A Robophysical Mantis Shrimp Model to Study Ultra-Fast "Impulsive" Biological and Synthetic Systems

Abstract

Breakthroughs in multi-scale, multi-material rapid fabrication and new materials have led to the increased use of robots as tools to understand biological systems in a growing field known as robophysics. Here, a mesoscale mantis shrimp robot, manufactured using laminate origami-inspired techniques called "Pop-up MEMS", is used to characterize the latching mechanics of mantis shrimp, an ultra-fast underwater striking predator. Mantis shrimp belong to a class of organisms that use latches to mediate spring actuation of an appendage at velocities and accelerations that far exceed what could be achieved via direct muscle actuation. The robophysical model demonstrates that a link of varying length in a four-bar linkage can effectively control the two degree of freedom mantis shrimp striking appendage through a torque reversal latch. A dynamic mathematical model of the mantis shrimp robot establishes that linkages can exhibit distinct dynamic phases that control energy transfer from stored elastic energy to ultra-fast motion. Four temporal phases were identified that enable control of the extreme cascade of mechanical power amplification. A non-dimensional performance metric of the kinetic energy ratio enabled analysis of potential energy transfer in the system. Using numerical optimization, linkage lengths were adjusted in the mantis shrimp scale robot in order to achieve striking velocities over 41 m/s in air. The extreme accelerations and speeds of the mantis shrimp robot necessitated improvements in flexure design and led to the development of an accelerated process for manufacturing pop-up MEMS devices using low-cost materials and tools. Lastly, a unique jumping robot was made leveraging the torque reversal mechanism discovered in mantis shrimp with an integrated Chebychev lambda straight line linkage to achieve vertical jumps.