Modeling Large Deformation Impact Dynamics for Legged Microrobot Locomotion: A Preliminary Formulation

A finite element dynamic model is developed to better understand impact events during large amplitude dynamics of a compliant, elastic-legged small-scale robot. The proposed motion of the robot would be achieved as a result of impulse forces generated from the forced collision of piezoelectrically-actuated, beam-like legs with the ground. The nominal robot leg is a prismatic continuous structure with uniform density, cross-sectional area and moment of inertia. Dynamic modeling in this work attempts to manage the non-negligible motion of the actuated beam tip in its axial direction at impact when large bending deformations are excited, which complicates prior analysis methods. For the micro-robot, this motion is proposed to be exploited as a means to produce locomotion in the horizontal direction, and hence must be accounted for. Finite element analysis approaches are adapted for the micro-robotic circumstances. Preliminary results are presented for the scenario of large deformation, unforced dynamics with impact, tested using centimeter-scale mock-ups for future thin-film based micro-robots. Needs and opportunities for further validation are briefly discussed.