During the voyage of the ship, disturbances from the sea dynamics are frequently changing, and the ship's operation mode is also varied. Hence, it is necessary to have a good controller for steam/water loop, as the control task is becoming more challenging in large scale ships. In this paper, a robust proportional-integral-derivative (PID) autotuning method is presented and applied to the steam/water loop based on single sine tests for every sub-loop in the steam/water loop. The controller is obtained during which the user-defined robustness margins are guaranteed. Its performance is compared against other PID autotuners, and results indicate its superiority

De Keyser, Robain

Ionescu, Clara-Mihaela

Liu, Shen

Zhao, Shiquan

English

Liu, Sheng

Ghent University Academic Bibliography

A Robust PID Autotuning Methodfor Steam/Water Loop in Large Scale ShipsShiquan Zhao1,2, Robin De Keyser1, Sheng Liu2 and Clara M. Ionescu11Research group on Dynamical Systems and Control, Ghent University, Belgium2College of Automation, Harbin Engineering UniversityShiquan.Zhao@UGent.be1 IntroductionDuring the voyage of the ship, disturbance from the sea ischangeable and frequent, and the ship operation mode isalso changeable. So it is needed to have good controlle forsteam/water loop in large scale ships [1]. Due to the stronginteraction and complexity existing in the steam/water loopin large scale ships, there is few study about the control forwhole system, and most study is about the control for singlesub-loop in this system. In this paper, a robust proportional-integral-derivative (PID) autotuning method [2] is presentedand applied to the system. Based on single sine tests forevery sub-loop in the steam/water loop, the controller isobtained during which the user-defined robustness marginsguaranteed. Its performance is compared against to otherPID autotuners, and results show its superiority.2 System Description and MethodologyThe steam/water loop works as follows. Firstly, the feed wa-ter is supplied into the boiler after heated in the economizer.Secondly, due to the higher density of the feed water, it willflow into the mud drum. Then, after heated in risers underthe burning of the fuel, the feed water turn into saturatedmixture of water and steam. Thirdly, the steam is separatedfrom the mixture and used in steam turbine. Finally, the usedsteam will be condensed, deoxygenated and pumped to theboiler once again [3]. The main control problems existingin this system include the following aspects, i) drum waterlevel control; ii) condensate and deaerator water level con-trol loop; iii) deaerator and exhaust pipe pressure control.The purpose of KC autotuner is to move a point B on theNyquist curve of process P(jω) to another point A on theNyquist curve of the loop L(jω))=P(jω))C(jω)) through thePID controller indicated by C(jω)). Hence, the system canhave a good dynamic characteristic. The tuning procedure issummarized as follows. i) Select a frequency ϖ ; ii) Performsine tests at frequency on the steam/water sub-loops; iii) De-fine a forbidden region for robustness in the Nyquist planeaccording to the loop modulus margin; iv) For each point onthe region border, calculate PID controller; v) Find the pointwhere the loop L(jω) is tangent to the forbidden region; vi)The PID controller from step v) are final.3 Results and ConclusionsIn order to validate the performance of the proposedmethod, other PID autotuners such as A˚stro¨m-Ha¨gglund(AH), Phase Margin (PM) and Kaiser-Rajka (KR) aredesigned. According to the results shown in Figure 1, thesteam/water loop obtained an ideal performance in trackingof system commands, and the proposed autotuning methodobtains better results in all sub-loops.0 100 200 300 400 500Time[sec]1.21.31.41.51.61.71.8Drum water level(m)AHPMKRKC0 10 20 30 40 50Time[sec]0.1220.1240.1260.1280.130.1320.134Exhaust Manifold Pressure(MPa)AHPMKRKC0 20 40 60 80 100Time[sec]25262728293031Deaerator Pressure(KPa)AHPMKRKC0 50 100 150 200 250 300Time[sec]0.520.540.560.580.60.620.640.660.680.7Deaerator Water Level(m)AHPMKRKC0 50 100 150 200Time[sec]0.360.380.40.420.440.460.480.5Condenser Water Level(m)AHPMKRKCFigure 1: System outputs with different PID controllersReferences[1] S. Liu, S. Zhao, Y. Wang, “Smooth Sliding ModeControl and Its Application in Ship Boiler Drum WaterLevel,” Mathematical Problems in Engineering, 2016.[2] R. De Keyser, C.M. Ionescu, C.I. Muresan, “Compar-ative Evaluation of a Novel Principle for PID Autotuning,”In 11th Asian Control Conference (ASCC), 2017, pp. 1164-1169.[3] L. Drbal, K. Westra, P. Boston, “”Power plant engi-neering,”Springer Science & Business Media, 2012.Book of Abstracts 37th Benelux Meeting on Systems and Control84

A robust PID autotuning method for steam/water loop in large scale ships

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