System for and method of controlling watercraft

Abstract

The present system includes a bow thruster (10), an outboard motor (1) provided as the only one outboard motor attached to a watercraft (100), and a controller (30). The bow thruster (10) includes a spouting port (21, 22) for a stream of water; the spouting port (21, 22) is disposed to be oriented in an obliquely front direction of the watercraft (100). The bow thruster (10) is disposed in the watercraft (100) to spout the stream of water in the obliquely front direction of the watercraft (100). The outboard motor (1) is attached to the watercraft (100) to be steered right and left. The controller (30) controls the outboard motor (1) and the bow thruster (10) to cause the watercraft (100) to move sideways by a net force (F3) of a first thrust (F1) generated by the bow thruster (10) and a second thrust (F2) generated by the outboard motor (1).

Description

[0001] The present invention relates to a system for controlling a watercraft, a watercraft provided with such a system and a method of controlling a watercraft.

[0002] There has been known so far a technology for causing a watercraft to move sideways (i.e., sway) by controlling a net force of thrusts generated by a plurality of outboard motors. For example, JP 2022-99788 A describes a watercraft equipped with two outboard motors. Each of the two outboard motors is enabled to be steered right and left. For example, when the watercraft is caused to sway leftward, a system for controlling the watercraft controls the thrusts and the rudder angles of the two outboard motors such that the net force of the thrusts is oriented leftward, while passing through the center of gravity of the watercraft. When the watercraft is caused to sway rightward, the system for controlling the watercraft controls the thrusts and the rudder angles of the two outboard motors such that the net force of the thrusts is oriented rightward, while passing through the center of gravity of the watercraft.

[0003] The technology described above requires a plurality of outboard motors for causing a watercraft to move sideways. It is an object of the present invention to provide a system for controlling a watercraft, a watercraft provided with such a system and a method of controlling a watercraft that enable a watercraft to move sideways by an outboard motor provided therein as the only one outboard motor. According to the present invention said object is solved by a system for controlling a watercraft having the features of independent claim 1, a watercraft according to claim 9 and a method of controlling a watercraft having the features of independent claim 10. Preferred embodiments are laid down in the dependent claims.

[0004] A system according to an aspect of the present teaching relates to a system for controlling a watercraft. The system according to the present teaching includes a bow thruster, an outboard motor provided as only one outboard motor attached to the watercraft, and a controller. The bow thruster includes a spouting port for a stream of water; the spouting port is disposed to be oriented in an obliquely front direction of the watercraft. The bow thruster is disposed in the watercraft to spout the stream of water in the obliquely front direction of the watercraft. The outboard motor is attached to the watercraft to be enabled to be steered right and left. The controller controls the outboard motor and the bow thruster to cause the watercraft to move sideways by a net force of a first thrust generated by the bow thruster and a second thrust generated by the outboard motor.

[0005] A method according to another aspect of the present teaching relates to a method of controlling a watercraft. The watercraft includes a bow thruster and an outboard motor provided as only one outboard motor attached thereto. The bow thruster includes a spouting port for a stream of water; the spouting port is disposed to be oriented in an obliquely front direction of the watercraft. The bow thruster is disposed in the watercraft to spout the stream of water in the obliquely front direction of the watercraft. The outboard motor is attached to the watercraft to be enabled to be steered right and left. The method according to the present aspect includes controlling the outboard motor and the bow thruster to cause the watercraft to move sideways by a net force of a first thrust generated by the bow thruster and a second thrust generated by the outboard motor.

[0006] According to the present invention, the outboard motor and the bow thruster are controlled to cause the watercraft to move sideways by the net force of the first thrust generated by the bow thruster and the second thrust generated by the outboard motor. Accordingly, the watercraft is enabled to move sideways by the outboard motor provided therein as the only one outboard motor.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a perspective view of a watercraft in which a system according to an embodiment is installed. FIG. 2 is a side view of an outboard motor. FIG. 3 is a top view schematically showing a configuration of the watercraft. FIG. 4 is a schematic diagram showing a configuration of the system. FIG. 5 is a diagram showing a thrust generated by a bow thruster and that generated by the outboard motor when the watercraft moves leftward. FIG. 6 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft moves left-rearward. FIG. 7 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft moves left-forward. FIG. 8 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft turns rightward, with being set in a right steering state. FIG. 9 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft turns leftward, with being set in the right steering state. FIG. 10 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft moves rightward. FIG. 11 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft moves right-rearward. FIG. 12 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft moves right-forward. FIG. 13 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft turns rightward, with being set in a left steering state. FIG. 14 is a diagram showing a thrust generated by the bow thruster and that generated by the outboard motor when the watercraft turns leftward, with being set in the left steering state. DETAILED DESCRIPTION OF EMBODIMENTS

[0008] An embodiment will be hereinafter explained with reference to drawings. FIG. 1 is a perspective view of a watercraft 100 in which a system (propulsion device for a watercraft) according to the embodiment is installed. The watercraft 100 includes an outboard motor 1, provided therein as the only one outboard motor, and a bow thruster 10. The elements of the watercraft are arranged and attached in consideration of a hull of the watercraft 100, wherein a (straight) front direction of the watercraft 100 extends from a stern of the hull to the bow of the hull. A (straight) rear direction of the watercraft 100 is directly opposite to the front direction of the watercraft 100. A straight sideways direction of the watercraft 100 is perpendicular to the (straight) front or rear direction of the watercraft 100 and is either a (straight) rightward direction of the watercraft 100 or a (straight) leftward direction of the watercraft 100. The front direction of the watercraft 100 and the straight sideways direction of the watercraft 100 are within a plane substantially parallel with a water surface.

[0009] The outboard motor 1 is attached to the stern of the watercraft 100. The outboard motor 1 generates a thrust for propelling the watercraft 100. FIG. 2 is a side view of the outboard motor 1. The outboard motor 1 is attached to the watercraft 100 through a bracket 11. The bracket 11 supports the outboard motor 1 such that the outboard motor 1 is made rotatable about a steering shaft 12. The steering shaft 12 extends in an up-and-down direction of the outboard motor 1. When the outboard motor 1 attached to the watercraft 100 and in propulsion position the steering shaft 12 extends in the up-and-down direction of the outboard motor 1 perpendicular to the front direction of the watercraft 100 and the straight sideways direction of the watercraft 100. The outboard motor 1 is enabled to be steered right and left within a steering range including the straight sideways direction of the watercraft 100. The outboard motor 1 is switchable from a neutral state, in which a propeller 6 is oriented in the straight rear direction of the watercraft 100, to a right steering state, in which the propeller 6 is oriented in a direction slanted rightward from the straight rear direction of the watercraft 100, and a left steering state in which the propeller 6 is oriented in a direction slanted leftward from the straight rear direction of the watercraft 100.

[0010] The outboard motor 1 includes an engine 2, a driveshaft 3, a propeller shaft 4, and a shift mechanism 5. The engine 2 generates the thrust for propelling the watercraft 100. The engine 2 includes a crankshaft 13. The crankshaft 13 extends in the up-and-down direction of the outboard motor 1. The driveshaft 3 is connected to the crankshaft 13. The driveshaft 3 extends in the up-and-down direction of the outboard motor 1. The propeller shaft 4 extends in a back-and-forth direction of the outboard motor 1. The propeller shaft 4 is connected to the driveshaft 3 through the shift mechanism 5. The propeller shaft 4 is provided with the propeller 6 attached thereto.

[0011] The shift mechanism 5 includes a forward moving gear 14, a rearward moving gear 15, and a dog clutch 16. When gear engagement of each gear 14, 15 is switched by the dog clutch 16, the direction of rotation transmitted from the drive shaft 3 to the propeller shaft 4 is switched. Movement of the watercraft 100 is thereby switched between forward movement and rearward movement.

[0012] When described in detail, the shift mechanism 5 is switchable among a forward moving state, a rearward moving state, and a neutral state. When the shift mechanism 5 is set in the forward moving state, the dog clutch 16 is connected to the forward moving gear 14. Accordingly, the rotation of the driveshaft 3 is transmitted to the propeller shaft 4 so as to rotate the propeller shaft 4 in a forward moving direction. When the shift mechanism 5 is set in the rearward moving state, the dog clutch 16 is connected to the rearward moving gear 15. Accordingly, the rotation of the driveshaft 3 is transmitted to the propeller shaft 4 so as to rotate the propeller shaft 4 in a rearward moving direction. When the shift mechanism 5 is set in the neutral state, the dog clutch 16 is released from being connected to each of the forward moving gear 14 and the rearward moving gear 15. Accordingly, the rotation of the driveshaft 3 is not transmitted to the propeller shaft 4.

[0013] FIG. 3 is a top view schematically showing a configuration of the watercraft 100. As shown in FIG. 3, the bow thruster 10 is attached to the watercraft 100 to spout a stream of water in an obliquely front direction of the watercraft 100, that is in front direction of the watercraft 100 and in sideways direction of the watercraft 100. The bow thruster 10 includes a first spouting port 21, a second spouting port 22, and a water stream generator 23. The first spouting port 21 is provided in a right lateral surface of the watercraft 100. The first spouting port 21 is disposed to be oriented in a right front direction of the watercraft 100. The second spouting port 22 is provided in a left lateral surface of the watercraft 100. The second spouting port 22 is disposed to be oriented in a left front direction of the watercraft 100. Each of the first and second spouting ports 21 and 22 is fixed in orientation.

[0014] The water stream generator 23 generates the stream of water to be spouted from one of the first and second spouting ports 21 and 22. The water stream generator 23 includes, for instance, a propeller and a motor. Alternatively, the water stream generator 23 may include a pump. The bow thruster 10 spouts the stream of water from the first spouting port 21 in the right front direction of the watercraft 100. The bow thruster 10 spouts the stream of water from the second spouting port 22 in the left front direction of the watercraft 100.

[0015] FIG. 4 is a schematic diagram showing a configuration of a system for controlling the watercraft 100. As shown in FIG. 4, the outboard motor 1 includes a shift actuator 7 and a steering actuator 8. The shift actuator 7 is connected to the dog clutch 16 of the shift mechanism 5. The shift actuator 7 actuates the dog clutch 16 to switch gear engagement of each gear 14, 15. Movement of the watercraft 100 is thereby switched between forward movement and rearward movement. The shift actuator 7 is, for instance, an electric motor. However, the shift actuator 7 may be another type of actuator such as an electric cylinder, a hydraulic motor, or a hydraulic cylinder.

[0016] The steering actuator 8 is connected to the outboard motor 1. The steering actuator 8 rotates the outboard motor 1 about the steering shaft 12. The outboard motor 1 is thereby changed in rudder angle. The rudder angle refers to an angle of the propeller shaft 4 with respect to the back-and-forth direction of the outboard motor 1. The steering actuator 8 is, for instance, an electric motor. However, the shift actuator 7 may be another type of actuator such as an electric cylinder, a hydraulic motor, or a hydraulic cylinder.

[0017] The outboard motor 1 includes an ECU (Electric Control Unit) 9. The ECU 9 includes a processor such as a CPU (Central Processing Unit) and memories such as a RAM (Random Access Memory) and a ROM (Read-Only Memory). The ECU 9 has stored programs and data for controlling the outboard motor 1. The ECU 9 controls the engine 2.

[0018] The system includes a steering wheel 24, a remote controller 25, and a joystick 26. As shown in FIG. 1, the steering wheel 24, the remote controller 25, and the joystick 26 are disposed in a cockpit of the watercraft 100.

[0019] The steering wheel 24 is a device for allowing an operator to manipulate the turning direction of the watercraft 100. The steering wheel 24 includes a sensor 240. The sensor 240 outputs a steering signal indicating the operating direction and the operating amount of the steering wheel 24.

[0020] The remote controller 25 includes a throttle lever 250 and a sensor 251. The throttle lever 250 is a device for allowing the operator to regulate the magnitude of the thrust generated by the outboard motor 1. Besides, the throttle lever 250 is a device for allowing the operator to switch the direction of the thrust generated by the outboard motor 1 between front and rear directions. The throttle lever 250 is operable from a neutral position to a forward moving directional side and a rearward moving directional side. The neutral position is a position located between the forward moving directional side and the rearward moving directional side. The sensor 251 outputs a throttle signal indicating the operating direction and the operating amount of the throttle lever 250.

[0021] The joystick 26 is operable by the operator to instruct the watercraft 100 to perform one of moving modes. The joystick 26 is tiltable from a neutral position in at least four directions of front, rear, right, and left. Moving the watercraft 100 in four or more directions, and furthermore, all directions may be instructible by the joystick 26. The joystick 26 is rotatable about a rotational axis Ax1. In other words, the joystick 26 is operable to be twisted clockwise and counterclockwise about the rotational axis Ax1 from the middle position.

[0022] The joystick 26 includes a sensor 260. The sensor 260 outputs a joystick signal indicating how the joystick 26 has been operated. The joystick signal includes the tilt direction and the tilt amount of the joystick 26. The joystick signal includes the twist direction and the twist amount of the joystick 26 as well.

[0023] The system includes a controller 30. The controller 30 includes a processor such as a CPU and memories such as a RAM and a ROM. The controller 30 has stored programs and data for controlling the outboard motor 1 and the bow thruster 10. The controller 30 is connected to the ECU 9 and the bow thruster 10 through wired or wireless communication. The controller 30 is connected to the steering wheel 24, the remote controller 25, and the joystick 26.

[0024] The controller 30 receives the steering signal from the sensor 240. The controller 30 receives the throttle signal from the sensor 251. The controller 30 receives the joystick signal from the sensor 260. The controller 30 outputs command signals to the ECU 9 based on the signals inputted thereto from the sensors 240, 251, and 260. The command signals are transmitted to the engine 2, the shift actuator 7, and the steering actuator 8 through the ECU 9. Besides, the controller 30 outputs a command signal to the bow thruster 10.

[0025] The controller 30 outputs a shift command for the shift actuator 7 in accordance with the operating direction of the throttle lever 250. In response, shifting between forward movement and rearward movement by the outboard motor 1 is made. The controller 30 outputs a throttle command for the engine 2 in accordance with the operating amount of the throttle lever 250. The ECU 9 controls the thrust generated by the outboard motor 1 in accordance with the throttle command. It should be noted that the throttle signal, outputted from the sensor 251, may be directly inputted to the ECU 9. The ECU 9 may output the throttle command to the engine 2 in accordance with the throttle signal inputted thereto from the sensor 251.

[0026] The controller 30 outputs a command signal for the steering actuator 8 in accordance with the operating direction and the operating amount of the steering wheel 24. When the steering wheel 24 is operated leftward from the neutral position, the controller 30 controls the steering actuator 8 such that the outboard motor 1 is set in the left steering state. Accordingly, the watercraft 100 turns leftward.

[0027] When the steering wheel 24 is operated rightward from the neutral position, the controller 30 controls the steering actuator 8 such that the outboard motor 1 is set in the right steering state. Accordingly, the watercraft 100 turns rightward. Besides, the controller 30 controls the rudder angle of the outboard motor 1 in accordance with the opening amount of the steering wheel 24.

[0028] The controller 30 outputs command signals to the engine 2, the shift actuator 7, the steering actuator 8, and the bow thruster 10 in accordance with the tilt direction and the tilt amount of the joystick 26. The controller 30 controls the engine 2, the shift actuator 7, the steering actuator 8, and the bow thruster 10 such that the watercraft 100 translates at a velocity corresponding to the tilt amount of the joystick 26 in a direction corresponding to the tilt direction of the joystick 26.

[0029] When the joystick 26 is being tilted forward, the controller 30 causes the watercraft 100 to move forward by the thrust generated by the outboard motor 1 (fore surging mode). When the joystick 26 is being tilted rearward, the controller 30 causes the watercraft 100 to move rearward by the thrust generated by the outboard motor 1 (aft surging mode).

[0030] When the joystick 26 is being tilted leftward or rightward, the controller 30 causes the watercraft 100 to sway leftward or rightward (swaying mode). In the swaying mode, the controller 30 controls the outboard motor 1 and the bow thruster 10 to cause the watercraft 100 to move sideways by a net force of the thrust generated by the bow thruster 10 (first thrust) and that generated by the outboard motor 1 (second thrust).

[0031] For example, when the joystick 26 is being tilted leftward, the controller 30 sets the left direction as a target moving direction. When the left direction is set as the target moving direction, as shown in FIG. 5, the controller 30 causes the bow thruster 10 to spout a stream of water right-forward from the first spouting port 21, while setting the outboard motor 1 to the right steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented left-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented left-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the left direction of the watercraft 100. Accordingly, the watercraft 100 translates straight leftward.

[0032] When the joystick 26 is being tilted left-rearward, the controller 30 sets the left rear direction as the target moving direction. When the left rear direction is set as the target moving direction, as shown in FIG. 6, the controller 30 causes the bow thruster 10 to spout a stream of water right-forward from the first spouting port 21, while setting the outboard motor 1 to the right steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented left-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented left-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the left rear direction of the watercraft 100. Accordingly, the watercraft 100 translates left-rearward.

[0033] When the joystick 26 is being tilted left-forward, the controller 30 sets the left front direction as the target moving direction. When the left front direction is set as the target moving direction, as shown in FIG. 7, the controller 30 causes the bow thruster 10 to spout a stream of water right-forward from the first spouting port 21, while setting the outboard motor 1 to the right steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented left-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented left-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the left front direction of the watercraft 100. Accordingly, the watercraft 100 translates left-forward.

[0034] The controller 30 controls the engine 2, the shift actuator 7, the steering actuator 8, and the bow thruster 10 such that the watercraft 100 turns at a velocity corresponding to the twisted amount of the joystick 26 in a direction corresponding to the twisted direction of the joystick 26 (turning mode).

[0035] For example, when the joystick 26 is twisted clockwise, with tilted leftward, the controller 30 sets the right turning direction as a target turning direction. When the right turning direction is set as the target turning direction, while the outboard motor 1 is set in the right steering state, the controller 30 causes the bow thruster 10 to spout a stream of water right-forward from the first spouting port 21, while keeping the outboard motor 1 in the right steering state. As shown in FIG. 8, the controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 passes through a position located behind the center of resistance (center of gravity) G1 of the watercraft 100. Accordingly, the watercraft 100 turns rightward.

[0036] When the joystick 26 is twisted counterclockwise, with tilted leftward, the controller 30 sets the left turning direction as the target turning direction. When the left turning direction is set as the target turning direction, while the outboard motor 1 is set in the right steering state, the controller 30 causes the bow thruster 10 to spout a stream of water right-forward from the first spouting port 21, while keeping the outboard motor 1 in the right steering state. As shown in FIG. 9, the controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 passes through a position located ahead of the center of resistance G1 of the watercraft 100. Accordingly, the watercraft 100 turns leftward.

[0037] When the joystick 26 is being tilted rightward, the controller 30 sets the right direction as the target moving direction. When the right direction is set as the target moving direction, as shown in FIG. 10, the controller 30 causes the bow thruster 10 to spout a stream of water left-forward from the second spouting port 22, while setting the outboard motor 1 to the left steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented right-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented right-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the right direction of the watercraft 100. Accordingly, the watercraft 100 translates straight rightward.

[0038] When the joystick 26 is being tilted right-rearward, the controller 30 sets the right rear direction as the target moving direction. When the right rear direction is set as the target moving direction, as shown in FIG. 11, the controller 30 causes the bow thruster 10 to spout a stream of water left-forward from the second spouting port 22, while setting the outboard motor 1 to the left steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented right-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented right-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the right rear direction of the watercraft 100. Accordingly, the watercraft 100 translates right-rearward.

[0039] When the joystick 26 is being tilted right-forward, the controller 30 sets the right front direction as the target moving direction. When the right front direction is set as the target moving direction, as shown in FIG. 12, the controller 30 causes the bow thruster 10 to spout a stream of water left-forward from the second spouting port 22, while setting the outboard motor 1 to the left steering state. Accordingly, the controller 30 causes the bow thruster 10 to generate the first thrust F1 oriented right-rearward, while causing the outboard motor 1 to generate the second thrust F2 oriented right-forward. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 is oriented in the right front direction of the watercraft 100. Accordingly, the watercraft 100 translates right-forward.

[0040] When the joystick 26 is twisted clockwise, with tilted rightward, while the outboard motor 1 is set in the right steering state, as shown in FIG. 13, the controller 30 causes the bow thruster 10 to spout a stream of water left-forward from the second spouting port 22, while keeping the outboard motor 1 in the left steering state. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 passes through a position located ahead of the center of resistance G1 of the watercraft 100. Accordingly, the watercraft 100 turns rightward.

[0041] When the joystick 26 is twisted counterclockwise, with tilted rightward, while the outboard motor 1 is set in the left steering state, as shown in FIG. 14, the controller 30 causes the bow thruster 10 to spout a stream of water left-forward from the second spouting port 22, while keeping the outboard motor 1 in the left steering state. The controller 30 controls the magnitude of the first thrust F1 generated by the bow thruster 10, that of the second thrust F2 generated by the outboard motor 1, and the rudder angle of the outboard motor 1 such that the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1 passes through a position located behind the center of resistance G1 of the watercraft 100. Accordingly, the watercraft 100 turns leftward.

[0042] In the system for controlling the watercraft 100 according to the present embodiment explained above, the outboard motor 1 and the bow thruster 10 are controlled to cause the watercraft 100 to move sideways by the net force F3 of the first thrust F1 generated by the bow thruster 10 and the second thrust F2 generated by the outboard motor 1. Accordingly, the watercraft 100 is enabled to move sideways by the outboard motor 1 provided therein as the only one outboard motor.

[0043] Besides, when the watercraft operator slightly adjusts the movement of the watercraft 100 by oblique movement, turning, or so forth, while causing the watercraft 100 to move sideways by the joystick 26, the outboard motor 1 is kept approximately constant in orientation; hence, smooth transition is enabled between the moving modes. For example, during the leftward swaying of the watercraft 100, when the watercraft operator slightly adjusts the movement of the watercraft 100 by obliquely leftward movement or leftward turning, while tilting the joystick 26 leftward, the outboard motor 1 is set in the right steering state all the while. On the other hand, during the rightward swaying of the watercraft 100, when the watercraft operator slightly adjusts the movement of the watercraft 100 by obliquely rightward movement or rightward turning, while tilting the joystick 26 rightward, the outboard motor 1 is set in the left steering state all the while. Because of this, the outboard motor 1 is not changed so much in rudder angle in transition between the moving modes; hence, smooth transition is enabled between the moving modes.

[0044] One embodiment of the present teaching has been explained above. Alternatively, the outboard motor 1 may include an electric motor instead of the engine 2. In the embodiment described above, the joystick 26 has been exemplified as an operating device for instructing one of the moving modes. Alternatively, the operating device may be another type of device such as a switch or a touch screen. The moving modes may be changed from one to another, not by a manual operation performed for the operating device by the watercraft operator, but by an automated watercraft operation performed by the controller 30.REFERENCE SIGNS LIST

[0045] 1: Outboard motor, 10: Bow thruster; 21: First spouting port, 22: Second spouting port, 30: Controller, 100: Watercraft, F1: First thrust, F2: Second thrust, F3: Net force

Claims

1. A system for controlling a watercraft (100), the system comprising: a bow thruster (10) configured to be disposed in the watercraft (100) to spout a stream of water in an obliquely front direction of the watercraft (100), the bow thruster (10) including at least one spouting port (21, 22) for the stream of water, the spouting port (21, 22) is disposed to be oriented in the obliquely front direction of the watercraft (100); an outboard motor (1) configured to be attached to the watercraft (100) to be steerable right and left, the outboard motor (1) is provided as only one outboard motor (1) attached thereto; and a controller (30) configured to control the outboard motor (1) and the bow thruster (10) to cause the watercraft (100) to move sideways by a net force (F3) of a first thrust (F1) generated by the bow thruster (10) and a second thrust (F2) generated by the outboard motor (1).

2. The system according to claim 1, wherein the controller (30) is configured to determine a target moving direction of the watercraft (100), and control a magnitude of the first thrust (F1) generated by the bow thruster (10), a magnitude of the second thrust (F2) generated by the outboard motor (1), and a rudder angle of the outboard motor (1) such that the net force (F3) of the first thrust (F1) and the second thrust (F2) is oriented in the target moving direction.

3. The system according to claim 1 or 2, wherein the outboard motor (1) is configured to be steerable within a steering range including a straight sideways direction of the watercraft (100).

4. The system according to claim 1, wherein the outboard motor (1) is switchable from a neutral state to a right steering state and a left steering state, the outboard motor (1) oriented in a straight rear direction of the watercraft (100) in the neutral state, the outboard motor (1) oriented in a direction slanted rightward from the straight rear direction of the watercraft (100) in the right steering state, the outboard motor (1) oriented in a direction slanted leftward from the straight rear direction of the watercraft (100) in the left steering state, the controller (30) is configured to determine a target moving direction of the watercraft (100), cause the bow thruster (10) to spout the stream of water right-forward and set the outboard motor (1) to the right steering state when the target moving direction of the watercraft (100) is either a left direction or an obliquely left direction, and cause the bow thruster (10) to spout the stream of water left-forward and set the outboard motor (1) to the left steering state when the target moving direction of the watercraft (100) is either a right direction or an obliquely right direction.

5. The system according to claim 4, wherein the controller (30) is configured to determine a target turning direction of the watercraft (100), control the outboard motor (1) and the bow thruster (10) such that the net force (F3) of the first thrust (F1) generated by the bow thruster (10) and the second thrust (F2) generated by the outboard motor (1) passes through a position located ahead of a center of resistance of the watercraft (100) when the target turning direction is a left turning direction, and control the outboard motor (1) and the bow thruster (10) such that the net force (F3) of the first thrust (F1) generated by the bow thruster (10) and the second thrust (F2) generated by the outboard motor (1) passes through a position located behind the center of resistance of the watercraft (100) when the target turning direction is a right turning direction.

6. The system according to at least one of the claims 1 to 5, wherein the bow thruster (10) includes a first spouting port (21) and a second spouting port (22), the first spouting port (21) is provided in a right lateral surface of the watercraft (100) and disposed to be oriented in a right front direction of the watercraft (100), the second spouting port (22) is provided in a left lateral surface of the watercraft (100) and disposed to be oriented in a left front direction of the watercraft (100).

7. The system according to claim 6, wherein first and second spouting ports (21, 22) are fixed in orientation, respectively.

8. The system according to claim 6 or 7, wherein the bow thruster (10) further includes a water stream generator (23) configured to generate the stream of water to be spouted from one of the first and second spouting ports (21, 22).

9. A watercraft (10) provided with a system according to at least one of the claims 1 to 8.

10. A method of controlling a watercraft (100), the watercraft (100) including a bow thruster (10) and an outboard motor (1), the bow thruster (10) disposed in the watercraft (100) to spout a stream of water in an obliquely front direction of the watercraft (100), the bow thruster (10) including at least one spouting port (21, 22) for the stream of water, the spouting port (21, 22) disposed to be oriented in the obliquely front direction of the watercraft (100), the outboard motor (1) attached to the watercraft (100) to be steered right and left, the outboard motor (1) provided as only one outboard motor (1) attached thereto, the method comprising: controlling the outboard motor (1) and the bow thruster (10) to cause the watercraft (100) to move sideways by a net force (F3) of a first thrust (F1) generated by the bow thruster (10) and a second thrust (F2) generated by the outboard motor (1).

11. The method according to claim 10, wherein the outboard motor (1) is switchable from a neutral state to a right steering state and a left steering state, the outboard motor (1) oriented in a straight rear direction of the watercraft (100) in the neutral state, the outboard motor (1) oriented in a direction slanted rightward from the straight rear direction of the watercraft (100) in the right steering state, the outboard motor (1) oriented in a direction slanted leftward from the straight rear direction of the watercraft (100) in the left steering state, the method further comprising: determining a target moving direction of the watercraft (100); causing the bow thruster (10) to spout the stream of water right-forward and setting the outboard motor (1) to the right steering state when the target moving direction of the watercraft (100) is either a left direction or an obliquely left direction; and causing the bow thruster (10) to spout the stream of water left-forward and setting the outboard motor (1) to the left steering state when the target moving direction of the watercraft (100) is either a right direction or an obliquely right direction.

12. The method according to claim 11, further comprising: determining a target turning direction of the watercraft (100); controlling the outboard motor (1) and the bow thruster (10) such that the net force (F3) of the first thrust (F1) generated by the bow thruster (10) and the second thrust (F2) generated by the outboard motor (1) passes through a position located ahead of a center of resistance of the watercraft (100) when the target turning direction is a left turning direction; and controlling the outboard motor (1) and the bow thruster (10) such that the net force (F3) of the first thrust (F1) generated by the bow thruster (10) and the second thrust (F2) generated by the outboard motor (1) passes through a position located behind the center of resistance of the watercraft (100) when the target turning direction is a right turning direction.

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