A Passive Jumping Mechanism

2019 ◽  
Author(s):  
Phanindra Tallapragada ◽  
Jake Buzhardt ◽  
Robert Seney
Keyword(s):  
Body Length ◽  
Center Of Mass ◽  
Jump Height ◽  
Normal Reaction ◽  
Inclined Plane ◽  
Geometric Center

Abstract In this paper we present a novel unactuated mechanism that utilizes gravity to jump. The passive jumper is a hoop whose center of mass does not coincide with its geometric center. When the hoop rolls down an inclined plane, the center of mass of the hoop moves along a cycloid. As the hoop gains speed moving down the inclined plane, the normal reaction between the hoop and the plane becomes insufficient to ensure contact between the hoop and the plane. This allows the hoop to ‘jump’. Experiments and analysis show that such a jump can be significant, with the jump height from the plane being as high as one body length (diameter) of the hoop. The mechanics of the passive jumping hoop powered by gravity investigated in this paper can inspire the design of actuated jumping robots that can both roll and jump.

Pelvic Kinematic Method for Determining Vertical Jump Height

2010 ◽  
Vol 26 (4) ◽  
pp. 508-511 ◽  
Author(s):  
Loren Z.F. Chiu ◽  
George J. Salem
Keyword(s):  
Vertical Jump ◽  
Center Of Mass ◽  
Reaction Force ◽  
Jump Height ◽  
Impulse Method ◽  
Vertical Jump Height ◽  
Reconstruction Methods ◽  
Kinematic Method ◽  
Mass Displacement ◽  
Vertical Jumps

Sacral marker and pelvis reconstruction methods have been proposed to approximate total body center of mass during relatively low intensity gait and hopping tasks, but not during a maximum effort vertical jumping task. In this study, center of mass displacement was calculated using the pelvic kinematic method and compared with center of mass displacement using the ground-reaction force-impulse method, in experienced athletes (n= 13) performing restricted countermovement vertical jumps. Maximal vertical jumps were performed in a biomechanics laboratory, with data collected using an 8-camera motion analysis system and two force platforms. The pelvis center of mass was reconstructed from retro-reflective markers placed on the pelvis. Jump height was determined from the peak height of the pelvis center of mass minus the standing height. Strong linear relationships were observed between the pelvic kinematic and impulse methods (R2= .86;p< .01). The pelvic kinematic method underestimated jump height versus the impulse method, however, the difference was small (CV = 4.34%). This investigation demonstrates concurrent validity for the pelvic kinematic method to determine vertical jump height.

scholarly journals 2D Video Analysis System to Analyze the Performance Model of Figure Roller Skating: A Pilot Study

Proceedings ◽  
2020 ◽  
Vol 49 (1) ◽  
pp. 155
Author(s):  
Cristian Romagnoli ◽  
Vincenzo Bonaiuto ◽  
Giorgio Gatta ◽  
Naomi Romagnoli ◽  
Anas Alashram ◽  
...  
Keyword(s):  
Video Analysis ◽  
Center Of Mass ◽  
Performance Model ◽  
Biomechanical Analysis ◽  
Knee Joints ◽  
Jump Height ◽  
Compensatory Strategy ◽  
Medium Level ◽  
Analysis System ◽  
High Level

Figure roller skating is a discipline composed of various movements which involve jumps, artistic figures and spins in a seamless program which has both technical and shapely difficult. A biomechanical analysis of a double salchow was performed using a 2D video analysis of one European and in two Italian roller skaters. On average, the high level (HL) roller skater showed a horizontal velocity of the center of mass higher than the average, especially in the prop stage, whereas the medium level (ML) and low level (LL) athletes reduced their velocity significantly. The spin angular velocity of the ML and LL skaters was always higher than of the HL. This phenomenon would seem to be a compensatory strategy for a lower jump height, with a reduced trunk-thigh angle and less thigh lever arm (coxo-femur/knee joints) during the take-off and landing phases of the double salchow jump.

scholarly journals Effect of Landing Posture on Jump Height Calculated from Flight Time

2020 ◽  
Vol 10 (3) ◽  
pp. 776 ◽  
Author(s):  
Daichi Yamashita ◽  
Munenori Murata ◽  
Yuki Inaba
Keyword(s):  
Vertical Velocity ◽  
Vertical Jump ◽  
Center Of Mass ◽  
Reaction Force ◽  
Three Dimensional ◽  
Flight Time ◽  
Whole Body ◽  
Anatomical Landmarks ◽  
Jump Height ◽  
Postural Changes

Flight time is widely used to calculate jump height because of its simple and inexpensive application. However, this method is known to give different results than the calculation from vertical velocity at takeoff. The purpose of this study is to quantify the effect of postural changes between takeoff and landing on the jump height from flight time. Twenty-seven participants performed three vertical jumps with arm swing. Three-dimensional coordinates of anatomical landmarks and the ground reaction force were analyzed. Two methods of calculating jump height were used: (1) the vertical velocity of the whole-body center of mass (COMwb) at takeoff and (2) flight time. The jump height from flight time was overestimated by 0.025 m compared to the jump height from the takeoff velocity (p < 0.05) due to the lower COMwb height at landing by −0.053 m (p < 0.05). The postural changes in foot, shank, and arm segments mainly contributed to decreasing the COMwb height (−0.025, −0.014, and −0.017 m, respectively). The flight time method is reliable and had low intra-participant variability, but it cannot be recommended for a vertical jump when comparing with others (such as at tryouts) because of the potential “cheating” effect of differences in landing posture.

scholarly journals Larger Countermovement Increases the Jump Height of Countermovement Jump

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 131 ◽  
Author(s):  
Alberto Sánchez-Sixto ◽  
Andrew Harrison ◽  
Pablo Floría
Keyword(s):  
Center Of Mass ◽  
The Self ◽  
Jump Height ◽  
Simulation Studies ◽  
Countermovement Jump ◽  
Jump Performance ◽  
Force Application ◽  
Mass Displacement ◽  
Biomechanical Parameters

Simulation studies show that jump performance can be improved by increasing the depth of countermovement. The purpose of this study was to determine how modifications to the depth of countermovement lead to changes in jump height and the biomechanical parameters related to center of mass displacement and force application. Twenty-nine competitive males participated in this investigation, performing nine countermovement jumps using a self-selected, a deep, and a shallow crouch position. Jump height and relative net vertical impulse were greater when using a deeper crouch position, compared to the self-selected position. Force application variables did not report differences, when the deeper countermovement was compared to the self-selected countermovement; although, the shallower countermovement showed higher values in force application parameters. The deeper countermovement jumps achieved higher velocities of the center of mass than the self-selected jumps, while shallower jumps produced lower velocities than the self-selected jumps. The results of this investigation were consistent with simulation studies, showing that deep countermovements increase net vertical impulse, leading to a higher jump height. In addition, the maximum downward velocity was higher, when the crouch position was deeper. Conversely, force-applied variables did not change when jump performance was increased.

scholarly journals A Mixed-Methods Approach to Evaluating the Internal Validity of the Reactive Strength Index

Sports ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 157
Author(s):  
Talin Louder ◽  
Brennan J. Thompson ◽  
Nile Banks ◽  
Eadric Bressel
Keyword(s):  
Mixed Methods ◽  
Center Of Mass ◽  
Internal Validity ◽  
Conventional Approach ◽  
Whole Body ◽  
Jump Height ◽  
Drop Height ◽  
Strength Index ◽  
Mixed Methods Approach ◽  
Body Center

The reactive capacity of the muscle-tendon complex is commonly assessed using the reactive strength index (RSI). Conventionally, the RSI is a ratio of rebound jump height to ground contact time in depth jumping. Several assumptions regarding the linear mechanics acting through the whole-body center of gravity may threaten the internal validity of computation and interpretation of RSI scores. First, it is common for rebound jump height to be predicted from rebound jump flight time. This assumes that the angular positioning of body segments is equivalent at the time instances of rebound jump take-off and landing. Prior literature supports a mixed-methods approach for computing the RSI that is void of this assumption. The mixed-methods approach gives a more valid estimation of rebound jump height. In this approach, rebound jump height is estimated from rebound jump take-off velocity of the whole-body center of mass. This is accomplished by subtracting an estimate of impact velocity, acquired using videography, from change in whole-body center of mass velocity estimated from integrated vertical ground reaction force data. Second, it is often assumed that vertical displacement of the whole-body center of mass during the drop phase of the depth jump is predicted perfectly from the height of the platform used to perform the drop. This assumption may affect the internal validity of comparing RSI scores across individuals and within individuals performing depth jumps from varied heights. The purpose of the present study was to investigate the internal validity of RSI scores computed using the conventional approach and impact velocity variability, which may affect the interpretation of RSI scores. Seventy physically active young adults performed depth jumps from drop heights of 0.51, 0.66, and 0.81 m. RSI was computed using the conventional approach and a mixed-methods approach featuring the use of 2-dimensional videography, body segment parameters, and force platform dynamometry. The two computational methods were compared using linear regression performed on data from each drop height. In addition, a 2 (computational method) by 3 (drop height) Analysis of Variance (ANOVA) was performed to evaluate for main effects and interactions in RSI data. Multiple one sample t-tests were performed to compare estimated and theoretical impact velocities. The ANOVA revealed no main effect or interactions between computational approaches (p = 0.467–0.938). Linear regression revealed moderately strong associations between RSI scores computed using the conventional and mixed-methods approaches (R2 = 0.685–0.741). Moreover, linear regressions revealed that the conventional approach tends to overestimate the mixed methods approach for RSI scores below 1.0 and underestimate the mixed methods approach for RSI scores above 1.0. Lastly, estimated impact velocities were observed to be as much as 13% lower versus theoretical (p < 0.001). Researchers with access to motion capture and force platform technology may consider using a mixed-methods approach for computing the RSI, which likely maximizes the internal validity of scores. In addition, results suggest for practitioners to practice caution when comparing conventional RSI scores across individuals.

The Dynamic Analyses of the Eccentric Cylinder Moving on the Inclined Plane

2013 ◽  
Vol 397-400 ◽  
pp. 330-334
Author(s):  
Juan Wei ◽  
Wen Pu Shi
Keyword(s):  
Rigid Body ◽  
Center Of Mass ◽  
Normal Pressure ◽  
Mass Center ◽  
Dynamic Problems ◽  
Inclined Plane ◽  
Dynamic Analyses ◽  
Eccentric Cylinder ◽  
The Moment ◽  
Theoretical Analyses

The conservation principle of energy and the mass center movement theorem of rigid body and the moment of momentum theorem relative to the center of mass were used to study the dynamic problems of the eccentric cylinder on the inclined plane. The mass center velocity and the acceleration of the cylinder and the normal pressure and the friction force of the cylinder acting on the inclined plane and etc are given. An example is introduced to show the variations of the physical variants, and the numerical results agree with the theoretical analyses.

scholarly journals Efecto de modificar la profundidad y velocidad del contramovimiento durante el salto vertical (Effects of countermovement depth and velocity modifications during the vertical jump)

Retos ◽  
2018 ◽  
pp. 287-290
Author(s):  
Alberto Sánchez-Sixto ◽  
Julio López-Álvarez ◽  
Pablo Floría
Keyword(s):  
Vertical Jump ◽  
Center Of Mass ◽  
Jump Height ◽  
Downward Movement ◽  
Movement Velocity ◽  
Jump Performance ◽  
Mass Displacement ◽  
Force Velocity ◽  
Initial Force ◽  
Propulsion Phase

Objetivo. El objetivo de la presente investigación fue evaluar el efecto de modificar la profundidad y la velocidad del contramovimiento en el salto vertical. Material y método. Once jugadores de deportes colectivos participaron en este estudio y realizaron 9 saltos con contramovimiento: 3 en los que ellos seleccionaban la velocidad y profundidad del contramovimiento (CMJ), 3 en los que incrementaban la profundidad del contramovimiento y seleccionaban libremente su velocidad (CMJP) y 3 en los que incrementaban la profundidad y velocidad del contramovimiento (CMJPR). La altura máxima, el tiempo, la fuerza, la velocidad y el desplazamiento del centro de masas fueron calculadas durante la fase de contramovimiento y de propulsión. Resultados. No se encontraron mejoras substanciales entre ninguno de los tres tipos de salto llevados a cabo por los participantes. En el CMJPR se consiguió incrementar substancialmente la fuerza máxima y la fuerza inicial con respecto al CMJ. En el CMJP todas las variables de fuerza fueron inferiores que en el CMJ. El tiempo de la fase de contramovimiento fue inferior en el CMJ en comparación con el CMJP, no existiendo diferencias con el CMJPR. El tiempo de la fase de propulsión fue inferior en el CMJ en comparación con los otros dos saltos. Conclusión. Incrementos en la profundidad del contramovimiento del CMJ a través de una orden simple, no fueron capaces de conseguir un aumento del rendimiento en el salto vertical en la presente investigación.Abstract. Purpose. The aim of the study was to evaluate the effects of countermovement depth and velocity modification in the vertical jump. Materials and methods. Eleven team sport players participated in this investigation performing nine countermovement jumps: 3 self-selected countermovement jumps (CMJ), 3 countermovement jumps with a deeper countermovement depth (CMJP) and 3 countermovement jumps with a deeper countermovement depth and a higher downward movement velocity (CMJPR). Jump height, time, force, velocity and center of mass displacement were measured during the countermovement and the propulsion phase. Results. No differences in jump height were found between the three types of jump. CMJPR showed a substantial increase in maximum force and initial force in comparison with the CMJ. CMJP force variables were lower than the values obtained during the CMJ. The time of the countermovement phase was lower in the CMJ in comparison with the CMJP, and no differences were found between the CMJ and the CMJPR. The time of the propulsion phase was lower than the other countermovement jumps performed. Conclusion. Increases in the countermovement depth of the CMJ through a simple instruction did not increase the vertical jump performance in the present investigation.

scholarly journals Qualitative Analysis of the Dynamics of a Trailed Wheeled Vehicle with Periodic Excitation

2021 ◽  
Vol 17 (4) ◽  
pp. 437-451
Author(s):  
E. A. Mikishanina ◽  
Keyword(s):  
Qualitative Analysis ◽  
Equations Of Motion ◽  
Center Of Mass ◽  
Uniform Motion ◽  
Periodic Excitation ◽  
Lagrange Equations ◽  
Wheel Pair ◽  
Wheeled Vehicle ◽  
Geometric Center ◽  
Angular Velocities

This article examines the dynamics of the movement of a wheeled vehicle consisting of two links (trolleys). The trolleys are articulated by a frame. One wheel pair is fixed on each link. Periodic excitation is created in the system due to the movement of a pair of masses along the axis of the first trolley. The center of mass of the second link coincides with the geometric center of the wheelset. The center of mass of the first link can be shifted along the axis relative to the geometric center of the wheelset. The movement of point masses does not change the center of mass of the trolley itself. Based on the joint solution of the Lagrange equations of motion with undetermined multipliers and time derivatives of nonholonomic coupling equations, a reduced system of differential equations is obtained, which is generally nonautonomous. A qualitative analysis of the dynamics of the system is carried out in the absence of periodic excitation and in the presence of periodic excitation. The article proves the boundedness of the solutions of the system under study, which gives the boundedness of the linear and angular velocities of the driving link of the articulated wheeled vehicle. Based on the numerical solution of the equations of motion, graphs of the desired mechanical parameters and the trajectory of motion are constructed. In the case of an unbiased center of mass, the solutions of the system can be periodic, quasi-periodic and asymptotic. In the case of a displaced center of mass, the system has asymptotic dynamics and the mobile transport system goes into rectilinear uniform motion.

scholarly journals Children balance theories and evidence in exploration, explanation, and learning.

2018 ◽  
Author(s):  
Elizabeth Bonawitz ◽  
Laura Schulz ◽  
Tessa J.P. van Schijndel ◽  
Daniel Friel
Keyword(s):  
Center Of Mass ◽  
Auxiliary Variable ◽  
Auxiliary Variables ◽  
Novelty Preference ◽  
Prior Beliefs ◽  
Children’S Learning ◽  
Geometric Center ◽  
Children's Learning

We look at the effect of evidence and prior beliefs on exploration, explanation and learning. In Experiment 1, we tested children both with and without differential prior beliefs about balance relationships (Center Theorists, mean: 82 months; Mass Theorists, mean: 89 months; No Theory children, mean: 62 months). Center and Mass Theory children who observed identical evidence explored the block differently depending on their beliefs. When the block was balanced at its geometric center (belief-violating to a Mass Theorist, but belief-consistent to a Center Theorist), Mass Theory children explored the block more, and Center Theory children showed the standard novelty preference; when the block was balanced at the center of mass, the pattern of results reversed. The No Theory children showed a novelty preference regardless of evidence. In Experiments 2 and 3, we follow-up on these findings, showing that both Mass and Center Theorists selectively and differentially appeal to auxiliary variables (e.g., a magnet) to explain evidence only when their beliefs are violated. We also show that children use the data to revise their predictions in the absence of the explanatory auxiliary variable but not in its presence. Taken together, these results suggest that children’s learning is at once conservative and flexible; children integrate evidence, prior beliefs, and competing causal hypotheses in their exploration, explanation, and learning.

The Center of Mass Influences Normal Attentional Orienting

1994 ◽  
Author(s):  
Marcia Grabowecky ◽  
Lynn C. Robertson ◽  
Anne Treisman
Keyword(s):  
Center Of Mass ◽  
Attentional Orienting
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