Effect of Added Mass on Human Unipedal Hopping

2002 ◽  
Vol 94 (3) ◽  
pp. 834-840 ◽  
Author(s):  
Gary P. Austin ◽  
Gladys E. Garrett ◽  
David Tiberio
Keyword(s):  
Body Mass ◽  
Vertical Force ◽  
Vertical Stiffness ◽  
Mass Spring Model ◽  
Simple Mass ◽  
Neuromuscular Assessment ◽  
Hip Flexion ◽  
Mass Spring ◽  
And Training ◽  
Insight Into

Although hopping is considered a children's activity, it can be used to provide insight into the neuromuscular and biomechanical performance of adults. This study investigated whether mass added during unipedal hopping altered the vertical stiffness, hopping period, and angular kinematics of the lower extremity of adults. Measures of two-dimensional kinematics and vertical force were made from 10 healthy men during hopping at a preferred period under three conditions: Body Mass, Body Mass + 10%, and Body Mass + 20%. Adding mass significantly increased hopping period and hip flexion without significantly affecting vertical stiffness, ankle dorsiflexion, or knee flexion. Overall, the findings agreed with predictions based on a simple-mass spring model. The results indicate unique kinetic and kinematic responses to increased mass during hopping may have potential application in neuromuscular assessment and training for the lower extremities.

Mechanics of running under simulated low gravity

1991 ◽  
Vol 71 (3) ◽  
pp. 863-870 ◽  
Author(s):  
J. P. He ◽  
R. Kram ◽  
T. A. McMahon
Keyword(s):  
Normal Gravity ◽  
Human Subjects ◽  
Center Of Mass ◽  
The Body ◽  
Vertical Force ◽  
Low Gravity ◽  
Vertical Stiffness ◽  
Mass Spring Model ◽  
Linear Spring ◽  
Mass Spring

Using a linear mass-spring model of the body and leg (T. A. McMahon and G. C. Cheng. J. Biomech. 23: 65–78, 1990), we present experimental observations of human running under simulated low gravity and an analysis of these experiments. The purpose of the study was to investigate how the spring properties of the leg are adjusted to different levels of gravity. We hypothesized that leg spring stiffness would not change under simulated low-gravity conditions. To simulate low gravity, a nearly constant vertical force was applied to human subjects via a bicycle seat. The force was obtained by stretching long steel springs via a hand-operated winch. Subjects ran on a motorized treadmill that had been modified to include a force platform under the tread. Four subjects ran at one speed (3.0 m/s) under conditions of normal gravity and six simulated fractions of normal gravity from 0.2 to 0.7 G. For comparison, subjects also ran under normal gravity at five speeds from 2.0 to 6.0 m/s. Two basic principles emerged from all comparisons: both the stiffness of the leg, considered as a linear spring, and the vertical excursion of the center of mass during the flight phase did not change with forward speed or gravity. With these results as inputs, the mathematical model is able to account correctly for many of the changes in dynamic parameters that do take place, including the increasing vertical stiffness with speed at normal gravity and the decreasing peak force observed under conditions simulating low gravity.

A Simple Vibration Analysis for Running Boards and Other Attached Components

2004 ◽  
Author(s):  
Shaun Richmond
Keyword(s):  
Vibration Analysis ◽  
Spring Model ◽  
Analysis Method ◽  
Simple Analysis ◽  
Car Body ◽  
Mass Spring Model ◽  
Frequency Components ◽  
Simple Mass ◽  
Wheel Flat ◽  
Mass Spring

Vibration of attached components such as running boards, hand grabs, brake components, etc. has become a serious problem. This paper sets out a simple analysis method for ensuring the survival of these components. A simple mass spring model is used to develop a transfer function into the car body. The frequency components of a wheel flat and 39/33 foot jointed track are then established and the excitation amplitudes for components attached to the car body calculated. The response of these components at their natural frequency is then used to calculate their resulting stress levels. Simple methods for performing this analysis are described

Effect of Frequency on Human Unipedal Hopping

2002 ◽  
Vol 95 (3) ◽  
pp. 733-740 ◽  
Author(s):  
Gary P. Austin ◽  
David Tiberio ◽  
Gladys E. Garrett
Keyword(s):  
Lower Extremity ◽  
Knee Flexion ◽  
Lower Extremities ◽  
Ankle Dorsiflexion ◽  
Vertical Force ◽  
Two Dimensional ◽  
Vertical Stiffness ◽  
Hip Flexion ◽  
Force Displacement ◽  
Healthy Males

All mature forms of locomotion involve periods of unilateral stance. Unipedal hopping may provide useful information about the neuromuscular and biomechanical capabilities of a single lower extremity in adults. This study investigated whether hopping influenced vertical stiffness and lower extremity angular kinematics during human unipedal hopping. Vertical force and two-dimensional kinematics were measured in 10 healthy males hopping at three frequencies: preferred, +20%, and −20%. At +20%, compared to preferred, vertical stiffness increased 55% as hip flexion, knee flexion, and ankle dorsiflexion decreased, while at −20% vertical stiffness decreased 39.4% as hip flexion, knee flexion, and ankle dorsiflexion increased. As in bipedal hopping, the force-displacement relationship was more springlike at the preferred rate and +20% than at −20%. Given the prevalence of unilateral stance during walking, running, and skipping, findings related to unipedal hopping may be useful in the rehabilitation or conditioning of lower extremities.

scholarly journals Asymptotic Description of Maximum Mistuning Amplification of Bladed Disk Forced Response

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Carlos Martel ◽  
Roque Corral
Keyword(s):  
Upper Bound ◽  
Amplification Factor ◽  
Forced Response ◽  
Spring Model ◽  
Bladed Disk ◽  
Mass Spring Model ◽  
Amplification Process ◽  
Simple Mass ◽  
Response Amplification ◽  
Mass Spring

The problem of determining the maximum forced response vibration amplification that can be produced just by the addition of a small mistuning to a perfectly cyclical bladed disk still remains not completely clear. In this paper we apply a recently introduced perturbation methodology, the asymptotic mistuning model (AMM), to determine which are the key ingredients of this amplification process and to evaluate the maximum mistuning amplification factor that a given modal family with a particular distribution of tuned frequencies can exhibit. A more accurate upper bound for the maximum forced response amplification of a mistuned bladed disk is obtained from this description, and the results of the AMM are validated numerically using a simple mass-spring model.

Deformation Analysis of a Compliant Underactuated Finger Grasping a Soft Object

2018 ◽  
Author(s):  
Nicolas Mouazé ◽  
Lionel Birglen
Keyword(s):  
Deformation Analysis ◽  
Spring Model ◽  
Rigid Objects ◽  
Proposed Model ◽  
Mass Spring Model ◽  
Soft Objects ◽  
Simple Mass ◽  
Computationally Intensive ◽  
Mass Spring ◽  
Soft Object

In the literature, many models of compliant fingers grasping rigid objects have been extensively discussed. However, when the objects are themselves deformable, as in many practical cases, the effect of compliant underactuated fingers onto these soft objects is generally not addressed due to the complexity of the model required for accurate results. This paper aims at addressing this issue by proposing to simulate deformations using a simple mass-spring model. This model discretizes the object similarly to how a pseudo-rigid body technique usually approximates the compliant finger. Comparisons between simulations using the proposed model and finite element analyses demonstrate that for a significant range of deformations our approach offers an efficient and accurate approximation while less computationally intensive.

scholarly journals Asymptotic Description of Maximum Mistuning Amplification of Bladed Disk Forced Response

2008 ◽  
Author(s):  
Carlos Martel ◽  
Roque Corral
Keyword(s):  
Upper Bound ◽  
Amplification Factor ◽  
Forced Response ◽  
Spring Model ◽  
Bladed Disk ◽  
Mass Spring Model ◽  
Amplification Process ◽  
Simple Mass ◽  
Response Amplification ◽  
Mass Spring

The problem of determining the maximum forced response vibration amplification that can be produced just by the addition of a small mistuning to a perfectly cyclical bladed disk still remains not completely clear. In this paper we apply a recently introduced perturbation methodology, the Asymptotic Mistuning Model (AMM), to determine which are the key ingredients of this amplification process, and to evaluate the maximum mistuning amplification factor that a given modal family with a particular distribution of tuned frequencies can exhibit. A more accurate upper bound for the maximum forced response amplification of a mistuned bladed disk is obtained from this description, and the results of the AMM are validated numerically using a simple mass-spring model.

scholarly journals Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Tiancheng Zhou ◽  
Caihua Xiong ◽  
Juanjuan Zhang ◽  
Di Hu ◽  
Wenbin Chen ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Design Method ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Spring Stiffness ◽  
Spatiotemporal Parameters ◽  
The Common ◽  
Hip Flexion ◽  
Optimal Stiffness ◽  
Insight Into

Abstract Background Walking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the metabolic penalty of the exoskeleton mass make it challenging to develop an exoskeleton that can reduce the metabolic energy during both gaits. Here we show that the metabolic energy of both walking and running can be reduced by regulating the metabolic energy of hip flexion during the common energy consumption period of the two gaits using an unpowered hip exoskeleton. Methods We analyzed the metabolic rates, muscle activities and spatiotemporal parameters of 9 healthy subjects (mean ± s.t.d; 24.9 ± 3.7 years, 66.9 ± 8.7 kg, 1.76 ± 0.05 m) walking on a treadmill at a speed of 1.5 m s−1 and running at a speed of 2.5 m s−1 with different spring stiffnesses. After obtaining the optimal spring stiffness, we recruited the participants to walk and run with the assistance from a spring with optimal stiffness at different speeds to demonstrate the generality of the proposed approach. Results We found that the common optimal exoskeleton spring stiffness for walking and running was 83 Nm Rad−1, corresponding to 7.2% ± 1.2% (mean ± s.e.m, paired t-test p < 0.01) and 6.8% ± 1.0% (p < 0.01) metabolic reductions compared to walking and running without exoskeleton. The metabolic energy within the tested speed range can be reduced with the assistance except for low-speed walking (1.0 m s−1). Participants showed different changes in muscle activities with the assistance of the proposed exoskeleton. Conclusions This paper first demonstrates that the metabolic cost of walking and running can be reduced using an unpowered hip exoskeleton to regulate the metabolic energy of hip flexion. The design method based on analyzing the common energy consumption characteristics between gaits may inspire future exoskeletons that assist multiple gaits. The results of different changes in muscle activities provide new insight into human response to the same assistive principle for different gaits (walking and running).

scholarly journals Review on the 3-D simulation for weft knitted fabric

2021 ◽  
Vol 16 ◽  
pp. 155892502110125
Author(s):  
Sha Sha ◽  
Anqi Geng ◽  
Yuqin Gao ◽  
Bin Li ◽  
Xuewei Jiang ◽  
...  
Keyword(s):  
Physical Models ◽  
Spring Model ◽  
Finite Element Analyses ◽  
Knitted Fabrics ◽  
Piecewise Function ◽  
Fabric Structure ◽  
Weft Knitted Fabric ◽  
Mass Spring Model ◽  
Virtual Display ◽  
Mass Spring

There are different kinds of geometrical models and physical models used to simulate weft knitted fabrics nowadays, such as loop models based on Pierce, piecewise function, spline curve, mass-spring model, and finite element analyses (FEA). Weft knitting simulation technology, including modeling and yarn reality, has been widely adopted in fabric structure designing for the manufacturer. The technology has great potentials in both industries and dynamic virtual display. The present article is aimed to review the current development of 3-D simulation technique for weft knitted fabrics.

scholarly journals Computational Approach to Seasonal Changes of Living Leaves

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Ying Tang ◽  
Dong-Yan Wu ◽  
Jing Fan
Keyword(s):  
Seasonal Changes ◽  
Markov Chain Model ◽  
Geometric Model ◽  
Environmental Parameters ◽  
Computational Approach ◽  
Chain Model ◽  
Color Changes ◽  
Mass Spring Model ◽  
Scanned Image ◽  
Mass Spring

This paper proposes a computational approach to seasonal changes of living leaves by combining the geometric deformations and textural color changes. The geometric model of a leaf is generated by triangulating the scanned image of a leaf using an optimized mesh. The triangular mesh of the leaf is deformed by the improved mass-spring model, while the deformation is controlled by setting different mass values for the vertices on the leaf model. In order to adaptively control the deformation of different regions in the leaf, the mass values of vertices are set to be in proportion to the pixels' intensities of the corresponding user-specified grayscale mask map. The geometric deformations as well as the textural color changes of a leaf are used to simulate the seasonal changing process of leaves based on Markov chain model with different environmental parameters including temperature, humidness, and time. Experimental results show that the method successfully simulates the seasonal changes of leaves.

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