Kinematic Analysis of a Novel Rimless Wheel With Independently Actuated Spokes

2005 ◽  
Author(s):  
Doug Laney ◽  
Dennis Hong
Keyword(s):  
Contact Point ◽  
Point Contact ◽  
Static Stability ◽  
Advantages And Disadvantages ◽  
Contact Points ◽  
Straight Line ◽  
Wide Range ◽  
Kinematic Analyses ◽  
General Mobility ◽  
The One

One of the major limitations of mobile robots for unstructured environments is their lack of general mobility. Wheeled, treaded, and legged robots each have their advantages and disadvantages, but they all lack the flexibility to be able to cope with a wide range of terrain. The actuated spoke wheel concept is presented in this paper as an alternative locomotive method that allows multiple modes of motion, which give it the ability to stride quickly using one contact point per wheel, walk with static stability with two contact points per wheel, or assume a stable stance using three contact points per wheel. This paper presents the preliminary kinematic analyses of the actuated spoke wheel with no-slip constraints at the ground contacts for a robot using a two actuated spoke wheel configuration. Straight-line motion and considerations for turning are discussed for the one- and two-point contact schemes followed by recommendations for future study.

Three-Dimensional Kinematic Analysis of the Actuated Spoke Wheel Robot

2006 ◽  
Author(s):  
Doug Laney ◽  
Dennis Hong
Keyword(s):  
Kinematic Analysis ◽  
Current Problem ◽  
Three Dimensional ◽  
Advantages And Disadvantages ◽  
Contact Points ◽  
Straight Line ◽  
Wide Range ◽  
General Mobility ◽  
Special Case ◽  
A Current

A current problem for mobile robots in unstructured environments is their lack of general mobility. Wheeled, treaded, and legged robots each have their advantages and disadvantages, but they all lack the flexibility to be able to cope with a wide range of terrain. The actuated spoke wheel system was presented in an earlier work as an alternative locomotive method that allows unique mobility capabilities to cope with various situations. This paper presents the three-dimensional kinematic analysis of the actuated spoke wheel system with no slip and no bounce constraints at the ground contacts for a robot using a two actuated spoke wheel configuration. The first analysis will cover the case when the axle is coplanar with the line connecting the contact points, called the pivot line, and show results from two examples, corresponding to steady state turning and, in the special case, straight-line walking. The second case will describe the configuration when the pivot line is skew with the axle, comparing the robot in this configuration to an SPPS spatial mechanism. This comparison will lead to the recommendation of a more general model, based on the SPPS mechanism, that will be used to analyze the motion in both configurations.

Multi-Agent Form Closure Capture of a Generic 2D Polygonal Object Based on Projective Path Planning

2006 ◽  
Author(s):  
Pankaj Sharma ◽  
Anupam Saxena ◽  
Ashish Dutta
Keyword(s):  
Path Planning ◽  
Contact Point ◽  
Point Contact ◽  
Object Boundary ◽  
Actual Object ◽  
Contact Points ◽  
Correct Orientation ◽  
Novel Approach ◽  
Form Closure ◽  
Multi Agent

The study of multi-agent capture and manipulation of an object has been an area of active interest for many researchers. This paper presents a novel approach using Genetic Algorithm to determine the optimal contact points and the total number of agents (mobile robots) required to capture a stationary generic 2D polygonal object. After the goal points are determined the agents then reach their respective goals using a decentralized projective path planning algorithm. Form closure of the object is obtained using the concept of accessibility angle. The object boundary is first expanded and the robots reach the expanded object goal points and then converge on the actual object. This ensures that the agents reach the actual goal points at the same time and have the correct orientation. Frictionless point contact between the object and robots is assumed. The shape of the robot is considered a circle such that it can only apply force in outward radial direction from its center and along the normal to the object boundary at the contact point. Simulations results are presented that prove the effectiveness of the proposed method.

Experimental Analysis of Damping across Joints in Metal Plates

2006 ◽  
Vol 5-6 ◽  
pp. 391-398 ◽  
Author(s):  
S.J.I. Walker ◽  
G.S. Aglietti ◽  
P.R. Cunningham
Keyword(s):  
Experimental Approach ◽  
Dynamic Behaviour ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Advantages And Disadvantages ◽  
Metal Plates ◽  
Engineering Sciences ◽  
Wide Range ◽  
Vibration Problems ◽  
The One

In the current world of engineering, structural vibration problems continue impact the design and construction of a wide range of products. Amid the parameters that determine the dynamic behaviour of a structure the one that takes into account the dissipation of energy resulting in the decay of the vibration is the least understood and the most difficult to quantify [1]. The estimation of damping factors is of interest in most branches of engineering sciences. In the field of aircraft structures the damping directly affects the fatigue life, a parameter which is applied conservatively due to the inherent complexity in modelling the damping of built up structures and the potentially catastrophic consequences of a fatigue failure. One of the most important problems is the limited knowledge of how joints affect the damping of the complete structure. This work therefore addresses this issue and focuses on the damping of joints in metal plates as part of a larger project to investigate the damping of built up structures. Various plate configurations are experimentally investigated using two different approaches. The results from the configurations are compared and discussed along with the advantages and disadvantages of each experimental approach. This enables a link to be identified between the damping magnitudes and the mode shapes and joint stiffnesses.

scholarly journals Teaching in Vocational Schools: Educational Alignment versus the Promotion of Talents

2013 ◽  
Vol 1 (1) ◽  
pp. 9-13
Author(s):  
Tina Koppitz
Keyword(s):  
Professional Identity ◽  
Education System ◽  
Teaching And Learning ◽  
The Other ◽  
Learning Theories ◽  
Learning Program ◽  
Advantages And Disadvantages ◽  
Wide Range ◽  
Educational Alignment ◽  
The One

Teaching and learning has fundamentally changed in the last thirty years. In this period, a wide range of novel teaching theories has been established. Recent research states that a teachers professional identity consists of a cognitive, psychological and also a social perspective. The identity of a teacher emerges when s/he interacts with his/her students or other people. As a result of these interactions, teachers treat the questions “who are they? and who do they want to become?. These questions pose different views on educational methodologies today. On the one side some professionals argue for learning in a community which supports establishing an average basis of knowledge among all pupils. This approach especially helps the struggling pupils, since a key component is that pupils learn from each other and align their knowledge. On the other side, however, others vote for an individual learning program. Here, in particular talents are promoted. The question is, what approach is more promising for the society of tomorrow. This work deals with the underlying theories, discusses the advantages and disadvantages of these learning theories and, as an example, additionally incorporates a focused view on the Austrian education system

scholarly journals THE GAZE OF SCHROEDINGER’S CAT: EYE-TRACKING IN PSYCHOLINGUISTICS

2018 ◽  
Author(s):  
Tatiana Chernigovskaya ◽  
◽  
Svetlana Alexeeva ◽  
Anzhalika Dubasava ◽  
Tatiana Petrova ◽  
...  
Keyword(s):  
Visual Perception ◽  
Eye Tracking ◽  
Language Processing ◽  
Experimental Studies ◽  
Text Type ◽  
Advantages And Disadvantages ◽  
Cognitive Studies ◽  
New Information ◽  
Wide Range ◽  
The One

The book addresses the study of reading mechanisms and visual perception using the method of eye-tracking. The authors conduct their research in the Laboratory for Cognitive Studies of Saint Petersburg State University that was the first in Russia to utilize eye-tracking in experimental studies of language more than 15 years ago. Psycholinguistic experiments aimed at analyzing reading in Russian are described; a systematic description of factors which influence reading process at different stages and linguistic levels from a single letter to a coherent text is provided. The mechanisms of separate graphemes recognition, activation and competition processes in word recognition, contextual integration processes, syntactic parsing, and anaphora resolution in eye-tracking experiments are described. The influence of the text type on its processing is demonstrated, the advantages and disadvantages of the infographics compared to verbal text are described, the relationship between visual perception of images and their verbalization is discussed. The significant role of context is highlighted: on the one hand, it helps the reader to anticipate new information, and on the other hand, it enables different multiple interpretations of a sentence or text. In the book a virtual assistant — Schroedinger’s cat — is used as a model of a subject who processes and transmits information. The book will appeal to linguists and cognitive psychologists who use eye-tracking in their research, as well as for the wide range of those who are interested in objective methods of studying language processing and human behavior.

A Simplified Analytical Model of Rolling/Sliding Behavior and Friction in Four-Point-Contact Ball Bearings and Screws

2017 ◽  
Author(s):  
Bo Lin ◽  
Molong Duan ◽  
Chinedum E. Okwudire ◽  
Jason S. Wou
Keyword(s):  
Analytical Model ◽  
Contact Point ◽  
Point Contact ◽  
Contact Angles ◽  
Friction Model ◽  
Contact Forces ◽  
Ball Bearings ◽  
Contact Points ◽  
Pure Rolling ◽  
Coulomb Friction Model

Four-point contact between ball and raceways is common in machine elements like ball bearings and ball screws. The ideal four-point-contact machine element is designed with pure rolling (i.e., no sliding at contact points) to minimize friction. However, this ideal may not always be achieved, leading to sliding and higher frictional forces. In this paper, a simplified analytical model for rolling/sliding behavior and friction in four-point contact is developed, based on Coulomb friction model and rigid body assumption. It is found that pure rolling is only possible when the contact-point geometry satisfies a certain relationship. When pure rolling condition fails to hold, the sliding contact point(s) can be determined analytically as a function of contact forces and contact angles. Case studies are presented to demonstrate how the proposed model could elucidate the roles of misalignments, manufacturing errors and loading conditions on rolling/sliding behavior and friction.

Numerical Simulation of Convective Heat Transfer in Structured Packed Beds of Particles With Different Particle Contact Treatment Methods

2012 ◽  
Author(s):  
S. S. Bu ◽  
J. Yang ◽  
S. Y. Li ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Contact Point ◽  
Point Contact ◽  
Treatment Method ◽  
Contact Method ◽  
Packed Beds ◽  
Treatment Methods ◽  
Contact Points ◽  
Flow And Heat Transfer ◽  
Sphere Contact

The treatment of sphere contact is a crucial issue on the numerical analysis of the flow and heat transfer in packed beds of particles. In this work, the effects of three different methods including introducing a gap, area contacting and cylindrically bridging on the flow and heat transfer performances of structured packed beds of particles are investigated with CFD methods. The simulation results have shown that the influence of different treatment methods on the contact point on flow and heat transfer gets greater as the porosity decreases and the Reynolds number increases. There are no large differences among these three methods on the pressure drop and heat transfer under laminar flow regime. Compared with the experimental results, cylindrically bridging method is proved to be reasonable to simplify the sphere–sphere contact points. Therefore, cylindrically bridging treatment method is encouraged to be used instead of point contact method between particles with CFD analysis in structured packed beds of particles.

Photoelastic Study of Friction

1991 ◽  
Vol 44 (11S) ◽  
pp. S60-S66
Author(s):  
James W. Dally ◽  
Yung-Mien Chen
Keyword(s):  
Large Scale ◽  
Fringe Pattern ◽  
Normal Load ◽  
Contact Point ◽  
Point Contact ◽  
Multiple Point ◽  
Multiple Points ◽  
Local Neighborhood ◽  
Contact Points ◽  
Data Points

A new method of measuring the normal and sliding loads associated with multiple point contact is introduced. A multiple point contact is modeled with a steel die with a profile that simulates a rough surface. A very large scale factor is used in modeling this surface. The steel die is placed in contact with a photoelastic model of a half plane and is subjected to a normal load. This normal load is partitioned over the multiple points of contact producing an isochromatic fringe pattern that describes the stress distribution in the local neighborhood of the contact points. A sliding load is then imposed on the model which destroys the symmetry of this fringe pattern. The fringe data in this pattern is sufficient to determine the local loads Pi and Qi and the local coefficient of friction fi = Qi / Pi at each contact point. An overdeterministic method is introduced which gives the solution for Pi, Qi and fi using many data points taken from the isochromatic pattern in the local neighborhood of the contacts.

Regional household poverty and mobility analysis – a transition probability approach

2020 ◽  
Vol 63 (3) ◽  
pp. 286-302
Author(s):  
Damian Mowczan ◽  
Keyword(s):  
Transition Probability ◽  
General Level ◽  
Transition Matrices ◽  
Equivalent Unit ◽  
Central Statistical ◽  
Per Capita ◽  
Probability Matrices ◽  
General Mobility ◽  
One Year ◽  
The One

The main objective of this paper was to estimate and analyse transition-probability matrices for all 16 of Poland’s NUTS-2 level regions (voivodeship level). The analysis is conducted in terms of the transitions among six expenditure classes (per capita and per equivalent unit), focusing on poverty classes. The period of analysis was two years: 2015 and 2016. The basic aim was to identify both those regions in which the probability of staying in poverty was the highest and the general level of mobility among expenditure classes. The study uses a two-year panel sub-sample of unidentified unit data from the Central Statistical Office (CSO), specifically the data concerning household budget surveys. To account for differences in household size and demographic structure, the study used expenditures per capita and expenditures per equivalent unit simultaneously. To estimate the elements of the transition matrices, a classic maximum-likelihood estimator was used. The analysis used Shorrocks’ and Bartholomew’s mobility indices to assess the general mobility level and the Gini index to assess the inequality level. The results show that the one-year probability of staying in the same poverty class varies among regions and is lower for expenditures per equivalent units. The highest probabilities were identified in Podkarpackie (expenditures per capita) and Opolskie (expenditures per equivalent unit), and the lowest probabilities in Kujawsko-Pomorskie (expenditures per capita) and Małopolskie (expenditures per equivalent unit). The highest level of general mobility was noted in Małopolskie, for both categories of expenditures.

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

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