Patent Description:
A ship including an air lubricating device to produce an air lubrication effect is known. <CIT>, for example, discloses a ship that includes an air lubricating device to blow air outward from a bottom of the ship. The ship is equipped with an air blowing device to blow air outward from the bottom of the ship and suppression means to suppress a relative decrease in thickness of an air layer put over a predetermined area of the ship bottom. The air blowing device has air outlets that are provided in a middle area, a port area, and a starboard area of the ship bottom.

<CIT> relates to an air lubrication system of a vessel, wherein the ejection of air bubbles is controlled based a fuel consumption efficiency of a motor, a draft, whether conditions, or a velocity of the vessel.

<CIT> and P<CIT> relate to control of an air lubrication system of a vessel, wherein the amount and/or starting/stopping of bubble ejection is controlled based on a draft, a load, a movement of the vessel, or an operating state of the engine.

The air lubricating device that is in operation exerts an effect of reducing resistance of a hull (hereinafter referred to as an "air lubrication effect") through air bubbles blown against the hull. The air lubrication effect with which the resistance of the hull is reduced helps to reduce energy consumed by a propulsion device of the ship. However, the air lubricating device in operation consumes energy for blowing air outward. Hence, it is preferred that the air lubricating device be operated when an effect of reducing consumed energy is properly produced in total in consideration of a balance between a decrease in energy consumed by the propulsion device and an increase in energy consumed by the air lubricating device, rather than allowing the air lubricating device to always operate.

It is, for example, conceivable that the air lubricating device runs or stops according to an operator's decision. However, this case cannot necessarily produce an air lubrication effect in a proper manner.

In terms of proper production of an air lubrication effect, the ship described in <CIT> does not provide a satisfactory solution.

In view of the above problem, an object of the present invention is to provide a technique that enables a control device to produce an air lubrication effect properly.

This is achieved by the features of the independent claim.

According to the present invention, a technique can be provided that enables a control device to produce an air lubrication effect properly.

Terms used herein will be described. In the present specification, a velocity of a ship hull relative to the water is simply referred to as a "ship velocity", and a hull draft at present is simply referred to as a "draft". Frictional resistance of the hull to the water is referred to as "resistance of the hull" and actual resistance of the hull at present is referred as "actual resistance of the hull". Unless otherwise described, increasing an amount of air bubbles being blown out includes starting an action of blowing air bubbles outward, and decreasing an amount of air bubbles being blown out includes stopping an action of blowing air bubbles outward. A time when the blow mechanism is blowing air out is sometimes referred to as a "time of blowing", and a time when the blow mechanism is not blowing air out is sometimes referred to as a "time of non-blowing".

In the present specification, a balance between an amount of energy consumption reduced by air lubrication and an amount of energy used for air lubrication is referred to as an "energy balance". A case in which the amount of reduced energy consumption is higher than the amount of energy usage is referred to as a "good" or "positive" energy balance. A case in which the amount of energy usage is higher than the amount of reduced energy consumption is referred to as a "no-good" or "negative" energy balance. An expression used when the energy balance is good is that an air lubrication effect is produced properly. An expression used when the energy balance gets better is "improve". An amount of fuel consumption can be converted into an amount of energy consumption by multiplying the amount of fuel consumption by a predetermined factor.

First, an outline of a control device according to the present invention will be described. A control device according to the present invention includes an air bubble controller configured to control a blow mechanism designed to blow an air bubble out through an air outlet formed in a hull. The air bubble controller starts blowing the air bubble outward or increases an amount of the air bubble blown outward when hull resistance of the hull satisfies a predetermined condition. According to this configuration, an air lubrication effect can be controlled depending on whether or not the predetermined condition is satisfied.

According to the invention, the control device includes a resistance calculator configured to calculate the hull resistance of the hull. The air bubble controller may start blowing the air bubble outward or increase the amount of the air bubble blown outward when the hull resistance calculated by the resistance calculator is higher than a reference value. In this case, the air lubrication effect can be used when the hull resistance is high. The hull resistance calculated by the resistance calculator may be actual hull resistance or assumed hull resistance.

According to the invention, the control device calculates the hull resistance based on at least one of a ship velocity of the hull, information on weather and oceanic conditions the hull is confronting, a draft of the hull, and a rudder angle of the hull. In this case, the hull resistance can be calculated with increased accuracy.

According to the invention, the hull includes a main engine to cause a propeller to rotate, and the resistance calculator calculates the hull resistance based further on an output from the main engine at present. In this case, the hull resistance can be calculated with further increased accuracy.

In one example, the air bubble controller may include a determinator to determine the reference value based on information about frictional resistance of the hull to water, in which the frictional resistance is set in advance concerning the hull. In this case, the reference value compatible with a characteristic of the hull can be determined.

The hull includes a main engine to cause a propeller to rotate, and the determinator may determine the reference value based further on at least one of an output from the main engine, an amount of fuel consumed by the main engine, and an amount of energy used by the blow mechanism. In this case, the reference value can be determined with increased accuracy using these items of information.

In one example, the determinator may determine the reference value based further on a draft of the hull at present. In this case, influence of the draft can be diminished.

In one example, the determinator may determine the reference value based further on a relationship between an amount of air blown out by the blow mechanism and an amount of energy used by the blow mechanism according to the draft. In this case, influence of the draft can be further diminished.

In one example, the determinator may determine the reference value based further on a relationship between an amount of fuel consumed by a main engine and an output from the main engine. In this case, influence of a worn component of the main engine can be diminished.

In one example, the air bubble controller may stop blowing the air bubble outward or decrease the amount of the air bubble blown outward when the hull resistance calculated by the resistance calculator is lower than a second reference value. In this case, the air bubble controller can control the air bubble such as stopping the air bubble in a timely manner.

In one example, the control device may determine the second reference value based on an amount of energy used by the blow mechanism at present. In this case, the control device can determine the second reference value according to the amount of energy usage at present.

In one example, the air bubble controller may increase or decrease the amount of the air bubble blown outward depending on a draft of the hull at present. In this case, the control device can determine the energy balance according to a change in the draft.

In one example, the control device may further include a transmitter to send out information about a status of the air bubble blown out by the blow mechanism. In this case, the control device can inform an operator of the status of the blown air bubble.

In one example, the control device may further include: a first calculator to calculate an energy reduction amount that is an amount of energy consumption reduced when the air bubble is blown out by the blow mechanism; and a second calculator to calculate an energy usage amount that is an amount of energy consumed to operate the blow mechanism, the energy reduction amount and the energy usage amount being calculated based on a ship velocity of the hull at present. The air bubble controller may start blowing the air bubble outward or increase the amount of the air bubble blown outward when the energy reduction amount calculated by the first calculator is larger than the energy usage amount calculated by the second calculator. In this case, the control device determines the energy balance using an energy reduction amount for the main engine and an energy usage amount for the blow mechanism. This provides improved determination accuracy.

In one example, the hull may include a main engine to cause a propeller to rotate. The first calculator may include: a reduction ratio calculator to calculate a fuel consumption reduction ratio according to the ship velocity and a draft of the hull; and a fuel consumption calculator to calculate a current fuel consumption amount of the main engine according to a current rotation rate of the main engine and a fuel supply status for the main engine. The first calculator may calculate the energy reduction amount according to the calculated fuel consumption reduction ratio and the current fuel consumption amount. In this case, the first calculator calculates the energy reduction amount according to the fuel consumption reduction ratio and the current fuel consumption amount. This helps to reduce calculation errors.

In one example, the blow mechanism may include: an engine; a power generator driven by the engine; and a compressor to compress air by electricity generated by the power generator and supply the compressed air to the air outlet. The second calculator may calculate the energy usage amount based on any one of an amount of fuel supplied to the engine, electricity generated by the power generator, and electricity used to drive the compressor. The control device, based on these items of information, may further perform a calculation: electricity used to drive the compressor/power generation efficiency of the power generator/efficiency of the engine = amounts of fuel consumed by the power generator and the engine that are necessary for the compressor to produce compressed air. In this case, the control device provides improve accuracy with which the energy usage amount is calculated.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. Identical reference marks are assigned to identical or equivalent components and members shown in the embodiments and modification examples, and the repeated description thereof is omitted as appropriate. In the drawings, the dimensions of members are scaled up or down as appropriate to facilitate understanding. In the drawings, illustration of members that are not essential for a description of the embodiments is partly omitted.

For separate components that have a common feature, ordinal numerals such as "first and second" are added to the beginning parts of names of these components to distinguish them from each other, and these ordinal numerals are omitted when the components are correctively referred to as their names. Terms that have ordinal numerals such as first and second are used to describe a variety of components. These terms are only used to distinguish one component from the other components and should not be construed to limit these components.

In embodiments disclosed in the present specification, a part that consists of several elements may be altered into a part such that the several elements of the part are integrated together. Conversely, a part that consists of a single element can consist of separate elements. Regardless of whether the elements are integrated or not, the part is satisfactory as long as the part is configured so as to attain the object of the invention.

In embodiments disclosed in the present specification, a part whose several functions are distributed may be altered into a part such that the several functions are partly or wholly converged. Conversely, a part whose several functions are converged can be altered into a part such that the several functions are partly or wholly distributed. Regardless of whether the functions are converged or distributed, the part is satisfactory as long as the part is configured so as to attain the object of the invention.

A control device <NUM> according to a first embodiment of the present invention will now be described with reference to the drawings. <FIG> is a schematic view showing a ship <NUM> to which the control device <NUM> according to the present invention is applied. In the present embodiment, the ship <NUM> includes a hull <NUM>, the control device <NUM>, a propulsion mechanism <NUM>, and a blow mechanism <NUM>. The propulsion mechanism <NUM> is a mechanism designed to generate propulsive force with which the hull <NUM> is propelled. The blow mechanism <NUM> constitutes an air lubricating mechanism that blows an air bubble B out through an air outlet <NUM> formed, for example, in a ship bottom of the hull <NUM> to produce an air lubrication effect with which resistance of the hull is reduced.

<FIG> is a schematic block diagram showing the control device <NUM> according to the present embodiment. The blocks shown in <FIG> and other block diagrams described later are implemented by any of devices, electronic circuits, and mechanisms such as computer processors, CPUs, and memory in terms of hardware and by any of computer programs and applications in terms of software. The drawings shown herein illustrate functional blocks implemented through coordination of these components. Thus, it will be understood by those skilled in the art that these functional blocks can be implemented in various forms by combinations of the hardware and software.

The control device <NUM> includes an air bubble controller <NUM>, a propulsion controller <NUM>, a command receiver <NUM>, a resistance calculator <NUM>, a transmitter <NUM>, an information acquisitor <NUM>, and a storage unit <NUM>. The air bubble controller <NUM> controls the blow mechanism <NUM>, which blows the air bubble B out through the air outlet <NUM> formed in the hull <NUM>. The propulsion controller <NUM> controls propulsive force generated by the propulsion mechanism <NUM> to propel the hull <NUM>. The command receiver <NUM> receives a command signal sent to instruct the propulsion mechanism <NUM> on a size of the propulsive force. The information acquisitor <NUM> acquires input data of various kinds described later. The storage unit <NUM> chronologically stores the acquired input data of various kinds and stores reference values or threshold values described later. The resistance calculator <NUM> and the transmitter <NUM> are described later.

In the control device <NUM>, one of the propulsion controller <NUM> and the air bubble controller <NUM> may be controlled in response to a state in which another of propulsion controller <NUM> and the air bubble controller <NUM> is controlled. This enables the blow mechanism <NUM> and the propulsion mechanism <NUM> to work in cooperation with each other and thus helps to improve an energy balance of the hull <NUM>.

The propulsion mechanism <NUM> may be any mechanism as long as the mechanism can propel the hull <NUM>. In the present embodiment, the propulsion mechanism <NUM> includes a diesel engine (hereinafter referred to as a "main engine <NUM>") acting as a prime motor <NUM>, and the main engine <NUM> causes a propeller <NUM> to rotate and generate propulsive force. The propulsion mechanism <NUM> consumes an amount of fuel according to a rotation rate and torque of the main engine <NUM> to run the main engine <NUM>. The propulsion mechanism <NUM> includes a speed regulator <NUM> to suppress a variation in rotation rate of the main engine <NUM>. The speed regulator <NUM> is also known as a governor. When the rotation rate of the main engine <NUM> changes in response to a variation in load, the speed regulator <NUM> regulates a quantity of supplied fuel to lessen the rotation rate change.

The propulsion controller <NUM> controls the main engine <NUM>. Based on an operation input to a controller device (hereinafter referred to as a "remote controller <NUM>") that is installed in a bridge or another part of the ship <NUM> to remotely control the main engine <NUM>, the propulsion controller <NUM> of the present embodiment is designed to control the main engine <NUM>, such as increasing or decreasing the rotation rate and stopping the main engine. The remote controller <NUM> has an operation handle <NUM> that is used as an operation part to instruct the propulsion mechanism <NUM> on the size of the propulsive force. The remote controller <NUM> sends the control device <NUM> a command signal C1 to instruct the control device on the size of the propulsive force in response to a position of the operation handle <NUM> (hereinafter referred to as a "handle position P"). The handle position P serves as an example of an operational state of the operation part.

The operation handle may be structured in any form with proviso that the operation handle allows an operator to input an operation to the controller device. For instance, the operation handle may include or may not include a movable operation part. For instance, the operation handle may be designed to detect a command by a touched place on a touch panel.

In the present embodiment, the control device <NUM> includes the command receiver <NUM> to receive the command signal C1. The propulsion controller <NUM> alters propulsive force generated by the propulsion mechanism <NUM> based on the command signal C1 received by the command receiver <NUM>. By changing the position of the operation handle <NUM> on the remote controller <NUM>, the operator can alter the propulsive force of the propulsion mechanism <NUM> within a predetermined range that includes zero, headway, and sternway.

The blow mechanism <NUM> is a mechanism that blows the air bubble B out into the water during sailing through the air outlet <NUM> formed, for example, in the ship bottom of the hull <NUM>. Since the hull <NUM> is partly covered with an air layer that is formed by the air bubble B blown out through the air outlet <NUM>, the hull resistance is reduced. In the present embodiment, the blow mechanism <NUM> includes an engine <NUM> to drive a power generator <NUM> and a compressor <NUM> driven on electricity generated by the power generator <NUM>.

By blowing the air bubble B outward and thereby reducing the resistance of the hull, energy consumed by the propulsion mechanism <NUM> can be reduced. However, this concurrently consumes energy in blowing the air bubble outward. Thus, it is important to blow the air bubble B outward in consideration of a balance between a decrease in consumed energy and an increase in consumed energy. As a result, it is preferable to control the blow mechanism <NUM> depending on whether a predetermined condition related to the balance on consumed energy is satisfied. Accordingly, the air bubble controller <NUM> of the present embodiment, when the predetermined condition is satisfied, controls the blow mechanism <NUM> so as to start blowing the air bubble B outward or increase an amount of the air bubble B blown outward. In other words, the air bubble B is blown outward when the air lubrication effect is properly produced.

Energy consumption by the blow mechanism <NUM> of the present embodiment will be described. The air bubble controller <NUM> controls the blow mechanism <NUM> to switch between a state in which the engine <NUM>, the power generator <NUM>, and the compressor <NUM> operate to blow the air bubble B outward and a state in which the engine <NUM> is stopped and the air bubble B is not blown outward. The blow mechanism <NUM> consumes a predetermined amount of fuel to operate the engine <NUM> during a time of blowing. A quantity into which the amount of the consumed fuel is converted by being multiplied by a predetermined factor is hereinafter referred to as an amount of energy used by the blow mechanism <NUM>.

In the present embodiment, the propulsion mechanism <NUM> includes the main engine <NUM> to cause the propeller <NUM> to rotate. The propeller <NUM> is not limited in configuration and may be a fixed-pitch propeller or a variable-pitch propeller, for example. In this example, the propeller <NUM> is a variable-pitch propeller <NUM> that changes a blade angle W of a propeller blade <NUM> in response to a blade angle command from the propulsion controller <NUM>. The variable-pitch propeller <NUM> includes a blade angle setter <NUM> to change the blade angle W in response to control from the propulsion controller <NUM>. The blade angle setter <NUM> detects an actual blade angle at present (hereinafter referred to as an "actual blade angle W2", executes feedback control using the actual blade angle W2, and implements the blade angle W in accordance with the blade angle command (hereinafter referred to as a "target blade angle W1".

With the variable-pitch propeller <NUM>, the propulsive force by the propulsion mechanism <NUM> can be altered by changing the blade angle W while running the main engine <NUM> at a constant rotation rate. An amount of fuel consumed by the main engine <NUM> can be cut down if the main engine is run at a rotation rate that provides relatively low fuel consumption.

In the propulsion controller <NUM> of this example, a relationship established between a rotation rate command for the main engine <NUM> (hereinafter referred to as a "target rotation rate N1") and the blade angle command for the propeller blade <NUM> so as to correspond to the handle position P of the operation handle <NUM> on the remote controller <NUM> is set as a combinator curve in advance. In one example, the combinator curve defines the relationship between the target rotation rate N1 and the target blade angle W1 with respect to each handle position P of the operation handle <NUM>, such as target rotation rate N1 = <NUM> rpm and target blade angle W1 = <NUM> deg when the handle position P is STOP; and target rotation rate N1 = <NUM> rpm and target blade angle W1 = <NUM> deg when the handle position P is N/FMAX.

The propulsion controller <NUM> also has control to mitigate influence of a sudden blade angle shift and change the target blade angle W1 at a predetermined rate (hereinafter referred to as a "CPP blade angle change rate") when the handle is suddenly operated.

The propulsion mechanism <NUM> includes a limiter <NUM> to protect the main engine <NUM> by executing limier control. The limiter <NUM> can be equipped with a limiter mechanism based on various principles. In the present embodiment, the limiter <NUM> includes an ALC limiter <NUM> to protect the main engine <NUM> from overload by executing limiter control. The ALC limiter <NUM> automatically lowers an output from the main engine <NUM> when an actual load on the main engine <NUM> at present (hereinafter referred to as an "actual load" exceeds a predetermined target load.

The ALC limiter <NUM> of the present embodiment compares the target load for the main engine <NUM> with the actual load. When the main engine is in a state in which the actual load is higher than the target load (hereinafter referred to as an "overload state", the ALC limiter <NUM> executes control to decrease the blade angle of the propeller blade <NUM> (hereinafter referred to as ALC control (automatic load control)". By decreasing the blade angle through ALC control, the limiter prevents the main engine <NUM> from being overloaded.

An example of the predetermined condition will be described. When the hull resistance is low, an effect of consumed energy reduction caused by the air lubrication effect is relatively low and the energy balance is no good. Hence, it is preferable to use the air lubrication effect when actual hull resistance R2 is high. Accordingly, in the present embodiment, the control device includes the resistance calculator <NUM> to calculate the actual hull resistance R2 of the hull <NUM>. The air bubble controller <NUM> is designed to start blowing the air bubble B outward or increase the amount of the air bubble B blown outward when the actual hull resistance R2 calculated by the resistance calculator <NUM> is higher than a reference value R1.

It is conceivable that the actual hull resistance R2 changes depending on conditions including a ship velocity, weather and oceanic information, a draft, and a rudder angle. The information on weather and oceanic conditions is information about tides, wind, and courses, for example. Thus, in terms of improvement of calculation accuracy, it is preferable to calculate the actual hull resistance with these conditions taken into account. Accordingly, in the present embodiment, the resistance calculator <NUM> calculates the actual hull resistance R2 based on at least one of the ship velocity of the hull <NUM>, the information on weather and oceanic conditions the hull <NUM> is confronting, the draft of the hull <NUM>, and the rudder angle of the hull <NUM>. The ship velocity, the information on weather and oceanic conditions, the draft, and the rudder angle of the hull <NUM> are sometimes collectively referred to as hull environmental information. The information on weather and oceanic conditions may be visually determined by the operator and may be input to the control device <NUM>.

The resistance calculator <NUM> may include a machine learning model <NUM> that gathers input data about the ship velocity, the weather and oceanic information, the draft, and the rudder angle and outputs the actual hull resistance R2. In one example, the machine learning model <NUM> can be implemented by machine learning (supervised learning) by which the ship velocity, the weather and oceanic information, the draft, and the rudder angle measured in testing of the ship at sea or during sailing are gathered as input objects and outputs of the actual hull resistance R2 are learned. The resistance calculator <NUM> may calculate the actual hull resistance R2 by going through a process of referring to a table of the ship velocity, the weather and oceanic information, the draft, and the rudder angle that is compiled in advance. The resistance calculator <NUM> may be designed to calculate the actual hull resistance R2 with information about hull contamination such as the attachment of a barnacle taken into account.

In terms of improvement of accuracy with which the actual hull resistance R2 is calculated, it is preferable to calculate the actual hull resistance with the output from the main engine <NUM> at present (hereinafter sometimes referred to as an "actual output") taken into account. Accordingly, in the present embodiment, the resistance calculator <NUM> calculates the actual hull resistance R2 based further on the output from the main engine <NUM> at present. The output from the main engine <NUM> may be the rotation rate of the main engine <NUM>, output torque of the main engine <NUM>, or shaft horsepower (dynamic power acting on a propulsion shaft <NUM>) calculated from the rotation rate and the output torque. The output from the main engine <NUM> at present can be acquired by acquisition mean based on a known principle.

In terms of improvement of calculation accuracy for the resistance calculator <NUM>, it is preferable to use the reference value R1 compatible with a characteristic of each individual of the hull <NUM>. Accordingly, in the present embodiment, the control device includes a determinator <NUM> to determine the reference value R1 based on information about frictional resistance of the hull to the water that is set in advance concerning the hull <NUM>. In one example, information about this frictional resistance is preset frictional resistance of the hull to the water (hereinafter referred to as "reference hull resistance"). In <FIG>, the determinator <NUM> is disposed in the air bubble controller <NUM>, for example. However, the determinator <NUM> may be disposed in any part other than the air bubble controller. The reference hull resistance may be a reference resistance value that is set concerning a target hull according to design or a reference resistance value that is measured in a test of the ship at sea or during sailing.

The determinator <NUM> may determine the reference value R1 by going through a process of referring to a table of the characteristic of each individual of the hull <NUM> that is compiled in advance. The characteristic of each individual of the hull <NUM> may be a characteristic determined according to design or a characteristic measured concerning each individual of the hull <NUM> in a test of the ship at sea or during sailing.

In terms of improvement of calculation accuracy for the resistance calculator <NUM>, it is preferable to use the reference value R1 compatible with a parameter that is likely to influence the calculation accuracy. Such a parameter is the output from the main engine <NUM>, the amount of fuel consumed by the main engine <NUM>, and the amount of energy used by the blow mechanism <NUM>, for example. Accordingly, in the present embodiment, the determinator <NUM> determines the reference value R1 based further on at least one of the output from the main engine <NUM>, the amount of fuel consumed by the main engine <NUM>, and the amount of energy used by the blow mechanism <NUM>.

In response to a change in the draft of the hull <NUM>, the amount of energy used by the blow mechanism <NUM> changes and the calculation accuracy is likely to decrease. Thus, it is preferable to acquire a change in the draft of the hull <NUM> and use the reference value R1 compatible with the acquired draft change. Accordingly, in the present embodiment, the determinator <NUM> determines the reference value R1 based further on the draft of the hull <NUM> at present. In the present embodiment, determining a value includes determining a value for the first time if no value is determined previously as well as updating a value if the value is determined previously.

When the draft of the hull <NUM> gets deeper, a depth of the water at which the air outlet <NUM> is located increases and water pressure applied to the air outlet from the seawater rises. When the water pressure surrounding the air outlet <NUM> rises, the amount of energy used by the blow mechanism <NUM> to blow an identical quantity of air outward increases. <FIG> is a graph schematically showing an example of a relationship between the amount of air blown out by the blow mechanism <NUM> and the amount of energy used by the blow mechanism <NUM>. As shown in the graph, the relationship between the amount of the blown air and the amount of energy used by the blow mechanism <NUM> changes depending on the draft of the hull <NUM>. If the amount of the blown air is the same, the amount of energy used is large for a deep draft compared to a shallow draft.

Thus, it is preferable to acquire the draft of the hull <NUM> and use the reference value R1 compatible with the acquired draft. Accordingly, in the present embodiment, the determinator <NUM> determines the reference value R1 based further on the relationship between the amount of the blown air and the amount of energy used by the blow mechanism <NUM> according to the draft.

If a component of the blow mechanism <NUM> is worn, the amount of air blown out by the blow mechanism <NUM> decreases, and the amount of energy used by the blow mechanism to blow an identical quantity of air outward increases. <FIG> is a graph schematically showing an example of a relationship between the amount of air blown out by the blow mechanism <NUM> and the amount of energy used by the blow mechanism <NUM>. As shown in the graph, the relationship between the amount of the blown air and the amount of energy used by the blow mechanism <NUM> changes depending on wear sustained by the component of the blow mechanism <NUM>. If the amount of the blown air is the same, the amount of energy used is large for a high degree of wear sustained by the component compared to a low degree of wear.

Thus, it is preferable to acquire a condition of wear sustained by the component of the blow mechanism <NUM> and use the reference value R1 compatible with the acquired wear condition. Accordingly, in the present embodiment, the determinator <NUM> determines the reference value R1 based further on the relationship between the amount of the blown air and the amount of energy used by the blow mechanism <NUM> according to the condition of wear sustained by the component of the blow mechanism <NUM>.

In one example, the condition of wear sustained by the component of the blow mechanism <NUM> may be a ratio of a period of use of a target component to a predetermined life span of the target component. When the period of use is relatively short, the degree of wear is low. A long period of use is regarded as a high degree of wear. In other words, the wear condition may be identified as a parameter depending on a past operating period of the blow mechanism <NUM>. The condition of wear sustained by the component may be identified based on information acquired from the blow mechanism <NUM> in a test of the ship at sea or during sailing.

If a component of the main engine <NUM> is worn, the output from the main engine <NUM> decreases, and the amount of fuel consumed by the main engine to produce an identical level of output increases. <FIG> is a graph schematically showing an example of a relationship between the output from the main engine <NUM> and the amount of fuel consumed by the main engine. As shown in the graph, the relationship between the output from the main engine <NUM> and the amount of fuel consumed by the main engine <NUM> changes depending on wear sustained by the component of the main engine <NUM>. If the output is the same, the amount of fuel consumption is large for a high degree of wear sustained by the component compared to a low degree of wear.

Thus, it is preferable to acquire a condition of wear sustained by the component of the main engine <NUM> and use the reference value R1 compatible with the acquired wear condition. Accordingly, in the present embodiment, the determinator <NUM> determines the reference value R1 based further on the relationship between the amount of fuel consumed by the main engine <NUM> and the output from the main engine <NUM>.

In one example, the condition of wear sustained by the component of the main engine <NUM> may be a ratio of a period of use of a target component to a predetermined life span of the target component. When the period of use is relatively short, the degree of wear is low. A long period of use is regarded as a high degree of wear. The condition of wear sustained by the component may be identified based on information acquired from the main engine <NUM> in a test of the ship at sea or during sailing.

If the hull resistance decreases while the air bubble B is blown outward, the effect of consumed energy reduction diminishes and the energy balance deteriorates. Hence, it is preferable to decrease the air bubble B blown outward in response to a decrease in hull resistance. Accordingly, in the present embodiment, the air bubble controller <NUM> is designed to stop blowing the air bubble B outward or decrease the amount of the air bubble B blown outward when the actual hull resistance R2 calculated by the resistance calculator <NUM> is lower than a second reference value Q1.

<FIG> is a graph schematically showing an example of a relationship between the amount of air blown out by the blow mechanism <NUM> and resistance of the hull.

As shown in the graph, when the actual hull resistance R2 gradually increases and reaches the reference value R1 with the blow mechanism <NUM> being in a state of non-blowing, the blow mechanism <NUM> gets into a state of blowing as indicated by an arrow V. When the actual hull resistance R2 gradually decreases and reaches the second reference value Q1 with the blow mechanism <NUM> being in a state of blowing, the blow mechanism <NUM> gets into a state of non-blowing as indicated by an arrow Y.

As shown in <FIG>, a dead-band is provided between the second reference value Q1 and the reference value R1. If such a dead-band is not provided, the blow mechanism <NUM> repeats start and stop in a short period of time and there is a risk that the amount of energy used by the blow mechanism <NUM> increases and the blow mechanism <NUM> deteriorates at an accelerated rate. Thus, in terms of avoidance of start and stop in a short period of time, the second reference value Q1 is set to a value smaller than the reference value R1 by a predetermined dead-band size. The predetermined dead-band size can be determined by simulation or experiment.

In terms of improvement of calculation accuracy for the resistance calculator <NUM>, actual energy balance is important. Thus, it is preferable to acquire the amount of energy used by the blow mechanism <NUM> at present and use the second reference value Q1 compatible with the acquired present energy usage amount. Accordingly, in the present embodiment, the determinator <NUM> determines the second reference value Q1 based on the amount of energy used by the blow mechanism <NUM> at present. The present amount of energy used by the blow mechanism <NUM> can be acquired based on any of an amount of fuel consumed by the engine <NUM>, electricity generated by the power generator <NUM>, and electricity used to drive the compressor <NUM>. The second reference value Q1 may be determined by an element other than the determinator <NUM>.

As described above, the amount of energy used by the blow mechanism <NUM> increases or decreases depending on the draft of the hull <NUM>. In other words, a trade-off point for the energy balance changes according to the draft. Accordingly, in the present embodiment, the air bubble controller <NUM> is designed to increase or decrease the amount of the air bubble B blown outward depending on the draft of the hull <NUM> at present. For instance, the amount of the air bubble B blown outward may decrease when the draft is deep and may increase when the draft is shallow, or vice versa.

Preferably, the operator can operate the ship according to a status of the blown air bubble B. Accordingly, in the present embodiment, the control device further includes the transmitter <NUM> to send out information about the status of the air bubble blown out by the blow mechanism <NUM>. In <FIG>, to inform the operator of the status of the blown air bubble B, the transmitter <NUM> sends information about the status of the blown air bubble to a display <NUM> outside to show the sent information, for example.

A process S110 executed by the control device <NUM> of the present embodiment configured as described above will be described. <FIG> is a flowchart showing the process S110 executed by the control device <NUM>.

When the process S110 starts, the control device <NUM> acquires at least one of pieces of the hull environmental information made up of the ship velocity, the information on weather and oceanic conditions, the draft, and the rudder angle of the hull <NUM> (step S111).

Following the execution of step S111, the control device <NUM> acquires the output from the main engine <NUM> (step S112).

Following the execution of step S112, the control device <NUM> calculates the actual hull resistance R2 based on the acquired hull environmental information and the output (step S113).

Following the execution of step S113, the control device <NUM> acquires at least one of pieces of pertinent information made up of the output from the main engine <NUM>, the amount of fuel consumed by the main engine <NUM>, and the amount of energy used by the blow mechanism <NUM> (step S114).

Following the execution of step S114, the control device <NUM> determines the reference value R1 based on the pertinent information acquired in step S114 (step S115).

Following the execution of step S115, the control device <NUM> determines whether or not the actual hull resistance R2 is higher than the reference value R1 (step S116).

If the actual hull resistance R2 is less than or equal to the reference value R1 (N in step S116), the control device <NUM> ends the process S110.

If the actual hull resistance R2 is higher than the reference value R1 (Y in step S116), the control device <NUM> starts blowing the air bubble B outward or increase the amount of the air bubble B blown outward (step S117).

Following the execution of step S117, the process S110 ends. The steps described above are merely steps in one example, and various modifications can be made.

The first embodiment has been described above.

Second to fourth embodiments of the present invention will be described below. In drawings and descriptions shown in the second to the fourth embodiments, identical reference marks are assigned to components and members identical or equivalent to those in the first embodiment. Descriptions shared with the first embodiment are omitted as appropriate, and components different from those in the first embodiment will be primarily described.

With reference to <FIG>, a control device <NUM> according to the second embodiment of the present invention will now be described. <FIG> is a schematic block diagram showing the control device <NUM> according to the present embodiment. As shown in the diagram, the present embodiment differs from the first embodiment in that the control device <NUM> of the present embodiment includes a first calculator <NUM>, a second calculator <NUM>, a reduction ratio calculator <NUM>, and a fuel consumption calculator <NUM>. Thus, these points of difference will be primarily described.

It is important to improve accuracy with which the energy balance is determined. For improved determination accuracy, it is preferable to determine the energy balance using an energy reduction amount D for the main engine <NUM> and an energy usage amount U for the blow mechanism <NUM>.

Hence, in the present embodiment, the control device further includes the first calculator <NUM> to calculate the energy reduction amount D, an amount of energy consumption reduced when the air bubble B is blown out by the blow mechanism <NUM>, and the second calculator <NUM> to calculate the energy usage amount U, an amount of energy consumed to operate the blow mechanism <NUM>, based on the ship velocity of the hull <NUM> at present.

The air bubble controller <NUM> is designed to start blowing the air bubble B outward or increase the amount of the air bubble B blown outward when the energy reduction amount D calculated by the first calculator <NUM> is larger than the energy usage amount U calculated by the second calculator <NUM>.

In terms of reduction of calculation errors, it is preferable to estimate a fuel consumption reduction ratio W that is a reduction rate represented by a ratio between amounts of the fuel consumed by the main engine <NUM> at a time of blowing and at a time of non-blowing and calculate the energy reduction amount D using the fuel consumption reduction ratio W and a current fuel consumption amount G.

The fuel consumption reduction ratio W varies with the ship velocity and the draft of the hull <NUM>. Hence, in the present embodiment, the first calculator <NUM> includes the reduction ratio calculator <NUM> to calculate the fuel consumption reduction ratio W according to the ship velocity and the draft of the hull <NUM> and the fuel consumption calculator <NUM> to calculate the current fuel consumption amount G of the main engine <NUM> according to a current rotation rate of the main engine <NUM> (hereinafter referred to as a "rotation rate N2") and a fuel supply status F for the main engine <NUM>. In one example, the first calculator <NUM> can calculate the fuel consumption reduction ratio W by going through a process of referring to a table of the ship velocity and the draft of the hull <NUM> that is compiled in advance.

The fuel supply status F may be a command value indicating a supply of the fuel to the main engine <NUM>. In one example, the fuel supply status F for the main engine <NUM> can be acquired from the speed regulator <NUM>. In this example, the speed regulator <NUM> includes a rack and pinion (not shown) and is designed to supply the main engine <NUM> with an amount of the fuel depending on a position of the rack. Thus, the fuel supply status F can be identified based on the rack position.

The air bubble controller <NUM> is designed to calculate the energy reduction amount D according to the fuel consumption reduction ratio W calculated by the reduction ratio calculator <NUM> and the current fuel consumption amount G calculated by the fuel consumption calculator <NUM>. For instance, the air bubble controller is able to calculate the energy reduction amount D by obtaining a result of multiplication of the fuel consumption reduction ratio W and the current fuel consumption amount G and multiplying the obtained result by a predetermined factor. The energy reduction amount D may be calculated by going through a process of referring to a table of the fuel consumption reduction ratio W and the current fuel consumption amount G that is compiled in advance.

In terms of reduction of calculation errors, it is preferable to calculate the energy usage amount U based on the amount of the fuel, generated electricity, or electricity used to drive the compressor. Accordingly, in the present embodiment, the second calculator <NUM> calculates the energy usage amount U based on any one of the amount of the fuel supplied to the engine <NUM>, electricity generated by the power generator <NUM>, and electricity used to drive the compressor <NUM>. In one example, the second calculator <NUM> is able to calculate the energy usage amount U by multiplying any one of the amount of the fuel supplied to the engine <NUM>, electricity generated by the power generator <NUM>, and electricity used to drive the compressor <NUM> by a predetermined factor.

A process S120 executed by the control device <NUM> of the present embodiment configured as described above will be described. <FIG> is a flowchart showing the process S120 executed by the control device <NUM>.

When the process S120 starts, the control device <NUM> acquires the ship velocity and the draft of the hull <NUM> to calculate the fuel consumption reduction ratio W according to the ship velocity and the draft (step S121).

Following the execution of step S121, the control device <NUM> acquires the rotation rate N2 of the main engine <NUM> and the fuel supply status F for the main engine <NUM> to calculate the current fuel consumption amount G of the main engine <NUM> according to the rotation rate N2 and the fuel supply status F (step S122).

Following the execution of step S122, the control device <NUM> calculates the energy reduction amount D based on the calculated fuel consumption reduction ratio W and the current fuel consumption amount G (step S123). In one example, the control device <NUM> can calculate the energy reduction amount D by multiplying the current fuel consumption amount G by the fuel consumption reduction ratio W to find an amount of reduced fuel consumption and multiplying the reduced fuel consumption amount by a predetermined factor.

Following the execution of step S123, the control device <NUM> calculates the energy usage amount U (step S124).

Following the execution of step S124, the control device <NUM> determines whether or not the energy reduction amount D is larger than the energy usage amount U (step S125). If the energy reduction amount D is less than or equal to the energy usage amount U (N in step S125), the control device <NUM> ends the process S120.

If the energy reduction amount D is larger than the energy usage amount U (Y in step S125), the control device <NUM> starts blowing the air bubble B outward or increase the amount of the air bubble B blown outward (step S126).

Following the execution of step S126, the process S120 ends. The steps described above are merely steps in one example, and various modifications can be made.

The second embodiment has been described above.

A third embodiment of the present invention is a control method for the control device <NUM>. The control method for the control device <NUM> that controls the blow mechanism <NUM> designed to blow the air bubble B out through the air outlet <NUM> formed in the hull <NUM> includes the step of starting blowing an air bubble outward or increasing an amount of the air bubble blown outward when a predetermined condition is satisfied.

The present embodiment produces action and an effect similar to those in the first embodiment.

A fourth embodiment of the present invention is a control program <NUM> (a computer program) for the control device <NUM>. The control program <NUM> for the control device <NUM> that controls the blow mechanism <NUM> designed to blow the air bubble B out through the air outlet <NUM> formed in the hull <NUM> causes a computer to execute the step of starting blowing an air bubble outward or increasing an amount of the air bubble blown outward when a predetermined condition is satisfied.

Such a function of the control program <NUM> may be installed, as an application program incorporating a plurality of modules corresponding to functional blocks of the control device <NUM>, in storage (e.g., the storage unit <NUM>) in the control device <NUM>. The control program <NUM> may be read into main memory for a computer processor (e.g., a CPU) built in the control device <NUM> and be executed.

Example embodiments of the present invention have been described in detail above. Any of the embodiments described above are merely specific examples shown for implementing the present invention. The details of the embodiments should not be construed to limit the scope of the technique of the present invention. Various design changes such as structural modifications, additions and deletions may occur insofar as they are within the scope of the present invention as defined by the appended claims. In the embodiments described above, contents to which such design changes can be applied are described with expressions such as "of the embodiment" and "in the embodiment". This, however, should not be construed to preclude design changes to be applied to other contents without such expressions.

Modification examples will now be described. In drawings and descriptions shown in modification examples, identical reference marks are assigned to components and members identical or equivalent to those in the embodiments. Descriptions shared with the embodiments are omitted as appropriate, and components different from those in the embodiments will be primarily described.

In the description of the embodiments, the propulsion mechanism <NUM> has the prime motor <NUM> that causes the propeller <NUM> to rotate and generate propulsive force. However, the propulsion mechanism is not limited to this example. The propulsion mechanism may be any as long as the mechanism can propel the hull. The propulsion mechanism may be, for example, a mechanism designed to discharge a gas or a similar thing and thereby generate propulsive force by reaction.

In the description of the embodiments, the prime motor <NUM> is a diesel engine. However, the prime motor is not limited to this example. The prime motor may be, for example, an internal combustion engine, an external combustion engine, or an electric motor other than a diesel engine.

In terms of improvement of calculation accuracy, the resistance calculator <NUM> may calculate the actual hull resistance based on a combination of two, three, or four out of the ship velocity of the hull <NUM>, information on weather and oceanic conditions the hull <NUM> is confronting, the draft of the hull <NUM>, and the rudder angle of the hull <NUM>.

In terms of appropriate determination of a reference value, the determinator <NUM> may determine the reference value based on a combination of two or three out of the output from the main engine <NUM>, the amount of fuel consumed by the main engine <NUM>, and the amount of energy used by the blow mechanism <NUM>.

The modification examples described above produce action and effects similar to those in the embodiments.

Claim 1:
A control device (<NUM>) comprising
an air bubble controller (<NUM>) configured to control a blow mechanism (<NUM>) configured to blow an air bubble (B) out through an air outlet (<NUM>) formed in a hull (<NUM>), wherein
the hull (<NUM>) includes a main engine (<NUM>) configured to cause a propeller (<NUM>) to rotate; characterized by
a resistance calculator (<NUM>) configured to calculate a hull resistance of the hull (<NUM>), wherein
the resistance calculator (<NUM>) is configured to calculate the hull resistance based on at least one of a ship velocity of the hull (<NUM>), information on weather and oceanic conditions the hull (<NUM>) is confronting, a draft of the hull (<NUM>), and a rudder angle of the hull (<NUM>), and based further on an output from the main engine (<NUM>) at present, and
the air bubble controller (<NUM>) is configured to start blowing the air bubble (B) outward or to increase an amount of the air bubble (B) blown outward when the hull resistance calculated by the resistance calculator (<NUM>) is higher than a reference value (R1).