Active Disturbance Rejection Control On Ship Dynamic Positioning System

This paper focused on simulation modeling and Active Disturbance Rejection Control (ADRC) of ship Dynamic Position System (DPS), the related four research tasks are listed as follows:1. Simulation model of DPS was established according to the data of a real ship, including system dynamic model, real-time thrust allocation logic, thrust model and noise model of sensors, which helped transform controller outputs to engineering controlled variables, pitch angle and rudder angle, online. Simulation tests of the established system were also conducted.2. As the key point of ADRC is disturbance estimation, all kinds of disturbance being exerted on the ship were analyzed firstly and classified into low-frequency disturbance and high-frequency disturbance. To counteract the low-frequency part, two different disturbance rejection control methods were proposed according to different conditions-(a) when the speed is measurable and (b) when the speed is immeasurable; to cancel the high-frequency part, two kinds of filters of Active Disturbance Rejection control were introduced. Simulation tests of the above solutions were also carried out. Thereafter, discussions on the influential factors of the ADRC’s performance were carried out, which provided a solid foundation for the following study.3. An important way to improve ADRC’s performance is to enhance the disturbance estimation accuracy of Extended State Observer (ESO), so two methods,1) Double-ESO based disturbance estimation model and2) Disturbance estimation model based on higher order information of disturbance, were proposed separately to solve two engineering problems in DPS,1) The achievable bandwidth of ESO is relatively low and2) The sampling interval is relatively large. Simulation tests on the problem of thruster-assisted position mooring control verified the proposed methods.4. Concerning the delay produced by the thruster system of the DPS, an ADR controller based on a model-free predictor was proposed, the third loop of the DPS was taken as an example for simulation test. The impact of the coupling influences with other loops was covered in the simulation tests which helped verify the proposed method for DPS with delay.