Closed-loop Reference Models for Output-Feedback Adaptive Systems

Closed-loop reference models have recently been proposed for states accessible adaptive systems. They have been shown to have improved transient response over their open loop counter parts. The results in the states accessible case are extended to single input single output plants of arbitrary relative degree.Comment: v1 Submitted to European Control Conference 2013, v2 Typos correcte

Psychobiological factors of resilience and depression in late life.

In contrast to traditional perspectives of resilience as a stable, trait-like characteristic, resilience is now recognized as a multidimentional, dynamic capacity influenced by life-long interactions between internal and environmental resources. We review psychosocial and neurobiological factors associated with resilience to late-life depression (LLD). Recent research has identified both psychosocial characteristics associated with elevated LLD risk (e.g., insecure attachment, neuroticism) and psychosocial processes that may be useful intervention targets (e.g., self-efficacy, sense of purpose, coping behaviors, social support). Psychobiological factors include a variety of endocrine, genetic, inflammatory, metabolic, neural, and cardiovascular processes that bidirectionally interact to affect risk for LLD onset and course of illness. Several resilience-enhancing intervention modalities show promise for the prevention and treatment of LLD, including cognitive/psychological or mind-body (positive psychology; psychotherapy; heart rate variability biofeedback; meditation), movement-based (aerobic exercise; yoga; tai chi), and biological approaches (pharmacotherapy, electroconvulsive therapy). Additional research is needed to further elucidate psychosocial and biological factors that affect risk and course of LLD. In addition, research to identify psychobiological factors predicting differential treatment response to various interventions will be essential to the development of more individualized and effective approaches to the prevention and treatment of LLD

Phylogenetics, Population Genetics, and Evolution of the Mallard Complex

Speciation is primarily regarded as an ancestral split that results in two distinct taxonomic units, and proceeds in stages along a continuum from initiation (i.e., population divergence) to completion (i.e., reproductively isolated species). Establishing how and why populations diverge, including the primary mechanisms influencing these events is a major objective for evolutionary scientists. Focusing on incipient forms, researchers attempt to disentangle the antagonistic nature of selection, genetic drift, and gene flow in the speciation process. In chapter 1, I investigate the phylogenetic relationships of 14 closely related taxa within the mallard complex (Anas spp.) that underwent a radiation within the past one million years. Using mitochondrial DNA (mtDNA) and 20 nuclear loci for one to five individuals per taxon, I further examine how recombination and hybridization affect species tree reconstructions. In general, relationships within major clades were robust to treatment of recombination (i.e., ignoring or filtering) and inclusion or exclusion of hybridizing taxa, but branch lengths and posterior support were sensitive to both treatments. Of the 14 taxa, the most confounded relationships were those within the New World (NW) group comprising the sexually dichromatic mallard (Anas platyrhynchos) and the monochromatic American black duck (A. rubripes; black duck ), mottled duck (A. fulvigula), and Mexican duck (A. [p.] diazi). Finally, I address discordance between nuclear, morphometric, and mitochondrial trees, particularly with regard to the placement of the Hawaiian duck (A. wyvilliana), Philippine duck (A. luzonica), and two spot-billed ducks (A. zonorhyncha and A. poecilorhyncha) and discuss how alternative modes of speciation (i.e., hybrid speciation) may lead to variance in these relationships. In Chapter 2, I attempt to disentangle the evolutionary relationships of the New World (NW) group using mtDNA and 17 nuclear loci for a larger per taxon sample size (24-25 individuals per taxon). In general, whereas both Florida and Gulf Coast mottled ducks were differentiated from one another and from the other taxa (mean ΦST = 0.024 - 0.064), mallards, American black ducks, and Mexican duck were not significantly differentiated among nuclear markers (mean ΦST \u3c 0.020). Using coalescent methods to estimate rates of gene flow between mallards and each of the monochromatic taxa generally supported hybridization, but I could not reject complete isolation for any pairwise comparison. Furthermore, species tree reconstructions revealed that phylogenetic relationships were sensitive to stochastic sampling of individuals likely due to incomplete lineage sorting or hybridization. I conclude that members of the NW Mallard group appear to be adaptive incipient morphs, and that future work should focus on genomic regions under selection to better understand the stage and process of speciation in this group. In Chapter 3, I use restriction site associated DNA (RAD) sequencing methods to generate a pseudorandom sampling of 3,563 autosomal and 172 sex-linked (Z chromosome) markers scattered across the genome to more rigorously test the mechanism of speciation between Mexican ducks (N = 105 individuals from six Mexican states and two US states) and mallards (N = 17). Specifically, I aim to determine the stage of speciation and whether speciation has been driven by few loci with large effects versus many loci with small effects, plumage associated differentiation, or genetic drift. Marker comparisons between mallards and Mexican ducks revealed strong discordance among autosomal ΦST = 0.014), sex-linked (mean ΦST = 0.091), and mtDNA (ΦST = 0.12) markers. In general, divergence at autosomal loci followed a stepping stone model, with a gradual transition in genotypic frequencies from North to South

Adaptive Augmentation of an Optimal Baseline Controller for a Hypersonic Vehicle

The aim of this work is to design an adaptive augmentation of an optimal baseline controller for the flight dynamics of a HSV (HyperSonic Vehicle) using model-reference adaptive control (MRAC). The baseline controller is able to track a bounded input with a desired dynamic and with zero steady state error. The adaptive augmentation is used to compensate the ncertainties, due to a poor knowledge of the physical system, that may degrade the baseline closedloop performances. The main contribution of this paper is the combination of a MDZM and a projection operator together with two modifications, proposed by the authors, to improve the performances of the closed loop. The adaptive controller has been implemented in Simulink and integrated to a NASA X-30 model. Simulation results are provided to show the effectiveness of the augmented controller notably in presence of aerodynamic uncertainties and control degradations

Adaptive Output-Feedback Control for A Class of Multi-Input-Multi-Output Plants with Applications to Very Flexible Aircraft

A dominant presence of parametric model uncertainties necessitates an adaptive approach for control of very flexible aircraft (VFA). This paper proposes an adaptive controller that includes a baseline design based on observers and parameter adaptation based on a closed-loop reference model (CRM), and is applicable for a class of multi-input multi-output (MIMO) plants where number of outputs exceeds number of inputs. In particular, the proposed controller allows the plant to have first-order actuator dynamics and parametric uncertainties in both plant and actuator dynamics. Conditions are delineated under which this controller can guarantee stability and asymptotic reference tracking, and the overall design is validated using simulations on a nonlinear VFA model.Boeing Strategic University Initiativ

Supplementary Materials to "Adaptive Output-Feedback Control for A Class of Multi-Input-Multi-Output Plants with Applications to Very Flexible Aircraft"

A dominant presence of parametric model uncertainties motivates an adaptive approach for control of very flexible aircraft (VFA). This paper proposes an adaptive controller that includes a baseline design based on observers and parameter adaptation based on a closed-loop reference model (CRM), and is applicable for a class of multi-input multi-output (MIMO) plants where number of outputs exceeds number of inputs. In particular, the proposed controller allows the plant to have first-order actuator dynamics and parametric uncertainties in both plant and actuator dynamics. Conditions are delineated under which this controller can guarantee stability and asymptotic reference tracking, and the overall design is validated on a nonlinear VFA model.Boeing Strategic University Initiative