The history of process optimization, as chronicled over Control's first 25 years, starts with advanced control: going beyond single-loop control to adequately regulate the critical variables of often complex and unruly processes.
The term "advanced control" was coined in the 1940s, according to Russell Rhinehart, now professor at Oklahoma State. At that time, proportional-integral (PI) control was most commonly done with pneumatic devices. As technology developed in the 1940s and 50s, people figured out how to couple these devices with each other, and how to get different pneumatic devices called lead-lag elements, cascade, feed-forward, ratio and so on.
With the promulgation of digital control systems in the 1970s and 1980s came new levels of automation and control. In the 1970s, "A whole host of
supervisory control techniques were programmed into a host computer. An experienced engineer could employ all sorts of tricks," wrote Greg McMillan, Terry Blevins and Willy Wojznis, in Control's May 2004 issue. "But each function generally required a separate device, and the tuning and maintenance of these were often too tricky for even the most accomplished personnel.
"In the 1980s, the PID hangovers from the 1970s became available as function blocks that could be configured at will within the basic process control system. Real-time simulations were developed to test configurations and train operators. The benefits from advanced regulatory control, instrument upgrades and migration from analog to distributed control far exceeded expectations. Continuous process control improvement became a reality."
In the 1990s, advanced process control (APC) technologies, including constrained multivariable predictive control (CMPC), artificial neural networks (ANNs), real-time optimization (RTO), performance monitoring and expert systems were commercialized.
"These new technologies required expensive software packages ($100,000 and up), separate computers, special interfaces and consultants to do the studies and implementations. The total bill could easily approach or exceed $1 million for a medium-sized project, the biggest chunk being the consultant's fee," wrote McMillan, et al.
Around the turn of the century, APC technologies were integrated into the basic process control system. "Along with lower license fees, the whole cost of system implementation decreased by a factor of 20 or more with the automation of a variety of steps including configuration, display, testing, simulation and tuning," they added. In recent times, those systems are increasingly integrated with business and enterprise systems to set priorities and measure results. "Now that we have the tools at our fingertips, how do we make the most of the opportunities the technologies can deliver?" they asked.
The frontiers of process optimization now lie well up in the business and enterprise levels, but APC implementations remain "incredibly hard," we wrote in 2012, due to complex implementation and maintenance requirements. Few companies have been able to fully optimize a process, and there remains a great deal of unrealized potential.