Versatile rotary actuators for small-scale robotic systems

Modern robotics has been greatly facilitated by the standardized tool sets surrounding actuation and sensing for human-scale systems, with the design and control techniques for electromechanical motors serving as a prime example. No such tool sets have become standard at the millimeter- and micrometer-scale however, often leaving actuation and sensing as bottlenecks when developing small-scale robotic systems. In this paper, we develop manufacturing and algorithmic tools for a promising class of small-scale rotary actuator – rotary pouch motors. We present a design approach that allows for integration of both actuation and sensing into low-profile, laminate linkages of almost arbitrary length and complexity and demonstrate this approach with the design of a three degree-of-freedom (DOF) spatial manipulator. We also present dynamic models of rotary pouch motors and integrate these models into estimation and control laws that we use for real-time control of a 1-DOF joint. The presented state-estimation algorithm exhibits a root-mean-square (RMS) error of approximately 0.87° and the presented control law demonstrates RMS tracking error of approximately 6.70° when tracking sinusoids up to 3 Hz. By developing rotary pouch motors as controllable dynamic systems, they can used in myriad small-scale robotic systems, including insect-scale legged robots and millimeter-scale manipulators.