Controlled manipulation using autonomous aerial systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 134-135).The main focus of the thesis is to design and control Autonomous Aerial Systems, also referred to as Unmanned Aerial Vehicles (UAVs). UAVs are able to hover and navigate in space using the thrust forces generated by the propellers. One of the simplest such vehicles that is widely used is a Quadrotor. While UAVs have been predominantly used for "fly and sense" applications, very few investigations have focused on using them to perform manipulation by contact. The latter is challenging because of the dual goal of performing manipulation and maintaining stable flight. Because Quadrotors can quickly reach a location, their ability to manipulate can be impactful in many scenarios. While efficient flight control of Quadrotor has been an active research area, using Quadrotor to perform manipulation is novel and challenging. In this thesis, a range of Quadrotor designs and control strategies are proposed in order to carry out autonomous manipulation of objects. We first derive a dynamic model of the Quadrotor that accounts for the presence of contact, object dynamics and kinematics. To improve manipulation performance, a passive light-weight end-effector interface between the Quadrotor and the object is proposed. The complexity of the dynamics is systematically reduced by making certain assumptions. The resulting dynamic model is divided into nonlinear subsystems on the basis of their degrees of freedom, for each of which separate controllers are designed. An efficient docking approach is proposed that permits fast and aggressive docking, even at very high speeds. Because a single Quadrotor UAS is limited in manipulation capability, a multi Quadrotor cooperative manipulation scheme is proposed. Control strategies are proposed to deal with kinematic and parametric uncertainties. A manipulation scheme to open a door with unknown hinge location is proposed. A nonlinear adaptive controller is implemented to perform efficient tracking in the presence of parametric uncertainty. In order to improve robustness to accidental contacts, a novel flexible Quadrotor, denoted as ParaFlex, is designed. The advantages of ParaFlex over a rigid Quadrotor are demonstrated. A Simulation, Test and Validation Environment (STeVE) is developed to facilitate smooth and efficient transition from design process to simulation to experiments.by Manohar B. Srikanth.Ph.D

Identification and authentication of Agnimantha plant species used in Ayurveda on the basis of anatomical and molecular phylogenetic analysis

Agnimantha plant species have been used in the Ayurvedic system of medicine for many years and is widely used as an ingredient in many ayurvedic formulations. However, the source for Agnimantha remained controversial as it is difficult to authenticate from various reports. Hence, the present study aims to identify and authenticate its original and substitute sources. As per the literature sources Clerodendrum phlomidis L.f., C. inerme (L.) Gaertn. and Premna serratifolia L. are considered Agnimantha species. The anatomy of the above mentioned species confirmed the presence of patches of up to 20 cells in the sclerenchyma of the root cortex, while in the absence of sclerenchyma of the stem cortex, abundant chambered crystals were also present in the bark of the stem and root in C. phlomidis as compared to C. inerme and P. serratifolia. Phylogenetic analysis using chloroplast (matK, trnH-psbA) and nuclear markers (ITS, rbcl) also indicates the close relation between C. inerme and P. serratifolia and hence places them both in the same clade, though C. phlomidis is closely related to the other species but placed in the adjacent clade. Hence, the study concludes that anatomical as well as molecular phylogenetic analysis reflect close relation between C. inerme and P. serratifolia. while a distant relation with C. phlomidis

Rendering stiffer walls: a hybrid haptic system using continuous and discrete time feedback

Instability in conventional haptic rendering destroys the perception of rigid objects in virtual environments. Inherent limitations in the conventional haptic loop restrict the maximum stiffness that can be rendered. In this paper we present a method to render virtual walls that are much stiffer than those achieved by conventional techniques. By removing the conventional digital haptic loop and replacing it with a part-continuous and part-discrete time hybrid haptic loop, we were able to render stiffer walls. The control loop is implemented as a combinational logic circuit on an field-programmable gate array. We compared the performance of the conventional haptic loop and our hybrid haptic loop on the same haptic device, and present mathematical analysis to show the limit of stability of our device. Our hybrid method removes the computer-intensive haptic loop from the CPU-this can free a significant amount of resources that can be used for other purposes such as graphical rendering and physics modeling. It is our hope that, in the future, similar designs will lead to a haptics processing unit (HPU)

Multicode MIMO for high data rate mobile ad-hoc networks

Abstract—In a mobile ad-hoc network scenario, where communication nodes are mounted on moving platforms (like jeeps, trucks, tanks, etc.), use of V-BLAST requires that the number of receive antennas in a given node must be greater than or equal to the sum of the number of transmit antennas of all its neighbor nodes. This limits the achievable spatial multiplexing gain (data rate) for a given node. In such a scenario, we propose to achieve high data rates per node through multicode direct sequence spread spectrum techniques in conjunction with V-BLAST. In the considered multicode V-BLAST system, the receiver experiences code domain interference (CDI) in frequency selective fading, in addition to space domain interference (SDI) experienced in conventional V-BLAST systems. We propose two interference cancelling receivers that employ a linear parallel interference cancellation approach to handle the CDI, followed by conventional V-BLAST detector to handle the SDI, and then evaluate their bit error rates. Keywords – Mobile ad-hoc networks, multicode V-BLAST, code domain interference, space domain interference, interference cancellation. I

“EFFECT OF NOVEL CORONA VIRUS ON MENTAL HEALTH OF MEDICAL AND NURSING PROFESSIONALS IN A TERTIARY CARE HOSPITAL”: EFFECT OF NOVEL CORONA VIRUS ON MENTAL HEALTH OF MEDICAL AND NURSING PROFESSIONALS

Objectives: The current study was planned to estimate the prevalence and pattern of physical symptoms and to identify the association between demographic, clinical variables and physical symptoms with mental health status. Methods: Medical and nursing professionals involved in COVID-19 care in a tertiary care hospital were invited to participate in a cross sectional study by using a self-administered online questionnaire within the period from November 2020 to February 2021. This online questionnaire collected information on demographic variables, clinical variables and physical symptoms prevalence in the last month and the responses to the Impact of Events Scale-Revised (IES-R) instrument. The association between demographic, clinical variables and physical symptoms with mental health were evaluated by linear regression. Results: A total of 143 participated with the mean age of 41.82 ± 7.26 years. IES-R scale which measured psychological impacts showed a mean score of 17.35 ± 12.53 and most of the participants 97 (67.8%) had minimal psychological impact. However, presence of physical symptom (anxiety) and coming in contact with suspected or infected materials predicted higher psychological impact and showed statistically significant association (p = 0.001). Conclusion: One third of the study participants showed psychological impact ranging from mild to moderate grade. This shows that mental health issues are on the rise which is often underdiagnosed, need to be focussed and plan interventions by policy makers

Visibility volumes for interactive path optimization

Abstract We describe a real-time system that supports design of optimal flight paths over terrains. These paths either maximize view coverage or minimize vehicle exposure to ground. A volume-rendered display of multi-viewpoint visibility and a haptic interface assists the user in selecting, assessing, and refining the computed flight path. We design a three-dimensional scalar field representing the visibility of a point above the terrain, describe an efficient algorithm to compute the visibility field, and develop visual and haptic schemes to interact with the visibility field. Given the origin and destination, the desired flight path is computed using an efficient simulation of an articulated rope under the influence of the visibility gradient. The simulation framework also accepts user input, via the haptic interface, thereby allowing manual refinement of the flight path

Genetic mapping identified three hotspot genomic regions and candidate genes controlling heat tolerance-related traits in groundnut

Groundnut productivity and quality have been impeded by rising temperatures in semi-arid environments. Hence, understanding the effects and molecular mechanisms of heat stress tolerance will aid in tackling yield losses. In this context, a recombinant inbred line (RIL) population was developed and phenotyped for eight seasons at three locations for agronomic, phenological, and physiological traits under heat stress. A genetic map was constructed using genotyping-by-sequencing with 478 single-nucleotide polymorphism (SNP) loci spanning a map distance of 1,961.39 cM. Quantitative trait locus (QTL) analysis using phenotypic and genotypic data identified 45 major main-effect QTLs for 21 traits. Intriguingly, three QTL clusters (Cluster-1-Ah03, Cluster-2-Ah12, and Cluster-3-Ah20) harbor more than half of the major QTLs (30/45, 66.6%) for various heat tolerant traits, explaining 10.4%–38.6%, 10.6%–44.6%, and 10.1%–49.5% of phenotypic variance, respectively. Furthermore, important candidate genes encoding DHHC-type zinc finger family protein (arahy.J0Y6Y5), peptide transporter 1 (arahy.8ZMT0C), pentatricopeptide repeat-containing protein (arahy.4A4JE9), Ulp1 protease family (arahy.X568GS), Kelch repeat F-box protein (arahy.I7X4PC), FRIGIDA-like protein (arahy.0C3V8Z), and post-illumination chlorophyll fluorescence increase (arahy.92ZGJC) were the underlying three QTL clusters. The putative functions of these genes suggested their involvement in seed development, regulating plant architecture, yield, genesis and growth of plants, flowering time regulation, and photosynthesis. Our results could provide a platform for further fine mapping, gene discovery, and developing markers for genomics-assisted breeding to develop heat-tolerant groundnut varieties