• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.109-115
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• 2012

In this paper, we consider the sway suppression control problem for container cranes with load hoisting. The proposed control law improves the positioning accuracy but also the sway suppression through fast stabilization of the under-actuated sway dynamics, which is based on a class of feedback linearizing control incorporated with an additional control including the sway angle and its rate as well as positioning errors and their rates. For the design of the additional control, a variable structure control with the proper sway damping and simple switching action is employed, thus preventing excessive overshoots of the trolley travelljng and effectively suppressing the residual sway of container arrived at the target position. Simulation results are provided to show effectiveness of the proposed controller in the presence of such uncertainties as winds and the variation of payload weights.

• Journal of the Korean Society of Physical Medicine
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• v.1 no.1
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• pp.77-92
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• 2006

Purpose : This study was to evaluate the effect of traditional balance training on balance in older adults. Methods : The subjects of this study were thirty elderly over 65 years old. Thirty subjects ranging aged from 66 to 85($74.0{\pm}5.83$) completed the study and participated three times a week for 5weeks. Subjects were assessed by utilizing two different balance measure : Static standing balance was measured by balance performance monitor(BPM). Dynamic balance was measured by timed up and go test(TUG). The scale for static standing balance was measured by using frequence(Hz), sway area($mm^2$), sway path(mm), max sway velocity(mm/s), ant/post sway angle($^{\circ}$), left/right sway angle($^{\circ}$), and sway number. Results : The change in frequency were statistically significant on pre-test and post-test(P<.05), 2. The change in sway area were statistically significant on pre-test and post-test (P<.05), 3. The change in sway path were statistically significant on pre-test and post-test(P<.05), 4. The change in max sway velocity were statistically significant on pre-test and post-test (P<.05), 5. The change in ant/post sway angle were statistically significant on pre-test and post-test (P<.05), 6. The change in left/right sway angle were statistically significant on pre-test and post-test(P<.05), 7. The change in sway number were statistically significant on pre-test and post-test(P<.05), 8. The score on timed up and go test shows statistically significant increase on pre-test and post-test (P<.05). Conclusion : This study suggest that traditional balance training have an effect on balance performance ability for elderly people. Therefore, the traditional balance training is recommended for older adults to improve balance performance ability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.958-965
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• 2007

The spreaders on container cranes are usually controlled to stop at the same time as their trolleys are stopped. Despite the use of adequate control systems, however, the spreaders usually have comparatively large sway movements, due to their suspension from the trolleys through cables. It is, therefore, important to accurately measure the attitudes of the spreaders, in order to suppress such sways by means of secondary control. Until now, most of conventional anti sway control systems focus on the direct control of the movements of trolleys. which seems not suitable to speed up the entire process - loading and unloading of containers. In this paper, we suggest a new anti sway control system: By using extra equipments - two propellers to suppress the sway and a PSD camera to measure the spreader's attitude - installed on the spreader and the trolley. the sway of the suspended load j, considerably suppressed. The effectiveness of the proposed scheme is verified by the computer simulation and experiment with the miniature of the container crane system.

• Journal of International Academy of Physical Therapy Research
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• v.4 no.2
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• pp.557-561
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• 2013

The purpose of this study to identified the effect of muscle strengthening of ankle joints on postural sway. The subjects of this study were 29 healthy adults aged between 20 and 30 years(male 18, female 11). All subjects received ankle muscle strengthening exercise for 3 times, 3 sessions, 30 minutes per week over 4weeks period. The measured item of muscle strength, postural sway. Data collected from all subjects the result were as follows. The ankle strength showed significant increase(p<.05). One leg stand test with eye close increase in static balance(p<.05), left-right sway distance and anterior-posterior sway distance with eye open and close in static balance(p<.05). The result findings show that strength of the ankle joint muscles is a factor which affects postural sway and the ankle joints are important in static balance.

• Journal of the Ergonomics Society of Korea
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• v.23 no.4
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• pp.1-8
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• 2004

The objective of this study is to identify the effects of material position and physical fatigue on postural stability. Ten male subjects participated in this study. After bicycling exercises, their centers of pressure (COPs) were measured under four material handling positions and four excercise levels. The measured COPs were then utilized to calculate postural sway length in each experimental condition. Subjects' postural stability was quantified using the sway length. Results showed that the effect of different material handling position was significant on the postural sway length in both the posterior-anterior axis and the medio-lateral axis. Results also showed that the postural sway length was increased as physical fatigue accumulated, significantly in subject's posterior-anterior axis. The results imply that bearing a material on the back or front with both hands appeared to cause least sway length and instability.

• The Journal of Korean Physical Therapy
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• v.16 no.2
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• pp.99-107
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• 2004

The purpose of this study was to investigate the effect of foot orthotic on postural sway. Subjects were 15 patients(7 men and 8 women) who prescribed foot orthotic at B hospital and L rehabilitation medicine clinic in Seoul. Postural sway during a single limb stance was measured using the CMS 10 Measuring System when subjects positioned on the balance trainer under two treatment conditions(orthotic and nonorthotic). RCSP(resting calcaneal stance position) while subjects were standing on the glass plate was measured using the angle finder after subjects were positioned in prone to divide equally lower leg and calcaneus using the goniometer. The result was as follows. There were significant difference between postural sway of orthotic and nonorthotic conditions(t=4.888, 4.589, p<0.001), and the leg of the small RCSP within a subject has the small postural sway index($x^2=26.000$, p<0.001). In conclusion, foot orthotics provide structural support for detecting and controlling postural sway in patients prescribed foot orthotics.

• Journal of Korean Physical Therapy Science
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• v.11 no.2
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• pp.5-17
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• 2004

The purpose of this study was to investigate the relationship between normal adults' resting calcaneal stance position(RCSP) and postural sway. Subjects were 70 normal adults(34 men and 36 women) in their twenties who attend S. University. Postural sway during a single limb stance was measured using the CMS 10 Measuring System when subjects positioned on the balance trainer in their bare foot. RCSP while subjects were standing on the glass plate was measured using the angle tinder after subjects were positioned in prone to divide equally lower leg and calcaneus using the goniometer. The result was as follows. There were significant weak positive correlations between RCSP and postural sway(r=0.362, p<0.01), the leg of the small RCSP within a subject has the small postural sway index($X^2=43.758$, p<0.001). There was no significant difference between groups of rearfoot valgus(RCSp<$2^{\circ}$) and those of rearfoot varus (RCSp>$2^{\circ}$) in the postural sway. In conclusion, there is a weak relationship between increasing the absolute value of RCSP and increasing postural sway.

• Journal of Power System Engineering
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• v.2 no.1
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• pp.73-79
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• 1998

In practical fields, the sway of crane systems leads to extra stress to the crane structure during the transporting operation and it is in close connection with its life. Usually, when we operate the cranes with high speed and manual control, the sway motion is irreducible. In this paper, a new type of crane system is proposed to avoid the irreducible sway of the crane systems. The proposed system is composed of mechanical arm with function of anti-sway based on conventional line system. By the anti-sway arm, we can realize to prevent the sway of the container box but cannot avoid the oscillation for the overall body of the crane. So, a controller design method to solve the above stated problem must be considered. The problem is solved by adopting the velocity pattern control methods of trapezoidal and curve types and its effectiveness is proved through experimental results.

• Journal of Korean Physical Therapy Science
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• v.16 no.4
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• pp.49-57
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• 2009

Background: The purpose of this study was to assess the test-retest reliability of balance measurements in older adults using balance measurement system(Good Balance). Methods: The subjects consisted of 49 female and 20 male in community-dwelling older adults. This study used a repeated-measure design. Each subject completed all the different tests once and they were then repeated with 2 minutes in between. Repeated two-ways analysis of variance(ANOVA), representing two test times and both sexes, was calculated for each of the two dependent variables. Intraclass correlation coefficients(ICCs) were used to assess the test-retest reliability. Results: 1) There was not significant difference between test and retest for mediolateral sway speed and anterioposterior sway speed under conditions of normal standing with eyes open, normal standing with eyes closed and semitandem standing with eyes open. There was not significant difference between males and females for mediolateral sway speed and anterioposterior sway speed under conditions of normal standing with eyes open, normal standing with eyes closed and semitandem standing with eyes open. There were not the interaction effects between genders and test time under three conditions. 2) The reproducibility between test and retest was excellent for anterioposterior sway speed(ICC=.77) under condition of normal standing with eyes open, and for mediolateral sway speed(ICC=.76) and anterioposterior sway speed(ICC=.84) under condition of semitandem standing with eyes open. The reproducibility between test and retest was fair to good for mediolateral sway speed(ICC=.64) under condition of normal standing with eyes open, for mediolateral sway speed(ICC=.63) and anterioposterior sway speed(ICC=.75) under condition of normal standing with eyes closed. Conclusion: Balance tests in older adults using balance measurement system(Good Balance) demonstrated acceptable levels of reliability.

• Physical Therapy Korea
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• v.17 no.3
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• pp.20-30
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• 2010

This study examined whether any changes by mental task types on postural control in chronic stroke persons. Sixteen chronic stroke persons (mean age=53.75 yr) and sixteen age-and gender-matched healthy controls (mean age=54.44 yr) took part in this study. Participants randomly performed three different tasks on the stable and unstable surfaces. The no mental task was to stand while holding a 100 g weight in each hand, the arithmetic task (mental task) was to perform a silent 1-backwards counting while standing and holding a 100 g weight in each hand, and the simple task (mental task) was to stand and hold with both hands a tray (200 g) on which a glass filled with water has been placed. Sway path and sway velocity of the center of pressure (COP) were measured to assess standing postural control by task performance using the force platform. According to the results, in stroke group, total sway path and total sway velocity of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable surface (p<.05), and sway path (anteroposterior AP, mediolateral ML) of COP, total and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the unstable surface (p<.05). Especially, sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In healthy control group, sway path (AP, ML, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased during arithmetic and simple task compared to no mental task on the stable and unstable surface (p<.05), and sway path (AP, total) of COP and sway velocity (AP, ML, total) of COP was significantly decreased under the simple task when compared to the arithmetic task on the unstable surface (p<.05). In conclusion, the findings of this study showed that arithmetic and simple task improved standing postural control for chronic stroke patients and the type of arithmetic and simple tasks were critical factor that reduced standing postural sway in dual-task conditions. Future research should determine whether dual-task conditions, including simple task, would be effective as a training program for standing postural control of stroke patients.