Manual Tracking in Two Dimensions

2000 ◽  
Vol 83 (6) ◽  
pp. 3483-3496 ◽  
Author(s):  
Kevin C. Engel ◽  
John F. Soechting
Keyword(s):  
Simple Model ◽  
Two Dimensions ◽  
Target Velocity ◽  
Manual Tracking ◽  
Video Monitor ◽  
Hand Motion ◽  
Target Acceleration ◽  
Straight Line ◽  
Perpendicular Component ◽  
Peak Speed

Manual tracking was studied by asking subjects to follow, with their finger, a target moving on a touch-sensitive video monitor. The target initially moved in a straight line at a constant speed and then, at a random point in time, made one abrupt change in direction. The results were approximated with a simple model according to which, after a reaction time, the hand moved in a straight line to intercept the target. Both the direction of hand motion and its peak speed could be predicted by assuming a constant time to intercept. This simple model was able to account for results obtained over a broad range of target speeds as well as the results of experiments in which both the speed and the direction of the target changed simultaneously. The results of an experiment in which the target acceleration was nonzero suggested that the error signals used during tracking are related to both speed and direction but poorly (if at all) to target acceleration. Finally, in an experiment in which target velocity remained constant along one axis but the perpendicular component underwent a step change, tracking along both axes was perturbed. This last finding demonstrates that tracking in two dimensions cannot be decomposed into its Cartesian components. However, an analytical model in a hand-centered frame of reference in which speed and direction are the controlled variables could account for much of the data.

Mapping with Monocular Vision in Two Dimensions

2010 ◽  
Vol 1 (4) ◽  
pp. 56-65 ◽  
Author(s):  
Nicolau Leal Werneck ◽  
Anna Helena Reali Costa
Keyword(s):  
Optical Axis ◽  
Two Dimensions ◽  
Obstacle Detection ◽  
Uniform Motion ◽  
Mapping Algorithms ◽  
Multiple Images ◽  
Line Segments ◽  
Straight Line ◽  
Camera Intrinsic Parameters ◽  
Over Time

This article presents the problem of building bi-dimensional maps of environments when the sensor available is a camera used to detect edges crossing a single line of pixels and motion is restricted to a straight line along the optical axis. The position over time must be provided or assumed. Mapping algorithms for these conditions can be built with the landmark parameters estimated from sets of matched detection from multiple images. This article shows how maps that are correctly up to scale can be built without knowledge of the camera intrinsic parameters or speed during uniform motion, and how performing an inverse parameterization of the image coordinates turns the mapping problem into the fitting of line segments to a group of points. The resulting technique is a simplified form of visual SLAM that can be better suited for applications such as obstacle detection in mobile robots.

Modelling of circular wave guides

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1092-1098 ◽  
Author(s):  
A. Delage ◽  
K. A. McGreer ◽  
E. Rainville
Keyword(s):  
Integrated Circuit ◽  
Beam Propagation Method ◽  
Two Dimensions ◽  
Effective Index ◽  
Radius Of Curvature ◽  
Index Method ◽  
Photonic Integrated Circuit ◽  
Circular Arcs ◽  
Straight Line ◽  
Wave Guides

In many circumstances the design of interconnects in a photonic integrated circuit can be simplified by using low loss curved wave guides in the shapes of circular arcs. Radiative losses associated with the curvature have been computed as a function of the radius of curvature. The technique takes advantage of the effective index method to reduce the problem from two dimensions to one dimension (1D) and uses a change of coordinate that transforms an arc of circle into a straight line. This transformation results in a monotonous increase of the refractive index as function of r (the distance from the centre of the circle) for original constant index regions. The new system is solved by discretizing this varying effective index onto many small layers of constant index over a window large enough to contain the region where the field is not negligible. A multilayer algorithm in 1D is then used to find complex propagation constants in which the imaginary part is related to the fundamental energy loss owing to the curvature. The solution also gives the shape of the field necessary to match the mode profiles at the junction between the straight and curved part of the wave guide. The basic change of variable has been extended to the finite difference solution of the scalar wave equation and to the beam propagation method.

On Misoriented Letters

Perception ◽  
1984 ◽  
Vol 13 (6) ◽  
pp. 687-694 ◽  
Author(s):  
Paola Bressan ◽  
Giovanni B Vicario
Keyword(s):  
Simple Model ◽  
Vertical Axis ◽  
Picture Plane ◽  
Two Dimensions ◽  
Point Of View ◽  
Horizontal Axis ◽  
Three Dimensions

An experiment is reported in which subjects were presented with misoriented letters and asked to identify the transformations to which normal letters had been subjected to produce the misorientation. When two or more transformations were equally justifiable from the geometrical point of view, they did not have necessarily the same relevance from the perceptual standpoint. For instance, it was easier for the subjects to see an upside-down letter R as the outcome of two reflections (one about the horizontal axis and one about the vertical axis) rather than of a 180° rotation in the picture plane. Contrary to expectation, for the same final result a reflection—a movement in three dimensions—was preferred to a rotation—a movement in two dimensions—and two reflections were preferred to a single rotation. To explain the distribution of the responses, a hypothesis on the ‘mode of appearance’ of equivocally oriented objects is presented. This postulates that the directional axes assigned to the objects tend to remain in correspondence with those of the environment. Moreover, the polarization of the up–down axis tends to be preserved, while that of the left-right axis does not. Implications of this simple model for the perception of misorientations are discussed.

On the planar stability of rigid-link binary walking robots

Robotica ◽  
2003 ◽  
Vol 21 (6) ◽  
pp. 667-675 ◽  
Author(s):  
Yu Zhou
Keyword(s):  
Simple Model ◽  
Walking Robots ◽  
Walking Robot ◽  
Research Results ◽  
Rigid Link ◽  
Straight Line ◽  
The Stability ◽  
State Nature

A binary walking robot moves as a result of bi-state actuator transitions. Because of the bi-state nature of binary joints, many research results about continuous walking robots cannot be applied to binary walking robots directly. In this paper, a new and simple model of rigid-link binary walking robot is proposed, around which related concepts are introduced, and formulas are derived. Based on this model, general characteristics and limitations of periodic gaits are discussed, and the stability qualities of several straight-line walking periodic gaits are studied in both pitch-greater-than-stroke and stroke-greater-than-pitch cases. Valuable results are obtained from the analysis, which should be followed in the design of rigid-link binary walking robots.

scholarly journals Humans can track but fail to predict accelerating objects

2021 ◽  
Author(s):  
Philipp Kreyenmeier ◽  
Luca Kaemmer ◽  
Jolande Fooken ◽  
Miriam Spering
Keyword(s):  
Eye Movements ◽  
Moving Objects ◽  
Hand Movement ◽  
Mechanistic Explanation ◽  
Velocity Model ◽  
Target Velocity ◽  
Visually Guided ◽  
Target Acceleration ◽  
Temporal Occlusion ◽  
Integration Mechanisms

Objects in our visual environment often move unpredictably and can suddenly speed up or slow down. The ability to account for acceleration when interacting with moving objects can be critical for survival. Here, we investigate how human observers track an accelerating target with their eyes and predict its time of reappearance after a temporal occlusion by making an interceptive hand movement. Before occlusion, the target was initially visible and accelerated for a brief period. We tested how observers integrated target motion information by comparing three alternative models that predicted time-to-contact (TTC) based on the (1) final target velocity sample before occlusion, (2) average target velocity before occlusion, or (3) target acceleration. We show that visually-guided smooth pursuit eye movements reliably reflect target acceleration prior to occlusion. However, systematic saccade and manual interception timing errors reveal an inability to consider acceleration when predicting TTC. Interception timing is best described by the final velocity model that relies on extrapolating the last available velocity sample before occlusion. These findings provide compelling evidence for differential acceleration integration mechanisms in vision-guided eye movements and prediction-guided interception and a mechanistic explanation for the function and failure of interactions with accelerating objects.

Uniaxial Wave Propagation in Realistic Viscoelastic Materials

1964 ◽  
Vol 31 (1) ◽  
pp. 17-21 ◽  
Author(s):  
R. J. Arenz
Keyword(s):  
Wave Propagation ◽  
Simple Model ◽  
Two Dimensions ◽  
Inversion Method ◽  
Viscoelastic Response ◽  
Material Dispersion ◽  
Response Characteristics ◽  
Dispersion Effects ◽  
Present Technique ◽  
Step Loading

The problem of wave propagation in a rod of viscoelastic material with step loading on the end is solved using realistic viscoelastic response characteristics covering approximately ten decades of logarithmic time. To overcome the inherent computational difficulties in the usual transform type of solution, an extension of the Schapery collocation inversion method to dynamic cases is proposed. The results indicate some material dispersion effects not evident in previous treatments using less adequate simple model representations. The present technique is also applicable to problems in two dimensions.

scholarly journals Target shape dependence in a simple model of receptor-mediated endocytosis and phagocytosis

2016 ◽  
Vol 113 (22) ◽  
pp. 6113-6118 ◽  
Author(s):  
David M. Richards ◽  
Robert G. Endres
Keyword(s):  
Simple Model ◽  
Theoretical Work ◽  
Cell Types ◽  
Two Dimensions ◽  
Spherical Particles ◽  
Nonspherical Particles ◽  
Receptor Mediated Endocytosis ◽  
Particle Uptake ◽  
Shape Dependence ◽  
Optimal Drug

Phagocytosis and receptor-mediated endocytosis are vitally important particle uptake mechanisms in many cell types, ranging from single-cell organisms to immune cells. In both processes, engulfment by the cell depends critically on both particle shape and orientation. However, most previous theoretical work has focused only on spherical particles and hence disregards the wide-ranging particle shapes occurring in nature, such as those of bacteria. Here, by implementing a simple model in one and two dimensions, we compare and contrast receptor-mediated endocytosis and phagocytosis for a range of biologically relevant shapes, including spheres, ellipsoids, capped cylinders, and hourglasses. We find a whole range of different engulfment behaviors with some ellipsoids engulfing faster than spheres, and that phagocytosis is able to engulf a greater range of target shapes than other types of endocytosis. Further, the 2D model can explain why some nonspherical particles engulf fastest (not at all) when presented to the membrane tip-first (lying flat). Our work reveals how some bacteria may avoid being internalized simply because of their shape, and suggests shapes for optimal drug delivery.

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