Control system for marine vessel, marine vessel, and control method for marine vessel

A control system for a marine vessel that has a propulsion device including an engine. The control system has an opening angle adjustment device configured to adjust a throttle opening angle of the engine, and a controller including a computing device and a non-transitory storage medium containing program instructions. The execution of the program instructions by the computing device causes the controller to judge whether or not a hull of the marine vessel has entered a planing state, set a predetermined mode in which the planing state is maintained, and upon determining that the predetermined mode is set and that the hull has entered the planing state, control the opening angle adjustment device to keep the hull in the planing state even when the hull has decelerated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2019-173742 filed on Sep. 25, 2019, which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a marine vessel, a control system for the marine vessel, and a control method for the marine vessel.

2. Description of the Related Art

Generally, in a marine vessel, as the speed of a hull increases with increase in the throttle opening angle of an engine in a propulsion device, the hull eventually shifts from a hump state into a planing state. In a case where a sailing speed is equal to or higher than a predetermined speed when it is judged that the hull is in the planing state, a driving control apparatus disclosed in Japanese Laid-open Patent Publication (Kokai) No. 2006-199136 uses this sailing speed as a target sailing speed to control the throttle opening angle.

When, for example, the marine vessel is maneuvered in shallows, the hull is required to plane as slowly as possible. However, if the throttle opening angle becomes too small, the hull cannot maintain its planing state, and on the other hand, if the throttle opening angle becomes too large, the speed of the hull becomes too high. It is difficult to manually adjust the throttle opening angle in order to keep the marine vessel planing at low speed.

SUMMARY OF THE INVENTION

The present invention provides a marine vessel, a control system for a marine vessel, and a control method for the marine vessel which are capable of maintaining a planing state of a hull at relatively low speed.

According to an embodiment of the present invention, a control system for a marine vessel, comprising: an opening angle adjustment unit configured to adjust a throttle opening angle of an engine in a propulsion device; and a controller configured to judge whether or not a hull has entered a planing state, set a predetermined mode in which the planing state is maintained, and in a case where the predetermined mode is set and it is judged that the hull has entered the planing state, control the opening angle adjustment unit so as to keep the hull in the planing state even when the hull has decelerated.

According to this arrangement, in a case where the predetermined mode is set and it is judged that the hull has shifted to the planing state, the opening angle adjustment unit is controlled so as to maintain the planing state of the hull even when the hull has decelerated. As a result, the planing state can be maintained at relatively low speed.

Further features of the present invention will become apparent from the following description of preferred embodiments with reference to the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, a description will be given of an embodiment of the present invention.FIG. 1is a top view of a marine vessel to which a control system for the marine vessel according to the embodiment is applied. The marine vessel11has a hull13, a plurality of (for example, two) outboard motors15as marine propulsion devices mounted on the hull13, and a plurality of (for example, a pair of) trim tabs20. A central unit10, a steering wheel18, and a throttle lever12are provided in the vicinity of a cockpit in the hull13.

In the following description, a fore-and-aft direction, a crosswise direction, and a vertical direction mean a fore-and-aft direction, a crosswise direction, and a vertical direction, respectively, of the hull13. For example, as shown inFIG. 1, a centerline C1extending in the fore-and-aft direction of the hull13passes through the center of gravity G of the marine vessel11. The fore-and-aft direction is the direction along the centerline C1. Fore or front means a direction toward the upper side ofFIG. 1along the centerline C1. Aft or rear means the direction toward the lower side ofFIG. 1along the centerline C1. The crosswise direction is defined based on a direction when the hull13is viewed from the rear. The vertical direction is a direction vertical to the fore-and-aft direction and the crosswise direction.

The two outboard motors15are mounted side by side on a stern of the hull13. To distinguish the two outboard motors15, the one located on the port side is referred to as an “outboard motor15A”, and the one located on the starboard side is referred to as an “outboard motor15B”. The outboard motors15A and15B are mounted on the hull13via respective mounting units14(14A and14B). The outboard motors15A and15B have respective engines16(16A and16B) which are internal combustion engines. The outboard motors15each obtain a propulsive force from propellers (not illustrated) that are rotated by driving force of the respective engines16.

The mounting units14A and14B each include a swivel bracket, a cramp bracket, a steering shaft, and a tilt shaft (none of them is illustrated). The mounting units14A and14B further include respective power trim and tilt mechanisms (PTT mechanisms)23(23A and23B) (FIG. 3). Each of the PTT mechanisms23turns the corresponding outboard motor15about the tilt shaft. This makes it possible to change an inclination angle of the outboard motors15with respect to the hull13, and hence a trim adjustment can be made, and the outboard motors15can be tilted up and down. Moreover, each of the outboard motors15is turnable about a center of turn C2(about the steering shaft) with respect to the swivel bracket. By operating the steering wheel18, each of the outboard motors15is turned about the center of turn C2in the crosswise direction (direction R1). Thus, the marine vessel11is steered.

The pair of trim tabs20is attached to the stern on the port side and the starboard side such that it can swing about a swing axis C3. To distinguish the two trim tabs20from each other, the one located on the port side is referred to as a “trim tab20A”, and the one located on the starboard side is referred to as a “trim tab20B”.

FIG. 2is a side view of the trim tab20A attached to the hull13. The trim tabs20A and20B have the same construction, and hence the construction of only the trim tab20A will be described. The trim tab20A has a trim tab actuator22A and a tab21A. The tab21A is attached to the rear of the hull13such that it can swing about the swing axis C3. For example, a base end portion of the tab21A is attached to the rear of the hull13, and a free end portion of the tab21A swings up and down (in a swinging direction R2) about the swing axis C3. The tab21A is an example of a posture control tab that controls the posture of the hull13.

The trim tab actuator22A is disposed between the tab21and the hull13such that it connects the tab21A and the hull13together. The trim tab actuator22A drives the tab21A to swing it with respect to the hull13. It should be noted that the tab21A indicated by a chain double-dashed line inFIG. 2is at a position where its free end portion is at the highest level (a position where the amount by which the tabs21is lowered by 0%), and this position corresponds to a retracted position. The tab21A indicated by a solid line inFIG. 2is at a position where its free end portion is at a lower level than the bottom (keel) of the marine vessel11. It should be noted that a range where the tab21A is able to swing is not limited to the one illustrated inFIG. 2. The swinging direction R2is defined with reference to the swing axis C3. The swing axis C3is perpendicular to the centerline C1and parallel to, for example, the crosswise direction. It should be noted that the swing axis C3may extend diagonally so as to cross the center of turn C2.

FIG. 3is a block diagram of a maneuvering system. The maneuvering system includes the control system for the marine vessel according to the present embodiment. The marine vessel11has a controller unit30, a throttle position sensor34, a steering angle sensor35, a hull speed sensor36, a hull acceleration sensor37, a posture sensor38, a receiving unit39, a display unit9, and a setting operation unit19. The marine vessel11also has engine rpm detection units17(17A and17B), turning actuators24(24A and24B), the PTT mechanisms23(23A and23B), the trim tab actuators22(22A and22B) (seeFIG. 2as well). The marine vessel11also has a throttle sensor25and an opening angle adjustment device (opening angle adjustment unit)26.

The controller unit30, the throttle sensor25, the opening angle adjustment unit26, the steering angle sensor35, the hull speed sensor36, the hull acceleration sensor37, the posture sensor38, the receiving unit39, the display unit9, and the setting operation unit19are included in the central unit10or disposed in the vicinity of the central unit10. The turning actuators24A and24B and the PTT mechanisms23A and23B are provided for the outboard motors15A and15B, respectively. The throttle position sensor34and the engine rpm detection units17are provided in the respective outboard motor15. The trim tab actuators22A and22B are included in the trim tabs20A and20B, respectively.

The controller unit30includes a CPU31, a ROM32, a RAM33, and a timer which is not illustrated. The ROM32stores a control program. The CPU31expands the control program stored in the ROM32into the RAM33to implement various types of control processes. The RAM33provides a work area for the CPU31to execute the control program.

Results of detection by the sensors25and34to38and the engine rpm detection units17are supplied to the controller unit30. The throttle sensor25detects the operational position of the throttle lever12operated. The throttle position sensor34detects the opening angle of a throttle valve, which is not illustrated. The opening angle adjustment unit26adjusts the opening angle of the throttle valve. In normal control, the CPU31controls the opening angle adjustment unit26based on the operational position of the throttle lever12, and when a planing mode (a predetermined mode) (which will be described later) in which a planing state is maintained is applied, controls the opening angle adjustment unit26according to situations. Thus, in the planing mode, the operational position of the throttle lever12and the actual opening angle of the throttle valve do not always correspond to each other.

The steering angle sensor35detects the turn angle of the steering wheel18that has been turned. The hull speed sensor36and the hull acceleration sensor37detect the speed (vessel speed) and the acceleration, respectively, of the marine vessel11(the hull13) while it is traveling.

The posture sensor38includes, for example, a gyro sensor, a magnetic direction sensor, and so forth. Based on a signal output from the posture sensor38, the controller unit30calculates a roll angle, a pitch angle, and a yaw angle. It should be noted that the controller unit30may calculate the roll angle and the pitch angle based on a signal output from the hull acceleration sensor37. The receiving unit39includes a GNSS (Global Navigation Satellite Systems) receiver such as a GPS and has a function of receiving GPS signals and various types of signals as positional information. A signal received by the receiving unit39is supplied to the CPU31. From a speed restricted area or the ground in its vicinity, an identification signal for providing notification that the area is a speed restricted area is transmitted. The speed restricted area means an area in a harbor or the like which requires to limit the speed of a marine vessel to a predetermined speed or lower. The receiving unit39also has a function of receiving the identification signal. It should be noted that the acceleration of the hull13may also be obtained from a GPS signal received by the receiving unit39.

The engine rpm detection units17detect the number of revolutions per unit time of the respective engines16(hereafter referred to as “the engine rpm”). The display unit9displays various types of information. The setting operation unit19includes an operator by which a vessel operator performs operations relating to maneuvering, a PTT operation switch, a setting operator by which a vessel operator makes various settings, and an input operator by which a vessel operator inputs various types of instructions (none of them is illustrated).

The turning actuators24turn the respective outboard motors15about the respective centers of turn C2with respect to the hull13. The turns of the outboard motors15A and15B about the respective centers of turn C2can change the direction in which the propulsive force acts on the centerline C1of the hull13. The PTT mechanisms23turn the respective outboard motors15about the tilt shaft to tilt the respective outboard motors15with respect to the cramp bracket. The PTT mechanisms23are operated by, for example, the PTT operation switch being operated. As a result, the inclination angles of the outboard motors15with respect to the hull13can be changed.

The trim tab actuators22A and22B are controlled by the controller unit30. For example, the controller unit30operates the trim tab actuators22A and22B by outputting control signals to them. The operation of each of the trim tab actuators22A and22B which are driving units causes the corresponding tab21to swing. It should be noted that actuators adopted for the PTT mechanisms23or the trim tab actuators22A and22B may be either a hydraulic type or an electric type.

It should be noted that the controller unit30may obtain results of detection by the engine rpm detection unit17via a remote control ECU, which is not illustrated. It should be noted that the controller unit30may also control the engines16via outboard motor ECUs (not illustrated) provided in the respective outboard motors15.

A signal output from the posture sensor38is also used to detect a turning state. The signal output from the posture sensor38includes a yaw rate (yaw turn angular velocity) which is an angular velocity of turn around a yaw axis. Based on the yaw rate output from the posture sensor38, the CPU31judges whether or not a traveling direction of the hull13is a straight traveling direction. When the yaw rate is equal to or smaller than a predetermined value, the CPU31judges that the traveling direction of the hull13is the straight traveling direction, and when the yaw rate is greater than the predetermined value, the CPU31judges that the traveling direction of the hull13is a turning direction. It should be noted that the CPU31may judge whether or not the traveling direction of the hull13has changed, based on time-series data on the yaw angle obtained from the magnetic direction sensor of the posture sensor38. It should be noted that in the present embodiment, it is not absolutely necessary to detect the turning state.

FIG. 4is a view showing the relationship between vessel speed and pitch angle. The throttle opening angle of the engine16in the outboard motor15is increased from a stopped state of the hull13, and the hull13reaches high speed, the hull13eventually shifts from a hump state to a planing state. Namely, as the vessel speed V obtained by the hull speed sensor36increases from zero, the pitch angle P of the hull13increases, and then the pitch angle P rapidly decreases. After that, when the vessel speed V further increases and the pitch angle P becomes substantially equal to zero, the planing state of the hull13becomes stable.

A state in which the speed of the hull13falls within a speed range indicated by diagonal lines inFIG. 4corresponds to a state in which the hull13is in a critical state between a non-planing state and the planing state. In other words, the state in which the speed of the hull13falls within the speed range indicated by the diagonal lines inFIG. 4corresponds to a state in which the hull13is in a critical state between a hump state and a planing state. The speed range indicated by the diagonal lines is a range from a critical minimum speed V1and a critical maximum speed V2. Even in the planing state, when the speed of the hull13enters the critical state, there is a possibility that the hull13will shift to the non-planing state if the throttle opening angle remains unchanged. It should be noted that in the strict sense, the range where the speed of the hull13is in the critical state varies with loads the hull13carries and positions of the hull's center of gravity.

A speed V0, which is a predetermined fixed value, is sufficiently higher than zero and lower than a speed at which the hull13enters the planing state. A maximum pitch angle P1, which is a maximum pitch angle in the critical state, is a fixed value. A minimum pitch angle P2, which is a minimum pitch angle in the critical state, is a fixed value. The critical minimum speed V1mentioned above is a speed at which the pitch angle P reaches the maximum pitch angle P1when the vessel speed V is higher than the speed V0. The critical maximum speed V2is a speed at which the pitch angle P reaches the minimum pitch angle P2when the vessel speed V is higher than the speed V0. The speed V0, the maximum pitch angle P1, and the minimum pitch angle P2are stored in the ROM32in advance.

It should be noted that in the present embodiment, it is not absolutely necessary to recognize the critical minimum speed V1. A set speed THV is a speed set at a higher value than the critical maximum speed V2. In the present embodiment, it is not necessary to use the set speed THV. It should be noted that a speed Vz is an example of the vessel speed in the planing state at not-low speed.

When maneuvered in shallows or the like, the hull13is required to plane as slowly as possible. However, it is difficult to manually adjust the throttle opening angle so as to keep the planing state at low speed. Thus, as described below with reference toFIG. 5, by using the critical maximum speed V2substantially as a target value of the vessel speed V, the CPU31controls the opening angle adjustment unit26so as to keep the planing state.

FIG. 5is a flowchart of a throttle control process. This process is implemented by the CPU31expanding a control program stored in the ROM32into the RAM33and executing the same. This process is started when, for example, the maneuvering system is activated. In this process, the CPU31acts as a control unit of the present invention.

First, in step S101, the CPU31carries out a setting process. In the setting process, settings are made based on matters input through the setting operation unit19. For example, when a user issues an instruction to set the planing mode, in which the planing state is maintained, by operating the setting operation unit19, the CPU31sets the planing mode. In step S102, the CPU31determines whether or not the planing mode is set. When the planing mode is not set, the process proceeds to step S104, in which the CPU31performs normal control. In the normal control, the CPU31controls the opening angle adjustment unit26based on the operational position of the throttle lever12(throttle operator). Then, in step S105, the CPU31carries out other processes, followed by the process returning to the step S101. Here, “other processes” mean various types of processes which are carried out according to, for example, settings made and operations performed with the setting operation unit19. For example, when an instruction to cancel the planing mode is issued using the setting operation unit19, the planing mode is canceled. Also, when an instruction to stop the maneuvering system is issued, a process that ends this flowchart is carried out.

As a result of the determination in the step S102, when the planing mode is set, the CPU31determines whether or not the hull13has entered the planing state. Here, whether or not the hull13has entered the planing state is determined according to whether or not the pitch angle P is equal to or smaller than the minimum pitch angle P2(P≤P2) in a state where the vessel speed V is higher than the speed V0(V0<V). When the pitch angle P is equal to or smaller than the minimum pitch angle P2(P≤P2) in a state where the vessel speed V is higher than the speed V0(V0<V), it is determined that the hull13has entered the planing state. As described above, the pitch angle P is obtained based on a signal output from the posture sensor38.

When the CPU31determines in the step S103that the hull13has not entered the planing state, the process proceeds to the step S104. On the other hand, the hull13has entered the planing state, the CPU31starts decelerating the hull13in step S106. Namely, the CPU31controls the opening angle adjustment unit26so as to reduce the throttle opening angle of the engine16by a predetermined amount irrespective of the operational position of the throttle lever12.

In step S107, the CPU31determines whether or not the planing mode is applied, and when the planing mode is not applied, the process proceeds to the step S104. It should be noted that in step S110, which will be described later, the planing mode may be canceled. On the other hand, when the planing mode is applied, the process proceeds to step S108, in which the CPU31determines whether or not the hull13is in the critical state between the planing state and the non-planing state. Namely, the CPU31determines whether or not the hull13has shifted from the planing state to the critical state. Here, whether or not the hull13is in the critical state is determined based on the vessel speed V and the pitch angle P. Specifically, when the pitch angle P is greater than the minimum pitch angle P2and equal to or smaller than the maximum pitch angle P1(P2<P≤P1) in a state where the vessel speed V is higher than the speed V0(V0<V), it is determined that the hull13is in the critical state.

As a result of the determination in the step S108, when the hull13is in the critical state, there is a possibility that if nothing is done, the hull13will shift to the non-planing state. To avoid that situation, in step S109, the CPU31controls the opening angle adjustment unit26so as to increase the throttle opening angle of the engine16by a predetermined amount irrespective of the operational position of the throttle lever12. This brings the hull13back from the critical state to the low-speed planing state. The CPU31proceeds then the process to the step S110.

As a result of the determination in the step S108, when the hull13is not in the critical state, the process proceeds to step S111, in which the CPU31determines whether or not the hull13is in the planing state. As a result of the determination in the step S111, when the hull13is in the planing state, the process proceeds to step S112, in which the CPU31controls the opening angle adjustment unit26so as to reduce the throttle opening angle of the engine16by a predetermined amount irrespective of the operational position of the throttle lever12. As a result, while the planing state is continuing after the start of deceleration, the throttle opening angle gradually decreases, causing the vessel speed V to decrease. Also when the hull13has shifted from the critical state to the planing state, the CPU31reduces the throttle opening angle of the engine16by only the predetermined amount. This prevents the speed of the hull13from becoming too high. Thus, the planing state at relatively low speed is maintained. After that, the CPU31proceeds the process to the step S110.

As described above, by repeating the steps S109and S112, the throttle angle is adjusted by using the critical maximum speed V2substantially as a target speed of the hull13.

On the other hand, when the CPU31determines in the step S111that the hull13is not in the planing state, the CPU31proceeds the process to the step S104. Namely, in this case, the hull13has entered the non-planing state, and hence control performed by the CPU31temporarily returns to the normal control. In the step S110, the CPU31carries out other processes as with the step S105, followed by the process returning to the step S107.

It should be noted that even in a case where the planing mode is set in a state where the hull13has entered the planing state, the opening angle adjustment unit26is controlled in step S112so as to reduce the throttle opening angle of the engine16by the predetermined amount. Thus, by adopting an appropriately small value as this predetermined amount, the hull13can be gradually decelerated. It should be noted that the predetermined amounts used in the respective steps S106, S109, and S112should not necessarily be the same.

According to the present embodiment, when it is judged that the planing mode is set and the hull13has entered the planing state, the hull13is decelerated. Then, the opening angle adjustment unit26is controlled to keep the hull13in the planing state even when the hull13has been decelerated. Specifically, when it is judged that the hull13has shifted from the planing state to the critical state while the planing mode is applied, the opening angle adjustment unit26is controlled so as to increase the throttle opening angle. Also, when it is judged that the hull13has shifted from the critical state to the planing state, the opening angle adjustment unit26is controlled so as to decrease the throttle opening angle. As a result, the vessel speed V is controlled by using the critical maximum speed V2substantially as a target value, and hence the planing state at relatively low speed can be maintained.

A description will now be given of another embodiment of the present invention. The present embodiment differs from the embodiment firstly described above in its throttle control process, and they are identical in the other features.

FIG. 6is a flowchart of a throttle control process according to the present embodiment. This throttle control process is carried out on the same condition and by the same component as the one described with reference toFIG. 5. In steps S201to205, the CPU31carries out the same processes as those in the steps S101to S105inFIG. 5.

As a result of the determination in the step S203, when the hull13has entered the planing state, the process proceeds to step S206, in which the CPU31obtains the vessel speed V at the time when the hull13shifts from a state other than the planing state to the planing state, and then the CPU31stores the obtained vessel speed V in the RAM33, which is an example of a storage unit. Then, in step S207, the CPU31sets a value based on the vessel speed V stored in the RAM33as the set speed THV. The stored vessel speed V is estimated to be a value close to the critical maximum speed V2, and hence the CPU31sets, for example, a value greater by a margin than the critical maximum speed V2as the set speed THV.

It should be noted that in the step S206, when the planing mode is set in the state where the hull13is not in the planing state, the above-mentioned vessel speed V can be obtained. Namely, in a case where the process proceeds from the step S203to the step S206after proceeding from the step S203to the step S204, the CPU31can obtain the above-mentioned vessel speed V. However, in a case where the planing mode is set after the hull13enters the planing state, the CPU31cannot obtain the above-mentioned vessel speed V. In this case, the CPU31sets a fixed value as the set speed THV in step S207. This fixed value is stored in the ROM32in advance. This fixed speed is a value obtained by, for example, adding a margin to a “value corresponding to the critical maximum speed V2”, which is experimentally known in advance. As described above, since the critical maximum speed V2varies with loads the hull13carries, the “value corresponding to the critical maximum speed V2” is a value obtained under average conditions. It should be noted that in the step S207, the fixed value may always be set as the set speed THV irrespective of the vessel speed V.

In step S208, the CPU31carries out the same process as in the step S106inFIG. 5. In steps S209to S214, a range from the critical maximum speed V2to the set speed THV is set as a target range, and the throttle opening angle is adjusted so that the vessel speed V can fall within this target range. Namely, the set speed THV corresponds to an upper limit to a target range of the vessel speed V, which is targeted so as to maintain the planing state at low speed. First, in the steps S209to S212, the CPU31carries out the same processes as those in the steps S107to S110inFIG. 5. When the CPU31determines in the step S209that the planing mode is not applied, the process proceeds to the step S204. When the CPU31determines in the step S210that the hull13is not in the critical state, the process proceeds to the step S213.

In the step S213, the CPU31obtains the present vessel speed V and determines whether or not the present vessel speed V is higher than the set speed THV (V>THV). In a state where the present vessel speed V is not higher than the set speed THV, the vessel speed V falls within the target range and the planing state at low speed is maintained, and thus the CPU31proceeds the process to the step S212. In a state where the present vessel speed V is higher than the set speed THV, the vessel speed V falls beyond the target range, and hence the process proceeds to the step S214, in which the CPU31carries out the same process as the one in the step S112inFIG. 5. The process then proceeds to the step S212. It should be noted that in the step S212, a process in which the process returns to the step S204when the hull13has entered the non-planing state is carried out in addition to the same process as the one in the step S110.

According to the present embodiment, as with the embodiment firstly described above, when it is judged that the hull13has shifted from the planing state to the critical state while the planing mode is applied, the opening angle adjustment unit26is controlled so as to increase the throttle opening angle. Also, in the present embodiment, when the present vessel speed V becomes higher than the set speed THV, the opening angle adjustment unit26is controlled so as to decrease the throttle opening angle. As a result, the vessel speed V is controlled to substantially fall within the target range between the critical maximum speed V2and the set speed THV. Therefore, the same effects as those in the embodiment firstly described above can be obtained from the standpoint of maintaining the planing state at relatively low speed.

It should be noted that as described above, the vessel speed V stored when the hull13has shifted into the planing state is a value close to the critical maximum speed V2. Here, the throttle opening angle may be adjusted by setting the stored vessel speed V as the target speed of the hull13. Alternatively, in the embodiment firstly described above, the throttle opening angle may be adjusted by setting the “value corresponding to the critical maximum speed V2”, which is experimentally known in advance, as the target speed for the hull13. In such cases, control can be performed in substantially the same manner as in the control performed in the embodiment firstly described above.

A description will now be given of further another embodiment of the present invention. The present embodiment differs from the embodiment secondly described above in that the set speed THV is varied according to the turning state of the hull and is identical with the embodiment secondly described above in the other features.

FIG. 7is a flowchart of a throttle control process according to the present embodiment. Processes in steps S301to S303are carried out immediately after the step S212(the other processes) inFIG. 6. It should be noted that the processes in steps S301to S303may be carried out either immediately before the step S212or as a part of the step S212.

First, in the step S301, based on a signal output from the posture sensor38, the CPU31determines whether or not the hull13is turning. When the hull13is turning, the process proceeds to the step S302, in which the CPU31sets a new set speed THV (i.e. updates the set speed THV) by adding a predetermined amount to the present set speed THV (i.e. upping the present set speed THV). The CPU31then returns the process to the step S209. The reasons to increase the set speed THV will be described below.

One reason is that while the hull13is turning, there is a possibility that the pitch angle P and the vessel speed V cannot be accurately detected. Another reason is that when the vessel speed V is obtained using a GPS, there is a high possibility that the vessel speed V smaller (slower) than it actually is will be obtained. Therefore, increasing the set speed THV can avoid a state where the hull13is likely to shift from the planing state to the critical state.

As a result of the determination in the step S301, when the hull13is not turning, the process proceeds to step S303, in which the CPU31resets the set speed THV to the original value (that was set in the step S207). It should be noted that when the set speed THV has not been updated, this set speed THV is maintained. Then, the CPU31return the process to the step S209.

According to the present embodiment, the same effects as those in the embodiment secondly described above can be obtained from the standpoint of maintaining the planing speed at relatively low speed. Moreover, during the time that it is detected that the hull13is turning, the set speed THV is set to a larger value as compared to the time that it is not detected that the hull13is turning, and hence the planing state can be maintained at relatively low speed even while the hull13is turning.

It should be noted that the predetermined value added in the step S302may be a fixed value. Alternatively, the amount of turn may be detected, and a value corresponding to the detected amount of turn may be added to the set speed THV in place of the predetermined value. In this case, the set speed THV appropriate to the state of turn can be set, and therefore, the planing state at low speed can be maintained irrespective of the extent to which the hull13turns.

A description will now be given of further another embodiment of the present invention. As compared to the embodiment firstly described above, the present embodiment focuses on a case where the throttle lever12is operated while the opening angle adjustment unit26is being controlled so as to keep the hull13in the planing state.

FIG. 8is a flowchart of a throttle control process according to the present embodiment. Processes in steps S401to S407are carried out immediately after the step S110(the other processes) inFIG. 5. It should be noted that the processes in steps S401to S407may be carried out either immediately before the step S110or as a part of the step S110.

In the step S401, the CPU31determines whether or not an operational position of the throttle lever12lies in an opening direction as compared to an operational position corresponding to a throttle opening angle under control (the present throttle opening angle). It should be noted that as described above, while the planing mode is applied, the operational position of the throttle lever12does not always correspond to an actual throttle opening angle. When the CPU31determines that the operational position of the throttle lever12lies in an opening direction as compared to the operational position corresponding to the throttle opening angle being controlled, the process proceeds to step S402, and when not, the process proceeds to the step S107. In the step S402, the CPU31determines whether or not the throttle lever12has been further operated in the opening direction as compared to the operational position corresponding to the throttle opening angle under control. When the CPU31determines that the throttle lever12has been further operated in the opening direction as compared to the operational position corresponding to the throttle opening angle under control, the process proceeds to step S403, and when not, the process proceeds to step S405.

In the step S403, it is judged that a vessel operator has an intention of shifting to a mode of a manual operation and starting acceleration, and therefore, the CPU31cancels the planing mode. Then, in step S404, the CPU31controls the opening angle adjustment unit26so that the throttle opening angle can gradually shift to the throttle opening angle corresponding to the operational position of the throttle lever12operated this time. The throttle opening angle under control is an opening angle corresponding to the critical maximum speed V2or its vicinity, whereas the throttle opening angle corresponding to the operational position of the throttle lever12immediately after being operated in the opening direction can be sufficiently higher than the opening angle corresponding to the critical maximum speed V2or its vicinity. In this case, if the throttle opening angle is immediately shifted to the one corresponding to the operational position of the throttle lever12after the operation this time, the hull13may be unintentionally rapidly accelerated. Thus, the speed of the hull13can be slowly changed by the throttle opening angle being gradually shifted to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation. The gap between the operational position of the throttle lever12and the actual throttle opening angle is gradually eliminated.

In the step S405, the CPU31determines whether or not the throttle lever12has been operated in a closing direction past the (present) throttle opening angle under control. Namely, the CPU31determines whether or not the throttle lever12has been operated in the closing direction and also the operational position of the throttle lever12after the operation is lower than the operational position corresponding to the throttle opening angle under control. When the CPU31determines that the throttle lever12has been operated in the closing direction past the (present) throttle opening angle under control, the process proceeds to step S406, and when not, the process proceeds to the step S107.

In the step S406, it is judged that the vessel operator has an intention of shifting to the mode of manual operation and starting deceleration, the CPU31cancels the planing mode. Thus, after the operational position of the throttle lever12has become lower than the operational position corresponding to the throttle opening angle under control, the planing mode is canceled. Namely, the planing mode is not canceled in a stage where the throttle lever12has been operated in a closing direction within a range where its operational position does not become lower than the operational position corresponding to the throttle opening angle under control.

Then, in step S407, the CPU31controls the opening angle adjustment unit26so that the throttle opening angle can gradually shift to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation this time. The throttle opening angle under control is an opening angle corresponding to the critical maximum speed V2or its vicinity, whereas the throttle opening angle corresponding to the operational position of the throttle lever12immediately after being operated slightly in the closing direction is likely to be sufficiently higher than the opening angle corresponding to the critical maximum speed V2or its vicinity. In this case, if the throttle opening angle is immediately shifted to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation this time, the hull13may be likely to accelerate even though the vessel operator has an intention of decelerating the hull13. Thus, after the operational position of the throttle lever12has become lower the operational position corresponding to the throttle opening angle under control, the planing mode is canceled and the throttle opening angle is gradually shifted to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation, and whereby the speed the hull13can change slowly. The gap between the operational position of the throttle lever12and the actual throttle opening angle is gradually eliminated. After the step S404or the step S407, the CPU31returns the process to the step S104inFIG. 5.

According to the present embodiment, the same effects as those in the embodiment firstly described above can be obtained from the standpoint of maintaining the planing state at relatively low speed. Moreover, in a situation where the operational position of the throttle lever12lies in the opening direction as compared to the operational position corresponding to the throttle opening angle under control while the planing state at low speed is being maintained, when the throttle lever12is further operated in the opening direction, the CPU31cancels the planing mode and gradually shifts the throttle opening angle to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation. This prevents unintended rapid acceleration. Also, in the above situation, when the throttle lever12is operated in the closing direction, after the operational position of the throttle lever12has become lower the operational position corresponding to the throttle opening angle under control, the CPU31cancels the planing mode and gradually shifts the throttle opening angle to the throttle opening angle corresponding to the operational position of the throttle lever12after the operation. As a result, a situation in which the hull13accelerates even though the throttle lever12has been operated in the closing direction can be avoided.

Appropriately lowering the tabs21of the trim tabs20can make it easier to maintain the planing state at low speed. For this purpose, in the embodiments described above, while the planing mode is applied, two tabs21may be controlled to be lowered by a predetermined amount.

For example, when the planing mode is set, the tabs21may be lowered even if the hull13has not entered planing state. In this case, referring toFIG. 5, for example, it may be considered to insert a step of lowering the tabs21between the step S102and the step S103and insert a step of raising the tabs21(putting them back to retracted positions) between a timing of the determination as NO in the step S107and a timing of a return to the step S104. Referring toFIG. 6, it may be considered to insert a step of lowering the tabs21between the step S202and the step S203and insert a step of raising the tabs21between a timing of the determination as NO in the step S209and a timing of a return to the step S204.

Alternatively, the tabs21may be lowered when both the condition that the planing mode is set and the condition that the hull13is in the planing state are satisfied. In this case, referring toFIG. 5, for example, a step of lowering the tabs21is inserted after the determination as YES in the step S103and before the step S107. At the same time, a step of raising the tabs21(putting them back to the retracted positions) may be inserted after the determination as NO in the step S107and before a return to the step S104. Referring toFIG. 6, a step of lowering the tabs21is inserted after the determination as YES in the step S203and before the step S209. At the same time, a step of raising the tabs21may be inserted after the determination as NO in the step S209and before the return to the step S204.

It should be noted that in the embodiments described above, whether or not the hull13is in the critical state is judged based on the vessel speed V and the pitch angle P in the steps S108and S210. The method of judgment, however, is not limited to this example. For example, whether or not the hull13is in the critical state may be judged based on the vessel speed V and the engine rpm N. Alternatively, whether or not the hull13is in the critical state may be judged based on the vessel speed V and the throttle opening angle.

It should be noted that in a case where an operation that lowers the tabs21of the trim tabs20is performed in parallel with the control that maintains the planing state at low speed in the planing mode, the predetermined amounts used in the steps S106, S109, S112, S208, S211, and S214may be set according to the amount by which the tabs21is lowered and/or the load the hull13carries.

It should be noted that interceptor tabs may be adopted as posture control tabs in place of the tabs21. In the water, each of the interceptor tabs changes its position from a position at which it projects from a bottom surface (vessel's bottom) of the hull13to a retracted position above the bottom surface of the hull13.

It should be noted that the number of outboard motors may be one or three or more. Also, the number of trim tabs may be three or more.

Marine vessels to which the present invention is applied are not limited to marine vessels equipped with outboard motors, but may be marine vessels equipped with other types of marine propulsion devices such as inboard/outboard motors (sterndrive or inboard motor/outboard drive) or inboard motors, and water jet drive.

The present invention is not limited to the specific embodiments described above, and various forms within the gist of the present invention are also included in the present invention. Some of the embodiments described above may be combined together as appropriate.