A fuzzy rule-based PID controller for dynamic positioning of vessels in variable environmental disturbances

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ORIGINAL ARTICLE

A fuzzy rule‑based PID controller for dynamic positioning of vessels in variable environmental disturbances Shengwen Xu1,2,3 · Xuefeng Wang1,2,3   · Jianmin Yang1,2,3 · Lei Wang1,2,3 Received: 29 April 2019 / Accepted: 2 November 2019 © The Japan Society of Naval Architects and Ocean Engineers (JASNAOE) 2019

Abstract Conventional dynamic positioning systems are based on PID controllers and an extended Kalman filter or a nonlinear state observer. However, it is nontrivial to tune the control parameters, and the station-keeping performance varies with environmental or loading conditions since the dynamics of the vessel are essentially nonlinear. To overcome these difficulties, a fuzzy rule-based PID controller is evaluated, which takes the estimated positioning error and low-frequency velocity as inputs, and outputs the time-varying PD control coefficients through fuzzy inference, while the integral control parameters are kept constant. The performance of the proposed controller is evaluated numerically through a time domain simulation of a dynamically positioned semi-submersible platform operating in variable environmental disturbances. Simulation results are compared with the conventional fixed gain PID controller, and the comparison results show that the proposed fuzzy PID controller can automatically tune the PD control coefficients according to the positioning accuracy and significantly improve the performance of the dynamic positioning system. Keywords  Fuzzy PID controller · Dynamic positioning system · Positioning accuracy · Variable environmental disturbances · Semi-submersible

1 Introduction The increasing demand for oil and gas in recent years has led to exploitation and exploration in harsher and deeper waters. To perform offshore operations in such fields, marine vessels are usually required to be positioned in a special area with high accuracy, which leads to the widespread use of dynamic positioning system (DPS). A dynamically positioned (DP) vessel is by the International Maritime Organization (IMO) and the certifying class societies (DNV, ABS, LR, etc.) defined as a vessel that maintains its position and heading (fixed location or pre-determined track) exclusively by means of active thrusters [1].

* Xuefeng Wang [email protected] 1



State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

2



Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration (CISSE), Shanghai 200240, China

3

School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China



As the most important part of the DPS, a significant amount of work has been carried out by experts around the design methodology of the control system. The earliest DP control system used the single-input single-out PID control algorithms in combination with low-pass or notch filter to control the horizontal modes of motion. Later in the 1970s, [2] proposed more advanced control methods based on multivariable optimal c