Attitude and Altitude Control of Unmanned Aerial-Underwater Vehicle Based on Incremental Nonlinear Dynamic Inversion

A vehicle able to navigate both in the air and underwater is referred to an unmanned aerial-underwater vehicle (UAUV). Aiming at the attitude and altitude control of UAUVs, an incremental dynamic inverse control (INDI) method with second-order low-pass filters is proposed. Based on the underwater motion model of an UAUV and the incremental attitude control model, the relationship between thrust increment and angular acceleration increment is obtained through Taylor series expansion and angular acceleration feedback. Subsequently, attitude and altitude controllers based on nonlinear dynamic inversion (NDI) and INDI are designed and their robustness is analyzed. By introducing second-order low-pass filters at the part of control and feedback, the accuracy of the angular acceleration estimation is improved and the time synchronization of the control system is ensured. Simulation results demonstrated that when introducing external disturbances and uncertainties, the INDI control with second-order low-pass filters proposed in this article can track the reference signal faster and more accurately than the NDI control.