The Effect of Body Position and Number of Supports on Wall Reaction Forces in Rock Climbing

1997 ◽  
Vol 13 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Franck Quaine ◽  
Luc Martin ◽  
Jean-Pierre Blanchi
Keyword(s):  
Body Weight ◽  
Contact Force ◽  
Body Position ◽  
Three Dimensional ◽  
Rock Climbing ◽  
Contact Forces ◽  
Vertical Posture ◽  
Reaction Forces ◽  
Force Data ◽  
Lower Contact

This manuscript describes three-dimensional force data collected during postural shifts performed by individuals simulating rock-climbing skills. Starting from a quadrupedal vertical posture, 6 expert climbers had to release their right-hand holds and maintain the tripedal posture for a few seconds. The vertical and contact forces (lateral and anteroposterior forces) applied on the holds were analyzed in two positions: an “imposed” position (the trunk far from the supporting wall) and an “optimized” position (the trunk close to the wall and lower contact forces at the holds). The tripedal postures performed in the two positions were achieved by the same pattern of vertical and contact forces exerted by the limbs on the holds. In the optimized position, the transfer of the forces was less extensive than in the imposed position, so that the forces were exerted primarily on the ipsilateral hold. Moreover, a link between the contact force values and the couple due to body weight with respect to the feet was shown.

Robust contact force estimation for robot manipulators in three-dimensional space

2006 ◽  
Vol 220 (9) ◽  
pp. 1317-1327 ◽  
Author(s):  
J Jung ◽  
J Lee ◽  
K Huh
Keyword(s):  
Contact Force ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Robust Estimator ◽  
Force Sensors ◽  
Force Estimation ◽  
Estimation Algorithms

Information on contact forces in robot manipulators is indispensable for fast and accurate force control. Instead of expensive force sensors, estimation algorithms for contact forces have been widely developed. However, it is not easy to obtain the accurate values due to uncertainties. In this article, a new robust estimator is proposed to estimate three-dimensional contact forces acting on a three-link robot manipulator. The estimator is based on the extended Kalman filter (EKF) structure combined with a Lyapunov-based adaptation law for estimating the contact force. In contrast to the conventional EKF the new estimator is designed such that it is robust to the deterministic uncertainties such as the modelling error and the sensing bias. The performance of the proposed estimator is evaluated through simulations of a robot manipulator and demonstrates robustness in estimating the contact force. The estimation results show that it can be potentially used to replace the expensive force sensors in robot applications.

Assessment of Hindlimb Locomotor Strength in Spinal Cord Transected Rats through Animal-Robot Contact Force

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Jeff A. Nessler ◽  
Moustafa Moustafa-Bayoumi ◽  
Dalziel Soto ◽  
Jessica Duhon ◽  
Ryan Schmitt
Keyword(s):  
Spinal Cord ◽  
Body Weight ◽  
Weight Bearing ◽  
Contact Forces ◽  
Ground Reaction Forces ◽  
Locomotor Training ◽  
Robotic Device ◽  
Thoracic Spinal Cord ◽  
Cord Injury ◽  
Reaction Forces

Robotic locomotor training devices have gained popularity in recent years, yet little has been reported regarding contact forces experienced by the subject performing automated locomotor training, particularly in animal models of neurological injury. The purpose of this study was to develop a means for acquiring contact forces between a robotic device and a rodent model of spinal cord injury through instrumentation of a robotic gait training device (the rat stepper) with miniature force/torque sensors. Sensors were placed at each interface between the robot arm and animal’s hindlimb and underneath the stepping surface of both hindpaws (four sensors total). Twenty four female, Sprague-Dawley rats received mid-thoracic spinal cord transections as neonates and were included in the study. Of these 24 animals, training began for 18 animals at 21 days of age and continued for four weeks at five min/day, five days/week. The remaining six animals were untrained. Animal-robot contact forces were acquired for trained animals weekly and untrained animals every two weeks while stepping in the robotic device with both 60 and 90% of their body weight supported (BWS). Animals that received training significantly increased the number of weight supported steps over the four week training period. Analysis of raw contact forces revealed significant increases in forward swing and ground reaction forces during this time, and multiple aspects of animal-robot contact forces were significantly correlated with weight bearing stepping. However, when contact forces were normalized to animal body weight, these increasing trends were no longer present. Comparison of trained and untrained animals revealed significant differences in normalized ground reaction forces (both horizontal and vertical) and normalized forward swing force. Finally, both forward swing and ground reaction forces were significantly reduced at 90% BWS when compared to the 60% condition. These results suggest that measurement of animal-robot contact forces using the instrumented rat stepper can provide a sensitive and reliable measure of hindlimb locomotor strength and control of flexor and extensor muscle activity in neurologically impaired animals. Additionally, these measures may be useful as a means to quantify training intensity or dose-related functional outcomes of automated training.

Optimal Contact Force Distribution for Multi-Limbed Robots

2005 ◽  
Vol 128 (3) ◽  
pp. 566-573 ◽  
Author(s):  
Dennis W. Hong ◽  
Raymond J. Cipra
Keyword(s):  
Contact Force ◽  
Dimensional Space ◽  
Contact Point ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Solution Space ◽  
Contact Forces ◽  
Force Distribution ◽  
New Strategy ◽  
Contact Force Distribution

One of the inherent problems of multi-limbed mobile robotic systems is the problem of multi-contact force distribution; the contact forces and moments at the feet required to support it and those required by its tasks are indeterminate. A new strategy for choosing an optimal solution for the contact force distribution of multi-limbed robots with three feet in contact with the environment in three-dimensional space is presented. The incremental strategy of opening up the friction cones is aided by using the “force space graph” which indicates where the solution is positioned in the solution space to give insight into the quality of the chosen solution and to provide robustness against disturbances. The “margin against slip with contact point priority” approach is also presented which finds an optimal solution with different priorities given to each foot contact point. Examples are presented to illustrate certain aspects of the method and ideas for other optimization criteria are discussed.

scholarly journals Effects of Differential Subgrade Settlement on Slab Track Deformation Based on a DEM-FDM Coupled Approach

2021 ◽  
Vol 11 (4) ◽  
pp. 1384
Author(s):  
Xuhao Cui ◽  
Rui Zhou ◽  
Gaoran Guo ◽  
Bowen Du ◽  
Hanlin Liu
Keyword(s):  
Contact Force ◽  
Three Dimensional ◽  
Coupled Model ◽  
Contact Forces ◽  
Railway Track ◽  
Slab Track ◽  
Maximum Value ◽  
Track System ◽  
Track Deformation ◽  
Maximum Contact

Slab track structures become deformed under the effects of differential subgrade settlement. According to the properties of the China Railway Track System (CRTS) II slab track on a subgrade, a three-dimensional (3D) coupled model based on both the discrete element method (DEM) and finite difference method (FDM) was developed. The slab track and subgrade were simulated using the FDM and DEM, respectively. The coupled model was verified. The deformation of the slab track and contact forces of gravel grains in the surface layer of the subgrade were studied under differential subgrade settlement. The effects of settlement wavelength, settlement amplitude, and other types of settlements were also discussed. The results demonstrate that the settlement amplitude and settlement wavelength of the subgrade have significant effects on track deformation. The deformation amplitude of the slab track increases nonlinearly with an increasing settlement amplitude of the subgrade. Increases in the settlement wavelength and amplitude of the subgrade significantly increase the maximum value of the contact force of the gravel grains in the subgrade. The maximum contact force of gravel grains near the boundaries of the settlement section can reach two to three times that of the unsettled condition, which makes it easy to accelerate the plastic settlement of the subgrade.

scholarly journals Design and Calibration of a Tri-Directional Contact Force Measurement System

2021 ◽  
Vol 11 (2) ◽  
pp. 877
Author(s):  
Rizwan Ahmed ◽  
Christian Maria Firrone ◽  
Stefano Zucca
Keyword(s):  
Contact Force ◽  
Measurement System ◽  
Force Measurement ◽  
Three Dimensional ◽  
Dynamic Contact ◽  
Forced Response ◽  
Contact Forces ◽  
Blade Vibration ◽  
Contact Models ◽  
Force Measurement System

In low pressure turbine stages, adjacent blades are coupled to each other at their tip by covers, called shrouds. Three-dimensional periodic contact forces at shrouds strongly affect the blade vibration level as energy is dissipated by friction. To validate contact models developed for the prediction of nonlinear forced response of shrouded blades, direct contact force measurement during dynamic tests is mandatory. In case of shrouded blades, the existing unidirectional and bi-directional contact force measurement methods need to be improved and extended to a tri-directional measurement of shroud contact forces for a comprehensive and more reliable validation of the shroud contact models. This demands an accurate and robust measurement solution that is compatible with the nature and orientation of the contact forces at blade shrouds. This study presents a cost effective and adaptable tri-directional force measurement system to measure static and dynamic contact forces simultaneously in three directions at blade shrouds during forced response tests. The system is based on three orthogonal force transducers connected to a reference block that will eventually be put in contact with the blade shroud in the test rig. A calibration process is outlined to define a decoupling matrix and its subsequent validation is demonstrated in order to evaluate the effectiveness of the measurement system to measure the actual contact forces acting on the contact.

Visualization of the Contact Force Solution Space for Multi-Limbed Robots

2005 ◽  
Vol 128 (1) ◽  
pp. 295-302 ◽  
Author(s):  
Dennis W. Hong ◽  
Raymond J. Cipra
Keyword(s):  
Contact Force ◽  
Dimensional Space ◽  
Contact Point ◽  
Three Dimensional ◽  
Solution Space ◽  
Entire Solution ◽  
Contact Forces ◽  
Static Equilibrium ◽  
Equilibrium Equations ◽  
Force Components

A new analytical method for determining, describing, and visualizing the solution space for the contact force distribution of multi-limbed robots with three feet in contact with the environment in three-dimensional space is presented. The foot contact forces are first resolved into strategically defined foot contact force components to decouple them, and then the static equilibrium equations are applied. Using the friction cone equation at each foot contact point, the problem is then transformed into a geometrical one. Using geometric properties of the friction cones and by simple manipulation of their conic sections, the entire solution space which satisfies the static equilibrium and friction constraints at each contact point can be found. Two representation schemes, the “force space graph” and the “solution volume representation,” are developed for describing and visualizing the solution space which gives an intuitive visual map of how well the solution space is formed for the given conditions of the system.

Characteristic Ground-Reaction Forces in Baseball Pitching

1998 ◽  
Vol 26 (1) ◽  
pp. 66-71 ◽  
Author(s):  
Bruce A. MacWilliams ◽  
Tony Choi ◽  
Mark K. Perezous ◽  
Edmund Y. S. Chao ◽  
Edward G. McFarland
Keyword(s):  
Body Weight ◽  
Lower Extremities ◽  
School Level ◽  
Clinical Impression ◽  
Ground Reaction Forces ◽  
High School Level ◽  
Overhand Throwing ◽  
Reaction Forces ◽  
Force Data ◽  
Throwing Motion

Overhand throwing requires contributions from and interaction between all limb segments. Most previous investigations have concentrated on the throwing arm itself, yet poor mechanics at the arm may originate in the lower extremities. Multicomponent ground-reaction forces of both the push-off and landing limbs were measured in six collegiate and one high school level baseball pitchers. Full body kinematics were simultaneously recorded to correlate phases in the pitching cycle with the force data. Pitchers were found to generate shear forces of 0.35 body weight in the direction of the pitch with the push-off leg and to resist forces of 0.72 body weight with the landing leg. Wrist velocity was found to correlate highly with increased leg drive. This study validates the clinical impression that the lower extremity is an important contributor to the throwing motion. Based on this study, strengthening of the lower extremities could be inferred to be important both to enhance performance and to avoid injury.

Correlation Between In Vivo Knee Contact Forces and External Measures During Gait

2012 ◽  
Author(s):  
Andrew J. Meyer ◽  
Darryl D. D’Lima ◽  
Scott A. Banks ◽  
David G. Lloyd ◽  
Thor F. Besier ◽  
...  
Keyword(s):  
Knee Osteoarthritis ◽  
Contact Force ◽  
Inverse Dynamics ◽  
Contact Forces ◽  
Clinical Environment ◽  
Total Knee ◽  
Surrogate Measures ◽  
Force Data ◽  
External Measure

Researchers have sought to explain the development and progression of knee osteoarthritis using in vivo estimates of knee contact forces. Unfortunately, it is not possible to measure knee contact forces in a clinical environment. Thus, studies often estimate knee contact forces using a variety of external measures. For example, inverse dynamics knee loads such as the adduction moment and superior force are frequently used as surrogate measures of medial and total knee contact force, respectively. Contraction of muscles spanning the knee is believed to increase knee contact force, and hence muscle electromyographic (EMG) signals are another external measure that may be indicative of internal contact force. The recent development of instrumented knee implants, such as the eTibia design [1], has provided access to in vivo knee contact force data during gait and other activities. However, few studies have correlated inverse dynamics loads, and none have correlated EMG signals, with total, medial, and lateral in vivo knee contact forces.

Ground Reaction Forces in the Triple Jump

1985 ◽  
Vol 1 (3) ◽  
pp. 233-239 ◽  
Author(s):  
Melvin R. Ramey ◽  
Keith R. Williams
Keyword(s):  
Body Weight ◽  
Ground Reaction Forces ◽  
Vertical Force ◽  
Mass Center ◽  
Considerable Variability ◽  
Distance Running ◽  
Reaction Forces ◽  
Single Force ◽  
Two Peaks ◽  
Force Data

Ground reaction forces were obtained for the three phases of the triple jump for four collegiate triple jumpers, two men and two women. A single force platform was used, which thereby required the subjects to execute three separate jumps to produce a single triple jump record. The vertical force records for each phase showed two peaks having magnitudes in the range of 7 to 12 times body weight (BW) and 3.3 to 5 BW, respectively. These magnitudes are substantially higher than has been reported by others for distance running, sprinting, and in some cases other jumps. The maximum horizontal forces act to decrease the velocity of the mass center, but to different degrees for the different subjects. The data show that for any phase of the jump there is considerable variability in the timing and magnitudes of the force records among the different subjects although general patterns are similar. The results suggest that the use of mean force data from a number of subjects may conceal important differences between the way individuals execute the jump.

Three-Dimensional Wear Prediction of Four-Degrees-of-Freedom Parallel Mechanism With Clearance Spherical Joint and Flexible Moving Platform

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Gengxiang Wang ◽  
Hongzhao Liu
Keyword(s):  
Contact Force ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Contact Forces ◽  
Force Model ◽  
Spherical Joint ◽  
Normal Contact ◽  
Tangential Contact ◽  
Moving Platform

Three-dimensional (3D) wear of the clearance spherical joint in four-degrees-of-freedom (DOF) parallel mechanism is predicted based on Archard's wear model. The flexible moving platform is treated as thin plate element based on absolute nodal coordinate formulation (ANCF). The tangent frame is introduced to formulate the constraint equation of universal joint. One of the spherical joints is treated as clearance joint. The normal and tangential contact forces are calculated based on Flores contact force model and modified Coulomb friction model. In order to predict 3D wear, the normal contact force, tangential contact velocity, and eccentricity vector are decomposed in the global coordinate system. Simulation results show that 3D wear occurred in three directions are not uniform each other.

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