对乙烯裂解炉建立实时监控模型具有重要的现实意义,而传统的多元统计过程监控方法都是假设过程处于单一工况下,而随着过程参数(进料负荷、产品组分等)的改变,工况也随之改变,传统方法便不再适用。本文针对工业过程中的多工况问题,提出了一种基于自适应模糊聚类的多模型过程监控方法,该方法可以减少监控方法对过程知识的依赖性,并且能够适应实际工业过程的非高斯性和非线性特征。首先对影响工况的过程变量利用自适应模糊聚类进行工况划分,然后对每种工况的建模数据分别利用最大方差展开(MVU)提取低维信息,再用支持向量数据描述(SVDD)建立多模型过程监控模型,最后再利用相应的统计指标进行过程监控。将上述方法应用在乙烯裂解炉上,并与基于高斯混合模型的多PCA方法(GMM-MPCA)进行了比较。仿真实验中,监控对裂解炉运行影响最大的33个变量,根据聚类有效性指标,将数据划分为5类时可以得到最佳的聚类效果。通过实验,将33维建模数据降到20维时误报率最小。仿真结果表明该方法在对非线性和非高斯性过程的监控上,能达到很好的效果,误报率和检测率均优于GMM-MPCA方法。
Modem manufacturing equipment has the characteristics of large scale, high complexity and multi-variable. It usually runs under closed-loop control. Conducting fault detection and diagnosis of this equipment at early time can reduce downtime, increase process safety and cut manufacturing costs. With the development of computers and intemet, a large amount of process data are collected and stored into the database which can be used to carry out fault detection and diagnosis. Traditional methods for process monitoring usually works under the assumption that the process only has one steady state mode, but when applied to the process with multi-state modes these methods don't have a good monitoring result. In order to solve this problem, this paper proposes a multiple models process monitoring method based on self-adaptive fuzzy c means cluster. It can have a good monitoring result of the process with multiple operation modes and reduce dependence on the process knowledge. First, classify the mode according to the process variables which have influence on the operating mode. Second, use Maximum Variance Unfolding (MVU) to reduce the dimension of each child-model data, and then build the Support Vector Data Description (SVDD) process monitoring model. At last, corresponding monitoring indices are constructed to detect process fault. The proposed method has been applied to the process monitoring of ethylene cracking furnace to show its efficiency. Gaussian Mixture Model-Multiple PCA (GMM-MPCA) method is chosen to be compared with. In the simulation, 33 variables which have main effect on the cracking furnace are chosen to monitor. According to the cluster validity index, the model data are divided into 5 sub-models. When the data's dimensions are reduced to 20, minimum false detection rate can be reached. The simulation result indicates that the proposed method has good monitoring result when applied to the nonlinear and nonGaussian process. The false detection rate and detection rate are all better tha