FIG. 5 shows the first thrust and the second thrust acting on the hull 2 in the right lateral movement mode. As shown in FIG. 5, in the right lateral movement mode, a first thrust acting line 4L-P of the first marine vessel propulsion device 4L and a second thrust acting line 4R-P of the second marine vessel propulsion device 4R intersect at the center of gravity G. In this case, a first thrust FL of the first marine vessel propulsion device 4L is a vector facing to front right (a forward right vector), and a second thrust FR of the second marine vessel propulsion device 4R is a vector facing to rear right (a rearward right vector). A resultant force of the first thrust FL and the second thrust FR becomes a resultant force FS. The resultant force FS becomes a vector facing to the right. Therefore, the resultant force FS, which faces to the right, acts as a thrust on the hull 2 with the center of gravity G as an acting point F0. Therefore, since no rotational moment acts on the hull 2, the hull 2 moves in parallel with the lateral direction rightward without pivot-turning. In addition, in the case of the left lateral movement mode, it can be understood that the left direction and the right direction are reversed with respect to the example shown in FIG. 5. It should be noted that the acting point F0 corresponds to an intersection point of a vector direction of the resultant force FS and the central line CL when viewed from a vertical direction.

The acting point F0 varies depending on an angle formed by the first thrust acting line 4L-P and the central line CL and an angle formed by the second thrust acting line 4R-P and the central line CL, and further varies depending on an angle formed by the first thrust acting line 4L-P and the second thrust acting line 4R-P. For example, when the angle formed by the first thrust acting line 4L-P and the central line CL and the angle formed by the second thrust acting line 4R-P and the central line CL are common (when the angle formed by the first thrust acting line 4L-P and the central line CL is equal to the angle formed by the second thrust acting line 4R-P and the central line CL), the acting point F0 is located on the central line CL. In this case, the larger the angle formed in the rear by the first thrust acting line 4L-P and the second thrust acting line 4R-P, the more rearward the acting point F0 is located on the central line CL.

When the magnitude or the direction of either the first thrust FL or the second thrust FR changes, the position of the acting point F0 and the magnitude or the direction of the resultant force FS change. For example, even in cases where the acting point F0 is the same, when the magnitude of either the first thrust FL or the second thrust FR changes, sometimes the vector direction of the resultant force FS will become an oblique lateral direction or the front-rear direction.

FIGS. 6A to 6D are transition diagrams that show a behavior of the hull 2 during the lateral movement mode. FIGS. 6A to 6D show a change in the resultant force FS and the movement of the hull 2 after the start of the lateral movement mode until the hull 2 approaches a shore 19 such as a pier or the like and comes alongside the shore 19 (that is, becomes a coming-alongside state). Pressing the left lateral movement switch 53 or the right lateral movement switch 54 corresponds to an instruction to laterally move the hull 2. It is assumed that the instruction to laterally move the hull 2 is accepted when the hull 2 is substantially stationary, but the instruction to laterally move the hull 2 is not limited to being accepted while the hull 2 is stationary. Although FIGS. 6A to 6D show the case of the right lateral movement mode, in the case of the left lateral movement mode, it can be understood that the left direction and the right direction are reversed with respect to each of FIGS. 6A to 6D.

When the right lateral movement switch 54 is pressed, the right lateral movement mode is started (see FIG. 6A). In order to hasten the start of the movement of the hull 2, the controller 40 controls the marine vessel propulsion devices 4L and 4R so as to generate a thrust to pivot-turn the hull 2 at the start of the lateral movement mode. Here, as an example, the controller 40 controls the marine vessel propulsion devices 4L and 4R so as to set the position of the acting point F0 to the rear of the center of gravity G, and to set the vector direction of the resultant force FS to the rightward (the lateral direction) with respect to the hull 2.

Here, the lateral direction is a direction perpendicular to the central line CL when viewed from above. That is, when an angle formed in an instruction direction and in the rear by the vector direction of the resultant force FS, which is the lateral direction, and the central line CL is defined as θ, the angle θ is 90°.

Then, the hull 2 first pivot-turns counterclockwise when viewed from above (the vertical direction). Concurrently with the pivot-turning or immediately after the pivot-turning starts, the hull 2 also starts to move the rightward. In general, when the hull 2 starts to move laterally from a stationary state, since a large load due to the water resistance and an inertia moment of the hull 2 is applied to the hull 2, if the position of the acting point F0 coincides with the center of gravity G, the start of the movement of the hull 2 is delayed (slows down). In order to deal with this issue, in a preferred embodiment of the present invention, since the hull 2 pivot-turns first, the subsequent lateral movement becomes smooth.

After the hull 2 pivot-turns, when the position and the direction of the resultant force FS are maintained, the hull 2 moves rightward while pivot-turning (see FIG. 6B). Then, the hull 2 eventually comes into contact with the shore 19. Although it depends on an initial attitude of the hull 2, the stern of the hull 2 often comes into contact with the shore 19 earlier than the bow of the hull 2 due to the counterclockwise pivot-turning of the hull 2. It should be noted that when the stern or the bow of the hull 2 comes into contact with the shore 19, a frictional force generated is larger than when the side portion of the hull 2 comes into contact with the shore 19, making it difficult for the hull 2 to drift away.

After that, the position of the resultant force FS (the position of the acting point F0) and the direction of the resultant force FS are maintained until an end condition (a predetermined condition), which will be described below, is satisfied. When the hull 2 docks as it is, in general, the hull 2 gradually becomes parallel to the shore 19. Then, when the end condition is satisfied, the controller 40 shifts to a lateral thrust generation mode. The lateral thrust generation mode is a final mode in the lateral movement mode. The lateral thrust generation mode controls the engines 3L and 3R and the marine vessel propulsion devices 4L and 4R so that the hull 2 comes alongside a docking place such as a pier and a state in which the hull 2 is pressed against the docking place (hereinafter, referred to as “a pressing state”) is maintained.

In the lateral thrust generation mode, the controller 40 applies a thrust in the lateral direction (a lateral thrust) to the hull 2 without applying a pivot-turning force to the hull 2. In other words, the controller 40 makes the position of the acting point F0 coincide with the center of gravity G, and maintains the vector direction of the resultant force FS in the lateral direction (to the rightward in FIG. 6D) with respect to the hull 2.

In the lateral thrust generation mode, the magnitude of the resultant force FS may be made smaller than that at the start of the lateral movement mode. By doing so, a control state similar to a so-called pressing mode is obtained. Alternatively, after a certain period of time has elapsed since shifting to the lateral thrust generation mode, the magnitude of the resultant force FS may be made smaller than that at the start of the lateral movement mode.

In this way, the controller 40 first generates the thrust to pivot-turn the hull 2, and thereafter (when the end condition is satisfied), applies the thrust in the lateral direction (the lateral thrust) to the hull 2. Substantially, the controller 40 performs a control so that a pivot-turning speed of the hull 2 decreases after generating the thrust to pivot-turn the hull 2 (the resultant force FS).

Here, the state of the lateral movement mode is considered as follows from a vector viewpoint. The controller 40 performs the control so as to shift the acting point F0 of the resultant force FS at the start of the lateral movement mode from the center of gravity G in the front-rear direction when viewed from the vertical direction and then bring the acting point F0 closer to the center of gravity G. After that, the controller 40 makes the acting point F0 coincide with the center of gravity G, and makes the direction of the vector of the resultant force FS become the lateral direction corresponding to the instruction to laterally move the hull 2.

FIG. 7 is a flow chart that shows the flow of a lateral movement mode process. In the controller 40, the lateral movement mode process is realized by the CPU expanding a program, which is stored in the ROM, to the RAM and executing the program. The lateral movement mode process is started in response to a pressing operation of the left lateral movement switch 53 or the right lateral movement switch 54 in the normal marine vessel maneuvering mode.

In step S101, the controller 40 starts a lateral movement control in the lateral movement mode. That is, the controller 40 controls the marine vessel propulsion devices 4L and 4R to generate the thrust to pivot-turn the hull 2 (see FIG. 6A). In step S102, the controller 40 determines based on the operation signal from the steering apparatus 14 whether or not there has been a steering operation (the rotation of the wheel portion of the steering apparatus 14). In the case it is determined that the steering operation has occurred, the controller 40 advances the lateral movement mode process to step S106. On the other hand, in the case it is determined that no steering operation has occurred, the controller 40 advances the lateral movement mode process to step S103.

In step S103, the controller 40 determines whether or not the end condition has been satisfied. Here, as an example, the end condition is that a predetermined period of time has elapsed from the start of the lateral movement mode (hereinafter, referred to as “a condition A”). In other words, when the predetermined period of time has elapsed since the start of the lateral movement mode, the controller 40 determines that the end condition has been satisfied. The predetermined period of time is set to, for example, a length equal to or longer than a time normally required from the start of docking until docking.

It should be noted that the end condition is not limited to the condition A. The controller 40 may determine whether or not the end condition has been satisfied, based on at least one of an elapsed time since the start of the lateral movement mode, a change in the direction of the hull 2 from the start of the lateral movement mode, a speed of the hull 2, a distance from the hull 2 to a movement target position (for example, the shore 19), a change in a position of the hull 2 from the start of the lateral movement mode, or an input from the marine vessel user. Specifically, the controller 40 may determine that the end condition has been satisfied based on that at least one of the condition A, a condition B, a condition C, a condition D, a condition E, or a condition F has been satisfied. Examples of the condition B, the condition C, the condition D, the condition E, or the condition F are shown below.

The condition B is that the change in the direction of the hull 2 from the start of the lateral movement mode exceeds a predetermined amount. In other words, the condition B is that a change amount of a pivot-turning angle of the hull 2 from the start of the lateral movement mode exceeds the predetermined amount. Whether or not the condition B has been satisfied is determined based on the detection result of the direction sensor included in the various sensors 56. The condition C is that a speed component of the hull 2 in the instruction direction (rightward or leftward) exceeds a predetermined speed. Whether or not the condition C has been satisfied is determined based on the detection result of the marine vessel speed sensor included in the various sensors 56 (the speed of the hull 2 detected by the marine vessel speed sensor). The condition D is that the distance from the hull 2 to the movement target position (for example, the shore 19) is within a predetermined distance. Whether or not the condition D has been satisfied is determined based on the detection result of the distance sensor included in the various sensors 56.

The condition E is that the change in the position of the hull 2 from the start of the lateral movement mode exceeds a predetermined value. Whether or not the condition E has been satisfied is determined based on the detection result of the position sensor included in the various sensors 56. The condition F is that an instruction to apply the thrust in the lateral direction (the lateral thrust) to the hull 2 has been inputted by the marine vessel user. For example, the marine vessel user is able to input the instruction to apply the thrust in the lateral direction (the lateral thrust) to the hull 2 by operating the another switch 55. The controller 40 is able to determine whether or not the condition F has been satisfied based on whether or not the instruction to apply the thrust in the lateral direction to the hull 2 has been inputted.

In the case that the condition A, the condition D, or the condition E is used, it is possible to shift to the pressing state in a situation where the hull 2 is expected to come alongside. In the case that the condition B is used, it is possible to shift to the pressing state in a situation where the hull 2 is not excessively inclined with respect to the shore 19. In the case that the condition C is used, it is possible to hasten shifting to the pressing state. In the case that the condition F is used, it is possible to shift to the pressing state at a timing desired by the marine vessel user.

In the case it is determined in step S103 that the end condition has not been satisfied, the controller 40 returns the lateral movement mode process to step S102. Therefore, a thrust generated at the start of the lateral movement control (the thrust to pivot-turn the hull 2) is maintained (see FIGS. 6B and 6C). On the other hand, in the case it is determined in step S103 that the end condition has been satisfied, the controller 40 advances the lateral movement mode process to step S104.

In step S104, the controller 40 shifts to the lateral thrust generation mode (see FIG. 6D). That is, by making the position of the acting point F0 coincide with the center of gravity G and making the vector direction of the resultant force FS become the lateral direction perpendicular to the central line CL, the controller 40 applies the thrust in the lateral direction to the hull 2 without applying the pivot-turning force to the hull 2.

In step S105, the controller 40 waits until there is an instruction to end the lateral movement mode. Therefore, the lateral thrust generation mode is continued. The instruction to end the lateral movement mode is able to be inputted, for example, by the marine vessel user operating the setting operation unit 38. In the case that there has been the instruction to end the lateral movement mode, the controller 40 ends the lateral movement mode process shown in FIG. 7.

In step S106, the controller 40 performs a thrust correction in response to the accepted steering operation, and advances the lateral movement mode process to step S103. Examples of the thrust correction will be described with reference to FIG. 8 and FIG. 9.

FIG. 8 and FIG. 9 are schematic diagrams that show a change in the resultant force FS when the steering operation is accepted after starting the lateral movement mode. FIG. 8 and FIG. 9 do not show a change in the attitude of the hull 2. Hereinafter, the length of an arrow indicating the vector of the resultant force FS corresponds to the magnitude of the resultant force FS, and the longer the arrow, the larger the magnitude of the resultant force FS.

After generating the thrust to pivot-turn the hull 2, when accepting the steering operation, the controller 40 corrects the pivot-turning speed of the hull 2 in response to the accepted steering operation. As a result, a pivot-turning radius or a pivot-turning direction may also be corrected.

For example, as shown in a case 80 of FIG. 8, consider the case that a steering operation to turn the rightward (clockwise) is accepted after generating a resultant force FS to pivot-turn the hull 2 counterclockwise. In this case, as shown in a case 81 of FIG. 8, the controller 40 brings the position of the acting point F0 closer to the center of gravity G, or decreases the magnitude of the resultant force FS. It should be noted that in the case 81, the controller 40 may bring the position of the acting point F0 closer to the center of gravity G and decrease the magnitude of the resultant force FS. Alternatively, as shown in a case 82 of FIG. 8, the controller 40 locates the position of the acting point F0 at an opposite position in the front-rear direction with respect to the center of gravity G. At that time, the magnitude of the resultant force FS does not matter, and it may be smaller than the initial value. Due to the controller 40 executing the control shown in the case 81 or the case 82, a counterclockwise pivot-turning speed of the hull 2 is decreased.

Next, as shown in a case 90 of FIG. 9, consider the case that a steering operation to turn the leftward (counterclockwise) is accepted after generating the resultant force FS to pivot-turn the hull 2 counterclockwise. In this case, as shown in a case 91 of FIG. 9, the controller 40 moves the position of the acting point F0 rearward so as to move away from the center of gravity G. Alternatively, as shown in a case 92 of FIG. 9, the controller 40 increases the magnitude of the resultant force FS. It should be noted that the controller 40 may move the position of the acting point F0 rearward so as to move away from the center of gravity G and increase the magnitude of the resultant force FS. Due to the controller 40 executing the control shown in the case 91 and/or the case 92, the counterclockwise pivot-turning speed of the hull 2 is increased.

It should be noted that the vector direction of the thrust to change the pivot-turning speed of the hull 2 is not limited to the lateral direction. Therefore, every time a steering operation is accepted, the pivot-turning speed of the hull 2 may be changed by changing at least one of the position of the acting point F0, the magnitude of the resultant force FS, or the vector direction of the resultant force FS in response to the accepted steering operation. It should be noted that it is not essential to perform the thrust correction in response to the steering operation. Therefore, steps S102 and S106 may be eliminated in the lateral movement mode process shown in FIG. 7.

According to a preferred embodiment of the present invention, the controller 40 executes the lateral movement mode, in which the thrust in the lateral direction is applied to the hull 2, by controlling the propulsion devices (the engines 3L and 3R and the marine vessel propulsion devices 4L and 4R) in response to receiving the instruction to laterally move the hull 2. The controller 40 controls the propulsion devices (the engines 3L and 3R and the marine vessel propulsion devices 4L and 4R) so as to generate the thrust to pivot-turn the hull 2 at least at the start of the lateral movement mode. As a result, since it is possible to hasten the start of the movement of the hull 2, it is possible to make the lateral movement of the hull 2 become smooth. For example, at the time of the lateral movement of the hull 2 for docking, it is possible to hasten the docking regardless of the degree of mastery of operation skills.

In addition, since the controller 40 applies the thrust in the lateral direction to the hull 2 after generating the thrust to pivot-turn the hull 2, it is possible to shift to the pressing state. In particular, since the controller 40 applies the thrust in the lateral direction to the hull 2 in response to the establishment of the predetermined condition, it is possible to shift to the pressing state at an appropriate timing after starting the lateral movement of the hull