Adaptive control design with guaranteed margins for nonlinear plants

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 139-142).Adaptive control is one of the technologies that improve both performance and safety as controller parameters can be redesigned autonomously in the presence of uncertainties. Considerable research has been accomplished in adaptive control theory for several decades and a solid foundation has been laid out for stability and robustness of adaptive systems. However, a large gap between theory and practice has been an obstacle to transition theoretical results into applications and it still remains. In order to reduce the gap, this thesis presents a unified framework for design and analysis of adaptive control for general nonlinear plants.An augmented adaptive control architecture is proposed where a nominal controller is designed in the inner-loop with an adaptive controller in the outer-loop. The architecture is completed by addressing three separate problems. The first problem is the design of adaptive control in the presence of input constraints. With a rigorous stability analysis, an algorithm is developed to remove the adverse effects of multi-input magnitude saturation. The second problem is the augmentation of adaptive control with a nominal gain-scheduling controller. Though adaptive controllers have been employed with gain-scheduling to various applications, no formal stability analysis has been developed. In the proposed architecture, adaptive control is combined with gain-scheduling in a specific manner while stability is guaranteed. The third problem is the development of analytic stability margins of the closed-loop plant with the proposed adaptive controller. A time-delay margin is derived using standard Lyapunov stability analysis as an analytic stability margin.The overall adaptive control architecture as well as the analytically derived margins are validated by a 6-DoF nonlinear flight dynamics based on the NASA X-15 hypersonic aircraft. Simulation results show that the augmented adaptive control is able to stabilize the plant and tracks desired trajectories with uncertainties in the plant while instability cannot be overcome only with the nominal controller. The time-delay margins are validated based on a generic transport model and they are compared with margins obtained from simulations studies. We utilize numerical methods to find less conservative time-delay margins.by Jinho Jang.Ph.D

Trust and human performance in automated formation flight station-keeping

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005.Includes bibliographical references (p. 81-84).This thesis primarily describes performance and decision heuristics of human operators intervention with an autonomous formation flight (AFF) system during monitoring of a station-keeping display. Due to mental and physical workloads, automation technologies have been applied to formation flight for precise station-keeping and resultant fuel reduction, shifting control authority from humans to machines. Accordingly, the human is not directly in the control loop, but just supervises whether or not the automation works as intended. One critical problem in AFF supervisory control is that the human pilot needs to intervene with AFF system when the automated systems malfunction or their functions degrade. Thus while monitoring a station-keeping display, operators should minimize incorrect decisions for safety and cost reduction. To examine design issues in such a display, a simulation was constructed that simulated two different control systems as well as the impact of different angles of bank. 20 subjects participated in the monitoring task simulation of the station-keeping display. During the experiments, subjects were asked to intervene with AFF system when the AFF system failed to keep the trailing aircraft in the vortex area. Subjects made the most incorrect decisions when the AFF system was operated with the oscillating controller and high angle of bank.(cont.) Trust of the human in the AFF system was found to be influenced by the damping ratio of the AFF controller. Most significantly, results showed that humans developed biased decision criteria to execute interventions because velocity feedback of the wing tip on this display was not adequately provided.by Jinho Jang.S.M

Service platform strategy : social networking and mobile service platform perspectives

Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 99-101).The significance of the service platform is increasing, while studies on this phenomenon remain scarce and insufficient. Most of the researches focus on products, market segmentation and how platform triggers innovation and there's a lack of researches that focus on services, the fast growing industry nowadays. In analyzing the service platform, it is important to understand the interactions between different players, such as application developers, content providers, network operators, and users. For that purpose, a value network analysis which analyzes the interactions for creating value between the key players is more suitable than the common value chain analysis which is one-directional and sequential. This thesis adopts the value network approach in an attempt to analyze the two different types of service platform, that is, social networking platform and mobile service platform. The Social Networking Service (SNS) is evolving beyond the bounds of a simple personal network and is gradually transforming into a social networking platform where SNS information is used to develop various new services. This thesis examines the positioning and interaction of the key players for the social networking platform and the values that the key players can gain and capture. The mobile service platform is becoming more important, as 3G mobile technologies are mature and widespread and the smartphone market is growing rapidly. For the mobile service platform, the market players are engaged in a severe competition to control the market through various strategies. The biggest current issue in the mobile market is the movement to open platform strategy to build an ecosystem in which third-party developers can participate. This thesis also examines the positioning and interaction of the key players surrounding the mobile service platform and the values that the key players can gain and capture. Ultimately, this thesis aims to suggest service platform strategies for service platform providers and third party developers from the perspectives of social networking platform and mobile service platform. For that purpose, case studies are conducted in depth. In this thesis, the term "service platform" is defined as a set of interfaces provided for the development of applications or contents as service and software grow into one.by Jang Hoon Yoo.S.M.in Engineering and Managemen

Quantization of Higher Spin Superfields in the anti-de Sitter Superspace

We describe a Lagrangian quantization of the free massless gauge superfield theories of higher superspins both in the anti-de Sitter and flat global superspaces.Comment: 9 pages, LaTe

Evidence for muon neutrino oscillation in an accelerator-based experiment

We present results for muon neutrino oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced muon neutrino beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy dependent disappearance of muon neutrino, which we presume have oscillated to tau neutrino. The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).Comment: 5 pages, 4 figure

Search for Charmless Two-body Baryonic Decays of B Mesons

We report the results of a search for the rare baryonic decays $B^0 \to p\bar{p}$, $\Lambda\bar{\Lambda}$, and $B^+ \to p\bar{\Lambda}$. The analysis is based on a data set of $31.7\times 10^6 B\bar{B}$ events collected by the Belle detector at the KEKB $e^+e^-$ collider. No statistically significant signals are found, and we set branching fraction upper limits ${\mathcal B}(B^0 \to p\bar{p}) < 1.2 \times 10^{-6}$, ${\mathcal B}(B^0 \to \Lambda\bar{\Lambda}) < 1.0 \times 10^{-6}$, and ${\mathcal B}(B^+ \to p\bar{\Lambda}) < 2.2 \times 10^{-6}$ at the 90% confidence level.Comment: 6 pages, 4 figures and 1 table. Submitted to Phys. Rev. D Rapid Communication

Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya

Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization

Some Consequences of Thermosolutal Convection: The Grain Structure of Castings

The essential principles of thermosolutal convection are outlined, and how convection provides a transport mechanism between the mushy region of a casting and the open bulk liquid is illustrated. The convective flow patterns which develop assist in heat exchange and macroscopic solute segregation during solidification; they also provide a mechanism for the transport of dendritic fragments from the mushy region into the bulk liquid. Surviving fragments become nuclei for equiaxed grains and so lead to blocking of the parental columnar, dendritic growth front from which they originated. The physical steps in such a sequence are considered and some experimental data are provided to support the argument

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012