Robust model predictive control for switched dynamic systems: asynchronous switching, stability and feasibility, and fault-tolerance




Tan, Tianyu

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Switched systems, as a superior modeling tool, are generally composed of a finite number of subsystems and a logical principle interpreted by switching signals that regulate the mode transitions between subsystems. Throughout the past few decades, switched systems have achieved phenomenal success in a wide range of engineering industries, such as the chemical process industry, robotics field, power electronics industry, generic engineering, smart automotive industry, waste treatment industry, etc. In addition to the prevalent industrial applications, switching dynamics has also stimulated broad interest in academia since the transient responses induced by mode transitions may introduce instability factors into the control synthesis and analysis even with all subsystems operating stably. Considering the exposure to the challenging and volatile industry environment, switching control systems may also face threats to numerous inevitable failures, e.g., asynchronous switching, unconstrained switching, and controller failures, and many switched systems may also encounter physical limitations owing to spatial and system constraints as well as external disturbances. To this end, the majority of previous studies have concentrated on switching control design against an individual fault, but few results are devoted to investigating the attenuation of the combined effect of multiple faults which happen simultaneously while fulfilling system constraints. Switched model predictive control (MPC), as an optimal control methodology of switched systems, can effectively incorporate system constraints into the optimization problem while providing optimal control actions with a certain degree of inherent robustness. However, how to ensure the closed-loop stability and recursive feasibility of the switched MPC algorithm is still an open problem nowadays. Therefore, to achieve the goal of reliable and executable switching controller design, this dissertation studies three problems in switched MPC and one switching stabilization control problem for a class of constrained switched systems from a theoretical context. Effective switched MPC algorithms are designed with guaranteed closed-loop stability and recursive feasibility. Additionally, a novel robust stability criterion for switched systems is explored subject to the aforementioned faults. In Chapter 1, we present a comprehensive literature review of state-of-the-art switching control techniques, fault-tolerant switching control design, and switched MPC synthesis and analysis as well as the motivations and objectives of this dissertation. Chapter 2 provides some notations and preliminaries which are useful in succeeding chapters. Chapter 3 studies the switched MPC problem without using terminal constraints with known switching sequences. Chapter 4 concerns the asynchronously switched MPC problem with mode-dependent dwell-time (MDT) constraints. Two stability criteria are claimed by driving state trajectories into the devised common terminal set. In Chapter 5, the stabilization problem for a class of constrained switched linear systems is investigated subject to multiple faults. A contractive set for initial states is established with MDT restriction and a non-conservative uniformly asymptotic stability condition is developed regarding the contractive set. In Chapter 6, we investigate the robust MPC (RMPC) for asynchronously switched linear systems in the presence of joint effects of controller failures and additive disturbances. Chapter 7 concludes this dissertation and provides some promising future research directions.



model predictive control, switched systems, robustness, asynchronous switching, fault-tolerance, stability and feasibility