A simple tool for disturbance resiliency diagnosis and feedforward control design

The ease with which a vector of two or more disturbances can be rejected by a control system can be quantified using the Disturbance Cost (DC), which is simply the amount of feedback action required in order to completely eliminate the effect of disturbance on the process outputs. A graphical representation of this measure, limited to vectors of two disturbances, can be expressed as contours of DC values as a function of frequency and disturbance direction. A useful property of the DC is its independence from specific controller tuning, and as such it is an appropriate screening tool for use at the preliminary process design stage. It is a useful tool for such applications as the investigation of control structure resilience to disturbances, for selecting from alternative feedback control structures, and to facilitate the design of feedforward control systems.