Study On Foot Trajectory Planning Of Double Closed-Chain Walking Leg And Its Interaction With Soil

Compared with wheeled robot and tracked robot,legged robot has been widely studied and developed because of its strong environmental adaptability.Walking leg is the key component of the foot robot,which not only determines the motion ability of the foot robot,but also the basis of the whole machine development.Aiming at the problems of more leg degrees of freedom,motor reciprocating drive commutation and more energy consumption of open-chain foot robot,in order to meet the needs of miniaturization,large load and easy control of walking legs.This paper combines the closed-chain linkage mechanism with the walking mechanism,proposes a two degree of freedom double closed-chain walking leg mechanism composed of parallel four-bar mechanism and crank slider mechanism,and carries out mechanism design,kinematics analysis,foot end trajectory planning,foot end soil interaction mechanics analysis and simulation research.The relevant research results are of great significance to further enrich and develop the basic theory of walking robot.The main research contents are as follows:(1)Walking leg configuration design and kinematics analysis.The advantages and disadvantages of open-chain Walking leg and closed-chain Walking leg are analyzed.According to the degree of freedom configuration and mechanism design criteria of walking leg,a new two degree of freedom double closed-chain walking leg is proposed.The kinematics of walking leg is analyzed based on D-H method and geometric analysis method,and the foot end coordinate equation and joint variable of walking leg are established respectively.(2)Trajectory planning and experimental study of foot end of walking leg.Analyze the foot end trajectory of typical closed-chain linkage,clarify the requirements of foot end trajectory planning,and select the compound cycloid trajectory as the target curve of foot end trajectory planning.Using genetic algorithm and fmincon()function interior point method,the size of walking leg is optimized,and the size of each connecting rod is obtained.The virtual prototype model of walking leg is constructed based on Adams software,and the motion simulation is carried out to obtain the foot end trajectory curve that meets the target curve.On this basis,according to the optimized rod size,the walking leg prototype is made by using 3D printing technology,and the foot end trajectory tracking experiment is carried out to verify the feasibility of foot end trajectory planning and the rationality of configuration design.(3)Study on interaction mechanics between foot end of walking leg and soil.The physical and pressure bearing characteristics of soil are analyzed.Based on Bekker pressure bearing model and janosi shear model,the interaction mechanical models between ordinary hemispherical foot end and hemispherical foot end with bulge and soil are established respectively.Taking Desert sandy soil as the research object,the effects of foot end load,foot end radius,bulge radius,bulge number,bulge height and other parameters on soil subsidence were analyzed.(4)Simulation analysis of the interaction between foot end of walking leg and soil.The soil constitutive model is established based on Mohr Coulomb elastic-plastic model.Taking the ordinary hemispherical foot end and the hemispherical foot end with bulge as examples,the finite element simulation models of the interaction between the two foot ends and the soil are established in ABAQUS software to analyze the soil stress and deformation under the two foot ends.According to different foot end load and foot end radius,the finite element simulation model of foot end and soil is constructed and simulated,and the variation curve of soil subsidence with foot end load and foot end radius is obtained.Through the comparison of theoretical derivation and simulation experiments,the correctness of the derivation of the mechanical model of the interaction between the foot end of walking leg and soil is verified.