MARINE VESSEL AND CONTROL DEVICE THEREFOR

Abstract

A control device for a marine vessel includes a hull, a pair of water resistance bodies, and a controller. The pair of water resistance bodies are provided on the hull, one on a left side and one on a right side of the hull, each independently movable between a first position in which a resistance received from water in a predetermined direction is adjustable to a first magnitude, and a second position in which a resistance is adjustable to zero or to a second magnitude smaller than the first magnitude. The controller is configured or programmed to acquire a relative distance between a buoy, which floats on the water in a free-drifting manner, and the hull. The controller is configured or programmed to control the pair of water resistance bodies based on the relative distance.

Claims

1. A control device for a marine vessel, the control device comprising: a hull; a pair of water resistance bodies on the hull, one on a left side and one on a right side of the hull, each independently movable between a first position in which a resistance received from water in a predetermined direction is adjustable to a first magnitude, and a second position in which a resistance is adjustable to zero or to a second magnitude smaller than the first magnitude; and a controller configured or programmed to: acquire a relative distance between a buoy, which floats on the water in a free-drifting manner, and the hull; and control the pair of water resistance bodies based on the relative distance.

2. The control device according to claim 1, wherein the controller is configured or programmed to set the pair of water resistance bodies to the second position when the relative distance is greater than a first distance and is equal to or less than a second distance that is greater than the first distance.

3. The control device according to claim 2, wherein the controller is configured or programmed to set one of the pair of water resistance bodies to the first position and another one of the pair of water resistance bodies to the second position when a relative orientation of the buoy with respect to the hull deviates from a target relative orientation by more than a predetermined angle, even if the relative distance is greater than the first distance and is equal to or less than the second distance.

4. The control device according to claim 2, wherein the controller is configured or programmed to set at least one of the pair of water resistance bodies to the first position when the relative distance is greater than the second distance.

5. The control device according to claim 4, wherein the controller is configured or programmed to set the pair of water resistance bodies to the first position when the relative distance is greater than the second distance and a relative orientation of the buoy with respect to the hull does not deviate from a target relative orientation by more than a predetermined angle.

6. The control device according to claim 4, wherein the controller is configured or programmed to set one of the pair of water resistance bodies to the first position and another one of the pair of water resistance bodies to the second position when the relative distance is greater than the second distance and a relative orientation of the buoy with respect to the hull deviates from a target relative orientation by more than a predetermined angle.

7. The control device according to claim 2, wherein the controller is configured or programmed to correct a position of the hull using two or more propulsion devices when the relative distance is equal to or less than the first distance.

8. The control device according to claim 2, wherein the controller is configured or programmed to correct a position of the hull using two or more propulsion devices when the relative distance is greater than a third distance that is greater than the second distance.

9. The control device according to claim 8, wherein the controller is configured or programmed to correct the position of the hull using the two or more propulsion devices when a state in which the relative distance is greater than the second distance and is equal to or less than the third distance has continued for more than a predetermined time.

10. The control device according to claim 1, wherein the buoy is connected to the hull by a connector.

11. The control device according to claim 1, wherein the predetermined direction corresponds to a front-rear direction of the hull.

12. The control device according to claim 11, wherein the water resistance bodies are each configured to pivot about a pivot shaft parallel to an up-down direction; the first position is a position where the water resistance bodies are perpendicular to the front-rear direction of the hull; and the second position is a position where the water resistance bodies are parallel to the front-rear direction of the hull.

13. The control device according to claim 1, wherein the buoy is configured to output information indicating a position thereof; and the controller is configured or programmed to acquire the relative distance based on a position of the hull and the information output from the buoy.

14. The control device according to claim 4, further comprising at least one sensor to detect the relative distance between the buoy and the hull.

15. The control device according to claim 1, wherein each of the pair of water resistance bodies is plate-shaped.

16. The control device according to claim 1, further comprising: a pair of water resistance assemblies each including: a rotary motor to move one of the pair of water resistance bodies between the first position and the second position; and a lifting motor to move one of the pair of water resistance bodies up and down relative to the hull.

17. A marine vessel comprising: the control device according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIGS. 1A and 1B are schematic top views of a marine vessel.

[0012] FIGS. 2A to 2D are schematic right-side views of the marine vessel.

[0013] FIG. 3 is a block diagram of a marine propulsion system.

[0014] FIG. 4 is a flowchart of a drift fishing mode process.

[0015] FIGS. 5A to 5E are schematic diagrams illustrating an example of a control in the drift fishing mode process.

[0016] FIGS. 6A and 6B are schematic diagrams illustrating modifications of the water resistance bodies.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0017] Example embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0018] FIGS. 1A and 1B are schematic top views of a marine vessel 1 that uses a control device according to an example embodiment of the present invention. The marine vessel 1 includes a hull 2. FIGS. 1A and 1B illustrate the states in which water resistance bodies 93 (e.g., resistance plates described in more detail below) mounted to the hull 2 are located in a second position and a first position, respectively.

[0019] A centerline C of the hull 2 extends through the center of the stern and the tip of the bow. The centerline C also extends through the center of gravity G (turning center) of the marine vessel 1. The front-rear direction is parallel to the centerline C (hereinafter parallel includes both parallel and substantially parallel). The forward direction is a direction along the centerline C in FIG. 1A from the stern toward the bow. The backward direction is a direction along the centerline C in FIG. 1A from the bow toward the stern. As used herein, the terms left and right are defined based on the perspective when the hull 2 is viewed from the rear. The up-down direction is a direction perpendicular to both the front-rear direction and the left-right direction (hereinafter perpendicular includes both perpendicular and substantially perpendicular).

[0020] The marine vessel 1 includes a steerable outboard motor 4 and a steerable trolling motor 5 as propulsion devices to propel the hull 2. The outboard motor 4 is located at the stern, while the trolling motor 5 is located at the bow. The outboard motor 4 and the trolling motor 5 may serve as the primary and auxiliary propulsion devices of the marine vessel 1, respectively.

[0021] The marine vessel 1 further includes a steering wheel 11 mainly used to steer, a remote control unit 12 mainly used to adjust the output of the outboard motor 4, and a joystick 13 mainly used to both steer and adjust the output of the outboard motor 4 (see FIG. 3). The remote control unit 12 includes two throttle levers (not illustrated) that are operated to adjust the engine output of the outboard motor 4 and to switch between forward and reverse travel. Each throttle lever is operable from a neutral position in both the forward and reverse directions.

[0022] As illustrated in FIG. 1A, the outboard motor 4 includes an outboard motor body 20 and a propeller 21. The outboard motor body 20 is attached to the stern via an attachment mechanism, specifically to a swivel bracket (not illustrated) of the attachment mechanism so as to be pivotable about a steering axis center K. The steering angle of the outboard motor 4 changes as the outboard motor body 20 pivots about the steering axis center K. The trolling motor 5 is configured to provide a propulsive force to the hull 2 in any direction around a rotation axis J2. For example, the trolling motor 5 may be electrically powered.

[0023] A pair of left and right water resistance assemblies 90L and 90R are arranged at the stern. The water resistance assemblies 90L and 90R each include a rotary motor 91, a lifting motor 92, a water resistance body 93 (e.g., a resistance plate), a fixed body 94, and a movable body 95. The water resistance assemblies 90L and 90R are arranged and configured symmetrically with respect to the centerline C. The water resistance assemblies 90L and 90R can be driven independently. Since their basic configurations are the same, the configuration of the water resistance assembly 90L will be described as a representative example.

[0024] The fixed body 94 is fixed to the stern, and the movable body 95 is movable in the up-down direction relative to the fixed body 94 (at least between a raised position and a lowered position). The water resistance body 93 is pivotable about the rotation axis J1 and is movable to the second position illustrated in FIG. 1A and to the first position illustrated in FIG. 1B. The rotation axis J1 is the axis center of a pivot shaft that is parallel to the up-down direction.

[0025] FIGS. 2A to 2D are schematic right-side views of the marine vessel 1.

[0026] FIGS. 2A and 2B illustrate a state where the water resistance body 93 is in the second position, while FIGS. 2C and 2D illustrate a state where the water resistance body 93 is in the first position. FIGS. 2B and 2D illustrate a state where the movable body 95 is in the raised position, while FIGS. 2A and 2C illustrate a state where the movable body 95 is in the lowered position in a drift fishing mode other than during normal sailing.

[0027] The lifting motor 92 drives the movable body 95 to move it up and down relative to the fixed body 94. The rotary motor 91 causes the water resistance body 93 to pivot about the rotational axis J1. The lifting motor 92 and the rotary motor 91 are automatically controlled by a controller 70 (described below) and can also be manually operated using a water resistance switch (SW) 30 (see FIG. 3).

[0028] The first position is a position where the water resistance body 93 is perpendicular to the front-rear direction. In this position, the water resistance body 93 defines an angle of 90 (hereinafter, 90 includes both 90 and substantially) 90 with respect to the centerline C as viewed from above. The second position is a position where the water resistance body 93 is parallel to the front-rear direction. In this position, the water resistance body 93 defines an angle of 0 (hereinafter, 0 includes both 0 and substantially) 0 with respect to the centerline C as viewed from above.

[0029] When at least a portion of the water resistance body 93 is submerged (e.g., when in the lowered position), the resistance received from the water in a predetermined direction (the front-rear direction in this example embodiment) is at a first magnitude in the first position (90) and at a second magnitude, smaller than the first magnitude, in the second position (0). In contrast, when the entire water resistance body 93 is above the water surface, the resistance it receives from water is zero.

[0030] FIG. 3 is a block diagram of a marine propulsion system including the control device for a marine vessel according to an example embodiment.

[0031] The marine propulsion system includes the controller 70, the outboard motor 4, the trolling motor 5, the steering wheel 11, the remote control unit 12, the joystick 13, a display 14, various sensors 15, various manual operators 16, and a memory 17. The marine propulsion system further includes the water resistance switch 30, a first global navigation satellite system (GNSS) sensor 31, a second GNSS sensor 32, a wind speed sensor 33, a tidal current sensor 34, the water resistance assemblies 90L and 90R, a receiver 35, and a buoy 36.

[0032] The water resistance switch 30 includes a left switch 30L and a right switch 30R, which are used to manually operate the water resistance bodies 93 of the water resistance assemblies 90L and 90R, respectively.

[0033] The controller 70 may include a CPU 71, a ROM 72, a RAM 73, and a timer (not illustrated), or processor circuitry configured to perform similar functions. The ROM 72 stores a control program. The CPU 71 loads the control program stored in the ROM 72 into the RAM 73 and executes it, thus implementing various control operations. The RAM 73 provides a workspace for the CPU 71 to execute the control program.

[0034] The outboard motor 4 includes an engine control unit (ECU) 81, a steering control unit (SCU) 82, a rotational speed sensor 83, an engine 84, a steering mechanism 85, various sensors 86, a steering angle sensor 87, and various actuators 88. The ECU 81 and the SCU 82 each include a CPU (not illustrated). The ECU 81 is configured or programmed to control the driving of the engine 84 according to commands from the controller 70. The SCU 82 is configured or programmed to control the driving of the steering mechanism 85 according to commands from the controller 70.

[0035] The steering mechanism 85 causes the outboard motor body 20 to pivot about the steering axis center K (see FIG. 1A), thus changing the orientation of the outboard motor body 20 in the left-right direction. This changes the direction of the propulsive force acting on the stern, where the outboard motor body 20 is mounted. The steering mechanism 85 may be either electric or hydraulic. The various actuators 88 may include a power trim and tilt (PTT) mechanism that causes the outboard motor 4 to pivot about the tilt axis.

[0036] The rotational speed sensor 83 detects the rotation rate (revolutions per unit time) of the engine 84. The various sensors 86 include a throttle opening sensor and the like. The steering angle sensor 87 detects the actual steering angle of the outboard motor 4. Note that the controller 70 may also obtain the actual steering angle from the steering command value output to the steering mechanism 85.

[0037] The trolling motor 5 includes an electric motor 50, a propeller (not illustrated) that generates a propulsive force when driven to rotate by the electric motor 50, and an electric steering unit 56 that rotates the electric motor 50 about the rotation axis J2.

[0038] The steering unit 56 includes, for example, a servo motor. The orientation of the trolling motor 5 can be changed by the steering operation of the steering unit 56. Specifically, the steering unit 56 rotates the electric motor 50 about the rotation axis J2 to change its orientation within a range of 360 degrees or more, thus altering the direction of the propulsive force. This changes the steering angle of the trolling motor 5, which in turn changes the direction of the propulsive force that the trolling motor 5 exerts on the hull 2.

[0039] The trolling motor 5 includes, in addition to the electric motor 50 and the steering unit 56, a motor control unit (MCU) 57, an SCU 58, a steering angle sensor 55, various sensors 60, and an actuator 61.

[0040] The MCU 57 and the SCU 58 each include a CPU (not illustrated). The MCU 57 is configured or programmed to control the driving of the electric motor 50 according to commands from the controller 70. The maximum output of the electric motor 50 may be less than that of the engine 84 of the outboard motor 4. The SCU 58 is configured or programmed to control the driving of the steering unit 56 according to commands from the controller 70, thus changing the direction of the propulsive force acting on the bow, where the trolling motor 5 is mounted.

[0041] The actuator 61 moves the trolling motor 5 between a use position and a storage position. Note that it is not essential to provide a function to enable the trolling motor 5 to transition between the use position and the storage position by power.

[0042] The steering angle sensor 55 detects the steering angle of the trolling motor 5, which changes in response to the steering operation of the steering unit 56. Detection signals from the steering angle sensor 55 and the various sensors 60 are supplied to the controller 70. It is not essential that the hull 2, the outboard motor 4, and the trolling motor 5 be equipped with all the sensors and actuators mentioned above.

[0043] Strictly speaking, the points where the propulsive forces of the propulsion devices act are their respective mounting locations on the hull 2. However, for convenience of explanation, it is assumed herein that the propulsive force of the trolling motor 5 acts on the bow, and the propulsive force of the outboard motor 4 acts at the location of the attachment mechanism at the stern.

[0044] The various sensors 15 include a hull speed sensor, a hull acceleration sensor, an orientation sensor, a distance sensor, an attitude sensor, and a position sensor (not illustrated). The various sensors 15 further include a sensor that detects the operation of the remote control unit 12, a sensor that detects the rotational angle position of the steering wheel 11, a sensor that detects the operation of each switch and paddle on the steering wheel 11, and a sensor that detects the operation of the joystick 13. The hull speed sensor detects the navigation speed (vessel speed) of the marine vessel 1 (hull 2). Detection signals from the various sensors 15 are supplied to the controller 70.

[0045] The various operators 16 include not only operators to maneuver the marine vessel but also setting operators to make various settings and input operators to enter various instructions (not illustrated). Some of the various operators 16 may be located on the steering wheel 11. The various operators 16 are operated by the vessel operator, and the operation signals are supplied to the controller 70. The memory 17 is a read-write non-volatile storage medium.

[0046] The controller 70 may establish predetermined communication with the various sensors 15 and the various operators 16 to exchange information with them. The display 14 displays various types of information.

[0047] The first GNSS sensor 31 and the second GNSS sensor 32 periodically receive GNSS signals from GNSS satellites. As a result, the controller 70 can acquire the current position of each of the GNSS sensors 31 and 32. The first GNSS sensor 31 and the second GNSS sensor 32 are located at different positions. For example, the first GNSS sensor 31 and the second GNSS sensor 32 are arranged at different positions along the front-rear direction. Accordingly, it is possible to determine the hull orientation based on the signals received by the GNSS sensors 31 and 32, without the need for an orientation sensor.

[0048] The wind speed sensor 33 detects the wind speed. The tidal current sensor 34 detects the relative tidal current speed and relative tidal current direction as observed from the hull 2. The configuration of the tidal current sensor 34 is not particularly limited. For example, the tidal current sensor 34 may emit ultrasonic waves at an angle into the sea and analyze the reflected ultrasonic waves to determine the relative tidal current speed and relative tidal current direction.

[0049] The controller 70 determines the absolute tidal current speed based on the relative tidal current speed and the vessel speed. The controller 70 also determines the absolute tidal current direction based on the relative tidal current direction and the direction of the vessel's movement. Hereinafter, unless otherwise specified, the terms tidal current speed and tidal current direction will refer to the absolute tidal current speed and the absolute tidal current direction, respectively.

[0050] The buoy 36 floats on the water and is allowed to drift freely in the drift fishing mode (described below). To minimize the wind effect (resistance), for example, the buoy 36 is designed to protrude less above the water and have a flat top shape. It is desirable for the buoy 36 to move in the same manner as the fishing line, even when exposed to the wind.

[0051] The buoy 36 includes a third GNSS sensor 37 and a transmitter 38. The third GNSS sensor 37 periodically receives GNSS signals from GNSS satellites. This allows the buoy 36 to acquire its current position. The transmitter 38 is configured to output information indicating the position to the outside.

[0052] The receiver 35 receives the information output from the transmitter 38. This allows the controller 70 to acquire the current position of the buoy 36. There is no particular limitation on the communication method between the transmitter 38 and the receiver 35. For example, medium-range or short-range wireless communication may be used.

[0053] The controller 70 is configured or programmed to acquire the relative distance D between the hull 2 and the buoy 36. For example, the controller 70 acquires the relative distance D based on the current position of the hull 2, which is acquired by the first GNSS sensor 31 or the second GNSS sensor 32, and the current position of the buoy 36, which is acquired by the receiver 35. The relative distance D may be acquired using a distance sensor provided on the hull 2, and the acquisition method may use radio waves, ultrasound, or light. In this context, it is not essential for the buoy 36 to include the third GNSS sensor 37 and the transmitter 38, nor is it essential for the hull 2 to include the receiver 35.

[0054] The controller 70 also acquires the relative orientation B of the buoy 36 with respect to the hull 2. The relative orientation B is defined as the angle defined between an imaginary line extending through the center of gravity G of the hull 2 and the buoy 36, as viewed from above, and the centerline C of the hull 2, in the forward direction (see FIG. 5A). For example, the controller 70 first acquires the hull orientation from the orientation sensor or the GNSS sensors 31 and 32. The controller 70 then acquires the relative orientation B based on the current position of the hull 2, the current position of the buoy 36, and the hull orientation.

[0055] In this example embodiment, there are a plurality of vessel maneuvering modes, which can be broadly classified into an outboard motor mode that does not utilize the trolling motor 5 and a cooperative mode that utilizes both the trolling motor 5 and the outboard motor 4. The outboard motor mode is a maneuvering mode in which the outboard motor 4 is controlled primarily based on the rotational operation of the steering wheel 11 and the operation of the remote control unit 12. Other maneuvering modes include a drift fishing mode, which utilizes the water resistance assemblies 90L and 90R to achieve operations suitable for drift fishing. In the drift fishing mode, the trolling motor 5 and/or the outboard motor 4 may also be used.

[0056] FIG. 4 is a flowchart of a drift fishing mode process. FIGS. 5A to 5E are schematic diagrams illustrating an example of a control in the drift fishing mode process.

[0057] The drift fishing mode process is implemented by the CPU 71, which loads a program stored in the ROM 72 or the like into the RAM 73 and executes it. This process is initiated according to an instruction to start the drift fishing mode received through the various operators 16.

[0058] After the process starts, the CPU 71 monitors the outputs of the sensors and the like and acquires or determines the latest values of the current position of the hull 2, the current position of the buoy 36, the hull orientation, the absolute tidal current direction, the relative orientation B of the buoy 36, and the like at regular time intervals. The absolute tidal current direction need not necessarily be determined using the tidal current sensor 34, instead it may be derived from the temporal changes (trajectory) of the current position of the buoy 36.

[0059] At the start of the process, the vessel operator floats the buoy 36 on the water. At this time, as illustrated in FIG. 5A, the buoy 36 may be connected to the hull 2 with a connector 39, such as a flexible string, to prevent it from being lost.

[0060] In addition, at the start of the process, the vessel operator pre-registers a target relative orientation T, which serves as a target value for the relative orientation B. The target relative orientation TO is stored in the memory 17. As an example, the target relative orientation TO is set to 90 to the left in the forward direction. Note that, in FIGS. 5A to 5E, the water resistance bodies 93 of the water resistance assemblies 90L and 90R are denoted as 93L and 93R, respectively.

[0061] In this process, a first distance D1, a second distance D2, and a third distance D3 are used for comparison with the relative distance D. The relationship among these distances is represented as D1<D2<D3. Their values are stored in the memory 17. For drift fishing, an appropriate relative distance D is one that satisfies the condition D1<DD2.

[0062] In step S101, the CPU 71 acquires the latest relative distance D in the manner described above. In step S102, the CPU 71 determines whether the relative distance D is equal to or less than the first distance D1 (DD1). If the condition DD1 is not satisfied, the process proceeds to step S104, where the CPU 71 determines whether the relative distance D is greater than the first distance D1 and is equal to or less than the second distance D2 (D1<DD2).

[0063] If the condition D1<DD2 is not satisfied, the process proceeds to step S108, where the CPU 71 determines whether the relative distance D is greater than the second distance D2 and is equal to or less than the third distance D3 (D2<DD3).

[0064] In step S104, if the CPU 71 determines that the condition D1<DD2 is satisfied, indicating that the relative distance D is within an appropriate range, the process proceeds to step S105. In step S105, the CPU 71 determines whether the angular deviation 40 in the relative orientation B of the buoy 36 from the target relative orientation T exceeds a predetermined angle 0 (0<). The value of the predetermined angle 0 is stored in the memory 17.

[0065] If the CPU 71 determines that the condition 0< is not satisfied, indicating that both the relative distance D and the relative orientation B are appropriate, the process proceeds to step S107. In step S107, the CPU 71 sets both the water resistance bodies 93L and 93R to the second position (0). In the case where step S107 is performed, it is considered that the wind has little effect on the hull 2, and that the hull 2 and the buoy 36 are floating along with the tidal current, as illustrated in FIG. 5A. Therefore, the appropriate relative distance D is maintained by setting both the water resistance bodies 93 to the second position.

[0066] On the other hand, if the condition 0< is satisfied, indicating that the relative orientation B is inappropriate, the process proceeds to step S106, where the CPU 71 performs relative orientation deviation correction control. In the relative orientation deviation correction control, the CPU 71 sets one of the water resistance bodies (one of the water resistance bodies 93L and 93R) to the first position and another (the other of the water resistance bodies 93L and 93R) to the second position. With respect to the control of the water resistance bodies 93L and 93R alone, the state corresponds to that illustrated in FIG. 5E.

[0067] Here, the water resistance body set to the first position (90) is the one that generates a rotational moment on the hull 2 in a direction to correct the angular deviation . In the example of FIG. 5E, this corresponds to the water resistance body 93L. When the water resistance body 93L is in the first position, it is subjected to resistance from the tidal current, causing a counterclockwise turning force about the center of gravity G to be exerted on the hull 2. As a result, the angular deviation is reduced. Such control makes it easier to maintain the relative orientation Be of the buoy 36 close to the target relative orientation TO, thus maintaining a favorable fishing environment.

[0068] In step S108, if the CPU 71 determines that the condition D2<DD3 is satisfied, indicating that the buoy 36 has deviated slightly to a farther side from the appropriate distance to the hull 2, the process proceeds to step S109. In step S109, the CPU 71 performs the same process as in step S105. In step S109, if the CPU 71 determines that the condition 0< is not satisfied, indicating that the relative distance D is inappropriate while the relative orientation B is appropriate, the process proceeds to step S111.

[0069] In step S111, the CPU 71 sets both the water resistance bodies 93L and 93R to the first position (90). In the case where step S111 is performed, it is considered that the wind effect on the hull 2 is greater than that on the buoy 36, which is less affected by the wind, and that the hull 2 has moved away from the buoy 36, as illustrated in FIG. 5B. Therefore, by setting both the water resistance bodies to the first position, the extent to which the movement of the hull 2 depends on the tidal current can be increased. In effect, this acts as a brake on the hull 2 to resist the force exerted by the wind. As a result, the hull 2 and the buoy 36 or the fishing line are restrained from moving differently, making the fishing environment more favorable. After step S111, the process proceeds to step S112.

[0070] In step S109, if the CPU 71 determines that the condition 0< is satisfied, this indicates that both the relative distance D and the relative orientation B are inappropriate. In this case, correcting the relative orientation B takes precedence over correcting the relative distance D, and the process proceeds to step S110, where the CPU 71 performs the same relative orientation deviation correction control as in step S106. With respect to the control of the water resistance bodies 93L and 93R alone, the state corresponds to that illustrated in FIG. 5E. Here, also, the water resistance body set to the first position (90) is the one that generates a rotational moment on the hull 2 in a direction to correct the angular deviation . In the example of FIG. 5E, this corresponds to the water resistance body 93L. After step S110, the process proceeds to step S112.

[0071] In step S112, the CPU 71 determines whether the condition D2<DD3 has continued to be satisfied for more than a predetermined time. The predetermined time begins counting when the determination in step S108 is Yes for the first time and is reset when step S113 is performed. If the CPU 71 determines that the condition D2<DD3 has not remained satisfied for more than the predetermined time, the process proceeds to step S114.

[0072] On the other hand, if the CPU 71 determines that the condition D2<DD3 has remained satisfied for more than the predetermined time, indicating that the relative distance D has remained in an inappropriate range for an extended period, the process proceeds to step S113. Additionally, if the CPU 71 determines that the condition D2<DD3 is not satisfied in step S108, this means that D3<D, indicating that the relative distance D has become too large, as illustrated in FIG. 5C, and the process proceeds to step S113.

[0073] In step S113, the CPU 71 performs a propulsion device control. In the propulsion device control, the CPU 71 corrects the position of the hull 2 using the outboard motor 4 and the trolling motor 5. Specifically, the CPU 71 is configured or programmed to control the outboard motor 4 and the trolling motor 5 such that the relative distance D satisfies D1<DD2 and the relative orientation B of the buoy 36 matches the target relative orientation T (with the angular deviation 40 being less than the predetermined angle 0, preferably zero). The propulsion device control may also involve controlling the water resistance bodies 93L and 93R. This restores the positional relationship between the hull 2 and the buoy 36 or the fishing line to an appropriate state (see FIG. 5A).

[0074] In step S102, if the CPU 71 determines that the condition DD1 is satisfied, indicating that the hull 2 and the buoy 36 have become too close due to the effect of a crosswind or the like, as illustrated in FIG. 5D, the process proceeds to step S103. In step S103, the CPU 71 performs the same propulsion device control as in step S113.

[0075] After steps S103, S106, S107, and S113, the process proceeds to step S114. In step S114, the CPU 71 performs other processes, and the process then returns to step S101. The other processes include those performed according to user instructions, such as processes based on other operations, a mode-switching process, and a process for terminating this process.

[0076] According to an example embodiment, the CPU 71, functioning as a controller, is configured or programmed to control the water resistance bodies 93 of the water resistance assemblies 90L and 90R based on the relative distance D. For example, in principle, the control is performed such that the hull 2 is located in a range that satisfies D1<DD2, maintaining the hull 2 in an appropriate position. In addition, when the angular deviation 40 exceeds the predetermined angle 0, the relative orientation deviation correction control (S106, S110) is performed, maintaining the hull 2 in an appropriate orientation. As a result, even under windy conditions, the hull 2 can move primarily along with the tidal current without requiring manual operation of the water resistance bodies 93, while minimizing the use of the propulsion devices to follow the buoy 36 thus improving quietness. This enables the provision of a comfortable drift fishing environment.

[0077] Moreover, if the relative distance D is either too short or too long, the propulsion device control (S103, S113) is performed. Furthermore, if the hull 2 remains in a range that satisfies D2<DD3 for too long, the propulsion device control (S113) is also performed. This makes it possible to address cases where the position and orientation of the hull 2 cannot be corrected by controlling the water resistance bodies 93 alone.

[0078] Note that the water resistance assemblies 90L and 90R need not necessarily be located at the stern. As long as they are provided in a pair on the left and right sides as illustrated in FIGS. 6A and 6B, their locations are not particularly limited.

[0079] FIGS. 6A and 6B are schematic diagrams illustrating modifications to the configuration of the water resistance assemblies 90L and 90R. As illustrated in FIG. 6A, the water resistance assemblies 90L and 90R may be arranged on the left and right sides of the hull 2, respectively. Alternatively, as illustrated in FIG. 6B, the water resistance assemblies 90L and 90R may be arranged in a pair, one on the left side and one on the right side, near the bow.

[0080] The water resistance bodies 93 are preferably provided as a pair, one on the left and one on the right of the hull, but there may be three or more of the water resistance bodies 93.

[0081] In configuring the water resistance bodies 93 such that the magnitude of resistance they receive from the water in a predetermined direction differs when they are in the first position and when they are in the second position, it is not essential that the predetermined direction be the front-rear direction, and the direction may be arbitrary. The water resistance bodies 93 need not necessarily be plate-shaped (e.g., relatively thin and flat structures) and may have other shapes. It is also not essential that the water resistance bodies 93 at the first position and at the second position be perpendicular to each other.

[0082] Although the present example embodiment includes two motors, the outboard motor 4 and the trolling motor 5, as propulsion devices, it suffices if two or more propulsion devices are provided to enable the hull 2 to turn. For example, one propulsion device may be provided at the bow, and two propulsion devices may be provided on either side of the stern. It is not essential that the propulsion devices each have an engine, and one or more may be electrically powered.

[0083] In addition, although the water resistance bodies 93 have been described as having their positions adjustable in two steps, they are not limited to this and may be configured for continuous adjustment or adjustment in three or more steps. For example, a trim tab may be used. Furthermore, the water resistance bodies 93 need not necessarily be configured to pivot underwater, and may be of a type that moves between an above-water position and an underwater position, such as a protruding type. If the water resistance bodies 93 are configured for continuous adjustment or adjustment in three or more steps, the left and right water resistance bodies 93 can be controlled to protrude by different amounts in the relative orientation deviation correction control (S106, S110).

[0084] If the focus is solely on reducing or preventing differing movements between the hull 2 and the buoy 36 or fishing lines through a simple control to improve the drift fishing environment, it is not essential to include the relative orientation deviation correction control (S106, S110) or the propulsion device control (S103, S113). It is also not essential to include step S112, and the process may proceed directly to step S114 after steps S110 and S111.

[0085] While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.