Patent Description:
Conventionally, a technique for automatically controlling the ship speed is disclosed as in Japanese Patent Application Publication No. <CIT>. Other examples are shown in <CIT> or <CIT>.

However, in the conventional configuration, there has been disclosed a control method for eliminating the difference between an actual ship speed and a ship speed target value based on the value of the engine speed associated with the ship speed target value. This control method only solved the difference between the actual ship speed and the ship speed target value, and did not take into account ride quality and safety of the passengers.

Therefore, a purpose of this disclosure is to improve the ride quality and safety performance of a passenger when performing the automatic ship speed control of a ship.

A ship speed control apparatus comprises a ship speed deviation calculation module configured to calculate a ship speed deviation based on a difference between an actual ship speed and a ship speed target value; and an input gain adjustment module configured to adjust an input gain into a throttle control function to a first gain value when the ship speed deviation is equal to or larger than a first threshold value; and to adjust the input gain to a second gain value larger than the first gain value and smaller than the initial value of the input gain when the ship speed deviation is smaller than the first threshold value and equal to or larger than the second threshold value.

A ship speed control method comprising calculating a ship speed deviation based on a difference between an actual ship speed (V) and a ship speed target value (Vt); adjusting an input gain into a throttle control function to a first gain value when the ship speed deviation is equal to or larger than a first threshold value; and adjusting the input gain to a second gain value larger than the first gain value and smaller than the initial value of the input gain when the ship speed deviation is smaller than the first threshold value and equal to or larger than the second threshold value.

A non-transitory computer-readable storage medium storing processor-executable instructions that, when executed, cause one or more processors to calculate a ship speed deviation based on a difference between an actual ship speed (V) and a ship speed target value (Vt); to adjust an input gain into a throttle control function to a first gain value when the ship speed deviation is equal to or larger than a first threshold value; and to adjust the input gain to a second gain value larger than the first gain value and smaller than the initial value of the input gain when the ship speed deviation is smaller than the first threshold value and equal to or larger than the second threshold value.

In this configuration, according to the actual ship speed, the control may be performed using the first gain value and the second gain value. Thus, the control may be performed in consideration of the ride quality and safety of the passenger.

The ship speed control apparatus may further comprise a speed stability determination module configured to determine that the actual ship speed becomes stable with respect to the ship speed target value; and to trigger the input gain adjustment module to adjust the input gain, when the ship speed deviation is equal to or less than a third threshold value; and the input gain adjustment module is configured to adjust the input gain to the first gain value under a condition, when the input gain adjustment module is being triggered by the speed stability determination module.

In this configuration, it is possible to perform control according to the actual ship speed without performing unnecessary control by determining whether or not the ship speed has been set.

In the ship speed control apparatus, the first gain value and the second gain value may be values obtained by dividing a preset initial value of the input gain.

In this configuration, the first gain value and the second gain value which are easy to stabilize the ship speed may be easily set.

The throttle control function of the ship speed control apparatus may be a control function under a proportional integral (PI) control.

In this configuration, it is possible to perform the PI control that efficiently approaches the ship speed target value.

The input gain adjustment module of the ship speed control apparatus may be further configured to adjust the first gain value or the second gain value only for the proportional gain under the PI control.

In this configuration, it is possible to follow the ship speed target value more gently.

The input gain adjustment module of the ship speed control apparatus may prohibit the subsequent adjustment of the input gain when the input gain adjustment module adjusts the input gain for a predetermined number of times.

In this configuration, the excessive adjustment of the input gain value is suppressed, and the ship speed control may be efficiently performed.

When the input gain becomes the first gain value as a result of adjusting the input gain, the input gain adjustment module of the ship speed control apparatus may prohibit the subsequent adjustment of the input gain.

In this configuration, ship speed control may be performed without unnecessary adjustment of the input gain.

The input gain adjustment module of the ship speed control apparatus may set an input gain to an initial value when a set ship speed is newly set by an input of a user.

In this configuration, the control to approach the ship speed target value may be performed more appropriately in response to the user's input.

The ship speed target value calculation module of the ship speed control apparatus may calculate the ship speed target value based on the set ship speed so that the actual ship speed approaches the set ship speed.

In this configuration, the ship speed target value may be calculated in accordance with the actual ship speed, and the ship speed may be controlled more efficiently.

The actual ship speed used in the ship speed control apparatus of the present invention, may be the speed over ground.

In this configuration, it is possible to surely approach the ship speed target value required by the passenger.

The ship speed control apparatus includes a ship speed target value calculation module, the ship speed deviation calculation module, an input gain adjustment module, a speed stability determination module, a proportional integral (PI) control module, and a rotation speed calculation module. The ship speed target value calculation module calculates a ship speed target value from a set ship speed. The ship speed deviation calculation module calculates a ship speed deviation based on a difference between the actual ship speed and the ship speed target value. The input gain adjustment module adjusts an input gain to a throttle control function when the ship speed deviation is larger than a threshold. The speed stability determination module determines that the ship speed has become stabled by comparing the ship speed with the threshold from the ship speed deviation. The PI control module calculates a directive ship speed to be given to the throttle by using the input gain. The rotation speed calculation module calculates an engine speed from the directive ship speed.

In this configuration, the directive ship speed given to the throttle is calculated using the input gain calculated using the actual ship speed, and the engine speed may be calculated from the directive ship speed, so that the control, according to the actual ship speed, may be performed. Thus, the control may be performed in consideration of the ride quality and safety of the passenger.

In the first embodiment, a ship speed control apparatus, a ship speed control method, and a ship speed control program, according to an embodiment of the present invention, will be described with reference to the drawings. <FIG> is a functional block diagram showing the configuration of the ship speed control apparatus <NUM> according to the first embodiment. <FIG> is a functional block diagram showing a configuration for controlling ship speed of the ship speed control apparatus <NUM>, according to the first embodiment. <FIG> is a flowchart showing the processing of the ship speed control apparatus <NUM>, according to the first embodiment. <FIG> is a flowchart showing a speed stability determination process in the ship speed control apparatus <NUM>, according to the first embodiment. <FIG> is a flowchart showing an input gain adjustment process in the ship speed control apparatus <NUM>, according to the first embodiment. <FIG> is a graph showing changes in the ship speed and proportional gain Kp in the ship speed control apparatus <NUM>, according to the first embodiment.

First, the effect of disturbance on the constant speed operation in an automatic ship speed control is shown. Ships may be affected by external disturbances (for example, following wave, opposite wave, tail wind, head wind) when performing the automatic ship speed control. Under this influence, the ship speed becomes unstable. In other words, the ride quality and comfortability of a person on board a ship may become unstable, and the safety of the person on board may not be secured.

The effect of the disturbance described above, may be eliminated by steering while the passenger makes fine manual adjustment. However, since such fine adjustment is largely due to the experience and knowledge of the passenger, it is difficult to make the fine adjustment at the time of the automatic ship speed control. For example, when the ship speed is brought close to the ship speed target value in the automatic ship speed control as shown in <CIT>, then the passenger's ride quality and comfortability may not be obtained only by quickly bringing the ship speed closer or setting the engine speed corresponding to the ship speed target value.

The ship speed control apparatus <NUM> of the present invention is used in order to secure the ride quality, comfort, and safety of a passenger while solving the above-mentioned problems. The ship speed control apparatus <NUM> uses the proportional gain Kp as an input gain and performs control according to the actual ship speed V. A detailed configuration of the ship speed control apparatus <NUM> is shown below.

As shown in <FIG>, the ship speed control apparatus <NUM> includes an Autopilot (AP) device <NUM> and an operation module <NUM>. The AP device <NUM> and the operation module <NUM> are mounted on a ship for performing autopilot control (i.e. automatic navigation control). Further, the ship speed control apparatus <NUM> is connected to a propulsion generation module <NUM> and a rudder <NUM>. The propulsion generation module <NUM> and the rudder <NUM> are provided in, for example, an outboard motor, an inboard motor, an outboard motor, and various propellers.

The AP device <NUM> includes an autopilot (AP) control module <NUM>, an autopilot (AP) operation module <NUM>, a sensor module <NUM>, and a display module <NUM>.

The AP control module <NUM>, the AP operation module <NUM>, the sensor module <NUM>, and the display module <NUM> are connected to each other by a data communication network <NUM> for ships. The AP control module <NUM>, the operation module <NUM>, and the propulsion generation module <NUM> are connected via, for example, a propulsion communication network (CAN, etc.). The AP control module <NUM> and the rudder <NUM> are connected via an analog voltage or data communication.

The AP control module <NUM> includes, for example, an arithmetic processing module such as a Central Processing Unit (CPU) and a storage module. The storage module stores a program to be executed by the AP control module <NUM>. The storage module is used when the CPU performs operations. The AP control module <NUM> includes a main control module <NUM> and a ship speed control module <NUM>.

The main control module <NUM> generally performs main control of the autopilot control (i.e. automatic navigation control) of the ship speed and a steering angle executed by the AP control module <NUM>. For example, the main control module <NUM> receives the setting of the autopilot control by the AP operation module <NUM>. The main control module <NUM> analyzes the set contents and controls the processing timing or the like of the ship speed control module <NUM> so as to realize the set autopilot control. The main control module <NUM> monitors the operation state received from the operation module <NUM>. The main control module <NUM> may also control the autopilot in consideration of the monitoring result.

The main control module <NUM> gives a set ship speed Vp from the AP operation module <NUM> to the ship speed control module <NUM>. Here, the set ship speed Vp is the ship speed (i.e. speed) to be finally followed in the autopilot control. The ship speed control module <NUM> may directly acquire the set ship speed Vp.

The ship speed control module <NUM> calculates a ship speed target value Vt from the set ship speed Vp. The ship speed target value Vt is a ship speed set to bring the actual ship speed V closer to the set ship speed Vp during the automatic ship speed control. The ship speed control module <NUM> performs a proportional integral (PI) control using the difference between the ship speed target value Vt and the actual ship speed V as an input to calculate a control ship speed for bringing the actual ship speed V closer to the ship speed target value Vt, and thereafter calculates a throttle operation value from the control ship speed.

The ship speed control module <NUM> sets a throttle command value using the following conditions, the actual ship speed V, the set ship speed Vp, the ship speed target value Vt, and the throttle operation value. The ship speed control module <NUM> outputs the throttle command value to the propulsion generation module <NUM>. The propulsion generation module <NUM> controls propulsive force according to the throttle command value. The ship speed control module <NUM> corresponds to the ship speed controller of the present invention.

The AP operation module <NUM> is realized by, for example, a touch panel, a physical button or a switch. The AP operation module <NUM> accepts an operation of setting related to the autopilot control. The AP operation module <NUM> outputs the setting contents to the AP control module <NUM>.

The sensor module <NUM> measures the speed (actual ship speed V) of the ship provided with the ship speed control apparatus <NUM> and ship azimuth (bow azimuth and stem azimuth). For example, the sensor module <NUM> is realized by a positioning sensor using a positioning signal of a Global navigation satellite system GNSS (For example, GPS), an inertial sensor (an acceleration sensor, an angular velocity sensor, etc.), a magnetic sensor, or the like.

The display module <NUM> is realized by, for example, a liquid crystal panel. The display module <NUM> displays information related to the navigation of the normal autopilot inputted from the AP control module <NUM>. Although the display module <NUM> may be omitted, it is preferable to have the display module <NUM>, and the user may easily grasp the control state and the navigation state of the autopilot.

The operation module <NUM> includes an operation lever and an operation state detection module. The operation lever accepts an operation from a user during manual navigation. The operation state detection module is realized by a sensor or the like. The operation state detection module detects an operation state of the operation lever. The operation state detection module outputs the detected operation state (angle) of the operation lever to the propulsion generation module <NUM>. During manual navigation, the propulsion generation module <NUM> generates a propulsive force of a size corresponding to the operation state. As described above, the operation state is monitored by the AP control module <NUM>. For example, at the time of switching from the manual operation to the autopilot control, the AP control module <NUM> executes the initial control of the autopilot control with reference to this operation state.

With reference to <FIG> and <FIG>, an outline of the processing of the ship speed control module <NUM> in the ship speed control apparatus <NUM> will be described. The ship speed control module <NUM> of the ship speed control apparatus <NUM> includes a ship speed target value calculation module <NUM>, a ship speed deviation calculation module <NUM>, a speed stability determination module <NUM>, an input gain adjustment module <NUM>, a proportional integral (PI) control module <NUM>, and a rotation speed (RPM) calculation module <NUM>.

The ship speed target value calculation module <NUM> receives an input of a set ship speed Vp. The ship speed target value calculation module <NUM> calculates a ship speed target value Vt (Target Vessel Speed Vt) from the set ship speed Vp (S101). The ship speed target value calculation module <NUM> outputs the ship speed target value Vt, to the ship speed deviation calculation module <NUM>. The ship speed target value calculation module <NUM> may be omitted. In this case, the set ship speed Vp is inputted to the ship speed deviation calculation module <NUM> as the ship speed target value Vt, as it is.

The ship speed deviation calculation module <NUM> acquires the ship speed target value Vt from the ship speed target value calculation module <NUM> and an actual ship speed V from a sensor module <NUM> of a ship <NUM>. The ship speed deviation calculation module <NUM> calculates a difference (Hereinafter, the ship speed deviation Δv) between the actual ship speed V and the ship speed target value Vt (S102). The ship speed deviation calculation module <NUM> outputs the ship speed deviation Δv to the speed stability determination module <NUM>.

The speed stability determination module <NUM> compares the ship speed deviation Δv with a threshold DB to determine whether or not the ship speed of the ship <NUM> has reached a predetermined speed (hereinafter referred to as constant speed) (S103). The threshold DB corresponds to a "third threshold" of the present invention.

When the ship speed deviation Δv is equal to or less than the threshold DB, the speed stability determination module <NUM> determines that the ship speed of the ship <NUM> has reached the constant speed, in other words, that it is within the range of the ship speed (V0, V1, V2, V3, V4) which may be determined as the constant speed of the ship speed target value Vt. On the other hand, when the ship speed deviation Δv is larger than the threshold DB, the speed stability determination module <NUM> determines that the ship speed of the ship <NUM> has not reached the constant speed. The speed stability determination module <NUM> outputs these results to the input gain adjustment module <NUM>.

The input gain adjustment module <NUM> determines an input gain (proportional gain Kp) from the comparison result of the ship speed deviation Δv and the threshold DB (S104). The input gain adjustment module <NUM> outputs the proportional gain Kp to the PI control module <NUM>. The proportional gain Kp is a predetermined value larger than <NUM>.

The PI control module <NUM> performs PI control using the input proportional gain Kp (S105). Accordingly, the PI control module <NUM> inputs the proportional gain Kp to the throttle control function to calculate the directive ship speed (S106). The PI control module <NUM> outputs the directive ship speed to the rotation speed calculation module <NUM>.

The rotation speed calculation module <NUM> calculates a set RPM (set engine speed) from the directive ship speed (S107). The rotation speed calculation module <NUM> gives the set RPM to the propulsion generation module <NUM>. The propulsion generation module <NUM> generates propulsive force according to the setting RPM. The ship <NUM> navigates by receiving this propulsion force, and its speed (actual ship speed V) is measured by the sensor module <NUM>. The actual ship speed V measured by the sensor module <NUM>, is fed back to the ship speed deviation calculation module <NUM>.

At this time, by executing the following control, the ship speed control apparatus <NUM> may navigate the ship <NUM> in consideration of the ride quality and comfortability of the passengers.

A more specific control method of the ship speed control apparatus <NUM> will be described with reference to <FIG> and <FIG>. First, with reference to the flowchart of <FIG>, a speed stability determination process in the ship speed control apparatus <NUM>, according to the first embodiment, will be described. <FIG> shows the details of the processing of the speed stability determination step S103 in the flowchart shown in <FIG>.

The speed stability determination module <NUM> determines whether or not there is a change in the set ship speed Vp (S111). If the set ship speed Vp is changed by the user's input (S111: Yes), then the speed stability determination module <NUM> sets the speed stability determination flag to FALSE (S112). When the ship speed of the ship <NUM> reaches a constant speed with respect to the ship speed target value Vt, the speed stability determination flag becomes TRUE. On the other hand, if the ship speed of the ship <NUM> does not reach the constant speed with respect to the ship speed target value Vt, the speed stability determination flag becomes FALSE.

If there is no change in the set ship speed Vp (S111: No), then the speed stability determination module <NUM> performs the processing of step S113 without changing the state of the speed stability determination flag.

The threshold DB is a predetermined value that may be determined by the passenger under conditions such as the specifications of the ship <NUM>, the load weight, and the disturbance resistance (weather, wind speed, and wind direction).

Further, the speed stability determination module <NUM> checks the status of the speed stability determination flag. When the speed stability determination flag is FALSE (S113: FALSE), then the speed stability determination module <NUM> sets initial values to the proportional gain Kp and an integral gain Ki (S114).

As described above, the proportional gain Kp may be a predetermined value larger than <NUM>. In the present embodiment, the proportional gain Kp is assumed to be <NUM> and the integral gain Ki is assumed to be <NUM>.

After setting the proportional gain Kp and the integral gain Ki, the speed stability determination module <NUM> performs ship speed control, calculates a ship speed deviation Δv in a predetermined cycle, and performs speed stability determination. Specifically, the speed stability determination module <NUM> compares the ship speed deviation Δv with the threshold DB (S115). When the ship speed deviation Δv is equal to or smaller than the threshold DB (S115: Yes), the speed stability determination flag is set to TRUE (S116). Thereafter, the speed stability determination module <NUM> sets the input gain adjustment prohibition flag to OFF (S117).

An input gain adjustment inhibition flag is a flag configured to determine whether the proportional gain Kp may be adjusted. Although the details will be described later, the input gain adjustment inhibition flag is set to ON when, for example, the proportional gain Kp is adjusted (twice). In other words, the adjustment of the proportional gain Kp is prohibited. In this case, an input gain adjustment flag specifies that the proportional gain Kp may be adjusted up to two times.

If the ship speed deviation Δv is larger than the threshold DB (S115: No), then the process returns to step S111.

When the speed stability determination flag is TRUE (S113: TRUE), then the speed stability determination module <NUM> performs an input gain adjustment processing (S118). The input gain adjustment process in step S118 will be described in detail with reference to <FIG>.

Next, with reference to the flowchart of <FIG>, the input gain adjustment process in the ship speed control apparatus <NUM>, according to the first embodiment, will be described. <FIG> shows details of the processing in step S104 of the input gain adjustment process in the flowchart shown in <FIG> and step S118 in <FIG>.

Firstly, an outline of the processing of the input gain adjustment module <NUM> will be described. In the present invention, the input gain adjustment module <NUM> adjusts a proportional gain Kp inputted to the PI control module <NUM>, and sets an integral gain Ki to a constant value. However, the integral gain Ki may be similarly adjusted. In other words, it is possible to adjust the integral gain Ki together with the proportional gain Kp if it is possible to improve the ride quality and safety performance of the passenger during the constant speed operation.

The input gain adjustment module <NUM> confirms an input gain adjustment prohibition flag (S121). When the input gain adjustment prohibition flag is OFF (S121: OFF), then the ship speed deviation Δv is compared with <NUM> times of the threshold DB. Three times the threshold DB corresponds to a "first threshold" of the present invention.

When the ship speed deviation Δv is <NUM> times or more of the threshold DB (Yes in S122), the input gain adjustment module <NUM> sets the proportional gain Kp to <NUM>/<NUM> of the initial value (S123). In the above case, it is set to <NUM>/<NUM> of the proportional gain Kp (<NUM>). That is, the proportional gain Kp is <NUM>. A value of <NUM>/<NUM> of the proportional gain Kp (<NUM> in this case) corresponds to a "first gain value" of the present invention.

After setting the proportional gain Kp (<NUM>) to <NUM>/<NUM>, the input gain adjustment module <NUM> sets the input gain adjustment prohibition flag to ON (S124). The input gain adjustment module <NUM> sets the input gain adjustment inhibition flag to ON even when the proportional gain Kp is changed to a predetermined number of times (<NUM> times in this embodiment).

When the ship speed deviation Δv is smaller than <NUM> times the threshold DB (S122: No), the input gain adjustment module <NUM> compares the ship speed deviation Δv with <NUM> times the threshold DB S125. The double of the threshold DB corresponds to a "second threshold" of the present invention.

When the ship speed deviation Δv is <NUM> times or more of the threshold DB and less than <NUM> times of the threshold DB (Yes in S125), the input gain adjustment module <NUM> sets the proportional gain Kp to <NUM>/<NUM> of the initial value S126. In the above case, it is set to <NUM>/<NUM> of the proportional gain Kp (<NUM>). That is, the proportional gain Kp is <NUM>. A value of <NUM>/<NUM> of the proportional gain Kp (<NUM> in this case) corresponds to a "second gain value" of the present invention.

When the input gain adjustment prohibition is ON (S121: ON), the input gain adjustment module <NUM> ends the loop of the processing shown in <FIG>. Similarly, if the ship speed deviation Δv is smaller than <NUM> times the threshold DB (S125: No), then the input gain adjustment module <NUM> ends the loop of processing shown in <FIG>.

By setting the proportional gain Kp in this way, the ship <NUM> may approach the ship speed target value Vt without performing rapid acceleration and rapid deceleration with respect to the ship speed target value Vt. That is, the ship <NUM> may navigate in consideration of the ride quality and the comfortability of the passengers.

<FIG> is a graph showing changes in the ship speed and proportional gain Kp and changes in the ship speed in the ship speed control apparatus <NUM>, according to the first embodiment. The example shown in <FIG> will be described with reference to an example of adjusting the proportional gain Kp when the SOG (ship speed) is changed from the ship speed V0 to the ship speed V4. The SOG is the "Speed Over Ground".

Changing from Vessel Speed V0 to Vessel Speed V1 - The ship (vessel) <NUM> is proceeding at a vessel speed V0 (<NUM> kn). The passenger sets the set ship speed Vp to the ship speed V1 (<NUM> kn). Thus, the ship speed target value calculation module <NUM> calculates the ship speed target value Vt from the set ship speed Vp. The ship speed target value calculation module <NUM> calculates a ship speed deviation Δv from an actual ship speed V of a ship <NUM> and a ship speed target value Vt.

A speed stability determination module <NUM> compares the ship speed deviation Δv with a threshold DB. When it is confirmed that the ship speed deviation Δv becomes equal to or less than the threshold DB (it is confirmed that the ship speed deviation Δv is stabled), the speed stability determination flag is set to TRUE, and the input gain adjustment prohibition flag S121 is set to OFF.

Thereafter, when the ship speed deviation Δv becomes <NUM> times or more and <NUM> times or less of the threshold DB, the input gain adjustment module <NUM> sets the proportional gain Kp to <NUM>/<NUM> of the initial value, that is, the proportional gain Kp = <NUM> (Around <NUM> sec in <FIG>).

The ship <NUM> is proceeding at a ship speed V1 (<NUM> kn). The passenger sets the set ship speed Vp to the ship speed V2 (<NUM> kn). An input gain adjustment module <NUM> resets the proportional gain Kp to an initial value, that is, the proportional gain Kp = <NUM>. The ship speed target value calculation module <NUM> calculates a ship speed target value Vt from a set ship speed Vp. The ship speed target value calculation module <NUM> calculates a ship speed deviation Δv from an actual ship speed V of a ship <NUM> and a ship speed target value Vt.

A speed stability determination module <NUM> compares the ship speed deviation Δv with a threshold DB. When it is confirmed that the ship speed deviation Δv becomes equal to or less than the threshold DB (it is confirmed that the ship speed deviation Δv is stabled), the speed stability determination flag is set to TRUE, and the input gain adjustment prohibition flag is set to OFF.

When the ship speed deviation Δv is smaller than <NUM> times of the threshold DB, the input gain adjustment module <NUM> does not change the proportional gain Kp from the initial value.

Changing from Vessel Speed V2 to Vessel Speed V3 - The ship <NUM> is proceeding at a ship speed V2 (<NUM> kn). The passenger sets the set ship speed Vp to the ship speed V3 (<NUM> kn). The input gain adjustment module <NUM> resets the proportional gain Kp to an initial value, that is, the proportional gain Kp = <NUM>. The ship speed target value calculation module <NUM> calculates a ship speed target value Vt from a set ship speed Vp. The ship speed target value calculation module <NUM> calculates a ship speed deviation Δv from an actual ship speed V of a ship <NUM> and a ship speed target value Vt.

A speed stability determination module <NUM> compares the ship speed deviation Δv with a threshold DB. When it is confirmed that the ship speed deviation Δv becomes equal to or less than the threshold DB (it is confirmed that the ship speed deviation Δv is stabled), then the speed stability determination flag is set to TRUE, and the input gain adjustment prohibition flag is set to OFF.

Thereafter, when the ship speed deviation Δv becomes <NUM> times or more of the threshold DB, the input gain adjustment module <NUM> sets the proportional gain Kp to <NUM>/<NUM> of the initial value, that is, the proportional gain Kp = <NUM> (Around <NUM> sec in <FIG>).

Changing from Vessel Speed V3 to Vessel Speed V4 - The ship (vessel) <NUM> is proceeding at a vessel speed V3 (<NUM> kn). The passenger sets the set ship speed Vp to the ship speed V4 (<NUM> kn). The input gain adjustment module <NUM> resets the proportional gain Kp to an initial value, that is, the proportional gain Kp = <NUM>. The ship speed target value calculation module <NUM> calculates a ship speed target value Vt from a set ship speed Vp. The ship speed target value calculation module <NUM> calculates a ship speed deviation Δv from an actual ship speed V of the ship <NUM> and a ship speed target value Vt.

A speed stability determination module <NUM> compares the ship speed deviation Δv with a threshold DB. After determining that the ship speed V4 becomes the constant speed, the input gain adjustment module <NUM> determines that the ship speed deviation Δv is equal to or less than the threshold DB, and does not change the proportional gain Kp from the initial value.

As described above, by setting the proportional gain Kp, the ship (vessel) <NUM> may approach the target vessel speed Vt without performing rapid acceleration and rapid deceleration with respect to the target vessel speed Vt. That is, the ship <NUM> may navigate in consideration of the ride quality and the comfortability of the passengers.

In the above example, the proportional gain Kp is changed up to twice. However, when the speed of the ship may be changed in consideration of the ride quality and the comfortability of the passenger in accordance with the change of the proportional gain Kp, the number of times of change of the proportional gain Kp is not limited to two.

Claim 1:
A ship speed control apparatus (<NUM>) comprising:
a ship speed deviation calculation module (<NUM>) configured to calculate a ship speed deviation based on a difference between an actual ship speed (V) and a ship speed target value (Vt); and
an input gain adjustment module (<NUM>) configured:
to adjust an input gain into a throttle control function to a first gain value when the ship speed deviation is equal to or larger than a first threshold value; and
to adjust the input gain to a second gain value larger than the first gain value and smaller than the initial value of the input gain when the ship speed deviation is smaller than the first threshold value and equal to or larger than the second threshold value.