Development of Novel Flapping Mechanism Technologies for Insect-inspired Micro Air Vehicles

Abstract

Insect-inspired micro air vehicles (MAVs) have the capacity for higher lift forces and greater manoeuvrability at low flight speeds compared to conventional flight platforms, making them suitable for novel indoor flight applications.
This thesis presents development studies of an actuated flapping mechanism
for an insect-inspired MAV. An original theoretical understanding has shown that the kinematical constraint of a flapping mechanism fundamentally determines its complexity and performance. An under-constrained mechanism is optimal but almost always requires a linear input. A power optimisation study has demonstrated that the only technologically mature actuation devices with viable power densities for flight are rotary. Consequently, previous airborne flapping MAVs utilised constrained rotary-input mechanisms which require conventional control surfaces that significantly reduce flight manoeuvrability.
A novel flapping mechanism, called the parallel crank-rocker (PCR), has been
developed. Unlike existing designs, the PCR is a partially-constrained rotary-input
mechanism with a dynamically adjustable wing angle of attack, hence offering
improved flight manoeuvrability. High-speed film analysis of a PCR prototype
confirmed that it replicates the wing kinematics and principal lift-enhancing unsteady aerodynamic mechanism (a bound leading edge vortex) of insect flight. A lift force of 6.4 g was measured at a wingbeat frequency of 13.2 Hz, which suggests a target of 20 Hz for flight.
Prototype “artificial muscle” linear actuators have been developed to drive an
optimal under-constrained flapping mechanism, utilising embryonic dielectric
elastomer technology. A single film demonstrator produced a maximum volume-specific energy density 4.5 times greater than muscle. Prototype actuators, optimised for flapping MAVs, were fabricated generating a comparable actuation strain to muscle (0.37).
This thesis has shown that controllable insect-inspired MAVs are feasible, but
only through the novel implementation of existing technologies, in the case of the
parallel crank-rocker mechanism, or the advancement of novel or embryonic
technologies, in the case of the dielectric elastomer bender actuator.

Date of Award	13 Nov 2008
Original language	English
Awarding Institution	University of Bristol
Supervisor	Stuart C Burgess (Supervisor)