Underwater glider attitude control method and system

Abstract

The invention discloses an underwater glider attitude control method and system, and belongs to the technical field of AUVs, and the control method comprises the steps: S1, building a kinetic model based on a coordinate transformation relation, a Newton-Euler equation and a kinetic energy theorem; s2, on the basis of the dynamic model, a preset performance controller is designed through a backstepping method, and high-precision control over the pitching motion of the underwater glider is achieved.The underwater glider dynamic model with the three degrees of freedom is established, the particularity of the pitching motion of the underwater glider is considered, a periodic performance function is introduced, and the performance of the underwater glider is improved. A self-adaptive preset performance controller is designed for the body speed and the pitch angle of the underwater glider, the dynamic performance and the steady-state performance of the underwater glider in the angle switching process are considered, and the posture and the speed of the underwater glider are controlled within a preset range.

Description

Technical Field

[0001] The present invention belongs to the technical field of AUVs, and in particular relates to an underwater glider attitude control method and system. Background Art

[0002] An underwater glider is an unmanned underwater vehicle (UUV) that glides underwater by changing its buoyancy and hydrodynamic properties. The main features of an underwater glider include: Energy saving: relying on the change of gravity and buoyancy for propulsion, no conventional thrusters are required; Efficient: continuous observation and data collection can be performed over a long period of time; Stability: Stable gliding for long periods of time underwater.

[0003] Pitch motion is the most common motion mode of underwater gliders, which causes underwater gliders to complete long-distance sawtooth profile gliding motion in the vertical plane. The pitch attitude motion control performance directly determines the stability of underwater gliders gliding in the vertical plane, while traditional control methods mainly focus on the performance of the system in a steady state. It is difficult to ensure good dynamic performance and steady-state performance at the same time, and there are certain limitations. Actual ocean observation operations require not only that underwater gliders can maintain good stable navigation, but also have the ability to respond to rapid motion state conversion. Based on this, the present invention designs an underwater glider attitude control method and system to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to design an underwater glider attitude control method and system, taking into account the navigation stability of the underwater glider in profile motion and the rapid response performance during state switching.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for controlling an underwater glider's attitude, the method comprising: S1: Establish a dynamic model based on coordinate transformation relations, Newton-Euler equations and kinetic energy theorem; S2: Based on the dynamic model, the preset performance controller is designed using the backstepping method to achieve high-precision control of the pitch motion of the underwater glider.

[0006] As a further description of the above technical solution: The S1 includes: S101: Construct the basic dynamics model of underwater glider based on coordinate transformation relationship, Newton-Euler equation and kinetic energy theorem; S102: Simplifying the basic kinetic model according to the assumed conditions to obtain a final kinetic model.

[0007] As a further description of the above technical solution: The S101 includes: S101-1: To facilitate the description of the motion state of the underwater glider, an inertial coordinate system is established. , fluid coordinate system and body coordinate system ; Since the inertial coordinate system of the underwater glider can be transformed into the body coordinate system through the rotation matrix composed of the attitude angle, the transformation from the fluid coordinate system to the body coordinate system is realized through the rotation matrix composed of the angle of attack and the sideslip angle. The angle of attack and the sideslip angle are defined as: ; ; Therefore, the following relationship exists: ; in, , and are the velocities in three directions in the glider body coordinate system, is the inertial coordinate system, is the body coordinate system, is the fluid coordinate system; ; S101-2: Define the generalized momentum of an underwater glider in an inertial frame , is the momentum of the underwater glider in the inertial coordinate system, is the angular momentum of the underwater glider in the inertial system. According to the Newton-Euler equation, the force and torque on the underwater glider can be expressed as: ; in, is the gravitational acceleration, k is the unidirectional vector in the z-axis direction, and are the forces and moments acting on the underwater glider by the external environment, For the quality of the drained water, They are the masses of the hull, attitude adjustment system, and buoyancy adjustment system. They are the positions of the shell, attitude adjustment system, and buoyancy adjustment system in the inertial coordinate system; ; in, is the position of the slider in the direction of the machine body axis, express In the body coordinate system The angle of rotation of the axis, express The eccentricity of Define the generalized momentum in the body coordinate system , is the momentum of the underwater glider in the body coordinate system, is the angular momentum of the underwater glider system. The generalized momentum in the inertial system and the generalized momentum in the body coordinate system have the following conversion relationship: ; Generalized Momentum Taking the derivative with respect to time, we get: ; Finally, the generalized force and torque expressions in the body coordinate system can be derived: ; in, and is the viscous hydrodynamic term, is the position of the underwater glider in the inertial system, is the angular velocity vector, is the velocity vector, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, represents the longitudinal velocity of the machine system, is the rolling angular velocity, represents the pitch angular velocity, represents the yaw angular velocity; S101-3: The total kinetic energy of the underwater glider system includes the kinetic energy of the shell, the kinetic energy of the attitude control system, the kinetic energy of the buoyancy control system and the kinetic energy of the additional mass. Therefore, according to the kinetic energy theorem, the kinetic energy of the underwater glider system can be expressed as: ; ; Among them, the additional mass matrix , represents the additional moment of inertia matrix, Represent the additional moment of inertia matrices of the shell, attitude control system, and buoyancy control system, respectively. , for The identity matrix of The generalized momentum of the underwater glider system in the body coordinate system can be expressed as Taking partial derivatives we get: ; Generalized momentum in the body coordinate system Taking the derivative and ignoring the small coupling terms, we finally get the equation of motion for the underwater glider as follows: ; in, and According to the kinetic energy theorem, and The expressions composed of .

[0008] As a further description of the above technical solution: The inertial coordinate system is a fixed reference system with the initial position of the underwater glider as the origin. The position of the geometric center of the glider in the inertial coordinate system is expressed as , in the inertial coordinate system, Newton's laws of motion hold true and are used to describe the position and attitude of the glider on the earth.

[0009] As a further description of the above technical solution: The body coordinate system is a coordinate system fixed to the underwater glider body, with the center of mass of the glider as the origin, and the coordinate axis moves with the movement of the glider. The velocity and angular velocity of the underwater glider in the body coordinate system are defined as and ,in, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, Indicates the longitudinal velocity of the machine system. is the rolling angular velocity, represents the pitch angular velocity, Represents the yaw angular velocity.

[0010] As a further description of the above technical solution: The fluid coordinate system is a reference system relative to the fluid and is used to describe the motion of the glider relative to the fluid.

[0011] As a further description of the above technical solution: The S102 includes: S102-1: Define the attitude angle of the underwater glider ,in, is the roll angle, is the pitch angle, is the yaw angle. Considering the pitch motion of the underwater glider in the vertical plane, the roll angle, yaw angle, roll angular velocity and yaw angular velocity of the glider are very small, so it is assumed that , , , , while considering the velocity of the underwater glider in the body coordinate system during the vertical plane movement and is small, so we assume , , ignoring the small coupling terms, under the above assumptions, the motion equations of the underwater glider are simplified, and finally the three-degree-of-freedom kinematic model of the underwater glider is established as follows: ; in, are the mass of the oil bag and the mass of the slider respectively, The position of the oil bag and the slider under the machine system. For the additional mass, is the additional moment of inertia, is the hydrodynamic parameter, is the control input, is the gravitational acceleration, taking into account the pitch angle The gliding efficiency of the underwater glider and the forward speed of the underwater glider are related to the pitch angle. and speed as a control target.

[0012] As a further description of the above technical solution: The S2 includes: S201: Considering the particularity of the pitch motion of the underwater glider, a new performance function is designed that is periodic and does not need to consider the initial state of the system. It is expressed as follows: ; in, represents the motion cycle of the underwater glider, represents the rate of decline of the performance function, The initial state used to constrain the performance function exists , Used to constrain the final value of the performance function, there is ; S202: Define tracking error , since the control objective of the tracking error is an inequality constraint, it is not convenient for controller design, so a nonlinear function error conversion function is introduced as follows: ; Among them, the conversion function satisfy ,and is a monotonically increasing function; S203: To ensure high-precision control of the underwater glider system, the tracking error satisfies the inequality constraint of the performance function , so the inequality constraints and nonlinear conversion functions can be mapped to obtain the conversion error of the system as follows: ; in, , Represents the conversion error of the system. Bounded Time satisfy , which ensures that the tracking error satisfies the inequality constraint of the performance function , used for high-precision control of underwater glider systems; S204: Design a preset performance controller based on the kinematic equations of the underwater glider and the backstepping method to ensure the conversion error of the system First, set the tracking value of the conversion error , respectively for velocity and pitch angle Perform controller design and define conversion error Tracking error , introduce virtual control quantity as follows: ; in, , represents preset performance controller parameters; Through the control input Virtual Control Quantity Tracking, , get the control input as follows: ; in, Represents preset performance controller parameters: ; S205: According to the kinematic equation analysis, the input of the underwater glider There is coupling, Separate controller design methods can achieve decoupling and define the conversion error Tracking error , introduce virtual control quantity as follows: ; in, , represents preset performance controller parameters; In order to further solve the control signal , introduce virtual control quantity right Tracking and defining virtual control quantities as follows: ; in, , , represents preset performance controller parameters; Finally, by controlling the input Virtual Control Quantity Tracking, , get the control input as follows: ; in, represents preset performance controller parameters; .

[0013] An underwater glider attitude control system, the system comprising a power model building module and a controller module; Dynamic model building module, used to build dynamic models based on coordinate transformation relations, Newton-Euler equations, and kinetic energy theorem; The controller module is used to design a preset performance controller, build an attitude controller using the backstepping method, obtain a control signal based on the measurable output signal, and complete high-precision control of the pitch motion of the underwater glider through the control signal.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: In the present invention, starting from the principle of underwater glider pitching motion, a three-degree-of-freedom underwater glider dynamics model is established. Taking into account the particularity of the underwater glider pitching motion, a periodic performance function is introduced. Aiming at the body speed and pitch angle control of the underwater glider, an adaptive preset performance controller is designed, which takes into account the dynamic performance and steady-state performance of the underwater glider's angle switching process, and its attitude and speed are controlled within a preset range. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the positional relationship structure of an underwater glider attitude control method and system proposed by the present invention; Figure 2 A control system structure diagram of an underwater glider attitude control method and system proposed by the present invention; Figure 3 A comparison diagram of the pitch angle error of the underwater glider in different control modes according to the third embodiment of the present invention; Figure 4 A comparison diagram of the speed error of the underwater glider in different control modes according to the third embodiment of the present invention; Figure 5 A comparison diagram of the pitch angles of the underwater glider in different control modes according to the third embodiment of the present invention; Figure 6This is a comparison diagram of the speed of the underwater glider in different control modes according to the third embodiment of the present invention; Figure 7 This is a comparison diagram of the pitch angles of the underwater glider in different control modes during periodic pitching motion according to the third embodiment of the present invention; Figure 8 This is a comparison diagram of the speed of the underwater glider in the periodic pitching motion under different control modes according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0017] Embodiment 1 The present invention provides a technical solution: a method for controlling the attitude of an underwater glider, the control method comprising: S1: Establish a dynamic model based on coordinate transformation relations, Newton-Euler equations and kinetic energy theorem; S2: Based on the dynamic model, the preset performance controller is designed using the backstepping method to achieve high-precision control of the pitch motion of the underwater glider.

[0018] Specifically, Figure 1 As shown, S1 includes: S101: Construct the basic dynamics model of underwater glider based on coordinate transformation relationship, Newton-Euler equation and kinetic energy theorem; S102: Simplifying the basic kinetic model according to the assumed conditions to obtain a final kinetic model.

[0019] Specifically, Figure 1 As shown, S101 includes: S101-1: To facilitate the description of the motion state of the underwater glider, an inertial coordinate system is established. , fluid coordinate system and body coordinate system ; Since the inertial coordinate system of the underwater glider can be transformed into the body coordinate system through the rotation matrix composed of the attitude angle, the transformation from the fluid coordinate system to the body coordinate system is realized through the rotation matrix composed of the angle of attack and the sideslip angle. The angle of attack and the sideslip angle are defined as: ; ; Therefore, the following relationship exists: ; in, , and are the velocities in three directions in the glider body coordinate system, is the inertial coordinate system, is the body coordinate system, is the fluid coordinate system; ; S101-2: Define the generalized momentum of an underwater glider in an inertial frame According to the Newton-Euler equation, the forces and moments on the underwater glider can be expressed as: ; in, is the gravitational acceleration, k is the unidirectional vector in the z-axis direction, and are the forces and moments acting on the underwater glider by the external environment, For the quality of the drained water, They are the masses of the hull, attitude adjustment system, and buoyancy adjustment system. They are the positions of the shell, attitude adjustment system, and buoyancy adjustment system in the inertial coordinate system; ; in, is the position of the slider in the direction of the machine body axis, express In the body coordinate system The angle of rotation of the axis, express The eccentricity of Define the generalized momentum in the body coordinate system , the generalized momentum in the inertial system and the generalized momentum in the body coordinate system have the following conversion relationship: ; Generalized Momentum Taking the derivative with respect to time, we get: ; Finally, the generalized force and torque expressions in the body coordinate system can be derived: ; in, and is the viscous hydrodynamic term, is the position of the underwater glider in the inertial system, is the angular velocity vector, is the velocity vector, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, represents the longitudinal velocity of the machine system, is the rolling angular velocity, represents the pitch angular velocity, represents the yaw angular velocity; S101-3: The total kinetic energy of the underwater glider system includes the kinetic energy of the shell, the kinetic energy of the attitude control system, the kinetic energy of the buoyancy control system and the kinetic energy of the additional mass. Therefore, according to the kinetic energy theorem, the kinetic energy of the underwater glider system can be expressed as: ; ; Among them, the additional mass matrix , represents the additional moment of inertia matrix, Represent the additional moment of inertia matrices of the shell, attitude control system, and buoyancy control system, respectively. , for The identity matrix of The generalized momentum of the underwater glider system in the body coordinate system can be expressed as Taking partial derivatives we get: ; Generalized momentum in the body coordinate system Taking the derivative and ignoring the small coupling terms, we finally get the equation of motion for the underwater glider as follows: ; in, and According to the kinetic energy theorem, and The expressions composed of .

[0020] As a further description of the above technical solution: The inertial coordinate system is a fixed reference system with the initial position of the underwater glider as the origin. The position of the geometric center of the glider in the inertial coordinate system is expressed as , in the inertial coordinate system, Newton's laws of motion hold true and are used to describe the position and attitude of the glider on the earth.

[0021] Specifically, Figure 1 As shown in the figure, the body coordinate system is a coordinate system fixed to the underwater glider body, with the center of mass of the glider as the origin, and the coordinate axis moves with the movement of the glider. The velocity and angular velocity of the underwater glider in the body coordinate system are defined as and ,in, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, Indicates the longitudinal velocity of the machine system. is the rolling angular velocity, represents the pitch angular velocity, Represents the yaw angular velocity.

[0022] Specifically, Figure 1 As shown, the fluid coordinate system is a reference system relative to the fluid and is used to describe the motion of the glider relative to the fluid.

[0023] Specifically, Figure 1 As shown, S102 includes: S102-1: Define the attitude angle of the underwater glider ,in, is the roll angle, is the pitch angle, is the yaw angle. Considering the pitch motion of the underwater glider in the vertical plane, the roll angle, yaw angle, roll angular velocity and yaw angular velocity of the glider are very small, so it is assumed that , , , , while considering the velocity of the underwater glider in the body coordinate system during the vertical plane movement and is small, so we assume , , ignoring the small coupling terms, under the above assumptions, the motion equations of the underwater glider are simplified, and finally the three-degree-of-freedom kinematic model of the underwater glider is established as follows: ; in, are the mass of the oil bag and the mass of the slider respectively, The position of the oil bag and the slider under the machine system. For the additional mass, is the additional moment of inertia, is the hydrodynamic parameter, is the control input, is the gravitational acceleration, taking into account the pitch angle The gliding efficiency of the underwater glider and the forward speed of the underwater glider are related to the pitch angle. and speed as a control target.

[0024] Specifically, Figure 2 As shown, S2 includes: S201: Considering the particularity of the pitch motion of the underwater glider, a new performance function is designed that is periodic and does not need to consider the initial state of the system. It is expressed as follows: ; in, represents the motion cycle of the underwater glider, represents the rate of decline of the performance function, The initial state used to constrain the performance function exists , Used to constrain the final value of the performance function, there is ; S202: Define tracking error , since the control objective of the tracking error is an inequality constraint, it is not convenient for controller design, so a nonlinear function error conversion function is introduced as follows: ; Among them, the conversion function satisfy ,and is a monotonically increasing function; S203: To ensure high-precision control of the underwater glider system, the tracking error satisfies the inequality constraint of the performance function , so the inequality constraints and nonlinear conversion functions can be mapped to obtain the conversion error of the system as follows: ; in, , Represents the conversion error of the system. Bounded Time satisfy , which ensures that the tracking error satisfies the inequality constraint of the performance function , used for high-precision control of underwater glider systems; S204: Design a preset performance controller based on the kinematic equations of the underwater glider and the backstepping method to ensure the conversion error of the system First, set the tracking value of the conversion error , respectively for velocity and pitch angle Perform controller design and define conversion error Tracking error , introduce virtual control quantity as follows: ; in, , represents preset performance controller parameters; Through the control input Virtual Control Quantity Tracking, , get the control input as follows: ; in, Represents preset performance controller parameters: ; S205: According to the kinematic equation analysis, the input of the underwater glider There is coupling, Separate controller design methods can achieve decoupling and define the conversion error Tracking error , introduce virtual control quantity as follows: ; in, , represents preset performance controller parameters; In order to further solve the control signal , introduce virtual control quantity right Tracking and defining virtual control quantities as follows: ; in, , represents preset performance controller parameters; Finally, by controlling the input Virtual Control Quantity Tracking, , get the control input as follows: ; in, represents preset performance controller parameters; .

[0025] Embodiment 2 An underwater glider attitude control system, the system comprising a power model building module and a controller module; Dynamic model building module, used to build dynamic models based on coordinate transformation relations, Newton-Euler equations, and kinetic energy theorem; The controller module is used to design a preset performance controller, build an attitude controller using the backstepping method, obtain a control signal based on the measurable output signal, and complete high-precision control of the pitch motion of the underwater glider through the control signal.

[0026] Embodiment 3 Matlab is used to simulate the underwater glider's precise control ability in pitch cycle motion. When the desired pitch angle is Switching in the middle, the expected speed is At the same time, in order to verify the effectiveness of the control algorithm proposed in this application, the algorithm is compared with the traditional linear quadratic control method. Figure 3 and Figure 4 They are the stability comparison of the pitch angle error and speed error of the underwater glider under different control algorithms. Figure 5 and Figure 6 They are the stability comparison of the pitch angle and speed of the underwater glider under different control algorithms. Figure 7 and Figure 8 The stability comparisons of the pitch angle and speed of the underwater glider in periodic motion under different control algorithms are shown. Through comparison, it can be found that compared with the traditional linear quadratic controller, the control algorithm proposed in this application has better dynamic performance and steady-state performance.

[0027] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for controlling the attitude of an underwater glider, characterized in that: The control method comprises: S1: Establish a dynamic model based on coordinate transformation relations, Newton-Euler equations and kinetic energy theorem; S2: Based on the dynamic model, the preset performance controller is designed using the backstepping method to achieve high-precision control of the pitch motion of the underwater glider.

2. The underwater glider attitude control method according to claim 1, characterized in that: The S1 includes: S101: Construct the basic dynamics model of underwater glider based on coordinate transformation relationship, Newton-Euler equation and kinetic energy theorem; S102: Simplifying the basic kinetic model according to the assumed conditions to obtain a final kinetic model.

3. The underwater glider attitude control method according to claim 2, characterized in that: The S101 includes: S101-1: To facilitate the description of the motion state of the underwater glider, an inertial coordinate system is established. , fluid coordinate system and body coordinate system ; Since the inertial coordinate system of the underwater glider can be transformed into the body coordinate system through the rotation matrix composed of the attitude angle, the transformation from the fluid coordinate system to the body coordinate system is realized through the rotation matrix composed of the angle of attack and the sideslip angle. The angle of attack and the sideslip angle are defined as: ； ； Therefore, the following relationship exists: ； in, , and are the velocities in three directions in the glider body coordinate system, is the inertial coordinate system, is the body coordinate system, is the fluid coordinate system; ； S101-2: Define the generalized momentum of an underwater glider in an inertial frame , is the momentum of the underwater glider in the inertial coordinate system, is the angular momentum of the underwater glider in the inertial system. According to the Newton-Euler equation, the force and torque on the underwater glider can be expressed as: ； in, is the gravitational acceleration, k is the unidirectional vector in the z-axis direction, and are the forces and moments acting on the underwater glider by the external environment, For the quality of the drained water, They are the masses of the hull, attitude adjustment system, and buoyancy adjustment system. They are the positions of the shell, attitude adjustment system, and buoyancy adjustment system in the inertial coordinate system; ； in, is the position of the slider in the direction of the machine body axis, express In the body coordinate system The angle of rotation of the axis, express The eccentricity of Define the generalized momentum in the body coordinate system , is the momentum of the underwater glider in the body coordinate system, is the angular momentum of the underwater glider system. The generalized momentum in the inertial system and the generalized momentum in the body coordinate system have the following conversion relationship: ； Generalized Momentum Taking the derivative with respect to time, we get: ； Finally, the generalized force and torque expressions in the body coordinate system can be derived: ； in, and is the viscous hydrodynamic term, is the position of the underwater glider in the inertial system, is the angular velocity vector, is the velocity vector, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, represents the longitudinal velocity of the machine system, is the rolling angular velocity, represents the pitch angular velocity, represents the yaw angular velocity; S101-3: The total kinetic energy of the underwater glider system includes the kinetic energy of the shell, the kinetic energy of the attitude control system, the kinetic energy of the buoyancy control system and the kinetic energy of the additional mass. Therefore, according to the kinetic energy theorem, the kinetic energy of the underwater glider system can be expressed as: ； ； Among them, the additional mass matrix , represents the additional moment of inertia matrix, Represent the additional moment of inertia matrices of the shell, attitude control system, and buoyancy control system, respectively. , for The identity matrix of The generalized momentum of the underwater glider system in the body coordinate system can be expressed as Taking partial derivatives we get: ； Generalized momentum in the body coordinate system Taking the derivative and ignoring the small coupling terms, we finally get the equation of motion for the underwater glider as follows: ； in, and According to the kinetic energy theorem, and The expressions composed of 。 4. The method for controlling the attitude of an underwater glider according to claim 3, characterized in that: The inertial coordinate system is a fixed reference system with the initial position of the underwater glider as the origin. The position of the geometric center of the glider in the inertial coordinate system is expressed as , in the inertial coordinate system, Newton's laws of motion hold true and are used to describe the position and attitude of the glider on the earth.

5. The method for controlling the attitude of an underwater glider according to claim 4, characterized in that: The body coordinate system is a coordinate system fixed to the underwater glider body, with the center of mass of the glider as the origin, and the coordinate axis moves with the movement of the glider. The velocity and angular velocity of the underwater glider in the body coordinate system are defined as and ,in, represents the linear velocity along the body axis, represents the lateral velocity of the machine system, represents the longitudinal velocity of the machine system, is the rolling angular velocity, represents the pitch angular velocity, Represents the yaw angular velocity.

6. The underwater glider attitude control method according to claim 5, characterized in that: The fluid coordinate system is a reference system relative to the fluid and is used to describe the motion of the glider relative to the fluid.

7. The underwater glider attitude control method according to claim 6, characterized in that: The S102 includes: S102-1: Define the attitude angle of the underwater glider ,in, is the roll angle, is the pitch angle, is the yaw angle. Considering the pitch motion of the underwater glider in the vertical plane, the roll angle, yaw angle, roll angular velocity and yaw angular velocity of the glider are very small, so it is assumed that , , , , while considering the velocity of the underwater glider in the body coordinate system during the vertical plane movement and is small, so we assume , , ignoring the small coupling terms, under the above assumptions, the motion equations of the underwater glider are simplified, and finally the three-degree-of-freedom kinematic model of the underwater glider is established as follows: ； in, are the mass of the oil bag and the mass of the slider respectively, The position of the oil bag and the slider under the machine system. For the additional mass, is the additional moment of inertia, is the hydrodynamic parameter, is the control input, is the gravitational acceleration, taking into account the pitch angle The gliding efficiency of the underwater glider and the forward speed of the underwater glider are related to the pitch angle. and speed as a control target.

8. The method for controlling the attitude of an underwater glider according to claim 7, characterized in that: The S2 includes: S201: Considering the particularity of the pitch motion of the underwater glider, a new performance function is designed that is periodic and does not need to consider the initial state of the system. It is expressed as follows: ； in, represents the motion cycle of the underwater glider, represents the rate of decline of the performance function, The initial state used to constrain the performance function exists , Used to constrain the final value of the performance function, there is ; S202: Define tracking error , since the control objective of the tracking error is an inequality constraint, it is not convenient for controller design, so a nonlinear function error conversion function is introduced as follows: ； Among them, the conversion function satisfy ,and is a monotonically increasing function; S203: To ensure high-precision control of the underwater glider system, the tracking error satisfies the inequality constraint of the performance function , so the inequality constraints and nonlinear conversion functions can be mapped to obtain the conversion error of the system as follows: ； in, , Represents the conversion error of the system. Bounded time satisfy , which ensures that the tracking error satisfies the inequality constraint of the performance function , used for high-precision control of underwater glider systems; S204: Design a preset performance controller based on the kinematic equations of the underwater glider and the backstepping method to ensure the conversion error of the system First, set the tracking value of the conversion error , respectively for velocity and pitch angle Perform controller design and define conversion error Tracking error , introduce virtual control quantity as follows: ； in, , represents preset performance controller parameters; Through the control input Virtual Control Quantity Tracking, , get the control input as follows: ； in, Represents preset performance controller parameters: ； S205: According to the kinematic equation analysis, the input of the underwater glider There is coupling, Separate controller design methods can achieve decoupling and define the conversion error Tracking error , introduce virtual control quantity as follows: ； in, , represents preset performance controller parameters; In order to further solve the control signal , introduce virtual control quantity right Tracking and defining virtual control quantities as follows: ； in, , represents preset performance controller parameters; Finally, by controlling the input Virtual Control Quantity Tracking, , get the control input as follows: ； in, represents preset performance controller parameters; 。 9. An underwater glider attitude control system, used to implement the underwater glider attitude control method according to claim 8, characterized in that: The system includes a power model building module and a controller module; Dynamic model building module, used to build dynamic models based on coordinate transformation relations, Newton-Euler equations, and kinetic energy theorem; The controller module is used to design a preset performance controller. The attitude controller is constructed using the backstepping method. The control signal is obtained based on the measurable output signal. The high-precision control of the pitch motion of the underwater glider is completed through the control signal, and its attitude and speed are controlled within the preset range.

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