scholarly journals Angular momentum regulation may dictate the slip severity in young adults

2019 ◽  
Author(s):  
Mohammad Moein Nazifi ◽  
Kurt Beschorner ◽  
Pilwon Hur
Keyword(s):  
Young Adults ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Upper Body ◽  
Group Differences ◽  
Normal Gait ◽  
Double Phase ◽  
Single Support Phase ◽  
Time Lead ◽  
Support Phase

AbstractFalls vastly affect the economy and the society with their high cost, injuries, and mortalities. Slipping is the main trigger for falling. Yet, individuals differ in their ability to recover from slips. Mild slippers can accommodate slips without falling, whereas severe slippers indicate inadequate or slow pre-or post-slip control that make them more prone to fall after a slip. Knowing the discrepancies in different kinematic and kinetic variables in mild and severe slippers helps pinpoint the adverse control responsible for severe slipping and falling. This study examined Center of Mass (COM) height, sagittal angular momentum (H), upper body kinematics, and the duration of single/double phase in mild and severe slippers for both normal walking and slipping to identify their differences and possible relationships. Possible causality of such relationships were also studied by observing the time-lead of the deviations. Twenty healthy young adults walked in a long walkway for several trials and were slipped unexpectedly. They were classified into mild and severe slippers based on their slip severity. No inter-group differences were observed in the upper extremity kinematics. It was found that mild and severe slippers do not differ in the studied variables during normal gait; however, they do show significant differences through slipping. Compared to mild slippers, sever slippers lowered their COM height following a slip, presented higher H, and shortened their single support phase (p-value<0.05 for all). Based on the time-lead observed in H over all other variables suggests that angular momentum may be the key variable in controlling slips.

RUNNING PATTERN GENERATION OF HUMANOID BIPED WITH A FIXED POINT AND ITS REALIZATION

2009 ◽  
Vol 06 (04) ◽  
pp. 631-656 ◽  
Author(s):  
BAEK-KYU CHO ◽  
ILL-WOO PARK ◽  
JUN-HO OH
Keyword(s):  
Fixed Point ◽  
Angular Momentum ◽  
Sagittal Plane ◽  
Center Of Mass ◽  
Maximum Velocity ◽  
Frontal Plane ◽  
Numerical Approach ◽  
Pattern Generation ◽  
Upper Body ◽  
Running Pattern

This paper discusses the generation of a running pattern for a humanoid biped and verifies the validity of the proposed method of running pattern generation via experiments. Two running patterns are generated independently in the sagittal plane and in the frontal plane and the two patterns are then combined. When a running pattern is created with resolved momentum control in the sagittal plane, the angular momentum of the robot about the Center of Mass (COM) is set to zero, as the angular momentum causes the robot to rotate. However, this also induces unnatural motion of the upper body of the robot. To solve this problem, the biped was set as a virtual under-actuated robot with a free joint at its support ankle, and a fixed point for a virtual under-actuated system was determined. Following this, a periodic running pattern in the sagittal plane was formulated using the fixed point. The fixed point is easily determined in a numerical approach. In this way, a running pattern in the frontal plane was also generated. In an experiment, a humanoid biped known as KHR-2 ran forward using the proposed running pattern generation method. Its maximum velocity was 2.88 km/h.

scholarly journals Assessing Gait Stability before and after Cochlear Implantation

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Katarzyna Kaczmarczyk ◽  
Michalina Błażkiewicz ◽  
Ida Wiszomirska ◽  
Katarzyna Pietrasik ◽  
Agnieszka Zdrodowska ◽  
...  
Keyword(s):  
Cochlear Implantation ◽  
Research Question ◽  
Center Of Mass ◽  
Strong Stability ◽  
Control Group ◽  
Gait Stability ◽  
Risk Of Falls ◽  
Single Support Phase ◽  
Experimental Group ◽  
Support Phase

Background. It is known that cochlear implantation may alter the inner ear and induce vestibular disorders. Research Question. How does cochlear implantation influence gait stability? Material and Methods. An experimental group of twenty-one subjects scheduled for cochlear implantation underwent gait testing twice, on the day before cochlear implantation (BCI) and three months after cochlear implantation (ACI), using a motion capture system. A control group of 30 age-matched healthy individuals were also tested. Results. In the experimental group, the gait stability ratio (GSR) was found to improve in 17 subjects after implantation, by an average of 6%. Certain other parameters also showed statistically significant improvement between the two experimental group tests: step time (p<0.001), single-support phase walking speed (p<0.05), and center of mass (CoM) (p<0.05). Using the CoM results of the control group, we devised a stability classification system and applied it to the pre- and postimplantation subjects. After implantation, increases were seen in the number of subjects classified in interval II (strong stability) and III (weak stability). The number of subjects in interval I (perfect stability) decreased by 1 and in interval IV (no stability) by 4. Significance. (1) Although cochlear implantation intervenes in the vestibular area, we found evidence that gait stability improves in most subjects after the surgery, reducing the risk of falls. (2) We found statistically significant improvements in individual parameters (such as single-support phase time), in GSR, and in CoM. (3) Based on CoM results, we proposed a new rule-of-thumb way of classifying patients into gait stability intervals, for use in rehabilitation planning and monitoring.

RUNNING PATTERN GENERATION WITH A FIXED POINT IN A 2D PLANAR BIPED

2009 ◽  
Vol 06 (02) ◽  
pp. 241-264 ◽  
Author(s):  
BAEK-KYU CHO ◽  
JUN-HO OH
Keyword(s):  
Fixed Point ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Maximum Velocity ◽  
Numerical Approach ◽  
Pattern Generation ◽  
Upper Body ◽  
Actual Environment ◽  
Virtual System ◽  
Running Pattern

This paper discusses the generation of a running pattern for a biped and verifies the validity of the proposed method of running pattern generation via experiments. When a running pattern is created with resolved momentum control, the angular momentum of the robot at the Center of Mass (COM) is set to zero, as the angular momentum causes the robot to rotate. However, this also induces unnatural motion of the upper body of the robot. To resolve this problem, the biped was set to a virtual under-actuated robot with a free joint at its support ankle, and a fixed point for a virtual system was determined. Following this, a new periodic running pattern was formulated using the fixed point. The fixed point is easily determined using a numerical approach. In an experiment, the planar biped ran forward using the proposed pattern generation method for running. Its maximum velocity was 2.88 km/h. In the future, faster running of the biped will be realized in a planar plane and the biped will run in an actual environment.

Biped Walking Control Based on Quadratic Programming and Differential Inequalities

2020 ◽  
Author(s):  
Stella Diniz Urban ◽  
Bruno Vilhena Adorno
Keyword(s):  
Quadratic Programming ◽  
Center Of Mass ◽  
Bipedal Walking ◽  
Differential Inequalities ◽  
Double Support ◽  
Cycle Simulation ◽  
Minimum Height ◽  
Joint Limits ◽  
Single Support Phase ◽  
Support Phase

This paper presents a novel method to control a bipedal walking based on quadratic programming and differential inequalities using geometric primitives. We allow the center of mass to move anywhere inside the support polygon during the walking cycle, as opposed to classic methods, which usually rely on tracking a desired trajectory for the zero moment point. The constraints keep the robot balance, the pelvis above a minimum height, and prevent the violation of joint limits during the complete walking cycle. Simulation results using the legs of the Poppy humanoid robot show that the trajectories of the closed-loop system converge to the desired center of mass position during the double support phase and the swing foot's trajectories converge to the desired pose during the single support phase while all constraints are obeyed.

When is Vestibular Information Important During Walking?

2004 ◽  
Vol 92 (3) ◽  
pp. 1269-1275 ◽  
Author(s):  
Leah R. Bent ◽  
J. Timothy Inglis ◽  
Bradford J. McFadyen
Keyword(s):  
Gait Cycle ◽  
Vestibular Stimulation ◽  
Upper Body ◽  
Foot Placement ◽  
Double Support ◽  
Vestibular Information ◽  
Heel Contact ◽  
Somatosensory Input ◽  
Single Support Phase ◽  
Support Phase

Locomotion relies on vision, somatosensory input, and vestibular information. Both vision and somatosensory signals have been shown to be phase dependently modulated during locomotion; however, the regulation of vestibular information has not been investigated in humans. By delivering galvanic vestibular stimulation (GVS) to subjects at either heel contact, mid-stance, or toe-off, it was possible to investigate when vestibular information was important during the gait cycle. The results indicated a difference in the vestibular regulation of upper versus lower body control. Upper body responses to GVS applied at different times did not differ in magnitude for the head ( P = 0.2383), trunk ( P = 0.1473), or pelvis ( P = 0.1732) showing a similar dependence on vestibular information for upper body alignment across the gait cycle. In contrast, foot placement was dependent on the time when stimulation was delivered. Changes in foot placement were significantly larger at heel contact (during the double support phase) than when stimulation was delivered at mid-stance (in the single support phase of the gait cycle; P = 0.0193). These latter results demonstrate, for the first time, evidence of phase-dependent modulation of vestibular information during human walking.

The Effect of the Toe on the Biped Robot

2013 ◽  
Vol 325-326 ◽  
pp. 1076-1082
Author(s):  
Seyed Mehdi Torklarki ◽  
Mohammad Danesh
Keyword(s):  
Reaction Force ◽  
Stability Margin ◽  
Biped Robot ◽  
Body Motion ◽  
Upper Body ◽  
Biped Robots ◽  
Double Support ◽  
The Stability ◽  
Single Support Phase ◽  
Support Phase

Evaluation of 9-DOF biped robots based on designated smooth and stable trajectories with two added toes is a challenging problem that is the focus of this paper. Simultaneously rotation of feet and toes is considered, which allows the robot to walk more efficiently and like a human being. A desired trajectory for the lower body is designed to increase the stability margin. This obtained by fitting proper polynomials at appropriate break points. Then, the upper body motion is planned based on the Zero Moment Point (ZMP) criterion to provide a stable motion for the biped robot. Next, dynamics equations are obtained for both single support phase (SSP) and double support phase (DSP). On the other hand, two biped robots, which one accompanied by toes, are also compared. Simulation results reveal that the biped robots with toes have better stability margin, less power consumption and more vertical reaction force.

scholarly journals Infrared effects in the late stages of black hole evaporation

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Éanna É. Flanagan
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Center Of Mass ◽  
Planck Scale ◽  
Black Hole Mass ◽  
Order Unity ◽  
Intrinsic Angular Momentum ◽  
Hole Position ◽  
Late Stages ◽  
Shear Tensor

Abstract As a black hole evaporates, each outgoing Hawking quantum carries away some of the black holes asymptotic charges associated with the extended Bondi-Metzner-Sachs group. These include the Poincaré charges of energy, linear momentum, intrinsic angular momentum, and orbital angular momentum or center-of-mass charge, as well as extensions of these quantities associated with supertranslations and super-Lorentz transformations, namely supermomentum, superspin and super center-of-mass charges (also known as soft hair). Since each emitted quantum has fluctuations that are of order unity, fluctuations in the black hole’s charges grow over the course of the evaporation. We estimate the scale of these fluctuations using a simple model. The results are, in Planck units: (i) The black hole position has a uncertainty of $$ \sim {M}_i^2 $$ ∼ M i 2 at late times, where Mi is the initial mass (previously found by Page). (ii) The black hole mass M has an uncertainty of order the mass M itself at the epoch when M ∼ $$ {M}_i^{2/3} $$ M i 2 / 3 , well before the Planck scale is reached. Correspondingly, the time at which the evaporation ends has an uncertainty of order $$ \sim {M}_i^2 $$ ∼ M i 2 . (iii) The supermomentum and superspin charges are not independent but are determined from the Poincaré charges and the super center-of-mass charges. (iv) The supertranslation that characterizes the super center-of-mass charges has fluctuations at multipole orders l of order unity that are of order unity in Planck units. At large l, there is a power law spectrum of fluctuations that extends up to l ∼ $$ {M}_i^2/M $$ M i 2 / M , beyond which the fluctuations fall off exponentially, with corresponding total rms shear tensor fluctuations ∼ MiM−3/2.

scholarly journals Effect of foot–floor friction on the external moment about the body center of mass during shuffling gait: a pilot study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Takeshi Yamaguchi ◽  
Kei Shibata ◽  
Hiromi Wada ◽  
Hiroshi Kakehi ◽  
Kazuo Hokkirigawa
Keyword(s):  
Friction Surface ◽  
Center Of Mass ◽  
Young Male ◽  
The Body ◽  
Low Friction ◽  
Surface Conditions ◽  
Normal Gait ◽  
External Moment ◽  
Body Center ◽  
Floor Condition

AbstractHerein, we investigated the effect of friction between foot sole and floor on the external forward moment about the body center of mass (COM) in normal and shuffling gaits. Five young male adults walked with normal and shuffling gaits, under low- and high-friction surface conditions. The maximum external forward moment about the COM (MEFM-COM) in a normal gait appeared approximately at initial foot contact and was unaffected by floor condition. However, MEFM-COM in a shuffling gait under high-friction conditions exceeded that under low-friction conditions (p < 0.001). Therein, MEFM-COM increased with an increasing utilized coefficient of friction at initial foot contact; this effect was weaker during a normal gait. These findings indicate that increased friction between foot sole and floor might increase tripping risk during a shuffling gait, even in the absence of discrete physical obstacles.

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