FlipWalker: Jacob's Ladder toy-inspired robot for locomotion across diverse, complex terrain

This paper introduces FlipWalker, a novel underactuated robot locomotion system inspired by Jacob's Ladder illusion toy, designed to traverse challenging terrains where wheeled robots often struggle. Like the Jacob's Ladder toy, FlipWalker features two interconnected segments joined by flexible cables, enabling it to pivot and flip around singularities in a manner reminiscent of the toy's cascading motion. Actuation is provided by motor-driven legs within each segment that push off either the ground or the opposing segment, depending on the robot's current configuration. A physics-based model of the underactuated flipping dynamics is formulated to elucidate the critical design parameters governing forward motion and obstacle clearance or climbing. The untethered prototype weighs 0.78 kg, achieves a maximum flipping speed of 0.2 body lengths per second. Experimental trials on artificial grass, river rocks, and snow demonstrate that FlipWalker's flipping strategy, which relies on ground reaction forces applied normal to the surface, offers a promising alternative to traditional locomotion for navigating irregular outdoor terrain.

Origami-inspired soft twisting actuator

Soft actuators have shown great advantages in compliance and morphology matched for manipulation of delicate objects and inspection in a confined space. There is an unmet need for a soft actuator that can provide torsional motion to e.g. enlarge working space and increase degrees of freedom. Towards this goal, we present origami-inspired soft pneumatic actuators (OSPAs) made from silicone. The prototype can output a rotation of more than one revolution (up to 435{\deg}), larger than previous counterparts. We describe the design and fabrication method, build the kinematics models and simulation models, and analyze and optimize the parameters. Finally, we demonstrate the potentially extensive utility of OSPAs through their integration into a gripper capable of simultaneously grasping and lifting fragile or flat objects, a versatile robot arm capable of picking and placing items at the right angle with the twisting actuators, and a soft snake robot capable of changing attitude and directions by torsion of the twisting actuators.