[CCoE Notice] Defense session information

[Knudsen, Rachel W]

PhD Dissertation by Saeed Salavati

Defense session date and time: Monday, December 7th, 2020, 1-2:30 pm

Session location: Zoom

Session Link: https://urldefense.com/v3/__https://us04web.zoom.us/j/71016455665?pwd=RUxPTFJwY2FPRHB3OXRQcDRaZGpSUT09__;!!LkSTlj0I!SphgaTzUJNZ7cKS5exV3BS_Ya6Q_tS3Jq85bHnluRwM26gQYuRgvR-VjAe5H77Ej4zc$ 

Meeting ID: 710 1645 5665


Title: Robust Control of Input-Delay Linear Parameter-Varying (LPV) Systems



By: Saeed Salavati



Chair of Committee: Karolos Grigoriadis
Co-Chair of Committee: Matthew Franchek
Committee Member: Gangbing Song
Committee Member: Zheng Chen
Committee Member: Robert Provence



Abstract: Practical systems are nonlinear and time-varying and thus linear techniques can expose their control design to extra conservatism. Nevertheless, the Linear Parameter-Varying (LPV) representation can effectively describe them, which in contrast to linearization, maintains the principal dynamic modes of the original system. Additionally, the LPV and gain-scheduling control design benefit from the wealth of robust and optimal control techniques to acquire better performance over classical linear methods. Moreover, the majority of engineering systems are affected by input delays. Since there is a lag between the control signal and the system’s response to it, input delay degrades a system’s performance by reducing the bandwidth and even causes instability in severe cases. This research on input-delay LPV systems addresses their robust control in the presence of parameter variations and also time-varying delays. Previous works have typically addressed the LPV systems with

state delays which are constant or mostly slowly varying. In contrast to such works, our first approach through the frequency-domain analysis assumes the delay and system parameters can vary arbitrarily within a priori known bounds which are pre-determined through tests. Then a low-pass filter is proposed to acquire robust stability over all parameter and delay variations for first-order time-delay systems which leads to a closed-form inequality for the filter tuning parameter in terms of nominal parameters and the delay and their bounds. The results are applied to Air-Fuel Ratio (AFR) control in Spark-Ignition (SI) lean-burn engines and automated Mean Arterial Blood Pressure (MAP) regulation for the clinical resuscitation of hypotensive patients. In our second approach, time-domain techniques are employed to stabilize input-delay LPV systems characterized via a prescribed level of performance for the closed-loop system. It is assumed that parameters and the delay rate are varying within a priori known bounds. Moreover, the problem of such systems under input constraints or saturation is addressed in this framework and stabilizability conditions are described via convex constraints, known as Linear Matrix Inequality (LMI) conditions, to be solved numerically. The results are applied to AFR control in conventional SI engines and the MAP LPV model estimation and control for clinically resuscitating patients with hypotension.


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