Mechanics Analysis And Numerical Simulation Of The Bionic Robot Fish Controlled By The GMMA

Many new type micro robots that can swim smoothly in liquids medium have urgently been demanded in industrial,national defensive,petrochemical and medical fields due to constraints of the environment or other special conditions.Especially the wireless driven robot with high flexibility has being more popular with people.For instance,by using micro robots,a delicate surgical operation can avoid dismantling and reassembling,which minimizes the patient's hurt.On the other hand,micro robots are often proposed to maintain factory pipelines or fault detection.The study on micro robot has enormously been developed with the coming forth and application of giant magnetostrictive materials,which can be controlled in wireless utilizing external magnetic field as a special intelligent material.Therefore,studying and designing advanced magnetic bionic robot fish has become a significative research choice. However,the key technologies and mechanism of this type of machine-driven fish should be further explored.In this paper,the mechanics model of a bionic robot fish,which is composed of muscle, tail and neural control system and simulated respectively by giant magnetostrictive material (GMM),elastic sheet and external magnetic field,is built.With the aid of its swimming mechanism,a GMM actuator(GMMA) is devised.The new type bionic robot fish controlled by GMMA,abandons traditional power system,paves a way for achieving micromation and has an extremely significance for working in pipelines.The effects of external magnetic field frequency,material parameters and geometrical parameters of fishtail on the average propulsion produced by swing tail are analyzed.It is found that the average driving force can reach a peak value when the forced external magnetic field has a same frequency as the tail system.Thus the robot fish swimming can be controlled by adjusting the frequency of the external magnetic field.The fishtail wakes for several system frequency modals are obtained through numerical simulation.The characteristics of tuna,pike and butterflyfish are simulated and the kinematic mechanism of swimming,acceleration and turning are discussed in detail.The numerical and analytical results show that the magnetostrictive effect of GMM can drive the fishtail's swing,and the tail vibration modes can be controlled by frequency and magnetic density of the altemant external magnetic field.Generally,the best efficiency is obtained in second order vibration mode of the fishtail,and the reverse Karman Vortex Street wake is observed with corresponding frequency.The best frequency of external magnetic field corresponding to fish tail swing is changed with different liquid medium,fish tail material or geometrical shape.It should be pointed out that the influence of the tail length on robot swimming is also marked and each order vibration mode has a best tail length.Therefore,in order to adapt fish to specific environment,the swimming posture can be adjusted by changing the tail length.According to the above findings,the optimized fish length and external magnetic field frequency,a new type bionic robot fish with two tails is devised,which can move forward and backward by changing the magnetic field.Considering nonlinear damping and geometric large deformation,steady and nonsteady solutions of the main tail's vibrational problem is discussed.Three kinds of fish tails are supposed,which are corresponding to square,tuna's and pike's tail respectively.It is found that the steady and nonsteady solutions are in accord with the dynamic characteristics of tuna and pike.Thus the influence of tail shape on robot fish performance is revealed,and the physical phenomenon of fish swimming is explained in this paper.Obviously,these study results have special using value for performance design of bionic robot fish.