Attitude Control of the Hydrobatic Intervention AUV Cuttlefish using Incremental Nonlinear Dynamic Inversion

In this paper, we present an attitude control scheme for an autonomous underwater vehicle (AUV), which is based on incremental nonlinear dynamic inversion (INDI). Conventional model-based controllers depend on an exact model of the controlled system, which is difficult to find, especially for marine vehicles subject to highly nonlinear hydrodynamic effects. INDI trades off model accuracy with sensor accuracy by incorporating acceleration feedback and actuator output feedback to linearize a nonlinear system incrementally. Existing research primarily focuses on studying INDI on unmanned aerial vehicles. However, there is barely any research on controlling marine vehicles using INDI. The control task we are performing is a 90 degrees pitch-up maneuver, where the dual-arm intervention AUV Cuttlefish transitions from a horizontal traveling pose to a vertical intervention pose. We compare INDI to a classical model-based control scheme in the maritime test basin at DFKI RIC, Germany, and we find that INDI keeps the AUV much more steady both in the transitioning phase as well as in the station keeping phase.