4,135 research outputs found
Kinematics and workspace analysis of a 3ppps parallel robot with u-shaped base
This paper presents the kinematic analysis of the 3-PPPS parallel robot with
an equilateral mobile platform and a U-shape base. The proposed design and
appropriate selection of parameters allow to formulate simpler direct and
inverse kinematics for the manipulator under study. The parallel singularities
associated with the manipulator depend only on the orientation of the
end-effector, and thus depend only on the orientation of the end effector. The
quaternion parameters are used to represent the aspects, i.e. the singularity
free regions of the workspace. A cylindrical algebraic decomposition is used to
characterize the workspace and joint space with a low number of cells. The
dis-criminant variety is obtained to describe the boundaries of each cell. With
these simplifications, the 3-PPPS parallel robot with proposed design can be
claimed as the simplest 6 DOF robot, which further makes it useful for the
industrial applications
Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2
Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy
Non-singular assembly mode changing trajectories in the workspace for the 3-RPS parallel robot
Having non-singular assembly modes changing trajectories for the 3-RPS
parallel robot is a well-known feature. The only known solution for defining
such trajectory is to encircle a cusp point in the joint space. In this paper,
the aspects and the characteristic surfaces are computed for each operation
mode to define the uniqueness of the domains. Thus, we can easily see in the
workspace that at least three assembly modes can be reached for each operation
mode. To validate this property, the mathematical analysis of the determinant
of the Jacobian is done. The image of these trajectories in the joint space is
depicted with the curves associated with the cusp points
An algebraic method to check the singularity-free paths for parallel robots
Trajectory planning is a critical step while programming the parallel
manipulators in a robotic cell. The main problem arises when there exists a
singular configuration between the two poses of the end-effectors while
discretizing the path with a classical approach. This paper presents an
algebraic method to check the feasibility of any given trajectories in the
workspace. The solutions of the polynomial equations associated with the
tra-jectories are projected in the joint space using Gr{\"o}bner based
elimination methods and the remaining equations are expressed in a parametric
form where the articular variables are functions of time t unlike any numerical
or discretization method. These formal computations allow to write the Jacobian
of the manip-ulator as a function of time and to check if its determinant can
vanish between two poses. Another benefit of this approach is to use a largest
workspace with a more complex shape than a cube, cylinder or sphere. For the
Orthoglide, a three degrees of freedom parallel robot, three different
trajectories are used to illustrate this method.Comment: Appears in International Design Engineering Technical Conferences &
Computers and Information in Engineering Conference , Aug 2015, Boston,
United States. 201
UBSegNet: Unified Biometric Region of Interest Segmentation Network
Digital human identity management, can now be seen as a social necessity, as
it is essentially required in almost every public sector such as, financial
inclusions, security, banking, social networking e.t.c. Hence, in today's
rampantly emerging world with so many adversarial entities, relying on a single
biometric trait is being too optimistic. In this paper, we have proposed a
novel end-to-end, Unified Biometric ROI Segmentation Network (UBSegNet), for
extracting region of interest from five different biometric traits viz. face,
iris, palm, knuckle and 4-slap fingerprint. The architecture of the proposed
UBSegNet consists of two stages: (i) Trait classification and (ii) Trait
localization. For these stages, we have used a state of the art region based
convolutional neural network (RCNN), comprising of three major parts namely
convolutional layers, region proposal network (RPN) along with classification
and regression heads. The model has been evaluated over various huge publicly
available biometric databases. To the best of our knowledge this is the first
unified architecture proposed, segmenting multiple biometric traits. It has
been tested over around 5000 * 5 = 25,000 images (5000 images per trait) and
produces very good results. Our work on unified biometric segmentation, opens
up the vast opportunities in the field of multiple biometric traits based
authentication systems.Comment: 4th Asian Conference on Pattern Recognition (ACPR 2017
Employer Attractiveness Through Social Media: A Phenomenological Study
The purpose of this paper is to gain insights into the subjective experience and perception of job seekers about the extensive use of social media as a source of recruitment and selection by the employers and its influence on the overall employer attractiveness. Four focus group interviews were conducted, audio-taped, transcribed, and analyzed by following the procedure of Interpretative Phenomenological Analysis (IPA) laid down by Smith and Osborn (2007). By employing IPA, the themes which emerged under the study are: ease of information; navigational usability and user friendliness; person-job fit and person-organization fit; reliability and timeliness; positive and cost effective marketing; value creation for the employers; and privacy concern. The present study posits to assist the human resource managers in formulating strategies pertaining to social media recruitment and selection so as to create an image of attractive employer. Although IPA has been predominantly used within health psychology, it has been uncommon in the recruitment literature so far. Since IPA is a phenomenological account of an individual’s personal experience and perception about an object or event, it allowed determining the richness of job seekers’ perception and the extent to which it is similar or different across each participant groups. Also, the current study is one of the pioneers in uncovering the perception of job seekers about social media recruitment and selection process in the Indian context
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