CN115774967A - Multi-joint bionic dolphin motion control method and system and underwater damage detection method - Google Patents
Multi-joint bionic dolphin motion control method and system and underwater damage detection method Download PDFInfo
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Abstract
The invention relates to a multi-joint bionic dolphin motion control method and system and an underwater damage detection method, and belongs to the field of damage detection of bionic robots. The method comprises the following steps: establishing a three-dimensional model and a three-dimensional model of a computational domain of the multi-joint bionic dolphin, carrying out pretreatment, importing a model file subjected to pretreatment into computational fluid dynamics analysis software to carry out hydrodynamic simulation to obtain a thrust curve and a hydrodynamic curve under a specified underwater working condition, carrying out subtraction and fitting to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; performing dynamic analysis on the dolphin to deduce a dolphin dynamic model; and completing dynamic coupling of the dolphin according to the dynamic model, the thrust curve and the speed-resistance fitting curve to obtain dynamic parameters of the dolphin, so that the output torque of each joint of the dolphin at each moment is controlled by applying a PWM (pulse width modulation) technology. The method can weaken the influence of the outside on the multi-joint bionic dolphin and improve the stability of the multi-joint bionic dolphin.
Description
Technical Field
The invention relates to the technical field of damage detection of bionic robots and underwater engineering structures, in particular to a multi-joint bionic dolphin motion control method and system and an underwater damage detection method.
Background
The underwater robot has wide application prospect in the field of damage detection of underwater engineering structures such as ports and bridge underwater structure parts, but the existing underwater robot generally adopts propeller propulsion, and the propulsion mode is slightly insufficient in efficiency, noise and maneuverability compared with bionic propulsion. The bionic propulsion is a future development direction of the small underwater robot by virtue of the excellent motion performance of the bionic propulsion. The underwater working condition is complex, and the application of bionic propulsion has the following two problems: first, the bionic propulsion has no propeller, and the working state of the propeller cannot be adjusted to maintain stable during working, but the working state is maintained stable by adjusting joint torque, but the dynamic prediction of the joint torque is very difficult. Secondly, the designed bionic robot is difficult to estimate the speed in advance and can only be obtained by experiments. However, the existing research has not been deeply studied, so there is a need in the art to provide a method capable of dynamically predicting the torque, acceleration, speed, displacement and other dynamic parameters of the joints of the bionic robot, and accordingly controlling the motion of the bionic robot to ensure the stability, so as to realize the damage detection and the positioning identification of the underwater engineering structure.
Disclosure of Invention
The invention aims to provide a multi-joint bionic dolphin motion control method, a system and an underwater damage detection method, which can obtain the torque of each joint of the multi-joint bionic dolphin through a dynamic coupling technology and predict the acceleration, speed and displacement parameters of each moment of the multi-joint bionic dolphin, so that the output torque of each joint of the multi-joint bionic dolphin at each moment is controlled according to the dynamic parameters, the influence of the outside on the multi-joint bionic dolphin is weakened, and the stability of the multi-joint bionic dolphin is improved; and a sonar system is additionally arranged on the head of the bionic dolphin, and damage detection and positioning identification of the underwater engineering structure are realized through a precise motion control method.
In order to achieve the purpose, the invention provides the following scheme:
in one aspect, the invention provides a multi-joint bionic dolphin motion control method, comprising:
establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain, and performing pretreatment to obtain a model file for completing pretreatment; the three-dimensional model is used for simulating the motion 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;
importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 mainly comprise whether the water area flows, the water flow speed and the water flow direction;
performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin;
completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, the acceleration, the speed and the displacement of each joint of the multi-joint bionic dolphin at each moment;
and according to the dynamic parameters of the multi-joint bionic dolphin, controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology.
Optionally, the establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain and performing preprocessing to obtain a model file for completing preprocessing specifically includes:
establishing 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;
and importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out model simplification and surface grid division pretreatment on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file for completing the pretreatment.
Optionally, the importing the model file after the pretreatment into computational fluid dynamics analysis software to perform hydrodynamic simulation to obtain a thrust curve and a hydrodynamic curve of the multi-joint bionic dolphin under a specified underwater working condition, and then performing subtraction and fitting on the thrust curve and the hydrodynamic curve to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each time, which specifically includes:
importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete the establishment of a computational domain, generating a volume grid, defining a boundary, and defining the deformation motion operation of the multi-joint bionic dolphin;
setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematic equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition;
according to a relative motion principle, synthesizing the linear motion of the multi-joint bionic dolphin under the specified underwater working condition, converting the synthesized speed into the flow of water flow to carry out hydrodynamic simulation, gradually increasing the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust, and obtaining hydrodynamic curves of the multi-joint bionic dolphin at different motion speeds in the acceleration motion process under the specified underwater working condition;
and according to the thrust curve and the hydrodynamic curve, calculating a difference and fitting a resistance curve which changes with the speed when the multi-joint bionic dolphin swings by a preset kinematic equation at each moment to serve as a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
Optionally, the performing a kinetic analysis on the multi-joint biomimetic dolphin to derive a kinetic model of the multi-joint biomimetic dolphin specifically includes:
and performing dynamic analysis on the multi-joint bionic dolphin, concentrating hydrodynamic force by adopting a Lagrange method, converting the dynamic analysis of the multi-joint bionic dolphin into dynamic analysis of a multi-rigid system, and deducing a dynamic model of the multi-joint bionic dolphin.
Optionally, the performing dynamic coupling on the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin specifically includes:
building a dynamic model of the multi-joint bionic dolphin in Matlab software, and setting the quality and length parameters of the multi-joint bionic dolphin in the dynamic model;
decomposing a force term in the dynamic model into a thrust minus resistance, wherein the thrust is a thrust corresponding to a thrust curve under the specified underwater working condition, obtaining the resistance at each moment according to a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtaining the resultant force of each joint of the multi-joint bionic dolphin at each moment by utilizing the thrust minus resistance calculation;
substituting resultant force of each joint of the multi-joint bionic dolphin into the dynamic model at each moment, calculating to obtain moment of each joint of the multi-joint bionic dolphin at each moment and displacement, speed and acceleration along the advancing direction, and returning to the step of obtaining resistance at each moment according to a speed-resistance fitting curve of each moment of the multi-joint bionic dolphin.
In another aspect, the present invention further provides a multi-joint bionic dolphin motion control system, comprising:
the three-dimensional model establishing and preprocessing module is used for establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain and preprocessing the three-dimensional model to obtain a model file which completes preprocessing; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
the hydrodynamic simulation module is used for importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing difference calculation and fitting on 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 condition mainly comprises whether the water area flows, the water flow speed and the water flow direction;
the dynamic analysis module is used for carrying out dynamic analysis on the multi-joint bionic dolphin and deducing a dynamic model of the multi-joint bionic dolphin;
the dynamic coupling module is used for completing dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, the acceleration, the speed and the displacement of each joint of the multi-joint bionic dolphin at each moment;
and the dolphin motion control module is used for controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology according to the dynamic parameters of the multi-joint bionic dolphin.
Optionally, the three-dimensional model building and preprocessing module specifically includes:
the three-dimensional model establishing unit is used for establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software;
and the preprocessing unit is used for importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out preprocessing of model simplification and surface grid division on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file which completes preprocessing.
Optionally, the hydrodynamic simulation module specifically includes:
the model file importing unit is used for importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete the establishment of a computational domain, generate a volume grid, define a boundary and define the deformation motion operation of the multi-joint bionic dolphin;
the thrust curve calculation unit is used for setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematic equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition;
the hydrodynamic force curve calculation unit is used for synthesizing the speed of the linear motion of the multi-joint bionic dolphin under the specified underwater working condition according to the relative motion principle, converting the synthesized speed into the flow of water flow to perform hydrodynamic force simulation, gradually increasing the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the thrust action, and obtaining hydrodynamic force curves of the multi-joint bionic dolphin under different motion speeds in the acceleration motion process under the specified underwater working condition;
and the speed-resistance fitting curve calculation unit is used for solving the difference and fitting a resistance curve which changes along with the speed when the multi-joint bionic dolphin swings by a preset kinematics equation at each moment according to the thrust curve and the hydrodynamic curve, and the resistance curve is used as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
Optionally, the kinetic analysis module specifically includes:
and the dynamic analysis unit is used for carrying out dynamic analysis on the multi-joint bionic dolphin, concentrating hydrodynamic force by adopting a Lagrange method, converting the dynamic analysis of the multi-joint bionic dolphin into dynamic analysis of a multi-rigid system, and deducing a dynamic model of the multi-joint bionic dolphin.
Optionally, the dynamic coupling module specifically includes:
the dynamic model building unit is used for building a dynamic model of the multi-joint bionic dolphin in Matlab software, and the quality and length parameters of the multi-joint bionic dolphin are set in the dynamic model;
each joint moment calculation unit is used for decomposing a force term in the dynamic model into thrust minus resistance, the thrust is corresponding thrust in a thrust curve under the specified underwater working condition, the resistance at each moment is obtained according to a 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 obtained by subtracting the resistance from the thrust;
and the dolphin displacement and speed calculation unit is used for substituting the resultant force of each joint of the multi-joint bionic dolphin into the dynamic model at each moment, calculating to obtain the moment of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the advancing direction, and returning to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of each moment of the multi-joint bionic dolphin.
On the other hand, the invention also provides an underwater damage detection method based on multi-joint bionic dolphin motion control, which comprises the following steps:
establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain, and performing pretreatment to obtain a model file for completing pretreatment; the head of the multi-joint bionic dolphin is equipped with a sonar system; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 comprise whether the water area flows, the water flow speed and the water flow direction;
performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin;
completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, acceleration, speed 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, a 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 that the multi-joint bionic dolphin is accurately controlled to perform uniform motion and positioning suspension near the detected underwater engineering structure, and the target identification and positioning of the damaged part of the underwater engineering structure are realized through a sonar system carried on the head of the multi-joint bionic dolphin.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention provides a method and a system for controlling the motion of a multi-joint bionic dolphin and an underwater damage detection method, wherein the method for controlling the motion of the multi-joint bionic dolphin comprises the following steps: establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain, and performing pretreatment to obtain a model file for completing pretreatment; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin, and the three-dimensional model in the computational domain is used for hydrodynamic simulation of the multi-joint bionic dolphin; importing the model file subjected to the pretreatment 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 a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment; performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin; completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, acceleration, speed and displacement of each joint of the multi-joint bionic dolphin at each moment; and according to the dynamic parameters of the multi-joint bionic dolphin, controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology. The method of the invention obtains the moment of each joint of the multi-joint bionic dolphin through a dynamic coupling technology, and predicts the acceleration, speed and displacement parameters of each moment, thereby controlling the output moment of each joint of the multi-joint bionic dolphin according to the kinetic parameters, weakening the influence of the outside on the multi-joint bionic dolphin, and improving the stability.
Furthermore, the sonar system is additionally arranged on the head of the multi-joint bionic dolphin, and damage detection and positioning identification of the underwater engineering structure can be realized by the accurate multi-joint bionic dolphin motion control method.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of a method for controlling the motion of a multi-joint bionic dolphin according to the present invention;
FIG. 2 is a schematic diagram of a thrust curve provided by an embodiment of the present invention;
FIG. 3 is a hydrodynamic curve diagram under a still water area working condition according to an embodiment of the present invention; wherein, the graphs (a) to (f) in FIG. 3 respectively correspond to the hydrodynamic force curves of the bionic dolphin moving at the speeds of 0.2m/s, 0.6m/s, 1m/s, 1.4m/s, 1.8m/s and 2.2m/s under the working condition of a still water area;
FIG. 4 is a schematic diagram of a velocity-resistance fitted curve under a still water area condition according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a kinetic analysis process provided by the present invention;
fig. 6 is a schematic diagram of a kinetic model built in Matlab software provided by the present invention;
FIG. 7 is a schematic process diagram of the kinetic coupling technique provided by the present invention;
FIG. 8 is a graphical representation of kinetic parameters provided by an embodiment of the present invention; wherein fig. 8 (a) is a graph of torque as a function of time, and fig. 8 (b) is a graph of various motion parameters (acceleration, velocity, displacement) as a function of time;
FIG. 9 is a flow chart of an underwater injury detection method based on multi-joint bionic dolphin motion control.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a multi-joint bionic dolphin motion control method, a system and an underwater damage detection method, which can obtain the torque of each joint of a multi-joint bionic dolphin through a dynamic coupling technology, and predict the acceleration, speed and displacement parameters of each moment of the multi-joint bionic dolphin, so that the output torque of each joint of the multi-joint bionic dolphin at each moment is controlled according to the dynamic parameters, the influence of the outside on the multi-joint bionic dolphin is weakened, and the stability of the multi-joint bionic dolphin is improved; and a sonar system is additionally arranged on the head of the bionic dolphin, and damage detection and positioning identification of the underwater engineering structure are realized through a precise motion control method.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
FIG. 1 is a flow chart of a method for controlling the motion of a multi-joint bionic dolphin according to the present invention. Referring to fig. 1, the invention relates to a multi-joint bionic dolphin movement control method, which specifically comprises the following steps:
step 1: establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain, and performing pretreatment to obtain a model file for completing pretreatment; the three-dimensional model is used for simulating the motion 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.
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; and importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out pretreatment of model simplification and surface grid division on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file for completing the pretreatment.
And 2, step: importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 mainly comprise whether the water area flows, and the water flow speed and direction.
Specifically, the model file which is subjected to the pretreatment is led into computational fluid dynamics analysis software Star-CCM + to complete calculation domain establishment, a volume grid is generated, a boundary is defined, and multi-joint bionic dolphin deformation motion operation is defined. Setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematics equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition. According to the relative motion principle, the linear motion of the multi-joint bionic dolphin under the specified underwater working condition is subjected to velocity synthesis, the synthetic velocity is converted into the flow of water flow to carry out hydrodynamic simulation, the water flow velocity is gradually increased until the theoretical propulsion velocity of the multi-joint bionic dolphin under the action of the thrust, and hydrodynamic curves of the multi-joint bionic dolphin under different motion velocities in the acceleration motion process under the specified underwater working condition are obtained. And according to the obtained thrust curve and hydrodynamic curve, calculating a difference and fitting a resistance curve which changes along with the speed when the multi-joint bionic dolphin swings by a preset kinematic equation at each moment to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
And step 3: and carrying out dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin.
Specifically, the dynamic analysis is carried out on the multi-joint bionic dolphin, a Lagrange method is adopted, hydrodynamic force is concentrated, the dynamic analysis of the multi-joint bionic dolphin is converted into the dynamic analysis of a multi-rigid system, and a dynamic model of the multi-joint bionic dolphin is deduced.
And 4, step 4: and completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under the specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin.
Specifically, a dynamic model of the multi-joint bionic dolphin is built in Matlab software, and the quality and length parameters of the multi-joint bionic dolphin are set in the dynamic model; decomposing a force term in the dynamic model into a thrust minus resistance, wherein the thrust is a thrust corresponding to a thrust curve under the specified underwater working condition, obtaining the resistance at each moment according to a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtaining the resultant force of each joint of the multi-joint bionic dolphin at each moment by utilizing the thrust minus resistance calculation; substituting the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculating to obtain the moment of each joint of the multi-joint bionic dolphin at each moment and the displacement, the speed and the acceleration along the advancing direction, and returning to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of each moment of the multi-joint bionic dolphin.
And 5: and according to the dynamic parameters of the multi-joint bionic dolphin, controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology.
Specifically, based on the dynamic parameters obtained by simulation, a PWM (pulse width modulation) technology is applied to write a control strategy, and the average power transmitted by the electric signals is adjusted by dispersing the effective electric signals into a discrete form, so that the output torque at the joints of the multi-joint bionic dolphin at each moment can be controlled, the influence of the outside on the multi-joint bionic dolphin is weakened, and the stability is improved.
The method can improve the stability of the multi-joint bionic dolphin in work, can predict the dynamic parameters of the multi-joint bionic dolphin to obtain the corresponding moment of each joint of the multi-joint bionic dolphin in work, and can adjust the average power transmitted by the electric signals by dispersing the effective electric signals into a discrete form through a PWM (pulse width modulation) technology, so that the output moment of each joint of each time can be controlled, the influence of the outside on the multi-joint bionic dolphin is weakened, and the stability is improved. When the multi-joint bionic dolphin moves by a certain kinematic equation, the method can also predict the parameters of acceleration, speed, displacement and the like of the multi-joint bionic dolphin at each moment. The maximum advancing speed and the corresponding kinematic equation can be further obtained by the method of the invention corresponding to a certain specific multi-joint bionic dolphin, namely the determined parameters of mass, length, volume and the like.
Taking the motion of a two-joint bionic dolphin in a still water area as an example, a specific embodiment of the multi-joint bionic dolphin motion control method is provided, and the method specifically comprises the following steps:
s1: and establishing a three-dimensional model of the two-joint bionic dolphin and a three-dimensional model of a calculation domain, and performing pretreatment to obtain a model file for completing pretreatment.
Establishing a three-dimensional model of a two-joint bionic dolphin (dolphin for short) and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software; the three-dimensional model is used for simulating the motion mode of the two-joint bionic dolphin; the calculation domain three-dimensional model is used for hydrodynamic simulation of the two-joint bionic dolphin. And importing the three-dimensional model of the two-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out pretreatment of model simplification and surface grid division on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file for completing the pretreatment.
S2: and importing the model file subjected to the pretreatment into computational fluid dynamics analysis software to carry out hydrodynamic simulation, and obtaining a thrust curve and a hydrodynamic curve under a still water area working condition and a speed-resistance fitting curve of the two-joint bionic dolphin at each moment.
And importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete calculation domain establishment, generating a volume grid, defining a boundary, defining deformation motion of the two-joint bionic dolphin and the like. Setting the water flow speed of a calculation domain to be 0m/s, and enabling the tail of the two-joint bionic dolphin to be in accordance with a preset theta 21 (t) and θ 32 And (t) swinging the equation, calculating a thrust curve of the two-joint bionic dolphin when swinging by using a preset kinematics equation, taking the thrust curve as a thrust curve under a still water area working condition, and deriving the thrust curve (thrust data) to an intermediate file table, wherein the hydrodynamic force at the moment is pure thrust as shown in fig. 2.
θ 21 (t)＝0.3878sin(3πt)
θ 32 (t)＝-0.5824sin(3πt+π/2)
Further, according to the principle of relative motion, the linear motion speed of the two-joint bionic dolphin under the action of the thrust is converted into the speed of water flow to perform hydrodynamic simulation, the speed of water flow is gradually increased until the theoretical propulsion speed of the two-joint bionic dolphin under the action of the thrust, and hydrodynamic numerical curves (hydrodynamic curves) at different motion speeds in the process of accelerating motion of the two-joint bionic dolphin when the two-joint bionic dolphin swings by a certain kinematic equation are calculated, as shown in fig. 3, the hydrodynamic force at the moment is the magnitude of resultant force, namely, the thrust minus the resistance.
Further, the obtained thrust curve and hydrodynamic curve are combined, a difference is obtained and a resistance curve which changes with the speed when the two-joint bionic dolphin swings by a preset kinematic equation at each moment is fitted to be used as a speed-resistance fitting curve of the two-joint bionic dolphin at each moment, as shown in fig. 4. In fig. 4, the abscissa represents the velocity v and the ordinate represents the resistance F. The formula for the velocity-drag fit curve at each time in fig. 3 is shown in table 1.
TABLE 1
S3: and performing dynamic analysis on the two-joint bionic dolphin, and deducing a dynamic model of the two-joint bionic dolphin.
And performing dynamic analysis on the two-joint bionic dolphin, concentrating the hydrodynamic force by adopting a Lagrange method, converting the dynamic analysis of the two-joint bionic dolphin into dynamic analysis of a multi-rigid-system, and deducing a dynamic model of the two-joint bionic dolphin.
FIG. 5 is a schematic diagram of the kinetic analysis process provided by the present invention. In the figure, X 0 Y 0 Is a terrestrial coordinate system, X 1 Y 1 、X 2 Y 2 、X 3 Y 3 Respectively are coordinate systems established on the dolphin body, the caudal peduncle and the caudal fin. As shown in fig. 4, the following assumptions are made for simplifying the process:
a. each part of the dolphin is simplified into a rod piece with uniform mass distribution, and the mass center is a geometric center and is regarded as a rigid body;
b. the change of the gravity center and the floating center generated by the swing of the tail handle and the tail fin is not considered;
c. only the advance working condition of the dolphin is considered, and the dolphin can only generate displacement in the X direction.
Dolphins have 3 degrees of freedom under this condition, the relationship of the joints is described by the transformation of a coordinate system, F 1 、F 2 、F 3 The dolphin body, the tail handle and the tail fin are respectively subjected to hydrodynamic force and integrated in the mass center of each part; m 21 、M 32 Is the moment at the junction of the parts of the dolphin body, where M 21 The moment at the joint of the dolphin body and the tail handle, M 32 The moment at the joint of the dolphin tail handle and the tail fin; the length of the tail fin and the tail handle is l respectively 2 、l 3 The mass of dolphin body, tail handle and tail fin is m 1 、m 2 、m 3 Performing dynamic analysis on the data by adopting a Lagrange method, and arranging the finally obtained result into a matrix form:
wherein, the first and the second end of the pipe are connected with each other,
the matrix (1) is a dynamic model obtained by derivation, and theta in the model (1) 21 、θ 32 Respectively representing the swing functions of the dolphin tail handle and tail fin; x 10 Representing dolphin edge X 0 Displacement of direction; f 1x Is dolphin body in X 0 The stress in the direction; f 2x 、F 2y Are respectively F 2 At X 0 Y 0 X of a coordinate system 0 Axis and Y 0 Projection on an axis; f 3x 、F 3y Are respectively F 3 At X 0 Y 0 X of a coordinate system 0 Axis and Y 0 Projection on the axis.
The kinetic model is at a given θ 21 (t)、θ 32 (t) in the case of M 21 (t)、M 32 (t)、X 10 (t), i.e. the swing function theta of the tail shank and tail fin given time t 21 (t)、θ 32 (t), the dolphin edge X at time t can be calculated 0 Displacement function X of direction 10 (t), moment of resistance M of shank and skeg 21 (t)、M 32 (t) of (d). Inverse problems can also be studied using this kinetic model, i.e. given M 21 (t)、M 32 (t) can be reversely deduced to 21 (t)、θ 32 (t)、X 10 (t)。
S4: completing the dynamic coupling of the two-joint bionic dolphin according to the dynamic model of the two-joint bionic dolphin, a thrust curve under a still water region working condition and a speed-resistance fitting curve of the two-joint bionic dolphin at each moment to obtain dynamic parameters of the two-joint bionic dolphin; the dynamic parameters comprise the moment, acceleration, speed and displacement of each joint of the two-joint bionic dolphin at each moment.
In Matlab softBuilding a dynamic model of the two-joint bionic dolphin in the piece, wherein as shown in fig. 6, velocity, acceleration and displacement are respectively represented by Velocity, acceleration and displacement in fig. 6;
the method is characterized in that the method is an integration module in Matlab and used for integration operation, wherein acceleration integration is speed, and speed integration is displacement;
the delay module in Matlab has the function of recording the data of the previous time step, and the data is used in the time step and used for recording the speed obtained in the previous time step in the dynamic model of the invention. X in FIG. 5 below the corresponding module 10 、θ 21 、θ 32 The three parametric representations are defined as generalized coordinates in the lagrange method.
Parameters such as the quality, the length and the like of the two-joint bionic dolphin are set in a Matlab software dynamic model.
Decomposing a force item in the dynamic model into a thrust minus resistance, wherein the thrust is a thrust corresponding to a thrust curve (namely a hydrodynamic curve when the water flow speed is 0 m/s) under the working condition of a still water area, further reading thrust data of a first time step in an intermediate file by Matlab, the speed of the two-joint bionic dolphin is 0m/s, the resistance is 0, and calculating by using the thrust minus resistance to obtain the resultant force of each joint of the two-joint bionic dolphin at the first time step so as to obtain F in the dynamic model 1x 、F 2x 、F 3x 、F 2y 、F 3y (ii) a And then substituting the resultant force of the first time step into a dynamics model to perform dynamics calculation, and calculating the moment, displacement, speed and acceleration of each joint of the two-joint bionic dolphin corresponding to the time step. And further, taking the speed as an initial condition of next-step dynamic model simulation, and substituting the speed into the speed-resistance curve obtained by fitting to obtain the resistance of the next step. Further, matlab reads the thrust data at the second time step in the intermediate file, where the resultant force (hydrodynamic force) is the readThe resistance calculated in the previous step is subtracted from the data of (a) and then the speed corresponding to the second time step is obtained through the simulation of a dynamic model. The above steps are repeated to complete the unidirectional dynamic coupling of the two-joint bionic dolphin, and the process is shown in figure 7. Finally, dynamic images of dynamic parameters such as moment, acceleration, speed, displacement and the like of each joint of the two-joint bionic dolphin under different working conditions are obtained, as shown in fig. 8.
Through the dynamic coupling, the moment of each joint of the two-joint bionic dolphin under different working conditions can be obtained, the PWM (pulse width modulation) technology is applied to compile a control strategy, the influence of the outside on the two-joint bionic dolphin during working can be weakened, and the stability is improved. Through dynamic coupling, when each joint of the two-joint bionic dolphin moves in various states, parameters such as acceleration, speed and displacement of the two-joint bionic dolphin at each moment can be predicted. The maximum motion speed and the corresponding kinematic equation of a specific two-joint bionic dolphin can be obtained by the method of the invention according to the determined parameters of mass, length, volume and the like.
S5: and according to the dynamic parameters of the two-joint bionic dolphin, controlling the output torque of each joint of the two-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology.
Based on the dynamic parameters obtained by simulation, a PWM (pulse width modulation) technology is applied to compile a control strategy, and the average power transmitted by the electric signals is adjusted by dispersing the effective electric signals into a discrete form, so that the output torque at the joint of the two-joint bionic dolphin at each moment can be controlled, the influence of the outside on the two-joint bionic dolphin is weakened, and the stability is improved.
Based on the method provided by the invention, the invention also provides a multi-joint bionic dolphin motion control system, which comprises the following steps:
the three-dimensional model building and preprocessing module is used for building a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain and preprocessing the three-dimensional models to obtain a model file subjected to preprocessing; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
the hydrodynamic simulation module is used for importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing difference calculation and fitting on 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 mainly comprise whether the water area flows, the water flow speed and the water flow direction;
the dynamic analysis module is used for carrying out dynamic analysis on the multi-joint bionic dolphin and deducing a dynamic model of the multi-joint bionic dolphin;
the dynamic coupling module is used for completing dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, the acceleration, the speed and the displacement of each joint of the multi-joint bionic dolphin at each moment;
and the dolphin motion control module is used for controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology according to the dynamic parameters of the multi-joint bionic dolphin.
The three-dimensional model building and preprocessing module specifically comprises:
the three-dimensional model establishing unit is used for establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software;
and the preprocessing unit is used for importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out preprocessing of model simplification and surface grid division on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file which completes preprocessing.
The hydrodynamic simulation module specifically comprises:
the model file importing unit is used for importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete the establishment of a computational domain, generate a volume grid, define a boundary and define the deformation motion operation of the multi-joint bionic dolphin;
the thrust curve calculation unit is used for setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematic equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition;
the hydrodynamic force curve calculation unit is used for carrying out speed synthesis on the linear motion of the multi-joint bionic dolphin under the specified underwater working condition according to a relative motion principle, converting the synthesis speed into the flow of water flow to carry out hydrodynamic force simulation, and gradually increasing the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust to obtain hydrodynamic force curves of the multi-joint bionic dolphin under different motion speeds in the acceleration motion process under the specified underwater working condition;
and the speed-resistance fitting curve calculation unit is used for solving the difference and fitting a resistance curve which changes along with the speed when the multi-joint bionic dolphin swings by a preset kinematic equation at each moment according to the thrust curve and the hydrodynamic curve, and the resistance curve is used as the speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
The dynamics analysis module specifically comprises:
and the dynamic analysis unit is used for carrying out dynamic analysis on the multi-joint bionic dolphin, concentrating hydrodynamic force by adopting a Lagrange method, converting the dynamic analysis of the multi-joint bionic dolphin into dynamic analysis of a multi-rigid system, and deducing a dynamic model of the multi-joint bionic dolphin.
The dynamic coupling module specifically comprises:
the dynamic model building unit is used for building a dynamic model of the multi-joint bionic dolphin in Matlab software, and the quality and length parameters of the multi-joint bionic dolphin are set in the dynamic model;
each joint moment calculation unit is used for decomposing a force term in the dynamic model into a thrust minus resistance, the thrust is a corresponding thrust in a thrust curve under the specified underwater working condition, the resistance at each moment is obtained according to a 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 obtained by subtracting the resistance from the thrust;
and the dolphin displacement and speed calculation unit is used for substituting the resultant force of each joint of the multi-joint bionic dolphin into the dynamic model at each moment, calculating to obtain the moment of each joint of the multi-joint bionic dolphin at each moment and the displacement, speed and acceleration along the advancing direction, and returning to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of each moment of the multi-joint bionic dolphin.
Based on the method provided by the invention, the invention also provides an underwater damage detection method based on the multi-joint bionic dolphin motion control, and as shown in fig. 9, the underwater damage detection method comprises the following steps:
step 901: establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain, and performing pretreatment to obtain a model file for completing pretreatment; the head of the multi-joint bionic dolphin is equipped with a sonar system; the three-dimensional model is used for simulating the motion 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;
step 902: importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 comprise whether the water area flows, the water flow speed and the water flow direction;
step 903: performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin;
step 904: completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, the acceleration, the speed and the displacement of each joint of the multi-joint bionic dolphin at each moment;
step 905: and according to the dynamic parameters of the multi-joint bionic dolphin, a 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 that the multi-joint bionic dolphin is controlled to perform uniform motion and positioning suspension at the detected underwater engineering structure, and the target identification and positioning of the damaged part of the underwater engineering structure are realized through a sonar system carried on the head of the multi-joint bionic dolphin.
By additionally arranging a sonar system on the head of the multi-joint bionic dolphin, the damage detection and positioning identification of the underwater engineering structure can be realized by the accurate multi-joint bionic dolphin motion control method.
In the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principle and the embodiment of the present invention are explained by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (10)
1. A multi-joint bionic dolphin motion control method is characterized by comprising the following steps:
establishing a three-dimensional model of a multi-joint bionic dolphin and a three-dimensional model of a computational domain, and performing pretreatment to obtain a model file for completing pretreatment; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 comprise whether the water area flows, the water flow speed and the water flow direction;
performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin;
completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, acceleration, speed and displacement of each joint of the multi-joint bionic dolphin at each moment;
and according to the dynamic parameters of the multi-joint bionic dolphin, controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology.
2. The method according to claim 1, wherein the establishing and preprocessing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain to obtain a preprocessed model file specifically comprises:
establishing 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;
and importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to carry out model simplification and surface grid division pretreatment on the three-dimensional model and the three-dimensional model of the calculation domain, so as to obtain a model file for completing the pretreatment.
3. The method according to claim 1, wherein the model file after the pretreatment 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 a specified underwater working condition, and then the thrust curve and the hydrodynamic curve are subjected to subtraction and fitting to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, specifically comprising:
importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete the establishment of a computational domain, generating a volume grid, defining a boundary and defining the deformation motion operation of the multi-joint bionic dolphin;
setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematic equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition;
according to the relative motion principle, the linear motion of the multi-joint bionic dolphin under the specified underwater working condition is subjected to velocity synthesis, the synthesis velocity is converted into the flow of water flow to carry out hydrodynamic simulation, the water flow velocity is gradually increased until the theoretical propulsion velocity of the multi-joint bionic dolphin under the action of thrust, and hydrodynamic curves of the multi-joint bionic dolphin under different motion velocities in the acceleration motion process under the specified underwater working condition are obtained;
and according to the thrust curve and the hydrodynamic curve, calculating a difference and fitting a resistance curve which changes with the speed when the multi-joint bionic dolphin swings by a preset kinematic equation at each moment to obtain a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
4. The method according to claim 1, wherein the performing a kinetic analysis on the multi-joint biomimetic dolphin to derive a kinetic model of the multi-joint biomimetic dolphin comprises:
and performing dynamic analysis on the multi-joint bionic dolphin, concentrating hydrodynamic force by adopting a Lagrange method, converting the dynamic analysis of the multi-joint bionic dolphin into dynamic analysis of a multi-rigid system, and deducing a dynamic model of the multi-joint bionic dolphin.
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, a thrust curve under a specified underwater condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, so as to obtain dynamic parameters of the multi-joint bionic dolphin, and the method specifically comprises the following steps:
building a dynamic model of the multi-joint bionic dolphin in Matlab software, and setting the quality and length parameters of the multi-joint bionic dolphin in the dynamic model;
decomposing a force term in the dynamic model into a thrust minus resistance, wherein the thrust is a thrust corresponding to a thrust curve under the specified underwater working condition, obtaining the resistance at each moment according to a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment, and obtaining the resultant force of each joint of the multi-joint bionic dolphin at each moment by utilizing the thrust minus resistance calculation;
substituting the resultant force of each joint of the multi-joint bionic dolphin at each moment into the dynamic model, calculating to obtain the moment of each joint of the multi-joint bionic dolphin at each moment and the displacement, the speed and the acceleration along the advancing direction, and returning to the step of obtaining the resistance at each moment according to the speed-resistance fitting curve of each moment of the multi-joint bionic dolphin.
6. A multi-joint bionic dolphin motion control system, comprising:
the three-dimensional model establishing and preprocessing module is used for establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain and preprocessing the three-dimensional model to obtain a model file which completes preprocessing; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
the hydrodynamic simulation module is used for importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 comprise whether the water area flows, the water flow speed and the water flow direction;
the dynamic analysis module is used for carrying out dynamic analysis on the multi-joint bionic dolphin and deducing a dynamic model of the multi-joint bionic dolphin;
the dynamic coupling module is used for completing dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, acceleration, speed and displacement of each joint of the multi-joint bionic dolphin at each moment;
and the dolphin motion control module is used for controlling the output torque of each joint of the multi-joint bionic dolphin at each moment by applying a PWM (pulse width modulation) technology according to the dynamic parameters of the multi-joint bionic dolphin.
7. The system of claim 6, wherein the three-dimensional model building and preprocessing module specifically comprises:
the three-dimensional model establishing unit is used for establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a computational domain in SolidWorks three-dimensional drawing software;
and the preprocessing unit is used for importing the three-dimensional model of the multi-joint bionic dolphin and the three-dimensional model of the calculation domain into Hypermesh software to perform preprocessing of model simplification and surface grid division on the three-dimensional model and the three-dimensional model of the calculation domain to obtain a model file subjected to preprocessing.
8. The system according to claim 6, wherein the hydrodynamic simulation module comprises:
the model file importing unit is used for importing the model file subjected to the pretreatment into computational fluid dynamics analysis software Star-CCM + to complete the establishment of a computational domain, generate a volume grid, define a boundary and define the deformation motion operation of the multi-joint bionic dolphin;
the thrust curve calculation unit is used for setting the water flow speed of a calculation domain to be zero, enabling the tail of the multi-joint bionic dolphin to swing, and calculating a thrust curve of the multi-joint bionic dolphin when swinging by a preset kinematic equation to serve as the thrust curve of the multi-joint bionic dolphin under a specified underwater working condition;
the hydrodynamic force curve calculation unit is used for carrying out speed synthesis on the linear motion of the multi-joint bionic dolphin under the specified underwater working condition according to a relative motion principle, converting the synthesis speed into the flow of water flow to carry out hydrodynamic force simulation, and gradually increasing the water flow speed until the theoretical propulsion speed of the multi-joint bionic dolphin under the action of thrust to obtain hydrodynamic force curves of the multi-joint bionic dolphin under different motion speeds in the acceleration motion process under the specified underwater working condition;
and the speed-resistance fitting curve calculation unit is used for calculating a difference according to the thrust curve and the hydrodynamic curve and fitting a resistance curve which changes along with the speed when the multi-joint bionic dolphin swings by a preset kinematic equation at each moment to serve as a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment.
9. The system of claim 6, wherein the kinetic analysis module specifically comprises:
and the dynamics analysis unit is used for carrying out dynamics analysis on the multi-joint bionic dolphin, centralizing hydrodynamic force by adopting a Lagrange method, converting the dynamics analysis of the multi-joint bionic dolphin into multi-rigid system dynamics analysis, and deducing a dynamics model of the multi-joint bionic dolphin.
10. An underwater damage detection method based on multi-joint bionic dolphin motion control is characterized by comprising the following steps:
establishing a three-dimensional model of the multi-joint bionic dolphin and a three-dimensional model of a calculation domain, and performing pretreatment to obtain a model file for completing pretreatment; the head of the multi-joint bionic dolphin is provided with a sonar system; the three-dimensional model is used for simulating the motion mode of the multi-joint bionic dolphin; the computational domain three-dimensional model is used for hydrodynamic simulation of the multi-joint bionic dolphin;
importing the model file subjected to the pretreatment 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 a specified underwater working condition, and then performing subtraction and fitting on 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 comprise whether the water area flows, the water flow speed and the water flow direction;
performing dynamic analysis on the multi-joint bionic dolphin, and deducing a dynamic model of the multi-joint bionic dolphin;
completing the dynamic coupling of the multi-joint bionic dolphin according to the dynamic model of the multi-joint bionic dolphin, a thrust curve under a specified underwater working condition and a speed-resistance fitting curve of the multi-joint bionic dolphin at each moment to obtain dynamic parameters of the multi-joint bionic dolphin; the dynamic parameters comprise the moment, the acceleration, the speed and the displacement of each joint of the multi-joint bionic dolphin at each moment;
and according to the dynamic parameters of the multi-joint bionic dolphin, a 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 that the multi-joint bionic dolphin is controlled to perform uniform motion and positioning suspension at the detected underwater engineering structure, and the target identification and positioning of the damaged part of the underwater engineering structure are realized through a sonar system carried on the head of the multi-joint bionic dolphin.
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