Soft Electrically Actuated Quadruped (SEAQ)-Integrating a Flex Circuit Board and Elastomeric Limbs for Versatile Mobility

Like their natural mammalian and reptilian counterparts, legged soft robots require robust walking dynamics and untethered functionality in order to swiftly maneuver through unstructured environments. Progress in this domain requires careful selection of soft limb actuators and integration of power and control electronics into a soft robotics platform capable of biologically relevant locomotion speeds without dependency on external hardware. We demonstrate this with an untethered soft palm-sized, 25 g soft electrically actuated quadruped, which is capable of crawling at a maximum speed of 0.56 body length per second (3.2 cm/s), andmaking 90 degrees turns in two complete gait cycles (similar to 5 s). The robot is composed of a flexible printed circuit board and electrically powered soft limbs that contain shape memory alloy (SMA) wires inserted between pre-stretched layers of a soft, thermally conductive elastomer. Its versatile mobility and robust dynamics are demonstrated by its ability to walk on a variety of surfaces-including inclines, rocky, and granular surfaces, and steps that are over half the robot height-andmaintain continuous forward locomotion through confined space or after being dropped from an elevated height. In addition to these locomotion studies, we perform an experimental study on the blocking force of a single actuator to provide independent support for the feasibility of untethered soft robot walking with SMA-based actuation.