Output-Feedback Control for Stochastic Nonlinear Systems Subject to Input Saturation and Time-Varying Delay

• Published in: IEEE transactions on automatic control Vol. 64; no. 1; pp. 359 - 364
• Main Authors: Min, Huifang, Xu, Shengyuan, Zhang, Baoyong, Ma, Qian
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bounded almost surely; Chemical reactors; Control systems design; Controllers; Delay effects; Delays; Design parameters; Error detection; Feedback control; input saturation; Nonlinear control; Nonlinear systems; Observers; Organic chemistry; Output feedback; Saturation; Stability analysis; stochastic nonlinear systems; Stochastic processes; Stochastic systems; Time delay systems; time-varying delay; Time-varying systems
• ISSN: 0018-9286; 1558-2523
• DOI: 10.1109/TAC.2018.2828084

This paper is concerned with the problem of global output-feedback control for a class of stochastic nonlinear time-delay systems in the presence of input saturation and unmeasurable states. As a distinctive feature, the growth assumptions imposed on the drift and diffusion terms are proven to be unnecessary, which can be removed through a technical lemma. In addition, by introducing an auxiliary system whose order is the same as the considered system, and using Lyapunov-Krasovskii functional, the adverse effects generated by input saturation and time-varying delay are eliminated. Then, based on state-observer and backstepping recursive design, an output-feedback controller is constructed to render the closed-loop system be globally bounded almost surely. Particularly, instead of converging to an arbitrarily small neighborhood of zero as in related results, the tracking error is ensured to be tuned by the design parameters and an input saturation error in the mean quartic sense. Finally, a stochastic chemical reactor system is established and shown to demonstrate the effectiveness of the proposed scheme.