Modeling and Control blog’s Greg McMillan continues to share his process control expertise with the world. He’s working on another book, PID Control in the third Millennium – Lessons Learned and New Approaches, which is targeted for release this summer.
Greg has recently updated and made available one of the book’s chapters, Industrial Applications of PID Control. Here’s the abstract for the chapter:
The industrial PID has many options, tools, and parameters for dealing with the wide spectrum of difficulties and opportunities in manufacturing plants. Some of the options such as “dynamic reset limit” have existed for decades but the full value and applicability has not been realized. Also, the possibilities extend considerably beyond the original intent into improving process efficiency, operability, and compliance for sustainable manufacturing. An enhanced PID developed for wireless measurements has been found to inherently eliminate oscillations from a wide variety of sources including discontinuous and delayed responses in the automation system and interactions between loops when used with a threshold sensitivity setting and the dynamic reset limit. The advancements in new techniques and a greater understanding of existing capabilities enable the PID to not only improve loop performance but to individually optimize unit operations.
The chapter explores PID challenges and solutions including practical and ultimate limits to PID performance, on-demand and adaptive tuning, positive feedback implementation of integral mode, dynamic reset limit (external reset), enhancements for wireless, deadtime compensation, fast setpoint response, signal linearization, open loop backup (kicker), poor final control element resolution, sensitivity, and backlash, slow final control element response, slow secondary loop response, large wireless update times, large analyzer cycle times, high process nonlinearity, high process deadtime, feedforward timing errors, split range nonlinearities and discontinuities, multiple inputs and outputs, energy use and production rate optimization, process interactions, communication and component failures, batch profile optimization, plantwide feedforward control, and impact of threshold sensitivity and noise on performance. Now that’s a lot of challenges!
He closes the chapter with some unit operations examples including biological reactors, chemical reactors, crystallizers, evaporators, and neutralizers.
Many of ideas conveyed in this chapter of the book come straight from our series of demo/seminars.
If you’re learning about PID control or trying to refresh your knowledge, I’d recommend you spend some time with this chapter from the book.