Study And Design Of The Large Scale Ship Drum Water Level Control System

The research object of this paper is the drum water level of the large scale ship. The main function of drum is transferring the heat from one form to another form, producing steam, forcing the turbine to run. Water level has a direct effect on steam and the safty of boiler. Therefore it is important and necessary for us to control water level of boiler and it is valuable to have study on water level control.The research question of this paper is how to control the drum water level in order to implement the best flexibility. During the sea war, it's necessary to tune the rudder accidently so as to regulate ship positon and avoid the collision sometimes. Because of the accidental power output which results in accidental changes of the drum water level and the response overshooting and the transient time, it's necessary to have study on the control of the water level in order to heignten the flexibility.The research approach of this paper is, on the basis of the water level dynamics, that a control scheme is offered. There are two important factors that steam current and feedwater current, which greatly influence the water level. By means that the influence of feedwater current on the water level follows the influence of steam current on the water level such that the water level deviation is eliminated, this paper presents a new control system scheme that the input is steam current, the feedback signal is supplying water current. Besides that, a subsystem of the servomechanism is designed and PID is executed.The control stratey in this paper is divided into two sections. In order to implement that the influence of feedwater current on the water level follows the influence of steam current on the water level, this paper makes some transform firstly and deduces the control rules. Secondly, this paper adopts PI, input feedback control, smith control and CMAC to manipulate the water level.The research tool of this paper is Matlab. The MATLAB is one of the most efficient sotware in the world. With the aspects of strong scientific arithmetic and visualization, especially 30 kinds of toolboxes used in different fields, it gives great help to design and analize a contro system.The research result is that, adopting the above control scheme, the step response is very good, which is gotten from the comparisions between the simulation curves of this paper and the references. At the same time, According to the analysis of Bode and Nyquist, the water level control system is stable; the limitation analysis proves that the simulation curve is right. At the same time, we find that the response time of the above sheme is too long. At last, this paper gives some advices.