Observability and observer design for switched linear systems

Hybrid vehicles, HVAC systems in new/old buildings, power networks, and the like require safe, robust control that includes switching the mode of operation to meet environmental and performance objectives. Such switched systems consist of a set of continuous-time dynamical behaviors whose sequence of operational modes is driven by an underlying decision process. This thesis investigates feasibility conditions and a methodology for state and mode reconstruction given input-output measurements (not including mode sequence). An application herein considers insulation failures in permanent magnet synchronous machines (PMSMs) used in heavy hybrid vehicles. Leveraging the feasibility literature for switched linear time-invariant systems, this thesis introduces two additional feasibility results: 1) detecting switches from safe modes into failure modes and 2) state and mode estimation for switched linear time-varying systems. This thesis also addresses the robust observability problem of computing the smallest structured perturbations to system matrices that causes observer infeasibility (with respect to the Frobenius norm). This robustness framework is sufficiently general to solve related robustness problems including controllability, stabilizability, and detectability. Having established feasibility, real-time observer reconstruction of the state and mode sequence becomes possible. We propose the embedded moving horizon observer (EMHO), which re-poses the reconstruction as an optimization using an embedded state model which relaxes the range of the mode sequence estimates into a continuous space. Optimal state and mode estimates minimize an L2-norm between the measured output and estimated output of the associated embedded state model. Necessary conditions for observer convergence are developed. The EMHO is adapted to solve the surface PMSM fault detection problem

Coherent transfer of light polarization to electron spins in a semiconductor

We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g-factors of electrons and light holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron spin qubits in semiconductors.Comment: 4 pages. Submitted to Physical Review Letter

Coherent control and decoherence of charge states in quantum dots

This Chapter contains a review of the recent results, both experimental and theoretical, related to optical control of carriers confined in semiconductor quantum dots. The physics of Rabi oscillations of exciton and biexciton occupations, as well as time-domain interference experiments are discussed. Next, the impact of carrier--phonon interaction in a semiconductor structure is described and modern methods of theoretical description of the carrier--phonon kinetics and of the resulting dephasing are presented.Comment: An introductory review chapter to appear in a book published by World Scientifi

Gaussian Quantum Information

The science of quantum information has arisen over the last two decades centered on the manipulation of individual quanta of information, known as quantum bits or qubits. Quantum computers, quantum cryptography and quantum teleportation are among the most celebrated ideas that have emerged from this new field. It was realized later on that using continuous-variable quantum information carriers, instead of qubits, constitutes an extremely powerful alternative approach to quantum information processing. This review focuses on continuous-variable quantum information processes that rely on any combination of Gaussian states, Gaussian operations, and Gaussian measurements. Interestingly, such a restriction to the Gaussian realm comes with various benefits, since on the theoretical side, simple analytical tools are available and, on the experimental side, optical components effecting Gaussian processes are readily available in the laboratory. Yet, Gaussian quantum information processing opens the way to a wide variety of tasks and applications, including quantum communication, quantum cryptography, quantum computation, quantum teleportation, and quantum state and channel discrimination. This review reports on the state of the art in this field, ranging from the basic theoretical tools and landmark experimental realizations to the most recent successful developments.Comment: 51 pages, 7 figures, submitted to Reviews of Modern Physic

Observability of user-interfaces for linear hybrid systems under collaborative control

Human interaction with automation is ubiquitous, occurring in many cyberphysical systems such as cell phones, automobiles, and commercial aircraft. When interacting with such systems, human users are only exposed to a simplified representation the complex system structure in the form of an interface. The human can observe system outputs and make control inputs via this interface. Problems with human-automation interaction occur when the interface does not provide enough information or provides misinformation about the underlying system, such that the human cannot determine the current state of the automation. The user\u27s knowledge of the current system state and prediction of the next system state is required for effective operation of an automated system. In this work, formal methods are employed to analyze user-interfaces of such cyberphysical systems in order to reveal state observability problems. The cyberphysical systems are modeled as hybrid systems, for which continuous behavior emerges from the laws of physics and discrete behavior results from logical conditions and rules governing the automation. Hybrid systems with LTI continuous dynamics under collaborative control are considered, where collaborative control indicates that some events and inputs are controlled by a human operator while other events and inputs are controlled by the automation. The human user is assumed to be a special type of state observer, with additional requirements beyond a standard (automated) state observer. To reflect these additional requirements, sufficient conditions for user-observability and user-predictability of linear hybrid systems under collaborative control are developed. Algorithms are generated to evaluate a user-interface based on these conditions for user-observability and user-predictability. Then, the algorithms are applied to a hybrid system model abstraction of the longitudinal dynamics of an aircraft flight management system