SHIP STATE ESTIMATION DEVICE, SHIP STATE ESTIMATION SYSTEM, SHIP STATE ESTIMATION METHOD, AND SHIP STATE ESTIMATION PROGRAM

A ship state including a rudder angle is estimated with high accuracy. A ship state estimator device is equipped with processing circuitry. The processing circuitry acquires an direction signal indicating an direction of a ship. The processing circuitry inputs the direction signal into a ship state estimator that outputs a ship state including a rudder angle, and estimates the ship state including the rudder angle.

TECHNICAL FIELD

BACKGROUND

The present disclosure relates to a technology for estimating a ship state including a rudder angle used for ship control.

The rudder angle sensor is expensive, difficult to install, and it may be financially and technically burdensome.

The purpose of the present disclosure is to estimate the ship state including the rudder angle with high accuracy in a configuration where the rudder angle sensor is not required.

SUMMARY

The ship state estimation device of the present disclosure is equipped with processing circuitry. The processing circuitry acquires an direction signal indicating an direction of the ship. The processing circuitry inputs the direction signal to a ship state estimator that outputs a ship state including at least a rudder angle of the ship when the direction signal of the ship is input, and estimates the ship state including the rudder angle of the ship. In this configuration, the rudder angle can be estimated with high accuracy without using a rudder angle sensor.

In the ship state estimation device of this disclosure, a turning signal for the ship is input to the ship state estimator. The processing circuitry uses the direction signal and the turning signal to estimate the ship state. In this configuration, the rudder angle can be estimated with high accuracy without using a rudder angle sensor.

In the ship state estimation device of this disclosure, the processing circuitry uses a equation of state to estimate a current ship state based on the ship state estimated previously. In this configuration, the ship state including the rudder angle can be estimated with high accuracy.

In the ship state estimation device of this disclosure, the processing circuitry estimates the ship state based on the equation of state and an observation equation which uses the direction signal. In this configuration, the ship state including the rudder angle can be estimated more accurately.

In the ship state estimation device of this disclosure, the processing circuitry further estimates at least one of a heading of the ship and a turnrate as the ship state. In this configuration, ship states other than the rudder angle can be estimated.

In the ship state estimation device of this disclosure, an initial value of the ship state estimation is based on the ship state when the ship is stopped or going straight. In this configuration, the initial value of the state estimator can be set with high accuracy.

In the ship state estimation device of this disclosure, the processing circuitry estimates the ship state based on a stochastic system as the ship state estimator. In this configuration, the ship state including the rudder angle can be estimated more accurately.

The ship state estimation device of this disclosure the processing circuitry acquires a command rudder angle relative to the ship and generates the turning signal based on the acquired command rudder angle and the rudder angle estimated by the ship state estimator. In this configuration, an accurate turning signal can be generated.

The ship state estimation device of the present disclosure the processing circuitry further acquires parameters relating to the characteristics of the ship and sets the state estimation model corresponding to the cruising state of the ship to the ship state estimator based on the parameters. In this configuration, the rudder angle can be estimated with high accuracy considering the cruising states.

The ship state estimation device of this disclosure the processing circuitry detects the direction of the ship and generates the direction signal. In this configuration, the ship state estimation device that estimates the ship state with high accuracy can be realized.

DETAILED DESCRIPTION

A ship state estimation device, a ship state estimation system, a ship state estimation method, and a ship state estimation program according to a first embodiment of the present disclosure will be described with reference to the figures.

FIG.1is a functional block diagram showing a configuration of a controller according to the first embodiment of the present disclosure.FIG.2is a functional block diagram showing a configuration of a ship control system according to the first embodiment of the present disclosure.

First, the configuration of the ship control system10is described usingFIG.2. As shown inFIG.2, the ship control system10includes the controller20(or “processing circuitry”), an operating module30, an observing value acquiring module40, and a display module50. The ship control system10is installed on the ship of a ship performing, for example, autopilot control (automatic cruising control). The controller20corresponds to the “ship state estimation device” of the present disclosure. The controller20of the ship control system10is connected to a rudder90. The rudder90is mounted on the ship. The controller20and the rudder90are connected, for example, via analog voltage or data communication.

Although not shown, propulsion generating devices such as screw propellers are also mounted on the ship. The controller20also controls the generation of propulsion to the propulsion generating devices, but a detailed explanation is omitted here.

The controller20, the operating module30, the observing value acquiring module40, and the display module50are connected to each other by, for example, a data communication network100for ships. The controller20generates a turning signal (or “steering signal”) and outputs it to the rudder90. The rudder90acquires the turning signal and controls the rudder in response to the turning signal. The specific generation method of the turning signal will be described later.

The operating module30is realized by, for example, a touch panel, physical buttons or switches. The operating module30accepts the operation of settings related to the autopilot control.

The observing value acquiring module40is a direction sensor, for example, and measures the heading ψ(psi). The observing value acquiring module40measures the heading ψ, and generates an direction signal of the measured heading ψ, at a predetermined sampling period. The observing value acquiring module40outputs the direction signal to the controller20. However, the observing value acquiring module40is not limited to a direction sensor, as long as it generates a signal corresponding to the direction. For example, the observing value acquiring module40may generate a signal of the course over the ground (COG) measured by the measured data of GPS mounted on the ship.

The display module50is realized by, for example, a liquid crystal panel. When, for example, information related to the autopilot control is input from the controller20, the display module50displays them. Although it is possible to omit the display module50, it is preferable to have it, and the presence of the display module50allows the user to easily grasp the autopilot control status, etc.

The controller20includes, for example, an arithmetic processing device such as a CPU and a storage module such as a semiconductor memory. The storage module stores a program to be executed by the controller20. In addition, the storage module is utilized when the CPU performs calculations.

As shown inFIG.1, functionally, the controller20includes an observation value receiver21, a ship state estimator22, a turning signal generator23, and a command rudder angle acquiring module230. The observation value receiver21acquires the direction signal from the observing value acquiring module40. The observation value receiver21outputs the direction signal to the ship state estimator22. The ship state estimator22uses the direction signal to estimate the ship state including the rudder angle δ, although detailed processing will be described later. The ship state estimator22outputs the estimated rudder angle δ to the turning signal generator23.

FIG.3is a conceptual diagram for generating the turning signal based on the estimated rudder angle and a command rudder angle. In the command rudder angle acquiring module230, the command rudder angle based on a declination angle, which is the difference between the heading and the set heading, is acquired. The turning signal generator23generates a turning signal using the acquired command rudder angle and the rudder angle δ estimated by the ship state estimator22.

For example, the turning signal generator23calculates a difference value between the acquired command rudder angle and the estimated rudder angle δ, and generates the turning signal based on the difference value. The turning signal generator23outputs the turning signal to the rudder90. For example, the turning signal generator23generates a turning signal of “PORT (+1)” when the difference value between the acquired command rudder angle and the estimated rudder angle is a positive value. The turning signal generator23generates a turning signal of “STBD (−1)” when the difference value between the acquired command rudder angle and the estimated rudder angle is a negative value. In this way, the controller20estimates the rudder angle using the direction signal indicating heading ψ. Therefore, the controller20can generate the turning signal without using a rudder angle sensor.

The ship state estimator22is equipped with a state estimator. The state estimator is set using a state estimation model based on the following concepts:

The turnrate (or “rate of turn”) r (t) and the rudder angle δ (t) can be represented by the following relationship, for example, by Nomoto's first-order delay model (estimation model).

The relationship between the turnrate r [k] and the heading ψ [k] is set appropriately by the relationship between the angular velocity and the direction. In addition, the relationship between the rudder angle ψ [k] and the turning signal r [k] is set appropriately by the relationship between the rudder angle, the turning signal, and the turnrate.

The state estimator is, for example, a Kalman filter. Based on Eq. (1), the equation of state of the Kalman filter is set as follows using heading ψ [k], turnrate r [k], and rudder angle δ [k].

The observation equation of the Kalman filter is set as follows.

The symbol s [k] is the turning signal and is set by 0, +1 and −1. The turning amount As [k] is set based on, for example, the turning signal and a turning amount coefficient based on the turnrate w and step time τ.

The symbol v [k] in Eq. (2) is system noise and is set accordingly. The symbol w [k] in Eq. (3) is observation noise and is set accordingly.

The symbol H is a transformation matrix, A is a coefficient vector for the turning signal s [k], and B is a coefficient vector for the system noise v [k]. Note that this example of setting is only an example, for example, the transformation matrix H can be set differently by using different models and discretization methods.

The ship state estimator22can estimate the heading ψ [k], the turnrate r [k] and the rudder angle δ [k] with high accuracy by sequentially computing the Kalman filter set in this way. That is, the ship state estimator22can estimate the ship state including the rudder angle δ [k] with high accuracy.

It is preferable that the estimator keeps (stores) each estimated ship state as data inside the ship state estimator22. Thus, the ship state estimator22can use the data of each ship state held to estimate the next ship state including the rudder angle δ [k], which can be estimated with higher accuracy. The data retention is not limited to the above configuration, and the ship state estimator22may be configured to be able to communicate with an external server or cloud system. Also, it may be retained in the external server or cloud by communication.

In this case, the ship state estimator22can estimate the ship state including the rudder angle δ (k) with higher accuracy by appropriately setting the system noise v(k) based on, for example, the specifications of the ship and the rudder wheel. By appropriately setting the observation noise w(k) based on, for example, the measurement accuracy of the observation value acquisition module40, the ship state estimator22can estimate the ship state including the rudder angle δ (k) with higher accuracy.

In addition, the ship state estimator22acquires the initial value of the equation of state when the ship is stationary or moving straight and utilizes the initial value. For example, while going straight, the initial value is set such that the direction signal is the value acquired by a sensor, etc. The turnrate is set to zero, the rudder angle is set to zero, and the turning signal is set to “STOP”. This enables to make the estimation process more stable. The ship state estimator22can estimate the ship state including the rudder angle δ [k] with higher accuracy.

The above processing is realized, for example, by processing of the flowchart shown inFIG.4.FIG.4is a flowchart showing the flow of schematic processing of the ship state estimation method and ship state estimation program according to the first embodiment of the present disclosure.

The observation value receiver21receives a ship state observation value including the direction signal (S11). The ship state estimator22inputs the direction signal and the turning signal to the ship state estimator22. The ship state estimator22estimates the ship state including the rudder angle δ of the ship (S12). The turning signal generator23uses the estimated rudder angle δ to generate the turning signal and outputs it to the rudder90(S13).

FIG.5is a graph of simulation results showing the relationship between the estimated and true values of the rudder angle and turnrate. InFIG.5, the horizontal axis is the elapsed time, and the vertical axis is the rudder angle and turnrate. The true value inFIG.5is the value held by the simulator.

As shown inFIG.5, the rudder angle estimated by the ship state estimator22is equivalent to the true value, and the rudder angle is estimated with high accuracy. Similarly, the turnrate estimated by the ship state estimator22is equivalent to the true value, and the turnrate is estimated with high accuracy.

Then, the controller20of the ship control system10can bring the heading of the ship closer to the set heading and hold the needle by incorporating measurement of the heading ψ, estimation of the rudder angle δ, turnrate r, and generation of the turning signal into a feedback controller (For example, a PD controller). At this time, by estimating the rudder angle δ with high accuracy, the ship control system10can realize highly accurate holding of the needle.

FIG.6is a graph of simulation results showing the relationship between the estimated and true values of direction. InFIG.6, the horizontal axis is elapsed time, and the vertical axis is heading ψ. The true value inFIG.6is heading under control performed using the estimated rudder angle.FIG.6shows the case where the set heading w is controlled to be held at 15 degrees.

As shown inFIG.6, the estimated heading w is equivalent to the true value, and the heading ψ is held with high accuracy. In the ship control system10, the direction signal indicating the heading ψ is applied, but the direction signal may indicate a direction than the direction ψ. In this case, the transformation matrix H or the like may be set according to the direction set as the direction signal.

In the ship control system10, the Kalman filter, which is a linear stochastic system, is utilized as the state estimator. The state estimator may be a state estimator that estimates the ship state based on a stochastic system. For example, the state estimator may be an extended Kalman filter, which is a nonlinear stochastic system, an Unscented Kalman filter, a particle filter, etc.

The ship state estimation device, ship state estimation system, ship state estimation method, and ship state estimation program according to the second embodiment of the present disclosure may be described with reference to the figures.

FIG.7is a functional block diagram showing the configuration of the control module according to the second embodiment of the present disclosure.FIG.8is a flow chart showing the process flow of the ship state estimation method and the ship state estimation program according to the second embodiment of the present disclosure.

As shown inFIGS.7and8, the controller20A of the ship state estimation system according to the second embodiment differs from the controller20of the ship control system10according to the first embodiment in that it is equipped with an estimation model setting module220and sets an estimation model. The other configuration and treatment of the controller20A is the same as that of the controller20, and a description of the similar modules is omitted.

In the estimation model setting module220, the ship characteristic estimation parameter value, which is the value of the parameter relating to the characteristics of the ship, is input from the observation value receiver21. The ship characteristic parameter values include, for example, at least one of pitch angle, ground speed, and shift position. Using the ship characteristic parameter values, the estimation model setting module220sets a state estimation model to be used for the state estimator (FIG.8: S20). For example, specifically, the estimation model setting module220utilizes the pitch angle to determine the presence or absence of hydro planning (gliding state) and sets the state estimation model. The estimation model setting module220uses the ground speed to set the state estimation model. The estimation model setting module220uses the shift position, that is, detects if the shift position is forward, neutral, or backward to set the state estimation model. Thus, the state estimator is set reflecting the cruising state of the ship. Therefore, the estimation accuracy of the rudder angle is improved.

In the ship control system described in each of the above embodiment, the state estimator may be replaced with a learned model using artificial intelligence such as machine learning or deep learning. For example, in the state estimation model that outputs an estimation result of the rudder angle by inputting a direction signal, the state estimation model that can obtain the most probable estimation result may be learned as a learned learning model and the estimation may be performed by this learned model.

Unless otherwise explicitly stated, articles such as “a” or “an” should generally be interpreted to include one or more described items. Accordingly, phrases such as “a device configured to” are intended to include one or more recited devices. Such one or more recited devices can also be collectively configured to carry out the stated recitations. For example, “a processor configured to carry out recitations A, B and C” can include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C. The same holds true for the use of definite articles used to introduce embodiment recitations. In addition, even if a specific number of an introduced embodiment recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations).

It will be understood by those within the art that, in general, terms used herein, are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

As used herein, the terms “attached,” “connected,” “mated” and other such relational terms should be construed, unless otherwise noted, to include removable, moveable, fixed, adjustable, and/or releasable connections or attachments. The connections/attachments can include direct connections and/or connections having intermediate structure between the two components discussed.

Numbers preceded by a term such as “approximately,” “about,” and “substantially” as used herein include the recited numbers, and also represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms “approximately,” “about,” and “substantially” may refer to an amount that is within less than10% of the stated amount. Features of embodiments disclosed herein preceded by a term such as “approximately,” “about,” and “substantially” as used herein represent the feature with some variability that still performs a desired function or achieves a desired result for that feature.