Stability-based Scale Estimation of Monocular SLAM for Autonomous Quadrotor Navigation

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We propose a novel method to deal with the scale ambiguity in monocular SLAM based on control stability. We analytically show that (1) using unscaled state feedback from monocular SLAM for control can lead to system instability, and (2) there is a unique linear relationship between the absolute scale of the SLAM system and the control gain at which instability arises. Using this property, our method estimates the scale by adapting the gain and detecting self-induced oscillations. Unlike conventional monocular approaches, no additional metric sensors are used for scale estimation. We demonstrate the ability of our system to estimate the scale for performing autonomous indoor navigation with a low-cost quadrotor MAV.