Abstract
We must take account of sensitivity and robust stability for parameter perturbations, characteristics of responses to reference commands, and performances of disturbance and sensor noise rejection, in control system design. This paper compares PID type control systems with I-PD type control systems from these view-points. The following properties are derived under some reasonable assumptions of the given plants and the designed controllers: 1) PID type controllers have superior characteristics with respect to robust stability, output sensor noise rejection, and rapidity of responses to reference commands; 2) Low sensitivity and good disturbance and error sensor noise attenuation can be realized by small control input in I-PD type control systems. It is also shown that the characteristics of PI-PD control systems lie between those of PID and I-PD type control systems. Guidances for controller design are proposed based on these quantative properties. A simple numerical example certifies these results.
