Depth control of ROV in nuclear power plant based on fuzzy PID and dynamics compensation

Depth control is very important for underwater robot in nuclear power plant, especially when the robot needs to perform special tasks at specific depths under the water. Aiming to realize the depth control for the nuclear environment, the paper proposes a depth control strategy combining fuzzy PID with dynamics compensation based on the fact that the water in the reactor pool is very calm. Firstly, we conducted the hydrodynamics analysis of the developed remotly operated vehilcle (ROV) using ANSYS FLUENT software to get the relationship between moving velocity and water resistance in heave direction. Then, field experiments were conducted to compensate the dynamics errors using least square method according to the real-time depth values collected by depth gauge. After that, the fuzzy PID controller was designed to tune the PID parameters using fuzzy rules based on the compensated relationship between outputs of propellers and depth values. Experiments were conducted with results showing that accuracy of the depth control strategy combing fuzzy PID with dynamics compensation can reach within 3 cm, which can fully meet the requirements of practical application in the reactor pool. The highlight of the paper is that we combine the fuzzy PID algorithm with compensated dynamics equation, which is very suitable to realize the depth control for ROV in nuclear power plant.