Locomotor Kinematics And Dynamics Of Tree Frog (Litoria Caerulea)

Research on locomotor kinematics and dynamics of tree frog can further improve animal’sadhesion and detachment mechanism, and be applied in the engineering field of bionic robots’climbing on wet surface. In this paper, tree frog’s three dimensional ground reaction forces of multiplelimbs and coordinated motions were measured by animal’s locomotive mechanics data acquisitionsystem. The system is based on PXIe and LabVIEW, including3×8sensor array,72channels dataacquisition and processing module, high speed camera and so on, synchronously collects forces andimages data.In order to study tree frog’s climbing ability, animals were induced to climb on different slopes.Tree frogs mainly used a diagonal gait when they climbed on six different inclined planes, bodykinematics and foot function were different. As the angle increased, tree frog’s velocity graduallytransformed from stride length-dependent to stride frequency-dependent, fore-aft forces and normalforces progressively supported by hindlimbs with respect to body weight center moved rearward,meanwhile, lateral forces didn’t change obviously. Combining kinematics and dynamic data, we canget that frogs utilize long stride length with small velocity and squat down posture to confront thesteeper slopes.In order to investigate tree frog’s static adhesive ability, animals were challenged to cling onto arotated platfrom. From0°to80°±9°, frogs kept crouched resting posture. From80°±9°to detachment,frogs changed their posture obviously at angles of106°±12°and131°±11°respectively. Along withthe rotated angle increased, lateral forces became bigger and frogs used opposing feet to pull inwards,fore-aft forces and normal forces can be calculated from simple trigonometry. Our experiment provedthat tree frogs use friction forces to enhance attachment on overhanging surfaces, smaller peel angleslead to higher attachment forces and thus can be explained by Kendall peeling model theory.By comparing tree frog’s static adhesive and climbing ability, locomotion pattern of tree frogswas influenced by angles of substrate inclination. Tree frogs adopted fast climbing on shallow slopesand used static adhesive on steep slopes. This locomotion pattern was related to fracture of the thinfilm.