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Photogrammetric transformation with panning
Abstracts-International Society of Biomechanics XIV Congress 1993 DYNAMOMETER DESIGNED FOR MEASURING 3-D FORCES APPLIED TO THE HANDS Karen Sogaard, Bjame Laursen, Gisela Sjogaard Department of Physiology, National Institute of Occupational Health, Copenhagen, Denmark In order to measure the forces applied to the hands during a floor cleaning task, a special handle, equipped with an upper and a lower transducer, each measuring orthogonal forces in 3 dimensions, was developed. The lower transducer was placed below both hands and recorded the total force on both hands. The upper transducer, placed between the two hands, enabled us to decompose the total force into the forces, acting on each of the two hands. A coordinate system was defined relative to the handle. A calibration matrix, including correction for cross-sensitivity, was established by loading the orthogonal axes of the transducers. A dynamic validation was achived by mounting a floor cleaning device at the end of the handle and performing a mopping task on a force plate. The force recordings from each of the transducers were compared to the force plate data transformed into the coordinate system of the handle. Both transducers were found to be in good agreement with the force plate, with deviations below 3 N during force variations in a range of 0 40 N. This documents, that the dynamometers are sufficiently accurate to be used for force registration. Of special interest is, that this allows to calculate the 3-D forces acting on each of the hands separately, which is very important in two handed work tasks where these forces may be of very different magnitude.
PHOTOGRAMMETRIC TRANSFORMATION WITH PANNING Keith A. Stivers, Gideon B. Ariel, Andrei G. Vorobiev, M. Ann Penny, Alexander M. Gouskov, Nikolai A. Yakunin International Center for Biomechanical Research, P.O. Box 1169, La Jolla, CA 92038, USA The purpose of this study is to present a technique called physical parameter transformation (PPT) which allows the use of panning cameras for the spatial coordinate reconstruction. This photogrammetric procedure involves 10 physical parameters. Calibration is implemented by minimizing the mapping error over a set of control points whose spatial and digitizer coordinates are known. The minimization for these physical parameters is nonlinear. The PPT is implemented such that orthogonality of the orientation matrix of the image to object coordinate system is guaranteed. Accuracy of the PPT with panning was investigated by filming two control objects each comprised of 15 symmetrically located points. Each object was 1 ma. Coordinates of all control points were located within .003m. The two control objects were horizontally translated 3m. apart. The panning angle was provided by an optical encoder yielding 10 minutes of resolution. Panning axis location and direction were determined by performing 2 normal PPT calibrations corresponding to different panning angles. The residual reconstruction error was .005m.
DYNAMIC MEASUREMENT DURING FREE LUMBAR MOVEMENT : VELOCITY-ANGLE CHARACTERISTICS David Sykes, Malcolm Tillotson and Kim Burton Spinal Research Unit, The University of Huddersfield, Huddersfield. HDl 3DH, UK The 3-Space lsotrak electromagnetic tracking device was used to record angular displacements of T12 about S2 in 5 healthy subjects during flexion (at 30 Hz over 3 seconds). The data were expressed as velocity/angle graphs for all or part of each movement. The graphs were examined for evidence of reproducibility of discrete velocity/angle values then locally smoothed and comparisons made with second order polynomials. Repeat measurements revealed consistency of velocity patterns and velocity/angle values within individuals. The velocity patterns differed between subjects and between the various components of the movements. Distinctive changes in individuals’ velocity patterns were found during a lifting task and also following manipulative treatment. The results suggest that the ISOTRAK is capable of identifying dynamic lumbar movement patterns. Velocity varies during the course of unconstrained lumbar movement and variations are angle specific within an individual. Consistent irregularities in velocity during what is ostensibly a smooth movement suggest individual influences from, say, morphological or neuromuscular factors. The technique has potential for discrimination in back pain patients, for ergonomic task analysis, and for providing an objective measure of therapeutic response.
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PHOTOGRAMMETRIC TRANSFORMATION WITH PANNING Keith A. Stivers, Gideon B. Ariel, Andrei G. Vorobiev, M. Ann Penny, Alexander M. Gouskov, Nikolai A. Yakunin International Center for Biomechanical Research, P.O. Box 1169, La Jolla, CA 92038, USA The purpose of this study is to present a technique called physical parameter transformation (PPT) which allows the use of panning cameras for the spatial coordinate reconstruction. This photogrammetric procedure involves 10 physical parameters. Calibration is implemented by minimizing the mapping error over a set of control points whose spatial and digitizer coordinates are known. The minimization for these physical parameters is nonlinear. The PPT is implemented such that orthogonality of the orientation matrix of the image to object coordinate system is guaranteed. Accuracy of the PPT with panning was investigated by filming two control objects each comprised of 15 symmetrically located points. Each object was 1 ma. Coordinates of all control points were located within .003m. The two control objects were horizontally translated 3m. apart. The panning angle was provided by an optical encoder yielding 10 minutes of resolution. Panning axis location and direction were determined by performing 2 normal PPT calibrations corresponding to different panning angles. The residual reconstruction error was .005m.
DYNAMIC MEASUREMENT DURING FREE LUMBAR MOVEMENT : VELOCITY-ANGLE CHARACTERISTICS David Sykes, Malcolm Tillotson and Kim Burton Spinal Research Unit, The University of Huddersfield, Huddersfield. HDl 3DH, UK The 3-Space lsotrak electromagnetic tracking device was used to record angular displacements of T12 about S2 in 5 healthy subjects during flexion (at 30 Hz over 3 seconds). The data were expressed as velocity/angle graphs for all or part of each movement. The graphs were examined for evidence of reproducibility of discrete velocity/angle values then locally smoothed and comparisons made with second order polynomials. Repeat measurements revealed consistency of velocity patterns and velocity/angle values within individuals. The velocity patterns differed between subjects and between the various components of the movements. Distinctive changes in individuals’ velocity patterns were found during a lifting task and also following manipulative treatment. The results suggest that the ISOTRAK is capable of identifying dynamic lumbar movement patterns. Velocity varies during the course of unconstrained lumbar movement and variations are angle specific within an individual. Consistent irregularities in velocity during what is ostensibly a smooth movement suggest individual influences from, say, morphological or neuromuscular factors. The technique has potential for discrimination in back pain patients, for ergonomic task analysis, and for providing an objective measure of therapeutic response.
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