Dynamic positioning ship obstacle avoidance control method based on obstacle avoidance function

Abstract

A dynamic positioning ship obstacle avoidance control method based on an obstacle avoidance function comprises the steps that firstly, actual pose and speed information of a ship is collected through a sensor, and an extended state observer is used for estimating the linear speed, the yaw rate and unknown uncertainty and interference based on the information and control input; secondly, designing an obstacle avoidance function combining an artificial potential energy function and an obstacle avoidance reference angle, and introducing the obstacle avoidance function as a vector into the design process of the controller; and finally, introducing an additional auxiliary dynamic variable. According to the method, dynamic positioning ship obstacle avoidance control, artificial potential field function and obstacle avoidance reference angle combination can be executed under input saturation, the safety distance between a ship and an obstacle is guaranteed, meanwhile, dependence of a ship heading propeller and energy consumption of frequent steering actions are reduced, the posture of the ship better conforms to engineering practical application, and the ship obstacle avoidance control method is suitable for engineering application. The combination of the two drives the ship to generate a smooth obstacle avoidance track.

Description

Technical Field

[0001] The invention relates to the technical field of ship motion control, in particular to an obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function. Background Art

[0002] The artificial potential field function method is widely used in the obstacle avoidance behavior of dynamically positioned ships because of its simplicity and ease of construction. However, the traditional artificial potential field function method relies on generating a repulsive field around obstacles, which makes the state of the ship difficult to control and does not conform to the actual specific marine operations. In addition, due to the change in the size of the repulsive force, it is difficult for dynamically positioned ships to track the expected path well. Secondly, it is worth noting that dynamically positioned ships mainly rely on bow thrusters to force the ship to turn, and frequent turning actions are bound to cause a waste of resources.

[0003] Therefore, from a practical point of view, it is necessary to study a novel obstacle avoidance function for dynamically positioned ships. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a dynamic positioning ship obstacle avoidance control method based on obstacle avoidance function, which can perform dynamic positioning ship obstacle avoidance control under the premise of input saturation, ensure the safe distance between the ship and the obstacle, and reduce the dependence on the ship's bow thruster and the energy consumption of frequent steering actions.

[0005] The technical problem to be solved by the present invention is achieved by the following technical solutions. The present invention is a dynamic positioning ship obstacle avoidance control method based on obstacle avoidance function, the method comprises:

[0006] Firstly, the actual position and velocity information of the ship is collected through sensors, and the extended state observer is used to estimate the linear velocity, yaw rate, and unknown uncertainties and disturbances based on this information and control input.

[0007] Secondly, an obstacle avoidance function combining artificial potential energy function and obstacle avoidance reference angle is designed and introduced into the controller design process as a vector.

[0008] Finally, an additional auxiliary dynamic variable is introduced.

[0009] The technical problem to be solved by the present invention can also be further achieved by the following technical solutions. For the above-mentioned obstacle avoidance control method for dynamically positioned ships based on obstacle avoidance function, the extended state observer is designed as follows:

[0010]

[0011]

[0012]

[0013] In the formula

[0014] Expressed as the estimated state of x,y,ψ,u,v,r,ζ1,ζ2,ζ3, Represented as the gain matrix of the observer;

[0015] The error dynamics of the observer is expressed as:

[0016]

[0017] in

[0018]

[0019] It is expressed as the estimation error;

[0020]

[0021] The technical problem to be solved by the present invention can also be further achieved by the following technical solutions. For the above-mentioned obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function, the obstacle avoidance function is designed as follows:

[0022]

[0023] Among them, α c is a positive constant, p0 is the center of the obstacle, ρ v is the distance between the ship and the obstacle, Indicates the collision avoidance range relative to obstacles;

[0024] The obstacle avoidance angle is designed as:

[0025] The desired ship obstacle avoidance heading angle is:

[0026]

[0027] in, is the heading angle of the edge of the extended sight cone;

[0028]

[0029]

[0030] ψ o is the navigation angle of the obstacle, U b is the current ship speed;

[0031] The sight cone expands by α in the positive and negative directions respectively. o angle, and define the candidate obstacle avoidance heading reference as

[0032]

[0033] When the obstacle or DP vessel is moving, each side of the expanded sight cone rotates around the center of the obstacle, ensuring that the line of sight always remains around the obstacle or DP vessel and accurately perceives its direction of movement.

[0034] The technical problem to be solved by the present invention can also be further achieved by the following technical solutions. For the above-mentioned obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function, the dynamic and kinematic models of the dynamically positioned ship are designed as follows:

[0035]

[0036]

[0037] Where: η=[x,y,ψ] T is the ground-fixed coordinate system X E O E Y E The position and yaw angle vector under; R(ψ) is represented by the rotation matrix

[0038]

[0039] υ=[u,v,r] T is in the vector coordinate system X B O B Y B Below, they are respectively expressed as longitudinal velocity u, lateral velocity v, and angular velocity r; M = diag[m 11 ,m 22 ,m 33 ] is the inertia matrix; ζ is the disturbance containing the fluid dynamic damping parameters and time-varying; τ i =[τ u ,τ v ,τ r ] T is the inclusion of τ u , τ v , τ r The input signal.

[0040] The technical problem to be solved by the present invention can also be further achieved by the following technical solutions. For the above-mentioned dynamic positioning ship obstacle avoidance control method based on obstacle avoidance function, the controller using the backstepping method is designed as follows:

[0041] The first step is to define the first tracking error as:

[0042] p1=η-η d -η o

[0043] in, ψ fdca is defined as follows:

[0044]

[0045] Select α as the virtual control input, and the kinematic control law is designed as

[0046]

[0047] Where K1 is a positive constant;

[0048] The second step is to define the second error vector as:

[0049]

[0050] in is used to avoid calculating the derivative of α;

[0051] The third step, β, used to handle input saturation, is defined as:

[0052]

[0053] Where K2 is a positive constant,

[0054] To stabilize p2, the dynamic control law is designed as

[0055]

[0056] Where K3 is a positive constant, first-order filter is introduced to replace the time derivative of α.

[0057] Compared with the prior art, the present invention provides a dynamic positioning ship obstacle avoidance control method based on obstacle avoidance function, which can perform dynamic positioning ship obstacle avoidance control under the premise of input saturation, and combines the artificial potential field function with the obstacle avoidance reference angle to ensure the safe distance between the ship and the obstacle, while reducing the dependence on the ship's bow thruster and the energy consumption of frequent turning actions. Secondly, the ship's posture is more in line with actual engineering applications. The combination of the two drives the ship to generate a smooth obstacle avoidance trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A model diagram of a dynamic positioning vessel of the present invention;

[0059] Figure 2The obstacle avoidance effect of the static obstacle of the present invention Figure 1 ;

[0060] Figure 3 The obstacle avoidance effect of the static obstacle of the present invention Figure 2 ;

[0061] Figure 4 The obstacle avoidance effect of the dynamic obstacle of the present invention Figure 1 ;

[0062] Figure 5 The obstacle avoidance effect of the dynamic obstacle of the present invention Figure 2 . DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0064] An obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function is proposed. The method is based on the consideration of actuator input saturation. Firstly, the actual position and velocity information of the ship is collected through sensors such as GPS, and the extended state observer is used to estimate the linear velocity, yaw rate, and unknown uncertainty and interference based on this information and control input.

[0065] Secondly, an obstacle avoidance function combining artificial potential energy function and obstacle avoidance reference angle is designed and introduced as a vector into the controller design process. The artificial potential energy function ensures the safe distance between the ship and the obstacle, while the obstacle avoidance reference angle is a heading angle that can achieve auxiliary obstacle avoidance and ensure the ship's posture when performing obstacle avoidance operations.

[0066] Finally, in order to deal with the input saturation problem, an additional auxiliary dynamic variable is introduced. The advantage is that the input saturation problem of the actuator is taken into account, which is more suitable for practical engineering applications. The design of the obstacle avoidance function reduces the energy waste caused by the frequent turning actions of the bow thruster when the dynamic positioning ship performs obstacle avoidance operations, as well as the problem of difficult control of the ship's attitude, which is more suitable for specific offshore engineering operations.

[0067] Specifically include:

[0068] (1) Observer design

[0069] An extended state observer is designed as follows to recover the uncertainty and disturbance of the model:

[0070]

[0071]

[0072] It is represented as the estimated state of x,y,ψ,u,v,r,ζ1,ζ2ζ3. It is represented as the gain matrix of the observer.

[0073] The error dynamics of the observer is expressed as:

[0074]

[0075]

[0076] in

[0077]

[0078] It is expressed as the estimation error;

[0079]

[0080] (2) Obstacle avoidance function design

[0081] The artificial potential field function obstacle avoidance method is introduced to ensure a safe distance between the ship and obstacles:

[0082]

[0083] Among them, α c is a positive constant, p0 is the center of the obstacle, ρ v is the distance between the ship and the obstacle, Indicates the collision avoidance range relative to obstacles.

[0084] (2.1) Obstacle avoidance angle design

[0085] The desired ship obstacle avoidance heading angle is:

[0086]

[0087] in, is the heading angle of the edge of the extended sight cone;

[0088]

[0089]

[0090] ψ ois the navigation angle of the obstacle, U b is the current ship speed;

[0091] The sight cone expands by α in the positive and negative directions respectively. o angle, and define the candidate obstacle avoidance heading reference as

[0092]

[0093] When the obstacle or DP vessel is moving, each side of the expanded sight cone rotates around the center of the obstacle to ensure that the line of sight always remains around the obstacle or DP vessel and accurately perceives its direction of movement.

[0094] (3) The dynamic and kinematic models of the dynamically positioned vessel are designed as follows:

[0095]

[0096]

[0097] Where: η=[x,y,ψ] T is the ground-fixed coordinate system X E O E Y E The position and yaw angle vector under; R(ψ) is represented by the rotation matrix

[0098]

[0099] υ=[u,v,r] T is in the vector coordinate system X B O B Y B Below, they are respectively expressed as longitudinal velocity u, lateral velocity v, and angular velocity r; M = diag[m 11 ,m 22 ,m 33 ] is the inertia matrix; ζ is the disturbance containing the fluid dynamic damping parameters and time-varying; τ i =[τ u ,τ v ,τ r ] T is the inclusion of τ u , τ v , τ r The input signal.

[0100] (4) The controller design using the backstepping method is as follows:

[0101] Define the first tracking error as follows:

[0102] p1=η-η d -η o

[0103]

[0104] in, ψ fdca is defined as follows:

[0105]

[0106] Select Lyapunov as follows

[0107]

[0108] Lyapunov's time derivative is definition in, It is used to avoid calculating the derivative of α, and a filter is introduced to replace the time derivative of α.

[0109]

[0110] Where β is used to process the input packet and is defined as:

[0111]

[0112]

[0113] Define the second Lyapunov as:

[0114] The time derivative is

[0115]

[0116] After sorting, you can get

[0117]

[0118] definition:

[0119] The derivative with respect to time is:

[0120]

[0121] Using Young's inequality, we can get:

[0122]

[0123] in, Arranging the above formulas, we can get:

[0124]

[0125] in, So there is The proof is complete.

[0126] The obstacle avoidance effect of the present invention on static obstacles is as follows: Figure 2-3 :

[0127] like Figure 2 As shown, the coordinate system in the figure is a two-dimensional rectangular coordinate system, the horizontal axis represents the horizontal direction, the vertical axis represents the vertical direction, the blue track is the expected path, and the red track is the actual path. It is not difficult to see from the figure that the dynamic positioning ship can detect the existence of obstacles and achieve good obstacle avoidance effect when it is close to the obstacles, and the obstacle avoidance effect is more radical;

[0128] Figure 3 The thrust components of a dynamically positioned ship and the magnitude of the yaw moment are shown. From this figure, it can be seen that the force of each thruster is well controlled within the constraints, successfully avoiding the input saturation problem of the controller.

[0129] To further verify the superiority of the proposed obstacle avoidance method, the obstacle avoidance effect of the present invention on dynamic obstacles is as follows: Figure 4-5 ;

[0130] Figure 4 The following figure shows the encounter between the ship and the obstacle. At t = 5s, the obstacle is on the left side of the ship and does not enter the monitoring range of the ship. The ship keeps tracking the expected track. At t = 30s and t＝40 sThe ship detects the obstacle and starts to avoid it, sailing away from the right side of the obstacle. At t = 80s, the ship successfully avoids the moving obstacle and tracks it according to the expected trajectory;

[0131] Figure 4 The simulation results verify that the proposed method can achieve a relatively aggressive obstacle avoidance effect even when the obstacle is moving, and maintain good trajectory tracking ability after avoiding the obstacle;

[0132] Figure 5 This is the thrust diagram of a dynamically positioned vessel in the presence of a moving obstacle. It can be seen from the diagram that the force of each thruster does not exceed the limit.

[0133] The advantage of the obstacle avoidance function algorithm proposed in the present invention is that it can perform obstacle avoidance control of a dynamically positioned ship under input saturation. The combination of the artificial potential field function and the obstacle avoidance reference angle ensures a safe distance between the ship and obstacles while reducing the reliance on the bow thruster of the ship and the energy consumption of frequent steering actions. In addition, the ship's posture is more in line with practical engineering applications. The combination of the two drives the ship to generate a smooth obstacle avoidance trajectory.

Claims

1. A method for dynamically positioned ship obstacle avoidance control based on obstacle avoidance function, characterized in that: The method includes Firstly, the actual position and velocity information of the ship is collected through sensors, and the extended state observer is used to estimate the linear velocity, yaw rate, and unknown uncertainties and disturbances based on this information and control input. Secondly, an obstacle avoidance function combining artificial potential energy function and obstacle avoidance reference angle is designed and introduced into the controller design process as a vector. Finally, an additional auxiliary dynamic variable is introduced.

2. The obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function according to claim 1, characterized in that: The extended state observer is designed as follows: In the formula Expressed as the estimated state of x,y,ψ,u,v,r,ζ1,ζ2,ζ3, Represented as the gain matrix of the observer; The error dynamics of the observer is expressed as: in It is expressed as the estimation error; 3. The obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function according to claim 1, characterized in that: The obstacle avoidance function is designed as follows: Among them, α c is a positive constant, p0 is the center of the obstacle, ρ v is the distance between the ship and the obstacle, Indicates the collision avoidance range relative to obstacles; The obstacle avoidance angle is designed as: The desired ship obstacle avoidance heading angle is: in, is the heading angle of the edge of the extended sight cone; ψ o is the navigation angle of the obstacle, U b is the current ship speed; The sight cone expands by α in the positive and negative directions respectively. o angle, and define the candidate obstacle avoidance heading reference as When the obstacle or DP vessel is moving, each side of the expanded sight cone rotates around the center of the obstacle, ensuring that the line of sight always remains around the obstacle or DP vessel and accurately perceives its direction of movement.

4. The obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function according to claim 1, characterized in that: The dynamic and kinematic models of the dynamically positioned vessel are designed as follows: Where: η=[x,y,ψ] T is the ground-fixed coordinate system X E O E Y E The position and yaw angle vector under; R(ψ) is represented by the rotation matrix υ=[u,v,r] T is in the vector coordinate system X B O B Y B Below, they are respectively expressed as longitudinal velocity u, lateral velocity v, and angular velocity r; M = diag[m 11 ,m 22 ,m 33 ] is the inertia matrix; ζ is the disturbance containing the fluid dynamic damping parameters and time-varying; τ i =[τ u ,τ v ,τ r ] T is the inclusion of τ u , τ v , τ r The input signal.

5. The obstacle avoidance control method for a dynamically positioned ship based on an obstacle avoidance function according to claim 1, characterized in that: The controller design using the backstepping method is as follows: The first step is to define the first tracking error as: p1=n-n d -or o in, ψ fdca is defined as follows: Select α as the virtual control input, and the kinematic control law is designed as Where K1 is a positive constant; The second step is to define the second error vector as: in is used to avoid calculating the derivative of α; The third step, β, used to handle input saturation, is defined as: Where K2 is a positive constant, To stabilize p2, the dynamic control law is designed as Where K3 is a positive constant, first-order filter is introduced to replace the time derivative of α.

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