Research On Dynamic Characteristics Of Bionic Fishtail Soft Actuator For Underwater Propulsion

Traditional underwater propellers are mainly rigid-body propellers,but such rigid-body propellers still have the defects of low efficiency,high noise,poor maneuverability,and poor concealment,especially in the observation of marine fish resources and submarine military reconnaissance.These defects make it difficult for many ocean exploration researches to be carried out scientifically and accurately.The underwater soft propeller has improved many deficiencies of the traditional underwater rigid propeller,and the soft actuator has been developed accordingly,and has gradually become the key component and main power source of the underwater soft propeller.In this paper,a new bidirectional multi-cavity structure is designed to simulate the fishtail soft actuator for underwater thruster,and the dynamic modeling method based on D ’Alembert’s principle is adopted to analyze the dynamic characteristics of the soft actuator.The main research content of this paper includes the following aspects:First,the preliminary design of the external and internal structures of the pneumatic bidirectional multi-chamber soft actuator is completed,and the oscillating motion of the soft actuator is realized.In addition,in terms of the manufacture of the soft actuator,the material was analyzed and selected,and Ecoflex0030 silicone rubber was selected among several schemes,the soft actuator mold was designed and 3D printed,and the manufacturing process of the soft actuator was completed.Secondly,the material mechanical models are compared and the Ogden model is selected as the constitutive model of Ecoflex00-30 silicone rubber material for the setting of material properties in the simulation analysis software.At the same time,the simulation software Abaqus is used to complete the study of the influence of the changes of chamber parameters on the bending performance of the soft actuator,and the simulation models and motion states between different pressure and bending Angle under each parameter are obtained.In addition,the end "balloon effect" and other local nonlinear deformation conditions were also found in the simulation analysis,which played a key visual reference role for the simplified model in mathematical modeling.Then,an innovative dynamic modeling method of bidirectional pneumatic soft actuator is proposed,and a preliminary uncompensated dynamic model of the soft actuator is established based on the static model by D ’Alembert ’s principle.Because the dynamic model is mainly based on complex differential equations,a fusion algorithm based on Taylor expansion and Runge-Kutta method is proposed to solve dynamic differential equations.The dynamic curves are not convergent,in other words,the dynamic model cannot represent the dynamic characteristics of the actuator,but the results in this chapter lay a foundation for the dynamic model compensation in the following chapter.Finally,aiming at the defects of the dynamic balance equation,a compensation method is proposed,which compensates the damping and mass of the dynamic balance equation.At the same time,the solution process of the equation is analyzed and the Runge-Kutta method is used to solve the equation quickly.Computational experiments show that the solution of the model can be controlled within 1 ms,and the actual control frequency can be up to 1 k Hz,which meets the requirements of real-time control.Moreover,bidirectional motion experiments are carried out to verify the proposed dynamic model.The experimental results show that the dynamic model has good precision and can represent the dynamic characteristics of the bionic fishtail soft actuator.