How does a woodpecker work? An impact dynamics approach  

作　　者：Yuzhe Liu Xinming Qiu Tongxi Yu Jiawei Tao Ze Cheng 

机构地区：[1]Department of Engineering Mechanics,Tsinghua University [2]Department of Mechanical and Aerospace Engineering,Hong Kong University of Science and Technology [3]Ningbo University

出　　处：《Acta Mechanica Sinica》2015年第2期181-190,共10页力学学报（英文版）

基　　金：support of the National Natural Science Foundation of China(NSFC)(Grant 11372163);the National Fundamental Research Program of China (Grant 2011CB610305);the support of the NSFC Key Project 11032001

摘　　要：To understand how a woodpecker is able accelerate its head to such a high velocity in a short amount of time,a multi-rigid-segment model of a woodpecker＇s body is established in this study.Based on the skeletal specimen of the woodpecker and several videos of woodpeckers pecking,the parameters of a three-degree-of-freedom system are determined.The high velocity of the head is found to be the result of a whipping effect,which could be affected by muscle torque and tendon stiffness.The mechanism of whipping is analyzed by comparing the response of a hinged rod to that of a rigid rod.Depending on the parameters,the dynamic behavior of a hinged rod is classified into three response modes.Of these,a high free-end velocity could be achieved in mode II.The model is then generalized to a multihinge condition,and the free-end velocity is found to increase with hinge number,which explains the high free-end velocity resulting from whipping.Furthermore,the effects of some other factors,such as damping and mass distribution,on the velocity are also discussed.To understand how a woodpecker is able accelerate its head to such a high velocity in a short amount of time,a multi-rigid-segment model of a woodpecker＇s body is established in this study.Based on the skeletal specimen of the woodpecker and several videos of woodpeckers pecking,the parameters of a three-degree-of-freedom system are determined.The high velocity of the head is found to be the result of a whipping effect,which could be affected by muscle torque and tendon stiffness.The mechanism of whipping is analyzed by comparing the response of a hinged rod to that of a rigid rod.Depending on the parameters,the dynamic behavior of a hinged rod is classified into three response modes.Of these,a high free-end velocity could be achieved in mode II.The model is then generalized to a multihinge condition,and the free-end velocity is found to increase with hinge number,which explains the high free-end velocity resulting from whipping.Furthermore,the effects of some other factors,such as damping and mass distribution,on the velocity are also discussed.

关 键 词：Woodpecker Muscle torque High impact velocity Whipping Hinged rod 

分 类 号：O354.5[理学—流体力学]