Improving performance: recent progress on vibration-driven locomotion systems

Improving locomotion performance is the primary objective in studying vibration-driven locomotion systems. In this paper, we report out recent progress within this topic from three aspects. First, dry friction-induced stick-slip motions, which are typical non-smooth dynamical behaviors, are analyzed and categorized based on sliding bifurcation analysis, and the sticking feature of the system is utilized to achieve directional locomotion as well as to increase average locomotion speed without additional energy input. Second, a strong global nonlinearity, bistability, is introduced into the internal oscillation, with which, unique benefits are obtained, including broad frequency bandwidth for high average locomotion speed and multiple locomotion modes. Third, by incorporating two internal oscillators into the system, planar locomotion capability is acquired; various trajectories can be executed by simply tuning the frequencies of the two internal oscillators. In addition to theoretical and numerical efforts, based on our designed prototypes, the proposed strategies and the achieved performance boosts are experimentally verified. We believe that this progress report, along with the discussions on challenging issues and directions worth exploring, could serve as a solid foundation and useful guideline of future research.