Ship speed control system and ship equipped with same

Abstract

The invention provides a ship speed control system and a ship equipped with the ship speed control system. The ship speed control system automatically controls a ship which is affected by large external disturbance so that the ship speed is constant. One embodiment of the present disclosure is a system (100) for controlling the sailing speed of a ship (10), the system (100) being provided with: a main propulsion device (11) for the ship, the main propulsion device (11) including an internal combustion engine (12) and a propeller (13) driven by the internal combustion engine (12); an auxiliary propulsion device (14) that assists the propulsion force of the ship (10) using natural energy; a ship speed detection device (20) for detecting the sailing speed of the ship (10); a host controller (30) that controls the main propulsion device (11); and a control device (40) for determining whether the sailing speed of the ship (10) is within a predetermined range including a preset ship speed (V0), and if the sailing speed of the ship (10) is not within the predetermined range, transmitting a signal for changing the rotational speed (N) of the propeller (13) to the host controller (30) on the basis of a calculation result based on a predetermined propeller rotational speed during ship speed constant control.

Description

Technical Field

[0001] The present invention relates to a ship speed control system and a ship equipped with the system. Background Art

[0002] In a general ship equipped with only an engine as a propulsion device, the ship speed is changed by changing the rotational speed of the engine. At this time, in a situation where the influence of external disturbances such as wind and sea conditions is slight, the change in ship speed is slow. However, in a situation where the influence of external disturbances causes a large change in ship speed, the ship is usually controlled by a crew member manually changing the rotational speed of the engine so as to achieve an arbitrary ship speed.

[0003] On the other hand, in a ship equipped not only with an engine but also with a device that utilizes natural energy such as wind to assist the ship's propulsion force (hereinafter referred to as an auxiliary propulsion device), the influence of external disturbances relatively increases, and thus the change in ship speed also easily becomes large. In a situation where the influence of external disturbances is large, it is necessary to adjust the engine rotational speed according to the change in ship speed. However, in practice, it is very cumbersome and unrealistic to frequently manually change the rotational speed.

[0004] In addition, keeping the sailing speed of a ship under the influence of external disturbances within a certain range is also suitable for making the ship sail according to a predetermined time and for suppressing fuel consumption by achieving efficient sailing without waste. In particular, when operating a large ship such as a bulk carrier (Bulker) that loads and transports bulk cargo into the cargo hold, it is more important to sail at a constant ship speed.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-44588

[0008] However, the actual situation is that so far, no specific technology has been particularly provided for keeping the ship speed constant under the influence of external disturbances in a ship equipped with an auxiliary propulsion device. Summary of the Invention

[0009] Therefore, an object of the present invention is to provide a ship speed control system and a ship equipped with the system, which automatically control the ship speed to be constant for a ship greatly affected by external disturbances.

[0010] One aspect of the present invention is a system for controlling the sailing speed of a ship, comprising:

[0011] The main propulsion device of the ship, including an internal combustion engine and a propeller driven by the internal combustion engine;

[0012] Auxiliary propulsion device for assisting the propulsion force of a ship using natural energy;

[0013] Ship speed detection device for detecting the sailing speed of the ship;

[0014] Main engine controller for controlling the main propulsion device;

[0015] Control device, which judges whether the sailing speed of the ship is within a specified range including a preset specified ship speed V0, and in the case of not being within the specified range, sends a signal to change the rotational speed N of the propeller to the main engine controller according to the calculation result based on the specified propeller rotational speed during constant ship speed control.

[0016] According to the ship speed control system described above, even in the case where the auxiliary propulsion force changes significantly due to the short-term change of natural energy, by automatically controlling the ship speed to be constant, for example, regarding the thrust of the main propulsion device composed of an internal combustion engine and the thrust obtained by the auxiliary propulsion device as being of the same degree, fuel consumption is suppressed and thrust is reduced, so that efficient navigation can be achieved without waste.

[0017] In the ship speed control system described above, during the control by the control device, the sailing speed of the ship can be continuously detected by the ship speed detection device.

[0018] In the ship speed control system described above, the sailing speed of the ship can be the speed relative to water or the speed relative to the ground.

[0019] In the ship speed control system described above, the average ship speed V of the ship within a specified measurement time ΔT can be calculated X , and judge whether the difference ΔV between the specified ship speed V0 and the average ship speed V X is within the specified range.

[0020] In the ship speed control system described above, in the case where the difference ΔV is not within the specified range, the increase or decrease process of the rotational speed N of the propeller can be implemented.

[0021] In the ship speed control system described above, the rotational speed N of the propeller can be increased or decreased step by step.

[0022] In the ship speed control system described above, after implementing the increase or decrease process of the rotational speed N of the propeller, when the ship speed V of the ship reaches the specified ship speed V0, the rotational speed N of the propeller can be maintained.

[0023] In the ship speed control system described above, after implementing the increase or decrease process of the rotational speed N of the propeller, in the case where the ship speed V of the ship does not reach the specified ship speed V0, the process of changing the rotational speed N of the propeller to N±ΔN can be carried out.

[0024] In the ship speed control system described above, ΔN can be calculated based on a calculation formula that includes the ship speed difference ΔV and the values inherent to the propeller as parameters.

[0025] In the ship speed control system described above, the following calculation formula can be used:

[0026] (Mathematical formula 1)

[0027] N = α3V 3 +α2V 2 +α1V+α0 ···(1)

[0028] (Mathematical formula 2)

[0029]

[0030] (Mathematical formula 3)

[0031]

[0032] (where α3, α2, and α1 are values inherent to the propeller).

[0033] In the ship speed control system described above, after the process of changing the rotational speed N of the propeller to N±ΔN and before performing the next process of changing to N±ΔN, a prescribed interval time T can be set.

[0034] In the ship speed control system described above, after the prescribed interval time T has elapsed, the average ship speed V of the ship within a prescribed measurement time ΔT is calculated X , and it is possible to perform again the process of determining whether the difference ΔV between the set ship speed V0 and the average ship speed V X is within a prescribed range.

[0035] The auxiliary propulsion device in the ship speed control system described above can be a sail-powered navigation device that receives wind by sails or kites provided on the hull of the ship.

[0036] The sails or kites of the sail-powered navigation device in the ship speed control system described above can be deformable or detachable and attachable in order to be able to change the force received from the wind.

[0037] The sails in the ship speed control system described above can be made of steel or FRP.

[0038] In addition to the first auxiliary propulsion device composed of a sail-powered navigation device, the ship speed control system described above can also include a second auxiliary propulsion device that obtains propulsion force through the Magnus effect.

[0039] A ship according to one aspect of the present invention is equipped with the ship speed control system described above.

[0040] The ship as described above is, for example, a bulk carrier.

[0041] Advantages of the Invention

[0042] According to the present invention, it is possible to provide a ship speed control system and a ship equipped with the system, which can automatically control the ship speed to be constant for a ship affected by a large external disturbance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a side view of the starboard side of a ship according to an embodiment of the present invention.

[0044] Figure 2 It is a plan view of the ship.

[0045] Figure 3 It is a schematic diagram showing the structure of the ship speed control system.

[0046] Figure 4 It is a flowchart showing an example of ship speed control using the ship speed control system.

[0047] Figure 5 It is a graph showing the change in ship speed for explaining an example of ship speed control using the ship speed control system.

[0048] REFERENCE SIGNS

[0049] 10... Ship

[0050] 11... Main engine (main propulsion device)

[0051] 12... Engine (internal combustion engine)

[0052] 13... Propeller

[0053] 14... Auxiliary propulsion device

[0054] 15... Sail propulsion device (first auxiliary propulsion device)

[0055] 15A... Support shaft

[0056] 15S... Sail

[0057] 16... Rotating sail (second auxiliary propulsion device that obtains propulsion force through the Magnus effect)

[0058] 17... Control device for the auxiliary propulsion device

[0059] 18... Kite

[0060] 20... Ship speed detection device

[0061] 21... Log

[0062] 22... Ground speed measuring instrument

[0063] 30…Main controller

[0064] 31…User interface

[0065] 40…Control device

[0066] 41…Storage device

[0067] 42…Computer

[0068] 100…Ship speed control system

[0069] N…Rotation speed of the propeller (before the start of control)

[0070] ΔN…Difference from the computationally optimal rotation speed derived based on the ship speed difference ΔV

[0071] t…Time

[0072] T…Control interval time (variable)

[0073] ΔT…Measurement time of the average ship speed

[0074] V0…Set ship speed

[0075] V…Ship speed

[0076] VR…Ship speed adjustable range

[0077] V X …Average ship speed within the specified measurement time ΔT

[0078] ΔV…Difference between the set ship speed V0 and the average ship speed V X Difference Detailed implementation manners

[0079] Next, the preferred implementation manners of the present invention will be described with reference to the accompanying drawings.

[0080] The ship 10 of the present implementation manner is equipped with a ship speed control system 100 and can sail under the control of this system. Hereinafter, first, the structure of the ship 10 will be briefly described, and then, the ship speed control system 100 of the ship 10 will be described.

[0081] (Ship)

[0082] In addition to the main engine (main propulsion device) 11, the ship 10 of the present implementation manner is also equipped with an auxiliary propulsion device 14 that utilizes natural energy such as wind to assist the propulsion force on the hull, and is also equipped with a ship speed detection device 20, a main controller 30, a control device 40, etc. (refer to Figure 3etc.). Hereinafter, the ship 10 as a bulk carrier will be exemplified and described, but this is only a preferred example of the ship 10, and the size and type of the ship 10 which is the object of the present application are not particularly limited.

[0083] The main engine 11 is a mechanism that functions as a main propulsion device that generates most of the propulsion force of the ship 10. In the present embodiment, a device including an engine 12 and a propeller 13 is adopted as the main engine 11 (refer to Figure 1 , Figure 3 ). The engine 12 is composed of a prime mover mechanism including an internal combustion engine that generates a force for rotating the propeller 13. The propeller 13 rotates by the rotational driving force of the engine 12, and moves the ship 10 forward or backward (refer to Figure 1 etc.).

[0084] The auxiliary propulsion device 14 is a device that utilizes natural energy such as wind to obtain auxiliary propulsion force to assist the propulsion force of the ship 10. The ship 10 of the present embodiment is provided with two types of auxiliary propulsion devices 14, namely, a sail navigation device 15 as a first auxiliary propulsion device and a rotary sail 16 as a second auxiliary propulsion device (refer to Figure 1 , Figure 2 ). In addition, in the present embodiment, a device that utilizes wind is described as the auxiliary propulsion device, but this is only an example of the method of utilizing natural energy. Although not described in detail in this specification, as other examples of the method of utilizing natural energy, there is a so-called air lubrication system that reduces seawater resistance by sending air to the bottom of the ship and making it stay, and a so-called kite system composed of a kite 18 that gives auxiliary propulsion force to the ship 10 by the wind (refer to Figure 1 , Figure 2 ) etc.

[0085] The sail navigation device 15 is a device composed of a sail 15S provided at, for example, the bow portion of the hull, and obtains propulsion force by receiving wind. In the present embodiment, a sail navigation device 15 with a sail 15S made of steel or FRP is adopted (refer to Figure 1 , Figure 2 ), but a sail navigation device 15 with a sail 15S made of fabric materials such as other sails, such as cloth or canvas, can also be adopted, and the material or structure of the sail 15S is not particularly limited. The sail 15S of the present embodiment has a substantially semi-cylindrical shape and is supported in a state capable of rotating about a support shaft 15A extending in the vertical direction on the hull, and can perform turning (rotation) to the left and right, and further telescoping (refer to Figure 2 etc.). The sail 15S can also be configured to be deformable (as an example, it can change the overall height by vertically displacing a part of the sail 15S divided into multiple shapes) so as to be able to change the force received by the wind.

[0086] The rotary sail 16 is provided, for example, at two locations on the hull as a second auxiliary propulsion device, and is configured to obtain propulsion force by the Magnus effect (see Figure 1 , Figure 2 ). Specifically, these rotary sails 16 are composed of cylindrical columns arranged to extend in the vertical direction, and generate propulsion force by the Magnus effect when rotating about the vertical axis. The rotary sail 16 of the present embodiment is controlled by the control device 17, operates based on signals sent by the control device 17, and its state and condition are monitored by the control device 17 (see Figure 2 , Figure 3 ). When the control device 17 detects that the rotary sail 16 is in an abnormal state, it sends a signal (failure alarm) notifying the abnormality to the control device 40 (see Figure 3 ).

[0087] The ship speed detection device 20 is a device for detecting the ship speed (navigation speed) of the ship 10. As the ship speed detection device 20, an electromagnetic log using electromagnetic induction, a Doppler sonar that calculates the frequency change of sound waves when ultrasonic waves are emitted from a device at the bottom of the ship and return to the bottom of the ship again, a device that measures using radio waves from artificial satellites, etc. can be used. In the present embodiment, as the ship speed detection device 20, a measurer for measuring the ship speed through water for observing fuel consumption, etc. (denoted by reference numeral 21 in Figure 3 ), such as a Doppler current meter or an electromagnetic current meter, and a measurer for measuring the ship speed relative to the ground for observing sea lanes, navigation distance, speed, etc., such as a satellite speed log or GPS (denoted by reference numeral 22 in Figure 3 ) are used (see Figure 3 ). In the present embodiment, during the period when the ship speed control system 100 is controlled by the control device 40, the ship speed (navigation speed) V of the ship 10 is always detected by the ship speed detection device 20.

[0088] The main engine controller 30 is a device that controls the main engine 11 according to the instruction signal received from the control device 40. In the present embodiment, a main engine controller (main engine remote controller) 30 capable of remote control is adopted, and it can be controlled from a position far from the main engine 11 (see Figure 3 ). Although detailed illustration is omitted, the main engine controller 30 is provided with a user interface 31 and is configured to be able to set the control state, the rotational speed control range of the main engine 11, etc.

[0089] The control device 40 is a device that determines whether the ship speed detected by the ship speed detection device 20 is within a specified range including the set ship speed V0, and sends a specified control signal when it is not within the specified range. The control device 40 of the present embodiment is composed of a device including a storage device 41 for storing a specified program, a computer 42 that executes processing in a specified order through this program, such as an IAS (Integrate Automatic System) (refer to Figure 3 ). Details will be described later. The control device 40 sends a start / stop signal for ship speed constant control, an acceleration / deceleration signal for the ship speed V, etc. to the main engine controller 30, and also receives an acceleration / deceleration completion signal, information related to the current rotation speed of the main engine 11, information that the rotation speed of the main engine 11 cannot be changed, a signal (fault alarm) notifying an abnormality of the main engine 11, etc. from the main engine controller 30 (refer to Figure 3 ).

[0090] (Ship speed control system)

[0091] The ship speed control system 100 is configured to variably control the rotation speeds of the engine 12 and the propeller 13 of the main engine 11 of the ship 10 affected by external disturbances to automatically keep the ship speed constant, so as to effectively utilize the thrust obtained by the auxiliary propulsion device 14 to reduce fuel. The ship speed control system 100 of the present embodiment is configured as a system composed of the above-mentioned main engine 11, auxiliary propulsion device 14, ship speed detection device 20, main engine controller 30, and control device 40 (refer to Figure 3 ).

[0092] An example of the ship speed constant control performed by the ship speed control system 100 will be described (refer to Figure 4 、 Figure 5 ).

[0093] (Preparation operation for ship speed constant control)

[0094] First, the rotation speeds of the engine 12 and the propeller 13 of the main engine 11 are increased to an arbitrarily set ship speed at which the ship speed V is within the range of the ship speed constant control target range (referred to as the "ship speed settable range" in this specification, denoted by the symbol VR in Figure 5 ), for example, 15 knots corresponding to Figure 5 (step 1). The ship speed settable range VR is a specified range of the ship speed V that can be controlled when automatically controlling the ship speed V to be constant through a program based on the set specified ship speed (set ship speed V0) (refer to Figure 5 ). In addition, the sail 15S is deployed in a timely manner on the way.

[0095] When the rotational speeds of the engine 12 and the propeller 13 reach this speed, an arbitrary set ship speed V0 value (as an example, 15 knots) is input to the control device 40 using an input device (not shown) (step 2), and the constant ship speed control is started (step 3). As the set ship speed V0 value, either the speed relative to water or the speed relative to land can be selected for input. Incidentally, the markings "FULL" and "NAV.FULL" in Fig. t refer to the output of the main engine 11. Generally, starting from a lower output of the main engine 11, the rotational speed of the propeller 13 and the ship speed increase in the order of "STOP", "DEAD SLOW", "SLOW", "HALF", "FULL", "NAV.FULL". Usually, it sails at "FULL" or "NAV.FULL".

[0096] In addition, when ΔN (the difference from the computationally optimal rotational speed derived from the ship speed difference ΔV) described later is within the rotational speed prohibition range, the rotational speed below the rotational speed prohibition range can be automatically reset (refer to Figure 5 ). The rotational speed prohibition range is set to avoid the possibility of the shaft of the propeller 13 being damaged by excessive torsional vibration stress during long-term operation within this rotational speed prohibition range.

[0097] (Constant ship speed control)

[0098] The control device 40 calculates the average ship speed V of the ship 10 during a measurement time ΔT [minutes] of a certain length X , calculates the difference ΔV between the set ship speed V0 and the average ship speed V X (the threshold value is variable, and the sign of the difference can be set with + / −) (step 4). In addition, regarding the rotational speed N of the propeller 13, the difference ΔN from the computationally optimal rotational speed is derived from the ship speed difference ΔV (step 4). Such a difference ΔN can be calculated based on a calculation formula using the ship speed difference ΔV and the inherent numerical values of the propeller 13 as parameters. As an example, in the present embodiment, as the calculation formula,

[0099] (Mathematical formula 4)

[0100] N = α3V 3 +α2V 2 +α1V + α0 ···(1)

[0101] (Mathematical formula 5)

[0102]

[0103] (Mathematical formula 6)

[0104]

[0105] (where α3, α2, and α1 are inherent values of the propeller)

[0106] The difference ΔN in rotational speed can be calculated using each of the expressions (1) to (3). In the present embodiment, when the wind during the navigation of the ship 10 affects the ship speed and changes to V ± ΔV, the propeller rotational speed is changed from the current rotational speed N to a new rotational speed N ± ΔN to control the ship speed V to maintain the set ship speed V0.

[0107] Next, it is determined whether the difference ΔV between the set ship speed V0 and the average ship speed V X exceeds a specified threshold value. The specified threshold value refers to a threshold value set above with the set ship speed V0 as the center (marked as "threshold value of set ship speed (+)" in Figure 5 ) and a threshold value set below (marked as "threshold value of set ship speed (-)" in Figure 5 ), and can be set to any value.

[0108] When the difference ΔV between the set ship speed V0 and the average ship speed V X does not exceed the specified threshold value (refer to the state towards the left in the two "Step 4" shown in Figure 5 ), the process of increasing or decreasing the rotational speed N of the propeller 13 is not performed. On the other hand, when the difference ΔV between the set ship speed V0 and the average ship speed V X exceeds the specified threshold value (when the difference ΔV is not within the specified range) (refer to the state towards the right in the two "Step 4" shown in Figure 5 ), the process of increasing or decreasing the rotational speed N of the propeller 13 is performed (Step 5). The increase or decrease process is implemented, for example, by having the computer 42 execute a specified sequence for the increase or decrease process based on an increase or decrease process program (hereinafter, for convenience, sometimes referred to as the "Load Down / Up program") stored in the storage device 41 of the control device 40. As an example, when the difference ΔV exceeds the upper threshold value (threshold value of set ship speed (+)), the above-described increase or decrease process is performed to decrease the rotational speed N of the propeller 13 and decelerate the ship speed V (refer to Figure 5 ).

[0109] When performing the increase or decrease process as described above, the rotational speed N of the propeller 13 can also be increased or decreased step by step. As an example, in the present embodiment, when decelerating (decreasing the rotational speed), the rotational speed is decreased in a step-by-step manner of decreasing one revolution per minute, and when accelerating (increasing the rotational speed), the rotational speed is increased in a step-by-step manner of increasing one revolution every four minutes (Step 6). In the Figure 5 shown curve graph, an example of decelerating by decreasing the rotational speed N of the propeller 13 step by step is shown (refer to Figure 5 ).

[0110] After the increase / decrease process is performed, the control device 40 determines whether a state satisfying a specified condition is achieved. When the condition is satisfied, the increase / decrease process program is closed, the increase / decrease process ends, and the rotational speed N of the propeller 13 is maintained (step 7). Various contents can be set as the specified condition. As an example, in the present embodiment, the following three conditions (hereinafter, referred to as Case 1, Case 2, and Case 3, respectively) are set. Case 1 is that the ship speed V reaches the set ship speed V0, and Case 2 is that the ship speed V is below the set ship speed V0 (in the case of the example shown in Figure 5 , the ship speed V is below the set ship speed V0) (see Figure 4 , Figure 5 ). Case 2 and Case 3 are processes of changing the rotational speed N of the propeller 13 to N±ΔN when the ship speed V does not reach the set ship speed V0. After the steady state (since a ship is different from a car, etc., and the speed changes slowly, even if the rotational speed is changed to a specified value, there is a time lag to reach the set ship speed. It takes time for the rotational speed and ship speed after the change to stabilize, and the state where they are stable is called the steady state), the ship speed V is above / below the set ship speed V0 (if it is the case of the example shown in Figure 5 , the ship speed V is below the set ship speed V0) (see Figure 4 , Figure 5 ). As an example, in the present embodiment, when the ship speed V does not reach the set ship speed V0, the process of changing the rotational speed N of the propeller 13 to N - ΔN is performed. If the ship speed V after the steady state is below the set ship speed V0, it corresponds to Case 2, and if the ship speed V after the steady state is above the set ship speed V0, it corresponds to Case 3, and the increase / decrease process program is closed (see Figure 4 , Figure 5 ).

[0111] If the increase / decrease process ends as described above and the rotational speed N of the propeller 13 is maintained (step 7), then after a specified time (e.g., T minutes), a state where a command signal for changing the rotational speed N is not accepted is achieved (step 8). At this time, the main engine controller 30 sends the meaning that the rotational speed of the main engine 11 cannot be changed to the control device 40 (see Figure 3 ). In this way, after the process of changing the rotational speed N of the propeller 13 to N±ΔN, a specified interval time T is set before the next process of changing to N±ΔN, thereby preventing rotational speed hunting (idle instability. Vibration occurring during idling. A phenomenon where the speed or position is unstable and fluctuates up and down near the indicated target value).

[0112] After the specified interval time T has elapsed after the increase / decrease process ends, the process returns to step 4 (step 9) as one cycle of the ship speed constant control process so far, and the average ship speed V of the ship 10 within the specified measurement time ΔT is calculated again X, the process of determining whether the difference ΔV between the set ship speed V0 and the average ship speed V X is within the specified range (step 4), and transferring to the next processing cycle. After that, the processes from step 4 to step 9 are repeated (refer to Figure 4 ).

[0113] According to the ship speed control system 100 described above, even when the auxiliary propulsion force changes significantly due to the short-term variation of natural energy, the ship speed V can be automatically controlled to be constant. In this way, for example, in the case of a tailwind, the thrust of the main engine 11 composed of the engine (internal combustion engine) 12 and the thrust obtained by the auxiliary propulsion device 14 are regarded as being of the same level, suppressing fuel consumption and reducing thrust. In this way, efficient navigation can be achieved without waste. In addition, automatically controlling the ship speed V to be constant of course also helps to achieve non-stop navigation by arriving at the destination as scheduled, and furthermore, it will not cause obstacles to logistics and the like.

[0114] In addition, although the above-described embodiment is a preferred embodiment of the present invention, it is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

[0115] Industrial Applicability

[0116] The present invention is applicable to a ship speed control system for controlling the navigation speed of a ship and a ship equipped with the system.

Claims

1. A ship speed control system, which is a system for controlling the navigation speed of a ship, comprising: The main propulsion device of the ship, including an internal combustion engine and a propeller driven by the internal combustion engine; An auxiliary propulsion device that uses natural energy to assist the propulsion force of the ship; A ship speed detection device that detects the navigation speed of the ship; A main engine controller that controls the main propulsion device; A control device that determines whether the navigation speed of the ship is within a specified range including a preset set ship speed V0, and when it is not within the specified range, based on the calculation result of the specified propeller rotation speed during constant ship speed control, sends a signal to the main engine controller to change the rotation speed N of the propeller.

2. The ship speed control system according to claim 1, wherein During the control by the control device, the ship speed detection device always detects the navigation speed of the ship.

3. The ship speed control system according to claim 2, wherein The navigation speed of the ship is the speed relative to water or the speed relative to the ground.

4. The ship speed control system according to claim 3, wherein Calculate the average ship speed V of the ship within the specified measurement time ΔT X , and determine whether the difference ΔV between the set ship speed V0 and the average ship speed V X is within the specified range.

5. The ship speed control system according to claim 4, wherein When the difference ΔV is not within the specified range, the increase or decrease process of the rotation speed N of the propeller is performed.

6. The ship speed control system according to claim 5, wherein The rotation speed N of the propeller is increased or decreased step by step.

7. The ship speed control system according to claim 6, wherein After performing the increase or decrease process of the rotation speed N of the propeller, when the ship speed V of the ship reaches the set ship speed V0, the rotation speed N of the propeller is maintained.

8. The ship speed control system according to claim 6, wherein After performing the increase or decrease process of the rotation speed N of the propeller, when the ship speed V of the ship does not reach the set ship speed V0, the process of changing the rotation speed N of the propeller to N±ΔN is performed.

9. The ship speed control system according to claim 8, wherein The ΔN is calculated based on a calculation formula including the difference ΔV of the ship speed and the inherent value of the propeller as parameters.

10. The ship speed control system according to claim 9, wherein As the calculation formula, the following is used: (Mathematical formula 1) N = α3V 3 + α2V 2 + α1V + α0…(1) (Mathematical formula 2) (Mathematical formula 3) Where α3, α2, and α1 are the inherent values of the propeller.

11. The ship speed control system according to claim 10, wherein After the process of changing the rotation speed N of the propeller to N±ΔN and before performing the next process of changing to N±ΔN, a specified interval time T is set.

12. The ship speed control system according to claim 11, wherein After the lapse of the specified interval time T, the average ship speed V of the ship within the specified measurement time ΔT is calculated. X , and then it is determined again whether the difference ΔV between the set ship speed V0 and the average ship speed V X is within the specified range.

13. The ship speed control system according to claim 12, wherein The auxiliary propulsion device is a sail navigation device that receives wind by a sail or a kite provided on the hull of the ship.

14. The ship speed control system according to claim 13, wherein The sail or kite of the sail navigation device can be deformed or disassembled to be able to change the force received by the wind.

15. The ship speed control system according to claim 14, wherein The sail is made of steel or FRP.

16. The ship speed control system according to claim 15, wherein the ship speed control system further includes a second auxiliary propulsion device that obtains propulsion force through the Magnus effect, in addition to the first auxiliary propulsion device constituted by the sail navigation device.

17. A ship equipped with the ship speed control system according to any one of claims 1 to 16.

18. The ship according to claim 17, wherein the ship is a bulk carrier.

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