Patent Application
20210229791
This application claims the benefit of priority to Japanese Patent Application No. 2020-012216, filed on Jan. 29, 2020. The entire contents of this application are hereby incorporated herein by reference.
The present invention relates to course control systems for marine vessels equipped with a marine propulsion device like an outboard motor, and also relates to the marine vessels.
When a marine vessel encounters a following wave that follows the marine vessel from diagonally behind while sailing, a broaching-to phenomenon or surf-riding phenomenon (also referred to simply as broaching or surf-riding) may occur, causing the marine vessel to lose rudder control and make a sudden movement of turning its head so as to make the longitudinal direction of the marine vessel parallel to the following wave. For such a marine vessel to recover from a state showing a sudden movement to a state showing no sudden movement (normal state), it is necessary to, for example, turn the rudder of the marine vessel in a direction opposite to a direction in which the marine vessel is turning its head, but it is difficult even for an experienced vessel operator to properly adjust the timing and amount of rudder control, and as a result, it is difficult for the marine vessel to recover from a sudden movement originating from broaching to a normal state by the vessel operator.
It is thus preferred that steering for recovering from a sudden movement of a marine vessel caused by a wave such as broaching is automated. As a technique of controlling the behavior of a marine vessel, a control apparatus that uses an output from an acceleration sensor provided in the marine vessel, to automatically control an engine rpm (revolutions per minute) so as to change the behavior of the marine vessel is known (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2009-286297).
Japanese Laid-open Patent Publication (Kokai) No. 2009-286297, however, does not mention that the rudder of the marine vessel is automatically controlled for the purpose of causing the marine vessel to recover from a sudden movement of the marine vessel caused by a wave. For this reason, there is still room for improvement in making it easier for the marine vessel to recover from a sudden movement originating from broaching.
The present invention provides course control systems for marine vessels, and marine vessels, which make it easy for marine vessels to recover from a sudden movement originating from broaching without relying on vessel operators.
According to an embodiment of the present invention, a course control system for a marine vessel includes a course changing mechanism that changes a course of the marine vessel, and a controller. The marine vessel has a propeller that provides propulsive force to the marine vessel. The controller is configured or programmed to detect a sudden movement of the marine vessel originating from broaching caused by a following wave of the marine vessel. The controller is further configured or programmed to, upon detecting the sudden movement of the marine vessel originating from the broaching, control a rotation rate of the propeller and/or cause the course changing mechanism to change the course of the marine vessel.
According to another embodiment of the present invention, a course control system for a marine vessel includes a controller configured or programmed to detect whether or not broaching has occurred or preconditions of occurrence of the broaching are satisfied based on a length between perpendiculars of a hull of the marine vessel, and a wavelength, a wave height, and a traveling direction of a following wave.
According to an embodiment of the present invention, in the course control system for a marine vessel, when a sudden movement of the marine vessel originating from broaching is detected, the controller causes the course changing mechanism to control the course of the marine vessel and/or controls the rotation rate of the propeller. As a result, it restores rudder control so that a vessel operator can control the course of the marine vessel through the rudder. Accordingly, the hull of the marine vessel is automatically prevented from becoming parallel to a following wave, and the marine vessel easily recovers from the sudden movement originating from broaching without relying on a vessel operator.
The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the embodiment with reference to the attached drawings.
Hereinafter, the embodiments will be described with reference to the drawings.
In the following description, a fore-and-aft direction, a crosswise direction, and a vertical direction refer to a fore-and-aft direction, a crosswise direction, and a vertical direction, respectively, of the hull 13. For example, as shown in
The two outboard motors 15A and 15B are attached to a stern of the hull 13 side by side. To distinguish the two outboard motors 15A and 15B, the one located on the port side is referred to as the “outboard motor 15A”, and the one located on the starboard side is referred to as the “outboard motor 15B”. The outboard motors 15A and 15B are mounted on the hull 13 via mounting units 14A an 14B, respectively. The outboard motors 15A and 15B include respective engines 16A and 16B, which are, e.g., internal combustion engines. The outboard motors 15A and 15B include respective propellers 25A and 25B that are turned by driving forces of the corresponding engines 16A and 16B and provide propulsive forces to the marine vessel 11.
The mounting units 14A and 14B each includes a swivel bracket, a clamp bracket, a steering shaft, and a tilt shaft (none of which are illustrated). The mounting units 14A and 14B further include power trim and tilt mechanisms (PTT mechanisms) 23A and 23B, respectively (
The pair of trim tab units 20A and 20B are attached to the stern on the port side and the starboard side such that they are able to swing about a swing axis C3. To distinguish the two trim tab units 20A and 20B from each other, the one located on the port side is referred to as the “trim tab unit 20A”, and the one located on the starboard side is referred to as the “trim tab unit 20B”.
The trim tab actuator 22A is disposed between the tab 21 and the hull 13 such that it connects the tab 21 and the hull 13 together. The trim tab actuator 22A actuates the tab 21 to swing it with respect to the hull 13. The tab 21 is capable of swinging down to a level lower than a swing position indicated by a solid line. It should be noted that the tab 21 indicated by a chain double-dashed line in
The controller 30, the throttle position sensor 34, the steering angle sensor 35, the hull speed sensor 36, the hull acceleration sensor 37, the posture sensor 38, the receiving unit 39, the display unit 9, and the setting operation unit 19 are included in the central unit 10 or disposed in the vicinity of the central unit 10. The turning actuators 24A and 24B and the PTT mechanisms 23A and 23B are provided for the respective outboard motors 15A and 15B. The engine rpm detectors 17A and 17B are provided in the respective outboard motors 15A and 15B. The trim tab actuators 22A and 22B are included in the trim tab units 20A and 20B, respectively.
The controller 30 includes a CPU 31, a ROM 32, a RAM 33, and a timer which is not illustrated. The ROM 32 stores control programs. The CPU 31 loads the control programs stored in the ROM 32 into the RAM 33 to implement various types of control processes. The RAM 33 provides a work area for the CPU 31 to execute the control programs.
Results of detection by the sensors 34 to 38 and the engine rpm detectors 17A and 17B are supplied to the controller 30. The throttle position sensor 34 detects the opening of a throttle valve, which is not illustrated. It should be noted that the opening of the throttle valve varies according to the operated amount of the throttle lever 12. The steering angle sensor 35 detects the turning angle of the steering wheel 18. The hull speed sensor 36 and the hull acceleration sensor 37 detect the speed and acceleration, respectively, of the marine vessel 11 (the hull 13) while it is sailing.
The posture sensor 38 includes, for example, a gyro sensor, a magnetic direction sensor, and so forth. Based on a signal output from the posture sensor 38, the controller 30 calculates a roll angle, a pitch angle, and a yaw angle of the hull 13. It should be noted that the controller 30 may calculate the roll angle and the pitch angle based on a signal output from the hull acceleration sensor 37. The receiving unit 39 includes a GNSS (Global Navigation Satellite Systems) receiver such as a GPS and includes a function of receiving GPS signals and various types of signals as positional information. From a speed restriction zone or land in the vicinity of the speed restriction zone, an identification signal providing notification that the area is a speed restriction zone is transmitted. The speed restriction zone refers to an area in a harbor or the like in which is required to limit the speed of a marine vessel to a predetermined speed or lower. The receiving unit 39 also includes a function of receiving the identification signal. It should be noted that the acceleration of the hull 13 may also be obtained from a GPS signal received by the receiving unit 39.
The engine rpm detectors 17A and 17B detect the number of revolutions of corresponding engines 16A and 16B per unit time (hereafter referred to as the engine rpm). It should be noted that the engine rpm varies depending on the opening of the throttle valve and the amount of fuel injected by a fuel injection device which is not illustrated. The opening of the throttle valve and the amount of fuel injected by the fuel injection device are controlled by the controller 30, and thus it can be said that the controller 30 controls the engine rpm, and by extension the rpm (or the rotation rate) of the propellers 25A and 25B (the propeller rpm). Therefore, the controller 30 also serves as a propeller rpm changing mechanism.
The display unit 9 displays various types of information. The setting operation unit 19 includes an operator that a vessel operator uses to perform operations relating to maneuvering, a PTT operating switch, a setting operator that a vessel operator uses to make various settings, and an input operator that a vessel operator uses to input various types of instructions (none of which are illustrated).
The turning actuators 24A and 24B turn the corresponding outboard motors 15A and 15B about the turning center C2 with respect to the hull 13. Turning the outboard motors 15A and 15B about the turning center C2 changes a direction in which a propulsive force acts with respect to the centerline C1 of the hull 13, which changes the course of the marine vessel 11. The mounting units 14A and 14B and the turning actuators 24A and 24B constitute a course changing mechanism of the marine vessel 11.
The PTT mechanisms 23A and 23B tilt the corresponding outboard motors 15A and 15B with respect to the clamp bracket by rotating the corresponding outboard motors 15A and 15B about the tilt shaft. The PTT mechanisms 23A and 23B are operated in response to, for example, operation of the PTT operating switch. As a result, the PTT mechanisms 23A and 23B change the inclination angles of the outboard motors 15A and 15B with respect to the hull 13.
The trim tab actuators 22A and 22B are controlled by the controller 30. For example, the trim tab actuators 22A and 22B operate in response to the controller 30 outputting control signals to them. In response to the operation of one of the trim tab actuators 22A and 22B, a corresponding tab 21 swings. It should be noted that actuators used for the PTT mechanisms 23A and 23B and the trim tab actuators 22A and 22B may be either hydraulic or electric.
It should be noted that the controller 30 may obtain results of detection by the engine rpm detectors 17A and 17B via a remote control ECU, which is not illustrated. The controller 30 may also use outboard motor ECUs (not illustrated) provided in the respective outboard motors 15A and 15B, to control the engine rpm and the propeller rpm of the outboard motors 15A and 15B.
In order for the marine vessel 11 to recover from such a sudden movement to a normal state, the rudder of the marine vessel 11 is turned in a direction opposite to a direction in which the marine vessel 11 is turning its head so that a difference between the traveling direction of the following wave 40 and the moving direction of the marine vessel 11 can be eliminated. In the present embodiment, upon detecting a sudden movement of the marine vessel 11 originating from broaching after detecting occurrence of the broaching, the controller 30 causes the course changing mechanism to control the moving direction of the marine vessel 11 so as to coincide with the traveling direction of the following wave 40. Alternatively, the controller 30, which works as the propeller rpm changing mechanism, may increase the rpm (rotation rate) of the propellers 25A and 25B by increasing the engine rpm so that the ship speed of the marine vessel 11 can increase, enabling the marine vessel 11 to escape the following wave 40 and restore rudder control. This also controls the moving direction of the marine vessel 11 so as to coincide with the traveling direction of the following wave 40 and thus enables the marine vessel 11 to recover from the sudden movement originating from broaching. Thus, in the present embodiment, increasing the rpm of the propellers 25A and 25B in addition to changing the course of the marine vessel 11 is employed as a way to cause the marine vessel 11 to recover from the sudden movement originating from broaching. It should be noted that the controller 30 also serves as a detector of the marine vessel 11, which not only detects an occurrence of broaching and a sudden movement of the marine vessel 11 originating from broaching but also judges whether or not the marine vessel 11 has recovered from a sudden movement originating from broaching and whether or not preconditions of occurrence of broaching are satisfied as will be described later.
Referring to
For example,
Namely, the pitch angle varies over time in different ways in the case where the marine vessel 11 encounters a following wave from right behind and the case where the marine vessel 11 encounters a head wave head-on. For this reason, based on variations in the pitch angle over time, the controller 30 is capable of judging whether or not a wave that the marine vessel 11 is now encountering is a following wave.
When the angle at which the marine vessel 11 encounters a wave (the angle which the moving direction of the marine vessel 11 forms with the traveling direction of the wave) changes, the absolute value of a change in the roll angle changes, too. For example, the absolute value of a change in the roll angle is the greatest when the marine vessel 11 encounters a wave that perpendicularly crosses the starboard of the hull 13. Thus, the angle at which the marine vessel 11 encounters a wave can be estimated by checking a change in the absolute value of the roll angle. It should be noted that the angle at which the marine vessel 11 encounters a wave may be visually observed by the vessel operator.
In the present embodiment, the angle at which the marine vessel 11 encounters a wave is referred to as an encounter angle. The encounter angle is an angle at which a wave travels toward the marine vessel 11 as the marine vessel 11 is seen from above. When a wave travels toward the marine vessel 11 from the front, the encounter angle is 0°. The encounter angle increases in a clockwise direction. For example, the encounter angle of a following wave that the marine vessel encounters from right behind (a wave traveling in the same direction as the moving direction of the marine vessel 11) is 180°, the encounter angle of a following wave that travels toward the marine vessel 11 from 30° behind the starboard of the marine vessel 11 is 150°, and the encounter angle of a following wave that travels toward the marine vessel 11 from 45° behind the port of the marine vessel 11 is 225°.
Referring again to
In the guidance (Revised Guidance to the Master for Avoiding Dangerous Situations in Adverse Weather and Sea Conditions, issued on Jan. 11, 2007) issued by the International Maritime Organization (hereafter referred to as “the IMO guidance”), it is said that the stability of a marine vessel decreases when the center of the marine vessel is riding on a crest of a following wave in a case where a wavelength λ of the wave is 0.6 to 2.3 times as long as a length L between perpendiculars of the marine vessel 11. It is also said that the marine vessel 11 is likely to surf-ride on a following wave in a case where a condition that a wave height H of the wave is equal to or greater than 0.04 times as long as the length L between the perpendiculars is satisfied in addition to the above condition.
Accordingly, in the step S62, the controller 30 judges whether or not the wavelength λ of the wave is 0.6 to 2.3 times as long as the length L between perpendiculars of the marine vessel 11. When the wavelength λ of the wave is less than 0.6 times as long as the length L between the perpendiculars or greater than 2.3 times as long as the length L between the perpendiculars, the process returns to the step S62, and when the wavelength λ of the wave is 0.6 to 2.3 times as long as the length L between perpendiculars of the marine vessel 11, the process proceeds to step S63.
In the step S63, the controller 30 further judges whether or not the wavelength λ of the following wave is equal to or greater than 0.04 times as long as the length L between the perpendiculars. When the wavelength λ of the following wave is less than 0.04 times as long as the length L between the perpendiculars, the process returns to the step S63, and when the wavelength λ of the wave is equal to or greater than 0.04 times as long as the length L between the perpendiculars, the process proceeds to step S64, in which the controller 30 in turn judges that the conditions of the occurrence of broaching (the broaching occurrence conditions) in which the marine vessel 11 may surf-ride on the following wave, are satisfied. The controller 30 then ends the process in
The wavelength λ of the wave in the step S62 is estimated based on a conversion graph illustrated in
Referring to
After that, the wavelength λ is obtained from the mathematical expression (1). Namely, the wavelength of a following wave is obtained based on the ship speed, acceleration, and moving direction of the marine vessel 11 and the traveling direction of the following wave.
λ(m)=1.56×(actual wave period (seconds)){circumflex over ( )}2 (1)
The wave height H of the wave is obtained by calculating the amount of change in a vertical position of the hull 13 by integrating a vertical component of the acceleration of the hull 13, which is measured by the hull acceleration sensor 37, two times.
It should be noted that the sequence of the steps in the process for judging whether or not the marine vessel 11 satisfies the broaching occurrence conditions is not limited to the one shown in
Referring again to
Then, the controller 30 judges whether or not the occurrence of broaching has been detected (step S53).
According to the IMO guidance, broaching may occur in cases where the encounter angle of a following wave is equal to or greater than 135° and equal to or smaller than 225°. As the ship speed of the marine vessel 11 increases, the time period over which the marine vessel 11 rides on the downward slope of the following wave increases, causing broaching to occur. The ship speed at which broaching occurs is referred to as a broaching occurrence critical speed. The broaching occurrence critical speed is specified with respect to each encounter angle, and when the ship speed of the marine vessel 11 becomes higher than the broaching occurrence critical speed, it is considered that broaching has occurred. According to the IMO guidance, the broaching occurrence critical speed with respect to each encounter angle is expressed by the mathematical expression (2).
Broaching occurrence critical speed (knot)=1.8×√{square root over (L(m))}/cos(180°−α) (2)
It should be noted that a ship speed at which there is a very high possibility of broaching even though broaching does not occur is referred to as a broaching occurrence marginal speed, and the broaching occurrence marginal speed with respect to each encounter angle is expressed by the mathematical expression (3).
Broaching occurrence marginal speed (knot)=1.4×√{square root over (L(m))}/cos(180°−α) (3)
In the above expressions (2) and (3), L is the length (m) between the perpendiculars of the marine vessel 11 (the hull 13), and α is the encounter angle (deg), which is specified as 135°≤α≤225°.
The broaching occurrence marginal zone enclosed by a broken line in
Thus, in the step S53, when the ship speed of the marine vessel 11 is not higher than the broaching occurrence critical speed, the controller 30 considers that the occurrence of broaching has not been detected, and the process returns to the step S53. When the ship speed of the marine vessel 11 is higher than the broaching occurrence critical speed, the controller 30 considers that the occurrence of broaching has been detected, and the process proceeds to the step S54.
In the step S54, the marine vessel 11 shifts into an avoidance mode. The avoidance mode is a mode in which the marine vessel 11 prepares for a motion of recovery from a sudden movement originating from broaching, which will be described later. In the avoidance mode, the controller 30 monitors the operated amount of the steering wheel 18 and the yaw rate of the hull 13.
Then, the controller 30 judges whether or not a sudden movement originating from broaching which may capsize the marine vessel 11 has been detected (step S55). Specifically, in a case where an actual yaw rate at the time when marine vessel 11 turned its head is equal to or greater than a yaw rate estimated from the amount of operation on the steering wheel 18 by the vessel operator, and the marine vessel 11 changed its course in a direction in which it would encounter a following wave, the controller 30 detects a sudden movement originating from broaching. Examples of the case where the marine vessel 11 changes its course in a direction in which it will encounter a following wave include a case where the marine vessel 11 changes its course to starboard when it is encountering a following wave from behind the starboard (the encounter angle is from 135° to) 180°, and a case where the marine vessel 11 changes its course to port when it is encountering a following wave from behind the port (the encounter angle is from 180° to 225°). When the actual yaw rate at the time when marine vessel 11 turned its head is smaller than the yaw rate estimated from the amount of operation on the steering wheel 18 by the vessel operator, or when the marine vessel 11 has changed its course in a direction opposite to a direction in which the marine vessel 11 would encounter a following wave, the controller 30 does not detect a sudden movement originating from broaching.
Here, the case where the actual yaw rate at the time when the marine vessel 11 turned its head is equal to or greater than the yaw rate estimated from the amount of operation on the steering wheel 18 by the vessel operator corresponds to a case where the course of the marine vessel 11 is different from a course estimated from the amount of operation on the steering wheel 18. It should be noted that in the present embodiment, a map showing the amounts of operation on the steering wheel 18 and the yaw rates estimated from the amounts of operation is prepared in advance and stored in, for example, the ROM 32. In the step S55, the controller 30 refers to this map.
In the step S55, when the controller 30 judges that a sudden movement originating from broaching has not been detected, the process returns to the step S55, and when the controller 30 judges that a sudden movement originating from broaching has been detected, the controller 30 changes, by using the course changing mechanism, the course of the marine vessel 11 so as to reduce a difference between the moving direction of the marine vessel 11 and the traveling direction of the following wave (step S56).
Then, the controller 30 judges whether or not the marine vessel 11 has recovered from the sudden movement originating from broaching (step S57). Specifically, the controller 30 judges whether or not the course of the marine vessel 11 has returned to a course which the marine vessel was taking before the occurrence of broaching. For example, when a difference between the moving direction of the marine vessel 11 after it changed its course in the step S56 and the moving direction of the marine vessel 11 before the occurrence of broaching is equal to or smaller than a predetermined value, the controller 30 judges that the marine vessel 11 has recovered from the sudden movement originating from broaching.
In the step S57, when the controller 30 judges that the marine vessel 11 has recovered from the sudden movement originating from broaching, the controller 30 ends the present process by causing the course changing mechanism to stop changing the course of the marine vessel 11, and when the controller 30 judges that the marine vessel 11 has not yet recovered from the sudden movement originating from broaching, the controller 30 increases the propeller rpm to a predetermined value (step S58). The case where the controller 30 judges in the step S57 that the marine vessel 11 has not recovered from the sudden movement originating from broaching corresponds to a case where the sudden movement of the marine vessel 11 is serious, the marine vessel 11 slides crosswise on the wave, and its crosswise movement component is greater than a predetermined value.
When the controller 30 increases the propeller rpm of to the predetermined value in the step S58, the marine vessel 11 accelerates and goes out of the broaching occurrence zone, resulting in rudder control being restored. As a result, the course of the marine vessel 11 becomes closer to a course which the marine vessel 11 was taking before the occurrence of the sudden movement originating from broaching.
Then, the controller 30 judges again whether or not the marine vessel 11 has recovered from the sudden movement originating from broaching (step S59). The way to judge in the step S59 whether or not the marine vessel 11 has recovered from the sudden movement originating from broaching is the same as the way to judge in the step S57 whether or not the marine vessel 11 has recovered from the sudden movement originating from broaching.
In the step S59, when the controller 30 judges that the marine vessel 11 has not recovered from the sudden movement originating from broaching, the process returns to the step S58, and when the controller 30 judges that the marine vessel 11 has recovered from the sudden movement originating from broaching, the controller 30 ends the present process.
According to the process in
Moreover, in the present embodiment, in order for the marine vessel 11 to recover from a sudden movement originating from broaching, the controller 30 causes the course changing mechanism to control the course of the marine vessel 11 first, and then the propeller rpm changing mechanism (the controller 30) increases the propeller rpm as appropriate. This prevents the marine vessel 11 from accelerating unexpectedly and making the vessel operator surprised.
Furthermore, in the present embodiment, even when the occurrence of broaching has been detected, the course of the marine vessel 11 is not changed until a sudden movement of the marine vessel 11 originating from broaching is detected. This keeps irregularities in the course of the marine vessel 11 to a minimum.
Additionally, in the present embodiment, when the controller 30 judges that the marine vessel 11 satisfies the broaching occurrence conditions, the tabs 21 of the tab units 20A and 20B are swung to the retracted position, so as to prevent behavior irregularities of the marine vessel 11, which occurs because of the tabs 21 encountering a following wave, from increasing.
While the embodiment of the present invention has been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
For example, although in the present embodiment, for the marine vessel 11 to recover from a sudden movement originating from broaching, the controller 30 changes the course of the marine vessel 11 using the course changing mechanism first, and then the propeller rpm changing mechanism (the controller 30) increases the propeller rpm, the method of recovering the marine vessel 11 from a sudden movement originating from broaching is not limited to this. For example, when detecting a sudden movement originating from broaching, first, the controller 30 may slightly change the course of the marine vessel 11 using the course changing mechanism, and then the propeller rpm changing mechanism (the controller 30) may slightly increase the propeller rpm. After that, if the marine vessel 11 has not recovered from the sudden movement originating from broaching, the controller 30 may change the course of the marine vessel 11 using the course changing mechanism to a large extent, and then the propeller rpm changing mechanism (the controller 30) may increase the propeller rpm to a large extent.
Moreover, the controller 30 may decrease the propeller rpm instead of increasing the propeller rpm. For example, the controller 30 may decrease the ship speed by decreasing the propeller rpm so that the marine vessel 11 can go out of the state in the broaching occurrence marginal zone in
It should be noted that as the posture control tabs, interceptor tabs may be used in place of the tabs 21. The interceptor tabs are attached to both sides of the stern of the hull 13 and shift their position in substantially the vertical direction. Specifically, each of the interceptor tabs changes its position in the water from a position at which it projects from a bottom surface (the vessel bottom) of the hull 13 to a position which is above the bottom surface of the hull 13. When the controller 30 judges in the step S51 that the marine vessel 11 satisfies the broaching occurrence conditions, the interceptor tabs shift to the retracted position.
Although in the embodiment, the marine vessel 11 is equipped with the outboard motors 15A and 15B, the marine vessel 11 may be equipped with other types of marine propulsion devices such as inboard/outboard motors (stern drive, inboard motor/outboard drive) and inboard motors. The marine vessel 11 may be moved by propulsive force provided by, for example, a water jet, rather than propulsive force provided by a propeller. In this case, the controller 30 increases the rpm of an impeller of the water jet to a predetermined value.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-012216 | Jan 2020 | JP | national |
