Mercator chart-based great circle route guidance and control method

Abstract

The application is a Mercator chart-based great circle route guidance and control method, belonging to the ship track tracking field, comprising the following steps: establishing a ship motion nonlinear mathematical model; designing a great circle route guidance strategy, so that the ship sails along the great circle route according to the expected heading; based on the ship motion nonlinear mathematical model, a third-order closed-loop gain shaping algorithm is used to design a final controller for controlling the ship to track the expected heading; the plan of the great circle route in the ship running process is converted to the Mercator projection chart to obtain the ship sailing trajectory along the great circle route under the Mercator projection. Through simulation verification, the application can effectively control the ship to sail along the great circle arc line, reduce the track error and improve the sailing efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ship track tracking, and relates to a great circle route guidance and control method based on Mercator chart. BACKGROUND

[0002] At present, ship track tracking is to track a straight route, however, when sailing at high latitude, ships are mostly sailed according to great circle route, at this time, the original track tracking method has limitations. Moreover, at present, the track tracking result is mostly displayed in a plane graph, which is not intuitive enough for actual application of the ship. The guidance of the great circle route based on the Mercator chart can better meet the needs of the ship sailing at high latitude, and the application of the track to the Mercator projection chart has strong practical significance for the actual application and track control field of the ship sailing.

[0003] The existing method is to directly regard the route between two places as a straight line, that is, to sail by the method of the rhumb line, or to connect a plurality of straight routes to form a great circle route, that is, the approximate great circle sailing method, which can meet the sailing needs, but the principle is still the sailing method of the rhumb line, and the working difficulty is very complicated. Therefore, how to enable the ship to sail along the great circle route directly at high latitude and to be applied to the Mercator projection chart is the key to promote the maritime practice and the research on the maritime technology. SUMMARY

[0004] In order to solve the above problems, the technical scheme adopted by the application is as follows: a great circle route guidance and control method based on Mercator chart, comprising the following steps:

[0005] establishing a ship motion nonlinear mathematical model;

[0006] designing a guidance strategy of the great circle route, so that the ship sails along the great circle route according to the expected heading;

[0007] based on the ship motion nonlinear mathematical model, using a three-order closed loop gain shaping algorithm to design a final controller for controlling the ship to track the expected heading;

[0008] converting the plane graph of the great circle route in the ship running process to the Mercator projection chart to obtain the ship sailing track along the great circle route under the Mercator projection.

[0009] Further, the ship motion nonlinear mathematical model is established as follows:

[0010] When analyzing the ship maneuvering motion, only the two degrees of freedom of the cross drift speed and the rudder angle speed are concerned, the corresponding linear equation of the ship is as follows:

[0011] (1)

[0012] In the formula, represents the rudder angle input, represents the first order derivative with respect to time, respectively represents the first order derivative with respect to time; the coefficient is determined by the basic parameters of the ship, and formula (1) is converted into a simple equation describing the response of the rudder to the yaw, i.e.:

[0013] (2)

[0014] In the formula, represents the rudder angle input, represents the rudder angle input derivative with respect to time, represents the yaw rate second order derivative with respect to time, are all maneuverability indexes;

[0015] Laplace transform is performed on formula (2), and the initial value assumption is made, and the following transfer function is obtained: :

[0016] (3)

[0017] In the formula, is the Laplace operator, represents the Laplace transform of the rudder angle input, represents the Laplace transform of the yaw rate, are all maneuverability indexes;

[0018] According to the relationship , the corresponding equation is obtained:

[0019] (4)

[0020] In formula (4), is the heading angle, is the Laplace operator, represents the Laplace transform of the rudder angle input, represents the Laplace transform of the heading angle, are all maneuverability indexes;

[0021] Simplification is performed on formula (4), and the following formula is derived:

[0022] (5)

[0023] wherein , is the Laplace operator, is the ship maneuverability index, while equation (5) is written in the form of a differential equation as follows

[0024] (6)

[0025] wherein, is the rudder angle, denotes the heading angle is taken with respect to time, denotes the heading angle is taken with respect to time, is the ship maneuverability index;

[0026] Dividing equation (6) by on both sides, we obtain:

[0027] (7)

[0028] wherein, is the rudder angle, denotes the heading angle is taken with respect to time, denotes the heading angle is taken with respect to time, is the ship maneuverability index;

[0029] For a statically unstable ship, the second term on the left side of equation (7) needs to be replaced by the nonlinear term and:

[0030] (8)

[0031] Thus, a nonlinear mathematical model of ship motion is established:

[0032] (9)

[0033] In equation (9): is the heading angle, is the rudder angle, denotes the heading angle is taken with respect to time, denotes the heading angle is taken with respect to time, is the ship maneuverability index, is a nonlinear parameter.

[0034] Further, the design of the great circle route guidance strategy is as follows:

[0035] S31: Calculate the course and distance of the great circle route:

[0036] Suppose the starting point coordinate of the ship is and the ending point coordinate is , the initial great circle heading at the starting point coordinate is calculated using the spherical triangle formula, then the great circle distance and heading formula is:

[0037] (10)

[0038] (11)

[0039] Where, is the great circle distance, is the starting point latitude, is the ending point latitude, is the longitude difference between the starting point and the ending point, is the initial great circle heading;

[0040] S32: Calculate the coordinates of the nearest point to the current ship position, the specific process is as follows:

[0041] Suppose the current ship position is , then the great circle distance between the current ship position and is , then:

[0042] (12)

[0043] (13)

[0044] In the formula: is the longitude difference between the starting point and the current ship position; is the latitude of the current ship position; is the longitude of the current ship position; is the great circle distance from the starting point to the current ship position; is the great circle azimuth of point relative to point, taking the current position as point, drawing a perpendicular line to the great circle route , the foot of the perpendicular is , forming a spherical right triangle , then:

[0045] (14)

[0046] (15)

[0047] (16)

[0048] where: is the vertical distance from to ; is the great circle distance from the start point to the current position point; is ; is the angle between the two great circle arcs and ; is the great circle azimuth of from ; is the great circle initial heading;

[0049] The coordinates and great circle heading of the target point are calculated by:

[0050] (17)

[0051] (18)

[0052] (19)

[0053] (20)

[0054] where: is the great circle initial heading; is the great circle distance from to ; is the longitude difference from the start point to ; is the latitude of ; is the longitude of ; is the latitude of the start point; is the longitude of the start point; is the latitude of the target point; is the longitude of the target point; is the great circle heading of ; is the great circle distance from the start point to ;

[0055] S33: Calculate target point coordinates and desired heading;

[0056] Let the position of the tracking target point be , which is located at a great circle distance before the foot point ;

[0057] (21)

[0058] (22)

[0059] (23)

[0060] (24)

[0061] where: is the point to the longitude difference of the point; is the great circle distance between and ; is the latitude of the point ; is the longitude of the point ; is the latitude of the point ; is the longitude of the point ; is the great circle heading of the point ; is the great circle heading of the point, i.e. the desired heading ; is the latitude of the point of arrival; is the longitude of the point of arrival.

[0062] Further, the process of designing the final controller using the third-order closed-loop gain shaping algorithm based on the nonlinear mathematical model of ship motion is as follows:

[0063] Let the bandwidth frequency of the closed-loop system of the ship be , then the complementary sensitivity function of the ship heading keeping control system is , that is, the closed-loop transfer function of the control system is as shown in formula (25):

[0064] (25)

[0065] , then the controller is:

[0066] (26)

[0067] From formula (26), the form of the controller is a typical PD controller in series with an oscillation link, and a constant is taken under the PD controller, and the ship heading keeping control system will greatly reduce the adjustment time without changing the stability. A normal number is added to the proportional part of the PD link in formula (26), and the form of the final controller is formula (27):

[0068] (27)

[0069] Further: the process of converting the plane of the great circle route during the ship sailing to the Mercator projection chart, get the ship in Mercator projection along the great circle route sailing trajectory as follows:

[0070] The predetermined route plane coordinates The predetermined great circle route plane coordinates Convert to Mercator projection longitude and latitude, using the following formula for conversion:

[0071] (28)

[0072] (29)

[0073] Wherein: The radius of the earth, The horizontal coordinate corresponding to the rectangular coordinate on the plane, The vertical coordinate corresponding to the rectangular coordinate on the plane; The Mercator projection coordinate longitude, The Mercator projection coordinate latitude;

[0074] The above longitude and latitude are in radian units, and are converted according to the following formula:

[0075] (30)

[0076] (31)

[0077] Wherein, The Mercator projection coordinate longitude in radian, The Mercator projection coordinate latitude in radian, The Mercator projection coordinate longitude in degrees, The Mercator projection coordinate latitude in degrees.

[0078] The great circle route guidance and control method based on Mercator chart of the present application, compared with other methods, the method of the present application can shorten the sailing time of the ship when sailing at a long distance, and the method of the present application is no longer limited to applying the sailing trajectory to the ordinary plane, but applies the running trajectory to the Mercator projection map, making it more in line with the actual application of ship navigation. BRIEF DESCRIPTION OF DRAWINGS

[0079] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0080] Figure 1 Method flowchart of the present application;

[0081] Figure 2 Meridian guidance principle diagram;

[0082] Figure 3 Spherical right triangle diagram;

[0083] Figure 4 Track comparison diagram of the present method and other methods;

[0084] Figure 5 Heading comparison diagram of the present method and other methods;

[0085] Figure 6 Rudder angle comparison diagram of the present method and other methods;

[0086] Figure 7 Track error comparison diagram of the present method and other methods. DETAILED DESCRIPTION

[0087] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict, and the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0088] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, and is by no means any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0089] Figure 1 Method flowchart of the present application;

[0090] A meridian guidance and control method based on Mercator chart,

[0091] S1: Establish a nonlinear mathematical model of ship motion, which is a nonlinear Nomoto mathematical model;

[0092] S2: designing a guiding strategy of great circle route, so that the ship sails along the great circle route according to the expected heading;

[0093] S3: based on a nonlinear mathematical model of ship motion, a third-order closed-loop gain shaping algorithm is used to design a final controller for controlling the ship to track the expected heading;

[0094] S4: converting the planar graph of the great circle route in the ship running process to the Mercator projection chart to obtain the ship sailing trajectory along the great circle route under the Mercator projection.

[0095] The steps S1 / S2 / S3 / S4 are sequentially executed;

[0096] The present application is implemented by using MATLAB software;

[0097] Further, the process of establishing a nonlinear Nomoto mathematical model of ship motion is as follows:

[0098] When analyzing the ship maneuvering motion, only the lateral drift speed and the rudder angle speed are concerned, the corresponding linear equation of the ship is:

[0099] (1)

[0100] In the formula, represents the rudder angle input, represents the first-order derivative with respect to time, represents the first-order derivative with respect to time, and the coefficient is determined by the basic parameters of the ship. Formula (1) is converted into a simple equation describing the rudder response, that is:

[0101] (2)

[0102] In the formula, represents the rudder angle input, represents the derivative of the rudder angle input with respect to time, represents the second-order derivative of the rudder angle speed with respect to time, and are both maneuverability indexes;

[0103] The Laplace transform is performed on formula (2), and the initial value assumption is made, and the following transfer function is obtained:

[0104] (3)

[0105] where is the Laplace operator, is the Laplace transform of the rudder input, is the Laplace transform of the yaw rate, are all maneuverability indices.

[0106] According to the relation , the corresponding equation is obtained:

[0107] (4)

[0108] In equation (4), is the heading angle, is the Laplace operator, is the Laplace transform of the rudder input, is the Laplace transform of the heading angle, are all maneuverability indices.

[0109] Simplifying equation (4), the following equation is derived:

[0110] (5)

[0111] where , is the Laplace operator, is the ship maneuverability index, and equation (5) is written in the form of a differential equation as follows

[0112] (6)

[0113] where, is the rudder angle, and represent the first and second derivatives of the heading angle with respect to time, is the ship maneuverability index.

[0114] Dividing both sides of equation (6) by , we obtain:

[0115] (7)

[0116] where, is the rudder angle, and represent the first and second derivatives of the heading angle with respect to time, is the ship maneuverability index.

[0117] For some statically unstable ships, the second term on the left side of equation (7) needs to be nonlinear Substitute, and:

[0118] (8)

[0119] Thus, the nonlinear mathematical model of ship motion is established:

[0120] (9)

[0121] In formula (9): is the bow angle, is the rudder angle, and represent the bow angle , the first-order derivative and the second-order derivative with respect to time, is the ship maneuverability index, is the nonlinear parameter.

[0122] Figure 2 The principle diagram of the great circle route guidance;

[0123] Figure 3 is the spherical right triangle diagram;

[0124] Further, the guidance strategy of the great circle route is designed, and the process of the ship sailing along the great circle route according to the expected heading is as follows:

[0125] S31: Calculate the great circle route heading and distance:

[0126] Suppose the starting point coordinate of the ship is , and the end point coordinate is , the initial great circle heading at the starting point coordinate is calculated by using the spherical triangle formula, and then the great circle distance and heading formula is:

[0127] (10)

[0128] (11)

[0129] Among them, is the great circle distance, is the starting point latitude, is the arrival point latitude, is the meridian difference between the starting point and the arrival point, is the initial great circle heading;

[0130] S32: Calculate the coordinates of the nearest point to the current ship position:

[0131] Suppose the current ship position is , then the great circle distance between the current ship position and is , and then:

[0132] (12)

[0133] (13)

[0134] where: is the difference in longitude from the start point to the current position point; is the latitude of the current position point; is the longitude of the current position point; is the great circle distance from the start point to the current position point; is the great circle distance from the current position point to the destination point; is the great circle azimuth of the point relative to the point, with the current position as the point, and the great circle course as the line; is the perpendicular distance from the point to the point; is the foot of the perpendicular, which forms a spherical right triangle with the point and the great circle course; then:

[0135] (14)

[0136] (15)

[0137] (16)

[0138] where: is the perpendicular distance from the start point to the destination point; is the great circle distance from the start point to the current position point; is the great circle distance from the current position point to the destination point; is the great circle distance from the start point to the current position point; is the great circle distance from the current position point to the destination point; is the angle between the two great circle arcs and ; is the great circle azimuth of the point relative to the point; is the great circle initial heading; The coordinates of the point and the great circle heading are calculated by: (17)

[0139] (18)

[0140] (19)

[0141] (20)

[0142] (21)

[0143] (22)

[0144] ​​​​​​In the formula: The initial course for the great circle; for arrive Great circle distance between points; From the starting point to The difference in longitude between points; for The latitude of the point; yes The longitude of the point; The latitude of the starting point; It is the longitude of the starting point; The latitude of the destination; It is the longitude of the destination; for Great circle heading of a point; From the starting point to Great circle range of a point;

[0145] S33: The process of calculating the target point coordinates and desired heading is as follows:

[0146] Let the position of the tracking target point be located at the foot of the perpendicular. Great circle distance in front place point;

[0147] (twenty one)

[0148] (twenty two)

[0149] (twenty three)

[0150] (twenty four)

[0151] In the formula: For point to The difference in longitude between points; for and The great circle distance between them; for The latitude of the point; yes The longitude of the point; for The latitude of the point; yes The longitude of the point; for Great circle heading of a point; for The great circle heading of a point, i.e., the desired heading; The latitude of the destination; is the longitude of the arrival point;

[0152] Further, the process of designing the final controller based on the nonlinear mathematical model of ship motion using the third-order closed-loop gain shaping algorithm is as follows:

[0153] Designing the controller using the third-order closed-loop gain shaping algorithm , let the bandwidth frequency of the closed-loop system of the ship be , then the complementary sensitivity function of the ship's course keeping control system at this time is That is, the closed-loop transfer function of the system is as shown in equation (56):

[0154] (25)

[0155] , then the controller is:

[0156] (26)

[0157] From equation (57), it can be seen that the form of the controller is a typical PD controller in series with an oscillation element, and a constant is taken under the PD controller, the ship's course keeping control system will greatly reduce the adjustment time without changing the stability. By analogy with this method, a normal number can be added to the proportional part of the PD loop in equation (57), and the present application takes , to obtain the form of the final controller as equation (58)

[0158] (27)

[0159] Further, the process of converting the planar graph of the great circle route during the ship's voyage to the Mercator projection chart to obtain the ship's voyage trajectory along the great circle route under the Mercator projection is as follows:

[0160] The planned route planar coordinates , the planned route planar coordinates are converted to Mercator projection longitude and latitude based on the following formula, and the conversion is performed using the following formula:

[0161] (28)

[0162] (29)

[0163] Wherein: is the radius of the earth, is the horizontal coordinate corresponding to the rectangular coordinate on the plane, is the vertical coordinate corresponding to the rectangular coordinate on the plane; is the Mercator projection coordinate longitude, is the Mercator projection coordinate latitude;

[0164] The above latitude and longitude in radian units are converted according to the following formula:

[0165] (30)

[0166] (31)

[0167] wherein, represents the Mercator projection coordinate longitude in radian, represents the Mercator projection coordinate latitude in radian, represents the Mercator projection coordinate longitude in degree, represents the Mercator projection coordinate latitude in degree.

[0168] To verify the effectiveness of the method of the present application, the following simulation experiment was performed to simulate the sailing path of the Yuanyang ship from the Bahamas Islands (approximate position: latitude 24°48.0'N, longitude 75°48.0'W) to the Strait of Gibraltar (approximate position: latitude 36°00.0'N, longitude 5°12.6'W), and the main parameters of the Yuanyang ship are as follows.

[0169] Table 1 Main design parameters of the Yuanyang ship

[0170]

[0171] The initial ship heading was set to 070° and the wind force condition of Beaufort scale 6 was set during the simulation. In order to reduce the simulation time, the earth radius was reduced by 1000 times. The simulation tested the performance of three sailing methods, including the great circle route guidance method proposed by the present application, the LOS constant heading line guidance method and the approximate great circle segmented guidance method based on LOS, and the simulation results are shown in Figure 4 — Figure 7 .

[0172] Figure 4 The comparison of the ship tracks of the present method and other methods is shown in the following figures. Whether it is the great circle route guidance method designed by the present application, the LOS constant heading line guidance method, or the approximate great circle segmented guidance method based on LOS, they can all stably sail along the planned route under the influence of the wind force of Beaufort scale 6.

[0173] Figure 5For the heading comparison chart of the method and other methods, the great circle navigation method starts to track the reference heading steadily after about 100 seconds, and then the heading of the ship gradually and evenly increases with the change of position. The rhumb line navigation method tracks the reference heading steadily at about 100 seconds, and then the heading of the ship remains stable. In comparison, the approximate great circle segmented navigation method constantly adjusts the heading in the whole simulation process because the heading needs to be adjusted in each navigation segment.

[0174] Figure 6 For the rudder angle comparison chart of the method and other methods, the great circle navigation method and the rhumb line navigation method are mainly in the controller adjustment stage in the first 100 seconds, so the rudder angle changes obviously. After about 100 seconds, the controller starts to track the reference signal steadily, and the rudder angle tends to be stable, and only small adjustments are made when the ship is disturbed by high-frequency waves. The approximate great circle segmented navigation method needs to change the heading in each navigation segment, so the ship uses a large rudder angle to adjust frequently in the whole simulation process.

[0175] Figure 7 For the track error comparison chart of the method and other methods, the maximum track error of the LOS-based rhumb line guidance method is about 25 meters in the whole navigation process, and the maximum track error of the LOS-based approximate great circle segmented guidance method is about 40 meters. In comparison, the maximum track error of the great circle route guidance and control strategy designed in the application is only 6 meters in the whole navigation process, which shows a significant advantage.

[0176] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A Mercator chart-based great circle route guidance and control method, characterized by: The method comprises the following steps: establishing a nonlinear mathematical model of ship movement; designing a guiding strategy of great circle route, so that the ship sails along the great circle route according to the expected heading; designing a final controller based on the nonlinear mathematical model of ship movement by using a third-order closed-loop gain shaping algorithm, so as to control the ship to track the expected heading; converting the plan of the great circle route in the ship sailing process to a Mercator projection chart to obtain the sailing track of the ship along the great circle route under the Mercator projection; the process of designing the guiding strategy of the great circle route, so that the ship sails along the great circle route according to the expected heading, is as follows: S31: calculating the heading and distance of the great circle route: Assume the initial coordinate of the ship is , the final coordinate is , and the initial great circle heading at the coordinate is calculated by using the spherical triangle formula, then the formula for calculating the great circle distance and heading is as follows: (1) (2) wherein, is the great circle range, is the latitude of the start point, is the latitude of the end point, is the longitude difference between the start point and the end point, is the great circle initial heading; S32: calculating the coordinates of the nearest point to the current ship position, and the specific process is as follows: Assuming the current ship position is , the great circle distance between the current ship position and is , then: (3) (4) where: is the difference in longitude from the start point to the current position point; is the latitude of the current position point; is the longitude of the current position point; is the great circle distance from the start point to the current position point; is the difference in latitude from the start point to the current position point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; is the great circle azimuth of the point relative to the point, with the current position as the origin point; (5) (6) (7) wherein: is the vertical distance from the point to ; is the great circle distance from the point to ; is the angle between the two great circle arcs and ; The coordinates of the point and the great circle heading are calculated by the following equations: (8) (9) (10) (11) In the formula: From the starting point to The difference in longitude between points; for The latitude of the point; yes The longitude of the point; for Great circle heading of a point; S33: calculating the target point coordinates and the expected heading; Let the position of the tracking target point be located at the foot point The great circle distance At the point Point; (12) (13) (14) (15) In the formula: for and The great circle distance between them; for The latitude of the point; yes The longitude of the point; for The great circle heading of a point, i.e., the desired heading; It is the longitude of the destination.

2. The Mercator chart-based great circle route guidance and control method according to claim 1, characterized by: the process of establishing the nonlinear mathematical model of ship movement is as follows: When analyzing ship maneuvering motions, if only the drift speed is considered... and bow angular velocity For these two degrees of freedom, the corresponding linear equations for the ship are: (16) In this equation, represents the rudder angle input, represents the first order derivative with respect to time, respectively represent the first order derivative with respect to time; the coefficient is determined by the basic parameters of the ship. Equation (1) is converted into a simple equation describing the yaw response to the rudder, i.e.: (17) In this equation, represents the rudder angle input, represents the rudder angle input is differentiated with respect to time, represents the yaw rate is differentiated twice with respect to time, are both maneuverability indicators; Taking Laplace transform to equation (2) and assuming the initial value , the transfer function is : (18) where is the Laplacian operator, represents the Laplace transform of the rudder angle input, represents the Laplace transform of the yaw rate, According to the relationship , the corresponding equation is obtained: (19) In formula (4), is a bow angle, denotes the Laplace transform of the bow angle, simplifying formula (4) to derive the following formula: (20) In the formula , is the ship maneuverability index, and formula (5) is written in the form of a differential equation as follows (21) wherein, denotes the heading angle the first derivative with respect to time, denotes the heading angle the second derivative with respect to time, is the ship maneuverability index; Dividing both sides of the equation of formula (6) by gives: (22) For statically unstable ships, the second term on the left of equation (7) needs to be replaced by the nonlinear term and: (23) thus, the nonlinear mathematical model of ship movement is established: (24) In formula (9) is a non-linear parameter.

3. The Mercator chart-based great circle route guidance and control method according to claim 2, characterized by: the process of designing the final controller based on the nonlinear mathematical model of ship movement by using the third-order closed-loop gain shaping algorithm is as follows: Let the bandwidth frequency of the closed loop system of the ship be Then the complementary sensitivity function of the ship's heading keeping control system at this time is That is, the closed loop transfer function of the control system is as shown in equation (25): (25) Controller is: (26) From equation (26), the form of the controller is a typical PD controller in series with an oscillatory element, and a constant is taken under the PD controller The ship course keeping control system will greatly reduce the adjustment time without changing the stability, and a normal number is added to the proportional part of the PD element in equation (26), and the form of the final controller is equation (27): (27)。 4. The Mercator chart-based great circle route guidance and control method according to claim 1, characterized by: the process of converting the plan of the great circle route in the ship sailing process to the Mercator projection chart to obtain the sailing track of the ship along the great circle route under the Mercator projection is as follows: Predefined route plane coordinates The predefined great circle route plane coordinates are converted to Mercator projected longitude and latitude using the following formula: (28) (29) wherein: is the earth radius, is the horizontal coordinate corresponding to the horizontal coordinate of the rectangular coordinate on the plane, is the vertical coordinate corresponding to the vertical coordinate of the rectangular coordinate on the plane; is the Mercator projection coordinate longitude, is the Mercator projection coordinate latitude; the latitude and longitude obtained above are in radian units, and are converted according to the following formula: (30) (31) wherein, represents the Mercator projection coordinate longitude in radian, represents the Mercator projection coordinate latitude in radian, represents the Mercator projection coordinate longitude in degree, represents the Mercator projection coordinate latitude in degree.

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