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Controlled functional differential equations: approximateand exact asymptotic tracking with prescribed transient performance
Published online by Cambridge University Press: 19 July 2008
Abstract
A tracking problem is considered in the context of a class $\mathcal{S}$ of multi-input, multi-output, nonlinear systems modelled by controlled functional differential equations. The class contains, as a prototype, all finite-dimensional, linear, m-input, m-output, minimum-phase systems with sign-definite “high-frequency gain". The first control objective is tracking of reference signals r by the output y of any system in $\mathcal{S}$: given $\lambda \geq 0$, construct a feedback strategy which ensures that, for every r (assumed bounded with essentially bounded derivative) and every system of class $\mathcal{S}$, the tracking error $e = y-r$ is such that, in the case $\lambda >0$, $\limsup_{t\rightarrow\infty}\|e(t)\|<\lambda$ or, in the case $\lambda=0$, $\lim_{t\rightarrow\infty}\|e(t)\| = 0$. The second objective is guaranteed output transient performance: the error is required to evolve within a prescribed performance funnel $\mathcal{F}_\varphi$ (determined by a function φ). For suitably chosen functions α, ν and θ, both objectives are achieved via a control structure of the form $u(t)=-\nu (k(t))\theta (e(t))$ with $k(t)=\alpha (\varphi (t)\|e(t)\|)$, whilst maintaining boundedness of the control and gain functions u and k. In the case $\lambda=0$, the feedback strategy may be discontinuous: to accommodate this feature, a unifying framework of differential inclusions is adopted in the analysis of the general case $\lambda \geq 0$.
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- Type
- Research Article
- Information
- ESAIM: Control, Optimisation and Calculus of Variations , Volume 15 , Issue 4 , October 2009 , pp. 745 - 762
- Copyright
- © EDP Sciences, SMAI, 2008
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