Design And Running Motion Research Of Less Power Closed-chain Elastic Bionic Legs

Legged robots have excellent terrain adaptability compared with the traditional wheeled and tracked robots.But for many years,there is no satisfying improvementfor the speed performance.In recent years,the legged robots with a good solution of control algorithm can obtain medium and high speed.The technical difficulty lies in the leg mechanical structure and the power system.This paper makes a breakthrough in the mechanical structure of the leg.The closed-chain linkage mechanism has whole-cycle high-frequency swing,can be driven with less power,and its drive system can be located on the chassis.By making full use of these characteristics,combined with the research on running characteristics,two kinds of closed-chain elastic bionic legs for running motion are proposed.The specific research contents are as follows:(1)According to the research on the characteristics of running motion,the design requirements of closed-chain elastic bionic legs are proposed.Firstly,with the gait research and the virtual leg technology,the regular gait of the common four-legged and multi-legged robots is simplified into two-legged,and it is proposed that the closed-chain elastic bionic legs should adopt the running gait at high speed.The inverted pendulum model is used to model the walking motion,and the SLIP model is further adopted to study the running motion characteristics.Four design requirements for the running motion of the closed-chain leg mechanism are proposed.Cl:There should be elasticized components in the closed-chain linkage to realize the flexibility of the leg;C2:The equivalent SLIP virtual spring stiffness of the leg is nonlinear and can increase gradually;C3:Leg mass is negligible;C4:The foot point trajectory of the closed-chain leg mechanism is symmetry about the hip joint,and the support phase trajectory is approximately an arc centered by the hip joint.(2)Two kinds of closed-chain elastic bionic leg structures(W type and S type)are proposed.Firstly,by studying the evolution process of animals,the three-section structure which is more conducive to running is proposed.With the variant design of Watt type and Stephenson type,W type and S type bionic legs conforming to the three-section structure are obtained,and dimensional design of the femur,tibia and tibia are performed according to the size of the cheetah's leg bones.Secondly,based on the study on leg muscle structure of the cheetah and the C1 design requirement,the elastic design is conducted.The W type bionic leg resembles the cheetah's gastrocnemius muscle,and the S type bionic leg resembles the cheetah's sartorius muscle and semi-membrane muscle.Thirdly,the kinematics analysis,the design and optimization for foot trajectory of W type and S type bionic legs are carried out according to C4 design requirements.Finally,the virtual stiffness of the two bionic legs satisfying the C2 design requirements is calculated.(3)The dynamic analysis of W type and S type closed-chain bionic legs is carried out.The relationship between the foot end and the crank drive torque is established by Lagrangian dynamic equation.Comparing with the simulation results,the correctness of the calculation results is verified.(4)The dynamics simulation analysis of W type and S type two bionic legs is carried out.The simulation model is built in Adams software,and the collision parameters between the foot end and the ground,the coefficient of the spring,and the control function of the crank are set.The performance differences between the two bionic legs in terms of kinematics performance,dynamic performance and energy consumption are compared by simulation,and it's turned out that S type is better than W type.(5)Prototype design and experiment of biped robot based on W type and S type bionic legs are conducted.The overall design of the robot and the sub-systems are performed,and the experimental prototype is built through the process of machining,assembly,etc.A bench experiment is carried out for two biped robots,which verifies the feasibility of the leg design and the accuracy of the leg trajectory.Then the walking and running motion gaits are realized through the experiments with S type bionic biped robot,and the running speed reaches 11 km/h.