Disseny i desenvolupament d’un entorn de simulació de l’articulació de l’húmer de suport a la planificació quirúrgica

L’objectiu d’aquest projecte és el disseny d’una eina de software que mitjançant la simulació permeti al metge prendre decisions després d’estudiar com afecten diferents modificacions en l’anatomia d’un pacient concret, concebudes per dotar una articulació d’una millor funcionalitat. Les modificacions que a estudiar se centren en l’articulació glenohumeral, que és la que permet la major part del moviment de la part superior del braç, i té com a superfícies articulars el cap de l’húmer i la glena. Es contemplen dos escenaris a simular: l’eliminació del múscul supraespinós (que es troba a la còfia rotadora del cap de l’húmer) i l’elecció de la pròtesi òptima, segons paràmetres geomètrics, per substituir l’articulació glenohumeral. En aquest projecte s’ha dissenyat un model musculoesquelètic de l’articulació glenohumeral partint d’un model existent de l’extremitat superior del cos, desenvolupat amb el programari de simulació OpenSim. S’ha ajustat el model per a simular els graus de llibertat de l’articulació, especificant els músculs necessaris per a actuar en aquesta, i afegint les translacions del cap de l’húmer, per tal de fer-lo més acurat. S’ha determinat el protocol de recollida de dades del moviment humà amb un sensor magnètic i el seu tractament per utilitzar-les com a dades experimentals d’entrada a l’OpenSim. Aquestes dades permeten escalar un model genèric a un subjecte concret, i reproduir en el model virtual el moviment experimental, per tal de determinar, entre altres, com actua cada múscul o quins esforços pateix cada articulació. S’ha desenvolupat un disseny bàsic d’una interfície amb l’editor d’interfícies d’usuari gràfiques de MATLAB que permet al metge estudiar com afecta a un pacient concret l’eliminació d’un múscul de la còfia rotadora o quina és la millor geometria de la pròtesi que es vol implantar en el pacient. Amb la utilització de MATLAB s’han aconseguit dos aspectes positius. El primer és que el metge pot disposar de les eines que ofereix OpenSim, sense necessitat d’aprendre a utilitzar el programa; la interfície li ofereix els models i les eines que necessita de manera més intuïtiva, i dóna els resultats de forma que els pugui interpretar fàcilment. El segon és que s’amplien les possibilitats de simulació d’OpenSim amb les capacitats de càlcul de MATLAB, el que permet fer diferents simulacions variant paràmetres i tractar els resultats

Can the use of an auditory feedback device improve the gait pattern of paediatric patients with hemiparesis?

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Evaluation of Optimal Control Approaches for Predicting Active Knee-Ankle-Foot-Orthosis Motion for Individuals With Spinal Cord Injury

Gait restoration of individuals with spinal cord injury can be partially achieved using active orthoses or exoskeletons. To improve the walking ability of each patient as much as possible, it is important to personalize the parameters that define the device actuation. This study investigates whether using an optimal control-based predictive simulation approach to personalize pre-defined knee trajectory parameters for an active knee-ankle-foot orthosis (KAFO) used by spinal cord injured (SCI) subjects could potentially be an alternative to the current trial-and-error approach. We aimed to find the knee angle trajectory that produced an improved orthosis-assisted gait pattern compared to the one with passive support (locked knee). We collected experimental data from a healthy subject assisted by crutches and KAFOs (with locked knee and with knee flexion assistance) and from an SCI subject assisted by crutches and KAFOs (with locked knee). First, we compared different cost functions and chose the one that produced results closest to experimental locked knee walking for the healthy subject (angular coordinates mean RMSE was 5.74°). For this subject, we predicted crutch-orthosis-assisted walking imposing a pre-defined knee angle trajectory for different maximum knee flexion parameter values, and results were evaluated against experimental data using that same pre-defined knee flexion trajectories in the real device. Finally, using the selected cost function, gait cycles for different knee flexion assistance were predicted for an SCI subject. We evaluated changes in four clinically relevant parameters: foot clearance, stride length, cadence, and hip flexion ROM. Simulations for different values of maximum knee flexion showed variations of these parameters that were consistent with experimental data for the healthy subject (e.g., foot clearance increased/decreased similarly in experimental and predicted motions) and were reasonable for the SCI subject (e.g., maximum parameter values were found for moderate knee flexion). Although more research is needed before this method can be applied to choose optimal active orthosis controller parameters for specific subjects, these findings suggest that optimal control prediction of crutch-orthosis-assisted walking using biomechanical models might be used in place of the trial-and-error method to select the best maximum knee flexion angle during gait for a specific SCI subject.Peer ReviewedPostprint (published version

Simulación predictiva de la marcha asistida para la personalización de ortesis activas para lesionados medulares

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Foot-ground contact modelling for computational prediction of human walking motion

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Evaluation of optimal control formulations for obtaining dynamically consistent walking motions

n recent years, interest has grown in predicting human motion, for example, to study cause-effect relations for a specific task [1]. To predict human motion, researchers typically use optimization-based methods that minimize a certain cost function. The objective of this study is to analyze two different optimal control formulations that track experimental data from a healthy gait cycle to obtain a dynamically consistent walking motion, i.e., with minimal residual wrench applied to the pelvis.Postprint (published version

Prediction of three-dimensional crutch walking patterns using a torque-driven model

Computational prediction of 3D crutch-assisted walking patterns is a challenging problem that could be applied to study different biomechanical aspects of crutch walking in virtual subjects, to assist physiotherapists to choose the optimal crutch walking pattern for a specific subject, and to help in the design and control of exoskeletons, when crutches are needed for balance. The aim of this work is to generate a method to predict three-dimensional crutch-assisted walking motions following different patterns without tracking any experimental data. To reach this goal, we collected gait data from a healthy subject performing a four-point non-alternating crutch walking pattern, and developed a 3D torque-driven full-body model of the subject including the crutches and foot- and crutch-ground contact models. First, we developed a predictive (i.e., no tracking of experimental data) optimal control problem formulation to predict crutch walking cycles following the same pattern as the experimental data collected, using different cost functions. To reduce errors with respect to reference data, a cost function combining minimization terms of angular momentum, mechanical power, joint jerk and torque change was chosen. Then, the problem formulation was adapted to handle different foot- and crutch-ground conditions to make it capable of predicting three new crutch walking patterns, one of them at different speeds. A key aspect of our algorithm is that having ground reactions as additional controls allows one to define phases inside the cycle without the need of formulating a multiple-phase problem, thus facilitating the definition of different crutch walking patterns.Postprint (author's final draft

Optimal control prediction of a dynamically consistent walking motion for a spinal cord-injured subject assisted by orthoses

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Influence of robotic orthosis dynamic parameters on optimization-based prediction of assisted walking

The numerical simulation by parameter optimization techniques has been proven to be a powerful tool in human walking dynamics research [1, 2]. Although there are several studies related to human walking dynamics, not much attention has been paid to the prediction of human gait assisted by robotic orthoses or exoskeletons. The aim of this work is to investigate the influence of some design parameters of an assistive orthosis on the injured subject’s gait dynamics by using a predictive parameter optimization approach.Postprint (published version

Kinematic model of savannah monitor locomotion

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