Nonlinear Disturbance Observer-Based Robust Control for Flapping-Wing Aerial Manipulators

Abstract

Flapping-wing aerial manipulators (FW-AEROMs) hold considerable promise for delivering high efficiency and minimal mass in robotic applications. Nevertheless, their inherently nonlinear, time-varying dynamics render them particularly vulnerable to modeling errors and environmental perturbations, thereby compromising manipulation stability. Existing robust and adaptive control approaches are often too complex or computationally demanding for real-time onboard implementation on such platforms. To address these challenges, this article proposes a parallel nonlinear disturbance observer-based (NDOB) robust controller tailored for the altitude and longitudinal dynamics of an X-shaped flapping-wing micro aerial vehicles. The proposed approach augments a baseline proportional-integral-derivative (PID) controller through a modular disturbance compensation mechanism, enabling real-time estimation and rejection of lumped disturbances arising from wind disturbances, payload variations, and manipulation-induced perturbations, without requiring controller redesign. A stability analysis of the coupled controller–observer system is provided to ensure convergence of the disturbance estimation and robust closed-loop behavior. Experimental validation on a commercial Flapper Nimble+platform equipped with multiple manipulators demonstrates that the proposed controller significantly enhances trajectory-tracking accuracy and disturbance rejection compared to the baseline PID controller. The results confirm the effectiveness and practical implementability of the proposed NDOB framework, representing the first experimentally validated model-based robust control architecture for FW-AEROMs.