Three-dimensional gesture comparison using curvature analysis of position and orientation

This paper introduces a reconfigurable closed-loop spatial mechanism that can be applied to repetitive motion tasks. The concept is to incorporate five pairs of non-circular gears into a six degree-of–freedom closed-loop spatial chain. The gear pairs are designed based on given mechanism parameters and a user defined motion specification of a coupler link of the mechanism. It is shown in the paper that planar gear pairs can be used if the spatial closed-loop chain is comprised of six pairs of parallel joint axes, i.e. the first joint axis is parallel to the second, the third is parallel to the fourth, ..., and the eleventh is parallel to the twelfth. This paper presents the synthesis of the gear pairs that satisfy a specified three-dimensional position and orientation need. Numerical approximations were used in the synthesis the non-circular gear pairs by introducing an auxiliary monotonic parameter associated to each end-effector position to parameterize the motion needs. The findings are supported by a computer animation. No previous known literature incorporates planar non-circular gears to fulfill spatial motion generation needs.

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Three‐dimensional curvature analysis of seismic waveforms and its interpretational implications

Geophysical Prospecting ◽

10.1111/1365-2478.12719 ◽

2018 ◽

Cited By ~ 1

Author(s):

Haibin Di ◽

Motaz Alfarraj ◽

Ghassan AlRegib

Keyword(s):

Three Dimensional ◽

Curvature Analysis ◽

Seismic Waveforms

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The Optimum Cage Position and Orientation on the ALIF with Facet Screw Fixation: A Finite Element Analysis and the Taguchi Method

Journal of Mechanics ◽

10.1017/jmech.2011.25 ◽

2011 ◽

Vol 27 (3) ◽

pp. 309-320 ◽

Cited By ~ 1

Author(s):

C.-Y. Fan ◽

C.-K. Chao ◽

C.-C. Hsu ◽

K.-H. Chao

Keyword(s):

Finite Element ◽

Taguchi Method ◽

Screw Fixation ◽

Three Dimensional ◽

Element Model ◽

Lateral Position ◽

Element Analysis ◽

Control Factors ◽

Position And Orientation ◽

Noise Factors

ABSTRACTAnterior Lumbar Interbody Fusion (ALIF) has been widely used to treat internal disc degeneration. However, different cage positions and their orientations may affect the initial stability leading to different fusion results. The purpose of the present study is to investigate the optimum cage position and orientation for aiding an ALIF having a transfacet pedicle screw fixation (TFPS). A three-dimensional finite element model (ALIF with TFPS) has been developed to simulate the stability of the L4/L5 fusion segment under five different loading conditions. The Taguchi method was used to evaluate the optimized placement of the cages. Three control factors and two noise factors were included in the parameter design. The control factors included the anterior-posterior position, the medio-lateral position, and the convergent-divergent angle between the two cages. The compressive preload and the strengths of the cancellous bone were set as noise factors. From the results of the FEA and the Taguchi method, we suggest that the optimal cage positioning has a wide anterior placement, and a diverging angle between the two cages. The results show that the optimum cage position simultaneously contributes to a stronger support of the anterior column and lowers the risk of TFPS loosening.

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A Unified Method for Computing Position and Orientation Workspaces of General Stewart Platforms

Volume 6: 35th Mechanisms and Robotics Conference, Parts A and B ◽

10.1115/detc2011-47836 ◽

2011 ◽

Author(s):

Oriol Bohigas ◽

Llui´s Ros ◽

Montserrat Manubens

Keyword(s):

Complex Shape ◽

Three Dimensional ◽

Stewart Platform ◽

Large Dimension ◽

Connected Components ◽

Cartesian Space ◽

Position And Orientation ◽

Stewart Platforms ◽

Orientation Workspace ◽

Unified Method

The workspace of a Stewart platform is a complex six-dimensional volume embedded in the Cartesian space defined by six pose parameters. Because of its large dimension and complex shape, such workspace is difficult to compute and represent, so that comprehension on its structure is being gained by studying its three-dimensional slices. While successful methods have been given to determine the constant-orientation slice, the computation and appropriate visualization of the constant-position slice (also known as the orientation workspace) has proved to be a challenging task. This paper presents a unified method for computing both of such slices, and any other ones defined by fixing three pose parameters, on general Stewart platforms involving mechanical limits on the active and passive joints. Additional advantages over previous methods include the ability to determine all connected components of the workspace, and any motion barriers present in its interior.

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Placing Three-Dimensional Models in an Uncalibrated Single Image of an Architectural Scene

Presence Teleoperators & Virtual Environments ◽

10.1162/1054746043280583 ◽

2004 ◽

Vol 13 (6) ◽

pp. 692-707 ◽

Cited By ~ 3

Author(s):

Sara Keren ◽

Ilan Shimshoni ◽

Ayellet Tal

Keyword(s):

Augmented Reality ◽

Three Dimensional ◽

3D Models ◽

Automatic Extraction ◽

Single Image ◽

Vanishing Points ◽

Correct Position ◽

3D Objects ◽

Position And Orientation ◽

Three Dimensional Models

This paper discusses the problem of inserting 3D models into a single image. The main focus of the paper is on the accurate recovery of the camera's parameters, so that 3D models can be inserted in the “correct” position and orientation. The paper addresses two issues. The first is an automatic extraction of the principal vanishing points from an image. The second is a theoretical and an experimental analysis of the errors. To test the concept, a system that “plants” virtual 3D objects in the image was implemented. It was tested on many indoor augmented-reality scenes. Our analysis and experiments have shown that errors in the placement of the objects are unnoticeable.

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Collaborated measurement of three-dimensional position and orientation errors of assembled miniature devices with two vision systems

10.1117/12.2014741 ◽

2013 ◽

Cited By ~ 2

Author(s):

Xiaodong Wang ◽

Wei Zhang ◽

Yi Luo ◽

Weimin Yang ◽

Liang Chen

Keyword(s):

Three Dimensional ◽

Vision Systems ◽

Position And Orientation ◽

Miniature Devices

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Singularity Analysis and Representation of 6DOF Parallel Robot Using Natural Coordinates

Journal of Robotics ◽

10.1155/2021/9935794 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Shangyuan Zou ◽

Hairui Liu ◽

Yanli Liu ◽

Jiafeng Yao ◽

Hongtao Wu

Keyword(s):

Structural Characteristics ◽

Three Dimensional ◽

Parallel Robot ◽

Singularity Analysis ◽

Forward Kinematics ◽

Natural Coordinates ◽

Planning And Control ◽

Position And Orientation ◽

Coupling Variables ◽

Representative Points

Singularity research is carried out. The problem, which is about six-dimensional parameters of position and orientation can not realize three-dimensional visualization for 6DOF parallel robot, has been solved. Firstly, according to the structural characteristics of the 6DOF parallel robot with the planar platform, the position and orientation of the mobile platform are described, respectively, and the six equations of forward kinematics are established by choosing the natural coordinates of three representative points as parameters. Then, the singularities of the 6DOF parallel robot with a planar platform are divided into input singularity and output singularity. Aiming at the output singularity, in combination with six constraint equations among the position vectors of three representative points, an analytical algorithm is proposed to express the coupling singularity of position and orientation and the analytical expression is derived. In further research, three kinds of output singularities are found, the spatial distribution of the output singular trajectory is determined, and a unified three-dimensional fully visualized description of six-dimensional coupling variables is realized for the first time. The problems of finding the singular orientation at a given position or the singular position at a given orientation are solved. The analysis of the singularity lays a solid foundation for the description of the three-dimensional complete visualization of a six-dimensional singularity-free workspace based on forward kinematics. What is more, it has great significance for both trajectory planning and control design of the parallel robot.

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