• Journal of Institute of Control, Robotics and Systems
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• v.18 no.12
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• pp.1106-1114
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• 2012

To achieve synchronized motion between a wearable robot and a human user, the redundancy must be resolved in the same manner by both systems. According to the seven DOF (Degrees of Freedom) human arm model composed of the shoulder, elbow, and wrist joints, positioning and orientating the wrist in space is a task requiring only six DOFs. Due to this redundancy, a given task can be completed by multiple arm configurations, and thus there exists no unique mathematical solution to the inverse kinematics. This paper presents analysis on the kinematic and dynamic aspect of the human arm movement and their effect on the redundancy resolution of the human arm based on a seven DOF manipulator model. The redundancy of the arm is expressed mathematically by defining the swivel angle. The final form of swivel angle can be represented as a linear combination of two different swivel angles achieved by optimizing different cost functions based on kinematic and dynamic criteria. The kinematic criterion is to maximize the projection of the longest principal axis of the manipulability ellipsoid for the human arm on the vector connecting the wrist and the virtual target on the head region. The dynamic criterion is to minimize the mechanical work done in the joint space for each two consecutive points along the task space trajectory. As a first step, the redundancy based on the kinematic criterion will be thoroughly studied based on the motion capture data analysis. Experimental results indicate that by using the proposed redundancy resolution criterion in the kinematic level, error between the predicted and the actual swivel angle acquired from the motor control system is less than five degrees.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.749-759
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• 2009

The purpose of this study was to provide basic information for improving a soft tennis forehand middle volley technique based on kinematic and kinetic analyses of volleys performed by four male national tennis players($33.3{\pm}2.16$ years). The results are as follows. The first phase of the stroke was the longest, covering 64.7% of the stroke time. The displacement of the center of gravity was 48.1% to the right and 54% to the front in the first phase. When impacted, the elbow joint showed the highest average velocity, 3.67m/s, and the upper arm segment displayed the highest angular velocity, $201^{\circ}/s$. The average of the elbow angle and the ball velocity were $149^{\circ}$ and 18.9m/s, respectively. In the ground reaction force, the left and right foot forces in both the x and y directions showed a statistically significant difference. This result seems to indicate that when the left foot is pushed to the right, the force of the right foot is proportional and symmetrical to the left, serving as a supporter.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.217-229
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• 2003

The purpose of this study was to present the basic data on improving the skills for 3 junior high school national badminton players in clear and drop motion through the 3-dimensional image analysis. Therefore, the results of this study are as follows: 1. In the duration times per phase, subject C relatively showed a similar time between clear and drop motion. Accordingly, C took a more effective motion than A and B. 2. In the velocities of racket head, subject A and C showed similar changes relatively. However, in case of subject B, the velocity was decreased before back swing(E2) and increased until impact(E3). 3. Regardless of clear and drop motion, the changing phases of joint angle for wrist and elbow showed similar changes comparatively. 4. In the angles of upper body, clear motion was average 85.0 degree and drop one was average 80.7 degree during the impact(E3). Hence, it showed that drop motion hit the ball bowing the upper body more than clear one. 5. In the angles of racket head, clear motion was average 87.7 degree and drop one was average 85.6 degree during the impact(E3). Consequently, drop motion was impacted forward more than clear one.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.97-108
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• 2006

C. H. OH, S. N. CHOI, T. G. NAM, The Kinematic Analysis of the Tennis Flat Serve Motion, Korean Jiurnal of Sports Biomechanics, Vol. 16, No. 2, pp. 97-108, 2006. By the comparison and the analysis of the different factors during the tennis flat serve motion such as the required time per section, the movement displacement of the racket, the velocity of the upper limbs joints, the physical center of gravity, and the angle and the angular velocity of the upper limbs joints between an ace player and a mediocre player, these following results were drawn. First, the experiment result of the total time required per section in a tennis flat serve motion showed that an ace player was faster than a mediocre player by 0.4 seconds. This result suggested that it was required to increase the speed of the racket head by a swift swing to perform an effective flat serve motion. Second, the experiment result of the movement displacement of the racket in the tennis flat serve motion showed that an ace player greatly moved toward the left side on an x-axis. But both an ace and a mediocre player were shown to be at the similar points on a y-axis at the moment of the impact of the racket. An ace player was also shown to be located at a higher position on a z-axis by 0.23m. Third, the velocity of the center of gravity of an ace player was faster in every phase than that of a mediocre player in a tennis flat serve motion. Fourth, the velocity of the upper limb joints of an ace player was faster in every phase than that of a mediocre player in a tennis flat serve motion. Fifth, the experiment result of the speed of the racket head in tennis flat serve motion showed that a mediocre player was faster than an ace player in the first phase, but the latter was faster than the former in the second, third, and the fourth phases. Sixth, at the moment of impact of a tennis flat serve, an ace player had greater flexion of the angle of the wrist joints by an 11.8 degree than a mediocre player. An ace player also had greater extension of the angle of the elbow joint and the shoulder joint respectively by a 5.2 degree and a 1.4 degree with a mediocre player. Seventh, an ace player had greater angular velocity of the upper limb joints and the hip joints than a mediocre player at the moment of the impact of tennis flat serve. Eighth, an ace player was shown to have a greater change of the forward and the backward inclination (or the anterior and posterior inclination) of the upper body

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.77-85
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• 2009

This study is aimed at providing information on injury prevention and skill improvement by inducing the accurate movements in exercise as well as understanding the principles of badminton drive movements. Movement displacement of racket head showed the similar patterns among those surveyed but, it seemed that slight differences resulted from external factors such as height, length of brachial and forearm and individual trend of swing locus. Regarding upper joint angle per phase, the angles of shoulder joint, elbow joint and wrist joint were closely associated in taking drive movements and they supported the segment order theory that power was conveyed from proximal into distal. It was shown that angular velocity of upper joint became larger in follow through movement after impact among all those surveyed, which meant the importance of follow through in racket sports such as badminton. In conclusion, this follow through movement acts as an important factor in racket sports in terms of pose stability maintenance, pose correction of movements and injury prevention of joints. In summary, when swings are made according to segment order theory, efficient movements can be taken.

• Korean Journal of Applied Biomechanics
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• v.20 no.2
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• pp.155-165
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• 2010

The purpose of this study was to analyze kinematic quantitative factors required of a forehand counter drive in table tennis through 3-D analysis. Four national table tennis players participated in this study. The mean of elapsed time for total drive motion was $1.009{\pm}0.23\;s$. At the phase of impact B1 was the fastest as 0.075 s. This may affect efficiency in the initial velocity and spin of the ball by making a powerful counter drive. The pattern of center of mass showed that it moved back and returned to where it was then moved forward. At the back swing, lower stance made wide base of support and a stronger and safer stance. It may help increasing the ball spin. Angle of the elbow was extended up to $110.75{\pm}1.25^{\circ}$ at the back swing and the angle decreased by $93.75{\pm}3.51^{\circ}$ at impact. Decreased rotation range of swinging arm increased linear velocity of racket-head and impulse on the ball. Eventually it led more spin to the ball and maximized the ball speed. Angle of knee joint decreased from ready position to back swing, then increased from the moment of the impact and decreased at the follow thorough. The velocity of racket-head was the fastest at impact of phase 2. Horizontal velocity was $7796.5{\pm}362\;mm/s$ and vertical velocity was $4589.4{\pm}298.4\;mm/s$ at the moment. It may help increase the speed and spin of the ball in a moment. The means of each ground reaction force result showed maximum at the back swing(E2) except A2. Vertical ground reaction force means suggest that all males and females showed maximum vertical power(E2), The maximum power of means was $499.7{\pm}38.8\;N$ for male players and $519.5{\pm}136.7\;N$ for female players.

• Clinics in Shoulder and Elbow
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• v.1 no.2
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• pp.221-229
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• 1998

We measured, with manual goniometer, the active and passive arc of motion of the shoulder in 31 healthy male subjects who were right-hand dominant and who ranged in age from twenty to thirty-one years. Among ten directions through the four motion plane, the range of motion on the dominant side were significantly smaller than those on the non-dominant side in the motion of six directions. We also measured the motion fraction of the glenohumeral and scapulothoracic movement using fluoroscope in 30-degree intervals of arm elevation in the scapular plane. The ratio of glenohumeral to scapulothoracic movement(θGH/θST) was 1.6 for the full range of motion in scapular plane. At the lower angles of abduction, scapulothoracic movement was slight compared with glenohumeral movement. The motion fraction of scapulothoracic joint was increased from 60-degree to 150 degree of arm angle especially between 120 to 150 degree. During arm elevation, scapula was also extended from 42 degrees to 20 degrees tilting as well as internal rotation. The measuring technique of glenohumeral to scapulothoracic movement(θGH/θST) with fluoroscopy could be applied to the simple radiographic measurement at the out-patient clinic in order to identify the pathology and recovery of shoulder motion after treatment.

• Journal of Veterinary Clinics
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• v.11 no.2
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• pp.529-537
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• 1994

Sector scanner which has a conical end is used to image through the intercostal space because heart is protected by the ribs. Cardiac data published all around the world were also obtained by sector scanner. Although scanners being used in every small animal practice and animal hospital at college in Korea include convex ape and linear type, linear type is not appropriate f3r cardiac scan because of a wide contact surface. The purpose of this study is to establish ultrasonographic images of normal cardiac structures by measuring shape, size of reflectable cardiac structure according to restraint position in scanning normal heart of the puppies with 6.5 MHz convex scanner(SonoAce 4500, Medison, Korea) used in our veterinary teaching hospital, Seoul national university. Seventeen male and female puppies considered having healthy hear by X-ray and clinical examination are used feom April to July 1994. Scanning point selection of probe head and the distinction of imaged cardiac structures were accomplished by necropsy and cardiac scanning performed through thoracotomy under general anesthesia. At 10 o'clock position of transducer(at an angle of 30$^{\circ}$ between imaginary line from elbow joint to 3rd sternum and probe head, 60$^{\circ}$ from body surface, 4th intercostal space of right thorax) with the marker of scanner toward the head of dogs right atrium, left atrium and left ventricle were observed in 2, 3, 4, 5 intercostal space(2cm from the sternum) of experimental dog positioned ventrodorsally under general anesthesia. Under these conditions, the numerical values of imaged diastolic hear are as follows : the distance from skin to apex(mean$\pm$S.D) 47.53$\pm$6.94mm, thickness of left ventricular wall 6.00$\pm$1.60mm, length of left ventricle 16.27$\pm$5.31mm, width of left ventricle 15,33$\pm$4.25mm, length of left atrium 12.33$\pm$3.82mm, width of left atrium 11. 33$\pm$3.94mm, length of right atrium 1.00$\pm$2.41mm, width of right atrium 11.21$\pm$2.76mm and the area of left ventricle 270.92$\pm$109.81mm$^2$, area of left atrium 98.00$\pm$41.08mm$^2$, area of right atrium 62.75$\pm$21.04mm$^2$.

• Journal of the Korean Arthroscopy Society
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• v.13 no.2
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• pp.155-160
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• 2009

Purpose: The purpose of this study was to evaluate the pain recovery pattern according to the integrity and to analyze the factors affecting the progress and level of pain postoperatively. Materials and Methods: We examined 153 patients, who were treated with arthroscopic rotator cuff repair. 101 rotator cuff tears were full-thickness tear and 52 were partial tear. The mean follow up duration was 20 months (12~30 months). We evaluated the visual analogue scale, range of motion, ASES (American Shoulder and Elbow Surgeons), and UCLA (University of California at Los Angeles) scores preoperatively and postoperatively. We analyzed the pain recovery pattern between partial and full thickness tear using Student T-test and the factors affecting the progress and level of postoperative pain using multiple regression analysis. Results: The change patterns of visual analogue scale after arthroscpoic repair were similar regardless of the tear integrity. The VAS showed a continuous decreasing pattern, but increased at first 3 weeks postoperatively and at 7 weeks postoperatively, and then, decreased thereafter. The average VAS was ${\leqq}2$ points by postoperative 3 months. The factor affecting the pain score at 3 months was related to the preoperative limitation in forward flexion ($r^2=0.377$, p=0.021). Conclusion: There was no differences of the pain recovery pattern according to the integrity, and the factor affecting the progress of postoperative pain was preoperative angle of forward elevation. So, the appropriate preoperative rehabilitation protocol that can improve motions of the shoulder joint would help to improve the level of postoperative pain and functional recovery.