Automatic steering device for ship

Abstract

To provide a technology capable of realizing constant-radius turning using a smaller steering angle.SOLUTION: An automatic steering device for a ship comprises a trajectory planning part to output the reference heading and the reference position of a hull based on a scheduled route, a feedback control part to output a feedback steering angle to make the hull's heading and position follow the reference heading and the reference position, and a feedforward control part to output a feedforward steering angle to make the hull's heading follow the reference heading during the turning operation. The trajectory planning part replaces a tidal current component with a pre-set upper limit value of the tidal current component if the tidal current component is equal to or greater than the upper limit value of the tidal current component in the calculation based on the deflection amount of the reach amount corresponding to the distance between a turning start position and a steering start position, and on the tidal current component.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a technique for automatically steering a ship. [Background technology]

[0002] The Track Control System (TCS) has the functions of holding and turning, and steers the ship to follow the planned route. The planned route consists of a straight route and an arced route. When a ship controlled by the Track Control System transitions from a straight route to an arced route, a course change operation is initiated from the straight route.

[0003] Such an operation can be realized by a curved-tracking system that performs open-loop control using a trajectory tracking method. In such a curved-tracking system, the arc course is composed of waypoints that indicate the start and end points of the turn, as well as the turning radius and angle.

[0004] Generally, as described in Non-Patent Documents 1-3, many route turning systems use closed-loop control. However, it is difficult to maintain a constant turning radius by closed-loop control. The main purpose of closed-loop control is to solve the regulator problem by closed-loop stability and disturbance rejection. Therefore, closed-loop control is insufficient to solve the servo problem by tracking response such as turning motion.

[0005] Since there is a trade-off between the regulator problem and the servo problem, it is difficult to solve both the regulator problem and the servo problem by feedback control alone. A route turning system that performs closed-loop control cannot adequately follow disturbance changes such as heading changes and tidal current components during turning, resulting in heading errors and route errors.

[0006] As a technology for performing open-loop control using a trajectory tracking method, an automatic ship steering device that can reduce arc distortion of a trajectory route is known (see Patent Document 1). This automatic ship steering device uses a two-freedom control system and generates a reference signal based on a trajectory plan, and achieves constant radius turning by applying a route turning system to the route keeping system. Here, the route turning system is based on a heading turning system.

[0007] However, according to the technology described in Patent Document 1, the feedforward rudder angle during turning becomes too large for practical use. A large rudder angle imparts excessive motion to the hull and places unnecessary strain on the steering gear. In hull control, it is desirable to keep the rudder angle to a minimum. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2014-15174 A [Non-patent literature]

[0009] [Non-Patent Document 1] Wlodzimierz Chocianowicz and Jerzy Pejas. Adaptive control system for steering the ship along the desired trajectory-based on the optimal control and filtering theory. IFAC Proceedings Volumes, 25(3):319-335, 1992. [Non-Patent Document 2] KY Pettersen and Henk Nijmeijer.Tracking control of an underactuated surface vessel.In Proceedings of the 37th IEEE Conference on Decision and Control (Cat.No.98CH36171), volume 4, pages 4561-4566.IEEE,1998. [Non-Patent Document 3] Yong Liu,Renxiang Bu,and Xiaori Gao.Ship trajectory tracking control system design based on sliding mode control algorithm.Polish Maritime Research,25(3):26-34,01 Sep.2018. [Non-Patent Document 4] TIFossen and T.Perez.Marine systems simulator, basic libraries and system examples for guidance, navigation and control,2008. Summary of the Invention [Problem to be solved by the invention]

[0010] The problem to be solved by the present invention is to provide a technique for realizing a constant radius turn with a smaller steering angle. [Means for solving the problem]

[0011] One embodiment is an automatic steering device for a ship that includes a trajectory planning unit that outputs a reference heading and reference position of the hull based on a planned route, a feedback control unit that outputs a feedback rudder angle to make the heading and position of the hull follow the reference heading and reference position, and a feedforward control unit that outputs a feedforward rudder angle to make the heading of the hull follow the reference heading during a turning operation, wherein the trajectory planning unit is characterized in that in a calculation based on the amount of course change of the reach amount, which is the distance between the turning start position and the steering start position, and a tidal component, if the tidal component is equal to or greater than a predetermined upper limit value of the tidal component, the trajectory planning unit replaces the tidal component with the upper limit value of the tidal component. [Brief description of the drawings]

[0012] [Figure 1] 3 is a diagram illustrating an outline of the operation of the marine automatic steering device according to the present embodiment. FIG. [Diagram 2] 1 is a block diagram showing a configuration of a marine automatic steering device according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a diagram showing ship motion and tidal current components. [Figure 4] 11 is a diagram showing a time series signal of a reference azimuth ψR and a time series signal of a reference steering angle δR. FIG. [Diagram 5] FIG. 2 is a diagram showing a reference orbit based on a skew angle. [Figure 6] FIG. 13 is a diagram showing an example of a time series of ugR up. [Figure 7] FIG. 13 illustrates a reach estimate of a reference trajectory. [Figure 8] FIG. 13 shows a reference trajectory with reach correction. [Figure 9] 1 is a table showing hull parameters and control gains of a target ship. [Figure 10] FIG. 13 is a diagram showing the heading error, course error, and commanded rudder angle in the case of the first-order model. [Figure 11] FIG. 13 is a diagram showing tidal flow estimation and sway speed bias estimation in the case of a first-order model. [Figure 12] FIG. 13 is a diagram showing heading error, course error, and commanded rudder angle for the nonlinear model. [Figure 13] FIG. 13 is a diagram showing tidal flow estimation and sway speed bias estimation in the case of a nonlinear model. [Figure 14] FIG. 4 is a diagram showing the amount of hull movement relative to the amount of course change. [Figure 15] FIG. 13 is a diagram showing a reach amount relative to a reference movement amount. [Figure 16] This figure shows the amount of course change and the amount of reach due to tidal current components when the ship speed is 10 kn. [Figure 17] This figure shows the amount of course change and the amount of reach due to tidal current components when the ship speed is 15 kn. [Figure 18] This is a diagram showing turning performance when the ship speed is 10 kn and the course deviation is 10 degrees. [Figure 19] This is a diagram showing the reach amount and commanded rudder angle when the course change amount changes at a ship speed of 15 kn. [Figure 20] This is a diagram showing the course error when the course deviation amount changes at a ship speed of 15 kn. [Figure 21] This figure shows the reach amount, commanded rudder angle, and course error when the ship speed is 10 kn and the course deviation is 15 deg. [Figure 22] This figure shows the reach amount, commanded rudder angle, and course error when the ship speed is 20 kn and the course deviation is 15 deg. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] (1 Overview) An overview of the marine vessel automatic steering device according to this embodiment will be described below. Fig. 1 is a diagram showing the outline of the operation of the marine vessel automatic steering device according to this embodiment.

[0015] The marine automatic steering device according to this embodiment applies a heading turning system to a course turning system, and performs the following by open-loop control:

[0016]

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[0017] Here, ρ is the turning radius, u is the ship speed (forward speed), r is the turning angular velocity, δ c is the commanded rudder angle, δ h max is the maximum steering angle in the azimuth turning system.

[0018] The marine automatic steering device according to this embodiment performs the following three processes in order to satisfy the above formula and suppress the occurrence of route errors.

[0019] The first is a process to correct the turning angular velocity to satisfy formula (1.1) in response to changes in ship speed over the ground. The second is a process to correct the drift angle to satisfy formula (1.2) in order to offset the lateral drift speed due to the tidal current components. The third is a process to move the course change start position forward from the arc control start point by the reach amount in order to remove course errors due to the lateral drift speed of the ship's motion.

[0020] These processes relate to the disturbance tidal components and cross flow speed. Tidal components cause the ship's position to move, and include components caused by not only tides but also wind force, etc. Tidal components cause the ship's position to deviate from the planned route, resulting in route error. On a straight route, the reference heading is constant, so the tidal components acting on the ship's hull are constant. On the other hand, on curved routes, including arced routes, the tidal components acting on the ship's hull change because they depend on the reference heading.

[0021] The marine vessel automatic steering device 1 (see FIG. 2) according to this embodiment makes the ship wake follow a circular arc on a planned route, as shown in FIG. 1. The planned route is specified by waypoints as the start and end points on an ECDIS (Electronic Chart Display and Information System), and is made up of a straight route and a circular arc. The circular arc route is determined by a center C, a radius ρ, and a turning angle ψ. set It is defined by:

[0022] The marine vessel automatic steering device 1 according to this embodiment starts a course change operation when the vertical foot position (point H) that passes through the ship position (point P) and is perpendicular to the planned course reaches the WOP (Wheel Over Point). Here, the WOP is a position on a straight course that is a reach amount before the start position of the circular course. In this embodiment, the length of the vertical foot, i.e., the distance from point P to point H, is calculated as the course error y e Let us assume that.

[0023] (2. Configuration of automatic steering device for ships) The configuration of the marine automatic steering device according to this embodiment will be described below. Fig. 2 is a block diagram showing the configuration of the marine automatic steering device according to this embodiment.

[0024] As shown in Fig. 2, the marine vessel automatic steering device 1 according to this embodiment is a device that controls a rudder to track the vessel position along a planned route, and includes a trajectory planning unit 12, a trajectory course error calculation unit 14, a feedback control unit 16, an adder 17, a feedforward control unit 18, and an identifier (not shown) that identifies each parameter. The vessel 24 is the object to be controlled by the marine vessel automatic steering device 1, and includes a rudder and a propulsion device such as a screw. The sensors 26 include a number of sensors provided on the vessel, including a speed log that measures vessel speed U, a gyrocompass that measures vessel speed direction ψ, and a GNSS (Global Navigation Satellite System) sensor that measures vessel position (x, y).

[0025] The trajectory planning unit 12 calculates a reference heading ψ based on the planned route output from the guidance system 2 such as ECDIS, the ship speed U output from the sensors 26, and the like. R A reference signal including a time series signal of x R ,y R The orbit / course error calculation unit 14 outputs a reference orbit, which is a time series signal of the reference direction ψ R , reference position x R ,y R The heading error ψ is the difference between the heading ψ and the ship position (x, y) output from the sensors 26. e, position error x e ,y e Output.

[0026] The feedback control unit 16 is composed of an estimator and a feedback gain device. It calculates the tidal current components estimated based on the heading error and position error output from the orbit / course error calculation unit 14 as an estimated tidal current. The feedback gain device multiplies the heading error and position error by a feedback gain to calculate the feedback rudder angle δ FB The trajectory planning unit 12 calculates the tidal current components in a reference coordinate system obtained by coordinate-transforming the estimated tidal current calculated by the feedback control unit 16, the oblique drift angle for countering the tidal current, and the reach amount, which is the distance between the turning start position and the steering start position.

[0027] The feedforward control unit 18 calculates a feedforward steering angle δ based on the reference heading and the yaw angle output by the trajectory planning unit 12. FF The adder 17 outputs the feedforward steering angle δ FF and feedback steering angle δ FB Adding these together gives the commanded rudder angle δ c The steering gear outputs a rudder angle based on the input command rudder angle to cause the hull to move.

[0028] According to the marine automatic steering device 1, a course keeping system and a course turning system are configured. The course keeping system configures a closed loop control system with the feedback control unit 16, and calculates the course error y e The feedback steering angle δ FB The route turning system configures an open loop control system with the trajectory planning unit 12 and the feedforward control unit 18, and controls the route error y e The feedforward steering angle δ is set to suppress the occurrence of FF Control.

[0029] (3. Route Turning System) The route turning system according to this embodiment will be described.

[0030] (3.1 Control Object) The controlled object of the course turning system will be described below. Fig. 3 is a diagram showing the ship motion and tidal current components.

[0031] As shown in Fig. 3, the controlled objects of the course turning system are ship motion and tidal current components. Regarding ship motion, u is the forward speed (surge speed), which is almost constant, ψ is the bow direction, r is the turning angular velocity (yaw angular velocity), v is the lateral flow velocity (sway velocity), and δ is the rudder angle. In addition, the subscript n represents the ground speed component, and u n ,v n are the ship's speeds in the northward and eastward directions, respectively.

[0032] The surge velocity and sway velocity have the following relationship:

[0033]

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[0034] The tidal component is the ground speed, and also includes components that move the ship due to wind force, etc.

[0035]

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[0036] The power flow components are estimated by an estimator (not shown in FIG. 2).

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[0038] (3.2 Reference trajectory) The reference orbit based on the reference signal will be explained. R Time series signal of and reference steering angle δ R 5 is a diagram showing a time series signal of the reference orbit based on the skew angle.

[0039] (3.2.1 Reference signal) The reference signal of the heading turning system applied to the route turning system is the reference heading ψ R and the reference direction ψ R The reference steering angle δ calculated based on R Here, the subscript R represents a reference signal. The reference signal is generated to satisfy the conditions for turning in a azimuth.

[0040] The course change conditions include the course change amount, the turning angular velocity, the rudder angle, the rudder speed, and the initial heading. R and δ R are time functions,

[0041]

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[0043] The reference signal is divided into three modes, and is output in the order of acceleration mode, constant speed mode, and deceleration mode. For details of the acceleration mode, constant speed mode, and deceleration mode, see Patent Document 1.

[0044] The reference signal has two characteristics. The first is that if the course change conditions other than the course change amount are the same, the ψ Ra remains unchanged, and ψ in the constant velocity mode Rv increases (constant speed time T v The second characteristic is that the reference rudder angle becomes smaller as the ship speed increases. The second characteristic is that the reference rudder angle becomes smaller as the ship speed increases. r / K r ,1 / K r This is because both become smaller.

[0045] (3.2.2 Reference orbit) The reference trajectory will now be described. Note that, in this description, it is assumed that the reference signal does not include an acceleration mode or a deceleration mode, but includes only a constant velocity mode.

[0046] The reference speed of the ship is u, v, and the reference direction is ψ R Based on

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[0052] The characteristics of the reference trajectory are explained. In Fig. 5, β = 0 (XOY coordinates) is a circular arc (center C, radius ρ) of the planned route, and β > 0 (X β OY β The reference orbit with a skew angle has the following three characteristics:

[0053] The first characteristic is that the reference trajectory rotates -β outside the planned route due to the cross current velocity. The second characteristic is that the turning center C β The coordinates of are (ρsinβ, ρcosβ). The third property is that C β If β is a small angle, the amount of movement is expressed by the following equation.

[0054]

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[0055] The above characteristics were analyzed under ideal conditions and are called the ideal characteristics of the reference trajectory. In this ideal characteristic, the reference heading is only in the constant speed mode, and the ideal reach is the ratio of the cross drift speed to the turning angular velocity, which is a constant value regardless of the amount of course change.

[0056] (3.2.3 Relationship between reference direction and reach amount) The relationship between the reference direction and the reach amount will be described.

[0057] The reference orientation according to this embodiment consists of acceleration mode, constant speed mode, and deceleration mode. In the acceleration mode and deceleration mode, the orientation change is small, so the time in the acceleration mode extends the reach amount, and the time in the deceleration mode does not affect the reach amount (see FIG. 4). Therefore, the reach amount can be calculated from the start of the acceleration mode as follows:

[0058]

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[0060] u(t)=u0,cos(ψ R (t))≒1-0.5(ψ R (t) 2 ≒1,ψ R (T a )≪1. Here, u0 is a constant value. Reach amount d r has the following three properties:

[0061] The first characteristic is d r is the amount of variation d ψRa and a fixed quantity x β It is the sum of d ψRa is proportional to the ship speed and acceleration time, and x β is the ratio Kv / Kr. Therefore, d rd ψRa The second characteristic is proportional to the course change conditions other than the course change amount (d ψRa The third characteristic is that if the ship speed is the same, the reference rudder angle will be the same. This characteristic is due to the fact that the ship parameters do not change.

[0062] (3.3 Route Error Model) The route error model is explained using velocity components on the reference trajectory.

[0063] The ground speed of a ship is the sum of the ship's hull component and the tidal component, as shown in Figure 3.

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[0067] The ground speed of the vessel on the reference heading is given by:

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[0070] By linearly approximating equation (1.23), the route error model is given by

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[0073] From equation (1.25), the error factors in turning can be roughly divided into those due to tidal components and those due to cross current speed. The error factors due to tidal components are u cR acts in the forward direction of the hull, and v cR acts in the lateral direction of the ship. As mentioned above in the explanation of the reference trajectory, the error factor due to the lateral flow velocity moves the reference trajectory outside the planned route. Therefore, in order to realize a turning trajectory with a constant radius, it is necessary to take measures against the error factors due to the tidal current components and the lateral flow velocity. In addition, the term u0ψ e is handled by the course keeping system.

[0074] (4. Route error correction method) This paper provides an overview of a route error correction method for correcting error factors in route turning.

[0075] The course error correction methods include turning velocity correction, drift angle correction, and reach correction. Turn velocity correction is cR is the tangential component of the current, which acts on the forward speed, so the turning angular velocity is corrected. cR is the normal component of the tidal current, which acts on the lateral velocity, and is offset by the drift angle. The reach correction is the correction of the lateral velocity by the reach amount d r The idea is to find the amount of reach and move the starting point of the turn forward by the amount of reach.

[0076] (4.1 Turning angular velocity correction) The turning angular velocity correction will be explained. gR up FIG. 13 is a diagram showing an example of a time series of

[0077] In order to achieve a constant radius turning trajectory, the turning angular velocity is

[0078]

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[0079] u gR is calculated from the surge speed of the ship and the current component u from equation (1.25). cR The surge speed tends to decrease because the steering force increases from the course control to the resistance. cR Since, from equation (1.26), it is a function of the reference heading, it changes during the turn. Therefore, the reference angular velocity is u gR The reference heading is calculated by the trajectory plan together with the reference rudder angle based on the remaining turning angle, the reference angular velocity and the set value of the initial heading.

[0080] The correction of the turning angular velocity is as follows: u gR When the following condition is met, the update value u gR up This is done using

[0081]

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[0082] In addition, when the turning angular velocity is corrected, the course change conditions are

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[0084] Therefore, the turning angular velocity correction is ψ set up This is repeated until it reaches zero.

[0085] As shown in Figure 6, the u gR up u gR Since it is updated intermittently according to the change of u gR There is an error with the waveform. The turning angular velocity is u gR up Since the turning radius is calculated from the updated velocity, the speed change after the update may cause a distortion error in the turning radius.

[0086] (4.2 Oblique angle correction) The drift angle correction will be described. In this embodiment, the drift angle correction β c to feedforward steering angle δ R βc The case where δ is applied will be explained. R βc is the reference direction ψ RReference steering angle δ R It can be generated from

[0087] β c From the following equation (1.31), ψ R Since it is a function of δ R It is related to β c Feedforward steering angle δ R βc By using β c The response of the course turning system can be improved. However, the feedforward rudder angle of the course turning system is

[0088]

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[0089] Commanded rudder angle δ c As shown in Figure 2, the following relationship exists:

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[0091] β c The feedforward control of the correction is zero as shown in the following equation.

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[0093] Similarly, feedback control

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[0095] β in the above formula c · The above formula explains the term β c The equivalent is added to the heading. Therefore, the heading error is

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[0098] In addition, β c The same method as for the reference azimuth can be applied to the δ. This improves the tracking response and reduces the transient error. FF t This is not adopted because it would increase the angle. This point will be explained in detail later. The command rudder angle should be the minimum necessary to control the ship's motion.

[0099] The drift angle for tidal correction is essentially the same for the course turning system and the course keeping system, as given by equation (1.34).

[0100] (4.3 Feedforward rudder angle for drift angle correction) Oblique angle correction β c to feedforward steering angle δ R βc The case where δ is applied will be described. R βc is the reference direction ψ R Reference steering angle δ R It can be generated from

[0101] β c From equation (1.31), ψ R Since it is a function of δ R It is related to β c Feedforward steering angle δ R βc By using β c The response of the course turning system can be improved. However, the feedforward rudder angle of the course turning system is

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[0103] (4.3.1 Feedforward steering angle) Oblique angle correction β c Feedforward steering angle δ R βc Using equation (1.8),

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[0107] Substituting equation (1.26) into equation (1.38), we get

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[0110] (4.3.2 Feedforward steering angle δ R βc (approximation of C βc The size of the stable ship (K r >0,T r > 0). The numerator and denominator of equation (1.43) are

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[0112] As a numerical example, in the above equation, r =0.1s ?1 ,T r =30s,δ set =13deg,u=10kn,U c =5kn,ρ=1Nm,u gR =u+Uc Substituting

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[0114] As a result, the sine term on the right hand side of equation (1.42) can be ignored and the cosine term becomes dominant,

[0115]

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[0116] The maximum value of the above formula is ψ cR =ψ c -ψ R From this, ψ cR =0 or ψ c =ψ R This occurs when δ FF The approximate solution from equation (1.37) is as follows:

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[0118] The numerical example above and ψ cR =0,δ R = δ set Using δ FF = 1.5 × 13 = 19.5 deg. δ FF To make it 13 deg, δ set = 13 / 1.5 = 8.6 deg. R βc To use δ, consider the above equation. set must be corrected.

[0119] However, it is not appropriate to change course-changing conditions depending on the magnitude of the tidal components. This does not include the case of correction of turning angular velocity. Even if the course-changing amount is the same, if the rudder angle setting value is different, the course-changing response will change. In that case, if hull parameter identification is performed, the identified values ​​will also fluctuate.

[0120] Therefore, the feedforward rudder angle δ FF t It would be more appropriate to use equation (1.33) rather than equation (1.38).

[0121] (4.4 Reach fix) The reach correction will be described. Fig. 7 is a diagram showing a reach estimate of a reference trajectory. Fig. 8 is a diagram showing a reference trajectory after the reach correction is performed.

[0122] (4.4.1 Importance of Modifications) As shown in Figure 7, reach correction modifies the position of maximum advance, which is the maximum value of the turning advance due to the lateral flow speed. Maximum advance (reach) is the deviation in the forward direction between the reference trajectory (the ship's wake in an actual ship) and the planned route. If there is an error in the reach estimation, it will directly lead to a route error, which is the difference between the planned route and the ship's wake.

[0123] Because the reach is affected by the trajectory plan, ship speed, and tidal components, the ship position is estimated by numerically calculating the ship position using an open-loop control system without using equation (1.16). In this calculation, the ship motion is treated as a mass motion. The maximum lateral distance (kick), which is the lateral deviation, is small, so it is not corrected.

[0124] It is advisable to perform the estimation calculation at least twice. The first time is when the planned route is drawn up as a rough estimate, and the second time is when the final value is obtained just before changing course, using the rough estimate as a reference. The second calculation is performed to allow the reach amount to adapt as much as possible to changes in ship speed and tidal current components. As shown in Figure 1, the course changing operation begins when the foot drop position (point H) of the ship's position (point P) reaches the WOP.

[0125] (4.4.2 Reach Calculation Procedure) The reach amount is calculated by the following procedure.

[0126] Step 1: For the sake of simplicity, the calculation is performed with the straight route planned direction ψ planis aligned with the X-axis. Ship motion is based on ship speed, reference heading and current components. The initial ship speed is the value at the start of the turn, and is given by the following formula.

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[0129] Forward speed u gR =u+u' c and course change conditions (course change amount ψ set , initial turning angular velocity r set =u gR ÷ρ, rudder speed setting value δ' set , steering angle setting value δ set ) and set the reference direction ψ in equation (1.7). R Request.

[0130] Step 2: The reference trajectory is calculated by integrating the sum of the ship speed and the tidal current components.

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[0133] Step 3: Calculate the reach amount from the ship trajectory and the circular arc course in equation (1.50). Reach amount d r In Figure 7, the intercepts of the tangents at the ship position end point P and the turning end point F are x p ,x f from

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[0135] The above equation is ψ set <0. However, the right-handed coordinate system and right-handed screw direction are positive. Note that d k is the amount of kick. The amount of reach varies depending on the course change conditions of the reference heading, the influence of ship speed and tidal current components, and the effect of turning angular velocity correction and drift angle correction.

[0136] (4.4.3 How to reduce reach error) Reach calculations are performed by replacing the ship's motion with the motion of a mass point and integrating its ground speed.

[0137] Effect of course change: Summarize the effect of course change on reach. The amount of reach does not depend on the size of the course change if all other conditions are the same. - Turn angular velocity correction is ground speed u gR is the speed threshold u set At that time, the turning angular velocity is updated, so the curvature of the reference trajectory changes, causing an error in the reach calculation. The smaller the change in course, the fewer the opportunities for correction.

[0138] Effect of ship speed and tidal current components: Summarize the effect of ship speed and tidal current components on reach amount. The amount of reach is proportional to the ship's speed. Even if the course change conditions and turning radius are the same, the amount of reach changes if the ship's speed changes. However, the fluctuation in the amount of reach is proportional to the c Proportional to / U. The amount of reach changes with the tidal current components. According to equation (1.50), the curvature of the reference trajectory is distorted when there is a tidal current component. The amount of reach may have an error depending on the magnitude of the distortion.

[0139] In the calculation of reach estimates, based on the above considerations, there are two methods for reducing reach errors: measures for course deviation and measures for tidal current components, as shown below.

[0140] Measures for course change: Reach course change

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[0143] Countermeasures against tidal currents: Reach tidal currents

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[0147] (4.4.4 Evaluation of Reach Modification) Reach correction is to move the starting position of the reference heading to point O' as shown in Figure 8. In Figure 8, the kick amount is also moved for convenience, but kick correction is not performed. Therefore, by moving forward by the reach amount, the reference trajectory approaches a circular arc, and the occurrence of course error can be reduced.

[0148] Reach correction has the advantage that it can effectively suppress course error by predicting the trajectory of the ship's motion during turning, and does not require rudder angle control. It is also possible to convert the lateral drift speed into a drift angle and correct it by the feedforward rudder angle. However, for the same reason as in the drift angle correction, this method is not adopted in this embodiment.

[0149] In the reach calculation, the turning angular velocity correction and the drift angle correction are used at the same time. The turning radius error is used to comprehensively evaluate the resulting reach correction. The turning radius error is calculated from Figure 8 as follows:

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[0151] (5. Verification) In the above-mentioned embodiment, in order to realize the route turning system by the trajectory tracking method of open loop control, turning angular velocity correction, drift angle correction and reach correction were proposed. The effectiveness of this method will be verified from the simulation results. Figure 9 is a table showing the hull parameters and control gains of the target ship.

[0152] This verification checks the following items: -Effect of route turning response by automatic ship steering system 1 · Validity of the analyzed reach characteristics -Validity of open-loop control using marine automatic steering system 1 -Effectiveness of closed-loop control by marine automatic steering system1

[0153] The simulation conditions are as follows. Specifications: e |≦60m,|δ c |≦15deg Setting value: ψ set dr =10deg,(U c / U) set Set =0.25. - Ship motion models are first-order and nonlinear (Mariner ship, length L = 161m). · Course change conditions: ψ set ={10,15,20,30}deg,δ set =13deg,δ · set =2deg s ?1 ·Turning conditions: U0={10,15,20}kn,ρ=1Nm,u set =1kn,1Nm=1852m ·Trend component: U c / U={0,0.1,0.2,0.25,0.3},ψ c =0~360deg, in 10deg increments, no wave components. The hull parameters and typical control gains of the target ship are shown in Fig. 9. In Fig. 9, U0 is the initial ship speed, f y is the route gain. The hull parameters are the identified nominal values.

[0154] (5.1 Route Turn Response) The results of the route turning response according to this embodiment are shown. Fig. 10 is a diagram showing the heading error, the route error, and the command rudder angle in the case of the first-order model. Fig. 11 is a diagram showing the tidal current estimation and the sway speed bias estimation in the case of the first-order model. Fig. 12 is a diagram showing the heading error, the route error, and the command rudder angle in the case of the nonlinear model. Fig. 13 is a diagram showing the tidal current estimation and the sway speed bias estimation in the case of the nonlinear model. Note that the first-order model coincides with the hull model of the control system, while the nonlinear model is different from the hull model of the control system and includes a rudder angle offset component.

[0155] In the simulation, the turning condition is U0=15kn,ψ set = 15deg, reach d r = 140.6m, kick amount d k =-1.1m. Even if the controlled model is different, the reach will be the same if the parameters are the same. The turning will start at 30 minutes and the error from that point on will be closely monitored.

[0156] As shown in Figures 10 and 11, the heading ψ is the reference heading ψ R , and the heading error ψ e =ψ-ψ R becomes zero, and the route error y e becomes almost zero, and the commanded rudder angle δ c is the feedforward steering angle δ FF Therefore, it can be confirmed that the simulation results satisfy the specifications, and the correction by the marine automatic steering device 1 according to this embodiment is appropriate.

[0157] As shown in Figs. 12 and 13, when the identified nominal value (see Fig. 9) is used, ψ e andy e Both are negligible, and δ c is δ FF Therefore, the simulation results in the case of a nonlinear model are almost equivalent to those in the case of a first-order model. If the nominal value is appropriate, the correction by the marine automatic steering device 1 according to this embodiment satisfies the specifications and has sufficient accuracy for practical use, even for a nonlinear model.

[0158] Therefore, the marine vessel automatic steering device 1 according to this embodiment can effectively suppress course errors during turning.

[0159] (5.2 Reach characteristic evaluation) The validity of the analyzed reach characteristics is evaluated. Fig. 14 is a diagram showing the ship movement amount relative to the course change amount. Fig. 15 is a diagram showing the reach amount relative to the reference movement amount. Fig. 14 is a diagram showing the course change amount ψ set For the reach amount d r , kick amount d k , the amount of movement of the reference direction d ψset ≒d ψRa and ideal reach x β Figure 15 shows the ψset For d r and x β This shows the following.

[0160] The relationship between the reference heading and the reach amount described in "3.2.2 Reference Track" can be confirmed to be appropriate from Figures 14 and 15. From Figure 14, it can be seen that the course change conditions other than the course change amount (d ψRa If the ship speed and the course change amount are the same, the reach amount will be the same even if the course change amount increases. r is the amount of variation d ψR and a fixed quantity x β It becomes the sum of d r d ψR is proportional to.

[0161] (5.3 Open-loop control results) The results of open loop control will now be described. Fig. 16 is a diagram showing the amount of course change and the amount of reach due to tidal current components when the ship speed is 10 kn. Fig. 17 is a diagram showing the amount of course change and the amount of reach due to tidal current components when the ship speed is 15 kn. Fig. 18 is a diagram showing turning performance when the ship speed is 10 kn and the amount of course change is 10 degrees. In Figs. 16 and 17, the amount of course change varies from 10 degrees to 30 degrees. In Figs. 16 to 18, the course error is corrected by turning angular velocity correction and reach correction.

[0162] Course change amount ψset Influence of: The influence of the course change amount described in "4.4 Reach correction" is appropriate, as can be confirmed from Figures 16 and 17 as follows. d r is ψ set However, U c Let / U={0,0.1}. d r The distortion of ψ set This is because there are more opportunities to correct the turning angular velocity. However, U c ≠ 0.

[0163] Ship speed U and current component U c Influence of: Figure 18 confirms that the influence of ship speed and current components described above in "4.4 Reach correction" is appropriate as follows. d r is proportional to U. d r The fluctuation of U c cos(ψ c -ψ plan ), where ψ plan =0. d r The distortion of U c Increases in proportion to the traverse velocity correction, resulting in greater distortion.

[0164] Turning performance improvement: In Figure 18, the upper left is d r The upper right shows d k The bottom left shows the radial error, and the bottom right shows the maximum value of the feedforward steering angle. From Fig. 18, the following can be confirmed. d r The variation of is proportional up to the ratio U0 / U = 0.25, but the distortion increases beyond that. d k is small, so there is no practical problem. · Both μ and σ are small, so there is no problem in practical use. δ FF U c cos(ψ c -ψ plan ) is proportional to U c As the turning angular velocity rR =(U0+U c )÷ρ vs. δ FF is set to its maximum value.

[0165] Therefore, it was confirmed that the contents explained in the section "4.4 Reach Correction" are valid, and the suppression of reach error according to this embodiment is effective.

[0166] (5.4 Closed-loop control results) The results of the closed loop control will now be described. Fig. 19 is a diagram showing the reach amount and commanded rudder angle when the course change amount changes at a ship speed of 15 kn. Fig. 20 is a diagram showing the course error when the course change amount changes at a ship speed of 15 kn. Fig. 21 is a diagram showing the reach amount, commanded rudder angle, and course error when the ship speed is 10 kn and the course change amount is 15 degrees. Fig. 22 is a diagram showing the reach amount, commanded rudder angle, and course error when the ship speed is 20 kn and the course change amount is 15 degrees.

[0167] The course error correction includes correction of turning angular velocity, correction of drift angle, and correction of reach. In addition, by suppressing the reach error, when the ratio U0 / U=0.3, (U0 / U) set = 0.25. Since the controlled object uses a nonlinear model, a steering angle offset of about 1 degree is included.

[0168] Course change amount ψ set The effect of: From Figures 19 and 20, the following can be seen: d in Figure 19 r and δ c In this case, fluctuations due to tidal current components occur proportionally, but distortion errors are almost nonexistent. · Route error y in Figure 20 e is proportional to the increase in course deviation. · Route error y in Figure 20 e occurs during a turn and is measured from the start of the turn to y e is accumulated. set is 30 degrees and y e Since the error is 30m, there is no need to take any measures to prevent this error. However, there is a way to forcibly move the reach amount and halve the error.

[0169] Ship speed U and current component U c Effect of ψ in Figs. 19 and 20 set From the case of =15deg and Figures 21 and 22, the following can be confirmed. d r is proportional to the ship speed, and δ c is inversely proportional to the ship speed. However, δ at U0=10kn c . There is no saturation due to the steering angle offset. y e If the amount of course change is the same, it is independent of the ship's speed.

[0170] Therefore, the marine automatic steering device 1 according to this embodiment satisfies the specifications and is effective in practical use.

[0171] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0172] 1. Automatic steering system for ships 12 Orbit Planning Division 16 Feedback control section 18 Feedforward control section 24 Hull 26 Sensors

Claims

1. 1. An automatic ship steering device comprising: a trajectory planning unit that outputs a reference heading and a reference position of a hull based on a planned route; a feedback control unit that outputs a feedback rudder angle so that the heading and position of the hull follow the reference heading and the reference position; and a feedforward control unit that outputs a feedforward rudder angle so that the heading of the hull follows the reference heading during a turning operation, The trajectory planning unit calculates the reach amount, which is the distance between the turning start position and the steering start position, based on the course change amount and the tidal component, and if the tidal component is equal to or greater than a preset upper limit value of the tidal component, replaces the tidal component with an upper limit value of the tidal component.

2. The marine automatic steering device according to claim 1, characterized in that, in calculating the reach amount, if the course change amount is equal to or greater than a preset upper limit of the course change amount, the trajectory planning unit replaces the course change amount with the upper limit of the course change amount.

3. 3. The marine automatic steering device according to claim 1, wherein the upper limit value of the tidal current component is a value obtained by multiplying the tidal current component by a value greater than 0 and less than 1.

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