SWATH ship motion simulation based on a self-tuning fuzzy control

A time simulation technique using the self-tuning fuzzy control algorithm is applied to control stabilizing fins to reduce the pitch motion of the SWATH ship in longitudinal regular waves. A back-propagation-based fuzzy controller using the gradient descent method is presented and incorporated with the previous mathematical model to simulate the SWATH ship motion. The effects of surge force and viscous force are included. Basically the fuzzy controller consists of five parts: (1) fuzzifier, (2) rule base, (3) database, (4) inference engine, and (5) defuzzifier. The calculations of the corresponding hydrodynamic coefficients at each time step follow the simplified technique developed before, which needs only one set of initial input data of the ship configuration. After comparing with the results using the static fuzzy controller, we find that the self-tuning fuzzy controller appears to be more practical and more efficient for operating stabilizing fins while the ship speed is high. Therefore, the fuzzy control with self-tuning algorithm developed here may offer a more efficient way to control fins of the SWATH ship and can also be regarded as a good basis for future studies in irregular waves.