The Bio-tensegrity Mechanism Of Lower Limb Musculoskeletal System Of Domestic Cat And Bionic Tensegrity Leg Design

At present,the lower limb joints of quadruped robots are almost all simplified and designed as hinge joints.However,since hinge joints are mostly rigid joints,in the dynamic state of high-speed motion,the lower limb joints of robots are prone to structural damage due to the impact of ground reaction,which also increases the difficulty of joint control and further increases the energy consumption.Literature research shows that the current research mostly uses high elastic materials in the leg mechanism or foot end of the robot,which plays a certain role in cushioning,but the overall effect is still not ideal.This article introduced the ideas of the tensioning body quadruped walking robot leg research,domestic cats leg bones-muscle system for bionic prototype,combining with domestic cats lower limb movement mechanics test,the gross anatomy upper extremity muscle system on the basis of the preliminary analytical and finite element modeling of tensioning mechanism and its effect on the properties of flexible joints and buffer,on this basis,has conducted the balance ability and the stability characteristics of the bionic design of walking leg,and then to have efficient movement characteristics of the innovative design and development of bionic quadruped robot provides important biological mechanics theoretical basis and technical support,has important scientific significance.Based on the biomechanics test of domestic cat,the paper collected and analyzed the biomechanics data of the test subjects in three gait types: walking at constant speed,running diagonally and running.The results showed that in the three locomotion gait,with the increase of the motion speed,the cat's front and rear limbs all decreased significantly in the touching stage,and gradually adjusted from accounting for about 50% of the gait cycle to accounting for about 30% of the gait cycle.During the gait cycle,the joints of the cat's front and rear limbs produced an adaptive motion adjustment of flexion and extension.At the same time,the results showed that the flexion and extension of all the joints except the hip joint showed an increasing trend with the increase of the motion speed.Walking in constant velocity,diagonal run,run three under the movement gait,the front and hind legs touch the ground time and decreases as the speed of movement,including walking in constant velocity,diagonal trot movement gait under contact time is greater than the hind foot touches the ground of the time,the running movement gait forelimbs touches the ground of time less than the touchdown of hind limbs;Under the three locomotion gait,the peak pressure of forelimb and hindlimb all increased with the increase of the motion speed,and all showed single peak change.The peak pressure of the forelimbs was always lower than that of the hind limbs.Except for the peak pressure of the rear limbs in the early stage of touching the ground under the gait of walking at a constant speed,the peak pressure of the rest reached the peak pressure in the middle stage of touching the ground.Combining with domestic cats lower limb skeletal muscle gross anatomy experiment,the cat(front and hind legs)of lower limbs in the musculoskeletal system functional joint(with hard pressure bones),flexible ligament(passive tensile)and muscle(active tensile body)connection features and function has carried on the preliminary analysis,determine the cat compression of lower limb skeletal muscle system of rigid body and flexible body of tensioning mode.Clear the lower limb joints before and after the ligament of join points,path,quantity,size,and so on characteristics,among them,arms elbow and legs knee joint ligament structure is complex,there are many functional ligament,analyses the points of lower limbs before and after the main function of the muscles,path,quantity,size,flex functional characteristics and the connection characteristics of flexion and extension,and found the cat lower limb muscle cells are main function across articular adhesion connection,have different shape,size and spatial distribution of complex configuration.Based on the CT images of the lower limbs of the domestic cat,the finite element model of the lower limbs of the domestic cat including the cruciate ligament,the medial and lateral collateral ligament and the patellar ligament was reconstructed by reverse engineering.The parameter sensitivity simulation analysis of young's modulus of ligaments was carried out with Abaqus software.The results showed that the smaller the young's modulus of the ligament,the smaller the radial stress along tibia and fibula,and the stronger the bending moment resistance.The magnitude of young's modulus of ligament has no significant effect on the axial stress of tibia and fibula.The design of the bionic tensioning mechanical leg was carried out in combination with the motion-mechanics experiment of the domestic cat,the gross anatomy experiment of the lower limb,the model reconstruction of the lower limb and the finite element analysis.The results show that the flexible members in the bionic leg absorb and store a large amount of impact energy through flexible deformation,improve the stress distribution of the rigid members,make the stress distribution of the bionic leg gradually reduce from the end foot to the leg,and effectively improve its impact resistance and bending resistance.Within the scope of study,the biomimetic tendon materials remain unchanged,and the softer the biomimetic ligament,the better the impact/bending resistance of the mechanical leg;while when the biomimetic ligament is soft and hard,the harder the biomimetic tendon is,the better the impact/bending resistance of the mechanical leg is.