Adaptive Control Barrier Functions for Near-Structure ROV Operations

This paper introduces a novel control design fo- cused on enhancing the operational safety and efficiency of inspection, maintenance, and repair (IMR) operations con- ducted by autonomous remotely operated vehicles. Specifically, we propose using a safeguarding controller based on an adaptive control barrier function (CBF) incorporating safety properties previously identified in the literature. This approach permits temporary safe set violations, using an integrative penalty term to strengthen safety measures when necessary. A nomi- nal nonlinear controller inside the safety bounds is proposed to ensure good reference tracking. The proposed controller is demonstrated in a simulation case study where an ROV (remotely operated vehicle) is set to clean an offshore monopile. The simulation includes unknown time-varying and step-like disturbances caused by water waves, the tether, ocean currents, and the high-pressure water jet. The proposed control law can react to the disturbances, and the ROV never leaves the defined safe set.