Design of a Fractional Order Sliding Mode Controller for Depth Control of AUV

Abstract

In recent time, Autonomous underwater vehicles (AUVs) have been developed by using numerous high end technologies which are used to explore ocean. Since many years, for autonomous underwater vehicle's (AUV's) depth control system is a big challenge due to unknown nonlinearities & presence of various environmental changes. Fractional derivatives and integrals are widely used for control applications in which controller are defined through large set of fractional order differential equations. In this paper, a Fractional order system is first approximated into integer order system and then Fractional order PID (FO-PID) controller has been designed. As fuzzy logic controller & gives more flexibility towards nonlinear & dynamic systems, a fuzzy logic controller has been designed for same fractional order system. To improve transient response a fractional order sliding mode controller (FO-SMC) is also designed in Simulink. All the simulation results for FOPID, Fuzzy & FOSMC are compared in MATLAB Simulink which shows that FO-SMC gives better response compared to FO-PID & Fuzzy Controller.