Nonlinear Dynamics Analysis And Stability Research Of Reconstruction Of Ummanned Metamorphic Vehicle Under Braking

A metamorphic mechanism means a new type of mechanism that can change its topology and degrees of freedom during motion.In this paper,the metamorphic mechanism is introduced into the field of automobile,and an unmanned metamorphic vehicle which can switch freely between wheeled driving and foot walking is proposed.The vehicle has thecharacteristics of fast global cell transformation.Because of its two forms of motion,it has high passability in complex terrain and high mobility on good pavement.In this paper,the reconstruction motion of unmanned metamorphic vehicle is studied which will brake in structured pavement,so it is necessary to establish a reconstructed kinematics and dynamics model.Then the stability change of the vehicle under the braking condition while the unmanned metamorphic is conudcting a reconstruction motion The details are as follows:Firstly,the body structure and leg mechanism of the unmanned metamorphic vehicle are introduced,and the driving brake reconstruction of the unmanned metamorphic vehicle is planned,divided into three stages.Secondly,the kinematics models of the leg mechanism unfolding and the coupled reconstruction process are established by using the D-H method,then according to the equivalent principle,the oscillating and stretching motion of the metamorphic core swing bar mechanism is simulated as the expanding motion of the folding leg mechanism In order to realize the smoothness of the reconstruction motion and the requirement of keeping the front and rear body level,the motion law of each revolute joint and the horizontal lifting mechanism are designed.Then,based on the Lagrange dynamics model of the simplified swing rod mechanism,the dynamic effect of the folding leg on the ummanned metamorphic vehicle during the expansion process was studied,and then the dynamic effect of the expansion leg on the ummanned metamorphic vehicle during the support process was studied.Based on nonlinear tire model,set up and solve the dynamics model of the metamorphic vehicle braking on reconstruction,analysis of the phase space diagram,phase plan and time domain chart of many initial points and the signal initial value under two different braking torque,found that,with the increase of braking torque,the unstability phenomenon of system caused by bifurcation will happen,then drawing the bifurcation diagram of the system state variables with the braking torque as the parameters The generation of bifurcation values was observed from a global point of view,and the bifurcation values at different stages of reconfiguration during braking were compared.The ZMP model of the metamorphic vehicle in the coupling reconstruction stage was established to analyze whether the metamorphic vehicle would topple under the deceleration condition.Finally,based on the assembled real vehicle,the braking experiments of the stages of folding legs unfolding and the folding legs supporting,and the coupling reconstruction experiments were carried out,these experiments verify the correctness of the theory of reconstruction under braking.