Japanese Sport makers earnestly started to develop various sporting goods for the top Winter Olympic Athletes. It was 1972, in the 70m Ski Jumping Event of the Sapporo Olympic Games, all 3 medals were won by Japanese jumpers. Since this splendid achievement, our sportswear development has been proceeded with the slogan, 'Faster, Farther and Safer'. Here we will show you our history of sports wear development.

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In the evaluation of hitting sound of a golf club driver, not only the radiated sound from the club head but also sound from the ball and the club shaft must be considered. In this study, the sound was divided into three time domains, before, while and after the impact. Three sounds were generated by wind roar generated by the club shaft, vibration of the ball and vibration of the club head. In the sensory evaluation, the sound was artificially composed by fundamental vibrations of the club face and the ball derived in the simulation and the method of paired comparisons was employed. When the ratio between ball and club face frequencies was 2:3, the sound obtained good sensory evaluation of 'powerful' and 'long distance'. This frequency ratio of 2:3 is perfect consonant.

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This sheet deals with characteristics of the oblique impact system, which is composed of the golf ball and elastic supported flat surface . 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. 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. Also, in the case of increase the tangential stiffness, the spin rate was decreased and the angel of reflection was increased.

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This paper deals with collision characteristics of a golf ball and its modeling. We made collision experiments between the golf ball and the steel block, and measured the acceleration of the steel block during the collision, and then discussed the collision characteristics of golf balls. The stiffness coefficient and the damping coefficient of balls are obtained by modelizing the collision. That model is valid in the low speed collision experiment but is not valid in the high speed experiment.

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The objective of this study was to grasp the relationship between golf club conditions and the rebound of a ball, and to investigate the factor of the relationship using a finite-element (FE) analysis on a ball colliding with a simplified club. The clubs were constructed by holding simplified clubheads by a locking ring fitted onto a steel shaft. The clubheads were designed based on the mass, volume and position of centre of gravity of commercial clubheads, so as to enable a typical golf impact. Three circular, hollow, titanium alloy bodies of constant mass, with increasing loft angle, were manufactured. FE models with linear elasticity of the clubs, which consisted of the clubheads, a locking ring and a shaft, were constructed. The FE model of the ball consisted of 8-node solid elements, and the material model was expressed as a hyperelastic/viscoelastic model. Impact experiments were also conducted for comparison to confirm the accuracy of the FE models. The results of impact simulations closely matched the experimental results. FE analyses, which varied Young's modulus of the shaft and an added mass attached to the shaft using the constructed models, were conducted to investigate the effect of club conditions upon the ball rebound. The effect for the rebound velocity tended to be small, and the rebound angle and spin rate were affected by the force on the shaft which prevented the clubhead from moving and the rotation of the clubhead which depended upon Young's modulus of the shaft and the weight and position of the added mass.

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The behaviour of each golf shot is determined by how each swing delivers the clubhead to the ball. However, everything is moving much too fast for the golfer to see what is happening on impact. The author has presented the mathematical formula between major parameters of impact and the trajectory. However, no one would like to carry a computer with you to get information of your shots at the golf course. A simple device, called "VECTORS" based on the above-mentioned formula, enables you to identify easily what is happening at impact from the flight of your shots. The obtained information on the impact, such as the alignment of the clubface and the path of the swing, can be used to correct your swing on the spot. Once you have acquired the 3-D image of the device, you do not carry the device with you on the course or driving ranges.

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The objective of this study was to examine the validity of the theoretical equations of ball velocity and ball rotation in side-foot soccer kicking. Five experienced male university soccer players performed side-foot kicks using a one-step approach for various attack angles and impact points. The kicking motions were captured three-dimensionally by two ultra-high-speed cameras at 2,500fps. The influences of the attack angle and the impact point on ball velocity and ball rotation were obtained experimentally. The theoretical equations of the ball velocity and the ball rotation were derived based on the impact dynamic theory. Using the theoretical equations, influences of the attack angle and the impact point on ball velocity and ball rotation were obtained theoretically. From the experimental and theoretical results, it was suggested that the theoretical equations were valid. These equations enabled theoretical study of factors affecting the ball behavior.

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In this research, we focus on a knuckle effect on a low-spinning or non-spinning soccer-ball with the aid of three-dimensional image analysis for high-speed video images. We analyzed the mechanism of knuckle effect and estimated the force acting on a soccer ball. It is made clear that there are some hydrodynamic differences between the knuckle effect ball and the spinning ball.

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Shooting machine of soccer or valley ball is developed. This apparatus is mainly consisting of two rollers and available to change ball speed, shooting direction, rotation speed and direction of ball rotation axis. Basic idea of this machine is depend on the patents of base ball shooting machine by Toyoji BABA, which also is able to shoot curved or less rotation ball. We made trial tests of these various changing balls. Special attention on this report is focused on the less rotation changing ball observation.

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The purpose of this study was to investigate the influence of estimation method of hip joint center(HJC) location on the three-dimensional hip joint moment during instep kicking motion. Twelve skilled soccer players participated in the experiment. Firstly, they were instructed to do ad hoc movements including hip flexion/extension and adduction/abduction movements performed on several planes in different orientations, followed by a circumduction movement. Then, subjects performed there maximal instep kick, which were recorded using morion capture system at 250Hz. HJC location were estimated by three different methods, the first and the second utilized the empilical relation between HJC location and the palpable bony landmarks, and the third was called functional method, which tried to fit spheres which had their center at the HJC to the trajectories of markers attached on the thigh during the calibration trial. We computed the hip adduction/abduction, flexion/extension, internal/external rotation moment from right toe-off to the ball impact based on three different HJC location estimates, and compared the peak value and timing among three methods. The results showed diffence in estimation methods had influence mainly on the peak and its timing of add/abd and int/ext moment after MHE.

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This paper describes the behavior of wake-flow field behind a soccer ball measured in a wind tunnel with no or low spin based on the aerodynamic force data acting on the soccer ball. The experiment was performed through visualization of the wake-flow field, the aerodynamic force measurement, the applications of tuft grid method and PIV. The tuft measurement and the force coefficient Cs measurement were synchronized at the ball speed of 26 m/sec. It was found that in the wake, two vortexes were shed and they rotated around the ball center axis in rather random manner and then, the two vortexes were merged to disappear near the center axis. This procedure was repeated. From the PIV measurement result, it was recognized that the size of wake-flow field becomes small for the wind velocity Reynolds number larger than the critical value.

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Less spinning soccer ball aerodynamics are studied by wind tunnel experiments. Aerodynamic force of unsteady lift and side ones acting on the ball at rest are measured and estimated flight trajectory. Well agreements of flight shift magnitude in lateral direction between observed and calculated ones are obtained. As a result, the cause of this strange behavior of the soccer ball is clarified by self-excited buffeting phenomenon of purely irregular behavior of horseshoe-shaped vortex and longitudinal twin one, which already discovered with supper critical Re number region of smooth sphere by S. Taneda(1976).

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High quality measurements of aerodynamic forces acting on golf ball under high speed rotation are very important for correct evaluations of golf ball aerodynamics. More than 3% longer distance of 300 yards ball flight may be achieved by improvements of aerodynamic performance of ball dimple patterns. But in this stage, these precise evaluations to measure aerodynamic forces are impossible because of racks of methods and techniques. We are trying this problem by air suspension balance method. Some valuations of atmospheric and supplying air pressure change effects on air force of Z-direction measurement of wind tunnel experiments are studied by introducing cancelling technique by using a dummy balance.

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This paper describes the trade-off condition between Pareto optimal solutions on the fluctuating punted kick by using Self-Organizing Maps. It was assumed that there were five objective functions and nine control parameters. Four of 5 objective functions are concerned with the fluctuation in the forward and the lateral directions, and the fifth objective function is the hang time. The relationship between five objective functions and nine control parameters was visualized by using Self-Organizing Maps. It was found that there was a trade-off between the hang time and the fluctuation.

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Pitching machine with three rollers for baseball can pitch balls at various speeds and pitch types that are developed by the authors. In this study, the influence that a hard-baseball with a seam has on the throw accuracy of the pitching machine with rollers is examined. Finite element models of a hard-baseball with a seam and the pitching machine with three rollers are made, and throw simulations are proceeded with consideration of the seam using dynamic finite element analysis software (ANSYS/ LS-DYNA). As for the analytical results, it is found that the seam of the ball does not influence the ball's speed or spin rate after release, while there is an effect of the seam on the throw's vertical and horizontal angles. In particular, the throw's vertical and horizontal angles easily produce a change if the roller diameter is narrow and the roller material, hard. Additionally, these analytical results are inspected by the throw experiments using the pitching machine.

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Analysis of actually pitched ball movement is important in various sports scenes such as amusement, science, and skill up for the pitching. We have been studying a method of spin detection of the pitched ball from image streams obtained by high speed camera. Our algorithm employs a set of linear equations composed by image coordinate of feature points that are corresponding between successive frame. In this paper, methods of ball radius estimation and feature points detection are described in detail, since the both are significantly affects on the performance of the algorithm.

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Though baseball glove has the history of 100 years or more, the design of glove has hardly changed for about 40 years. It means that it is very difficult to change glove design because of its complexity. The design of present glove is mainly based on the experiences of craftsmen. However, it is necessary to improve the performance of gloves that we design by objective information. In this study, we investigate glove deformation in ball catching movement and we utilize it to improve the performance of gloves.

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Shock absorption performance of helmets is improved by selecting appropriate shell and liner materials. In this study, the influence of liner material on shock absorption performance of baseball helmets was investigated. An impact test using a baseball ball launcher was conducted to investigate the shock absorption performance of expanded polystyrene (EPS) with different expansion ratios. The failure of EPS was observed in impact pictures captured using a high-speed video camera and SEM images. It was found that the acceleration of the head model, the pressure on the surface of the head model, and energy absorption depend greatly on the expansion ratio and thickness of EPS.

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An existence of soft stiffness in an impacting instrument (e.g. tennis racket, golf club, baseball bat, etc.) increases the COR for the collision with a ball. This phenomenon is well known as a trampoline effect in which the higher COR is obtained because of the reduction of the ball deformation due to the compression of the soft spring. In a rubber baseball bat, it is useful to attach a soft material sheet covered with a barrel for an effective usage of the trampoline effect. In the present paper, the effect of soft material sheet on COR is investigated by using the finite element impact analysis. It is found that the existence of the soft material increases the COR but enlarges the deformation of the ball during the impact, the restitution of the soft material begins at the early stage of the impact and a thick sheet which has the low values of Young's modulus is effective to increase the COR.

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Previous studies reported that the maximum elbow angular velocity related to the maximum hand velocity. Although the maximum elbow angular velocity was influenced by a motion-dependent torque (centripetal force, gyroscopic precession, and coriolis force-dependent torque), which joint motion and/or what dynamic factor causes the angular velocity were not so clear. The purpose of this study was to clarify the kinetic factors contributed to the maximum elbow angular velocity of throwing arm in baseball pitching by using a 3D dynamical model. The throwing motions were captured by 10 infrared cameras at 250 Hz for 8 baseball players. Throws were made under three different speed conditions: slow, medium, and fast. The kinetic factors were computed using the throwing model including 7 segments (trunk, right and left upper arms, forearms, and hands) with 17 degrees of freedom. The results showed that the maximum elbow angular velocity was mainly generated by the trunk counterclockwise rotation via elbow extension centripetal force. The maximum angular velocity was mainly adjusted by the trunk anterior lean via elbow extension gyroscopic precession and coriolis force.

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It will be useful very much in various sports scenes such as motion analysis in live- or archive data if the motion capturing is possible without any attachment onto players body for measuring their motion. In this paper we propose a method to detect the pitching motion in baseball from singleview image stream. The silhouette of extracted target figure is compared with element poses in the dictionary. The basic idea to generate the pose dictionary from 15-joints model of human body and it usage for motion detection is shown.

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The authors have recently developed a system for analyzing the spin on a baseball (Koseki et al., 2007). In the present study we analyzed the spin pitched by a professional pitcher. He pitched eight different pitches, each twice, from official pitching mound. The image of ball in the period from just before to 500 ms after the ball release was taken with a high speed video camera at 1000 fps. English alphabets E, M, A, and I were marked on the ball for image processing. Feature points from the image stream were assembled into a set of linear equations that represents orientation change between consecutive two frames by rotation matrix R, and the direction of spin axis and spin rate were obtained. Both values varied considerably depending on pitches. The recording of spin was suggested to be valuable for training if the data could be combined with those of motion analysis.

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The purpose of this study was to clarify the role of each upper limb and trunk during the forward swing of T-batting motion by using an instrumented bat via an inverse kinetic approach. Seven collegiate male baseball players' motion were captured by VICON 612 system (9 cameras, 250Hz) and kinetic data of each hand were collected by using a bat instrumented with strain gauges (1OOOHz). The torque impulse about the shoulder adduction/abduction axis was the largest among all calculated values. The sum of the positive works generated by the knob-side upper limb was considerably larger than those generated by the barrel-side upper limb, which indicated that the role of the knob-side upper limb was to obtain the bat head speed during the forward swing. As for the negative works, the barrel-side upper limb generated the greater sum of work, which indicated that this limb may have been used as energy absorber. The torso joint play a significant role to accelerate angular rotation of trunk and endure the load due to centripetal force exerted on the bat prior to impact.

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The purpose of this study was to quantify the contribution of the upper limb joint torques and shoulder joint reaction force to the bat head speed during baseball batting motion. The upper limb segments and bat were modeled as a system of seven rigid segments, and each elbow joint was modeled as a one-axis revolute joint to consider the degree of freedom (DOF) of the joint. Each hand was considered to be connected with the bat through zero DOF joint. The equation of motion with respect to the upper limbs and bat was obtained from the equation of motion for each segment and from equations for constraint condition in which adjacent segments are connected by joint. The dynamic contributions of the joint moments, shoulder joint force, motion dependent term and gravity term to the bat head speed were derived from the dynamic equation of the system. Collegiate male baseball players' motion were captured by V1C0N 612 system (9 cameras, 250Hz) and kinetic data of each hand were collected with an instrumented bat with strain gauges (1OOOHz). From the results, not only joint moments but also motion dependent term make significant role for generating bat head speed during forward swing motion in baseball batting.

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Luge sport is adopted as one of the sled sports in the Winter Olympics game, and it is one of a certain very popular sports in Europe. A player rides on the sled, and drives on the course at a speed which reaches best 140km/h on the ice track. It becomes the important point of view of the performance boost how aerodynamic drag is reduced in sliding. The influence of the driving form that it is formed by a sled with the player was verified at 2m x 2m Low-speed Wind Tunnel of Wind Tunnel Technology Center in JAXA. We lowered front projection area when I compared the sled of the improvement type with the current model, and that the improvement type that raised a rectification effect reduced aerodynamic drag of about 7-9% was checked. In Single use sled, a riding form to lift a femoral region a little was advantageous to aerodynamic drag reduction. In addition, it was observed affecting the flow of air the shape of pod of sled. That improvement could reduce aerodynamic drag to Doubles use sled equally was checked.

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We study the dynamics of sequential turning motions of snowboarder. We assume that the snowboarder is described by a stick-picture figure and only his ankle joints can be bended or extended. The snowboarder rides on a snowboard by normal stance, namely the front of his body always faces to the right-hand side of the snowboard. Assuming a frictional resistant force between the side edge of snowboard and snow surface, we deduce a set of simultaneous equations of motion for this snowboarder riding on the snowboard. We solved these equations of motion numerically under realistic conditions of repeated turns on a flat slope by snowboarding. We found the successful timing of bending as well as extending the ankle joints during repeated turns. The results are shown as animation on computer display.

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The purpose of this study is to establish the system to measure physical form in snowboarding turn, the correction method to improve accuracy and the analysis method to indicate physical form. This system consists of 3D gyro sensor, 3-axis acceleration sensor and 3-axis magnetic sensor. Initial physical form is obtained from 3-axis acceleration sensor and 3-axis magnetic field sensor, gliding physical form is obtained form 3D gyro sensor. The correction method reduces the drift error of gyro sensor using Extended Kalman Filter, the analysis method provides joint angle from information of this measurement system. As a result of experiment on the carving turn by the snowboarder in a skiing ground, the physical form was obtained quantitatively. This measurement system and correction method can analyze the major features of snowboarding turn and this method may be able to quantitatively evaluate the skill of snowboarders.

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The purpose of this study is to establish the system to obtain the information about skier's dynamics motion in skiing ground. This system consists of the measurement system of motion, reaction force from the snow surface, and the analysis method. This motion measurement system provides physical form, angular velocity and acceleration, the measurement system of reaction force from the snow surface provides 6-axis reaction forces and moments. The analysis method can estimates joint torque from inverse dynamics analysis using obtained measurement data. From the experimental data on the carving turn by a skier in a skiing ground, we could obtain the skier's dynamic motion quantitatively. Consequently, the proposed system could catch the characteristic of skiing turn. The obtained results contribute to clarification of mechanism of skier's motion.

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The turning motion of an alpine snow ski is produced by centripetal force and the moment around the center of mass. Both the force and moment are produced by resistance forces from the surface of the snow. We measure three-dimensional compact snow cutting forces, apply multiple regression analysis to determine empirical equations of these forces. The equations of motion of the system including these forces are solved numerically. The developed skiing simulator uses these results in real time. During skiing using the simulator, the subjects are instructed by an expert system. The advice is generated by an expert system using the measured data such as a flexion angle of the subject's knee and the rules for the skiing instruction. Then it is given to the subjects with a computer's artificial voice.

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Mid-foot sole of the shoes has important functions ensuring stability and shock absorbing to protect runners from injuries. Then, runners have to carefully choose the shoes with an appropriate sole structure suitable to individual running style. Subjective evaluation of the shoes, however, does not necessarily guarantee the best choice, necessitating us to employ some quantitative and objective evaluations. The purpose of this study is to clarify how subjective evaluations for stability and shock absorbing are affected by objective measurements regarding 3-D foot motion, plantar pressure and sole deformation in running. To accomplish this, simultaneous measurement of these data was done, together with a sensory test, using the shoes with four different sole structures. Empirical results suggested that runner's subjective evaluations regarding shock absorbing and stability are related primarily to sole hardness and antero-posterior difference in the deformation of the medial portion of rear-foot sole, respectively.

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The impact force which runners receive passively during running reaches approximately 1.5〜5.0 times the body weight. The joint movements of lower extremity have strategy which absorbs the impact force. In addition, shoes have an important role of absorbing the impact force. This study investigated the relationship between the impact force and joint movements wearing different shoes. Eight subjects ran at 3.5m/s wearing 3-types of shoes with different shock-absorbing capacities. Shoes with thicker outer-sole were defined as shoes with higher shock-absorbing. GRF, joint angle, joint angular velocity, sole angle which is angle between foot and ground at touch down, and time of maximum joint angular velocity were sampled and computed. Time of GRF first peak and loading rate were longer and smaller significantly and knee joint angle at touchdown tended to be smaller when runners wore shoes with higher shock-absorbing. It was suggested that shoes with higher shock-absorbing attenuated the impact to the body and influenced running motion.

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Footwear requires some functions to prevent the injuries and enhance the performance during various sports. Motion analysis is important to decide the functions. Using a force plate is an effective way to carry out the analysis quantitatively. Ground reaction forces can be obtained from a force plate during the contact phase. However, contact condition at any position of contact area cannot be specified because the ground reaction force is showing the reaction force of the whole contact area. The purpose of this study was to measure in- and out- plane loading distributions of shoe sole. In order to detect the distributions, a specific shoe loaded with 5 force sensors was developed. Then, by using the shoe, in- and out- plane forces in running were measured at specific positions of the shoe sole. As a result of this measurement, the behaviors of component forces were completely different in each contact area. It implies that contact loading conditions are different at any positions of the shoe sole.

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The purposes in this study were to evaluate the contact area between the shoe sole and the ground in running by using a textile sensor and to determine the influence of sole bending stiffness distribution on the contact condition and center of pressure. A textile sensor is a flexible and thin sensor that has applied compression properties on the multi-layer fabric. The result of contact area obtained from the textile sensor corresponded to that from vertical coordinates of sole markers by using motion capture system. Center of pressure moved within the contact area during support phase. The velocity of center of pressure obtained by the shoe with a slit line under MP joint was small during kicking phase. In this shoe, the backward end of contact area moved forward. The shift of contact area is caused from the local bending of the shoes sole. The result indicates that the noncontiguous bending stiffness of a shoe sole prevents center of pressure from moving smoothly.

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In the previous paper, we realized the simple self-sustained humanlike robust walking & running NANBA of humanoid biped robot GENBE based on distributed control of physical body in a martial art utilizing instability without ZMP (Zero Moment Point) control, which uses only small active power with simple chaotic limit cycle utilizing instability, further developing into autonomous walking, running, instantaneous turn and the simple autonomous shock avoidance during falling down and instantaneous rising up. Instability makes the natural movement. This paper made clear experimentally by using high-speed video camera the mechanism of robustness of humanoid biped robot GENBE who walks and runs everywhere even on the ice and snow.

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The acquisition of skills in the use of sporting implements is the quest of sports enthusiasts everywhere. Developmental players wish to gain the skill of the elite sports person, amateurs seek those skills of the professional and the weekend enthusiast just wants to improve. Many sports employ a variety of implements such as clubs in golf, bats in cricket, racquets in tennis and swords in the martial arts and in many cases the swing motion is quite similar. In this paper a method for measuring swing path of a variety of sporting implements is proposed. This method is a refinement of that previously investigated [1] and uses a combination of inertial sensors to track the path of the swing. From this data a graphical visualization of the motion is presented to the athlete using near real time feedback using a wireless link. The visualization is based on the physical movement but abstracted somewhat. As a form of biofeedback it is overlaid with idealised templates of an optimal swing enabling the athlete to learn the swing skill in a novel manner.

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Targeting is a skill that is used in many sports and other activities. The electroencephalogram (EEG) has previously been used to measure target sports [1-4]. The intention phenomenon is indicated by the pre-shot alpha in the EEG [1]. This paper details the design of a computer based simulation to induce the intention phenomenon. The simulation consisted of a targeting task under three different targeting conditions - no bias, constant bias, and variable bias. Twelve participants were involved in the study and their EEG was measured during the targeting tasks. The results indicated that intention could be induced using a computer based simulation.

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The aim of this study is to evaluate the breast stroke motion using new measurement system and analysis method. The measurement system consists of 3-axis gyro sensors, 3-axis acceleration sensors, and 3-axis magnetic field sensors and it is attached to the subject's body. The analysis method corrects the drift error of gyro sensor and provides joint angle using sensor fusion and inverse kinematics. The information about swimmer's motion in hydrospace is easily obtained by using this system. The experimental results indicated the breast stroke motion quantitatively. This measurement system and analysis method can analyze the major features of swimming motion in breast stroke. This method may be able to quantitatively evaluate the skill of swimmer, and to apply to other swimming strokes.

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25 world records were born in the swimming races of the 2008 Olympic Games in Beijing. The swimmer's wear rate of Lazer Racer, a drag reduction swim suit, among the gold medalists was 94%. The effectiveness of the swimsuit was quite apparent The reason of the drag reduction was to reduce the surface viscous friction drag and to reduce the projection cross-sectional area due to its compression effectiveness. Before Beijing Olympic started, expecting new records by these gold medalists with LZR Racer were calculated by dividing a race into two phases, a start & turn phase and a steady propulsive phase, on the assumption that theses gold medalists had the same swimming techniques of the previous world record holders. Although the drag reduction rate used in this calculation was modified according to one of the manufacturer announcement, each expecting new records was an approximate value of the new world records in Beijing Olympics. It was found that the speed increase effect by the swimsuit

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The objectives of this study were to investigate the effect of trunk undulation on the swimming performance in underwater dolphin kick, and to clarify the ideal trunk undulation form. The reference swimming motion of an elite swimmer was firstly acquired from the video analysis, and input into the swimming human simulation model SWUM, which have been developed by the authors. The trunk motion was next optimized by the simulation for two objective functions: maximizing swimming speed and maximizing propulsive efficiency. The following findings were obtained: The swimming motion of maximizing propulsive efficiency and the reference swimming are considerably similar to each other. In both cases, the trunk moves as a seesaw with a node; whereas, the lower limbs form a traveling wave in the absolute space. The trunk undulation with the appropriate amplitudes and phases, especially bending at the chest, is important in realizing the swimming motion which maximizes propulsive efficiency.

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This study examines the fundamental motion characteristics of windsurfing planing on flat water. A theory describing aerodynamic and hydrodynamic forces acting on the sail, board, fin and sailor is, provided as a background. The balance equations of forces and moments are derived using these forces. A Windsurfing model is analyzed by solving its balance equations numerically .The relationships of board velocity, leeway angle, etc. with sail angle are derived. When the true wind velocity changes from low to high speed and vice versa, the board speed exhibits a hysteretic jump phenomenon. The board can change direction by very small change of the pressure-center position of the sail. Moreover, the polar performances are plotted with change in sail trim. These results agree qualitatively with experience.

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The purpose of this research is to estimate the angular velocity and direction of the rotational axis of the flying disc by a tri-axial accelerometer. A subject performed throwing by using the flying disc attached the accelerometer. And, the closed up release point image was acquired using the high speed cameras. The angular velocity was estimated from the translational acceleration. The direction of the rotational axis was estimated from the component of the centrifugal acceleration. Each estimated value was compared to the value calculated by the high speed cameras. The angular velocity estimated by both the accelerometer and the high speed cameras were similar. And it was observed that the rotational axis on the sensor coordinate system changed during flight phase.

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