Output Feedback SOSM Control of Constrained Systems With Unmatched Uncertainties

In this work, we devise an output feedback second-order sliding mode (SOSM) control protocol for a category of nonlinear systems with unmatched uncertainties and asymmetric output constraints. The procedure of the design and analysis for this control tactic primarily encompasses the following steps. To begin with, a nonlinear mapping is introduced to convert the output-constrained SOSM system into a new SOSM dynamics without output constraints. Next, through adopting a scaling transformation with properly scheduled gains, a SOSM controller via output feedback is explicitly constructed. Third, it is theoretically certified that the presented control strategy insures both the finite-time convergence of the whole system and the compliance with the preset asymmetric output constraint. Eventually, the simulation studies on a practical application example confirm the feasibility and benefits of the proposed algorithm. Distinct from the prevailing outcomes in the literature, our control frame reveals two compelling features. One is that the output constraint issue is tackled via the system conversion based control. The other is that the proposed output feedback control design is independent of the separation principle, i.e., the finite-time convergence for the total closed-loop SOSM system embracing a state feedback SOSM controller and a discontinuous observer is together analyzed. Note to Practitioners—The paper considers a class of asymmetric output-constrained nonlinear systems subject to unmatched uncertainties, whose models are pervasively adopted in the engineering fields, e.g., manufacturing sector, transportation, etc. For such systems, the output feedback SOSM control issue hitherto has not been tackled, since under the circumstance that merely the output information is obtainable, the unmatched uncertainties and the output constraints are simultaneously considered. To this end, we successfully establish a novel output feedback SOSM control scheme by introducing the nonlinear mapping, the scaling transformation and the backstepping-like technique. Moreover, the finite-time convergence of the entire system is analyzed and corroborated via the Lyapunov method, and the fulfillment of the pre-specified asymmetric output constraint is assured, which make the proposed strategy more engineering-oriented. In future work, the efforts will be directed towards the validation of the proposed approach on an experimental platform for electric vehicles.