Fixed-depth control based fuzzy PID in series of bionic underwater vehicle propelled by multiple undulatory fins

The paper introduces a new type underwater vehicle propelled by multiple undulatory fins, which propulsion control system is made up of four isomorphic bionic undulatory fins configured according to the crisscross orthogonal structure. The fixed-depth control of this vehicle is the mainly studied by the paper. Aiming at its structure and dynamics, a dual-loops control structure based the fuzzy PID in series is proposed to design the fixed-depth control system of this vehicle. The pitching controller designed according to fuzzy adaptive PID method acts as the inner-loop controller. As the outer-loop controller, the task decomposing module transforms the depth control objective to the pitching channel´s objective adopting the expert PID control strategy. The paper studies the structure, strategy and parameter design method of the fixed-depth control system in detail, builds a simulation model, and then primarily verified the validities of the control system structure and control strategy proposed by this paper through simulation.