Exclusive Content & Downloads from ASQ

Stability and Sensitivity of an EWMA Controller

Summary: The performance of a process control algorithm based on EWMA statistic is analyzed. A simple condition relating the EWMA weight and the estimated process gain is shown to ensure that the control strategy is stable for a first-order multiple-input, single-output process that may be drifting or wandering. A similar condition is shown to guarantee stability for a second-order, single-input process. An expression is derived for the output mean squared deviation from target as a function of the algorithm parameters, how quickly the process drifts or wanders, and the amount of noise. The results are illustrated in the context of an epitaxial growth process.

Anyone with a subscription, including Site and Enterprise members, can access this article.

Other Ways to Access content:

Join ASQ

Join ASQ as a Full member. Enjoy all the ASQ member benefits including access to many online articles.

Subscribe to Journal of Quality Technology

Access this and ALL OTHER Journal of Quality Technology online articles. You'll also receive the print version by mail.

  • Topics: Statistical Process Control (SPC)
  • Keywords: Exponentially weighted moving average control charts (EWMA),Stability,Statistical process control (SPC),Feedback control
  • Author: Ingolfsson, Armann; Sachs, Emanuel
  • Journal: Journal of Quality Technology