Since the impairment level and remaining ability change depending on the athlete in cross country sit-skiing, the optimal sitting posture and shape of the equipment also change. Generally, the shape of the equipment is determined by improving the prototype based on feedback from the athletes, so it costs and is time consuming. In this study, a multibody dynamics simulation model which can calculate the kinematic effects of the equipment shape and athlete’s sitting posture was constructed. In the human model, hip, shoulder, elbow and wrist joints have degrees-of-freedom of motion and other joints are constrained. The sit-ski and pole models are constructed as single rigid bodies, respectively. The velocity, joint torques of shoulder, elbow and wrist joints and contact force were calculated when the joint angles were given. An experimental plan to obtain the data of actual pushing motion was also described.
This research is related to the tools used in the paratriathlon, which are expected to win medals at the Tokyo Paralympic games. The paratriathlon is a sport where strategy and experience are greatly influenced by the characteristics of the activities performed throughout the three competition events. Moreover, since many tools are used in the game, they are considered part of the competition. This time, we focused on the development of equipment related to the Bike event (hand bike), which accounts for about 50% of the competition time and has a major impact on winning and losing. Foot placement is very important for athletes with lower limb motor dysfunction. Therefore, a foot support that can be operated as much as possible using the entire sole is desired. However, if the design change makes it possible to operate using the entire sole, the shape of the foot support (Proto-type: Pt) may increase the air resistance, because the front projection area increases. Therefore, we have developed a footrest that minimizes the forward projection area while obtaining stable operability. In this study, we measured the air resistance of the Conventional-type (Ct) and the Pt equipment to better enable them to be operated with the entire sole. We found that the drag of the Pt was approximately 2.5 times the drag of the Ct.
The objective of this study was to investigate effects on the rebound characteristics for running-specific prostheses of the dynamic behavior of the blade which was obtained using an impact testing apparatus developed in our previous study. The impact load perpendicular to the ground line was measured by a piezoelectric type load cell attached on the impactor, and the load parallel to the ground line was calculated by applying the response of the strain gauge affixed on the blade to the beam theory. A motion of the impactor and blade was taken by two synchronized high-speed video cameras. The deformation of the blade was obtained from the positional coordinate of the blade by tracking markers attached on the surface using the digital image correlation method. The velocity ratio was defined by dividing the rebound velocity by the incidence velocity of the impactor which was calculated using the high-speed images. The deformation behavior for the straight part of the blade has the tendency to be classified into two main types: the deformation in both directions of the planter and dorsal flexion and the deformation in the direction of the dorsal flexion during impact. When the blade is deformed in the direction of the plantar flexion, the velocity ratio tends to correlate with the energy absorption rate. This suggests that it is effective to observe the dynamic behavior of the blade from the directions of perpendicular and parallel to the ground line in order to evaluate the rebound characteristics of the blade.
In order to reveal the effect of forearm prosthesis on running motion, we measured arm swing motion of the athletes with unilateral below-elbow amputation wearing forearm prosthesis by optical motion capture, and estimated net forces and torques exerted on the shoulder and elbow joints by inverse dynamics. The results showed that wearing forearm prosthesis increased vertical, anteroposterior and lateral forces exerted on the trunk, and also increased flexion-extension torques at the shoulder and elbow joints. The arm swing was found to generate downward force in the contact phases, and upward force in the airborne phases. This result suggests that wearing forearm prosthesis increases vertical ground reaction force and step length of a runner.
Scrumming is an important set play in rugby football which frequently determines who wins the game. A pack of eight forwards (players) are required to coordinate their pushes, and timing, to exert pressure in the desired direction and so defeat the opposing pack. However, it has been difficult to objectively assess their cooperation due to technical limitations. We propose a convenient measurement method designed to evaluate the cooperation of players while scrumming by attaching compact inertial measurement units (IMUs) to the waists of the players. The acceleration and quaternions captured by the IMU allow us to calculate the acceleration vector and its peak time, and player posture. We found inter-trial changes in acceleration and posture between players during the scrums. Our proposed measurement system makes it easy to detect player coordination during joint actions in sports such as rugby.
Decreasing the muscle strength of lower limbs due to aging or fatigue leads to fall accidents during walking or stepping stairs. In order to evaluate the changes of muscle activity, it is important to quantitatively measure the muscular characteristics for a long time by using wearable instruments. In this study, a portable sensing system composed of thin pressure sensors was developed to evaluate the muscle activity as hardness changes of body segments, and the system was applied to investigate the muscle activities in lower limbs during several motions. Long-term changes of the muscle activities were obtained in the case of walking and going up and down stairs with the sensor units attached to the lower limb. As the results, difference of individual muscle activity and their cooperative characteristics could be measured in the motions.
In this study, we evaluate the effectiveness of the posture estimation method using an inertial sensor in the standing position generating small translational acceleration. Optimal motion capture system mainly used for motion analysis is expensive and takes many times for measurement and analysis. Inertial sensor consists of acceleration sensor and gyro sensor is inexpensive than optimal motion capture system, and the measurement using inertial sensor is easy. The estimation method is established the sensor fusion algorithm focused on the local coordinate system by using the Extended Kalman filter, and we estimated the 3D posture in the relative coordinate system by using the acceleration and the angular velocity. The measurement experiment was conducted to clarify the accuracy of the estimation method using the stabilometer generating disturbance, the wearable motion sensors installing inertial sensor and the motion capture system. We compared the results for ankle joint angle, knee joint angle and hip joint angle estimated by previous method and proposal method and focused on translational acceleration and segment acceleration. We indicated the effectiveness of proposed method measurement of standing with small translational acceleration.
The purpose of this study is dynamic motion analysis of load control treadmill using inertial sensor and ground reaction force. The wearable sensor system based on inertial sensor outputs angular velocity and acceleration. The posture information is estimated by the sensor fusion using the Extended Kalman filter. The treadmill installs the force plates, and the load control system using propulsion force is installed. The hip, knee and ankle joint torque are calculated by the inertial sensor outputs, the posture information and the force plate output using the Newton-Euler method. The gait measurement experiment was conducted by using the treadmill and the wearable sensor system. The analysis results indicated the difference of joint torque by change of target load in the treadmill. Furthermore, the joint torque including the effect of inclination is calculated, the characteristics gait motion in the load control type treadmill was considered approaching the inclination and the actual road condition.
The purpose of this study was to realize the induced speed analysis of the baseball pitching motion using inertial measurement units (IMUs). The upper limb with a ball was modelled as a linked three-rigid-segment system consisting of the hand with a ball, forearm and upper arm. The linear/angular motion of each segment was estimated using the angular velocity output of the IMUs. The dynamic contributions of the joint torque term, the motion-dependent term (MDT), the gravitational term, and the modeling error term to the generation of ball speed and valgus/varus axial torque at elbow were obtained through the equation of motion of the system. Furthermore, the generating factor of the MDT was considered using a recurrent formula derived from the equation of motion. The results of dynamic contribution analysis obtained from estimated motion data using the IMUs (estimated data) showed that 1)the MDT was the great contributor to the generation of ball speed prior to the ball release and, 2) the joint torque was the main contributor to the generation of valgus/varus axial torque at elbow during the pitching motion. These results show mostly good agreements with those obtained from the analysis of a motion-capture system.
The purpose of this study was to develop a single rigid-body-model to represent the ball, hand and forearm of a given pitching arm for an accurate determination of the valgus stress. In a past study, a single rigid-body-model was applied to determine the valgus stress and found that the determined valgus stress was well-correlated to, but substantially overestimated, the corresponding values determined with a three-segment model (consisted of a combined segment of baseball & hand, forearm and upper arm). A major reason for the overestimation is presumably that the ball, hand and forearm were assumed to be aligned straight and the inertia properties of the single-rigid-body was defined as the sum of the inertia properties of the three segments in this aligned position. To solve this problem, we computed the inertia properties of the single rigid body for various virtual positions of hand and ball to find out the best position with which the valgus stress can be determined accurately. Fourteen university students and 20 junior high school students served as subjects. Each subject was asked to throw 3~5 pitches of fastball and another 1~5 pitches of breaking-balls. The motion of each segments was captured with a motion capture system (VICON, Oxford Metrics) and an inverse dynamic procedure was applied to determine the valgus stress. The results showed that the best virtual position of the hand and ball was at 43% of the distance from the wrist toward the 3rd knuckle. This virtual position resulted in the valgus stress of 37.0 ± 12.0 Nm, for the corresponding value of 37.2±11.4 Nm with a three-segment model. This model may be combined with a single inertia sensor, so that the risk of elbow injury can be evaluated accurately and easily.
Stretch sensor-based wearable sensing systems have attracted attention as a technology for human motion tracking in daily life because of their flexibility and wearing comfort. Some previous works proposed methods to estimate joint angles and postures from stretch sensors using machine learning techniques. However, they did not consider sensor shifts due to donning/doffing and long-term use, which may decrease their estimation accuracy. Therefore, this study proposes a joint angle measurement system robust for sensor shifts by using stochastic machine learning. We first developed a smart brace with two stretch sensors instrumented at different heights. For learning an estimation model, the device was gradually shifted and stretch sensor readings of the device and ground truth of knee joint angle from inertial measurement units were obtained during stepping motion. Then, Gaussian mixture models were fitted to the probabilistic distribution of the dataset in each brace shift and the GMMs of all shifts were integrated as the estimation model. By using the model for Gaussian mixture regression, the system estimated joint angle by adaptively changing these models according to brace shifts. The performance of the proposed method was evaluated by comparison with a conventional learning method using measurement data sets at proper and shifted positions.
A world-class cross-country ski player was aimed at a men's time race by the classical style at the 5.3 km course at Vuokatti in Finland. A wearable high-precision Global Navigation Satellite System (GNSS) was attached to his head in order to detect sub-technique used during the time race. Double poling is important sub-technique for the classical technique because it is faster than any other sub-techniques. The total performance is expected to be improved by increasing the usage rate of the double poling sub-technique. In this report, we focused on the detection of the double poling sub-technique. From the results of our study, it was suggested that high-precision GNSS can be used effectively to detect double poling sub-technique as well as other sub-techniques of classical style of cross-country ski race. Moreover, we found a certain law required for automatic discrimination of the double poling sub-technique from the vertical movement of the head with respect to the speed which obtained by the high-precision GNSS.
The purpose of this study was to examine the possibility of a system which realizes a simple quantification and immediate feedback of generating mechanism of kicking side leg during soccer instep kick, using inertial measurement units (IMUs). The angular velocity outputs of the IMUs attached on lower trunk, thigh, shank and foot segments can estimate the posture of each segment and carried out induced speed analysis. The dynamic contributions of the individual terms such as, joint torque term, gravitational force term, and motion-dependent term (MDT) to the generation of the foot center of gravity (CG)’s speed was quantified using the equation of the target system with estimated segmental position data. The results of this study show that almost good agreements between estimated motions with IMU outputs and measured motions obtained by a motion-capture system in terms of mechanism of the foot CG’s speed generation. Though there was a difference in joint torque term from the kicking foot take-off to support foot contact. Dynamic contribution analysis obtained from Constructed immediate feedback system with respect to the mechanism of speed generation using IMUs could be used to evaluate performance at sports fields.
The compensation effect of control variables in putting was investigated by uncontrolled manifold (UCM) analysis. No one can repeat any movements precisely because of the existence of motor redundancy which enable to achieve the same objective with different set of control variables. In UCM analysis, to quantify the compensation effect of control variables, the valiance of control variables was decomposed into two orthogonal components, one that affects the value of objective variables (VORT) and another that maintain its value (VUCM). Ten participants were asked to hit the 3 and 5 m putts twenty times respectively and a motion capture system (Eagle, Motion Analysis corp.) was used to measure the motions. Relative positions between joints were used to explain the position of the clubhead and to carry out UCM analysis. The result of ANOVA showed that the ratio (VUCM/VORT) at the top of the swing was lower than those at start and impact (p < 0.01). It was also revealed that some control variables have larger VUCM across the movements (p < 0.01) and another set of them has larger VORT around the top of the swing (p < 0.05). These findings suggest that golfers need to restrain only the some of the variability of control variables.
Physical strength tests such as grip strength and jumping stand are performed to evaluate the muscle mass and strength of the whole body to lead a healthy life. Quantitative evaluation is required, for example, the ratio of flexion strength to extension strength (HQ ratio) of the knee joint is pointed out to be related to the flesh of the lower limb. It has been pointed out that knee extension muscle strength is related to standing broad jump and the whole body muscle mass, but there are very few measurement methods that can easily estimate knee flexion muscle strength. Therefore, in this study, we decided to develop a method to estimate the flexion strength of the knee. Taking into account the standing backward double jump, we set various jump conditions as a cross-sectional study and examined the relationship with each muscle strength of the lower limbs.
The aim of this study is to evaluate the performance of a shoulder bag with a function that fits the body during walking. The load applied to the shoulder was measured using a small triaxial force sensor, the walking motion of the body and the shaking of the bag were evaluated using a motion analysis device. 12 participants walked for about 2 minutes on the treadmill. Two types of bags named “FIXTOTE” with different sizes（M and S）were used in this study. Each of the two types of bags has two conditions（without strap（without condition）and use strap（with condition））. The force of load on shoulder, the shake of bag and the step length were measured. It was clarified that the combined force of the load on the shoulder decreased, the shake of the bag was suppressed when the strap was used rather than not used. The step length has no significant difference whether the strap used or not. This study revealed the dispersion effect of load on shoulder, the suppression effect of bag shaking during walking and the influence on walking motion.
Currently, elderly people account for more than 25% of the population in Japan. Hence, Locomotive syndrome accompanying aging is a problem Japan faces. Locomotive syndrome is a condition in which walking motion becomes difficult due to aging. This research is focused on Sarcopenia, which is one of the causes for Locomotive syndrome. Sarcopenia is the decline of general muscle strength due to aging or disease. To prevent sarcopenia, it is necessary to give effective stimulation and load to antigravity muscles. We developed a self-paced “Load-controlled Treadmill” with a single-belt and two built-in force plates which strengthen the soleus muscles, which is a one of antigravity muscles. In this paper, we investigated the difference between single-belt treadmills and split-belt treadmills. Two subjects attached motion capture systems and shoes to measure reaction force. They walked 30s with constant load r = 0, 10, 20, 30[N] on both treadmills. Result showed that the angular range of motion of ankle joints when walking on single-belt treadmills was up to 2.7 times larger than when walking on sprit-belt treadmills. This result suggests that people can efficiently perform both efferent and afferent contractions of soleus and gastrocnemius muscles on single-belt treadmills walking. Force reading showed that the ankle joint moment when walking on single-belt is larger during terminal stance phase. Suggested that kicking force is stronger and muscle activity is greater when walking on single-belt treadmills perhaps. The results, as a whole, suggest that single-belt treadmills better simulates actual walking.
Human seems to maintain the upright posture by controlling and combining the hip, knee and ankle joints adequately. Especially when the posture is disturbed much mechanically, human steps the leg forward and resists the disturbance to prevent falling. The adaptive maneuver to step forward is observed quite often in a daily life, but the stepping mechanism is not elucidated enough from the neural and mechanical point of views. To understand the mechanism stepping maneuver, we developed a rigid-body link model to emulate the human stepping maneuver. In this study, our model is consisted of four rigid bodies and the model moves in two–dimensionally. The lower extremities have the shank and thigh including the foot, and the distal point of the leg on the stepping side is free end, while the distal point of the support side is placed on the floor and rotates as the ankle motion. The model learned the stepping maneuver with reinforcement learning. In this study, the reward function was expressed as standing the upper body, minimizing the joint torques, and maintaining the posture in a long time possibly. In the early learning, the model didn’t stand. However, after learning enough, the model kept standing by stepping forward even when a disturbance of load was applied the body. Even though our model isn’t driven by the muscle forces or not enough similar to the human musculoskeletal structure, the model could be useful to understand the mechanism of the stepping maneuver.
The aim of this study was to estimate the pole deformation by using an instrumented pole measuring exerted force by each hand in pole vaulting. Ten sets of strain gauges, two of them for measurements of axial force along the pole and rest of them for bending moments, attached on the pole. The pole was modeled as a series of 11 rigid segments connecting their adjacent segments via virtual joints with rotational spring. The stiffness of the individual spring component was identified from the pole loading test. One male pole vaulter participated in this experiment. A motion capture system was used to measure the 3D coordinate data of 47 and 24 reflective markers attached to the whole-body and the pole, respectively. The deformation of pole was estimated from the force and moment measured by instrumented pole, and the stiffness of the pole. Estimation of the pole deformation was compared with the measured of that.
Human motion trajectories vary widely from time to time to adapt to the situation. This is the case of one person. But as our body builds are different, motion trajectories vary in a wide variety of ways from person to person. Thus, human motion control is none other than the problem of tacit and nonverbal world. Usual explicit and verbal rational approaches are not effective. We need to find the best way to move by trial and error. But there is no performance indicator available. Usually we look at the supervising motion and try to follow it. But as our body builds are different, this does not work well. We must find our way by ourselves. Therefore, trial and error are essential and to improve our trial, we need a performance indicator. But Euclidian Space approach which is the basis of explicit and verbal rational approach does not work effectively due to its orthonormality and unit constraints. It is pointed out in this paper that if we introduce Mahalanobis Distance, which is a non-Euclidian Space approach free from orthogonality and unit constraints, we can establish a quantitative performance indicator and by coupling MD with a pattern approach, we can learn to control our motions by trial and error effectively.
As Para-badminton was adopted as an official event at the Tokyo 2020 Paralympic Games. However, little research and development of badminton wheelchairs in Japan has been conducted. In this study, we focused on the chairwork movement, which is the important technique in wheelchair sports and evaluated that of the wheelchair badminton. Furthermore, we clarified the movement characteristics of the chairwork in wheelchair badminton and to obtain knowledge for new wheelchair development. In this study, the new and old of 2 type wheelchairs were used. New type was made by Mg base alloy material and old one was made by Al base alloy material. First of all, the subject got on the new type wheelchair and stooped after driving 1 drive forward from the end of the court and then stopped after driving 1 drive backward. Five sets of this series of operations were measured. After that, we exchanged to an old type wheelchair and measured 5 sets in the same way. The above operation was measured by recording the locus of the reflective marker using eight infrared cameras. As a result, wheelchair that maintains the speed after driving because the speed of the new model is the same as the old model or higher than that of the old model. It was confirmed that there was. As a feature of the operation, it was confirmed that there was a difference in tendency between the forward movement and the backward movement based on the displacement of the wheelchair speed.
Tokyo Paralympics holding is decided in 2020, and competition wheelchair research and development have been conducted to win many medals of Japan. As competition wheelchair research, light-weighting of wheelchair mass has progressed, the influence on human by changes of wheelchair mass is not clarified. In this study, electromyography (EMG) and acceleration of center position of wheelchair mass were measured and compared, aimed to elucidate influence on human by changes of wheelchair mass. 3 kinds of competition wheelchair having different masses were used in measure. In the experiment, subjects ran 20 m in fixed speed of 10 km/h using competition wheelchairs having different masses. Wheelchair driving was performed 5 times in each wheelchair. Then, integral EMG in each muscles and 2-axis composite acceleration composed by vertical direction of wheelchair (Z-axis) and horizon direction (Y-axis) which was vertical direction against running direction were measured and compared in each competition wheelchair. The result of the study led to the conclusion as follow: influence on human by changes of competition wheelchairs masses was varied by subjects.
The objective of this study was to investigate the relationship between biomechanical parameters and manipulability by simulating a forward liner operation of a competition wheelchair using an inverse dynamics analysis. The motion was represented by inputting the joint angle of shoulder, elbow, and wrist obtained by an optical motion capture system into the musculoskeletal model. The simulation model was represented by restraining the contact area between the body model and the frame and seat of the wheelchair. A hand manipulability was defined as the angle between the vector of hand force which was estimated from the simulation and the major axis of manipulating force ellipsoid which was available for evaluating a robot arm and was calculated from the posture of the upper limb. The effectiveness of the hand manipulability for an evaluation of wheelchair operability was verified by investigating effects of the hand manipulability on biomechanical parameters. As a result, the hand force tends to depend on the relationship between the muscle force and the hand manipulability. The hand manipulability has a possibility of evaluating the wheelchair operability with a view to reducing the burden of the upper limb.
Wheelchairs are designed not only for daily use but also for competition. In recent years, due to the widespread use of these wheelchairs for competition, the sports population for disabled sports has increased. There is, however, a risk that secondary sports will occur if disabled sports are performed. There are various causes of secondary failures, but it has been pointed out that the accumulation of fatigue during competition is caused by the occurrence of failures. The purpose of this study is to develop a classifier that detects the fatigue state from the driving acceleration of a wheelchair user. In this study, the driving acceleration was extracted from the transition of the elbow joint angle during wheelchair driving, and the feature value was calculated. Using machine learning method SVM and random forest, non-fatigue state and fatigue state were classified. The performance of the classifier was evaluated using 10-fold cross validation, and the SVM classifier obtained F measure 0.740 and AUC 0.720.
We proposed a measurement device of 3-axis foot gripping force during Functional Reach Test (FRT). 3-axis force sensors were embedded in a shoe insole under foot fingers. These force sensors were so thin and light weight that the insole with the force sensors could be inserted into a shoe in our measurement experiments. The vertical force while standing and shear force while pulling by foot fingers were measured to compare our measurement device with other measurement devices. From this comparing experiment, it showed that the outputs between our proposed device and other device had 22% difference about vertical force and 17% difference about shear force. The 3-axis foot gripping force during FRT was measured by our proposed device. From the results, it observed that large vertical force was applied to first finger. It also observed that there was difference between shear force applied to first finger and other fingers. These results mean that our proposed device is useful for measuring 3-axis foot gripping force during FRT.
The micro-blower is a thin, compact, real silent, non-vibration, and lightweight air pump. In this study, firstly, we developed the prototype blood pressure (BP) monitoring system, based on the finger volume-oscillometric method, using the micro-blower. Secondly, we compared the BP measured by sphygmomanometer as a reference with the BP derived from transmission mode PPG, side-incident mode PPG, and reflection mode PPG using prototype system. The results showed that the standard deviation (S.D.) of differences between the BP derived from side-incident mode PPG and the reference BP was ± 7.88 mmHg (the Association for the Advancement of Medical Instrumentation criteria for sphygmomanometers: S.D. of difference less than ± 8 mmHg). These results suggest that our prototype system has an acceptable performance as a finger-type wearable blood pressure monitor and could help to improve health in daily life.
In recent years, population aging is continuing and people with physical disabilities is increasing. Device that supports the operation of life equipment and communication is indispensable not only to improve the living environment for people with disabilities and support their independence, but also to reduce the burden on caregivers. In this research, we developed a gaze input device that can be used by people with physical disabilities such as neuropathy and limb defect. This device consists only of a personal computer and UVC camera. We created a program to detect eye movements from images captured in real time from UVC camera and operate the mouse cursor on a personal computer. Detect eye position and identify the gaze direction were performed using image processing. Using the identified gaze direction, the mouse cursor movement processing of the personal computer was realized. Also, click processing was realized using blinking eyes. We think that people with physical disabilities can operate not only the mouse cursor but also various devices by using eye movements.
The present study aimed at examining the direct relationship between the degrees of freedom (DoF) of embodied systems and postural fluctuation. An embodied system consists of various DoF and can be a complex system. Postural fluctuation can be easily measured and considered as a representative of system dynamics. Therefore, it is expected to be useful for a fall risk assessment among elderly people. Recently, clinical studies have applied both linear and nonlinear methods of assessment to evaluate static and dynamic balance abilities. In our presentation, we report on the result of our experiment that examined the effect of joint DoF fixation on postural dynamics. Young healthy male participants were asked to maintain their balance during a single leg standing task without fixation or with ankle/knee joint fixation. The time series data of the center of pressure (COP) were collected and analyzed using linear and nonlinear methods. The static index (COP trajectory length) did not significantly differ across the conditions. However, the dynamic index (sample entropy) was significantly lower under the ankle-fixation condition in the mediolateral (ML) direction. These results suggest that although the static balance ability was not affected, dynamic balance ability, in terms of complexity, was reduced under the ankle-fixation condition in the ML direction by constraining the DoF.
Electrocardiogram (ECG) derived from the head has the potential to be the available measurement for heart rate monitoring in the exercise using only smart glasses. Therefore, we investigated the suitable electrode position on the frame of smart glass for high accuracy detectable of R-peak wave of ECG derived from head. Head ECG was measured from three kinds of position on the frame of smart glass (left and right skin on the nose, temple) in 5 healthy male participants. The experimental was started with a 1 min stationary state period. Next 40 W exercise load for 1 min using cycle ergometer. The band pass filter from 8 Hz to 25 Hz adapted to head lead ECG. The result showed that the electrode position of highest detection ratio (DR) was position of left on the nose. In addition, the DR was 95%. On the one hand, DR were decreased according to exercise load. As future work, development of signal processing to reduce noise will be needs. In conclusion these finding suggest that HR derived from head ECG might be practical index in life.
In this study, we devised an active device which is used to suppress the essential tremor in human limb. The tremor can be observed in most human arms under excessive stress or chills, even he/she is at physically well condition. Therefore, the tremor may cause anyone a bad effect on precise operation, e.g. welding and surgery. In this work, experiments are performed where the simulated microscopic surgery is imposed on subjects whose fingers are equipped with the active mass damper attenuating the tremor in their hands. The damper is actively driven according to the state feedback controller designed according to the linear two-degrees-of-freedom vibration system model. Subjects were asked to grip a needle having a relatively small diameter using tweezers, and were also asked to insert it in a needle with a larger diameter. Tremors were measured while the subjects kept the tip of the needle in place. The damper was shown to be effective for attenuating vibration in human fingers.
We proposed a bi-stable vibration system composed of elastic springs and mass blocks supporting from an oblique direction. From experimental results and numerical analysis results, it was confirmed that stochastic resonance was reliably generated using the proposed bi-stable vibration system of this study, and amplitude amplification effect about several times higher than normal vibration response was obtained. Compared to the conventional bi-stable vibration model, the larger amplitude is obtained, the degree of freedom directions other than the movement direction of the mass block are guided, and it is shown that the influence of accidental impact load from outside is small. And investigated important design factors of bi-stable vibration system and gained useful knowledge for future research.
The ear canal temperature measured using thermistor has the potential to be the available as core body temperature using the earphone in the outdoor exercise. However, the ear canal temperature effected of ambient temperature. The core body temperature measurement need to calibration. The dual-heat-flux method is one of the calibration method. Therefore, the aim of this study is to calculate core body temperature from the ear canal temperature based on the dual-heat-flux method. We measured the eardrum (reference), ear canal (inner ear air and inner ear surface) and near ear temperature in 10 healthy male participants. The core body temperature was calculated from the ear canal and near ear temperature. The result showed that the calculated temperature of some participants was closer to the eardrum temperature than the ear canal temperature. In conclusion these finding suggest that the core body temperature calculated from the ear canal temperature measured using thermistor might be used in the outdoor exercise.
A lot of rehabilitation robots have been developed and used in the practice of medicine. However, the effect of these devices are not quantified and the guidelines for the device settings are unclear. The purpose of this study is to quantify the improvement effect of a rehabilitation device. As a rehabilitation device, we focused on a stabilometer with COP feedback system for improving subject’s balance. The effect was quantified by a balance evaluation index based on the standard deviation of COM displacement and acceleration estimated from force plate measurement. As a result, balance evaluation of three subjects were improved after applying the stabilometer. To investigate the origin of the sway reducing effect, we assumed that the head acceleration is important because the balance improved subjects reduced the head acceleration. We assumed that the coordination of two joint strategy mode (the ankle strategy and the hip strategy) contributes to reduce the head acceleration. The correlation of two joint strategy mode in the experiment indicated that the assumption is valid. However, the reduction of the ankle strategy mode was more dominant for balance improvement by the stabilometer.
This research is aimed at developing a simple support application that allows general users to easily approximate the ideal motion. The application performs 3D pose estimation using “Lifting from the Deep” from monocular camera images that can be easily acquired by the user, and evaluates whether the target motion is close to the ideal teacher motion. The evaluation is performed based on the DTW distance of the difference data of the target time series parameter. The proposed application has been shown to be useful for supporting exercise guidance in rowing experiments.
The objective of our research is to develop the pose estimation algorithm for Karate motions using RGB Camera. Kata is the representation of Karate’s self-defense techniques strung together into a performance routine. Kata is judged based on several technical and physical criteria; including speed and strength. For this reason, quality evaluation for Karate motions by technology is difficult. In this research, we created a data set targeting karate movement. We also developed the pose estimation algorithm for Karate motions by deep learning using this data set.
The aerodynamic coefficients of the turbo-jav (a short javelin for junior or disabled athletes) up to 26 degree angle of attack were obtained using Magnetic Suspension and Balance System (MSBS). Ordinary thin models are susceptible to interference caused by mechanical supports. However, MSBS can eliminate the support interference because the model is floating supported by magnetic force instead of mechanical supports. Drag, lift force and pitching moment coefficients were measured in the wind tunnel tests at the wind speed 25 m/s (Re = 6.4 × 104) from 0 to 26 degrees angle of attack. This experiment agreed well with the results of the calculation using ANSYS FLUENT. Especially for pitching moments, the present measurement agreed the calculation better than the previous results using mechanical supports. It suggested that the results using MSBS was more reliable. In addition, the experimental results suggested that the aerodynamic characteristics of the turbo-jav depended on the fins of the turbo-jav but not on the rotation angle around air flow axis of the turbo-jav.
The ski jumper rapidly changes the body posture from crouching to flight posture during take off. In this study, the relationship between flight distance and take-off motion, in terms of trunk angle of attack and lift-drag ratio, was investigated through aerodynamics simulations that reproduce the take-off motion dynamically. The trunk angle of attack was extracted from two-dimensional image in the sagittal plane of the take-off motion. From the results of the numerical simulation it was found that athletes with higher lift-drag ratio at the initial take-off posture had longer flight distance and the frontal pressure on these athletes was relatively lower.
Ski jumping is a sport which competes the flight distance and the flight form. Generally, it is assumed that lower air permeability of ski jumping suit fabric is advantageous for getting more lift. Therefore, one of the regulations for ski jumping competition is that the outstretched fabric should have a medium air permeability of a minimum of 40 L/m2/s at a water pressure of 10 mm Aq. However, the effect of the air permeability of ski jumping suits on aerodynamic characteristics has not been completely clarified yet. The purpose of this study is to investigate the effect of air permeability of jumping suit fabric on aerodynamic characteristics. In the present study, four types of fabric with different air permeability were installed, and the flow behavior around the surface of the fabric clothed elliptic cylinder was investigated by wind tunnel experiments. The stall delay occurred by alterations in the air flow between the inner surface of fabric with higher air permeability and the elliptic cylinder, and the air flows out of the elliptic cylinder surface into the separation region. The stall characteristics for the fabric-clothed elliptic cylinder also vary, depending on the air permeability of the fabric. The higher air permeability improves the stall characteristics.
In cycling sports, fluid resistance accounts for ninety percent of all resistance at maximum speed. To date, studies on fluid resistance in track race have examined about bicycle and racer’s position on the bike for the reducing drag force. However, these studies have not revealed the relation of cycle wear and fluid resistance. In This study, we focused on the effect of fabric to reduce drag force in track race. To clarify where body parts increase air resistance, we first employed computer fluid dynamics. From results of simulation, the head, arms, and legs are identified as the major sources of drag on a track race. Based on results, we tested three kinds of fabrics by measuring drag force on cylinder model and full-scale mannequin. The reduction in drag force was observed in both experiments, and finally almost eight percent of drag force was reduced on skinsuit that was made from compared fabric.
Using the world’s largest 1-m MSBS (Magnetic Suspension and Balance System) and low-turbulence wind tunnel at Tohoku University, we successfully measured the aerodynamics force acting on a non-spinning women’s javelin with no supporting rod. The primary advantage of the MSBS is the complete elimination of any support, which can interference with the measurements. The advantage of the world's largest 1m-MSBS at Tohoku University is that it is possible to employ a real javelin at relatively high AoA. A women’s javelin was used for the wind tunnel tests. It was found that the drag and the Lift increase with increasing the angle of attack up to 18 °. The pitching moment increases up to about 9 °, and it decreases up to 18 °. The pitching moment becomes negative above 12 °. The nose-up rotation was determined as positive. We also confirmed the support interferences with using a pseudo supporting rod. The tip of the pseudo supporting rod was set at the distance of 2 mm away from the surface of the javelin at the angle of attack of 0 °.It was confirmed that there are some differences between the aerodynamics forces with the pseudo supporting rod and those without it. The absolute aerodynamic forces without the pseudo supporting rod become smaller.
The aerodynamics of the javelin is treated as a rigid body in spite of it flies with vibration in actual flight, and it seems there is no wind tunnel test result considered the effect of vibration. The objective of this study is to evaluate the effect of vibration for the aerodynamic force acting on the javelin using 1-m Magnetic Suspension and Balance System (1-m MSBS) in Institute of Fluid Science, Tohoku University. 1-m MSBS can conduct the dynamic wind tunnel test by controlling the coil current. However, the natural vibration frequency of javelin is too high to control with 1-m MSBS. We attempted to control the generation and suppression of natural vibration by adopting the notch-filter which is commonly used to prevent the resonance phenomenon. As a result, it became possible to control the amplitude of vibration. With this method, we performed wind tunnel test with a wind speed of 25 m/s, and angle of attack of 0° to 18°. Although the amplitude of the vibration was only 4.4% respect to the maximum diameter of javelin, a few percent difference was recognized in the aerodynamic coefficient of drag, lift and pitching moment.
Throwing the javelin is a field event in athletics. There are specific regulations to which the javelin must conform. In this study, optimization of the flight distance was carried out using a genetic algorithm. Tips with three different shapes were designed within the rules. One design was that of a typical commercially available tip. The second design was thinner and the third design thicker than the commercially available tip. The aerodynamic forces acting on the three types of javelin with respect to the angle of attack (AoA) were calculated using a commercial solver. In this optimization study, the design variables were the initial conditions determined by the thrower, and the objective function was the flight distance. The flight distances were estimated by numerical integration of the equations of motion. It was found that the flight distance for the thinner design was shorter than that for the other two types. The key for longer flight distances is that the drag should be small (AoA should be kept small) in the first half of the flight, and that the lift should be large (AoA should be large) in the second half of the flight.
Archery has many competitors around the world, but new materials are used for the parts of bows as technology develops in recent years. Due to the diversification of new materials, there are increasing number of unexplained areas of archery performance. One of them is the arrow feather (Vain). Vain is roughly divided into rotary and non-rotary types. Currently, the rotary type is mainly the drag type, but if a lift type rotary vane can be developed, the rotational force can be obtained with a low drag, so it is considered that a vane with better performance can be achieved. If we can clarify the characteristics and common points of Vain that lead to higher scores, we can expect to develop new vanes. In wind tunnel experiments, using a jig with an arrow model, measurement and analysis were performed on the rotational performance and convergence performance of the arrow model at a uniform flow velocity of 20 m/s (1/3 of the actual arrow speed). To evaluate the performance of Vane, the rotational performance was evaluated by the number of revolutions for each of the non-converging motion (at rest) and the converging motion (vibration), and the convergence performance was evaluated by the time until convergence of vibration. In the performance evaluation of off-the-shelf products, it became clear that rotary vanes can be further classified into those with top pitches and those that do not, and those with many users worldwide do not have top pitches.
Located in heavy snow areas, Research Centre for Winter Sports Science of Kitami Institute of Technology has been promoting the development of the design of ski boots which can improve the Japanese skiers’ speed in alpine ski competition. Previous experimental studies have shown that the small deformation of foot bed and the quick lean angle of the leg during turn (1),(2),(3),(4),(5),(7) greatly influence the improvement of skiers’ speed. In the present work, a numerical analysis has been carried out to examine the effect of small parts mounted on the bottom part of foot bed on the mechanical response of ski boots. Firstly, an experiment has been carried out on world-level Japanese top skiers as subjects to simulate the lean time, and the time variation pressure measured by sensor installed inside the boots. The time variation pressure was converted into nodal load and used as external load in the numerical analysis. As a result, it is shown that the lean angle during turn was increased when the part is installed under the foot bed. Relations between the part and the deformation of foot bed are discussed.
Many prototype boards are produced and evaluated in design process of snowboard. The process requires much development cost and time because of trial and error. Snowboarding simulation methods have been developed to solve this problem. Although snow has both discrete and continuum properties, the conventional simulation methods are treated snow as only a continuum. Few snowboard simulation methods reproduce discrete behavior of snow. In this study, we propose a snowboarding simulation with the distinct element method (DEM), which can reproduce the dynamic discrete behavior of snow. For verification of developed the simulation, some test snowboards with different shape and experimental slope with small plastic pipes are made. The simulation results are compared with the test results to verify the effectiveness of the simulation method. As a result, the trajectory and board posture in the simulation show a similar tendency in the test when the board shape is changed.
This study focuses on the mechanics of skateboarding. Skateboard has become so popular that it has been officially certified at the 2020 Tokyo Olympics. There are many “tricks” in skateboarding. However, the tricks are acquired by the riders empirically. Its mechanical principle and conditions to succeed have not been clarified theoretically yet. In the present study, the mechanical principle and conditions to succeed of “Ollie”, which is one of the basic tricks, were clarified theoretically. For this purpose, the simulation model of skateboarding based on the multibody dynamics analysis was constructed. The motion of the rider was acquired by using a motion capture system. By inputting the acquired motions of the feet, Ollie was reproduced in the simulation. In addition, a parameter study was conducted to investigate the conditions to succeed. Regarding the principle, it was clarified that the upward momentum given to the skateboard by the kicking down of the right foot is preserved, and it is realized by switching the rotation direction of the skateboard with the left foot. In terms of conditions, it was found that more technical control is required when the kick angle is large, that the track mounting position has little effect, and that there are conditions in the movement of the left and right feet.
This paper presents further development of the new edge model of a curling stone introduced in our previous paper. Precise measurements of edge angles of curling stones showed that the edge angles of each running band are about 10 degrees and the inner edge angles are larger than the outer edge angles. The cutting force by edges was formulated as a function of inner and outer edge angles, band width, translational and angular velocities based on various experimental results of ice, metal, plastic and other materials. The force increases with the edge angles and decreases with the increasing translational and angular velocities.
A method to classify similar tennis swing forms is necessary to evaluate an accurate hitting feel, which is caused by the collision of the tennis strings and the ball. In this study, we proposed a discrimination method for tennis swing forms based on a motion capture system, which consists of six cameras. We measured 3 different types of swinging 5 times each. By the motion analysis, we defined characteristic parameters, that vary according to the differences between the classified tennis swing forms: flat type and spin type. After that, we applied the multiple regression analysis to the obtained characteristics, and created a discrimination prediction system of the swing types. Furthermore, we tried to propose a simplified measuring method using IMU sensors. As a result, it could be assumed that there is a correlation between motion capture analysis and IMU．
The purpose of this paper is to build a selection index for tennis rackets. By investigating the effect of the racket on its stroke motion, derived motion indices were used to evaluate the tennis racket. During its swing, the feature points of the motion are derived by calculating the contribution of each part of the body in the tennis stroke motion, and the analysis is performed focusing on the feature points. The subjects of the study were three male senior tennis players and two male beginner players. Stroke motion and the three-dimensional information of each part of the human body was recorded with twelve motion capture cameras and six rackets with different characteristics. By using three-dimensional information, characteristic markers of the tennis strokes were derived. The vertical position of the marker was analyzed, and the change in the stroke motion of each racket was examined. Focusing on the swing variation from racket to racket, the sum of standard deviations was used. The analysis was performed by comparing the sum of standard deviation and swing speed. As a result, the relationship between the sum of the standard deviation and the swing speed for the stroke motion was shown.
This sample was prepared using MS-word. This research formulates an optima control model for simulating violin bowing-like movements, a kind of human arm's constrained reaching movements, which are characterized by nearly straight hand paths, and discusses the strategy underlying the human arm’s motion control mechanism through examining the model’s effectiveness. Actually, a constrained condition that evaluates linearity of the hand point is incorporated into the criterion function of the previous three-joint arm’s minimum energy model with a freezing-like mechanism in its hand joint. Consequently, the following results are obtained: (1) the experimentally-measured hand-joint angle changes quite a bit during constrained reaching movements contrary to unconstrained reaching movements; (2) the newly introduced hand-point linearity evaluating term makes the hand path get close to the straight line connecting the start and target points; (3) the constrained reaching movements reproduced by the proposed model agree well with those measured. The above results suggest that the proposed model is effective in simulating violin bowing-like movements, and that the human arm’s motion control mechanism can be subject to some energy minimizing strategy.