Patent Description:
There has been conventionally known a type of system for automatically controlling a watercraft such that the watercraft moves toward a specified target spot. For example, a system described in <CIT> controls an outboard motor for a watercraft such that the watercraft moves toward a specified target spot in an autopilot mode. When the watercraft approaches the target spot, the system moors the watercraft in the target spot.

As a type of automated control for watercraft, there has been also conventionally known a keeping control for keeping a watercraft located in a target spot. When the watercraft is remote from the target spot under the conventional keeping control, an outboard motor is controlled to move the watercraft to the target spot in either a bow mode or a stern mode preliminarily set by a user. The bow mode serves to direct the bow of the watercraft to the target spot, whereas the stern mode serves to direct the stern of the watercraft to the target spot.

When the watercraft is remote from the target spot under the conventional keeping control, the outboard motor is controlled to move the watercraft to the target spot in either the bow mode or the stern mode preliminarily set by the user. Because of this, chances are that, when the watercraft is remote from the target spot, it takes time for the watercraft to move to the target spot depending on the position of the watercraft; hence, there is still room for improvement for the conventional keeping control. It is an object of the present invention to provide a system and a method, whereby a watercraft can be easily kept located in a target spot under an automated control. According to the present invention said object is solved by system for controlling a watercraft having the features of independent claim <NUM>. Moreover, according to the present invention said object is solved by a method of controlling a watercraft having the features of independent claim <NUM>. Preferred embodiments are laid down in the dependent claims.

A system (or means) according to an aspect of the present disclosure relates to a system for controlling a watercraft and includes a marine propulsion device, an input device, and a controller. The input device is configured to output an operating signal indicating a first mode selected in accordance with an operation thereof. The controller receives the operating signal. The controller controls the marine propulsion device such that the watercraft is kept located in a target spot under selection of the first mode. When it is intended to move the watercraft to the target spot from a first spot remote from the target spot under selection of the first mode, the controller selects in which of modes, composed of a bow mode orienting a bow of the watercraft toward the target spot and a stern mode orienting a stern of the watercraft toward the target spot, the marine propulsion device is controlled depending on a position of the target spot with respect to the first spot so as to control the marine propulsion device such that the watercraft is moved from the first spot to the target spot in one selected from the bow mode and the stern mode.

A system according to another aspect of the present disclosure relates to a system for controlling a watercraft and includes a marine propulsion device, an input device, and a controller. The input device is configured to output an operating signal indicating a first mode selected in accordance with an operation thereof. The controller receives the operating signal. The controller controls the marine propulsion device such that the watercraft is kept located in a target spot under selection of the first mode. When it is intended to move the watercraft to the target spot from a first spot remote from the target spot under selection of the first mode, the controller selects in which of modes, composed of a bow mode orienting a bow of the watercraft toward the target spot, a stern mode orienting a stern of the watercraft toward the target spot, and a compass direction keeping mode keeping constant a compass direction of the watercraft, the marine propulsion device is controlled depending on a position of the target spot with respect to the first spot so as to control the marine propulsion device such that the watercraft is moved from the first spot to the target spot in one selected from the bow mode, the stern mode, and the compass direction keeping mode.

A method according to yet another aspect of the present disclosure relates to a method of controlling a watercraft including a marine propulsion device and an input device and includes the following processes. The first process relates to receiving an operating signal indicating a first mode selected in accordance with an operation of the input device. The second process relates to controlling the marine propulsion device such that the watercraft is kept located in a target spot under selection of the first mode. The third process is executed when it is intended to move the watercraft to the target spot from a first spot remote from the target spot under selection of the first mode and relates to selecting in which of modes, composed of a bow mode orienting a bow of the watercraft toward the target spot and a stern mode orienting a stern of the watercraft toward the target spot, the marine propulsion device is controlled depending on a position of the target spot with respect to the first spot so as to control the marine propulsion device such that the watercraft is moved from the first spot to the target spot in one selected from the bow mode and the stern mode.

A method according to still another aspect of the present disclosure relates to a method of controlling a watercraft including a marine propulsion device and an input device and includes the following processes. The first process relates to receiving an operating signal indicating a first mode selected in accordance with an operation of the input device. The second process relates to controlling the marine propulsion device such that the watercraft is kept located in a target spot under selection of the first mode. The third process is executed when it is intended to move the watercraft to the target spot from a first spot remote from the target spot under selection of the first mode and relates to selecting in which of modes, composed of a bow mode orienting a bow of the watercraft toward the target spot, a stern mode orienting a stern of the watercraft toward the target spot, and a compass direction keeping mode keeping constant a compass direction of the watercraft, the marine propulsion device is controlled depending on a position of the target spot with respect to the first spot so as to control the marine propulsion device such that the watercraft is moved from the first spot to the target spot in one selected from the bow mode, the stern mode, and the compass direction keeping mode.

In the system and the method according to the present disclosure, when it is intended to move the watercraft from the first spot to the target spot under selection of the first mode for controlling the marine propulsion device such that the watercraft is kept located in the target spot, the controller selects either in which of the bow mode and the stern mode or in which of the bow mode, the stern mode, and the compass direction keeping mode the marine propulsion device is controlled depending on the position of the target spot with respect to the first spot. Accordingly, the watercraft can be efficiently moved to approach the target spot; hence, the watercraft can be easily kept located in the target spot.

Overall, according to the present disclosure, it is possible to provide a system and a method whereby a watercraft can be easily kept located in a target spot under automated control.

A preferred embodiment will be hereinafter explained with reference to drawings. <FIG> is a perspective view of a watercraft <NUM> to which marine propulsion devices 1a and 1b according to the preferred embodiment are mounted. The marine propulsion devices 1a and 1b are mounted to the watercraft <NUM> as a plurality of marine propulsion devices. In the present preferred embodiment, the marine propulsion devices 1a and 1b are outboard motors. The marine propulsion devices 1a and 1b are attached to the stern of the watercraft <NUM>. The marine propulsion devices 1a and 1b are disposed in alignment in the width direction of the watercraft <NUM>. Each marine propulsion device 1a, 1b generates a thrust for propelling the watercraft <NUM>.

<FIG> is a side view of the marine propulsion device 1a. The structure of the marine propulsion device 1a will be hereinafter explained; however, the structure of the marine propulsion device 1a is also true of the marine propulsion device 1b. The marine propulsion device 1a is attached to the watercraft <NUM> through a bracket 11a. The bracket 11a supports the marine propulsion device 1a such that the marine propulsion device 1a is rotatable about a steering shaft 12a.

The marine propulsion device 1a includes a drive unit 2a, a drive shaft 3a, a propeller shaft 4a, and a shift mechanism 5a. The drive unit 2a is an internal combustion engine. The drive unit 2a includes a crankshaft 13a. The crankshaft 13a extends in the up-and-down direction of the marine propulsion device 1a. The drive shaft 3a is connected to the crankshaft 13a. The propeller shaft 4a extends in the back-and-forth direction of the marine propulsion device 1a. The propeller shaft 4a is connected to the drive shaft 3a through the shift mechanism 5a. A propeller 6a is attached to the propeller shaft 4a.

The shift mechanism 5a includes a forward moving gear 14a, a rearward moving gear 15a, and a dog clutch 16a. When gear engagement of each gear 14a, 15a is switched by the dog clutch 16a, the shift mechanism 5a is switched among a forward moving state, a rearward moving state, and a neutral state.

<FIG> is a schematic diagram showing a configuration of a watercraft operating system for the watercraft <NUM>. As shown in <FIG>, the marine propulsion device 1a includes a shift actuator 7a and a steering actuator 8a.

The shift actuator 7a is connected to the dog clutch 16a of the shift mechanism 5a. The shift actuator 7a actuates the dog clutch 16a to switch gear engagement of each gear 14a, 15a. In response, the shift mechanism 5a is switched among the forward moving state, the rearward moving state, and the neutral state. The shift actuator 7a is, for instance, an electric motor. However, the shift actuator 7a may be another type of actuator such as an electric cylinder, a hydraulic motor, or a hydraulic cylinder.

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

The marine propulsion device 1a includes a first drive controller 9a. The first drive controller 9a 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 first drive controller 9a stores programs and data for controlling the marine propulsion device 1a. The first drive controller 9a controls the drive unit 2a.

The marine propulsion device 1b includes a drive unit 2b, a shift actuator 7b, a steering actuator 8b, and a second drive controller 9b. The drive unit 2b, the shift actuator 7b, the steering actuator 8b, and the second drive controller 9b in the marine propulsion device 1b are configured in similar manner to the drive unit 2a, the shift actuator 7a, the steering actuator 8a, and the first drive controller 9a in the marine propulsion device 1a, respectively.

The watercraft operating system (or means) includes a steering wheel <NUM>, an operating device <NUM>, a first input device <NUM>, and a second input device <NUM>. The steering wheel <NUM>, the operating device <NUM>, the first input device <NUM>, and the second input device <NUM> are disposed in a cockpit of the watercraft <NUM>. The steering wheel <NUM>, the operating device <NUM>, the first input device <NUM>, and the second input device <NUM> are manually operable.

The steering wheel <NUM> is a device for allowing an operator to operate the turning direction of the watercraft <NUM>. The steering wheel <NUM> includes a sensor <NUM>. The sensor <NUM> outputs a steering signal indicating the operating direction and the operating amount of the steering wheel <NUM>.

The operating device <NUM> includes a first throttle lever 25a and a second throttle lever 25b. The first throttle lever 25a is a device for allowing the operator to regulate the magnitude of the thrust generated by the marine propulsion device 1a. The first throttle lever 25a is also a device for allowing the operator to switch the direction of the thrust generated by the marine propulsion device 1a between a forward moving direction and a rearward moving direction. The first throttle lever 25a is operable from a neutral position to a forward moving position and a rearward moving position. The neutral position is a position located between the forward moving position and the rearward moving position. The first throttle lever 25a includes a sensor <NUM>. The sensor <NUM> outputs a throttle signal indicating the operating direction and the operating amount of the first throttle lever 25a.

The second throttle lever 25b is a device for allowing the operator to regulate the magnitude of the thrust generated by the marine propulsion device 1b. The second throttle lever 25b is also a device for allowing the operator to switch the direction of the thrust generated by the marine propulsion device 1b between the forward moving direction and the rearward moving direction. The second throttle lever 25b is configured in similar manner to the first throttle lever 25a. The second throttle lever 25b includes a sensor <NUM>. The sensor <NUM> outputs a throttle signal indicating the operating direction and the operating amount of the second throttle lever 25b.

The watercraft operating system includes a watercraft operating controller <NUM>. The watercraft operating controller <NUM> includes a processor such as a CPU and memories such as a RAM and a ROM. The watercraft operating controller <NUM> stores programs and data for controlling the marine propulsion devices 1a and 1b. The watercraft operating controller <NUM> is connected to the first and second drive controllers 9a and 9b through wired or wireless communication. The watercraft operating controller <NUM> is connected to the steering wheel <NUM>, the operating device <NUM>, the first input device <NUM>, and the second input device <NUM> through wired or wireless communication.

The watercraft operating controller <NUM> receives the steering signal from the sensor <NUM>. The watercraft operating controller <NUM> receives the throttle signal from each sensor <NUM>, <NUM>. The watercraft operating controller <NUM> outputs command signals to the first and second drive controllers 9a and 9b based on the signals received from the sensors <NUM>, <NUM>, and <NUM>. The command signal is transmitted to the shift actuator 7a and the steering actuator 8a through the first drive controller 9a. The command signal is transmitted to the shift actuator 7b and the steering actuator 8b through the second drive controller 9b.

For example, the watercraft operating controller <NUM> outputs a command signal for the shift actuator 7a depending on the operating direction of the first throttle lever 25a. In response, shifting between forward movement and rearward movement is performed by the marine propulsion device 1a. The watercraft operating controller <NUM> outputs a throttle command for the drive unit 2a depending on the operating amount of the first throttle lever 25a. The first drive controller 9a controls the output rotational speed of the marine propulsion device 1a in accordance with the throttle command.

The watercraft operating controller <NUM> outputs a command signal for the shift actuator 7b depending on the operating direction of the second throttle lever 25b. In response, shifting between forward movement and rearward movement is performed by the marine propulsion device 1b. The watercraft operating controller <NUM> outputs a throttle command for the drive unit 2b depending on the operating amount of the second throttle lever 25b. The second drive controller 9b controls the output rotational speed of the marine propulsion device 1b in accordance with the throttle command.

The watercraft operating controller <NUM> controls each steering actuator 8a, 8b such that each marine propulsion device 1a, 1b is rotated about the steering shaft 12a thereof depending on the operating direction and the operating amount of the steering wheel <NUM>. The watercraft operating controller <NUM> controls the rudder angle of each marine propulsion device 1a, 1b depending on the operating amount of the steering wheel <NUM>.

The watercraft operating system includes a position sensor <NUM>. The position sensor <NUM> detects the position of the watercraft <NUM>. The position sensor <NUM> is a GNSS (Global Navigation Satellite System) receiver such as a GPS (Global Positioning System) receiver. However, the position sensor <NUM> may be a type of sensor other than the GNSS receiver. The position sensor <NUM> outputs a signal indicating the position of the watercraft <NUM>. The watercraft operating controller <NUM> is connected to the position sensor <NUM> in communicable manner. The watercraft operating controller <NUM> obtains the position of the watercraft <NUM> based on the signal outputted thereto from the position sensor <NUM>. Besides, the watercraft operating controller <NUM> obtains the speed of the watercraft <NUM> based on the signal outputted thereto from the position sensor <NUM>. The watercraft operating system may include another type of sensor for detecting the speed over ground or the speed through water of the watercraft <NUM>. The speed over ground refers to the speed of the watercraft <NUM> with respect to the ground, whereas the speed through water refers to the speed of the watercraft <NUM> with respect to water (seawater).

The watercraft operating system includes a compass direction sensor <NUM>. The compass direction sensor <NUM> detects the course of the watercraft <NUM>. The compass direction sensor <NUM> is, for instance, an IMU (Inertial Measurement Unit). However, the compass direction sensor <NUM> may be a type of sensor other than the IMU. The watercraft operating controller <NUM> is connected to the compass direction sensor <NUM> in communicable manner. The watercraft operating controller <NUM> obtains the course of the watercraft <NUM> based on a signal outputted thereto from the compass direction sensor <NUM>.

The watercraft operating system includes a wind direction measuring instrument <NUM> and a wind speed measuring instrument <NUM>. The wind direction measuring instrument <NUM> and the wind speed measuring instrument <NUM> output measurement results thereof to the watercraft operating controller <NUM>. The watercraft operating controller <NUM> obtains a wind direction and a wind speed based on signals outputted thereto from the wind direction measuring instrument <NUM> and the wind speed measuring instrument <NUM>. In the present preferred embodiment, the wind direction measuring instrument <NUM> and the wind speed measuring instrument <NUM> may be omitted.

The first input device <NUM> is disposed on, for instance, a watercraft operating device such as a joystick. The first input device <NUM> is operable by the operator to select one of control modes of each marine propulsion device 1a, 1b. The first input device <NUM> includes at least one switch for selecting one of the control modes. The first input device <NUM> may not necessarily include the at least one switch, and alternatively, may include another type of device such as a touchscreen. The first input device <NUM> outputs an operating signal indicating the control mode selected in accordance with the operation by the operator.

The watercraft operating controller <NUM> receives the operating signal from the first input device <NUM>. The watercraft operating controller <NUM> executes automated watercraft control for the watercraft <NUM> by controlling the rudder angle and the thrust of each marine propulsion device 1a, 1b in accordance with the selected control mode.

The second input device <NUM> is operable by the operator to perform control mode setting. The second input device <NUM> is, for instance, a touchscreen. The second input device <NUM> is not limited to the touchscreen, and alternatively, may include another type of device such as at least one switch. The second input device <NUM> outputs an operating signal indicating the setting of the control mode selected by the operator. The watercraft operating controller <NUM> receives the operating signal from the second input device <NUM>.

The control modes include a first mode and a second mode. In the first mode, the watercraft operating controller <NUM> controls each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in a target spot. The target spot is, for instance, the position of the watercraft <NUM> located when the first mode has been selected by the first input device <NUM>. In other words, the watercraft operating controller <NUM> controls each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in the position thereof located at a point of time when the operating signal, indicating the first mode, has been received by the watercraft operating controller <NUM>.

In the second mode, the watercraft operating controller <NUM> controls each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in the target spot, while the bow of the watercraft <NUM> is kept oriented in a target compass direction. In the second mode, the target spot and the target compass direction are, for instance, the position and the compass direction of the watercraft <NUM> located and oriented when the second mode has been selected by the first input device <NUM>. In other words, the watercraft operating controller <NUM> controls each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in the target spot (P0), while being kept oriented in the compass direction thereof oriented at a point of time when the operating signal, indicating the second mode, has been received by the watercraft operating controller <NUM>. The second mode is a mode including transverse movement of the watercraft <NUM> in a low-speed range. It should be noted that the target compass direction may be arbitrarily set by the operator using the second input device <NUM>.

As shown in <FIG> and <FIG>, when it is intended to move the watercraft <NUM> to the target spot P0 from a first spot P1 (the present position of the watercraft <NUM>) remote from the target spot P0 under selection of the first mode, the watercraft operating controller <NUM> selects in which of a bow mode and a stern mode each marine propulsion device 1a, 1b should be controlled depending on the position of the target spot P0 with respect to the first spot P1 and controls each marine propulsion device 1a, 1b in the selected mode such that the watercraft <NUM> is moved from the first spot P1 to the target spot P0.

<FIG> is a diagram showing a series of motions performed by the watercraft <NUM> when the bow mode is selected. The bow mode is a mode which the watercraft <NUM> is moved to the target spot P0 with the bow of the watercraft <NUM> facing the target spot P0. For example, a Cartesian coordinate system with x- and y-axes is herein assumed. The center of gravity of the watercraft <NUM> is set as the origin of the Cartesian coordinate system; the x- and y-axes divide the coordinate plane into four quadrants defined as first to fourth quadrants. When the target spot P0 is located in the first or second quadrant, the watercraft operating controller <NUM> selects the bow mode. In <FIG>, the target spot P0 is located in the first quadrant. The y-axis is an axis that passes through the center of gravity of the watercraft <NUM>, the middle of the bow of the watercraft <NUM>, and the middle of the stern of the watercraft <NUM>. The x-axis is an axis that passes through the center of gravity of the watercraft <NUM> and is perpendicular to the y-axis.

As shown in <FIG>, the stern mode is a mode in which the watercraft <NUM> is moved from the stern of the watercraft <NUM> to the target spot P0 with the stern of the watercraft <NUM> facing the target spot P0. When the target spot P0 is located in the third or fourth quadrant, the watercraft operating controller <NUM> selects the stern mode. In <FIG>, the target spot P0 is located in the fourth quadrant.

A determination regarding in which of the first to fourth quadrants the target spot P0 is located is made based on, for instance, difference in angle α between the compass direction from the first spot P1 to the target spot P0 and the compass direction of the bow of the watercraft <NUM> located in the first spot P1. As shown in <FIG>, when the difference in angle α is an acute angle, the first spot P1 is supposed to be located in the first or second quadrant; hence, the watercraft operating controller <NUM> selects the bow mode. As shown in <FIG>, when the difference in angle α is an obtuse angle, the first spot P1 is supposed to be located in the third or fourth quadrant; hence, the watercraft operating controller <NUM> selects the stern mode.

In the first mode, the watercraft operating controller <NUM> determines whether or not the watercraft <NUM> is remote from the target spot P0 by a predetermined distance or greater. In other words, the watercraft operating controller <NUM> determines whether or not the distance to the target spot P0 from the present position of the watercraft <NUM> is a predetermined threshold or greater. When the distance to the target spot P0 from the present position of the watercraft <NUM> is the predetermined threshold or greater, the watercraft operating controller <NUM> selects in which of the bow mode and the stern mode each marine propulsion device 1a, 1b should be controlled and controls each marine propulsion device 1a, 1b in the selected mode such that the watercraft <NUM> is moved from the present position to the target spot P0.

When controlling each marine propulsion device 1a, 1b such that the bow of the watercraft <NUM> is oriented toward the target spot P0 by selecting the bow mode under selection of the first mode, the watercraft operating controller <NUM> determines whether or not the turning speed of the watercraft <NUM> is a predetermined speed or less. When the turning speed of the watercraft <NUM> is the predetermined speed or less, the watercraft operating controller <NUM> switches the bow mode into the stern mode and controls each marine propulsion device 1a, 1b in the stern mode.

When controlling each marine propulsion device 1a, 1b such that the stern of the watercraft <NUM> is oriented toward the target spot P0 by selecting the stern mode under selection of the first mode, the watercraft operating controller <NUM> determines whether or not the turning speed of the watercraft <NUM> is the predetermined speed or less. When the turning speed of the watercraft <NUM> is the predetermined speed or less, the watercraft operating controller <NUM> switches the stern mode into the bow mode and controls each marine propulsion device 1a, 1b in the bow mode.

Specifically, as shown in <FIG>, chances are that the watercraft <NUM> is swept, while spinning, from the target spot P0 by the effect of wind or tide. In the example shown in <FIG>, the watercraft <NUM> receives wind W blowing from the northeast. In other words, the watercraft <NUM> is more likely to be affected and moved by the wind W at the bow than at the stern; hence, the watercraft <NUM> is swept, while spinning counterclockwise. In this case, the target spot P0 is located in the first quadrant; hence, the watercraft operating controller <NUM> selects the bow mode and controls each marine propulsion device 1a, 1b such that the watercraft <NUM> turns clockwise. However, the wind W blowing from the northeast acts on the watercraft <NUM> so as to spin the watercraft <NUM> counterclockwise; hence, chances are that the turning speed gets slow and the bow of the watercraft <NUM> cannot be oriented to the target spot P0 even after elapse of a predetermined period of time. Because of this, when the turning speed of the watercraft <NUM> is the predetermined speed or less, the watercraft operating controller <NUM> switches the bow mode into the stern mode and controls each marine propulsion device 1a, 1b in the stern mode.

As shown in <FIG>, chances are that the watercraft <NUM> is swept from the target spot P0, while spinning counterclockwise, by receiving the wind W blowing from the northeast and tide T flowing from the southwest. In the example shown in <FIG>, the target spot P0 is located in the third quadrant; hence, the watercraft operating controller <NUM> selects the stern mode and controls each marine propulsion device 1a, 1b such that the watercraft <NUM> turns clockwise. However, the wind W blowing from the northeast acts on the watercraft <NUM> so as to spin the watercraft <NUM> counterclockwise; hence, chances are that the turning speed gets slow and the stern of the watercraft <NUM> cannot be oriented to the target spot P0 even after elapse of the predetermined period of time. Because of this, when the turning speed of the watercraft <NUM> is the predetermined speed or less, the watercraft operating controller <NUM> switches the stern mode into the bow mode and controls each marine propulsion device 1a, 1b in the bow mode.

In the first mode, the watercraft operating controller <NUM> determines whether or not the speed through water of the watercraft <NUM> is a predetermined speed or less. When the speed through water of the watercraft <NUM> is the predetermined speed or less in the first mode, the watercraft operating controller <NUM> switches the first mode into the second mode and controls each marine propulsion device 1a, 1b in the second mode. When switching the first mode into the second mode depending on the speed through water of the watercraft <NUM>, the watercraft operating controller <NUM> controls each marine propulsion device 1a, 1b, for instance, such that the watercraft <NUM> is kept located in the target spot P0, while being kept oriented in the compass direction thereof oriented when the first mode has been switched into the second mode. The predetermined speed is, for instance, a speed enough to keep the position and the compass direction of the watercraft <NUM> by idling of each marine propulsion device 1a, 1b in the second mode.

It should be noted that when switching the first mode into the second mode depending on the speed through water of the watercraft <NUM>, the watercraft operating controller <NUM> may control each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in the target spot P0, while being kept oriented in the compass direction thereof oriented when the first mode has been selected by the first input device <NUM>. When switching the first mode into the second mode, the watercraft operating controller <NUM> may inform an operator of this switching through a touchscreen or an informing device.

After switching the first mode into the second mode, the watercraft operating controller <NUM> determines whether or not the watercraft <NUM> is remote from the target spot P0 by a predetermined distance or greater. In other words, after switching the first mode into the second mode, the watercraft operating controller <NUM> determines whether or not the distance to the target spot P0 from the present position of the watercraft <NUM> is a predetermined threshold or greater. When the distance to the target spot P0 from the present position of the watercraft <NUM> is the predetermined threshold or greater, it is difficult to keep the position and the compass direction of the watercraft <NUM> in the second mode; hence, the watercraft operating controller <NUM> switches the second mode into the first mode and controls each marine propulsion device 1a, 1b in the first mode. When switching the second mode into the first mode, the watercraft operating controller <NUM> may inform the operator of this switching through the touchscreen or the informing device.

In the watercraft operating system according to the present preferred embodiment explained above, when it is intended to move the watercraft <NUM> from the first spot P1 to the target spot P0 under selection of the first mode for controlling each marine propulsion device 1a, 1b such that the watercraft <NUM> is kept located in the target spot P0, the watercraft operating controller <NUM> selects in which of the bow mode and the stern mode each marine propulsion device 1a, 1b should be controlled depending on the position of the target spot P0 with respect to the first spot P1. Accordingly, the watercraft <NUM> can be efficiently moved to approach the target spot P0; hence, the watercraft <NUM> can be easily kept located in the target spot P0.

Besides, the first mode is switched into the second mode depending on the speed through water of the watercraft <NUM>, whereas the second mode is switched into the first mode depending on the distance to the target spot P0 from the present position of the watercraft <NUM>; hence, among the control modes, suitable one for the condition of the watercraft <NUM> can be automatically selected.

Each marine propulsion device is not limited to the outboard motor, and alternatively, may be another type of propulsion device such as an inboard engine outboard drive or a jet propulsion device. The structure of each marine propulsion device is not limited to that in the preferred embodiment described above and may be changed. For example, each drive unit 2a, 2b is not limited to the internal combustion engine, and alternatively, may be an electric motor. Yet alternatively, each drive unit 2a, 2b may be a hybrid system of an internal combustion engine and an electric motor. The number of marine propulsion devices is not limited to two. The number of marine propulsion devices may be more than two.

The watercraft operating controller <NUM> is configured to select either the bow mode or the stern mode under selection of the first mode based on difference in angle α between the direction from the first spot P1 to the target spot P0 and the compass direction of the bow of the watercraft <NUM> located in the first spot P1. However, the watercraft operating controller <NUM> may select either the bow mode or the stern mode depending on the wind direction and the wind speed. Alternatively, the watercraft operating controller <NUM> may select either the bow mode or the stern mode depending on the difference in angle α and both the wind direction and the wind speed. Yet alternatively, with respect to both the bow mode and the stern mode, a length of time required to achieve orientation toward the target spot P0 may be calculated depending on at least either the difference in angle α or both the wind direction and the wind speed; then, the watercraft operating controller <NUM> may be configured to select one shorter in length of time required to achieve orientation toward the target spot P0 than the other from the bow mode and the stern mode.

The first mode may further include a compass direction keeping mode for keeping the compass direction of the watercraft <NUM>. The compass direction keeping mode is identical to the control mode to be executed in the second mode. Specifically, when it is intended to move the watercraft <NUM> from the first spot P1 to the target spot P0 under selection of the first mode, a selection may be made regarding in which of the bow mode, the stern mode, and the compass direction keeping mode each marine propulsion device 1a, 1b should be controlled depending on the position of the target spot P0 with respect to the first spot P1. For example, the watercraft operating controller <NUM> may select the compass direction keeping mode when the distance to the target spot P0 from the present position of the watercraft <NUM> is less than a predetermined threshold.

Claim 1:
A system for controlling a watercraft (<NUM>), the system comprising:
a marine propulsion device (1a, 1b);
an input device (<NUM>) configured to output an operating signal indicating a first mode selected in accordance with an operation thereof; and
a controller (<NUM>), wherein
the controller (<NUM>) is configured to receive the operating signal from the input device (<NUM>),
the controller (<NUM>) is configured to control the marine propulsion device (1a, 1b) such that the watercraft (<NUM>) is kept located in a target spot under selection of the first mode, characterized in that
when the controller (<NUM>) receives instructions according an intention to move the watercraft (<NUM>) to the target spot from a first spot remote from the target spot under selection of the first mode, the controller (<NUM>) is configured to select in which of a bow mode and a stern mode the marine propulsion device (1a, 1b) is controlled depending on a position of the target spot with respect to the first spot so as to control the marine propulsion device (1a, 1b) such that the watercraft (<NUM>) is moved from the first spot to the target spot in one selected from the bow mode and the stern mode, the bow mode orienting a bow of the watercraft (<NUM>) toward the target spot, the stern mode orienting a stern of the watercraft (<NUM>) toward the target spot.