1. A method for determining the maximum sailing speed based on the attack angle of a sail of an unmanned sailing boat is characterized by comprising the following steps:

setting a target sailboat and parameters of the target sailboat; establishing a sailing ship model of the target sailing ship according to the parameters of the target sailing ship;

setting different attack angles of the sails, and obtaining different lift coefficients and resistance coefficients according to the parameters of the target sailing boat; calculating to obtain the lift force and the resistance force under different attack angles of the sail according to the different lift force coefficients and the different resistance coefficients;

obtaining a relative wind speed according to the set absolute wind speed and the set relative wind direction angle; inputting the relative wind speed, the lift force, the resistance, the lift force coefficient and the resistance coefficient into the sailing ship model, and calculating to obtain the boosting force, the side thrust, the boosting force coefficient and the side thrust coefficient;

selecting a relative wind direction angle interval corresponding to the boosting coefficient larger than zero as a navigation area range of the target sailing boat; setting a desired course in the navigation area range, establishing a rudder stress model and setting a rudder angle to keep the sailing boat in the desired navigation direction;

establishing a motion model and a motion coordinate system of the target sailing boat; inputting the absolute wind speed, the relative wind direction angle, the expected course, the boosting force and the side thrust into the motion model to obtain the speed, the rudder angle and the drift angle of the target sailing ship;

and selecting the attack angle of the sail corresponding to the maximum sailing speed of the target sailing boat obtained through the motion model in the expected sailing direction.

2. The method for determining the maximum sailing speed based on the angle of attack of the sail of an unmanned sailing vessel as claimed in claim 1, wherein the calculating the lift and the resistance at different angles of attack of the sail according to the different lift coefficients and resistance coefficients comprises:

calculating the lift force F under different attack angles of the sail_LAnd resistance F_DThe expression of (a) is:

in the formula, ρ_aIs the air density; s_WThe lateral projection area of the sail; v_aRelative wind speed; c_LIs the coefficient of lift; c_DIs the coefficient of resistance.

3. The method for determining the maximum sailing speed based on the angle of attack of the sail of an unmanned sailing vessel as claimed in claim 2, wherein the step of inputting the relative wind speed, the lift force, the resistance, the lift coefficient and the resistance coefficient into the sailing vessel model and calculating the thrust force, the side thrust, the thrust coefficient and the side thrust coefficient comprises the steps of:

setting the bow direction as x and the starboard direction as y, and connecting the sailLifting force F_LAnd resistance F_DDecomposing to obtain the boosting force X along the course of the ship_WAnd a lateral thrust Y perpendicular to the course of the ship_WThe calculation expression is:

coefficient of lift of sail C_LAnd coefficient of resistance C_DDecomposing to obtain the boosting coefficient C along the ship course_XAnd a lateral thrust coefficient C perpendicular to the course of the ship_YThe calculation expression is:

in the formula, θ is a relative wind direction angle.

4. The method for determining the maximum sailing speed based on the attack angle of the sail of the unmanned sailing boat as claimed in claim 3, wherein the establishing of the rudder stress model includes:

the expression of the rudder stress model is as follows:

in the formula, delta is a rudder angle; alpha is alpha_RThe angle of attack of the rudder blade; rho is the density of the seawater; v_SIs the speed of the ship; l is_RThe rudder is long; d_RThe rudder width is adopted; c_Xδ、C_Yδ、C_NδRespectively is the thrust coefficient, the side thrust coefficient and the steering moment coefficient of the rudder blade, X_R、Y_R、N_RRespectively the rudder boosting force, the rudder side thrust and the rudder turning moment.

5. The method for determining the maximum sailing speed based on the angle of attack of the sail of an unmanned sailboat according to claim 4, wherein the establishing of the motion model and the motion coordinate system of the target sailboat comprises:

defining a global coordinate system o₀–x₀y₀z₀And a ship-associated coordinate system o-xyz, wherein the conversion relational expression of the global coordinate system and the ship-associated coordinate system is as follows:

wherein u is the forward direction speed; v is the traverse direction velocity; r is the yaw angular velocity; psi is the ship heading angle;

according to the stress of the ship and the rudder, the motion model is established by combining the motion coordinate system, and the expression is as follows:

wherein m is the total weight of the ship; i is_zzThe moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; j. the design is a square_zzThe additional moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; m is_XAnd m_YRespectively the additional mass in the advancing direction and the transverse moving direction under the ship-associated coordinate system; x_H、Y_H、N_HResistance and moment of resistance of the bare vessel; x_R、Y_R、N_RActing force and moment for the rudder; x_S、Y_S、N_SThe auxiliary power of the sail, the side thrust of the sail and the turning moment of the sail are obtained.

6. The method according to claim 1, wherein after selecting the sail attack angle corresponding to the maximum sailing speed of the target sailboat obtained by the motion model in the desired sailing direction, the method further comprises:

and determining the range of the attack angle of the sail corresponding to the maximum sailing speed of the target sailing boat.

7. The method for determining the maximum speed based on the angle of attack of the sail of an unmanned sailing vessel as claimed in claim 1, wherein the adjustment is performed by a variable-parameter PID autopilot system, and when the desired heading deviates from the actual heading, the variable-parameter PID autopilot system provides a rudder force and moment to the target sailing vessel to adjust the actual heading to the desired heading.

Background

The unmanned sailing boat is a multipurpose novel dynamic observation platform driven by ocean clean energy (wind energy), can be used for offshore operation, and has the advantages of real-time data transmission function and low operation cost. The unmanned sailing boat is mainly different from the traditional unmanned boat in that the unmanned sailing boat has no built-in power system and only depends on the acting force of wind on a sail as the power for sailing. The changes of the wind speed and the wind direction not only affect the course of the sailing boat, but also affect the sailing speed of the sailing boat. Under a certain wind speed, the propulsion force of the sailing boat is influenced by the wind direction, the attack wind sail angle and the ship course. At present, the attack angle control strategy of the sailing sail of the unmanned sailing boat is generally researched only by considering the action of boosting force, but the sailing sail provides the boosting force for the boat body and can generate side thrust and yaw moment, the drift angle and rudder angle of the sailing boat can be increased by the larger side thrust and yaw moment, the resistance of the boat is increased, and the sailing speed is further reduced. Therefore, if the unmanned sailing boat can reach the maximum sailing speed, the influence of the sail boosting force and the side thrust on the unmanned sailing boat needs to be comprehensively considered.

Disclosure of Invention

The invention provides a method for determining the maximum sailing speed based on the attack angle of a sail of an unmanned sailing boat, which aims to overcome the technical problems.

The invention discloses a method for determining the maximum sailing speed based on the attack angle of a sail of an unmanned sailing boat, which comprises the following steps:

setting a target sailboat and parameters of the target sailboat; establishing a sailing ship model of the target sailing ship according to the parameters of the target sailing ship;

setting different attack angles of the sails, and obtaining different lift coefficients and resistance coefficients according to the parameters of the target sailing boat; calculating to obtain the lift force and the resistance force under different attack angles of the sail according to the different lift force coefficients and the different resistance coefficients;

obtaining a relative wind speed according to the set absolute wind speed and the set relative wind direction angle; inputting the relative wind speed, the lift force, the resistance, the lift force coefficient and the resistance coefficient into the sailing ship model, and calculating to obtain the boosting force, the side thrust, the boosting force coefficient and the side thrust coefficient;

selecting a relative wind direction angle interval corresponding to the boosting coefficient larger than zero as a navigation area range of the target sailing boat; setting a desired course in the navigation area range, establishing a rudder stress model and setting a rudder angle to keep the sailing boat in the desired navigation direction;

establishing a motion model and a motion coordinate system of the target sailing boat; inputting the absolute wind speed, the relative wind direction angle, the expected course, the boosting force and the side thrust into the motion model to obtain the speed, the rudder angle and the drift angle of the target sailing ship;

and selecting the attack angle of the sail corresponding to the maximum sailing speed of the target sailing boat obtained through the motion model in the expected sailing direction.

Further, the calculating, according to the different lift coefficients and the different drag coefficients, to obtain the lift and the drag at different angles of attack of the sail includes:

calculating the lift force F under different attack angles of the sail_LAnd resistance F_DThe expression of (a) is:

in the formula, ρ_aIs the air density; s_WThe lateral projection area of the sail; v_aRelative wind speed; c_LIs the coefficient of lift; c_DIs the coefficient of resistance.

Further, the step of inputting the relative wind speed, the lift force, the resistance force, the lift force coefficient and the resistance coefficient into the sailing ship model, and calculating to obtain the boosting force, the side thrust force, the boosting force coefficient and the side thrust force coefficient comprises the following steps:

setting the bow direction as x and the starboard direction as y, and setting the sail lift force F_LAnd resistance F_DDecomposing to obtain the boosting force X along the course of the ship_WAnd a lateral thrust Y perpendicular to the course of the ship_WThe calculation expression is:

coefficient of lift of sail C_LAnd coefficient of resistance C_DDecomposing to obtain the boosting coefficient C along the ship course_XAnd a lateral thrust coefficient C perpendicular to the course of the ship_YThe calculation expression is:

in the formula, θ is a relative wind direction angle.

Further, the building of the rudder stress model includes:

the expression of the rudder stress model is as follows:

in the formula, delta is a rudder angle; alpha is alpha_RThe angle of attack of the rudder blade; rho is the density of the seawater; v_SIs the speed of the ship; l is_RThe rudder is long; d_RThe rudder width is adopted; c_Xδ、C_Yδ、C_NδRespectively is the thrust coefficient, the side thrust coefficient and the steering moment coefficient of the rudder blade, X_R、Y_R、N_RRespectively as a ship rudder boosting powerRudder side thrust and rudder turn moment.

Further, the establishing of the motion model and the motion coordinate system of the target sailing ship includes:

defining a global coordinate system o₀–x₀y₀z₀And a ship-associated coordinate system o-xyz, wherein the conversion relational expression of the global coordinate system and the ship-associated coordinate system is as follows:

wherein u is the forward direction speed; v is the traverse direction velocity; r is the yaw angular velocity; psi is the ship heading angle;

according to the stress of the ship and the rudder, the motion model is established by combining the motion coordinate system, and the expression is as follows:

wherein m is the total weight of the ship; i is_zzThe moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; j. the design is a square_zzThe additional moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; m is_XAnd m_YRespectively the additional mass in the advancing direction and the transverse moving direction under the ship-associated coordinate system; x_H、Y_H、N_HResistance and moment of resistance of the bare vessel; x_R、 Y_R、N_RActing force and moment for the rudder; x_S、Y_S、N_SThe auxiliary power of the sail, the side thrust of the sail and the turning moment of the sail are obtained.

Further, after the selecting the angle of attack of the sail corresponding to the maximum speed of the target sailing boat obtained through the motion model in the desired heading, the method further includes: and determining the range of the attack angle of the sail corresponding to the maximum sailing speed of the target sailing boat.

Further, a variable-parameter PID automatic steering system is adopted for adjustment, when the expected course is deviated from the actual course, the variable-parameter PID automatic steering system provides rudder action force and moment for the target sailing boat, and the actual course is adjusted to the expected course.

The method is based on the internal relation between the acting force coefficient of the sail and the attack angle of the sail, comprehensively considers the boosting force and the side thrust of the sail, and combines target sailing parameters to establish a sailing model; synthesizing rudder stress factors and establishing a rudder stress model; and establishing a sailing ship motion model by using a response type three-degree-of-freedom ship maneuvering separation (MMG) method, thereby calculating the condition that the unmanned sailing ship meets the requirement of the maximum navigational speed under different relative wind direction angles. By utilizing the strategy for obtaining the sail attack angle of the target sailing boat at the maximum sailing speed, more reliable guarantee is provided for the unmanned sailing boat to stably sail at the maximum sailing speed in the expected sailing direction.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2(a) is a three-dimensional modeling diagram of a target sailboat of the present invention;

FIG. 2(b) is a schematic diagram of a controller structure of a target sailing boat in accordance with the present invention;

FIG. 3 is a force diagram of the sail of the present invention acting on a target sailboat;

FIG. 4 is a graph of the coefficient of force of the sail of the present invention as a function of angle of attack;

FIG. 5 is a graph of the force variation curve of the sail of the present invention

FIG. 6 shows the wind direction angle of 55 relative to the wind direction, C_XAnd C_YA curve graph varying with angle of attack;

FIG. 7 is a graph showing the relationship between the maximum sail thrust coefficient and the corresponding lateral thrust coefficient;

FIG. 8 is a coordinate system diagram of the sailboat motion of the present invention;

FIG. 9 is a simulation of a sailboat motion model of the present invention;

FIG. 10 is a graph of speed versus angle of attack for a 55 relative wind angle according to the present invention;

FIG. 11(a) is a graph showing the variation of the sail force of the ship with the relative wind direction angle of 55 degrees;

FIG. 11(b) is a graph showing the variation of the drift angle and rudder angle of a ship with a relative wind direction angle of 55 degrees;

FIG. 12(a) is a graph showing the variation of the speed of flight at a relative wind direction angle of 25 to 50 degrees;

FIG. 12(b) is a graph showing the variation of the speed of the wind in the range of 60 to 70 degrees relative to the wind direction according to the present invention;

FIG. 12(c) is a graph showing the variation of the speed of flight at a relative wind direction angle of 75 to 90 degrees according to the present invention;

FIG. 12(d) is a graph showing the variation of the relative wind direction angle of 95 to 115 with respect to the speed of the aircraft according to the present invention;

FIG. 12(e) is a graph showing the variation of the speed of flight at 120-125 deg. relative wind direction according to the present invention;

FIG. 12(f) is a graph showing the variation of the speed of flight at 120-135 degree relative wind direction according to the present invention;

FIG. 12(g) is a graph showing the variation of the relative wind direction angle of 150 to 165 DEG in the speed of the present invention;

FIG. 12(h) is a chart showing the variation of the speed of the wind of 170-180 degrees relative to the wind direction according to the present invention;

FIG. 13 is a graph illustrating control of the optimum angle of attack for different relative wind directions according to the present invention;

FIG. 14 is a graph of maximum speed for different relative wind directions according to the present invention;

FIG. 15 is a sailing track diagram of an unmanned sailing ship for a course-fixed sailing comparison test.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the present embodiment provides a method for determining a maximum sailing speed based on an attack angle of a sail of an unmanned sailing boat, including:

step 101, setting a target sailboat and parameters of the target sailboat; establishing a sailing ship model of the target sailing ship according to the parameters of the target sailing ship;

specifically, the present embodiment takes a catamaran as a target sailboat, as shown in fig. 2(a), which is a three-dimensional modeling diagram of the catamaran, and the main parameters of the target sailboat include: the length of the ship total length, the length of the ship vertical lines, the type width, the width of the single sheets, the sheet interval, the area of the wind sail, the chord length of the wind sail, the extension length of the rudder blade, the type depth, the full-load draught, the full-load displacement, the diamond coefficient, the square coefficient, the height of the wind sail, the camber of the wind sail and the chord length of the rudder blade. As shown in fig. 2(b), the target sailboat is provided with a wind condition sensor, which includes a wind direction sensor and a wind speed sensor, and is mounted on the target sailboat for measuring a relative wind direction angle and a relative wind speed. The controller sends an instruction to the sail rotating motor according to the wind condition signal to carry out sail rotating control; the attitude and position sensor measures information such as the ship bow direction, the transverse inclination angle, the longitude and latitude position and the like by using a Kalman filtering position fusion algorithm. And the controller sends an instruction to the steering engine according to the attitude and position signals of the sailing boat to carry out course control.

Step 102, setting different attack angles of the sails, and obtaining different lift coefficients and resistance coefficients according to the parameters of the target sailing boat; calculating to obtain the lift force and the resistance force under different attack angles of the sail according to the different lift force coefficients and the different resistance coefficients;

specifically, as shown in fig. 3, the bow direction is defined as the x-axis direction, and the ship starboard direction is defined as the y-axis direction. Theta is the relative wind direction angle of the sailing boat, defines the relative wind direction angle of the incoming wind in the direction of the bow as 0 degree, and increases the rotation in the anticlockwise direction, and the value range is 0-360 degrees. Alpha is the attack angle of the sail, which is the included angle between the middle section line of the sail and the relative wind direction, the sail rotates clockwise along the relative wind direction, the attack angle of the sail is positive, otherwiseIs negative. The angle of attack alpha of the sail is the lift coefficient C of the sail_LAnd sail resistance coefficient C_DIs determined.

According to the theory of the aerodynamic characteristics of the sail, when air flows through the airfoil cambered surface of the target sailing boat, after the sail is subjected to the wind action, the sail resistance F along the opposite wind direction is generated due to the viscous action of the air_DThe sail lift force F vertical to the relative wind direction is generated due to the pressure difference of the upper surface and the lower surface of the sail_L. The sail lift and drag are directly proportional to the air density, the sail area and half the square of the relative wind speed. Calculating lift force F according to dimensionless lift coefficient and drag coefficient_LAnd resistance F_DThe expression of (a) is:

in the formula, ρ_aIs the air density; s_WThe lateral projection area of the sail; v_aRelative wind speed; c_LIs the coefficient of lift; c_DIs the coefficient of resistance.

Low speed air flow is considered as an incompressible fluid, according to the sail aerodynamic characteristics theory, C_LAnd C_DOnly the angle of attack alpha of the sail is relevant and there is a one-to-one correspondence.

In the embodiment, a CFD technology is adopted to carry out numerical simulation on the aerodynamic performance of the target sailboat in a steady state, and a calculation domain and boundary conditions are adopted to carry out numerical simulation on the sail to calculate the lift coefficient and the resistance coefficient of the sail. The basic dimensions of the target sailboat of the sail are: the aspect ratio is 2.70, the camber ratio is 10.5%, and the chord length of the sail is 50 cm. The sail is assumed to be vertical to the horizontal plane and is a rigid wing sail, and does not generate elastic deformation under aerodynamic force. As shown in FIG. 4, the variation range of the attack angle is 0-90 degrees, and a working condition is calculated at intervals of 3 degrees. And calculating the lift coefficient and the resistance coefficient of the sail through numerical simulation.

103, obtaining a relative wind speed according to the set absolute wind speed and the set relative wind direction angle; inputting the relative wind speed, the lift force, the resistance, the lift force coefficient and the resistance coefficient into the sailing ship model, and calculating to obtain the boosting force, the side thrust, the boosting force coefficient and the side thrust coefficient;

specifically, as shown in FIG. 4, the sail lift F is adjusted_LAnd resistance F_DDecomposing to obtain the boosting force X along the course of the ship_WAnd a lateral thrust Y perpendicular to the course of the ship_WThe calculation expression is:

coefficient of lift of sail C_LAnd coefficient of resistance C_DDecomposing to obtain the boosting coefficient C along the ship course_XAnd a lateral thrust coefficient C perpendicular to the course of the ship_YThe calculation expression is:

in the formula, θ is a relative wind direction angle.

Since the target sailing boat in this embodiment is a symmetrical wing, the range of the relative wind direction angle is 0 to 180 °, the sail boost coefficient and the side thrust coefficient corresponding to different relative wind direction angles and different sail attack angles can be obtained by calculation through expressions (2) and (3) according to the curve of the sail acting force coefficient changing with the attack angle as shown in fig. 4, the interval of the relative wind direction angles of 5 ° is taken, and the fitting curve surface is shown in fig. 5. As can be seen from fig. 5, under different relative wind angles, the thrust coefficient and the lateral thrust coefficient of the sail increase first and then decrease with the increase of the angle of attack, but the stationing point and the change rate are different, which greatly affects the strategy of sailing the sail at the maximum sailing speed. The curve of the acting force variation curve of the sail shown in fig. 5 shows that the curve of the boosting coefficient of the sail and the curve of the side boosting coefficient of the sail along with the attack angle at the relative wind direction angle of 55 degrees can be obtained from the curve data of the acting force variation curve of the sail shown in fig. 7. As can be seen from FIG. 7, the thrust coefficient and the side thrust coefficient attack angle of the sail increase synchronously within the range of 0-15 degrees, the thrust coefficient attack angle of the sail does not change obviously within the range of 15-39 degrees, the maximum value is reached at 30 degrees, and the increase rate of the side thrust coefficient of the sail within the attack angle range is large. The maximum sail boost coefficient and the corresponding side thrust coefficient obtained under different relative wind direction angles can be obtained according to fig. 6, and a relation curve of the maximum sail boost coefficient and the corresponding side thrust coefficient as shown in fig. 7 is fitted. As can be seen from fig. 7, the maximum assist coefficient approaches zero or is smaller than zero when the relative wind direction angle is smaller than 25 °.

104, selecting a relative wind direction angle interval corresponding to the boosting coefficient larger than zero as a navigation area range of the target sailing ship; setting a desired course in the navigation area range, establishing a rudder stress model and setting a rudder angle to keep the sailing boat in the desired navigation direction;

specifically, as can be seen from fig. 7, the navigable area refers to a relative wind area where the target sailing boat can navigate with a fixed heading, and the windward ship changing operation is performed in the non-navigable area. As shown in FIG. 7, the maximum sail boost coefficient increases and then decreases as the relative wind direction angle increases. When the relative wind direction angle is in the range of 0-25 degrees, the maximum boosting coefficient of the sail approaches to or is less than zero, and the sailing boat cannot be propelled to sail, so that the relative wind direction angle is defined to be a navigable area in the range of 25-180 degrees. In the corresponding sail side thrust coefficient curve, a side thrust coefficient greater than 0 indicates that the sail side thrust direction points to the starboard of the ship, and a side thrust coefficient less than 0 indicates that the sail side thrust direction points to the port of the ship.

The rudder and the ship body have disturbance interference effect, and the rudder fluid power and moment relationship is as follows:

wherein, t_RThe derating coefficient is the derating coefficient of the ship body and the rudder; alpha is alpha_HAnd x_HThe interference coefficient of the ship body and the rudder is obtained; x is the number of_RThe vertical distance between the rudder and the center of gravity of the ship body; f_NIs the positive pressure of the rudder. Decrement coefficient t_RAnd interference coefficient alpha_HAnd x_HThe approximate calculation formula of (c) is:

rudder positive pressure F_NThe approximate calculation formula is:

wherein A is_RIs the rudder area; f. of_αThe slope of the lift coefficient of the rudder at an attack angle of 0 degrees is shown; u shape_RTaking actual ship speed as the effective speed flowing into the rudder; alpha is alpha_RIs the effective angle of attack of the rudder; lambda is the rudder aspect ratio; delta is a rudder angle of the ship; gamma is a rectification coefficient; beta is a_RThe drift angle is at the rudder; c_bDesigning a square coefficient for a ship; b is the width of the ship; l is the length of the ship; u, v are the speed of the vessel in the x, y directions, respectively.

And establishing an expression of a rudder stress model by combining the acting force borne by the sail as follows:

in the formula, delta is a rudder angle; alpha is alpha_RThe angle of attack of the rudder blade; rho is the density of the seawater; v_SIs the speed of the ship; l is_RThe rudder is long; d_RThe rudder width is adopted; c_Xδ、C_Yδ、C_NδRespectively is the thrust coefficient, the side thrust coefficient and the steering moment coefficient of the rudder blade, X_R、Y_R、N_RRespectively the rudder boosting force, the rudder side thrust and the rudder turning moment.

The rudder angle is set to keep the sailboat in the desired heading.

105, establishing a motion model and a motion coordinate system of the target sailing ship; inputting the absolute wind speed, the relative wind direction angle, the expected course, the boosting force and the side thrust into the motion model to obtain the speed, the rudder angle and the drift angle of the target sailing ship;

establishing motion coordinates of sailing boat, defining the motion coordinates for describing sailing boat navigationThe vessel coordinate system oxy plane and the global coordinate system o₀x₀y₀As shown in fig. 8, the three-degree-of-freedom motions of the ship include forward (ox direction), traverse (oy direction) and yaw (rotation in the ox plane) motions. The advancing speed of the ship is u, the transverse moving speed is v, and the initial rocking angular speed is r. The combined speed of u and V is sailing speed V_sThe bow direction ox and sailing speed V_sThe included angle beta of the ship is a ship drift angle, and the drift angle of the ship course along the counterclockwise direction of the bow is regulated to be positive. Direction ox of bow and coordinate system o along with ship₀x₀The included angle psi is the ship initial angle, and the ship initial angle is specified to be positive along the positive north and the clockwise direction. The ship rudder angle delta and the right rudder are defined to be positive. The marine true wind speed (absolute wind speed) at the position of the ship is V_tAbsolute wind direction angle of theta_tThe north-positive incoming wind is defined as 0 ° and the counterclockwise direction is positive. The relative wind speed of the ship is V by combining with the sailing speed analysis of the sailing ship_aAnd the relative wind direction angle of the ship is theta, the relative wind direction of the ship pointing to the bow is set to be 0 DEG, and the counter-time direction is positively increased.

Through analysis of sailing ship motion, a conversion relation between a global coordinate system and a ship-associated coordinate system is obtained

As shown in fig. 9, a three-degree-of-freedom motion model of the sailing ship is established by using a ship maneuvering separation (MMG) model method.

Wherein m is the total weight of the ship; i is_zzThe moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; j. the design is a square_zzThe additional moment of inertia of the sailing boat to the z axis under a boat-associated coordinate system; m is_XAnd m_YRespectively the additional mass in the advancing direction and the transverse moving direction under the ship-associated coordinate system; x_H、Y_H、N_HResistance and moment of resistance of the bare vessel; x_R、 Y_R、N_RFor ruddersForces and moments; x_S、Y_S、N_SThe auxiliary power of the sail, the side thrust of the sail and the turning moment of the sail are obtained.

And (4) calculating the force and the moment of the catamaran, and approximately estimating the viscous water power by adopting a noble island model.

Combining target sailing boat parameters, building a sailing boat motion control model platform after integrating a sailing boat model, a sailing boat motion model and a rudder stress model, as shown in fig. 9, the input quantities are absolute wind speed, a relative wind direction angle, an expected course, boosting force and side thrust, the output quantities are sailing boat speed, sailing boat acting force, a boat drift angle and a boat rudder angle when the sailing boat is in a balanced state, the input quantities are set to have the expected course of 0 degree, the real wind speed is 12m/s, the input relative wind direction angle is 25-180 degrees, 5 degrees are used as sampling intervals, the attack angle range is 3-90 degrees, and 3 degrees are used as sampling intervals. Corresponding boosting coefficient (C) when the relative wind direction angle is 55 degrees_X) And side thrust coefficient (C)_Y) Along with the change curve of the attack angle, the change of the thrust coefficient is not large within the range of the attack angle from 15 degrees to 39 degrees, and the attack angle is the largest when being 30 degrees. The corresponding side thrust coefficient increases at a greater rate.

Inputting an attack angle import model of 3-39 degrees, and calculating corresponding navigational speed, sail acting force, rudder angle and drift angle.

As shown in fig. 10, at a relative wind direction angle of 55 °, the sailing boat's speed rises first and then falls as the angle of attack increases. When the attack angle rises from 3 degrees to 15 degrees, the navigation speed rises from 2.61kn to 3.71kn, and the rising speed is high; the attack angle is 15 degrees and 18 degrees, and the difference of the navigational speeds is not large; when the angle of attack rises from 18 degrees to 33 degrees, the change of the navigational speed shows a small descending trend. When the attack angle is 36-39 degrees, the lateral force of the sail is relatively large, the bow cannot reach the expected course (i actual course angle-expected course angle i >1 degree) and no effective speed is output, so that the attack angle range is abandoned.

As shown in fig. 11(a), the sail boost increases with increasing angle of attack in the range of 3 ° to 30 °, and the boost decreases from 33 °. In the range of 3-33 degrees, the side thrust of the sail is continuously increased along with the increase of the attack angle. The attack angle is in the range of 3-15 degrees, the acceleration difference between the boosting force and the side thrust of the sail is not large, the attack angle is in the range of 15-30 degrees, the boosting force of the sail is accelerated and suddenly reduced, and the side thrust of the sail keeps accelerated and ascended. Over 30 deg., the sail boosting force begins to fall, and the sail side thrust acceleration also begins to fall.

As shown in fig. 11(b), in the range of 3 ° to 33 °, the drift angle increases with an increase in the angle of attack, and the rudder angle (± representative direction) increases with an increase in the angle of attack. And selecting the attack angle of 15 degrees or 18 degrees according to the maximum evaluation index of the navigational speed. When the attack angle is 18 degrees, the rudder angle is 14 degrees, the drift angle is 4 degrees, the boosting force of the sail is 78N, and the side thrust of the sail is 82N; when the attack angle is 15 degrees, the rudder angle is 11 degrees, the drift angle is 3 degrees, the boosting force of the sail is 77N, and the side thrust of the sail is 69N. The loads of the steering engine and the sail rotating motor are comprehensively considered, and the attack angle is selected to be 15 degrees.

As shown in fig. 12(a), (b), (c), (d), (e), (f), (g), and (h), other relative wind direction angles are divided into eight groups of 25 ° to 50 °, 60 ° to 70 °, 75 ° to 90 °, 95 ° to 115 °, 120 ° to 125 °, 130 ° to 145 °, 150 ° to 165 °, and 170 ° to 180 °, and according to the above method, the flight speed varies with the angle of attack at different wind direction angles, and the simulation calculation result does not output a value of an invalid velocity value. The relative wind direction angle is 25 degrees, and the corresponding attack angle is 9 degrees; the relative wind direction angle is within the range of 30-55 degrees, and the corresponding attack angle is 15 degrees; the relative wind direction angle is 60-70 degrees, and the corresponding attack angle is 21 degrees; the relative wind direction angle is 75-90 degrees, and the corresponding attack angle is 36 degrees; the relative wind direction angle is 95-115 degrees, and the corresponding attack angle is 45 degrees; the relative wind direction angle is 120-125 degrees, and the corresponding attack angle is 48 degrees; the relative wind direction angle is 130-145 degrees, and the corresponding attack angle is 54 degrees; the relative wind direction angle is 150-165 degrees, and the corresponding attack angle is 60 degrees; the relative wind direction angle is 170-180 degrees, and the corresponding attack angle is 69 degrees;

and matching the attack angle corresponding to the maximum navigational speed under different wind direction angles by taking the obtained curve as the basis of the optimal attack angle control strategy.

And 106, selecting the attack angle of the sail corresponding to the maximum sailing speed of the target sailing boat obtained through the motion model in the expected sailing direction.

Specifically, it can be seen from the above embodiments that, for a target sailing boat, the corresponding angle of attack at the maximum speed is selected within the range of the available relative wind direction angle. As shown in fig. 13, according to the adjacent attack angles, a linear interpolation method is used for fitting to obtain an optimal sail attack angle control strategy curve at the maximum speed within the navigable area.

The speed corresponding to the optimum sail attack angle is shown in fig. 14, the relative wind direction angle is in the range of 25 degrees to 110 degrees, the maximum speed of the sailing boat is increased along with the increase of the relative wind direction angle, and when the relative wind direction angle is 110 degrees, the speed reaches the maximum 4.02 kn. The relative wind direction angle is in the range of 110-180 degrees, and the maximum sailing speed of the sailing boat is reduced along with the increase of the relative wind direction angle.

In the embodiment, the variable-parameter PID automatic steering system is adopted for adjustment, the sailing boat controls the heading of the bow through a rudder, and the ship steering control system adjusts the steering angle in real time to keep the actual heading of the sailing boat consistent with the expected heading. The input variable of the PID controller is a difference e between an expected course angle and an actual course angle_ψThe output variable of the controller is the commanded rudder angle. The expression of the control law of the controller is as follows:

wherein, K_p、K_d、K_iPID control proportion coefficient, differential coefficient and integral coefficient; delta is an output steering angle, and the steering angle is controlled within a range of-35 degrees to 35 degrees according to steering experience. In order to enhance the response sensitivity and the control precision of the controller at different sailing speeds, the PID controller parameters are set by adopting a variable parameter method, and the variable parameter PID controller is designed to ensure that the unmanned sailing boat has better course keeping capability under different sailing working conditions.

The fixed course navigation contrast test under the cruising condition:

as shown in fig. 15, the expected course angle is 90 °, the distance from the starting point S to the target point G is 110m, the unmanned sailing boat adopts the control strategy of the present invention, the sailing time is 101S, and the average sailing speed is 1.089 m/S; the sailing time of the unmanned sailing boat is 117s and the average speed is 0.940m/s by adopting a conventional control strategy. The control strategy of the invention can reduce the sailing time of the unmanned sailing boat by 16s and improve the average sailing speed by 15.8 percent.

The course-fixed navigation analysis method is used for analyzing according to the expected course angle of 90 degrees, and the test results are shown in the table 1:

TABLE 1

The test result shows that compared with the conventional control strategy, the control strategy of the invention has the advantages that the average navigational speed is improved by more than 4.9 percent, and the average navigational speed can be improved by 17.7 percent to the maximum extent. Therefore, under the cruising working condition, the control strategy of the invention has better applicability.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.