Nonlinear Dynamics Analysis of a Deformable Robot Executing Driving Reconstruction

Abstract

A deformable robot is a new type of robot that utilises a metamorphic mechanism into the field of robotics and switches between vehicular and humanoid states during reconstruction processes. In the process of driving reconstruction of the deformable robot, the nonlinear vibration will be generated due to the excitation of uneven roads, and tipping instability of the deformable robot may occur. To address this phenomenon, the effect of road excitation on the stability of the deformable robot during driving reconstruction process was investigated based on a nonlinear dynamics analysis method. In this study, a kinematic model for the coupled reconstruction process of a deformable robot was developed using the homogeneous coordinate transformation method. A nonlinear dynamics equation for the variable-centre-of-mass system of the robot was derived for the driving reconstruction process. Nonlinear dynamics analysis methods were applied to analyze the nonlinear response and the change of the system stability of the deformable robot driving reconstruction under the influence of different road excitation amplitudes, excitation frequencies, and reconstruction speeds. The accuracy of the established nonlinear dynamics model was further verified through experiments. It is shown that when the road excitation amplitude exceeds \(0.07\;{\text{m}}\) or the excitation frequency exceeds \(7.2\;{\text{Hz}}\), irregular chaotic motion as well as tipping instability may occur. With the increase of reconstruction time, the stability of the deformable robot is enhanced during driving reconstruction. When the reconstruction time exceeds 18 s, the driving reconstruction of the deformable robot can be stably executed on typical roads.