柔性机器鱼的动力学建模及其游动性能分析

Analysis of Dynamic Modelling and Swimming Performance of Soft Robotic Fish

生物学研究表明,当鱼类尾鳍的摆动频率与其固有频率接近时,可获得快速高效的游动性能,而固有频率又与鱼体本身的黏弹性机械特性、水动力学特性等因素存在着复杂关系。根据Lighthill细长体理论,通过建立柔性机器鱼的动力学模型,求解其在流体环境中的固有频率,并结合鳕鱼的生物学数据,进一步分析了在"谐振"状态下机器鱼动力学参数与游动性能之间的关系。结果表明,机器鱼的共振频率是由鱼体本身和周围流体来共同决定的,鱼体摆动长度越长,截面尺寸越小,对应的共振频率越小。同时发现当鱼体波波速或滑移率不变时,鱼体游动速度与其共振频率成正比。上述结论均与现有生物学数据相吻合。总体上,该研究从柔性机器鱼的动力学出发,初步探索了鱼体动力学参数与其游动性能之间的关系。

Biological studies show that fish has a fast and efficient swimming performance,when the tail-beating frequency approaches to its resonance frequency of fish body.And it is determined by the mechanical properties of viscoelastic body and fluid dynamics,etc.Based on Lighthill’s slender theory,a dynamic model of robotic fish was developed in present research,and the natural frequencies were also solved.Furthermore,combined with the biological data of Saithe,the relationship between the dynamic parameters and swimming performance was analyzed under the resonance swimming state.The results show that the resonance frequency can be determined by both fish body and fluid environment,and it decreases with the diameter of cross-section or fish length.When the wave speed of midline motion or the slip ratio is fixed,the forward velocity is proportional to its resonant frequency.These analytical results are consistent with the biological observations.Overall,from the aspect of dynamic analysis,the relationship between the mechanical properties of fish body and swimming performance is preliminary explored.