AU2019210622B2

AU2019210622B2 - Vessel conversion module, vessel and method

Info

Publication number: AU2019210622B2
Application number: AU2019210622A
Authority: AU
Inventors: Adnan Al Sousy; Basel Shuhaiber
Original assignee: Al Marakeb Manufacturing Boats Est
Current assignee: Al Marakeb Manufacturing Boats Est
Priority date: 2016-10-04
Filing date: 2019-08-01
Publication date: 2021-03-04
Anticipated expiration: 2037-09-29
Also published as: AU2017236007B2; GB201616820D0; AU2019210622A1; GB2554689B; AU2017236007B9; GB2554689A; AU2017236007A1

Abstract

A vessel conversion module (10) for converting a vessel into an unmanned surface vehicle (USV). The vessel conversion module comprises a casing and a plurality of conversion components. The conversion components comprise: a navigation unit comprising a global positioning system (GPS) receiver; a wireless communications interface; a plurality of electronically operable switches for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; a motor control circuit for coupling to the vessels motor control system for controlling engine speed; a steering control circuit for coupling to the vessels steering control system for controlling the direction of the vessel; memory for storing a navigation control program; and a processor coupled to the conversion components for communication therewith. The processor is arranged to execute the navigation control program, the navigation control program being configured to cause control commands to be sent to the plurality of switches, the motor control circuit and the steering control circuit to control movement of the vessel in accordance with input signals received from the navigation unit and/or the wireless communications interface. (Figure 1) 1/6 10 3 6 20 28 - - - - - -12 L - ----14 64 16 42 581 HOS 622 FIGi1

Description

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Vessel Conversion Module, Vessel and Method

Related applications

This application is a divisional of Australian patent application number 2017236007, filed 29 September 2017, which itself claims priority to UK patent application number GB1616820.5, filed 4 October 2016. The content of each of the aforementioned applications is incorporated herein by reference in its entirety.

Background of the Invention

An unmanned surface vehicle (USV) is a vessel which includes a hull arranged to be driven through water by propulsion means. A USV further includes a number of devices which are integrated together in order to control the motion of the USV.

A USV can be remotely operated via a wired or wireless communications interface. Advances in artificial intelligence and robotics have also enabled the development of USVs capable of autonomous navigation.

The present inventor has devised a way of producing a USV that may be simple and/or cost effective.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

Summary of the Invention

According to a first aspect of the present invention, there is provided a vessel conversion module for converting a vessel into an unmanned surface vehicle (USV), the vessel conversion module comprising: a casing; and a plurality of conversion components, the conversion components comprising: a navigation sensor unit comprising a global positioning system (GPS) receiver; a wireless communications interface; a plurality of electronically operable switches for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; a motor control circuit for coupling to the vessels motor control system for controlling engine speed; a steering control circuit for coupling to the vessels steering control system for controlling the direction of the vessel; memory for storing a navigation control program; and a processor coupled to the conversion components for communication therewith, the processor being arranged to execute the navigation control program, the navigation control program being configured to cause control commands to be sent to the plurality of switches, the motor control circuit and the steering control circuit to control movement of the vessel in accordance with input signals received from the navigation sensor unit and/or the wireless communications interface, wherein the navigation control program comprises a waypoint based track control algorithm configured to: (a) calculate a straight-line distance between a reference point on the vessel and a reference point at a current waypoint; (b) determine whether the straight-line distance is less than a distance from a current track at which the vessel should start turning; (c) if the determination at step (b) is false, determine a perpendicular distance between the vessel and the current track, the perpendicular distance being perpendicular with respect to the current track; (d) determine whether the perpendicular distance is less than or equal to a damping distance; (e) if the determination at step (d) is true, set a point towards which the vessel should head as a point on the current track that is a distance equal to the damping distance from the vessel; (f) if the determination at step (d) is false, determine whether the perpendicular distance is less than or equal to 1.5 times the damping distance; (g) if the determination at step (f) is true, set the point towards which the vessel should head as a point on the current track that intersects a straight line joining the vessel to the current track at an angle of 450 to the current track; (h) if the determination at step (f) is false, set the point towards which the vessel should head as a point on the current track that intersects a straight line joining the vessel to the current track at an angle of 900 to the current track; and (i) calculate a heading signal for commanding the steering control circuit and a speed signal for commanding the motor control circuit

2A

The vessel conversion module of the first aspect of the invention may enable a conventional vessel to be converted into a USV in a simple and cost effective manner, in contrast to known USVs, which are a combination of disparate devices, often from different manufacturers, integrated together in order to control the motion of the USV. The module can control the vessel's steering and throttle to precisely track predetermined routes with specified speeds to perform autonomous navigation.

According to a second aspect of the present invention, there is provided a vessel comprising a hull, an engine, a steering system and a vessel conversion module according to the first aspect, wherein the plurality of electronically operable switches are coupled to the vessel's engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; the motor control circuit is coupled to the vessel's motor control system for controlling engine speed; and the steering control circuit is coupled to the vessel's steering control system for controlling the direction of the vessel.

According to a third aspect of the present invention, there is provided a method of converting a vessel into an unmanned surface vehicle (USV), the method comprising the steps of: providing a vessel conversion module according to the first aspect; interfacing the plurality of electronically operable switches with the vessel's engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; interfacing the motor control circuit with the vessel's motor control system for controlling engine speed; and interfacing the steering control circuit with the vessel's steering control system for controlling the direction of the vessel.

Optional features of the invention are defined in claims 2 to 8 and 11 to 13.

These and other aspects of the present invention will become apparent from, and clarified with reference to, the embodiments described herein.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer

2B

or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic system diagram of a vessel conversion module according to an embodiment of the invention;

Figure 2 is a flow chart illustrating a plurality of operating modes of the navigation control program of the module of Figure 1 arranged in a hierarchy;

Figure 3 is a schematic system diagram illustrating steering possibilities of a track control algorithm of the navigation control program of the module of Figure 1;

Figure 4 is a flow chart illustrating the track control algorithm;

Figure 5 is a flow chart illustrating a heading control algorithm that works with the track control algorithm of Figure 4; and;

Figure 6 is a flow chart illustrating a speed control algorithm that works with the track control algorithm of Figure 4.

Specification Description of Embodiments of the Invention

By way of a non-limiting overview, embodiments of the present invention relate to a vessel conversion module for converting a conventional vessel into a USV. The module can include all of the building blocks of a USV i.e. the USV conversion components in a compact unit that can be easily fitted into vessels of any size. All of the USV conversion components can be distinct from components of the vessel. The module casing can include all of the connectors required to facilitate simple interfacing of the USV conversion components with a vessel's engine and steering systems, and in some cases other system as described in more detail below.

Referring to Figure 1, the vessel conversion module is shown generally at 10. The module 10 comprises a splash proof aluminium two casing 12 which defines a hollow chamber. The casing 12 preferably comprises a single casing unit with dimensions approximating 20x20x8 cm. In the illustrated embodiment the casing 12 houses all of the USV conversion components; however in other embodiments the conversion components can be spread amongst two or more casing units arranged to be electrically and/or communicatively coupled with one another, or some components can be mounted externally with respect to the casing. The casing(s) can be formed of any suitable material, such as metal, fibre reinforced composites or a plastics material.

The casing 12 defines a mounting structure 14, so as to enable the casing to be mounted to a surface of the vessel. The mounting structure 14 in this embodiment is a pair of flanges, each of which extends from the casing 12. The flanges may together define a mounting plane which corresponds to a surface profile of a vessel and can be provided with one or more holes 16, through which mechanical fastening means such as screws or bolts may be received. Alternatively, the casing 12 can define a surface arranged to be bonded directly to the vessel. The casing may instead be mounted to the vessel by any other appropriate fastening means.

A power input connector 18 is provided and arranged to be coupled to a battery, such as the vessel's battery, through a standard two pin connection. The operating voltage is shown as 12V DC, but can for example be in the range of 6V DC to 16V DC.

The module 10 further comprises a navigation sensor unit 20 for providing information relating to the vessels position, speed and direction.

The navigation sensor unit 20 comprises a system for determining the location of the module; for example, the navigation sensor unit 20 can comprise a global positioning system (GPS) receiver 22.

The navigation sensor unit 20 can comprise an inertial navigation system (INS) 24 comprising one or more accelerometers and gyroscopes to determine one or more of the vessel's position, orientation and speed. Alternatively, these functions may be carried out by the GPS 22. Alternatively, the INS 24 may carry out these functions to back up the GPS 22, in case the GPS 22 fails, for example. The INS 24 may also carry out the functions to provide confirmation of the results obtained by the GPS 22. Alternatively, the GPS 22 may back up, or provide confirmation for, the INS 24.

The navigation sensor unit 20 can comprise a compass 26 to determine the orientation of the vessel. The compass 26 may be a solid state compass. The compass functionality could alternatively or additionally be carried out by the GPS 22 or the INS 24.

The module 10 further comprises a wireless communications interface 28 for enabling a user to control the functionality of the module 10.

The wireless communications interface 28 can comprise an internet protocol (IP) mesh radio 30. The mesh radio 30 enables a user stationed at a separate ground control station 32 to remotely control the vessel, and can also provide an ability to control the vessel from anywhere on the boat using a computing device 34 such as a mobile phone or tablet via an on-board Wi-Fi connection. The mesh radio 30 also enables integration and control of other on-board devices 36 such as a gimbal camera, long range acoustic device, radar, satellite communication, CAN bus gateway and an IP camera.

The wireless communications interface 28 can further comprise a radio frequency (RF) unit 38. The RF unit 38 enables a hand-held radio control (RC) transmitter 40 to control the vessel remotely at line of sight, such as from a pontoon or the shoreline.

The module 10 further comprises a plurality of switches 42. The switches 42 can comprise relays, operable to control the state of on-board function and devices 44; for example, the switches 42 can start and stop the engine of the vessel and/or lower and raise the anchor of the vessel. The mechanism by which the switches 42 are integrated into the vessel can vary depending on the vessel to which they are applied.

For example, the switches 42 can be hard-wired into the existing electrical system. In one specific example, for a Yanmar 6LPA-STZP2 engine, the engine's control panel can be wired to two of the switches 42 for remote engine start and stop.

The module 10 further comprises a motor control circuit 44 for controlling the speed of the engine 46. The mechanism by which this is achieved can depend on the type of vessel to which the module 10 is applied. The motor control circuit 44 can for example function as a variable resistor arranged to vary an output signal for controlling operation of a vessel's throttle servo motor 48. The motor control circuit 44 can send out a pulse width modulation (PWM) signal or an analog signal. The signal can be sent to a servo that mechanically controls engine throttle. For vessels which have a gearbox 50, a gear shifting actuator 52 can be controlled in a similar manner by the motor control circuit 44. For older and/or less sophisticated vessels, an actuator can be mechanically coupled to the vessels throttle and/or shift control to actuate them as a user would; the motor control circuit 44 can be coupled to the actuator(s) to control them. The motor control circuit 44 can therefore directly control the speed of the vessel.

The module 10 further comprise a steering control circuit 54 for controlling the direction of travel of the vessel. Similarly to the motor control circuit 44, the steering control circuit 54 can function as a variable resistor arranged to vary an output signal for controlling operation of a vessel's autopilot steering pump 56 to move the rudder. Many vessels include an autopilot steering pump 56 and therefore the module 10 is provided with a standard two pin connector 58 to interface. The module 10 can be coupled to a rudder position sensor 60 for providing feedback on the current rudder position. Many vessels include rudder position sensor 60 and therefore the module 10 is provided with a standard four pin connector 62 for interfacing with the rudder position sensor 60. For older and/or less sophisticated vessels, an actuator can be mechanically coupled to the vessels steering control to move it as a user would, and a rudder position sensor can be mechanically coupled to the rudder and interfaced with the module. Thus, the steering control circuit is designed to function as a motor position controller where the hydraulic pump acts as the motor and the rudder sensor acts as an encoder which provides feedback. The steering control circuit 54 can therefore directly control the steering of the vessel.

The module 10 further comprises a processor 64 comprising inputs and outputs. In the illustrated embodiment the processor is a 1.2 GHz quad-core ARM Cortex-A5 processor. However any suitable processor can be provided and different processing functions can be spread amongst a plurality of communicatively coupled processors. The processor is coupled to a memory on which is stored a navigation control program.

The processor 64 receives input signals from the navigation sensor unit 20, the rudder position sensor 60 and the wireless communications interface 28.

The processor 64 is configured to execute the navigation control program to provide control commands to the switches 42, the motor control circuit 44 and the steering control circuit 54 to control motion of the vessel.

The navigation control program can be configured to enable a user to directly operate the shift, throttle and steering actuators 52, 48, 56 via the communications interface 28.

The navigation control program can also be configured to autonomously controls the vessel a based on user defined waypoints and speed(s); in the illustrated embodiment, this mode comprises a track control algorithm (see Figure 3), a speed control algorithm (see Figure 4) and a heading control algorithm (see Figure 5).

While in the illustrated embodiment the vessel conversion module 10 includes each of the specified conversion components identified above, in other embodiments the vessel conversion module 10 can comprise a processor as described with suitable connectors for coupling the module to commercial off the shelf conversion components such as a GPS receiver and the like.

Referring now to Figure 2, the navigation control program 66 has four operational modes. The four modes can be arranged in a hierarchy.

At step 68 the system determines whether a user override has been activated. This can for example be achieved by a user pressing a user override button on the RC input device 40. When user override is detected, at step 70 the processor functions such that input commands provided via the communications interface 28 are fed directly into the shift, throttle and steering actuators 52, 48, 56 so that the vessel can be remotely operated via the RF link.

If user override is not detected, at step 68 the system determines at step 72 whether a hold mode is activated. The navigation control program can default to hold mode once autonomous activity has concluded, as described below. Hold mode can be activated through a button on the RC link or through the ground control station software. If hold mode is detected, at step 74 the processor does not provide control commands to the switches 42, the motor control circuit 44 or the steering control circuit 54. However, the vessel may be controlled manually from the conventional vessel helm controls.

If hold mode is not detected at step 72, the system determines at step 76 whether manual mode is activated. Similar to hold mode, this mode can be activated through a button on the RC link or through the ground control station software. If so, at step 78 navigation controls received from a user input device 32, 34 through the IP mesh radio link are actioned by the processor. As described in more detail below, a user can set waypoints and a desired speed for the navigation control program to implement, or a user can use a joystick function on the input device to directly control motion of the vessel through the mesh radio 30 in an analogous manner to the RF link control described above.

If manual mode is not activated at step 76, at step 80 the system determines if autonomous mode is activated. If so, at step 82 the processor executes a track control algorithm to provide signals to the outputs to move the vessel though a set of predefined waypoints at defined speed(s). Once the track control algorithm terminates, the navigation control program 66 can default to hold mode.

The user override mode has the highest priority, and it can override any other mode, while other modes cannot override it unless it is deactivated. The manual, hold and autonomous modes are on the same priority level and once one of them is activated it automatically disables the other two.

Figure 3 is a diagram illustrating how the track control algorithm selects a target point for the vessel in accordance with the length of a perpendicular line joining the vessel to a current desired track (line) between a target waypoint and the immediately preceding waypoint. Reference should be made to the following nomenclature:

PThead The points towards which the vessel should head WPcurr The vessel's current waypoint Tcurr The vessel's current track

Dv The vessel's damping distance Dm The vessel's damping distance at top speed Vv The vessel's current GPS speed Vm The vessel's top speed in knots DTP Distance from the waypoint at which the vessel starts turning DVT Length of the perpendicular line joining the vessel to Tcurr Dvp Length of the line joining the vessel to WPcurr n Number of uploaded waypoints

The damping distance for the vessel can be calculated as follows:

Dv = Dm (Vv/Vm)

Given that the damping distance is a function of the vessel's speed, the track control algorithm allows for smooth and precise track control at all speeds.

Referring additionally to Figure 4, a flowchart illustrating the track control algorithm is shown generally at 90.

At step 92 a determination is made as to whether the vessel has reached the final waypoint. If so, the hold mode is initiated.

If not, at step 94 a determination is made as to whether the user set waypoint 1 as the initial waypoint. If the starting waypoint is 2 (i.e. i=2) then Tcurr=Ti=T2 and WPcurr = WPi = WP2. The same rationale applies to all waypoints other than waypoint 1. However, if the starting point is waypoint 1 (i.e. i=1) then Tcurr= Ti+1 =T2 and WPcurr = WPi = WP1.

At step 96 the straight-line distance DvP between a reference point on the vessel and a reference point at the current waypoint is calculated. This can be achieved in software using the GPS position and the map location of the waypoint.

At step 98 a determination is made as to whether the straight-line distance Dv calculated at step 96 is less than the lateral offset DTP from the desired track Tcurr at which the vessel should start turning. This can be the same distance as the radius of the waypoint WPcurr.

If the determination at step 98 is true, the vessel has reached the target waypoint WPcurr and the algorithm returns to step 92, incrementing i by 1.

If the determination at step 98 is false, at step 100 the perpendicular distance DVT between the vessel and the desired track is calculated. This can be achieved in software using the GPS position and the map location of the waypoints which define the track.

The track control algorithm then proceeds to set a point towards which the vessel should head PThead.

At step 102, a determination is made as to whether the perpendicular distance DVT is less than or equal to the vessel's damping distance Dv.

If so, at step 104 the point towards which the vessel should head PThead is set as a point on the vessel's current track Tcurrthat is a distance equal to the vessel's damping distance Dv from the vessel. The track control algorithm then proceeds to calculate the desired heading and speed, as described in more detail below.

If the determination at step 102 is false, at step 106 a determination is made as to whether the perpendicular distance DVTis less than or equal to 1.5 times the vessel's damping distance 1.5Dv.

If so, at step 108 the point towards which the vessel should head PThead is set as a point on the vessel's current track Tcurr that intersects a straight line joining PThead to the vessel at an angle of 450 to the vessel's current track Tcurr. The track control algorithm then proceeds to calculate the desired heading and speed, as described in more detail below.

If the determination at step 106 is false, at step 110 the point towards which the vessel should head PThead is set as a point on the vessel's current track Tcurr that intersects a straight line joining PThead to the vessel at an angle of 900 to the vessel's current track Tcurr. The track control algorithm then proceeds to calculate the desired heading and speed, as described in more detail below.

Referring additionally to Figure 5, the heading controller 112 of the algorithm is shown. The heading controller 112 seeks to ensure that the vessel maintains the desired heading DH determined by the track control algorithm.

The desired heading DH is fed into a subtraction unit 116 along with a heading estimate HE obtained from a Kalman Filter. An error signal e(t) output from the subtraction unit 116 is then fed into a PID controller 118 to output a steering angle SA.

A saturation function SF is then applied to the steering angle SA. The saturation function SF is speed dependent and limits the maximum steer angle SA according to the vessel's speed. The saturation function SF is tuned according to the vessel at hand allowing for aggressive maneuvers on agile vessels. The saturation function SF can be disabled allowing for full movement of steering when the vessel is completely unmanned and has no crew on-board.

The resulting steering output is then fed to the steering control circuit 54 to control the vessel's autopilot steering pump 56 to move the rudder.

Referring additionally to Figure 6, the speed controller 113 of the algorithm is shown. The speed controller 113 seeks to ensure that the vessel runs at the desired speed and commands reduction of speed in case an aggressive turn is encountered. Reference should be made to the following nomenclature:

VAP Speed specified by track control algorithm HEsharp Heading error aggressiveness threshold VD Desired speed Sr Speed reduction factor (Vessel dependent)

At step 120, knowing the speed specified by track control algorithm VAP, a determination is made as to whether the current heading error is greater than a heading error aggressiveness threshold HEsharp. The heading error is obtained from the subtraction of the desired heading DH from the heading estimate HE obtained from the Kalman Filter.

If so, a vessel dependent speed reduction factor Sr is applied to the speed specified by track control algorithm VAPtO produce a slower desired speed VD.

If not, the desired speed VD remains as the speed specified by track control algorithm VAP.

The desired speed VD is then fed into a subtraction unit 122 along with a speed V GPS obtained from the GPS 22. An error signal e(t)' output from the subtraction unit 122 is then fed into a PID controller 124.

The resulting speed output is then fed to the motor control circuit 44 to control the vessel's motor 46.

Thus, unlike commercial off the shelf (COTS) marine autopilots, the vessel conversion module 10 according to the illustrated embodiment features a speed controller 113 which receives commands from a track control algorithm 90. The speed controller 113 interacts with a heading controller 112 where it commands reductions in speed depending on the heading error reported by the heading controller 112. This interaction allows the vessel to slow down sharp turns in order to achieve precise tracking of the pre-defined route while the vessel maintains it higher speed along relatively straight tracks.

The vessel conversion can be easily integrated into vessels with different propulsion and steering systems. It can be customized to work with vessels that use water-jet propulsion, outboard engines, stern-drives or inboard drives. Furthermore, it allows a user to easily integrate, remotely control and monitor other sensors and devices on the vessel.

A vessel can be converted into a USV by: providing a vessel conversion module according to an embodiment of the invention; interfacing the plurality of electronically operable switches with the vessels engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; interfacing the motor control circuit with the vessel's motor control system for controlling engine speed; and interfacing the steering control circuit with the vessel's steering control system for controlling the direction of the vessel.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parenthesis shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. Parts of the invention may be implemented by means of hardware comprising several distinct elements, or by one or more suitably programmed computing devices. In a device claim enumerating several parts, several of these parts may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A vessel conversion module for converting a vessel into an unmanned surface vehicle (USV), the vessel conversion module comprising: a casing; and a plurality of conversion components, the conversion components comprising: a navigation sensor unit comprising a global positioning system (GPS) receiver; a wireless communications interface; a plurality of electronically operable switches for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; a motor control circuit for coupling to the vessels motor control system for controlling engine speed; a steering control circuit for coupling to the vessels steering control system for controlling the direction of the vessel; memory for storing a navigation control program; and a processor coupled to the conversion components for communication therewith, the processor being arranged to execute the navigation control program, the navigation control program being configured to cause control commands to be sent to the plurality of switches, the motor control circuit and the steering control circuit to control movement of the vessel in accordance with input signals received from the navigation sensor unit and/or the wireless communications interface, wherein the navigation control program comprises a waypoint based track control algorithm configured to: (a) calculate a straight-line distance between a reference point on the vessel and a reference point at a current waypoint; (b) determine whether the straight-line distance is less than a distance from a current track at which the vessel should start turning; (c) if the determination at step (b) is false, determine a perpendicular distance between the vessel and the current track, the perpendicular distance being perpendicular with respect to the current track; (d) determine whether the perpendicular distance is less than or equal to a damping distance; (e) if the determination at step (d) is true, set a point towards which the vessel should head as a point on the current track that is a distance equal to the damping distance from the vessel;

(f) if the determination at step (d) is false, determine whether the perpendicular distance is less than or equal to 1.5 times the damping distance; (g) if the determination at step (f) is true, set the point towards which the vessel should head as a point on the current track that intersects a straight line joining the vessel to the current track at an angle of 450 to the current track; (h) if the determination at step (f) is false, set the point towards which the vessel should head as a point on the current track that intersects a straight line joining the vessel to the current track at an angle of 900 to the current track; and (i) calculate a heading signal for commanding the steering control circuit and a speed signal for commanding the motor control circuit.

2. A vessel conversion module according to any one of the preceding claims, wherein the casing defines a mounting structure arranged to enable the module to be coupled to a surface of the vessel.

3. A vessel conversion module according to any one of the preceding claims, wherein the navigation sensor unit further comprises an inertial navigation system (INS) and/or a compass.

4. A vessel conversion module according to any one of the preceding claims, wherein the wireless communications interface comprises an IP mesh radio.

5. A vessel conversion module according to any one of the preceding claims, wherein the wireless communications interface comprises an RF radio.

6. A vessel conversion module according to any one of the preceding claims, wherein the module further comprises a rudder position sensor input for receiving rudder position information from a rudder position sensor on the vessel and providing this to the processor and/or steering control circuit.

7. A vessel conversion module according to any one of the preceding claims, wherein the navigation control program control further comprises a heading control algorithm configured to: (j) subtract a heading estimate from the heading signal to produce a steering error signal; (k) provide the error signal as an input to a PID controller to obtain a steering angle;

(1) apply a speed dependent saturation function to the steering angle to limit the maximum steer angle according to the vessel's current speed; and (m) output a new heading signal to the steering control circuit.

8. A vessel conversion module according to any one of the preceding claims, wherein the navigation control program control further comprises a speed control algorithm configured to: (n) determine whether a current heading error is greater than a heading error aggressiveness threshold and if so, apply a speed reduction factor to the speed signal; (o) subtract a GPS speed from the speed signal to produce a speed error signal; (p) provide the speed error signal as an input to a PID controller; (q) output a new speed signal to the motor control circuit.

9. A vessel comprising a hull, an engine, a steering system and a vessel conversion module according to any one of the preceding claims, wherein the plurality of electronically operable switches are coupled to the vessel's engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; the motor control circuit is coupled to the vessel's motor control system for controlling engine speed; and the steering control circuit is coupled to the vessel's steering control system for controlling the direction of the vessel.

10. A method of converting a vessel into an unmanned surface vehicle (USV), the method comprising the steps of: providing a vessel conversion module according to any one of claims 1 to 8; interfacing the plurality of electronically operable switches with the vessel's engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel; interfacing the motor control circuit with the vessel's motor control system for controlling engine speed; and interfacing the steering control circuit with the vessel's steering control system for controlling the direction of the vessel.

11. A method according to claim 10, whereby the step of interfacing the plurality of electronically operable switches comprises hard wiring the switches with the vessel's engine system and/or anchor system for starting and stopping the engine of the vessel and/or lowering and raising the anchor of the vessel.

12. A method according to claim 10 or claim 11, whereby the step of interfacing the motor control circuit with the vessel's motor control system for controlling engine speed comprises electrically coupling the motor control circuit to the vessel's throttle actuator and optionally a motor shift actuator provided on the vessel.

13. A method according to any one of claims 10 to 12, whereby the step of interfacing the steering control circuit with the vessel's steering control system for controlling the direction of the vessel comprises electrically coupling the steering control circuit to the a steering pump on the vessel and optionally a rudder position sensor on the vessel.