Research On Adhesive Locomotion Mechanism And Bionics Design Of Rock-climbing Fish

Adhesion is an ability to stay on the surface of an object in nature that evolved to cope with various external forces in the living environment.The interaction forces of biological adhesion are not only attractive van der Waals forces,but also many other types of forces,such as chemical bond forces,capillary forces,mechanical coupling,negative pressure suction,diffusion forces from one material to another,electrostatic forces and magnetic forces.Locomation is one of the most important parts of an animal's life,and is a necessary skill for hunting,mating,migration and other activities.The locomotion patterns of animals in nature are various,from the cheetah running on land with four legs to the kangaroo jumping with two legs,from the hummingbird hovering in the air to the carrier pigeon flying with wings,from the dolphin leaping on the water to the swordfish flying in the water.At present,the researches on biological adhesive focuses on geckos,snails,tree frogs and other known species are abundant.Biologists have abundant studies on animal movement,and have found various forms of movement,but there are still deficiencies in the bionic practice,mainly focusing on the common land biped/quadruped walking,air flapping wing flight,and swimming with wagging tail in water.Nature is a vast reservoir of novel forms of adhesion and movement to be discovered and learned.In the practice of mobile robots,fixed-point stay can not only more effectively complete specific tasks,but also reduce the energy consumption required in the movement and improve the overall working time of the robot.Beaufortia kweichowensis is a small native Chinese fish from Guizhou and GuangxiProvince,local called "rock-climbing fish".Not only does it stick to rough,polluted rock surfaces,but it swims quickly against the current without being swept away.Therefore,the research on the adhesion behavior of rock-climbing fish is of great significance for the motion of mobile robots on rough surfaces.In this paper,the mechanism and bionics of adhesion and locomotion of the rock-climbing fish in guizhou province were studied.First of all,through a series of basic experiment to determine the adhesion of rock-climbing fish is negative pressure suction mainly,then the surface morphology analysis in the ventral fins and the lips skin of rock-climbing fish is conducted by laser confocal microscopy and microstructure characteristics and the overlay of gas and liquid on the epidermis of the fish are obtained.This provides reference for physical model to reveal the adhesion mechanism of rock-climbing fish;Through optical microscope,the ventral gas-liquid coverage of the guizhou rock-climbing fish in the states of fresh water,dehydration,rehydration and surfactant addition was observed,providing experimental evidence for the origin of bubbles on the surface of the rock-climbing fish,and establishing the theoretical model of the gas-liquid coverage phenomenon of the rock-climbing fish.The adhesion tenacity of rock-climbing fish on hydrophobic/hydrophilic surface with different roughness and liquid with different viscosity was studied by mechanical measuring device,and the theoretical adhesion model of rock-climbing fish was established.Through the biological observation and analysis of the locomotion process of various wall surfaces of rock-climbing fish by high-speed photography,the corresponding motion mechanical parameters were analyzed based on the coordinates of digital marker points,which provided the physical model reference basis for revealing the locomoton mechanism of the rock-climbing fish.Finally,on the basis of the rock-climbing fish adhesion and locomotion mechanism,on the premise that biological similarity based adhesive locomotion theory model of rock-climbing robotic fish,bioni'c rock-climbing fish design method is put forward.Based on bionic rock-climbing fish,the performance and movement characteristics of the bionic robotic fish prototype are tested and analyzed.Contrast climb rock fish to the bionic robotic fish in the similarities and mode of movement,it is proved that the superiority of bionic robotic fish in wall moving skill.The outline of this thesis is as follows,In chapter 1,introduction,the research background and significance of the thesis are proposed.The reviews on the history and present situration of the bio-adhesion,locomotion and bio-robot are introduced.At the end,the main research contents,research methods and research route of this thesis are summarized.In chapter 2,the underwater adhesion mechanism of rock-climbing fish.The adhesive behavior of rock-climbing fish under water is studied experimentally and theoretically.The negative pressure adhesion mechanism of rock-climbing fish,the surface microstructure around the sucker and the special pattern of microbubbles on the surface,and the enhancing effect of microbubbles on negative pressure suction force are observed.Based on the model of the bubble in the tube which impedes the liquid flow,the super-high concentration of bubble in the liquid in the narrow gap limits the liquid flow velocity and thus produces the sealing effect,and the negative pressure adhesion model under the bubble seal in the narrow gap is established.In chapter 3,the origin and pattern of microbubbles in rock-climbing fish.Through microscopic observation and related experiments,it is found that the bubbles of rock-climbing fish can be divided into two types:internal supplementary bubbles and external recoverable bubbles.The external bubbles provide gas sources from the internal bubbles.The size of the two bubbles is the same and the pressure is the same.Combined with the bubble fixation effect on the surface of microstructure,a bubble fixation model based on the accumulator balloon surface microstructure of rock-climbing fish was established.In chapter 4,the surface tenacity of the rock-climbing fish sucker.The adhesion tenacity of rock-climbing fish sucker was tested by making experimental surfaces with different wettability,roughness,stiffness and experimental liquid with different viscosity.The adhesion tenacity of rock-climbing fish sucker is not limited by the roughness on the hydrophobic surface,while the hydrophilic surface energy is obviously limited by the roughness.According to Wenzel and Cassie model,the adhesion model based on rough surface was established under the influence of multiple factors,and the tenacity rule of sucker with bubble sealing effect on rough surface with different wettability,roughness,stiffness and viscosity was explained.In chapter 5,the anisotropic friction mechanism of the rock-climbing fish sucker.The distribution of body orientation in the face of water flow direction,the tangential friction force a nd the direction of applied force were calculated.In combination with the changes in the abdominal cavity after the fin changes recorded by Micro-CT,the anisotropic friction mechanism under the influence of the fin folding amplitude on both sides was obtained,and it is proposed that the fixed end height could be improved by varying the angle between the cantilever bars with different lengths(fin lifting effect).In chapter 6,the dynamic adhesive crawling mechanism of rock-climbing fish.By analyzing the images of crawling forward and backward in slow state and fleeing in fast state,the transition rules of fin folding and waist muscle contraction were found,and the adhesive wave motion model based on the double anisotropic suckers and two girdle muscles of rock-climbing fish was obtained.In chapter 7,the development of bionic robot.Based on the motion mode of variable friction of ventral fin and contraction and propulsion of the gridle muscle,an adhesive wave motion robot imitating rock-climbing fish is made.In chapter 8,summaries and prospections,the main research contents of the thesis are summarized.The further work is prospected.