Locomotion Property Of Quadruped Robot With Spine Joint

Most of current quadruped robots have similar construction: a stiff body and four compliant legs.But spine motion is usually apparent in running quadruped mammals,especially the cheetah.As high–speed running becomes the recent focus of quadruped robots,more and more roboticists are gradually interested in the quadruped robot with spine joint.In existing research about the quadruped robot with spine joint,control algorithm is the main content,but basic locomotion property is rarely studied.In order to make progress in quadruped robots’ high-speed running,it is necessary to study the effect of spine motion on system’s locomotion property,based on its dynamics.Because learning more about the locomotion property of the quadruped robot with spine joint is important to its structure design and control algorithm research.In this paper,the simplified model and dynamics of the quadruped robot with spine joint are set up firstly.Secondly,the periodic locomotion of the simplified model is generated.Thirdly,the effect of spine motion on contact time and the largest ground force is analyzed.Finally,in order to verify the theoretical analysis,prototype experiments are carried out.The simplified model of the quadruped robot with spine joint is set up,based on two simplified models of the quadruped robot with stiff body and the morphological characteristics of cheetahs’ body movement.The simplified model of the quadruped robot with spine joint is named as the model with spine joint.According to the Euler–Lagrange equation,the dynamics of the model with spine joint is derivated,which is the basis of analyzing the system’s basic properties.Based on a method of generating the periodic locomotion of the two simplified models of the quadruped robot with stiff body,the periodic locomotion of the model with spine joint is studied.The Poincare Mapping Function of the model with spine joint is derivated and its Poincare Mapping Fixed Points are searched using the Newton–Raphson Method.The simulation results show the method is also effective to the model with spine joint.The simulation study of the locomotion property of the quadruped robot with spine joint is done and the effect of spine motion on contact time and the largest ground force is mainly analyzed,based on the periodic locomotion and dynamics of the simplified models ofquadruped robots.In the process of analysis,an approximate equivalence method is used.According to the Vertical–Spring–Oscillator model,the two-dimension planar locomotion of the simplified models is approximately regarded as one-dimension vertical vibration.The results show that spine motion has no effect on the contact time,but can decrease the largest ground force.Finally,in order to verify the theoretical analysis,the experiment platform is built,and four prototype experiments are carried out.The effect of spine motion on horizontal speed,energy efficiency,contact time and the largest ground force is studied.The results show that the theoretical analysis is correct and spine motion can also improve system’s horizontal speed and energy efficiency.