Tuning PID Controllers on Integrating Process with Complex Dynamics

Tuning PID controllers for integrating processes, such as levels, can be frustrating and counterintuitive.  For example, reducing the controller proportional gain on an oscillating loop can actually increase the oscillation amplitude!   This presentation will show how to recognize an integrating process, measure the process dynamics and provide a straightforward method to calculate PID tuning parameters.  Most importantly, this method can be used to calculate controller tuning to achieve the control response that optimizes the process performance.  For example, in some cases the best process performance requires aggressive tuning with good load regulation capability.  In other cases it might require the “least aggressive” tuning that maintains a process variable (e.g. level) within the maximum allowable deviation from setpoint yet provides maximum attenuation of process variability.  This tuning method can also be applied to lag dominant or “near integrating” processes which greatly reduces the time to measure process dynamics.  The tuning method can also be used on more complex integrating processes such as “Integrator plus Lag” or “Integrator plus Lead”.  Plant examples will be used to illustrate the concepts and results.