Research On Kinematical Reaction Force Of Gekko Gecko On Inclines And Abducting Detachment Of Toe

Locomotion is an essential character of animals and many animals have excellent moving ability, which results from the delicate sense of the reaction forces acting on body and modulating the behavior to adapt to the motion requirement. With respect to extraordinary climbing ability, a representative kind of animal is the gecko, which is capable of moving freely on slopes of any inclinations, including horizontal floor, vertical walls and even inverted ceilings. Research of biomechanics on geckos climbing on slopes is of great importance to 1) understanding nature, perfection of the kinematic mechanics of animals, especially creeping ones, further the evolution research; 2) learning from nature, further inspiring the structural design, gait planning and force-feedback control of bio-robot, especially bio-mimetic gecko robot.This paper first introduces the development of force measuring equipment, which is used to reveal how geckos adjust their reaction forces and locomotion behaviors in response to the angles of slopes and direction of motion is systematically studied; then how geckos attach their feet to the substrate reliably and then exerting enough forces for inclined movement is illustrated in the macroscopic view; at last, the biomechanical properties of hyperextension of a toe is studied and then how geckos detach rapidly from substrates is revealed.The main work and production of the paper are as follows:Based on the self-developed 3D force sensor, Force Measuring Array(FMA) and locomotion behavior observation system was developed. Compared to traditional Force Measuring Platform(FMP), the newly developed system pushed through the limitation of duty factor on measurement of the complete reaction forces of single foot, thus the research on synergistic effect among animals’ limbs during locomotion became possible.Continuous 3D reaction forces acting on geckos’ feet during geckos moving on three typical inclines(horizon floor, vertical walls and inverted ceilings) were measured. The reaction forces were linked to locomotion behaviors, then a new expression of the reaction forces is put forward as Pattern of Reaction Force(PRF) to clearly show the relationship among three components of reaction forces as well as the internal connection among reaction forces acting on each feet. Three mechanical models of geckos moving on the inclines were also established, which showed that geckos can adjust PRF in response to the effect of gravity on locomotion to obtain multi-profit, i.e., enhancement of locomotion stability and maneuverability.The reaction forces acting on fore-and hind- limbs during geckos moving on various angles of inclines(0°~180°) were measured, threshold angles of inclines that PRF changes were also obtained. Research on reaction forces acting on single foot revealed that accurate force control largely enhanced the locomotion performance as well as the stability during geckos moving on various inclines. A model of synergy among hierarchical kinetic units was established to clarify that the synergy among hierarchical kinetic units was a necessary condition for geckos moving on inverted substrates.By observing the contact mode and measuring the reaction forces between geckos’ feet and the substrates, the critical angles between reliable attaching feet and the substrates of various inclinations were measured; a mechanical model of reliable attachment of geckos’ feet was also established. Limited by the friction coefficient between geckos’ heel and the substrates, geckos could only climbing on slopes of inclination less than 17° without the help of adhesion toes. Limited by the performance of adhesive units, geckos cannot hang on a slope of inclination lager than 120° with single limb, nevertheless, with the help of frictional adhesion property of the feet and the synergy among limbs, locomotion on slope of inclination lager than 120° became possible.With the help of neuroscience, the neural stem of single toe corresponding to the attachment and detachment was stimulated by electric current, no relationship was found between the measured forces and external loading forces when the toe abducted, which indicates that the feet can keep on to support locomotion stalely and reliably during detachment. A model of partitioned non-continuous single toe during abducting detachment was established, which was in good agreement with the experimental results, indicated that the model with cohesion elements was effective and can further inspire the design of bio-inspired adhesive system.