Abstract: During avian flight, the wing flapping motion exhibits pronounced time-asymmetry. However, the time-asymmetric flapping data of avian species are extremely scarce, and there are little well-established theories and methodologies. Inspired by this, a study on time-asymmetric flapping strategies and control systems for morphing flight robot was conducted, with the aim of exploring the practical implementation of this mechanism in such vehicles and evaluating its effects on aerodynamic performance and energy efficiency. Through the analysis of flight videos of the Milvus migrans lineatus, time-asymmetry wing joint rotations were extracted, thereby the Tang model was proposed. Specifically, the Tang model consists of a three-rods model and avian flapping formula. In this model, the wing bones of the Milvus migrans lineatus are simplified as three hinged links. By combining a cosine-based flapping angle formula with modulation polynomials, the wing joints rotational motion of the Milvus migrans lineatus is reconstructed in uniform form. Meanwhile, the Tang model serves as a dedicated framework for wing–tail coordinated deformation and provides essential theoretical support. Simulation analyses were conducted to evaluate morphing flight robots’ performance across downstroke time ratios k and flapping frequencies to optimize the lift-to-drag ratio. Subsequently, a bionic flapping mechanism and a time-asymmetric flapping control system based on Field-Oriented Control (FOC) were designed, enabling precise adjustment of the flapping speed and the duration of the downstroke. Experimental results show that under different downstroke time ratios, the system exhibits rapid dynamic response and high steady-state accuracy. Under the condition of a downstroke time ratio k= 0.4, its energy efficiency improves by 4.8%, and the motion posture of the bionic wing closely resembles that of the Milvus migrans lineatus, demonstrating superior bionic performance. The proposed model and findings are expected to enhance aerodynamic efficiency and reduce energy consumption in morphing flight robots, providing practical guidance for future morphing flight robots’ design.

Key words: Flapping wing aircraft')">Flapping wing aircraft, Asymmetric flapping, Field-oriented control, Tang model, Aerodynamic efficiency optimization