On the stability of passive dynamic walker with flat foot and series ankle spring

BACKGROUND: The abductor hallucis (AbH) is a key muscle in the stability of the foot by supporting the medial longitudinal arch (MLA). Individuals with flat foot show a flattening of the MLA with a decreased selective AbH activity relative to the other foot extrinsic muscles during functional movement. OBJECTIVE: To examine the selective muscle activity of the abductor hallucis (AbH) during single-leg mini-squat (SMS) in subjects with flat foot and normal individuals. METHODS: Twenty-four healthy adults (13 men and 11 women) with flat or normal feet participated in this study. All subjects performed single minisquat (SMS), and data were collected using sEMG from the AbH, TA, and GCM during SMS. RESULTS: An inter-gender comparison of the EMG data revealed no difference. The EMG activity of the AbH in individuals with flat foot was significantly lower than that of individuals with normal feet. Moreover, the AbH/TA ratio in subjects with flat foot, , was significantly lower than that in subjects with normal feet. CONCLUSION: In a clinical setting, clinicians should focus on strengthening exercises of the AbH muscle due to reduced activation of the AbH muscle in individuals with flat foot. The selective muscle activity of the AbH muscle during SMS should be emphasized.

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Dynamic Modeling and Control of a Novel One-Legged Hopping Robot

Robotica ◽

10.1017/s0263574720001447 ◽

2021 ◽

pp. 1-19

Author(s):

Amin Khakpour Komarsofla ◽

Ehsan Azadi Yazdi ◽

Mohammad Eghtesad

Keyword(s):

Sliding Mode ◽

Main Body ◽

Lagrange Equations ◽

Flat Foot ◽

Modeling And Control ◽

System A ◽

Hopping Robot ◽

Hopping Robots ◽

The Stability ◽

And Control

SUMMARY In this article, a novel mechanism for planar one-legged hopping robots is proposed. The robot consists of a flat foot which is pinned to the leg and a reciprocating mass which is connected to the leg via a prismatic joint. The proposed mechanism performs the hopping by transferring linear momentum between the reciprocating mass and its main body. The nonlinear equations of the motion of the robot are derived using the Euler–Lagrange equations. To accomplish a stable jump, appropriate trajectories have been planned. To guarantee a stable response for this nonlinear system, a sliding-mode controller is implemented. The performance of the hopping robot is investigated through numerical simulations. The results confirm the stability of the hopping robot through the jump cycle on a flat surface and in climbing up and down ramp and stairs.

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Rotational Stability Index (RSI) point: postural stability in planar bipeds

Robotica ◽

10.1017/s0263574710000597 ◽

2010 ◽

Vol 29 (5) ◽

pp. 705-715 ◽

Cited By ~ 1

Author(s):

Goswami Dip ◽

Vadakkepat Prahlad

Keyword(s):

Postural Stability ◽

Stability Index ◽

Rotational Stability ◽

Stability Criteria ◽

Flat Foot ◽

Biped Robots ◽

Zero Moment Point ◽

Foot Posture ◽

Zero Moment ◽

The Stability

SUMMARYThe postural stability of bipedal robots is investigated in perspective of foot-rotation during locomotion. With foot already rotated, the biped is modeled as an underactuated kinematic structure. The stability of such biped robots is analyzed by introducing the concept of rotational stability. The rotational stability investigates whether a biped would lead to a flat-foot posture or the biped would topple over. The rotational stability is quantified as a ground reference point named “rotational stability index (RSI)” point. Conditions are established to achieve rotational stability during biped locomotion using the concept of the RSI point. The applicability of the RSI point is illustrated through experimentation for the landing stability analysis of the bipedal jumping gaits.The traditional stability criteria such as zero-moment point (ZMP) [M. Vukobratovic and B. Borovac, “Zero-moment point – thirty five years of its life,” Int. J. Humanoid Robot. 1(1), 157–173 (2004)] and foot-rotation indicator (FRI) [A. Goswami, “Postural stability of biped robots and the foot-rotation indicator (FRI) point,” Int. J. Robot. Res. 18(6), 523–533 (1999)] are not applicable to analyze biped's postural stability when foot is already rotated. The RSI point is established as a stability criteria for planar bipedal locomotion in presence of foot rotation.

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Outdoor Environments Walking by Biped Passive Dynamic Walker with Constraint Mechanism

Journal of Robotics and Mechatronics ◽

10.20965/jrm.2010.p0363 ◽

2010 ◽

Vol 22 (3) ◽

pp. 363-370 ◽

Cited By ~ 4

Author(s):

Kazuyuki Hyodo ◽

◽

Sadayoshi Mikami ◽

Sho’ji Suzuki ◽

Keyword(s):

Bipedal Walking ◽

Control Constraint ◽

Outdoor Environments ◽

Outdoor Walking ◽

The Stability ◽

Passive Dynamic Walker

This paper verified the stability of passive dynamic bipedal walking indoors and outdoors using a foot shape enhancing walking stability and implementing control constraint. Outdoor walking is difficult for walkers due to the unpredictable aspects of loose slopes, bumpy surfaces, and uneven friction on roads.

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Effect of Toe-Joint and Heel Height on Balancing of a Standing Biped

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2014-38350 ◽

2014 ◽

Author(s):

Ehsan Kouchaki ◽

Mohammad Jafar Sadigh

Keyword(s):

Phase Plane ◽

Inverted Pendulum ◽

Upper Body ◽

Control Performance ◽

Flat Foot ◽

Ankle Strategy ◽

Heel Height ◽

Foot Model ◽

The Stability ◽

The Relationship

Postural control of a standing bipedal model with toe-joints is studied. The model contains an inverted pendulum as the upper body and a foot, which consists of a heel-link and a toe-link. Taking advantage of ankle strategy, the biped is actuated by two torques at ankle-joint and toe-joint to regulate the upper body in upright position. To assess the stability of the system the Lyapunov exponents phenomena are used and the stability regions are calculated in the phase plane. To investigate the effect of toe-joint on control performance and the stability, the results are compared with those of a flat foot model without toe-joint. The relationship between heel’s height and balancing stability is investigated as well. The results show that toe-joint enhances stability of the system and reduces the actuator demand. This effect is more important especially in the case with high heel foot.

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Open discussion

Symposium - International Astronomical Union ◽

10.1017/s0074180900029533 ◽

1982 ◽

Vol 99 ◽

pp. 605-613

Author(s):

P. S. Conti

Keyword(s):

Buenos Aires ◽

Large Mass ◽

List Type ◽

Common Phenomenon ◽

Open Discussion ◽

The Stability ◽

Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

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Symmetric Multistep Methods Revisited: II. Numerical Experiments

International Astronomical Union Colloquium ◽

10.1017/s0252921100031602 ◽

1999 ◽

Vol 173 ◽

pp. 309-314 ◽

Cited By ~ 3

Author(s):

T. Fukushima

Keyword(s):

Multistep Methods ◽

Computational Time ◽

Integration Time ◽

Implicit Methods ◽

Symmetric Methods ◽

Celestial Bodies ◽

The Stability ◽

Predictor Corrector ◽

Symmetric Multistep Methods ◽

Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

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Uniformity of Magnification from Different Electron Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060179 ◽

1967 ◽

Vol 25 ◽

pp. 32-33

Author(s):

Godfrey C. Hoskins ◽

V. Williams ◽

V. Allison

Keyword(s):

Diffraction Grating ◽

The Other ◽

Carbon Replica ◽

Electron Microscopes ◽

The Stability

The method demonstrated is an adaptation of a proven procedure for accurately determining the magnification of light photomicrographs. Because of the stability of modern electrical lenses, the method is shown to be directly applicable for providing precise reproducibility of magnification in various models of electron microscopes.A readily recognizable area of a carbon replica of a crossed-line diffraction grating is used as a standard. The same area of the standard was photographed in Phillips EM 200, Hitachi HU-11B2, and RCA EMU 3F electron microscopes at taps representative of the range of magnification of each. Negatives from one microscope were selected as guides and printed at convenient magnifications; then negatives from each of the other microscopes were projected to register with these prints. By deferring measurement to the print rather than comparing negatives, correspondence of magnification of the specimen in the three microscopes could be brought to within 2%.

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