| Quadruped robot has good stability and environmental adaptability,but its structure design and performance still have a lot of improvement.The load-bearing construction of quadruped robot is one of the research focuses of robot.The emergence and development of bionics provides a new idea for mechanism design and performance improvement of quadruped robot.Cats have excellent jumping ability,climbing ability and balance ability.Based on the research on the characteristics of cat chest,this paper designs the structure of imitating cat chest,and puts forward a new solution for the problem of load-bearing construction of quadruped robot.The jumping motion of quadruped robot is not only a common motion of robot,but also a unique motion mode of quadruped robot.By imitating the special structure design of cat chest,the quadruped robot has stronger buffering ability.Based on medical imaging(MRI&CT)technology,reverse engineering technology and combined with gross anatomy,the macro configuration and joint structure size of cat thoracic cavity were tested and characterized,and the relationship and movement mode between various parts were determined;based on biological anatomy,the connection mode between thoracic vertebrae,the connection mode between ribs and thoracic vertebrae,and the number and connection mode of soft tissues such as tendons and muscles were clarified;combined with the relationship analysis,the structure of cat thoracic cavity was characterized The biological coupling model of thoracic vertebrae was constructed based on the joint and movement mode;the axis of rib and sternum was extracted based on the image sub comparison,and the axis equation was used for modeling.In this paper,the changes of chest bending angle of cats under different running conditions were studied.The high-speed camera system was used to test the trot,stride,continuous somersault and jumping kinematics of cats.The results of thoracic vertebra motion analysis showed that in the process of trot,in order to obtain a more stable movement state,the chest bending angle of cats was small;in the process of stride test,the chest was in the same position as carrying important organs The length change ratio was 22.6%;in the process of the rollover test,the chest of the cat changed little during the continuous rollover process,but the change range of the thoracic vertebra angle increased when landing;through the comparison of different height jump process,the maximum bending angle and the maximum bending angle time of the cat chest had great differences.Therefore,we conclude that cats protect themselves from injury by actively adjusting the shape of their chest.The dynamics of cat’s jumping landing process was studied.The plantar pressure,the position of the center of mass(COM)and the angle of the center of mass were collected by the pressure plate test system and the high-speed camera system.By calculating the mechanical energy,kinetic energy,rotational energy,gravitational potential energy and energy absorbed by the forelimb,the impact energy absorbed by the chest during the jump landing process is obtained.It is found that the impact energy absorbed by the chest increases with the increase of jumping height,and the impact time is prolonged and the impact force is reduced by adjusting the angular velocity of the center of mass angle.Based on the structure,kinematics and dynamics of the cat chest,the bionic design of the four segment three joint chest was completed.Based on the bionic prototype structure,the connection mode between the rib and the thoracic vertebra is adjusted appropriately.The results show that the bionic mechanism has the function of bearing and buffering. |
