Kinematics Characteristics And Simulation Analysis Of Goat Trunk

The traditional quadruped robot design takes more account of the robot leg structure design,motion control algorithm,and rarely considers the trunk structure design.The curved trunk structure of quadruped mammals in nature has a positive effect on speed,stability and energy utilization.Goats have excellent balance,good running speed,good endurance,and their trunk has great research value.Based on the biological and kinematics characteristics of goat trunk,this paper establishes a goat trunk biological model by combining medical data acquisition,reverse engineering,finite element analysis and so on.Through kinematics experiments,the bionic trunk is designed and simulated to provide theoretical basis and data support for the design and control of the trunk part of quadruped robot.Local anatomy of the goat trunk was carried out to determine the specific distribution and morphological characteristics of the spinal skeleton,ligament,intervertebral disc and spinal cord.Through size measurement and analysis,it is found that the size of transverse process decreases first and then increases,the size of spinous process increases first and then decreases,the length of vertebral body increases,and the amplitude of increase changes little compared with the size of transverse process and spinous process.It is found that the sensitivity of thoracic and lumbar vertebrae to force is different in the vertical and lateral direction of sagittal plane and in different stress intervals.The biological model of goat trunk was established by medical imaging combined with reverse engineering and finite element analysis was carried out.The results show that the larger position of the shape variable is mainly distributed in the front end of the applied force position,the two ends of the spinal model are very small,the spinous process position variable is the largest,and the deformation from the tip of the spinous process decreases gradually.The stress of the vertebral body is larger than that of the pedicle,and the stress of the spinous and transverse processes is smaller.The stress of intervertebral disc is mainly distributed in the upper and lower ends of intervertebral disc,and the effect force of middle part is very small.The kinematics experiment of goat trunk shows that the angle range of three points basically accords with the law of L2 position >T9 position >T13-L1 position.The angle of T9 position is mostly positive degree,most of L2 position is extension state,most of them are negative degree,most of them are bending state,T13-L1 position is positive degree,but less than T9 position.The thoracic and lumbar vertebrae joints of goats are similar in stretching and bending.The simulation of the virtual prototype of the bionic trunk mechanism shows that the flexible trunk is larger than the rigid trunk in terms of speed,displacement and kinetic energy,and the flexible trunk 2 and the flexible trunk3 with three bending points are larger than the flexible trunk 1 with only one bending point.In terms of displacement and velocity,biomimetic flexible trunk2 using goat trunk kinematics experimental data is superior to flexible trunk 3without motion data.Although the kinetic energy of rear foot and trunk center point of flexible trunk 2 is smaller than that of flexible trunk 3,the value is very small.Therefore,applying the kinematics parameters of goat torso to the motion control of the robot will improve the motion effect of the robot and provide a certain basis and reference for the design and control of the quadruped robot.