Depth Control of a 1 DOF Underwater System Using a Model-Free High Order Sliding Mode Control

The underwater vehicle control has two problems to deal with; parametric uncertainty and unknown disturbance. Sliding Mode Control (SMC) effectively addresses these issues and is therefore a viable choice for controlling underwater vehicles. On the other hand, this method is known to be susceptible to chatter, which is a high frequency signal induced by the switching control. In this paper a new control methodology called Model-free High Order Sliding Modes Control (HOSMC) is introduced. HOSMC principal characteristic is that it keeps the main advantages of the standard SMC, removing the chattering effects, this advantage is achieved without model knowledge. Real time experiments in a 1 DOF (Degree Of Freedom) underwater system are conducted to show control effectiveness. Finally, a comparative study regarding PID control and conventional SMC is given.