Automatic steering device for ship

Abstract

This automatic steering device for a ship comprises: a trajectory planning unit that outputs a reference bearing and a reference position of a hull of a ship on the basis of a planned route; a feedback control unit that outputs a feedback steering angle in order to cause the bearing and position of the hull to match the reference bearing and reference position; and a feedforward control unit that outputs a feedforward steering angle that causes the bearing of the hull to match the reference bearing during a turning operation. The automatic steering device is characterized in that during calculations based on a tidal current component and a veering amount of a reach amount, which is the distance between a turning start position and a steering start position, the trajectory planning unit replaces the tidal current component with a preset upper limit value of the tidal current component when the tidal current component is equal to or greater than the upper limit value of the tidal current component.

Description

Automatic steering system for ships

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

[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 shifts from the straight route of the planned route to an arced route, a course change operation is initiated from the straight route.

[0003] Such 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 arcuate course is composed of waypoints that indicate the start and end points of the turn, as well as the radius and angle of the turn.

[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 using closed-loop control. The main purpose of closed-loop control is to solve the regulator problem by providing closed-loop stability and disturbance rejection. Therefore, closed-loop control is insufficient to solve the servo problem caused by tracking response, such as in turning motion.

[0005] Because 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 using only feedback control. A route turning system using 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, a marine automatic steering system that can reduce arc distortion of a trajectory course is known (see Patent Document 1). This marine automatic steering system uses a two-freedom control system and generates a reference signal based on a trajectory plan, and achieves constant-radius turns by applying a course turning system to the course-keeping system. Here, the course turning system is based on a heading turning system.

[0007] However, the technology described in Patent Document 1 results in a feedforward rudder angle during turning that is unsuitable for practical use. A large rudder angle imposes excessive motion on the hull and places unnecessary strain on the steering gear. In hull control, it is desirable to keep the rudder angle to the minimum necessary.

[0008] JP 2014-15174 A

[0009] 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. 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. 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. T. I. Fossen and T. Perez. Marine systems simulator, basic libraries and system examples for guidance, navigation and control, 2008.

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

[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 the current component, if the current component is equal to or greater than a predetermined upper limit value of the current component, replaces the current component with the upper limit value of the current component.

[0012] It is a figure which shows the outline of the operation of the marine vessel automatic steering device which concerns on this embodiment. It is a block diagram which shows the structure of the marine vessel automatic steering device which concerns on this embodiment. It is a figure which shows the hull motion and the tidal current component. It is a figure which shows the reference direction ψ Ｒ Time series signal and reference steering angle δ Ｒ 1 is a diagram showing a time series signal of u and a reference trajectory based on the yaw angle. ｇＲ ｕｐ1 is a diagram showing an example of a time series of. A diagram showing a reach estimate of a reference trajectory. A diagram showing a reference trajectory with reach correction applied. A table showing hull parameters and control gains of a target ship. A diagram showing heading error, course error, and commanded rudder angle in the case of a first-order model. A diagram showing tidal current estimation and sway speed bias estimation in the case of a first-order model. A diagram showing heading error, course error, and commanded rudder angle in the case of a nonlinear model. A diagram showing tidal current estimation and sway speed bias estimation in the case of a nonlinear model. A diagram showing hull movement amount relative to course change amount. A diagram showing reach amount relative to reference movement amount. A diagram showing course change amount and reach amount due to tidal current components in the case of a ship speed of 10 kn. A diagram showing course change amount and reach amount due to tidal current components in the case of a ship speed of 15 kn. A diagram showing turning performance in the case of a ship speed of 10 kn and a course change amount of 10 degrees. A diagram showing reach amount and commanded rudder angle when the course change amount changes at a ship speed of 15 kn. A diagram showing course error when the course change amount changes at a ship speed of 15 kn. 10 shows the reach, commanded rudder angle, and course error when the ship speed is 10 kn and the course change amount is 15 degrees, and 11 shows the reach, commanded rudder angle, and course error when the ship speed is 20 kn and the course change amount is 15 degrees.

[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 automatic steering system for a vessel according to this embodiment applies a heading turning system to a course turning system, and performs the following through open-loop control:

[0016]

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

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

[0019] The first is a process to correct the turning angular velocity to satisfy equation (1.1) in order to respond to changes in ship speed over the ground. The second is a process to correct the drift angle to satisfy equation (1.2) in order to offset the lateral drift speed due to the tidal current component. 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 are related to the disturbance current components and cross current speed. Current components cause the ship's position to shift and include components caused by not only currents but also wind forces. Current components can 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 current components acting on the ship's hull are constant. On the other hand, on curved routes, including arced routes, the current 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 causes the vessel wake to 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 composed of a straight route and a circular arc. The circular arc route has a center C, a radius ρ, and a turning angle ψ. ｓｅｔ 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 used as the course error y ｅ Let's say.

[0023] (2. Configuration of the Marine Autopilot Device) The configuration of the marine autopilot device according to this embodiment will be described below. Fig. 2 is a block diagram showing the configuration of the marine autopilot device according to this embodiment.

[0024] As shown in Figure 2, the marine vessel automatic steering device 1 according to this embodiment is a device that controls a rudder to track the position of the vessel 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 multiple sensors provided on the vessel, such as a speed log that measures the vessel speed U, a gyrocompass that measures the vessel speed heading ψ, and a GNSS (Global Navigation Satellite System) sensor that measures the 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 and a reference signal including a time series signal of the reference position x Ｒ , y Ｒ The trajectory planning unit 12 outputs a reference trajectory, which is a time-series signal of the reference direction ψ Ｒ , reference position x Ｒ , y Ｒ and the heading error ψ, which 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 unit. It calculates the estimated tidal current component based on the heading error and position error output from the orbital course error calculation unit 14. The feedback gain unit 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 of a reference coordinate system obtained by coordinate transformation of the estimated tidal current calculated by the feedback control unit 16, the oblique 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 the feedforward steering angle δ based on the reference heading and the drift 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, causing the ship to move.

[0028] The automatic steering system for a vessel 1 includes a course-keeping system and a course-turning system. The course-keeping system includes a closed-loop control system using a 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 turning and achieve a constant radius. ＦＦ Control.

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

[0030] (3.1 Controlled 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 Figure 3, the control objects of the course turning system consist of ship motion and current components. Regarding ship motion, u is the forward speed (surge speed), ψ is the bow direction, r is the turning angular velocity (yaw angular velocity), v is the sway velocity, and δ is the rudder angle. 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 speed and sway speed have the following relationship:

[0033] Here, U is a substantially constant hull speed, and β is a drift angle that indicates a right turn with a positive value.

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

[0035] Here, the subscript ｃ represents the tidal current component, and u ｃ , v ｃ are the northward and eastward current velocities, respectively, and U ｃ is the tidal current speed, ψ ｃ is the tidal direction.

[0036] The power flow components are calculated as power flow estimated values ​​by an estimator not shown in FIG.

[0037] where the subscript ^ denotes the estimated value.

[0038] (3.2 Reference Orbit) The reference orbit based on the reference signal will be described. Ｒ Time series signal and reference steering angle δ Ｒ 5 is a diagram showing a reference orbit based on a drift angle.

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

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

[0041] where f is a fourth-order function, t is time, and the subscript ｒ represents the ship motion around yaw, and K ｒ is the turning force gain, T ｒ is the time constant,

[0042] where the subscript ｖ represents the ship motion in the sway direction, and K ｖ is the cross flow gain.

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

[0044] The reference signal has two characteristics. First, if the course change conditions other than the course change amount are the same, the ψ Ｒａ remains unchanged, and the constant velocity mode ψ Ｒｖ increases (constant velocity time T ｖ 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 Trajectory) The reference trajectory will be described below. Note that the description here is based on the assumption that the reference signal does not include the acceleration mode and deceleration mode, but only the constant velocity mode.

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

[0047] Here, the subscript Ｒ represents the component based on the reference heading. By integrating the above equation with respect to time [0, τ] (τ corresponds to the course change time), the reference trajectory is

[0048] where the reference orientation is the simplified ψ Ｒ =r Ｒ t is used. From equations (1.3) and (1.4) in the above equation,

[0049] Substituting the above, the reference trajectory is as shown in Figure 5:

[0050] Here, ρ is the turning radius,

[0051] is.

[0052] The characteristics of the reference trajectory will be explained. In FIG. 5, β=0 (XOY coordinates) is the arc of the planned route (center C, radius ρ), 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 course due to the cross current velocity. The second characteristic is that the turning center C β The coordinates of are (ρ sin β, ρ cos β). The third property is that C β The amount of movement is expressed as follows, assuming that β is a small angle.

[0054] Here, x β is the ideal reach amount, and the ideal reach amount is the hull parameter K ｖ , K ｒ The ratio of y β corresponds to a kick, and time r Ｒ The small negative value occurs when τ-β=0. A numerical example is ρ=1852m, u=15kn, K ｒ = 0.1 s －１ , K ｖ = -7.4 m s －１ Also, from u = ρr, x β = 74 m, y β =-1.48m, |y β |≪x β becomes.

[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 in the constant velocity mode only, and the ideal reach is the ratio of the cross drift velocity 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 is comprised of acceleration mode, constant velocity mode, and deceleration mode. Since the orientation change is small in acceleration mode and deceleration mode, the time in acceleration mode extends the reach amount, while the time in deceleration mode does not affect the reach amount (see Figure 4). Therefore, the reach amount can be calculated from the start of acceleration mode as follows:

[0058] Here, d ｒ is the reach amount, d ψＲａ is the amount of movement in acceleration mode,

[0059]

[0060] u(t) = u ０ , cos(ψ Ｒ (t))≒1-0.5(ψ Ｒ (t) ２ ≒1, ψ Ｒ (T ａ ) <<1. Here, u ０ is a constant value. Reach amount d ｒ has the following three properties:

[0061] The first characteristic is d ｒ is the amount of fluctuation d ψＲａ and a fixed quantity x β It is the sum of . ψＲａ is proportional to the ship speed and acceleration time, and x β is the ratio Kv / Kr. ｒ Had 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 hull parameters do not change.

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

[0063] As shown in Figure 3, the ground speed of the ship is the sum of the ship component and the current component.

[0064] Here, the subscript ｇ represents the ground component of the ship's speed, and the subscript ｎ represents the ground component of the ship velocity shown in the following equation.

[0065] where Ω Ｅ Ｂ is the matrix that transforms from ship-fixed coordinates to Earth-fixed coordinates,

[0066] where the subscript Ｔ represents the transposed matrix.

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

[0068] where the subscript Ｒ denotes the reference direction, and ψ ｅ = ψ-ψ Ｒ is the heading error,

[0069] is.

[0070] By linearly approximating equation (1.23), the route error model becomes:

[0071] where ψ ｅ is linearized as a small angle, cosψ ｅ ≒1, sinψ ｅ ≒ψ ｅ , uψ ｅ ≒u ０ ψ ｅ and ０ is a constant value u ｃＲ , v ｃＲ are the tangential and normal velocity components at the reference direction, respectively, and

[0072] where ψ ｃＲ = ψ ｃ -ψ Ｒ is.

[0073] From equation (1.25), the error factors in turning can be roughly divided into those caused by tidal current components and those caused by cross current speed. ｃＲ acts in the forward direction of the hull, and vｃＲ acts in the lateral direction of the ship. As mentioned above in the explanation of the reference trajectory, the error factor caused by the lateral flow velocity moves the reference trajectory outside the planned course. Therefore, in order to realize a turning trajectory with a constant radius, it is necessary to take measures against the error factors caused by the tidal current component and the lateral flow velocity. In addition, the term u ０ ψ ｅ is handled by the course-keeping system.

[0074] (4. Route Error Correction Method) A route error correction method for correcting error factors in route turning will be outlined below.

[0075] The course error correction method includes turning angular velocity correction, drift angle correction, and reach correction. 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 therefore offset by the drift angle. ｒ The method involves calculating the distance and moving the starting point for maneuvering forward by the amount of reach.

[0076] (4.1 Turn Angular Velocity Correction) Turn angular velocity correction will be described. ｇＲ ｕｐ FIG. 10 is a diagram showing an example of a time series of

[0077] To achieve a constant radius turning trajectory, the turning angular velocity is

[0078] where r is the turning angular velocity, u ｇＲ is the tangential reference velocity and ρ is the turning radius.

[0079] u ｇＲ is calculated from equation (1.25) by the surge speed of the ship and the current component u ｃＲ The surge speed tends to decrease because the steering amount increases from course maintenance due to the course change operation, resulting in resistance. ｃＲ Since is a function of the reference heading from equation (1.26), it changes during the turn. Therefore, the reference angular velocity is u ｇＲThe reference heading is calculated by trajectory planning, along with the reference rudder angle, based on the remaining turning angle, reference angular velocity and initial heading settings.

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

[0081] where the subscript ｕｐ represents the initial value or the updated value, and u ｓｅｔ is the velocity threshold.

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

[0083] where r ｓｅｔ ｕｐ is the rotation angular velocity update value, ψ ｓｅｔ ｕｐ is the updated course change amount.

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

[0085] As shown in FIG. 6, u ｇＲ ｕｐ Ha 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 updating may cause a distortion error in the turning radius.

[0086] (4.2 Drift Angle Correction) 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 Ｒ Reference steering angle δ Ｒ can be generated from

[0087] β ｃis given by the following equation (1.31): 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 However, the feedforward rudder angle of the course turning system is

[0088] Here, the subscript ｃ indicates the current component. β ｃ The correction of is performed by the feedforward control section 18 and the feedback control section 16.

[0089] Commanded rudder angle δ ｃ As shown in FIG. 2, the following relationship holds:

[0090] where δ ＦＢ , δ ｈ , δ ｔ is the feedback steering angle, δ ＦＦ , δ ＦＦ ｈ = δ Ｒ , δ ＦＦ ｔ is the feedforward steering angle, and the subscript ｈ , ｔ represent heading control and route control, respectively.

[0091] β ｃ The corrective feedforward control is zero as shown in the following equation:

[0092] where δ Ｒ βｃ is the equation (1.38) described later, and β ｃ This corresponds to the feedforward steering angle.

[0093] Similarly, feedback control

[0094] Here, f １ , f ２ The following omits the proportional gain, differential gain, and correction amount feedback terms of the azimuth control loop.

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

[0096] On the other hand, δ ｈ Excluding estimates and corrections, ψ ｅ Multiplying by the feedback gain,

[0097] Therefore, δ ｔ β of ・ ｃ The term is ψ in the above equation. ・ ｅ is set to correspond to the term.

[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 current correction is essentially the same in 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) 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 Ｒ Reference steering angle δ Ｒ can be generated from

[0101] β ｃ is obtained from equation (1.31) as 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 However, the feedforward rudder angle of the course turning system is

[0102] and the steering angle setting value δ ｓｅｔ In this case, δ ＦＦ is subject to steering limitations, resulting in the course turning system not functioning properly.

[0103] (4.3.1 Feedforward rudder angle) Drift angle correction β ｃ Feedforward steering angle δ Ｒ βｃ is expressed using equation (1.8).

[0104] Here, u ・ = 0, Coriolis term ψ ・ Ｒ ２ β ｃ The derivative of

[0105] Also, u ｃＲ , v ｃＲ The derivative of

[0106] Here, U ・ ｃ =0.

[0107] Substituting equation (1.26) into equation (1.38) gives

[0108] Here, C βｃ is the coefficient,

[0109] is.

[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

[0111] becomes.

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

[0113] becomes.

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

[0115] This becomes:

[0116] The maximum value of the above equation 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 of equation (1.37) is given by the following equation:

[0117]

[0118] The above numerical example and ψ ｃＲ = 0, δ Ｒ = δ ｓｅｔ Using δ ＦＦ = 1.5 × 13 = 19.5 deg. ＦＦ To make it δ = 13 deg, 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 current components. This does not apply to corrections to turning angular velocity. Even if the course change amount is the same, if the rudder angle setting value is different, the course-changing response will change. If hull parameter identification is then performed, the identified values ​​will also fluctuate.

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

[0121] (4.4 Reach Correction) 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 reach correction.

[0122] (4.4.1 Importance of correction) As shown in Figure 7, reach correction modifies the position of the maximum advance, which is the maximum value of the turning advance due to the cross current speed. The 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 current components, the ship position is estimated by numerical calculation using an open-loop control system, without using equation (1.16). In this calculation, the ship's motion is treated as mass motion. The maximum lateral distance (kick), which is the lateral deviation, is small, so no correction is required.

[0124] It is desirable to perform the 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 calculated just before changing course, using that rough estimate as a reference. The second calculation is performed to adapt the reach amount as much as possible to changes in ship speed and current components. As shown in Figure 1, the course change operation begins when the foot drop position (point H) of the ship's position (point P) reaches WOP.

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

[0126] Step 1: For the sake of simplicity, the calculation is performed using the planned heading ψ of a straight course as shown in Figure 7. ｐｌａｎ is 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.

[0127] Here, u = u ０ (initial value), v = K ｖ δ ｒｏ and δ ｒｏ is the rudder angle offset. The estimated current speed u^ ｃ , v^ ｃ ψ ｐｌａｎ Transform the coordinates using U ｃ , ψ'ｃ Converting to

[0128] becomes.

[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 Ｒ Ask for.

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

[0131] where τ is ψ Ｒ is ψ ｓｅｔ Time to reach θ Ｒ is the corrected direction,

[0132] Here, for β, the turning angular velocity correction and the drift angle correction are performed using equations (1.4) and (1.9).

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

[0134] Here, P ｘ , P ｙ is the position (x, y) of point P, α is the inclination of point P, Δ is the small amount of change, ψ ｓｅｔ is the amount of course change.

[0135] The above equation is ψ ｓｅｔ < 0. However, the right-handed coordinate system and right-handed screw direction are positive. 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 current components, and the effects of correction of turning angular velocity and drift angle.

[0136] (4.4.3 Reach Error Suppression Method) Reach calculation is performed by replacing the hull motion with mass motion and integrating the ground speed.

[0137] Effect of course change amount: Summarize the effect of course change amount on reach amount. - Reach amount does not depend on the magnitude of course change amount if the course change conditions other than the course change amount are the same. - Turning angular velocity correction is based on the ground speed u ｇＲ is the speed threshold u ｓｅｔ At that time, the turning angular velocity is updated, which changes the curvature of the reference trajectory and causes an error in the reach calculation. The smaller the course change, the fewer opportunities there are for correction.

[0138] Effect of ship speed and current components: Summarize the effect of ship speed and current components on reach. Reach is proportional to ship speed. Even if the course change conditions and turning radius are the same, the reach will change if the ship speed changes. However, the fluctuation in reach is proportional to the ｃ / U. The amount of reach changes with the tidal current component. 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 be affected by an error depending on the magnitude of this distortion.

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

[0140] Countermeasures for course change: Reach course change

[0141] where ψ ～ ｓｅｔ is a limit value, and its range is set by the following formula:

[0142]

[0143] Countermeasures against tidal current components: Reach tidal current components

[0144] where U ～ ｃ is the limit value,

[0145] Here, (U ｃ / U)ｓｅｔ is the set value of the ratio between the ship speed U and the tidal current component Uc, and its range is set by the following equation.

[0146]

[0147] (4.4.4 Evaluation of Reach Correction) A reach correction is performed by moving the start position of the reference heading to point O', as shown in Figure 8. Although the kick amount is also moved in Figure 8 for convenience, no kick correction is 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 a turn, and does not require rudder angle control. It is also possible to convert the lateral drift speed into a drift angle and correct it using the feedforward rudder angle. However, for the same reasons 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:

[0150] Here, e is the radial error, μ is the mean, σ is the standard deviation, and n is the number of data.

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

[0152] In this verification, the following items are confirmed: - The effect of the course turning response by the marine vessel automatic steering device 1 - The validity of the analyzed reach characteristics - The validity of the open-loop control by the marine vessel automatic steering device 1 - The effectiveness of the closed-loop control by the marine vessel automatic steering device 1

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

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

[0155] In the simulation, the turning condition is U ０ = 15 kn, ψ ｓｅｔ = 15 deg, reach amount d ｒ = 140.6 m, kick amount d ｋ = -1.1 m. The reach amount will be the same if the parameters are the same, even if the controlled model is different. Turning will start at 30 minutes, and the error thereafter 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 that the correction made by the marine vessel automatic steering system 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 and y ｅ are both negligible, and δ ｃ is δ ＦＦ Therefore, the simulation results for the nonlinear model are almost equivalent to those for the first-order model. If the nominal value is appropriate, the correction by the marine vessel automatic steering device 1 according to this embodiment satisfies the specifications and has sufficient accuracy for practical use, even for the 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 amount of hull movement relative to the amount of course change. Fig. 15 is a diagram showing the amount of reach relative to the amount of reference movement. Fig. 14 shows the amount of course change ψ ｓｅｔ For the reach amount d ｒ , kick amount d ｋ , the movement amount of the reference direction d ψｓｅｔ ≒d ψＲａ and ideal reach x β 15 shows the ψｓｅｔ For d ｒ and x β This shows the following.

[0160] It can be confirmed from Figures 14 and 15 that the relationship between the reference heading and the reach amount described in Section 3.2.2 "Reference Track" is appropriate.ψＲａ If the amount of change in course is increased and the ship speed is the same, the amount of reach will remain the same. ｒ is the amount of fluctuation d ψＲ and a fixed quantity x β It becomes the sum of d ｒ Had ψＲ is proportional to.

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

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

[0163] Ship speed U and current component U ｃ Influence of: It can be confirmed from Figure 18 that the influence of ship speed and current components described above in "4.4 Reach Correction" is appropriate as follows: 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 Figure 18, the following can be confirmed: ｒ The fluctuation of ０ It is proportional up to / U=0.25, but distortion increases beyond that. ｋ is small, so there is no practical problem. Both μ and σ are small, so there is no practical problem. ＦＦ is U ｃ cos(ψ ｃ -ψ ｐｌａｎ ) is proportional to U ｃ As the turning angular velocity r Ｒ = (U ０ +U ｃ ) ÷ δ for ρ 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 that the suppression of reach errors according to this embodiment is effective.

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

[0167] The course error correction includes correction of turning angular velocity, correction of drift angle, and correction of reach. In addition, by suppressing reach error, the ratio U ０ When / U = 0.3, (U ０ / 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 influence of: The following can be confirmed from Figures 19 and 20. ｒand δ ｃ In Fig. 20, the fluctuation due to the tidal current component occurs proportionally, but the distortion error is almost non-existent. ｅ is proportional to the increase in the amount of course change. ｅ occurs during a turn, and ｅ is accumulated. ｓｅｔ is 30 degrees and y ｅ However, there is a way to forcibly move the reach amount and reduce the error by half.

[0169] Ship speed U and current component U ｃ Influence of ψ in Figs. ｓｅｔ When the angle is 15 deg, the following can be confirmed from Figs. 21 and 22. ｒ is proportional to the ship speed, and δ ｃ is inversely proportional to the ship speed. ０ = δ of 10 kn ｃ There is no saturation due to the steering angle offset. ｅ If the amount of course change is the same, it is independent of the ship's speed.

[0170] Therefore, the marine vessel 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 embodied 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 within the scope and spirit of the invention, and are also included in the inventions described in the claims and their equivalents.

[0172] 1 Automatic steering device for ships 12 Trajectory planning unit 16 Feedback control unit 18 Feedforward control unit 24 Hull 26 Sensors

Claims

1. An automatic ship steering device comprising 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 calculates the reach amount, which is the distance between the turning start position and the steering start position, based on the amount of course change 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 the upper limit value of the tidal component.

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

3. An automatic marine steering device as described in claim 1 or 2, characterized in that 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.

Images