サイドステップおよびクロスステップによる走方向変換動作のキネマティクス的研究

While rugby is a collision sport, many anterior cruciate ligament (ACL) injuries of the knee involve noncontact changes of direction. This study investigates the risk factors of ACL injury in rugby players by establishing the relationship between noncontact directional change by the players and the consequent alteration of the player’s center of gravity (CG) and knee joint motion. Methods: Photographs were taken when players at a university rugby football club changed their direction of movement by 45° or 90° (n = 10). The player’s motions were assessed to determine 3- and 2-dimensional coordinate values of markers on the players by using the direct linear transformation method. The values were used to calculate knee joint flexion 40 ms after foot grounding, the CG position (height and rearward position), and the abduction angle of the knee joint. A paired t test was used for statistical analysis; a probability level of less than 5 % was considered significant. Results and Discussion: No significant differences were observed in the knee flexion angle between a 45° and a 90° change in direction. However, the CG position (height and rearward position) and the abduction angle of the knee joint increased as the magnitude of the change in direction increased (p < 0.01). Because increases in the rearward CG and abduction angle of the knee joint are considered risk factors for ACL injury, the risk of ACL injury is predicted to go up as the magnitude of the change in direction increases.

Various assistive machines have been developed to prevent falling accidents of the elderly. In order to achieve advanced support using robot technology, it is important to acquire data or real-time state estimation of user's various motions. However, a lot of expensive and sophisticated sensors utilized to estimate user's state accurately are difficult to use in general households or institutions. In this article, we propose a method to estimate the user's state utilizing a few inexpensive and simple sensors. We focused on CoG (Center of Gravity) to estimate user's state, but when utilizing less sensors than required to calculate the human link model parameters, the position of CoG is underspecified. Then we considered the range of value of unknown parameters to calculate candidates of CoG. The range of CoG candidates can become narrow enough to estimate human state in real-time by properly selecting and placing the sensors. Therefore, the evaluation of CoG candidates allows us to determine where and which sensors to set when designing assistive robots. We firstly selected some sensors which can be generally found on assistive machines, and we created sets of measurements using the number of unknown parameters. From the result of the experiment using a motion capture system, we confirmed that the range of the candidates was considerably narrow when using some of the created measurement sets. We validated the proposed method to estimate user's CoG candidates by actually placing the sensors according to the designed measurement sets and confirmed that the CoG candidates corresponded to those obtained using the motion capture system.

During leg flexion from erect posture, postural stability is organized in advance during "anticipatory postural adjustments" (APA). During these APA, inertial forces are generated that propel the centre of gravity (CoG) laterally towards stance leg side. This study examined how fear of falling (FoF) may influence this anticipatory postural control of medio-lateral (ML) stability. Ten young healthy participants performed a series of leg flexions at maximal velocity from low and high surface heights (6 and 66 cm above ground, respectively). In this latter condition with increased FoF, stance foot was placed at the lateral edge of the support surface to induce maximal postural threat. Results showed that the amplitude of ML inertial forces generated during APA decreased with FoF; this decrease was compensated by an increase in APA duration so that the CoG position at time of swing foot-off was located further towards stance leg side. With these changes in ML APA, the CoG was propelled in the same final (unipodal) position above stance foot as in condition with low FoF. These results contrast with those obtained in the literature during quiet standing which showed that FoF did not have any influence on the ML component of postural control. It is proposed that ML APA are modified with increased FoF, in such a way that the risk of a sideway fall induced by the large CoG motion is attenuated.

Several U.S. Navy rotorcraft models are equipped with Health and Usage Monitoring Systems. On-board or on-ground Regime Recognition (RR) programs are used to develop individual rotorcraft usage spectrums to compute component and airframe fatigue life expended (FLE). FLE is a function of rotorcraft gross weight (GW) and center of gravity (CG), but neither are monitored by sensors. Thus GW and CG computation algorithms based on measured engine torque curves and trim equations during hover are developed and incorporated into RR. The algorithms are validated using numerous fleet flights with known GWs and CG positions. Excellent correlation between predicted and actual values is observed with low standard error of estimate. The in-flight variation of GW and CG is determined with the help of recorded fuel weight. RR is used to analyze 32,000 h of data from 111 rotorcraft to develop GW and CG utilization distributions. Furthermore, GW variation is modeled with a beta probability distribution and the joint probability distribution of GW and CG utilization is determined to assess airframe and dynamic component fatigue lives.

Blended Wing Body (BWB) aircraft configurations have been proposed for significant fuel efficiency improvement on commercial transport. In order to fly with the optimum lift-to-drag ratio throughout most of the mission, an adaptation of the center of gravity (CG) by fuel redistribution is proposed. The most aft location of the CG which still is controllable is mainly limited by actuator bandwidth whereas the front CG location is limited by control authority of the trailing edge control surfaces. This paper provides an optimization of the CG position with regards to minimization of fuel consumption. Layout of the fuel tank system is illustrated. Moreover, active stabilization of faulty CG positions is discussed.

Gravity center position is one important index to evaluate the stability of vehicles. A high precision gravity center measure system is proposed in this paper, which can be used in weight and gravity center measuring for large heavy vehicles. Based on a static gravity measuring principle with three measuring points, a hydraulic driven 2-DOF motion platform is developed. By means of a degree-of-freedom control, the platform can realize accurate positioning to construct two intersected planes and work out the three-dimensional coordinates of the vehicle gravity center. Experiments demonstrate that the system's measurement error in weight is less than 0.3%, in Gravity center position measurement is less than 3mm in X and Y direction, and in Z direction is no greater than 5mm.

Color-motion asynchrony (CMA) refers to an illusion in which we perceive a change in color earlier than a change in motion direction when the two changes occur simultaneously. This phenomenon may indicate that color is processed earlier than motion in the visual system. However, the very existence of CMA is under question owing to contradictory findings and methodological deficits in previous studies. Here, we used both the motion and color correspondence tasks (experiment 1) and the temporal order judgment (TOJ) task (experiment 2) to re-examine CMA. Colored dots moved in one direction and changed their color/direction at some time, whereas the relative timing between color and direction changes varied across trials. In the correspondence task, participants reported which direction/color of dots with a particular color/direction lasted longer, the one before or after the change? In the TOJ task, participants reported whether the change in color or the change in motion direction occurred earlier. Results indicated that participants perceived the change in color earlier than the change in motion direction in either the motion or color correspondence task, with a stronger asynchrony in the former. In the TOJ task, although participants showed no difference in psychophysical measures, they responded faster when the change in color occurred before (versus after) the change in direction. Drift-diffusion modeling (DDM) revealed a lower decision threshold when the change in color occurred before (versus after) the change in direction, indicating less cautiousness was excised in judgment when the color changed earlier. These results confirmed the veracity of CMA in different tasks and point to the viability of analyzing response times in traditional psychophysical studies.

BackgroundThe ability to perform a rapid change of direction (COD) is a critical skill in numerous court- and field-based sports. The aim of this review is to investigate the effect of different physical training forms on COD performance.MethodsA systematic review of the literature was undertaken using the following databases: PubMed, SPORTDiscus and Google Scholar. Studies were eligible if they met the following criteria: (1) a COD test measuring performance before and after the training intervention, with specific description of the test in terms of length and number of changes in a direction with specified angles, (2) involve training intervention like plyometric, strength, sprint, specific COD training, or a combination of these training forms targeting the lower extremities, (3) the study had to state training background in terms of which sport they participated in and their competitive level and a detailed methodological description. Non-English articles were excluded. Percentage difference and effect sizes were calculated in order to compare the effects of different training interventions.ResultsA range of studies performing plyometrics, strength, sprint, specific COD training, training with post-activation potentiation or a combination of these training forms were examined. The percentage of change and effect size (ES) were calculated. Seventy-four studies met the inclusion criteria, comprising 132 experimental groups and 1652 unique subjects. The review revealed no clear consensus on which training form is optimal to develop COD performance. All training forms resulted in an increase in performance from almost no ES to large ES.ConclusionsThe results of the study indicate that COD ability is a specific skill, whereas the COD task, the sports require determines which training form is the most effective to develop COD ability. Training targeting improvement in COD performance should address the duration of the training in line with which energy system is utilized. The complexity of the COD task with respect to the individual athlete must be considered. Consequently, the number of changes in direction and the angles of the task are relevant when organizing training.

In these two decades, the technology of bipedal and humanoid robots has been made great progress. Up so far, many bipedal and humanoid robots are successfully developed (Hirai et al., 1998; Takanishi et al., 1985; Ogura et al., 2004; Kaneko et al., 2004; Nakasaka et al., 2004; Loffler et al., 2003; Lohmeier et al., 2004). In these robots, the gait planning and control for bipedal walking are based on ZMP concept (Vukobratovich et al., 1990; Goswami, 1999; Kakami, 2000). There are generally two methods for implementation of the dynamic and stable walking. The first one is based on a multiple rigid body robot model (Takanishi et al., 1985). This model is comparatively precise, but it requires a huge computation cost. The second one is simply based on the assumption that the whole robot mass is concentrated to robot’s CoG (Center of Gravity). The typical approach is using a 3D inverted pendulum model (Kajita & Kobayashi, 1987; Kajita et al., 2002; 2003; Zhu et al., 2003, 2004), in which, the robot locomotion in the sagittal and lateral planes are supposed to be independent. However, up to now, the bipedal walking nature and limitations of walking speed, stride, stride motion time, and so on, have not been completely understood. Partially this is because (1) few attentions are paid on the motion in double support phase and its effect to whole bipedal walking; (2) the investigation is not done intensively even for single support phase; for example, motion in sagittal plane are simply dealt with independent of the motion in lateral plane in most literatures on biped and humanoid robots. As revealed latter, in fact, such an approach is improper since the motions in the two planes are strongly coupled together. (3) ZMP is fixed to a point in robot sole for most of bipedal or humanoid robots. This paper mainly discusses the above first two problems based on ZMP concept and an inverted pendulum model with the assumption that ZMP is fixed at the center of the robot sole in single support phase. To do this, the relation between the motions in the sagittal and lateral planes is investigated first. By dividing a whole bipedal walking cycle into a double support, a deceleration, and an acceleration phases, and synchronizing the motions in the sagittal and lateral planes, we point out that the motions in these two planes are strongly coupled together, in other words, the motion in the lateral plane greatly restricts the motion in the sagittal plane, vice versa. Then, the role of the double support phase in biped walking is discussed. By changing the start and finish points of the double support phases in the lateral plane, the walking parameters such as walking speed, walking period, phase stride

Three-wheeled motor vehicles have been around for close to a half a century now, but they have largely remained in the realm of recreational or concept vehicles. Due to increasing fuel prices and an emphasis on fuel efficient design, the automotive industry is exploring the three-wheeled option now more than ever as a mainstream daily-use vehicle. The trend is evident from the Automotive X-Prize which featured six teams with three-wheeled vehicle designs to meet the fuel efficiency target [1]. A three-wheeled vehicle design offers vast potential for improvement in overall fuel efficiency over their four wheeled counterparts, as it lends itself to a tear-drop shape which is highly aerodynamic and is also likely to be lighter and have lower rolling resistance. These factors have considerable impact on improving fuel efficiency, but such a design also presents challenges in terms of vehicle stability and can be susceptible to roll-over or spin out in certain scenarios. The primary factor that determines the stability of a three-wheeled vehicle is its center of gravity (CG). This paper uses a model-based approach to explore the CG position limits for stable operation of a front wheel drive three wheel vehicle and aims to give an empirical basis for deciding CG position limits for future three wheel vehicle design. ADAMS/Car is used to model the vehicle and the model is validated using test data from a commercially available three-wheeled vehicle. The performance of the model is then studied for various CG positions and the limits of safe operation are established for this particular model.

The aim of this study was to investigate the manoeuvrability of a ship in different Center of Gravity (CG) conditions. Free Running Model Tests (FRMT), such as 35°turning circle tests, 20/20 zigzag manoeuvring tests, and 10/10 zigzag manoeuvring tests, were conducted in three GM and three trim conditions with 1/65.83 scaled KRISO Container Ship (KCS). The test results indicated that KCS in the lower GM condition and the trim by bow condition showed reduced advance and tactical diameter in turning circle tests and increased overshoot angles in zigzag tests, and those manoeuvring indices were strongly related with roll angle. In addition, sensitivity indices for three-axis CG position were suggested with prior research, and it showed that y-axis CG position significantly affected manoeuvrability of KCS due to the low GM. Therefore, in the case of KCS, it is evident that the roll angle during manoeuvre is closely related with manoeuvring indices.

Aging effects on postural responses to self-imposed balance perturbations

Measurement on Morphology and Kinematics of Crucian Vertebral Joints

The purpose of this study was to employ inertial measurement units (IMU) with an eye-tracking device to investigate different swing strategies between two levels of batters. The participants were 20 healthy males aged 20 to 30 years old, with ten professional and ten amateur batters. Eye gaze position, head, shoulder, trunk, and pelvis angular velocity, and ground reaction forces were recorded. The results showed that professional batters rotated segments more rhythmically and efficiently than the amateur group. Firstly, the professional group spent less time in the preparation stages. Secondly, the maximum angular velocity timing of each segment of the professional group was centralized in the swing cycle. Thirdly, the amateur group had significantly earlier gaze timing of the maximum angular velocity than the professional group. Moreover, the maximum angular velocity timing of the gaze was the earliest parameter among the five segments, and significantly earlier (at least 16.32% of cycle time) than the maximum angular velocity of the head, shoulder, trunk, and pelvis within the amateur group. The visual-motor coordination strategies were different between the two groups, which could successfully be determined by wearable instruments of IMU.

Alignment of the body in typical symmetrical standing was studied by photographing fifteen subjects in profile on a reaction board. Two aspects of alignment were studied: (1) the anteroposterior position of the body landmarks of knee joint, hip joint, shoulder joint, and ear, compared to the ankle joint; and (2) the positions of the partial centers of gravity above the knee and hip, as a measure of how the body is balanced above these joints. The knee, hip, shoulder, and ear were forward of the ankle in all subjects. On average, the knee was 3.8 (+/- 2.0), the hip 6.2 (+/- 1.3) the shoulder 3.8 (+/- 1.9), and the ear 5.9 (+/- 1.6) cm (+/-S.D.) anterior to the ankle. The positions of landmarks were positively correlated with one another but not highly. The position of the center of gravity could be predicted well from the positions of the landmarks within individual subjects' data, but not across subjects. The centers of gravity above the knee and hip were calculated by subtracting the mass and position of the segments below the joint from the whole-body center of gravity. The center of gravity above the knee was located on average 1.4 (+/- 1.1) cm in front of the joint, and that of the hip 1.0 (+/- 1.6) cm behind the trochanter. Thus, at both knee and hip in typical standing, there exist slight gravitational torques tending to extend the joints.