A simplified fractional-order fuzzy logic controller with dynamic parameters for an unmanned underwater vehicle

The performance of a fuzzy logic controller (FLC) largely depends on its inference rules and control inputs. In this paper, fractional calculus is introduced into the fuzzy control inference rules. It can accumulate overall information within a certain range of a function, which is helpful for the system to resist external disturbances. Firstly, a control scheme of a simplified fractional-order fuzzy logic controller (FD-SIFLC) with dynamic parameters is proposed for the controller design of an unmanned underwater vehicle (UUV). The presented control method employs a single-input FLC with fractional calculus, and the scale factor changes with the relative error magnitude. The controlled system maintains the accuracy of its depth control while enabling other variables to exhibit better transient and steady-state performance. By using Matlab/Simulink (R) to conduct simulation experiments, the control performance of FD-SIFLC and SIFLC for the depth control of UUV is compared. During the simulation, the controlled system is disturbed by ocean waves. The simulation results show that, compared with SIFLC, FD-SIFLC can make the response curve of each variable smoother. Moreover, the proposed control method can improve the working efficiency and service life of an UUV control system.