Bijoy K. Ghosh

Pose estimation using line-based dynamic vision and inertial sensors

An observer problem from a computer vision application is studied. Rigid body pose estimation using inertial sensors and a monocular camera is considered and it is shown how rotation estimation can be decoupled from position estimation. Orientation estimation is formulated as an observer problem with implicit output where the states evolve on SO(3). A careful observability study reveals interesting group theoretic structures tied to the underlying system structure. A locally convergent observer where the states evolve on SO (3) is proposed and numerical estimates of the domain of attraction is given. Further, it is shown that, given convergent orientation estimates, position estimation can be formulated as a linear implicit output problem. From an applications perspective, it is outlined how delayed low bandwidth visual observations and high bandwidth rate gyro measurements can provide high bandwidth estimates. This is consistent with real-time constraints due to the complementary characteristics of the sensors which are fused in a multirate way.

Visually guided ranging from observations of points, lines and curves via an identifier based nonlinear observer

Abstract In this paper we consider the problem of estimating the range information of features on an affine plane in R 3 by observing its image with the aid of a CCD camera, wherein we assume that the camera is undergoing a known motion. The features considered are points, lines and planar curves located on planar surfaces of static objects. The dynamics of the moving projections of the features on the image plane have been described as a suitable differential equation on an appropriate feature space. This dynamics is used to estimate feature parameters from which the range information is readily available. In this paper the proposed identification has been carried out via a newly introduced identifier based observer. Performance of the observer has been studied via simulation.

Sensor-based hybrid position/force control of a robot manipulator in an uncalibrated environment

The paper is devoted to the problem of controlling a robot manipulator for a class of constrained motions. The task under consideration is to control the manipulator, such that the end-effector follows a path on an unknown surface, with the aid of a single camera assumed to be uncalibrated with respect to the robot coordinates. To accomplish a task of this kind, we propose a new control strategy based on multisensor fusion. We assume that three different sensors-that is, encoders mounted at each joint of the robot with six degrees of freedom, a force-torque sensor mounted at the wrist of the manipulator, and a visual sensor with a single camera fixed to the ceiling of the workcell-are available. Also, we assume that the contact point between the tool grasped by the end-effector and the surface is frictionless. To describe the proposed algorithm that we have implemented, first we decouple the vector space of control variables into two subspaces. We use one for controlling the magnitude of the contact force on the surface and the other for controlling the constrained motion on the surface. This way, the control synthesis problem is decoupled and we are able to develop a new scheme that utilizes sensor fusion to handle uncalibrated parameters in the workcell, wherein the surface on which the task is to be performed is assumed to be visible, but has an a priori unknown position.

Line segment based map building and localization using 2D laser rangefinder

We study a new scheme for map building and describe localization techniques for a mobile robot equipped with a 2D laser rangefinder. We propose to use line segments as the basic element for the purpose of localization and to build the map. Line segments do provide considerable geometric information about the scene that can also be used for accurate and fast localization. We introduce a new closed line segment (CLS) map which consists of only line segments and defines a closed and connected region. Virtual line segments are drawn, for the spots that do not adequately describe a line segment on the range data. These are further explored via navigation and we argue that the CLS map provides an efficient mobile robot exploration scheme. All these techniques have been implemented on our Nomad XR4000 mobile robot and results are described in this paper.

The genome of Cyanothece 51142, a unicellular diazotrophic cyanobacterium important in the marine nitrogen cycle

Unicellular cyanobacteria have recently been recognized for their contributions to nitrogen fixation in marine environments, a function previously thought to be filled mainly by filamentous cyanobacteria such as Trichodesmium. To begin a systems level analysis of the physiology of the unicellular N2-fixing microbes, we have sequenced to completion the genome of Cyanothece sp. ATCC 51142, the first such organism. Cyanothece 51142 performs oxygenic photosynthesis and nitrogen fixation, separating these two incompatible processes temporally within the same cell, while concomitantly accumulating metabolic products in inclusion bodies that are later mobilized as part of a robust diurnal cycle. The 5,460,377-bp Cyanothece 51142 genome has a unique arrangement of one large circular chromosome, four small plasmids, and one linear chromosome, the first report of a linear element in the genome of a photosynthetic bacterium. On the 429,701-bp linear chromosome is a cluster of genes for enzymes involved in pyruvate metabolism, suggesting an important role for the linear chromosome in fermentative processes. The annotation of the genome was significantly aided by simultaneous global proteomic studies of this organism. Compared with other nitrogen-fixing cyanobacteria, Cyanothece 51142 contains the largest intact contiguous cluster of nitrogen fixation-related genes. We discuss the implications of such an organization on the regulation of nitrogen fixation. The genome sequence provides important information regarding the ability of Cyanothece 51142 to accomplish metabolic compartmentalization and energy storage, as well as how a unicellular bacterium balances multiple, often incompatible, processes in a single cell.

Global proteomics reveal an atypical strategy for carbon/nitrogen assimilation by a cyanobacterium under diverse environmental perturbations

Cyanobacteria, the only prokaryotes capable of oxygenic photosynthesis, are present in diverse ecological niches and play crucial roles in global carbon and nitrogen cycles. To proliferate in nature, cyanobacteria utilize a host of stress responses to accommodate periodic changes in environmental conditions. A detailed knowledge of the composition of, as well as the dynamic changes in, the proteome is necessary to gain fundamental insights into such stress responses. Toward this goal, we have performed a large-scale proteomic analysis of the widely studied model cyanobacterium Synechocystis sp. PCC 6803 under 33 different environmental conditions. The resulting high-quality dataset consists of 22,318 unique peptides corresponding to 1955 proteins, a coverage of 53% of the predicted proteome. Quantitative determination of protein abundances has led to the identification of 1198 differentially regulated proteins. Notably, our analysis revealed that a common stress response under various environmental perturbations, irrespective of amplitude and duration, is the activation of atypical pathways for the acquisition of carbon and nitrogen from urea and arginine. In particular, arginine is catabolized via putrescine to produce succinate and glutamate, sources of carbon and nitrogen, respectively. This study provides the most comprehensive functional and quantitative analysis of the Synechocystis proteome to date, and shows that a significant stress response of cyanobacteria involves an uncommon mode of acquisition of carbon and nitrogen.

Some new results on the simultaneous stabilizability of a family of single input, single output systems

Abstract In this paper, we obtain sufficiency conditions on the problem of simultaneous stabilization of a parameterized family of single input, single output plants by a non-switching compensator. The sufficiency conditions include simultaneous stabilization and simultaneous pole assignment of a finite number of plants.

Arabidopsis Transcriptome Reveals Control Circuits Regulating Redox Homeostasis and the Role of an AP2 Transcription Factor

Sensors and regulatory circuits that maintain redox homeostasis play a central role in adjusting plant metabolism and development to changing environmental conditions. We report here control networks in Arabidopsis (Arabidopsis thaliana) that respond to photosynthetic stress. We independently subjected Arabidopsis leaves to two commonly used photosystem II inhibitors: high light (HL) and 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Microarray analysis of expression patterns during the period of redox adjustment to these inhibitors reveals that 20% and 8% of the transcriptome are under HL and DCMU regulation, respectively. Approximately 6% comprise a subset of genes common to both perturbations, the redox responsive genes (RRGs). A redox network was generated in an attempt to identify genes whose expression is tightly coordinated during adjustment to homeostasis, using expression of these RRGs under HL conditions. Ten subnetworks were identified from the network. Hierarchal subclustering of subnetworks responding to the DCMU stress identified novel groups of genes that were tightly controlled while adjusting to homeostasis. Upstream analysis of the promoters of the genes in these clusters revealed different motifs for each subnetwork, including motifs that were previously identified with responses to other stresses, such as light, dehydration, or abscisic acid. Functional categorization of RRGs demonstrated involvement of genes in many metabolic pathways, including several families of transcription factors, especially those in the AP2 family. Using a T-DNA insertion in one AP2 transcription factor (redox-responsive transcription factor 1 [RRTF1]) from the RRGs, we showed that the genes predicted to be within the subnetwork containing RRTF1 were changed in this insertion line (Δrrtf1). Furthermore, Δrrtf1 showed greater sensitivity to photosynthetic stress compared to the wild type.

Some Problems In Perspective System Theory And Its Application To Machine Vision

This paper introduces identifiability problems that arise in linear dynamical systems with perspective observation function. Such a perspective problem finds its application in the field of Computer Vision specifically in the area of motion estimation of a rigid body with point, line or curve correspondence. The basic result of this paper is to study the correspondence problems in an unifying framework and it is shown that these problems arise as a special case of a more general Perspective System Problem. Problems in perspective system theory introduced in this paper are new.

Plasticity of the Systemic Inflammatory Response to Acute Infection during Critical Illness: Development of the Riboleukogram

Background Diagnosis of acute infection in the critically ill remains a challenge. We hypothesized that circulating leukocyte transcriptional profiles can be used to monitor the host response to and recovery from infection complicating critical illness. Methodology/Principal Findings A translational research approach was employed. Fifteen mice underwent intratracheal injections of live P. aeruginosa, P. aeruginosa endotoxin, live S. pneumoniae, or normal saline. At 24 hours after injury, GeneChip microarray analysis of circulating buffy coat RNA identified 219 genes that distinguished between the pulmonary insults and differences in 7-day mortality. Similarly, buffy coat microarray expression profiles were generated from 27 mechanically ventilated patients every two days for up to three weeks. Significant heterogeneity of VAP microarray profiles was observed secondary to patient ethnicity, age, and gender, yet 85 genes were identified with consistent changes in abundance during the seven days bracketing the diagnosis of VAP. Principal components analysis of these 85 genes appeared to differentiate between the responses of subjects who did versus those who did not develop VAP, as defined by a general trajectory (riboleukogram) for the onset and resolution of VAP. As patients recovered from critical illness complicated by acute infection, the riboleukograms converged, consistent with an immune attractor. Conclusions/Significance Here we present the culmination of a mouse pneumonia study, demonstrating for the first time that disease trajectories derived from microarray expression profiles can be used to quantitatively track the clinical course of acute disease and identify a state of immune recovery. These data suggest that the onset of an infection-specific transcriptional program may precede the clinical diagnosis of pneumonia in patients. Moreover, riboleukograms may help explain variance in the host response due to differences in ethnic background, gender, and pathogen. Prospective clinical trials are indicated to validate our results and test the clinical utility of riboleukograms.