System design and quasi-sliding mode control of an AUV for ocean research and monitoring

The VORAM (vehicle for ocean research and monitoring) autonomous underwater vehicle (AUV), is developed in KRISO (Korea Research Institute of Ships and Ocean engineering) for the observation and investigation of seabed. This paper describes the design and configuration of the AUV system and presents a discrete-time quasi-sliding mode controller with parameter uncertainties and long sampling interval. The proposed controller makes the system stable in the presence of system uncertainties and even external disturbances. Depth keeping control and contouring control are performed for a numerical model of the AUV with full nonlinear equations of motion to verify the effectiveness of the proposed control schemes when the vehicle has long sampling interval. The experimental results agree with the simulations. As sampling interval becomes large the effectiveness of the proposed control law is more prominent compared with the conventional sliding mode controller.