Arrangement, method and computer storage medium for manoeuvring watercraft

Abstract

An arrangement, a method and a computer storage medium for manoeuvring a watercraft (W). The arrangement (100) comprises a primary steering device (1) and a secondary steering device (2) arranged to assist the primary steering device (1) in the directional control of the watercraft. A controller unit (5) is configured to receive a desired turning rate or a steering signal and a measured yaw rate of the watercraft (W). The controller unit (5) is further configured to carry out a comparison of the desired turning rate with the measured yaw rate, and determine a manoeuvring error based on said comparison. The controller unit (5) controls the secondary steering device (2) for reducing said manoeuvring error.

Description

[0001] ARRANGEMENT , METHOD AND COMPUTER STORAGE MEDIUM FOR MANOEUVRING WATERCRAFT

[0002] BACKGROUND

[0003] The invention relates to an arrangement for manoeuvring a watercraft .

[0004] The invention further relates to a method for manoeuvring a watercraft .

[0005] The invention still further relates to a computer storage medium for manoeuvring a watercraft .

[0006] Manoeuvring of a watercraft , such as motorboats and sai l boats , may be greatly complicated by effects of wind and flows of water . This is especially obvious at low speeds of the watercraft . For solution to thi s problem, it is commonly known to equip the watercrafts with manoeuvering thrusters , i . e . bow thrusters and stern thrusters , that are transversal propulsion devices to make the watercraft more manoeuvrable . However, operating the manoeuvering thrusters is complicated and requires lot of attention, causing thus inconvenience and uncertainty to user thereof .

[0007] BRIEF DESCRIPTION

[0008] Viewed from a first aspect , there can be provided an arrangement for manoeuvring a watercraft , the arrangement comprising a controller unit for manoeuvring a watercraft , configured to receive a desired turning rate , receive a measured yaw rate of the watercraft , carry out a comparison of the desired turning rate with the measured yaw rate , determine a manoeuvring error based on said comparison, and control solely a secondary steering device arranged to assist a primary steering device that is arranged to take a primary care of a directional control of the watercraft in the directional control of the watercraft for reducing said manoeuvring error . Thereby an arrangement for manoeuvring a watercraft which is easy to use and simplifies the manoeuvring may be achieved .

[0009] Viewed from a further aspect , there can be provided a method for manoeuvring a watercraft , the method comprising

[0010] - receiving a desired turning rate of the watercraft ,

[0011] - receiving a measured yaw rate of the watercraft ,

[0012] - carrying out a comparison of the desired turning rate with the measured yaw rate ,

[0013] - determining a manoeuvring error based on said compari son, and

[0014] - controlling solely a secondary steering device arranged to assist a primary steering device in the directional control of the watercraft for reducing said manoeuvring error .

[0015] Thereby a method for manoeuvring a watercraft which is easy to carry out and simplifies the manoeuvring may be achieved .

[0016] Viewed from a still further aspect , there can be provided a computer storage medium for manoeuvring a watercraft comprising code for execution by a proces sor, the code , when executed by a processor, causing the processor to perform the method mentioned above .

[0017] Thereby a computer storage medium for manoeuvring a watercraft which helps and simpli fies the manoeuvring may be achieved .

[0018] The arrangement , the method and the computer storage medium for manoeuvring a watercraft are characterised by what is stated in the independent claims . Some other embodiments are characterised by what is stated in the other claims . Inventive embodiments are also disclosed in the specification and drawings of this patent application . The inventive content of the patent application may also be defined in other ways than defined in the following claims . The inventive content may also be formed of several separate inventions , especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups . Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas . Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments .

[0019] Various embodiments of the aspects mentioned above may comprise at least one feature from the following paragraphs :

[0020] In one embodiment , the controller unit is configured to receive a steering signal indicating an actual or desired steering angle of the primary steering device , wherein the controller unit is further configured to determine the desired turning rate on basis of parameters including the steering signal .

[0021] An advantage is that a simple arrangement and method for manoeuvring a watercraft may be achieved .

[0022] In one embodiment , the controller unit is configured to determine the desired turning rate based on parameters that include speed of the watercraft .

[0023] An advantage is that a natural and neutral turning behavior of the watercraft may be provided .

[0024] In one embodiment , the controller unit is configured to determine the desired turning rate on the basis of parameters that further include a distance between a turning centre of the watercraft and the primary steering device . An advantage is that the distance provides a simple and intuitive way for tuning the watercraft turning characteristics towards more agile or more stable behaviour .

[0025] In one embodiment , the distance between the turning centre of the watercraft and the primary steering device is dependent on the speed of the watercraft .

[0026] An advantage is that the manoeuvring characteristics of the watercraft may be tuned to have different turning behaviour at different speeds .

[0027] In one embodiment , the steering sensor is arranged to measure the angle of the primary steering device , such as to a rudder or a steerable propul sion device , and wherein the steering angle is an angle of the primary steering device .

[0028] An advantage is that said angle can be used directly to define desired turn rate and a sensor providing the angle is readily available with many watercrafts that feature an autopilot .

[0029] In one embodiment , the steering sensor is arranged to measure the angle of a user interface device provided for control ling manoeuvring of the watercraft , such as a steering wheel or a j oystick, and wherein the steering angle is related to an angle of the user interface device .

[0030] An advantage is that in many watercrafts the user interface device is located inside the watercraft and well protected from various elements of weather .

[0031] In one embodiment , the steering signal or the desired turning rate is provided by a remote control device . An advantage is that the helmsman or operator of the watercraft may take a position that is the best suitable one in the current manoeuvring task .

[0032] In one embodiment , the steering signal or the desired turning rate is provided by an autopi lot , a Guidance , Navigation and Control system or a track keeping system .

[0033] An advantage is that manoeuvring may be automati zed .

[0034] In one embodiment , the secondary steering device comprises a bow unit , such as a bow thruster .

[0035] An advantage is that the bow thruster is probably most widely used manoeuvring aid on watercrafts and can be readily available .

[0036] In one embodiment , the secondary steering device comprises a stern unit , such as a stern thruster .

[0037] An advantage is that there may be more room for fitting the stern unit than a bow unit in some watercrafts .

[0038] In one embodiment , the secondary steering device comprises a bow unit and a stern unit .

[0039] An advantage is that manoeuvring capabil ities of the watercraft may be further improved and diversified .

[0040] In one embodiment , the arrangement comprises a compass device or a heading sensor, and the controller unit is configured to receive a signal indicative of a desired heading of the watercraft and a signal indicative of an actual heading provided by the compass device or a heading sensor, wherein the controller unit is configured to control the secondary steering device such that difference between the desired heading and the actual heading is reduced, and optionally that the yaw rate of the watercraft is controlled toward zero .

[0041] An advantage is that the watercraft heading can be maintained at low speeds where traditional autopilot is not effective .

[0042] In one embodiment , the arrangement compri ses a wind gauge , and wherein the controller unit is configured to control the secondary steering device such that wind gauge is showing headwind, and optionally that the yaw rate of the watercraft is controlled toward zero .

[0043] An advantage is that the bow of the watercraft can be held into the wind at low or zero speeds or even when watercraft is drifting backwards which traditional autopilot is not capable of doing while hoisting or lowering sails or anchoring .

[0044] In one embodiment , the controller unit is further configured to use a direct compensation control system, such as a feedforward control system, for providing additional control to the secondary steering device to directly limit or cancel effects of disturbances .

[0045] An advantage is that the response of the control system to said disturbances caused e . g . by wind can be faster as watercraft response and measurement delays are not included in this type of control signal .

[0046] In one embodiment , the secondary steering device is configured to assist the primary steering device in the directional control of the watercraft only in a predetermined speed range of the watercraft . An advantage is that the secondary steering device is used only in the efficient operating area and controlled to preserve energy outside this area .

[0047] In one embodiment , the assistance that the secondary steering device i s configured to provide is proportional to the speed of the watercraft , and optionally configured to be zero outside of the predetermined speed range of the watercraft .

[0048] An advantage is that the provided turning assistance can be adapted to the watercraft speed range to compensate for primary steering speed dependent inefficiencies .

[0049] In one embodiment , the secondary steering device comprises the bow unit and the stern unit, and the controller unit is configured to control the secondary steering device such that the watercraft is arranged to move laterally, i . e . sideways in relation to the longitudinal axis L, or laterally and longitudinally, i . e . sideways in relation to the longitudinal axis L and in direction of the longitudinal axis L , while maintaining the heading .

[0050] An advantage is that manoeuvring abilities of the watercraft e . g . in harbours may be further improved for circumstances when lateral movement is desired without turning .

[0051] In one embodiment , the method comprises using a direct compensation control system, such as a feedforward control system, for adj usting control ling the secondary steering device .

[0052] An advantage is that the response of the control system to said disturbances caused e . g . by wind can be faster as watercraft response and measurement delays are not included in this type of control signal . In one embodiment , the method comprises providing a signal indicative of a desired compass heading of the watercraft and a signal indicative of an actual heading, and control ling the secondary steering device such that difference between the desired compass heading and the actual compas s heading is reduced, and optionally that the yaw rate of the watercraft is controlled toward zero .

[0053] An advantage is that the watercraft heading can be maintained at low speeds where traditional autopilot is not effective .

[0054] In one embodiment , the method comprises providing a signal indicative of wind direction and control ling the secondary steering device such that the watercraft is kept into the wind, and optionally that the yaw rate of the watercraft is controlled toward zero .

[0055] An advantage is that the bow of the watercraft can be held into the wind at low or zero speeds or even while drifting rearwards which traditional autopilot is not capable of doing while hoisting or lowering sails or anchoring .

[0056] In one embodiment , the method comprises assisting the pri mary steering device in the directional control of the watercraft by the secondary steering device only if the speed of the watercraft is in a predetermined speed range .

[0057] An advantage is that the provided turning assistance can be adapted to the speed range where primary steering is not effective .

[0058] In one embodiment , the method comprises adj usting the assistance provided by the secondary steering device proportionally to the speed of the watercraft in a predetermined speed range and adj usting said assistance to zero outside of said predetermined speed range .

[0059] An advantage is that the secondary steering device is used only in the efficient operating area and controlled to preserve energy outside this area .

[0060] Based on the above mentioned, it should be noted that different embodiments mentioned in the above paragraphs may combined in any possible suitable manner for implementing the present invention .

[0061] BRIEF DESCRIPTION OF FIGURES

[0062] Some embodiments illustrating the present disclosure are described in more detail in the attached drawings , in which

[0063] Figure 1 is a schematic top view of an arrangement and method for manoeuvring a watercraft ,

[0064] Figure 2 illustrates a flow diagram of a control loop of an arrangement and method for manoeuvring a watercraft ,

[0065] Figure 3 illustrates a flow diagram of another control loop of an arrangement and method for manoeuvring a watercraft ,

[0066] Figure 4 illustrates a flow diagram of a third control loop of an arrangement and method for manoeuvring a watercraft ,

[0067] Figure 5 illustrates a flow diagram of a fourth control loop of an arrangement and method for manoeuvring a watercraft ,

[0068] Figure 6 illustrates a flow diagram of a fifth control loop of an arrangement and method for manoeuvring a watercraft , and

[0069] Figure 7 illustrates a flow diagram of a sixth control loop of an arrangement and method for manoeuvring a watercraft . In the figures , some embodiments are shown simplified for the sake of clarity . Similar parts are marked with the same reference numbers in the figures .

[0070] DETAILED DESCRIPTION

[0071] Figure 1 is a schematic top view of an arrangement and method for manoeuvring a watercraft and Figure 2 illustrates a flow diagram of a control loop of an arrangement and method for manoeuvring a watercraft .

[0072] The watercraft W is shown in very simplified way in Figure 1 . It may be any vehicle or vessel known as such designed for travel across or through water bodies , such as a boat , a ship, a hovercraft , etc .

[0073] In one embodiment , the watercraft W is a motorboat . In one embodiment , the watercraft W is a sailing boat .

[0074] The watercraft W has a longitudinal axis L and a turning centre T around which the watercraft W rotates . Typically, in watercrafts the turning centre lies in between the centre of lateral resistance and the centre of gravity . In sailing boats the turning centre T typically lies in the ballast .

[0075] The arrangement 100 comprises a controller unit 5 for manoeuvring the watercraft W . The controller unit 5 is configured to receive a desired turning rate ( signal ) and a measured yaw rate of the watercraft W . The controller unit 5 carries out a comparison of the desired turning rate with the measured yaw rate and determines a manoeuvring error based on said comparison . The controller unit 5 controls a secondary steering device 2 that is arranged to assist a primary steering device 1 in the directional control of the watercraft for reducing said manoeuvring error . It is to be noted that the controller unit 5 controls only the secondary steering device 2 . The primary steering device 1 is controlled by another means .

[0076] In one embodiment , the controller unit 5 receives a steering signal indicating an actual or des ired steering angle of a primary steering device 1 that is arranged to take a primary care of a directional control of the watercraft . The control ler unit 5 further receives a measured yaw rate of the watercraft W . The controller unit 5 determines a desired turning rate on basis of parameters including the steering signal , and carries out a comparison of the desired turning rate with the measured yaw rate . The controller unit 5 determines manoeuvring error based on said comparison, and controls a secondary steering device 2 to assist the primary steering device 1 in the directional control of the watercraft for reducing said manoeuvring error .

[0077] The primary steering device 1 i s configured to take a primary care of a directional control of the watercraft . Said directional control comprises control ling the turning or turn rate of the watercraft W .

[0078] In one embodiment , the primary steering device 1 comprises one or more rudder 7 . In one embodiment , the primary steering device 1 comprises one or more steerable propul sion device 8 shown by dashed lines in Figure 1 as an alternative to the rudder . The steerable propul sion device 8 may comprise e . g . a steerable propeller or a water j et device . In one embodiment , the primary steering device 1 is an outboard motor . In one embodiment , the primary steering device 1 is an inboard motor with a stern drive .

[0079] In one embodiment , the primary steering device 1 also provides the propulsion that gives the thrust moving the watercraft W longitudinally . In another embodiment , the watercraft W comprises a separate propulsion arrangement (not shown) giving the thrust moving the watercraft W longitudinally . In still another embodiment , the watercraft is moved by wind through e . g . at least one sail . A secondary steering device 2 is arranged to assist the primary steering device 1 in the directional control of the watercraft W and to make it more manoeuvrable . In one embodiment , the secondary steering device 2 comprises at least one manoeuvring thruster, such as a bow thruster 11 or a stern thruster . In one embodiment , the secondary steering device 2 comprises a retractable and / or azimuthing / turning thruster 14 , shown by dashed lines and arranged between the turning centre T and the bow of the watercraft W in Figure 1 . Said thruster 14 may also be arranged to a rear side of the turning centre T .

[0080] In one embodiment , the steering sensor 3 is configured to produce a steering signal indicating an actual or desired steering angle of the primary steering device 1 in relation to , e . g . , the longitudinal axis L of the watercraft or in relation to some another refence . For instance , if the primary steering device 1 comprises the rudder 7 , the steering signal may indicate or relate to the angle of a rudder axle ( or another component of a rudder mechanism) in relation to the longitudinal axis L of the watercraft . It is to be noted that "signals" mentioned in this disclosure are typically electrical signals .

[0081] In one embodiment , the steering sensor 3 is physically cou- pled to the primary steering device 1 and the steering angle is an angle of the primary steering device 1 . For example , the steering sensor 3 may be arranged to observe or monitor of turning movements of an axle of the rudder . In one embodiment , the steering sensor 3 is physically cou- pled to a user interface device 6 that is used for controlling manoeuvring of the watercraft W and the steering angle is related to an angle of said user interface device. In one embodiment, the user interface device 6 is a steering wheel 9 and the steering sensor 3 is measuring a rotation angle of said steering wheel. In one embodiment, the user interface device 6 is a joystick 10 and the steering sensor 3 is measuring an inclination angle or a rotation angle of said joystick, or both the inclination angle and the rotation angle thereof.

[0082] In one embodiment, a steering signal 38, i.e., a signal indicating an actual or desired steering angle of the primary steering device, or a desired turning rate 17 is provided by a remote control device 47. The remote control device 47 can be moved in the watercraft or even outside thereof into a position where the helmsman has an optimal view regarding the current manoeuvring task.

[0083] In one embodiment, the steering signal is provided by an autopilot 48 or a guidance, navigation and control / track keeping system 49. This provides an alternative, i.e., an automatized, way to a manual operation or steering of the watercraft via e.g. the steering wheel or the joystick.

[0084] In one embodiment, the steering sensor 3 has a mechanical contact or engagement with the primary steering device 1 or a component thereof. In one embodiment, the steering sensor 3 has a non-contacting coupling to the primary steering device 1 or a component thereof.

[0085] The steering sensor 3 may be, e.g., a potentiometer, a magnetic sensor or an optical sensor.

[0086] In embodiments where the primary steering device 1 comprises plurality of devices, such as rudders, steerable propulsion devices, etc., the steering angles of said devices may differ in some extent , due to , e . g . , differences in their positions in the watercraft or the state of the watercraft . In these embodiments , the steering sensor 3 may be coupled to the user interface device 6 and the steering signal indicates or relates to the steering angle thereof , or alternatively the steering sensor 3 may be coupled to the plurality of devices and the steering signal indicates or relates to a real angle of at least one of the plurality of devices , or to a calculated or theoretical angle that is defined based on real angles of the plurality of devices .

[0087] In one embodiment , the primary steering device comprises at least two propulsion devices arranged side by side , for instance at the stern, and able to turn the watercraft by controlling one of said propulsion devices to give thrust that differs from thrust of another of said propulsion devices . Said thrusts may even be oppositely directed . This kind of propulsion devices may be stationary arranged in the watercraft , i . e . they do not turn in relation to the watercraft . In this embodiment , the steering sensor 3 may be coupled to the user interface device 6 and the steering signal indicates or relates to the steering angle of the user interface device i . e . desired steering angle .

[0088] A yaw rate sensor 4 that is configured to measure a yaw rate of the watercraft W, i . e . the turn rate of the watercraft W and produce thereby a yaw rate measurement 24 .

[0089] In one embodiment, the yaw rate sensor 4 comprises a micromechanical gyro sensor . In one embodiment , the yaw rate sensor 4 is an inertial measurement unit ( IMU) .

[0090] In one embodiment , speed 39 of the watercraft in direction of the longitudinal axis L is measured by a speed sensor 15 and fed in the controller unit 5 . The controller unit 5 may be or included in e . g . a computer, a computation unit , a programmable logic controller ( PLC) or any device comprising at least one processor and a memory configured to store the program code needed for running the arrangement and the method . In one embodiment , said computer is configured to control multiple systems of the watercraft , not only the arrangement 100 and the method .

[0091] In one embodiment , the controller unit 5 is configured to determine the desired turning rate based on parameters that include speed of the watercraft W .

[0092] In one embodiment , the controller unit 5 is configured to determine the desired turning rate based on parameters that include a distance D between a turning centre T of the watercraft W and the primary steering device 1 .

[0093] In one embodiment the controller unit 5 is configured to determine a desired turning rate on basis of parameters including the steering signal , speed of the watercraft W and the distance D between a turning centre T of the watercraft and the primary steering device 1 . In one embodiment, the desired turning rate is calculated according to an equation : yref= (o<rd • Vb / D) X C wherein, yref = desired turning rate o<rd = steering signal vb= speed of the watercraft

[0094] D = distance between the turning centre T and the primary steering device

[0095] C = adj ustment coefficient , typically C = 1 . In sailing boats , said distance D may be a distance between hydrodynamical centres of a keel and the rudder . In motorboats said distance D may be a distance between from a centre of gravity of the watercraft W to a hydrodynamical centre of the rudder or the location of the steerable propulsion device .

[0096] In one embodiment , the distance D is constant . In another embodiment, the distance D is dependent on the speed of the watercraft . In one embodiment , the distance D increases as the speed of the watercraft increases . Thus , the watercraft may be more agi le or quicker to turn at lower speeds , and more stable at higher speeds .

[0097] The operations the controller unit 5 is configured to perform may be implemented entirely as instructions executed by the controller unit 5 or may be implemented in a combination of executable instructions and hardware , such as one or more inductors , capacitors , resistors , digital signal processors , and other analog and / or digital electronic devices . In one embodiment , a program code is stored in a computer storage medium . When said code is executed by the processor, the processor causes the controller unit 5 to perform the method described in this description .

[0098] In one embodiment , such as shown in Figure 2 , the arrangement 100 and the controller unit 5 is configured to perform the operations described herein . A block of ref erence / set point generation 16 receives speed 39 of the watercraft measured by the speed sensor 15 as well as the steering signal 38 from the steering sensor 3 .

[0099] The block of ref erence / set point generation 16 produces a yaw rate reference 17 that is provided to a first sum block 18 . The first sum block 18 also receives the yaw rate measurement 24 provided by the yaw rate sensor 4 . The first sum block 18 combines the yaw rate reference and the yaw rate measurement , carries out a comparison of the desired turning rate with the measured yaw rate, and produces a manoeuvring error ( output ) 19 that is then provided to a first controller 20 .

[0100] The first controller 20 provides a control ( output) 21 that is used for controlling the secondary steering device 2 for minimi zing the manoeuvring error 19 . The secondary steering device 2 then produces a thrust 22 that have an effect to the watercraft W, to state of motion and the yaw rate 23 thereof . The yaw rate 23 is measured by the yaw rate sensor 4 . Thus , the controller unit 5 is configured to use a feedback loop system in control ling the secondary steering device 2 and pursuing to limit the manoeuvring error 19 .

[0101] Thus , it is not controlled the primary steering device 1 but the secondary steering device 2 . In other words , the primary steering device 1 may be kept in its position or state while the secondary steering device 2 is controlled or adj usted .

[0102] Typically, the secondary steering device 2 i s effective in a certain speed range of the watercraft W only . For instance , a bow thruster loses its ability or effect on turning the watercraft as the speed is above a certain threshold speed . In other words , the assistance provided by the bow thruster in the directional control of the watercraft is useless or at least substantially useless above said threshold speed . In one embodiment , the secondary steering device 2 is configured to assist the primary steering device 1 only in a predetermined speed range of the watercraft W . When the speed is outside the predetermined speed range , the assistance is zero , i . e . the secondary steering device is not active . In one embodiment , the assistance ( i . e . power or thrust ) provided by the secondary steering device 2 is proportional to the speed of the watercraft . In one embodiment , the assistance of the secondary steering device 2 reaches its maximum at a lower speed, decreases with increasing speed until reaches zero at a predetermined speed .

[0103] Figure 3 illustrates a flow diagram of another control loop of an arrangement and method for manoeuvring a watercraft . In one embodiment , the controller unit 5 is further configured to use a direct compensation control system, in some cases known as feedforward control system or open-loop control , for further controlling the secondary steering device 2 to quickly limit or cancel effects of disturbances caused e . g . by wind, more precisely by a side wind component of wind .

[0104] The embodiment shown in Figure 3 comprises the same features as the embodiment shown in Figure 2 , and additionally a "feedforward control loop" . In said feedforward control loop a signal proportional but with an effect opposite to the measured side wind component is added to the feedback control signal . The wind gauge 13 is arranged to measure the speed of wind and its direction and send signals 30 , 34 representing these to a feed forward controller 26 . The wind gauge 13 turns with the watercraft W and thus the wind direction measurement 34 depends on the heading 25 . A second sum block 27 combines an output of the feed forward controller 26 with the control ( output ) 21 , and a combined control 28 is provided for the secondary steering device 2 . The direct compensation control system is used for compensating influence of wind in control ling the secondary steering device 2 . The direct compensation control system does not , or at least is not intended to , turn the watercraft as such but j ust enhances the control / response of the secondary steering device 2 . It is to be noted that the direct compensation control system can be adapted in all the embodiments described in this disclosure .

[0105] Figure 4 illustrates a flow diagram of a third control loop of an arrangement and method for manoeuvring a watercraft . In some embodiments of the arrangement 100 and the method, they are provided with at least one special steering mode for specific purposes or situations needed in handling of the watercraft . In one embodiment , the special steering mode is arranged to be turned on and off by the user of the arrangement .

[0106] In one embodiment of the special steering modes , the arrangement 100 comprises a compass device or a heading sensor 12 that is configured to give an actual compass heading or a compass heading measurement 32 , i . e . the heading in which direction the longitudinal axis L of the watercraft is pointing . The compass heading measurement 32 is fed to a third sum block 33 . A heading setpoint 41 is also fed to the third sum block 33 . The heading setpoint 41 represents the desired compass heading in which the watercraft W is desired to point , and it may be input to the controller unit 5 by a helmsman of the watercraft , for instance . In one embodiment , the heading setpoint 41 is the compas s heading of the watercraft W at the very moment the special steering mode is activated .

[0107] The third sum block 33 produces a heading error 37 that is fed to a second controller 31 . The second controller 31 creates a control signal that may then be used for controlling the secondary steering device 2 .

[0108] In one embodiment , such as shown in Figure 4 , the controller unit 5 is arranged to carry out controlling the yaw rate of the watercraft W toward zero , in other words it i s pursued to travel on a straight course and to minimi ze / stabili ze the turning of the watercraft . For this purpose , in one embodiment the first sum block 18 is configured to receive a yaw rate reference 40 the value of which is zero, and the first sum block produces manoeuvring error 19 that is fed to the first controller 20 . In another embodiment (not shown) , the yaw rate measurement 24 is fed directly but negatively inverted to the first controller 20 . The control signal created by the first controller 20 is provided to the second sum block 27 that creates the combined control signal 28 on basis of the control signals created by the first controller 20 and the second controller 31 .

[0109] Figure 5 illustrates a flow diagram of a fourth control loop of an arrangement and method for manoeuvring a watercraft .

[0110] As already disclosed, the arrangement 100 may comprise a wind gauge 13 that is arranged to measure the speed of wind and its direction 34 and send signals representing these to a feed forward controller 26 . In one embodiment of the special steering modes , the arrangement 100 is configured to keep a bow 42 of the watercraft against the wind . For this purpose , the wind gauge 13 is configured to provide the wind direction measurement 34 to the third sum block 33 . Additionally, said third sum block 33 receives a wind direction setpoint 43 that may be input to the controller unit 5 by a helmsman of the watercraft , for instance . Typical ly, the wind gauge 13 i s configured to show zero angle when the bow is pointing into the wind, and thus value of the wind direction setpoint 43 fed to the third sum block 33 is zero . Thus , a second controller 31 arranged for receiving a wind direction error 35 provided by the third sum block 33 is pursuing to turn the bow in the wind . The wind direction error 35 is fed to the second controller 31 . The second controller 31 creates a control signal that may then be used for controlling the secondary steering device 2 .

[0111] It is to be noted that in some cases the wind direction setpoint 43 may have another value than zero , and then the second controller 31 is pursuing for directing the bow some another direction than in the wind .

[0112] The special steering mode configured to keep the bow 42 in the wind can be activated at any time , i . e . regardless of the prevailing wind direction . Thus , there may be a substantial need for turning the watercraft until the bow is in the wind . In one embodiment , the arrangement 100 is provided with a wind direction dependent yaw rate reference generator 29 that is configured to control said turning the bow into the wind . The wind direction dependent yaw rate reference generator 29 receives the wind direction error 35 from the third sum block 33 and provides the yaw rate reference 40 to the first sum block 18 . The first sum block 18 calculates a yaw rate error 19 based on the yaw rate reference 40 and the yaw rate measurement 24 provided by the yaw rate sensor 4 . The yaw rate error 19 i s one embodiment of the manoeuvring error utilized in the first controller 20 that gives the control signal 21 to the second sum block 27 . The second sum block 27 is configured to combine the control signal 21 with a control signal 36 created in the second controller 31 and the combined control 28 controls the secondary steering device 2 .

[0113] Figure 6 illustrates a flow diagram of a fifth control loop of an arrangement and method for manoeuvring a watercraft , and Figure 7 illustrates a f low diagram of a sixth control loop of an arrangement and method for manoeuvring a watercraft . In one embodiment , the secondary steering device 2 comprises a stern unit 2a and a bow unit 2b as shown in Figure 1 . The stern unit 2a is arranged to a rear side of the turning centre T, i . e . to the part of the watercraft extending from the turning centre towards the stern of the watercraft W, whereas the bow unit 2b is arranged between the turning centre T and the bow of the watercraft W . In one embodiment , the secondary the stern unit 2a and the bow unit 2b are of same type , such as a tunnel thruster, a thruster arranged below the bottom of the watercraft , or a retractable and / or azimuthing / turning thruster, but this is not always necessary .

[0114] In one embodiment of the special steering modes , the controller unit 5 is configured to control the secondary steering device 2 comprising the stern unit 2a and the bow unit 2b such that the thrust provided by the stern unit 2a is directed to the opposite side or direction as the thrust provided by the bow unit 2b . This enables to strengthen the turning of the watercraft W, for instance . In one embodiment , such as shown in Figure 6 , thi s is reali zed by providing a reverse control signal to the stern unit 2a compared to the control signal provided to the bow unit 2b .

[0115] In one embodiment , the control of the stern unit 2a and the bow unit 2b is provided with a gain and / or limit factor 44 . This makes it possible to weight the thrust of one of the units 2a, 2b in relation to another of said units , and preferably to adj ust said relation . Thus , the effect of the units 2a, 2b to the manoeuvring can be balanced, even if the si ze or the distance to the turning centre T of the stern unit 2 a differs from the si ze or the distance of the bow unit 2b . Alternatively the location of the turning centre T can be moved / af f ected by changing the weights between bow and stern thrusters . In one embodiment of the special steering modes , the controller unit 5 is configured to control the secondary steering device 2 comprising the stern unit 2a and the bow unit 2b such that the thrust provided by the stern unit 2a is directed to the same side or direction as the thrust provided by the bow unit 2b or such that both the bow and the stern of the watercraft move in the same lateral direction . This makes it possible to , e . g . , prevent the watercraft from moving with the wind, i . e . , to neutralize the effect of the crosswind, or move the watercraft sideways by the thrust created by the stern and the bow units 2a, 2b . The heading of the watercraft W can be maintained while moving the watercraft sideways by the feedback control that utili zes the compass device / heading sensor and the yaw rate sensor as described in this description . In addition, the speed 39 and / or the steering signal 38 may be utili zed in a sideways reference generation 45 for creating sideways control 46 that are used in controlling the stern and the bow units 2a, 2b . The sideways control 46 may be equal to both of said units 2a, 2b, or alternatively unequal . In one embodiment , the sideways reference generation 45 is reali zed by using a j oystick or corresponding control device or remote control or autopilot or a guidance , navigation and control / track keeping system .

[0116] In one embodiment , the sideways movement accomplished by the stern and the bow units 2a , 2b is combined with a longitudinal movement component , i . e . a movement in direction of the longitudinal axis L the watercraft . This way the watercraft can move along a diagonal path, i . e . sideways in addition to longitudinal movement while maintaining the heading of the longitudinal axis L stable .

[0117] The invention is not limited solely to the embodiments described above , but instead many variations are possible within the scope of the inventive concept defined by the claims below . Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conj unction with or replace the attributes of another embodiment or application .

[0118] The drawings and the related description are only intended to il lustrate the idea of the invention . The invention may vary in detail within the scope of the inventive idea defined in the following claims .

[0119] REFERENCE SYMBOLS

[0120] 1 primary steering device

[0121] 2 secondary steering device

[0122] 3 steering sensor

[0123] 4 yaw rate sensor

[0124] 5 controller unit

[0125] 6 user interface device

[0126] 7 rudder

[0127] 8 steerable propulsion device

[0128] 9 steering wheel

[0129] 10 j oystick

[0130] 11 bow thruster

[0131] 12 compass device / heading sensor

[0132] 13 wind gauge

[0133] 14 retractable thruster

[0134] 15 speed sensor

[0135] 16 ref erence / set point generation

[0136] 17 yaw rate reference

[0137] 18 first sum block

[0138] 19 manoeuvring error

[0139] 20 first controller

[0140] 21 control

[0141] 22 thrust

[0142] 23 yaw rate

[0143] 24 yaw rate measurement

[0144] 25 heading

[0145] 26 feed forward controller

[0146] 27 second sum block

[0147] 28 combined control

[0148] 29 wind direction dependent yaw rate reference generator

[0149] 30 wind speed measurement

[0150] 31 second controller

[0151] 32 compass heading measurement

[0152] 33 third sum block 34 wind direction measurement

[0153] 35 wind direction error

[0154] 36 control

[0155] 37 heading error

[0156] 38 steering signal

[0157] 39 speed

[0158] 40 yaw rate reference

[0159] 41 heading setpoint

[0160] 42 bow

[0161] 43 wind direction setpoint

[0162] 44 gain / limit

[0163] 45 sideways reference generation

[0164] 46 sideways control

[0165] 47 remote control device

[0166] 48 autopilot

[0167] 49 track keeping system

[0168] 100 arrangement

[0169] D distance

[0170] L longitudinal axis

[0171] T turning centre

[0172] W watercraft

Claims

CLAIMS1 . An arrangement for manoeuvring a watercraft (W) , the arrangement ( 100 ) comprising- a controller unit ( 5 ) for manoeuvring a watercraft (W) , configured to- receive a desired turning rate ,- receive a measured yaw rate of the watercraft (W) ,- carry out a comparison of the desired turning rate with the measured yaw rate ,- determine a manoeuvring error based on said comparison, and- control solely a secondary steering device ( 2 ) arranged to assist a primary steering device ( 1 ) that is arranged to take a primary care of a directional control of the watercraft in the directional control of said watercraft for reducing said manoeuvring error .2 . The arrangement as claimed in claim 1 , wherein the controller unit ( 5 ) is configured to- receive a steering signal indicating an actual or desired steering angle of the primary steering device ( 1 ) , wherein the controller unit ( 5 ) is further configured to- determine the desired turning rate on basis of parameters including the steering signal .3 . The arrangement as claimed in claim 2 , wherein- a steering sensor ( 3 ) is arranged to measure the angle of the primary steering device ( 1 ) and wherein- the steering angle is an angle of the primary steering device ( 1 ) .4 . The arrangement as claimed in claim 2 , wherein- the steering sensor (3) is arranged to measure the angle of a user interface device (6) provided for controlling the primary steering device (1) , and wherein- the steering angle is related to an angle of the user interface device (6) .

5. The arrangement as claimed in any of the preceding claims, wherein- the primary steering device (1) is a rudder (7) .

6. The arrangement as claimed in any of claims 1 - 4, wherein the primary steering device (1) is a steerable propulsion device (8) , such as a propeller or a water jet device.

7. The arrangement as claimed in any of claims 4 - 6, wherein- the user interface device (6) is a steering wheel (9) , and- the steering sensor (3) is configured to measure a rotation angle of said steering wheel (9) .

8. The arrangement as claimed in any of claims 4 - 6, wherein- the user interface device (6) is a joystick (10) , and- the steering sensor (3) is configured to measure an inclination angle and / or a rotation angle of said joystick (10) .

9. The arrangement as claimed in any of the preceding claims, wherein- the steering signal or the desired turning rate is provided by a remote control device (47) .

10. The arrangement as claimed in any of the preceding claims, wherein- the steering signal or the desired turning rate is provided by an autopilot (48) .

11. The arrangement as claimed in any of the preceding claims, wherein- the steering signal or the desired turning rate is provided by a guidance, navigation and control / track keeping system (49) .

12. The arrangement as claimed in any of the preceding claims, wherein- secondary steering device (2) comprises a bow thruster (11) •13. The arrangement as claimed in any of the preceding claims, wherein- the controller unit (5) is configured to receive- a signal indicative of a desired heading and- a signal indicative of an actual heading provided by a compass device or a heading sensor (12) , and- the controller unit (5) is configured to control the secondary steering device (2) such that- difference between the desired heading and the actual heading is reduced, and optionally that- the yaw rate of the watercraft (W) is controlled toward zero.

14. The arrangement as claimed in any of the preceding claims, wherein- the controller unit (5) is configured to receive a signal indicative of wind direction provided by a wind gauge (13) , and- the controller unit is configured to control the secondary steering device (2) such that- the bow of the watercraft is pointing into wind , and optionally that- the yaw rate of the watercraft (W) is controlled toward zero.

15. The arrangement as claimed in any of the preceding claims, wherein- the controller unit (5) is further configured to use a direct compensation control system for adjusting controlling the secondary steering device (2) to directly limit or cancel effects of disturbances.

16. The arrangement as claimed in any of the preceding claims, wherein- the secondary steering device (2) is configured to assist the primary steering device (1) in the directional control of the watercraft only in a predetermined speed range of the watercraft (W) .

17. The arrangement as claimed in any of the preceding claims, wherein- the assistance that the secondary steering device (2) is configured to provide is proportional to the speed of the watercraft .

18. The arrangement as claimed in any of the preceding claims, wherein- the secondary steering device (2) comprises- a stern unit (2a) arranged to a rear side of the turning centre T of the watercraft (W) , and a bow unit (2b) arranged between the turning centre (T) and the bow of the watercraft (W) , and wherein- the controller unit (5) is configured to control the secondary steering device (2) such that the thrust provided by the stern unit (2a) is directed to the same side or to the opposite side of the watercraft (W) as the thrust provided by the bow unit (2b) .

19. The arrangement as claimed in claim 18, wherein- the controller unit is configured to control the secondary steering device (2) such that- the watercraft (W) is arranged to move sideways or diagonally and maintain the heading .20 . The arrangement as claimed in any of the preceding claims , wherein the controller unit ( 5 ) is configured to determine the desired turning rate on basis of parameters further including- speed of the watercraft (W) and, optionally,- a distance ( D) between a turning centre (T ) of the watercraft and the primary steering device ( 1 ) .21 . A method for manoeuvring a watercraft (W) , the method comprising- receiving a desired turning rate of the watercraft (W) ,- receiving a measured yaw rate of the watercraft (W) ,- carrying out a comparison of the desired turning rate with the measured yaw rate ,- determining a manoeuvring error based on said compari son, and- controlling solely a secondary steering device ( 2 ) arranged to assist a primary steering device ( 1 ) in the directional control of the watercraft for reducing said manoeuvring error .22 . The method as claimed in claim 21 , comprising- receiving a steering signal indicating an actual or desired steering angle of the primary steering device ( 1 ) ,- determining the desired turning rate of the watercraft (W) on basis of parameters including the steering signal .23 . The method as claimed in claim 21 or 22 , comprising- using a direct compensation control system for adj usting controlling the secondary steering device ( 2 ) .24 . The method as claimed in any of claims 21 23 , com- prising- providing a signal indicative of a desired compass heading of the watercraft, and- controlling the secondary steering device (2) such that- difference between the desired compass heading and an actual compass heading is minimized, and optionally that- the yaw rate of the watercraft (W) is controlled toward zero.

25. The method as claimed in any of claims 21 - 24, comprising- providing a signal indicative of wind direction, and- controlling the secondary steering device (2) such that- the watercraft (W) is kept into the wind, and optionally that- the yaw rate of the watercraft (W) is controlled toward zero.

26. The method as claimed in any of claims 21 - 25, comprising- assisting the primary steering device (1) in the directional control of the watercraft by the secondary steering device (2) only if the speed of the watercraft (W) is in a predetermined speed range.

27. The method as claimed in any of claims 21 - 26, comprising- adjusting the assistance provided by the secondary steering device (2) proportionally to the speed of the watercraft .

28. The method as claimed in any of claims 21 - 27, wherein- the secondary steering device (2) comprises- a stern unit (2a) arranged to a rear side of the turning centre T of the watercraft (W) , anda bow unit (2b) arranged between the turning centre (T) and the bow of the watercraft (W) , and the method comprises- controlling the secondary steering device (2) such that the thrust provided by the stern unit (2a) is directed to the same side or to the opposite side of the watercraft (W) as the thrust provided by the bow unit (2b) .

29. The method as claimed in claim 28, comprising- controlling the secondary steering device (2) such that- the watercraft (W) is arranged to move sideways or diagonally and maintain the heading.

30. The method as claimed in any of claims 21 - 28, comprising- including speed of the watercraft, and optionally a distance (D) between a turning centre (T) of the watercraft and the primary steering device (1) , in the determining the desired turning rate of the watercraft (W) .

31. A computer storage medium comprising code for execution by a processor, the code, when executed by a processor, causing the processor to perform any of the methods of claims 21 to 30.

Images