Modeling and Improvement for String-Based Drive Mechanism in Insect-like Flapping Wing Micro Air Vehicle

Abstract

Most of the driving mechanisms used in micro flapping wing vehicles are gear and linkage transmission mechanisms, which convert the unidirectional rotation of the motor into the reciprocating flapping of the driving mechanism. However, gear and linkage transmission mechanisms occupy a larger space and weight with certain energy losses. This article introduces a drive mechanism that is different from gear and linkage mechanisms, namely the string-based mechanism. In this study, the working principle and various parameters in string-based mechanisms are analyzed, and the flapping trajectory and amplitude of the mechanism is simulated. Following that, this article proposes an improved method of the cam mechanism, designs the trajectory of a cam mechanism, and a physical design is carried out with a driving mechanism width of 22 mm. Subsequently, the experiments are conducted to compare the flapping trajectory of the actual mechanism with the simulation trajectory, thereby verifying the simulation accuracy. The results prove that, in a string-based mechanism, the ratio of the radius of the pulley to the installation radius of the double-layer bearings has a direct impact on the flapping amplitude, and optimizing the design of cam mechanisms can effectively reduce the tensile and relaxation phenomena in string-based mechanisms. The above conclusion was verified in physical experiments, where the modified cam mechanism effectively reduced the stuck phenomenon in the string-based mechanism.

Aerodynamic Analysis of Hovering Flapping Wing Using Multi-Plane Method and Quasi-Steady Blade Element Theory

“…Figure 10 shows the schematic diagram of the wing shape in the body coordinate system after simulation using the multi-plane method. The three curves in Figure 10 represent the motion trajectories P 1−b , P 2−b , P 3−b in the body coordinate system, where ψ = −ψ max cos(2π f t) represents trajectory of the leading edge spar, which is driven by a string-based mechanism and has been found in previous studies to have a trajectory similar to a standard sine wave [4] (shown in Figure 11). For simplicity, it is directly represented here as a sine wave.…”

“…The parameters of the captured footage are listed in Table 2. The structure used to drive the wings is based on the previously designed string-based mechanism [4], which has the advantage of producing wing flapping angles similar to a standard sine wave and lower flapping angular velocities at the ends of the flapping stroke. The processed results of the data captured at 28.7 Hz are shown in Figure 23.…”

“…Flapping-wing micro air vehicles, especially flapping-wing drones capable of hovering, have been a focus of research for scientists and researchers as part of the micro-UAV community. Unlike conventional quadcopter drones and microhelicopters, the means by which flapping-wing air vehicles achieve hovering is not through unidirectional rotating blades but rather, similar to hummingbirds and certain insects in nature, by generating aerodynamic forces capable of counteracting gravity through the reciprocating flapping of wings [1][2][3][4].…”