6,050 research outputs found
Rotation symmetry axes and the quality index in a 3D octahedral parallel robot manipulator system
The geometry of a 3D octahedral parallel robot manipulator system is specified in terms of two rigid octahedral structures (the fixed and moving platforms) and six actuation legs. The symmetry of the system is exploited to determine the behaviour of (a new version of) the quality index for various motions. The main results are presented graphically
Fast Monte-Carlo Localization on Aerial Vehicles using Approximate Continuous Belief Representations
Size, weight, and power constrained platforms impose constraints on
computational resources that introduce unique challenges in implementing
localization algorithms. We present a framework to perform fast localization on
such platforms enabled by the compressive capabilities of Gaussian Mixture
Model representations of point cloud data. Given raw structural data from a
depth sensor and pitch and roll estimates from an on-board attitude reference
system, a multi-hypothesis particle filter localizes the vehicle by exploiting
the likelihood of the data originating from the mixture model. We demonstrate
analysis of this likelihood in the vicinity of the ground truth pose and detail
its utilization in a particle filter-based vehicle localization strategy, and
later present results of real-time implementations on a desktop system and an
off-the-shelf embedded platform that outperform localization results from
running a state-of-the-art algorithm on the same environment
Algorithms for detecting dependencies and rigid subsystems for CAD
Geometric constraint systems underly popular Computer Aided Design soft-
ware. Automated approaches for detecting dependencies in a design are critical
for developing robust solvers and providing informative user feedback, and we
provide algorithms for two types of dependencies. First, we give a pebble game
algorithm for detecting generic dependencies. Then, we focus on identifying the
"special positions" of a design in which generically independent constraints
become dependent. We present combinatorial algorithms for identifying subgraphs
associated to factors of a particular polynomial, whose vanishing indicates a
special position and resulting dependency. Further factoring in the Grassmann-
Cayley algebra may allow a geometric interpretation giving conditions (e.g.,
"these two lines being parallel cause a dependency") determining the special
position.Comment: 37 pages, 14 figures (v2 is an expanded version of an AGD'14 abstract
based on v1
Discrimination by Customers
Customers discriminate by race and gender, with considerable negative consequences for female and minority workers and business owners. Yet anti-discrimination laws apply only to discrimination by firms, not by customers. We examine efficacy and privacy reasons for why this may be so, as well as changing features of the market that, by blurring the line between firms and customers, make current law increasingly irrelevant. We conclude that, while there are reasons to be cautious about regulating customer behavior, those reasons do not justify acceding to customer discrimination altogether. To open a discussion of the regulatory options that take account of the most significant concerns, we offer a modest proposal. This proposal does not create a legal obligation on the part of customers themselves, but rather requires firms that already have nondiscrimination obligations to do more to reduce the occurrence, and consequences, of discrimination by customers
Design of a Modified Stewart Platform Manipulator for Misalignment Correction
This thesis work is about the design of a modified Stewart platform manipulator for misalignment correction. The common version of the Stewart platform uses six actuators. The traditional Stewart platform of this kind has a moving top plate and a fixed base plate. However, in this research, the modified design of the traditional Stewart platform is studied. It is designed to be an easy connect-disconnect platform that can wrap around different structures with different cross sections and symmetrically designed. It is able to adjust position easily by using four identical but independent linear actuators populated evenly in two parts fastened to the top and bottom base by ball joints with each part been symmetrical to the other.
To design two symmetrical parts and an adjustable clamp are a major objective of the thesis. One symmetrical part flipped upside down produces the other. The adjustable clamp was printed in 3D and can be used to align regular structural shapes especially circle of various diameter. To correct the misalignment, a failure study was carried out to determine the two equal but opposite loads required to correct misalignment in two plastic beams. Five loads were applied which showed that the smaller the load, the better the misalignment. This study showed that it is better to fix the base at a location where it does not move. To investigate that the modified Stewart platform can resist structure stiffness, the actuator assembly was analyzed using ANSYS software. The results showed that the deformation and maximum stress is less that the structure stiffness, which proves why the assembly can resist structural stiffness. The results support that the modified Stewart platform can be used for misalignment correction
Lightweight design and encoderless control of a miniature direct drive linear delta robot
This paper presents the design, integration and experimental validation of a miniature light-weight delta robot targeted to be used for a variety of applications including the pick-place operations, high speed precise positioning and haptic implementations. The improvements brought by the new design contain; the use of a novel light-weight joint type replacing the conventional and heavy bearing structures and realization of encoderless position measurement algorithm based on hall effect sensor outputs of direct drive linear motors. The description of mechanical, electrical and software based improvements are followed by the derivation of a sliding mode controller to handle tracking of planar closed curves represented by elliptic fourier descriptors (EFDs). The new robot is tested in experiments and the validity of the improvements are verified for practical implementation
Past, Present, and Future of Simultaneous Localization And Mapping: Towards the Robust-Perception Age
Simultaneous Localization and Mapping (SLAM)consists in the concurrent
construction of a model of the environment (the map), and the estimation of the
state of the robot moving within it. The SLAM community has made astonishing
progress over the last 30 years, enabling large-scale real-world applications,
and witnessing a steady transition of this technology to industry. We survey
the current state of SLAM. We start by presenting what is now the de-facto
standard formulation for SLAM. We then review related work, covering a broad
set of topics including robustness and scalability in long-term mapping, metric
and semantic representations for mapping, theoretical performance guarantees,
active SLAM and exploration, and other new frontiers. This paper simultaneously
serves as a position paper and tutorial to those who are users of SLAM. By
looking at the published research with a critical eye, we delineate open
challenges and new research issues, that still deserve careful scientific
investigation. The paper also contains the authors' take on two questions that
often animate discussions during robotics conferences: Do robots need SLAM? and
Is SLAM solved
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