C-Quad: A Miniature, Foldable Quadruped with C-Shaped Compliant Legs Ahmet Furkan G¨ uc ¸, Mert Ali ˙ Ihsan Kalın, Cem Karakadıo˘ glu, and Onur ¨ Ozcan Bilkent University, Mechanical Engineering Department, Ankara, Turkey Abstract— C-Quad is an origami-inspired, foldable, minia- ture robot whose legs and body are all machined from one PET sheet each. The already famous compliant legs are modified such that they can be manufactured from a flat PET sheet and folded into the C-shape wanted. The compliant legs enable the miniature robot to run fast and scale obstacles with ease due to the geometry of the legs. C-Quad has four legs that are manufactured separately from the main body frame, which is also manufactured from a single PET sheet. All of its legs are actuated individually with a total of four DC motors. Despite the thin PET film, the structural rigidity and robustness of the body frame is increased by using specialized folds and locks. The manufacturing and assembly of the robot takes approximately 2.5 hours. C-Quad carries a battery, an Arduino Pro Micro control board, a bluetooth communication module, custom made encoders and commercially available IR sensors for motor speed control and motor drivers, all of which weighs 38 grams. By using very simple control strategies, it can achieve the speed of 2.7 Bodylengths/sec, can perform in-place turns and can climb over obstacles more than half of its height. Index Terms— Origami-Inspired Robots, Print-and-Fold Robots, Foldable Legged Robots, Unconventional Manufactur- ing, Miniature Robots. I. I NTRODUCTION Miniaturization of robots offers interesting opportunities to the robotics community by decreasing the costs of robots and providing them the ability to explore and inspect confined spaces such as ruins, crash sites and pipelines [1]. On the other hand miniature robotics is still facing big challenges especially due to manufacturing, assembly, actuation and power issues of small robots. Miniature robotics have a variety of manufacturing techniques that suggest solutions to the manufacturing and assembly problems such as laser cut- ting materials and creating multilayer composite structures in Smart Composite Microstructure (SCM) [2], [3], MEMS fabrication [4] and 3D printing for lightweight robots [5]. All these techniques have advantages and disadvantages such as SCM is very powerful at creating cheap and miniature robots but requires multilayer processing and good alignment between layers, MEMS fabrication can make very small robots however the equipment required are significantly more expensive than the other techniques, and 3D printing can make very small and lightweight robots but structures are often very rigid and brittle. Origami-inspired (more cor- rectly Kirigami-inspired, since cutting is involved) “foldable robots” technique is another miniature robot manufacturing method that is closely related to the SCM method. This method offers laser-machining single sheets in 2D and folding them into more complex 3D miniature shapes or mechanisms. Using foldable robots technique, we can make Fig. 1. The foldable, miniature, C-shaped-legged quadruped, C-Quad. cheaper compliant robots that do not require alignment of multiple layers, however designing the crease patterns can often get very complex. In the design and manufacturing of the C-Quad (Fig. 1), we leveraged this foldable robots technique. Foldable robots and other SCM and its relative fabrication methods offer compact designs with not only increasing the compliance and robustness or the structures but also enabling cheap and time saving manufacturing and assembly processes. Multilayer fabrication-based SCM and relative processes so far enabled fabrication of many famous minia- ture robots such as RoACH family of robots [6], [7], DASH [8], and HAMR [9]. The single layer derivative of SCM, the foldable robots technique, was initially proposed as the idea of origami inspired printable robotics [10], and exploited in a variety of works in miniature robotics to grasp [11], [12], fly [13], crawl [14], [15] and walk [16], [17], [18]. Moreover, mechanisms that can fold itself has been developed with the aid of shape-memory sheets [19]. In the design of the C-Quad, we wanted to use a leg design that would provide the robot a high mobility. Originally, RHex showed impressive rough terrain locomotion capabili- ties using C-shaped compliant legs [20]. More recently a sim- ilar leg design is implemented by Maryland Microrobotics Laboratory on a robot much smaller (sub-2 grams) using 3D printed rigid materials, which proved that even without the compliance, C-shaped leg structure can help a miniature robot walk on rough terrain [5]. C-Quad uses a similar C- shaped leg structure that is compliant. Most foldable robots utilize simple fourbar transmissions that can be manufactured on a single sheet of material in 978-1-5386-3742-5/17/$31.00 © 2017 IEEE 26 Proceedings of the 2017 IEEE International Conference on Robotics and Biomimetics December 5-8, 2017, Macau SAR, China