Prescribing Transient and Asymptotic Behavior to Deterministic Systems with Stochastic Initial Conditions

We study a containment control problem (CCP) and a shape control problem (SCP) for systems whose initial condition is a random variable with known distribution. The two control problems both require exponential convergence to a desired trajectory, which is complemented by either; i) a required cumulative distribution over a prescribed containment set at a specific transient time for the CCP, or; ii) a maximum distance between an attained and a desired probability density function of the state for the SCP. For the CCP, we obtain solutions for both linear and nonlinear systems by designing the closed-loop such that the initial pdf shrinks or contracts to a desired trajectory. For the SCP, we obtain solutions for linear systems and an admissible desired pdf, by designing the closed-loop such that the evolution of the pdf at the transient time is similar to the target pdf

Toward controlled ultra-high vacuum chemical vapor deposition processes

How will we push our thin film performances to new heights? This is one of the central questions for researchers in this field. The functionality of the thin films is key to the performance of many of our components, which are used in products ranging from cameras and cars to satellites. Our goal is to produce these components with exactly the desired properties for the job at hand. One of the methods for achieving this is by increasing the purity of the film, through a reduction of unwanted molecular structures in the thin film layer. This effort is comparable to building a bridge with a desired stiffness. Applying unintended materials or constructions will change the stiffness properties of the bridge and make the job very difficult. For thin films, this has to be done at nanoscale level, where a small amount of misplaced molecules can already cause a noticeable performance difference. In our work, we present methods to build desired structures with the highest attainable purity. Problems that arise in trying to achieve this are related to how well we can construct the thin film that we want, while we operate in the circumstances that allow for the highest purity. To solve some of these problems, we have implemented a measurement apparatus that allows us to more accurately select the building blocks for the thin films. In doing so, we are apparently the first to actively control atomic partial pressure levels in an ultra-high vacuum environment through feedback

Toward observable UHVCVD:Modeling of flow dynamics and AAS partial pressure measurement implementation

Ultra-high vacuum chemical vapor deposition is a thin film deposition process that features excellent film purity, but is sensitive to the processing variations (such as, the precursors and their dispensers, the reactor’s initial condition, etc.). In this paper, we present the design of a ultra-high vacuum chemical vapor deposition reactor with in-situ partial pressure atomic absorption spectroscopy measurement that improves reproducibility and observability of such a process. Our main contributions are: (i). a conceptual control systems design of ultra-high vacuum chemical vapor deposition; (ii). atomic absorption spectroscopy based sensor design for the real-time in-situ partial pressure measurements; (iii). a flux dynamical model; (iv). experimental reactor design; and (v). experimental validation of model components and the atomic absorption spectroscopy measurement technique. Our results show that the proposed sensor systems are able to provide real-time measurements of the partial pressure inside the reactor and our proposed flux dynamical model agrees with the measured partial pressure. The latter allows us to use it in the design of model-based output feedback control of the partial pressure