Dynamic Modeling And Optimal Design Of Series Wheel-legged Mechanism

The wheel-legged compound mobile vehicle combines the advantages of the foot-type mobile vehicle and the wheel-type mobile vehicle,and can adapt to various terrain conditions by switching the foot and wheel modes.It is widely used in high-risk and high-intensity occasions such as rescue and disaster relief,military transportation and mineral mining.In the future unmanned era,the application of wheel-legged vehicles will become the mainstream,so it has become a current research hotspot.The wheel-legged compound vehicle is a nonlinear system with multiple degrees of freedom,and the single-wheel-legged mechanism is the basis of this complex system.This thesis studies and analyzes the series wheel-legged mechanism through bionic structure design,static school core,kinematic modeling,foot trajectory planning,dynamic modeling,multi-objective algorithm optimization and prototype experimental verification.The main contents of this thesis are as follows:First,design the overall scheme of the series wheel-leg mechanism.According to the performance requirements of the wheel-legged mechanism,and analyzes the shortcomings of the current wheel-legged mechanism,this thesis designs the suspension system in the wheel-type mode and the leg structure in the foot-type mode in detail.In addition,a wheel-legged switching device module is added,so as to realize the rapid switching of foot and wheel modes.And use ABAQUS software to carry out the static checking and analysis of the wheel-legged mechanism.Second,the kinematics characteristics and foot-end trajectory planning of the wheel-legged mechanism in the foot-wheel mode are studied.Based on the geometrical numerical method,the relationship between the wheel runout and each drive joint angle in the wheeled driving mode is obtained,and it is verified with the suspension model established by ADAMS.At the same time,the D-H method is used to establish the expression of the position change of the foot end and the rotation angle of each driving joint in foot walking,and the trajectory curve of the foot end of the compound cycloid is improved.The kinematic model is established in Robotic Toolbox in MATLAB,which verifies the correctness of the forward and inverse kinematics derivation,and provides a basis for the subsequent dynamic modeling and optimization design.Thirdly,the dynamic characteristics of the wheel-leg mechanism in the foot-wheel mode are studied.For the wheeled driving mode,the theoretical model established by the Lagrange method is compared with the ADAMS model,the correctness of the Lagrange method model is verified,and the smooth performance of the suspension on the C-level road surface is analyzed.For the foot-walking mode,combined with the Hunt-Crossley contact model of the foot-to-ground collision,the dynamic models of the single-leg flight phase and the landing phase are established,and the dynamic models established in the SIMSCAPE module of MATLAB are compared and analyzed,which verifies the correctness of the Lagrange model.Finally,under the condition of satisfying the size and installation conditions,taking the maximum foot-end motion space and the small wheelbase change as the optimization goals,the multi-objective genetic algorithm is used to optimize the size parameters of the wheel-leg mechanism.Finally,the kinematic performance experiment of the single-legged prototype is carried out to verify the feasibility of the overall scheme and the reliability of the mechanical system.This thesis provides some ideas for the further study of wheel-legged vehicles through the dynamic modeling and optimization design analysis of the series wheel-legged mechanism.