Decomposition of 3D Joint Angle by Kinematic Modeling of Free Flight Pigeon Forelimb

Birds utilize complex coupled motions in their forelimbs to maintain exceptional flight performance. Understanding these dynamics is essential for designing biomimetic unmanned aerial vehicles (UAVs). Typically, the forelimb skeleton of birds is modeled as a spatial six-bar linkage mechanism through the analysis of physical specimens. However, the detailed description of skeletal transformations in birds during free flight remains uncharted. To address this gap, we propose an open-chain kinematic model to simulate the skeletal motion variations of pigeons (Columba livia) in free flight. Kinematic data of pigeon wings were collected during free flight, and the skeletal model was fitted to the collected data using global optimization. This allowed us to derive the joint motion angles of the skeleton during the take-off, leveling flight, and landing phases. This study elucidates the mechanisms of bird wing deformation, providing valuable insights and guidance for developing bio-inspired flying robots.