title: The influence of sensory delay on the yaw dynamics of a flapping insect.
abstract: In closed-loop systems, sensor feedback delays may have disastrous implications for performance and stability. Flies have evolved multiple specializations to reduce this latency, but the fastest feedback during flight involves a delay that is still significant on the timescale of body dynamics. We explored the effect of sensor delay on flight stability and performance for yaw turns using a dynamically scaled robotic model of the fruitfly, Drosophila. The robot was equipped with a real-time feedback system that performed active turns in response to measured torque about the functional yaw axis. We performed system response experiments for a proportional controller in yaw velocity for a range of feedback delays, similar in dimensionless timescale to those experienced by a fly. The results show a fundamental trade-off between sensor delay and permissible feedback gain, and suggest that fast mechanosensory feedback in flies, and most probably in other insects, provide a source of active damping which compliments that contributed by passive effects. Presented in the context of these findings, a control architecture whereby a haltere-mediated inner-loop proportional controller provides damping for slower visually mediated feedback is consistent with tethered-flight measurements, free-flight observations and engineering design principles.
authors.affiliation: California Institute of Technology, Mail Code 138-78, Pasadena, CA 91125, USA. elzingam@caltech.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Elzinga
authors.forename: William B
authors.initials: WB
authors.lastname: Dickson
authors.forename: Michael H
authors.initials: MH
authors.lastname: Dickinson
mesh_terms: D000818:Animals; D004330:Drosophila; D005426:Flight, Animal / Q000502:physiology*; D008954:Models, Biological; D012371:Robotics