| The quality of a product with respect to a certain characteristic is partially determined by the variability of the distribution of values of the characteristic in the long run (the smaller the variability, the better the product). Statistical process control (SPC) and engineering process control (EPC) are tools to help manage this variability. SPC drives the reduction of variability by monitoring the process with one, or more, of several charts and making changes to the process when a point, or points, in the chart(s) appears suspicious. In some systems, residual disturbances remain even after SPC efforts have been dedicated to remove them. In any case, some kind of process adjustment may be necessary. With EPC the reduction in variability is accomplished by regulating a controllable variable to maintain the quality characteristic close to target. Design of experiments (DOE) may be used in an exploratory way to separate irrelevant variables from the most important ones that affect the quality characteristic of interest.; The objectives of this research are to: (1) advance a new framework for using DOE, SPC, and EPC in a unified way to achieve efficient control and monitoring of industrial processes; and (2) to extend the applicability of the framework through the theoretical development of monitoring and adjustment policies and through the elucidation of the efficiency and robustness properties of such policies. |
