Practical modelling and control system design methods for CAE systems

Practical modelling and control system design methods for CAE (computer-aided engineering) systems are presented. The practical model matching method (PMM) is effective in designing conventional PID (proportional, integral, derivative) control systems used widely in industrial processes, and some extended types of PID control systems such as decoupling PID control sytems and digital PID control sytems. In order to design a control system by the PMM method, a transfer function for process dynamics that has a simple structure is needed. The cutoff frequency characteristics that determine the stability and response characteristics of the control system are also essential for control system design. An effective modeling method is proposed that identifies a transfer function by process response data that show the cutoff frequency characteristics exactly and reduces it to a simple structured transfer function. The combination of the modeling method and the PMM method is applicable to various dynamics such as processes with delay time, dead time, overshooting, reverse shooting and oscillation. A CAE system developed on a laptop personal computer using the methods is outlined.