical chcuit to the operating field of the power unit contiolling the steering engine to become energized. The power unit will apply rudder^and in so doing operate a large three-finger distributor, which is incorporated as the rudder feed-back transmitter (6). Connected to the opposite side of the differential from that of the compass motor is the feed-back motor (7). This wiU receive the transmission from the feed-feed-back trans-mitter and will reposition the drum until the trofley contacts are on the insulated strips of the drum (position 4). This automatically de-energizes the rudder motor so tiiat the rudder itself does not move any further. The sliip begins to answer the helm, the compass repeater system indicates tiie movement, operates the compass motor and r^ositions the drum (position 5). Contact is made between the drum and the opposite trolley roller c o n t ^ to that ia position 2, energizing the appropriate tiolley coil and rotating the whole contact roller assembly as far as the rudder angle setting allows. Thus movement of the roller assembly will be twice that of the origmal movement in order to allow the rudder to be moved back through amidships and into the opposite sense (position 6). This contact at the same time will operate, the other breaker switch and in so doing operate the cycle tO apply rudder. The feed-back trans-mitter wiil function and will reposition the contaa drum via the feed-bade motor until the trolley contacts are on tiie insulated strips of the drum (position 7). The automatic hdmsman will continue to operate in this way, maintaining the same-smooth rhythmic cycle to give substantially stiai^t course keeping.

The angle of rudder apphed will be determined by the time period prior to the feed-back system operating. This is governed t^* the mechanism of the feed-back transmitter and the ratio of the gearing between the feed-back motor and the contact drum. Similarly, the movement of the trofley roller contact

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assembly .will affed this period,, the goyernmg factor being the angle of the trolley roller contacts rdative to the contact drum, which is directiy influenced by the rudder angle and yaw adjustmems.

It will be seen that the system is essentially a " hunting " one, although this effect does not make itself felt on the ship. The normal period of hunting wiih

depend on the yaw and rudder settings.

To safeguard against the possibility of the helm going " hird Over " ouX of coritrol, limit switches are incorporated which wffl break the circuit to the contrbl motor connected to the steering engme in the event of a failure of the feed-back transmitter.

This very simple method of automatically controlling the steering engme of a ship has b^m in Use for many years and in fact forms the basis of eadi of tiu systems to be described.

To meet the requirement to steer automatically a wide variety of vessels, each with its own particular characteristics and jroblems, especially those of space limitation, a number of different types of mechanûal hebnsmen have bewi devéloped whidi are all suitable for the control of any type of power assisted

steering en^ne.

The simplest provides automatic steering only and is intended for use in vessels where the main system of manual stosring is by tdemotor transmitter. The directional control imit already described is used and the yaw and rudder angle adjustments illustrated in Fig. 6 are included. An additional feature that bäs always been very much a requirement in all types of automatic hehnsmeny is tihe " course adjustment ". This eriables small corrections to be made tó the required course when steering automatically without interfering with the operation of the automatic hdmsman. The control knob for adjusting the course is mKhanically coupled to the feed-bade motor of tjtie directional contiol unit. When the course adjustment knob is engaged, it operates micro-switt^ that isolate the compass repeater circuit to the cornpäss motor. A drcuit from a step-by-step transmitter is at the same time coupled to the compass motor and tbs diredional control unit is positioned by rotating tiie knob and thus applyir^ rudder sufficient to automatically alter Ûœ course to be steered; A typicd installation of this shnple automatic helmsman is shown in Fig. 8 of the deep-water trawle- Prince Charles. The separate gyro-stœrii^ repeater forward of the main stearing position will be rioted.

Hand Electric Steering

It may seem stiange that the simple equipment just decribed was produced mudi later tihan more comprehensive systems embodying hand electiic steering control. This was due to the comparativdy slow adoption of gyro-compasses {and automatic steering) in the smaller classes of vessel, including trawlers. It was because of the requirement for automatic steering in ships with small wheelhouses that the single, straightforward automatic helmsman was produced ahhough since then its use has not been confined to these types of vessel.

As origmally conceived, the ability to control the steering engine manually by electric mearis was by way of being a bonus when an a:ütomatic hdmsman was -fitted. The prirnary reason for the hand electric steering wheel was pwhaps more to enable quick alterations of course (or course adjustments) to be made wtei using the automatic helmsman without reverting to tdemotor steering control than to act as an alternative means of steering the ship. Because of tite simplidty of operation and ease of movement the sriiall " hand electric " wheel became more and more popular arid in pradice was frequfäitiy used instead of the telemotor transniitteir. At tihis stage it was significant that the hand électif wheel exactiy simulated ihe movement of the large telemotor wheel in that the operation was " follow-up ", that is to say, the movement of the wheel was proportional to the degree of rudder appli^.

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Using the metihod of automatic contiol already described which, of course, did a,way with tiie mechanical link to the tdemotor transmitter (as Fig. 5) but stâl incorpoc^ing hand etectric steering and gyro-steering repeater, a.system was evolved in which the main wheelhouse control unit was intended for instaUation immediately alongside the main tdemotor steering imit. This concept, streamlined and given a modem design of form, remains as the sfandard alternative installation to the siniple form (Fig. 8), They are both designed to permit retiospêctive installation in existing sMps for wïdch the requirement is stated.

By 1955 the move to deam up the miscellaiiy of mstniriierits distributed about tihe wheelhouse was already evident in all classes of vessel. There were several reasons for this process of rationalization. Very great strides had been made in the development and introduction of a wide variety of new and often novel aids to navigation and contiol and there seemed almost a dangira: of ships' officers suffering from a sort of technical indigestion. The new devices in many cases seemed to lend themsdves to grouping or were suitable for re-engineering to this end—often it can be said at the behest of shipownd-s. At tihe same time, owners were faced with ari increasingly urgent need for economy combined witii a decrease in available trained crew members. Peihaps also it was becoming really necessary to offer inducements in the way of advanced operating techniques as well as personal comfort.

One effect of this drive to concentrate information and control services was the introdudion of the single steering control unit tihat incorporated the tdemotor tiansmitter, haxid dectric steering and automatic steering, still a fairly bulky piece of whedhouse fmniture but certainly occupying less s p ^ as well as lobkihg tidier than the separate installations.

The new comprdiensive console well illustra:ted how possible it was to combine instruments of diffd^nt manufacture while at the same time providing tihe nôMSsary ready access for servicing and adjustment. As shown in Fig. 9, the diange from any method of steering control to anotiher could be made almost instantaneously by the moveutent of a single lever. It is also wortih noting that to meet all objoctions on the score of safety aod reliability, inasmuch as this was something of a reyohxtioaary conçut, the complds console and power unit for connexion to the steering enipne preswved in every way the accepted appearance of robusmess m steering control units.

While noting that the combined steering console and the earlier separate units are still in majority demand, it must be emphasized that the instrum^t ih Fig. 9 represents what may well be the last of an era. A more radical change in steering ccmtrol has been in service for a number of years and there is every s i ^ tImt it- is being more widely adopted for new buildings in all classes and typfô of vessd.

Steering Engirm

Before going on to discuss new technique and particularly the introduction of more advanced metiiods of automatic control, it is important to remenriier that we have been shipniates witih ä pièce of distant control mechamsm connected with aiitomatiqn ever since the hand-operated tiller at the rudder head was replaced by a steering wheel whidi was hand operated with ropes wired round the barrel, the rotation of which one way or the other determined the movement of t ^ rndder. The distance firom tihe steering whed to the rudder head was a matter of a few feet and since the ship was iri any case conned from aft, the task of steering, though heavy, was not over difficult for the very brawny seamen of those days. Iri larger ships it was necessary to employ a double wheel, i.e., one at each end of the barrel and in very rough weather the wheel, which was really one of the most in:q)ortant mecha^beed items on board had to be double-manned, it was the graulual Introduction of steam plus the change In con-struction from wood to iron and then to sted whidi led to tiie changes upon which ésîgn of the modem steering gear is founded. Employment of machinery.

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first for paddles and later for screws, made it convenient to place the conning position of the ship amidships, making a kind of bridge, hence the perpetuation of this name, between and supported by the padtÙe boxes with a voiœ pipe to the starting platform of the engines bdow.

Availability of steam suggested the use of the reciprocatmg principle to turn the rudder-head by power, la early days when the screw ship took over from the paddle-ship a redprocating engine was mounted on the aft engùje-room bulkhead in thie casmg, operatii^ tihe rudder head by means of rods and diains on the port and starboard sides respectively, the steering wheel itself acting as a species of throttle to the redprocating engine with its rods arid chains.

As steamers mcreased in size it was more convenient, because of the larger size of the rudder head, to place the reciprocating engine operating it at tiie after end in a steering flat. With this arose the need for some method of distant control. The hydraulic principle and tite tiller motor provided the solution, first in association with hydrauhc rams as the size and power of ships ipCTea^ and later, much later in fact, when eilectricity c^me into its own for auxiliary purposes aboard ship, eledric motors were used to control the variable delivery pumps which actuated the oil pressing in the rams. That method, in prindple, has. been standard in s h ^ for many years and it is still difficult to find anything to beat it for reliabihty and flexibility.

The modem tendency with many vessds, particularly those devoted to the carriage of bulk cargoes, is to plàœ everytmng aft. A late devdopment in steding gear is the rotary-vane type in whidi the rams and cylinders of the conventional electro-hydraulic steering engine are replaced by a series of two or more, usually three, vertical vanes which are secured direct to :tiie rudder stock. A stator or cyUnder divided into sections by fixed vanes which aUow the designed rotational movement of tihe rudder, endoses the movmg vanes and is secured to the sbxp^s structure. If fluid is admitted under pressure to one side of tiie moving Vanes, the vanes and rudder stock will rotate, thus tuming tite rudder. This system requires less dedc space and as the arrangement has fewer moving parts, installation costs are reduced. The cost of the f otary-vane types can be 1^ than that of an equivalent 4-râm type and weight is greatly reduced. A Peering engine of this type ÜKtalled in the 11,000-ton tariker Monsoon is shown in Fig. 1Ô.

There are soriie who favour all-electric stea-ing engines in which an electric motor is attached directiy to the rudder head but tihe combined hydrauhc and etedric engine is stiU the most popular. It is also to be noted in this coimexion that we may experience dianges in the whole technique of steering if the tendency to employ sideways " movement deviœs " persists. Of course, the joint functions of steering and propulsion are embodied in cycloidàl propdling arid large outboard propulsion devices with a 360 degree rarige of steering witii full thrust at all angles.

As will be seen, it is true to say that the modem steering engine depends for its primary method of operation on an adequate and safegûarded eledric supply. It may also be said that the increasing relknce on eledric current in ships has reached the stage where a failure in eledric supply is tantamount to a failure in ship operation. Moreover, great strides have l>een made in this field, and witih the provision of multi-supply sources and channels and all manner of emer^ncy arrangements there is no doubt that ov^ners are justified in accepting a more or less inevitable situation.

Cto this basis, and spurred by the urgent necessity to make a positive and realistic apprpach to tihe incr^singly complex problems of ship controi, a new appreciation was made in whidi steerir^ control was accepted äs thë essential nucleus of aÜ systenis. This therefore formed the subjed of the first re-engineering project.

Auto-Electric Steering Control

R,eference has already been made to the increasing use of the small hand electiic stewing wheel incasrporated in the separate and combined automatic

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66 P A I N : A N E V O L U T I O N I N S W P C O N T R O L

helmsmen. It seemed a logical step, therefore, to Use this method instead of the telemotor transmitter as the primary means of steering a ship. To meet operational requhements a second and quite independent hand electiic conurol system was added. The well-tried method of automatic steering was mcorporated.

To provide for the probable need to embody the main steering control îasembly in combined instrument consoles of possibly a variety of makes, tiie project was engineered to require access for servicing only at the after end. This was a nwjor advance in instriiment techniques permitted lar^ly by the reliance on electio-medianical rather than electionic metiiods. The s ^ e facility also allowed the steering console to be sited diredly against a bulÜiead— an important feature in small ships where space in the wheeQiouse is limited.

The older systems employed a àngle after power unit actually to operate the steaing engine without othd* modification. The new systan induded two such rniits, requiring only one to be in operation at a time. Facilities were provided to permit any two methods of control to be switdied to one after power Unit witii the third metiiod switehed to tite other at " stand-by ". In practice, primary hand dectric and automatic control were groupied together, with secondary hand dectrk control being used as the stand-by syst^ on the second after power unit.

To increase the flexibility of installation in all ^pes of vessd provision was made to use two varieties of after power unit selected acccrding to tiie tihnist loading of the steering engine. This not only made installation problems easier in tihat the srnall after power units matched the restrided space in small ships but also to some degree matched tiie cost to the size of the vessel.

In any case the installation could be tailored to the space available. Fig. 11 shows tiie Canberra installation with large after power units and Fig. 14 the sniall power units in the trawler William Wilberforce. Xn both wiU be seen the rudder-angle transmitter cormected diredly to the rudder stock. In this connexion it will be noted that the cost of all hydraulic gear forward of tibe steöing engine presented a saving whatever tihe type of vessel. Stiüül further devdopments substitute a single after power unit metiiod. hi this case a further saving is adxteved in botii cost of the system and instEÜlation. But this does not represent the ultimate in means of controlling a steering engine.

There axe, of course, a number of types of afl-electeic steering engines in use and here the problem of control with the auto-electric system is actually sim-plified. Instead of after power units to operate the control ^^ve of the steering engine a feed-bade trarismitier is connected to the rudder stock for automatic steering. The feed-back transinitter can also be used with some rotary yane-type steering engines, again with a decrease in cost. Fig. 13 illustrates the use of the feed-back transmitter technique in the 11,000-ton tanker Monsoon, in this instance with a type of rotary-vane steering engine and is for comparison with the two after power unit systems used in William fVilberforce and Canberra.

Electric Principles of the Auto-Electric System

The initial eledrical input obtained from two entirely different mains power supplies is connected to a single four-pole, two-way switeh tp provide a change-over in tihe event of a power failure on one Une. This switeh, which is located in tiie whedhouse contiol console, gives two completejy separate operating circuits for the three forms of control from the bridge unit—" Hand ", " Auto " and " Secondary ^'—wluch are selected through a nuister sdector switch also in the bridge console, the two inputs are usually connected in sudi a way that one will provide the operating supply for " Hand " and " Auto " contiol while the other is for " Secondary ".

A further changeover switch in a separate breaker switch panel in the steering flat enables eitiier of tihe control operating circuits to be ahemated between either after power unit.

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P M N : A N E V O L U T I O N I N S H I P C O N T R O L 67

" Hand " Control

The supply input passes to the main terminal block in the bridge console to complete the followmg circuits through mains suppressor, fuses and the mastdr selector switch i—

The field circuit of the after power unit selected for" Hand"and" Auto" contiol, via the main terminal block of the bridge console and the breaker panel and changeover switch in the steering compartment.

The motor fidd circuit and the clutdi unit of the after power Unit are energized and the " Power On " indicator lamp in the bridge console for " Hand " and " Auto " position is lit.

The haridwhed on the bridge console will operate port and starboard switches as it is tumed one way or the other. This will complete the following circuits and apply rudder as required :—

The control circmt (with, say, port helm applied). Current will pass via the port switch on the handwheel t&ough the main terminal block to tile breaker panel and the chan^over switch in tite steering coriipartment and thence to the selected after power uriit.

The return circuit is nmde through the limit switch arid back through the breaker panel and cHan^over switch to the bridge consolé breaker switehes and thence to complete the after power unit motor armatiire circuit.

The after power unit will operate and in so doing position the control valve of the steering en^ne causing rudder to be applied. This will continue as long as the handwheel is kept over, until such time as the hard-over positiori on the rack travel of tiie after power unit is reached, which wfll open tiie limit switdi and the control circuit for the motor.

" Auto " Control

" Auto " contiol is governed by the refwater circuits from the gyro-compass operating the brains unit in the bridge console. The brains unit wUl automatic-ally determme the corredii^ l ^ m required xo suit vtójang conditions subjed to <%rtatn corrections t^ing set on tihe Unit as described earlier.

When tihe operatmg lever is put to ** Auto " t>yo circuits are completed initially as in the " Hand " position.

The compass r^)eater circuits are conneded to the (xinipass motor of the br^ns unit. The trolley rollers and tlw contact drum vrill then rotate so fhat contact will he made bdween one roUer arid one segment of the contad drum, dqididing dn whether port or starboard helm is to be applied, this will complete Ö M çontrol circuit via the limit switches of the afba* power unit sdected for use, as with " ï f a n d " Controi. Hw control circuit will conq>lete the mot<»: armature circuit, the after power unit wOl operate and apply rudder.

It will be appreciated that it is essaitial for the correct operatiori of the brains imits that a f^-back circuit is made from the after power unit. This is obtained from a large three-finger distributor, which is iricorporated in the after pow«: unit as the feed-back ti^iismitter. Connexion is made from this transmittd to the breaker paiiel, tiie diangeovo: switdi and thence though the briii^ console to the feed-back motor ofthe brains unit.

Secondary Control

On switching to " Secondary " control,, the supply input passes from the bridge unit to tiie master control switch and theiux to complete the field drcuit of the opposite, afttt power unit to that used for " Auto " arid " Hand " control and to Hght tite indicator lamp for "Secondary" control. "Secondary" control will operate separate port and starboard switches as applicable. This will apply rudder as required by completing tiie following circuits :—

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terminal block to the breaker panel and changeover sv/iïiâi in the steering compartment and thence to thé other after powra- unit to that used for " Hand " or " Auto " control. The retum drcuit is made from the other side of the limit switches in the after power unit, back through the breaker panel and diange-oyer switdies to the breaker switdies in the bridge unit. The switches will operate and in so doing complete the motor armature drcuit.

Motor Armature Circuit : The mains supply, conneded to the breaker

switches, completes a circuit tihrough tihe contad made by the dÈiangeover switch and thence to the motor armature of the other after power unit to that used for " Hand " or " Auto " control. The after power unit will operate and in so doing will position the control valve of the steering engine, causing mdder to be applied.

An installation of this type is shown in Fig. 14 of the trawler William Wilber^

force buüt by Cook, Wdton & Gemmeïi Ltd. for F. T. Ross & Co. Ltd. It

wül be noted that the main steering wheel is simflar in appearance and operation to the hand electric wheel shown in Fig, 9. Secondary control is by push-buttons located at the top of the unit.

Thus, dthough a somewhat revolutionary change from traditional methods of steering control, the main system continued to provide the familiar " follow-up " type of whed.

Technically it was considered that a less complicated method of control would provide greater effidency and would also pennit a further re-engineering to reduce cost This meant, however, a complete dqaartuie from tradition ajid it was po-haps with some hesitation that in 1957 Houlder Brothers installed a *' dired-ading " version of the auto-dedric system iri their 18,500rton tanker

Denby Grange (Fig. 15). Thé spoked wheel was replaced with a small half-hoop

aeroplane-type wheel with a limited movement of about twenty degrees port and starboard. Electrical operation of this main control was simflar to the secondary " push button " method although using entirely separate circuits. The simple movement of the wheel gave rudder operatitm at a constant speed and still further reduced the effort required to steer the ship. It is significant as Ulustrat-i Ulustrat-i ^ the effUlustrat-icUlustrat-iency and relUlustrat-iabflUlustrat-ity of the system that HoUlustrat-iüder Brothers have continued to usé the most up-to-date version of auto-electric in all their new buildings since the Denby Grange.

Remote Steering Control

If main steering control could be vested in eledric wires, then a simflar but subsidiary method could very simpiy be incorporated in the system, thus providing at low cost additional steering facilities wherever required. For instance, it could control cable laying opitions at the bow as shovm iri Fig. 16 of the bow-baulk control compartment in the cable and wireless repair ship

Retriever which enabled steering control to be taken over at the tum of a switch.

In tiüs operation a small lever performs the same function as a whed or push buttons.

" Combined " Auto-Electric Steering Controls

Several of the electro-hydraulic and eledric steering en^es in general use provide hand electric instead of telemotor steering contiol. In co-operation with the manufadurers concemed the auto-electric ^ t e m has been combined with these standard steering controls to provide, in the same or similar small whed-house unit, all the facihties of the complete auto-electric system. Such a combination was installed in Monsoon. As already explamed, the steering engine in this vessel is of tihe rotary vane type and uses a feed-back transmitta: for automatic steering contiol instead of after power units.

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P A I N : A N E V O L U T I O N I N SHIP C O N T R O L 69

Bjidikr Angle Indicator

Although all varieties of the auto-electric main and auxihary steering control ünits incorporate a " niddey applied " indicator, rudder-an^ indicators opiated by a mdder-angle transroitter connected to the rudder stodc are always included in the system as essential safeguards.

Centralized Control

A further step in the development of the auto-dectric system was taken in April 1959 when a paper entitied " Centraflzed Coritrol in Trawlers " was presented to tite 2nd World Fishing Boat Congress of the Food and Agriculture Organization of the United Nations held in Rome, tt is rdevant here to quote from that paper. In conclusion the authors said :

" An early decision by û\& owners to take advantage of centralized control would enable the nayal architect to prepare the most economical whedhouse dföign leading to a change in tbe size and shape of the bridgp and a saving in wei^t and cost. Installation problems would be modified and stream-lined. An economy io manpower would be achieved with, at the s ^ e time, reduction in fatigue and increase io operating effidency."

Fig. 17 is of one of the sdiemes postulated in the paper for grouping instra-ments and may be compared wijih Fig. 18, which is of the combined instrumait console installed in the .deep-water trawler D.B. Finn built by Cook, WdtOn & Cr^nmeU Ltd. for the St. Andrew's Steam Fishing Co. The remote steering control and hiding indicator to starboard wfll be noted. AltCTnatively, and in much larger ships, the whedhouse contiol unit in Fig. 19 of tite Retriever and the bridge of the P & O-Orient Liiw's Canberra in Fig. 20 are interesting examples of very recent adaptations of these techniques.

The Canberra is a particularly interesting ship, incoiporating many notablte features germane to the present discussion ^ d it will be worthwhfle to note how cominehensive is her contiol system. Fig. 21 ôws the conîlete anto-etectric system for the Canberra in schematic forni. Induded are the main and secondary steering coiôl units (Figs. 20 and 24), twin after power units and mdder feed-back tiansmitter (Fig. l i ) , long-range mdder ang^ indicator for the wheelhouse (Fig. 20) and miniature iiulicator for the engine-room contiol console (Fig. 22) ; bearing repeaters, for the bridge wings and a repeater for the passeof^r observa-tion lounge and the . secondary steering cabind aft ; longrrange heading indicator for the wheelhouse (Fig. 20) and a special table-mounted repeater, for tiie conunarider's cabin. The system includes à steering contiol position changraver switch which is sited iri tiie after steering cabinet.

On »tamining Fig. 20 more closdy, it will be rioted that the wheefliouse is divided athwartshlps by a large navigation console stmdùre. Thtó consists basically of a diart table with Decca navigator, echo sounder and radar displays including a special large-scale Kelvin & Hüï^es photographic plotting display. Ón the after bulkhead the console constracted by Clifford & SneU LÏd., incor-porates ail the warning, alarm arid iritcrcommunication contiols and displays, lighting, ventUation and watertight door controls and the stabilizer controls. ForwM'd of the navigation console can be seen the main auto-electric steering contro! unit with the Kelvin & Hughes fransmitting magnetic-compass repeater alongside and to port. A reflector from the same standard compass projects from the deckhead. On the forward bulkhead amiddiips are two instrument panels. The upper incorporates the mdder angle in^cator and revolution indicators whilè that below indudes a gyro heading indicator, echo sounding i n d i c a ^ and radio telephone. Together they provicte the immediate fadlities required for close-rwigé navigation, particjilarly in pilotage waters. Qose at hand are the athwartshlps propdter controls, which are also duplicated at each wing of thé bridge, i n tbis installation the nmm-cngine order telegraphs are placed either sidc:in the wheelhouse stmcture.

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70 P A I N : A N E V O L U T I O N I N S H I P C O N T R O L

There is, of course, nothing new in the basic idea of grouping information and control services and it wifl be seen that a lot of prpgress has been made along these lines. It is probably true to say that the greatest shipbome advances haye been achieved in the dectrical and machinery di^artinents. Fig. Ä of the main-engiae-room control console i n Canberra illustrates tibis. The reason could be that the suppliers of tihose services are Often also responsible for tiie means of cprurol. Moreover, main propulsion and auxfliary macätinwy have changed quite radically while navigation has remained very much tite same, whatever means are used to achieve the desired result.

It is very rarely that the layout of two wheelhouses is the sariie, a l t h o i ^ ships of the sanw dass may be similar. Every owner and superintendent lias his own ideas, and it is often difficult to justify expraditure on devices that apparently are extra to the basic needs of navigation. In the smaller ship more progress has been made towards what may be called " one man " operation. This has to some extent been <lk:tated by operational necessity.

Fig. 23 shows the main propulsion and stecrmg contiol unit in the 110-ft. near-water tralwler Hazelhead. Gyro-controflisd automatic steering is not mcluded because it is not required in thetype of operation of tilmt dass of vessél. The main steering contiol unit is therefore the same as that forming the secondary steering imit in laiger vessels, as fbr instance in Canberra (Fig. 24). Main-e n ^ Main-e o r ^ tdMain-egraphs, rMain-evoliiticri and variablMain-e-pitch propMain-eljMain-er cpntrols form tihe outer portions of tihe complete console construded by Bloctube Controb Ltd.

The much more comprehensive console in the D.B. Finn (Fig. 18), also constiructed by Bloctube Controls Ltd., incorporates Marconi equipnierit and incliules twb radars, three echo sounders, communication and fishing operation controls as well as auto-electric steering control and standard engine ordd: telegraphs.

The ufdversality of the system is shown by the fact that the steeruig conttol Uriit iri Fig. 25, or its variants, is used in several of the vessels mentioned in ttds paper. Free standing and incorporated in combined instrument consoles, it rang^ from thé smaUest trawlers to. the largest liner and indudes cargo vessels and tankers. The smaUest vessel fitted is the Isambard Brunei, a 75ft. yacht built by Brooke Marine Ltd. for Mr. Walter Flack ; perhaps the most elaborate systxm wifl be used in the' guided-weapon destroyers for the Admiralty. This configuration is shown in Fig. 26.

It must also be emphasized that the auto-electric steering control system wUt accept an input from any type of gyro-d)n^>ass as the datum for automatic steOTng controi.

Although the basic principles have been proved in service use in these widely differing types óf v e ^ l the system is under constant examination and review to incorporate new tei^hniques and changes in the light of operational experience. Thus &e desCTiptions and illustrations inchided in this paper represent tihe past and present, and are only an indication of foture possibihties.

The Future

The possibility of very great changes m ship contiol inethods lies in the future, there is at least one sponsoröd programme to study the problems of automatic ship controi. Automatic engine-room contiol is already postulated. The object in eadi and every case is to redùce ship operating cost, but not at the expense of safe and- timdy arrival.

Before a ship can be given a course programme to follow a prescribed tiack, some type of device is necessary to receive, analyse and ddermine the changes to course steered,-required for instance by variations of drift and perhaps speed. It would then be necessary to determine the ship's position at frequent intervals witii fair accuracy and to ccaivert ä great-circle trade into a series of rhumb lines economicîdly positioned along the desired track.

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P A I N : A N E V O L U T I O N I N S H J P C O N T R O L 71

Ship position fixing can be achieved in dear weather by astral observations. This depemlenoe on dear visit^ty would not be acceptable in an autoniatic system. Other means such as Decca aïe avaUable for very accurate short-range position fixing and the further developmerit of this or a Loran-type system wo^d extend the ran^ Of usefulness but would probably stUl have geographical and phj^ical limitations. Inertial systems provide extreme accuracy within a certam time scale but requhe a very high degree of precision engineering, which means they are at present impracticable for ^sneraï commercial use on the grounds of cost. Nevertheless, inertial navigation systems are already at sea, on and certainly under the suifaœ. It seems probable that the most successful inertial systems wfll be those that are combined with radio or radàr methods of position finding, brought into use from time to time to provide a check.

It must, however, be considered a possibility for the futiire, having as it does, the important feature of being independent of sources outside the vessel.

There is a further possibihty, as yet only experimental, but showing great promise. This is the use of artificial satellites to provide ravigational fixes, using perhaps doppler tediniques and atomic clocks for tii:^^ data. Such experimental sateUites have already been placed in orbit and others are planned.

The goal of a continuous or at least suffidentiy frequent determination of the position of the ship in all conditions can be considéréd attainable withm the forseeable f u t ^ and commerdaUy practicable. It will undoubtedly be possible, as in the past, to take advantage of the more speedy advances in cpntrol and navigatiori techniques develop^ for use in the air. After all, an aircraft's cockpit may be considered as a very good example of centialized contiol. It is also wortiiy of note that the basic pilots' instrument layout in aircraft of aU . types has achieved a high degree of standardization or at least of simUarity.

In step with po;»tion fixing, methods of using this infoririation arid of traris-lating it into automatic ship control of varying degree are being developed. The auto-eléctric steering control system and gyro datum already discussed,

mth some modifications, are quite capable of forming the nucleus of suàh

systems. Already the auto-electric systan, as far as it has been devdoi»d, can monitor itself automaticdly, to the extent of indicating deviation from the fequhed couKe and eyrai a divergence by the gyro-compass from the settling position, the gyro-con^ass itself can also be incorporated in the main steei-mg control console but there are arg^ents against tttis. The gyro-coriipass can accept an automatic ship speed input and the indusion of a transriiitting type magnetic compass with facilities for swîtehîng the automatic helimman to use this information as datum wiU provide an emeigency stand-by system.

Computer techniques are in an advanced stage commerdaUy and have many

applications. It be possible to use and adapt these to ship use. i

The óievitable increase in dectronics must face the criticism of increased ƒ

maintenance and the suspîdcâi of unreliability. To offset this it should be noted that the basic units bf the control system—the gyro-compass and/or transmitting magnetic compass, tihe steering control system and propulsion machinery controls—aU use weU-tried and proven electro-mechanical techniques and these would not be changed.

Qearly, this is a sphere in which we miist " make haste slowly ", not discarding old methods UntU new ones aie proved. It can bé visualized that a combination system wUl be introduced as a first step. As a basis for discussion the sdiematic bridge layout in Fig. 27 is offared. It postulate the use of present methods for emergency and dose-range ship handling and fully automatic means for normal ocean navigation.

The trarisiriitting gyro-compass provides tihe prindple datum for automatic steering and repeaters. A transmitting magnetic compass is induded to provide emergency serviœ if the gyro fails. At the same time a double gyro-compass installation could be made as a safeguard, but apart from the cost it wouÜ seem preferable (and moré acceptable in the early stages) to retain a magnetic compass.

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7 2 P A I N : . A N E V O L U T K ) N I N S H » C O N T R O L

Received position data are resolved into latitiide and lon^tude aut(»natically and. together with ship speed and course, are fed to tiie conversion unit for transriiission to the autoniatic track plotter. In emdgency, the rame informa-tion is manuaUy set on the computer units. At the plotter the actual and required course to maintam the set track is compared ; and computed corrective measures, in t^ms of course alterations, are fed from the plotter to the automatic hdmsman.

In the system suggested, anergency-avoiding action is taken manuaUy and overrides automatic cpntrol, whidi wiïl subsequentiy take any action to regain the reqmred tiack when the next position fix is obtained.

It wiU be noted that although main propulsion madiinery is under bridge conU'ol whert required, the automatic unit does not itself control ship's speed. It is su^ested ttàt it would be more economical to maintairi a coristant speed when iri automatic controL A change in revolutions on passage is really a matter of dedsion in the light of circumstances, some of whidb are outside the scope of the automat.

At titte autoniatic steering unit the fundion of the manually adjusted yaw and radder controls is taken oyer by a " trend " analyser whidi wiÜ aûtomaticaUy respond to changes in the effed of sea, wind, ship speed and load conditions to vary the amount of permissible yaw and the angle of rudder and amount of rudder bias control used. The main steering uMt is a separate installation, incorporating p^haps thé digine-room tel^raphs.

Remote steering positions are placed at each whig to provii!^ controls for manœuvring or overriding ahd instantaneous control in emergency. Sideways moyement contiols for dose range and îndependént manœuvring are also placed at tihe same positions.

It will be obsd^ed that a standard magnetic compass is positioned above the wheelhouse for taking beûings in emergency and indudes a.roflector for hehns-noan's use. The unit incorporates tihe transmittmg fadUties atready menticaied. The radar displays are tme north stabilized from the transmitting gyro-compass i f required. They are not linked to the automatic contiol system althou^ dosely assodated! It is beheved that for tiie foreseeable future the prindple rôle of radar wiU be to continue to provide a very useful aid to navigation and in certain conditions to act as a warnmg device.

Although not Ulustrated, a fiirther manually operated remote controi position m ^ well be required, p^cularly in large "all aft" vessels. It has ahèady been su^ested that safe and adequate control is sometimes difipcidt in pilotage waters from a position placed weU aft. In these ships, particularly the largo biük carriers, it may be necessary to place a flyirig-bridge structure forward simply to provide a good view and to raiable the essential manœuvring controls to be sited conveniently. The auto-electnc system makes provision for this eventuality by tihe inclusion of a self-contained remote steering control as iUustrated in Fig. 28. This inchutes a gyro steering repeater, mdder angte indicator and a dired-acting steering control lever. The latter, it will be noted is simflar to the secondary control provided in the main auto-dedric contiol imit shown in Fig. 25. this remote contiol is watertight and can be free-stantoig, bulkhead mounted or incorporated in an instrument console. It may, therefore, have a number of uses in many types of vessel, including for instance icebroakera, where contiol may be necessary from the crow's nest. Equally, it may be used at a secoht^ry position on the poop or elsewhere.

Two importam considerations (truisms) govem the design of the suggested autoniatic control sj^tem :—

(1) No system will be able completely to dispense with the obligation to maintain an adequate visual " look-out ".

(2) No automatic device wffl replace the human element in taking the final decision a:nd action m em^gency.

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P A I N : A N E V O L U T I O N I N S H I P C O N I H O L 73

The " interim " system, therefore, includes the basic navigation faculties, atxcpts that close-range manœuvring remains a human prerogative, but provides automatic methods to be used at the discretion of the human controllers. It also makes provision for the vessel to be manœuyred alongside or in confined waters independentiy of outside assistance if this should be necessary.

It has not been the purpose in this paper to delve into all the other facets of ship work and control, altieit they are more or less closely related and great strides are being taken to introduce automation in almost every sphere.

The expressions " wheelhouse " and " bridge " have been perpetuated ddiberately because of the common understanding of their present function. The future may weU show that a title more aptly descriptive of their realfundion will be the comprehensive ** coritrol centre In warships the term is used to describe a place and fundion separate from the bridge ; in commercial applica-tions it nmy be synonymous.

As a final thought it will perhaps be sufficient to repeat the earlier condusion that thé Ultimate airii is to achieve an economy In manpower with at the same time a redudion in fatigue and increase in operating efficiency.

Ackno wledgments

The author would like to express his thanks to the various shipowners and builders for their permission to publish material and photographs, to S^ G. Brown Limited and the author's colleagues, the American Bo«;h Arma Corporation, the Food and Agriculture Organisation of the United Nations and to Commander A. C. Hairdy ajid Mr. J. N . Hendry, both Members of this Institution, for their co-operation and guidance in the preparation of the paper.

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Fig. l~A very Early Type of Non-transmitting Gyro Compass

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P A I N : A N E V O L U T I O N I N S H I P C O N T R O L 75 TANK ELECTRO MA6NET QYRO POSITION SENSrNS COILS SPIN AXI$ GYRO ROTOR WHEEL (ONLY ONE SHOWN GYRO KALL P E N D U L U M S T O P ± 6 0 ' ELECTROMAGNETS PICKOFF COIL DECOUPLING COMMUTATOR FLEXIBLE SILVER CONDUCTOR VERTICAL TORSION WIRE VERTICAL AXIS

Fig. 3—Diagram of Gyro Ball Assembly

FLOATING GIM0AL SYRO. SPIN MOTOR HORIZONTAL AXIS HORIZONTAL TORSION WIRE FLEXIBLE SILVER COKOUCTOR AZIMUTH DRIVE

VERTICAL TORSION WIRE

STOP £ 60

D A M P

TILT GIMBAL

GYRO B A U . AZIMUTH GIMBAL

HORIZONTAL TORSION WIRE

TILT DRIVE

Fig. 4—Diagrarn of Sensitive Element Assembly

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P A I N : A N E V O L U T I O N I N SHIP C O N T R O L

Fig. 5—An Early Automatic Helmsman

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Fig. 7—Cycle of Operation of Automatic Helmsman

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P A I N : A N E V O L U T I O N I N S H I P C O N T R O L Sl

Fig. 13—Feed-back Transmitter used with Rotary Vane-type Steering Engine in Monsoon

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Fig. 18—Centralized Control Console, including Auto-electric Steering Control Unit in Wkeelkouse of 210ft. trawler D.B. Finn

fig^ 19—Wkeelkouse Control Console, including Auto-electric Steering Contrvl Uriit in Retriever

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-90 P A I N : A N E V O L U T I O N I N S H I P C O N T R O L