Adaptive trajectory tracking control for VTOL UAVs with unknown time-varying mass using an extended I&I estimator

This article presents an adaptive control scheme for vertical takeoff and landing unmanned aerial vehicles subject to time-varying mass based on the immersion and invariance scheme in an extended form. For the varying mass parameter in the position control, a generalized I&I adaptive law is proposed with higher dimension to estimate the mass and its derivatives. The stability of the resulting estimation error manifold, which is in a cascade form, is guaranteed by introducing smooth saturation functions in the position control law. The attitude control is designed by employing a smooth function with positive integrable time-varying function to compensate unknown time-varying moment of inertia to achieve asymptotic attitude tracking. Simulation and experimental results verify the effectiveness of the proposed method under different cases, and the robustness to time-varying parameter is assured.