Exploiting the bistable dynamics in a two-module vibration-driven robot for locomotion performance enhancement

Abstract

Vibration-driven locomotion systems have great potential for designing micro locomotion robots, and improving the locomotion performance is one of the research focuses. This paper investigates how to integrate bistability with the vibration-driven mechanism to form novel designs and to enhance the locomotion performance, thereby advancing the current state of the art. To this end, a two-module vibration-driven robot with a bistable pre-buckling beam is designed, which is equivalently modeled into a nonlinear lumped-mass system. Its steady-state locomotion is first approximated through the harmonic balance (HB) method, and the results show that the presence of the sticking behavior caused by the dry friction prevents the HB method from accurately predicting the robot's velocity. Hence, numerical approaches are employed in this research, which not only reveals the effects of the actuation parameters on the bistable dynamics and the steady-state locomotion performance of the robot, but also uncovers the unique advantages that the bistability brings to the robot. On one hand, the robot can present different locomotion modes corresponding to different levels of the average steady-state velocity and can switch among them without increasing the actuation energy; on the other hand, the robot can adapt to variable payloads and maintain high speeds. Based on a bistable two-module vibration-driven robot prototype, these bistability-induced characteristics and merits are verified experimentally. The findings of this paper would provide a design basis and useful guidelines for the development of bistable vibration-driven locomotion robot.