A vehicle driven by electric motors has been expected to find uses as personal mobility vehicles. We have been developing an electric skateboard as a candidate of personal mobility vehicles in the future. It is necessary to control the center of gravity of a driver on the board for being a comfortable transportation. The control design requires knowledge of human body dynamics on lateral motion. As a first step, we developed an electric skateboard with load measuring devices and tried to clarify the mechanism of human body dynamics by impulse response. To analyze the human body dynamics precisely, we applied a velocity servo control instead of acceleration control. Comparing with previous studies, the electric skateboard can apply large external force to the subject. We assumed a model based on hip strategy which keeps upper trunk perpendicular to the horizon consequently. As a result, feedback parameters of posture control on free standing delay time could be derived.

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The purpose of this study was to investigate the relationship between foot impact acceleration and landing impact on the ball sport movements. 5 subjects performed 5 movements (jogging, cutting, sidestep, take-off and landing) that often used in ball sports. Ground reaction force (GRF) and impact acceleration were recorded. The result showed the timing of impact peak acceleration was substantially consisted with that of vertical GRF 1^<st>peak. Therefore the relationship between peak acceleration value and vertical GRF 1^<st>peak value on each movement was investigated. Strong correlations were found on all movements. As the result of this study showed that landing impact that have measured by force plate can be estimated by accelerometer, allowing impact measurement in field.

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As of April 2012, "Budo", Japanese traditional martial arts, became a compulsory part of health and physical education at junior high schools in Japan, with schools being given the option to choose from judo, kendo, and sumo. Recently, some students died or suffered injuries in judo accidents, and it is feared that such accidents could become common. In this study, we examined cases of head injury suffered by students in judo accidents. The incidence of injury showed two peaks occurring in the first year of junior high and senior high school. In most cases, the judo accident impacted the victim's head, particularly the occipital region. Most of the victims suffered subdural hemorrhage. Osotogari, a judo throwing technique, was found to be the most common cause of head injury. This was true in the alive case of the accidents as well as those who died from head injury.

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In many junior high schools, judo became a compulsory course in 2012. However, the number of participants, in particular beginners, who die or arc injured in judo is higher than that for other sports. For this reason, there is a fear that there will be a drastic increase in the number of judo-related accidents leading to death or injury in junior high schools. Thee most serious form of head injury is acute subdural hematoma (ASDH). Therefore, we need to prevent acute subdural hematoma that is the primary cause of death. In this study, we developed the theoretical model to describe the response of the brain in the skull during the occiput impact. Then, the effects of material properties of impact objects and headgears on the relative displacement between brain and skull were discussed. Moreover, the theoretical model was compared with the experiment of brain-skull physical model.

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Developing procedure for quantitative evaluation of product safety is necessary to manufacture safe and secure products. In this paper, a human head was focused on as a main theme because head injury is thought to be one of the most dangerous injuries. Finite element method analysis should be useful method to evaluate product safety. So some human head finite element models were constructed, but these mainly focused on only dynamic impact condition. We think in developing safety products, quasi-static impact conditions are also important Therefore the finite element human head models which can both simulate dynamic and quasi-static impact conditions are constructed And also head fracture criteria are discussed using constructed head model and a single bone simulation

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Emergency situations such as a car accident, it is important in life-saving activities that quickly detects the driver's vital. There is a heart sound as a method to obtain the non-contact vital signs, such as a mat attached to the microphone studies to measure the heart rate and breathing have been made. However, such studies measuring the vital vehicle driver at the time of the accident has not been performed yet. In this study, in-vehicle car, which is aimed at developing a system that can determine instantly driver and occupant injury. The system calculates the heart rate to detect heart sounds from microphone device prototype. The measurement showed efficacy to examine whether it can measure corresponding to heart rate variability by measuring the heart rate at rest and after exercise is performed and numerical comparison of the contact device.

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Many researches have been going on related to the activity of kicking in the foot ball. But there have been few researches to clarify the relation of the stiffness of a foot joint and its effect. In this paper, we focused on in-step kick activity which is performed quite often in the foot ball match. And we developed a pendulum like kicking model which is allowed to adjust the knee joint stiffness in the Sagittal plane to achieve the activity of left leg kicking. Then the experiments were conducted to clarify the relation of the foot stiffness and its influence including the velocity of the ball.

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This study constructed finite element models of the simplified foot and soccer ball, and examined the factors affecting the ball behavior in curve kick. A 3D finite element model of the foot was developed using the barefoot and footwear shapes, which were obtained from a 3D laser scanner. A finite element model of the ball consisted of composite shell elements that include a hyperelastic model to define the latex bladder layer and a viscoelastic model to define the outer panels. Five experienced male university soccer players performed curve kicks. The kicking motions were captured three-dimensionally by two high-speed cameras at 2,500 fps. The models were validated by comparing the results of the finite element analysis to those of the experiment. Simulations of the ball behavior were conducted using the finite element models. The simulation results indicated the following. The ball velocity is largely affected by the foot velocity immediately before impact but barely affected by the Young's modulus of the shoe upper and the coefficient of friction. The ball rotation is affected by the foot velocity immediately before impact and the coefficient of friction; however, these factors had no significant effect.

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The "opposite-field hitting" is enabled by hitting the ball with the bat angled horizontally and facing its impacting surface toward the opposite field (the first mechanism: conventional theory). Theoretically, the batters can adopt other approach to successfully hit the ball toward the opposite field: Assuming that the batter hits the lower part of the ball with a bat positioned horizontally and facing toward the center field, the batted ball should travel upward toward the center field. If, however, the bat facing toward the center field is tilted downward to position the head slightly lower than the grip, the batted ball should travel upward and toward the opposite field (the second mechanism). The present study was conducted to determine the contributions of these mechanisms in opposite-field hitting. The 146 trials were analyzed and found that the contribution of the second mechanism (69%) was greater than the first (31%).

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Wood, metal, and various composite materials are used in the manufacture of a baseball bat. Aluminum alloy bats are advantageous in terms of improved strength, lower cost, etc. The restitution performance of a hollow aluminum alloy bat is related to the hoop frequency of the bat barrel. In this study, a numerical analysis model of the aluminum alloy bat was created, and the validity of this bat model was investigated via an eigenvalue analysis. Furthermore, the bat-ball coefficient of restitution (BBCOR) was calculated by analyzing the impact between the bat and ball, the relation between BBCOR and hoop frequency was investigated.

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This sheet deals with characteristics of the oblique impact system, which is composed of the golf ball and elastic supported clubface. The impact system is modeled by both a nonlinear spring and a nonlinear dashpot using Hertz's contact theory. This model is applied to the oblique impact system of golf ball and elastic supported clubface. The characteristics of the oblique impact were obtained by using this model. The results show that the spin rate increased in proportion to the angle of incidence and impact velocity and a coefficient of friction. Also, in the case of increase the tangential stiffness, the spin rate was decreased.

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This paper describes a simple analytic model on oblique collision of a golf ball. In the golf, competition result is affected considerably by carry and trajectory of the golf ball. Therefore, the oblique collision has been reported both in experiments and numerical simulations in many people. Then, we need to study oblique collision behavior of a golf ball in numerical simulation by using simple model which is constituted by non-liner spring, non-liner damper and slider. In the results, the normal force during the collision is agreement but frictional force is different in the comparison of simple model results and FEM. The frictional force in simple model and FEM discussed.

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In order to investigate the effects of gravity center position of golf club head on the behavior of club shaft, deformation of shafts while a golf swing was simulated by the finite element method. As results, the following two points are obtained. Firstly, after the top of swing the deflection of the tip position of the shaft is enlarged by the bending moment caused by the centrifugal force due to the off-centered gravity center of club head from the shaft axis. Secondly, the longer the distance from the impact face to the gravity center of club head becomes, the larger the deflection of the tip position of the shaft is generated with the larger bending moment caused by the centrifugal force.

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A new shape hockey stick has been developed Its 1st modal node of vibration and centre of percussion are positioned near the head more than conventional sticks. By using the stick, hockey players could hit ball hard under usual standing position. In this study we made wooden models of the new shape stick and conventional shape stick. The coefficient of restitution of the models has been evaluated by a baseball bat performance test.

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