‘Grey Model'-Based Simulation Tool for Predictive Product Quality Control

A modified grey model is represented for predicting the product quality index and generating the grey process control chart. The model considers the first sample datum in the numerical solution of the whitened differential equation. This datum is introduced by the refitting smoothed cumulative values and numerical solution of the whitened equation with the last value as initial point. Values predicted in this manner and those predicted in the regular GM (1,1) model were calculated with a specially elaborated MATLAB program. The numbers obtained were compared with reference data. The modified model demonstrates higher accuracy compared to the regular GM as demonstrated by several actual examples. The proposed model is used to design a special simulation tool. The graphical interface of the tool allows to the user to introduce the sample data, control limits and required mean value. After this, the tool outputs the predicted quality index with its error and generates a process control chart with the predicted product quality index.