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Dynamics of millimeter-scale hexapod microrobotics with PZT-polymer micro-actuators

This paper examines the dynamics of a type of millimeter-scale hexapod microrobot based on piezoelectric actuation. These robots [1], having a 5mm × 2 mm footprint, are formed from integrated thin-film lead zirconate titanate (PZT) and high-aspect-ratio parylene-C polymer structures. The in-chip dynamics of the microrobots are measured when actuated with tethered electrical signal, to demonstrate the resonant behavior of different parts of the robot. Out-of-chip robot motion is then actuated by external vibration after the robot has been detached from its silicon tethers to external power. A dynamic model for robot and ground interaction is presented and validated to explain robot locomotion in the vibrating field using the in-chip measurements of actuator dynamics and certain additional design information. The model accounts for the interaction between the robot and ground, for multiple resonances of the robot leg, and for rigid robot body motion in 3 degrees of freedom. The dynamic model with first vertical and lateral resonant modes of leg shows a good match with experimental results for the motion of the robot on a vibrating surface actuated within low-frequency range.