Bio-Inspired Undulatory Locomotion Control Strategy for Novel Soft Robot Based on Auxetic Structures

This paper presents a novel locomotion soft robot that exploits the properties of auxetic structures to achieve bio-inspired undulatory locomotion. To reduce the dependence on computation and control strategies, we propose to develop a soft structure using a combination of positive Poisson’s ratio lattice structure and negative Poisson’s ratio lattice structure that creates a dorsoventral undulating wave pattern under compressive load. This is combined with a laterally undulating gait pattern exhibited by giant salamanders. The soft structure is actuated with nylon cables attached to servo motors, mimicking muscles. We use finite element analysis (FEA) methods to accurately model the soft structure’s deflection pattern, which is then used to create a control strategy for the robot. We develop a mathematical model and a subsequent gait pattern based on the sequential actuation of the nylon cables. The gait was experimentally tested and further improved with closed-loop error compensation. The research proves linear locomotion is possible through the proposed design with the lowest computational requirements.