Multi-joint bionic dolphin motion control method, system and underwater damage detection method

Abstract

The present invention relates to a multi-joint bionic dolphin motion control method, system and underwater damage detection method, belonging to the field of bionic robot damage detection. The method comprises: establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain and performing pre-processing, importing the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, obtaining a thrust curve and a hydrodynamic curve under a specified underwater working condition, performing difference and fitting to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; performing a dynamic analysis on the dolphin to derive a dolphin dynamics model; completing the dolphin's dynamic coupling according to the dynamics model, the thrust curve and the speed-resistance fitting curve to obtain the dolphin's dynamics parameters, thereby applying PWM pulse width modulation technology to control the output torque at each joint of the dolphin at each moment. The method of the present invention can weaken the influence of the outside world on the multi-joint bionic dolphin and improve its stability.

Description

Technical Field

[0001] The present invention relates to the technical field of bionic robots and underwater engineering structure damage detection, and in particular to a multi-joint bionic dolphin motion control method and system and an underwater damage detection method. Background Art

[0002] Underwater robots (AUVs) have broad application prospects in damage detection of underwater engineering structures, such as harbors and bridges. However, existing AUVs generally use propellers for propulsion, which is somewhat inferior to bionic propulsion in terms of efficiency, noise level, and maneuverability. Bionic propulsion, with its superior motion performance, will be the future development direction for small AUVs. However, underwater working conditions are complex, and the application of bionic propulsion faces two challenges: First, bionic propulsion lacks propellers, and stability cannot be adjusted during operation. Instead, it relies on adjusting joint torque, but dynamic prediction of joint torque is extremely difficult. Second, it is difficult to pre-estimate the velocity of a designed bionic robot; it can only be determined experimentally. Existing research has not explored this in depth. Therefore, there is an urgent need to develop a method that can dynamically predict the joint torque and dynamic parameters such as acceleration, velocity, and displacement of a bionic robot. This method can be used to control the motion of the bionic robot to ensure stability, thereby enabling damage detection and location identification of underwater engineering structures. Summary of the Invention

[0003] The purpose of the present invention is to propose a multi-joint bionic dolphin motion control method, system and underwater damage detection method, which can obtain the torque of each joint of the multi-joint bionic dolphin through dynamic coupling technology, and predict its acceleration, velocity and displacement parameters at each moment, so as to control the output torque of the joint of the multi-joint bionic dolphin at each moment according to the above dynamic parameters, weaken the influence of the outside world on the multi-joint bionic dolphin, so as to improve its stability; and by installing a sonar system on the head of the bionic dolphin, through precise motion control methods, damage detection and positioning identification of underwater engineering structures can be realized.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] In one aspect, the present invention provides a multi-joint bionic dolphin motion control method, comprising:

[0006] Establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional computational domain model and performing pre-processing to obtain a pre-processed model file; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; the three-dimensional computational domain model is used for hydrodynamic simulation of the multi-joint bionic dolphin;

[0007] The pre-processed model file is imported into computational fluid dynamics analysis software for hydrodynamic simulation to obtain thrust curves and hydrodynamic curves of the multi-joint bionic dolphin under specified underwater working conditions. The thrust curves and hydrodynamic curves are then subtracted and fitted to obtain speed-resistance fitting curves of the multi-joint bionic dolphin at various moments. The specified underwater working conditions mainly include whether there is flow in the water area, as well as the speed and direction of the water flow.

[0008] Performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin;

[0009] According to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment;

[0010] According to the dynamic parameters of the multi-joint bionic dolphin, the PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment.

[0011] Optionally, the step of establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of the computational domain and performing pre-processing to obtain a pre-processed model file specifically includes:

[0012] Establish a 3D model of a multi-joint bionic dolphin and a 3D model of the computational domain in SolidWorks 3D drawing software;

[0013] The three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain are imported into Hypermesh software to perform model simplification and surface mesh division pre-processing on the three-dimensional model and the three-dimensional model of the computational domain to obtain a model file that has completed the pre-processing.

[0014] Optionally, the pre-processed model file is imported into computational fluid dynamics analysis software for hydrodynamic simulation to obtain a thrust curve and a hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then the thrust curve and the hydrodynamic curve are subtracted and fitted to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, specifically including:

[0015] Importing the pre-processed model file into the computational fluid dynamics analysis software Star-CCM+ to complete the establishment of the calculation domain, generate the body mesh, define the boundary, and define the multi-joint bionic dolphin deformation motion operation;

[0016] Set the water velocity in the computational domain to zero, let the multi-joint bionic dolphin's tail swing, and calculate the thrust curve of the multi-joint bionic dolphin when it swings according to the preset kinematic equation. This is used as the thrust curve of the multi-joint bionic dolphin under the specified underwater working condition.

[0017] Based on the principle of relative motion, the linear motion of the multi-joint bionic dolphin under specified underwater working conditions is synthesized, and the synthesized speed is converted into water flow for hydrodynamic simulation. The water flow speed is gradually increased until the theoretical propulsion speed of the multi-joint bionic dolphin under thrust is reached. The hydrodynamic curves of the multi-joint bionic dolphin at different motion speeds during the accelerated motion under specified underwater working conditions are obtained.

[0018] According to the thrust curve and the hydrodynamic curve, the resistance curve of the multi-joint bionic dolphin changing with speed at each moment when the multi-joint bionic dolphin swings according to the preset kinematic equation is calculated and fitted as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0019] Optionally, performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin specifically includes:

[0020] The dynamic analysis of the multi-joint bionic dolphin was carried out. The Lagrangian method was used to concentrate the hydrodynamic force, and the dynamic analysis of the multi-joint bionic dolphin was converted into the dynamic analysis of a multi-rigid body system. The dynamic model of the multi-joint bionic dolphin was derived.

[0021] Optionally, the dynamic coupling of the multi-joint bionic dolphin is completed according to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and the dynamic parameters of the multi-joint bionic dolphin are obtained, which specifically includes:

[0022] A dynamic model of the multi-joint bionic dolphin is constructed in Matlab software, and mass and length parameters of the multi-joint bionic dolphin are set in the dynamic model;

[0023] Decomposing the force term in the dynamic model into thrust minus resistance, where the thrust is the thrust corresponding to the thrust curve under the specified underwater working condition, obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and calculating the resultant force of each joint of the multi-joint bionic dolphin at each moment by subtracting the resistance from the thrust;

[0024] Substitute the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculate the torque of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the forward direction, and return to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0025] On the other hand, the present invention also provides a multi-joint bionic dolphin motion control system, comprising:

[0026] The three-dimensional model establishment and pre-processing module is used to establish a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of the computational domain and perform pre-processing to obtain a model file that has completed the pre-processing; the three-dimensional model is used to simulate the movement mode of the multi-joint bionic dolphin; the three-dimensional model of the computational domain is used for hydrodynamic simulation of the multi-joint bionic dolphin;

[0027] A hydrodynamic simulation module is used to import the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, obtain the thrust curve and hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then perform subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions mainly include whether there is flow in the water area and the speed and direction of the water flow;

[0028] A dynamics analysis module, used for performing dynamics analysis on the multi-joint bionic dolphin and deriving a dynamics model of the multi-joint bionic dolphin;

[0029] A dynamic coupling module is used to complete the dynamic coupling of the multi-joint bionic dolphin based on the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment;

[0030] The dolphin motion control module is used to control the output torque of each joint of the multi-joint bionic dolphin at each moment by applying PWM pulse width modulation technology according to the dynamic parameters of the multi-joint bionic dolphin.

[0031] Optionally, the three-dimensional model building and pre-processing module specifically includes:

[0032] A three-dimensional model building unit, used to build a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software;

[0033] The pre-processing unit is used to import the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain into the Hypermesh software to perform pre-processing of model simplification and surface mesh division on the three-dimensional model and the computational domain three-dimensional model to obtain a model file that has completed pre-processing.

[0034] Optionally, the hydrodynamic simulation module specifically includes:

[0035] A model file importing unit is used to import the pre-processed model file into the computational fluid dynamics analysis software Star-CCM+ to complete the establishment of the calculation domain, generate the volume grid, define the boundary, and define the multi-joint bionic dolphin deformation motion operation;

[0036] A thrust curve calculation unit is used to set the water flow velocity in the calculation domain to zero, make the multi-joint bionic dolphin's tail swing, and calculate the thrust curve of the multi-joint bionic dolphin when it swings according to a preset kinematic equation, which is used as the thrust curve of the multi-joint bionic dolphin under specified underwater working conditions;

[0037] A hydrodynamic curve calculation unit is used to synthesize the speed of the linear motion of the multi-joint bionic dolphin under specified underwater working conditions based on the principle of relative motion, convert the synthesized speed into the flow of water to perform hydrodynamic simulation, gradually increase the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust is reached, and obtain the hydrodynamic curves of the multi-joint bionic dolphin at different movement speeds during the accelerated motion process under specified underwater working conditions;

[0038] The speed-resistance fitting curve calculation unit is used to calculate the difference and fit the resistance curve of the multi-joint bionic dolphin at each moment when the multi-joint bionic dolphin swings according to the preset kinematic equation based on the thrust curve and the hydrodynamic curve, as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0039] Optionally, the kinetic analysis module specifically includes:

[0040] The dynamics analysis unit is used to perform dynamics analysis on the multi-joint bionic dolphin. It adopts the Lagrangian method to concentrate the hydrodynamic force, transforms the dynamics analysis of the multi-joint bionic dolphin into the dynamics analysis of a multi-rigid body system, and derives the dynamics model of the multi-joint bionic dolphin.

[0041] Optionally, the dynamic coupling module specifically includes:

[0042] A dynamic model building unit is used to build a dynamic model of the multi-joint bionic dolphin in Matlab software, and set the mass and length parameters of the multi-joint bionic dolphin in the dynamic model;

[0043] Each joint torque calculation unit is used to decompose the force term in the dynamic model into thrust minus resistance, where the thrust is the thrust corresponding to the thrust curve under the specified underwater working condition, obtain the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and calculate the resultant force of each joint of the multi-joint bionic dolphin at each moment by subtracting the resistance from the thrust;

[0044] The dolphin displacement and speed calculation unit is used to substitute the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculate the torque of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the forward direction, and return to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0045] On the other hand, the present invention also provides an underwater damage detection method based on multi-joint bionic dolphin motion control, comprising:

[0046] A three-dimensional model of a multi-joint bionic dolphin and a three-dimensional computational domain model are established and pre-processed to obtain a pre-processed model file; the head of the multi-joint bionic dolphin is equipped with a sonar system; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; and the three-dimensional computational domain model is used for hydrodynamic simulation of the multi-joint bionic dolphin;

[0047] Importing the pre-processed model file into computational fluid dynamics analysis software for hydrodynamic simulation, obtaining a thrust curve and a hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then performing subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions include whether there is flow in the water area and the speed and direction of the water flow;

[0048] Performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin;

[0049] According to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment;

[0050] According to the dynamic parameters of the multi-joint bionic dolphin, PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment, so as to accurately control the multi-joint bionic dolphin to move at a uniform speed and position suspension near the underwater engineering structure to be inspected. The target identification and positioning of the damaged part of the underwater engineering structure are achieved through the sonar system installed on the head of the multi-joint bionic dolphin.

[0051] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0052] The present invention provides a multi-joint bionic dolphin motion control method, system and underwater damage detection method, wherein the multi-joint bionic dolphin motion control method comprises: establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of the computational domain and performing pre-processing to obtain a model file that has completed the pre-processing; the three-dimensional model is used to simulate the motion mode of the multi-joint bionic dolphin, and the three-dimensional model of the computational domain is used for hydrodynamic simulation of the multi-joint bionic dolphin; the model file that has completed the pre-processing is imported into computational fluid dynamics analysis software to perform hydrodynamic simulation, and obtain the thrust curve, hydrodynamic curve and the multi-joint bionic dolphin's motion curve at each moment under the specified underwater working condition. speed-resistance fitting curve of the multi-joint bionic dolphin; perform dynamic analysis on the multi-joint bionic dolphin to derive the dynamic model of the multi-joint bionic dolphin; complete the dynamic coupling of the multi-joint bionic dolphin based on the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment; based on the dynamic parameters of the multi-joint bionic dolphin, apply PWM pulse width modulation technology to control the output torque at each joint of the multi-joint bionic dolphin at each moment. The method of the present invention obtains the torque of each joint of the multi-joint bionic dolphin through dynamic coupling technology, and predicts its acceleration, velocity, and displacement parameters at each moment, thereby controlling the output torque of the joint of the multi-joint bionic dolphin at each moment according to the above dynamic parameters, weakening the influence of the outside world on the multi-joint bionic dolphin and improving stability.

[0053] Furthermore, by adding a sonar system to the multi-joint bionic dolphin head, the present invention can also realize damage detection and positioning identification of underwater engineering structures through the precise multi-joint bionic dolphin motion control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0055] Figure 1 This is a flow chart of a multi-joint bionic dolphin motion control method of the present invention;

[0056] Figure 2 A schematic diagram of a thrust curve provided by an embodiment of the present invention;

[0057] Figure 3 Schematic diagram of hydrodynamic curve under still water conditions provided by an embodiment of the present invention; Figure 3 (a) to (f) correspond to the schematic diagrams of the hydrodynamic curves of the bionic dolphin moving at speeds of 0.2 m / s, 0.6 m / s, 1 m / s, 1.4 m / s, 1.8 m / s, and 2.2 m / s in still water conditions;

[0058] Figure 4 A schematic diagram of a speed-resistance fitting curve under still water conditions provided by an embodiment of the present invention;

[0059] Figure 5 A schematic diagram of the kinetic analysis process provided by the present invention;

[0060] Figure 6 This is a schematic diagram of the dynamic model built in the Matlab software provided by the present invention;

[0061] Figure 7 A schematic diagram of the process of the dynamic coupling technology provided by the present invention;

[0062] Figure 8 A graph of kinetic parameters provided by an embodiment of the present invention; wherein Figure 8 (a) is a curve diagram showing the change of torque with time. Figure 8 (b) is a graph showing the changes of various motion parameters (acceleration, velocity, displacement) over time;

[0063] Figure 9 The present invention is a flow chart of an underwater damage detection method based on multi-joint bionic dolphin motion control. DETAILED DESCRIPTION

[0064] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0065] The purpose of the present invention is to propose a multi-joint bionic dolphin motion control method, system and underwater damage detection method, which can obtain the torque of each joint of the multi-joint bionic dolphin through dynamic coupling technology, and predict its acceleration, velocity and displacement parameters at each moment, so as to control the output torque of the joint of the multi-joint bionic dolphin at each moment according to the above dynamic parameters, weaken the influence of the outside world on the multi-joint bionic dolphin, so as to improve its stability; and by installing a sonar system on the head of the bionic dolphin, through precise motion control methods, damage detection and positioning identification of underwater engineering structures can be realized.

[0066] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Figure 1 This is a flow chart of a multi-joint bionic dolphin motion control method of the present invention. Figure 1 The present invention provides a multi-joint bionic dolphin motion control method, which specifically includes:

[0068] Step 1: Establish a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain and perform pre-processing to obtain a model file that has completed pre-processing; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; the three-dimensional model of the computational domain is used for hydrodynamic simulation of the multi-joint bionic dolphin.

[0069] Specifically, a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain are established in SolidWorks three-dimensional drawing software; the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain are imported into Hypermesh software to perform model simplification and surface mesh division pre-processing on the three-dimensional model and the computational domain three-dimensional model to obtain a model file that has completed pre-processing.

[0070] Step 2: Import the pre-processed model file into computational fluid dynamics analysis software for hydrodynamic simulation to obtain the thrust curve and hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then subtract and fit the thrust curve and hydrodynamic curve to obtain the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions mainly include whether the water area is flowing and the water flow speed and direction.

[0071] Specifically, the pre-processed model file is imported into the computational fluid dynamics analysis software Star-CCM+ to complete the computational domain establishment, generate the volume mesh, define the boundary, and define the deformation motion operation of the multi-joint bionic dolphin. The computational domain water velocity is set to zero, the multi-joint bionic dolphin's tail is allowed to swing, and the thrust curve of the multi-joint bionic dolphin when swinging according to the preset kinematic equation is calculated as the thrust curve of the multi-joint bionic dolphin under the specified underwater working condition. According to the principle of relative motion, the linear motion of the multi-joint bionic dolphin under the specified underwater working condition is synthesized by velocity, and the synthesized velocity is converted into the flow of water for hydrodynamic simulation. The water velocity is gradually increased until the theoretical propulsion velocity of the multi-joint bionic dolphin under the above thrust is achieved. The hydrodynamic curves of the multi-joint bionic dolphin at different motion speeds during the accelerated motion under the specified underwater working condition are obtained. Based on the thrust curve and hydrodynamic curve obtained above, the resistance curve of the multi-joint bionic dolphin at each moment when swinging according to the preset kinematic equation is subtracted and fitted, which is the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0072] Step 3: Performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin.

[0073] Specifically, a dynamic analysis of the multi-joint bionic dolphin is conducted. The Lagrangian method is used to concentrate the hydrodynamic force, and the dynamic analysis of the multi-joint bionic dolphin is converted into a dynamic analysis of a multi-rigid body system, and the dynamic model of the multi-joint bionic dolphin is derived.

[0074] Step 4: According to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin.

[0075] Specifically, a dynamic model of the multi-joint bionic dolphin is constructed in Matlab software, and the mass and length parameters of the multi-joint bionic dolphin are set in the dynamic model; the force term in the dynamic model is decomposed into thrust minus resistance, the thrust is the thrust corresponding to the thrust curve under the specified underwater working condition, the resistance at each moment is obtained according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and the resultant force of each joint of the multi-joint bionic dolphin at each moment is calculated by subtracting the resistance from the thrust; the resultant force of each joint of the multi-joint bionic dolphin at each moment is substituted into the dynamic model, and the torque of each joint of the multi-joint bionic dolphin at each moment and the displacement, velocity and acceleration along the forward direction are calculated, and the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment is returned.

[0076] Step 5: According to the dynamic parameters of the multi-joint bionic dolphin, PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment.

[0077] Specifically, based on the dynamic parameters obtained by simulation, PWM pulse width modulation technology is used to write the control strategy. By dispersing the effective electrical signal into discrete forms, the average power transmitted by the electrical signal can be adjusted. That is, the output torque at the joints of the multi-joint bionic dolphin can be controlled at each moment, thereby weakening the influence of the outside world on the multi-joint bionic dolphin and improving stability.

[0078] The inventive method can improve the stability of the multi-joint bionic dolphin when working, and the dynamic parameters of the multi-joint bionic dolphin can be predicted by the method, and the torque corresponding to each joint at each moment when the multi-joint bionic dolphin works can be obtained. By PWM pulse width modulation technology, the average power transmitted by the electric signal can be adjusted by dispersing the effective electric signal into a discrete form, and the output torque at each joint at each moment can be controlled, thereby weakening the influence of the outside world on the multi-joint bionic dolphin and improving stability. And when the multi-joint bionic dolphin moves with a certain kinematic equation, the parameters such as acceleration, speed, displacement at each moment can also be predicted by the inventive method. Corresponding to a certain specific multi-joint bionic dolphin, namely the parameters such as definite mass, length, volume, its maximum forward velocity and corresponding kinematic equation can also be further obtained by the inventive method.

[0079] Taking the movement of a two-joint bionic dolphin in still water as an example, a specific embodiment of the multi-joint bionic dolphin movement control method of the present invention is provided. The method embodiment specifically includes the following steps:

[0080] S1: Establish a three-dimensional model of the two-joint bionic dolphin and a three-dimensional model of the computational domain and perform pre-processing to obtain a model file that has completed pre-processing.

[0081] A 3D model of a two-jointed bionic dolphin (Dolphin) and a 3D computational domain model were created in SolidWorks 3D drawing software. The 3D model was used to simulate the motion of the two-jointed bionic dolphin, and the computational domain model was used to simulate the hydrodynamics of the two-jointed bionic dolphin. The 3D model and the computational domain model were then imported into Hypermesh software for pre-processing, including model simplification and surface meshing, to obtain a pre-processed model file.

[0082] S2: Importing the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, and obtaining thrust curves, hydrodynamic curves, and speed-resistance fitting curves of the two-joint bionic dolphin at various moments under still water conditions.

[0083] The pre-processed model file is imported into the computational fluid dynamics analysis software Star-CCM+ to complete the calculation domain establishment, generate the body mesh, define the boundary, define the deformation motion of the two-joint bionic dolphin, etc. Set the calculation domain water flow velocity to 0m / s, and let the two-joint bionic dolphin tail follow the preset θ 21 (t) and θ 32 (t) equation swing, calculate the thrust curve of the two-joint bionic dolphin when it swings according to the preset kinematic equation, as the thrust curve under the static water working condition, such as Figure 2As shown, the hydrodynamic force at this time is pure thrust, and the thrust curve (thrust data) is exported to the intermediate file table.

[0084] θ 21 (t)=0.3878sin(3πt)

[0085] θ 32 (t) = -0.5824sin(3πt+π / 2)

[0086] Furthermore, based on the principle of relative motion, the linear motion speed of the two-joint bionic dolphin under the above thrust is converted into the speed of water flow for hydrodynamic simulation. The water flow speed is gradually increased until the theoretical propulsion speed of the two-joint bionic dolphin under the above thrust is reached. The hydrodynamic value curve (i.e., hydrodynamic curve) of the two-joint bionic dolphin at different motion speeds during the accelerated motion process when the two-joint bionic dolphin swings according to a certain kinematic equation is calculated, as shown in FIG. Figure 3 As shown, the hydrodynamic force at this time is the resultant force, that is, thrust minus resistance.

[0087] Furthermore, by combining the thrust curve and hydrodynamic curve obtained above, the resistance curve of the two-joint bionic dolphin that changes with speed at each moment when the two-joint bionic dolphin swings according to the preset kinematic equation is calculated and fitted, and the speed-resistance fitting curve of the two-joint bionic dolphin at each moment is obtained, such as Figure 4 shown. Figure 4 The horizontal axis is velocity v and the vertical axis is resistance F. Figure 3 The formulas for the speed-resistance fitting curves at various moments are shown in Table 1.

[0088] Table 1

[0089]

[0090]

[0091] S3: Performing dynamic analysis on the two-joint bionic dolphin to derive a dynamic model of the two-joint bionic dolphin.

[0092] The dynamics analysis of the two-joint bionic dolphin is carried out. The Lagrangian method is used to concentrate the hydrodynamic force, and the dynamics analysis of the two-joint bionic dolphin is transformed into the dynamics analysis of a multi-rigid body system. The dynamic model of the two-joint bionic dolphin is derived.

[0093] Figure 5 This is a schematic diagram of the dynamic analysis process provided by the present invention. In the figure, X0Y0 is the earth coordinate system, and X1Y1, X2Y2, and X3Y3 are the coordinate systems established on the dolphin's body, caudal peduncle, and caudal fin, respectively. Figure 4 As shown, the following assumptions are made to simplify the process:

[0094] a. The various parts of the dolphin are simplified as rods with uniform mass distribution, with the center of mass as the geometric center, and are treated as rigid bodies;

[0095] b. The changes in the center of gravity and center of buoyancy caused by the swinging of the caudal peduncle and caudal fin are not considered;

[0096] c. Only the forward working condition of the dolphin is considered, and the dolphin only produces displacement in the X direction.

[0097] Under this condition, the dolphin has three degrees of freedom. The relationship between the joints is described by the transformation of the coordinate system. F1, F2, and F3 are the hydrodynamic forces acting on the dolphin's body, caudal peduncle, and caudal fin, respectively, and are integrated into the center of mass of each part. 21 、M 32 is the moment at the connection between the dolphin's body parts, where M 21 is the moment at the connection between the dolphin body and the caudal peduncle, M 32 is the moment at the connection between the dolphin's caudal peduncle and the caudal fin; the lengths of the caudal fin and caudal peduncle are l2 and l3 respectively, and the masses of the dolphin's body, caudal peduncle, and caudal fin are m1, m2, and m3 respectively. The Lagrangian method is used to perform dynamic analysis on them, and the final results are organized into a matrix form:

[0098]

[0099] in,

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] The matrix (1) is the derived dynamic model. In the model (1), θ 21 ,θ 32 represent the swing functions of the dolphin's caudal peduncle and tail fin respectively; X 10 represents the displacement of the dolphin along the X0 direction; F 1x is the force on the dolphin's body in the X0 direction; F 2x 、F 2y are the projections of F2 on the X0 axis and Y0 axis of the X0Y0 coordinate system respectively; F 3x 、F 3y They are respectively the projections of F3 on the X0 axis and Y0 axis of the X0Y0 coordinate system.

[0106] The dynamic model is given by θ 21 (t), θ32 (t) case, we can get M 21 (t), M 32 (t), X 10 (t), that is, the swing function θ of the caudal peduncle and caudal fin at a given time t 21 (t), θ 32 (t), we can calculate the displacement function X of the dolphin along the X0 direction at time t 10 (t), drag moment M of the caudal peduncle and caudal fin 21 (t), M 32 (t). This dynamic model can also be used to study the inverse problem, that is, given M 21 (t), M 32 (t) can be inferred from θ 21 (t), θ 32 (t), X 10 (t).

[0107] S4: According to the dynamic model of the two-joint bionic dolphin, the thrust curve under the calm water working condition and the speed-resistance fitting curve of the two-joint bionic dolphin at each moment, the dynamic coupling of the two-joint bionic dolphin is completed to obtain the dynamic parameters of the two-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity and displacement of each joint of the two-joint bionic dolphin at each moment.

[0108] The dynamic model of the two-joint bionic dolphin was constructed in Matlab software, as shown in Figure 6 As shown, Figure 6 Velocity, Acceleration, and displacement represent velocity, acceleration, and displacement respectively; It is an integration module in Matlab, used for integration operations, where the acceleration integral is velocity, and the velocity integral is displacement; It is a delay module in Matlab, and its function is to record the data of the previous time step. It is used in the current time step. In the dynamic model of the present invention, it is used to record the speed obtained in the previous time step. Figure 5 The X below the corresponding module 10 ,θ 21 ,θ 32 The three parameters represent the generalized coordinates defined in the Lagrangian method.

[0109] Set the mass, length and other parameters of the two-joint bionic dolphin in the Matlab software dynamics model.

[0110] The force term in the dynamic model is decomposed into thrust minus resistance. The thrust is the thrust corresponding to the thrust curve under the still water condition (i.e., the hydrodynamic curve when the water velocity is 0 m / s). Furthermore, Matlab reads the thrust data of the first time step in the intermediate file. At this time, the speed of the two-joint bionic dolphin is 0 m / s and the resistance is 0. The resultant force of each joint of the two-joint bionic dolphin in the first time step is calculated by subtracting the resistance from the thrust, thereby obtaining F in the dynamic model. 1x 、F 2x 、F 3x 、F 2y 、F 3y ; Then, the resultant force of the first time step is substituted into the dynamic model for dynamic calculation, and the torque, displacement, velocity, and acceleration of each joint of the two-joint bionic dolphin corresponding to the time step are calculated. Further, the velocity is used as the initial condition for the next step of the dynamic model simulation, and the velocity is substituted into the fitted speed-resistance curve to calculate the magnitude of the resistance in the next step. Furthermore, Matlab reads the thrust data of the second time step in the intermediate file. The resultant force (hydrodynamic force) at this time is the read data minus the resistance calculated in the previous step, and the speed corresponding to the second time step is obtained by the dynamic model simulation. This process is repeated to complete the one-way dynamic coupling of the two-joint bionic dolphin. The process is as follows: Figure 7 Finally, the dynamic images of the torque, acceleration, velocity, displacement and other dynamic parameters of each joint of the two-joint bionic dolphin under different working conditions are obtained, as shown in Figure 8 shown.

[0111] Through the above dynamic coupling, the torque of each joint of the two-joint bionic dolphin under different working conditions can be obtained. The application of PWM pulse width modulation technology to the writing of the control strategy can reduce the influence of the external environment on the two-joint bionic dolphin during operation and improve stability. Through dynamic coupling, when the joints of the two-joint bionic dolphin move in different states, its acceleration, velocity, displacement and other parameters at each moment can be predicted. For a specific two-joint bionic dolphin, that is, with a certain mass, length, volume and other parameters, the maximum movement speed and the corresponding kinematic equation can also be obtained through the method of the present invention.

[0112] S5: According to the dynamic parameters of the two-joint bionic dolphin, PWM pulse width modulation technology is applied to control the output torque at each joint of the two-joint bionic dolphin at each moment.

[0113] Based on the dynamic parameters obtained by simulation, PWM pulse width modulation technology is used to write the control strategy. By dispersing the effective electrical signal into discrete forms, the average power transmitted by the electrical signal can be adjusted. That is, the output torque at the joints of the two-joint bionic dolphin can be controlled at each moment, thereby weakening the external influence on the two-joint bionic dolphin and improving stability.

[0114] Based on the method provided by the present invention, the present invention also provides a multi-joint bionic dolphin motion control system, the system comprising:

[0115] The three-dimensional model establishment and pre-processing module is used to establish a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of the computational domain and perform pre-processing to obtain a model file that has completed the pre-processing; the three-dimensional model is used to simulate the movement mode of the multi-joint bionic dolphin; the three-dimensional model of the computational domain is used for hydrodynamic simulation of the multi-joint bionic dolphin;

[0116] A hydrodynamic simulation module is used to import the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, obtain the thrust curve and hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then perform subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions mainly include whether there is flow in the water area and the speed and direction of the water flow;

[0117] A dynamics analysis module, used for performing dynamics analysis on the multi-joint bionic dolphin and deriving a dynamics model of the multi-joint bionic dolphin;

[0118] A dynamic coupling module is used to complete the dynamic coupling of the multi-joint bionic dolphin based on the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment;

[0119] The dolphin motion control module is used to control the output torque of each joint of the multi-joint bionic dolphin at each moment by applying PWM pulse width modulation technology according to the dynamic parameters of the multi-joint bionic dolphin.

[0120] The three-dimensional model building and pre-processing module specifically includes:

[0121] A three-dimensional model building unit, used to build a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software;

[0122] The pre-processing unit is used to import the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain into the Hypermesh software to perform pre-processing of model simplification and surface mesh division on the three-dimensional model and the computational domain three-dimensional model to obtain a model file that has completed pre-processing.

[0123] The hydrodynamic simulation module specifically includes:

[0124] A model file importing unit is used to import the pre-processed model file into the computational fluid dynamics analysis software Star-CCM+ to complete the establishment of the calculation domain, generate the volume grid, define the boundary, and define the multi-joint bionic dolphin deformation motion operation;

[0125] A thrust curve calculation unit is used to set the water flow velocity in the calculation domain to zero, make the multi-joint bionic dolphin's tail swing, and calculate the thrust curve of the multi-joint bionic dolphin when it swings according to a preset kinematic equation, which is used as the thrust curve of the multi-joint bionic dolphin under specified underwater working conditions;

[0126] A hydrodynamic curve calculation unit is used to synthesize the speed of the linear motion of the multi-joint bionic dolphin under specified underwater working conditions based on the principle of relative motion, convert the synthesized speed into the flow of water to perform hydrodynamic simulation, gradually increase the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust is reached, and obtain the hydrodynamic curves of the multi-joint bionic dolphin at different movement speeds during the accelerated motion process under specified underwater working conditions;

[0127] The speed-resistance fitting curve calculation unit calculates the difference and fits the resistance curve of the multi-joint bionic dolphin at each moment when the multi-joint bionic dolphin swings according to the preset kinematic equation based on the thrust curve and the hydrodynamic curve, as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0128] The kinetic analysis module specifically includes:

[0129] The dynamics analysis unit is used to perform dynamics analysis on the multi-joint bionic dolphin. It adopts the Lagrangian method to concentrate the hydrodynamic force, transforms the dynamics analysis of the multi-joint bionic dolphin into the dynamics analysis of a multi-rigid body system, and derives the dynamics model of the multi-joint bionic dolphin.

[0130] The dynamic coupling module specifically includes:

[0131] A dynamic model building unit is used to build a dynamic model of the multi-joint bionic dolphin in Matlab software, and set the mass and length parameters of the multi-joint bionic dolphin in the dynamic model;

[0132] Each joint torque calculation unit is used to decompose the force term in the dynamic model into thrust minus resistance, where the thrust is the thrust corresponding to the thrust curve under the specified underwater working condition, obtain the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and calculate the resultant force of each joint of the multi-joint bionic dolphin at each moment by subtracting the resistance from the thrust;

[0133] The dolphin displacement and speed calculation unit is used to substitute the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculate the torque of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the forward direction, and return to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

[0134] Based on the method provided by the present invention, the present invention also provides an underwater damage detection method based on multi-joint bionic dolphin motion control, such as Figure 9 As shown, the underwater damage detection method includes:

[0135] Step 901: Establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional computational domain model and performing pre-processing to obtain a pre-processed model file; the head of the multi-joint bionic dolphin is equipped with a sonar system; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; the three-dimensional computational domain model is used for hydrodynamic simulation of the multi-joint bionic dolphin;

[0136] Step 902: Importing the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, obtaining a thrust curve and a hydrodynamic curve of the multi-jointed bionic dolphin under specified underwater working conditions, and then performing subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-jointed bionic dolphin at each moment; the specified underwater working conditions include whether there is flow in the water area, as well as the speed and direction of the water flow;

[0137] Step 903: performing a dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin;

[0138] Step 904: Based on the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment;

[0139] Step 905: Based on the dynamic parameters of the multi-joint bionic dolphin, PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment, thereby controlling the multi-joint bionic dolphin to perform uniform motion and position suspension at the underwater engineering structure to be inspected, and the target identification and positioning of the damaged part of the underwater engineering structure is achieved through the sonar system installed on the head of the multi-joint bionic dolphin.

[0140] By adding a sonar system to the head of a multi-joint bionic dolphin, the present invention can realize damage detection and positioning identification of underwater engineering structures through the precise multi-joint bionic dolphin motion control method of the present invention.

[0141] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0142] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A multi-joint bionic dolphin motion control method, characterized in that: include: Establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain and performing pre-processing to obtain a pre-processed model file; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; The three-dimensional model of the computational domain is used for hydrodynamic simulation of a multi-jointed bionic dolphin; Importing the pre-processed model file into computational fluid dynamics analysis software for hydrodynamic simulation, obtaining a thrust curve and a hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then performing subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions include whether there is flow in the water area and the speed and direction of the water flow; Performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin; According to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment; According to the dynamic parameters of the multi-joint bionic dolphin, the PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment.

2. The method according to claim 1, characterized in that The three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain are established and pre-processed to obtain a pre-processed model file, specifically including: Establish a 3D model of a multi-joint bionic dolphin and a 3D model of the computational domain in SolidWorks 3D drawing software; The three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain are imported into Hypermesh software to perform model simplification and surface mesh division pre-processing on the three-dimensional model and the three-dimensional model of the computational domain to obtain a model file that has completed the pre-processing.

3. The method according to claim 1, characterized in that The pre-processed model file is imported into computational fluid dynamics analysis software for hydrodynamic simulation to obtain the thrust curve and hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then the thrust curve and the hydrodynamic curve are subtracted and fitted to obtain the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, specifically including: Importing the pre-processed model file into the computational fluid dynamics analysis software Star-CCM+ to complete the establishment of the calculation domain, generate the body mesh, define the boundary, and define the multi-joint bionic dolphin deformation motion operation; Set the water velocity in the computational domain to zero, let the multi-joint bionic dolphin's tail swing, and calculate the thrust curve of the multi-joint bionic dolphin when it swings according to the preset kinematic equation. This is used as the thrust curve of the multi-joint bionic dolphin under the specified underwater working condition. Based on the principle of relative motion, the linear motion of the multi-joint bionic dolphin under specified underwater working conditions is synthesized, and the synthesized speed is converted into water flow for hydrodynamic simulation. The water flow speed is gradually increased until the theoretical propulsion speed of the multi-joint bionic dolphin under thrust is reached. The hydrodynamic curves of the multi-joint bionic dolphin at different motion speeds during the accelerated motion under specified underwater working conditions are obtained. According to the thrust curve and the hydrodynamic curve, the resistance curve of the multi-joint bionic dolphin changing with speed at each moment when the multi-joint bionic dolphin swings according to the preset kinematic equation is calculated and fitted as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

4. The method according to claim 1, wherein The dynamic analysis of the multi-joint bionic dolphin is performed to derive a dynamic model of the multi-joint bionic dolphin, specifically including: The dynamic analysis of the multi-joint bionic dolphin was carried out. The Lagrangian method was used to concentrate the hydrodynamic force, and the dynamic analysis of the multi-joint bionic dolphin was converted into the dynamic analysis of a multi-rigid body system. The dynamic model of the multi-joint bionic dolphin was derived.

5. The method according to claim 1, wherein The dynamic coupling of the multi-joint bionic dolphin is completed according to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and the dynamic parameters of the multi-joint bionic dolphin are obtained, which specifically include: A dynamic model of the multi-joint bionic dolphin is constructed in Matlab software, and mass and length parameters of the multi-joint bionic dolphin are set in the dynamic model; Decomposing the force term in the dynamic model into thrust minus resistance, where the thrust is the thrust corresponding to the thrust curve under the specified underwater working condition, obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and calculating the resultant force of each joint of the multi-joint bionic dolphin at each moment by subtracting the resistance from the thrust; Substitute the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculate the torque of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the forward direction, and return to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

6. A multi-joint bionic dolphin motion control system, characterized in that: include: A three-dimensional model building and pre-processing module is used to build a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain and perform pre-processing to obtain a pre-processed model file; the three-dimensional model is used to simulate the movement of the multi-joint bionic dolphin; The three-dimensional model of the computational domain is used for hydrodynamic simulation of a multi-jointed bionic dolphin; A hydrodynamic simulation module is used to import the pre-processed model file into computational fluid dynamics analysis software to perform hydrodynamic simulation, thereby obtaining a thrust curve and a hydrodynamic curve of the multi-jointed bionic dolphin under specified underwater working conditions, and then performing subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-jointed bionic dolphin at each moment; the specified underwater working conditions include whether there is flow in the water area and the speed and direction of the water flow; A dynamics analysis module, used for performing dynamics analysis on the multi-joint bionic dolphin and deriving a dynamics model of the multi-joint bionic dolphin; A dynamic coupling module is used to complete the dynamic coupling of the multi-joint bionic dolphin based on the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment; The dolphin motion control module is used to control the output torque of each joint of the multi-joint bionic dolphin at each moment by applying PWM pulse width modulation technology according to the dynamic parameters of the multi-joint bionic dolphin.

7. The system according to claim 6, characterized in that The three-dimensional model building and pre-processing module specifically includes: A three-dimensional model building unit, used to build a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software; The pre-processing unit is used to import the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the computational domain into the Hypermesh software to perform pre-processing of model simplification and surface mesh division on the three-dimensional model and the computational domain three-dimensional model to obtain a model file that has completed pre-processing.

8. The system according to claim 6, wherein: The hydrodynamic simulation module specifically includes: A model file importing unit is used to import the pre-processed model file into the computational fluid dynamics analysis software Star-CCM+ to complete the establishment of the calculation domain, generate the volume grid, define the boundary, and define the multi-joint bionic dolphin deformation motion operation; A thrust curve calculation unit is used to set the water flow velocity in the calculation domain to zero, make the multi-joint bionic dolphin's tail swing, and calculate the thrust curve of the multi-joint bionic dolphin when it swings according to a preset kinematic equation, which is used as the thrust curve of the multi-joint bionic dolphin under specified underwater working conditions; A hydrodynamic curve calculation unit is used to synthesize the speed of the linear motion of the multi-joint bionic dolphin under specified underwater working conditions based on the principle of relative motion, convert the synthesized speed into the flow of water to perform hydrodynamic simulation, gradually increase the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust is reached, and obtain the hydrodynamic curves of the multi-joint bionic dolphin at different movement speeds during the accelerated motion process under specified underwater working conditions; The speed-resistance fitting curve calculation unit is used to calculate the difference and fit the resistance curve of the multi-joint bionic dolphin at each moment when the multi-joint bionic dolphin swings according to the preset kinematic equation based on the thrust curve and the hydrodynamic curve, as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.

9. The system according to claim 6, wherein: The kinetic analysis module specifically includes: The dynamics analysis unit is used to perform dynamics analysis on the multi-joint bionic dolphin. It adopts the Lagrangian method to concentrate the hydrodynamic force, transforms the dynamics analysis of the multi-joint bionic dolphin into the dynamics analysis of a multi-rigid body system, and derives the dynamics model of the multi-joint bionic dolphin.

10. An underwater damage detection method based on multi-joint bionic dolphin motion control, characterized in that: include: Establish a 3D model of the multi-joint bionic dolphin and a 3D model of the computational domain and perform pre-processing to obtain a pre-processed model file; The head of the multi-jointed bionic dolphin is equipped with a sonar system; the three-dimensional model is used to simulate the movement of the multi-jointed bionic dolphin; The three-dimensional model of the computational domain is used for hydrodynamic simulation of a multi-jointed bionic dolphin; Importing the pre-processed model file into computational fluid dynamics analysis software for hydrodynamic simulation, obtaining a thrust curve and a hydrodynamic curve of the multi-joint bionic dolphin under specified underwater working conditions, and then performing subtraction and fitting of the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; the specified underwater working conditions include whether there is flow in the water area and the speed and direction of the water flow; Performing dynamic analysis on the multi-joint bionic dolphin to derive a dynamic model of the multi-joint bionic dolphin; According to the dynamic model of the multi-joint bionic dolphin, the thrust curve under the specified underwater working condition, and the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, the dynamic coupling of the multi-joint bionic dolphin is completed to obtain the dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters include the torque and acceleration, velocity, and displacement of each joint of the multi-joint bionic dolphin at each moment; According to the dynamic parameters of the multi-joint bionic dolphin, PWM pulse width modulation technology is applied to control the output torque of each joint of the multi-joint bionic dolphin at each moment, thereby controlling the multi-joint bionic dolphin to perform uniform motion and position suspension at the underwater engineering structure being inspected. The target identification and positioning of the damaged part of the underwater engineering structure are achieved through the sonar system installed on the head of the multi-joint bionic dolphin.

Images