A previous post about the Derivative Term focused on its weaknesses. As noted, the primary challenge associated with the use of Derivative and PID Control is the volatility of the controller’s response when in the presence of noise. Noise is a major stumbling block for Derivative and PID Control as production data is routinely replete with process noise and other sources of variability. The use of PID Control in such an environment can drive frenetic changes in a loop’s Controller Output (CO) and unnecessarily wear out the associated Final Control Element (FCE). In summary: Little to gain; lots to lose.Read More
Studies show that when individuals are given a set of three options they are instinctively biased to prefer the middle one. When this finding is applied to purchasing behavior a common outcome is that consumers pick the middle priced option with little-to-no rationale other than a desire to avoid being viewed as either too cheap or too lavish. It’s known as the Compromise Effect. While the PID controller offers three options – P-Only, PI and PID – the rationale for selecting the middle option is generally clear. But PI Control is not only the instinctive choice, on many occasions it is also the superior and simpler one.Read More
Effective Disturbance Rejection
“When your only tool is a hammer, every problem looks like a nail” – a concept attributed to Abraham Maslow. Such can be the situation with process control and the PID controller. For decades practitioners have applied the PID to tackle the majority of challenges related to process control. Fortunately for practitioners the PID is more like a Swiss Army Knife as it can take different forms. The focus of this post is on a pair of applications of P-Only Control – or Proportional-Only Control.