High-speed Motion Capture System Research Articles

Trajectory Prediction Analysis of Basketball Players’ Movements Based on DSM Optimization Algorithm

In this paper, the action trajectory of basketball players is predicted and analyzed by the DSM optimization algorithm. Data on the movements of basketball players, including position, speed and acceleration are collected. The motion trajectory is predicted by the DSM optimization algorithm. At present, computer technology is more and more applied in sports training. Based on this, this paper studies the simulation of basketball players’ motion trajectory prediction. After describing the research background and significance, this paper constructs a human joint model and then proposes the motion process DSM algorithm to simulate the jump shot action of basketball players. In this paper, the algorithm and model are tested, and the experiment adopts the run-jump fatigue model to produce fatigue. The infrared high-speed motion capture system and three-dimensional force measuring table are used to collect the kinematics and dynamics data of the sudden stop jump shot before and after fatigue. The experimental results show that the trajectory prediction simulation proposed in this paper is feasible.

Effects of Kinesio taping on lower limb biomechanical characteristics during the cutting maneuver in athletes after anterior cruciate ligament reconstruction.

To determine the effects of Kinesio taping (KT) on the biomechanical characteristics of the lower limbs during the 90° cutting maneuver in anterior cruciate ligament (ACL) reconstruction (ACLR) athletes. Eighteen ACLR athletes were recruited and subjected randomly to three taping conditions, KT, placebo taping (PT), and no taping (NT), followed by a 90° cutting test. A nine-camera infrared high-speed motion capture system (Vicon, T40, 200 Hz) was used to record the kinematic parameters of the lower limbs during the cutting maneuver, and a three-dimensional dynamometer (Kistler, 1000 Hz) was used to record the kinetic parameters of the lower limbs. A one-way repeated measures analysis of variance was conducted to compare the differences in the lower limb kinematic and kinetic characteristics of ACLR athletes subjected to these interventions. During the landing phase, the knee valgus angle reduced significantly with KT than with NT (95% confidence interval = -1.399 to -0.154; P = 0.025), whereas no significant difference was observed between PT and NT (95% confidence interval = -1.251 to 0.217; P = 0.236). No significant differences were observed in the other kinematic variables among the three taping conditions (P > 0.05). During the landing phase, no significant differences in the kinetic variables were observed among the three taping conditions (P > 0.05). Although KT does not improve the kinetic variables of athletes after ACLR during the 90° cutting maneuver, it reduces the knee valgus angle, which could reduce the risk of secondary ACL injury.

Effects of ankle Kinesio taping on knee and ankle joint biomechanics during unanticipated jumps in collegiate athletes.

Most biomechanical research on the application of Kinesio taping (KT) to the ankle joint focused on testing anticipated movements. However, ankle sprains frequently occur in real life in unanticipated situations, where individuals are unprepared and face sudden external stimuli. This situation is completely different from the anticipated situation. The aim of the present study was to investigate the effects of ankle KT application on the kinematic and kinetic characteristics of the knee and ankle joints during unanticipated jump tasks in collegiate athletes. Eighteen healthy collegiate athletes experienced three taping conditions in a randomized order: no taping (NT), placebo taping (PT), and KT, and performed unanticipated jump tasks. A 9-camera infrared high-speed motion capture system was employed to collect knee and ankle kinematic data, and a 3-dimensional force plate was utilized to collect knee and ankle kinetic data during the tasks. During the right jumps, KT significantly increased peak knee flexion angle (P = 0.031) compared to NT and significantly decreased peak vertical ground reaction force (P < 0.001, P = 0.001) compared to NT and PT. During the left jumps, KT significantly reduced peak ankle inversion angle (P = 0.022, P < 0.001) and peak ankle inversion moment (P = 0.002, P = 0.001) compared to NT and PT. During unanticipated jump maneuvers, KT reduced peak ankle inversion angle, peak vertical ground reaction force, and peak ankle inversion moment and increased peak knee flexion angle in collegiate athletes.

The analysis of infrared high-speed motion capture system on motion aesthetics of aerobics athletes under biomechanics analysis.

This paper uses an infrared high-speed motion capture system based on deep learning to analyze difficult movements, which helps aerobics athletes master difficult movements more accurately. Firstly, changes in joint angle, speed of movement, and ground pressure are used to analyze the impact and role of motion fluency and completion based on a biomechanical perspective. Moreover, based on the existing infrared high-speed motion capture systems, the Restricted Boltzmann Machine (RBM) model is introduced to construct an unsupervised similarity framework model. Next, the motion data is reorganized based on three-dimensional information to adapt to the model's input. Then, the framework performs similar frame matching to obtain a set of candidate frames that can be used as motion graph nodes. After the infrared high-speed motion capture system and inertial sensors are simultaneously applied to subjects, the multi-correlation coefficients (CMC) values of the hip, knee, and ankle angles are 0.94 ± 0.06, 0.98 ± 0.01, and 0.87 ± 0.09, respectively. The two systems show a high degree of correlation in the measurement results, and the knee joint is the most significant correlation. Finally, a motion graph is constructed to control its trajectory and adjust its motion pattern. The infrared high-speed motion capture system optimized for deep learning can extract features from human bone data and capture motion more accurately, helping trainers to fully understand difficult movements.

Gap selection and steering during obstacle avoidance in pigeons.

The ability of birds to fly through cluttered environments has inspired biologists interested in understanding its underlying mechanisms, and engineers interested in applying its underpinning principles. To analyse this problem empirically, we break it down into two distinct, but related, questions: How do birds select which gaps to aim for? And how do they steer through them? We answered these questions using a combined experimental and modelling approach, in which we released pigeons (Columbia livia domestica) inside a large hall with an open exit separated from the release point by a curtain creating two vertical gaps - one of which was obstructed by an obstacle. We tracked the birds using a high-speed motion capture system, and found that their gap choice seemed to be biased by their intrinsic handedness, rather than determined by extrinsic cues such as the size of the gap or its alignment with the destination. We modelled the pigeons' steering behaviour algorithmically by simulating their flight trajectories under a set of six candidate guidance laws, including those used previously to model target-oriented flight behaviours in birds. We found that their flights were best modelled by delayed proportional navigation commanding turning in proportion to the angular rate of the line-of-sight from the pigeon to the midpoint of the gap. Our results are consistent with this being a two-phase behaviour, in which the pigeon heads forward from the release point before steering towards the midpoint of whichever gap it chooses to aim for under closed-loop guidance. Our findings have implications for the sensorimotor mechanisms that underlie clutter negotiation in birds, uniting this with other kinds of target-oriented behaviours including aerial pursuit.

Research on Knee Joint Load and Influencing Factors of Typical Tai Chi Movements.

Background Tai chi is recognized worldwide for its rehabilitation abilities and healthcare benefits. However, in recent years, some movements associated with tai chi have been shown to damage the lower limb joints. The purpose of this study was to investigate and compare the effects of different movements, postures, center of mass (COM) movements, and range of knee movement of tai chi exercises on knee joint load. Methods Fourteen professional tai chi practitioners in two postures (high and low) were enrolled to perform the following four typical tai chi movements: wild horse's mane (WHM), repulse monkey (RM), wave-hand in cloud (WHIC), and grasp the bird's tail (GBT). Kinematic and kinetics data were synchronously collected using the Vicon infrared high-speed motion capture system and a three-dimensional (3D) force measurement platform. Variance analysis and partial correlation analysis were performed to investigate factors influencing peak knee joint moment and vertical ground reaction force (VGRF). Results The results showed that the peak knee extension and abduction moment were larger in WHM and RM than those in WHIC and GBT (p < 0.05). WHM was associated with greater rotation moment than the other typical movements (p < 0.05). VGRF and joint moment among different poses were significantly different. Low-pose tai chi typical movements were associated with greater VGRF, knee joint extension and abduction, and rotation moments than high-pose movements (p < 0.05). The anteroposterior and mediolateral COM displacements were strongly and positively associated with VGRF (p < 0.001), while the mediolateral COM displacement was negatively associated with knee extension moment (p < 0.001). The knee internal-external rotation ROM and anteroposterior and mediolateral COM displacements were positively associated with knee abduction moment (p < 0.01). Conclusion For long-term tai chi exercises, choosing a suitable posture based on an individual exercise level and reasonable control of knee ROM and COM displacement can reduce the risk of knee injury during exercise.

Comparative Study on Biomechanics of Two Legs in the Action of Single-Leg Landing in Men’s Badminton

This study aims to analyze the biomechanical difference between the two legs of male badminton players when they land on one leg, thereby providing some guidance for preventing sports injury. Ten male badminton players were selected as the subjects. They did the single-leg landing movement successfully three times. The kinematic data were obtained by the Vicon infrared high-speed motion capture system. The kinetic data were obtained by the KISTLER three-dimensional forcing measuring platform. The data were processed and analyzed. The center of gravity of the right leg on the X and Y axes were 0.25 ± 0.05 and 0.21 ± 0.04 m, respectively, which were lower than that of the left leg (p

The effects of visual cognitive tasks on landing stability and lower extremity injury risk in high-level soccer players

BackgroundVisual cognition plays a pivotal role in sports. It is widely recognized that there is an intriguing coupling that they could affect each other through interaction between visual cognition and motor control, but few studies linked the effects of visual cognitive tasks on landing stability to postural control and injury risk. Research questionWhether visual cognitive tasks affect the landing stability and lower limb injury risk of professional soccer players? MethodsThe current study used a three-dimensional Multiple Object Tracking (MOT) task to simulate visual cognitive difficulties experienced in soccer matches. Fifteen male high-level soccer athletes (height: 181.43 ± 7.36 cm, weight: 75.37 ± 10.67 kg, training years: 10.07 ± 2.98 yr) from our school team were recruited and completed a landing action from a high platform with and without MOT tasks. Vicon infrared high-speed motion capture system and three-dimensional force measuring platform were used to collect various outcomes simultaneously. ResultsThe Time to Stabilization (TTS) during landing was significantly prolonged, while the Medial-Lateral Stability Index (MLSI), Anterior-Posterior Stability (APSI), Dynamic Postural Index Stability Index (DPSI), the trajectory lengths, and envelope area of COP during landing were also increased during MOT dual-task. DiscussionThe decline of these indicators reflected the deterioration in postural stability and greater requirements for maintaining balance which could increase the risk of injury in soccer athletes. We advocate that adequate visual attention and visual information processing might play critical roles in maintaining dynamic balance through the supraspinal neural network.

On the kinematics of forelimb landing of frog Rana rugulosus

A frog can jump several times higher than its own height and then land smoothly on the ground. During the buffering phase, both forelimbs touch the ground and compact quickly to absorb most of the impact energy. However, the adjustment of the joint angles of the forelimb and the induced cushioning effect during the landing process have not been thoroughly investigated. In this study, we statistically summarized the angular displacements of forelimb joints with respect to landing velocities by using a high-speed motion capture system. It is found many joint angles were linearly influenced by landing velocity at both ground touching moment and maximum compression moment. Moreover, the double-peak pattern of ground reactive force was measured, which attributes to the forelimb landing and the followed abdomen/hindlimb landing. Before the appearance of the first peak, the compression of the forelimb and the reactive force revealed a linear relationship regardless of velocity, implying that the forelimbs act as a constant stiffness spring in landing. Accordingly, a simple spring-mass model was proposed and verified by simulation for forelimb cushioning of the frog. We anticipate our achievements to inspire the design of future landing mechanisms.

Motion Characteristics of the Appendages of Mole Crickets during Burrowing

Mole crickets, Gryllotalpa orientalis, have a pair of fully specialized forelegs for burrowing and employ an efficient underground excavating pattern, which provides excellent biological example for design of bionic underground excavation equipment. In this study, the excavating pattern and kinematic features of mole crickets were obtained by using high-speed motion capture system and employing a transparent hydrogel as the analogue for soil. The two-dimensional motion characteristics of the forelegs of mole crickets during burrowing were captured and analyzed. The results show that the forelegs of the mole cricket employ a unique excavating pattern, which consists of foreword digging and horizontal expansion. We label this pattern a digging-expanding mode. An excavating cycle includes the digging and expanding motion of the forelegs, rotation caused by the midlegs and hindlegs, and forward thrust by the hindlegs. The excavating motion of the left and right forelegs is alternately carried out. This study can inspire the design of bionic tunnelling mechanisms and underground excavation equipment.

Knee Joint Kinematics and Kinetics During Walking and Running After Surgical Achilles Tendon Repair.

Background:Despite the increasing incidence of Achilles tendon (AT) ruptures, there is a lack of information on the possible risks associated with regular running and walking for exercise after an injury. There are some known kinematic gait changes after an AT rupture, especially at the knee. However, it is not clear whether runners with AT ruptures may be at risk for secondary knee injuries during shod or barefoot running/walking.Purpose/Hypothesis:The purpose of this study was to compare the kinematics and kinetics of barefoot walking and barefoot and shod running between athletes with a history of AT ruptures and a healthy control group. We hypothesized that there would be increased knee joint loads in the affected limb of the AT rupture group, especially during shod running.Study Design:Controlled laboratory study.Methods:Ten patients who had undergone surgical treatment of a unilateral acute AT rupture (6.1 ± 3.7 years postoperatively ) and 10 control participants were matched according to age, sex, physical activity, weight, height, and footfall type. The kinematics and kinetics of barefoot walking and barefoot and shod running were recorded using a high-speed motion capture system synchronized with force platforms.Results:The main outcome measures were lower extremity joint angles and moments during the stance phase of walking and running. After AT repair, athletes had increased internal knee abduction moments during shod and barefoot running compared with the healthy control group (P < .05, η2 > 0.14). There were no significant differences in kinematics and kinetics during walking between the AT rupture and healthy control groups (P ≥ .05).Conclusion:After an AT rupture, athletes had increased internal knee abduction moments during running compared with the healthy control group.Clinical Relevance:The increased abduction loads on the knee in patients with an AT rupture could lead to further running-related injuries. However, barefoot walking may be used as a proprioceptive exercise without an increased risk of overuse injuries in these patients.

Hip Joint Torques During the Golf Swing of Young and Senior Healthy Females

Hip joint torques during the golf swing of young and senior healthy females Female participation in golf has increased throughout the past few decades and now comprises approximately 20% of all golf participants. However, little is known regarding the biomechanics of the golf swing for women, and even less is known about hip torques. PURPOSE: To describe and compare the hip torques associated with the golf swing of healthy young and senior female golfers. METHODS: 21 right-handed, female golfers, aged from 18-70 years old volunteered. Age groups were divided into young (18 – 39) and senior (40 – 70). Subjects completed 10 swings with a standardized driver. A high speed motion capture system and force plates were used to collect kinematic and kinetic data. . 3-D hip torques for trail and lead legs were calculated using inverse dynamic analyses. 2-way mixed model ANOVAs (group by leg) were calculated, with club head velocity as a covariate. RESULTS: There were no differences between the groups for BMI (24.6 ± 3.5), handicap (22 ± 7), or club head velocity (30.1 ± 4.2 m/s). The trail hip extensor torque was the largest torque produced by both groups. A main effect for leg was found for hip internal rotator torque (p=.024) with the largest torques produced by the trail leg. There was an interaction between the legs by groups for hip abductor torque (p=.043); the young group had larger torques for the lead leg, while the senior group had no difference between legs. Club head velocity was significantly (p<.05) correlated with hip internal rotator torques of both the lead and trail leg (r=.7 and .56, respectively), however, when separated by group, these correlations were only significant for the young group (r-.8; p=.001).Table: No title available.CONCLUSIONS: Overall, hip torques in the trail leg were larger, which suggests their important contribution to the golf swing. These findings are similar to previous literature for healthy male golfers.

Head Stabilization in the Pigeon: Role of Vision to Correct for Translational and Rotational Disturbances.

Stabilization of the head in animals with limited capacity to move their eyes is key to maintain a stable image on the retina. In many birds, including pigeons, a prominent example for the important role of head stabilization is the characteristic head-bobbing behavior observed during walking. Multimodal sensory feedback from the eyes, the vestibular system and proprioceptors in body and neck is required to control head stabilization. Here, we trained unrestrained pigeons (Columba livia) to stand on a perch that was sinusoidally moved with a motion platform along all three translational and three rotational degrees of freedom. We varied the frequency of the perturbation and we recorded the pigeons' responses under both light and dark conditions. Head, body, and platform movements were assessed with a high-speed motion capture system and the data were used to compute gain and phase of head and body movements in response to the perturbations. Comparing responses under dark and light conditions, we estimated the contribution of visual feedback to the control of the head. Our results show that the head followed the movement of the motion platform to a large extent during translations, but it was almost perfectly stabilized against rotations. Visual feedback only improved head stabilization during translations but not during rotations. The body compensated rotations around the forward-backward and the lateral axis, but did not contribute to head stabilization during translations and rotations around the vertical axis. From the results, we conclude that head stabilization in response to translations and rotations depends on different sensory feedback and that visual feedback plays only a limited role for head stabilization during standing.

Differences in the kinematics of booster-seated pediatric occupants using two different car seats

ABSTRACTObjective: The objective of this article is to compare the performance of forward-facing child restraint systems (CRS) mounted on 2 different seats.Methods: Two different anthropomorphic test device (ATD) sizes (P3 and P6), using the same child restraint system (a non-ISOFIX high-back booster seat), were exposed to the ECE R44 regulatory deceleration pulse in a deceleration sled. Two different seats (seat A, seat B) were used. Three repetitions per ATD and mounting seat were done, resulting in a total of 12 sled crashes. Dummy sensors measured the head tri-axial acceleration and angular rate and the thorax tri-axial acceleration, all acquired at 10,000 Hz. A high-speed video camera recorded the impact at 1,000 frames per second. The 3D kinematics of the head and torso of the ATDs were captured using a high-speed motion capture system (1,000 Hz). A pair-matched statistical analysis compared the outcomes of the tests using the 2 different seats.Results: Statistically significant differences in the kinematic response of the ATDs associated with the type of seat were observed. The maximum 3 ms peak of the resultant head acceleration was higher on seat A for the P3 dummy (54.5 ± 1.9 g vs. 44.2 ± 0.5 g; P =.012) and for the P6 dummy (56.0 ± 0.8 g vs. 51.7 ± 1.2 g; P =.015). The peak belt force was higher on seat A than on seat B for the P3 dummy (5,488.0 ± 198.0 N vs. 4,160.6 ± 63.6 N; P =.008) and for the P6 dummy (7,014.0 ± 271.0 N vs. 5,719.3 ± 37.4 N; P =.015). The trajectory of the ATD head was different between the 2 seats in the sagittal, transverse, and frontal planes.Conclusion: The results suggest that the overall response of the booster-seated occupant exposed to the same impact conditions was different depending on the seat used regardless of the size of the ATD. The differences observed in the response of the occupants between the 2 seats can be attributed to the differences in cushion stiffness, seat pan geometry, and belt geometry. However, these results were obtained for 2 particular seat models and a specific CRS and therefore cannot be directly extrapolated to the generality of vehicle seats and CRS.

Chimpanzee ankle and foot joint kinematics: Arboreal versus terrestrial locomotion.

Many aspects of chimpanzee ankle and midfoot joint morphology are believed to reflect adaptations for arboreal locomotion. However, terrestrial travel also constitutes a significant component of chimpanzee locomotion, complicating functional interpretations of chimpanzee and fossil hominin foot morphology. Here we tested hypotheses of foot motion and, in keeping with general assumptions, we predicted that chimpanzees would use greater ankle and midfoot joint ranges of motion during travel on arboreal supports than on the ground. We used a high-speed motion capture system to measure three-dimensional kinematics of the ankle and midfoot joints in two male chimpanzees during three locomotor modes: terrestrial quadrupedalism on a flat runway, arboreal quadrupedalism on a horizontally oriented tree trunk, and climbing on a vertically oriented tree trunk. Chimpanzees used relatively high ankle joint dorsiflexion angles during all three locomotor modes, although dorsiflexion was greatest in arboreal modes. They used higher subtalar joint coronal plane ranges of motion during terrestrial and arboreal quadrupedalism than during climbing, due in part to their use of high eversion angles in the former. Finally, they used high midfoot inversion angles during arboreal locomotor modes, but used similar midfoot sagittal plane kinematics across all locomotor modes. The results indicate that chimpanzees use large ranges of motion at their various ankle and midfoot joints during both terrestrial and arboreal locomotion. Therefore, we argue that chimpanzee foot anatomy enables a versatile locomotor repertoire, and urge caution when using foot joint morphology to reconstruct arboreal behavior in fossil hominins.

Do athletes alter their running mechanics after an Achilles tendon rupture?

BackgroundOver the past thirty years, there has been dramatic increase in incidence of Achilles tendon rupture in the athletic population. The purpose of this study was to compare the lower extremity mechanics of Achilles tendon ruptured runners with healthy controls.MethodsThe participants with a past history of an Achilles tendon repair (n = 11) and healthy control (n = 11) subgroups were matched on sex, age, type of regular physical activity, mass, height, footfall pattern and lateral dominancy. Running kinetics and kinematics of the ankle, knee and hip were recorded using a high-speed motion capture system interfaced with a force platform. Achilles tendon length was measured using ultrasonography. Main outcome measures were lower extremity joint angles and moments during stance phase of running and Achilles tendon lengths.ResultsAthletes from Achilles tendon group had an affected gastro-soleus complex. Athletes with history of Achilles tendon rupture had reduced ankle range of motion during second half of the stance phase of running (Δ7.6°), an overextended knee during initial contact (Δ5.2°) and increased affected knee range of motion (Δ4.4°) during the first half of stance phase on their affected limb compared to the healthy control group. There was a 22% increase in the maximal hip joint moment on contralateral side of the Achilles tendon group compared to the healthy controls.ConclusionThese results suggest a compensation mechanism, relatively extended knee at initial ground contact against the deficit in the muscle-tendon complex of the triceps surae. Overextension during sporting activities may place the knee at risk for further injury. Avoidance of AT lengthening and plantarflexion strength deficit after surgery and during rehabilitation might help to manage AT rupture since these factors may be responsible for altered running kinematics.

Validation of Instrumented Insoles for Measuring Height in Vertical Jump.

The purpose of this study was to validate a new instrumented insole called ECnsole for measuring flight time during vertical jump performance. 66 participants performed 3 different jump tests (squat jump, countermovement jump and Abalakov jump) twice with flight times determined using an instrumented insole composed of 4 pressure sensors (PreECnsole) and an accelerometer sensor (AccECnsole), a laser platform (Sport Jump System Pro), and a high-speed motion capture system (HSC); the latter 2 systems are considered as reference methods. One-way analysis of variance (ANOVA), simple linear regression, and the Bland-Altman method were used to assess validity. Regardless of the jump test performed, the ECnsole system showed a systematic bias close to 0 and a low random error (average random error: ±2.8 cm; ±3.1 cm PreECnsole and AccECnsole vs. HSC system respectively and ± 2.3 cm; ±2.9 cm PreECnsole and AccECnsole vs. SJS system respectively). The associations between PreECnsole and AccECnsole with the HSC were very high (R 2 =0.967 and 0.958 respectively). Furthermore, the associations between PreECnsole and AccECnsole with the SJS were very high (R 2 =0.978 and 0.966 respectively) as well. Therefore, the ECnsole system can be considered an alternative method for measuring jump height during vertical jump performance.

The Influence of the Parameters of the Vertical Runner Model on Ground Reaction Force in Different Running Styles

The purpose of this study is to analyze the differences in two running styles: rear-foot strike (RFS), in which the heel lands first and fore-foot strike (FFS), in which the ball of the foot lands before the heel comes down. These running styles were compared in term of vertical mathematical model parameters and motion-analyzed data. The ground reaction forces were measured by force platform with the same subjects performing each style of running at various velocities ranging from 2.23 m/s to 4.47 m/s. A unique set of parameters of the model for each trial was computed by nonlinear programming to minimize the sum of the relative standard error of the ground reaction force and the relative error of rebound velocity. Motion-analyzed data was measured by a high-speed motion capture system. The differences in running styles were considered by using results from parameters of a multi-degree-of-freedom model and motion analysis. The results of this study indicate that the FFS needs less energy than RFS because of the contact style and the impulse as internal forces. And it also indicates that the ratio of the upper to lower mass of the vertical mathematical model is higher in FFS than in RFS. A previous study also showed that the effective mass related to the first peak of ground reaction force was smaller in FFS than that in RFS. For this reason, FFS may reduce the risk of running injuries such as injuries to the hip, knee and ankle joints by reducing the impact to the body.

Golfers do not respond to changes in shaft mass properties in a mechanically predictable way

A common belief in the golf community is that a lighter shaft allows the golfer to swing the club faster. From a mechanical point of view, reducing the mass of the shaft would result in a faster swing. However, a golfer is not a purely mechanical system, and so it is simplistic to assume that identical loads will be applied when swinging different clubs. Therefore, the purpose of this study was to test the hypothesis that golfers behave similar to a mechanical model when swinging clubs of varying mass. A torque driven model estimated the effects caused by the addition of 22 g to the shaft. Twelve golfers hit balls with a standard driver as well as a driver fitted with the same 22 g increase in mass. Club kinematics were collected with a high-speed motion capture system. The model predicted a 1.7 % lower club head speed for the club with additional mass. One subject showed a similar reduction (1.4 %), but one subject showed an increase in club head speed by 3.0 %. Ten subjects did not show any significant differences. These results suggest that golfers do not respond to changes in club mass in a mechanically predictable way.

Parallel Architecture Manipulators for Use in Masticatory Studies

There is considerable scientific and commercial interest in understanding the mechanics of mastication. In this paper, the authors develop quantitative engineering tools to enable this process by: (i) designing a general purpose mastication simulator test-bed based on parallel architecture manipulator, capable of producing the requisite motions and forces; and (ii) validating this simulator with a range of test-foods, undergoing various mastication cycles under controlled and monitored circumstances. Such an implementation provides a test bed to quantitatively characterize the mastication based on “chewability index”. Due to the inherent advantages of locating actuators at the base (ground) in terms of actuator efforts and structural rigidity as well as benefits of using prismatic sliders compared to revolute actuators, the 6-P-U-S system was chosen. A detailed symbolic kinematic analysis was then conducted. For the practical implementation of the test-bed, the analytical Jacobian was examined for singularities and the design was adapted to ensure singularity free operation. A comprehensive parametric study was undertaken to obtain optimal design parameters for desired workspace and end effector forces. Experiments captured jaw motion trajectories using the high speed motion capture system which served as an input to the hardware-in-the-loop simulator platform.