Multi-rate suboptimal digital redesign of a cascaded continuous-time inputtime-delay system

This paper presents a new multi-rate control scheme for optimal digital-red esign approach of the input time-delay continuous-time cascaded system. It shows that the states of the multi-rate sampled-data system with the digita lly redesigned control law closely match those of the original cascaded con tinuous-time closed-loop system with analogue control law at any instant be tween sampling periods. Moreover, the developed digital control law can be implemented using low-cost microcomputers with a relatively longer sampling period. Also, it utilizes the innovative one-duration description of input time-delay sampled-data system which is suitable for any value of input ti me delay, even larger than one sampling period. As a digitized continuous-t ime system with a very small sampling period may become an unstable and/or non-minimum phase model, even if the original system is stable and/or minim um phase. A new method, with different sampling rates, suboptimal digital-r edesign of a cascaded continuous-time system with different input time dela ys is accessible in this paper. An illustrative example is presented to dem onstrate the effectiveness of the proposed design methodology. (C) 2000 Els evier Science Ltd. All rights reserved.