Active Pitch Control of an Oscillating Foil with Biologically-Inspired Boundary Layer Feedback
Year: 2010
Type: dissertation
Abstract: We present a high-fidelity numerical study of atwo-dimensional °apping airfoil, ad- dressing the hypothesis that
boundary layer feedback control can enable improved in
flapping light. To this end, we model a novel biologically-inspired
feedback controller which adjusts wing motion in response to the
flow-induced bending load experienced by sensory hairs mounted on
the wing. Such hairs have been observed on bats, and biological
studies suggest that an associated feedback controller may play an
important role in enabling bats' well-known mastery of light. The
coupled °uid and structural equations of our model are solved
numerically by a Discontinuous Galerkin finite element method,
combined with an Arbitrary Lagrangian-Eulerian (ALE) formulation to
account for airfoil motion. Feedback control is deed by a simple
proportional-derivative (PD) control law relating hair sensor
feedback to an applied torque at the pivot point of the wing. We
also include a torsional spring at the pivot point to model passive
aeroelasticity, following prior work by Israeli [5]. Our results
show that hair sensors are well-suited for detecting flow
separation, and sensors placed near the leading edge enable better
light than sensors placed near the trailing edge. We
compute a performance envelope for a purely passive flapping
airfoil, and demonstrate that our active feedback controller
enables improvements of up to 5% in propulsive efficiency. We also
present gust alleviation experiments, where we find that an optimal
PD controller reduces lift deviation by 33% compared to a
spring-only airfoil. Mechanisms for these improvements
are discussed. Our findings suggest that boundary layer feedback
control may plausibly contribute to the outstanding °ight abilities
of bats, and may also provide valuable clues for designing robust
and maneuverable Micro Air Vehicles (MAVs).
Author: Hemant Chaurasia
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2284554136