Comparison Study on Motion Characteristics of Three 2-DOF Pointing Devices

2014 ◽  
Author(s):  
Kang Wu ◽  
Jingjun Yu ◽  
Guanghua Zong ◽  
Xianwen Kong
Keyword(s):  
Optical Sensors ◽  
Parallel Manipulators ◽  
The Self ◽  
Pointing Device ◽  
Basic Image ◽  
Motion Characteristics ◽  
Self Motion ◽  
Human Eyes ◽  
Realistic Images ◽  
Two Degree Of Freedom

Two degree-of-freedom (DOF) manipulators have been widely applied in pointing devices. Besides the commonly used gimbal platforms, two different kinds of parallel platforms base on parallel manipulators are presented as real applications in this paper. In a situation, a pointing device acquires and tracks a remote target via optical sensors amounted on the device. As the authors’ recent research, there are image distortions caused by deflected camera axis while the pointing device changing its attitudes. The paper refers the phenomena to the self-motion characteristics as the 2-DOF platforms rotate around the fixed platform axis. Basic image distortion principles of the three platforms are illustrated and discussed. Relationship between the self-motion and revolution are analyzed via the graphic approach and simulated on the software. Results indicate that these different phenomena are due to the different inherent characters of the platform’s freedom lines and freedom disks. Conclusions revealed in this paper would help the engineers with the type selections and applications, especially for the remote virtual reality devices which can provide realistic images for the human eyes. This work will facilitate the image processing and improve the measuring accuracy for the pointing devices.

A Comparative Study on Motion Characteristics of Three Two-Degree-of-Freedom Pointing Mechanisms

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
Jingjun Yu ◽  
Kang Wu ◽  
Guanghua Zong ◽  
Xianwen Kong
Keyword(s):  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Pure Rolling ◽  
Motion Characteristics ◽  
And Control ◽  
Self Motion ◽  
Tracking Devices ◽  
Two Degree Of Freedom ◽  
Typical Difference ◽  
Composition Theorem

Two-degree-of-freedom (2DOF) pointing mechanisms have been widely used in areas such as stabilized platforms, tracking devices, etc. Besides the commonly used serial gimbal structures, another two types of parallel pointing mechanisms, i.e., spherical parallel manipulators (SPMs) and equal-diameter spherical pure rolling (ESPR) parallel manipulators, are increasingly concerned. Although all these pointing mechanisms have two rotational DOFs, they exhibit very different motion characteristics. A typical difference existing in these three pointing mechanisms can be found from their characteristics of self-motion, also called spinning motion by the authors. In this paper, the spinning motions of three pointing mechanisms are modeled and compared via the graphical approach combined with the vector composition theorem. According to our study, the spinning motion is essentially one component of the moving platform's real rotation. Furthermore, image distortions caused by three spinning motions are identified and distinguished when the pointing mechanisms are used as tracking devices. Conclusions would facilitate the design and control of the pointing devices and potentially improve the measuring accuracy for targets pointing and tracking.

ON ELLIPTIC SELF-MOTIONS OF PLANAR PROJECTIVE STEWART–GOUGH PLATFORMS

2013 ◽  
Vol 37 (4) ◽  
pp. 1057-1071 ◽  
Author(s):  
Georg Nawratil
Keyword(s):  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
The Self ◽  
Local Degree ◽  
Self Motion

It has been previously shown that non-architecturally singular parallel manipulators of Stewart–Gough type, where the planar platform and the planar base are related by a projectivity, have either so-called elliptic self-motions or pure translational self-motions. As the geometry of all manipulators with translational self-motions is already known, we focus on elliptic self-motions. We show that these necessarily one-parameter self-motions have a second, instantaneously local, degree of freedom in each pose of the self-motion. More-over, we introduce a geometrically motivated classification of elliptic self-motions and study the so-called orthogonal ones in detail.

The directions of nystagmus and apparent self-motion evoked by caloric tests and angular accelerations

2002 ◽  
Vol 11 (6) ◽  
pp. 349-355
Author(s):  
Ognyan I. Kolev
Keyword(s):  
Motion Perception ◽  
Frontal Plane ◽  
Vertical Axis ◽  
The Body ◽  
The Self ◽  
Whole Body ◽  
Caloric Stimulation ◽  
Infrared Video ◽  
Axis Rotation ◽  
Self Motion

Purpose: To further investigate the direction of (I) nystagmus and (II) self-motion perception induced by two stimuli: (a) caloric vestibular stimulations and (b) a sudden halt during vertical axis rotation. Subjects and methods: Twelve normal humans received caloric stimulation at 44°C, 30°C, and 20°C while in a supine position with the head inclined 30° upwards. In a second test they were rotated around the vertical axis with the head randomly placed in two positions: tilted 30° forward or tilted 60° backward, at a constant velocity of 90°/sec for 2 minutes and then suddenly stopped. After both tests they were asked to describe their sensations of self-motion. Eye movements were recorded with an infrared video-technique. Results: Caloric stimulation evoked only horizontal nystagmus in all subjects and induced a non-uniform complex perception of angular in frontal and transverse planes (the former dominated) and linear movements along the antero-posterior axis (sinking dominated) of the subject's coordinates. The self-motion was felt with the whole body or with a part of the body. Generally the perception evoked by cold (30°C) and warm (44°C) calorics was similar, although there were some differences. The stronger stimulus (20°C) evoked not only quantitative but also qualitative differences in perception. The abrupt halt of rotation induced self-motion perception and nystagmus only in the plane of rotation. The self-motion was felt with the whole body. Conclusion: There was no difference in the nystagmus evoked by caloric stimulation and a sudden halt of vertical axis rotation (in head positions to stimulate the horizontal canals); however, the two stimuli evoked different perceptions of self-motion. Calorics provoked the sensation of self-rotation in the frontal plane and linear motion, which did not correspond to the direction of nystagmus, as well as arcing and a reset phenomenon during angular and linear self-motion, caloric-induced self-motion can be felt predominantly or only with a part of the body, depending on the self-motion intensity. The findings indicate that, unlike the self-motion induced by sudden halt of vertical axis rotation, several mechanisms take part in generating caloric-induced self-motion.

Workspace optimization of a class of zero-torsion parallel wrists

Robotica ◽  
2018 ◽  
Vol 37 (7) ◽  
pp. 1174-1189 ◽  
Author(s):  
Yuanqing Wu ◽  
Marco Carricato
Keyword(s):  
Tilt Angle ◽  
General Class ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Geometric Properties ◽  
Large Rotation ◽  
Workspace Optimization ◽  
Two Degree Of Freedom

SUMMARYWe present singularity-free workspace optimization of a class of two-degree-of-freedom (2-DoF) parallel wrists with large rotation range capability. The wrists in consideration are kinematically equivalent to two families of 2-DoF homokinetic couplings. The first family comprises fully parallel wrists with N (N ≥ 3) double-universal ($\mathcal{UU}$) legs. The second family comprises spherical N-$\mathcal{UU}$ parallel wrists with interconnecting revolute ($\mathcal{R}$) joints. Both families belong to the more general class of zero-torsion parallel manipulators, and are, therefore, collectively referred to as zero-torsion wrists (ZTWs). We carry out a unified singularity-free workspace optimization by utilizing geometric properties of zero-torsion motion manifolds. Our work may serve as a conceptual guide to the design of ZTWs for large tilt-angle applications.

Motion Performance Analysis of Double-Cylinder Parallel Manipulators

2009 ◽  
Author(s):  
Hong Zhou ◽  
Shehu T. Alimi ◽  
Aravind Ravindranath ◽  
Hareesh Vepuri
Keyword(s):  
Performance Analysis ◽  
Parallel Manipulator ◽  
Critical Role ◽  
Parallel Manipulators ◽  
Degree Of Freedom ◽  
Serial Manipulators ◽  
Operation Speed ◽  
Transmission Angle ◽  
Motion Performance ◽  
Two Degree Of Freedom

Double-cylinder parallel manipulators are closed-loop two-degree-of-freedom linkages. They are preferred to use because of their simplicity plus the common advantages of parallel manipulators such as high stiffness, load-bearing, operation speed and precision positioning. Like other parallel manipulators, the output motion of double-cylinder parallel manipulators is not as flexible as two-degree-of-freedom serial manipulators. The motion performance analysis plays a critical role for this type of parallel manipulator to be applied successfully. In this paper, the linkage feasibility conditions are established based on the transmission angle. When feasibility conditions are satisfied, there is no dead position during operation. The workspace is generated by using curve-enveloping theory. The singularity characteristics are analyzed within the workspace. The motion performance index contours within the workspace are produced using the condition number of the manipulator Jacobian matrix. The results of this paper provide guidelines to apply this type of parallel manipulator.

The Breathing Light Illusion

2017 ◽  
Author(s):  
Simone Gori ◽  
Enrico Giora ◽  
D. Alan Stubbs
Keyword(s):  
The Self ◽  
White Spot ◽  
Physical Stimulus ◽  
Black Background ◽  
Static View ◽  
Self Motion

This chapter discusses the Breathing Light Illusion. The Breathing Light Illusion is a size and brightness illusion elicited by the self-motion of the observer. The stimulus consists of a circular white spot that is presented on a black background, characterized by blurred boundaries. The blurred spot, which in static view seems to glow and exhibits a self-luminance appearance, is perceived as wider, brighter, and more diffuse when it is approached but smaller, darker, and sharper when one recedes from it. A possible explanation of the phenomenon is related to the superimposition of the afterimage on the physical stimulus during dynamical viewing.

scholarly journals Being Moved by the Self and Others: Influence of Empathy on Self-Motion Perception

PLoS ONE ◽  
2013 ◽  
Vol 8 (1) ◽  
pp. e48293 ◽  
Author(s):  
Christophe Lopez ◽  
Caroline J. Falconer ◽  
Fred W. Mast
Keyword(s):  
Motion Perception ◽  
The Self ◽  
Self Motion ◽  
Being Moved

scholarly journals Introducing the Theory of Bonds for Stewart Gough Platforms With Self-Motions1

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Georg Nawratil
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Manipulators ◽  
Geometric Characterization ◽  
Basic Facts ◽  
Self Motion ◽  
Three Degrees Of Freedom

We transfer the basic idea of bonds, introduced by Hegedüs, Schicho, and Schröcker for overconstrained closed chains with rotational joints, to the theory of self-motions of parallel manipulators of Stewart Gough (SG) type. Moreover, we present some basic facts and results on bonds and demonstrate the potential of this theory on the basis of several examples. As a by-product we give a geometric characterization of all SG platforms with a pure translational self-motion and of all spherical three-degrees of freedom (DOF) RPR manipulators with self-motions.

scholarly journals Visual self-motion feedback affects the sense of self in virtual reality

2019 ◽  
Author(s):  
Aubrieann Schettler ◽  
Ian Holstead ◽  
John Turri ◽  
Michael Barnett-Cowan
Keyword(s):  
Body Image ◽  
Virtual Reality ◽  
Visual Feedback ◽  
Sense Of Self ◽  
Body Schema ◽  
The Body ◽  
The Self ◽  
Top Down ◽  
Biological Sex ◽  
Self Motion

AbstractWe assessed how self-motion affects the visual representation of the self. We constructed a novel virtual reality experiment that systematically varied an avatar’s motion and also biological sex. Participants were presented with pairs of avatars that visually represented the participant (“self avatar”), or another person (“opposite avatar”). Avatar motion either corresponded with the participant’s motion, or was decoupled from the participant’s motion. The results show that participants identified with i) “self avatars” over “opposite avatars”, ii) avatars moving congruently with self-motion over incongruent motion, and importantly iii) identification with the “opposite avatar” over the “self avatar” when the opposite avatar’s motion was congruent with self-motion. Our results suggest that both self-motion and biological sex are relevant to the body schema and body image and that congruent bottom-up visual feedback of self-motion is particularly important for the sense of self and capable of overriding top-down self-identification factors such as biological sex.

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