METHOD OF CONTROLLING VESSEL, CONTROL SYSTEM AND VESSEL

Abstract

A method of controlling a vessel having a plurality of thrusters, where the vessel is configured to operate in a bias mode where at least two of the thrusters provide thrust forces at least partly in opposite thrust directions, the method including estimating, by a control system, an operational condition associated with the vessel; and commanding, by the control system and based on the estimation, execution of a countermeasure associated with an activation of the bias mode, a deactivation of the bias mode or a change of a bias level of the bias mode. A control system and a vessel are also provided.

Claims

1. A method of controlling a vessel comprising a plurality of thrusters, where the vessel is configured to operate in a bias mode where at least two of the thrusters provide thrust forces at least partly in opposite thrust directions, the method comprising: estimating, by a control system, an operational condition associated with the vessel; and commanding, by the control system and based on the estimation, execution of a countermeasure associated with an activation of the bias mode, a deactivation of the bias mode, or a change of a bias level of the bias mode.

2. The method according to claim 1, wherein the estimation of the operational condition includes estimating at least one parameter of one or more external disturbances acting on the vessel.

3. The method according to claim 2, wherein the at least one parameter comprises a direction, a variation of the direction, a magnitude and/or a variation of the magnitude.

4. The method according to claim 2, wherein each external disturbance comprises an external force.

5. The method according to claim 1, further comprising providing, by the control system, a mode of the vessel, wherein the estimation of the operational condition is made using the model.

6. The method according to claim 1, further comprising receiving, by the control system, sensor data from one or more sensors, wherein the estimation of the operational condition is made using the sensor data.

7. The method according to claim 6, further comprising storing the sensor data as historic sensor data, and wherein the estimation of the operational condition is made using the historic sensor data.

8. The method according to claim 1, further comprising determining the bias level based on the operational condition, wherein the countermeasure includes activating a control of the vessel in the bias mode at the determined bias level.

9. The method according to claim 1, wherein the countermeasure comprises a notification to a human user of the vessel.

10. A control system for controlling a vessel having a plurality of thrusters, where the vessel is configured to operate in a bias mode where at least two of the thrusters provide thrust forces at least partly in opposite thrust directions, the control system comprising at least one data processing device and at least one memory having at least one computer program stored thereon, the at least one computer program including program code which, when executed by the at least one data processing device, causes the at least one data processing device to: estimate an operational condition associated with the vessel; and command based on the estimation, execution of a countermeasure associated with an activation of the bias mode, a deactivation of the bias mode or a change of a bias level of the bias mode.

11. A vessel comprising a control system for controlling a vessel including a plurality of thrusters, where the vessel is configured to operate in a bias mode where at least two of the thrusters provide thrust forces at least partly in opposite thrust directions, the control system including at least one data processing device and at least one memory having at least one computer program stored thereon the at least one computer program including program code which, when executed by the at least one data processing device, causes the at least one data processing device to: estimate an operational condition associated with the vessel; command based on the estimation execution of a countermeasure associated with an activation of the bias mode, a deactivation of the bias mode or a change of a bias level of the bias mode, and the plurality of thrusters, wherein the vessel is configured to operate in the bias mode where at least two of the thrusters provide thrust forces at least partly in opposite thrust directions.

12. The vessel according to claim 11, further comprising one or more sensors arranged to provide sensor data to the control system, wherein the estimation of the operational condition is made using the sensor data.

13. The vessel according to claim 12, wherein the at least one computer program comprises program code which, when executed by the at least one data processing device, causes the at least one data processing device to store the sensor data as historic sensor data, and wherein the estimation of the operational condition is made using the historic sensor data.

14. The method according to claim 2, wherein each external disturbance comprises an external force.

15. The method according to claim 2, further comprising providing, by the control system, a model of the vessel, wherein the estimation of the operational condition is made using the model.

16. The method according to claim 2, further comprising receiving, by the control system, sensor data from one or more sensors, wherein the estimation of the operational condition is made using the sensor data.

17. The method according to claim 2, further comprising determining the bias level based on the operational condition, wherein the countermeasure includes activating a control of the vessel in the bias mode at the determined bias level.

18. The method according to claim 2, wherein the countermeasure comprises a notification to a human user of the vessel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein:

[0048] FIG. 1: schematically represents a top view of a vessel;

[0049] FIG. 2: schematically represents a top view of the vessel when operating in a normal mode;

[0050] FIG. 3: schematically represents a top view of the vessel when operating in a directional bias mode; and

[0051] FIG. 4: schematically represents a top view of the vessel when operating in a non-directional bias mode.

DETAILED DESCRIPTION

[0052] In the following, a method of controlling a vessel comprising a plurality of thrusters, a control system for controlling a vessel, and a vessel comprising a control system, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0053] FIG. 1 schematically represents a top view of a marine vessel 10. The vessel 10 may for example be a ship or a floating production storage and offloading (FPSO) unit. The vessel 10 comprises a plurality of thrusters, here a first thruster 12a, a second thruster 12b, a third thruster 12c and a fourth thruster 12d. One, several or all of the thrusters 12a-12d may also be referred to with reference numeral 12.

[0054] Each thruster 12 is rotatable in a horizontal plane (parallel with the drawing plane of FIG. 1) into different thrust directions. Each thruster 12 may comprise a propeller and an engine driving the propeller. By increasing an engine speed of the engine and hence a rotational speed of the propeller, the thrust force of the thruster 12 can be increased, and vice versa. The thrusters 12 are here exemplified as azimuthing thrusters. Each engine may for example be an internal combustion engine, such as a diesel engine, or an electric motor. In the latter case, the electric motor may be electrically powered by a power plant comprising one or more internal combustion engines.

[0055] The vessel 10 further comprises a control system 14. The control system 14 of this example comprises a data processing device 16 and a memory 18. The memory 18 has a computer program stored thereon. The computer program comprises program code which, when executed by the data processing device 16, causes the data processing device 16 to perform, or command performance of, various steps described herein.

[0056] As shown in FIG. 1, a model 20 of the vessel 10 is stored in the memory 18. The model 20 may for example be a nonlinear model of the vessel 10 describing the motion of the vessel 10 in the horizontal plane. The vessel 10 may comprise a rudder (not shown). The rudder may be included in the model 20.

[0057] The vessel 10 of this example further comprises one or more sensors, here exemplified as a position sensor 22. The position sensor 22 is arranged to provide position data 24 to the control system 14. The position data 24 is indicative of a position of the vessel 10 in the horizontal plane. The position sensor 22 may for example be a GPS device. The position data 24 is one example of sensor data according to the present disclosure. In this example, the control system 14 is configured to estimate an operational condition of the vessel 10 based on the position data 24. As mentioned above, the vessel 10 may use a wide range of sensors alternative to, or in addition to, the position sensor 22 to provide sensor data based on which the control system 14 can estimate the operational condition of the vessel 10.

[0058] The vessel 10 of this example further comprises an output device, here exemplified as a display 26, and an input device 28. The display 26 is configured to provide a visual notification 30 to a human user 32. The input device 28 can be manually operated by the human user 32.

[0059] FIG. 2 schematically represents a top view of the vessel 10. As shown, the vessel 10 is acted on by a substantially constant primary external force 34a, constituting one example of an operational condition according to the present disclosure. The primary external force 34a may for example be a force from wind or waves. The primary external force 34a is one example of an external disturbance according to the present disclosure.

[0060] The first thruster 12a provides a first thrust force 36a, the second thruster 12b provides a second thrust force 36b, the third thruster 12c provided a third thrust force 36c, and the fourth thruster 12d provided a fourth thrust force 36d. One, several or all of the thrust forces 36a-36d may also be referred to with reference numeral 36.

[0061] FIG. 2 further shows a primary reference direction 38a and a secondary reference direction 38b, here orthogonal to the primary reference direction 38a. In this example, the primary external force 34a has a primary direction in the primary reference direction 38a.

[0062] In FIG. 2, the vessel 10 operates in a normal mode 40 to keep the vessel 10 at a stationary position without rotation in the horizontal plane. In the normal mode 40, all thrusters 12 point in the same, or substantially in the same, thrust direction for minimum energy consumption, here parallel with the primary reference direction 38a. In FIG. 2, all thrusters 12 have the same thrust direction with respect to the vessel 10.

[0063] Based on the position data 24, the control system 14 calculates the thrust forces 36 and the thrust directions needed to keep the vessel 10 at the stationary position. In case a magnitude of the primary external force 34a is increased, the thrust forces 36 of the thrusters 12 may be increased, and vice versa, to avoid the vessel 10 leaving the stationary position. Small variations of the primary direction can be compensated by varying the thrust directions of the thrusters 12.

[0064] FIG. 3 schematically represents a top view of the vessel 10 when operating in a directional bias mode 42a. The directional bias mode 42a is one example of a bias mode according to the present disclosure. In FIG. 3, a magnitude of the primary external force 34a varies. This circumstance constitutes a further example of an operational condition according to the present disclosure.

[0065] In the directional bias mode 42a, the thrusters 12 provide thrust forces 36 in opposite thrust directions, here in the primary reference direction 38a. Thus, the thrust forces 36 partly cancel out each other. This enables smoother loads on the engines. In this specific and non-limiting example, a second thrust direction of the second thruster 12b is opposite to a first thrust direction of the first thruster 12a, and a fourth thrust direction of the fourth thruster 12d is opposite to a third thrust direction of the third thruster 12c. However, since the first thrust force 36a and the third thrust force 36c are larger than the second thrust force 36b and the fourth thrust force 36d, respectively, the thrust forces 36 can compensate against the primary external force 34a to keep the vessel 10 stationary.

[0066] Since the thrusters 12 provide thrust forces 36 in opposite thrust directions, the energy consumption is higher in the directional bias mode 42a than in the normal mode 40. However, since a thrust force 36 can more quickly be decreased than increased and since the thrust force 36 is proportional to a propeller speed of the thruster 12 squared, the response of the vessel 10 is increased and the vessel 10 can react faster to variations in the magnitude of the primary external force 34a. The bias level of the directional bias mode 42a can for example be increased by increasing all thrust forces 36 and vice versa.

[0067] FIG. 4 schematically represents a top view of the vessel 10 when operating in a non-directional bias mode 42b. The non-directional bias mode 42b is a further example of a bias mode according to the present disclosure. One or both of the bias modes 42a, 42b may also be referred to with reference numeral 42.

[0068] As shown, the vessel 10 is acted on not only by the primary external force 34a but also by a secondary external force 34b. The secondary external force 34b has a secondary direction in the secondary reference direction 38b. In FIG. 4, magnitudes of both the primary external force 34a and the secondary external force 34b vary. This circumstance constitutes a further example of an operational condition according to the present disclosure. The primary external force 34a may for example be a force from wind and the secondary external force 34b may for example be a force from waves. One or both external forces 34a, 34b may also be referred to with reference numeral 34.

[0069] In the non-directional bias mode 42b, the thrusters 12 provide thrust forces 36 partly in opposite thrust directions. Thus, the thrust forces 36 partly cancel out each other. In this specific and non-limiting example, each thruster 12 is positioned in a unique thrust direction and each thrust direction provides a thrust force 36 partly in the primary direction of the primary external force 34a and partly in the secondary direction of the secondary external force 34b. The thrust direction of the second thruster 12b is here angled between 90 degrees and 270 degrees to the thrust direction of the first thruster 12a. Correspondingly, the thrust direction of the fourth thruster 12d is here angled between 90 degrees and 270 degrees to the thrust direction of the third thruster 12c.

[0070] The thrusters 12 thus work against each other both in the primary direction and in the secondary direction. In this way, the thrusters 12 can compensate against both the primary external force 34a and the secondary external force 34b to keep the vessel 10 stationary. Variations of directions and magnitudes of any of the external forces 34 are mainly compensated by varying thrust forces 36, while thrust directions may be only slightly varied.

[0071] The non-directional bias mode 42b increases the responsiveness of the vessel 10 in both the primary reference direction 38a and in the secondary reference direction 38b. The bias level of the non-directional bias mode 42b can for example be increased by increasing all thrust forces 36 and vice versa.

[0072] A method of controlling the vessel 10 is implemented in the control system 14. The method comprises estimating, by the control system 14, the operational condition of the vessel 10. The method further comprises commanding, by the control system 14, execution of a countermeasure associated with an activation of the bias mode 42, a deactivation of the bias mode 42, or a change of a bias level of the bias mode 42.

[0073] In this example, the operational condition may be estimated based on the position data 24. To this end, historic, current and/or future position data 24 may be used. Moreover, algorithms may be applied to the position data 24 and any other sensor data. For example, future position data 24 may be estimated based on trends in historic position data 24 using an algorithm. If for example the vessel 10 oscillates in the primary reference direction 38a, as determined based on the position data 24, the control system 14 can, e.g., using the model 20, conclude that there is an external force 34 acting on the vessel 10 in the primary reference direction 38a with a certain magnitude and with a certain variation of the magnitude.

[0074] The control system 14 here uses the model 20 to determine the operational condition. The operational condition may be evaluated continuously or repeatedly. For example, based on deviations of a current position, e.g., as determined based on the position data 24, the control system 14 can determine a direction and a magnitude of one or more external forces 34 acting on the vessel 10.

[0075] The control system 14 may then evaluate the operational condition in view of one or more bias modes 42. For example, if the operational condition includes an external force 34 acting on the vessel 10 having a relatively low variation of direction and a relatively low variation of magnitude, as in FIG. 2, it may be considered that the operational condition does not meet any bias mode criterion and the normal mode 40 (i.e., deactivated bias mode 42) may be evaluated as most appropriate. For example, if the operational condition includes an external force 34 acting on the vessel 10 having a relatively low variation of direction but a relatively high variation of magnitude, as in FIG. 3, it may be considered that the operational condition meets a directional bias mode criterion associated with the directional bias mode 42a and the directional bias mode 42a may be evaluated as most appropriate. Thus, by knowing the direction of the external force 34, the magnitude of the external force 34, and variations thereof, a minimum of bias can be applied and can be adjusted as the external force 34 varies over time.

[0076] According to a further example, if the operational condition includes two external forces 34 acting on the vessel 10 in different directions and at least one of the external forces 34 has a variation of magnitude, as in FIG. 4, it may be considered that the operational condition meets a non-directional bias mode criterion associated with the non-directional bias mode 42b and the non-directional bias mode 42b may be evaluated as most appropriate. In order to make the evaluations, the control system 14 may for example use a look-up table, e.g., stored in the memory 18, that maps parameter intervals for the parameters magnitudes, variations of the magnitudes, directions, and variations of the directions, of the external forces 34, to either the normal mode 40, the directional bias mode 42a or the non-directional bias mode 42b. For the directional bias mode 42a and the non-directional bias mode 42b, the parameters may also be mapped to a certain bias level. The control system 14 thus automatically determines if the current operational condition requires activation of any of the directional bias mode 42a and the non-directional bias mode 42b or an increase of the bias level to improve performance, or if the current operational condition allows deactivation of any of the directional bias mode 42a and the non-directional bias mode 42b or a decrease of the bias level to reduce energy consumption.

[0077] The countermeasure may for example be an automatic activation or a deactivation of the directional bias mode 42a by the control system 14, or an automatic activation or a deactivation of the non-directional bias mode 42b by the control system 14. According to one further example, the countermeasure may be constituted by the notification 30 provided by the control system 14 to the human user 32 advising to manually activate or deactivate any of the directional bias mode 42a and the non-directional bias mode 42b, or to change a bias level, using the input device 28. In any case, the method enables an optimal use of the bias mode 42, leading to improved performance, reduced energy consumption and reduced wear and tear in comparison with when the human user 32 activates or deactivates the bias mode 42 based on a behavior of the vessel 10 as perceived by the human user 32. The method enables the bias mode 42 to be activated and deactivated at the right time and with a suitable bias level. The method for example reduces a risk of at the right time and reduces a risk of overlooking deactivation of the bias mode 42.

[0078] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.