84.6 Friday, Jan. 6 The influence of sensory feedback delays on the yaw dynamics of insect flight ELZINGA, M.J.*; DICKSON, W.B.; DICKINSON, M.H.; Caltech; IO Rodeo; Univ. of Washington email@example.com
In closed loop systems, even modest sensor feedback delays may have potentially disastrous implications for performance and stability. Flies have evolved multiple specializations to reduce this latency in their sensory systems, yet even the mechanosensing haltere–which provides the fastest feedback during flight–involves a delay that is significant on the timescale of body dynamics. We explored the effect of sensor delay on flight stability and performance for flapping flight in the context of yaw turns through the use of a dynamically scaled robotic model of the fruit fly, Drosophila melanogaster. To perform this analysis we implemented a real-time feedback system that performed active turns in response to measured torque about the functional yaw axis. Active control over yaw torque was enabled through the modulation of a parameter governing the bilateral asymmetry in the angle of attack. With the robot under proportional control, we performed step and impulse response experiments in yaw velocity for a range of virtual feedback delays, similar in dimensionless timescale to those experienced by a fly. The results show a fundamental tradeoff between sensor delay and permissible feedback gain, and demonstrate a gain threshold, below which the system is stable regardless of delay. Proportional feedback control provides a method of active damping that is relevant even for delayed feedback on suitable timescales. Presented in the context of these findings, a control architecture whereby a haltere-mediated inner loop proportional controller provides damping for a visually mediated low-pass filter is consistent with tethered flight measurements, free flight observations, and engineering design principles.