CN109866904B

CN109866904B - Motion and speed control method of bionic jellyfish underwater robot

Info

Publication number: CN109866904B
Application number: CN201910281993.7A
Authority: CN
Inventors: 王卓; 孙延超; 徐沈方; 秦洪德; 张佩; 吴淼; 张士伟
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2019-04-09
Filing date: 2019-04-09
Publication date: 2020-06-02
Anticipated expiration: 2039-04-09
Also published as: CN109866904A

Abstract

A motion and speed control method of a bionic jellyfish type underwater robot belongs to the field of control of bionic robots. The existing nonlinear oscillator has the problem of low convergence speed of frequency and amplitude in the rhythmic motion control of the bionic robot, and a corresponding speed control method is lacked. A motion and speed control method of a bionic jellyfish underwater robot is provided, wherein a bionic jellyfish power model is designed; establishing an oscillator model of each joint of the bionic jellyfish, and changing the waveform of an oscillator; designing a coupling mode between two oscillators, determining and establishing the coupling mode among the oscillators, realizing the mutual coordination among joints where the oscillators are located, realizing the control of the bionic jellyfish motion, drawing a frequency and average speed change curve according to the motion control, finding a corresponding motion frequency, and calculating a periodic speed change curve as an expected speed; the speed is controlled according to the desired speed. The algorithm of the invention has good convergence on the motion of the bionic jellyfish and can stably control the motion speed.

Description

Motion and speed control method of bionic jellyfish underwater robot

Technical Field

The invention relates to a control method of a bionic robot, in particular to a motion control and speed control method of a bionic jellyfish.

Background

Compared with other fishes, the jellyfishes have the characteristics of small volume, light weight, high flexibility, low metabolic rate and the like, and can effectively utilize the fluctuation motion of water flow. By utilizing the characteristics, people are interested in the research of the bionic jellyfish and aim to develop a bionic jellyfish prototype.

The bionic jellyfish also has a plurality of important application scenes in engineering. The bionic jellyfish can operate in a water area with a complex environment, has a large cavity space for placing instruments and equipment, and plays an important role in the scenes of marine organism investigation, marine rescue, marine resource exploration and the like. In addition, the bionic jellyfish has the characteristics of lower noise, stronger concealment and motion stability, is not easy to find in detection and investigation, and has remarkable advantages compared with other underwater robots.

The coordinated motion of the bionic robot in time sequence and space is two core problems of research, and the problem is that the rule of biological motion in life is generally summarized to extract a motion model. Modern neurology finds that the instinctive rhythmic behaviors of breathing, walking and the like of higher animals are instructions sent by a central nervous pattern generator of the spinal cord and the brain stem which are positioned in the middle layer of the nervous system. With the development of bionics, a coupled nonlinear oscillator is used to simulate instructions from a Central nervous pattern generator (CPGs) for controlling the rhythmic motion of a bionic robot. Coupled nonlinear oscillators are commonly used for motion control of bionic salamanders, bionic fish, bionic snakes and the like.

The control method of the bionic jellyfish is less researched at home and abroad. Therefore, the invention designs a motion control method for the bionic jellyfish underwater robot.

In addition, with the development of science and technology, bionics is receiving more and more attention from people. Bionics is a comprehensive edge science that emerged in the 60's of the 20 th century. Bionics achieves the goal of the original technology of improvement or innovation in the traditional industry by observing, simulating, making the shape, motion mechanism, control mode, propulsion principle of the living being. Because underwater organisms have evolved for thousands of years, the underwater organisms have the capability and characteristics of living underwater for a long time. If the characteristics of underwater organisms are integrated into the underwater robot through design and manufacture, the underwater robot also has excellent characteristics of good cruising ability, low noise and the like.

In the propulsion mode of underwater creatures, the swing propulsion is common, and the jet propulsion is more original. The jellyfish has good stability and flexible movement capability through jet propulsion, the jellyfish jet propulsion mode is more and more concerned by people, and people begin to research bionic jellyfishes. Compared with other fishes, the jellyfishes have the characteristics of small volume, light weight, high flexibility, low metabolic rate and the like, and can effectively utilize the fluctuation motion of water flow. By utilizing the characteristics, people are interested in the research of the bionic jellyfish and aim to develop a bionic jellyfish prototype.

The bionic jellyfish also has a plurality of important application scenes in engineering. The bionic jellyfish can operate in a water area with a complex environment, has a large cavity space for placing instruments and equipment, and plays an important role in the scenes of marine organism investigation, marine rescue, marine resource exploration and the like. In addition, the bionic jellyfish has the characteristics of lower noise, stronger concealment and better motion stability, is not easy to find in detection and investigation, and has remarkable advantages compared with other underwater robots.

Since the bionic jellyfish has the characteristics, researchers begin to pay attention to the development and development of the bionic jellyfish, and develop some bionic jellyfish prototypes. Several motion control methods suitable for the bionic jellyfish appear at home and abroad, and the motion modes of the bionic jellyfish such as linear motion, steering motion and the like are realized, but no method for controlling the speed of the bionic jellyfish exists due to the periodic change characteristics of the motion of the bionic jellyfish, and the indexes such as speed, acceleration and the like have the characteristic of periodic change.

Therefore, the invention discloses a speed control method for a bionic jellyfish type underwater robot based on a Central Pattern Generator (CPG) technology.

Disclosure of Invention

The invention aims to solve the problems that the convergence speed of frequency and amplitude is low and a bionic jellyfish speed control method is lacked in the rhythmic motion control process of a bionic robot of the conventional nonlinear oscillator, and provides a motion control method and a speed control method of a bionic jellyfish underwater robot based on an improved oscillator.

A motion control method of a bionic jellyfish underwater robot based on an improved oscillator comprises the following steps:

designing a bionic jellyfish power model;

establishing an oscillator model of each joint of the bionic jellyfish, and changing the waveform of an oscillator by adopting a non-harmonic gait generation method;

and step three, designing a coupling mode between the two oscillators, determining and establishing the coupling mode among the multiple oscillators, realizing the mutual matching and coordination among the joints where the multiple oscillators are located, completing various motion modes, and realizing the control of the overall coordination motion of the bionic jellyfish.

A speed control method of a bionic jellyfish underwater robot comprises the following steps:

designing a bionic jellyfish power model;

designing a coupling mode between two oscillators, determining and establishing the coupling mode among the oscillators, realizing the mutual matching and coordination among joints where the oscillators are located, completing various motion modes and realizing the control of the overall coordination motion of the bionic jellyfish;

step four, drawing a frequency and average speed change curve according to the motion control process of the step three;

finding out corresponding motion frequency on the frequency and average speed change curve according to the average expected speed, and then calculating a stable periodic speed change curve according to the motion frequency through the result of combining a non-harmonic gait oscillator equation and a bionic jellyfish kinetic equation, and taking the stable periodic speed change curve as the expected speed;

and step six, according to the obtained expected speed, carrying out speed control through PID.

The invention has the beneficial effects that:

the invention realizes the convergence speed of the oscillator model under the influence of frequency and amplitude, the oscillator model designed by the invention can achieve the expected convergence effect in a half movement period under the influence of frequency and amplitude, and has good convergence and stability compared with the two prior technical schemes:

compared with a Hopf oscillator, the CPGs-based oscillator model has higher amplitude and frequency convergence rate, and the method is applied to the bionic fish robot and has better motion effect. But compared with the algorithm of the invention, the convergence rate of the frequency and the amplitude is smoother, and the convergence rate is faster when the amplitude and the frequency change slightly or small disturbance is met.

As for the existing triangular waveform control method, a bionic robot motion control method based on a triangular waveform is provided, and the obstacle avoidance behavior of the bionic jellyfish is realized through the method. But compared with the algorithm, the convergence process of the motion is smoother, and the control output curve has no pole jump.

The bionic jellyfish speed control research realizes the convergence speed of the oscillator model under the influence of frequency and amplitude, and the oscillator model designed by the invention can achieve the expected convergence effect within a half movement period under the influence of frequency and amplitude and has good convergence and stability. The speed control method for the bionic jellyfish, which is provided by the patent of the invention, combines the control performances of the motion modes of the steering motion and the linear motion of the bionic jellyfish of the existing Hopf oscillator and the triangular waveform control method, and can realize the stable control of the speed of the bionic jellyfish according to the expected speed.

Drawings

FIG. 1 is a flow chart of a method of motion control in accordance with the present invention;

FIG. 2 is a non-harmonic gait representation of a method of motion control in accordance with the invention;

FIG. 3 is a schematic illustration of jellyfish displacement propulsion for a method of motion control in accordance with the present invention;

FIG. 4 is a diagram of the coupling relationship of a bionic jellyfish oscillator for the method of motion control according to the present invention;

FIG. 5 is a schematic diagram of various dimensional parameters of a bionic jellyfish in a motion control method according to the present invention;

FIG. 6 is a single oscillator frequency switching diagram of a method of motion control in accordance with the present invention;

FIG. 7 is a single oscillator amplitude increase plot for a method of motion control in accordance with the present invention;

FIG. 8 is a graph of single oscillator amplitude reduction for a method of motion control in accordance with the present invention;

FIG. 9 is a graph showing the velocity profile of a bionic jellyfish according to the method of motion control according to the present invention;

FIG. 10 is a graph showing the displacement of a bionic jellyfish according to the method of motion control according to the present invention;

FIG. 11 is a method flow diagram of a speed control method according to the present invention;

FIG. 12 is a non-harmonic gait representation of a speed control method according to the invention;

FIG. 13 is a schematic illustration of jellyfish displacement propulsion for a speed control method in accordance with the present invention;

FIG. 14 is a coupling relationship diagram of a bionic jellyfish oscillator according to the speed control method of the present invention;

FIG. 15 is a schematic diagram of various dimensional parameters of a bionic jellyfish in a speed control method according to the present invention;

FIG. 16 is a frequency-stabilized average velocity mapping curve of the velocity control method according to the present invention;

FIG. 17 is a speed control simulation diagram according to the present invention;

fig. 18 is a flow chart of speed control implementation from step four to step six of the speed control method according to the present invention.

Detailed Description

The first embodiment is as follows:

the motion control method of the bionic jellyfish underwater robot based on the improved oscillator comprises the following steps:

designing a bionic jellyfish power model;

The second embodiment is as follows:

different from the first specific embodiment, in the first step of the motion control method of the bionic jellyfish underwater robot based on the improved oscillator of the embodiment, the process of designing the bionic jellyfish dynamic model is as follows:

the movement of the jellyfishes in the water is a periodic movement with a regular rhythm. The movement process of the jellyfish can be subdivided into a contraction stage and a relaxation stage, and two cycles of the jellyfish are mutually closely connected to provide continuous power for the movement of the jellyfish. The main factors influencing the movement speed of the bionic jellyfish are the volume of water discharged during movement, and the ratio of the contraction time to the relaxation time.

Due to the particularity of the motion of the bionic jellyfish, a positive acting force relative to the motion direction is provided when the cavity is contracted, and a reverse acting force relative to the motion direction is generated when the cavity is relaxed, so that the ratio of the contraction time to the relaxation time is an important parameter for considering the motion of the bionic jellyfish. Let k be the ratio of the systolic time to the diastolic time. k is between 0 and 1, the smaller the k value is, the larger the propelling force generated by the bionic jellyfish is, and the larger the obtained average speed is.

Because the bionic jellyfish is propelled by water drainage, the larger the water drainage volume is, the larger the positive acting force can be obtained in unit time. The influence of the frequency in unit time on the motion of the bionic jellyfish is that the larger the frequency is, the more the contraction and relaxation times of the motion of the bionic jellyfish are, and the larger the thrust can be provided.

One movement cycle of the bionic jellyfish is similar to the movement of the real jellyfish and is propelled in a drainage mode.

The motion of the bionic jellyfish is powered by the steering engine, the water in the bionic jellyfish cavity is reduced by the rotation of the steering engine around the shaft, the bionic jellyfish mechanical arm is enabled to drain water, and the bionic jellyfish obtains forward propelling force by the drainage.

Step one, as shown in fig. 4, a bionic jellyfish with a group of tentacles is designed, each motion cycle of the bionic jellyfish is designed according to each motion condition of the real jellyfish, and a steering engine provides motion power for the bionic jellyfish:

when the steering engine drives the mechanical arm to contract, the mechanical arm is pulled to contract to the position with the minimum radius, the volume in the cavity of the bionic jellyfish is reduced, the backward drainage effect is generated, and the bionic jellyfish obtains forward propulsion force in a mechanical arm drainage mode, so that the bionic jellyfish is propelled to move forward;

when the steering engine drives the mechanical arm to relax, the mechanical arm is pulled to return to the position with the maximum radius of the relaxation, the volume in the bionic jellyfish cavity is increased, and one motion cycle of the bionic jellyfish is finished; the invention relates to a jellyfish drainage propulsion schematic diagram as shown in figure 3;

sending a periodic motion control signal to the bionic jellyfish, and carrying out periodic contraction and relaxation motion on the bionic jellyfish;

step two, the bionic jellyfish is under the action of propulsive force, fluid resistance, additional mass force and inertia force under water, and the stress balance equation of the bionic jellyfish obtained by integrating the stress conditions in the motion process is as follows:

T＝D+G+F (1)

wherein T represents propulsive force which is generated by the bionic jellyfish discharging water and is opposite to the water discharging direction; d represents fluid resistance, which is resistance generated when fluid resists the movement of the jellyfish; g represents additional mass force, and is acting force caused by driving surrounding fluid to accelerate when the motion posture of the bionic jellyfish is changed; f represents inertia force, which is the inertia of the bionic jellyfish, and in order to enable the bionic jellyfish to keep the tendency of the original movement posture, the tendency is represented as inertia acting force:

D(t)＝0.5C_d(t)ρS(t)v²(t) (3)

wherein t represents time, Δ t represents time variation, Δ V represents fluid volume variation in the bionic jellyfish cavity, d (V) represents differentiation of V, and d (V) represents differentiation of V, namely representing variation of motion speed of the bionic jellyfish;

and (3) combining the formulas (1) to (5) to obtain a bionic jellyfish kinetic equation:

in the formula, C_d(t) represents a shape drag coefficient, λ (t) represents an additional drag coefficient; and:

coefficient of shape resistance

Coefficient of additional resistance

Step three, designing various size parameters of the bionic jellyfish, as shown in figure 5:

the side area, the liquid volume in the cavity and the projection area can be expressed by the following expressions, and the change of the liquid volume in the cavity is considered, so the change of the total volume in the cavity is used for replacing the change of the liquid volume in the cavity, and the volumes of the duct and the watertight cabin are not subtracted;

z₂(t)＝l₁sin(θ₁(t))+z₁(11)

z₃(t)＝l₂sin(θ₂(t))+z₂(t) (12)

d(t)＝max(2z₂(t),2z₃(t)) (13)

h(t)＝h₁(t)+h₂(t)+z₁(14)

h₁(t)＝l₁cos(θ₁(t)) (15)

h₂(t)＝l₂cos(θ₂(t)) (16)

wherein, theta₁∈(0°～90°),θ₂E (-45-90 degrees); t represents thrust; d represents a fluid resistance; g represents additional mass force; f represents an inertial force; ρ represents the density of the fluid; v represents the fluid volume in the cavity of the bionic jellyfish; s_vRepresenting the cross-sectional area of the bionic jellyfish; c_dexpressing shape resistance coefficient, S expressing bionic jellyfish projection area, v expressing bionic jellyfish movement speed, α expressing additional resistance coefficient, m expressing jellyfish mass, d (t) expressing bell-shaped body diameter, h (t) expressing bell-shaped body height, C_f,lam(t) represents a surface friction resistance coefficient; re (t) represents Reynolds number; v' represents fluid kinematic viscosity; τ represents a positive time constant that adjusts the switching speed; s (τ y) represents a unipolar sigmoid function, e^-τyA function representing the shape of the simulation as a monopole sigmoid; z is a radical of₁Represents a hemispherical head radius; l₁Represents the upper arm length; h is₁Representing a projection of the upper arm on the centerline; z is a radical of₂Representing the upper arm drawing a circle radius around the centerline; theta₁Representing the included angle between the upper arm and the central line; l₂Represents the lower arm length; h is₂Represents the projection of the lower arm on the centre line; z is a radical of₃Representing the lower arm drawing a circle radius around the centerline; theta₂Representing the angle of the lower arm with the centre line; k represents the ratio of the contraction time to the relaxation time of the bionic jellyfish.

The third concrete implementation mode:

different from the second specific embodiment, in the second step of the motion control method of the bionic jellyfish underwater robot based on the improved oscillator of the present embodiment, an oscillator model of each joint of the bionic jellyfish is established, and a process of changing a waveform of the oscillator by using a non-harmonic gait generation method is specifically as follows:

simulating the motion of one joint of the bionic jellyfish by using a single oscillator, taking the amplitude of the oscillator as the amplitude of the motion of the corresponding joint, taking the frequency of the oscillator as the frequency of the motion of the corresponding joint, and taking the coupling strength of the oscillator as the degree of mutual influence among the joints when the bionic jellyfish moves;

step two, the following factors need to be comprehensively considered when designing and selecting a proper oscillator and considering the coupling mode of the oscillator:

1. the general structure of the CPG mainly comprises the determination of the type and the number of oscillators, and the selection of the output of the oscillators as an angle position control signal for driving the joint or a moment control signal for the motor. And typically one oscillator corresponds to one degree of freedom of the robot joint.

2. Inter-oscillator coupling type and topology, which will affect the synchronization conditions between the oscillators and the generation of gait.

3. The waveform of the oscillator, which determines the motion trajectory of the joint in each cycle, depends on which waveform is generated by the selected oscillator, and can be transformed by adding filters.

4. The influence of the parameters in the model on the output signal, i.e. how the control parameters can adjust some important characteristics of the oscillator, such as the frequency, amplitude, phase lag (in gait transitions) or waveform of the oscillator.

The application of the oscillator to the bionic jellyfish also needs to satisfy the following points:

5. the non-linear equation should be simple to reduce the computation time of the microprocessor.

6. The definition of the frequency, amplitude and phase difference of the output signal should be clear so that the switching of the control signal is easy to obtain.

7. The amplitude and frequency switching under various conditions has good switching speed and stability.

8. The effect of the feedback signal, i.e. the regulation effect of the feedback on the CPG model.

Taking a joint as an oscillator node, wherein the oscillator is a Hopf oscillator which is a model of a central nervous mode generator, and simulating the motion of each joint through simple harmonic vibration of the oscillator; the Hopf oscillator well meets two points of 5 and 6, and a basic model of the Hopf oscillator is as follows:

in the formula, x_i,y_iThe output quantity of the ith oscillator is the corresponding rotation angle of the bionic jellyfish steering engine; f. of_iIs the oscillation frequency of the ith oscillator;

step two, introducing parameters related to the amplitude of the oscillator on the basis of the step two to form a limit stable loop, namely:

and w_i＝2πf_i，

When the following conditions are satisfied:

current amplitude r_iApproaches the amplitude R after stabilization; and after stabilization x_i,y_iIs equal to the newly changed frequency, a limit stability loop can be formed;

in the formula, h (x)_i,y_iR) is in respect of x_i,y_iR is a function of the amplitude after stabilization; r is_iIs expressed in the current amplitude, w_iRepresents an angular velocity;

step two, according to the condition 7, an oscillator model with faster and more stable switching frequency amplitude is expected to be designed, and h (x) is designed_i,y_iR) function derived oscillatorThe oscillator converges at a certain amplitude to realize the rhythmic motion of the joint, and can also adjust the amplitude and the frequency to change the motion state of the joint; wherein the equation of the oscillator is:

wherein k is a positive proportional term coefficient;

step two and five, the oscillator is applied to each joint of the bionic jellyfish, and each f_iAre all equal, then f_iThe bionic jellyfish movement frequency; output x of oscillator_i,y_iAll the bionic jellyfish control input quantities can be used as the control input quantities of the bionic jellyfish, namely the rotation angles of the steering engines corresponding to all joints; r is the amplitude of the output waveform after stabilization, namely the range of the rotation angle of the steering engine corresponding to the bionic jellyfish, and when the bionic jellyfish is applied, the R needs to be amplified in equal proportion or reduced to the range of the angle of the expected movement of the joint corresponding to the bionic jellyfish; k is a positive proportional coefficient, when the oscillator receives external disturbance or adjusts parameters of the oscillator, the value of k corresponds to the convergence performance of the oscillator, the convergence of the oscillator is quicker when k is larger, and when the k is applied to the bionic jellyfish, the value of k needs to be determined according to the performance of an actual steering engine, and the larger the k is, the better the k is.

The fourth concrete implementation mode:

the third difference from the third specific embodiment is that the third embodiment is a motion control method of the bionic jellyfish underwater robot based on the improved oscillator, wherein the motion frequency f of the bionic jellyfish_iThe Chunlin Zhou is used to provide a way to generate non-harmonic gait, as shown in FIG. 2, setting different frequencies involved in one cycle to cause waveform asymmetry, the shape of the waveform determines the switching of the frequencies, and setting the higher frequency component f₁Is a rising phase, lower frequency component f₂If it is a falling phase, then:

the total frequency can be expressed as:

wherein f represents the total frequency; f. of₁Represents the rising phase frequency; f. of₂representing the falling phase frequency α indicating the proportion of the period of the rising segment to the total period.

The fifth concrete implementation mode:

different from the fourth specific embodiment, in the third step, a coupling mode between two oscillators is designed, so that the coupling mode between the oscillators is determined and established, the mutual coordination between the joints where the oscillators are located is realized, various motion modes are completed, and the process of controlling the overall coordinated motion of the bionic jellyfish is realized, specifically:

the movement of animals or people is not only the movement of one joint, but also the mutual coordination of a plurality of joints, and finally the purpose of a certain movement mode is achieved. For example, when a person walks, the cooperation of a plurality of joints such as a hip joint, a knee joint, and an ankle joint is involved. Therefore, the bionic jellyfish also needs to establish the connection between the oscillators through the coupling among the oscillators, and the control of the overall coordinated motion is realized.

Step three, designing a coupling mode between the two oscillators, which comprises the following steps:

in the formula, c_ix_jCoupling strength of x-dimension output quantity of j joint for i joint;

if c is₁c₂If not equal to 0, bidirectional coupling is performed;

if c is₁＝0||c₂If 0, the coupling is unidirectional;

step two, establishing a coupling mode among a plurality of oscillators, which is expressed as:

when k is i, c_k＝0；

Expressing the coupling of the oscillators in a directed graph mode, wherein each oscillator node is a vertex, the coupling between the oscillators is an edge, and the coupling strength is the length of the edge;

the coupling of e.g. 3 oscillators can be expressed as a matrix,

as a coupling term c in the oscillator i_jx_jWherein

The above parts relate to a general coupling mode of the oscillator, and if the oscillator is applied to the bionic jellyfish, the number of the oscillators needs to be determined according to the number of joints of the bionic jellyfish; determining the distribution mode of the oscillator according to the symmetry of the joint of the bionic jellyfish; determining whether the two oscillators are coupled or not according to the correlation between the bionic jellyfish joints; according to the frequent gait switching condition in the practical application process of the bionic jellyfish, the unidirectional coupling or bidirectional coupling mode is determined.

The sixth specific implementation mode:

different from the fifth specific embodiment, the fifth embodiment is a motion control method of the bionic jellyfish underwater robot based on the improved oscillator, and fig. 4 shows the arrangement and coupling relationship of the bionic jellyfish oscillator of the invention.

In the third step, the number of the oscillators is determined according to the number of the joints of the bionic jellyfish; determining the distribution mode of the oscillator according to the symmetry of the joint of the bionic jellyfish; determining whether the two oscillators are coupled or not according to the correlation between the bionic jellyfish joints; according to the frequent gait conversion condition in the practical application process of the bionic jellyfish, the method for determining the adoption of the one-way coupling or the two-way coupling is specifically as follows:

the oscillators are distributed in a pairwise centrosymmetric manner;

each tentacle of the bionic jellyfish is regarded as a driving mechanism, and the driving mechanisms are not coupled, so that the driving mechanisms can independently move, and the steering movement is conveniently realized; the upper arm and the lower arm of each motion mechanism are mutually influenced when moving, and only the upper arm and the lower arm of each motion mechanism are coupled;

because the unidirectional coupling can reduce the calculated amount compared with the bidirectional coupling and can also meet the practical application of the bionic robot under the condition that the quick gait conversion is not a key requirement, in the text, each tentacle of the jellyfish of the bionic robot is driven by the two oscillators in a unidirectional coupling mode; the upper arm and the lower arm are mainly affected by the swing of the upper arm on the motion of the lower arm, a unidirectional coupling mode that the lower end is coupled with the upper end is adopted, and a unidirectional coupling factor is arranged in an oscillator equation of the lower arm.

The seventh embodiment:

different from the sixth specific embodiment, in the motion control method of the bionic jellyfish underwater robot based on the improved oscillator, the number of the bionic jellyfishes with a group of tentacles is 4-8.

The specific implementation mode is eight:

the seventh embodiment is different from the seventh embodiment in that the motion control method of the bionic jellyfish underwater robot based on the improved oscillator in the embodiment includes the steps of designing 4 bionic jellyfishes with a group of tentacles.

The specific implementation method nine:

different from the eighth specific embodiment, in the motion control method of the bionic jellyfish underwater robot based on the improved oscillator in the embodiment, the number of the bionic jellyfishes with one group of tentacles is 6.

The detailed implementation mode is ten:

different from the specific embodiment, the motion control method of the bionic jellyfish underwater robot based on the improved oscillator in the embodiment comprises the steps of designing 8 bionic jellyfishes with a group of tentacles.

The concrete implementation mode eleven:

the method is different from the specific embodiment in that the motion control method of the bionic jellyfish underwater robot is based on the improved oscillator, the oscillator model of the bionic jellyfish is slightly different from the model, and the method mainly depends on the appearance of the bionic jellyfish and the particularity of the motion mode. The bionic jellyfish design model adopted by the invention is provided with 8 joints, and the adopted oscillators are 8 oscillators; the bionic jellyfish is provided with 4 driving mechanisms which are centrosymmetrically distributed around a central line, each driving mechanism is composed of two joints, and oscillators are distributed in a pairwise centrosymmetric mode; the 4 driving mechanisms are not coupled, so that the driving mechanisms can move independently, and the steering movement is convenient to realize; the motion of the upper arm and the lower arm of each motion mechanism has mutual influence, and only the upper arm and the lower arm of each motion mechanism are coupled; because the calculation amount of the unidirectional coupling can be reduced compared with the bidirectional coupling, and the actual application of the bionic robot can be met under the condition that the rapid gait conversion is not a key requirement, each tentacle of the jellyfish of the bionic robot is driven by adopting a unidirectional coupling mode of two oscillators; the influence of the swing of the upper arm on the motion of the lower arm is mainly caused between the upper arm and the lower arm, so the unidirectional coupling factor is in an oscillator equation of the lower arm;

with lower end coupling for each direction of driveThe upper end is in a unidirectional coupling mode, and the same control parameters are adopted for upper end driving mechanisms in different directions so as to ensure the coordination consistency of jellyfish movement; the coupling parameters are expressed in a matrix in an 8 x 8 coupling matrix, except that

All other items are 0; wherein the content of the first and second substances,

representing the coupling strength of the upper end driving mechanism to the lower end driving mechanism; the size of the coupling parameters is determined by debugging in experiments.

The specific implementation mode twelve:

as shown in fig. 11, the speed control method of the bionic jellyfish underwater robot of the present embodiment includes the following steps:

designing a bionic jellyfish power model;

because the speed control of the bionic jellyfish is different from other bionic robots, the speed of the bionic jellyfish is a periodically changed curve after being stabilized, and if the speed control of the bionic jellyfish is to be realized, the speed control refers to the control of the average speed in the period of the bionic jellyfish. But the desired average speed given cannot be used directly for motion control.

The frequency, the amplitude and the waveform asymmetry ratio of the oscillator can be used as parameters for controlling the motion of the bionic jellyfish, and only the frequency is used as a control variable for controlling the change of the motion speed of the bionic jellyfish.

finding out corresponding motion frequency on a frequency and average speed change curve according to the average expected speed during speed control, and then calculating a stable periodic speed change curve according to the motion frequency through a result of combination of a non-harmonic gait oscillator equation and a bionic jellyfish kinetic equation, and taking the stable periodic speed change curve as the expected speed;

and step six, according to the obtained expected speed, carrying out speed control through PID. As shown in fig. 18.

PID refers to a PID controller, which is a common feedback loop component in industrial control applications, and is known as a proportional-integral-derivative controller, and is composed of a proportional unit P, an integral unit I, and a derivative unit D. The basis of PID control is proportional control; integral control may eliminate steady state errors, but may increase overshoot; differential control can accelerate the response speed of the large inertia system and weaken the overshoot tendency.

The key to this theory and application is how to better correct the system after making the correct measurements and comparisons.

The specific implementation mode is thirteen:

a twelfth difference from the detailed embodiment is that, in the speed control method of the bionic jellyfish underwater robot of the embodiment, in the first step, the process of designing the bionic jellyfish dynamic model includes:

Step one, as shown in fig. 14, a bionic jellyfish with a group of tentacles is designed, each motion cycle of the bionic jellyfish is designed according to each motion condition of the real jellyfish, and a steering engine provides motion power for the bionic jellyfish:

when the steering engine drives the mechanical arm to relax, the mechanical arm is pulled to return to the position with the maximum radius of the relaxation, the volume in the bionic jellyfish cavity is increased, and one motion cycle of the bionic jellyfish is finished; FIG. 13 is a schematic view of the present invention relating to the propulsion of jellyfish drainage;

T＝D+G+F (1)

D(t)＝0.5C_d(t)ρS(t)v²(t) (3)

coefficient of shape resistance

Coefficient of additional resistance

Step three, designing various size parameters of the bionic jellyfish, as shown in fig. 15:

z₂(t)＝l₁sin(θ₁(t))+z₁(11)

z₃(t)＝l₂sin(θ₂(t))+z₂(t) (12)

d(t)＝max(2z₂(t),2z₃(t)) (13)

h(t)＝h₁(t)+h₂(t)+z₁(14)

h₁(t)＝l₁cos(θ₁(t)) (15)

h₂(t)＝l₂cos(θ₂(t)) (16)

wherein, theta₁∈(0°～90°),θ₂E (-45-90 degrees); t represents thrust; d represents a fluid resistance; g represents additional mass force; f represents an inertial force; ρ represents the density of the fluid; v represents the fluid volume in the cavity of the bionic jellyfish; s_vRepresenting the cross-sectional area of the bionic jellyfish; c_dexpressing shape resistance coefficient, S expressing bionic jellyfish projection area, v expressing bionic jellyfish movement speed, α expressing additional resistance coefficient, m expressing jellyfish mass, d (t) expressing bell-shaped body diameter, h (t) expressing bell-shaped body height, C_f,lam(t) represents a surface friction resistance coefficient; re (t) representsReynolds number; v' represents fluid kinematic viscosity; τ represents a positive time constant that adjusts the switching speed; s (τ y) represents a unipolar sigmoid function, e^-τyA function representing the shape of the simulation as a monopole sigmoid; z is a radical of₁Represents a hemispherical head radius; l₁Represents the upper arm length; h is₁Representing a projection of the upper arm on the centerline; z is a radical of₂Representing the upper arm drawing a circle radius around the centerline; theta₁Representing the included angle between the upper arm and the central line; l₂Represents the lower arm length; h is₂Represents the projection of the lower arm on the centre line; z is a radical of₃Representing the lower arm drawing a circle radius around the centerline; theta₂Representing the angle of the lower arm with the centre line; k represents the ratio of the contraction time to the relaxation time of the bionic jellyfish.

The specific implementation mode is fourteen:

different from the thirteenth specific embodiment, in the speed control method of the bionic jellyfish underwater robot of the present embodiment, in the second step, an oscillator model of each joint of the bionic jellyfish is established, and a process of changing a waveform of the oscillator by using a non-harmonic gait generation method is specifically:

and w_i＝2πf_i，

When the following conditions are satisfied:

in the formula, h (x)_i,y_iR) is in respect of x_i,y_iR is a function of the amplitude after stabilization; r is_iRepresenting the current amplitude value;

step two, according to the condition 7, an oscillator model with faster and more stable switching frequency amplitude is expected to be designed, and h (x) is designed_i,y_iR) function gets the oscillator, the oscillator is converged and realized the rhythmic motion of the joint with certain amplitude, and can also regulate amplitude and frequency in order to change the kinematic state of the joint; wherein the equation of the oscillator is:

wherein k is a positive proportional term coefficient;

step two and five, the oscillator is applied to each joint of the bionic jellyfish, and each f_iAre all equal, then f_iThe bionic jellyfish movement frequency; output x of oscillator_i,y_iAll the bionic jellyfish control input quantities can be used as the control input quantities of the bionic jellyfish, namely the rotation angles of the steering engines corresponding to all joints; r is the amplitude of the output waveform after stabilization, namely the range of the rotation angle of the steering engine corresponding to the bionic jellyfish, and when the bionic jellyfish is applied, the R needs to be amplified in equal proportion or reduced to the range of the angle of the expected movement of the joint corresponding to the bionic jellyfish; k is a positive proportional coefficient, when the oscillator receives external disturbance or modulates parameters of the oscillator, the value of k corresponds to the convergence performance of the oscillator, the convergence of the oscillator is faster as k is larger, and when the k is applied to the bionic jellyfish, the value of k needs to be according to the actual conditionThe larger the steering engine, the better, depending on its performance.

The concrete implementation mode is fifteen:

different from the fourteenth specific embodiment, in the speed control method of the bionic jellyfish underwater robot of the present embodiment, the motion frequency f of the bionic jellyfish is_iThe Chunlin Zhou is used to provide a way to generate non-harmonic gait, as shown in FIG. 12, setting different frequencies involved in one cycle to cause waveform asymmetry, the shape of the waveform determines the switching of the frequencies, and setting the higher frequency component f₁Is a rising phase, lower frequency component f₂If it is a falling phase, then:

the total frequency can be expressed as:

The specific implementation mode is sixteen:

different from the fifteenth specific embodiment, in the third step, a coupling mode between two oscillators is designed, so that the coupling mode between the oscillators is determined and established, the joint where the oscillators are located is matched with each other to complete various motion modes, and the process of controlling the overall coordinated motion of the bionic jellyfish is specifically as follows:

if c is₁c₂If not equal to 0, bidirectional coupling is performed;

if c is₁＝0||c₂If 0, the coupling is unidirectional;

when k is i, c_k＝0；

the coupling of e.g. 3 oscillators can be expressed as a matrix,

as a coupling term c in the oscillator i_jx_jWherein

Seventeenth embodiment:

sixthly, different from the specific embodiment, the speed control method of the bionic jellyfish underwater robot is provided, and fig. 14 shows the arrangement and coupling relationship of the bionic jellyfish oscillator disclosed by the invention.

the oscillators are distributed in a pairwise centrosymmetric manner;

The specific implementation mode is eighteen:

different from the seventeenth embodiment, the speed control method of the bionic jellyfish underwater robot in the embodiment includes the steps of designing 4-8 bionic jellyfishes with a group of tentacles.

The detailed embodiment is nineteen:

different from the eighteenth specific embodiment, the speed control method of the bionic jellyfish underwater robot in the embodiment includes the step of designing 4 bionic jellyfishes with a group of tentacles.

The specific implementation mode twenty:

different from the nineteenth concrete embodiment, the speed control method of the bionic jellyfish underwater robot in the embodiment includes the steps that the number of bionic jellyfishes with a group of tentacles is 6.

The specific implementation mode is twenty one:

twenty different from the specific embodiment, the speed control method of the bionic jellyfish underwater robot in the embodiment includes the step of designing 8 bionic jellyfishes with a group of tentacles.

Specific embodiment twenty-two:

different from the twenty-first specific embodiment, in the speed control method of the bionic jellyfish underwater robot of the present embodiment, the oscillator model of the bionic jellyfish is slightly different from the above model, and mainly depends on the shape of the bionic jellyfish and the particularity of the motion mode. The bionic jellyfish design model adopted by the invention is provided with 8 joints, and the adopted oscillators are 8 oscillators; the bionic jellyfish is provided with 4 driving mechanisms which are centrosymmetrically distributed around a central line, each driving mechanism is composed of two joints, and oscillators are distributed in a pairwise centrosymmetric mode; the 4 driving mechanisms are not coupled, so that the driving mechanisms can move independently, and the steering movement is convenient to realize; the motion of the upper arm and the lower arm of each motion mechanism has mutual influence, and only the upper arm and the lower arm of each motion mechanism are coupled; because the calculation amount of the unidirectional coupling can be reduced compared with the bidirectional coupling, and the actual application of the bionic robot can be met under the condition that the rapid gait conversion is not a key requirement, each tentacle of the jellyfish of the bionic robot is driven by adopting a unidirectional coupling mode of two oscillators; the influence of the swing of the upper arm on the motion of the lower arm is mainly caused between the upper arm and the lower arm, so the unidirectional coupling factor is in an oscillator equation of the lower arm;

the driving mechanisms in each direction adopt a one-way coupling mode that the lower ends are coupled with the upper ends, and the driving mechanisms at the upper ends in different directions adopt the same control parameters so as to ensure the coordination consistency of jellyfish movement; the coupling parameters are expressed in a matrix in an 8 x 8 coupling matrix, except that

All other items are 0; wherein the content of the first and second substances,

(1) Simulation experiment of motion control method

The bionic jellyfish kinetic model designed by the patent can be obtained by combining the formulas (1) - (5) with the formulas (11) - (18).

The kinetic model parameters are shown in table 1 and table 2.

Table 1 and table 2 show the structural parameters of the bionic jellyfish:

TABLE 1 jellyfish static structural parameters

TABLE 2 other parameters

Simulation analysis

In order to verify the feasibility of the algorithm, the influence of frequency and amplitude on the convergence rate of the oscillator model is verified. The aim of adjusting the motion state of the bionic robot is achieved by changing the oscillation frequency of the oscillator or changing the influence of the amplitude on the output quantity of the oscillator. The switching speed of the oscillation frequency or amplitude is a factor in measuring the quality of the oscillator. An ideal oscillator should have fast frequency and amplitude switching and stability so as to satisfy the application of the bionic robot in various practical situations. The single oscillator model of equation (3) is used.

Fig. 6 is a case of frequency switching with the amplitude of the analog single oscillator unchanged:

starting from 3s with frequency f_iSwitching from 1 to 2, the switching time is about half a cycle, the amplitude R is 1, and the proportionality coefficient k is 10. As can be seen in fig. 6, the oscillator has stability and a fast response speed at the time of frequency switching.

Simulating switching of amplitude, frequency f_iIs 1 and the coefficient k of the scale term is 10. Fig. 7 switches the amplitude R from 1 to 2 at 3s, and fig. 8 switches the amplitude R from 2 to 1 at 3 s. The switching of the amplitude is divided into two cases of increasing and decreasing the amplitude, and the switching time is less than one period.

The oscillator model designed by the invention can achieve the expected convergence effect within a half movement period under the influence of frequency and amplitude, and has good convergence and stability. The motion control method proposed by the patent of the invention is combined with a bionic jellyfish kinetic model for simulation.

Combining equations (6) to (18) with tables 1 and 2, the kinetic equation of the bionic jellyfish suitable for the design herein can be obtained, and equations (22), (23), (21), (26) and (27) can immediately obtain the non-harmonic gait coupled oscillator equation of the bionic jellyfish suitable for the design herein. The non-harmonic gait oscillator equation and the bionic jellyfish kinetic equation are combined to carry out the bionic jellyfish motion simulation, and the bionic jellyfish speed displacement change curve under the conditions of the graph 9 and the graph 10 can be obtained.

fig. 9 and 10 show a time-varying curve of the speed of the bionic jellyfish and a time-varying curve of the displacement of the bionic jellyfish at an initial speed of 2m/s with a total frequency of 0.2, where α is 0.8, and fig. 9 shows that the speed rapidly increases when the bionic jellyfish arm contracts, the speed slowly decreases when the bionic jellyfish arm relaxes, and the stable average speed 0.2017m/s of the movement of the bionic jellyfish, and fig. 10 shows that the bionic jellyfish moves in a continuous forward movement posture although the curve has small fluctuation, and the bionic jellyfish reaches a maximum displacement 9.8233m at 40 s.

(2) Simulation experiment of speed control method

The maximum rotation angular speed of a common steering engine is 0.13s/60 degrees, so the upper limit of the set frequency is 2.6s during simulation^-1fig. 16 shows α ═ 0.6, 0.7, and 0.8, initial velocity 0m/s, and frequency sampling range [0,2.6]the motion frequency corresponding to the desired average speed is obtained from the curve, α is 0.7, the initial speed is 0.1, and the desired speed is 1.326 when the PID parameters are 10, 1, and 1, respectively.

Simulation analysis

The bionic jellyfish kinetic equation can be obtained through the joint vertical type (1) - (5), and the kinetic relation formula of the bionic jellyfish designed by the patent can be obtained by substituting the data of the formulas (11) - (18) combined with the data of the tables (1) and (2) into the bionic jellyfish kinetic equation.

The equations (23), (21) and (26) are combined to obtain a bionic jellyfish non-harmonic oscillator model, and then the oscillator coupling relation of fig. 14 is brought into the bionic jellyfish non-harmonic oscillator model to obtain the bionic jellyfish non-harmonic oscillator equation designed by the patent. And finally, combining the dynamic relational expression of the bionic jellyfish, the bionic jellyfish non-harmonic oscillator equation and the bionic jellyfish speed control method provided by the invention to obtain the simulation result of the figure 17. It can be seen from fig. 17 that the bionic jellyfish speed control method provided by the patent of the invention realizes the speed control of the bionic jellyfish, so that the uniform speed of the bionic jellyfish is stabilized at 1.326 m/s.

The present invention is capable of other embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and scope of the present invention.

Claims

1. The motion control method of the bionic jellyfish underwater robot based on the improved oscillator is characterized by comprising the following steps: the method comprises the following steps:

designing a bionic jellyfish power model;

2. The motion control method of the bionic jellyfish underwater robot based on the improved oscillator as claimed in claim 1, characterized in that: in the first step, the process of designing the bionic jellyfish power model comprises the following steps:

step one, design the bionical jellyfish that has a set of tentacle, design every motion cycle of bionical jellyfish according to every motion condition of true jellyfish, provide the power of motion for bionical jellyfish by the steering wheel:

when the steering engine drives the mechanical arm to relax, the mechanical arm is pulled to return to the position with the maximum radius of the relaxation, the volume in the bionic jellyfish cavity is increased, and one motion cycle of the bionic jellyfish is finished;

T＝D+G+F (1)

D(t)＝0.5C_d(t)ρS(t)v²(t) (3)

wherein t represents time, Δ t represents time variation, Δ V represents fluid volume variation in the bionic jellyfish cavity, d (V) represents differentiating V, and d (V) represents differentiating V;

coefficient of shape resistance

Coefficient of additional resistance

Step three, designing various size parameters of the bionic jellyfish:

side area, intracavity liquid volume, projection area expression is as follows:

z₂(t)＝l₁sin(θ₁(t))+z₁(11)

z₃(t)＝l₂sin(θ₂(t))+z₂(t) (12)

d(t)＝max(2z₂(t),2z₃(t)) (13)

h(t)＝h₁(t)+h₂(t)+z₁(14)

h₁(t)＝l₁cos(θ₁(t)) (15)

h₂(t)＝l₂cos(θ₂(t)) (16)

wherein, theta₁∈(0°～90°),θ₂E (-45-90 degrees); t represents thrust; d represents a fluid resistance; g represents additional mass force; f represents an inertial force; ρ represents the density of the fluid; v represents the intracavity content of the bionic jellyfishA volume of fluid; s_vRepresenting the cross-sectional area of the bionic jellyfish; c_dRepresenting the shape drag coefficient; s represents the projection area of the bionic jellyfish; v represents the bionic jellyfish movement speed; λ represents an additional drag coefficient; m represents the mass of the jellyfish; d (t) represents the diameter of the bell; h (t) represents the height of the bell; c_f,lam(t) represents a surface friction resistance coefficient; re (t) represents Reynolds number; v' represents fluid kinematic viscosity; τ represents a positive time constant that adjusts the switching speed; s (τ y) represents a unipolar sigmoid function, e^-τyA function representing the shape of the simulation as a monopole sigmoid; z is a radical of₁Represents a hemispherical head radius; l₁Represents the upper arm length; h is₁Representing a projection of the upper arm on the centerline; z is a radical of₂Representing the upper arm drawing a circle radius around the centerline; theta₁Representing the included angle between the upper arm and the central line; l₂Represents the lower arm length; h is₂Represents the projection of the lower arm on the centre line; z is a radical of₃Representing the lower arm drawing a circle radius around the centerline; theta₂Representing the angle of the lower arm with the centre line; k represents the ratio of the contraction time to the relaxation time of the bionic jellyfish.

3. The motion control method of the bionic jellyfish underwater robot based on the improved oscillator as claimed in claim 2, characterized in that: in the second step, an oscillator model of each joint of the bionic jellyfish is established, and a process of changing the waveform of the oscillator by adopting a non-harmonic gait generation method is specifically as follows:

secondly, taking one joint as an oscillator node, wherein the oscillator is a Hopf oscillator, and simulating the motion of each joint through simple harmonic vibration of the oscillator; the basic model of the Hopf oscillator is as follows:

and w_i＝2πf_i，

When the following conditions are satisfied:

step two and step four, designing h (x)_i,y_iR) function gets the oscillator, the oscillator is converged and realized the rhythmic motion of the joint with certain amplitude, and can also regulate amplitude and frequency in order to change the kinematic state of the joint; wherein the equation of the oscillator is:

wherein k is a positive proportional term coefficient;

step two and five, the oscillator is applied to each joint of the bionic jellyfish, and each f_iAre all equal, then f_iThe bionic jellyfish movement frequency; output x of oscillator_i,y_iAll can be used as the control input quantity of the bionic jellyfishNamely corresponding to the rotation angle of the steering engine of each joint; r is the amplitude of the output waveform after stabilization, namely the range of the rotation angle of the steering engine corresponding to the bionic jellyfish, and when the bionic jellyfish is applied, the R needs to be amplified in equal proportion or reduced to the range of the angle of the expected movement of the joint corresponding to the bionic jellyfish; k is a positive proportional coefficient, when the oscillator receives external disturbance or adjusts parameters of the oscillator, the value of k corresponds to the convergence performance of the oscillator, and when the bionic jellyfish generator is applied, the value of k is determined according to the performance of an actual steering engine; wherein, the motion frequency f of the bionic jellyfish_iIn the non-harmonic gait mode, different frequencies related to one period are set to cause waveform asymmetry, the shape of the waveform determines the switching of the frequency, and a higher frequency component f is set₁Is a rising phase, lower frequency component f₂If it is a falling phase, then:

the total frequency can be expressed as:

4. The motion control method of the bionic jellyfish underwater robot based on the improved oscillator as claimed in claim 3, characterized in that: in the third step, a coupling mode between the two oscillators is designed, so that the coupling mode between the oscillators is established, the joint where the oscillators are located is matched and coordinated with each other, various motion modes are completed, and the process of controlling the overall coordinated motion of the bionic jellyfish is realized, specifically:

if c is₁c₂If not equal to 0, bidirectional coupling is performed;

if c is₁＝0||c₂If 0, the coupling is unidirectional;

when k is i, c_k＝0；

Expressing the coupling of the oscillators in a directed graph mode, wherein each oscillator node is a vertex, the coupling between the oscillators is an edge, and the coupling strength is the length of the edge; then determining the number of oscillators according to the number of joints of the bionic jellyfish; determining the distribution mode of the oscillator according to the symmetry of the joint of the bionic jellyfish; determining whether the two oscillators are coupled or not according to the correlation between the bionic jellyfish joints; determining to adopt a one-way coupling or two-way coupling mode according to the frequent gait switching condition in the practical application process of the bionic jellyfish; wherein, the number of the oscillators is determined according to the number of the joints of the bionic jellyfish; determining the distribution mode of the oscillator according to the symmetry of the joint of the bionic jellyfish; determining whether the two oscillators are coupled or not according to the correlation between the bionic jellyfish joints; according to the frequent gait conversion condition in the practical application process of the bionic jellyfish, the method for determining the adoption of the one-way coupling or the two-way coupling is specifically as follows:

the oscillators are distributed in a pairwise centrosymmetric manner;

each tentacle of the bionic jellyfish is regarded as a driving mechanism, and the driving mechanisms are not coupled, so that the driving mechanisms can independently move, and the steering movement is conveniently realized; the upper arm and the lower arm of each motion mechanism are coupled under the condition that the upper arm and the lower arm of each motion mechanism are mutually influenced;

each tentacle of the bionic machine jellyfish is driven by the two oscillators in a one-way coupling mode; and the upper arm and the lower arm are coupled by adopting a unidirectional coupling mode of coupling the lower end and the upper end, and the unidirectional coupling factor is arranged in an oscillator equation of the lower arm.

5. The motion control method of the bionic jellyfish underwater robot based on the improved oscillator as claimed in claim 4, characterized in that: step one, the designed bionic jellyfish is provided with a group of tentacles with 8 tentacles, a bionic jellyfish design model is provided with 8 joints, and 8 oscillators are adopted; the bionic jellyfish is provided with 4 driving mechanisms which are centrosymmetrically distributed around a central line, each driving mechanism is composed of two joints, and oscillators are distributed in a pairwise centrosymmetric mode; the 4 driving mechanisms are not coupled, so that the driving mechanisms can move independently, and the steering movement is convenient to realize; the motion of the upper arm and the lower arm of each motion mechanism has mutual influence, and only the upper arm and the lower arm of each motion mechanism are coupled; each tentacle of the bionic machine jellyfish is driven in a one-way coupling mode of two oscillators; the influence of the swing of the upper arm on the motion of the lower arm is mainly caused between the upper arm and the lower arm, and the unidirectional coupling factor is in an oscillator equation of the lower arm;

All other items are 0; wherein the content of the first and second substances,

indicating the strength of the coupling of the upper end drive to the lower end drive.

6. A speed control method of a bionic jellyfish underwater robot is characterized by comprising the following steps: the method comprises the following steps:

designing a bionic jellyfish power model;

7. The speed control method of the bionic jellyfish-like underwater robot according to claim 6, characterized by comprising the following steps: in the first step, the process of designing the bionic jellyfish power model comprises the following steps:

T＝D+G+F (1)

D(t)＝0.5C_d(t)ρS(t)v²(t) (3)

coefficient of shape resistance

Coefficient of additional resistance

Step three, designing various size parameters of the bionic jellyfish:

side area, intracavity liquid volume, projection area expression is as follows:

z₂(t)＝l₁sin(θ₁(t))+z₁(11)

z₃(t)＝l₂sin(θ₂(t))+z₂(t) (12)

d(t)＝max(2z₂(t),2z₃(t)) (13)

h(t)＝h₁(t)+h₂(t)+z₁(14)

h₁(t)＝l₁cos(θ₁(t)) (15)

h₂(t)＝l₂cos(θ₂(t)) (16)

wherein, theta₁∈(0°～90°),θ₂E (-45-90 degrees); t represents thrust; d represents a fluid resistance; g represents additional mass force; f represents an inertial force; ρ represents the density of the fluid; v represents the fluid volume in the cavity of the bionic jellyfish; s_vRepresenting the cross-sectional area of the bionic jellyfish; c_dRepresenting the shape drag coefficient; s represents the projection area of the bionic jellyfish; v represents the bionic jellyfish movement speed; λ represents an additional drag coefficient; m represents the mass of the jellyfish; d (t) represents the diameter of the bell; h (t) represents the height of the bell; c_f,lam(t) represents a surface friction resistance coefficient; re (t) represents Reynolds number; v' represents fluid kinematic viscosity; τ represents a positive time constant that adjusts the switching speed; s (τ y) represents a unipolar sigmoid function, e^-τyA function representing the shape of the simulation as a monopole sigmoid; z is a radical of₁Represents a hemispherical head radius; l₁Represents the upper arm length; h is₁Representing a projection of the upper arm on the centerline; z is a radical of₂Representing the upper arm drawing a circle radius around the centerline; theta₁Representing the included angle between the upper arm and the central line; l₂Represents the lower arm length; h is₂Represents the projection of the lower arm on the centre line; z is a radical of₃Representing the lower arm drawing a circle radius around the centerline; theta₂Representing the angle of the lower arm with the centre line; k represents the ratio of the contraction time to the relaxation time of the bionic jellyfish.

8. The speed control method of the bionic jellyfish-like underwater robot according to claim 7, characterized by comprising the following steps: in the second step, an oscillator model of each joint of the bionic jellyfish is established, and a process of changing the waveform of the oscillator by adopting a non-harmonic gait generation method is specifically as follows:

when the following conditions are satisfied:

wherein k is a positive proportional term coefficient;

step two and five, the oscillator is applied to each joint of the bionic jellyfish, and each f_iAre all equal to f_iThe bionic jellyfish movement frequency; output x of oscillator_i,y_iAll the bionic jellyfish control input quantities can be used as the control input quantities of the bionic jellyfish, namely the rotation angles of the steering engines corresponding to all joints; r is the amplitude of the output waveform after stabilization, namely the range of the rotation angle of the steering engine corresponding to the bionic jellyfish, and when the bionic jellyfish is applied, the R needs to be amplified in equal proportion or reduced to the range of the angle of the expected movement of the joint corresponding to the bionic jellyfish; k is a positive proportional coefficient, when the oscillator receives external disturbance or adjusts parameters of the oscillator, the value of k corresponds to the convergence performance of the oscillator, and when the bionic jellyfish generator is applied, the value of k is determined according to the performance of an actual steering engine; wherein, the motion frequency f of the bionic jellyfish_iIn the non-harmonic gait mode, different frequencies related to one period are set to cause waveform asymmetry, the shape of the waveform determines the switching of the frequency, and a higher frequency component f is set₁Is a rising phase, lower frequency component f₂If it is a falling phase, then:

the total frequency can be expressed as:

9. The speed control method of the bionic jellyfish-like underwater robot according to claim 8, characterized by comprising the following steps: in the third step, a coupling mode between the two oscillators is designed, so that the coupling mode between the oscillators is established, the joint where the oscillators are located is matched and coordinated with each other, various motion modes are completed, and the process of controlling the overall coordinated motion of the bionic jellyfish is realized, specifically:

if c is₁c₂If not equal to 0, bidirectional coupling is performed;

if c is₁＝0||c₂If 0, the coupling is unidirectional;

when k is i, c_k＝0；

Wherein the content of the first and second substances,

representing the coupling term c in the oscillator i_jx_j；

Expressing the coupling of the oscillators in a directed graph mode, wherein each oscillator node is a vertex, the coupling between the oscillators is an edge, and the coupling strength is the length of the edge; then determining the number of oscillators according to the number of joints of the bionic jellyfish; determining the distribution mode of the oscillator according to the symmetry of the joint of the bionic jellyfish; determining whether the two oscillators are coupled or not according to the correlation between the bionic jellyfish joints; determining to adopt a one-way coupling or two-way coupling mode according to the frequent gait switching condition in the practical application process of the bionic jellyfish;

the oscillators are distributed in a pairwise centrosymmetric manner;

10. The speed control method of the bionic jellyfish-like underwater robot according to claim 9, characterized by comprising the following steps: step one, the number of a group of tentacles for designing the bionic jellyfish is 4, the bionic jellyfish design model is provided with 8 joints, and 8 oscillators are adopted; the bionic jellyfish is provided with 4 driving mechanisms which are centrosymmetrically distributed around a central line, each driving mechanism is composed of two joints, and oscillators are distributed in a pairwise centrosymmetric mode; the 4 driving mechanisms are not coupled, so that the driving mechanisms can move independently, and the steering movement is convenient to realize; the motion of the upper arm and the lower arm of each motion mechanism has mutual influence, and only the upper arm and the lower arm of each motion mechanism are coupled; each tentacle of the bionic machine jellyfish is driven in a one-way coupling mode of two oscillators; the influence of the swing of the upper arm on the motion of the lower arm is mainly caused between the upper arm and the lower arm, and the unidirectional coupling factor is in an oscillator equation of the lower arm;

All other items are 0; wherein the content of the first and second substances,