Automatic Steering Device for Ships

Abstract

To provide a technology capable of mooring a ship more closely to a destination.SOLUTION: An automatic steering system includes: a reference trajectory generation unit that generates a reference trajectory including a trajectory from a departure point to a destination point, a reference distance represented by a time function of a surge direction distance from the departure point to the destination point, and a reference azimuth represented by a time function of an azimuth; a movement control unit that controls a ship through distance control of causing a position of the ship to follow the reference distance and route control of causing the position of the ship to follow the trajectory and causing the azimuth of the ship to follow the reference azimuth; a retention control unit that controls the ship so as to retain the position of the ship; and a switching unit that, when an intersection between an orthogonal line, which passes the position of the ship and is orthogonal to the trajectory, and the trajectory reaches the destination point, switches from control by the movement control unit to control by the retention control unit. The distance control includes a feed forward control of causing a ship body distance, which is a distance from a departure position to the intersection, to follow the reference distance, and a feedback control of causing a distance difference between the reference distance and ship body distance to converge to zero.SELECTED DRAWING: Figure 9

Description

Technical Field

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

Background Art

[0002] In recent years, automation for moving objects on land, sea, air, and even underwater has been actively developed. The applications of automated moving objects cover a wide range, including transportation, investigation, exploration, and rescue. A familiar example of an automated moving object is a robotic vacuum cleaner that autonomously moves indoors for cleaning. Such an automated moving object has its trajectory planning and implementation, as well as control of posture, speed, position, etc., managed and controlled by a computer when a commander gives the purpose and destination.

[0003] In an autonomous ship, which is an automated ship, the same control as that of the above-described moving object is performed. The technology related to autonomous ships is roughly classified into motion control for any one of berthing, following, and avoidance. As a control technology related to autonomous ships, there is known a technology for controlling a ship to be controlled to move from a stopped state at a departure point, turn on the way, and stop at a destination. It is also important that such a technology has versatility applicable to many ships.

[0004] As is well known, a ship has characteristics such as a large inertial force and a weak braking force compared to other navigable bodies, and a very small resistance from the fluid at low speeds. Therefore, hull positioning control (SPC: Ship Positioning Control) is one of the core elements of an autonomous ship. SPC plans a reference trajectory for realizing a given planned route, navigation speed, and turning conditions, and makes the hull position follow it, and is an extension of a hull position holding system (DPS: Dynamic Positioning System).

[0005] It is difficult to stop a ship without using DPS while maintaining an arbitrary bow azimuth and hull position. The technology described in Non-Patent Document 1 realizes stopping control using DPS. According to the technology described in Non-Patent Document 2 using SPC, there is a problem that the ship will pass beyond the destination because the ship speed lags behind and follows the deceleration of the reference speed.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] The problem to be solved by the present invention is to provide a technology capable of stopping a ship while bringing it closer to the destination.

Means for Solving the Problems

[0008] The automatic steering device for a ship according to the embodiment controls a ship including a propulsion drive device capable of controlling the speeds in the surge direction and the sway direction and the angular velocity around yaw, and a sensor for detecting the heading and the hull position. The automatic steering device for a ship includes a reference trajectory generation unit that generates a reference trajectory including a trajectory from a starting point to an arrival point, a reference distance that is a time function of the surge direction distance from the starting point to the arrival point, and a reference azimuth that is a time function of the azimuth, a distance control that causes the position of the ship to follow the reference distance, and a path control that causes the position of the ship to follow the trajectory and causes the azimuth of the ship to follow the reference azimuth, thereby controlling the ship, a holding control unit that controls the ship so as to hold the position of the ship, and a switching unit that switches from the control by the movement control unit to the control by the holding control unit when an intersection of an orthogonal line passing through the position of the ship and orthogonal to the trajectory and the trajectory reaches the arrival point. The distance control performs a feedforward control that causes a hull distance, which is a distance from the starting position to the intersection, to follow the reference distance, and a feedback control that converges a distance error between the reference distance and the hull distance to zero.

Effects of the Invention

[0009] According to the present invention, the ship can be brought closer to the destination and stopped.

Brief Description of the Drawings

[0010]

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Figure 18

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] (1 Hull Positioning Control) (1.1 Configuration of Marine Autopilot) A system including the marine autopilot according to this embodiment will be described. FIG. 1 is a block diagram showing the overall configuration of a system including the marine autopilot.

[0013] As shown in Fig. 1, the marine automatic steering apparatus 1 in the present embodiment controls a ship having a hull 2 equipped with a propulsion drive device 3 and sensors 4. In the present embodiment, the propulsion drive device 3 is a drive device capable of controlling the speeds in the surge direction and the sway direction and the angular velocity around yaw. In the present embodiment, it is configured as an azimuth thruster provided at the bow and the stern of the hull 2.

[0014] The sensors 4 include a gyrocompass that detects the bow azimuth of the hull 2, a speedometer that detects the speed of the hull 2 through water, and a GNSS sensor that detects the hull position from a satellite positioning system (GNSS) such as GPS. Note that the sensors 4 may include sensors capable of detecting the bow azimuth and the hull position, respectively.

[0015] The marine automatic steering apparatus 1 includes a reference trajectory generation unit 11 and a control unit 12. The reference trajectory generation unit 11 generates a reference trajectory based on the planned route output by the route planning unit 5. The control unit 12 outputs a command to the propulsion drive device 3 based on the bow azimuth and the hull position detected by the sensors 4 so that the hull 2 follows the reference trajectory generated by the reference trajectory generation unit 11, and controls the hull speed and the angular velocity.

[0016] (1.2 Planned Route) The planned route will be described. Fig. 2 is a diagram showing the form of the planned route.

[0017] As shown in Fig. 2, the planned route includes a starting point, a destination point, a forward speed, and turning conditions, and is configured by a combination of a straight line and an arc. In Fig. 2, O-XY is a earth-fixed coordinate, ψ plan is the planned azimuth, point A is the starting point, and point B is the destination point. Also, each of points C, S, and F is the center point, starting point, and ending point of the turn, and ρ set is the turning radius, and ψ set is the turning angle.

[0018] (1.3 Hull Positioning Control) The hull positioning control will be described. Fig. 3 is a diagram showing the classification of the control system in the hull positioning control.

[0019] The hull positioning control by the control unit 12 of the marine automatic steering apparatus 1 controls the ship so as to accelerate the forward speed from point A, turn at a constant speed, then decelerate and reach the arrival point B and hold the ship position in the planned route shown in FIG. 2.

[0020] As shown in FIG. 3, the hull positioning control has two control modes: a moving mode and a hovering mode. The control unit 12 executes distance control DC and course control TC in the moving mode, and executes hull position holding control DP including static control and path sequence control (see Non-Patent Document 3) in the hovering mode.

[0021] The reference trajectory is generated by the reference trajectory generation unit 11 based on the planned route, and is composed of the azimuth, position, and time that satisfy the trajectory plan. Specifically, the reference trajectory includes a trajectory from the starting point to the arrival point, a reference distance that is a time function of the surge direction distance from the starting point to the arrival point, and a reference azimuth that is a time function of the azimuth. The control unit 12 determines the hull position along the reference trajectory using a point H that is the intersection of a line passing through the hull position and orthogonal to the reference trajectory and the reference trajectory as the reference of the reference trajectory.

[0022] In the moving mode, the control unit 12 causes the bow azimuth and the hull position to follow the azimuth and position associated with this time at the time set in the reference trajectory, and when the point H reaches the point B, switches the control mode from the moving mode to the hovering mode. Further, in the hovering mode, the control unit 12 corrects the error between the end point B' in the control by the moving mode and the hull position, which is located near the point B, by static control, and when the end point B' and the arrival point B are different, moves the hull position from the end point B' to the arrival point B by path sequence control. Note that the movement from the end point B' to the arrival point B may be controlled by other control rules than the path sequence control. According to Non-Patent Document 3, the magnitude of the transient phenomenon of the holding response is proportional to the distance between the end point B' and the point B. In order to reduce this phenomenon, in the static control, the arrival point is replaced with the end point B' instead of the point B.

[0023] (2 Controlled object) The controlled object will be described. FIG. 4 is a diagram showing a controlled object including a hull model and a drive machine model. As shown in FIG. 4, the controlled object is a catamaran composed of a hull model and a drive machine model.

[0024] (2.1 Hull model) The hull model will be described. The hull model has the subscript in the surge direction u , the subscript in the sway direction v , and the subscript around the yaw r and is represented as

[0025]

Number

[0026]

Number

[0027] FIG. 5 shows the ship speed (speed relative to water) characteristics of the hull parameters. In FIG. 5, only T r is shown among the hull parameters, but the other variables {K r , K u , T u , K v , T v} are also assumed to be related to the ship speed. The low-speed range characteristics at T r ignore the propulsion resistance and assume the inertia term as the main one. From FIG. 5, the hull parameters have the following ship speed characteristics.

[0028] 1. The holding mode range is |u| ≦ 2 kn and is constant. 2. The moving mode range is u > 2kn and is proportional to the ship speed.

[0029] (2.2 Drive model) The drive model will be described. The azimuth thruster model of the drive (hereinafter referred to as ATM) controls the thrust vector by its propeller rotation speed (not reversing) and its direction. There are limitations on the rotation speed and the thrust angle. In FIG. 4, the rotation speed λ and the thrust F with respect to the water of the two ATMs are

[0030]

Number

[0031] The relationship between the command amount and the thrust angle is

[0032]

Number

[0033]

Number

[0034] Therefore, the output of the ATM is multiplied by a scale factor in the above formula, and

[0035]

Number

[0036] (3 Control system) (3.1 Configuration of the Control Unit) The configuration of the control unit will be described. Fig. 6 is a diagram showing the configuration of the control unit.

[0037] As shown in Fig. 6, the control unit 12 includes a movement control unit 121 that performs distance control DC and route control TC in the movement mode, a holding control unit 122 that performs hull position holding control DP in the holding mode, and a switching unit 123. The switching unit 123 switches the control system from the movement mode to the holding mode by switching the control subject from the movement control unit 121 to the holding control unit 122 when the point H based on the hull position reaches the point B. (3.2 Definition of Error) (3.2.1 Movement Mode) As shown in Fig. 7, the error in the movement mode is set from the point P of the hull position, the foot of the perpendicular point H, and the reference position point R. The azimuth error ψ e , the route error y e , and the distance error d e are

[0038]

Equation

[0039] (3.2.2 Holding Mode) Fig. 8 shows the state after switching from the movement mode to the holding mode. The switching of the control mode is made when the point H reaches the arrival point B as described above, and at this time, the arrival point is replaced from point B to point B'. This replacement is specifically as shown in the following equation.

[0040] [Mathematics] Here, B’, ψ B’ are the final x, y coordinates and orientation in the movement mode, respectively.

[0041] Subscript K indicates the orientation error ψ in the holding mode e k , the position error x of the hull coordinates e k , y e k are

[0042] [Mathematics] becomes. Here, Ω B E (ψ) is the matrix for converting from the earth coordinates (subscript E ) to the hull coordinates (subscript B ), and

[0043] [Mathematics] is.

[0044] (3.3 Distance Control) The distance control DC converges the distance error to zero by trajectory tracking control. The trajectory tracking control is composed of a two-degree-of-freedom control system including a reference distance, feedforward control, and feedback control. The feedforward control makes the hull distance follow the reference distance, and the feedback control forms a closed-loop system with the controlled object and converges the distance error to zero.

[0045] (3.3.1 Reference Distance and Feedforward Control) The configuration of the distance control DC by the distance control unit is shown in Fig. 9. In Fig. 9, RG is the reference distance generator, s is the Laplace operator, C d FF (s) is the feedforward controller, C d FB (s) is the feedback controller, P x(s)=P u (s)·s -1 is the distance hull model.

[0046] The reference distance generator outputs the reference distance D R (s), and the feedforward controller outputs the feedforward rotation Λ R (s) from the reference distance D FF (s). The feedback controller outputs the feedback rotation Λ e (s) from the distance error D FB (s), stabilizes the closed loop of the distance control DC, and removes the disturbance D D (s). The command propeller rotation Λ u (s) of the control amount is given by the following equation.

[0047]

Equation

[0048] Using trajectory tracking control, the transfer characteristics of the distance error D e (s) are

[0049]

Equation

[0050] The feedforward rotation Λ FF (s) is given by the following equation.

[0051]

Equation

[0052]

Equation

[0053]

Number

[0054] The reference distance d R and the feedforward rotation λ FF satisfy the orbital conditions of the distance as shown in Fig. 10.

[0055]

Number

[0056]

Number

[0057] (3.3.2 Feedback Control) The feedback controller consists of an estimator and state feedback,

[0058]

Number

[0059] (3.4 Course Control) The course control TC converges the course error y e to zero by azimuth control and course error control. The commanded thrust angle θ r of the course control is given by the following formula.

[0060]

Number

[0061] (3.4.1 Azimuth Control) The azimuth control HC converges the azimuth error ψe to zero, has the functions of azimuth holding and course changing, and has the same configuration as the distance control DC. Therefore, the azimuth control HC is obtained by replacing the distance in the distance control DC with the azimuth. The commanded thrust angle Θ h (s) of the azimuth control HC is

[0062]

Number

[0063] The reference azimuth ψ R and the feedforward thrust angle θ FF satisfy the azimuth turning condition

[0064]

Number

[0065]

Number

[0066] (3.4.2 Course Error Control) Course error control forms a closed-loop system with sway hull motion, converges the course error to zero, and corrects the error caused by tidal current components. The course error controller C t (s) filters the course error Y e (s) and multiplies it by the control gain.

[0067] [Number] It becomes. Here, T y is the filter time constant, f y is the course gain, f i is the integral gain. The effect of the disturbance component that moves the hull position is compensated by the function of the integrator. For the setting of the control gain in the above equation, refer to Non-Patent Document 5.

[0068] (3.5 Reach Amount Estimation) The reach amount estimation executed by the reference trajectory generation unit 11 determines the position to start a course change during a course turn, dominates the course error during the turn, and is called WOP (Wheel Over Point). The position of WOP is a distance forward from point S in Fig. 2 by the reach amount. The reach amount is calculated from the reference position and the course position. The reference position x R , y R is

[0069] [Number] is obtained from. Here, ψ R is the reference azimuth, ρ set is the turning radius.

[0070] As shown in Fig. 11, the course position is obtained from the model of the trajectory plan, the drive unit, and the hull motion. When the feedforward command set in the trajectory plan is input to the drive unit

[0071] [Number] is obtained. Here, the feedforward rotation λ FF is for keeping the ship speed at a constant state (set value u set ).

[0072] The hull positions x and y are obtained using the hull motions r, u, and v

[0073]

Equation

[0074] The results of obtaining the reference position and the course position are shown in Fig. 12. In Fig. 12, the markers on the line indicate the reference azimuth ψ R in 10-degree increments, and the hull parameters and turning conditions in the moving mode use the values described later in Section 4.1

[0075] The reach is determined from the positional relationship between the maximum value of the reference position and the course position corresponding to ψ R = 90 degrees in Fig. 12

[0076]

Equation

[0077] (3.6 Control in the holding mode) In the holding mode, the control unit 12 performs static control and path sequence control through operation management. The static control and path sequence control are implemented by three controllers. Each of the three controllers ensures the closed-loop stability and disturbance rejection with respect to the hull motions of surge, sway, and yaw, and has the same configuration as the feedback controller C d FB (s) for distance control DC. Therefore, each of the three controllers is obtained by replacing the distance in the feedback controller C d FB (s) with surge, sway, and yaw. Each hull parameter uses the ultra-low speed correspondence for the holding mode. Each of the three controllers

[0078] [Number] becomes. Here, the subscript k represents the holding mode, and C x (s), C y (s), C ψ (s) are the controllers for surge, sway, and yaw, respectively.

[0079] (4 Verification) Verify the effectiveness of the ship's automatic steering device according to this embodiment by simulation.

[0080] (4.1 Simulation Conditions) Explain the simulation conditions.

[0081] In the simulation, the calculation time is 30 minutes. The first half (18.3 minutes) is controlled in the moving mode, and the second half (11.7 minutes) is controlled in the holding mode. The time step is 0.1 s. The disturbance component in the simulation is a tidal current component with a northward direction of 1.0 kn and an offset around the azimuth of 0.3 deg / s.

[0082] The hull parameters in the simulation are shown in the following table.

[0083]

Table 1

[0084] [Number] is.

[0085] Note that in equations (4) to (6), since T3 << |T|, the coefficient corresponding to T3 is omitted. T3 is used for the generation of the reference signals D R (s), Ψ R (s).

[0086] The set values of the planned route in the simulation are shown below.

[0087]

Number

[0088] In the simulation, the constant rotational speed of the drive is λ0 = 110 rpm, and the angle limit is 45 deg.

[0089] In the simulation, the main control parameters are common in the movement mode and the holding mode, the proportional gain is K p = 1, the damping coefficient is ζ = 1÷√2, and the damping coefficient of the integral gain is ζ i = 0.9. The coefficient for converting the sway direction command speed to an angle is c θ v = 45 deg / 10 kn. The reach amount uses equation (41).

[0090] (4.2 Simulation Results) The simulation results will be described. Figures 13 to 18 all show the simulation results. Figures 13 and 14 are diagrams showing the planned route and the ship position track when the tidal current is zero and when there is a tidal current, respectively. Figure 15 is a diagram showing the response of the hull movement. Figure 16 is a diagram showing the response of the error. Figure 17 is a diagram showing the response of the command. Figure 18 is a diagram showing the response of the drive output.

[0091] As shown in Figure 13, when there is no disturbance component, point B’ is within a radius of 1 m from point B. As shown in Figure 14, when there is a disturbance component, the route error y e is caused by the disturbance component, but point B’ is within a radius of 10 m from point B. Also, in the ship position track in the movement mode to reach point B’, the distance error d eis the same as the case without disturbance components, and the error caused by the disturbance is corrected. On the other hand, the course error y e becomes larger than the case without disturbance components, and it becomes difficult to correct the error as the ship speed decreases.

[0092] As shown in Fig. 15, the surge speed u, sway speed v, and yaw angular velocity r generate biases under the influence of disturbance components.

[0093] As shown in Fig. 16, in the moving mode, the distance error d e corresponding x e and the course error y e converge to zero, and the azimuth error ψ e has a drift angle. The drift angle varies due to the term caused by the tidal current component and the term caused by the generation of r and v due to the rudder angle offset of r0 correction. The following table shows the case of being sufficiently static.

[0094]

Table 2

[0095] Fig. 17 shows the response of the command. Fig. 18 shows the response of the drive motor output, and no saturation occurs.

[0096] From the results of the above simulations, it was confirmed that the control by the ship automatic steering device 1 according to the present embodiment operates appropriately.

[0097] 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, replacements, and changes can be made without departing from the gist of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0098] 1 Ship automatic steering device 2 Ship hull 3 Propulsion drive device 4 Sensors 11 Reference trajectory generation unit 12 Control unit 121 Movement control unit 122 Holding control unit 123 Switching unit

Claims

1. A marine autopilot for controlling a ship comprising a propulsion drive device capable of controlling the speeds in the surge direction and sway direction and the angular velocity around yaw, and a sensor for detecting the bow azimuth and the hull position, a reference trajectory generation unit that generates a reference trajectory including a trajectory from a starting point to an arrival point, a reference distance that is a time function of the surge direction distance from the starting point to the arrival point, and a reference azimuth that is a time function of the azimuth, based on a planned route, a movement control unit that controls the ship by distance control for making the position of the ship follow the reference distance and course control for making the position of the ship follow the trajectory and the azimuth of the ship follow the reference azimuth, a holding control unit that controls the ship so as to hold the position of the ship, a switching unit that switches from control by the movement control unit to control by the holding control unit when an intersection of an orthogonal line passing through the position of the ship and orthogonal to the trajectory and the trajectory reaches the arrival point, wherein the distance control performs feedforward control for making a hull distance, which is the distance from the starting position to the intersection, follow the reference distance, and feedback control for converging a distance error between the reference distance and the hull distance to zero. A marine autopilot characterized by this.

2. The reference trajectory generation unit calculates a reach amount based on a positional relationship between a reference position based on the reference azimuth and turning radius, and a course position based on the reference trajectory, a drive machine model of the propulsion drive device, and a hull model of the ship. The marine autopilot according to claim 1, characterized by this.

3. The course position is calculated based on the drive machine model and the hull model into which a feedforward command by the feedforward control is input. The marine autopilot according to claim 2, characterized by this.

4. The controller that performs the course control filters a course error, which is the distance between the trajectory in the orthogonal line direction and the position of the ship, and multiplies it by an integral gain. The marine autopilot according to any one of claims 1 to 3, characterized by this.

5. The controller is C ｔ (s) for the controller, T ｙ as the filter time constant, f ｙ as the course gain, f ｉ as the integral gain, 【Number 1】 The marine autopilot according to claim 4, characterized by being represented by

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