MutBug: A lightweight and compact crawling robot that can run on both sides

Double-sided crawling robots have potential to be quite useful for real-world applications. For example, double-sided crawling robots keep crawling even when they are turned over. In this letter, we present a lightweight and compact crawling robot that can run on both sides. To make this possible, two design strategies are proposed: the shared hip joints and the low profile differential drive based on orthogonally oriented four-bars. The shared hip joints allow the robot to have a thin body by reducing redundant structures. The orthogonally oriented four-bars, which can be installed in the limited thin body structure, enable the robot to equally transmit the motor's crank motion to the multiple legs. Thanks to these design strategies, the robot not only has compact size but also successful alternating gait. In result, the MutBug has body thickness of 15 mm and runs at the maximum speed of 0.53 m/s.