SMARTI: A 60-mg Steerable Robot Driven by High-Frequency Shape Memory Alloy Actuation

We introduce the Shape Memory Alloy (SMA) Robotic Travelling Insect, or SMARTI, a 60-mg crawling microrobot that uses multiple high-frequency SMA actuators to enable controlled steering and path following. The primary breakthrough that facilitated the creation of the SMARTI prototype was the development of a 6-mg high bandwidth SMA bending actuator, allowing for the design of a new modular microrobotic system propelled by anisotropic friction. The carbon fiber structure allows for a robust, flexible robotic system that exhibits high durability and longevity. Additionally, the SMARTI uses off-board position and attitude feedback via a motion capture system to independently actuate its left and right legs which provides the necessary control authority for intelligent speed and heading manipulation. The SMARTI's steering performance is demonstrated experimentally via a series of closed-loop path following tasks during which it reaches a maximum sustained speed of 46 mm/s and turning rate of 107 dps while maintaining tracking errors as low as 1.7 mm. The locomotion results presented herein are novel in the realm of SMA actuated robotics, and at the sub-gram scale, this combination of speed and maneuverability is currently unparalleled.