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Title:
BOAT CONTROL DEVICE
Document Type and Number:
WIPO Patent Application WO/2002/085702
Kind Code:
A1
Abstract:
In addition to the main throttles (10, 11) for controlling the boat at high speeds, a secondary control device is provided for use in a docking mode at low speed. It includes a joystick (20) which may be deflected in a direction corresponding to the desired low-speed direction of movement of the boat. Control circuitry (21) then determines which of the stern propellers (6, 8) and bow and stern thrusters (14, 15) need to be activated at low thrust levels to produce the slow movement in the desired direction.

Inventors:
Griffin, Colin George c/o Sealine International Limited Whitehouse Road Kidderminster Worcestershire DY10 1HT . (GB)
Wainwright, Gerard Bernard (Hargrove Wall under Heywood Church Stretton Shropshire SY6 7DP, GB)
Application Number:
PCT/GB2002/001840
Publication Date:
October 31, 2002
Filing Date:
April 22, 2002
Export Citation:
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Assignee:
SEALINE INTERNATIONAL LIMITED (Whitehouse Road Kidderminster Worcestershire DY10 1HT, GB)
Griffin, Colin George c/o Sealine International Limited Whitehouse Road Kidderminster Worcestershire DY10 1HT . (GB)
Wainwright, Gerard Bernard (Hargrove Wall under Heywood Church Stretton Shropshire SY6 7DP, GB)
International Classes:
B63H21/22; (IPC1-7): B63H21/22
Domestic Patent References:
WO2001076938A22001-10-18
WO2000013967A12000-03-16
WO2001012505A12001-02-22
WO2000013967A12000-03-16
WO2001012505A12001-02-22
Foreign References:
US4747359A1988-05-31
US4691659A1987-09-08
US5016553A1991-05-21
JPH10181692A1998-07-07
JPH08192794A1996-07-30
JPH06270891A1994-09-27
Attorney, Agent or Firm:
Price, Paul Anthony King (D. Young & Co 21 New Fetter Lane London EC4A 1DA, GB)
Download PDF:
Claims:
CLAIMS
1. A boat comprising: a hull having a bow and a stern ; a main propulsion system including at least one stern propeller arranged to produce thrust longitudinally of the hull; an auxiliary propulsion system including at least a bow thruster arranged to produce thrust transversely of the hull; a primary control device operable by a pilot of the boat to control the main propulsion system including setting a high thrust level; and a secondary control device operable by the pilot to control the main and auxiliary propulsion systems including limiting the thrust level of the main propulsion system to a low thrust level.
2. A boat according to Claim 1, wherein the secondary control device defines a plurality of movement directions of the boat including movement directions additional to forward and backward movement directions and is operable by the pilot to select one of the movement directions and to respond to the selection by controlling the main and auxiliary propulsion systems to implement the selected movement direction.
3. A boat according to Claim 2, wherein the movement directions include a forward and starboard movement direction, a forward and port movement direction, a backward and port movement direction and a backward and starboard movement direction.
4. A boat according to Claim 2 or 3, wherein the movement directions include starboard and port movement directions.
5. A boat according to any preceding claim, wherein the main propulsion system comprises two such stern propellers.
6. A boat according to any preceding claim, wherein the auxiliary propulsion system also includes a stern thruster arranged to produce thrust transversely of the hull.
7. A boat according to any preceding claim, wherein the primary control device comprises a throttle which is pushed forwards from a neutral position to select forward movement and the level of forward thrust and is pulled backwards from the neutral position to select backward movement and the level of backward thrust, wherein at least the level of forward thrust may be set at said high thrust level.
8. A boat according to at least Claim 2, wherein the secondary control device is arranged so that the movement operations required from the pilot to select the movement directions of the boat generally correspond in direction with the movement directions themselves.
9. A boat according to any preceding claim, wherein the secondary control device comprises a joystick.
10. A boat according to Claims 8 and 9, wherein the joystick has generally equi angularly spacedapart movement operations.
11. A boat according to Claim 10, wherein the joystick has eight movement operations.
12. A boat according to any preceding claim, wherein operation of the primary control device is arranged to switch off the secondary control device.
13. A secondary control device for a boat comprising a hull having a bow and a stern, a main propulsion system including at least one stern propeller arranged to produce thrust longitudinally of the hull, an auxiliary propulsion system including a bow thruster and a stern thruster arranged to produce thrust transversely of the hull, and a primary control device operable by a pilot of the boat to control the main propulsion system including setting a high thrust level, wherein the secondary control device comprises a joystick and is arranged: in response to the joystick being pushed forwards by the pilot to output control signals for instructing a low forward thrust level from the main propulsion system; in response to the joystick being pushed to the right by the pilot to output control signals for instructing a low starboard thrust level from the bow and stern thrusters; in response to the joystick being pulled backwards by the pilot to output control signals for instructing a low backward thrust level from the main propulsion system; and in response to the joystick being pushed to the left by the pilot to output control signals for instructing a low port thrust level from the bow and stern thrusters.
14. A secondary control device according to Claim 13, wherein the main propulsion system comprises port and starboard stern propellers and the secondary control device is further arranged: in response to the joystick being pushed forwards and to the right by the pilot to output control signals for instructing a low forward thrust level from the port stern propeller and a low port thrust level from the bow thruster ; in response to the joystick being pulled backwards and to the right by the pilot to output control signals for instructing a low backward thrust level from the port stern propeller and a low starboard thrust level from the bow thruster; in response to the joystick being pulled backwards and to the left by the pilot to output control signals for instructing a low backward thrust level from the starboard stern propeller and a low port thrust level from the bow thruster ; and in response to the joystick being pushed forwards and to the left by the pilot to output control signals for instructing a low forward thrust level from the starboard stern propeller and a low starboard thrust level from the bow thruster.
15. A boat substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings.
16. A secondary control device for a boat, substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings.
Description:
BOAT CONTROL DEVICE BACKGROUND OF THE INVENTION The invention relates generally to a boat, and to providing improved control of the boat at low speeds typical of docking manoeuvres.

US-A-5,016,553 discloses a boat which has a main propeller and a stern thruster which is used for low speed steering control. The throttle lever may be pushed backwards and forwards to control the engine driving the main propeller. The throttle lever may also be moved from side to side to control the stern thruster.

WO-00/13967 discloses a boat with a waterjet drive and a bow thruster. In a docking mode, a joystick may be used for slow speed manoeuvring. The joystick may be twisted about its vertical axis to swing the waterjet nozzle from side to side. The joystick may be rocked fore and aft to raise and lower a reversing bucket positioned behind the waterjet nozzle. The joystick may also be rocked from side to side to produce port and starboard thrust from the bow thruster. A similar type of joystick is also disclosed in WO-01/12505.

JP-10-181692 discloses a joystick used to control the direction of movement of a ship by controlling, inter alia, a stern propeller and a bow thruster.

JP-8-192794 discloses a ship having a stern propeller and bow and stern thrusters. At low speeds, only the bow and stern thrusters are used to turn the ship. At medium speeds, both the rudder and the bow and stern thrusters are used. At high speeds, only the rudder is used. There is no disclosure of a joystick.

JP-6-270891 discloses a ship that can be made to perform zig-zag translational (sideways) movement by using a joystick. The joystick is deflected, in the desired direction of travel and a stern propeller and a bow thruster are commanded to move the ship in that direction, but in a zig-zag manner.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a boat comprising: a hull having a bow and a stern ; a main propulsion system including at least one stern propeller arranged to produce thrust longitudinally of the hull;

an auxiliary propulsion system including at least a bow thruster arranged to produce thrust transversely of the hull; a primary control device operable by a pilot of the boat to control the main propulsion system including setting a high thrust level; and a secondary control device operable by the pilot to control the main and auxiliary propulsion systems including limiting the thrust level of the main propulsion system to a low thrust level.

The secondary control device may be used as a dedicated control device for low-speed manoeuvring in a docking mode of operation. It is usual for a bow thruster only to be able to produce a low thrust level. This low thrust level will complement the limited, low thrust level of the main propulsion system, so that the two propulsion systems may work together in a balanced manner to achieve low-speed movement of the boat.

The pilot of the boat still has available the primary control device (e. g. a pair of side-by-side engine throttles when the boat has two main engines) that may be used to power the boat up to a high speed so that it can operate in a full-performance or cruise mode.

After being out on the open water, and using the primary control device to control the main propulsion system, permitting the boat to travel at high speed as a result of the permitted high thrust level, the pilot will approach the intended dock. The pilot may then cease to use the primary control device, and will switch over to using the physically-separate secondary control device. The secondary control device is only capable of producing low thrust levels, unlike the primary control device, and thus the pilot (even if inexperienced) will not during the critical docking manoeuvre have an accident as a result of accidentally commanding a high thrust level. Instead, the low thrust level during the docking mode permits the pilot to gradually and gently manoeuvre the boat using the main and auxiliary propulsion systems to achieve the desired docking. Irrespective of whatever inputs the pilot makes to the secondary control device, he or she will not inadvertently command a high thrust level that could produce rapid and undesired movement of the boat which, in the close confines of a dock or marina, could result in a collision.

Also, the secondary control device integrates the control of the main and auxiliary propulsion systems in a single device, which an inexperienced pilot may find easier to control and manipulate when docking, rather than having to use separate low- speed control devices for the main and auxiliary propulsion systems, which an inexperienced pilot might find difficult to coordinate together to work in a satisfactory docking-mode manner.

In our preferred embodiment, the secondary control device defines a plurality of movement directions of the boat including movement directions additional to forward and backward movement directions and is operable by the pilot to select one of the movement directions and to respond to the selection by controlling the main and auxiliary propulsion systems to implement the selected movement direction.

For example, the movement directions include generally diagonal movement directions.

Preferably, the movement directions include starboard and port movement directions.

The main propulsion system may comprise two stern propellers. It is preferable for the auxiliary propulsion system to include a stern thruster in addition to the bow thruster.

In many embodiments, the primary control device comprises a throttle which is pushed forwards from a neutral position to select forward movement and the level of forward thrust and is pulled backwards from the neutral position to select backward movement and the level of backward thrust, wherein at least the level of forward thrust may be set at said high thrust level.

Preferably, the secondary control device is arranged so thatt the movement operations required from the pilot to select the movement directions of the boat generally correspond in direction with the movement directions themselves.

This produces an intuitive arrangement that may be particularly suited to an inexperienced pilot. At docking time, the pilot simply chooses to use the secondary control device and manipulates it in a command direction corresponding to the actual desired direction of movement of the boat. For example, if the secondary control device is a joystick, the pilot may simply push the joystick forward in order to command forward low-speed movement of the boat. Pushing the joystick forwards

and to the right will cause the boat to creep forwards whilst also moving slightly to the right. The same principle can also be applied to other compass directions.

Preferably, the primary control device has a higher precedence than the secondary control device. In other words, it can override the secondary control device should the pilot suddenly need to perform a manoeuvre requiring high output thrust, or else once the boat has been moved away from the dock and the pilot wishes to switch from docking mode to cruising mode. Activating the primary control device, such as pushing forward the main engine throttles, will switch off the secondary control device so that it can no longer inadvertently be operated during medium or high speed cruising.

Conveniently, the two control devices are provided at the helm of the boat, such as on the dashboard. The primary control device may be provided to one side of the steering wheel. The secondary control device may be provided at one end of the dash. This would suit the pilot who in a docking mode might wish to stand to the side of the boat in order to be able to observe over the side of the boat and control the docking manoeuvre, whilst still having the secondary control device easily to hand for commanding the low-speed docking manoeuvres that are required.

In a second aspect of the present invention, there is provided a secondary control device for a boat comprising a hull having a bow and a stern, a main propulsion system including at least one stern propeller arranged to produce thrust longitudinally of the hull, an auxiliary propulsion system including a bow thruster and a stern thruster arranged to produce thrust transversely of the hull, and a primary control device operable by a pilot of the boat to control the main propulsion system including setting a high thrust level, wherein the secondary control device comprises a joystick and is arranged: in response to the joystick being pushed forwards by the pilot to output control signals for instructing a low forward thrust level from the main propulsion system; in response to the joystick being pushed to the right by the pilot to output control signals for instructing a low starboard thrust level from the bow and stern thrusters ;

in response to the joystick being pulled backwards by the pilot to output control signals for instructing a low backward thrust level from the main propulsion system; and in response to the joystick being pushed to the left by the pilot to output control signals for instructing a low port thrust level from the bow and stern thrusters.

In our preferred embodiment, the main propulsion system comprises port and starboard stern propellers and the secondary control device is further arranged: in response to the joystick being pushed forwards and to the right by the pilot to output control signals for instructing a low forward thrust level from the port stern propeller and a low port thrust level from the bow thruster; in response to the joystick being pulled backwards and to the right by the pilot to output control signals for instructing a low backward thrust level from the port stern propeller and a low starboard thrust level from the bow thruster; in response to the joystick being pulled backwards and to the left by the pilot to output control signals for instructing a low backward thrust level from the starboard stern propeller and a low port thrust level from the bow thruster; and in response to the joystick being pushed forwards and to the left by the pilot to output control signals for instructing a low forward thrust level from the starboard stern propeller and a low starboard thrust level from the bow thruster.

Thus, the secondary control device provides a dedicated device which operates in a low-thrust mode particularly suited to docking manoeuvres, so that no high-thrust commands will be issued that might endanger the boat during the low speeds required for docking. Also, the operation of the joystick is intuitive, in that it is simply manipulated in the same direction that the boat is required to move. After using the joystick to instruct a gentle movement in one direction, e. g. to starboard in order to move sideways towards a dock, the joystick may be allowed to return to its neutral position (e. g. under the effect of biasing springs) and then just as the boat finally approaches the dock the pilot may push the joystick to the left in order to slow down the boat by generating some port thrust from the bow and stern thrusters. This will slow down the boat so that it will have lost its momentum by the time it has reached close proximity to the dock.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings which are diagrammatic or schematic.

BRIEF DESCRIPTION OF THE DRAWINGS Fig 1 is a plan view of a boat in accordance with the present invention.

Fig. 2 is a forward-looking perspective view of the helm of the boat of Fig. 1.

Fig. 3 is a diagram relating directions of movement of the boat to the engines or thrusters of the boat of Fig. 1 that are operated for particular directions of movement.

Fig. 4 is an alternative embodiment to the boat of Fig. 1.

Fig. 5 is a further alternative embodiment to the boat of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In Fig. 1, a boat 1 has a hull 2 with a bow 3 and a stern 4.

A main propulsion system comprises a port engine 5 driving a port stern propeller 6, and a starboard engine 7 driving a starboard stern propeller 8.

The helm of the boat shown in Fig. 2 has a steering wheel 9 for controlling a rudder (not shown). Left and right throttles 10,11 are connected (by means not shown) to respective electronic digital control units 12,13 for the left and right engines 5, 7.

The throttles 10,11 function as a primary control device for controlling the engines 5,7. By pushing the throttles 10,11 forward from their neutral positions the engines 5,7 are commanded through the electronic digital control units 12, 13 to produce a high level of forward thrust from the stern propellers 6,8.

By pulling the throttles 10,11 back to their neutral positions, the level of forward thrust is decreased. Pulling back through the neutral positions, the engines 5, 7 are commanded to produce reverse thrust from the propellers 6,8 which may be increased up to a high reverse thrust level.

The throttles 10,11 may be operated independently, rather than being operated in a ganged-operation manner, in order to set different thrust levels to be produced by the engines 5,7.

The boat also includes an auxiliary propulsion system in the form of a reversible bow thruster 14 for producing port thrust for propelling the bow to port, and starboard thrust for propelling the bow to starboard. The auxiliary propulsion system

also comprises a stern thruster 15. The thruster may be switched on and switched to produce port thrust for propelling the stern to port, and it may be reversed in direction of rotation to produce starboard thrust for propelling the stern to starboard.

The bow and stern thrusters 14,15 are powered by respective electronic motors 16,17 although an alternative such as hydraulic motors could be used.

The bow and stern thrusters 14,15 produce a constant, low level of thrust when they are switched on, with the direction of thrust being dependent on the direction of rotation of the impeller of the thruster. Alternatively, the thrusters could be of variable speed and thus variable output thrust.

In order to be able if necessary to operate the thrusters in isolation, respective thruster switches 18, 19 are provided on the dashboard at the helm for the bow and stern thrusters 14,15. Toggling a switch to the left will produce port thrust from the respective thruster, and toggling the switch to the right from its central neutral position will produce starboard thrust from the respective thruster.

Trying to achieve docking at low speed by using the throttles 10,11 and the independent thruster switches 18,19 can be difficult for an inexperienced pilot because of the need to coordinate the manipulation of the control elements 10,11,18,19 and also to avoid commanding a high thrust by means of the throttles 10,11 which could cause an accident when trying to dock.

Accordingly, the boat includes a secondary control device which comprises a joystick 20 connected to electronic control circuitry 21, which in turn is connected to the electronic digital control units 12,13 of the main engines 5,7 and to the electronic motors 16,17 of the bow and stern thrusters 14,15. In this way, the joystick 20 acting through the control circuitry 21 may coordinate together the functioning of the engines and motors so as to provide overall control of the thrust output in terms of the level of the thrust and the direction or thrust vector of the thrust. By limiting the overall thrust output to a low level, a pilot using the joystick 20 during a docking manoeuvre will not inadvertently command a high thrust level output that could cause an accident. Also, because of the inherent intuitive functioning of the joystick and the fact that it coordinates together the operations of the main engines and the thrust motors it is possible for the pilot simply to select a desired direction of movement by using the

joystick without having to consider how to achieve the desired movement direction of the boat in terms of activating the engines and thrust motors.

As may be seen in Fig. 1, the mounting plate 22 may be provided with a depiction of the boat. This helps to convey to the pilot the fact that, for example, if he pushes the joystick forwards, towards the bow of the boat, the resulting low-speed movement which will be commanded will also be in the forward direction. The same is true of any of the other seven directions in which the joystick may be deflected.

Overall, the eight directions of deflection of the joystick are equi-angularly spaced at 45° apart from one another.

Referring to Fig. 3, eight different movement directions of the boat are indicated, with reference to compass directions, and those actual movement directions of the boat are achieved by deflecting the joystick in the same direction.

Pushing the joystick forwards will cause the electronic control circuitry 21 to command the electronic digital control units 12,13 of the engines 5,7 to produce a low level of forward thrust from the propellers 6,8. During docking, the engines 5,7 may be left at idle or tickover, and simply engaged to produce a low level of forward thrust when the joystick 20 is pushed forwards by the pilot.

The forward thrust will be commanded for as long as the joystick 20 is pushed forwards. When the joystick 20 is released, and returned by biasing means to its central or neutral upright position, no more thrust will be commanded, and the boat will therefore carry on coasting forwards at low speed. When it is wished to brake the forward motion, the joystick 20 is pulled backwards. This results in the propellers 6,8 producing a low level of reverse thrust that provides a braking effect.

Pushing the joystick to the NE position would indicate that the pilot has selected a corresponding NE movement direction for the boat. The electronic control circuitry 21 implements this by instructing the digital control unit 12 to have the port engine 5 produce a low level of forward thrust from the port propeller 6. At the same time, the control circuitry 21 also instructs the motor 16 to produce some port-acting thrust from the bow thruster 14. This thrust will try to push the bow to port. This will counteract the clockwise torque produced by the port propeller 6 about the centre of mass of the boat. The bow thruster 14 will not entirely counteract the clockwise torque from the port propeller 6. The overall result is that the boat will proceed

forwards whilst turning slightly to the right. Overall, the movement is in a generally NE direction.

An alternative way of achieving movement in the NE direction would be to command the port engine 5 to produce a low level of forward thrust, and to switch on the stern thruster 15 to produce starboard thrust at its fixed low level of output.

A yet further alternative would be to have both engines 5,7 drive their propeller 6,8 to produce an overall low level of forward thrust. At the same time, both the bow thruster 14 and the stern thruster 15 would be switched on by the control circuitry 21 to produce starboard thrust. The result would be translational movement of the boat in the NE direction with little or no rotation about its centre of mass. In other words, the bow would continue to point in the same direction as the boat progresses in an NE direction. The boat would not turn gently into the NE direction as occurs with the arrangement specified in Fig. 3. However, having both main propellers and both the bow and stern thrusters producing thrust would be likely to produce a slightly higher level of net thrust in the NE direction than would be the case with the control arrangement shown in Fig. 3, and thus the boat would be likely to travel at a slightly faster, albeit still low speed. Because very low speeds are desirable during the docking mode, it is envisaged for this reason that the arrangement specified in Fig. 3 is to be preferred.

Working round the other compass point directions (E, SE etc) the appropriate engine and thruster combinations are shown in Fig. 3. For the"diagonal"movement directions of the boat (i. e. NE, SE, SW, NW) it is possible for the main propeller and thruster selections used for the SE, SW and NW directions to be implemented in alternative embodiments along the same lines as the alternatives already discussed in relation to the NE movement direction.

The joystick 20 is not proportional. In other words, deflecting the joystick in a particular direction simply switches on the selected desired movement in that direction.

Before entering the docking mode by manipulating the joystick 20 of the secondary control device, the throttles 10,11 of the primary control device would be set to their neutral positions.

If during the docking operation the throttles 10,11 are moved (for example the throttles are pushed forwards) then the throttles 10,11 will override the secondary control device. Specifically, they will switch off or disable the joystick 20 from having any further command input effect.

To reenter the docking mode, the throttles 10,11 would need to be returned to their neutral positions, and an ON button 23 of the joystick 20 would need to be pressed. If it is desired specifically to switch off the joystick 20, an OFF button 24 may be pressed.

Further buttons are also provided on the mounting plate 22 of the joystick.

Specifically, there is an ANTI-CLOCKWISE button 25 which when pressed will result in the secondary control device commanding the bow and stern thrusters 14,15 to operate so as to produce anti-clockwise rotation of the boat about its centre of mass.

Specifically, the bow thruster produces port thrust, and the stern thruster produces starboard thrust.

There is also a CLOCKWISE button 26 which, when pressed, will result in the control circuitry 21 activating the thruster motors 16,17 such that the bow and stern thrusters 14,15 will produce clockwise rotation of the boat about its centre. This involves the bow thruster 14 being switched on to produce starboard thrust, and the stern thruster 15 being switched on to produce port thrust.

The compass diagram shown in Fig 3 shows that this embodiment has eight defined movement directions for the boat. A different number of movement directions could be provided. The joystick 20 could even be made to be continuously adjustable to sweep around through 360° when deflected from its central neutral position. In this way, full flexibility would be provided in selecting a movement direction of the boat by moving the joystick 20 in the corresponding deflection direction relative to its mounting plate 22.

The embodiment shown in Fig. 4 is a simpler version of the embodiment of Fig. 1. The boat of Fig. 4 omits the stern thruster 15. This make the embodiment of Fig. 4 slightly less satisfactory than the embodiment of Fig. 1, because when it is desired to move the boat to starboard or to port (the E direction or the W direction of Fig. 3) only the bow thruster 14 is available. The resulting sideways movement will still be produced, but there will be some rotation about the centre of mass. For this

reason, it might be desirable to omit the possibility of the E direction and/or the W direction. The remaining six of the eight movement directions would have to suffice.

Movement to the right could be achieved in a zig-zag manner by commanding a burst of NE movement followed by a burst of SE movement, and so on.

The embodiment shown in Fig. 5 has only a single engine 30 arranged along the longitudinal centre line of the boat. There are twin contra-rotating propellers 31.

Also, there is only a single electronic digital control unit 32. To achieve NE movement, the stern propeller 31 would produce a low level of forward thrust. The bow thruster 14 would produce starboard thrust. This would cause the boat to move forwards whilst turning slightly to the right, overall progressing in a generally NE direction.

To move in the SE direction, the propeller 31 would produce a low level of backward thrust. The bow thruster 14 would produce port thrust. This would result in the boat slowly moving backwards whilst gently swinging round to the right. Overall, the motion would be in the SE direction.

To move in the SW direction, rearward thrust from the propeller 31 would be combined with starboard thrust from the bow thruster 14.

To move in the NW direction, forward thrust from the propeller 31 would be combined with port thrust from the bow thruster 14.

Should there be a failure in the secondary control device, such as a failure of the control circuitry 21, then control will revert to the default option of using the main throttles 10,11 and the standard thruster switches 18,19.

Providing the secondary or subsidiary control with a manual input in the form of a joystick 20 enables the pilot of the boat to control the docking manoeuvre in an easy manner. Specifically, only one control element needs to be manipulated in order to control the main engine (s) and the lateral thruster (s) in a coordinated manner. The manual input directions of manipulation of the joystick correspond to the desired movement directions of the boat, so that operation of the joystick is intuitive. For example, pushing the joystick forwards will produce forward movement of the boat.

Pushing the joystick to the SE position will produce corresponding SE motion of the boat. When the desired amount of slow motion during docking in a particular direction has been activated, the joystick 20 is allowed to spring back to its central

position. The motion may then be cancelled by pressing the joystick in the opposite direction to bring the boat to a halt.

At the present time, there is no input via twisting the joystick. This could be used for additional functions, such as setting the sensitivity for the joystick displacement.

In the illustrated embodiments, the propellers and thrusters have fixed thrust directions. In other words, they do not for example pivot from side to side, or pivot up and down. The fixed nature of the thrust directions assists in determining which particular stern propeller or propellers or transverse thruster or thrusters need to be activated to achieve movement in a particular commanded direction of movement.

It will be appreciated that the above description is non-limiting and refers to preferred forms of the invention Many modifications may be made within the scope of the invention. Although features believed to be of particular significance are identified in the appended claims, the applicant claims protection for any novel feature or idea described herein and/or illustrated in the drawings, whether or not emphasis has been placed thereon.