Analysis and actuation design of a novel at-scale 3-DOF biomimetic flapping-wing mechanism inspired by flying insects.

Insects' flight is imbued with endless mysteries, offering valuable inspiration to the flapping-wing robots. Particularly, the multi-mode wingbeat motion such as flapping, sweeping and twisting in coordination presents advantages in promoting unsteady aerodynamics and enhancing lift force. To achieve the flapping-twisting-sweeping motion capability, this paper proposes an at-scale three-degree-of-freedom (3-DOF) mechanism driven by three piezoelectric actuators, which consists of three four-bar mechanisms and a parallel spherical mechanism. Compliant hinges are utilized as rotating joints for power transmission. The DOF and the kinematics analysis are performed. The aerodynamic model of the wing and the mechanical model of the compliant hinges are considered to investigate the required driving force response of the mechanism with wing loads. By employing nonlinear programming techniques, the geometric parameters of three piezoelectric actuators are reverse-designed to match the dynamic response of the mechanism in two flapping conditions. The significance of this work lies in proposing a novel concept of an at-scale multi-DOF wingbeat mechanism, demonstrating the feasibility of this mechanism to mimic the flexible and multi-mode wingbeat movement of insects, and providing an initial mechanism-drive solution.