Kinematics And Nonlinear Dynamics Analysis Of Reconstruction Of Unmanned Metamorphic Vehicle

In order to have both the high speed of the wheel mechanism and the flexibility of the foot mechanism,this paper designs an unmanned metamorphic vehicle which can switch freely between the wheel form and the foot form.As a new type of wheel-legged robot,its shape switching has the characteristics of fast and global.In order to ensure the smoothness and stability of the quick global reconstruction motion under the parking condition,the motion trajectory of each joint is planned,and the kinematics and dynamics models of the process are established.A nonlinear dynamics model is established for its rapid global reconstruction motion in straight line driving.The specific work contents are as follows:Firstly,the components of the unmanned metamorphic vehicle are analyzed and introduced,and the phase planning of its reconstruction movement is expounded.In view of the parking coupling reconstruction motion process,the trajectory planning of each joint is carried out based on the ride comfort.On this basis,the forward kinematics model of the process is established by using the screw method and the D-H parameter method respectively,and the simulation analysis is carried out.The singularity is solved based on the forward kinematics model and the stability of the process is analyzed according to the stability criterion of zero-moment point.For the landing process,the inverse kinematics of the process is solved by P-K subproblem method based on the optimized foot position and posture of the supported state of the unmanned metamorphic vehicle,and the expansion motion law of each leg joint at the optimal landing point in the supported state is obtained.Secondly,based on the kinematics,the Lagrange equation is derived according to the screw theory,and the dynamics model of parking coupling reconstruction motion of the unmanned metamorphosis vehicle is established.The driving torque required to satisfy the ride comfort of each joint is simulated and analyzed.Then,for the coupling reconstruction motion of the straight line driving of the unmanned metamorphic vehicle,the vehicle is regarded as the mass block of the centroid change and the nonlinear vibration dynamics model is established based on the nonlinear foot wheel.The influence of road sinusoidal excitation on the stability of the nonlinear vibration system is studied by using the stability analysis methods of nonlinear dynamics categories such as maximum Lyapunov exponential spectrum,bifurcation diagram,phase plane diagram and Poincare cross section diagram.It is found that when the angular frequency and amplitude of sinusoidal excitation of pavement are around a certain value,the nonlinear vibration system will enter a chaotic motion state and become unstable.Finally,the kinematics experiment of parking coupling reconstruction is carried out on the prototype of unmanned metaminergic vehicle.By comparing the experimental data with the simulation data,it is concluded that the levelness,smoothness and stability of the unmanned metamorphic vehicle in the coupling reconfiguration process are excellent.