The Effect of the Phase Angle between the Forewing and Hindwing on the Aerodynamic Performance of a Dragonfly-Type Ornithopter

Abstract

Dragonflies achieve agile maneuverability by flapping four wings independently. Different phase angles between the flapping forewing and hindwing have been observed during various flight modes. The aerodynamic performance depends on phase angle control, as exemplified by an artificial flying ornithopter. Here, we present a dragonfly-like ornithopter whose phase angle was designed to vary according to the phase lag between the slider-cranks of the forewing and hindwing. Two microelectromechanical systems (MEMS) differential pressure sensors were attached to the center of both forewing and hindwing to evaluate the aerodynamic performance during flapping motions when the phase angle was changed. By varying the phase angle in both the tethered condition and free-flight, the performance of the forewing remained approximately constant, whereas that of the hindwing exhibited obvious variations; the maximum average value was two-fold higher than the minimum. The experimental results suggest that simple phase angle changes enable a flying ornithopter to control flight force balance without complex changes in the wing kinematics.

Experimental Study of the Aerodynamic Interaction between the Forewing and Hindwing of a Beetle-Type Ornithopter

“…We can configure the forewing to a fixed or flapping mode by changing the position of the pin attachment on the crank mechanism. In addition, the feathering motion of the hindwings is caused by passive deformation which is similar to that of beetles and similar to that reported for previous ornithopters [28][29][30]. On the other hand, no feathering motion occurs in the forewings, which is similar to beetles.…”

“…The sensors were also attached to the forewing and hindwing of a dragonfly-type ornithopter; the findings revealed that the differential pressure of the hindwing changed according to the phase lag between the forewings and the hindwings [30]. As indicated by previous research, the MEMS differential pressure sensor has helped to quantitatively evaluate the local aerodynamic force generated on flapping wings [27][28][29][30].…”

“…To evaluate the aerodynamic forces on the wing during flapping flight, we developed a measurement method using micro-electro-mechanical systems (MEMS) differential pressure sensors that can be placed on the wing surfaces of insects or insect-modeled ornithopters [26][27][28][29][30]. By attaching the MEMS sensor to a butterfly wing, we confirmed that a differential pressure of 10 Pa occurred at the center of the forewing during take-off [27].…”

“…Using the experimental results, we evaluated the aerodynamic characteristics of beetle-type flapping flight. Figure 1 shows the design and images of the developed beetle-type ornithopter, which is based on our previous ornithopters [28][29][30] and driven by an electric motor with an externally located power supply. Thus, the ornithopter was composed of a long and thin body (more similar to a butterfly than a beetle).…”

“…The hindwing is composed of the same paper and involves frames constructed of carbon rods with a diameter of 0.5 mm and plastic corner materials with dimensions of 0.75 mm × 0.75 mm. The flapping motions of both the forewing and the hindwing are driven by converting the rotational motion of the motor using a slider-crank mechanism, as shown in Figure 1b,c [30]. The stroke plane angles of both the fore-and hindwings are 90 • , which indicates that the stroke plane is perpendicular to the body axis.…”