• Journal of Institute of Control, Robotics and Systems
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• v.11 no.1
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• pp.58-66
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• 2005

Usual human gait can be modeled as continual impact phenomenon that happens due to the topological change of the kinematic structure of the two feet. The human being adapts his own control algorithm to minimize the ill effect due to the collision with the environment. In order to operate a Humanoid robot like the human being, it is necessary to understand the physics of the impact and to derive an analytical model of the impact. In this paper, specially, we focus on impact analysis of the kicking motion in playing soccer. At the instant of impact, the external impulse exerted on the ball by the foot is an important property. Initially, we introduce the complete external impulse model of the lower-extremity of the human body and analyze the external impulses for several kicking postures of the lower-extremity. Secondly, a trajectory-planning algorithm of a ball, in which the initial velocity and the launch angle of the ball are calculated for a desired trajectory of the ball, will be introduced. The aerodynamic effect such as drag force and lift force is also considered. We carry out numerical simulation and experimentation to verify the effectiveness of the proposed analytical methodology.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.392-397
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• 2014

Recently, there is an increase in the need for precision linear stages with vacuum compatibility in such areas as lithography equipment for wafer or mask manufacturing, mask mastering equipment for optical data storage and electron beam equipment. A simple design, high stiffness and low cost can be achieved by using ball bearings. However, a ball bearing have friction and wear problems just as in ambient air. In order to decrease the friction, a special finish, a diamond-like carbon (DLC) film coating, is applied to the surface of a guide rail by sputtering deposition. This paper presents the result of an experimental investigation on the control performance of a ball bearing-guided linear motion stage under two environmental conditions: in air and vacuum. A comparison between the results with and without the DLC coating was also considered in the experimental investigation.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.641-646
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• 2014

In this paper, we propose a controller for a ball and beam system which reduces the measurement error effect under AC and DC noise. The ball and beam system measures data through a sensor. If sensor noise is included in a controller via the feedback channel, the signal is distorted and the entire system cannot work normally. Therefore, some appropriate action for the measurement error effect is essential in the controller design. Our controller is equipped with a gain-scaling factor and a compensator to reduce the effect of measurement error in the feedback signal. Effectively, our proposed controller can reduce the AC and DC noise of a feedback sensor. We analyze the proposed controller by Laplace transform technique and illustrate the improved control performance via an experiment for a ball and beam system.

• Physical Therapy Korea
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• v.10 no.3
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• pp.109-126
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• 2003

This study was designed 10 investigate the effects of therapeutic gymnastic ball exercise on pain, flexibility, lumbar disability level and daily activity levels in male patients of the armed forces medical hospital who complain of chronic low back pain. Twenty-three males were placed in the experimental group and twenty-nine males were placed in the control group. All of the subjects were chosen on the basis of availability among in-patients who were diagnosed with low back pain. The control patients were matched to the experimental group and they were selected considering gender, pain duration and age. Gymnastic ball exercise therapy was developed by the author with the assistance of a rehabilitation specialist. Gymnastic ball exercise therapy includes muscle relaxation, flexibility, muscle strength and posture development exercises. The gymnastic ball exercise therapy was carried out by the experimental group three times a week for eight weeks. Before and after the experiments, the intensity of pain, the lumbar joint mobility (flexibility), the lumbar disability levels, and the daily activity levels of the subjects were measured, respectively. The intensity of pain and the lumbar disability levels were measured by the Visual Analogue Scale, the level of flexibility by a measurement ruler, and the level of disability by the Oswestry Low Back Pain Disability Scale. Data were analysed using a t-test, a paired t-test and an unpaired t-test. The results were as follows: 1. The intensity of pain in the lumbar spine in the experimental group was significantly decreased compared with that of the control group during the 4th week and 8th week. 2. The flexibility of the lumbar spine in the experimental group was significantly increased compared with that of the control group during the 4th week and 8 week. 3. The level of pain caused by anterior, posterior, left lateral and right lateral bending and by rotation in experimental group was significantly decreased compared with that of the control group. 4. The Oswestry Disability score of the experimental group was significantly increased compared with that of control group. These findings indicate that gymnastic ball exercise therapy could be effective in decreasing pain and lumbar disability, and increasing the daily activity levels and lumbar flexibility in patients with chronic low back pain. The study also suggests that gymnastic ball exercise therapy could be an essential factor for effective nursing intervention for patients suffering from chronic low back pain.

• The Journal of Korean Physical Therapy
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• v.33 no.4
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• pp.202-209
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• 2021

Purpose: This study examined whether various lower extremity exercises using a Swiss ball in the standing position could improve balance, muscle strength, gait, and fall efficacy in stroke patients. Methods: Twenty-one stroke patients were randomly divided into three groups, each with seven participants. For four weeks, experimental group 1 performed various lower extremity exercises using a Swiss ball, while experimental group 2 executed the same exercises without a Swiss ball, and the control group underwent general physical therapy. The subjects' knee extensor muscle strength, balance, gait, and fall efficacy were evaluated before and after the intervention using portable muscle strength measurement, the Berg Balance Scale (BBS), G-walk, and the Korean Falls Efficacy Scale (K-FES). Results: Knee extensor strength increased significantly in all three groups after the intervention; in particular, a significant increase was seen in experimental groups 1 and 2 compared to the control group. Moreover, all three groups had significantly better BBS scores and higher cadence after the intervention; notably, experimental group 1 had better scores and increased cadence than the control group. Additionally, gait speed was significantly increased in the experimental group 1 than in the control group. The step length of the non-affected leg was also significantly higher in the same group. The K-FES score improved significantly in all three groups, but there was no significant difference between the groups. Conclusion: This study suggests that lower extremity exercises with or without a Swiss ball could be effective interventions to improve muscle strength, balance, gait, and fall efficacy in stroke patients.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.47-53
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• 2010

The purpose of this paper is to build on automatic system for the shot ball transfer hoist. The shot ball is used to remove completely paint or leftovers before spreading the new paint on a large vessels surface. The shot ball is made of melted iron through cooling process, and it is transferred to hopper by electromagnet of hoist. Currently, the transfer process of the shot ball is performed by manual operation, and the transfer process is inefficient. So we have developed an automatic system to replace the manual system. The developed automation systems have efficient and accurate position control performance.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.45-51
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• 1999

Thermal expansion of the ball screw can directly affect the accuracy of positioning along the travel axis in the semi-closed loop type CNC Lathe. In this paper, use of MACRO variables can make the thermal displacement of the ball screw estimated. Also, the estimated displacements of the ball screw are controlled by calculating the interval of pitch error rate in the Numerical Control(NC). Under the constant operating conditions, the thermal expansion of the ball screw was measured to confirm the effectiveness of the compensation method in the CNC Lathe. By using this method the results show that the thermal displacement of the ball screw could be reduced to 20% compared with ordinary method.

• Journal of International Academy of Physical Therapy Research
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• v.1 no.2
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• pp.149-154
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• 2010

The purpose of this study was to investigate the effects of swiss ball exercise and taping therapy on back muscle strength on normal college students. The aim of this study was to find effective method for back muscle strengthening. Subjects of 30 college students divided 3 groups(taping therapy group: 10, swiss ball group: 10, control group: 10). All subjects inquired physical conditions and normal exercise habits for data base. Back muscle strength measured before and after 3 weeks intervention. Taping therapy was displayed stable a growth curve in continuative a growth graph of back muscle strength better than swiss ball exercise, because it was taping therapy by periodic effect. The result of this study known to effective either taping therapy or swiss ball exercise, but both taping therapy and swiss ball exercise were effect to increase in back muscle strength.

• Tribology and Lubricants
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• v.20 no.3
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• pp.140-144
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• 2004

Water-lubrication ball bearings are required to install in aqueous medium where water is used as coolant or working fluid. However water-lubricated frictional characteristics of stainless steel ball bearing is not will known compared to oil-lubricated frictional characteristics. Furthermore study on friction at high temperature is rare because bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is mostly based on change of failed bearings and parts. Ball bearings and ball screws are used to transmit power in the control rod drive mechanism for an integral reactor and are lubricated with high temperature and high pressure chemically-controlled water. Bearings and power transmitting mechanical elements for a nuclear reactor require high reliability and high performance during estimated lifetime, and their performance should be verified. In this paper, experimental research results of frictional characteristics of water-lubricated ball bearing are reported.

• Structural Engineering and Mechanics
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• v.85 no.6
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• pp.809-823
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• 2023

In this work, dynamic stability analysis of the ball after contacting with the earth in the volleyball game is presented. Via spherical shell coordinate, the governing equations and general boundary conditions of the ball after contacting with the earth in the volleyball game is studied. Via Comsol multi-physics simulation, some results are presented and a verification between the outcomes is studied. Harmonic differential quadrature method (HDQM) is utilized to solve the dynamic equations with the aid of boundary nodes of the current spherical shell structure. Finally, the results demonstrated that thickness, mass of the ball and internal pressure of the ball alters the frequency response of the structure. One important results of this study is influence of the internal pressure. Higher internal pressure causes lower frequency and hence reduces the stability of the ball.