Toward an insect-inspired event-based autopilot combining both visual and control events

This paper presents the autopilot and the behavior of a “simulated bee” traveling along two different tunnels using both visual and control events. The computational gain of an event-based PID controller compared to its time-based version is usually discussed because the event detector is computationally expensive. By combining visual and control events, the newly suggested event-based autopilot requires very low computational resources. In particular, the event detector which computes the control error and tests its magnitude is activated only when a new contrast is detected by the optic motion detectors that assesses the optic flow, i.e. only when the magnitude of the optic flow error could have changed. This new event-based control strategy used faithfully the visual information already available in the optic flow sensor to reduce even further the computational cost. The “simulated bee” was equipped with: (i) a minimalistic compound eye comprising 10 or 8 local motion sensors (depending of the tunnel configuration) measuring the optic flow magnitude, (ii) two optic flow regulators updating the control signals whenever specific optic flow criteria changed and (iii) three event-based controllers taking into account both error signals and visual events, each one in charge of its own translational dynamics. The “simulated bee” managed to travel safely along the tunnels without requiring any speed or distance measurements, using very low computational resources, by (i) concomitantly adjusting the side thrust, vertical lift and forward thrust only when both a visual contrast and a change of optic flow control error were detected, and (ii) avoiding collisions with the surface of the tunnels and decreasing or increasing its speed, depending on the clutter rate perceived by motion sensors.