Predictor-Feedback Prescribed-Time Stabilization of LTI Systems With Input Delay

Abstract

This article first deals with the problem of prescribed-time stability of linear systems without delay. The analysis and design involve the <i>Bell polynomials</i>, <i>the generalized Laguerre polynomials</i>, <i>the Lah numbers</i>, and a suitable <i>polynomial-based Vandermonde matrix</i>. The results can be used to design a new controller&#x2014;with time-varying gains&#x2014;ensuring prescribed-time stabilization of controllable linear time-invariant (LTI) systems. The approach leads to similar results compared to Holloway <i>et al.</i> 2019, but offers an alternative and compact control design (especially for the choice of the time-varying gains). Based on the preliminary results for the delay-free case, we then study controllable LTI systems with single input and subject to a constant input delay. We design a predictor feedback with time-varying gains. To achieve this, we model the input delay as a transport partial differential equation (PDE) and build on the cascade PDE&#x2013;ordinary differential equation setting (inspired by Krstic 2009) so as the design of the prescribed-time predictor feedback is carried out based on the backstepping approach, which makes use of <i>time-varying kernels</i>. We guarantee the bounded invertibility of the backstepping transformation, and we prove that the closed-loop solution converges to the equilibrium in a prescribed time. A simulation example illustrates the results.