Locomotor Kinematics And Dynamics Of Tree Frog(Rhacophus Denynsi) On Cylindrical Surface

Tree frog,with respect to extraordinary climbing ability,is presentative wet adhesion animal and often across layers of obstacles to reach surface of leaves by catching on small branches or trunks with their long toes.Therefore,it can be more comprehensive to understand tree perched quadruped choose a more appropriate way of attachment and adhesion locomotion mechanism living in complex external environment by researching locomotor kinematics and dynamics of tree frogon cylindr ical surface.It also has profound significance to development of bionic climbing robots.A new force measuring array with quasi-cylindr ical surface and locomotion behavior observation system was developed.This quasi-cylindrical force-measuring array is assembled by 24 pieces of 3D sensors with there solution of milli-Newton,which were installed from top to bottom in 4 columns and 6 lines,and sensors in neighbouring columns were stagger in height.Three cameras were used to record crawling behaviors of animals simultaneously when they climb force measuring platform.Ground reaction force modes of tree frog on two differences roughness surface over quasi-cylindrical substrate were constructed.The results revealed that roughness hada certain effect on locomotion stability,and locomotion was more stable on adhesion substrates than non-adhesion substrates.There had no significant effect on lateral force and fore-aft force,while having a significant effect on normal grip force(normal force onrough surface was about 1.5 times than smooth surface).Tree frog applied an inward compressive normal force to base surface rather than adhesion normal force to outward and created a lateral friction force.The conclusion suggests that feet of tree frog attaches to curved and non-adhesive substrate surface by applying a clamping grip force during locomotion on high curvature surface.From morphological view,hind-limb of tree frog is stronger than fore-limb,however results show that three-dimensional reaction force of fore-limb is larger than hind-limb.Fore-limb plays a leading role.Functions of adhesion pads and tubercles in locomotionand differences between them were researched.Our study demonstrated how tree frogs use adhesion pads for climbing smooth surfaces and cope with curved and anti-adhesive substrates by applying clamping grips.Compared to adhesion pads,subarticular pads can withstand higher friction forces in potentially different directions(probably 6.6 times larger than friction forces of adhesive pads),and SEM images of subarticular pads also reveal shallow cells with presence of nano-pillars found on adhesive pads.Subarticular pads are ideal for climbing narrow substrates like twigs or branches.The use of gripping forces on curved structures increases climbing efficiency and reduces dependence on specialised adhesive structures.In addition,effective attachment of adhesion structure often depends on shearing and loading forces.Function of gripping force is actually as auxiliary foce.