Black armbands for APC? (and other rebellious sentiments regarding advanced process control)

摘要

People often ask: "Why is advanced process control (APC) utilization low?" Or: "Why are so many manipulated variables (MVs) clamped?" These questions show progress, because many people do not recognize a "defeated" APC, much less understand what brought it about. APC is generally considered a high level of technological accomplishment and process control sophistication, with people reluctant to criticize it. The APC wave of the past 20 years is settling out, and it is appropriate to take an objective look at APC's record. Plenty has been written about its successes; this article takes a much-needed look at some of its better known (if not well understood) problem areas. APC is conventionally considered a universal and near-perfect process control technology with users increasingly coming out of the closet about its shortfalls, including papers suggesting industry has more poor-performing APCs than well-performing ones. A serious problem not to be ignored are clamped MVs. Surprisingly, most current thinking suggests industry should forge ahead with more of the well-established rote APC approach including more performance monitoring, more consultancy-level support, and more operator training. This is a prescription to work harder, not smarter, and ignore past lessons. This prescription is likely throwing good money after bad, if the real nature of APC limitations means changes are needed at the design stage.