Design of Robust Proportional-(Proportional-Derivative) Controller for an Autonomous Underwater Vehicle Using Quantitative Feedback Theory in the Diving Plane

In this paper, a robust proportional-(proportional-derivative) controller is designed for an autonomous underwater vehicle using quantitative feedback theory in the presence of plant uncertainty and disturbances in diving plane motion. The controller is designed in cascade feedback in the presence of parametric uncertainty, ocean currents, sea waves, and fin error. The proportional-derivative controller controls the angle of the vehicle pitch and an outer proportional loop controller will control the vehicle depth. Since using classical methods to adjust proportional-derivative for the inner loop and proportional for the outer loop, despite the plant uncertainty and the presence of disturbances, is complex and time-consuming. therefore, the quantitative feedback theory technique, as a robust controller method, is used in this research. System stability is considered in the design process. All design steps are based on linearized equations of motion but the performance of the proportional-(proportional-derivative) controller designed by the robust quantitative feedback theory method is simulated numerically for nonlinear dynamic equations of motion. The simulation results show that the designed proportional-(proportional-derivative) controller using quantitative feedback theory offers robust stability, disturbance rejection, and proper reference tracking over a range of autonomous underwater vehicle parametric uncertainties.