Design of PAM and PWM digital controllers for cascaded analog systems

This paper discusses the relationship among various recently developed constant state-feedback digital redesign methods. Then, for a unity-output feedback system with an analog plant in cascade with an analog controller, the best and simple Chebyshev quadrature digital redesign method is utilized to find new pulse-amplitude-modulated (PAM) and pulse-width-modulated (PWM) digital controllers for effective digital control of the analog plant. The digital controllers are determined from existing or pre-designed analog controllers as in the case of PID controllers for industrial control processes and robotics, phase lead-lag compensators for servo-mechanisms and regulator systems and guidance-autopilots for aircraft and missiles etc. The proposed method provides an alternative methodology for indirect digital design of a continuous-time unity-output feedback system and enables us to accurately and effectively implement an existing or pre-designed cascaded analog controller via a digital controller. (C) 1998 Elsevier Science Ltd. All rights reserved.