Study On Bearing Characteristics Based On Yak Leg Biology

With the development of science and technology and the progress of The Times,robots are playing a more and more important role in the development of today’s society.Robots can replace people to complete a lot of dangerous work,greatly improving work efficiency.Compared with wheeled and tracked robots,legged robots have higher stability and adaptability,and quadruped robots have always been a research hotspot in the field of robotics.In recent years,with the development of quadruped robot research,quadruped robot has been able to achieve basic movements such as running and jumping,climbing,turning and retreating on structured road.However,the stability of quadruped robot walking under high load state is far from that of quadruped animals.Yak is an important transportation animal in China,which can carry 18% of its own weight.In the complex plateau environment with steep terrain and dangerous roads,yaks are more stable and reliable than horses when crossing glaciers and snow fields.On rugged and steep mountain roads,riding yaks is smoother than horse walking.Encounter marshes shoal,more show its superiority.In this paper,the design requirements of the leg,the key part that affects the carrying capacity and stable walking of quadruped robot,are taken as the starting point,and the yak leg is taken as the research object to observe its structure and movement characteristics and study its carrying mechanism,so as to provide theoretical basis and technical support for the leg design of yak quadruped robot with high carrying characteristics.The gross anatomy experiment of yak leg was carried out by gross anatomy method.The specific distribution of bone,cartilage,ligament and tendon of yak leg was determined.Yak is a tetrapod,and its leg structure conforms to the general pattern of typical tetrapods.The leg is a structural system composed of muscles,bones,ligaments and tendons.Bones are connected by joints,and tendons are connected by muscles and bones,and ligaments are attached to each joint.Yak legs are skeletally framed with attached muscles and muscle groups.High speed camera system was used to observe the movement of yak,and the characteristics of its leg movement were analyzed.The front and rear legs of yaks were divided into landing stage and hanging stage in one movement cycle,and the duty cycle and the characteristics of joints were obtained.The results showed that the landing period accounted for 42.9% and the suspension period accounted for 57.1%,and the vertical direction of foreleg joint and wrist joint varied greatly.In a movement cycle,the landing stage of yak hind legs accounts for about 40%,and the suspension stage accounts for about 60%.The knee joint and hock joint of hind legs vary greatly in the vertical direction.Mechanical properties of yak leg were tested and analyzed by electronic universal testing machine.The stress-strain curves of yak forelegs were obtained by tensile and compression tests,and the variation characteristics of leg muscles,ligaments and bones during tensile and compression tests were analyzed.During stretching,muscles and ligaments tighten.During compression,ligaments play almost no role,and energy is absorbed and stored mainly through the contraction of leg muscles.The CT and MRI medical image data of yak legs under stable standing condition were collected by using medical image technology.Based on the techniques of medical image processing and reverse engineering modeling,the bone-cartilage models and leg composite models of yak were established.The front and back legs are composed of 3bones,2 cartilage and 5 elastic elements that simulate muscles and ligaments.Finite element analysis software ANSYS was used to simulate the bone-cartilage model and three-dimensional composite model of yak’s front and rear legs,and analyze the stress distribution and deformation of leg bones under different loads.The results showed that the radial bone of yak foreleg was the main bearing part,and the tarsal bone of yak hind leg was the main bearing part.Foreleg brachial bone and hind leg femur have the largest shape variation during loading process.In the composite model with simulated muscle and ligament,the stress and deformation of each bone decreased significantly,indicating that yak leg muscle and ligament play an important role in bearing capacity.