Simulation Based Fault Detection and Design Modification for Highly Dynamic Robotic Systems Open Access
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The current approach to creating and improving robots and their control systems follows a cycle where complex mechanisms and controllers are iteratively designed, briefly debugged in a simulated environment, built, tested and then redesigned to address anomalous behaviors that were observed during in situ testing. During the initial cycles of this procedure, when unvetted control systems are tested on physical hardware, easily avoidable errors (e.g., unexpected collisions from inexact link geometry measurements or parasitic oscillation in actuators and passive elements) can have catastrophic consequences. Although testing robots in situ can be costly, often entirely new phenomena emerge from situated testing that were not observed throughout early computerized simulation-based testing. The discovery of such unanticipated behavior is currently considered a normal occurrence during robotics testing in situ. This anticipated unanticipated behavior---the expectance of the unknown during robot operation---is due in part to the increased complexity of robotic systems (e.g., uneven terrain, impacting collision, unpredictable contact conditions) compared to typical automotive or aerospace applications that rely heavily on simulation-based testing before physical testing. I have investigated a statistical approach to simulation, where the indeterminacy of physical models or uncertainty in the structure of a mechanism or its environment is represented as a collection of particles in many parallel simulations. The aim of this approach is to inform roboticists of the possible unknown or unexpected behaviors that a robotic system may exhibit in order to address these faults before they have been observed on the physical system. Our approach excites many of the errors caused by modeling, sensory, actuation, and communication error or uncertainty and can assist roboticists in determining whether certain robot designs, control systems, or modeling assumptions might result in hard-to-predict behavior; I use this information to predict the robustness or brittleness control policies and then validate the predictions in situ, on low-cost quadrupedal robots. This dissertation presents tools for automating and or simplifying a roboticist's typical workflow (i.e., designing, testing, controlling, and debugging robots). These tools aim to inform roboticists of the possible unknown or unexpected behaviors that a robotic system may exhibit in order to address these faults before they have been observed on the physical system. The goal of this dissertation is to greatly accelerate the design-build-test cycle of research in robotics by providing a readily usable virtual testing and design framework for robot hardware and software.