Patent Description:
Boating can be challenging at times. Quickly changing weather conditions and other unexpected circumstances may require a helmsman and/or person in charge of navigation of a marine vessel to abandon an ongoing maneuver and quickly come up with a new plan.

For instance, when entering a natural harbor many things can happen which necessitate aborting the maneuver. The harbor can be unexpectedly crowded with boats, and/or something on the boat may break at the wrong time. Maneuvering in such scenarios may be challenging due to limited maneuvering space.

Accidents, such as man-over-board events, may also occur which require a fast response to the event and sometimes relatively complicated maneuvering of the vessel.

Some support systems for assisting in boat maneuvering and navigation are known. For instance, <CIT> discloses automated systems for assisting control of a marine vessel. The system comprises a return navigation module configured to maneuver the boat to retrace a travelled path. In particular, there is disclosed an automated tender function which navigates a vessel to and from a pier without anyone on board.

<CIT> describes a marine rescue system comprising a rescue flotation device arranged to navigate in reverse direction along a path travelled by a vessel in order to rescue a person having fallen overboard.

However, there is a continuing need for improved systems that promote easy boating.

It is an object of the present disclosure to promote easy boating. This object is at least in part obtained by a control unit for controlling a marine vessel to avoid an undesired situation. The control unit comprises processing circuitry and a storage medium. The control unit is arranged to receive path data from one or more sensor devices indicative of a path travelled by the marine vessel in a forward direction and to store the received path data by the storage medium. The control unit is arranged to receive a trigger signal from an input device, and, in response to the trigger signal, determine a set of candidate locations associated with a pre-determined required space for turning, determine a location for turning the vessel around by selecting the candidate closest to the current location or the candidate reached by a minimum of control maneuvers, navigating to the location, turning the vessel around at the location, and navigating the vessel along the path in reverse direction.

This way a helmsman or other person may activate the assistance system in, e.g., a stressful situation, whereupon the vessel autonomously turns around and goes back the way it came. This path is likely to be free of underwater obstacles like reefs and shallows and may thus be safely traversed.

The control unit may be arranged to navigate the vessel along the path in reverse direction by generating control commands for one or more out of a rudder, an engine, and/or a thruster.

According to some aspects, the input device is a manual input device operable from a position on-board the vessel. This manual input device may, e.g., be an easily accessible button, perhaps located next to a steering wheel of the vessel, which can be pushed as soon as something happens which necessitates aborting a current maneuver by the vessel, such as a docking operation or the like. The input device may also be a portable device arranged to be wirelessly connected to the control unit, such as a remote control device or even a smartphone device or the like. This portable device is optionally arranged attachable to a jacket, life-vest, or other personal equipment.

According to other aspects, the control unit is arranged to navigate the vessel along the path in the reverse direction up to a location associated with a man-over-board (MOB) event. Thus, if a person falls overboard, the situation avoidance system can be triggered in order to autonomously navigate the vessel back to the location of the MOB event, along the path travelled by the vessel after the MOB event occurred. Advantageously, the triggering of the autonomous navigation system does not require any particular boating skills, which means that anyone can trigger the system, even if they lack boating experience. The system can also be triggered remotely by a person having fallen overboard, which is an advantage, especially if the person overboard was the only person on the vessel to start with.

Optionally, the control unit is arranged to initially bring the vessel to a halt in response to the trigger signal. The system may then be paused waiting for a second trigger signal which functions like a confirmation signal to start the situation avoidance maneuver, i.e., to start maneuvering back along the path.

According to other aspects, the control unit is arranged to reverse the vessel following bringing the vessel to a halt in response to the trigger signal. Reversing may be preferred in some scenarios where it is difficult to turn the boat around, and where going forward is not a good option.

According to some aspects, the marine vessel is a sailing vessel. In this case the control unit may be arranged to turn into the wind and trigger a function for dowsing one or more sails in response to the trigger signal. This feature may be advantageously combined with the feature of bringing the vessel to a halt for a pre-determined amount of time.

The system may operate based on a number of different types of sensor data, or on combinations of different types of sensor data, such as global positioning system (GPS) data, data from a radar sensor and/or from a lidar sensor and/or from a vision-based sensor such as a camera or infra-red vision sensor. Using combinations of different types of sensor data increases system robustness. At the same time, it is an advantage that the system can function based only on one type of sensor data.

According to further aspects, the control unit is arranged to receive obstacle data indicative of an obstacle in vicinity of the path, and to adjust navigation of the vessel along the path to avoid the obstacle. This way moving objects can be accounted for and maneuvers may be performed for avoiding collisions with such objects. These moving objects primarily comprise other marine vessels but drifting passive objects may also appear which it is desired to avoid. The obstacle data may comprise any of radar sensor data, lidar sensor data, vision-based sensor data, and/or automatic identification system (AIS) data.

The control unit may further be arranged to receive weather data indicative of a wind condition along the path from a wind sensor and to adjust the navigation along the path in dependence of the wind data. For instance, it may be desirable to maintain a windward position slightly offset from the travelled path in order to improve maneuvering margin with respect to, e.g., underwater obstacles and the like.

The disclosed systems may also be combined with automated systems for anchoring. Thus, according to some aspects, the control unit is arranged to determine a suitable location for anchoring in a vicinity of the path, and after navigating the vessel along the path in reverse direction, to automatically deploy an anchor at the determined suitable location for anchoring, or to automatically activate a virtual anchoring function, where the control unit is arranged to keep the determined suitable location by controlling a driveline of the marine vessel.

The location for anchoring may advantageously be determined in dependence of the anchoring capabilities of the vessel.

There is also disclosed herein marine vessels such as powerboats and sailboats, methods, computer programs, computer readable media, and computer program products associated with the above discussed advantages.

<FIG> illustrates an example scenario <NUM> where a marine vessel <NUM>, here a powerboat, is entering a natural harbor area <NUM>, such as a cove. The navigation into the natural harbor is challenging due to the presence of obstacles such as shoals and reefs, i.e., underwater obstacles <NUM>, <NUM>. There are also other boats <NUM> nearby which are to be avoided. More often than not, unexpected things happen which necessitates aborting the maneuver and navigating back out from the area. For instance, it may turn out that the place is already full of other boats, something on the own boat may break, or the helmsman may for some reason not be able to complete the maneuver. This type of situation may be challenging, especially to less experienced persons.

<FIG> illustrates another example scenario <NUM>' where the marine vessel <NUM> is instead entering a harbor area with wharfs <NUM>. When entering the area, it turns out that there is no space left for docking, which means hat the helmsman needs to safely bring the boat out from a confined area.

The present disclosure relates to autonomous situation avoidance systems for marine vessels which are arranged to assist a helmsman in these types of situations. Whenever the helmsman or someone else on board the vessel <NUM> determines that the current maneuver needs to be aborted, that person may generate a trigger signal. This trigger signal can, e.g., be generated by pressing a dedicated button, by activating a function via a control interface, or by a wireless device such as a dedicated radio remote control or a smartphone. The assistance system will then, in response to the trigger signal, determine a location L for turning the vessel <NUM> around, navigate to the location L, turn the vessel around at the location L, and then navigate the vessel <NUM> in a reverse direction R along the path T which the vessel followed in forward direction F when entering the area.

<CIT> describes a system for assisting reversal of an articulated vehicle, such as a truck with a trailer. This reverse assist system records a predefined number of positions along a track which the vehicle follows in a forward direction. The driver may then be assisted by the system when reversing the vehicle along the same track. The positions may, e.g., be recorded using a global positioning system (GPS). The situation avoidance systems disclosed herein operate based on a similar principle. A control unit continuously records track data as the vessel <NUM> travels in forward direction. This track data can then be used to navigate the vessel <NUM> in reverse direction to follow the path taken into the area. Global positioning data normally forms the base for the stored track. However, this data may sometimes be associated with large errors, e.g., due to a limited view of the sky or due to multipath reflections of the GPS signals received from the GPS satellites. The systems disclosed herein therefore optionally relies on additional track data sources, such as radar systems, lidar system, and/or vision-based sensor systems.

The rationale for navigating back along the same track followed when entering into the situation is that this track is very likely to be free from underwater obstacles like reefs and shoals, since none were hit in the forward direction, and thus represents a feasible route away from the entered area.

It is appreciated that obstacles, such as other boats <NUM>, may appear along the track T when navigating in reverse direction R. These boats <NUM> are of course to be avoided, if possible, during the navigation in reverse direction. Methods comprising optional features for avoiding such obstacles will be discussed below.

<FIG> schematically illustrates a control system <NUM> for performing the type of situation avoidance maneuvers discussed above. The system comprises a control unit <NUM> for controlling a marine vessel <NUM> to avoid an undesired situation. The control unit <NUM> comprises processing circuitry <NUM> and a storage medium <NUM>. The control unit <NUM> is arranged to receive path data <NUM> from one or more sensor devices <NUM>, <NUM>, <NUM>, <NUM>, indicative of a path T travelled by the marine vessel <NUM> in a forward direction F and to store the received path data by the storage medium <NUM>. The control unit <NUM> is arranged to receive a trigger signal <NUM>, <NUM>' from an input device <NUM>, <NUM>', and, in response to the trigger signal <NUM>, <NUM>', determine a location L for turning the vessel <NUM> around, navigating to the location L, turning the vessel around at the location L, and navigating the vessel <NUM> along the path T in reverse direction R.

The received path data may just comprise a sequence of position fixes obtained from a GPS sensor <NUM>, possibly comprising heading and speed data. Navigating the vessel <NUM> along the path T in reverse direction R then comprises steering the vessel using the position fixes as waypoints in a straight-forward manner. However, additional path data may be used instead of or in combination with the GPS data to increase system accuracy and robustness. In fact, some scenarios may require more accurate path data than that provided by a satellite navigation system like GPS. Such data may optionally be obtained from a radar sensor <NUM> and/or a lidar sensor which provides information related to objects in vicinity of the path T, from a vision-based sensor <NUM> such as camera, stereo-camera or infra-red vision sensor which generates visual data, or from a sonar sensor <NUM> which generates a profile of the seabed over which the vessel <NUM> has travelled. These different data types and their use in navigating along the path T in reverse direction will be discussed in more detail below.

It is appreciated that the path travelled by the vessel from the place of activation of the trigger signal to the location L is comprised in the path T to be navigated along in the reverse direction R.

Optionally, the control unit <NUM> is arranged to initially bring the vessel <NUM> to a halt in response to the trigger signal <NUM>, <NUM>', prior to navigating to the location L. The time duration of the initial halting of the vessel may be configurable or pre-determined. For instance, the system may be configured to bring the vessel <NUM> to a halt in response to a first trigger signal, and then await a second trigger signal before navigating to the location L, turning the vessel around at the location L, and navigating the vessel <NUM> along the path T in reverse direction R. This second trigger signal would then have a function similar to that of a confirmation signal.

The distance to travel in the reverse direction may be associated with a pre-configured maximum distance, after which the vessel is brought to a halt. The navigation function may of course be terminated by an operator at any time, at which manual control can be assumed again.

The input device may be a manual input device <NUM> operable from a position on-board the vessel <NUM>. This input device may for instance be realized as a simple to reach button similar to a man-over-board (MOB) alarm button found on some vessels. The input device may also be realized as a menu choice in an existing navigation system interface on the vessel. For instance, the vessel <NUM> may comprise a display located in connection to the controls of the vessel for displaying, e.g., sea charts, radar images, and the like. This display may comprise a touch-screen function or other input device for triggering the situation avoidance maneuver.

The input device can also be a portable device <NUM>' arranged to be wirelessly connected to the control unit210. This portable device <NUM>' may be realized as a relatively simple remote control device which transmits a radio signal to a radio receiver arranged on the vessel. The portable device <NUM>' may also be a smartphone or other device which connects to the control unit <NUM> via wireless link, such as a Wi-Fi link in the family of wireless network protocols based on the IEEE <NUM> family of standards, a Bluetooth wireless link, or the like.

According to some aspects, the control unit <NUM> is arranged to navigate the vessel <NUM> along the path T in the reverse direction R up to a location associated with a man-over-board (MOB) event. This MOB event may, for instance, be associated with a geographical position fix determined when a MOB alarm function was triggered. For instance, a person on board the vessel <NUM>, or even the person who has fallen into the water, may trigger a MOB alarm function of the vessel which in turn results in a geographical position fix associated with the MOB event. The person in the water, or a person still on board the vessel <NUM> may then activate the situation avoidance maneuver to turn the boat around and navigate along the path T in reverse direction to the MOB event location, where, hopefully, the person in the water can be rescued.

In case the vessel is a sailing boat, the control unit <NUM> may optionally be configured to turn the vessel into the wind, dowse sails, start engines, and then navigate back to a person in the water or generally navigate away from an undesired situation. Thus, according to some aspects, the control unit <NUM> is arranged to turn the vessel <NUM> into the wind and trigger a function for dowsing one or more sails in response to the trigger signal <NUM>, <NUM>'. The wind direction (into which to turn) may be obtained from a wind sensor <NUM> in a known manner.

Notably, the person in the water may have triggered this situation avoidance maneuver wirelessly from the position in the water. The portable device <NUM>' is optionally arranged attachable to a jacket, life-vest or other personal equipment for situations such as this. Thus, a person having fallen into the water is able to halt the vessel and trigger the vessel to return to the position of the person in the water. This is particularly advantageous if the person falling into the water is the only person on board the vessel, or the only person capable of maneuvering the vessel back to the MOB location. According to some aspects, the trigger signal is automatically generated when a dead man's switch is activated.

Some scenarios comprise very little space for maneuvering the vessel. For instance, in the scenario <NUM>' illustrated in <FIG>, the space between the wharves <NUM> may not permit turning the vessel around. In such scenarios the vessel may need to be reversed initially to a location where the vessel can be turned around. Of course, the space required to turn a vessel around varies from vessel to vessel. Some vessels are equipped with thrusters that permit turning the vessel around on the spot, while other vessels only comprise a propeller aft on the vessel and therefore require more space for turning the vessel around. Thus, according to some aspects, the control unit <NUM> is arranged to reverse the vessel <NUM> following bringing the vessel to a halt in response to the trigger signal <NUM>, <NUM>'. The space required to turn the vessel around may be pre-configured or determined from scenario to scenario based, e.g., on data from a wind sensor <NUM>. If the control unit <NUM> is not able to fit the space required for turning into the current location of the vessel based on, e.g., sea chart data or radar sensor data, the control unit may reverse the vessel a distance to a location where there is enough space for turning the vessel around. Alternatively, the control unit may determine that there is enough room for turning the vessel around if the vessel is navigated some distance forward.

According to the invention, the control unit <NUM> determines a set of candidate locations L for turning the boat around by identifying locations on a sea chart or map which are associated with the pre-determined required space for turning the boat around. The predetermined space for turning the boat around may, e.g., be defined by a circle of a given radius. The radius is optionally determined as a function of current weather conditions. For instance, if the wind is strong, then a larger circle may be selected compared to if the wind is not very strong, optionally based on a pre-determined look-up table. Also, if the current scenario comprises large waves, then a larger space for turning the boat around may be required. One example of identifying locations on a sea chart or map which are associated with the pre-determined required space for turning the boat around is to move a circle having a pre-determined radius over the sea chart or map in vicinity of the vessels current location, and detect places on the sea chart or map where no obstacles are comprised in the circle. These locations then constitute candidate locations for turning the boat around. The best such candidate can then be selected, e.g., as the candidate closest to the current location, or the candidate deemed most easily reached, e.g., by a minimum of control maneuvers. The locations of other vessels <NUM> can also be considered when determining the location L for turning the vessel <NUM> around.

Generally, a cost function can be formulated based on various metrics for selecting the best candidate location for turning the vessel <NUM> around. This cost function may take the form of <MAT> where Ci is the total cost associated with the i-th candidate location Li. The cost function comprises N different metrics. Each metric is associated with a pre-determined weight wk indicating how important the metric is in relation to other metrics, and a respective metric cost function ck. For instance, one metric may be associated with the distance from the current location of the vessel to the candidate location for turning the vessel around. A candidate location far away from the current location of the vessel is then assigned a larger metric cost compared to a location more close to the current location of the vessel. Another metric may be associated with the number of other vessels within some pre-determined distance of the candidate location, the more vessels the higher the cost of that particular candidate location. A third metric may be associated with the number of turns which have to be executed in order to reach the candidate location, where a more straight path to the candidate location is preferred over a location which requires many maneuvers around obstacles in order to reach. A fourth metric may be related to the free space of the candidate location, such that a small sized space for turning the vessel around (even if sufficient to turn the boat around) is associated with larger cost compared to a location with a free space well beyond the requirement.

The control systems disclosed herein may be based solely on one type of sensor data indicative of the path T travelled by the marine vessel <NUM> in the forward direction F, or on more than one type of data. Normally, the path data comprises GPS data, however, reverse path following may also be performed based on other types of sensor data.

For instance, the sensor data can be obtained from a rearward looking sensor recording a vision-based image sequence of the travelled path or a radar image sequence of the travelled path seen when looking out from the rear of the vessel. This recorded image sequence can then be used in combination with a corresponding forward looking sensor to navigate along the path T in reverse direction R with high accuracy. This is because, to navigate along the same path in reverse direction, the recorded image sequence should at least approximately match the sensor data from the forward looking sensor as the path is followed. Any deviation from the path will result in a mismatch between the image data recorded by the rearward looking sensor when travelling in forward direction and the image data recorded by the forward looking sensor when travelling in the reverse direction. Thus, by matching image sequences the vessel can be navigated along the path in reverse direction.

It is noted that some sensors are capable of a <NUM> degree view from the vessel, such as some omni-directional radar sensors. This sensor data need only be rotated <NUM> degrees in order to allow navigating back along the path T in the reverse direction R.

A bearing and distance to some landmark, obtained from a radar sensor or from a lidar sensor, is in fact sufficient to determine the path T. By loading such a sequence of bearings and distances from memory, reversing the sequence in time, and then controlling the vessel to obtain a sequence which is equal to, or at least similar to, the bearing and distance data stored in the forward direction, the same path will be followed in reverse direction.

If more than one type of sensor data is used jointly to navigate along the path T in reverse direction, then the different types of data may be weighted in relation to the accuracy in the data.

As shown in <FIG> above, moving obstacles, such as other marine vessels <NUM> and perhaps also drifting passive objects, may be present in vicinity of the travelled path T. Some optional variants of the autonomous assistance systems disclosed herein are arranged to detect and to avoid such objects when navigating along the path T in the reverse direction R. Thus, according to some aspects, the control unit is arranged to receive obstacle data indicative of an obstacle <NUM> in vicinity of the path T, and to adjust navigation of the vessel <NUM> along the path T to avoid the obstacle <NUM>. The obstacle data indicative of an obstacle <NUM> in vicinity of the path T may, e.g., comprise any of radar sensor detection data, lidar sensor detection data, vision-based sensor data, and/or automatic identification system (AIS) data. Adjusting navigation of the vessel <NUM> along the path T may, e.g., comprise adjusting boat speed to avoid collision (or even halting the vessel entirely for some time) while the other vessel crosses the path T, or performing minor evasive maneuvering. For instance, the track to be followed in the reverse direction may be defined by a nominal track Tn and a maximum track error e, as illustrated in <FIG>. The control unit <NUM> is then allowed to adjust vessel heading to avoid collision with an obstacle <NUM> as long as the distance from the vessel <NUM> to the nominal track Tn is below the predetermined maximum track error e.

The control unit <NUM> may also be arranged to receive weather data indicative of a wind condition along the path T from a wind sensor <NUM>, and to adjust the navigation along the path T in dependence of the wind data. For instance, with reference to <FIG>, in case of very strong winds from a given direction W, it may be desirable to maintain a windward position in relation to the nominal track Tn, i.e., to navigate along the track at an offset towards the wind, while keeping within the 'corridor' <NUM> defined by the nominal track Tn and the maximum error e.

With reference again to <FIG>, the control unit may have one or more actuators at its disposal for controlling the vessel <NUM>. Most vessels will comprise a rudder <NUM> for turning the vessel, and an engine <NUM> for powering the vessel. However, some vessels also comprise thrusters which may improve the maneuverability of the vessel, especially in tight spaces where there is not very much room for maneuvering. According to some aspects, the control unit <NUM> is arranged to navigate the vessel <NUM> along the path T in reverse direction R by generating control commands for one or more out of a rudder <NUM>, an engine <NUM> and/or a thruster <NUM>.

Some vessels may also comprise anchoring systems <NUM> which can be triggered from the control unit <NUM>. Such anchoring systems may be triggered at a location determined suitable for anchoring by the control unit <NUM>. This may be a configurable option that can be selected by a user of the system when triggering the situation avoidance maneuver. According to such options, the control unit <NUM> is arranged to determine a suitable location for anchoring A in a vicinity of the path T, and to deploy an anchor <NUM> at the suitable location for anchoring A. The suitable location for anchoring may be determined based on a set of pre-configured anchoring capabilities of the vessel <NUM>. For instance, a requirement may be placed on maximum depth and possibly also seabed properties. A suitable location for anchoring is associated with a minimum required free space. It is appreciated that this minimum required free space may be configured in dependence of the type of vessel, and optionally also in dependence of the anchoring depth at the location A. According to an example, a suitable location for anchoring may be determined by searching for a location on a sea chart with a depth smaller than the maximum depth for anchoring, and having an area above the minimum required area configured for the vessel when anchoring at the depth of the location.

The anchoring system <NUM> can instead be a virtual anchoring function, where the control unit is arranged to keep the suitable position by controlling the driveline. Thus, a virtual anchoring system is independent of the sea depth or seabed properties.

<FIG> is a flow chart which summarizes the methods discussed above. There is shown a method for controlling a marine vessel <NUM> to avoid an emergency situation. The method comprises receiving S1 path data <NUM> from one or more sensor devices <NUM>, <NUM>, <NUM>, <NUM>, <NUM> indicative of a path T travelled by the marine vessel <NUM> in a forward direction F, storing S2 the received path data, receiving S3 a trigger signal <NUM>, <NUM>' from an input device <NUM>, <NUM>', and, in response to the trigger signal <NUM>, <NUM>', determining S4 a location L for turning the vessel <NUM> around, navigating to the location S5, turning S6 the vessel around at the location L, and navigating S7 the vessel <NUM> along the path T in reverse direction R.

<FIG> schematically illustrates, in terms of a number of functional units, the components of a control unit <NUM> according to embodiments of the discussions herein. This control unit <NUM> is configured to execute at least some of the functions discussed above for control of a marine vessel <NUM>. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

The control unit <NUM> may further comprise an interface <NUM> for communications with at least one external device as discussed in connection to <FIG> above.

Claim 1:
A control unit (<NUM>) for controlling a marine vessel (<NUM>) to avoid an undesired situation, the control unit (<NUM>) comprising processing circuitry (<NUM>) and a storage medium (<NUM>), wherein the control unit (<NUM>) is arranged to receive path data (<NUM>) from one or more sensor devices (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) indicative of a path (T) travelled by the marine vessel (<NUM>) in a forward direction (F) and to store the received path data by the storage medium (<NUM>), characterized in that the control unit (<NUM>) is arranged to receive a trigger signal (<NUM>, <NUM>') from an input device (<NUM>, <NUM>'), and, in response to the trigger signal (<NUM>, <NUM>'), determine a set of candidate locations associated with a pre-determined required space for turning, determine a location (L) for turning the vessel (<NUM>) around by selecting the candidate closest to the current location or the candidate reached by a minimum of control maneuvers, navigate to the location (L), turn the vessel around at the location (L), and navigate the vessel (<NUM>) along the path (T) in reverse direction (R).