In Situ Calibration and Motion Capture Transformation Optimization Improve Instrumented Treadmill Measurements

2009 ◽  
Vol 25 (4) ◽  
pp. 401-406 ◽  
Author(s):  
Saryn R. Goldberg ◽  
Thomas M. Kepple ◽  
Steven J. Stanhope
Keyword(s):  
Motion Capture ◽  
Center Of Pressure ◽  
Force Plate ◽  
Coordinate Systems ◽  
Optimization Scheme ◽  
Shear Loads ◽  
In Situ Calibration ◽  
Calibration Matrix ◽  
Force Data

We increased the accuracy of an instrumented treadmill’s measurement of center of pressure and force data by calibrating in situ and optimizing the transformation between the motion capture and treadmill force plate coordinate systems. We calibrated the device in situ by applying known vertical and shear loads at known locations across the tread surface and calculating a 6 × 6 calibration matrix for the 6 output forces and moments. To optimize the transformation, we first estimated the transformation based on a locating jig and then measured center-of-pressure error across the treadmill force plate using the CalTester tool. We input these data into an optimization scheme to find the transformation between the motion capture and treadmill force plate coordinate systems that minimized the error in the center-of-pressure measurements derived from force plate and motion capture sources. When the calibration and transformation optimizations were made, the average measured error in the center of pressure was reduced to approximately 1 mm when the treadmill was stationary and to less than 3 mm when moving. Using bilateral gait data, we show the importance of calibrating these devices in situ and performing transformation optimizations.

Effect of Sensor Failure on Dynamometry Calibration

2020 ◽  
Author(s):  
Nicholas Vlajic ◽  
Michael Jonson ◽  
Manton Guers
Keyword(s):  
Degrees Of Freedom ◽  
Fluid Dynamic ◽  
Least Square ◽  
Elastic Model ◽  
Sensor Failure ◽  
Static Loads ◽  
Six Degrees Of Freedom ◽  
In Situ Calibration ◽  
Calibration Matrix

Abstract Dynamometers are used to measure integrated fluid dynamic loads such as thrust, torque or side forces. To resolve all of three force and three moment components, multiple embedded force gages are often used. Due to arrangement, static loads, and redundancy, the number of sensor channels can exceed the six degrees of freedom needed to resolve the generalized rigid body forces. This paper considers modeling of the force gages as simple springs to develop an elastic model of the dynamometer. The method was applied to a dynamometer consisting of six three-component force gages arranged in an axisymmetric ring. A calibration matrix based on the elastic model with individual force gage sensitivities was shown to match a full calibration matrix where properly summed force gage voltages were obtained under global load application. The elastic model was then extended to consider calibration matrices where sensors were assumed to fail. In this scenario, several virtual loads were applied to the dynamometer and the calibration matrix was obtained by minimizing the least square error. It was found that nearly half of the sensors could be lost and still a virtual calibration could be applied to the measurements. Extending the least square idea, an actual in-situ calibration matrix was formed by striking the dynamometer with a diverse set of instrumented hammer strikes. This calibration matrix also agreed with the other calibrations at frequencies below where system dynamics become important.

Characterization of a System for Studying Human Gait during Slope Walking

2005 ◽  
Vol 21 (2) ◽  
pp. 153-166 ◽  
Author(s):  
Andrea N. Lay ◽  
Chris J. Hass ◽  
D. Webb Smith ◽  
Robert J. Gregor
Keyword(s):  
Neural Control ◽  
Center Of Pressure ◽  
Reaction Force ◽  
Force Plate ◽  
Human Locomotion ◽  
Human Gait ◽  
Testing System ◽  
Force Data ◽  
Kinetics Of

Sloped walking surfaces provide a unique environment for examining the bio-mechanics and neural control of locomotion. While sloped surfaces have been used in a variety of studies in recent years, the current literature provides little if any discussion of the integrity, i.e., validity, of the systems used to collect data. The goal of this study was to develop and characterize a testing system capable of evaluating the kinetics of human locomotion on sloped surfaces. A ramped walkway system with an embedded force plate was constructed and stabilized. Center of pressure and reaction force data from the force plate were evaluated at 6 ramp grades (0, 5, 15, 25, 35, and 39%). Ground reaction force data at 0% grade were effectively the same as data from the same force plate when mounted in the ground and were well within the range of intrasubject variability. Collectively, data from all tests demonstrate the fidelity of this ramp system and suggest it can be used to evaluate human locomotion over a range of slope intensities.

scholarly journals Tidal Calibration of Multicomponent Borehole Strainmeters and Validation of the Method Using Surface Waves

2021 ◽  
Author(s):  
Norio Matsumoto ◽  
Osamu Kamigaichi
Keyword(s):  
Calibration Method ◽  
Strain Waves ◽  
Regional Strain ◽  
In Situ Calibration ◽  
Strain Data ◽  
Chile Earthquake ◽  
Seismic Strain ◽  
Calibration Matrix ◽  
Tidal Loading

Abstract We conducted in-situ calibration of fifteen multicomponent borehole strainmeters deployed in and around the expected focal zones of the Nankai megathrust earthquake. The in-situ calibration method compares tidal strain observed by the borehole strainmeters with predicted tidal strains from the solid Earth’s tide and oceanic tidal loading. Then we obtained a calibration matrix to transfer observed strain data to the regional strain field. We estimated the oceanic tidal loading accurately using a Green’s function, which takes the depth of deployment into consideration. We calculated four sets of calibration matrices using combinations of any three of a group of four gauges as well as a calibration matrix using all four gauges. The estimated calibration matrix was validated by comparing observed seismic strain waves after applying the calibration matrix with theoretical seismic strain waves excited by the 2010 Chile earthquake (Mw 8.8). The in-situ calibration was found to be appropriate for all eleven Ishii-type borehole strainmeters and for one of the four Gladwin Tensor Strainmeters (GTSMs). It was also effective with respect to two shear strains for two of the other three GTSMs.

A Novel Multi-Dimension Force Platform Calibration Design and Error Analysis

2013 ◽  
Vol 347-350 ◽  
pp. 201-204
Author(s):  
Z.Y. Mao ◽  
Ping Cai
Keyword(s):  
Center Of Pressure ◽  
Reaction Force ◽  
Force Plate ◽  
Force Platform ◽  
Balance Function ◽  
Human Balance ◽  
Calibration Device ◽  
Calibration Matrix ◽  
Function Assessment ◽  
Least Squares Approach

Multi-dimension force platform (MFP) is commonly used in human balance function assessment to measure the ground reaction force and the center of pressure (COP). For improving the precision of measurement and simplification the calibration process, this paper devised a generalized load calibration device which can calibrate six axis force simultaneously. Based on the load shift principle, the true loads in every axis were determined when a generalized load was applied on the platform. After experimental verification on force plate devised by our laboratory, the calibration matrix C was calculated based on least-squares approach. The result showed that the crosstalk was kept below the thresholds of most common, commercial force platform.

Assessing the Ergonomic Benefits of a New Adjustable Forklift Backrest

2020 ◽  
Vol 64 (1) ◽  
pp. 976-980
Author(s):  
Pranav Madhav Kuber ◽  
Ehsan Rashedi
Keyword(s):  
Comparative Study ◽  
Motion Capture ◽  
Center Of Pressure ◽  
Body Movement ◽  
Pressure Change ◽  
Motion Capture System ◽  
Design Features ◽  
Wide Range ◽  
Body Sizes ◽  
The Mean

A new forklift backrest has been developed by incorporating adjustability concepts into the design to facilitate comfort to a wide range of users. We have conducted a comparative study between the new and original backrests to assess the effectiveness of design features. Using the phenomenon of restlessness, discomfort of the user was associated with the amount of body movement, where we have used a motion- capture system and a force platform to quantify the individuals’ movement for a wide range of body sizes. Meanwhile, subjective comfort and design feedback were collected using a questionnaire. Our results showed a reduction in the mean torso movement and the maximum center of pressure change of location by 300 and 6 mm, respectively, for the new design. Taking advantage of adjustability feature, the new backrest design exhibited enhanced comfort for longer durations and reduced magnitude of discomfort for a wide range of participants’ body sizes.

scholarly journals Performance of the SoLid reactor neutrino detector

2019 ◽  
Vol 219 ◽  
pp. 08003
Author(s):  
Maja Verstraeten
Keyword(s):  
Quality Control ◽  
Energy Resolution ◽  
Neutrino Detector ◽  
Channel Response ◽  
In Situ Calibration ◽  
Reactor Neutrino ◽  
Li Isotope ◽  
Better Than

The SoLid Collaboration is currently operating a 1.6 ton neutrino detector near the Belgian BR2 reactor. Its main goal is the observation of the oscillation of electron antineutrinos to previously undetected flavour states. The highly segmented SoLid detector employs a compound scintillation technology based on PVT scintillator in combination with LiF-ZnS(Ag) screens containing the 6Li isotope. The experiment has demonstrated a channel-to-channel response that can be controlled to the level of a few percent, an energy resolution of better than 14% at 1 MeV, and a determination of the interaction vertex with a precision of 5 cm. This contribution highlights the major outcomes of the R&D program, the quality control during component manufacture and integration, the current performance and stability of the full-scale system, as well as the in-situ calibration of the detector with various radioactive sources.

scholarly journals Habitual Physical Activity as a Determinant of the Effect of Moderate Physical Exercise on Postural Control in Older Men

2012 ◽  
Vol 7 (1) ◽  
pp. 58-65 ◽  
Author(s):  
Rafał Stemplewski ◽  
Janusz Maciaszek ◽  
Maciej Tomczak ◽  
Robert Szeklicki ◽  
Dorota Sadowska ◽  
...  
Keyword(s):  
Physical Activity ◽  
Postural Control ◽  
Sagittal Plane ◽  
Center Of Pressure ◽  
Force Plate ◽  
Frontal Plane ◽  
Habitual Physical Activity ◽  
Similar Reaction ◽  
Mean Velocity ◽  
Ergometer Exercise

The aim of the study was to compare the effect of exercise on postural control (PC) among the elderly with lower or higher level of habitual physical activity (HPA). The study involved 17 elderly men (mean age 72.9 ± 4.79 years). Mean velocity of the center of pressure (COP) displacements was measured using a force plate both before and after cycle ergometer exercise. A significantly higher increase in mean velocity of COP displacements and its component in the sagittal plane were observed in the group with lower level of HPA in comparison with the group with higher HPA level. Simultaneously, a relatively similar reaction to the exercise in the frontal plane was observed in both groups, possibly connected to the specific type of used exercise, which mainly activated the sagittal muscles.

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