Modelling a Single-Wheel Testbed for Planetary Rover Applications

2010 ◽  
Author(s):  
Rishad A. Irani ◽  
Robert J. Bauer ◽  
Andrew Warkentin
Keyword(s):  
Dynamic Model ◽  
Sandy Soil ◽  
Dynamic Effect ◽  
Soil Deformation ◽  
Planetary Rover ◽  
New Model ◽  
Static Models ◽  
Force Data

This paper presents a dynamic model for a smooth wheel travelling through loose sandy soil. Many models that are used for such wheel-soil interactions are typically static or quasi-static models. The new model builds upon these widely-used models by adding the dynamic effect of the soil deformation. The new model is validated using experiments that were carried on a new single wheel testbed which was constructed at Dalhousie University. During experiments with a smooth wheel it was noticed that the track of the wheel had repeatable ridges. Moreover, it was noticed that the corresponding torque and force data also had oscillations in it with the periods of the harmonic coinciding with the ridges in the sand left by the track of the wheel.

The Effects of Static Frictions on the Drilling Process of Hammer-Drill System

2005 ◽  
Author(s):  
Y. Xu ◽  
K. L. Yung ◽  
S. M. Ko
Keyword(s):  
Dynamic Model ◽  
Cutting Process ◽  
Drilling Process ◽  
Normal Impact ◽  
New Model ◽  
Mars Mission ◽  
Dynamic Analyses ◽  
Drill System

Static frictions are neglected in many dynamic analyses mainly due to inappropriate modeling of them. A new dynamic model describing the nonlinear and discrete features of static frictions is proposed in this paper. Using the new model, the drilling process of the hammer-drill system utilized in the EAS’ Mars mission is analyzed. It is shown that most important functions of the hammer-drill system are realized by static frictions, which were not observed before the introduction of the new model of static frictions. Static frictions provide the torsional force on the drill and make the normal impact happen before the rotation, which is critical to the efficiency of the cutting process of the hammer-drill system.

scholarly journals Is modelling complexity always needed? Insights from modelling PrEP introduction in South Africa

2020 ◽  
Vol 42 (4) ◽  
pp. e551-e560 ◽  
Author(s):  
Hannah Grant ◽  
Anna M Foss ◽  
Charlotte Watts ◽  
Graham F Medley ◽  
Zindoga Mukandavire
Keyword(s):  
South Africa ◽  
Condom Use ◽  
Dynamic Model ◽  
Hiv Risk ◽  
Dynamic Models ◽  
Static Model ◽  
Hiv Intervention ◽  
Time Horizons ◽  
Static Models ◽  
The Impact

Abstract Background Mathematical models can be powerful policymaking tools. Simple, static models are user-friendly for policymakers. More complex, dynamic models account for time-dependent changes but are complicated to understand and produce. Under which conditions are static models adequate? We compare static and dynamic model predictions of whether behavioural disinhibition could undermine the impact of HIV pre-exposure prophylaxis (PrEP) provision to female sex workers in South Africa. Methods A static model of HIV risk was developed and adapted into a dynamic model. Both models were used to estimate the possible reduction in condom use, following PrEP introduction, without increasing HIV risk. The results were compared over a 20-year time horizon, in two contexts: at epidemic equilibrium and during an increasing epidemic. Results Over time horizons of up to 5 years, the models are consistent. Over longer timeframes, the static model overstates the tolerated reduction in condom use where initial condom use is reasonably high ($\ge$50%) and/or PrEP effectiveness is low ($\le$45%), especially during an increasing epidemic. Conclusions Static models can provide useful deductions to guide policymaking around the introduction of a new HIV intervention over short–medium time horizons of up to 5 years. Over longer timeframes, static models may not sufficiently emphasise situations of programmatic importance, especially where underlying epidemics are still increasing.

New Model with Spring and Simulation of Flexible Manipulator

2014 ◽  
Vol 513-517 ◽  
pp. 3840-3843
Author(s):  
Ying Tian ◽  
Jian Hua Qian ◽  
Qing Song Liu ◽  
Jie Yuan
Keyword(s):  
Computer Simulation ◽  
Dynamic Model ◽  
Elastic Energy ◽  
Lagrange Equation ◽  
Rigid Bodies ◽  
Flexible Manipulator ◽  
Dynamic Parameters ◽  
New Model ◽  
Real Model ◽  
Model Computer

For easily calculated and more accurate dynamic model of single flexible manipulator, a new model was built through connection of spring and two rigid bodies. It is approximate to the real model of single manipulator in trajectory of end point. With simplifying manipulator and introducing simplified and Predetermined elastic energy of manipulator, Lagrange equation was used to built dynamic model based on the new model. And based on dynamic model, computer simulation result of dynamic parameters with Matlab software proved that the new model is available simple and easily-adjusted.

Modeling and Designing a Variable-Displacement Open-Loop Pump

1996 ◽  
Vol 118 (2) ◽  
pp. 267-271 ◽  
Author(s):  
N. D. Manring ◽  
R. E. Johnson
Keyword(s):  
Closed Form ◽  
Dynamic Model ◽  
Dynamic Effect ◽  
Open Loop ◽  
Volume Discharge ◽  
Pumping System ◽  
Actuation System ◽  
Parameter Variations ◽  
Displacement Pump ◽  
Variable Displacement

This study develops closed-form equations that may be used to guide the up-front design of a variable-displacement pump. In particular, the initial design of the control actuation system and the controller flow-gain is considered. A dynamic model of the pumping system is also presented and the dynamic effect of parameter variations such as actuator volume, discharge-hose volume, controller flow-gain and system leakage is discussed.

Rapid calculation method for estimating static and dynamic performances of closed hydrostatic guideways

2017 ◽  
Vol 69 (6) ◽  
pp. 1040-1048 ◽  
Author(s):  
Zhiwei Wang ◽  
Yi Liu ◽  
Feng Wang
Keyword(s):  
Dynamic Model ◽  
Lagrange Equation ◽  
Dynamic Stiffness ◽  
Step Response ◽  
Nonlinear Spring ◽  
Content Type ◽  
New Model ◽  
Linear Spring ◽  
Spring Coefficient ◽  
Better Than

Purpose The purpose of this paper is to establish a simplified model of the closed hydrostatic guideway for the rapid analysis of static and dynamic characteristics. Further, the influence of compressibility and dynamic frequency are taken into consideration in the new dynamic model. Design/methodology/approach The new model is based on the second kind of Lagrange equation. In this model, the closed hydrostatic guideway is supported by 12 pads, and each oil pad is equivalent to a nonlinear spring-damper system. The equivalent spring coefficient and damper coefficient of the oil pad are extracted by the three different equivalent methods. Finally, the validation experiments of step load response and dynamic stiffness are conducted on a hydrostatic guideway. Findings For solving the step response, the linear spring-damper model and the nonlinear spring-damper Model 1 are better than the nonlinear spring-damper Model 2. The accuracy of the three methods are very high for static stiffness calculation. For the calculation of dynamic stiffness, the nonlinear spring-damper Model 2 is better than the nonlinear spring-damper Model 1. The linear spring-damper model has low precision for dynamic stiffness calculation, especially at high frequency. The accuracy of the new model is validated by experiments. Originality/value The equivalent method of nonlinear spring-damper system has higher accuracy. Different equivalent methods should be adopted for different load types. The computational speeds of the new dynamic model with the three methods are much better than finite element method (about ten times).

scholarly journals Configurable 3D Rowing Model Renders Realistic Forces on a Simulator for Indoor Training

2020 ◽  
Vol 10 (3) ◽  
pp. 734 ◽  
Author(s):  
Ekin Basalp ◽  
Patrick Bachmann ◽  
Nicolas Gerig ◽  
Georg Rauter ◽  
Peter Wolf
Keyword(s):  
Dynamic Model ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Smooth Transition ◽  
Model Parameters ◽  
Interaction Forces ◽  
New Model ◽  
Perceived Realism ◽  
Water Interaction ◽  
Resistive Forces

In rowing, rowers need outdoor and indoor training to develop a proficient technique. Although numerous indoor rowing machines have been proposed, none of the devices can realistically render the haptic, visual, and auditory characteristics of an actual rowing scenario. In our laboratory, we developed a simulator to support rowing training indoors. However, rendered forces with the initial rowing model, which was based on a simplified fluid dynamic model that approximated the drag/lift forces, were not perceived realistic enough for indoor training by expert rowers. Therefore, we implemented a new model for the blade–water interaction forces, which incorporates the three-dimensional rotation of the oar and continuously adjusts drag/lift coefficients. Ten expert rowers were asked to evaluate both models for various rowing aspects. In addition, the effect of individualization of model parameters on the perceived realism of rowing forces was elaborated. Based on the answers of the experts, we concluded that the new model rendered realistically resistive forces and ensured a smooth transition of forces within a rowing cycle. Additionally, we found that individualization of parameters significantly improved the perceived realism of the simulator. Equipped with a configurable rowing model, our simulator provides a realistic indoor training platform for rowers.

scholarly journals Dynamic self-cleaning in gecko setae via digital hyperextension

2012 ◽  
Vol 9 (76) ◽  
pp. 2781-2790 ◽  
Author(s):  
Shihao Hu ◽  
Stephanie Lopez ◽  
Peter H. Niewiarowski ◽  
Zhenhai Xia
Keyword(s):  
Dynamic Model ◽  
Inertial Force ◽  
Dynamic Effect ◽  
Optimal Performance ◽  
The Self ◽  
Biomimetic Design ◽  
Dry Adhesives ◽  
Strong Adhesion ◽  
Self Cleaning ◽  
Gecko Feet

Gecko toe pads show strong adhesion on various surfaces yet remain remarkably clean around everyday contaminants. An understanding of how geckos clean their toe pads while being in motion is essential for the elucidation of animal behaviours as well as the design of biomimetic devices with optimal performance. Here, we test the self-cleaning of geckos during locomotion. We provide, to our knowledge, the first evidence that geckos clean their feet through a unique dynamic self-cleaning mechanism via digital hyperextension. When walking naturally with hyperextension, geckos shed dirt from their toes twice as fast as they would if walking without hyperextension, returning their feet to nearly 80 per cent of their original stickiness in only four steps. Our dynamic model predicts that when setae suddenly release from the attached substrate, they generate enough inertial force to dislodge dirt particles from the attached spatulae. The predicted cleaning force on dirt particles significantly increases when the dynamic effect is included. The extraordinary design of gecko toe pads perfectly combines dynamic self-cleaning with repeated attachment/detachment, making gecko feet sticky yet clean. This work thus provides a new mechanism to be considered for biomimetic design of highly reuseable and reliable dry adhesives and devices.

DYNAMIC APPROACH TO ANALYSIS OF ANGULAR DISTRIBUTIONS OF FISSION AND QUASIFISSION FRAGMENTS

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1125-1133 ◽  
Author(s):  
V. A. DROZDOV ◽  
D. O. EREMENKO ◽  
O. V. FOTINA ◽  
S. Yu. PLATONOV ◽  
O. A. YUMINOV ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Angular Momentum ◽  
Dynamic Model ◽  
Angular Distributions ◽  
Dynamic Approach ◽  
Dinuclear System ◽  
New Model ◽  
Angular Correlations

The dynamic model is proposed for description of the angular distributions of quasifission fragments. The model is able to describe experimental anisotropy of the angular distributions of fissionlike fragments for the 32 S , 28 Si +208 Pb reactions. It is also shown that the new model allows the description of the experimental mass-angular correlations in the quasifission fragment yields for the 64 Ni +197 Au reaction at 383 and 418 MeV of incident energies. The analysis was performed with the angular momentum and deformation dependent relaxation time of the tilting mode. Information on the dinuclear system lifetimes were obtained.

Optimal Timing of Policy Announcements in Dynamic Election Campaigns*

2020 ◽  
Vol 135 (3) ◽  
pp. 1725-1797
Author(s):  
Yuichiro Kamada ◽  
Takuo Sugaya
Keyword(s):  
Dynamic Model ◽  
Optimal Timing ◽  
Election Campaign ◽  
Election Campaigns ◽  
Policy Space ◽  
Policy Positions ◽  
Static Models ◽  
Long Time

Abstract We construct a dynamic model of election campaigns. In the model, opportunities for candidates to refine/clarify their policy positions are limited and arrive stochastically along the course of the campaign until the predetermined election date. We show that this simple friction leads to rich and subtle campaign dynamics. We first demonstrate these effects in a series of canonical static models of elections that we extend to dynamic settings, including models with valence and a multidimensional policy space. We then present general principles that underlie the results from those models. In particular, we establish that candidates spend a long time using ambiguous language during the election campaign in equilibrium.

scholarly journals The Value of Incumbency When Platforms Face Heterogeneous Customers

2020 ◽  
Vol 12 (4) ◽  
pp. 229-269
Author(s):  
Gary Biglaiser ◽  
Jacques Crémer
Keyword(s):  
Dynamic Model ◽  
Network Externalities ◽  
Market Outcomes ◽  
Dynamic Framework ◽  
Static Models ◽  
Heterogeneous Consumers

We study competition for the market in a dynamic model with network externalities, focusing on the efficiency of market outcomes. We propose a representation of the strategic advantages of incumbency and embed it in a dynamic framework with heterogeneous consumers. Then, we completely identify the conditions under which inefficient equilibria with several platforms emerge at equilibrium; explore the reasons why these inefficient equilibria arise; and compute the value of incumbency and analyze why static models generally exaggerate it. (JEL D43, D62, L13, L86)

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