Implementation of Model-Based Optimal Temperature Profiles for Autoclave Curing of Composites Using a Knowledge-Based System

Abstract

The manufacture of composite parts using the autoclave curing process requires the specification of the autoclave temperature as a function of time. It is desired to obtain a part meeting given specifications in the minimum amount of time. A recently developed methodology was used to optimize the process using a mathematical simulation of the cure process. The optimal profile so obtained was implemented on a full-sized autoclave which is interfaced to a proprietary control system running on a Hewlett-Packard computer, using a knowledge-based system (KBS) as a supervisor. In order to account for discrepancies between the simulation and the actual process, we have followed a strategy that uses process trend analysis of the simulation output as the basis for control. The whole process is split up into episodes based on an analysis of the variable profiles. This information is used in conjunction with other knowledge about the system embedded in the KBS to adjust the set point of the autoclave temperature so that the process follows the same trends as dictated by the model-based optimization. Using this system, it was possible to guide the cure robustly along anoptimal path, consistently yielding superior quality parts despite the variability of the raw materials. This procedure allows us to optimize a process independently using even an inexact simulation and apply the optimal profiles obtained therefrom