Abstract-In this paper, a new robust integral of signum of error (RISE) feedback type controller is designed for a class of uncertain nonlinear systems. Unlike the previous versions of RISE feedback type controllers, the proposed controller does not require prior knowledge of upper bounds of the vector containing the uncertainties of the dynamical system plus desired system dynamics (and their derivatives) for the control gain selection. The aforementioned enhancement is made possible via the design of a time-varying compensation gain as opposed to a constant gain used in previous RISE feedback type controllers. Asymptotic stability of the error signals and the boundedness of the closed-loop system signals are ensured via Lyapunov based arguments. Numerical simulation studies are presented to illustrate the viability of the proposed method.
In this work, we present a novel continuous robust controller for a class of multi-input/multi-output nonlinear systems that contains unstructured uncertainties in their drift vectors and input matrices. The proposed controller compensates uncertainties in the system dynamics and achieves asymptotic tracking while requiring only the knowledge of the sign of the leading principal minors of the input gain matrix. A Lyapunov-based argument backed up with an integral inequality is applied to prove the asymptotic stability of the closed-loop system. Simulation results are presented to illustrate the viability of the proposed method.Keywords: nonlinear uncertain dynamical systems; multi-input/multi-output systems; robust control; Lyapunov methods
Nomenclature x(t) System states x (i) (t) ith-order time derivative of x(t) H(·), h(·) Functional containing uncertain components G(·), g(·)Real-valued matrix with nonzero leading principal minors τ (t), τ 1 (t), τ 2 (t) Control inputs X(t) Combined state vector S(X) Symmetric positive definite matrix D Diagonal matrix with entries ±1 U(X) Unity upper triangular matriẋ τ (t) Time derivative of control input ϕ (X, x (n) ) Auxiliary function m Positive bounding constant m (X) Positive non-decreasing bounding function x r (t) Reference trajectory e 1 (t) Output tracking error e i (t) Auxiliary error signals for i = 2, . . ., n r(t) Filtered error signal a i, j Positive-valued coefficients generated via a Fibonacci number series I m m × m identity matrix 0 m × 1
Twin-rotor multi-input multi-output system (TRMS) is a popular experimental setup utilized mostly for development and evaluation of aerovehicle control algorithms. Motivated by its popularity, construction steps of a TRMS setup in an academic setting are presented in this paper. Specifically, design of mechanical and electronic hardware components and development of related computer software are described in detail. Preliminary experiment results are also presented to demonstrate the performance of the system. ß 2015 Wiley Periodicals, Inc. Comput Appl Eng Educ 23:578-586, 2015; View this article online at wileyonlinelibrary.com/journal/cae;
Abstract-In this study, online identification of state delays is discussed. First, a novel adaptive time delay identification technique is proposed for general classes of autonomous nonlinear systems subject to state delays. As an extension, this technique is modified to design a tracking controller for general classes of nonlinear systems subject to state delays. The main novelty of this controller is that identification of unknown state delays is ensured while output tracking objective is satisfied. Extensive numerical simulations are presented that demonstrate the efficiency of the time delay identification algorithm and the tracking controller.
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