A sighted aerial robot with fast gaze and heading stabilization

Autonomous guidance of micro-air vehicles (MAVs) in unknown environments is a challenging task because these artificial creatures have small aeromechanical time constants, which make them prone to be disturbed by gusts of wind. Flying insects are subject to quite similar kinds of disturbances, yet they navigate swiftly and deftly. Flying insects display high- performance visuo-motor control systems that have stood the test of time. They can therefore teach us how vision can be used for immediate and vital actions. We built a 50-gram tethered aerial demonstrator, called OSCAR II, which manages to keep its gaze steadily fixating a target (a dark edge), in spite of nasty thumps that we deliberately gave to its body with a custom-made "slapping machine". The robot\´s agile yaw reactions are based on: (1) a mechanical decoupling of the eye from the body, (2) an active coupling of the robot\´s heading with its gaze, (3) a Visual Fixation Reflex (VFR), (4) a Vestibulo-Ocular Reflex (VOR), (5) an accurate and fast actuator (voice coil motor, VCM). The actuator is a 2.4-gram voice coil motor that is able to rotate the eye with a rise time as small as 12 ms, that is, much shorter than the rise time of human oculo-motor saccades. In connection with a micro-rate gyro, this actuator endows the robot with a high performance "vestibulo ocular reflex" that keeps the gaze locked onto the target whatever perturbations in yaw affect the robot\´s body. Whenever the robot is destabilized (e.g., by a slap applied on one side), the gaze keeps fixating the target, while being the reference to which the robot\´s heading is servoed. It then takes the robot only 0.6 s to realign its heading with its gaze.