CaseCrawler: A Lightweight and Low-Profile Crawling Phone Case Robot

The CaseCrawler is a lightweight and low-profile movable platform with a high payload capacity; it is capable of crawling around carrying a smartphone. The body of the robot resembles a phone case but it has crawling legs stored in its back. It is designed with a deployable, in-plane transmission that is capable of crawling locomotion. The CaseCrawler's leg structure has a knee joint that can passively bend only in one direction; this allows it to sustain a load in the other direction. This anisotropic leg allows a crank slider to be used as the main transmission for generating the crawling motion; the crank slider generates a motion only within a 2D plane. The crank slider deploys the leg when the slider is pushed and retracts it when pulled; this enables a low-profile case that can fully retract the legs flat. Furthermore, by being restricted to swinging within a plane, the hip joint is highly resistant to off-axis deformation, this results in a high payload capacity. As a result, the CaseCrawler has a body thickness of 16 mm (the transmission without the gearbox is only 1.5 mm) and a total weight of 22.7 g; however, it can carry a load of over 300 g, which is 13 times its own weight. To show the feasibility of the robot for use in real-world applications, in this study, the CaseCrawler was employed as a movable platform that carries a 190 g mass, including a smartphone and its cover. This robot can crawl around with the smartphone to enable the phone to charge itself on a wireless charging station. In the future, if appropriate sensing and control functions are implemented, the robot will be able to collect data or return to the owner when needed.