A model-free backstepping with integral sliding mode control for underactuated ROVs

This paper addresses the trajectory tracking problem for an underactuated underwater robot, or remote operated vehicle-ROV. The main contribution is a controller that enforces robust tracking without any explicit dependency of the dynamic model by combining Backstepping with second order (integral) sliding modes (SOSM); this establish the nontrivial extension of SOSM to underactuated systems or backstepping without model dependency. This is achieved by designed regressor-free SOSM as the the auxiliary input control at each iteration of the backstepping procedure. Integral sliding modes are enforced for all time and for any initial condition. Performance of the proposed tracking controller is verified using numerical simulations, implemented in a full nonlinear noninertial underactuated ROV model.