Patent Description:
In the case that a relatively small marine vessel is navigating in ocean waves, when a marine vessel speed of the marine vessel is increased, a hull of the marine vessel may be subjected to impacts caused by the marine vessel colliding with a wave or the marine vessel landing on the water after riding over the wave. Also, in the case that the marine vessel rides over the wave, the marine vessel speed decreases when the marine vessel rises toward the wave crest, and the marine vessel speed increases when the marine vessel descends toward the trough of the wave. Therefore, the riding comfort of the marine vessel is deteriorated.

Accordingly, techniques for controlling the marine vessel speed in response to a parameter that indicates the behavior of the marine vessel in the ocean waves have been proposed. For example, in a technique described in <CIT>, the marine vessel speed is controlled based on an acceleration of the hull in a vertical direction. Specifically, in the case that the acceleration of the hull in the vertical direction exceeds a limit value, a deceleration command is transmitted to a main engine, and the marine vessel speed is reduced to a predetermined value at which the marine vessel will not be damaged. Furthermore, in a technique described in <CIT>, the marine vessel speed is controlled based on a pitching angular velocity. Specifically, when the pitching angular velocity is positive, since the hull is decelerated in response to the height of the wave, an engine control to accelerate the hull is performed.

However, in the technique described in <CIT>, in the case of using a relatively inexpensive acceleration sensor whose data update cycle (whose data obtaining cycle) is not so short, it is not possible to accurately measure a transient characteristic of an acceleration in the vertical direction when an impact has occurred on the hull, and as a result, the marine vessel speed is controlled based on a vertical acceleration that deviates from an actual situation, and the impact may not be appropriately reduced. Furthermore, in the technique described in <CIT>, when the marine vessel rides over the wave, since a damping motion around a pitch axis occurs in the hull, for example, since the damping motion around the pitch axis occurs in the hull even though the marine vessel is descending from the wave crest, the bow may lift, and as a result, the pitching angular velocity may become positive and the hull may be accelerated. That is, the marine vessel that naturally accelerates as it descends from the wave crest may accelerate further. Therefore, there is still room for improvement in the riding comfort of the marine vessel when navigating in the ocean waves.

It is the object of the present invention to provide a speed control method for marine vessels and a marine vessel that are each able to further improve the riding comfort of a marine vessel navigating in ocean waves.

According to the present invention said object is solved by speed control method for a marine vessel having the features of independent claim <NUM>. Moreover said object is solved by a marine vessel according to claim <NUM>. Preferred embodiments are laid down in the dependent claims.

According to a preferred embodiment, a speed control method for a marine vessel includes applying a subtraction processing to a throttle opening of a power source of the marine vessel based on a vertical speed of a hull of the marine vessel.

According to another preferred embodiment, a marine vessel includes a controller configured or programmed to control a marine vessel speed of the marine vessel. The controller is configured or programmed to apply a subtraction processing to a throttle opening of a power source of the marine vessel based on a vertical speed of a hull of the marine vessel.

According to the preferred embodiments, the subtraction processing is applied to the throttle opening or the throttle opening is controlled based on the vertical speed of the hull instead of the acceleration of the hull in the vertical direction. Since the vertical speed of the hull is equivalent to the integral of the vertical acceleration of the hull (the acceleration of the hull in the vertical direction), the vertical speed of the hull is easier to be measured than the vertical acceleration of the hull, and it is also possible to accurately measure its transient characteristic. In addition, the vertical speed of the hull will not be reversed when the marine vessel descends from the wave crest. Therefore, since it is possible to accurately understand the behavior of the marine vessel riding over the wave by using the vertical speed of the hull, it is possible to appropriately control the throttle opening so as to suppress the inappropriate behavior of the marine vessel, and as a result, it is possible to further improve the riding comfort of the marine vessel navigating in the ocean waves.

Hereinafter, preferred embodiments will be described with reference to the drawings.

<FIG> is a side view of a marine vessel <NUM> to which a speed control method for a marine vessel according to a preferred embodiment is applied. In <FIG>, the marine vessel <NUM> is, for example, a relatively small planing boat, and includes a hull <NUM> and at least one, for example, two outboard motors <NUM> that function as propulsion devices and are attached to a stern of the hull <NUM>. Each of the outboard motors <NUM> generates a propulsive force of the marine vessel <NUM> by rotating a propeller. In addition, a cabin <NUM> that also serves as a cockpit is provided on the hull <NUM>.

<FIG> is a block diagram for schematically explaining a configuration of a marine vessel propulsion control system <NUM> mounted on the marine vessel <NUM> shown in <FIG>. As shown in <FIG>, the marine vessel propulsion control system <NUM> includes the outboard motors <NUM>, a boat control unit (BCU) <NUM> (functioning as a controller), a multi-function display (MFD) <NUM>, a global positioning system (GPS) <NUM>, an inertial measurement unit (IMU) <NUM>, a compass <NUM>, a remote control unit <NUM>, a joystick <NUM>, a steering mechanism <NUM>, a marine vessel maneuvering panel <NUM>, remote control engine control units (remote control ECUs) <NUM>, a main operation unit <NUM>, and steering control units (SCUs) <NUM>. Respective components of the marine vessel propulsion control system <NUM> are communicably connected to each other.

The GPS <NUM> obtains a current position of the marine vessel <NUM> and transmits the current position of the marine vessel <NUM> to the BCU <NUM>. The IMU <NUM> measures the behavior of the hull <NUM> and transmits the measurement result to the BCU <NUM>. The compass <NUM> obtains an azimuth of the marine vessel <NUM> and transmits the azimuth of the marine vessel <NUM> to the BCU <NUM>.

The remote control unit <NUM> includes levers 20a corresponding to the respective outboard motors <NUM>. By operating each lever 20a, a marine vessel user is able to switch an acting direction of the propulsive force generated by the corresponding outboard motor <NUM> between a forward moving direction and a backward moving direction, and adjust the magnitude of the output of the corresponding outboard motor <NUM> so as to adjust a marine vessel speed of the marine vessel <NUM>. At this time, the remote control unit <NUM> transmits a signal to control the outboard motor <NUM> to the BCU <NUM> and the remote control ECUs <NUM> in response to the operation of the lever 20a. The joystick <NUM>, which is a control stick to maneuver the marine vessel <NUM>, transmits a signal to move the marine vessel <NUM> in a tilting direction of the joystick <NUM> to the BCU <NUM> and the remote control ECUs <NUM>. The steering mechanism <NUM> enables the marine vessel user to determine the course of the marine vessel <NUM>. The marine vessel user is able to turn the marine vessel <NUM> to the left or right by rotatably operating a steering wheel 22a of the steering mechanism <NUM> leftward or rightward. At this time, the steering mechanism <NUM> transmits a steering angle corresponding to the rotation operation of the steering wheel 22a to the remote control ECUs <NUM> and the SCUs <NUM>.

The main operation unit <NUM> includes a main switch 25a and an engine shutoff switch 25b. The main switch 25a is an operator to collectively start and stop engines <NUM> which are power sources of the respective outboard motors <NUM>, and the engine shutoff switch 25b is a switch to emergency-stop the engines <NUM> of the respective outboard motors <NUM>. The MFD <NUM> includes, for example, a color LCD display, and functions as a display to display various kinds of information and also functions as a touch panel to accept inputs from the marine vessel user. The marine vessel maneuvering panel <NUM> includes switches (not shown) corresponding to various kinds of marine vessel maneuvering modes. By operating the corresponding switch, the marine vessel user shifts the marine vessel <NUM> to a desired marine vessel maneuvering mode. Each of the SCUs <NUM> is provided corresponding to each of the outboard motors <NUM>, and controls a steering unit (not shown), which horizontally turns the corresponding outboard motor <NUM> with respect to the hull <NUM> of the marine vessel <NUM>, to change the acting direction of the propulsive force of each of the outboard motors <NUM>.

The BCU <NUM> obtains the situation of the marine vessel <NUM> based on signals transmitted from the respective components of the marine vessel propulsion control system <NUM>, determines the magnitude of the propulsive force to be generated by each of the outboard motors <NUM> and the acting direction of the propulsive force to be taken, and transmits the result of the determination to each of the remote control ECUs <NUM>. One remote control ECU <NUM> is provided corresponding to each of the outboard motors <NUM>. In response to signals transmitted from the BCU <NUM>, the steering mechanism <NUM>, the remote control unit <NUM>, the joystick <NUM>, etc., each of the remote control ECUs <NUM> transmits signals to control the engine <NUM> of each of the outboard motors <NUM> and the steering unit to an engine ECU <NUM> of each of the outboard motors <NUM> and the SCU <NUM>, and adjusts the magnitude and the acting direction of the propulsive force of each of the outboard motors <NUM>.

The engine ECU <NUM> of each of the outboard motors <NUM> adjusts an opening of a throttle valve <NUM> of the engine <NUM> based on a throttle opening command value, which is one of the signals transmitted from the remote control ECU <NUM>. It should be noted that the BCU <NUM> executes the speed control method for the marine vessel according to the preferred embodiment.

In the speed control method for the marine vessel according to the preferred embodiment, since the main purpose is to reduce the impact caused by the marine vessel <NUM> landing on the water after riding over the wave, the marine vessel speed of the marine vessel <NUM> is decreased when the marine vessel <NUM> rides over the wave. In addition, since the behavior of the marine vessel <NUM> changes when the marine vessel <NUM> rides over the wave, in order to appropriately perform the impact reduction at the time of landing on the water due to the decrease in the marine vessel speed (deceleration), it is necessary to accurately obtain the behavior of the marine vessel <NUM> in the ocean waves.

As a parameter that indicates the behavior of the marine vessel <NUM> in the ocean waves, an acceleration in a vertical direction of the hull <NUM> (hereinafter, referred to as "a vertical acceleration"), a pitching angular velocity of the hull <NUM>, or a speed in the vertical direction of the hull <NUM> (hereinafter, referred to as "a vertical speed") can be considered. However, when the marine vessel <NUM> rides over the wave, since a damping motion around a pitch axis occurs in the hull <NUM>, the pitching angular velocity is affected not only by a posture change of the hull <NUM> directly caused by the wave, but also by the damping motion around the pitch axis. For example, the bow may lift due to the damping motion around the pitch axis during descent from the wave crest where the pitching angular velocity should normally be negative, and as a result, the pitching angular velocity may become positive. Therefore, it cannot be said that the pitching angular velocity is optimal as the parameter that indicates the behavior of the marine vessel <NUM> in the ocean waves.

In addition, since the impact at the time of landing on the water is represented by a multiple of the acceleration, in a control to reduce the impact applied to the hull <NUM> (hereinafter, referred to as "a posture control"), it is considered natural to use the vertical acceleration of the hull <NUM> as a physical quantity.

However, for the relatively small marine vessel <NUM>, since the vertical acceleration of the hull <NUM> finely varies in a very fast cycle, it is difficult for the IMU <NUM> to accurately measure the vertical acceleration of the hull <NUM>. For example, <FIG> shows a measurement result of the vertical acceleration in the case that the vertical acceleration of the hull <NUM> of the marine vessel <NUM> navigating in the ocean waves is sampled at a cycle of <NUM> seconds (indicated by a solid line), and a measurement result of the vertical acceleration in the case that the same vertical acceleration is sampled at a cycle of <NUM> seconds (indicated by a broken line). Comparing these measurement results with each other, it can be seen that a steep change in the vertical acceleration, which is measurable in the case that sampling is performed at the cycle of <NUM> seconds, becomes unmeasurable in the case that sampling is performed at the cycle of <NUM> seconds. In addition, since a sampling rate of the IMU <NUM> is generally <NUM> seconds, it is not possible for the IMU <NUM> to accurately measure a steep change in the vertical acceleration of the hull <NUM>. Therefore, in the case of using the vertical acceleration of the hull <NUM> measured by the IMU <NUM>, the posture control will be performed based on the vertical acceleration that deviates from the actual situation, and there is a possibility that it is not possible to appropriately perform the impact reduction at the time of landing on the water.

On the other hand, since the vertical speed of the hull <NUM> is equivalent to the integral of the vertical acceleration of the hull <NUM>, unlike the vertical acceleration of the hull <NUM>, a steep change in the vertical speed of the hull <NUM> does not occur, and it is possible to accurately measure the change in the vertical speed of the hull <NUM> even by the IMU <NUM>. In addition, since the vertical speed of the hull <NUM> is obtained by integrating the vertical acceleration of the hull <NUM>, as a result, the vertical speed of the hull <NUM> will reflect the steep change in the vertical acceleration. Therefore, in the case of using the vertical speed of the hull <NUM>, it is possible to perform the posture control based on a parameter that does not deviate from the actual situation. Therefore, in the preferred embodiment, the posture control is performed by using the vertical speed of the hull <NUM>, which functions as an index of the impact applied to the hull <NUM>, instead of the vertical acceleration of the hull <NUM>.

<FIG> shows a block diagram of a posture control controller <NUM> that is implemented by the speed control method for the marine vessel according to the preferred embodiment. In the preferred embodiment, the posture control controller <NUM> shown in <FIG> controls the opening of the throttle valve <NUM> (hereinafter, simply referred to as "a throttle opening") based on the vertical speed of the marine vessel <NUM> (the vertical speed of the hull <NUM>).

As shown in <FIG>, the posture control controller <NUM> includes an upper limit throttle opening block <NUM>, a Kalman filter <NUM>, a vertical speed block <NUM>, a coefficient multiplier <NUM>, a gain multiplier <NUM>, a subtractor <NUM>, and a throttle opening command value block <NUM>. It should be noted that the posture control controller <NUM> is implemented in the BCU <NUM>.

In the posture control controller <NUM>, first, based on the signal transmitted from the remote control unit <NUM>, the upper limit throttle opening block <NUM> sets the throttle opening (value) designated by the marine vessel user using the lever 20a as an upper limit throttle opening (value). In addition, the upper limit throttle opening block <NUM> transmits the upper limit throttle opening to the coefficient multiplier <NUM> and the subtractor <NUM>.

The Kalman filter <NUM> estimates the vertical speed (value) of the marine vessel <NUM> based on the measurement results of the behavior of the marine vessel <NUM> transmitted from the IMU <NUM> and the GPS <NUM>, and the vertical speed block <NUM> transmits the estimated vertical speed (value) to the gain multiplier <NUM>. The coefficient multiplier <NUM> calculates a vertical speed gain (a predetermined gain) by multiplying the upper limit throttle opening (value) by a vertical speed gain coefficient, and transmits the calculated vertical speed gain to the gain multiplier <NUM>. It should be noted that in the preferred embodiment, "-K", which is a negative value, is set as the vertical speed gain coefficient with reference to a return amount of the throttle opening at the time of riding over the wave of the marine vessel performed by a veteran marine vessel user. However, the vertical speed gain coefficient is not limited to this value "-K", and may be changed in response to the specifications of the marine vessel <NUM>, the sea conditions, and/or the marine vessel user's preference.

The gain multiplier <NUM> calculates a subtraction throttle opening (value) by multiplying the vertical speed (value) by the vertical speed gain, and transmits the calculated subtraction throttle opening (value) to the subtractor <NUM>. The subtractor <NUM> calculates the throttle opening command value by subtracting the subtraction throttle opening (value) from the upper limit throttle opening (value), and the throttle opening command value block <NUM> transmits the calculated throttle opening command value to the engine ECU <NUM> of each of the outboard motors <NUM>. Each engine ECU <NUM> controls the opening of the throttle valve <NUM> based on the throttle opening command value to adjust the marine vessel speed of the marine vessel <NUM>.

That is, in the posture control controller <NUM>, although the opening of the throttle valve <NUM> is controlled based on the throttle opening command value, which is obtained by applying a subtraction processing to the upper limit throttle opening by using the subtraction throttle opening, since the subtraction throttle opening is obtained by multiplying the vertical speed by the vertical speed gain, for example, as the marine vessel <NUM> rides over a large wave and the vertical speed of the hull <NUM> increases, the subtraction throttle opening increases and, as a result, the throttle opening command value decreases. That is, as the vertical speed of the hull <NUM> increases, the throttle opening command value decreases and the opening of the throttle valve <NUM> decreases, so the marine vessel speed of the marine vessel <NUM> decreases. As a result, it is possible to reduce the impact caused by the marine vessel <NUM> landing on the water after riding over the wave.

Generally, in a motion coordinate system of the marine vessel <NUM>, since the downward direction is positive with respect to the vertical direction, when the marine vessel <NUM> rides over the wave, the vertical speed becomes a negative value. Furthermore, as in the preferred embodiment, in the case that a negative value is set as the vertical speed gain coefficient, when the marine vessel <NUM> rides over the wave, the subtraction throttle opening obtained by multiplying the vertical speed by the vertical speed gain coefficient becomes a positive value. In addition, in the preferred embodiment, since the throttle opening command value is calculated by subtracting the subtraction throttle opening, which is a positive value, from the upper limit throttle opening, in the case that the marine vessel <NUM> rides over the wave, the throttle opening command value becomes smaller than the upper limit throttle opening. As a result, the opening of the throttle valve <NUM> is decreased, and the marine vessel speed of the marine vessel <NUM> decreases.

On the other hand, when the marine vessel <NUM> descends from the wave crest, the vertical speed becomes a positive value. Therefore, when the marine vessel <NUM> descends from the wave crest, the subtraction throttle opening obtained by multiplying the vertical speed by the vertical speed gain coefficient becomes a negative value. In addition, since the throttle opening command value is calculated by subtracting the subtraction throttle opening, which is a negative value, from the upper limit throttle opening, when the marine vessel <NUM> descends from the wave crest, the throttle opening command value becomes larger than the upper limit throttle opening. As a result, the opening of the throttle valve <NUM> is increased, and the marine vessel speed of the marine vessel <NUM> increases. That is, in the preferred embodiment, since the marine vessel speed of the marine vessel <NUM> increases when the marine vessel <NUM> descends from the wave crest, it is possible to recover the marine vessel speed that has been reduced in order to reduce the impact caused by landing on the water, and it is possible to prevent a delay in arrival at the destination of the marine vessel <NUM>.

In addition, in the case of obtaining the throttle opening command value, when the subtraction throttle opening is constant, the marine vessel <NUM> is excessively decelerated when the marine vessel speed is low while the marine vessel <NUM> cannot be sufficiently decelerated when the marine vessel speed is high. In particular, in the latter case, it is not possible to sufficiently reduce the impact caused by the marine vessel <NUM> landing on the water after riding over the wave.

Therefore, in the preferred embodiment, the vertical speed gain for obtaining the subtraction throttle opening is calculated by multiplying the upper limit throttle opening by the vertical speed gain coefficient. As a result, the subtraction throttle opening changes in response to the upper limit throttle opening. Specifically, when the upper limit throttle opening is large (that is, when the marine vessel speed is high), since the subtraction throttle opening becomes large and the throttle opening command value is largely subtracted, the marine vessel <NUM> is sufficiently decelerated. As a result, it is possible to sufficiently reduce the impact caused by the marine vessel <NUM> landing on the water after riding over the wave. Moreover, when the upper limit throttle opening is small (that is, when the marine vessel speed is low), the subtraction throttle opening becomes small, and excessive deceleration of the marine vessel <NUM> is suppressed. As a result, it is possible to prevent a significant delay in arrival at the destination of the marine vessel <NUM>.

Even in the case that the vertical speed gain is calculated by multiplying the marine vessel speed by the vertical speed gain coefficient instead of the upper limit throttle opening, when the marine vessel speed is high, it is possible to sufficiently decelerate the marine vessel <NUM> by increasing the subtraction throttle opening. Therefore, it is also conceivable to calculate the vertical speed gain by using the marine vessel speed instead of the upper limit throttle opening. However, since the marine vessel speed changes as a result when the posture control is executed and the marine vessel speed changes even if an external disturbance is applied to the marine vessel <NUM>, the deceleration gain calculated by using the marine vessel speed becomes unstable, and as a result, there is a possibility that the posture control is unstable.

Therefore, in the preferred embodiment, as described above, the vertical speed gain is calculated by using the upper limit throttle opening instead of the marine vessel speed. For example, even in the case that the posture control is executed or in the case that an external disturbance is applied to the marine vessel <NUM>, in principle, since the marine vessel user does not change the operation amount of the lever 20a, the deceleration gain calculated by using the upper limit throttle opening is stable, and as a result, it is possible to stabilize the posture control. Moreover, since the vertical speed gain is calculated by multiplying the upper limit throttle opening by the vertical speed gain coefficient, the vertical speed gain is proportional to the upper limit throttle opening.

In addition, in the case that regardless of the magnitude of the vertical speed of the hull <NUM>, when the marine vessel <NUM> rides over the wave, the subtraction throttle opening is subtracted from the upper limit throttle opening, the acceleration and deceleration of the marine vessel <NUM> are repeated each time the marine vessel <NUM> encounters a wave, which is not preferable from the viewpoint of improving the riding comfort. Furthermore, there is a possibility that the average marine vessel speed will unnecessarily decrease and the arrival of the marine vessel <NUM> at its destination will be delayed.

Therefore, in the posture control controller <NUM>, when the vertical speed of the hull <NUM> is equal to or lower than a vertical speed threshold (a predetermined vertical speed value), the vertical speed block <NUM> sets the vertical speed to <NUM> regardless of the estimation performed by the Kalman filter <NUM>. As an example, the predetermined vertical speed value is within <NUM> to <NUM> [m/s]. As a result, the subtraction throttle opening becomes <NUM>, the upper limit throttle opening is not subtracted, and the marine vessel speed of the marine vessel <NUM> does not change. As a result, repetition of the acceleration and deceleration of the marine vessel <NUM> is suppressed to further improve the riding comfort, and it is possible to prevent the delay in arrival at the destination of the marine vessel <NUM> by suppressing the average marine vessel speed from decreasing unnecessarily.

Moreover, when the vertical speed of the hull <NUM> is higher than the vertical speed threshold, since the vertical speed block <NUM> transmits the vertical speed estimated by the Kalman filter <NUM> to the gain multiplier <NUM>, the subtraction throttle opening does not become <NUM>, the upper limit throttle opening is subtracted, and the marine vessel speed of the marine vessel <NUM> decreases.

In addition, although not applying the subtraction processing to the upper limit throttle opening when the vertical speed of the hull <NUM> is equal to or lower than the vertical speed threshold, is nothing other than tolerating the impact caused by landing on the water to some extent, impact tolerance varies by the marine vessel user. Therefore, the marine vessel <NUM> may be configured so that the vertical speed threshold is able to be arbitrarily set in response to the preference of the marine vessel user. In this case, for example, the MFD <NUM> may be configured so that the marine vessel user is able to input an arbitrary vertical speed threshold, or the MFD <NUM> may be configured to display a plurality of options for the vertical speed threshold so that the marine vessel user is able to select a desired vertical speed threshold. In the case that the marine vessel user prioritizes suppressing a decrease in the average marine vessel speed over improving the riding comfort, the vertical speed threshold is set high, and on the other hand, in the case that the marine vessel user prioritizes improving the riding comfort over suppressing a decrease in the average marine vessel speed, the vertical speed threshold is set low.

Moreover, in the case that the vertical speed is denoted as Vz, the vertical speed threshold is denoted as Vz threshold, and the vertical speed gain is denoted as Vz gain, the posture control controller <NUM>, for which the vertical speed threshold is set, can be expressed programmatically as the following Expression <NUM>.

<FIG> are diagrams for explaining how the posture control is performed in the preferred embodiment. As shown in <FIG>, when the marine vessel <NUM> is not riding over the wave, since the vertical speed Vz of the hull <NUM> is approximately <NUM>, in the posture control controller <NUM>, the subtraction throttle opening is also approximately <NUM>, and the upper limit throttle opening is not subtracted. As a result, since the throttle opening command value is maintained at the upper limit throttle opening and the throttle opening does not decrease, a marine vessel speed V, which is the speed in the traveling direction of the marine vessel <NUM>, is also maintained.

On the other hand, as shown in <FIG>, when the marine vessel <NUM> rides over a relatively large wave and the vertical speed Vz of the hull <NUM> becomes larger than the vertical speed threshold, in the posture control controller <NUM>, the subtraction throttle opening becomes a magnitude corresponding to the vertical speed Vz, and the upper limit throttle opening is subtracted. As a result, since the throttle opening command value decreases from the upper limit throttle opening and the throttle opening also decreases, the marine vessel speed V of the marine vessel <NUM> also decreases. As a result, it is possible to sufficiently reduce the impact caused by the marine vessel <NUM> landing on the water after riding over the wave.

Further, as shown in <FIG>, when the marine vessel <NUM> rides over a relatively small wave and the vertical speed Vz of the hull <NUM> remains equal to or lower than the vertical speed threshold, as described above, since the vertical speed block <NUM> sets the vertical speed to <NUM>, the subtraction throttle opening becomes <NUM>, and the upper limit throttle opening is not subtracted. As a result, since the throttle opening command value is maintained at the upper limit throttle opening and the throttle opening does not decrease, the marine vessel speed V, which is the speed in the traveling direction of the marine vessel <NUM>, is also maintained.

According to the preferred embodiment, in the posture control, the subtraction throttle opening, which is calculated based on the vertical speed of the hull <NUM> instead of the vertical acceleration of the hull <NUM>, is subtracted from the upper limit throttle opening. Since the vertical speed of the hull <NUM> is equivalent to the integral of the vertical acceleration of the hull <NUM>, the vertical speed of the hull <NUM> is easier to be measured than the vertical acceleration of the hull <NUM>, and it is also possible to accurately measure its transient characteristic such as a steep change. In addition, the vertical speed of the hull <NUM> will not be reversed when the marine vessel <NUM> descends from the wave crest. Therefore, since it is possible to accurately understand the behavior of the marine vessel <NUM> riding over the wave by using the vertical speed of the hull <NUM>, it is possible to appropriately control the throttle opening so as to suppress the inappropriate behavior of the marine vessel <NUM>, and as a result, it is possible to further improve the riding comfort of the marine vessel <NUM> navigating in the ocean waves.

In addition, in the preferred embodiment, since the subtraction throttle opening changes in response to both the vertical speed of the hull <NUM> and the upper limit throttle opening, for example, even in the case that the marine vessel speed of the marine vessel <NUM> is low, but the marine vessel <NUM> rides over a relatively large wave and the vertical speed of the hull <NUM> increases, or in the case that the marine vessel <NUM> rides over a wave, which is not so large, and the vertical speed of the hull <NUM> is not so large, but the marine vessel speed of the marine vessel <NUM> is high, it is possible to appropriately lower the throttle opening command value, and it is possible to reliably improve the riding comfort of the marine vessel <NUM>.

In addition, in the preferred embodiment, when the marine vessel <NUM> rides over the wave, since the posture control controller <NUM> decreases the throttle opening command value to reduce the marine vessel speed V of the marine vessel <NUM> even if the marine vessel user does not move the lever 20a of the remote control unit <NUM>, even if the marine vessel user is a beginner and is not accustomed to operating the lever 20a when the marine vessel <NUM> rides over the wave, it is possible to sufficiently reduce the impact caused by landing on the water.

When determining the throttle opening command value in the posture control, referencing many parameters may cause the control to become complicated and diverge. On the other hand, in the posture control of the preferred embodiment, since only the vertical speed of the marine vessel <NUM> and the upper limit throttle opening are used as parameters, the control is simple, and it is possible to suppress the divergence of the control.

Claim 1:
A speed control method for a marine vessel (<NUM>) comprising:
processing to a throttle opening of a power source (<NUM>) of the marine vessel (<NUM>) based on a vertical motion of a hull (<NUM>) of the marine vessel (<NUM>), characterized by applying a subtraction processing to the throttle opening of the power source (<NUM>) of the marine vessel (<NUM>) based on a vertical speed of a hull (<NUM>) of the marine vessel (<NUM>).