• Journal of the Korea Computer Graphics Society
• /
• v.1 no.2
• /
• pp.201-212
• /
• 1995

This paper presents a new method of dynamics-based synthesis of bipedal, especially human, walking. The motion of the body at a time point is determined by ground reaction force and torque under the support foot and joint torques of the body at that time point. Motion synthesis involves specifying conditions that constrain ground reaction force and torque, and joint torques so that a given desired motion may be achieved. There are conditions on a desired motion which end-users can think of easily, e.g. the goal position and orientation of the swing foot for a single step and the time period of a single step. In this paper, we specify constraints on the motion of the support foot, which end-users would find difficult to specify. They are constraints which enforce non-sliding, non-falling, and non-spinning the support foot. They are specified in terms of joint torques and ground reaction force and torque. To satisfy them, both joint torques and ground reaction force and torque should be determined appropriately. The constraints on the support foot themselves do not give any good clues as to how to determine ground reaction force and torque. For that purpose, we specify desired trajectories of the application point of vertical ground reaction force (ground pressure) and the application point of horizontal ground reaction (friction) force. The application points of vertical pressure and friction force are good control variables, because they are indicators to kinds of walking motions to synthesize. The synthesis of a bipedal walking motion, then, consists of finding a trajectory of joint torques to achieve a given desired motion, so that the constraints are satisfied under the condition of the prescribed center of pressure and center of friction. Our approach is distinguished from many other approaches, e.g. the inverted-pendulum approach, in that it captures and formulates dynamics of the support foot and reasonable constraints on it.

• Korean Journal of Applied Biomechanics
• /
• v.18 no.1
• /
• pp.203-212
• /
• 2008

The purpose of this study is to propose appropriate model for 3 staged Didimsae movement to Jajinmori rhythm and to provide information for ideal foot step movements. For the locational change of body center, the height of body center is lowered at the moment of forward step and during forward intersection of the feet, forward direction linear motion is converted to vertical motion to maintain stability. Speed change of body center reduces flow of body on step forward moment and controls rapid forward movement for stabled movement and position when preventing fast forward horizontal direction movement of centroid speed while knee joint and foot joint are vertically risen for heel bone contacts the ground. For angle changes of joints, in order to prevent hyperextension of lower leg, hip joint is extended and knee joint is curved to secure stability of movement for smooth curves and extension. When centroid of foot joint is moved from top of the feet to whole foot sole and when left foot makes dorsal curve, stabled movement is accomplished.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2002.05a
• /
• pp.132-135
• /
• 2002

In the present study, an electro-mechanical KAFO (knee-ankle-foot orthosis) which satisfies both the stability in stance and the knee flexion in swing was developed and evacuated in eight polio patients. A knee joint control algorithm suitable for polio patients who are lack of the stability in pre-swing was also developed and various control systems and circuits were also designed. In addition, knee flexion angles and knee moments were measured and analyzed for polio patients who used the developed KAFO with the three-dimensional motion analysis system. Energy consumption was also evaluated for the developed KAFO by measuring the movement of the COG (center of gravity) during gait. From the present study, the designed foot switch system successfully determined the gait cycle of polio patients and controlled knee joint of the KAFO, resulting in the passive knee flexion or foot clearance during swing phase. From the three-dimensional gait analysis for polio patients, it was found that the controlled-knee gait with the developed electro-mechanical KAFO showed the knee flexion of 40$^{\circ}$∼45$^{\circ}$ at an appropriate time during swing. Vertical movements of COG in controlled-knee gait (gait with the developed electro-mechanical KAFO) were significantly smaller than those in looked knee gait(gait with the locked knee Joint). and correspondingly controlled-knee gait reduced approximately 40% less energy consumption during horizontal walking gait. More efficient gait patterns could be obtained when various rehabilitation training and therapeutic programs as well as the developed electro-mechanical KAFO were applied for polio patients.

• Journal of the Korea Concrete Institute
• /
• v.20 no.3
• /
• pp.335-343
• /
• 2008

In order to improve the workability in erecting Precast Concrete (PC) members and enhance the seismic resistance capacity of the joints in PC moment frames, a new PC column and its construction process are introduced in this paper. This column is manufactured by centrifugal force in keeping the hollow tube inside; the hollow is little bit wide and the grout can be poured from top to bottom after erection at site so that more compact grouting is possible in horizontal joint. The repeated cyclic loading test for four full scaled specimens was conducted to evaluate the seismic resistance capacity of the joint designed by the proposed system. For the continuity of main reinforcements in column, two connecting methods are used in designing specimens; one is to use mechanical connector and other is lab splice. From the cyclic lateral loading test, it was found that the seismic capacity of the developed PC column joint is comparable to that of monolithic joint.

• Journal of Oral Medicine and Pain
• /
• v.24 no.4
• /
• pp.455-466
• /
• 1999

The purpose of this study was to investigate the magnitude of mandibular rotational torque movements in subjects with TMJ sounds, and to analyse correlation between quantitative characteristics of TMJ sounds and mandibular rotational torque movement. Twenty dental college students with TMJ clicking and twenty students without any TMD signs and symptoms were examined by mean of SonoPak and Rotate program of BioPAK system(Bioresearch Inc. MilWaukee, wisconsin, USA) in this study. Mandibular rotational torque movements were recorded and analysed during maximum mouth opening, protrusion, and lateral excursion in frontal and horizontal planes. The obtained results were as follows: 1. On maximum mouth opening, mandibular rotational angle and distance of clicking group were significantly greater than those of control group in frontal plane. (P<0.05). 2. During maximum mouth opening closing, maximum mandibular rotational angle and distance of clicking group were significantly greater than those of control group in frontal plane. (P<0.01). 3. On protrusion, mandibular rotational angle and distance of clickin group were significantly greater than those of control group in horizontal plane. (P<0.05). 4. On lateral excursion, there was no significant difference in mandibular rotational angle and distance between clicking group and control group in frontal and horizontal planes. 5. There were significant correlations between peak amplitude of TMJ sounds and maximum mandibular rotational distance during maximum mouth opening (r=-.481) and mandibular rotational distance on maximum mouth opening (r=-.455) in horizontal plane. 6. There were significant correlations between Above 300/(0-300)Hz ratio of TMJ sounds and mandibular rotational angle (r=-.499) and distance (r=-.457) on maximum mouth opening in frontal plane.

• Journal of Oral Medicine and Pain
• /
• v.22 no.2
• /
• pp.207-217
• /
• 1997

This study was performed for Investigation of the magnitude of mandibular positional change in maximum mouth opening. protrusion, lateral excursion, gum and peanut chewing with BioPAK system(Bioresearch Inc. USA) which can analyze mandibular rotational torque movements. For this study 17 female patients with Temporomandibular joint(TMJ) closed lock and 18 female control without any Temporomandibular disorders(TMDs) signs and premature occlusal contact were included. The obtained results were as follows : 1. In maximum mouth opening, the mandibular rotational angle and distance of patients were significantly greater than those of control group in horizontal plane(P<0.05). 2. In protrusion, the mandibular rotational angle and distance of patients were significantly greater than those of control group in frontal and horizontal plane(P<0.01, P<0.05). 3. The mandibular rotational angle and 야stance in lateral excursion to affected side of patients were significantly greater than those in lateral excursion to non-affected side in frontal plane(P<0.05). 4. The mandibular rotational angle in gum chewing to affected side of patients was significantly greater than that in gum chewing to non-affected side in frontal plane. 5. The mandibular rotational angle and distance in peanut chewing to affected side of patients were significantly greater than those in peanut chewing to non-affected side in frontal and horizontal plane. 6. The mandibular rotational angle and distance in peanut chewing to affected side of patients were greater than those in gum chewing, and was the same result in control group in frontal and horizontal plane.

• Korean Journal of Applied Biomechanics
• /
• v.26 no.3
• /
• pp.303-308
• /
• 2016

Objective: This study evaluated the vertical and horizontal forces in the frontal plane acting on a pedal due to the vertical alignment of the lower limbs. Method: Seven male subjects (age: $25.3{\pm} 0.8years$, height: $175.4{\pm}4.7cm$, weight: $74.7{\pm}14.2kg$, foot size: $262.9{\pm}7.6mm$) participated in two 2-minute cycle pedaling tests, with the same load and cadence (60 revolutions per minute) across all subjects. The subject's saddle height was determined by the height when the knee was at $25^{\circ}$ flexion when the pedal crank was at the 6 o'clock position (knee angle method). The horizontal force acting on the pedal, vertical force acting on the pedal in the frontal plane, ratio of the two forces, and knee range of motion in the frontal plane were calculated for four pedaling phases (phase 1: $330{\sim}30^{\circ}$, phase 2: $30{\sim}150^{\circ}$, phase 3: $150{\sim}210^{\circ}$, phase 4: $210{\sim}330^{\circ}$) and the complete pedaling cycle. Results: The range of motion of the knee in the frontal plane was decreased, and the ratio of vertical force to horizontal force and overall pedal force in the complete cycle were increased after vertical alignment. Conclusion: The ratio of vertical force to horizontal force in the frontal plane may be used as an injury prevention index of the lower limb.

• Korean Journal of Applied Biomechanics
• /
• v.14 no.2
• /
• pp.27-40
• /
• 2004

The objective of this study is to identify the kinematic variables of giant swing backward to handstand as well as individual variations of each athlete performing this skill, which in turn will provide the basis for developing suitable training methods and for improving athlete's performance in actual games. For this end, 3 male athletes, members of the national team, who are in ${\Box}{\Box}H{\Box}{\Box}$ University, have been randomly chosen and their giant swing backward to handstand performance was recorded using two digital cameras and analyzed in 3 dimensional graphics. This study came to the following conclusion. 1. Proper time allocation for giant swing backward to handstand are: Phase 1 should provide enough time to attain energy for swing track of a grand round movement. The phase 3 is to throw the body up high in the air and stay in the air as long as possible to smoothen up the transition to the next stage and the phase 4 should be kept short with the moment arm coefficient of the body reduced. 2. As for appropriate changes of locations of body center, the phase 1 should be comprised of horizontal, perpendicular, compositional to make up a big rotational radius. Up to the Phase 3 the changes of displacements of vertical locations should be a good scale and athlete's body should go up high quickly to increase the perpendicular climbing power 3. When it comes to the speed changes of body center, the vertical and horizontal speed should be spurred by the reaction of the body in Phase 2 and Phase 3. In the Phase 4, fast vertical speed throws the body center up high to ensure enough time for in-the-air movement. 4. The changes of angles of body center are: in Phase 2, shoulder joint is stretching and coxa should be curved up to utilize the body reaction. In the Phase 4, shoulder joint and coxa should be stretched out to get the body center as high as possible in the air for stable landing. 5. The speeds of changes in joints angles are: in the Phase 2 should have the speed of angles of shoulder joints increase to get the body up in the air as quickly as possible. The Phase 3 should have the speed of angles in shoulder joint slow down, while putting the angles of a knee joint up to speed as quickly as possible to ensure enough time for in-the-air movement.

• Journal of Biosystems Engineering
• /
• v.38 no.2
• /
• pp.138-148
• /
• 2013

Purpose: Determining an appropriate path is a top priority in order for a robot to maneuver in a dynamically efficient way especially in a pick-and-place task. In a non-standardized work environment, current robot arm executes its motion based on the kinematic displacements of joint variables, though resulting motion is not dynamically optimal. In this research we suggest analyzing and applying motion patterns of the human arm as an alternative to perform near optimum motion trajectory for arbitrary pick-and-place tasks. Methods: Since the motion of a human arm is very complicated and diverse, it was simplified into two links: one from the shoulder to the elbow, and the other from the elbow to the hand. Motion patterns were then divided into horizontal and vertical components and further analyzed using kinematic and dynamic methods. The kinematic analysis was performed based on the D-H parameters and the dynamic analysis was carried out to calculate various parameters such as velocity, acceleration, torque, and energy using the Newton-Euler equation of motion and Lagrange's equation. In an attempt to assess the efficacy of the analyzed human motion pattern it was compared to the virtual motion pattern created by the joint interpolation method. Results: To demonstrate the efficacy of the human arm motion mechanical and dynamical analyses were performed, followed by the comparison with the virtual robot motion path that was created by the joint interpolation method. Consequently, the human arm was observed to be in motion while the elbow was bent. In return this contributed to the increase of the manipulability and decrease of gravity and torque being exerted on the elbow. In addition, the energy required for the motion decreased. Such phenomenon was more apparent under vertical motion than horizontal motion patterns, and in shorter paths than in longer ones. Thus, one can minimize the abrasion of joints by lowering the stress applied to the bones, muscles, and joints. From the perspectives of energy and durability, the robot arm will be able to utilize its motor most effectively by adopting the motion pattern of human arm. Conclusions: By applying the motion pattern of human arm to the robot arm motion, increase in efficiency and durability is expected, which will eventually produce robots capable of moving in an energy-efficient manner.

• Korean Journal of Applied Biomechanics
• /
• v.18 no.1
• /
• pp.97-105
• /
• 2008

The kinematic variables for swimming and fin-swimming start motions were analyzed and compared using 3-dimensional cinematography. For the swimming start, the arm segment moved towards the upper rear and trunk towards the upper front followed by a descent towards the lower front, while the fin-swimming start motion showed movement towards the lower front for all segments. The total body center of gravity for the swimming start showed horizontal movement far to the front followed by a rapid descent while the fin-swimming start showed close movement towards the lower front in a short period of time. Upon entering the water, the center of gravity for swimming showed high vertical velocities while fin swimming had high horizontal velocities. For both swimming and fin swimming, the upper extremity velocity had more influence on the total center of gravity velocity than the lower extremities. Flexion of the hip joint was observed before the jump for the fin swimming start while the swimming start showed two flexions in mid-air succeeding the jump. The flexion and extension movements at the knee joint during the fin-swimming start motion were shown to be larger and more rapid than those of fin-swimming.