Localization of visually indistinguishable mature lettuce heads using spatial information

This paper describes an approach to recognizing and localizing centers of mature lettuce heads in the field when the lettuce leaves obscure the distinctions between plants. This is of great value when using an automatic harvester in cluttered or closely planted vegetation. The aim of this work is to investigate and verify the potential use of spatial rather than visual clues for recognition and localization, with a view to implementing a more robust and sophisticated system if promise is shown. Colour/texture information was difficult to use so spatial information was used instead. A laser range finder was used to generate a height plot from above the plants. Lettuce examples were used to learn the radial distribution of the lettuce model. This was compared with the distributions of arbitrary locations in new scans to locate possible lettuce locations. Planting distance information was then used to localize the final lettuce positions. The algorithm was able to successfully locate 15 out of 16 sample lettuces

Classification of Bidens in wheat farms

Bidens pilosa L (commonly known as cobbler's peg) is an annual broad leaf weed widely distributed in tropical and subtropical regions of the world and is reported to be a weed of 31 crops including wheat. Automatic detection of Bidens in wheat farms is a nontrivial problem due to their similarity in color and presence of occlusions. This paper proposes a methodology which could be used to discriminate Bidens from wheat to be used in operations such as autonomous weed destruction. A spectrometer is used to analyze the optical properties of Bidens and wheat leaves while achieving high classification results. However, due to the practical constraints of using spectrometers, a color camera based technique is proposed. It is shown that the color based segmentation followed by shape based validation algorithm gives rise to high detection rates with lower false detections. We have experimentally evaluated the algorithm with Bidens detection rate of 80% and a 10% false alarm rate

MPC and PSO based control methodology for path tracking of 4WS4WD vehicles

© 2018 by the authors. Four wheel steering and four wheel drive (4WS4WD) vehicles are over-actuated systems with superior performance. Considering the control problem caused by the system nonlinearity and over-actuated characteristics of the 4WS4WD vehicle, this paper presents two methods to enable a 4WS4WD vehicle to accurately follow a predefined path as well as its reference trajectories including velocity and acceleration profiles. The methodologies are based on model predictive control (MPC) and particle swarm optimization (PSO), respectively. The MPC method generates the virtual inputs in the upper controller and then allocates the actual inputs in the lower controller using sequential quadratic programming (SQP), whereas the PSO method is proposed as a fully optimization based method for comparison. Both methods achieve optimization of the steering angles and wheel forces for each of four independent wheels simultaneously in real time. Simulation results achieved by two different controllers in following the reference path with varying disturbances are presented. Discussion about two methodologies is provided based on their theoretical analysis and simulation results

Dual RNA sequencing of group B Streptococcus-infected human monocytes reveals new insights into host–pathogen interactions and bacterial evasion of phagocytosis

Streptococcus agalactiae, also known as Group B Streptococcus (GBS) is a frequent cause of infections, including bacteraemia and other acute diseases in adults and immunocompromised individuals. We developed a novel system to study GBS within human monocytes to define the co-transcriptome of intracellular GBS (iGBS) and host cells simultaneously using dual RNA-sequencing (RNA-seq) to better define how this pathogen responds to host cells. Using human U937 monocytes and genome-sequenced GBS reference strain 874,391 in antibiotic protection assays we validated a system for dual-RNA seq based on measures of GBS and monocyte viability to ensure that the bacterial and host cell co-transcriptome reflected mainly intracellular (iGBS) rather than extracellular GBS. Elucidation of the co-transcriptome revealed 1119 dysregulated transcripts in iGBS with most genes, including several that encode virulence factors (e.g., scpB, hvgA, ribD, pil2b) exhibiting activation by upregulated expression. Infection with iGBS resulted in significant remodelling of the monocyte transcriptome, with 7587 transcripts differentially expressed including 7040 up-regulated and 547 down-regulated. qPCR confirmed that the most strongly activated genes included sht, encoding Streptococcal Histidine Triad Protein. An isogenic GBS mutant strain deficient in sht revealed a significant effect of this gene on phagocytosis of GBS and survival of the bacteria during systemic infection in mice. Identification of a novel contribution of sht to GBS virulence shows the co-transcriptome responses elucidated in GBS-infected monocytes help to shape the host–pathogen interaction and establish a role for sht in the response of the bacteria to phagocytic uptake. This study provides comprehension of concurrent transcriptional responses that occur in GBS and human monocytes that shape the host–pathogen interaction

Streptococcus agalactiae glyceraldehyde-3-phosphate dehydrogenase (GAPDH) elicits multiple cytokines from human cells and has a minor effect on bacterial persistence in the murine female reproductive tract

Streptococcus agalactiae glyceraldehyde 3-phosphate dehydrogenase (GAPDH), encoded by gapC, is a glycolytic enzyme that is associated with virulence and immune-mediated protection. However, the role of GAPDH in cellular cytokine responses to S. agalactiae, bacterial phagocytosis and colonization of the female reproductive tract, a central host niche, is unknown. We expressed and studied purified recombinant GAPDH (rGAPDH) of S. agalactiae in cytokine elicitation assays with human monocyte-derived macrophage, epithelial cell, and polymorphonuclear leukocyte (PMN) co-culture infection models. We also generated a S. agalactiae mutant that over-expresses GAPDH (oeGAPDH) from gapC using a constitutively active promoter, and analyzed the mutant in murine macrophage antibiotic protection assays and in virulence assays in vivo, using a colonization model that is based on experimental infection of the reproductive tract in female mice. Human cell co-cultures produced interleukin (IL)-1β, IL-6, macrophage inflammatory protein (MIP)-1, tumor necrosis factor (TNF)-α and IL-10 within 24 h of exposure to rGAPDH. PMNs were required for several of these cytokine responses. However, over-expression of GAPDH in S. agalactiae did not significantly affect measures of phagocytic uptake compared to an empty vector control. In contrast, oeGAPDH-S. agalactiae showed a small but statistically significant attenuation for persistence in the reproductive tract of female mice during the chronic phase of infection (10–28 days post-inoculation), relative to the vector control. We conclude that S. agalactiae GAPDH elicits production of multiple cytokines from human cells, and over-expression of GAPDH renders the bacterium more susceptible to host clearance in the female reproductive tract. One-sentence summary: This study shows Streptococcus agalactiae glyceraldehyde 3-phosphate dehydrogenase, an enzyme that functions in glycolysis, gluconeogenesis and virulence, modifies phagocytosis outcomes, including cytokine synthesis, and affects bacterial persistence in the female reproductive tract

Vision assisted tracking and time optimal acquisition of moving objects using a manipulator

status: publishe

Force control for path following of a 4WS4WD vehicle by the integration of PSO and SMC

© 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group. The aim of this paper is to present a novel control method for a four-wheel steer and four-wheel drive (4WS4WD) vehicle. The novelty is in the integration of sliding mode control (SMC) and particle swarm optimization (PSO) that is proposed to solve the control problem caused by the nonlinear, highly coupled and over-actuated characteristics of the four-wheel steer and four-wheel drive (4WS4WD) vehicle. The validity of the control method is evaluated by two criterions, namely path following performance assessed by the vehicle's position errors with respect to the reference path, and motion quality reflected by the smoothness of vehicle's velocities and accelerations. In vehicle modelling, a kinematic model and a dynamic model considering all slip forces are proposed for the controller design. Simulation results are provided to demonstrate the applicability of the proposed methodology and its robustness

Integration of sliding mode based steering control and PSO based drive force control for a 4WS4WD vehicle

© 2017, Springer Science+Business Media, LLC. The aim of this paper is to present a novel approach to enable a four-wheel steer four-wheel drive (4WS4WD) vehicle to follow a predefined path under force control. The novelty is in the combination of a sliding mode controller that determines the steering angles using a kinematic model and a real-time particle swarm optimization based controller that determines the drive torques using a dynamic model. The dynamic model takes into account all the slip forces acting on the vehicle. The combined controllers are then used to drive the 4WS4WD vehicle to follow a path. In order to enable the implementation of the controllers, the path to be followed is generated using 7-order Bézier curves that can provide smooth kinematic and dynamic reference profiles. Simulation results are provided to demonstrate the applicability of the proposed methodology and its robustness