Abstract
The fuzzy switched PID controller which combines fuzzy PD and conventional PI controller is proposed for ship track-keeping autopilot In this paper. By using rudder angle, the whole voyage is divided into two operating regimes which named transient operating regime and steady operating regime respectively. The fuzzy PD controller is employed in transient operating regime for increasing response, reducing overshoot and shorting transition time. And conventional PI controller is used to improve the stable accuracy in steady operating regime. The global controller is achieved by fuzzy blending of all local controllers. Routh stability criterion is utilized to obtain the stability condition of closed-loop system. The simulation results show the effectiveness of proposed method.
Highlights
Ship autopilot mainly used to keep the course at designed trajectory within minimum deviation
The fuzzy switched PID controller which combines fuzzy PD and conventional PI controller is proposed for ship track-keeping autopilot In this paper
Assuming heading be changed by 30 ̊ to right direction, the curve of track-keeping, course error and rudder angle changing have been shown in Figures 5 and 6 respectively, they illuminate that the proposed fuzzy switched PID controller has fast response, slight overshoot and high accuracy in whole voyage
Summary
Ship autopilot mainly used to keep the course at designed trajectory within minimum deviation. In terms of characteristics of nonlinear and underactuated of cargo ship, finding an effective autopilot control algorithm has been the significant topic in area of ship steering control. During straight-line voyage, the control requirement mainly focuses on stable accuracy, which are called tack-keeping. Autopilot operating in the mode of track-keeping process, so we called is as steady operating regime in this paper. The course-changing process is generally short-term and countable, so it can be called transient operating regime. The fuzzy switching PID control algorithm combines Takagi-Sugeno PD controller with general PI controller to improve the control performance in terms of fast response and high stable accuracy throughout the voyage. During track-keeping process, the so called TS-PD controller is employed to keep the stability accuracy, and when course-changing process, the general PD controller is used to improve the response speed. The fuzzy switched inference guarantees the smooth characteristic between adjacent controllers
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