【作者】 王东林；

【导师】 俞国胜；

【作者基本信息】 北京林业大学 ， 机械设计及理论， 2008， 博士

【摘要】 中密度纤维板生产过程由备料、纤维分离、干燥、施胶施蜡、铺装、热压、裁边等工序组成,其中热压工序是中密度纤维板生产过程中关键工序之一。热压过程各工艺参数的控制对中密度纤维板的质量影响较大,准确地控制热压过程各工艺参数,根据当前热压周期中各主要参数智能地调节热压过程,是最终生产出合格的产品、提高产品质量、提高生产经济效益的一个重要措施。本文在深入探讨热压过程中板坯成型的内在机理的基础上,根据生产工艺要求,以智能控制算法为核心,利用可编程控制器构成了基于现场总线的分布式智能控制系统,对中密度纤维板的各个生产过程进行分别控制,集中监控,以提高生产效率和产品质量。主要研究了如下内容:1、着重研究了中密度纤维板热压成型过程中内部热量和水分传递的机理、被压过程中板坯的物理力学行为及其变迁过程的机理、剖面密度分布形成及其变迁的机理,在总结前人研究成果的基础上,通过理论分析,根据在实际生产线上取得的实验数据,建立了板坯内热量传递及其温度分布的数学模型、水分传递及其含水率分布的数学模型、受压板坯的物理力学行为变迁及其板坯本构关系(即受压板的应力应变规律)的数学模型、纤维板剖面密度分布(VDP)形成的数学模型。利用以上模型创造性地提出了准确计算热压时间的方法,并可以之预测产品的密度分布情况,为热压工艺的设计和进一步有效控制热压过程提供了理论依据。2、初次在中密度纤维板生产的热压过程中运用了模糊PID调节的智能控制手段,实现对热压压力的模糊PID调节,按照模糊规则给出其PID调节参数,并结合可编程控制器(PLC)实现对热压过程的优化控制。初步尝试了基于板材密度的闭环过程控制,突破了以往完全根据经验按照设定工艺曲线控制热压过程的工艺流程。3、尝试了使用先进的γ、β射线等检测技术实现对纤维板成板分层密度的实时在线检测;建立了基于PROFIBUS现场总线技术的分布式智能控制系统(DCS),采用现场总线技术通过一定的配置组态构成了控制网络,实现中密度纤维板生产线在生产控制上的离散化、网络化和智能化;采用PLC(可编程控制器)作为现场监控级,对生产过程涉及的各个工段及其控制参数进行基于智能控制算法的现场调节;根据输入输出点数的多少进行PLC的硬件组态并编写了PLC的热压控制程序;利用组态软件WINCC编写了上位机监控的人机界面,实时显示各工段的技术状况,实现工艺曲线的设定和显示。更多还原

【Abstract】 Medium-density Fiberboard’s production involves the processes of materials preparing, textile fiber separation, drying, gluing, waxing, forming, hot-pressing, side-cutting, there among, hot-pressing is one of the most crucial processes in the production and its parameters closely interrelate with the quality of medium-density fiberboard. Accurately controlling the course of the processes parameters and intelligent regulating, the hot-pressing procession according to the principal parameters in current cycle can be qualified to produce the final product, which is also an important economic measurement to improve product quality and increase productivity. Depended on the in-depth study of internal mechanism for semi-finished fiberboard forming in hot-pressing processes, and oriented by algorithm and intelligent cybernetics, this paper studies the Distributed Intellectual Controlled System based on fieldbus composed by Programmable Controller while the system improves the production efficiency and product quality through the processes respectively controlling and centralized monitoring. Main results and conclusions are as follows:1. The paper chiefly discusses the transfer mechanism of the interior heat and humidity, the physical behavior of the mat and mechanism of the transferring course during hot-pressing, and the density distribution and transformation of fiberboard along the thickness direction. Based on the researching achievements before and theoretical analysis, Guided by the theory and experimental data from producing line, the mathematic models are established for heat transfer and temperature distribution inside the board, for the humidity transfer and humidity content distribution of the board, for the physical behavior transformation and relationship between stress and of the stressed board, and for the formation of VDP of fiberboard.Through these models, the way to accurately calculate hot-pressing time was proposed, and the density distribution of the product can also be forecasted, which providing theoretical basis for the hot-pressing’s design and further control.2. Distributed Intellectual Controlled System of fuzzy PID regulation was designed and adopted in the process of medium-density fiberboard hot-pressing for the first time, which realized the fuzzy PID regulation for hot-pressure, provided the PID adjusting parameters according to the vague rules, and achieved the optimized controlling for hot-pressing associated with PLC. Another preliminary attempt, closed-loop process control which based on the density of fiberboard, becomes the breakthrough for substituting the former technique’s curves experienced-oriented processing circuit.3. Advanced ultrasonic test technology was preliminary tentatively used to accomplish the real-time testing for different layers of MDF. Based on PROFIBUS technology, a distributed intelligent control system was established to achieve a production process of Medium-density Fiberboard which provides discretization, network and intelligence of producing line for MDF in the term of producing line control. PLC was served as the control core in site-monitored level and used to real-timely adjust every process and controlling parameters of the production process, according to the intelligent control algorithm. The hardware was configurated for PLC and hot-pressing control program is developed according to the input and output counts. Human-machine interactive monitoring interface was programmed based on host computer utilized WINCC configuration software to show the real-time technical situation of each section and achieving the setup and display of the technology curve.更多还原