Geometric-based prescribed performance control for unmanned aerial manipulator system under model uncertainties and external disturbances.

In this paper, a robust control strategy with a cascade structure is designed for the underactuated unmanned aerial manipulator (UAM) to perform favorable trajectory tracking, in the presence of model uncertainties and time-varying external disturbances (e.g. wind drag). In the position loop, a geometric distance is adopted as the criterion for the thrust design. Besides, both the model uncertainties and external disturbances are compensated by employing a robust term. In the attitude loop, the prescribed performance guarantees are enforced in the controller design to standardize transient performance on attitude errors. In particular, just relying on the necessary feedback states, an auxiliary system, the adaptive control technique, and the disturbance observer are respectively designed to estimate the model uncertainties and external disturbances. Through the Lyapunov stability theory analysis, the proposed approach based on a geometric distance can effectively track the desired trajectory. The results of the comparative simulations study demonstrate the effectiveness and advantages of the proposed approach.