The sweep-back effect of a flexible flapping wing is investigated through fluid-structure interaction analysis. The
aeroelastic analysis is carried out by using an efficient fluid-structure interaction analysis tool, which is based on the
modified strip theory and the flexible multibody dynamics. To investigate the sweep-back effect, the aeroelastic analysis
is performed on various sweep-back wing models defined by sweep-chord ratio and sweep-span ratio, and then the
sweep-back effect on the aerodynamic performance is discussed. The aeroelastic results of the sweep-back wing analysis
clearly confirm that the sweep-back angle can help a flexible flapping wing to generate greater twisting motion, resulting
in the aerodynamic improvement of thrust and input power for all flapping-axis angle regimes. The propulsive efficiency
can also be increased by the sweep-back effect. The sweep angle of a flapping wing should be considered as an
important design feature for artificial flexible flapping wings.
Bio-inspired design to make artificial flappers fly does not just imitate biological systems as closely as possible, but also
transferring the flappers' own functionalities to engineering solutions. This paper summarizes some key technical issues
and the states-of-art of bio-inspired design of flapping UAVs with an introduction to authors' recent research results in
In the preliminary design phase of the bio-inspired flapping-wing MAV (micro air vehicle), it is necessary to predict the
aerodynamic forces around the flapping-wing under flapping-wing motion at cruising flight. In this study, the efficient
quasi-steady flapping-wing aerodynamic model for MAV application is explained and it is experimentally verified. The
flapping-wing motion is decoupled to the plunging and pitching motion, and the plunging-pitching motion generator with
load cell assembly is developed. The compensation of inertial forces from the measured lift and thrust is studied to
measure the pure aerodynamic loads on the flapping-wing. Advanced ratio is introduced to evaluate the unsteadiness of
the flow and to make an application range of flapping-wing aerodynamic model.
The present study proposed a coupling method for the fluid-structural interaction analysis of a flexible flapping wing. An
efficient numerical aerodynamic model was suggested, which was based on the modified strip theory and further
improved to take into account a high relative angle of attack and dynamic stall effects induced by pitching and plunging
motions. The aerodynamic model was verified with experimental data of rigid wings. A reduced structural model of a
rectangular flapping wing was also established by using flexible multibody dynamics and a modal approach technique,
so as to consider large flapping motions and local elastic deformations. Then, the aeroelastic analysis method was
developed by coupling these aerodynamic and structural modules. To measure the aerodynamic forces of the rectangular
flapping wing, static and dynamic tests were performed in a low speed wind-tunnel for various flapping pitch angles,
flapping frequencies and the airspeeds. Finally, the aerodynamic forces predicted by the aeroelastic analysis method
showed good agreement with the experimental data of the rectangular flapping wing.
This paper investigates the stabilization and control for flapping-wing flight of a simple flapping-wing vehicle. The
aerodynamic forces and moments of flapping-wing flight are estimated by modified strip theory. From the resultant
forces of the aerodynamics the flight dynamic analyses have been performed. For simulating cruising flight, one of the
proper conditions has been chosen through parametric study and is assigned to the dynamics. As a result the trajectory
and the body orientation of the vehicle are obtained which shows phugoid and short period motion in trim condition.
With an adequate tail-wing pitch control, the vehicle simulated level-up movement from a trim condition to another.
The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending
actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of
flapping-wing motion. Thus, IPMC can be an adequate smart material for the generation of the flapping-wing motions.
In this research, a flapping actuator module operated at the resonant frequency is developed using an IPMC actuator.
First, IPMC actuators are fabricated to investigate the mechanical characteristics of IPMC as an actuator. The
performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained
according to the input voltage and IPMC dimensions. Second, the empirical performance model and the equivalent
stiffness model of the IPMC actuator are established. Third, flapping actuator modules using the first resonance
frequency are developed, and their flapping frequency and stroke characteristics are investigated. Fourth, adequate
flapping models for a flapping actuator module are selected, and dimensional data such as wing area and wing mass are
obtained. Finally, the flapping actuator module is designed and manufactured to adjust the flapping models and its
performance is tested. Experimental results demonstrate the potential IPMC has for use as a flapping actuator.
In the present study, we have developed a smart flapping wing with a MFC (macro-fiber composites) actuator. To mimic the flying mechanisms of nature's flyers such as birds or insects, the aerodynamic characteristics related to the birds and ornithopters are investigated. To measure the aerodynamic forces of flapping devices, a test stand consisting of two loadcells is manufactured, and the dynamic tests are performed for an onithopter. The smart flapping wing is designed and manufactured using composite materials and MFC actuators. The camber of the wing can be changed by using the surface actuators to enhance the aerodynamic performance of the wing. Finally, aerodynamic tests are performed in a subsonic wind tunnel to evaluate the dynamic characteristics of the smart flapping wing. Experimental results show that unsteady flow effects are increased with low velocity in high flapping frequency regions, and that the deformation of the wing surface generated by the MFC is enough to control the lift and thrust. The lift generated by the smart flapping wing can be increased by 20% when the MFC is actuated.