Cockroft, Stephen John (2015-12)
ENGLISH ABSTRACT: The quest to understand and optimize human movement performance has advanced rapidly in recent years through innovations in movement science and technology. Motion capture technologies have become significantly more mobile, powerful and unobtrusive, enabling new research opportunities. This has resulted in the continuous development of novel quantitative methods for observing and interpreting expert performance in professional sports. A contribution is presented towards this ongoing endeavor via original methodologies for measurements of cycling kinematics using wireless inertial and magnetic measurement systems (IMMSs) and technique analysis of expert rugby union goal kicking using stereophotogrammetry.
Three studies are presented detailing the design and validation of sensor fusion algorithms for IMMS tracking of cycling kinematics. The algorithms utilize a nonlinear complementary filtering structure together with domain constraints related to pendulum and planar motion. Using stereophotogrammetry to validate the tracking performance, it is shown that these filter adaptations eliminate typical measurement errors caused by continuous and time-varying dynamic accelerations and magnetic field disturbances. The first of the IMMS studies illustrated the use of a functional calibration technique to estimate the radius of rotation of an IMMS attached to the thigh. This technique was shown to reduce IMMS tracking errors per axis to 1°. A detailed assessment of the effect of soft tissue artifact on hip angle measurements is also given, and estimates of hip kinematics in the sagittal plane were accurate to within 1-2°. The following two studies focus on IMMS tracking of crank angles in the presence of severe magnetic interference, which precludes the use of traditional static pose calibrations. Two magnetometer-free algorithms are presented, one not requiring a sensor-to-segment calibration and another utilizing a functional calibration technique. Both methods were found to perform with accuracies of 2-3°. A novel optical motion capture method for tracking the crank angle was also developed using a two-segment definition.
Three more studies present a novel technique analysis of fifteen professional goal kickers using stereophotogrammetry. The first study investigated the distance and angulation of the individual steps of the run-up as well as foot positioning relative to the tee and found that anthropometry did not play a major role in determining run-up geometry. The second study assessed phase timing, speed and acceleration during the approach and found that this only had a moderate to small association with foot speed at ball contact. The third study reports on rotational alignment of the thorax, pelvis and feet relative to the tee and target and discusses evidence for a tension arc movement strategy in the spine rotation angle. The most important finding in all three studies was high inter-individual variability and low intra-individual variability, which highlights the nonlinear, athlete-specific dynamics of motor control in sports.
In short, this work contributes towards understanding and overcoming challenges to cycling analysis using IMMSs. The tracking algorithms are resistant to errors caused by magnetic interference, centripetal accelerations and sensor-to-segment calibration. Similarly, the technique analysis of rugby goal kicking contributes towards evidence-based coaching by providing novel methodologies and data for understanding performance.
AFRIKAANSE OPSOMMING: Die strewe om menslike bewegingsprestasie te verstaan en te optimeer het in die onlangse tyd snelle vooruitgang beleef met vernuwende bewegingswetenskap en -tegnologie. Bewegingvasleggingstegnologie is deesdae beduidend sterker, meer mobiel en onopvallend, wat nuwe navorsingsgeleenthede skep. Dít lei tot die voortgesette ontwikkeling van nuwe kwantitatiewe metodes om die prestasie van beroepsportlui waar te neem en te vertolk. Hierdie navorsing lewer ’n bydrae tot dié deurlopende pogings in die vorm van oorspronklike metodologieë vir die meting van fietsrykinematika met behulp van draadlose traagheids- en magnetiese metingstelsels (TMMS’e), sowel as tegniekontleding van doelskoppe deur beroepsrugbyspelers met behulp van stereofotogrammetrie.
Die drie studies wat hier aangebied word, toon die besonderhede van die ontwerp en bekragtiging van sensorfusie-algoritmes vir die TMMS-nasporing van fietsrykinematika. Die algoritmes maak gebruik van ’n nieliniêre aanvullende filterstruktuur, tesame met domeinbeperkings vir slinger- en vlakbewegings. Met behulp van stereofotogrammetrie om die nasporingsprestasie te bekragtig, word daar aangetoon dat hierdie filteraanpassings tipiese metingsfoute uitskakel wat gewoonlik uit deurlopende en tydwisselende dinamiese versnellings en versteurings in die magnetiese veld spruit. Die eerste van die TMMS-studies illustreer die gebruik van ’n funksionele kalibreertegniek om die draai-omtrek te skat van ’n TMMS wat aan die bobeen vasgemaak is. Daar word bewys dat hierdie tegniek TMMS-nasporingsfoute per as tot 1° verminder. Hierdie studie bied ook ’n voerige beoordeling van die sagteweefselartefak by heuphoekmetings, en kon heupkinematika op die sagittale vlak akkuraat tot op 1-2° na skat. Die volgende twee studies konsentreer op TMMS-nasporing van draaihoeke in die teenwoordigheid van erge magnetiese inmenging, wat die gebruik van tradisionele statiese houdingskalibrering onmoontlik maak. Twee magnetometer-vrye algoritmes is ontwikkel – een sonder ’n sensor-tot-segment-kalibrering en een wat van ’n funksionele kalibreertegniek gebruik maak. Albei metodes het akkurate resultate tot op 2-3° na opgelewer. Daarbenewens is ’n vernuwende optiese bewegingvasleggingsmetode ontwikkel vir die nasporing van die draaihoek met behulp van ’n tweesegment-definisie.
Drie verdere studies bied ’n voerige tegniekontleding van 15 beroepsdoelskoppers met behulp van stereofotogrammetrie. In die eerste studie word die afstand en hoek van die individuele treë in die aanloop sowel as die voetplasing in verhouding tot die skopring ondersoek, en word daar bevind dat antropometrie geen beduidende rol in die bepaling van aanloopgeometrie gespeel het nie. Die tweede studie beoordeel fasetydsberekening, snelheid en versnelling in die aanloop, en dui op slegs ’n matige tot swak verband met voetsnelheid by balkontak. Die derde studie doen verslag oor die draairigting van die toraks, pelvis en voete in verhouding tot die skopring en teiken, en bespreek die bewyse vir ’n spanningsboog-bewegingstrategie in die draaihoek van die ruggraat. Die belangrikste bevinding in ál drie studies is hoë inter-individuele veranderlikheid en lae intra-individuele veranderlikheid, wat die nieliniêre, atleetspesifieke dinamika van motoriese beheer in sport beklemtoon.
Die metodes wat vir hierdie studie ontwikkel is, dra by tot die verstaan en oorkomming van die uitdagings van fietsryanalise deur middel van TMMS’e. Die nasporingsalgoritmes wat ontwikkel is tydens die studie is immuun teen foute veroorsaak deur magnetiesesteuring, sentripitaleversnelling en sensor-tot-segment kalibrasie. Die tegniekontleding van rugbydoelskoppe in hierdie studie bied ook ’n magdom nuwe kennis oor bewegingspatrone by beroepspelers en lê die grondslag vir bewysgegronde afrigting en oefening.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98101
This item appears in the following collections: Doctoral Degrees (Mechanical and Mechatronic Engineering)49