Mitigating Peak Impact Forces by Customizing the Passive Foot Dynamics of Legged Robots

2020 ◽  
Vol 12 (5) ◽  
Author(s):  
Jesse J. Rond ◽  
Michael C. Cardani ◽  
Matthew I. Campbell ◽  
Jonathan W. Hurst
Keyword(s):  
High Frequency ◽  
Legged Locomotion ◽  
Control Algorithms ◽  
Maximum Compression ◽  
Impact Forces ◽  
Damping Material ◽  
Physical Testing ◽  
Force Peak ◽  
High Frequency Vibrations ◽  
The Impact

Abstract Impact forces are a destructive, yet common occurrence in legged locomotion. Every step produces a collision when the leg’s inertia stops as a result of ground contact. This results in peak forces and high-frequency vibrations that resonate through the system, damage components, and complicate control algorithms. Prior research considers how damping material, such as rubber, mitigates these effects. However, this paper shows the benefits of spring protection where both stiffness and maximum compression are customized to the leg. The spring mitigates the impact force peak by gradually bringing the leg’s inertia to rest. The maximum compression point (i.e., a hard stop) then provides a rigid surface that is ideal for stance. We provide a foot design methodology, validated through simulation and physical testing, that first considers springs in isolation, then in tandem with damping. We show that the coupling of springs and dampers reduces rigid body collisions and foot vibrations in a way that traditional methods—reliant on damping—have yet to achieve.

Eliminating Peak Impact Forces by Customizing the Passive Foot Dynamics of Legged Robots

2019 ◽  
Author(s):  
Jesse J. Rond ◽  
Michael C. Cardani ◽  
Matthew I. Campbell ◽  
Jonathan W. Hurst
Keyword(s):  
High Frequency ◽  
Legged Locomotion ◽  
Legged Robots ◽  
Control Algorithms ◽  
Rigid Surface ◽  
Maximum Compression ◽  
Impact Forces ◽  
Damping Material ◽  
Physical Testing ◽  
High Frequency Vibrations

Abstract Impact forces are a destructive, yet common occurrence in legged locomotion. Every step produces a collision when the leg’s inertia immediately stops upon ground contact. This results in peak impact forces and high frequency vibrations that resonate through the system, damage components, and complicate control algorithms. Rubber or other damping material is the assumed solution for mitigating these impacts. However, we show the benefit of using foot springs where both stiffness and maximum compression are customized to the leg. Such springs eliminate peak impact forces by gradually bringing the leg’s inertia to rest. The maximum compression point (i.e. a hard stop) then provides a rigid surface during stance. We provide a methodology for designing this passive dynamic foot that is validated through simulation and physical testing. Our results show this methodology reduces rigid body impacts and foot vibrations in a way traditional methods, reliant upon rubber or damping, are yet to achieve.

A gear rattle model accounting for oil squeeze between the meshing gear teeth

2005 ◽  
Vol 219 (9) ◽  
pp. 1075-1083 ◽  
Author(s):  
R Brancati ◽  
E Rocca ◽  
R Russo
Keyword(s):  
High Frequency ◽  
Oil Viscosity ◽  
Damping Force ◽  
Oil Film ◽  
One Dimensional ◽  
Gear Teeth ◽  
High Frequency Vibrations ◽  
The Impact ◽  
Gear Rattle ◽  
Lubrication Conditions

In this paper a non-linear one-degree-of-freedom model for analysis of gear rattle vibrations in automotive manual transmissions is presented. In order to take into account the damping effects owing to the oil in the gap between two teeth of a meshing gear, a simple one-dimensional model for the oil-film squeeze effects is proposed. The squeeze model assumes that the damping force is proportional to the oil viscosity and to the extension of the oil film in the plane of curvature of the teeth, which may depend on the lubrication conditions (dry sump, splash, bath). The results provided from several numerical simulations, carried out with reference to helical involute tooth pairs, confirm the capability of oil in reducing the high-frequency vibrations subsequent to the impact between the teeth. In particular, the influence exerted by oil viscosity and gap extension on the rattle characteristics is investigated through the analysis of the transient response of the driven gear by imposing a harmonic motion to the driving gear.

Vibration monitoring and strength of structural elements taking into account the inertial properties of materials under broadband vibration

2020 ◽  
Author(s):  
О.B. Skvortsov
Keyword(s):  
High Frequency ◽  
Cyclic Strength ◽  
Vibration Monitoring ◽  
Structural Elements ◽  
High Frequency Vibration ◽  
Latent Defects ◽  
Current State ◽  
Properties Of Materials ◽  
High Frequency Vibrations ◽  
The Impact

The paper considers influence of the inertial properties of structural materials on mechanical stresses under high-frequency vibrations. The necessity of considering acceleration estimates when creating vibration monitoring systems focused on the incorporating cyclic strength is proved. The importance of the effects of high-frequency vibration in the local areas of the structural material is noted, taking into account the formation of latent defects and reducing the fatigue limit during gigacycle fatigue. Recommendations are given concerning supplement to the vibration monitoring system, taking into account the decrease in strength under high-frequency vibration when solving problems of diagnostics, forecasting and protection with new innovative solutions. It provides increased reliability of the diagnosis and protection of equipment. In addition to evaluating the current state of the unit based on the results of vibration intensity measuring, the proposed solutions allow additional assessing the degree of wear and taking into account the impact of fatigue processes in the operation of a multi-level automatic protection system of the equipment.

Simulation of vibration piercing of pipe blank at press

2020 ◽  
Vol 76 (11) ◽  
pp. 1128-1138
Author(s):  
S. R. Rakhmanov
Keyword(s):  
High Frequency ◽  
Deformation Zone ◽  
Pipe Blank ◽  
Equipment Operation ◽  
Metal Deformation ◽  
Technological Tool ◽  
High Frequency Vibrations ◽  
Pipe Blanks ◽  
Wave Phenomena

In some cases, the processes of piercing or expanding pipe blanks involve the use of high-frequency active vibrations. However, due to insufficient knowledge, these processes are not widely used in the practice of seamless pipes production. In particular, the problems of increasing the efficiency of the processes of piercing or expanding a pipe blank at a piercing press using high-frequency vibrations are being solved without proper research and, as a rule, by experiments. The elaboration of modern technological processes for the production of seamless pipes using high-frequency vibrations is directly related to the choice of rational modes of metal deformation and the prediction resistance indicators of technological tools and the reliability of equipment operation. The creation of a mathematical model of the process of vibrating piercing (expansion) of an axisymmetric pipe blank at a piercing press of a pipe press facility is an actual task. A calculation scheme for the process of piercing a pipe plank has been elaborated. A dependence was obtained characterizing the speed of front of plastic deformation propagation on the speed of penetration of a vibrated axisymmetric mandrel into the pipe workpiece being pierced. The dynamic characteristics of the occurrence of wave phenomena in the metal being pierced under the influence of a vibrated tool have been determined, which significantly complements the previously known ideas about the stress-strain state of the metal in the deformation zone. The deformation fields in the zones of the disturbed region of the deformation zone were established, taking into account the high-frequency vibrations of the technological tool. It has been established that the choice of rational parameters (amplitude-frequency characteristics) of the vibration piercing process of a pipe blank results in significant increase in the efficiency of the process, the durability of the technological tool and the quality of the pierced blanks.

Global Algorithmic Capital Markets

2018 ◽  
Keyword(s):  
Public Policy ◽  
Capital Markets ◽  
Systemic Risk ◽  
High Frequency ◽  
Investor Protection ◽  
High Frequency Trading ◽  
Market Making ◽  
Market Governance ◽  
Policy Objectives ◽  
The Impact

This book illustrates and assesses the dramatic recent transformations in capital markets worldwide and the impact of those transformations. ‘Market making’ by humans in centralized markets has been replaced by supercomputers and algorithmic high frequency trading operating in often highly fragmented markets. How do recent market changes impact on core public policy objectives such as investor protection, reduction of systemic risk, fairness, efficiency, and transparency in markets? The operation and health of capital markets affect all of us and have profound implications for equality and justice in society. This unique set of chapters by leading scholars, industry insiders, and regulators sheds light on these and related questions and discusses ways to strengthen market governance for the benefit of society at large.

scholarly journals Crisis Management in Higher Education in the Time of Covid-19: The Case of Actor Training

2021 ◽  
Vol 11 (3) ◽  
pp. 132
Author(s):  
Anna McNamara
Keyword(s):  
Higher Education ◽  
Crisis Management ◽  
High Frequency ◽  
High Reliability ◽  
Actor Training ◽  
Management Actions ◽  
The Usa ◽  
The Uk ◽  
The Impact ◽  
High Frequency Words

The impact of Covid-19 placed Higher Education leadership in a state of crisis management, where decision making had to be swift and impactful. This research draws on ethea of mindfulness, actor training techniques, referencing high-reliability organisations (HRO). Interviews conducted by the author with three leaders of actor training conservatoires in Higher Education institutions in Australia, the UK and the USA reflect on crisis management actions taken in response to the impact of Covid-19 on their sector, from which high-frequency words are identified and grouped thematically. Reflecting on these high-frequency words and the thematic grouping, a model of mindful leadership is proposed as a positive tool that may enable those in leadership to recognise and respond efficiently to wider structural frailties within Higher Education, with reference to the capacity of leaders to operate with increased mindfulness, enabling a more resilient organisation that unlocks the locus of control.

Analytical Solution for Rotational Rub-Impact Plate Under Thermal Shock

2016 ◽  
Vol 32 (3) ◽  
pp. 297-311
Author(s):  
T.-Y. Zhao ◽  
H.-Q. Yuan ◽  
B.-B. Li ◽  
Z.-J. Li ◽  
L.-M. Liu
Keyword(s):  
Thermal Shock ◽  
High Frequency ◽  
Equations Of Motion ◽  
Low Frequency ◽  
Cantilever Plate ◽  
Analysis Method ◽  
Multiple Frequency ◽  
Width Direction ◽  
Blade Tip ◽  
High Frequency Vibrations

AbstractThe analysis method is developed to obtain dynamic characteristics of the rotating cantilever plate with thermal shock and tip-rub. Based on the variational principle, equations of motion are derived considering the differences between rubbing forces in the width direction of the plate. The transverse deformation is decomposed into quasi-static deformation of the cantilever plate with thermal shock and dynamic deformation of the rubbing plate under thermal shock. Then deformations are obtained through the calculation of modal characteristics of rotating cantilever plate and temperature distribution function. Special attention is paid to the influence of tip-rub and thermal shock on the plate. The results show that tip-rub has the characteristics of multiple frequency vibrations, and high frequency vibrations are significant. On the contrary, thermal shock shows the low frequency vibrations. The thermal shock makes the rubbing plate gradually change into low frequency vibrations. Because rub-induced vibrations are more complicated than those caused by thermal shock, tip-rub is easier to result in the destruction of the blade. The increasing friction coefficient intensifies vibrations of the rubbing plate. Minimizing friction coefficients can be an effective way to reduce rub-induced damage through reducing the surface roughness between the blade tip and the inner surface of the casing.

Convection of a binary mixture under high-frequency vibrations

2013 ◽  
Vol 341 (4-5) ◽  
pp. 477-482 ◽  
Author(s):  
Sergey M. Ishutov ◽  
Bela I. Myznikova ◽  
Boris L. Smorodin
Keyword(s):  
Binary Mixture ◽  
High Frequency ◽  
High Frequency Vibrations
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