Fractional Sliding Mode Control of Underwater ROVs Subject to Non-differentiable Disturbances

Some hydrodynamic phenomena of an underwater Remotely Operated Vehicle (ROV), such as turbulence, cavitation, and multi-phase fluidic regimes, are associated to continuous but nowhere differentiable functions. These disturbances stand as complex forces potentially influencing the ROVs during typical navigation tasks. In this paper; the tracking control of a ROV subject to rionsmooth Holder disturbances is proposed based on a fractional order robust controller that ensures exponential tracking. Notably, the controller gives rise to a closed-loop system with the following characteristics: a) continuous control signal that alleviates chattering effects; b) the fractional sliding motion is substantiated on a proposed resetting memory principle; c) the control is robust to model uncertainties; and d) exact rejection of Holder disturbances in finite-time. A representative simulation study reveals the feasibility of the proposed scheme.