High-speed Motion Analysis Research Articles

Human stick balancing: tuning Lèvy flights to improve balance control.

State-dependent, or parametric, noise is an essential component of the neural control mechanism for stick balancing at the fingertip. High-speed motion analysis in three dimensions demonstrates that the controlling movements made by the fingertip during stick balancing can be described by a Lèvy flight. The Lèvy index, alpha, is approximately 0.9; a value close to optimal for a random search. With increased skill, the index alpha does not change. However, the tails of the Lèvy distribution become broader. These observations suggest a Lèvy flight that is truncated by the properties of the nervous and musculoskeletal system; the truncation decreasing as skill level increases. Measurements of the cross-correlation between the position of the tip of the stick and the fingertip demonstrate that the role of closed-loop feedback changes with increased skill. Moreover, estimation of the neural latencies for stick balancing show that for a given stick length, the latency increases with skill level. It is suggested that the neural control for stick balancing involves a mechanism in which brief intervals of consciously generated, corrective movements alternate with longer intervals of prediction-free control. With learning the truncation of the Lèvy flight becomes better optimized for balance control and hence the time between successive conscious corrections increases. These observations provide the first evidence that changes in a Lèvy flight may have functional significance for the nervous system. This work has implications for the control of balancing problems ranging from falling in the elderly to the design of two-legged robots and earthquake proof buildings.

Muscle activation and force production in Parkinson's patients during sit to stand transfers

Objective. The purpose of this study was to compare the kinematics, muscle activation, and force production between Parkinson's patients and healthy, age-matched participants during sit-to-stand transfers. Design. This cross-sectional study employed a 2 × 2 × 3 multivariate analysis of variance to test for significant differences between and within groups. Background. The underlying mechanisms that predispose an individual to lose strength during the clinical progression of Parkinson's disease have proved to be elusive, especially during performance of functional tasks such as the sit to stand transfer. Methods. Twenty-four men (mean age: 71.5 years) categorized as Parkinson's patients ( n=13) and healthy adults ( n=11) participated in this study. Two force platforms measured antero-posterior and vertical force components as well as peak torque. Muscle activation was measured by a six channel, bilateral electromyography system. A lower-body kinematic assessment was conducted utilizing a highspeed motion analysis system. Results. No statistically significant differences were found between groups for the outcome variables measured. However, Parkinson's patients did exhibit significant within-group bilateral differences for the variables of knee angle at seat-off, peak vertical force and peak torque. Conclusion. Data from this study reveal that persons with mild to moderate Parkinson's disease exhibit moderately altered bilateral mechanics when performing a sit to stand transfer compared to their healthy peers. Relevance The inability to produce constant equilateral force when performing functional tasks could be an indicator for the increased propensity of falls or other instabilities in this population.

Effects of Non-throwing Arm on Trunk and Throwing Arm Movements in Baseball Pitching

The purpose of this study was to investigate the effects of non-throwing arm on trunk and throwing arm movements in baseball pitching. Ten right-handed collegiate baseball players were asked to throw baseballs under two conditions, the normal and the restricted conditions. Under the restricted condition, non-throwing arm was fixed to the trunk by a rubber band. Their motions were analyzed by three-dimensional high-speed motion analysis and compared between two conditions. Under the restricted condition, upper torso rotated more counterclockwise and trunk twist angle decreased, at the instant of stride foot contact on the ground. It might be because the moment of inertia of upper torso and upper extremities along the trunk axis was smaller without non-throwing arm movement. Additionally, the maximum angular velocities of shoulder internal rotation and elbow extension as well as pitched ball velocity were lower under the restricted condition. When trunk twist, which stretches trunk rotator musculature, is small, the energy exerted by the musculature and transferred to throwing arm would decrease. Therefore, non-throwing arm in baseball pitching motion is considered to contribute to enhance pitched ball velocity by controlling the moment of inertia of upper torso and upper extremities along the trunk axis.

Particle Velocity on Solid-Propellant Surface Using X-Ray Real-Time Radiography

In a solid rocket motor using aluminized composite solid propellant and submerged nozzle, two-phase flow needs to be investigated by both experiment and computation. The boundary conditions for the ejecting particles constrain their trajectories; hence, these affect the two-phase flow calculations and, thus, significantly affect the evaluation of the slag accumulation. A new method to determine the velocities of particles on the solid-propellant surface was developed, which is based on the x-ray real-time radiography (RTR) technique and coupled with the two-phase flow numerical simulation. A method was developed to simulate the particle ejection from the propellant surface. The moving trajectories of metal particles in a firing combustion chamber were measured by using the RTR high-speed motion analyzer. Image-processing software was also developed for the RTR images so that the trajectories of particles could be obtained. Numerical simulations with different propellant-surface boundary conditions were performed to calculate particle trajectories. By comparing the two trajectories, an appropriate boundary condition on the propellant surface was inferred. The present method can be extended to study the impingement of particles on a wall and other related two-phase flows.

Burst Tests of Filament-wound Graphite-epoxy Tubes

A test program was conducted to investigate the failure modes of undamaged and damaged graphite-epoxy cylindrical tubes subjected to internal pressure. Some tubes were intentionally damaged by either a longitudinal-line cut or a single-point impact. Both types of damage were intended to simulate fiber breakage caused by a local damage. The objectives of the program were to investigate the failure modes of graphite-epoxy cylindrical tubes subjected to internal pressure, with and without local damage, and to qualitatively determine the relative burst pressure degradation associated with preexisting local damage to the tubes. A high-speed motion analyzer was used to record images of the fractures. The images provide the failure mode information that was not available in existing literature. Testing was conducted under three conditions: hydraulic pressurization, pneumatic pressurization with solid inserts, and pneumatic pressurization with inert propellant inserts. A tube with a longitudinal cut can fail by three different modes: a local leakage mode, a bursting mode with fracture initiating from the cut, or a bursting mode with complete tube disintegration. In testing of impact-damaged tubes, the results show that the burst pressure decreases with increasing impact load. At an impact load of 1493N (335 lb), the burst pressure decreases by 33% compared to the undamaged condition.

Relationship between bat mass properties and bat velocity

The relationship between bat mass properties (mass and moment of inertia) and bat velocity (linear and angular) was investigated for baseball and softball. Seventeen male collegiate baseball players and 17 female collegiate softball players were tested swinging aluminium alloy bats engineered with various mass and moments of inertia. Motions of reflective markers attached to the pitched ball, bat handle and bat barrel were tracked with a high-speed three-dimensional motion analysis system. Linear velocity of the bat's `sweet spot' (defined here as 15 cm from the end of the bat barrel towards the handle) and angular velocity of the bat were calculated from the motion data. Analysis of variance revealed significant differences (P < 0.05) in bat linear velocity among the baseball bats tested (24.7–26.8 m · s−1) and among softball bats tested (19.4–22.2 m · s−1). Variations in bat angular velocity were non-significant for both the baseball bats (2080–2280 ° s−1) and softball bats (1740–1890 ° s−1). Regression analysis showed a linear correlation between bat linear velocity and bat moment of inertia, both for baseball and softball. Results from this study suggest that if limitations in bat velocity are desired, bat moment of inertia – not bat mass – should be regulated.

Analysis of the chain-flail debarking using a high speed motion analysis system

Chain-flail delimbing-debarking technology is suitable for multi-tree processing of small-diameter trees. In the chain-flail debarking process, the rotation speed of the chain drum ranges 300-500 rpm. Therefore, a high-speed motion analysis is the only method to show what really happens in the debarking process. In this study, it was noticed that debarking occurs in a very short time (about 0.5 ms) when the chain hits the timber. If the chain hits the side of the tree, the chain just slides on the surface of the tree and is not able to debark the tree efficiently. In the determination of the impact force there is a clear correlation between the results obtained by a load cell mounted at the hitting point of the chain and those calculated using the impact time determined with a high-speed motion analysis system. This information makes it possible to determine the maximum impact force of the chain without measuring it.

Relationship of Pelvis and Upper Torso Kinematics to Pitched Baseball Velocity

Generating consistent maximum ball velocity is an important factor for a baseball pitcher’s success. While previous investigations have focused on the role of the upper and lower extremities, little attention has been given to the trunk. In this study it was hypothesized that variations in pelvis and upper torso kinematics within individual pitchers would be significantly associated with variations in pitched ball velocity. Nineteen elite baseball pitchers were analyzed using 3-D high-speed motion analysis. For inclusion in this study, each pitcher demonstrated a variation in ball velocity of at least 1.8 m/s (range: 1.8–3.5 m/s) during his 10 fastball pitch trials. A mixed-model analysis was used to determine the relationship between 12 pelvis and upper torso kinematic variables and pitched ball velocity. Results indicated that five variables were associated with variations in ball velocity within individual pitchers: pelvis orientation at maximum external rotation of the throwing shoulder (p = .026), pelvis orientation at ball release (p = .044), upper torso orientation at maximum external rotation of the throwing shoulder (p = .007), average pelvis velocity during arm cocking (p = .024), and average upper torso velocity during arm acceleration (p = .035). As ball velocity increased, pitchers showed an increase in pelvis orientation and upper torso orientation at the instant of maximal external rotation of the throwing shoulder. In addition, average pelvis velocity during arm cocking and average upper torso velocity during arm acceleration increased as ball velocity increased. From a practical perspective, the athlete should be coached to strive for proper trunk rotation during arm cocking as well as strength and flexibility in order to generate angular velocity within the trunk for maximum ball velocity.

Co-current air–water two-phase flow patterns in vertical triangular microchannels

Characteristics of co-current upward air–water two-phase flow patterns in vertical equilateral triangular channels with hydraulic diameters of 2.886, 1.443 and 0.866 mm were investigated experimentally. Flow regimes were identified by both visual observations using a high-speed motion analyzer and dynamic pressure-drop measurements. The experimental results show that the typical flow patterns encountered in the conventional, large-sized vertical circular tubes, such as dispersed bubbly flow, slug flow, churn flow and annular flow, were also observed in the channels having larger hydraulic diameters ( d h=2.886 and 1.443 mm). However, for the smallest channel ( d h=0.866 mm), dispersed bubbly flow pattern, characterized by randomly dispersed bubbles in continuous liquid phase, was not found, although the other typical flow patterns remained in the channel. Moreover, the experiments reveal that, for the channel of d h=0.866 mm, a so-called capillary bubbly flow pattern, characterized by a single train of bubbles, essentially ellipsoidal in shape and spanning almost the entire cross-section of the channel, existed at low gas flow rates. It is further found that in the slug flow regime, slug-bubbles were substantially elongated. Finally, flow regime transition boundaries for the triangular microchannels were compared with relevant flow regime transition models and correlations as well as the existing experimental data for small round tubes and square channels.

High power diode laser surface treatment of mullite crucible material

Alumina, as well as alumina/silica mixtures are well characterised materials used in a multitude of applications from insulators, crucibles to vacuum system windows. In this paper we present the application of a high power diode laser (HPDL) to surface treat the material from its sintered form into an amorphous, glass type glaze. The process has been monitored using a high speed motion analysis system. The laser treated glaze material is robust and exhibits good adherence to the bulk ceramic. The samples are analysed via XRD, EDX and optical microscopy. This technique could have potential applications in vacuum sealing or surface treatment of ceramic workpieces.

ELECTROSTATIC CHARGE ON SPRAY DROPLETS OF AQUEOUS SURFACTANT SOLUTIONS

Electrostatic charges on individual spray droplets were measured using a refined form of the Millikan oil drop method. The measurement system consisted of three main sections; a droplet generation cell, a settling column and a charge measurement chamber. The trajectories required for calculation of charge were determined using a high-speed motion analyzer coupled to a long-focal-length microscope. Charges on droplets were manipulated by the addition of surface-active agents into the spray solution. Droplet charge was a function of the type and concentration of the surfactant added. For ionic surfactants, it showed a maximum at low surfactant concentrations, decreased with further surfactant addition and was constant after the CMC. The charge on cationic surfactants was always more than that observed with the anionic surfactants. Nonionic surfactants displayed a steady increase in droplet charge with increasing concentration. The charges were lower compared to the ionic surfactants.

Analysis of Pedestrian Gait and Perception-Reaction at Signal-Controlled Crosswalk Intersections

Pedestrian accident analysis and reconstruction remain the most difficult areas for the accident analyst. Although data relating to average pedestrian walking speeds, perception-reaction, and pedestrian accident reconstruction can be found in the literature, proper pedestrian study data pertaining to real-life situations are lacking. Pedestrians were observed at signal-controlled crosswalk intersections, and their perception-reaction to the crosswalk signal, acceleration rate to reach constant walking velocity, and average walking speed once steady state velocity is achieved were determined. Experimental test data collected regarding pedestrian gait analysis, initiation, and steady state walking speeds are presented. “Real world” pedestrian observations were gathered at a variety of intersections, ranging from busy downtown intersections to suburban intersections throughout the greater Los Angeles area. Kinematic data on pedestrian movements were obtained using high-speed digital video. A high-speed video motion analysis system was used to reduce the data and to obtain the mean acceleration and time to steady state walking velocity. Perception-reaction data collected on 288 subjects show a significant percentage of the pedestrians initiating movement within 1 s of Walk light illumination. Some differences were observed when the state of anticipation was being considered, and these results are presented. The mean acceleration (0.14 ± 0.09 g) and steady state velocity (1.36 ± 0.24 m/s) values did not demonstrate a significant difference between males and females. The width of the street or initial state of anticipation did not have an effect on either mean acceleration values or steady state velocities.

Vibration Characteristic of Heated Rod Induced by Subcooled Flow Boiling

A subcooled boiling loop with annular flow channel on an electrically heated rod at the channel axial center was used to make an experimental approach to investigate the vibration characteristic induced by subcooled flow boiling. The experiments were carried out to measure vibration induced in the rod under different conditions of incoming coolant subcooling temperature of 10–80 K, coolant flow rates of 0.1–0.35 × 10−3 m3/s and imposed linear power densities of 17–600 W/cm. Distilled water was used as coolant in the loop. The vibration behavior of the rod was measured by using an accelerometer. Also, a high-speed motion analyzer system was used to analyze the bubble behaviors in the different subcooled boiling conditions. The results show the intensive SBIV (subcooled boiling-induced vibration) which highly depends on dynamic force generated by rapid growth and collapse of vapor bubbles under high heat flux loading whilst they still attach to the heating surface. These behaviors were influenced strongly by the conditions of subcooling temperature, linear power density and flow rate.

LINERLESS LABEL DEVELOPMENT AIDED BY HIGH-SPEED MOTION ANALYSIS

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Leg kinematics and muscle activity during treadmill running in the cockroach, Blaberus discoidalis : I. Slow running

We have combined high-speed video motion analysis of leg movements with electromyogram (EMG) recordings from leg muscles in cockroaches running on a treadmill. The mesothoracic (T2) and metathoracic (T3) legs have different kinematics. While in each leg the coxa-femur (CF) joint moves in unison with the femurtibia (FT) joint, the relative joint excursions differ between T2 and T3 legs. In T3 legs, the two joints move through approximately the same excursion. In T2 legs, the FT joint moves through a narrower range of angles than the CF joint. In spite of these differences in motion, no differences between the T2 and T3 legs were seen in timing or qualitative patterns of depressor coxa and extensor tibia activity. The average firing frequencies of slow depressor coxa (Ds) and slow extensor tibia (SETi) motor neurons are directly proportional to the average angular velocity of their joints during stance. The average Ds and SETi firing frequency appears to be modulated on a cycle-by-cycle basis to control running speed and orientation. In contrast, while the frequency variations within Ds and SETi bursts were consistent across cycles, the variations within each burst did not parallel variations in the velocity of the relevant joints.

On holey polymer grids by condensation/dip-coating/draining/drying

Abstract Carbon-coated holey polymer film (HPF), or ‘holey carbon grid’ used to support fragile samples, is a crucial part of Cryo-TEM technique. A film with high porosity and uniform hole size as well as mechanical strength is needed. Efforts to develop a reliable preparation method date back to the 1950s. Today's favorite by far for routine application employs condensation, dip-coating, drainage and drying.it is not difficult, it affords control of hole size, and its yield is comparatively good. In this study, the mechanisms of hole generation and film formation were uncovered by means of in situ microscopy at medium working distance, super-VHS video recording and a high-speed motion analyzer, SEM and TEM. Clean microscope slides were treated with Amine 105 (Kao-Atlas Co. Japan) to make the surface hydrophobic. A slide was then immersed in liquid nitrogen and exposed for 3 to 6 seconds to air with relative humidity of 30 to 60%.

First temporal and spatial quantification of single-shot electrohydraulic lithotripsy in vitro.

Single electrohydraulic lithotripsy (EHL) discharges from a human ureter were analyzed with a mechanical high-speed motion analysis camera. We found a cavitation bubble, at 650 mJ, 4-11 mm in size, with a lifetime of 400-500 microseconds. Varying sizes and lifetimes were found using single-shot analysis, as well as in different shot-sequences. This supports similar observations by recent investigations of cavitation bubble size with high-shutter-speed videofilm, which have depicted events at shutter speeds of 4000/s, i.e., an approximate exposure time of 250 microseconds. Due to the occurrence of high-voltage interference from the EHL high-voltage generator, no other technical electronic event timing equipment has so far been available capable of mechanical high-speed film motion analysis, while at the same time avoiding high-voltage interference.

Kinematic and Kinetic Comparison between Baseball Pitching and Football Passing

Kinematic and kinetic aspects of baseball pitching and football passing were compared. Twenty-six high school and collegiate pitchers and 26 high school and collegiate quarterbacks were analyzed using three-dimensional high-speed motion analysis. Although maximum shoulder external rotation occurred earlier for quarterbacks, maximum angular velocity of pelvis rotation, upper torso rotation, elbow extension, and shoulder internal rotation occurred earlier and achieved greater magnitude for pitchers. Quarterbacks had shorter strides and stood more erect at ball release. During arm cocking, quarterbacks demonstrated greater elbow flexion and shoulder horizontal adduction. To decelerate the arm, pitchers generated greater compressive force at the elbow and greater compressive force and adduction torque at the shoulder. These results may help explain differences in performance and injury rates between the two sports.

Experimental Motion Analysis of Radially Rotating Beams Using High-Speed Camera and Motion Analyzer

Although strain gauges can be attached to a system for vibration analysis, wires connected to the strain gauges may disturb the system and affect the accuracy of the strain measurement. As an alternative, this work presents the use of a high-speed camera combined with a motion analyzer to study the motion of rotating flexible beams. One end of the beam is rigidly connected to a motor, while the other end is free. White stickers placed on selected points on a given beam are the reference points in a digitization process. The modes of the vibrating beams can be filmed and analyzed. The vibration parameters, such as deflection and frequency, can be obtained by using a film motion analyzer. The results show that the beam does not behave in a clamped-free or a pinned-free fashion, but instead occurs at an intermediate boundary between these two classical conditions.

Experimental Motion Analysis of Radially Rotating Beams Using High-Speed Camera and Motion Analyzer

Although strain gauges can be attached to a system for vibration analysis, wires connected to the strain gauges may disturb the system and affect the accuracy of the strain measurement. As an alternative, this work presents the use of a high-speed camera combined with a motion analyzer to study the motion of rotating flexible beams. One end of the beam is rigidly connected to a motor, while the other end is free. White stickers placed on selected points on a given beam are the reference points in a digitization process. The modes of the vibrating beams can be filmed and analyzed. The vibration parameters, such as deflection and frequency, can be obtained by using a film motion analyzer. The results show that the beam does not behave in a clamped-free or a pinned-free fashion, but instead occurs at an intermediate boundary between these two classical conditions.