Study Of Dynamic Characteristics Of Quadruped Robot's Single Leg With The Active Variable Stiffness And Passive Variable Stiffness's Flexible Joint

In the wake of developments in science and technology,man has become more capable of conquering nature.The demand for mobile robots working in a complex and dangerous environment has attracted more and more attention.By virtue of its discrete foothold,legged robot can move flexibly on a complex and changeable ground.However,the current research on the mechanism of biological movement is not enough.The robot that has been developed now has many problems,and there are many unsolved problems in technology,such as rigid drive,low energy utilization and the landing impact.A single legged robot based on active variable stiffness and passive variable stiffness' s flexible joints are designed in this paper,and its dynamic characteristics were studied.The dissertation mainly deals with the following items:Firstily,in view of the principles of bionics,a single leg structure of flexible joint with active variable stiffness and passive variable stiffness is designed.The leg has 3 degrees of freedom.The structural optimization and spatial motion analysis were carried out.The correctness of the theory of active variable stiffness and passive variable stiffness is verified.Secondly,from the point of view of energy consumption,and in the case of no motor drive,the single leg jumps in the vertical direction is analyzed.The Hertz contact(spring damping)model is used to describe the normal contact force between the foot and the ground.A two-dimensional springing model considering the elastic contact between the foot and the ground is established and analyzed.Then,under the circumstance of motor drive,the dynamic model of the single leg touches the ground and leaves the ground is established respectively.In the model,the mathematical function of the passive variable stiffness and the active variable stiffness is introduced as the part of the elastic potential energy.From the energy consumption,the energy flow principle model of flexible joint and single leg system is established.It reveals that the main function of the passive variable stiffness and the active variable stiffness is highly consistent with bionics.Finally,the prototype of the experimental single leg is assembled,in order to control the target's movement,a fuzzy PID control method is introduced to test the jumping of the single leg prototype in the vertical direction.It verifies the rule of the active stiffness function of a flexible rotary joint on the single leg jump.and it realized real-time on-line adjustment of single leg stiffness.Comparing with the fixed stiffness,the variable stiffness has many advantages over the fixed stiffness.The correctness and feasibility of the theory are verified,and the target of high speed,high stability and high adaptability of the single leg jumping is initially achieved.