• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.147.5-147
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• 2001

This paper describes a gait algorithm and a velocity limitation method for a Leg-Wheel Robot. The gait algorithm enables the robot to preserve continuous locomotion even if the velocity command varies extensively. The velocity limitation method restricts the commanded velocity when it exceeds the mechanical limitation of the robot. Combined use of the velocity limitation method with the gait algorithm ensures the continuity of locomotion, and makes the gait pattern efficient with a long step length and low frequency of leg phase change. These methods can be applied to locomotion on unexplored rough terrain even if the range of roughness is unknown.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.6
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• pp.441-446
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• 2007

An experimental study on the countercurrent two-phase flow in narrow rectangular channels has been peformed. Countercurrent flow limitation (CCFL) was investigated using air and water in 760mm long, 100mm wide, vertical test sections with 1 and 3mm channel gaps. Tests were systematically performed with downward liquid superficial velocities and upward gas velocities covering 0 to 0.125 and 0 to 3.5m/s ranges, respectively. As the gap width of rectangular channel increased the CCFL water superficial velocity decreased for the given air superficial velocity. Slight increase of the air superficial velocity resulted in the abrupt decrease of water velocity when $j_g=2{\sim}4m/s$. The critical superficial velocity of air, at which the downward flow of water was no longer allowed, also decreased with the increase of gap width. The experimental results were compared with the previous correlations, which were mainly for round tubes, and the qualitative trends were found to be partially acceptable. However the quantitative discrepancies were hardly neglected. New correlation of CCFL was developed and showed good agreement with the experimental data.

• Journal of Korean Physical Therapy Science
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• v.17 no.3_4
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• pp.51-58
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• 2010

Purpose: The purpose of this study was to examine changes of postural sway between the normal group and treatment group of same people through COP movements. Methods: Fifty men with no history of sensory, neurological and orthopedic disorders were participated in this study. Participants were tested on single limb balance during 30 seconds on EMED system with bared foot. Each of them performed two methods and 5 trials totally each method: (1) non-treated group (2) treated group(with big toe flexion limitation). Data on the moving length, average velocity, instantaneous maximum velocity, mediolateral(x axis) maximum velocity, and anteroposterior(y axis) maximum velocity of COP were measured in single limb standing position. Results: The moving length and average velocity of COP were significant difference between normal and treatment group(p<0.05). On correlation of parameters, the faster average velocity of COP, the higher moving length, instantaneous maximum velocity, mediolateral maximum velocity, and anteroposterior maximum velocity of COP increase. The more Instantaneous maximum velocity of COP, the faster is anteroposterior maximum velocity of COP. Conclusions: Limitation of big toe flexors function affected single limb balance of the normal.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.638-647
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• 1996

Robot manipulators for harvesting fruits must be controlled to track the desired path of end-effector to avoid obstacles under the consideration of collision free area and safety path. This paper presents a robot path control algorithm to secure a collision free area with the recognition of work environments. The flexible space, which does not damage fruits or branches of tree due to their flexibility and physical properties , extends the workspace. Now the task is to control robot path in the extended workspace with the consideration of collision avoidance and velocity limitation at the time of collision concurrently. The feasibility and effectiveness of the new algorithm for redundant manipulators were tested through simulations of a redundant manipulator for different joint velocities.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.1
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• pp.82-88
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• 2009

The output of the encoder is a digital pulse, which is also easy to be connected to a digital controller. There are various angular velocity detecting methods of M, T, and M/T. Each of them has its own properties. There is a common limitation that the angular velocity detection period is strongly dependent on the destination velocity magnitude in case of ultimate low range. They have ultimately long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a zero velocity detectable sensor algorithm with the dual encoder system. The sensor algorithm is able to keep detection period moderately at near zero velocity and even detect zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the algorithm validity.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.76-85
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• 2007

An optical rotary encoder is easy to implement for automatic control applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using the encoder, there are various angular velocity detecting methods, M-, T-, and M/T-method. Each of them has a property of its own. They have common limitation that the angular velocity detection period is strongly subject to the destination velocity magnitude in case of ultimate low range. They have ultimate long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a dual encoder system with two encoders of normal resolution. The dual encoder system is able to keep detection period moderately at near zero velocity and even detects zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the dual encoder system validity.

• The Journal of the Acoustical Society of Korea
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• v.29 no.1E
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• pp.11-27
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• 2010

Nowadays, ultrasound Doppler imaging is widely used in assessing cardiovascular functions in the human body. However, a major drawback of ultrasonic Doppler methods is that they can provide information on blood flow velocity along the ultrasound beam propagation direction only. Thus, the blood flow velocity is estimated differently depending on the angle between the ultrasound beam and the flow direction. In order to overcome this limitation, there have been many researches devoted to estimating both axial and lateral velocities. The purpose of this article is to survey various two-dimensional velocity estimation methods in the context of Doppler imaging. Some velocity vector estimation methods can also be applied to determine tissue motion as required in elastography. The discussion is mainly concerned with the case of estimating a two-dimensional in-plane velocity vector involving the axial and lateral directions.

• PNF and Movement
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• v.16 no.2
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• pp.267-273
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• 2018

Purpose: Leg length discrepancy (LLD) is one of the risk factors for postural imbalance. This study aimed to investigate the effect of induced leg length discrepancy on the limitation of stability (LOS) and static postural balance. Methods: Thirteen adults (males, 7; females 6) participated in this study. The LOS and static postural balance [sway length, sway area, and sway velocity of center of gravity (COG) displacement] were measured by the balance trainer system. The subjects were asked to move the COG for the anterior, posterior, and left and right directions maximally and to keep standing on the platform with and without induced LLD for 30 s in the open and closed eyes conditions, respectively. The LLD was artificially induced to 2 cm using insole. Wilcoxon test was used to compare the LOS and the static postural balance between with and without induced LLD. Results: The anterior and posterior LOS significantly decreased in induced LLD (p<0.05), and the left and right LOS were not significantly different between with and without LLD (p>0.05). Sway length, sway area, and sway velocity of the COG displacement significantly decreased in induced LLD (p<0.05). Conclusion: This study suggests that induced LLD could decease the antero-posterior LOS and increased the static postural balance. Therefore, the LLD could disturb the postural balance.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.873-878
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• 2000

Semiconductor packaging technology is changed rapidly according to the trends of the micro miniaturization of multimedia and information equipment. For I/O limitation and fine pitch limitation, DIP and SOP/QFP are replaced by BGA/CSP. This is one of the surface mount technology(SMT). Solder ball is bumped n the die pad and connected onto mounting board. In ball bump formation, vacuum suction type ball alignment process is widely used, However this type has some problems such as ionization, static electricity and difficulty of fifo(first-input first-out) of solder balls. Seesaw type is reducing these problems and has a structural simplicity and economic efficiency. Ball cartridge velocity and ball aligned plate angle are Important variables to improve the ball alignment Process. In this paper, seesaw-type CSP solder ball loader is developed and the optimal velocity and plate angle are proposed.

• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.17-22
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• 2020

Recently, the decrease in thin film thickness has been actively studied by changing several physical elements such as the increase in revolution velocity of lower substrate equipped with AC or DC motor. In this paper, we propose a novel spin coater control system that changes AC or DC motor and common use software with limitation of velocity and position control into step motor and LABVIEW software based on GUI to control revolution velocity and position more precisely. By determining six input values of rotation velocity 1, 5, 10, 25, 50, 100 PPS, we fabricated six samples using coating target, TA(tantalum) on silicon substrate and measured their thin film thickness by SEM. Hence, this research can be applied to inferring thin film thickness of tantalum regarding any value of revolution velocity without additional experiments and for linear reference model via property analysis of thin film thickness using other thin-film materials.