WO2012010818A1

WO2012010818A1 - Improvements in proximity detection

Info

Publication number: WO2012010818A1
Application number: PCT/GB2011/001062
Authority: WO
Inventors: Fiona Mary Mcrae Mair; Natasha Louise Wood
Original assignee: Auto Ranging And Bearing Solutions Llp
Priority date: 2010-07-22
Filing date: 2011-07-15
Publication date: 2012-01-26
Also published as: GB2496078A; GB201012276D0; GB2496078B; GB201302772D0

Abstract

This invention provides a position monitoring system for a vessel having a vessel control system. The system has a plurality of electromagnetic sensors (2) arranged at intervals substantially around the perimeter of the vessel for detecting objects (40, 42, 52) in the proximity of the vessel. A central processing unit (4) communicates with the sensors (2) and determines the position of any objects in the proximity of the vessel. The central processing unit (4) has a memory (18) associated with it that contains data defining at least one detection zone (20, 30) adjacent or proximate to the vessel. The central processing unit (4) is programmed to, upon detection that the sensors (2) have sensed an object in any one of said at least one detection zones (28, 30), output a signal to at least one of an alarm system and the vessel control system (10).

Description

Improvements in Proximity Detection

This invention relates to proximity detection systems, in particular to proximity detection systems used in marine vessel navigation and control systems.

The modern day marine vessel is equipped with a number of systems designed to detect and track objects around the vessel, for the purposes of navigation and collision avoidance. These are collectively known as position monitoring equipment (P E) and such systems include Global Positioning systems (GPS), marine navigation radar, water speed indicators, magnetic and gyro compasses, as well as a suite of environmental and motion sensors.

The primary sensing system used for the detection of objects around vessels is marine radar. Typically marine radars have antennae mounted high on a ships mast, which emits a pulse train of radar energy and receives echo return signals reflected from objects that the emitted radar energy strikes. Typically these antennae rotate to provide a swept radar beam. The returning echoes from the reflecting object can therefore be used to determine the range from the time of flight as well as an approximate bearing based on the direction at which the antenna was pointing at the time of the received reflection.

Radar beams for marine vessels are generally in the shape of a beam narrow in azimuth (of the order of a few degrees) and broad in elevation forming a fan beam shape. The projected energy spreads spherically from the antenna forming a curved wave-front. This beam shape is optimised for detecting reflections from objects at long range with good precision, whilst not being very efficient at close quarters to the vessel. Despite the location high on a vessels mast, the radar is unlikely to provide a complete view of the immediate vessel surroundings, with at least some of the perimeter being obscured by installation metal work or other vessel super-structure in close proximity to the radar.

Traditional marine radars are unable to see the area close to the perimeter of the vessel. Many modern vessels are equipped with vessel control systems for controlling the position of the vessel which include, but are not limited to auto navigation equipment, auto helm, auto tiller, auto pilot and dynamic positioning systems. Depending on the class of the dynamic positioning system, the vessel may be equipped with one or more sensors or position monitoring equipment (PME) for monitoring position or with position reference sensors (PRS) for measuring relative position between the vessel and a nearby static or moving object. The dynamic positioning system generally uses measurements supplied by the PRS' to control the ships position, for example to perform the task of station keeping, or for conducting operator instigated moves.

Current PRS' rely on the pre-installation of artificial targets on the object providing the reference point and the sensor accurately measures the relative position between itself and this target or a multitude of targets. One of the major shortcomings of these current systems is that the target needs to be pre-installed and maintained on the installation before the vessel arrives at its location, or else must be passed to the installation and setup before the PRS can be enabled as a position reference by the dynamic positioning system.

These systems therefore require correct corresponding parts on the ship and the location. Where different ships of different origin require position monitoring at a common location then either each one must set up their own artificial targets, or only vessels having the correct equipment for the installed targets can take advantage of position monitoring at that location. When manually station holding or navigating, in particular in close quarters to other vessels, in a large vessel it is often necessary to take quick and decisive action in collision avoidance situations. These types of occurrences are not common but do happen. In some circumstances the time taken to identify the problem and, on a large modern vessel, to cross the bridge to the necessary control location can make the difference between avoidance and collision.

The present invention proposes an improved proximity detection system for a vessel to address at least some of the known issues surrounding such systems. According to a first aspect of the present invention there is provided a position monitoring system for a vessel having a vessel control system comprising: a plurality of electromagnetic sensors arranged at intervals substantially around the perimeter of the vessel for detecting objects in the proximity of the vessel; a central processing unit for communicating with the sensors and determining the position of any objects in the proximity of the vessel and wherein the central processing unit has a memory means associated therewith that contains data defining at least one detection zone adjacent or proximate to the vessel; and the central processing unit is programmed to, upon detection that the sensors have sensed an object in any one of said at least one detection zones, output a signal to at least one of an alarm system and the vessel control system.

Preferably the memory means contains data defining a plurality of detection zones. The central processing unit may be programmed to, upon detection that the sensors have sensed an object in a first one of said plurality of detection zones, output a signal to said alarm system and if the sensed object moves into a predetermined second one of said plurality of detection zones, output a signal to said vessel control system indicative that the vessel control system should take action.

In one arrangement the data defining at least one detection zone plurality of detection zones includes at least a first zone and a second zone, the second zone being in closer proximity to the vessel that the first zone. Preferably each of the at least one detection zones is defined by a user.

The memory means may contain data relating to the physical location of the sensors relative to a point of origin. Preferably the point of origin is the centre of motion of the vessel and defines a reference point for a vessel co-ordinate frame. For each sensor the memory means can contain information relating to: the offset of the sensor in three dimensions from the point of origin; the azimuth of a line perpendicular to the front face of the sensor relative to a vessel centre line; and an angle of elevation indicative of the angular offset of the front face of the sensor from vertical. In a preferred arrangement the processing unit is programmed to collate the information from the plurality of sensors and to output a signal representative of the collated information for the sensors to a graphical display. The processing unit may be programmed to monitor each of the sensors to detect if there are any faults with individual sensors. Signals sent from the sensors to the processing unit may include a unique sensor identification code and the central processor may be programmed to record and store on the memory means the time at which it receives each signal from the sensors. The central processing unit may further comprise a timer and the central processing unit is programmed to compare the time between signals to a pre-determined interval. If the time since the last received signal exceeds the pre-determined interval the central processing unit is programmed to raise an error flag for that sensor. Preferably each sensor is configured to determine and sends signals to the central processing unit relating to position, relative velocity and size of any objects detected by the sensor.

Each sensor may be configured to determine the position of detected objects relative to the sensor and the central processing unit may be programmed to transform the position of detected objects relative to the sensor to positions relative to the vessel coordinate frame.

The central processing unit may be programmed to identify and correlates, in the vessel co-ordinate frame, objects detected by two or more sensors.

The positioning monitoring system may have a visually sensible display and an input means to enable a user to configure the display. Preferably the user may, via the input means, group detected objects together so as to form a larger object returning more than one detection signal to one or more sensors.

In a preferred arrangement the user can select a detected object, or group of linked objects, as a reference object and the reference object is displayed on the visually sensible display as a fixed object and an icon representative of the vessel and any other detected objects are displayed as moving objects relative to the selected reference object.

Preferably each sensor determines and sends signals to the processor relating to position, relative velocity and size of any objects detected by the sensor and the visually sensible display displays a scaled representation of the vessel and scaled representations of detected objects.

Raising an alarm may comprise raising one or more of: an audible alarm and a visual alarm.

In a preferred arrangement, via the visually sensible display and the input means, a user can select and drag any one of the representation of the vessel or any of the representations of detected objects to a more convenient visual location on the visually sensible display and the remainder of the representations of objects will all move relative to the selected and dragged representation.

In a preferred arrangement the detected object closest to the vessel is displayed as a static object on the visually sensible display and the representations of all other objects, including that of the vessel move relative to the statically displayed object.

According to a second aspect of the invention there is provided a vessel control system comprising a position monitoring system according to the first aspect of the invention and a controller to control one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel.

The controller is preferably configured such that if the signal from the position monitoring system is indicative that a sensed object is too close to the vessel, the controller controls the one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel so as to avoid a collision with said sensed object.

According to a third aspect of the invention there is provided a method of monitoring the position of a vessel having a plurality of electromagnetic sensors arranged at intervals substantially around the perimeter of the vessel for detecting objects in the proximity of the vessel; the method comprising: sensing the position of any objects in the proximity of the vessel and defining at least one detection zone adjacent or proximate to the vessel and when the sensors sense an object in any one of said at least one detection zones, output a signal to at least one of an alarm system and the vessel control system.

Preferably defining at least one detection zone comprises defining a plurality of detection zones; the method further comprising: if the sensors sense an object in a first one of said plurality of detection zones, outputting a signal to said alarm system, and if the sensed object moves into a predetermined second one of said plurality of detection zones, output a signal to said vessel control system.

Preferably sensing the position of any objects in the proximity of the vessel comprises sensing the location of the objects relative to the sensors; and the method further comprises: storing data relating to the physical location of each of the sensors relative to the centre of motion of the vessel, the centre of motion defining a reference point for a vessel co-ordinate frame; and transforming the sensed position of detected objects relative to the sensor to positions relative to the vessel co-ordinate frame.

Storing data relating to the physical location of each of the sensors may comprise storing information relating to one or more of: the offset of the sensors in three dimensions from the point of origin; and the azimuth and elevation of the front face of the sensor relative to a vessel centre line passing through the origin.

The method may further comprise: monitoring signals including a unique sensor identification code received from each sensor; recording and storing data relating to the time at which it each signal from the sensors is received, to compare the time between signals to a pre-determined interval; and if the time since the last received signal exceeds the pre-determined interval, the central processing unit, raising an error flag for that sensor.

In one embodiment the method further comprises: displaying the vessel and any sensed objects on a visually sensible display.

The sensors may determine and send signals relating to position, relative velocity and size of any objects detected by the sensor and the method may further comprise. displaying a scaled representation of the vessel and scaled representations of detected objects.

According to a forth aspect of the invention there is provided a method of controlling a vessel comprising: monitoring the position of a vessel according to the method of the third aspect of the invention; and: in response to the output signal to the vessel control system controlling one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel. The method of controlling a vessel may further comprise: when a signal from the position monitoring system is indicative that a sensed object is too close to the vessel, the controlling one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel so as to prevent a collision with said sensed object.

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

Figure 1 shows a schematic layout of a vessel having a system of the invention;

Figure 2 shows a network diagram of a system of the invention;

Figure 3 shows a graphical display of a system of the invention; and Figures 4 and 5 show the azimuth and elevation angles.

Referring to the Figures a vessel position monitoring system for a vessel is shown which consists of several components which are described in detail below. Overall the system comprises network of electromagnetic sensors 2 that form the eyes of the system. A central processing unit (CPU) 4 communicates with the sensor array 6 and collates the information ready for presentation to the system operator as well as system interaction via a graphical user interface 8. The CPU 4 communicates with a control system 10 of the vessel and is capable of controlling the vessel 12 in the event of certain cases detected by the sensors 2. Sensor Technologies

The sensor 2 is the basic measurement element of the system and can sense the range, relative velocity, bearing or positional geometry and the size of an obstacle in its field of view. The sensors 2 may operate in several areas of the electromagnetic spectrum depending on the particular application. In one embodiment of the invention the sensors 2 could be a mechanically swept pulsed laser beam, capable of accurately measuring the outline of an obstacle within a few hundred metres, defining the objects cross section, and position relative to the sensor 2 as well as its relative velocity. In another embodiment of the sensor, technology could be employed for the detection of the infra red radiation emitted by an object which itself is a heat source greater than the surrounding environment. This would be the case for example for a person lost overboard, allowing that individual to be quickly located and rescued. In another embodiment of the invention, the sensor 2 could be a low power microwave transceiver, making use of frequency spectra freely available in the various industrial, scientific and medical bands (ISM), or the marine navigation bands. For accurate object microwave detection the microwave waveform will usually be Frequency Modulated Continuous Wave (FMCW) with a linear frequency chirp, or Linear Frequency Shift Keying (LFSK). Either types of waveform can be used to accurately measure range with a resolution dependent on the bandwidth of modulation whilst simultaneously measuring the relative velocity between the sensor 2 and the object using the Doppler principle. In the case of FMCW, the Doppler measurement is extracted by analysing the range shift measured on the up-ramp and down-ramp portions of the waveform, whilst LFSK allows the measurement of a Doppler shift by measuring the phase jump at successive frequency shifts.

Whilst the choice of waveform is important for range and velocity measurement, to accurately determine the position of the object in a Cartesian co-ordinate frame relative to the sensor 2, it is necessary to determine the polar bearing relative to the sensor's baseline. This can be achieved in several ways including; a) by mechanically steering the sensor's antenna; b) by electronically steering the beam by the use of phase shifters, and or post processing multiple receive channels using digital beam forming techniques; or c) the use of mono-pulse techniques by summing and differencing a plurality of beam patterns generated and received at the sensor 2 depending on the axis at which the bearing is to be determined, generally in an azimuth or elevation direction. Any of these techniques can be used to accurately determine the polar bearing of an object of interest.

Having measured the objects position and velocity relative to the sensor 2, finally the sensor is able to provide information on the objects reflectivity by calculating statistics such as signal to noise ratio, or the radar cross section of the reflector. Such information can be useful in determining the size of the reflector, and with temporal monitoring, will determine that that object being observed is a worthy candidate for closer tracking and inspection, or is more transient in nature and can be discounted as reflections from the sea surface or 'clutter' associated with wave surface topology.

Depending on the size of the vessel 12, and the area of the perimeter that is to be sensed, several sensors 2 will be required dependant on the coverage provided by a single sensor in azimuth and elevation, and any redundancy of coverage between sensors 2 desired for the system in terms of the overlap of neighbouring sensor beams.

The physical location of the sensors 2 on the vessel perimeter is dependent on the mode of operation. Figure 1 , for example, diagrammatically describes a setup for a large vessel. The vessel perimeter has a number of sensors 2 equally spaced to cover the area around the perimeter. In this case each of the sensors 2 is a mono-pulse F CW radar with two conical shaped beams for discerning the bearing to a reflective object. These sensors 2 however could be replaced with any of the types of electromagnetic sensor that have been mentioned previously. The sensors 2 are shown connected together on a digital communications network 14, connecting to a central processing unit 4, which in turn connects to a visual display 8. For one embodiment of the invention, where the sensor array 6 is being used as an aid to vessel dynamic positioning, the sensors 2 will be placed to coincide with the location of the object to be tracked.

Most current dynamic positioning systems require a physical target to be placed on the object to be monitored. In the case of laser measurement systems, the target will be a highly reflective tape such as the type that is used in road signage or a prismatic cluster of some configuration. Microwave measurement systems generally require a receptive antenna or transponder that is highly reflective at the microwave frequency of transmission, or imparts a modulation to the reflected signal allow the reflection to be easily identified at the receiver. It is an advantage of this invention that it has the ability to track a 'target-less' object, i.e. without the need for the installation of an artificial reflector to be used in conjunction with the system. This provides the user with the advantage that any large obstacle can be used to provide a relative reference for operation of the dynamic positioning system without the need for prior setup.

All sensors 2 within the system are enabled with a digital communication protocol, which could be any of the many that are generally used to communicate between modern computers, and that are suitable for high speed, time critical messaging, whilst being approved for use on marine installations. In one embodiment of the invention, Ethernet is used to communicate between a sensor 2 and the CPU 4. In another embodiment, a controller area network (CAN) is the preferred communication method. Either of these protocols as well as other protocols allow daisy chaining together many sensors 2 in a network to make efficient use of data and power distribution through a single cable. In another embodiment, the use of wireless communications using a wireless local area networking (WLAN) allows sensors 2 to be more mobile, provided a local power source is available such as a fixed supply or battery; communication back to the CPU 4 is achieved wirelessly without the need for fixed cable installation. For vessels that are subject to strict regulation for intrinsically safe operation of equipment due to working restrictions of explosive gas atmospheres, data communication between sensor and CPU 4 can be conducted optically via a glass fibre link.

The data link between the sensors 2 and the CPU 4 is used to communicate the sensors 2 findings in terms of the position, relative velocity and sizing information about one or more objects that have been detected by the sensors 2. The sensors 2 communicate these measurements as a digital message at regular intervals. The same communication channel can also be used by the CPU 4 to relay configuration information to any of the sensors 2 in the array 6. This allows the user of the system to configure the sensor array 6 for different modes of operation, or configure the sensors 2 to prioritise particular targets of interest.

Referring to Figure 2 the network for the system is shown in which two arrays 6 of sensors 2 are linked together on a network. As shown there may be a number of arrays of sensors 2 connecting to the CPU, e.g. one for the port and one for the starboard side of the vessel.

Central Processing Unit (CPU) subsystem

The CPU 4 controls the whole system. Its primary functions are:

a) to store information about the dimensional locations of the sensors 2 around the vessels perimeter relative to a user defined origin;

b) to collate the information transmitted from all connected sensors 2 as described in the previous section;

c) to analyse this data and fuse this information in to a format that can be relayed to the graphical user interface 8;

d) to provide a means to log this information to a non volatile storage system;

e) relay configuration information from the graphical user interface 8 to all or specific sensors 2 in the network and

f) provide a physical output to a dynamic positioning system 10 or similar control system relaying information about the position, relative velocity and size of object(s) that have been selected by the user for monitoring purposes.

Other functions include monitoring the health of each of the sensors 2 in the connected network, and allowing maintenance duties such as software or firmware upgrades of all or specific sensors 2.

The CPU 4 stores information about the physical location of each of the sensors 2 around the perimeter of the vessel 12 relative to a known point which is defined at the installation of the system referred to herein as the point the origin 16.

The dimensions of the vessel and the location of the point of origin within its boundary are also stored with the CPU 4. The point of origin 16 is the centre of motion of the vessel which would normally be located on the centre line 17 of the vessel, a line that generally splits the vessel 2 in two passing through the bow and the stern. The CPU 4 data for the location of each sensor 2 includes the offsets in three axes from the origin to the centre of the sensor. The CPU data also includes the azimuth of a line perpendicular to the front face of the sensor relative to a vessel centre line and an angle of elevation indicative of the angular offset of the front face of the sensor from vertical. In, for example the bow section of a vessel the hull is curved in two directions, towards the bow of the vessel and towards the centre line. By storing sensor data of the azimuth (A, Figure 4) of a line perpendicular to the front face of each sensor relative to a vessel centre line the CPU can use this angle to take into consideration any angular offset between the sensor and the centre line of the vessel when mapping the position of the detected object relative to the sensor to the vessel co-ordinate frame. By storing sensor data of the angle of elevation (B, Figure 5) indicative of the angular offset of the front face of the sensor from vertical, the CPU can use this data to take into consideration any angular offset between the sensor and the upright of the vessel when mapping the position of the detected object relative to the sensor to the vessel co-ordinate frame. For example, if a sensor detects an object at a position having coordinates Xi , Yi , ZL then by knowing the offset of the sensor in three dimensions X₂, Y₂, Z₂, from the origin, the CPU can transform the object co-ordinates onto the vessel co-ordinate frame relative the origin to give object position X(i₊₂), Y₍i₊₂₎, ₍1₊2₎· However, this is only an effective transformation if the sensors are parallel to the centreline of the vessel and are vertically aligned. In reality, and especially if it is necessary to detect objects in close proximity to the vessel, it will most likely be necessary that the sensors are angled downwards to some degree towards the water and therefore, to accurately transform the sensed position onto the vessel co-ordinate frame it will be necessary to know this angle of elevation. Furthermore, as the bow of the vessel curves at the front, and, so as to enable some sensors to have better forward sensing, the sensors will not always be parallel to the centre line of the vessel but will be angularly offset therefrom. By storing sensor data of the azimuth of a line perpendicular to the front face of each sensor relative to a vessel these angular offsets from the centre line can also be taken into consideration when transforming the sensed object co-ordinates to the vessel coordinate frame relative the centre of motion of the vessel.

This information therefore allows local sensor measurements defined in a local sensor co-ordinate frame to be transformed to a vessel global co-ordinate frame.

All sensors 2 which are individually identified and are connected on one or more networks controlled and monitored by the CPU 4. The CPU 4 monitors and controls the flow of information on each network acting as a server. Each sensor 2 reports position, relative velocity and size of objects that have been detected within its sensing perimeter. The information it identifies and reports can be considered as 'raw' targets since they may be observations of objects within the vicinity of the vessel 12, or be reflections from clutter in the environment, such as multi-path reflections from the sea surface, or unwanted signals from the topology of the sea surface. The raw information received by the CPU 4 is collated and further analysed. The object of the analysis is to identify coherent targets which temporally exist from one message to the next. This is achieved by transforming the position of the raw targets from the local sensor co-ordinate frame to a global co-ordinate frame which matches that of the vessel, and which is meaningful for communication to any graphical user display 8 or to any connected vessel control or dynamic positioning system 10. Targets should be correlated in this global coordinate frame between neighbouring sensors 2 especially when where two sensors 2 fields of view are overlapping.

Temporal monitoring or tracking of objects delivered by messages from each sensor 2 allows the CPU 4 to make decisions about detected obstacles around the vessel 12. The aim of this object tracking is to filter out reflective clutter returned by the sea surface or multi-path reflections from the sea surface, whilst allowing true persistent obstacles to be reliably detected and delivered to the graphical display. These objects are referred to herein as 'tracked' objects.

Tracked objects are the only objects that are delivered to the graphical display 8 to be displayed to the user. The user has the ability to select any of these tracked objects for the purposes of a reference, and elect to supply information about these objects from the CPU 4 via a physical communications link to a dynamic positioning system or other vessel control system 10.

The dynamic positioning system 10 is physically linked to the CPU 4 via a cable. Data transfer across this link could be by any digital communications protocol approved for use in marine installations. In one embodiment of the invention, an RS422 serial connection is used to communicate updates to the dynamic positioning system at a mutual baud rate. In another embodiment, Ethernet communications protocols are used.

Within the CPU 4 is a memory means 18 for non-volatile storage of the data received by and processed by the CPU. The purpose of this data storage is to provide a record of the objects detected by the sensor array 6 for post analysis for a variety of reasons. Firstly, this data is a record of the performance of the system and a means of resolving any technical issues. Secondly, the data is recorded from a safety viewpoint, and can be referenced in the event of any incident involving the host vessel and other objects.

The CPU 4 is continually monitoring traffic on the sensor array 6 network. Each sensor 2 transmits in each communication a unique id as part of its message header, enabling the CPU 4 to determine the source of the message. The CPU 4 records the time at which it received the last message from each sensor 2, and uses an internal timer to record the time elapsed since the last message from the same sensor 2. The acceptable time period between messages is either defined by the user or pre programmed into the CPU. Should the time period expire without an incoming signal this would constitute a problem with the sensor 2, and would be flagged to the graphical display 8.

Graphical Display

The graphical display 8 can be presented on a variety of display interfaces depending on the type of installation. The display interface 8 can consists of an LCD monitor 20 which may be a touch screen device 22 and/or may include a hand operated pointing device 24to enable the operator to interact with the system. The display interface 8 need not be restricted to this format, and it would be possible to use other known display technologies with the system.

The graphical display interface 8 has the following primary functions:

a) the clear display of a scaled representation the host vessel including the position of sensors 2 monitoring its perimeter;

b) the display of one or more obstacles detected by the sensor network and tracked by the CPU 4. The display shows the scaled position of the obstacle relative to the vessel 12 as well as information about its size and relative velocity.

There may be one or more graphical displays. A master display 8 will be connected to the CPU 4 and in many cases this will suffice. However, additional displays 26 can be networked via a connection to one or more remote terminals or repeaters. It is possible to have a multitude of these extra display consoles allowing for multiple user locations on a modern vessel bridge, or other areas of the vessel where the system display would be advantageous.

Operational Functionality

The system operates to use the sensed data/objects and links into the vessel navigational and /or dynamic positioning system 10.

Two zones are defined around the vessel, one inner zone 28 in close proximity to the vessel and one outer zone 30 at a further proximal distance to the vessel, The two zones preferably are adjacent one another although there may be situations in which the two zones may be apart from one another.

The outer zone 30 acts as a warning zone and has the function if the vessel 12 is coming into close proximity to another object. It will not always be necessary to take action in this case but an alarm is raised, which may be audible or visual, to alert the person or persons who are responsible for the control of the vessel. For example, if a large vessel is holding position close to an oil rig and there are operations going on, for example the transfer of goods, from the foredeck this will be the area of primary focus of personnel. If the stern of the vessel started to swing towards the oil rig then as the sensors 2 detected the rig coming into the outer zone an alarm would be raised to alert the person in control of the ships position and action could be taken to remedy the situation. In another example, in a close manoeuvring situation, if a vessel were to enter an area behind the vessel without the ships personnel becoming aware the warning system can alert them that that vessel is there.

The inner zone 28 is an 'action' zone and if an object enters the action zone then a signal is immediately sent to the system controlling the ships propulsion 32 and or direction 34, e.g. the navigation, engine management, or dynamic positioning system, which automatically takes evasive action by operation of the ships propellers 36, thrusters 38, or steering system, to reduce the likelihood of collision.

The zones 28, 30 can be bands of equidistance around the vessel; however the zones may alternatively be set up by the user for specific scenarios and need not be symmetrical about the vessel. If for example a vessel is station keeping alongside an object 52 on its starboard side it may want the range of the sensors 2 there to be very specific to the station keeping distance. For example, if a vessel is keeping station fifty meters from an object 52 it may set its outer zone 30 limit at forty-two meters and its action zone 28 at thirty meters, on its starboard side. In this way the majority of the time neither zone will be activated as the vessel will be fifty meters from its target. If the vessel drifts over eight meters towards the object 52, the object 52 will enter the outer zone 30 and an alarm will be raised allowing for manual intervention. If no manual intervention was forthcoming and the vessel drifted to within thirty meters of the object then the inner zone 28 will be activated, a message sent to the dynamic positioning system 10 and automatic control will result to move the vessel 12 away from the object 52.

On the port side of the vessel 12 where there is no such station keeping target the zones may be set at greater distance to perform more general watch keeping duties. In another example, if the vessel 12 is moving forwards, both zones 28, 30 may be biased in a direction ahead of the vessel.

The user can select objects on the screen 20 and 'safe flag' them to prevent the system taking over control to avoid evasive action. This may be used, for example, where a pilot vessel is coming alongside a cargo vessel to transfer or pick up a harbour pilot. In these cases it is, of course, important that the pilot vessel is allowed to come alongside the vessel without any such evasive manoeuvres. In one embodiment the CPU 4 is interfaced with other maritime systems, such as Automatic Identification System (AIS), and specific vessels can be safe flagged by their AIS identification. Linking the systems together will enable the system of the invention to automatically correlate sensed objects to available AIS information and thereby not alarm or take evasive action if AIS safe listed vessels approach, thereby removing the necessity to safe list the same vessel each time it approaches. In operation the user may select one or more displayed obstacles 40, 42 and link these obstacles together to represent a single object 50. For example, at close proximity individual legs of an oil rig will be identified as separate objects by the system, however the user can select them on the graphical display 8 and link them together to identify them as a single object 50. Furthermore the system can communication information about an obstacle 50 or multiple obstacles to the host dynamic positioning system 10 by means of message or series of messages and the dynamic positioning system 10 can use the information form the system of the invention to keep its position relative to certain identified objects.

Display Modes

The display 8 is split in to distinct areas. A seascape area 54 is used on which to graphically represent the vessel and tracked objects, whilst a control area consists of several control buttons 58 allowing access to system control functions.

Within the seascape area 54 a representation of the host vessel 60 is shown marked with the positions of the one or more sensors 62 in the array on the vessels perimeter. This representation of the vessel is to scale within the seascape based on dimensional information supplied by the user, but is not static and reacts to several different stimuli. Although shown in a head up' position it will be appreciated that when overlaid on a seascape the seascape may be shown in a 'north' up position and the vessel direction shown relative to the 'north up' seascape.

Additionally displayed within the seascape are tracked objects that are communicated from the CPU 4. These objects are displayed on the seascape in their Cartesian positions relative to the vessel location. The user can zoom in and out on the seascape, as well as, via the user interface, 'grab' the representation of the vessel 60 or any object and move it around the seascape to optimise its viewing position. The location of the vessel and all objects on the display will move relative the grabbed object or vessel.

The user can elect to group together any objects on the screen, or create multiple groups of objects. The user can select a single object, or one or more groups of objects, and choose for its information to be delivered to the connected dynamic positioning system.

Once in this mode, the closest selected object or object group to the vessel will remain fixed on the screen, whist all other objects as well as the vessel will be displayed dynamically in their relative Cartesian positions, optionally with relative velocity vectors back to the vessel. The colour of an object or group can be modified to give a visual indication that it is being delivered to the dynamic positioning system. The user can at any time 'grab' the fixed object or object group and move it to another visually more convenient location. The user can zoom in or out to expand or contract the scene showed within the seascape. The user can at any time elect to unfix this fixed object and fix one of the other selected objects or object groups that are being delivered to the control or dynamic positioning system 10. The user can choose to deselect any object or object group and stop its positional information being delivered to the control or DYNAMIC POSITIONING system.

Claims

CLAIMS:

1 A position monitoring system for a vessel having a vessel control system comprising:

a plurality of electromagnetic sensors arranged at intervals substantially around the perimeter of the vessel for detecting objects in the proximity of the vessel;

a central processing unit for communicating with the sensors and determining the position of any objects in the proximity of the vessel and

wherein the central processing unit has a memory means associated therewith that contains data defining at least one detection zone adjacent or proximate to the vessel and

the central processing unit is programmed to, upon detection that the sensors have sensed an object in any one of said at least one detection zones, output a signal to at least one of an alarm system and the vessel control system.

2 A position monitoring system according to claim 1 wherein the memory means contains data defining a plurality of detection zones.

3 A position monitoring system according to claim 2 wherein if the central processing unit is programmed to, upon detection that the sensors have sensed an object in a first one of said plurality of detection zones, output a signal to said alarm system and if the sensed object moves into a predetermined second one of said plurality of detection zones, output a signal to said vessel control system indicative that the vessel control system should take action.

4 A position monitoring system according to any one of claims 2 or 3 wherein the data defining at least one detection zone plurality of detection zones includes at least a first zone and a second zone, the second zone being in closer proximity to the vessel that the first zone.

5 A positioning monitoring system according to any preceding claim wherein each of the at least one detection zones are defined by a user. 6 A positioning monitoring system according to any preceding claim wherein memory means contains data relating to the physical location of the sensors relative to a point of origin. 7 A positioning monitoring system according to claim 6 wherein the point of origin is the centre of motion of the vessel and defines a reference point for a vessel coordinate frame.

8 A positioning monitoring system according to claim 6 or claim 7 wherein, for each sensor, the memory means contains information relating to: the offset of the sensor in three dimensions from the point of origin; the azimuth of a line perpendicular to the front face of the sensor relative to a vessel centre line; and an angle of elevation indicative of the angular offset of the front face of the sensor from vertical. 9 A positioning monitoring system according to any preceding claim wherein the central processing unit is programmed to collate the information from the plurality of sensors and to output a signal representative of the collated information for the sensors to a graphical display. 10 A positioning monitoring system according to any preceding claim wherein the central processing unit is programmed to monitor each of the sensors to detect if there are any faults with individual sensors.

11 A positioning monitoring system according to claim 10 wherein signals sent from the sensors to the central processing unit includes an unique sensor identification code and, wherein the central processing unit is programmed to records the detect and store on the memory means the time at which it receives each signal from the sensors, the central processing unit further comprising a timer, and the central processing unit programmed to compare the time between signals to a pre-determined interval.

12 A positioning monitoring system according to claim 11 wherein, if the time since the last received signal exceeds the pre-determined interval, the central processing unit is programmed to raise an error flag for that sensor. 13 A positioning monitoring system according to any preceding claim wherein each sensor is configured to determine and sends signals to the central processing unit relating to position, relative velocity and size of any objects detected by the sensor. 14 A positioning monitoring system according to claim 7 or 8 wherein each sensor is configured to determine the position of detected objects relative to the sensor and the central processing unit is programmed to transform the position of detected objects relative to the sensor to positions relative to the vessel co-ordinate frame. 15 A positioning monitoring system according to claim 14 wherein the central processing unit is programmed to identify and correlate, in the vessel co-ordinate frame, objects detected by two or more sensors.

16 A positioning monitoring system according to any previous claim further having a visually sensible display and an input means to enable a user to configure the display.

17 A positioning monitoring system according to claim 16 wherein a user can , via the input means, group detected objects together so as to form a larger object returning more than one detection signal to one or more sensors.

18 A positioning monitoring system according to claim 16 or 17 wherein the user can select a detected object, or group of linked objects, as a reference object and wherein the reference object is displayed on a the visually sensible display as a fixed object and an icon representative of the vessel and any other detected objects are displayed as moving objects relative to the selected reference object.

19 A positioning monitoring system according to claim 9 wherein each sensor determines and sends signals to the processor relating to position, relative velocity and size of any objects detected by the sensor and the visually sensible display displays a scaled representation of the vessel and scaled representations of detected objects.

20 A positioning monitoring system according to any preceding claim wherein raising an alarm comprises raising one or more of: an audible alarm and a visual alarm. 21 A positioning monitoring system according to claim 16 configured such that, via the visually sensible display and the input means, a user can select and drag any one of the representation of the vessel or any of the representations of detected objects to a more convenient visual location on the visually sensible display and wherein the remainder of the representations of objects will all move relative to the selected and dragged representation.

22 A positioning monitoring system according to claim 16 wherein the detected object closest to the vessel is displayed as a static object on the visually sensible display and the representations of all other objects, including that of the vessel move relative to the statically displayed object.

23 A vessel control system comprising a position monitoring system according to any preceding claim and a controller to control one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel.

24 A vessel control system according to claim 23 wherein the controller is configured such that if the signal from the position monitoring system is indicative that a sensed object is too close to the vessel, the controller controls the one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel so as to avoid a collision with said sensed object.

25 A method of monitoring the position of a vessel having a plurality of electromagnetic sensors arranged at intervals substantially around the perimeter of the vessel for detecting objects in the proximity of the vessel; the method comprising:

sensing the position of any objects in the proximity of the vessel;

defining at least one detection zone adjacent or proximate to the vessel; and when the sensors sense an object in any one of said at least one detection zones, output a signal to at least one of an alarm system and the vessel control system.

26 A method according to claim 25 wherein defining at least one detection zone comprises defining a plurality of detection zones; the method further comprising:

if the sensors sense an object in a first one of said plurality of detection zones, outputting a signal to said alarm system, and if the sensed object moves into a predetermined second one of said plurality of detection zones, output a signal to said vessel control system.

27 A method according to claim 25 or claim 26 wherein:

sensing the position of any objects in the proximity of the vessel comprises sensing the location of the objects relative to the sensors; and the method further comprises:

storing data relating to the physical location of each of the sensors relative to the centre of motion of the vessel, the centre of motion definings a reference point for a vessel co- ordinate frame;

and transforming the sensed position of detected objects relative to the sensor to positions relative to the vessel co-ordinate frame.

28 A method according to claim 27 wherein storing data relating to the physical location of each of the sensors comprises storing information relating to one or more of: the offset of the sensors in three dimensions from the point of origin; and the azimuth and elevation of the front face of the sensor relative to a vessel centre line passing through the origin. 29 A method according to any one of claims 25 to 28 further comprising:

monitoring signals including a unique sensor identification code received from each sensor;

recording and storing data relating to the time at which it each signal from the sensors is received,

to compare the time between signals to a pre-determined interval; and if the time since the last received signal exceeds the pre-determined interval, the central processing unit, raising an error flag for that sensor.

30 The method according to any one of claims 25 to 29 further comprising:

displaying the vessel and any sensed objects on a visually sensible display.

31 The method according to claim 30 wherein the sensors determine and send signals relating to position, relative velocity and size of any objects detected by the sensor, the method further comprising: displaying a scaled representation of the vessel and scaled representations of detected objects.

32 A method of controlling a vessel comprising:

monitoring the position of a vessel according to the method of any one of claims 25 to 31 ; and

in response to the output signal to the vessel control system controlling one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel.

33 A method of controlling a vessel according to claim 32 comprising:

when a signal from the position monitoring system is indicative that a sensed object is too close to the vessel, the controlling one or more of: the position of the vessel, engines of the vessel, steering of the vessel and thrusters of the vessel so as to prevent a collision with said sensed object.