scholarly journals Mapping and determining the center of mass of a rotating object using a moving observer

2018 ◽  
Vol 37 (1) ◽  
pp. 83-103 ◽  
Author(s):  
Timothy P Setterfield ◽  
David W Miller ◽  
John J Leonard ◽  
Alvar Saenz-Otero
Keyword(s):  
Angular Rate ◽  
Center Of Mass ◽  
Computational Cost ◽  
Target Object ◽  
Factor Graph ◽  
Visual Sensor ◽  
Fixed Frame ◽  
Computational Performance ◽  
Kinematic Factor ◽  
Graph Mapping

For certain applications, such as on-orbit inspection of orbital debris, defunct satellites, and natural objects, it is necessary to obtain a map of a rotating object from a moving observer, as well to estimate the object’s center of mass. This paper addresses these tasks using an observer that measures its own orientation, angular rate, and acceleration, and is equipped with a dense 3D visual sensor, such as a stereo camera or a light detection and ranging (LiDAR) sensor. The observer’s trajectory is estimated independently of the target object’s rotational motion. Pose-graph mapping is performed using visual odometry to estimate the observer’s trajectory in an arbitrary target-fixed frame. In addition to applying pose constraint factors between successive frames, loop closure is performed between temporally non-adjacent frames. A kinematic constraint on the target-fixed frame, resulting from the rigidity of the target object, is exploited to create a novel rotation kinematic factor. This factor connects a trajectory estimation factor graph with the mapping pose graph, and facilitates estimation of the target’s center of mass. Map creation is performed by transforming detected feature points into the target-fixed frame, centered at the estimated center of mass. Analysis of the algorithm’s computational performance reveals that its computational cost is negligible compared with that of the requisite image processing.

scholarly journals Fast contrast enhancement by adaptive pixel value stretching

2018 ◽  
Vol 14 (8) ◽  
pp. 155014771879380
Author(s):  
Gang Cao ◽  
Huawei Tian ◽  
Lifang Yu ◽  
Xianglin Huang
Keyword(s):  
Contrast Enhancement ◽  
Dynamic Range ◽  
Computational Cost ◽  
Computer Applications ◽  
Visual Sensor ◽  
Visual Sensor Network ◽  
Image Contrast Enhancement ◽  
Quantitative Performance ◽  
Pixel Value ◽  
Adaptive Gamma Correction

In this article, we propose a fast and effective method for digital image contrast enhancement. The gray-level dynamic range of contrast-distorted images is extended maximally via adaptive pixel value stretching. The quantity of saturated pixels is set intelligently according to the perceptual brightness of global images. Adaptive gamma correction is also novelly used to recover the normal luminance in enhancing dimmed images. Different from prior methods, our proposed technique could be enforced automatically without complex manual parameter adjustment per image. Both qualitative and quantitative performance evaluation results show that, comparing with some recent influential contrast enhancement techniques, our proposed method achieves comparative or better enhancement quality at a surprisingly lower computational cost. Besides general computer applications, such merit should also be valuable in low-power scenarios, such as the imaging pipelines used in small mobile terminals and visual sensor network.

Fast Electrostatic Force and Moment Calculations in Multibody-Based Simulations of Coarse-Grained Biopolymers

2011 ◽  
Author(s):  
Mohammad Poursina ◽  
Jeremy Laflin ◽  
Kurt S. Anderson
Keyword(s):  
Force Field ◽  
Long Range ◽  
Electrostatic Force ◽  
Center Of Mass ◽  
Computational Cost ◽  
Field Approximation ◽  
The Body ◽  
Divide And Conquer ◽  
Coarse Grained ◽  
Coarse Grain

In molecular simulations, the dominant portion of the computational cost is associated with force field calculations. Herein, we extend the approach used to approximate long range gravitational force and the associated moment in spacecraft dynamics to the coulomb forces present in coarse grained biopolymer simulations. We approximate the resultant force and moment for long-range particle-body and body-body interactions due to the electrostatic force field. The resultant moment approximated here is due to the fact that the net force does not necessarily act through the center of mass of the body (pseudoatom). This moment is considered in multibody-based coarse grain simulations while neglected in bead models which use particle dynamics to address the dynamics of the system. A novel binary divide and conquer algorithm (BDCA) is presented to implement the force field approximation. The proposed algorithm is implemented by considering each rigid/flexible domain as a node of the leaf level of the binary tree. This substructuring strategy is well suited to coarse grain simulations of chain biopolymers using an articulated multibody approach.

On the Adoption of a Terrestrial Reference Frame

1980 ◽  
Vol 56 ◽  
pp. 145-153
Author(s):  
Dennis D. McCarthy
Keyword(s):  
Reference Frame ◽  
Polar Motion ◽  
Center Of Mass ◽  
Terrestrial Reference Frame ◽  
Fixed Frame ◽  
The Earth ◽  
International Polar ◽  
Definition Of ◽  
Observational Techniques ◽  
Fixed System

AbstractThe report of the IAU Working Group on Nutation endorsed by Commissions 4, 8, 19 and 31 at the 1979 General Assembly points out that “… the complete theory of the general nutational motion of the Earth about its center of mass may be described by the sum of two components, astronomical nutation, commonly referred to as nutation, which is nutation with respect to a space-fixed coordinate system, and polar motion, which is nutation with respect to a body-fixed system …”. Unlike the situation for the space-fixed frame, there is not an adequate, formally accepted, body-fixed system for this purpose. The Conventional International Origin (CIO) as it is presently defined is no longer acceptable because of recent improvements in observational techniques. The effective lack of this type of terrestrial reference frame limits the complete description of the general nutational motion of the Earth. In the absence of a terrestrial reference frame suitable for specifying the orientation of the Earth, it is suggested that a body-fixed system could be represented formally in a manner analogous to that used to represent the space-fixed frame. This procedure would be quite similar to methods employed currently by the International Polar Motion Service and the Bureau International de l’Heure, and would allow for the use of observations from new techniques in the definition of a terrestrial reference frame to be used to specify the complete nutational motion of the Earth.

Experimental and Novel Analytical Trajectory Optimization of a 7-DOF Baxter Robot: Global Design Sensitivity and Step Size Analyses

2017 ◽  
Author(s):  
Mostafa Bagheri ◽  
Peiman Naseradinmousavi ◽  
Rasha Morsi
Keyword(s):  
Global Optimization ◽  
Cost Function ◽  
Trajectory Optimization ◽  
Computational Cost ◽  
Joint Space ◽  
Design Sensitivity ◽  
Target Object ◽  
Size Analysis ◽  
Step Size ◽  
Novel Approach

In this paper, we present a novel nonlinear analytical coupled trajectory optimization of a 7-DOF Baxter manipulator validated through experimental work utilizing global optimization tools. The robotic manipulators used in network-based applications of industrial units and even homes, for disabled patients, spend significant lumped amount of energy and therefore, optimal trajectories need to be generated to address efficiency issues. We here examine both heuristic (Genetics) and gradient based (GlobalSearch) algorithms for a novel approach of “S-Shaped” trajectory (unlike conventional polynomials), to avoid being trapped in several possible local minima along with yielding minimal computational cost, enforcing operational time and torque saturation constraints. The global schemes are utilized in minimizing the lumped amount of energy consumed in a nominal path given in the collision-free joint space except an impact between the robot’s end effector and a target object for the nominal operation. Note that such robots are typically operated for thousands of cycles resulting in a considerable cost of operation. Due to the expected computational cost of such global optimization algorithms, step size analysis is carried out to minimize both the computational cost (iteration) and possibly cost function by finding an optimal step size. Global design sensitivity analysis is also performed to examine the effects of changes of optimization variables on the cost function defined.

scholarly journals BraggNN: fast X-ray Bragg peak analysis using deep learning

IUCrJ ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhengchun Liu ◽  
Hemant Sharma ◽  
Jun-Sang Park ◽  
Peter Kenesei ◽  
Antonino Miceli ◽  
...  
Keyword(s):  
Deep Learning ◽  
Near Field ◽  
Center Of Mass ◽  
Computational Cost ◽  
Ground Truth ◽  
High Energy ◽  
Peak Shape ◽  
X Ray ◽  
Shape Fitting ◽  
Performance Improvements

X-ray diffraction based microscopy techniques such as high-energy diffraction microscopy (HEDM) rely on knowledge of the position of diffraction peaks with high precision. These positions are typically computed by fitting the observed intensities in detector data to a theoretical peak shape such as pseudo-Voigt. As experiments become more complex and detector technologies evolve, the computational cost of such peak-shape fitting becomes the biggest hurdle to the rapid analysis required for real-time feedback in experiments. To this end, we propose BraggNN, a deep-learning based method that can determine peak positions much more rapidly than conventional pseudo-Voigt peak fitting. When applied to a test dataset, peak center-of-mass positions obtained from BraggNN deviate less than 0.29 and 0.57 pixels for 75 and 95% of the peaks, respectively, from positions obtained using conventional pseudo-Voigt fitting (Euclidean distance). When applied to a real experimental dataset and using grain positions from near-field HEDM reconstruction as ground-truth, grain positions using BraggNN result in 15% smaller errors compared with those calculated using pseudo-Voigt. Recent advances in deep-learning method implementations and special-purpose model inference accelerators allow BraggNN to deliver enormous performance improvements relative to the conventional method, running, for example, more than 200 times faster on a consumer-class GPU card with out-of-the-box software.

scholarly journals Advances in Hierarchical Model Reduction and combination with other computational reduction methods

2018 ◽  
Author(s):  
Giulia Meglioli ◽  
Matteo Zancanaro ◽  
Francesco Ballarin ◽  
Simona Perotto ◽  
Gianluigi Rozza
Keyword(s):  
Hierarchical Model ◽  
Computational Cost ◽  
Order Reduction ◽  
Reduced Basis ◽  
Element Discretization ◽  
Modal Expansion ◽  
Reduction Techniques ◽  
Computational Performance ◽  
Reduction Methods ◽  
Computational Reduction

In this work we present address the combination of the Hierarchical Model (Hi-Mod) reduction approach with projection-based reduced order methods, exploiting either on Greedy Reduced Basis (RB) or Proper Orthogonal Decomposition (POD), in a parametrized setting. The Hi-Mod approach, introduced in, is suited to reduce problems in pipe-like domains featuring a dominant axial dynamics, such as those arising for instance in haemodynamics. The Hi-Mod approach aims at reducing the computational cost by properly combining a finite element discretization of the dominant dynamics with a modal expansion in the transverse direction. In a parametrized context, the Hi-Mod approach has been employed as the high-fidelity method during the offline stage of model order reduction techniques based on RB or POD. The resulting combined reduction methods, which have been named Hi-RB and Hi-POD, respectively, will be presented with applications in diffusion-advection problems, fluid dynamics and optimal control problems, focusing on the approximation stability of the proposed methods and their computational performance.

scholarly journals Polarized skylight-based heading measurements: a bio-inspired approach

2019 ◽  
Vol 16 (150) ◽  
pp. 20180878 ◽  
Author(s):  
Julien Dupeyroux ◽  
Stéphane Viollet ◽  
Julien R. Serres
Keyword(s):  
Computational Cost ◽  
Field Studies ◽  
Compound Eyes ◽  
High Definition ◽  
Visual Sensor ◽  
Robotic Vision ◽  
Dorsal Rim Area ◽  
Desert Ants ◽  
Linearly Polarized ◽  
Direction Of Polarization

Many insects such as desert ants, crickets, locusts, dung beetles, bees and monarch butterflies have been found to extract their navigation cues from the regular pattern of the linearly polarized skylight. These species are equipped with ommatidia in the dorsal rim area of their compound eyes, which are sensitive to the angle of polarization of the skylight. In the polarization-based robotic vision, most of the sensors used so far comprise high-definition CCD or CMOS cameras topped with linear polarizers. Here, we present a 2-pixel polarization-sensitive visual sensor, which was strongly inspired by the dorsal rim area of desert ants' compound eyes, designed to determine the direction of polarization of the skylight. The spectral sensitivity of this minimalistic sensor, which requires no lenses, is in the ultraviolet range. Five different methods of computing the direction of polarization were implemented and tested here. Our own methods, the extended and AntBot method, outperformed the other three, giving a mean angular error of only 0.62° ± 0.40° (median: 0.24°) and 0.69° ± 0.52° (median: 0.39°), respectively (mean ± standard deviation). The results obtained in outdoor field studies show that our celestial compass gives excellent results at a very low computational cost, which makes it highly suitable for autonomous outdoor navigation purposes.

Leveraging synergetic information resources for angular motion control of unmanned spacecraft

2021 ◽  
pp. 127-141
Author(s):  
Vladimir S. KOVTUN ◽  
Aleksandr N. PAVLOV ◽  
Boris V. SOKOLOV ◽  
Dmitry A. PAVLOV ◽  
Valentin N. VOROTYAGIN
Keyword(s):  
Motion Control ◽  
Transitive Closure ◽  
Angular Rate ◽  
Center Of Mass ◽  
Control Process ◽  
Measured Data ◽  
Binary Relations ◽  
Spacecraft Control ◽  
Rate Vector ◽  
Unmanned Spacecraft

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

LEVERAGING SYNERGETIC INFORMATION RESOURCES FOR ANGULAR MOTION CONTROL OF UNMANNED SPACECRAFT

2021 ◽  
pp. 127-141
Author(s):  
Vladimir S. KOVTUN ◽  
Aleksandr N. PAVLOV ◽  
Boris V. SOKOLOV ◽  
Dmitry A. PAVLOV ◽  
Valentin N. VOROTYAGIN
Keyword(s):  
Motion Control ◽  
Transitive Closure ◽  
Angular Rate ◽  
Center Of Mass ◽  
Control Process ◽  
Measured Data ◽  
Binary Relations ◽  
Spacecraft Control ◽  
Rate Vector ◽  
Unmanned Spacecraft

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

Study on Industrial Automation with SCARA Robot Vision System Design

2013 ◽  
Vol 675 ◽  
pp. 72-76 ◽  
Author(s):  
Xin Wu ◽  
Hong Yin He ◽  
Gong Jin Lan ◽  
Jin Tian Tang
Keyword(s):  
Vision System ◽  
Center Of Mass ◽  
Robot Vision ◽  
Target Object ◽  
Object Identification ◽  
Initial Image ◽  
Industrial Automation ◽  
Scara Robot ◽  
Filtering Method ◽  
Good Object

To realize scara robot in industrial automation work environment identifying target objects independently, this paper puts forward a kind of machine vision solution based on opencv . First the k neighbor average filtering method and otsu is used to the initial image filtering and segmentation, and given a method based on pixel area, using the target object itself geometric characteristics and center of mass calibration to identify, locate purpose. The experimental results show that the system can achieve good object identification orientation effect in more complex industrial automation environment, so as to provide the necessary information for scara robot to grab target objects.This kind of robot vision system play an important role in industrial automation.

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