Robustness Improvement by Dynamic State Feedback Stabilization

A general perception is that dynamic state feedback controllers may have superior capabilities compared to the static feedback ones. Although, for nominal systems, such superiority does not exist, it may hold true for systems other than the nominal one. This thesis investigates such capabilities of dynamic state feedback controllers. First, the case of systems with time-invariant uncertainties is considered. It appears that only a limited number of example systems exist for which dynamic feedback controller has superior ability to improve tolerable uncertainty bounds. This thesis shows that not only the available ones but there exist a class of systems for which such improvement may occur. This claim has been verified by presenting more numerical examples in the category. Second, this thesis considers the class of systems with feedback delays, more specifically, systems having both input and output delays. The superiority of dynamic feedback controllers for such systems appears to be not investigated so far in literature. However, it is observed, for the first time, that if one considers a dynamic state feedback controller but with an artificial delay in its state then the tolerable delay margin improves considerably. The performance of such a controller is investigated thoroughly for scalar systems using a continuous pole placement technique for delay systems

New Results on Delay-Dependent Stability Analysis and Stabilization of Time-Delay Systems

The interconnection between physical systems is accomplished by flow of information, energy and material, alternatively known as transport or propagation. As such flows may take a finite amount of time, the reaction of real world systems to exogenous or feedback control signals, from automatic control perspective, are not instantaneous. This results time-delays in systems connected by real-world physical media. Indeed, examples of time-delay systems span biology, ecology, economy, and of course, engineering. To this end, it is known that an arbitrary small delay may destabilize a stable system whereas, a delay in the controller may be used to stabilize a system that is otherwise not stabilizable by using a delay-free controller. In general, the presence of time-delay in a system makes the system dynamics infinite-dimensional, and analysis of such systems is complex.This thesis investigates stability analysis and stabilization of time-delay systems. It proposes a delay-decomposition approach for stability analysis of systems with single delay that leads to a simple LMI condition using a Lyapunov-Krasovskii functional. Moreover, a static state feedback controller is designed for systems with state and input-delay using this delay-decomposition approach. Numerical comparison of the present results vis-`a-vis the existing ones for the systems with constant delay considered shows that the present ones are superior. Next, a PI-type controller is implemented for systems with input-delay to improve the tolerable delay bound. Other problems considered is to analyze the stability of systems with two delays. As the number of delays incorporated in the system dynamics increases, it becomes further complex for analysis

Dynamics of Hot QCD Matter -- Current Status and Developments

The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.Comment: Compilation of the contributions (148 pages) as presented in the `Hot QCD Matter 2022 conference', held from May 12 to 14, 2022, jointly organized by IIT Goa & Goa University, Goa, Indi

Sliding mode controller design via delay-dependent H∞H_{\infty } H ∞ stabilization criterion for load frequency regulation

Abstract This work presents a control approach based on sliding-mode-control (SMC) to design robust $$H_{\infty }$$ H ∞ state feedback controllers for load frequency regulation of delayed interconnected power system (IPS) with parametric uncertainties. Considering both state feedback control strategy and delayed feedback control strategy, two SMC laws are proposed. The proposed control laws are designed to improve the stability and disturbance rejection performance of delayed IPS, while stabilization criteria in the form of linear matrix inequality are derived by choosing a Lyapunov–Krasovskii functional. An artificial time-delay is incorporated in the control law design of the delayed feedback control structure to enhance the controller performance. A numerical example is considered to study the control performance of the proposed controllers and simulation results are provided to observe the dynamic response of the IPS

A novel PID controller for pressure control of artificial ventilator using optimal rule based fuzzy inference system with RCTO algorithm

Abstract In order to improve the pressure tracking response of an artificial ventilator system, a novel proportional integral derivative (PID) controller is designed in the present work by utilizing an optimal rule-based fuzzy inference system (FIS) with a reshaped class-topper optimization algorithm (RCTO), which is named as (Fuzzy-PID). Firstly, a patient-hose blower-driven artificial ventilator model is considered, and the transfer function model is established. The ventilator is assumed to operate in pressure control mode. Then, a fuzzy-PID control structure is formulated such that the error and change in error between the desired airway pressure and actual airway pressure of the ventilator are set as inputs to the FIS. The gains of the PID controller (proportional gain, derivative gain, and integral gain) are set as outputs of the FIS. A reshaped class topper optimization algorithm (RCTO) is developed to optimize rules of the FIS to establish optimal coordination among the input and output variables of the FIS. Finally, the optimized Fuzzy-PID controller is examined for the ventilator under different scenarios such as parametric uncertainties, external disturbances, sensor noise, and a time-varying breathing pattern. In addition, the stability analysis of the system is carried out using the Nyquist stability method, and the sensitivity of the optimal Fuzzy-PID is examined for different blower parameters. The simulation results showed satisfactory results in terms of peak time, overshoot, and settling time for all cases, which were also compared with existing results. It is observed in the simulation results that the overshoot in the pressure profile is improved by 16% with the proposed optimal rule based fuzzy-PID as compared with randomly selected rules for the system. Settling time and peak time are also improved 60–80% compared to the existing method. The control signal generated by the proposed controller is also improved in magnitude by 80–90% compared to the existing method. With a lower magnitude, the control signal can also avoid actuator saturation problems

Measurement of the lifetime and Λ\Lambda separation energy of Λ3H^{3}_{\Lambda}\mathrm H

The most precise measurements to date of the $^{3}_{\Lambda}\mathrm H$ lifetime $\tau$ and $\Lambda$ separation energy ${\rm B}_{\Lambda}$ are obtained using the data sample of Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV collected by ALICE at the LHC. The $^{3}_{\Lambda}\mathrm H$ is reconstructed via its charged two-body mesonic decay channel ($^{3}_{\Lambda}\mathrm{H} \rightarrow$ $^3$He + $\pi^-$ and the charge-conjugate process). The measured values $\tau = [253 \pm 11 \text{ (stat.)} \pm 6 \text{ (syst.)}]$ ps and ${\rm B}_{\Lambda}= [72 \pm 63 \text{ (stat.)} \pm 36 \text{ (syst.)}]$ keV are compatible with predictions from effective field theories and conclusively confirm that the $^{3}_{\Lambda}\mathrm H$ is a weakly-bound system.The most precise measurements to date of the HΛ3 lifetime τ and Λ separation energy BΛ are obtained using the data sample of Pb-Pb collisions at sNN=5.02  TeV collected by ALICE at the LHC. The HΛ3 is reconstructed via its charged two-body mesonic decay channel (HΛ3→He3+π- and the charge-conjugate process). The measured values τ=[253±11(stat)±6(syst)]  ps and BΛ=[102±63(stat)±67(syst)]  keV are compatible with predictions from effective field theories and confirm that the HΛ3 structure is consistent with a weakly bound system.The most precise measurements to date of the $^{3}_{\Lambda}\mathrm H$ lifetime $\tau$ and $\Lambda$ separation energy ${\rm B}_{\Lambda}$ are obtained using the data sample of Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV collected by ALICE at the LHC. The $^{3}_{\Lambda}\mathrm H$ is reconstructed via its charged two-body mesonic decay channel ($^{3}_{\Lambda}\mathrm{H} \rightarrow$$^3$He + $\pi^-$ and the charge-conjugate process). The measured values $\tau = [253 \pm 11 \text{ (stat.)} \pm 6 \text{ (syst.)}]$ ps and ${\rm B}_{\Lambda}= [102 \pm 63 \text{ (stat.)} \pm 67 \text{ (syst.)}]$ keV are compatible with predictions from effective field theories and confirm that the $^{3}_{\Lambda}\mathrm H$ structure is consistent with a weakly-bound system

KS0\mathrm {K_S}^{0}- and (anti-)Λ\Lambda -hadron correlations in pp collisions at s=13{\sqrt{s}} = 13 TeV

International audienceTwo-particle Azimuthal correlations are measured with the ALICE apparatus in pp collisions at $\sqrt{s} = 13$ TeV to explore strangeness- and multiplicity-related effects in the fragmentation of jets and the transition regime between bulk and hard production, probed with the condition that a strange meson ($\mathrm {K_S}^{0}$) or baryon ($\Lambda$) with transverse momentum $p_{\mathrm T} >3$ GeV/$c$ is produced. Azimuthal correlations between kaons or $\Lambda$ hyperons with other hadrons are presented at midrapidity for a broad range of the trigger ($3< p_\mathrm {T}^\mathrm {trigg} < 20$ GeV/$c$) and associated particle $p_{\mathrm T}$ (1 GeV/$c< p_\mathrm {T}^\mathrm {assoc} < p_\mathrm {T}^\mathrm {trigg}$), for minimum-bias events and as a function of the event multiplicity. The near- and away-side peak yields are compared for the case of either $\mathrm {K_S}^{0}$ or $\Lambda$(${\overline{\Lambda }}$) being the trigger particle with that of inclusive hadrons (a sample dominated by pions). In addition, the measurements are compared with predictions from PYTHIA 8 and EPOS LHC event generators

Pseudorapidity distributions of charged particles as a function of mid- and forward rapidity multiplicities in pp collisions at s\sqrt{s} = 5.02, 7 and 13 TeV

The multiplicity dependence of the pseudorapidity density of charged particles in proton–proton (pp) collisions at centre-of-mass energies $\sqrt{s}~=~5.02$, 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range ($|\eta | < 1.5$). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval $|\eta |<1$. The multiplicity dependence of the pseudorapidity density of charged particles is measured with mid- and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. The results can be used to constrain models for particle production as a function of multiplicity in pp collisions