Automatic steering systems for ships

Abstract

To provide a berthing and un-berthing technology suitable for a ship with a variable pitch propeller and a side thruster.SOLUTION: An automatic steering device for a ship comprises a propulsion driving device with a variable pitch propeller, a bow thruster, and with a rudder, and comprises sensors to detect a bow azimuth and a hull position. An automatic steering device for a ship comprises a reference signal generating part, a control part, and a non-interfering processing part: the reference signal generating part generates reference signals of a reference position and a reference azimuth in the surge and the sway directions to guide a ship to a target position and a target direction; the control part outputs a virtual control variable to make the hull position in the sway direction follow the reference signal, the virtual control variable in the yaw direction to the bow azimuth follow the reference azimuth, and the pitch angle of the variable pitch propeller to make the hull position in the surge direction follow the reference signal; and the non-interfering processing part outputs the propeller rotation speed of the bow thruster and a rudder angle as the controlled variables so that the moment in the yaw direction for the virtual control variable in the sway direction becomes 0 and the force in sway direction for the virtual control variable in the yaw direction becomes 0 by the bow thruster propulsion force.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to a technology for automatically steering ships. [Background technology]

[0002] In recent years, research and development related to docking and undocking navigation has been actively pursued in the field of ship navigation technology. Realizing docking and undocking navigation requires ship position control technology that moves the ship's position from the starting point, turns it along the way, and stops it at the target location. As this type of technology, docking and undocking control using ship position control developed by the present inventor is known (see Non-Patent Documents 1 and 2). This docking and undocking control targets double-ended ships equipped with propellers at both the bow and stern.

[0003] Incidentally, large ships generally have variable-pitch propellers with variable pitch, a rudder, and a bow thruster located at the bow of the hull that generates thrust directed in the left-right direction of the ship. As a technology related to the present invention, control technology that applies an expert system for controlling such ships is known (see Non-Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Non-Patent Document 1] Fuyuki Hane, Design of a ship positioning device using decoupling and path sequencing, Proceedings of the Japan Society of Naval Architects and Ocean Engineers Conference, No. 30, pp. 33-41, May 2020. [Non-Patent Document 2] Fuyuki Hane, Performance Improvement of Hull Positioning Control by Correcting Acceleration / Deceleration Errors, Route Errors, and Reach Estimation, Proceedings of the Japan Society of Naval Architects and Ocean Engineers, No. 33, pp. 1-7, Nov 2021. [Non-Patent Document 3] Kazunari Hanyu, Shintaro Miyoshi, Development of an Automatic Docking Control System for the Realization of Unmanned Vessels - Automatic Docking Control of a Single Axis, Single Rudder, and Single Bow Thruster -, Proceedings of the Japan Society of Naval Architects and Ocean Engineers Conference, No. 34, pp. 21-24, May 2022. [Non-Patent Document 4] Fuyuki Hane, Design of a reference signal considering initial heading conditions and steering gear constraints: Application to ship course control, Transactions of the Society of Instrument and Control Engineers, Vol. 44, No. 4, pp. 333-342, 2008. [Non-Patent Document 5] Fuyuki Hane, Design of a Course-Holding System Using Analytical Methods Based on Course-Holding Control, Transactions of the Japan Society of Naval Architects and Ocean Engineers, Vol. 23, pp. 33-44, Jun 2016. [Overview of the project] [Problems that the invention aims to solve]

[0005] The problem that this invention aims to solve is to provide a docking technology suitable for ships equipped with a variable-pitch propeller, a rudder, and side thrusters. [Means for solving the problem]

[0006] In one embodiment, an automatic steering system for a ship that controls a ship having a propulsion drive system having a variable pitch propeller, a bow thruster and a rudder, and sensors for detecting the heading and hull position, comprises a reference signal generation unit that generates reference signals which are time-series signals of a reference position and reference heading in the surge direction and sway direction, respectively, for guiding the ship to a target position and target heading; a virtual control quantity in the sway direction that causes the hull position in the sway direction to follow the reference signal in the sway direction; and a unit that causes the heading to follow the reference signal of the reference heading. The system includes a control unit that outputs a virtual control quantity in the yaw direction and the pitch angle of the variable-pitch propeller that causes the hull position in the surge direction to follow a reference signal in the surge direction, and a decoupling processing unit that decouples the coupled motion of the sway and yaw so that the moment in the yaw direction becomes 0 with respect to the virtual control quantity in the sway direction and the force in the sway direction becomes 0 with respect to the virtual control quantity in the yaw direction due to the thrust of the bow thruster, and outputs the propeller rotation speed of the bow thruster and the rudder angle of the rudder as control quantities. [Brief explanation of the drawing]

[0007] [Figure 1] This is a block diagram showing the overall configuration of a control system, including an automatic steering system for ships. [Figure 2] This is a diagram of the ship's hull model. [Figure 3] This figure shows the time-series characteristics of the pitch angle θ. [Figure 4] This figure shows the rudder force characteristics with respect to surge speed u. [Figure 5] This is a block diagram showing the configuration of a ship's automatic steering system. [Figure 6] This is a block diagram showing the configuration of the reference signal generation unit. [Figure 7] This diagram shows the sequence of reference signals. [Figure 8] This diagram shows the direction control by the control unit. [Figure 9] This is a diagram showing the configuration of the decoupling processing unit. [Figure 10] This figure shows the parameters for the docking plan in the simulation. [Figure 11] This figure shows the reference signal setting values ​​in the simulation. [Figure 12] This figure shows the ship's track as simulated in the absence of external disturbances. [Figure 13] This figure shows the ship's track as simulated in the presence of external disturbances. [Figure 14] This figure shows the ship's motion as simulated without external disturbances. [Figure 15] This figure shows the ship's motion as simulated under the presence of external disturbances. [Figure 16] This figure shows the error obtained from the simulation without disturbances. [Figure 17] This figure shows the error obtained from the simulation when disturbances are present. [Figure 18] This figure shows the force and response obtained from a simulation without disturbances. [Figure 19] This figure shows the force and response obtained from a simulation in the presence of disturbances. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings.

[0009] (1 Control System) A control system including a ship's automatic steering system according to this embodiment will be described. Figure 1 is a block diagram showing the overall configuration of the control system including a ship's automatic steering system.

[0010] As shown in Figure 1, the automatic steering system 1 for ships in this embodiment controls a ship having a hull 2 ​​equipped with a propulsion drive unit 3 and sensors 4.

[0011] The propulsion drive unit 3 is a drive unit that can control the surge speed u, sway speed v, and yaw angular velocity r, and comprises a propulsion unit and a steering unit. The propulsion drive unit 3 comprises a controllable pitch propeller (CPP) and a bow thruster as the propulsion unit, and a flap rudder as the steering unit.

[0012] Sensors 4 include a gyrocompass for detecting the heading of the hull 2, a speedometer for detecting the speed of the hull 2 ​​relative to the water, and a GNSS sensor for detecting the hull's position from a satellite positioning system (GNSS) such as GPS. Sensors 4 only need to include sensors capable of detecting the heading and hull position, respectively.

[0013] The automatic steering system 1 for ships controls the surge speed u, sway speed v, and yaw angular velocity r of the ship's hull motion in order to perform ship docking control. The surge speed u is controlled by the pitch angle θ of the CPP, and the sway speed v and yaw angular velocity r are controlled by the rudder angle δ and the propeller rotation speed λ of the bow thruster. bt It is controlled by the following: Therefore, the automatic steering system for ships 1 controls the pitch angle θ, rudder angle δ, and propeller rotation speed λ. btUsing this, the ship is controlled so that the hull position coincides with the azimuth and position of the target value. The configuration of the ship's automatic steering device 1 will be described in detail later.

[0014] (2 Control object) (2.1 Hull model) The hull model will be described. Fig. 2 is a diagram showing the hull model.

[0015] As shown in Fig. 2, O-XY is the earth-fixed coordinate, OB-XBYB is the hull-fixed coordinate, and OB is the center of gravity.

[0016] <L In the following equations, u represents the surge speed, v represents the sway speed, r represents the yaw angular velocity, ψ represents the bow azimuth, θ represents the pitch angle of the CPP, and δ represents the rudder angle. Also, the subscript bt indicates the bow thruster, and λ bt indicates the propeller rotation speed of the bow thruster. It is assumed that the rotation speed of the CPP is constant.

[0017] When the hull motion model is expressed by linear terms of three degrees of freedom, the following equation is obtained.

[0018]

Equation

[0019] (2 Control object) (2.1 Hull model) The hull model will be described. Fig. 2 is a diagram showing the hull model.

Equation

[0020] Ω (bold) B E is a subscript B Subscripts from the hull fixed coordinates represented E This is a matrix that transforms to Earth-fixed coordinates (index E) represented by the following equation.

[0021]

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[0022] (2.2 CPP Model and Steering Force Model) We assume the characteristics of the CPP model and the rudder force model. Figure 3 shows the time-series characteristics of the pitch angle θ. Figure 4 shows the rudder force characteristics with respect to surge velocity u.

[0023] The characteristics of the CPP model are determined by the rotational speed λ and pitch angle θ of the CPP. λ0 is assumed to be constant. The surge velocity u is proportional to the pitch angle θ, and the proportionality constant is K. u Figure 3 shows the relationship between pitch angle θ and surge velocity u. In Figure 3, the subscript R This indicates a reference signal which will be described in detail later, and the reference signal u of the surge velocity R The reference signal θ is the pitch angle. R It is assumed that there is a delay time relative to . The rudder force is u R It is proportional to.

[0024] Figure 4 shows the turning force gain K of the rudder force with respect to surge velocity u. r and lateral flow gain K v It shows the characteristics of subscripts. set represents the set value. As shown in Figure 4, K r ,K v , u setThis is determined for . Furthermore, it is assumed that almost no rudder force is generated when u < 0.

[0025] (2.3 Bow Thruster Model) Let's explain the bow thruster model.

[0026] The thrust of the bow thruster model is the propeller rotation speed λ bt It is proportional to and the constant of proportionality is K bt Let's assume that the positive direction of rotational speed is the sway direction.

[0027] (3. Automatic steering systems for ships) (3.1 Configuration of automatic steering systems for ships) The configuration of a ship's automatic steering system will be explained. Figure 5 is a block diagram showing the configuration of a ship's automatic steering system.

[0028] The automatic steering system for ships 1 guides and moves the ship's bearing and position at the start of docking to target bearing and position values ​​using a trajectory-following method. As shown in Figure 5, the automatic steering system for ships 1 comprises a reference signal generation unit 11, a control unit 12, and a decoupling processing unit 13. Setting information including multiple set values ​​is input to the automatic steering system for ships 1.

[0029] The reference signal generation unit 11 generates a reference signal that guides and moves the hull 2 ​​to the target value based on the initial value and target value included in the setting information. Here, the initial value indicates the position and bearing of the hull 2 ​​at the starting point, and the target value indicates the position and bearing of the hull 2 ​​at the destination point.

[0030] The control unit 12 performs feedforward control to improve tracking performance and feedback control to improve closed-loop stability and disturbance rejection. The decoupling processing unit 13 separates the coupled motion of the sway and yaw through decoupling.

[0031] (3.2 Hull Model) Let me explain the hull model.

[0032] A ship hull model used in the automatic steering system 1 for ships

[0033]

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[0034]

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[0035] (3.3 Reference signal generation section) The configuration and operation of the reference signal generation unit will be described.

[0036] (3.3.1 Configuration of the reference signal generation unit) The configuration of the reference signal generation unit will now be explained. Figure 6 is a block diagram showing the configuration of the reference signal generation unit.

[0037] As shown in Figure 6, the reference signal generation unit 11 comprises a generation management unit 110, a surge signal generation unit 111A, a sway signal generation unit 111B, and a yaw signal generation unit 111C. In Figure 6, the set position and set heading are conditions for the trajectory plan, where the set position includes the hull position x in the surge direction and the hull position y in the sway direction of the hull 2 ​​at the starting point, and the set heading is the bow heading ψ of the hull 2 ​​at the starting point.

[0038] When moving the starting value to a target value, if the deviation from the target value is directly input to the control system, it will converge in an uncontrolled state. The generation management unit 110 plans the movement path and provides management signals according to the movement path to the surge signal generation unit 111A, sway signal generation unit 111B, and yaw signal generation unit 111C in a predetermined order.

[0039] The surge signal generation unit 111A generates a reference signal x, which is a time-series signal of the reference position in the surge direction. R The sway signal generation unit 111B generates a reference signal y, which is a time-series signal of the reference position in the sway direction. R The yaw signal generation unit 111C generates the reference signal ψ, which is a time-series signal of the reference direction. R Generates.

[0040] (3.3.2 Reference signal) Let's explain the reference signal. Figure 7 shows the sequence of the reference signal.

[0041] Figure 7 shows the sequence of reference signals generated by the reference signal generation unit 11. In Figure 7, FF and FB represent the operating states of feedforward control and feedback control, respectively. Reference signal x R This value fluctuates constantly from the start until it reaches the target value, and the reference signal x R A first section in which only feedforward control that follows the reference signal x is performed, and a second section in which reference signal x R The system includes a first section that follows the first section, followed by a second section in which feedforward control and feedback control are performed. R ,ψ R Each of these is varied towards the target value during the first interval without overlapping with each other. In this embodiment, the reference signal ψ R After the reference signal y is changed, R The reference signal y is varied. R ,ψ R Tracking to x is achieved through feedforward control and feedback control. In this way, x R Feedback control for the reference signal y R,ψ R This is performed after the tracking control is completed.

[0042] The reference signal setting is based on the x, y, and ψ values ​​at that time, as shown in the following equation.

number

[0043] The reference signal is given by the following equation. For details of this equation, please refer to Non-Patent Document 4.

[0044]

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[0045]

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[0046] (3.4 Control Unit) The operation of the control unit will now be explained. Figure 8 shows the direction control performed by the control unit.

[0047] The control unit 12 receives the reference signal x R Position control that makes the hull position x follow, and reference signal y R Position control that makes the hull position y follow, and reference signal ψ R This performs heading control to make the ship's heading ψ follow the reference signal x. R While the reference signal y fluctuates, R or reference signal ψR Since only one of the two parameters fluctuates, the control unit 12 controls the hull 2, resulting in 2-degree-of-freedom control.

[0048] As shown in Figure 8, the three controls performed by the control unit 12 consist of feedforward control and feedback control, respectively. Although only heading control is shown as an example in Figure 8, the position control of the ship's position x,y is configured in a similar manner.

[0049] To explain using heading control as an example, feedforward control makes the ship's heading follow a reference heading, while feedback control forms a closed-loop system with the controlled object to correct the heading error ψ e This aims to converge the value to zero, thereby reducing errors caused by disturbance components.

[0050] In orientation control and the two position controls, feedforward control and feedback control operate as shown in Figure 7. Two-degree-of-freedom control is performed using surge-direction position control and orientation control, followed by two-degree-of-freedom control using surge-direction position control and sway-direction position control. When two-degree-of-freedom control is performed, surge-direction position control is performed solely by feedforward control.

[0051] The controlled variable in equation (6) is given by the following equation from Figure 8.

[0052]

number

[0053] (3.4.1 Feedforward control) The controlled variable for feedforward control is obtained from the derivative of equation (10) as follows:

[0054]

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[0055] (3.4.2 Feedback control) This section explains the control variables in feedback control. The error in feedback control is shown in Figure 8 in Earth coordinates.

[0056]

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[0057]

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[0058] The control variable, using the above error amount, is given by the following equation. For details of this equation, please refer to Non-Patent Document 5.

[0059]

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[0060]

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[0061] The feedback controller consists of a state estimator and state feedback, and takes into account the uncertainty of the hull parameters to remove disturbances including wave components and bias components of the propulsion drive unit 3.

[0062] (3.5 Decoupling Processing Unit) The configuration of the decoupling processing unit will now be explained. Figure 9 shows the configuration of the decoupling processing unit.

[0063] In the hull model represented by Equation (6), the virtual control amounts δ v , δ r are all inputs related to steering and are usually the same. In this embodiment, since the marine automatic steering device 1 uses the virtual control amounts as they are, the decoupling processing unit 13 performs decoupling as follows.

[0064] Decouple the forces and moments acting on the coupled motion of sway and yaw by the thrust of the bow thruster. From Equation (4), the coupled motion is

[0065]

Equation

[0066] (3.5.1 Decoupling related to the virtual control amount δ v ) Regarding the virtual control amount δ v , decouple it so that the moment becomes Mr = 0 in Equation (17). Substitute

[0067]

Equation

[0068]

Equation

[0069]

Equation

[0070] (3.5.2 Decoupling related to the virtual control amount δ r ) Regarding the virtual control amount δ<​v Decoherence is applied so that = 0. Equation (17)

[0071]

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[0072]

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[0073]

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[0074] (3.5.3 Configuration of the decoupling processing unit) When the thrust of the bow thruster decouples the force in the sway direction and the moment around the yaw, the decoupling processing unit 13 is configured as shown in Figure 9. The decoupling processing unit 13 is derived from equations (20) and (26)

[0075]

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[0076] (4. Verification) The automatic steering system for ships according to this embodiment will be verified by simulation to confirm its effectiveness. However, the delay time shown in Figure 3 will be set to zero for simplification.

[0077] (4.1 conditions) (4.1.1 Docking Plan and Reference Signal Settings) The touchdown plan and reference signal setting values in the simulation will be described. FIG. 10 is a diagram showing the parameters of the touchdown plan in the simulation. FIG. 11 is a diagram showing the reference signal setting values in the simulation.

[0078] (4.1.2 Reference Signal) The reference signal in the simulation is as follows.

[0079] 1. After the hull starts moving forward, the azimuth is rotated to ψ = 0 deg. 2. The azimuth is held after being rotated, and the sway direction position is moved to y = 50 m. 3. After the sway direction position is moved, it is held, and the surge direction position is moved to x = 600 m.

[0080] (4.1.3 Hull Parameters) The hull parameters in the simulation are as follows.

[0081] Length of ship: L = 160.93 m Seawater density: ρ w = 103.10 3 kg·m -3 Mass: m = m’×0.5ρ w L 3 = 1.7129·10 7 kg, m’ = 798·10 -5 (The subscript ’ indicates a dimensionless quantity.) Moment of inertia: J = J’×0.5ρ w L 5 = 2.1791·10 <00OO106>kg·m 2 , J’ = 39.2·10 -5 Bow thruster: K bt = 0.003 kgf·rpm -1 , l bt = 75 K u = 0.01 kgf·rpm -1 , T u = 60 s, K v = -0.05 kgf·s-1 ,T v =50s,K r = 0.005 kgf·m·s -1 ,T r = 50s C v =-9.6849·10 5 rpm, C r =5.7095·10 6 rpm S v =2.6963,S r =1.5895,C K = -10m, σ = 0.058953m -1

[0082] (4.1.4 Disturbances) The disturbance in the simulation consists of a tidal component and a bias component, and the magnitude of the tidal component is U c = 0.2 m·s -1 , direction of the tidal current component ψ c Let =45deg, and set the yaw bias component to r bias = 0.2deg·s -1 Let's assume that.

[0083] (4.1.5 Control Parameters) The main control parameter in the ship's automatic steering system 1 in the simulation is the proportional gain K. p = 1, and the damping coefficient ζ = 0.7071.

[0084] (4.2 Results) The simulation results are explained below. Figures 12 and 13 show the ship's track from the simulation under the case of no disturbance and the case of disturbance, respectively. Figures 14 and 15 show the ship's motion from the simulation under the case of no disturbance and the case of disturbance, respectively. Figures 16, 16, and 17 show the errors from the simulation under the case of no disturbance and the case of disturbance, respectively. Figures 18 and 19 show the forces and responses from the simulation under the case of no disturbance and the case of disturbance, respectively.

[0085] As shown in Figure 12, in the absence of disturbances, the hull position aligns with the berthing plan. As shown in Figure 13, in the presence of disturbances, the error in heading correction is greater for the hull position compared to the absence of disturbances.

[0086] As shown in Figure 14, in the absence of disturbances, the hull motion follows the reference signal, although a v error occurs during heading correction. As shown in Figure 15, in the presence of disturbances, the hull motion exhibits a large transient response but settles down over time.

[0087] As shown in Figure 16, in the case of no disturbance, x e This occurs during feedforward control, but converges to zero due to the feedback control mechanism. As shown in Figure 17, the error is larger with disturbances compared to without disturbances, but converges to zero due to the disturbance error correction mechanism.

[0088] As shown in Figure 18, in the absence of disturbances, the sway and yaw motions are controlled to be independent of each other due to the decoupling effect, so the ship's automatic steering system 1 can guide the ship's position to the target value. As shown in Figure 19, in the presence of disturbances, although there is an effect of the disturbances, the coupled motion is reduced due to the decoupling effect, so the ship's automatic steering system 1 can guide the ship's position to the target value even in the presence of disturbances.

[0089] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0090] 1. Automatic steering system for ships 2 hull 3. Propulsion drive system 4. Sensors 11 Reference signal generation section 12 Control Unit 13. Decoherence Processing Unit

Claims

1. An automatic steering system for ships that controls a ship comprising a propulsion drive unit having a variable-pitch propeller, a bow thruster and a rudder, and sensors for detecting the ship's heading and hull position, A reference signal generation unit generates reference signals which are time-series signals of the reference position and reference direction in the surge direction and sway direction, respectively, for guiding the aforementioned vessel to the target position and target direction. A control unit that outputs a virtual control quantity in the sway direction that causes the hull position in the sway direction to follow a reference signal in the sway direction, a virtual control quantity in the yaw direction that causes the bow heading to follow a reference signal for the reference heading, and the pitch angle of the variable pitch propeller that causes the hull position in the surge direction to follow a reference signal in the surge direction. The decoupling processing unit decouples the coupled motion of sway and yaw such that the moment in the yaw direction becomes zero with respect to the virtual control amount in the sway direction, and the force in the sway direction becomes zero with respect to the virtual control amount in the yaw direction, and outputs the propeller rotation speed of the bow thruster and the rudder angle of the rudder as control variables. A ship's automatic steering system equipped with the following features.

2. The coupled motion of the aforementioned sway and yaw is, F ｖ is the force acting on the sway motion of the ship, M ｒ is the moment acting on the yaw motion of the ship, λ ｂｔ is the propeller rotation speed of the bow thruster, δ is the rudder angle of the rudder, K ｂｔ is the proportionality constant of the thrust of the bow thruster proportional to the propeller rotation speed, l ｂｔ is the distance from the center of gravity of the ship to the bow thruster, m is the hull weight, J is the moment of inertia around the center of gravity of the ship, K ｖ is the turning force gain of the rudder force of the rudder, K ｒ is the cross-flow gain of the rudder force of the rudder, T ｖ is the time constant in the sway direction, T ｒ is the time constant around yaw, then [Math 1] The automatic steering device for ships according to claim 1, characterized by being represented by the following.

3. In the aforementioned ship hull model, u is the surge velocity, v is the sway velocity v, r is the yaw angular velocity, s is the Laplace operator, and θ ｕ control amount in the surge direction, δ ｖ The virtual control quantity in the sway direction, δ ｒ As a virtual control variable in the yaw direction [Math 2] It is represented by, [Math 3] And here, K ｕ θ is the proportionality constant of the surge velocity, which is proportional to the pitch angle θ, and T ｕ is the time constant in the surge direction, and K ｖ ' is K ｖ This is obtained by multiplying by a coefficient based on the thrust of the bow thruster, K ｒ ' is K ｒ The automatic steering device for ships according to claim 2, characterized in that it is obtained by multiplying by a coefficient based on the thrust of the bow thruster.

4. The reference signal in the surge direction constantly fluctuates from the start until it reaches the target position in the surge direction. The automatic steering device for ships according to any one of claims 1 to 3, characterized in that the reference signal in the sway direction and the reference signal in the yaw direction vary so as not to overlap with each other.

5. The control unit performs tracking of the sway direction reference signal, tracking of the reference direction reference signal, and tracking of the surge direction reference signal, respectively, using feedforward control and feedback control. After tracking the reference signal in the surge direction is performed solely by feedback control, tracking the reference signal in the surge direction is performed using feedforward control and feedback control. The automatic steering system for ships according to claim 4, characterized in that the sway direction reference signal and the reference direction reference signal are varied only by feedback control while tracking the surge direction reference signal is performed.

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