Coulomb Friction Crawling Model Yields Linear Force–Velocity Profile

2019 ◽  
Vol 86 (5) ◽  
Author(s):  
Ziyou Wu ◽  
Dan Zhao ◽  
Shai Revzen
Keyword(s):  
Kinetic Energy ◽  
Velocity Profile ◽  
Entire Range ◽  
Coulomb Friction ◽  
Viscous Friction ◽  
Governing Equations ◽  
Average Speed ◽  
Force Velocity ◽  
Linear Force ◽  
Work Done

Conventional wisdom would have it that moving mechanical systems that dissipate energy by Coulomb friction have no relationship between force and average speed. One could argue that the work done by friction is constant per unit of distance travelled, and if propulsion forces exceed friction, the net work is positive, and the system accumulates kinetic energy without bound. We present a minimalistic model for legged propulsion with slipping under Coulomb friction, scaled to parameters representative of single kilogram robots and animals. Our model, amenable to exact solutions, exhibits nearly linear (R2 > 0.96) relationships between actuator force and average speed over its entire range of parameters, and in both motion regimes, it supports. This suggests that the interactions inherent in multilegged locomotion may lead to governing equations more reminiscent of viscous friction than would be immediately obvious.

Anodal transcranial direct current stimulation enhances strength training volume but not the force–velocity profile

2020 ◽  
Vol 120 (8) ◽  
pp. 1881-1891 ◽  
Author(s):  
Carlos Alix-Fages ◽  
Amador García-Ramos ◽  
Giancarlo Calderón-Nadal ◽  
David Colomer-Poveda ◽  
Salvador Romero-Arenas ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Strength Training ◽  
Direct Current ◽  
Transcranial Direct Current Stimulation ◽  
Training Volume ◽  
Direct Current Stimulation ◽  
Force Velocity

Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

2021 ◽  
Vol 57 (1) ◽  
pp. 015012
Author(s):  
Unofre B Pili ◽  
Renante R Violanda
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Conservation Law ◽  
Gravitational Potential Energy ◽  
Time Data ◽  
Home Based ◽  
Basic Physics ◽  
Free Falling ◽  
Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

scholarly journals The Rotating Rigid Body Model Based on a Non-twisting Frame

2020 ◽  
Vol 30 (6) ◽  
pp. 3199-3233 ◽  
Author(s):  
Cristian Guillermo Gebhardt ◽  
Ignacio Romero
Keyword(s):  
Kinetic Energy ◽  
Rigid Body ◽  
Conservation Laws ◽  
Rotation Rate ◽  
Governing Equations ◽  
New Model ◽  
Body Model ◽  
Integration Schemes ◽  
Rigid Body Model ◽  
Unit Vectors

Abstract This work proposes and investigates a new model of the rotating rigid body based on the non-twisting frame. Such a frame consists of three mutually orthogonal unit vectors whose rotation rate around one of the three axis remains zero at all times and, thus, is represented by a nonholonomic restriction. Then, the corresponding Lagrange–D’Alembert equations are formulated by employing two descriptions, the first one relying on rotations and a splitting approach, and the second one relying on constrained directors. For vanishing external moments, we prove that the new model possesses conservation laws, i.e., the kinetic energy and two nonholonomic momenta that substantially differ from the holonomic momenta preserved by the standard rigid body model. Additionally, we propose a new specialization of a class of energy–momentum integration schemes that exactly preserves the kinetic energy and the nonholonomic momenta replicating the continuous counterpart. Finally, we present numerical results that show the excellent conservation properties as well as the accuracy for the time-discretized governing equations.

Force/Velocity Control of a Pneumatic Gantry Robot for Contour Tracking With Neural Network Compensation

2008 ◽  
Author(s):  
Mohammed Abu-Mallouh ◽  
Brian Surgenor
Keyword(s):  
Neural Network ◽  
Coulomb Friction ◽  
Tangential Velocity ◽  
Limiting Factor ◽  
Contour Tracking ◽  
Velocity Control ◽  
Hybrid Controller ◽  
Controller Performance ◽  
Force Velocity ◽  
Gantry Robot

In this paper, the application of a pneumatic gantry robot to contour tracking is examined. A hybrid controller is structured to control the contact force and the tangential velocity, simultaneously. A previous study provided controller tuning and model validation results for a fixed gain PI-based force/velocity controller. Performance was limited by system lag and Coulomb friction. New results demonstrate that even with perfect friction compensation, the limiting factor is the system lag. A neural network (NN) compensator was subsequently developed to counter both effects. Results for straight and curved edged workpieces are presented to demonstrate the effectiveness of the NN compensator and the capabilities of a pneumatic gantry robot.

scholarly journals Doppler telemetry system for the evaluation of low speed movements in the atmosphere

2004 ◽  
Vol 17 (3) ◽  
pp. 313-324 ◽  
Author(s):  
Mihail Tanase ◽  
Corneliu Toma ◽  
Dan Popa ◽  
Ioan Lie
Keyword(s):  
Radio Telemetry ◽  
Telemetry System ◽  
Movement Execution ◽  
Average Speed ◽  
Low Speed ◽  
Movement Sense ◽  
Low Costs ◽  
Work Done

This paper is a result of the work done by the authors in the field of movement evaluation at low speed in the atmosphere and low costs of the movement execution. Theoretical and constructive solutions are offered for telemetry of the following features of movement: instant and average speed movement sense and direction, instant position related to a fixed referential. The presented solution, the Doppler radio telemetry system with active fixed referential-described in the paper-was practically realized and experimentally its utility has been demonstrated.

scholarly journals The theory of the chain fountain revisited

2021 ◽  
Vol 2090 (1) ◽  
pp. 012166
Author(s):  
Dragos-Victor Anghel
Keyword(s):  
Energy Transfer ◽  
Kinetic Energy ◽  
Significant Role ◽  
Mechanical Work ◽  
Scientific Consensus ◽  
Energy And Momentum ◽  
Work Done

Abstract We analyze the chain fountain effect-the chain siphoning when falling from a container onto the floor. We argue that the main reason for this effect is the inertia of the chain, whereas the momentum received by the beads of the chain from the bottom of the container (typically called “kicks”) plays no significant role. The inertia of the chain leads to an effect similar to pulling the chain over a pulley placed up in the air, above the container. In another model (the so called “scientific consensus”), it was assumed that up to half of the mechanical work done by the tension in the chain may be wasted when transformed into kinetic energy during the pickup process. This prevented the chain to rise unless the energy transfer in the pickup process is improved by the “kicks” from the bottom of the container. Here we show that the “kicks” are unnecessary and both, energy and momentum are conserved-as they should be, in the absence of dissipation-if one properly considers the tension and the movement of the chain. By doing so, we conclude that the velocity acquired by the chain is high enough to produce the fountain effect. Simple experiments validate our model and certain configurations produce the highest chain fountain, although “kicks” are impossible.

scholarly journals Determining strength training needs using the force-velocity profile of elite female handball and volleyball players

2020 ◽  
pp. 174795412096404
Author(s):  
Leonidas Petridis ◽  
Gergely Pálinkás ◽  
Zsófia Tróznai ◽  
Bettina Béres ◽  
Katinka Utczás
Keyword(s):  
Velocity Profile ◽  
Strength Training ◽  
Body Mass ◽  
Female Athletes ◽  
Vertical Jump ◽  
Body Height ◽  
Maximum Velocity ◽  
Total Force ◽  
Volleyball Players ◽  
Force Velocity

The aim of this study was to assess the vertical jump performance and the force-velocity profile of elite female handball and volleyball players. Forty-one female athletes were measured, 28 handball players (age: 24.0 ± 3.6 years, body height: 1.75 ± 0.05 m, body mass: 69.0 ± 7.3 kg) and 13 volleyball players (age: 24.1 ± 5.2 years, body height: 1.83 ± 0.07 m and body mass: 74.9 ± 7.9 kg). All players performed unloaded and loaded countermovement jumps (CMJ) on a force platform. The theoretical maximal force ( F0), the theoretical maximum velocity ( v0), the theoretical maximal power ( Pmax), the slope of the F-v relationship ( Sfv) and the force-velocity imbalance ( FVimb) were calculated. Mean value of vertical jump height was 0.33 ± 0.03m, with no difference between handball and volleyball players. Mean values of F0, v0, Pmax, Sfv and FVimb for all players were 31.2 ± 2.6 N/kg, 3.10 ± 0.50 m·s−1, 24.2 ± 3.2 w/kg, -10.32 ± 2.09 Ns/m/kg and 28.1 ± 13.3% respectively. Two players had a low magnitude velocity-deficit, whereas most of the players exhibited a low to high force-deficit. A strong correlation was found between the ratio of measured to optimal F-v slope with the change in the proportion of net force to total force during unloaded and loaded conditions. The findings suggest that it would be beneficial for these athletes to first decrease their force deficit through mainly maximal strength training before implementing training to further maximize power output. Establishment of the F-v profile could be a useful diagnostic tool for coaches to optimize strength training and to design training intervention based on the individual need of each athlete.

Influence of Resisted Sled-Pull Training on the Sprint Force-Velocity Profile of Male High-School Athletes

2020 ◽  
Vol 34 (10) ◽  
pp. 2751-2759
Author(s):  
Micheál J. Cahill ◽  
Jon L. Oliver ◽  
John B. Cronin ◽  
Kenneth Clark ◽  
Matt R. Cross ◽  
...  
Keyword(s):  
High School ◽  
Velocity Profile ◽  
High School Athletes ◽  
Male High School ◽  
Force Velocity

Association of the Vertical and Horizontal Force-Velocity Profile and Acceleration With Change of Direction Ability in Various Sports

2020 ◽  
pp. 1-21
Author(s):  
Andrés Baena-Raya ◽  
Alberto Soriano-Maldonado ◽  
Filipe Conceição ◽  
Pedro Jiménez-Reyes ◽  
Manuel A. Rodríguez-Pérez
Keyword(s):  
Velocity Profile ◽  
Horizontal Force ◽  
Change Of Direction ◽  
Force Velocity
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