Abstract: “This paper presents a nonlinear PID (NPID) controller which controls the glycol temperature of a regasification system for LNG-fuelled engines. The NPID controller has a parallel structure of linear PD action and nonlinear I action. A nonlinear function is employed to scale the error as input of the integral and implemented as a Takagi- Sugeno (T-S) fuzzy model. The controller parameters are optimally tuned by assuming that it is operated in both warming-up and running modes, and the parameters are switched according to the operation mode. Furthermore, the stability problem of the overall system is verified based on the circle criterion. A set of simulation works is carried out to validate the efficiency of the proposed controller.”

Keywords: NPID controller, regasification system, T-S fuzzy model, circle criterion