Dynamics And Fabrication Technology Of Sensing-structure Integrated Caudal Fins For Micro-robotic Fish

Micro-robotic fish is a kind of intelligent,miniature,low cost unmanned underwater vehicles,the properties such as high propulsive efficiency and high maneuverability make it becomes the hotspot of development.Since the information gathering of the flow field around the micro-robotic fish has great significance to the development of the micro-robotic fish,it has become a fairly important area of the development.Among the plenty information of the flow field,due to its convenience of collecting,extracting pressure data from the surface of micro-robotic fish has great benefit to verify bionic principles.Besides,the surface pressure can also be a crucial criterion of trajectory control.Nevertheless,existing pressure sensors has quite huge volume compared with the micro-robotic fish,which will lead to an awful influence of the shape of streaming shell,and will also effect the gathering of flow field information.In order to understand the mechanism how micro-robotic fish generates propulsion,quasi-steady approximation and blade method are used in this paper to establish a dynamic model for micro-robotic fish using rigid caudal fins to propel.A piezoelectric driven micro-robotic fish is used to acquire the unknown coefficients in the dynamic model established and verify the accuracy.The results of the calculation of the dynamic model and experiment data demonstrate that this model is accord with the swimming rule of the micro-robotic fish,and the model can mirror the data change of motion parameters.The comparison between these two results also proves that the signal of pressure from caudal fins can be used as the criterion of trajectory forecasting.For overcome the influence of external installing pressure sensor,two integration methods of the strain sensor and structures of caudal fins are proposed in this paper,by detect the strain change to calculate the pressure on the caudal fin.The first one is a capacitance strain sensor fabricated by spin-coating method using carbon-fiber-resin composite materials as structure of the caudal fins and electrode and Polyvinylidene Fluoride(PVDF)as the dielectric material.Another is a resistance strain sensor fabricated by laser directly carving the carbon-fiber-resin composite materials to produce micro-gap.With the pressure acting on the caudal fin,the micro-gap separate and the resistance of the caudal fin increases.Both methods are sealed with Thermoplastic polyurethane elastomer rubber film(TPU)and pressure sensitive adhesive(PSA).Both caudal fins are tested in air and under water,and the results indicate that the capacitance caudal fin have great pressure detection ability in air,but it loses sensing ability under water.The resistance caudal fin however have great sensing ability under water.By construct the underwater platform,the complicated interaction between caudal fin and water are tested.Through analyzing the data acquired from caudal fin,the fluid state on the surface of the caudal fin under different waving condition is acquired.