Spine Stiffness Characteristics Of Quadruped Robot With Spine Joint

With the development of robot technology, quadruped robots with spine joints are the focus in the field of robots by far. At first, roboticists had studied the rigid spine quadruped robots. By changing the control algorithm to improve the movement performance of quadruped robots is the research focus. Some roboticists ignore the structure design of quadruped robots. It's not necessary to study the structure design of quadruped robots. It just needs to imitate animals' skeletal structure[1]. The movement performance of these quadruped robots can't satisfy people's requirements. Biologists find quadruped mammals that have spine motion in the process of movement. And the spine motion can improve the movement speed,energy efficiency and stability of quadruped mammals. The study about the spine characteristics is almost in a blank. Further study of spine characteristics, which can help to understand the spine acting mechanisms of quadruped mammals, can provide the foundation for physical design of quadruped robots.Firstly, a simplified model of the quadruped robot with spine joint is established according to the skeletal structure of cheetahs. And the kinetic equation of the quadruped robot with a spine joint is derived based on the lagrange equation of the second kind.According to generation method of the periodic motion of the spring-rod model,searching the initial conditions of generating the periodic motion of the quadruped robot is introduced. And then the periodic motion of the quadruped robot is researched.Secondly, the spine stiffness characteristic of the quadruped robot is researched. The effect of spine stiffness on movement speed is analysed. According to the dynamic characteristic of the quadruped robot with a spine joint, the kinetic equation that can reflect spine joint angle directly is achieved. The spine stiffness characteristic is researched on the basis of the kinetic equation, and the setting strategy of spine stffness is proposed. -Thirdly, the spine stiffness characteristic curve of the quadruped robot with a spine joint is optimized. Stability of the quadruped robot with a spine joint is regarded as the optimizing index; gait sensitivity norm is regarded as the optimizing criterion; and Nelder-Mead simplex is regarded as the optimization method to optimize the spine stiffness characteristic curve. The optimization results show that the optimized spine stiffness characteristic curve increases the stability of the quadruped robot with a spine joint.Finally, under the situation of the optimization spine stiffness characteristic curve,physical experiment researches are done to demonstrate the simulation analysis. The experiment platform, based on which three physical experiments are done, is introduced. We verify whether the optimized spine stiffness characteristic curve can improve the stability of the quadruped robot or not. Whether the optimized spine stiffness characteristic curve can promote the speed and energy efficiency of the quadruped robot with a spine joint or not are researched.