A Control System Design Method for the Real Order Phase Lead-Lag Compensator Based on Frequency Characteristics
Naoto Yajima, Kazuo KUROKAWA · Transactions of the Society of Instrument and Control Engineers · 2001
The control system design method for the controlled object having such a higher order lag element and a dead time element as used in general for the process control system is treated in this paper. Two types of the transfer function with the real order element are used in the control system design method. One is the transfer function of the controlled object approximated the real order lag element and a dead time system to a higher order controlled object. The other is the transfer function of the compensator with the real order phase lead-lag element proposed previously to control this controlled object. The principle of the design for the system composed of these elements is based on frequency characteristics. In this design, parameters of the compensator for a given phase margin, a gain margin and a peak gain in Nichols chart are intended to decide.The derivation of parameters of the compensator to satisfy specifications of these frequency characteristics is described, and then the property of the control system is confirmed by the transient responses. From results of the unit step response and the consideration to specifications of the system design, a suitable range of the parameter of the compensator is researched in detail. And then a suitable combination of the peak gain and the phase margin is obtained for a given specification of the frequency characteristics. The usability of this control system design method is appreciated through some examples.Moreover, the application of the principle of this controll system design method to the control system using the most general PID compensator has shown.