Low-order multi-rate linear time-invariant decentralized trackers using the new observer-based sub-optimal method for unknown sampled-data nonlinear time-delay system with closed-loop decoupling

This paper presents the low-order multi-rate linear time-invariant decentralized trackers using the new observer-based sub-optimal method for a class of unknown sampled-data nonlinear time-delay system with closed-loop decoupling. For the unknown sampled-data nonlinear time-delay system, we assume that the inner time delay is clearly known. Under this prerequisite, the appropriate (low-) order decentralized linear observer for the unknown sampled-data nonlinear system is determined by the off-line observer/Kalman filter identification (OKID) method with artificial delay input and actual delay output. Then, the above observer has been further improved based on the proposed new observer-based sub-optimal approach. Sequentially, the decentralized tracker with the high gain property is proposed, so that the closed-loop system has the decoupling property. The proposed approach constructs complete mathematics method including the concept of optimal control theory and state-matching digital redesign technique and is quite useful for the complicated interconnected large-scale sampled-data nonlinear time-delay system with unknown system equation.