Browsing by Author "Holley, James"

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    Estimation and Control of Series Elastic Actuators for Decentralized Systems
    (2018-04-20) Holley, James; O'Malley, Marcia K
    Robotic applications continue to move out of factories and laboratories into ev- eryday applications. This movement drives a different paradigm for robotics; towards softer, compliant actuators intended for interacting with unknown environments and humans. The series elastic actuator, a robotic actuator with intentionally designed compliance, is a leading candidate for use in robots making the transition to human environments. Compliance in actuation provides its own engineering challenges. Series elastic actuators provide an additional degree of freedom, resonances, and more complicated controllers to operate. A series elastic estimator is proposed that models additional degrees of freedom and provides disturbance rejection in order to provide more accu- rate signals to the control of the actuator, and to higher level systems that may be controlling several robotic actuators together. Furthermore, any system that may interact with humans necessarily requires a element of safety. Passive systems are systems that do not produce any energy of their own. Additionally, passive systems in parallel or in feedback yield a passive system. For this reason, providing a guarantee of passivity in a system is a safety measure for deeming a robotic system fit for human interaction. In this thesis, an extension of a novel series elastic torque controller, disturbance observer torque control, can beguaranteed passive with relatively little trade off. Finally, a nonlinear torque controller is proposed that allows torque control to converge at a rapid exponential rate. Such a controller is not only important for torque control of the actuator, but leverages a larger proof on dynamics of a robot comprised of series elastic actuators. It separates actuator dynamics from robot dynamics, allowing a high level controller to assume it is comprised of rigid actuators, opening the door for more control schemes to be developed for robots without having to consider the extra complexity introduced by compliant actuators.