Analog implementation of an integral resonant control scheme

Integral resonant control (IRC) has been introduced as a high performance controller design methodology for flexible structures with collocated actuator–sensor pairs. IRC has a simple structure and is capable of achieving significant damping, over several modes, while guaranteeing closed-loop stability of the system in the presence of unmodeled out-of-bandwidth dynamics. IRC can be an ideal controller for various industrial damping applications, if packaged in a simple easy-to-implement electronic module. This work proposes an analog implementation of the IRC scheme using a single Op-Amp circuit. The objective is to show that with simple analog realization of the modified IRC scheme, it is possible to damp a large number of vibration modes. A brief discussion about the modeling, circuit considerations, implementation and experimental results is presented in order to validate the usefulness and practicality of the proposed analog IRC implementation

High-bandwidth control of a piezoelectric nanopositioning stage in the presence of plant uncertainties

Inversion-based feedforward techniques have been known to deliver accurate tracking performance in the absence of plant parameter uncertainties. Piezoelectric stack actuated nanopositioning platforms are prone to variations in their system parameters such as resonance frequencies, due to changes in operating conditions like ambient temperature, humidity and loading. They also suffer from nonlinear effects of hysteresis, an inherent property of a piezoelectric actuator; charge actuation is applied to reduce the effects of hysteresis. In this work, we propose and test a technique that integrates a suitable feedback controller to reduce the effects of parameter uncertainties with the inversion-based feedforward technique. It is shown experimentally that the combination of damping, feedforward and charge actuation increases the tracking bandwidth of the platform from 310 to 1320 Hz

Global Gene Expression Analysis Reveals Evidence for Decreased Lipid Biosynthesis and Increased Innate Immunity in Uninvolved Psoriatic Skin

Psoriasis is a genetically determined inflammatory skin disease. Although the transition from uninvolved into lesional skin is accompanied by changes in the expression of multiple genes, much less is known about the difference between uninvolved skin from psoriatic patients as opposed to skin from normal individuals. Multiple biochemical and morphological changes were reported decades ago in uninvolved psoriatic skin but remain poorly understood. Here, we show dysregulation of 223 transcripts representing 179 unique genes in uninvolved psoriatic skin, 178 of which were not previously known to be altered in their expression. The proteins encoded by these transcripts are involved in lipid metabolism, antimicrobial defenses, epidermal differentiation, and control of cutaneous vasculature. Cluster analysis of transcripts with significantly altered expression identified a group of genes involved in lipid metabolism with highly correlated gene expression. Promoter analysis showed enrichment for binding sites of three transcription factors; peroxisome proliferator-activator receptor alpha (PPARA), sterol regulatory element-binding protein (SREBF), and estrogen receptor 2 (ESR2), suggesting that the coordinate regulation of lipid metabolic genes may be related to the action of these factors. Taken together, our results identify a “pre-psoriatic” gene expression signature, suggesting decreased lipid biosynthesis and increased innate immunity in uninvolved psoriatic skin