Research And Implementation Of Dilution Hydraulic Headbox Ontology Control System

Headbox is one of the key components in a paper machine, which is animportant hub that is connected to “pulp flow delivery” and “paper forming”, socalled the "heart" of the paper machine. With the continuous improvement ofpaper-making technology, as well as the requirements for paper quality becomehigher, headbox is developed to air-cushioned type, semi-hydraulic type,hydraulic type, dilution hydraulic type from open type. While the research on thecontrol of dilution hydraulic headbox is only at the stage of the imitation andexploration at home. Therefore, it’s necessary to sum up a complete set of thecontrol scheme.This paper is supported by SME technology innovation fund (No:10C26216103241) of Xi’an Science&Technology Plan Project, named “Qualitycontrol system of BQCS-type paperboard production lin”. The structure andmechanism of dilution headbox hydraulic have been analyzed in this paper, theadvanced control scheme for this headbox has been proposed and implementedby S7-300PLC.The main work and contributions:(1) Propose of control scheme of dilution hydraulic headboxThe structure of dilution hydraulic headbox is introduced, and thetechnology such as distributor, diluted water regulation, rectifier and gunitingprocess is summarized. On the basis of analyzing interference factors of dilutionhydraulic headbox operation, a complete set of control scheme is proposed inthis paper: pulse attenuation is used to eliminate the fluctuations of pulsepressure, temperature system is used to stabilize temperature; frequencyconversion is used to control pressure, in order to control the quality in MD;diluted water adjustment technology is employed to control the CD quantity, andzero differential pressure control is adopted to ensure the uniformity of CDdistribution; In addition, the angle and guniting spot will be changed directly bylip position control. (2) Research of control algorithmThe main theoretical basis of this paper contains automatic control theory,computer control theory, IMC theory, neural network control theory and so on.IMC has many characteristic features, such as simple structure, easy design, lessadjustable parameters on line and the clear adjustment policy, it can be used toadjusted the dynamic quality and robustness of the system more clearly.Especially, its control effect is better in large time-delay system. The neuralnetwork has a strong ability of non-linear fitting and self-learning. Total pressurecontrol is the most important and most valuable control in the dilution hydraulicheadbox control system. Conventional control strategies is used other controls,but NN-IMC-PID control algorithm is used in the total pressure control syetem.Total pressure control is simulated by using a lot of different control algorithmsin MATLAB, the simulation result shows the effectiveness of the algorithm.(3) Implementation of control system based on the S7-300PLCAccording to control features of the dilution hydraulic headbox, this paperpresents a complete set of control scheme is proposed in this paper. Firstly, thework is to select the hardware of control system, instrumentation, and theactuator. Secondly according to the needs of process and project implementation,the Step7is chosen as the programming soft for the PLC program, and theWINCC is chosen as compile software of upper computer. At last, a completeDCS system has been designed when hardware and software of the system areprovided, and the control system is implemented on S7-300PLC platform.