System for propelling watercraft, watercraft, and method of propelling watercraft

Abstract

The present watercraft propulsion system (100) includes a principal propulsion device (3), an auxiliary propulsion device (4), a steering actuator (33), a steering motor (56), and a main controller (101). The principal propulsion device (3) is attached to a hull (2) of a watercraft. The auxiliary propulsion device (4) is attached to the hull (2) and has a smaller rated output than the principal propulsion device (3). The steering actuator (33) changes a rudder angle of the principal propulsion device (3). The steering motor (56) changes a rudder angle of the auxiliary propulsion device (4). The main controller (101) controls the steering actuator (33) and the steering motor (56) such that a rudder rate of the principal propulsion device (3) is made smaller than a rudder rate of the auxiliary propulsion device (4) when steering of the hull 2 is executed in a state that not the principal propulsion device (3) but the auxiliary propulsion device (4) only generates a thrust.

Description

[0001] The present invention relates to a system for propelling a watercraft, a watercraft, and a method of propelling a watercraft.

[0002] There has been disclosed a configuration that a watercraft includes a plurality of propulsion devices (see e.g., JP 2024-060160 A). In JP 2024-060160 A, a principal propulsion device with a large output and an auxiliary propulsion device with a small output are installed on a hull of the watercraft. For example, the principal propulsion device is used in high-speed cruising toward a destination. By contrast, in the vicinity of the destination, the principal propulsion device is stopped, while the auxiliary propulsion device is used for minutely adjusting the position and the compass direction of the hull.

[0003] When steering of the watercraft is executed in such a situation as described above that the watercraft is propelled only with the auxiliary propulsion device, the principal propulsion device is changed in rudder angle in a comparable manner to the auxiliary propulsion device so as to reduce resistance to be caused when the watercraft turns. However, the principal propulsion device has a large inertia; hence, chances are that vibrations with a large magnitude are caused in the watercraft.

[0004] It is an object of the present invention to provide a system for propelling a watercraft, a watercraft, and a method of propelling a watercraft, whereby vibrations to be caused in steering of the watercraft can be inhibited in magnitude.

[0005] This object is achieved by a system for propelling a watercraft according to claim 1 and a method according to claim 12. Preferred embodiments are laid down in the dependent claims. A system for propelling a watercraft according to an aspect includes a principal propulsion device, an auxiliary propulsion device, a principal propulsion device rudder angle changing mechanism, an auxiliary propulsion device rudder angle changing mechanism, and a controller. The principal propulsion device is attached to a hull of the watercraft. The auxiliary propulsion device is attached to the hull and has a smaller rated output than the principal propulsion device. The principal propulsion device rudder angle changing mechanism is configured to change a rudder angle of the principal propulsion device. The auxiliary propulsion device rudder angle changing mechanism is configured to change a rudder angle of the auxiliary propulsion device. The controller is configured to control the principal propulsion device rudder angle changing mechanism and the auxiliary propulsion device rudder angle changing mechanism such that a rudder rate of the principal propulsion device is made smaller than a rudder rate of the auxiliary propulsion device when steering of the hull is executed in a state that not the principal propulsion device but the auxiliary propulsion device only generates a thrust.

[0006] A method of propelling a watercraft according to another aspect relates to a method executed by a system for propelling the watercraft. The system includes a principal propulsion device, an auxiliary propulsion device, a principal propulsion device rudder angle changing mechanism, and an auxiliary propulsion device rudder angle changing mechanism. The principal propulsion device is attached to a hull of the watercraft. The auxiliary propulsion device is attached to the hull and has a smaller rated output than the principal propulsion device. The principal propulsion device rudder angle changing mechanism changes a rudder angle of the principal propulsion device. The auxiliary propulsion device rudder angle changing mechanism changes a rudder angle of the auxiliary propulsion device. The method includes controlling the principal propulsion device rudder angle changing mechanism and the auxiliary propulsion device rudder angle changing mechanism such that a rudder rate of the principal propulsion device is made smaller than a rudder rate of the auxiliary propulsion device when steering of the hull is executed in a state that not the principal propulsion device but the auxiliary propulsion device only generates a thrust. A controller disclosed herein may be configured to perform respective control steps by being configured in hardware and / or software. When being configured by software, the controller can be said to be programmed to perform respective constrol steps.

[0007] When steering of the hull is executed, the principal propulsion device is made smaller in rudder rate than the auxiliary propulsion device; hence, the principal propulsion device having a large inertia can be made small in rudder rate, whereby vibrations to be caused in the hull by changing the rudder angle of the principal propulsion device can be inhibited in magnitude. Besides, although the principal propulsion device is made small in rudder rate, the auxiliary propulsion device is not made small in rudder rate; hence, when a user of the watercraft quickly performs a steering operation, the hull can be quickly changed in bow direction in response to the steering operation.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a plan view of a watercraft in which a watercraft propulsion system according to a preferred embodiment is installed. FIG. 2 is a side view of the watercraft. FIG. 3 is a diagram showing a configuration of a principal propulsion device. FIG. 4 is a diagram showing a configuration of an auxiliary propulsion device. FIG. 5 is a rear view of the auxiliary propulsion device seen from behind the watercraft. FIG. 6 is a schematic diagram showing a configuration of a drive unit. FIG. 7 is a diagram showing a configuration of the watercraft propulsion system installed in the watercraft. FIG. 8 is a perspective view of a joystick unit. FIG. 9 is a table for explaining states of the principal and auxiliary propulsion devices under each of the following modes: an electric mode, an engine mode, a dual mode, and an extender mode. FIG. 10 is composed of diagrams for explaining steering of the watercraft executed in a state that each of the principal and auxiliary propulsion devices generates a thrust. FIG. 11 is a chart showing change in time of the rudder angle of the auxiliary propulsion device and change in time of the rudder angle of the principal propulsion device in the state that each of the principal and auxiliary propulsion devices generates a thrust. FIG. 12 is composed of diagrams for explaining steering of the watercraft executed in a state that not the principal propulsion device but the auxiliary propulsion device only generates a thrust. FIG. 13 is a chart showing change in time of the rudder angle of the auxiliary propulsion device and change in time of the rudder angle of the principal propulsion device in the state that not the principal propulsion device but the auxiliary propulsion device only generates a thrust. FIG. 14 is a flowchart showing a series of control actions to be executed by a watercraft propulsion system. DETAILED DESCRIPTION OF EMBODIMENTS

[0009] A preferred embodiment will be hereinafter explained with reference to drawings.

[0010] FIG. 1 is a plan view of a watercraft 1 in which a watercraft propulsion system (system for propelling a watercraft) 100 according to the preferred embodiment is installed. FIG. 2 is a side view of the watercraft 1 in which the watercraft propulsion system 100 according to the preferred embodiment is installed.

[0011] The watercraft 1 includes a hull 2, a principal propulsion device 3, and an auxiliary propulsion device 4. The principal propulsion device 3 is an engine propulsion device using an engine as a power source thereof. The principal propulsion device 3 is an outboard motor. The auxiliary propulsion device 4 is an electric propulsion device using an electric motor as a power source thereof. The auxiliary propulsion device 4 is an outboard motor. The auxiliary propulsion device 4 has a smaller rated output than the principal propulsion device 3. The principal and auxiliary propulsion devices 3 and 4 are attached to a stern 2a of the hull 2. The principal and auxiliary propulsion devices 3 and 4 are disposed to be aligned on the stern 2a in the right-and-left direction of the hull 2. The principal propulsion device 3 is disposed in the middle of the hull 2 in the right-and-left direction. The auxiliary propulsion device 4 is disposed on an outer side (the left side in the present preferred embodiment) of the middle of the hull 2 in the right-and-left direction.

[0012] The hull 2 includes an operating seat 5, a steering wheel 6, a remote control lever 7, a joystick 8, and a gauge 9. The operating seat 5 serves as a seat on which a user (or watercraft operator) is seated for operating the hull 2. The steering wheel 6 serves as an operating device operated by the user for changing the route of the watercraft 1. The remote control lever 7 serves as an operating device operated by the user to change the magnitude (output) and the direction (forward or rearward moving direction) of a thrust generated from the principal propulsion device 3 and corresponds to an accelerator operating device. The joystick 8 serves as an operating device operated by the user for operating the watercraft 1 instead of the steering wheel 6 and the remote control lever 7. The gauge 9 serves as a display device for displaying a variety of information for operating the watercraft 1.

[0013] FIG. 3 is a diagram showing a configuration of the principal propulsion device 3. The watercraft 1 includes an attachment mechanism 11 for attaching the principal propulsion device 3 to the hull2. The attachment mechanism 11 includes a clamp bracket 12, a tilt shaft 13, a swivel bracket 14, and a steering shaft 15. The clamp bracket 12 is detachably fixed to a transom plate provided on the stern 2a of the hull 2. The tilt shaft 13 is horizontally disposed in the clamp bracket 12 along the right-and-left direction. The swivel bracket 14 is joined to the clamp bracket 12, while being pivotable about the tilt shaft 13. The steering shaft 15 is attached to the swivel bracket 14. The principal propulsion device 3 is attached to the swivel bracket 14, while being pivotable about the steering shaft 15. Accordingly, when the principal propulsion device 3 is pivoted about the steering shaft 15, it is made possible to change a ruder angle (a compass directional angle formed by a thrust direction with respect to the center line of the hull 2). Besides, when the swivel bracket 14 is pivoted about the tilt shaft 13, it is made possible to change a trim angle of the principal propulsion device 3. The trim angle refers to an angle at which the principal propulsion device 3 is attached to the hull 2.

[0014] The principal propulsion device 3 includes an engine cover 16 (top cowling), an upper case 17, and a lower case 18. The engine cover 16, the upper case 17, and the lower case 18 compose a housing of the principal propulsion device 3. The upper case 17 is disposed on the lower side of the engine cover 16. The lower case 18 is disposed on the lower side of the upper case 17.

[0015] The principal propulsion device 3 includes an engine 19, a drive shaft 20, a shift mechanism 21, a propeller shaft 22, a propeller 23, and a shift rod 24. The engine 19 is a prime mover. The engine 19 is disposed inside the engine cover 16. The engine 19 is disposed such that the axis of a crankshaft thereof is disposed along the up-and-down direction. The drive shaft 20 is coupled to the lower end of the crankshaft. The drive shaft 20 transmits a mechanical power of the engine 19 to the propeller shaft 22 through the shift mechanism 21. The shift mechanism 21 is disposed on the lower end of the drive shaft 20. The propeller shaft 22 extends rearward from the lower side of the drive shaft 20 in the horizontal direction. The propeller shaft 22 serves as a rotational shaft of the propeller 23. The propeller 23 is disposed on the rear side of a lower part of the lower case 18. The propeller 23 serves as a propulsion member for the watercraft 1. The propeller 23 is fixed to the propeller shaft 22. The shift rod 24 operates the shift mechanism 21.

[0016] The shift mechanism 21 has a plurality of shift positions (shift states) including a forward moving position, a rearward moving position, and a neutral position. The neutral position is a shift position for producing a blocking state that the rotation of the drive shaft 20 is not transmitted to the propeller shaft 22. The forward moving position is a shift position for producing a state that the rotation of the drive shaft 20 is transmitted to the propeller shaft 22 so as to rotate the propeller shaft 22 in a forward moving rotational direction. The rearward moving position is a shift position for producing a state that the rotation of the drive shaft 20 is transmitted to the propeller shaft 22 so as to rotate the propeller shaft 22 in a rearward moving rotational direction. The forward moving rotational direction refers to a direction in which the propeller 23 is rotated to apply a thrust oriented in the forward moving direction to the hull 2. The rearward moving rotational direction refers to a direction in which the propeller 23 is rotated to apply a thrust oriented in the rearward moving direction to the hull 2. The shift mechanism 21 is switched in shift position by the shift rod 24. The shift rod 24 extends in the up-and-down direction, while being in parallel to the drive shaft 20. The shift rod 24 is configured to operate the shift mechanism 21 by rotated about the axis thereof.

[0017] The principal propulsion device 3 includes a starter motor 25, an electric power generator 26, an engine ECU (Electric Control Unit) 27, and a throttle actuator 28. The starter motor 25 starts the engine 19. The starter motor 25 is controlled by the engine ECU 27. The electric power generator 26 generates electric power; then, the electric power is supplied to electric components included in the principal propulsion device 3. The electric power generated by the electric power generator 26 is used for charging a battery 130 (to be described) stored in the hull 2. The throttle actuator 28 actuates a throttle valve 29 in the engine 19 so as to change the throttle opening degree thereof, whereby the engine 19 is changed in amount of intake air. The throttle actuator 28 is made in the form of, for instance, an electric motor. The action of the throttle actuator 28 is controlled by the engine ECU 27.

[0018] The engine ECU 27 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 engine ECU 27 has stored programs and data for controlling the starter motor 25, the throttle actuator 28, a shift actuator 30, a tilt / trim actuator 35 (to be described), and so forth based on command signals transmitted thereto from a remote control ECU 106.

[0019] The principal propulsion device 3 includes the shift actuator 30. The shift actuator 30 drives the shift rod 24 so as to change the shift position of the shift mechanism 21. The shift actuator 30 is made in the form of, for instance, an electric motor. The shift actuator 30 is controlled by the engine ECU 27.

[0020] The principal propulsion device 3 includes a steering rod 31. The steering rod 31 is fixed to the upper case 17. The watercraft 1 includes a steering device 32. The steering device 32 is joined to the steering rod 31. The steering device 32 drives the steering rod 31 in accordance with operating the steering wheel 6. The principal propulsion device 3 is pivoted about the steering shaft 15 by the steering device 32. Accordingly, a rudder angle control is enabled. The steering device 32 includes a steering actuator 33 (exemplary principal propulsion device rudder angle changing mechanism). The principal propulsion device 3 includes a steering ECU 34. The steering ECU 34 controls the steering actuator 33. The steering ECU 34 may be disposed in the principal propulsion device 3, or alternatively, may be disposed in the hull 2. The steering actuator 33 may be made in the form of an electric motor, or alternatively, may be made in the form of a hydraulic actuator.

[0021] The steering ECU 34 includes a processor such as a CPU and memories such as a RAM and a ROM. The steering ECU 34 has stored programs and data for controlling the steering actuator 33 based on either an operating angle signal transmitted thereto from a steering wheel unit 65 (to be described) or a rudder angle command signal transmitted thereto from the remote control ECU 106.

[0022] The watercraft 1 includes the tilt / trim actuator 35. The tilt / trim actuator 35 changes the trim angle of the principal propulsion device 3 with respect to the hull 2. The tilt / trim actuator 35 includes, for instance, a fluid pressure cylinder. The tilt / trim actuator 35 is controlled by the engine ECU 27. The tilt / trim actuator 35 causes the swivel bracket 14 to pivot about the tilt shaft 13, whereby the principal propulsion device 3 is pivoted about the tilt shaft 13.

[0023] FIG. 4 is a diagram showing a configuration of the auxiliary propulsion device 4. FIG. 5 is a rear view of the auxiliary propulsion device 4 seen from behind the watercraft 1.

[0024] The watercraft 1 includes a bracket 41 for attaching the auxiliary propulsion device 4 to the hull 2. The bracket 41 is attached to the stern 2a of the hull 2. The auxiliary propulsion device 4 is supported by the bracket 41.

[0025] The auxiliary propulsion device 4 includes a base 42, an upper housing 43, a lower housing 44, a cover 45, a cowl 46, a drive unit 47, and a steering unit 48. The base 42 is supported by the bracket 41. The upper housing 43 extends downward from the base 42. The lower housing 44 is made in the shape of a tube (duct) and is disposed below the upper housing 43. The cover 45 covers the base 42 from below. The cowl 46 covers the base 42 from above. The cover 45 and the cowl 46 are exemplified as a first housing. The upper housing 43 and the lower housing 44 are exemplified as a second housing.

[0026] The drive unit 47 is disposed inside the lower housing 44. FIG. 6 is a schematic diagram showing a configuration of the drive unit 47. The drive unit 47 includes a propeller 49 and an electric motor 50. The propeller 49 generates a thrust. The electric motor 50 drives the propeller 49. The electric motor 50 includes a rotor 51 and a stator 52.

[0027] The rotor 51 is made in the shape of a tube to which the propeller 49 is fixed on the radially inner side thereof. The rotor 55 is rotatably supported by the lower housing 44. The rotor 51 includes a plurality of permanent magnets 53. The permanent magnets 53 are disposed along the circumferential direction of the rotor 51. It should be noted that in FIG. 6, the reference numeral 53 is assigned to only one of the permanent magnets without being assigned to the remaining thereof.

[0028] The stator 52 encloses the rotor 51 from radially outside. The stator 52 is fixed to the lower housing 44. The stator 52 includes a plurality of coils 54. The coils 54 are disposed along the circumferential direction of the stator 52. When the coils 54 are electrified, electromagnetic forces are generated, whereby the rotor 51 is rotated. The propeller 49 is rotated in accordance with the rotation of the rotor 51, whereby the thrust can be generated. It should be noted that in FIG. 6, the reference numeral 54 is assigned to only one of the coils without being assigned to the remaining thereof.

[0029] As shown in FIG. 4, the steering unit 48 is disposed in a space between the cover 45 and the cowl 46. The steering unit 48 changes right and left the direction of the thrust generated by the drive unit 47. The steering unit 48 includes a steering shaft 55 and a steering motor 56 (exemplary auxiliary propulsion device rudder angle changing mechanism). The steering shaft 55 is joined to the upper and lower housings 43 and 44. The steering motor 56 generates a driving force for rotating the steering shaft 55 about the axis thereof. The steering unit 48 may include a reduction gear that reduces the speed of the rotation of the steering motor 56 and transmits the rotation reduced in speed to the steering shaft 55. When the steering motor 56 is driven, the upper and lower housings 43 and 44 are rotated about the steering shaft 55, whereby the direction of the thrust generated by the drive unit 47 is made changeable right and left.

[0030] The watercraft 1 includes a tilt unit 60 and a tilt angle sensor 61. The tilt unit 60 includes a tilt cylinder 62. The tilt cylinder 62 may be a hydraulic cylinder of an electric pump type that an electric pump is caused to flow a hydraulic oil. The tilt cylinder 62 is rotatably joined at one end thereof to a lower support portion 41a of the bracket 41. The tilt cylinder 62 is rotatably joined at the other end thereof to the base 42 through a cylinder coupling bracket 63. The bracket 41 supports a tilt shaft 64 at an upper support portion 41b thereof. The base 42 is joined to the bracket 41 through the tilt shaft 64, while being rotatable about the tilt shaft 64. The tilt shaft 64 extends in the right-and-left direction of the hull 2. The base 42 is configured to be rotatable with respect to the bracket 41 in the up-and-down direction. Accordingly, the auxiliary propulsion device 4 is made movable up and down by rotating about the tilt shaft 64 with respect to the hull 2.

[0031] FIG. 7 is a diagram showing a configuration of the watercraft propulsion system 100 installed in the watercraft 1. The watercraft propulsion system 100 includes the principal and auxiliary propulsion devices 3 and 4 described above. The watercraft propulsion system 100 includes a main controller 101, an intra-watercraft network (CAN (Controller Area Network)) 102, an outboard motor control network 103, a control panel network 104, the steering wheel unit 65, a remote control unit 70, the remote control ECU 106, a joystick unit 80, a GPS (Global Positioning System) receiver 108, and a compass sensor 109. The main controller 101 controls the hull 2 as a whole. The main controller 101 includes a processor such as a CPU and memories such as a RAM and a ROM. The main controller 101 has stored programs and data for controlling the hull 2 as a whole. The main controller 101 is connected to the intra-watercraft network 102 established in the hull 2.

[0032] The remote control unit 70, the joystick unit 80, the remote control ECU 106, the GPS receiver 108, and the compass sensor 109 are connected to the intra-watercraft network 102.

[0033] The remote control ECU 106, the steering wheel unit 65, and both the engine ECU 27 and the steering ECU 34 in the principal propulsion device 3 are connected to the outboard motor control network 103. The main controller 101, the remote control ECU 106, the gauge 9, and the auxiliary propulsion device 4 are connected to the control panel network 104. Signals may be transmitted and received in the intra-watercraft network 102, the outboard motor control network 103, and the control panel network 104 through either wired communication or wireless communication, or alternatively, through the Internet.

[0034] The main controller 101 transmits and receives signals to and from a plurality of units connected to the intra-watercraft network 102 and controls not only the principal and auxiliary propulsion devices 3 and 4 but also the other units. The main controller 101 has a plurality of control modes and controls the respective units in aspects preliminarily set in accordance with the control modes, respectively.

[0035] The steering wheel unit 65 is connected to the outboard motor control network 103. The steering wheel unit 65 outputs an operating angle signal, indicating the operating angle of the steering wheel 6, to the outboard motor control network 103. The operating angle signal is received by the remote control ECU 106 and the steering ECU 34. The steering ECU 34 responds to either the operating angle signal generated by the steering wheel unit 65 or a rudder angle command generated by the remote control ECU 106 and controls the steering actuator 33 in response to either the operating angle signal or the rudder angle command. Accordingly, the rudder angle of the principal propulsion device 3 is controlled.

[0036] The remote control unit 70 includes the remote control lever 7. The remote control unit 70 generates and outputs an operating position signal, indicating the operating position of the remote control lever 7, to the intra-watercraft network 102.

[0037] The joystick unit 80 includes the joystick 8. The joystick unit 80 generates an operating position signal indicating the operating position of the joystick 8. The joystick unit 80 includes operating buttons 81 to 85. The joystick unit 80 generates operating signals of the operating buttons 81 to 85 disposed thereon.

[0038] FIG. 8 is a perspective view of the joystick unit 80. The joystick unit 80 includes the joystick 8 enabled to not only tilt forward, rearward, rightward and leftward (i.e., in all compass directions of 360 degrees) but also turn (twist) about the axis thereof. The joystick unit 80 includes a joystick button 81, keeping mode setting buttons 82 to 84 (exemplary mode transitioning command portion), and the thrust setting button 85 (exemplary thrust command portion).

[0039] The joystick button 81 serves as an operating device to be operated by the user when a joystick mode, which is a control mode (watercraft operating mode) with the joystick 8, is selected by the user. As is described below in detail, under the joystick mode, the watercraft 1 is enabled to be operated by operating the joystick 8. Besides, a joystick holding operation is enabled by, for instance, holding down the joystick button 81. The thrust can be kept constant in the joystick holding operation. For example, the thrust can be kept constant when the joystick holding operation is performed, with the joystick 8 being operated.

[0040] The keeping mode setting buttons 82 to 84 serve as operating buttons to be operated by the user for setting control modes related to keeping the position and / or the compass direction (each of which is an exemplary keeping function). Specifically, the keeping mode setting button 82 is operated for setting a fixed spot keeping mode (called "Stay Point" mode) for keeping both the position of the watercraft 1 and the compass direction of the bow (or the stern) of the watercraft 1. The keeping mode setting button 83 is operated for setting a position keeping mode (called "Fish Point" mode) for keeping the position of the watercraft 1 without keeping the compass direction of the bow (or the stern) of the watercraft 1. The keeping mode setting button 84 is operated for setting a compass direction keeping mode (called "Drift Point" mode) for keeping the compass direction of the bow (or the stern) of the watercraft 1 without keeping the position of the watercraft 1. The fixed spot keeping mode, the position keeping mode, and the compass direction keeping mode are examples of the keeping function.

[0041] When each of the keeping mode setting buttons 82 to 84 is operated by the user, a signal for starting a keeping mode associated therewith is outputted to the main controller 101; then, when each of the keeping mode setting buttons 82 to 84 is operated again by the user, a signal for stopping the keeping mode associated therewith is outputted to the main controller 101. For example, when the keeping mode setting button 82 is operated by the user, the fixed spot keeping mode is executed; then, when the keeping mode setting button 82 is operated again by the user, a signal for stopping the fixed spot keeping mode is outputted to the main controller 101.

[0042] The thrust setting button 85 serves as an operating button to be operated by the user for setting the thrust of the auxiliary propulsion device 4. The thrust setting button 85 includes a plus button 85a and a minus button 85b. For example, the magnitude of the thrust is set in a plurality of stages. When the plus button 85a is operated, the thrust is increased in magnitude. When the minus button 85b is operated, the thrust is reduced in magnitude. The setting, made by the thrust setting button 85, is outputted as an output signal to the main controller 101.

[0043] The remote control ECU 106 shown in FIG. 7 includes a processor such as a CPU and memories such as a RAM and a ROM. The remote control ECU 106 has stored programs and data for executing controls to be described below. The remote control ECU 106 outputs a thrust command to the engine ECU 27 through the outboard motor control network 103. The thrust command includes a shift command for instructing a shift position and an output command for instructing an engine output (e.g., engine rotational speed). The remote control ECU 106 outputs the rudder angle command to the steering ECU 34 through the outboard motor control network 103.

[0044] The remote control ECU 106 executes different control actions depending on the control modes of the main controller 101. For example, under a control mode for operating the watercraft 1 (watercraft operating mode) with the steering wheel 6 and the remote control lever 7, the remote control ECU 106 outputs the thrust command (the shift command and the output command) to the engine ECU 27 in accordance with the operating position signal generated by the remote control unit 70. The remote control ECU 106 outputs the rudder angle command to the steering ECU 34 in accordance with the operating angle signal generated by the steering wheel unit 65.

[0045] On the other hand, under a control mode for operating the watercraft 1 without operating the steering wheel 6 and the remote control lever 7, the remote control ECU 106 operates in accordance with the command issued by the main controller 101. The remote control ECU 106 outputs the thrust command (the shift command and the output command) to the engine ECU 27 in accordance with an operating position signal generated by the main controller 101. The remote control ECU 106 outputs the rudder angle command to the steering ECU 34 in accordance with the operating angle signal generated by the main controller 101. It should be noted that the rudder angle command includes a command for instructing a target value of the rudder angle and a command for instructing a rudder rate of the principal propulsion device 3, i.e., a speed at which the principal propulsion device 3 is changed in rudder angle.

[0046] For example, under the control mode for operating the watercraft 1 with the joystick 8, the main controller 101 generates the thrust command (the shift command and the output command) and the rudder angle command in accordance with the signal generated by the joystick unit 80; then, the remote control ECU 106 receives the thrust command and the rudder angle command and outputs the thrust command and the rudder angle command to the principal propulsion device 3.

[0047] The engine ECU 27 drives the shift actuator 30 in accordance with the shift command so as to control the shift position. The engine ECU 27 drives the throttle actuator 28 in accordance with the output command so as to control the throttle opening degree. The steering ECU 34 drives the steering actuator 33 in accordance with the rudder angle command so as to control the rudder angle of the principal propulsion device 3.

[0048] The auxiliary propulsion device 4 includes a motor controller 110 and a steering controller 111. The motor controller 110 and the steering controller 111 are connected to the intra-watercraft network 102. The motor controller 110 and the steering controller 111 actuate the auxiliary propulsion device 4 in response to commands outputted thereto from the main controller 101. The main controller 101 outputs a thrust command and a rudder angle command to the auxiliary propulsion device 4. The thrust command includes a shift command (rotational direction command) and an output command. The shift command serves as a rotational direction command for causing the propeller 49 to stop, rotate in a forward moving rotational direction, or rotate in a rearward moving rotational direction. The output command serves as a command for instructing a magnitude of the thrust to be generated, i.e., a target value for the thrust (as well as the rotational speed). The rudder angle command includes a command for instructing a target value for the rudder angle and a command for instructing a rudder rate of the auxiliary propulsion device 4, i.e., a speed at which the auxiliary propulsion device 4 is changed in rudder angle.

[0049] The motor controller 110 controls the electric motor 50 in accordance with the shift command (rotational direction command) and the output command. The motor controller 110 includes a processor such as a CPU and memories such as a RAM and a ROM. The motor controller 110 has stored programs and data for controlling the electric motor 50.

[0050] The steering controller 111 controls the steering motor 56 in accordance with the rudder angle command. The steering controller 111 includes a processor such as a CPU and memories such as a RAM and a ROM. The steering controller 111 has stored programs and data for controlling the steering motor 56.

[0051] The main controller 101 outputs a tilt command to the motor controller 110 through the intra-watercraft network 102. The motor controller 110 causes the tilt cylinder 62 to expand and contract in accordance with a tilt command signal such that the auxiliary propulsion device 4 performs a tilt-up motion or a tilt-down motion. The motor controller 110 receives a detection signal inputted thereto from the tilt angle sensor 61. Accordingly, the motor controller 110 obtains information regarding the tilt angle of the auxiliary propulsion device 4 and is enabled to transmit the information regarding the tilt angle to the main controller 101.

[0052] The GPS receiver 108 receives radio waves from artificial satellites circulating about the Earth, specifies the position of the watercraft 1, and outputs not only position data indicating the position of the watercraft 1 but also velocity data indicating the moving speed of the watercraft 1. The position data and the velocity data are obtained by the main controller 101 and are used for displaying or controlling at least either the position or the compass direction of the watercraft 1.

[0053] The compass sensor 109 detects the compass direction of the watercraft 1 and generates compass direction data. The compass direction data are obtained by the main controller 101.

[0054] The gauge 9 is connected to the main controller 101 through the control panel network 104. As described above, the gauge 9 displays a variety of information for operating the watercraft 1. The gauge 9 is connected to the remote control ECU 106, the motor controller 110, and the steering controller 111 through the control panel network 104. The gauge 9 displays a variety of information regarding the operating state of the principal propulsion device 3, that of the auxiliary propulsion device 4, the position or the compass direction of the watercraft 1, and so forth. The gauge 9 may be provided with an input device 9a including a touchscreen, one or more buttons, and so forth. When operated by the user, the input device 9a may be configured to output an operating signal to the control panel network 104, whereby various settings or commands are made executable.

[0055] The watercraft propulsion system 100 includes a power switch unit 120. The power switch unit 120 serves as a switch operated by the user so as to power on the principal propulsion device 3 and then further start and stop the engine 19. The power switch unit 120 includes a power switch 121, a start switch 122 (exemplary principal propulsion device command portion), and a stop switch 123 (exemplary principal propulsion device command portion). The power switch 121 serves as a switch for powering on and powering off the principal propulsion device 3. The power switch 121 also serves as a power-supply switch for the watercraft propulsion system 100 per se. The start switch 122 serves as a switch for starting the engine 19. When the start switch 122 is operated, the engine 19 starts cranking. The stop switch 123 serves as a switch for stopping the engine 19.

[0056] When the power switch 121 is operated to be turned on, the remote control ECU 106 executes a control for electrifying the principal propulsion device 3. When the power switch 121 is operated to be turned on, a power supply relay (not illustrated in the drawing), interposed between the battery 130 (of e.g., 12V) and the principal propulsion device 3, is turned on. When the start switch 122 is operated, while the principal propulsion device 3 is in a powered-on state, the remote control ECU 106 issues a start command to the engine ECU 27. Accordingly, the engine ECU 27 actuates the starter motor 25 (see FIG. 3) to start the engine 19. While the engine 19 is operating, the battery 130 is charged with the electric power generated by the electric power generator 26 (see FIG. 3). When the stop switch 123 is operated, while the engine 19 is operating, the remote control ECU 106 issues a stop command to the engine ECU 27. In response to the stop command, the engine ECU 27 executes a control for stopping the engine 19. The remote control ECU 106 outputs principal propulsion device state information, indicating whether or not the principal propulsion device 3 is in the powered-on state and whether or not the engine 19 is in a started state, to the main controller 101 through the intra-watercraft network 102.

[0057] The watercraft propulsion system 100 includes a power switch unit 140. The power switch unit 140 is connected to the auxiliary propulsion device 4 to power on or power off the auxiliary propulsion device 4. The power switch unit 140 includes a power switch 141 (exemplary auxiliary propulsion device command portion). When the power switch 141 is operated to be turned on or turned off, while the power switch 121 is in a turned-on state, a circuit interposed between the auxiliary propulsion device 4 and a battery 145 (of e.g., 48V) for electrifying the auxiliary propulsion device 4 is closed or opened, whereby the auxiliary propulsion device 4 is enabled to be powered on or powered off. The motor controller 110 outputs auxiliary propulsion device state information, indicating whether or not the auxiliary propulsion device 4 is in a powered-on state, i.e., whether or not the auxiliary propulsion device 4 is in a drivable state, to the main controller 101 through the intra-watercraft network 102. The battery 145 is enabled to receive the electric power generated by the electric power generator 26 (see FIG. 3) in the principal propulsion device 3 through a DC / DC converter 146 (voltage converter).

[0058] The watercraft propulsion system 100 includes an application switch panel 150. The application switch panel 150 is connected to the intra-watercraft network 102. The application switch panel 150 includes a plurality of function switches 151, each of which serves to issue a command for executing a function preliminarily defined in association therewith. For example, the function switches 151 may include a switch for issuing a command for operating the watercraft 1 in an automated manner. More specifically, the function switches 151 may include a switch associated with automated steering for keeping the compass direction of the watercraft 1, a switch associated with automated steering for keeping the route of the watercraft 1, a switch associated with automated steering for causing the watercraft 1 to sequentially pass through a plurality of specified spots, a switch associated with automated steering for moving the watercraft 1 in a predetermined sailing pattern (a zigzag pattern, a spiral pattern, etc.), and so forth. Besides, the function switches 151 may be associated with a function for tilting up the auxiliary propulsion device 4 and / or that for tilting down the auxiliary propulsion device 4.

[0059] The main controller 101 executes controls for the principal and auxiliary propulsion devices 3 and 4 under a plurality of control modes. The control modes include a plurality of modes defined depending on the states of the principal and auxiliary propulsion devices 3 and 4. Specifically, the main controller 101 executes an electric mode, an engine mode, a dual mode, and an extender mode. The main controller 101 operates under any of the control modes based on the principal propulsion device state information and the auxiliary propulsion device state information.

[0060] FIG. 9 is a table for explaining actions enabled to be performed by the principal and auxiliary propulsion devices 3 and 4 under each of the following modes: the electric mode, the engine mode, the dual mode, and the extender mode.

[0061] The engine mode serves as a control mode executed when the engine 19 in the principal propulsion device 3 is in the started state, while the auxiliary propulsion device 4 is in a powered-off state. In other words, the engine mode serves as a control mode for causing only the principal propulsion device 3 to generate a thrust. Under the engine mode, when the steering wheel 6 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; however, the auxiliary propulsion device 4 is not enabled to change in rudder angle even when the steering wheel 6 is operated. Under the engine mode, when the remote control unit 70 is operated, the throttle actuator 28 and the shift actuator 30 are driven, whereby the principal propulsion device 3 is enabled to generate a thrust; however, the auxiliary propulsion device 4 is not enabled to generate a thrust even when the remote control unit 70 is operated. Under the engine mode, when the joystick unit 80 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; however, the auxiliary propulsion device 4 is not enabled to change in rudder angle even when the joystick unit 80 is operated. Besides, under the engine mode, when the joystick unit 80 is operated, the throttle actuator 28 and the shift actuator 30 are driven, whereby the principal propulsion device 3 is enabled to generate a thrust; however, the auxiliary propulsion device 4 is not enabled to generate a thrust even when the joystick unit 80 is operated. It should be noted that the state "the principal propulsion device 3 is enabled to generate a thrust" refers to a state that the principal propulsion device 3 is enabled to generate a thrust by driving the throttle actuator 28 and the shift actuator 30. On the other hand, the state "the auxiliary propulsion device 4 is enabled to generate a thrust" refers to a state that the auxiliary propulsion device 4 is enabled to generate a thrust by driving the electric motor 50.

[0062] The electric mode serves as a control mode executed when the auxiliary propulsion device 4 is in the powered-on state by operating the power switch 141 to be turned on but the engine 19 is not in the started state (exemplary stopped state) without operating the start switch 122. The electric mode serves as a control mode executed for causing only the auxiliary propulsion device 4 to generate a thrust. Under the electric mode, when the steering wheel 6 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; however, the auxiliary propulsion device 4 is not enabled to change in rudder angle even when the steering wheel 6 is operated. Under the electric mode, even when the remote control unit 70 is operated, both the principal and auxiliary propulsion devices 3 and 4 are not enabled to generate thrusts. Under the electric mode, when the joystick unit 80 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; on the other hand, the steering motor 56 is driven when the joystick unit 80 is operated, whereby the auxiliary propulsion device 4 is enabled to change in rudder angle. Under the electric mode, when the joystick unit 80 is operated, the electric motor 50 is driven, whereby the auxiliary propulsion device 4 is enabled to generate a thrust; however, the principal propulsion device 3 is not enabled to generate a thrust even when the joystick unit 80 is operated.

[0063] The dual mode and the extender mode serve as control modes executed when the auxiliary propulsion device 4 is in the powered-on state as a result of operating the power switch 141 to be turned on, while the engine 19 in the principal propulsion device 3 is in the started state as a result of operating the start witch 122 to be turned on. The dual mode serves as a control mode for utilizing both the thrusts generated by the principal and auxiliary propulsion devices 3 and 4. The extender mode serves as a control mode for utilizing only the thrust generated by the auxiliary propulsion device 4, whereas the engine 19 operates for generating electric power for charging the battery 145. From the perspective of thrust generating aspects, the electric mode and the extender mode are identical to each other.

[0064] The dual mode and the extender mode may be switched in an automated manner depending on the magnitude of a thrust to be required. For example, the dual mode and the extender mode may be switched in an automated manner in accordance with operating the thrust setting button 85 provided in the joystick unit 80 to regulate (increase and reduce) the magnitude of the thrust. For example, the magnitude of the thrust can be set in a plurality of stages. When the magnitude of the thrust is greater than a predetermined value, the main controller 101 is enabled to set the dual mode as the control mode; by contrast, when the magnitude of the thrust is less than or equal to the predetermined value, the main controller 101 is enabled to set the extender mode as the control mode. Besides, which to select between the dual mode and the extender mode may be made by a setting or command by the user. For example, such a setting or command is made by operating the input device 9a provided in the gauge 9.

[0065] Under the dual mode and the extender mode, when the steering wheel 6 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; however, the auxiliary propulsion device 4 is not enabled to change in rudder angle even when the steering wheel 6 is operated. Under the dual mode, when the remote control unit 70 is operated, the throttle actuator 28 and the shift actuator 30 are driven, whereby the principal propulsion device 3 is enabled to generate a thrust. However, under the dual mode and the extender mode, even when the remote control unit 70 is operated, the auxiliary propulsion device 4 is not enabled to generate a thrust. Under the dual mode and the extender mode, when the joystick unit 80 is operated, the steering actuator 33 is driven, whereby the principal propulsion device 3 is enabled to change in rudder angle; on the other hand, the steering motor 56 is driven when the joystick unit 80 is operated, whereby the auxiliary propulsion device 4 is enabled to change in rudder angle. Under the dual mode, when the joystick unit 80 is operated, the electric motor 50 is driven, whereby the auxiliary propulsion device 4 is enabled to generate a thrust; on the other hand, the throttle actuator 28 and the shift actuator 30 are driven when the joystick unit 80 is operated, whereby the principal propulsion device 3 is enabled to generate a thrust. Under the extender mode, when the joystick unit 80 is operated, the electric motor 50 is driven, whereby the auxiliary propulsion device 4 is enabled to generate a thrust; however, the principal propulsion device 3 is not enabled to be generate a thrust when the joystick unit 80 is operated. Thus, when the thrust to be required is large in magnitude, the principal and auxiliary propulsion devices 3 and 4 generate thrusts under the dual mode; by contrast, when the thrust to be required is small in magnitude, not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust under the extender mode.

[0066] From the perspective of operating aspects, the control modes for the main controller 101 can be classified into a normal mode, a joystick mode, and a keeping mode.

[0067] The normal mode serves as a control mode for executing a steering control in accordance with the operating angle signal generated by the steering wheel unit 65 and for executing a thrust control in accordance with the operating signal (operating position signal) of the remote control lever 7. The normal mode serves as, for instance, a default control mode of the main controller 101. The steering control refers to, specifically, a control action executed by the steering ECU 34 to drive the steering actuator 33 in accordance with the operating angle signal generated by the steering wheel unit 65 or the rudder angle command outputted from the remote control ECU 106. Accordingly, the body of the principal propulsion device 3 pivots right and left to change in rudder angle, whereby the direction of the thrust is changed right and left with respect to the hull 2. The thrust control refers to, specifically, a control action executed by the engine ECU 27 to drive the shift actuator 30 and the throttle actuator 28 in accordance with the thrust command (the shift command and the output command) issued from the remote control ECU 106 to the engine ECU 27. Accordingly, the forward moving position, the rearward moving position, or the neutral position is set as the shift position in the principal propulsion device 3; simultaneously, the engine output (specifically, the engine rotational speed) is changed.

[0068] The joystick mode serves as a control mode for executing the steering control and the thrust control in accordance with the operating signal of the joystick 8 in the joystick unit 80. When the joystick button 81 is pressed down in the joystick unit 80, the main controller 101 transitions to the joystick mode.

[0069] Under the joystick mode, the steering control and the thrust control are executed for the principal propulsion device 3 in a state that the principal propulsion device 3 is enabled to generate a thrust and is also enabled to change in rudder angle under the engine mode or the dual mode described above. In other words, the main controller 101 issues the steering angle command and the thrust command to the remote control ECU 106; then, the remote control ECU 106 outputs the steering angle command and the thrust command to the steering ECU 34 and the engine ECU 27, respectively.

[0070] Under the joystick mode, the steering control is executed for the principal propulsion device 3 in a state that only change in rudder angle is enabled for the principal propulsion device 3 under the electric mode or the extender mode described above. In other words, the main controller 101 issues the rudder angle command to the remote control ECU 106; then, the remote control ECU 106 outputs the rudder angle command to the steering ECU 34.

[0071] Besides, under the joystick mode, the steering control and the thrust control are executed for the auxiliary propulsion device 4 in a state that the auxiliary propulsion device 4 is enabled to generate a thrust and is enabled to change in rudder angle under the electric mode, the dual mode, or the extender mode. The steering control executed for the auxiliary propulsion device 4 refers to, specifically, a control action executed by the steering controller 111 in the auxiliary propulsion device 4 to control and cause the steering motor 56 to drive the steering unit 48 in accordance with the steering angle command issued from the main controller 101 to the steering controller 111. Accordingly, the drive unit 47 and the upper housing 43 in the auxiliary propulsion device 4 pivot right and left, whereby the direction of the thrust is changed right and left with respect to the hull 2. The thrust control executed for the auxiliary propulsion device 4 refers to, specifically, an action executed by the motor controller 110 in the auxiliary propulsion device 4 to control the rotational direction and the rotational speed of the electric motor 50 in accordance with the thrust command (the shift command and the output command) outputted from the main controller 101 to the motor controller 110. Accordingly, the rotational direction of the propeller 49 is set to either the forward moving rotational direction or the rearward moving rotational direction; simultaneously, the rotational speed of the propeller 49 is changed.

[0072] The joystick mode includes two types of mode settings: a first joystick mode and a second joystick mode. When the command for selecting the joystick mode is issued by the joystick button 81 under the dual mode, the main controller 101 executes the control processing under the first joystick mode. On the other hand, when the command for selecting the joystick mode is issued by the joystick button 81 under any of the modes other than the dual mode (i.e., the electric mode, the engine mode, or the extender mode), the main controller 101 executes the control processing under the second joystick mode.

[0073] Under the first joystick mode, when the joystick 8 is tilted, the main controller 101 interprets the direction of tilting the joystick 8 as a command for instructing a moving direction, while interpreting the amount of tilting the joystick 8 as a command for instructing the magnitude of the thrust oriented in the moving direction. Besides, when the joystick 8 is turned (twisted) about the axis thereof, the main controller 101 interprets the direction of twisting the joystick 8 (with reference to the neutral position thereof) as a command for instructing a bow turning direction, while interpreting the amount of twisting the joystick 8 (with reference to the neutral position thereof) as a command for instructing a bow turning speed. Here, the main controller 101 inputs the rudder angle command and the thrust command for realizing the above-mentioned commands to the remote control ECU 106; then, the remote control ECU 106 inputs the rudder angle command the thrust command for realizing the above-mentioned commands to the steering controller 111 and the motor controller 110 in the auxiliary propulsion device 4, respectively. The remote control ECU 106 transmits the rudder angle command and the thrust command to the steering ECU 34 and the engine ECU 27 in the principal propulsion device 3, respectively. Accordingly, the principal propulsion device 3 is changed in rudder angle to the rudder angle instructed as described above and controls the shift position and the engine rotational speed so as to generate the thrust instructed as described above. On the other hand, the auxiliary propulsion device 4 controls the steering motor 56 to change the drive unit 47 and the upper housing 43 in rudder angle to the rudder angle instructed as described above and controls the rotational direction and the rotational speed of the electric motor 50 so as to generate the thrust instructed as described above.

[0074] Under the second joystick mode, when the joystick 8 is tilted in the back-and-forth direction, the main controller 101 interprets the tilt operation for the joystick 8 as the thrust command (the shift command and the output command). The main controller 101 ignores tilting the joystick 8 in the right-and-left direction. In other words, when the joystick 8 is operated to tilt, only a back-and-forth directional component of the tilt operation for the joystick 8 is accepted as an effective input; then, the back-and-forth directional component is interpreted as the thrust command. Specifically, the back-and-forth directional component is interpreted as a forward moving shift command when having a value to be obtained when the joystick 8 is tilted forward; contrarily, the back-and-forth directional component is interpreted as a rearward moving shift command when having a value to be obtained when the joystick 8 is tilted rearward. Then, the magnitude of the back-and-forth directional component is interpreted as a command for instructing the magnitude of the thrust (the output command). The thrust command, interpreted as described above, is inputted from the main controller 101 to the remote control ECU 106 (under the engine mode) or the motor controller 110 (under the electric mode or the extender mode). On the other hand, under the second joystick mode, when the joystick 8 is twisted about the axis thereof, the main controller 101 interprets the twist operation for the joystick 8 as the rudder angle command. In other words, the main controller 101 inputs the rudder angle command, depending on the direction and the amount of twisting the joystick 6 about the axis thereof, to the remote control ECU 106 (under the engine mode, the electric mode, or the extender mode) or the steering controller 111 (under the electric mode or the extender mode).

[0075] The fixed spot keeping mode (Stay Point mode), the position keeping mode (Fish Point mode), and the compass direction keeping mode (Drift Point mode), set by operating the keeping mode setting buttons 82, 83, and 84, respectively, as described above are examples of the keeping function. Under the keeping mode, the output and the rudder angle of at least one of the principal and auxiliary propulsion devices 3 and 4 are controlled without any manual operation by the watercraft operator.

[0076] For example, under the fixed spot keeping mode (Stay Point mode), the main controller 101 controls the output and the rudder angle of the principal propulsion device 3 and those of the auxiliary propulsion device 4 based on the position data and the velocity data, both of which are generated by the GPS receiver 108, and the compass direction data generated by the compass sensor 109. Accordingly, fluctuations in position and compass direction of the hull 2 are inhibited. Under the fixed spot keeping mode (Stay Point mode), the principal and auxiliary propulsion devices 3 and 4 are used in combination such that the hull 2 is enabled to move transversely. Because of this, under the fixed spot keeping mode, each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust and is controlled in rudder angle. Under the fixed spot keeping mode, an automated operation is executed based on the dual mode.

[0077] On the other hand, under the position keeping mode (Fish Point mode), the main controller 101 controls the output and the rudder angle of at least one of the principal and auxiliary propulsion devices 3 and 4 based on the position data and the velocity data, both of which are generated by the GPS receiver 108. Accordingly, fluctuations in position of the hull 2 are inhibited. Under the position keeping mode (Fish Point mode), any of the following control actions is executed: a control action that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust, while each of the principal and auxiliary propulsion devices 3 and 4 is controlled in rudder angle, a control action that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust, while each of the principal and auxiliary propulsion devices 3 and 4 is controlled in rudder angle, and a control action that not the auxiliary propulsion device 4 but the principal propulsion device 3 only generates a thrust, while not the auxiliary propulsion device 4 but the principal propulsion device 3 only is controlled in rudder angle. Under the position keeping mode, an automated operation is executed based on the dual mode, the electric mode, the extender mode, or the engine mode.

[0078] Yet on the other hand, under the compass direction keeping mode (Drift Point mode), the main controller 101 controls the output and the rudder angle of at least one of the principal and auxiliary propulsion devices 3 and 4 based on the compass direction data generated by the compass sensor 109. Accordingly, fluctuations in compass direction of the hull 2 are inhibited. Under the compass direction keeping mode (Drift Point mode), any of the following control actions is executed: a control action that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust, while each of the principal and auxiliary propulsion devices 3 and 4 is controlled in rudder angle, a control action that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust, while each of the principal and auxiliary propulsion devices 3 and 4 is controlled in rudder angle, and a control action that not the auxiliary propulsion device 4 but the principal propulsion device 3 only generates a thrust, while not the auxiliary propulsion device 4 but the principal propulsion device 3 only is controlled in rudder angle. Under the compass direction keeping mode, an automated operation is executed based on the dual mode, the electric mode, the extender mode, or the engine mode.

[0079] FIG. 10 is composed of diagrams for explaining steering of the watercraft 1. FIG. 10(a) is a plan view of the joystick unit 80. FIG. 10(b) is a schematic plan view of the watercraft 1. In FIG. 10(b), under the dual mode, the principal propulsion device 3 generates a thrust (indicated by arrow A2), while the auxiliary propulsion device 4 generates a thrust (indicated by arrow A1 ) as well, whereby the watercraft 1 is moved forward (see arrows A1 and A2). When the joystick 8 is twisted leftward as indicated by arrow L in FIG. 10(a), the main controller 101 causes each of the principal and auxiliary propulsion devices 3 and 4 to change in rudder angle such that the watercraft 1 is moved leftward. Specifically, as shown in FIG. 10(c), the main controller 101 causes each of the principal and auxiliary propulsion devices 3 and 4 to change in rudder angle (see arrow C) such that a thrust generated from each of the principal and auxiliary propulsion devices 3 and 4 is oriented in a right front direction. The main controller 101 outputs a rudder angle command to the steering ECU 34 of the principal propulsion device 3 through the remote control ECU 106. The steering ECU 34 drives the steering actuator 33 based on the rudder angle command, whereby the principal propulsion device 3 is changed in rudder angle. The main controller 101 outputs a rudder angle command to the steering controller 111 in the auxiliary propulsion device 4. The steering controller 111 drives the steering motor 56 based on the rudder angle command, whereby the auxiliary propulsion device 4 is changed in rudder angle.

[0080] FIG. 11 is a chart showing change in time of the rudder angle of the auxiliary propulsion device 4 and change in time of the rudder angle of the principal propulsion device 3 in the state that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust. The horizontal axis indicates time, while the vertical axis indicates the rudder angle. For example, the rudder angle of each of the principal and auxiliary propulsion devices 3 and 4 is defined as 0 degrees when the thrust generated from each of the principal and auxiliary propulsion devices 3 and 4 is oriented along the back-and-forth direction. Then, the rudder angle is set to gradually increase to have a positive value with change in orientation of the thrust to the right side; by contrast, the rudder angle is set to gradually reduce to have a negative value with change in orientation of the thrust to the lefts side. Change in time of the rudder angle of the auxiliary propulsion device 4 is indicated by a graph G1 (of dashed dotted line), while change in time of the rudder angle of the principal propulsion device 3 is indicated by a graph G2 (of solid line). Besides, the maximum rudder angle of the auxiliary propulsion device 4 is set to be θ1, while that of the principal propulsion device 3 is set to be θ2.

[0081] As shown in FIG. 11, when steering of the hull 2 is executed in the state that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust, the main controller 101 controls the steering actuator 33 and the steering motor 56 such that the principal and auxiliary propulsion devices 3 and 4 are made equal in rudder range to each other. In the example of the present preferred embodiment, the maximum rudder angle θ1 of the auxiliary propulsion device 4 is set to be greater than the maximum rudder angle θ2 of the principal propulsion device 3. Besides, an operating command for changing the rudder angle to the maximum rudder angle θ1 is transmitted to the main controller 101 by operating the joystick 8. When the auxiliary propulsion device 4 begins to change in rudder angle, the principal propulsion device 3 simultaneously begins to change in rudder angle as well; then, the principal and auxiliary propulsion devices 3 and 4 are changed in rudder angle at an equal speed. Then, when reaching the maximum rudder angle θ2, the rudder angle of the principal propulsion device 3 is kept at the maximum rudder angle θ2. On the other hand, even after reaching the rudder angle θ2, the rudder angle of the auxiliary propulsion device 4 continues to be changed; then, when reaching the maximum rudder angle θ1, the rudder angle of the auxiliary propulsion device 4 is kept at the maximum rudder angle θ1.

[0082] Thus, when the steering operation is executed by the joystick 8 in the state that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust (under the dual mode), the main controller 101 causes the principal and auxiliary propulsion devices 3 and 4 to change in rudder angle at an equal speed.

[0083] On the other hand, under the electric mode and the extender mode, the auxiliary propulsion device 4 generates a thrust but the principal propulsion device 3 does not generate a thrust.

[0084] When steering of the hull 2 is thus executed under the electric mode and the extender mode that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust as described above, the main controller 101 controls the steering actuators 33 and the steering motor 56 such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4.

[0085] On the other hand, the following explanation relates to a control action to be executed when steering of the watercraft 1 is executed in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust. FIG. 12 is composed of diagrams for explaining the steering of the watercraft 1. FIG. 12(a) is a plan view of the joystick unit 80. FIG. 12(b) is a schematic plan view of the watercraft 1. In FIG. 12(b), under the electric mode or the extender mode, not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust (depicted with arrow A1 ), whereby the watercraft 1 is moved forward. As indicated with arrow L in FIG. 12(a), when the joystick 8 is twisted leftward, the main controller 101 causes each of the principal and auxiliary propulsion devices 3 and 4 to change in rudder angle (see arrow C in FIG. 12(c)) such that the watercraft 1 is moved leftward.

[0086] FIG. 13 is a chart showing change in time of the rudder angle of the auxiliary propulsion device 4 and change in time of the rudder angle of the principal propulsion device 3 in the state that not the principal propulsion device 3 but the auxiliary propulsion devices 4 only generates a thrust. The settings for the horizontal and vertical axes are identical to those in FIG. 11. Change in time of the rudder angle of the auxiliary propulsion device 4 is indicated by a graph G1 (of dashed dotted line), while change in time of the rudder angle of the principal propulsion device 3 is indicated by a chart G2' (of solid line).

[0087] As shown in FIG. 13, when steering of the hull 2 is executed in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust, the main controller 101 controls the steering actuator 33 and the steering motor 56 such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. The main controller 101 calculates the rudder rate of the principal propulsion device 3 by processing the rudder rate of the auxiliary propulsion device 4 (or the rudder rate of the principal propulsion device 3 from which a thrust is being generated) with weighted average filtering and first-order lag filtering and controls the steering actuator 33 so as to obtain the rudder rate.

[0088] It should be noted that FIG. 13 shows that the rudder angle is changed from 0 degrees; however, even when the rudder angle is changed from any angle other than 0 degrees, the steering motor 56 and the steering actuator 33 are controlled in a comparable manner such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4.

[0089] It should be noted that such a control action in steering as described above is executed when the joystick 8 is operated under the joystick mode, when the rudder angle is controlled under the position keeping mode and the compass direction keeping mode, both of which compose the keeping mode, and when the rudder angle is controlled in an automated operation associated with one selected among the function switches 151, with the joystick holding operation being performed. In other words, when steering of the hull 2 is executed in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust, the control action is executed such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. On the other hand, as described above, when steering of the hull 2 is executed in the state that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust, the control action is executed such that the principal and auxiliary propulsion devices 3 and 4 are changed in rudder angle at an equal speed.

[0090] Next, a series of control actions to be executed by the watercraft propulsion system 100 according to the present preferred embodiment will be explained; simultaneously, a method of propelling a watercraft will be described below. FIG. 14 is a flowchart showing the series of control actions to be executed by the watercraft propulsion system 100 according to the present preferred embodiment. It should be noted that the series of control actions shown in FIG. 14 are executed by the watercraft propulsion system 100 under the joystick mode, the position keeping mode, the compass direction keeping mode, or the automated operation for keeping the compass direction with performing of the joystick holding operation.

[0091] First, in step S1, the main controller 101 determines whether or not the auxiliary propulsion device 4 is in the powered-on state. The main controller 101 is enabled to determine whether or not the auxiliary propulsion device 4 is in the powered-on state based on the auxiliary propulsion device state information transmitted thereto from the motor controller 110.

[0092] When it is determined that the auxiliary propulsion device 4 is in the powered-on state in step S1, the main controller 101 determines whether or not the engine 19 in the principal propulsion device 3 is in the started state in step S2. The main controller 101 is enabled to determine whether or not the engine 19 in the principal propulsion device 3 is in the started state based on the principal propulsion device state information transmitted thereto from the remote control ECU 106.

[0093] In step S2, when it is determined that the engine 19 in the principal propulsion device 3 is not in the started state, the control processing proceeds to step S3. When it is determined that the engine 19 is not in the started state in step S2, the main controller 101 executes the electric mode.

[0094] In step S3, when steering is requested in a state that the auxiliary propulsion device 4 generates a thrust, the control processing proceeds to step S4. By contrast, when steering is not requested in step S3, the control processing ends. It is determined that steering is requested when the joystick 8 is operated under the joystick mode, when steering is required in the automated control under the position keeping mode and the compass direction keeping mode, and when steering is required in the automated operation, with the joystick holding operation being performed.

[0095] When steering is requested in step S3, the main controller 101 executes the following in step S4. The main controller 101 generates a rudder angle command for the auxiliary propulsion device 4 and then transmits the rudder angle command to the steering controller 111; besides, the main controller 101 generates a rudder angle command for the principal propulsion device 3 and then transmits the rudder angle command to the steering ECU 34 through the remote control ECU 106. Under the joystick mode, the main controller 101 generates the rudder angle command based on the operation of the joystick 8. Under the position keeping mode and the compass direction keeping mode, the main controller 101 generates the rudder angle command on an as-needed basis under the automated control associated with the one operated in the keeping mode setting buttons 83 and 84. On the other hand, when the automated operation is executed, with the joystick holding operation being performed, the main controller 101 generates the rudder angle command in accordance with the automated operation.

[0096] Here, the main controller 101 generates the rudder angle command to be transmitted to the steering controller 111 and that to be transmitted to the steering ECU 34 such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. The main controller 101 generates a rudder rate of the principal propulsion device 3 by processing a rudder rate, included in the rudder angle command to be transmitted to the steering controller 111 in the auxiliary propulsion device 4, with weighted average filtering and first-order lag filtering; then, with the use of the rudder rate herein generated, the main controller 101 generates the rudder angle command to be transmitted to the steering ECU 34 in the principal propulsion device 3. The steering controller 111 drives the steering motor 56 in response to the rudder angle command transmitted thereto, while the steering ECU 34 drives the steering actuator 33 in response to the rudder angle command transmitted thereto.

[0097] Based on the above, the control action can be executed such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. Change in rudder angle is controlled for each of the principal and auxiliary propulsion devices 3 and 4 as described above; then, the control processing ends.

[0098] In step S2, when it is determined that the engine 19 in the principal propulsion device 3 is in the started state, the control processing proceeds to step S5. The main controller 101 determines whether or not the thrust is set to have a magnitude less than or equal to a predetermined value in step S5. The magnitude herein set for the thrust refers to a magnitude to be set for the thrust by the thrust setting button 85.

[0099] In step S5, when it is determined that the thrust is set to have a magnitude less than or equal to the predetermined value, the main controller 101 executes the extender mode. In this case, the control processing proceeds to step S3; then, when steering is requested as described above, the process in step S4 is executed.

[0100] By contrast, in step S5, when it is determined that the thrust is set to have a magnitude greater than the predetermined value, the control action is executed under the dual mode as described above.

[0101] As shown in FIG. 9, under the dual mode, the auxiliary propulsion device 4 is changed in rudder angle together with the principal propulsion device 3. In step S6, when steering is required in the state that each of the principal and auxiliary propulsion devices 3 and 4 generates a thrust, the main controller 101 executes the following in step S7. The main controller 101 generates a rudder angle command for the auxiliary propulsion device 4 and transmits the rudder angle command to the steering controller 111; besides, the main controller 101 generates a rudder angle command for the principal propulsion device 3 and transmits the rudder angle command to the steering ECU 34 through the remote control ECU 106. In step S7, the main controller 101 generates the rudder angle command to be transmitted to the steering controller 111 and that to be transmitted to the steering ECU 34 such that the principal and auxiliary propulsion devices 3 and 4 are made equal in rudder rate to each other. The steering controller 111 drives the steering motor 56 in response to the rudder angle command transmitted thereto, while the steering ECU 34 drives the steering actuator 33 in response to the rudder angle command transmitted thereto.

[0102] Accordingly, the control action is executed such that the principal and auxiliary propulsion devices 3 and 4 are made equal in rudder rate to each other. Change in rudder angle is executed for each of the principal and auxiliary propulsion devices 3 and 4 as described above; then, the control processing ends. It should be noted that in a state that the principal propulsion device 3 generates a thrust, the principal and auxiliary propulsion devices 3 and 4 can be made equal in rudder rate to each other because vibrations to be caused are less affected by steering of the principal propulsion device 3.

[0103] In step S1, when it is determined that the auxiliary propulsion device 4 is in the powered-off state, the control action is executed under the engine mode. Then, in step S8, when steering is requested in the state that the principal propulsion device 3 generates a thrust, the main controller 101 generates a rudder angle command and transmits the rudder angle command to the steering ECU 34 through the remote control ECU 106 in step S9. The rudder rate, included in the rudder angle command, may be comparable to that in step S7.

[0104] It should be noted that the above-mentioned processes in steps S1 to S9 are repeatedly executed during execution of the joystick mode, the position keeping mode, the compass direction keeping mode, or the automated operation with performing of the joystick holding operation.

[0105] The watercraft 1 and the watercraft propulsion system 100 according to the present preferred embodiment have the following features.

[0106] When steering of the hull 2 is executed in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust, the steering actuator 33 and the steering motor 56 are controlled such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. Accordingly, the principal propulsion device 3 having a large inertia can be made small in rudder rate, whereby vibrations to be caused in the hull 2 in steering of the principal propulsion device 3 can be inhibited in magnitude. Besides, the principal propulsion device 3 is made small in rudder rate, whereas the auxiliary propulsion device 4 is not made small in rudder rate; hence, when the user quickly performs a steering operation, the hull 2 can be quickly changed in bow direction in response to the steering operation.

[0107] The rudder rate of the principal propulsion device 3 is calculated by processing the rudder rate of the auxiliary propulsion device 4 with at least either weighted average filtering or first-order lag filtering, whereby the principal propulsion device 3 can be made smaller in rudder rate than the auxiliary propulsion device 4.

[0108] The joystick 8 is provided for operating the steering actuator 33 and the steering motor 56; then, steering of the hull 2 is executed by operating the joystick 8. Accordingly, vibrations to be caused in the hull 2 in steering of the hull 2 with the joystick 8 can be inhibited in magnitude. Besides, when the user quickly operates the joystick 8, the hull 2 can be quickly changed in bow direction in response to the steering operation.

[0109] The principal propulsion device 3 is an engine propulsion device using the engine as the power source thereof, whereas the auxiliary propulsion device 4 is an electric propulsion device using the electric motor as the power source thereof. The principal propulsion device 3 is made in the form of the engine propulsion device, whereby it is inevitable for the principal propulsion device 3 to have a large inertia; hence, vibrations with a large magnitude are caused when change in rudder angle is executed for the principal and auxiliary propulsion devices 3 and 4 at an equal rudder rate. However, in the present preferred embodiment, the principal propulsion device 3 can be made smaller in rudder rate than the auxiliary propulsion device 4; hence, vibrations to be caused can be inhibited in magnitude.

[0110] The principal propulsion device 3 is attached to the hull 2, while being rotatable in the right-and-left direction; besides, the steering actuator 33 rotates the principal propulsion device 3 with respect to the hull 2 in the right-and-left direction, whereby the principal propulsion device 3 is changed in rudder angle. Thus, when changed in rudder angle, the principal propulsion device 3 is rotated right and left not in part but entirely; hence, the principal propulsion device 3 exerts a large inertia. However, in the present preferred embodiment, the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4; hence, vibrations to be caused can be inhibited in magnitude.

[0111] The keeping mode setting buttons 82 to 84 are provided to be operated for issuing commands for transitioning to the control modes composing the keeping mode for keeping at least either the position or the compass direction of the hull 2; then, during execution of the one selected among the control modes, the steering actuator 33 and the steering motor 56 are controlled such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. Accordingly, during execution of the selected control mode associated with the one operated among the keeping mode setting buttons 82 to 84, vibrations to be caused in the hull 2 in steering of the principal propulsion device 3 can be inhibited in magnitude.

[0112] One preferred embodiment of the present invention has been explained above. However, the present invention is not limited to the preferred embodiment described above and a variety of changes can be made without departing from the gist of the present invention.

[0113] In the preferred embodiment described above, the principal propulsion device 3 uses the engine as the power source thereof, whereas the auxiliary propulsion device 4 uses the electric motor as the power source thereof; however, the principal and auxiliary propulsion devices 3 and 4 may not be limited in configuration to the above. For example, each of the principal and auxiliary propulsion devices 3 and 4 may use an engine as the power source thereof, or alternatively, may use an electric motor as the power source thereof. In short, the advantageous effects of the present invention can be exerted as long as the principal propulsion device 3 has a large inertia and has a larger rated output than the auxiliary propulsion device 4.

[0114] In the preferred embodiment described above, the principal propulsion device 3 is changed in rudder angle when entirely rotated with respect to the hull 2 in the right-and-left direction. However, the principal propulsion device 3 may be configured to be rotated only at the lower part thereof in the right-and-left direction as with the auxiliary propulsion device 4 (of a lower unit steering type).

[0115] In the preferred embodiment described above, the joystick 8 is exemplified as the steering member; besides, as shown in FIG. 9, even when the steering wheel 6 and the remote control lever 7 are operated, steering of the hull 2 is not enabled in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust. However, the control actions to be executed by operating the steering wheel 6 and the remote control lever 7 are not limited to the above. Specifically, under the electric mode and the extender mode, when the remote control lever 7 is operated, only the auxiliary propulsion device 4 may be caused to generate a thrust; on the other hand, when the steering wheel 6 is operated, the steering actuator 33 and the steering motor 56 may be controlled such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4.

[0116] In the preferred embodiment described above, the steering controller 111 and the steering motor 56 are disposed in the auxiliary propulsion device 4; however, the steering controller 111 and the steering motor 56 are not limited in positional arrangement to this. The steering controller 111 and the steering motor 56 may be disposed in part or entirely in the hull 2.

[0117] In the preferred embodiment described above, both weighted average filtering and first-order lag filtering are executed such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4. However, either weighted average filtering or first-order lag filtering may be executed for the purpose. Alternatively, the processing to be executed for the purpose may not be limited to weighted average filtering and first-order lag filtering; alternatively, limitations may be imposed on the rudder rate of the principal propulsion device 3. In short, any suitable processing may be employed as long as the principal propulsion device 3 can be made smaller in rudder rate than the auxiliary propulsion device 4.

[0118] In the preferred embodiment described above, the maximum rudder angle θ1 of the auxiliary propulsion device 4 is set to be greater than the maximum rudder angle θ2 of the principal propulsion device 3; however, the relation in magnitude between the maximum rudder angles θ1 and θ2 may not be limited to the above. The maximum rudder angle θ2 may be greater than or equal to the maximum rudder angle θ1.

[0119] In the preferred embodiment described above, the control action is executed such that the principal propulsion device 3 is made smaller in rudder rate than the auxiliary propulsion device 4 in steering under the joystick mode, steering in the automated operation under the position keeping mode, steering in the automated operation under the compass direction keeping mode, or steering in the automated operation for keeping the compass direction with performing of the joystick holding operation. However, the control action may not be necessarily executed in the above-mentioned settings of steering. In short, the control action may be executed in any suitable setting of steering as long as steering of the hull 2 is executed in the state that not the principal propulsion device 3 but the auxiliary propulsion device 4 only generates a thrust.INDUSTRIAL APPLICABILITY

[0120] According to the present invention, it is made possible to provide a system for propelling a watercraft, a watercraft, and a method of propelling a watercraft, whereby vibrations to be caused in steering can be inhibited in magnitude.REFERENCE SIGNS LIST

[0121] 1: Watercraft, 2: Hull, 2a: Stem, 3: Principal propulsion device, 4: Auxiliary propulsion device, 5: Operating seat, 6: Steering wheel, 7: Remote control lever, 8: Joystick, 9: Gauge, 9a: Input device, 11: Attachment mechanism, 12: Clamp bracket, 13: Tilt shaft, 14: Swivel bracket, 15: Steering shaft, 16: Engine cover, 17: upper case, 18: Lower case, 19: Engine, 20: Drive shaft, 21: Shift mechanism, 22: Propeller shaft, 23: Propeller, 24: Shift rod, 25: Starter motor, 26: Electric power generator, 27: Engine ECU, 28: Throttle actuator, 29: Throttle valve, 30: Shift actuator, 31: Steering rod, 32: Steering device, 33: Steering actuator, 34: Steering ECU, 35: Tilt / trim actuator, 41: Bracket, 41a: Lower support portion, 41b: Upper support portion, 42: Base, 43: Upper housing, 44: Lower housing, 45: Cover, 46: Cowl, 47: Drive unit, 48: Steering unit, 49: propeller, 50: Electric motor, 51: Rotor, 52: Stator, 53: Permanent magnet, 54: Coil, 55: Steering shaft, 56: Steering motor, 60: Tilt unit, 61: Tilt angle sensor, 62: Tilt cylinder, 63: Cylinder coupling bracket, 64: Tilt shaft, 65: Steering wheel unit, 70: Remote control unit, 80: Joystick unit, 81: Joystick button, 82: Keeping mode setting button, 83: Keeping mode setting button, 84: Keeping mode setting button, 85: Thrust setting button, 85a: Plus button, 85b: Minus button, 100: Watercraft propulsion system, 101: Main controller, 102: Intra-watercraft network, 103: Outboard motor control network, 104: Control panel network, 106: Remote control ECU, 108: GPS receiver, 109: Compass sensor, 110: Motor controller, 111: Steering controller, 120: Power switch unit, 121: Power switch, 122: Start switch, 123: Stop switch, 130: Battery, 140: Power switch unit, 141: Power switch, 145: Battery, 146: DC / DC converter, 150: Application switch panel, 151: Function switch

Claims

1. A system (100) for propelling a watercraft (1), comprising: a principal propulsion device (3) configured to be attached to a hull (3) of the watercraft (1); an auxiliary propulsion device (4) configured to be attached to the hull (3), the auxiliary propulsion device (4) having a smaller rated output than the principal propulsion device (3); a principal propulsion device rudder angle changing mechanism (33) configured to change a rudder angle of the principal propulsion device (3); an auxiliary propulsion device rudder angle changing mechanism (56) configured to change a rudder angle of the auxiliary propulsion device (4); and a controller (101) configured to control the principal propulsion device rudder angle changing mechanism (33) and the auxiliary propulsion device rudder angle changing mechanism (56) such that a rudder rate of the principal propulsion device (3) is made smaller than a rudder rate of the auxiliary propulsion device (4) when steering of the hull (3) is executed in a state that not the principal propulsion device (3) but the auxiliary propulsion device (4) only generates a thrust.

2. The system (100) according to claim 1, wherein the controller (101) is further configured to calculate the rudder rate of the principal propulsion device (3) by processing the rudder rate of the auxiliary propulsion device (4) with at least either weighted average filtering or first-order lag filtering.

3. The system (100) according to claim 1 or 2, further comprising: a steering member (8) configured to operate the principal propulsion device rudder angle changing mechanism (33) and the auxiliary propulsion device rudder angle changing mechanism (56), wherein the steering of the hull (3) is executed by operating the steering member (8).

4. The system (100) according to claim 3, wherein the steering member (8) is a joystick (8).

5. The system (100) according to any one of claims 1 to 4, wherein the principal propulsion device (3) is an engine propulsion device using an engine as a power source thereof, and the auxiliary propulsion device (4) is an electric propulsion device using an electric motor as a power source thereof.

6. The system (100) according to any one of claims 1 to 5, wherein the auxiliary propulsion device (4) includes the auxiliary propulsion device rudder angle changing mechanism (56), the auxiliary propulsion device (4) includes a first housing (45, 46) fixed in position with respect to the hull (3) in a right-and-left direction, and a second housing (43, 44) disposed below the first housing (45, 46) so as to be rotatable in the right-and-left direction, and a propeller (49) disposed in the second housing (43, 44), and the auxiliary propulsion device (4) is changed in rudder angle when the second housing (43, 44) is rotated with respect to the first housing (45, 46) in the right-and-left direction.

7. The system (100) according to any one of claims 1 to 6, wherein the principal propulsion device (3) is attached to the hull (3) so as to be rotatable in a right-and-left direction, and the principal propulsion device rudder angle changing mechanism (33) causes the principal propulsion device (3) to rotate with respect to the hull (3) in the right-and-left direction such that the principal propulsion device (3) is changed in rudder angle.

8. The system (100) according to any one of claims 1 to 7, further comprising: a mode transitioning command portion (82-84) configured to be operated for issuing a command for transitioning to a keeping mode for keeping at least either a position of the hull (3) or a compass direction of the hull (3), wherein the controller (101) is further configured to control the principal propulsion device rudder angle changing mechanism (33) and the auxiliary propulsion device rudder angle changing mechanism (56) during execution of the keeping mode such that the rudder rate of the principal propulsion device (3) is made smaller than the rudder rate of the auxiliary propulsion device (4).

9. The system (100) according to any one of claims 1 to 8, further comprising: a principal propulsion device command portion (122, 123) configured to issue a command for starting or stopping the principal propulsion device (3); and an auxiliary propulsion device command portion (141) configured to issue a command for starting or stopping the auxiliary propulsion device (4), wherein when the principal propulsion device (3) is in a stopped state and the auxiliary propulsion device (4) is in a started state, not the principal propulsion device (3) but the auxiliary propulsion device (4) is only enabled to generate the thrust.

10. The system (100) according to any one of claims 1 to 9, further comprising: a principal propulsion device command portion (122, 123) configured to issue a command for starting or stopping the principal propulsion device (3); an auxiliary propulsion device command portion (141) configured to issue a command for starting or stopping the auxiliary propulsion device (4); and a thrust command portion (85) configured to issue a command for instructing a magnitude of the thrust, wherein when the magnitude of the thrust has a predetermined value or less in a state that each of the principal and auxiliary propulsion devices (3, 4) is in a started state, not the principal propulsion device (3) but the auxiliary propulsion device (4) only generates the thrust.

11. A watercraft (1) comprising: a hull (3); and the system (100) recited in any one of claims 1 to 10, the system (100) disposed in the hull (3).

12. A method of propelling a watercraft (1), the method executed by a system (100) for propelling the watercraft (1), the system (100) including a principal propulsion device (3), an auxiliary propulsion device (4), a principal propulsion device rudder angle changing mechanism (33), and an auxiliary propulsion device rudder angle changing mechanism (56), the principal propulsion device (3) attached to a hull (3) of the watercraft (1), the auxiliary propulsion device (4) attached to the hull (3), the auxiliary propulsion device (4) having a smaller rated output than the principal propulsion device (3), the principal propulsion device rudder angle changing mechanism (33) changing a rudder angle of the principal propulsion device (3), the auxiliary propulsion device rudder angle changing mechanism (56) changing a rudder angle of the auxiliary propulsion device (4), the method comprising: controlling the principal propulsion device rudder angle changing mechanism (33) and the auxiliary propulsion device rudder angle changing mechanism (56) such that a rudder rate of the principal propulsion device (3) is made smaller than a rudder rate of the auxiliary propulsion device (4) when steering of the hull (3) is executed in a state that not the principal propulsion device (3) but the auxiliary propulsion device (4) only generates a thrust.

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