scholarly journals Approximating displacement with the body velocity integral

2009 ◽  
Author(s):  
R. L. Hatton ◽  
H. Choset
Keyword(s):  
The Body ◽  
Body Velocity

Kinematic Analysis of Olympic Hurdle Performance: Women's 100 Meters

1985 ◽  
Vol 1 (2) ◽  
pp. 163-173 ◽  
Author(s):  
Ralph Mann ◽  
John Herman
Keyword(s):  
Elite Athlete ◽  
Olympic Games ◽  
Lower Leg ◽  
The Body ◽  
Performance Variables ◽  
Body Velocity ◽  
The Difference ◽  
Foot Position ◽  
Support Time ◽  
Leg Position

Selected kinematic variables in the performance of the Gold and Silver medalists and the eighth-place finisher in the women's 100-meter hurdles final at the 1984 Summer Olympic Games were investigated. Cinematographic records were obtained for all track hurdling events at the Games, with the 100-meter hurdle performers singled out for initial analysis. In this race, sagittal view filming records (100 fps) were collected at the 9th hurdle of the performance. Computer generated analysis variables included both direct performance variables (body velocity, support time, etc.) and body kinematics (upper leg position, lower leg velocity, etc.) that have previously been utilized in the analysis of elite athlete hurdlers. The difference in place finish was related to the performance variables body horizontal velocity (direct), vertical velocity (indirect), and support time (indirect). The critical body kinematics variables related to success included upper and lower leg velocity during support into and off the hurdle (direct), relative horizontal foot position (to the body) at touchdown into and off the hurdle (indirect), and relative horizontal foot velocity (to the body) at touchdown into the hurdle.

Stabilization of gaze during circular locomotion in darkness. II. Contribution of velocity storage to compensatory eye and head nystagmus in the running monkey

1992 ◽  
Vol 67 (5) ◽  
pp. 1158-1170 ◽  
Author(s):  
D. Solomon ◽  
B. Cohen
Keyword(s):  
Time Constant ◽  
Beat Frequency ◽  
Maximum Velocity ◽  
The Body ◽  
Head Movements ◽  
Velocity Storage ◽  
Gait Velocity ◽  
Slow Phase ◽  
Eccentric Rotation ◽  
Body Velocity

1. Yaw eye in head (Eh) and head on body velocities (Hb) were measured in two monkeys that ran around the perimeter of a circular platform in darkness. The platform was stationary or could be counterrotated to reduce body velocity in space (Bs) while increasing gait velocity on the platform (Bp). The animals were also rotated while seated in a primate chair at eccentric locations to provide linear and angular accelerations similar to those experienced while running. 2. Both animals had head and eye nystagmus while running in darkness during which slow phase gaze velocity on the body (Gb) partially compensated for body velocity in space (Bs). The eyes, driven by the vestibuloocular reflex (VOR), supplied high-frequency characteristics, bringing Gb up to compensatory levels at the beginning and end of the slow phases. The head provided substantial gaze compensation during the slow phases, probably through the vestibulocollic reflex (VCR). Synchronous eye and head quick phases moved gaze in the direction of running. Head movements occurred consistently only when animals were running. This indicates that active body and limb motion may be essential for inducing the head-eye gaze synergy. 3. Gaze compensation was good when running in both directions in one animal and in one direction in the other animal. The animals had long VOR time constants in these directions. The VOR time constant was short to one side in one animal, and it had poor gaze compensation in this direction. Postlocomotory nystagmus was weaker after running in directions with a long VOR time constant than when the animals were passively rotated in darkness. We infer that velocity storage in the vestibular system had been activated to produce continuous Eh and Hb during running and to counteract postrotatory afterresponses. 4. Continuous compensatory gaze nystagmus was not produced by passive eccentric rotation with the head stabilized or free. This indicates that an aspect of active locomotion, most likely somatosensory feedback, was responsible for activating velocity storage. 5. Nystagmus was compared when an animal ran in darkness and in light. the beat frequency of eye and head nystagmus was lower, and the quick phases were larger in darkness. The duration of head and eye quick phases covaried. Eye quick phases were larger when animals ran in darkness than when they were passively rotated. The maximum velocity and duration of eye quick phases were the same in both conditions. 6. The platform was counterrotated under one monkey in darkness while it ran in the direction of its long vestibular time constant.(ABSTRACT TRUNCATED AT 400 WORDS)

A Velocity Metric for Rigid-Body Planar Motion

2010 ◽  
Author(s):  
Joseph M. Schimmels ◽  
Luis E. Criales
Keyword(s):  
Rigid Body ◽  
Average Distance ◽  
The Body ◽  
Body Motion ◽  
Length Scale ◽  
Translational Velocity ◽  
Body Velocity ◽  
Assembly Problem ◽  
Instantaneous Center ◽  
Selection Of

A planar rigid-body velocity metric based on the instantaneous velocity of all particles that constitute a rigid body is developed. A measure based on the discrepancy in the translational velocity at each particle for two different planar twists is introduced. The calculation of the measure is simplified to the calculation of the product of: 1) the discrepancy in angular velocity, and 2) the average distance of the body from the instantaneous center associated with the twist discrepancy. It is shown that this measure satisfies the mathematical requirements of a metric and is physically consistent. It does not depend on either the selection of length scale or the frames used to describe the body motion. Although the metric does depend on body geometry, it can be calculated efficiently using body decomposition. An example demonstrating the application of the metric to an assembly problem is presented.

scholarly journals Velocity measurements in regions of upstream influence of a body in aligned-fields MHD flow

1971 ◽  
Vol 50 (2) ◽  
pp. 209-231 ◽  
Author(s):  
Bruce M. Lake
Keyword(s):  
Uniform Magnetic Field ◽  
Major Part ◽  
Free Stream ◽  
Mhd Flow ◽  
The Body ◽  
Velocity Measurements ◽  
Flow Disturbance ◽  
Fixed Distance ◽  
Body Velocity ◽  
Axis Of Symmetry

Experiments are described in which velocities were measured ahead of a semi-infinite Rankine body moving parallel to a uniform magnetic field in a conducting fluid. The flow disturbance in front of the body is found to increase in length as N½, where N is the interaction parameter. In most of the experiments this parameter was varied from 4 to about 50. Measurements made along the axis of symmetry in the flow show that there is a relatively short region of stagnant fluid directly ahead of the body. The major part of the disturbance is found to consist of a much longer region in which the flow undergoes transition from conditions in the free stream to conditions near the body. Velocity profiles across the flow in this region show that for increased N, at a fixed distance ahead of the body, the velocity defect increases and the disturbance becomes more confined radially. Although the radial gradients in the flow increase with N, they are found to be much smaller than would be expected in a flow containing thin current layers. A physical model of the flow which has currents and pressures consistent with these results is discussed.

Determination of First and Second Order Instant Screw Parameters from Landmark Trajectories

1992 ◽  
Vol 114 (2) ◽  
pp. 274-282 ◽  
Author(s):  
H. J. Sommer
Keyword(s):  
Least Squares ◽  
Weighted Least Squares ◽  
Angular Acceleration ◽  
Second Order ◽  
The Body ◽  
Least Squares Estimators ◽  
Linear Relationships ◽  
Count Distribution ◽  
Body Velocity ◽  
Instant Screw Axis

Least squares methods were developed to determine instant screw axis (ISA) and angular acceleration axis (AAA) parameters in experimental and analytical studies. The algorithms provide linear relationships for rigid body velocity and acceleration descriptors based on position, velocity, and acceleration data for individual points on the body. Weighted least squares estimators are presented for statistical weighting on individual landmarks as well as for variance weighting to reduce systematic measurement effects. The methods include instantaneous second order screw motion which describes differential geometry of screw axodes. Two spatial mechanism examples provide recommendations for landmark count, distribution, and placement.

scholarly journals Biomechanics of Frog Swimming: I. Estimation of the Propulsive Force Generated by Hymenochirus Boettgeri

1988 ◽  
Vol 138 (1) ◽  
pp. 399-411 ◽  
Author(s):  
JULIANNA M. GAL ◽  
R. W. BLAKE
Keyword(s):  
Recovery Phase ◽  
Added Mass ◽  
The Body ◽  
Force Balance ◽  
Upper And Lower Bounds ◽  
Power Stroke ◽  
Propulsive Force ◽  
Body Velocity ◽  
Hymenochirus Boettgeri ◽  
Single Sequence

Ciné films were used to study swimming in the frog, Hymenochirus boettgeri (Tornier) during near-vertical breathing excursions. The animals generally decelerated during hindlimb flexion (recovery phase) and accelerated throughout hindlimb extension (power phase). Body velocity patterns of frogs are distinct from those of other drag-based paddlers, such as angelfish and water boatman, where the body is accelerated and decelerated within the power stroke phase. The propulsive force, estimated for a single sequence from quasi-steady drag and inertial considerations, was positive throughout extension. The upper and lower bounds of this estimate were calculated by considering additional components of the force balance, including the net effect of gravity and buoyancy, and the longitudinal added mass forces associated with the body. Consideration of the force balance implies that simple drag-based propulsion may not be sufficient to explain the swimming patterns observed in frogs.

A Linear Algebra Approach to the Analysis of Rigid Body Velocity From Position and Velocity Data

1983 ◽  
Vol 105 (2) ◽  
pp. 92-95 ◽  
Author(s):  
A. J. Laub ◽  
G. R. Shiflett
Keyword(s):  
Angular Velocity ◽  
Rigid Body ◽  
Matrix Theory ◽  
The Body ◽  
Instantaneous Velocity ◽  
Body Motion ◽  
Translational Velocity ◽  
Velocity Data ◽  
Algebra Approach ◽  
Body Velocity

The instantaneous velocity of a rigid body in space is characterized by an angular and translational velocity. By representing the angular velocity as a matrix and the translational component as a vector the velocity of any point in the rigid body may be found if the position of the point and the parameters of the angular and translational velocities are known. Alternatively, the parameters of the rigid body velocity may be determined if the velocity and position of three points fixed in the body are known. In this paper, a new matrix-theory-based method is derived for determining the instantaneous velocity parameters of rigid body motion in terms of the velocity and position of three noncollinear points fixed in the body. The method is shown to possess certain advantages over traditional vectoral solutions to the same problem.

CFD-BASED SELF-PROPULSION SIMULATION FOR FROG SWIMMING

2014 ◽  
Vol 14 (06) ◽  
pp. 1440012 ◽  
Author(s):  
JIZHUANG FAN ◽  
WEI ZHANG ◽  
YANHE ZHU ◽  
JIE ZHAO
Keyword(s):  
Flow Field ◽  
Large Range ◽  
Hydrodynamic Forces ◽  
The Body ◽  
Joint Motion ◽  
Mechanism Analysis ◽  
Hydrodynamic Problem ◽  
Pressure Distributions ◽  
Body Velocity ◽  
Computational Fluid Dynamics Cfd

Mechanism analysis of frog swimming is an interesting subject in the field of biofluid mechanics and bionics. Computing the hydrodynamic forces acting on a frog is difficult due to its characteristics of explosive propulsion and large range of joint motion. To analyze the flow around the body and vortices in the wake, in this paper, the method based on Computational Fluid Dynamics (CFD) was utilized to solve the velocity and pressure distributions in the flow field and on the frog. The hydrodynamic problem during the propulsive phase of a frog, Xenopus laevis, was calculated using the CFD software FLUENT. A self-propulsion simulation was performed which computed the body velocity from the joint trajectory input and CFD solved the hydrodynamic forces, and visual CFD results of the hydrodynamic forces and flow field structures were obtained.

scholarly journals A Vehicle-Model-Aided Navigation Reconstruction Method for a Multicopter during a GPS Outage

Electronics ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 528
Author(s):  
Yifan Xu ◽  
Qian Zhang ◽  
Jingjuan Zhang ◽  
Xueyun Wang ◽  
Zelong Yu
Keyword(s):  
Dynamic Model ◽  
Reconstruction Algorithm ◽  
The Body ◽  
Model Parameters ◽  
Reconstruction Method ◽  
Navigation Systems ◽  
Integrated Navigation ◽  
Vehicle Model ◽  
Body Velocity ◽  
Navigation Accuracy

The integrated navigation of inertial navigation systems (INS) and the Global Positioning System (GPS) is essential for small unmanned aerial vehicles (UAVs) such as multicopters, providing steady and accurate position, velocity, and attitude information. Nevertheless, decreasing navigation accuracy is a serious threat to flight safety due to the long-term drift error of INS in the absence of GPS measurements. To bridge the GPS outage for multicopters, this paper proposes a novel navigation reconstruction method for small multicopters, which combines the vehicle dynamic model and micro-electro-mechanical system (MEMS) sensors. Firstly, an induced drag model is introduced into the dynamic model of the vehicle, and an efficient online parameter identification method is designed to estimate the model parameters quickly. Secondly, the body velocity can be calculated from the vehicle model and accelerometer measurement. In addition, the nongravitational acceleration estimated from body velocity and radar height are utilized to yield a more accurate attitude estimate. Fusing the information of the attitude, body velocity, magnetic heading, and radar height, a navigation system based on an error-state Kalman filter is reconstructed. Then, an adaptive measurement covariance algorithm based on a fuzzy logic system is designed to reduce the weight due to the disturbed acceleration. Finally, the hardware-in-loop experiment is carried out to demonstrate the effectiveness of the proposed method. Simulation results show that the proposed navigation reconstruction algorithm aided by the vehicle model can significantly improve navigation accuracy during a GPS outage.

A Meshless Boundary Element Method for Simulating Slamming in Context of Generalized Wagner

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Jens B. Helmers ◽  
Geir Skeie
Keyword(s):  
Free Surface ◽  
Boundary Element Method ◽  
Boundary Element ◽  
The Body ◽  
Body Contour ◽  
Analytical Functions ◽  
Smooth Body ◽  
Body Velocity ◽  
Body Location ◽  
Element Method

A boundary element method (BEM) designed for solving the symmetric generalized Wagner formulation is presented. The flow field is parameterized with analytical functions and can describe the kinematics at any free surface or body location using a small set of parameters obtained from a collocation scheme. The method is fast and robust for all deadrise angles, even for flat plate impacts where classical BEMs usually fail. The method is easy to implement and is easy to apply. Given a smooth body contour the only additional input is the requested accuracy. There is no mesh involved. When solving the temporal problem, we exploit the analytical distribution of free surface velocities and apply an integral equation formalism consistent with the Wagner formulation. The output of the spatial and temporal scheme is a set of functions and parameters suitable for fast computation of the complete kinematics for any impact trajectory given the position of the keel and the body velocity. The method is developed to be combined with seakeeping programs for statistical impact and whipping assessment.

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