Temperature control of diffusion/CVD furnaces using robust multivariable loop-shaping techniques

Abstract

Describes the application of modern tools from robust control theory to the design of high-performance multivariable temperature controllers for diffusion furnaces. The process is modeled from input-output data, collected in an identification experiment at the desired operating conditions. An important component of the identification is the computation of uncertainty bounds describing the confidence limits of the model, in a manner consistent with robust control theory. The identification results are then used to design an H-infinity controller with a cascade, hierarchical structure. The gain-scheduling of several linear controllers is also investigated in an effort to achieve good performance in a wide range of operating conditions. Experimental results demonstrate the success of the approach.