The goal of this thesis is to develop a soft multiple-degree-of-freedom (multi-DOF) load cell that is robust and light weight for use in robotics applications to sense three axes of force and a single axis of torque. The displacement of the magnet within the elastomer changes the magnetic flux density which is sensed by two 3-axis Hall effect sensors. Experimental measurements of magnetic flux density within the area of interest were used to formulate analytic expressions that relate magnet field strength to the position of the magnet. The displacement and orientation measurement and the material properties of the elastomer are used to calibrate and calculate the applied load. The ability to measure 3-DOF force and axial torque was evaluated with combined loading applied by a robotic arm (KUKA, LBR r820 iiwa). The decoupled results show the 4-DOF load cell was able to distinguish 3-axis force and 1-axis torque with 6.9% averaged error for normal force, 4.3% and 2.6% for shear force in the X and Y axis and 8.6% for the torque. The results show good accuracy for a soft multi-axis sensor that would be applicable in many robotic applications where high accuracy is not required.

A digital twin project is launched by the Integrative Systems Biology (ISB) research team and led by Gunnar Cedersund. The digital twin project is based on biological models of physiological processes, that can interact and be tailored for a specific person. However, the digital twin can currently not analyse movements of a human body. In this master thesis, the aim was to create a useful pipeline that expands the digital twin project with biomechanical modelling of movements, and also visualises the twins by letting the concept take human form. The biomechanical analysis was done in the software OpenSim, where the movements of a motion captured dance were analysed. To generate a simulation of the motion with an acceptable error in a reasonable computation time, a musculoskeletal model was created in OpenSim and scaled to best fit the anthropometry of the dancer. Then, the motion was estimated with an optimised procedure by using the scaled model and the motion capture data. The Root-Mean Squared (RMS) error of the estimated dance with accuracy 10-6 was 2.39 cm. In this thesis, the torque in each joint for the dance motion was estimated. The loads and muscle forces can also be estimated in OpenSim. One useful application is for calculating energy consumption. In order to calculate muscle forces, external forces needs to be measured while recording motion capture. This is something that will be focused on in the future, when continuing with this project. The visualisation of the digital twins were made in Unreal Engine with MetaHuman avatars. The dance recorded in motion capture, were applied to the avatars in order to make them dance. The recorded dance was the same for both OpenSim and Unreal Engine, so the dance could both be viewed and analysed. In conclusion, we have added a new feature to the existing digital twin technology: movements and simulation of the musculoskeletal system. This new feature can in the future be used for both medical purposes such as movement-based rehabilitation as well as for integration into dance performances.

<p> This pilot study was performed in order to examine the potential beneficial effects of cervical spinal manipulative therapy on volunteers suffering from post-concussive neck syndrome. The study of concussions and post-concussive neck syndrome is still a relatively new topic in the existing literature. Little research has been done in the area of spinal manipulation and the treatment of volunteers suffering from post-concussive neck syndrome, from a biomechanical standpoint.</p> <p> Forty-one volunteers who were suffering from post-concussive neck syndrome were recruited from McMaster University in Hamilton, Ontario to participate in the study. In order to assess the severity of neck complaints, the severity of their post-concussive symptoms and overall general health, the volunteers completed the Neck Disability Index, the Visual Analog Scale, the Standardized Assessment of Concussion and the Short Form-36 Health Survey. During testing sessions, volunteers were fitted with several light emitting markers placed strategically on the head, mid-back, sacrum and heels of the volunteers' footwear. Each volunteer would then walk on a treadmill for four separate five minute trials, after an initial familiarization period. The 3D position of these markers during gait were recorded by a rear-mounted kinematic data acquisition system (Optotrak 3020). After the initial five minute walk (trial 1), the volunteer was treated with a cervical spinal manipulation, and immediately resumed walking for the second trial on the treadmill. The volunteers performed four walking trials in total.</p> <p> Both manual and automated procedures were used to identify the multiple right-heel treadmill surface contacts during each five minute walk. Objective biomechanical outcome measures used in the study included relative phase measurements between the head and thorax in the transverse plane, the Biomechanical Efficiency Quotient and the Neck-Walk Index.</p> <p> Clinically significant results in relative measurements, post-intervention, were found when certain volunteers were removed (due to slow walking velocity). These differences can be attributed to the intervention of spinal manipulation which caused a significant increase in cervico-thoracic spinal motion, which appeared to decrease again at 35 minutes. This is clinically significant because it poses the theory that initial short-term biomechanical changes in the cervical spine are caused by SMT.</p> <p> Clinically significant results in the Biomechanical Efficiency Quotient were found when specific volunteers were removed. The results however, were in the opposite direction than was previously hypothesized. The reason for the increase in BEQ post-manipulation compared to pre-manipulation could be a result of the familiarization walking period before the initial trial. By allowing volunteers several minutes to get accustomed to walking on the treadmill, a learning effect had taken place, decreasing the variability in their gait in the initial pre-intervention trial. Although BEQ increased in the second and third trials, it decreased again at 35 minutes post-intervention, meaning the walking economy had once again increased.</p> <p> The specific intervention of cervical spinal manipulative therapy was hypothesized to change the variability of head movement disturbances during gait (Neck-Walk Index). No reference in the literature is made in relation to Neck-Walk Index and how it evaluates change in head carriage, post-intervention. This study suggests however, that although results approached significance, cervical manipulative therapy did not change biomechanical head carriage in this volunteer population.</p> <p> With respect to future studies, several recommendations have been made in this thesis which are aimed at increasing the clinical significance of the results. This would be done through the incorporation of more affected volunteers (increase in functional disability due to post-concussive neck syndrome), the incorporation of a more lengthy and specific treatment protocol (to sustain biomechanical and physical changes), and an increased treadmill walking velocity (to assess antiphasic movements more easily).</p> / Thesis / Master of Science (MSc)

In recent years, consumers have witnessed a technological revolution that has delivered more-realistic experiences in their own homes. Expanding technologies have provided larger displays with higher resolutions, faster refresh rates, and stereoscopic capabilities. These advances have increased the level of display fidelity—the objective degree of exactness with which real-world sensory stimuli are reproduced by a display system. Similarly, the latest generation of video game systems (e.g., Nintendo Wii and Xbox Kinect) with their natural, gesture-based interactions have delivered increased levels of interaction fidelity—the objective degree of exactness with which real-world interactions can be reproduced in an interactive system. Though this technological revolution has provided more realistic experiences, it is not completely clear how increased display fidelity and interaction fidelity impact the user experience because the effects of increasing fidelity to the real world have not been empirically established. The goal of this dissertation is to provide a better understanding of the effects of both display fidelity and interaction fidelity on the user experience. For the context of our research, we chose virtual reality (VR) games because immersive VR allows for high levels of fidelity to be achieved while games usually involve complex, performance-intensive tasks. In regard to the user experience, we were concerned with objective performance metrics and subjective responses such as presence, engagement, perceived usability, and overall preferences. We conducted five systematically controlled studies that evaluated display and interaction fidelity at contrasting levels in order to gain a better understanding of their effects. In our first study, which involved a 3D object manipulation game within a three-sided CAVE, we found that stereoscopy and the total size of the visual field surrounding the user (i.e., field of regard or FOR) did not have a significant effect on manipulation times but two high-fidelity interaction techniques based on six degrees-of-freedom (DOF) input outperformed a low-fidelity technique based on keyboard and mouse input. In our second study, which involved a racing game on a commercial game console, we solely investigated interaction fidelity and found that two low-fidelity steering techniques based on 2D joystick input outperformed two high-fidelity steering techniques based on 3D accelerometer data in terms of lap times and driving errors. Our final three studies involved a first-person shooter (FPS) game implemented within a six-sided CAVE. In the first of these FPS studies, we evaluated display fidelity and interaction fidelity independently, at extremely high and low levels, and found that both significantly affected strategy, performance, presence, engagement, and perceived usability. In particular, performance results were strongly in favor of two conditions: low-display, low-interaction fidelity (representative of desktop FPS games) and high-display, high-interaction fidelity (similar to the real world). In the second FPS study, we investigated the effects of FOR and pointing fidelity on the subtasks of searching, aiming, and firing. We found that increased FOR affords faster searching and that high-fidelity pointing based on 6-DOF input provided faster aiming than low-fidelity mouse pointing and a mid-fidelity mouse technique based on the heading of the user. In the third FPS study, we investigated the effects of FOR and locomotion fidelity on the subtasks of long-distance navigation and maneuvering. Our results indicated that increased FOR increased perceived usability but had no significant effect on actual performance while low-fidelity keyboard-based locomotion outperformed our high-fidelity locomotion technique developed for our original FPS study. The results of our five studies show that increasing display fidelity tends to have a positive correlation to user performance, especially for some components such as FOR. Contrastingly, our results have indicated that interaction fidelity has a non-linear correlation to user performance with users performing better with "traditionalThe results of our five studies show that increasing display fidelity tends to have a positive correlation to user performance, especially for some components such as FOR. Contrastingly, our results have indicated that interaction fidelity has a non-linear correlation to user performance with users performing better with "traditional", extremely low-fidelity techniques and "natural", extremely high-fidelity techniques while performing worse with mid-fidelity interaction techniques. These correlations demonstrate that the display fidelity and interaction fidelity continua appear to have differing effects on the user experience for VR games. In addition to learning more about the effects of display fidelity and interaction fidelity, we have also developed the Framework for Interaction Fidelity Analysis (FIFA) for comparing interaction techniques to their real-world counterparts. There are three primary factors of concern within FIFA: biomechanical symmetry, control symmetry, and system appropriateness. Biomechanical symmetry involves the comparison of the kinematic, kinetic, and anthropometric aspects of two interactions. Control symmetry compares the dimensional, transfer function, and termination characteristics of two interactions. System appropriateness is concerned with how well a VR system matches the interaction space and objects of the real-world task (e.g., a driving simulator is more appropriate than a 2D joystick for a steering task). Although consumers have witnessed a technological revolution geared towards more realistic experiences in recent years, we have demonstrated with this research that there is still much to be learned about the effects of increasing a system's fidelity to the real world. The results of our studies show that the levels of display and interaction fidelity are significant factors in determining performance, presence, engagement, and usability. / Ph. D.

Bakgrund: Inhämtning av kunskap om och kvantifiering av belastning i ländryggen är en essentiell aspekt för att adressera den belastning och ländryggssmärta som finns bland vårdpersonal som utför fysiskt krävande arbete. Mätningen och utvärderingen av denna belastning utgör en betydande del av det preventiva arbetet för att identifiera riskfaktorer och främja en hälsosam arbetsmiljö.  Syfte: Denna översiktsstudie syftar till att granska den aktuella vetenskapliga litteraturen om kompressions- och skjuvkrafter som påverkar ländryggen hos vårdpersonal under patienthantering. Studien undersöker de vanligaste mätmetoderna för att mäta dessa krafter, den kompressions- och skjuvkraft ländryggen utsätts för hos vårdpersonal under patienthantering, efterlevnaden av riktlinjer för tunga lyft samt effekterna av olika interventioner på uppmätt ländryggsbelastning.  Metod: Denna översiktsstudie har genomförts i enlighet med Statens beredning för medicinsk och social utvärderings (SBU) metodbok. Bedömning av BIAS-risk utfördes med hjälp av SBU;s bedömningsmallar baserade på en modifierad version av QUADAS-2. Vetenskapliga artiklar samlades in via sökningar i PubMed-databasen.  Resultat: Totalt inkluderades 14 studier i denna studie. Dessa studier omfattade sammanlagt 337 deltagare. Alla inkluderade studier utvärderade både kompressionskrafter och skjuvkrafter som utfallsmått och använde reliabla samt validerade mätmetoder som mätinstrument. Resultaten tyder på att belastningen på vårdarnas ländryggar ofta överstiger de rekommenderade nivåerna för kompressions- och skjuvkrafter.  Slutsats: Studien ger signifikant bevisning för en potentiell positiv effekt av olika hjälpmedel på ländryggsbelastning, men det finns även motstridig forskning som pekar på motsatt resultat. Det finns tydliga indikationer på att använda rätt teknik under lyft och att bibehålla en ergonomisk kroppsställning kan bidra till att minska risken för belastningsrelaterade skador och främja hälsa och välbefinnande.

We consider the design of finite element methods for inverse problems with full-field data governed by elliptic forward operators. Such problems arise in applications in inverse heat conduction, in mechanical property characterization, and in medical imaging. For this class of problems, novel finite element methods have been proposed (Barbone et al., 2010) that give good performance, provided the solutions are in the H^1(Ω) function space. The material property distributions being estimated can be discontinuous, however, and therefore it is desirable to have formulations that can accommodate discontinuities in both data and solution. Toward this end, we present a mixed variational formulation for this class of problems that handles discontinuities well. We motivate the mixed formulation by examining the possibility of discretizing using a discontinuous discretization in an irreducible finite element method, and discuss the limitations of that approach. We then derive a new mixed formulation based on a least-square error in the constitutive equation. We prove that the continuous variational formulations are well-posed for applications in both inverse heat conduction and plane stress elasticity. We derive a priori error bounds for discretization error, valid in the limit of mesh refinement. We demonstrate convergence of the method with mesh refinement in cases with both continuous and discontinuous solutions. Finally we apply the formulation to measured data to estimate the elastic shear modulus distributions in both tissue mimicking phantoms and in breast masses from data collected in vivo.

Modeling the liver deformation forms the basis for the development of new clinical applications that improve the diagnosis, planning and guidance in liver surgery. However, the patient-specific modeling of this organ and its validation are still a challenge in Biomechanics. The reason is the difficulty to measure the mechanical response of the in vivo liver tissue. The current approach consist of performing minimally invasive or open surgery aimed at estimating the elastic constant of the proposed biomechanical models. This dissertation presents how the use of medical image analysis and evolutionary computation allows the characterization of the biomechanical behavior of the liver, avoiding the use of these minimally invasive techniques. In particular, the use of similarity coefficients commonly used in medical image analysis has permitted, on one hand, to estimate the patient-specific biomechanical model of the liver avoiding the invasive measurement of its mechanical response. On the other hand, these coefficients have also permitted to validate the proposed biomechanical models. Jaccard coefficient and Hausdorff distance have been used to validate the models proposed to simulate the behavior of ex vivo lamb livers, calculating the error between the volume of the experimentally deformed samples of the livers and the volume from biomechanical simulations of these deformations. These coefficients has provided information, such as the shape of the samples and the error distribution along their volume. For this reason, both coefficients have also been used to formulate a novel function, the Geometric Similarity Function (GSF). This function has permitted to establish a methodology to estimate the elastic constants of the models proposed for the human liver using evolutionary computation. Several optimization strategies, using GSF as cost function, have been developed aimed at estimating the patient-specific elastic constants of the biomechanical models proposed for the human liver. Finally, this methodology has been used to define and validate a biomechanical model proposed for an in vitro human liver. / Martínez Martínez, F. (2014). Determining the Biomechanical Behavior of the Liver Using Medical Image Analysis and Evolutionary Computation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/39337

The characterization of the mechanical behavior of soft living tissues is a big challenge in Biomechanics. The difficulty arises from both the access to the tissues and the manipulation in order to know their physical properties. Currently, the biomechanical characterization of the organs is mainly performed by testing ex-vivo samples or by means of indentation tests. In the first case, the obtained behavior does not represent the real behavior of the organ. In the second case, it is only a representation of the mechanical response of the indented areas. The purpose of the research reported in this thesis is the development of a methodology to in-vivo characterize the biomechanical behavior of two different organs: the breast and the cornea. The proposed methodology avoids invasive measurements to obtain the mechanical response of the organs and is able to completely characterize of the biomechanical behavior of them. The research reported in this thesis describes a methodology to in-vivo characterize the biomechanical behavior of the breast and the cornea. The estimation of the elastic constants of the constitutive equations that define the mechanical behavior of these organs is performed using an iterative search algorithm which optimizes these parameters. The search is based on the iterative variation of the elastic constants of the model in order to increase the similarity between a simulated deformation of the organ and the real one. The similarity is measured by means of a volumetric similarity function which combines overlap-based coefficients and distance-based coefficients. Due to the number of parameters to be characterized as well as the non-convergences that the solution may present in some regions, genetic heuristics were chosen to drive the search algorithm. In the case of the breast, the elastic constants of an anisotropic hyperelastic neo-Hookean model proposed to simulate the compression of the breast during an MRI-guided biopsy were estimated. Results from this analysis showed that the proposed algorithm accurately found the elastic constants of the proposed model, providing an average relative error below 10%. The methodology was validated using breast software phantoms. Nevertheless, this methodology can be easily transferred into its use with real breasts. In the case of the cornea, the elastic constants of a hyperelastic second-order Ogden model were estimated for 24 corneas corresponding to 12 patients. The finite element method was applied in order to simulate the deformation of the human corneas due to non-contact tonometry. The iterative search was applied in order to estimate the elastic constants of the model which approximates the most the simulated deformation to the real one. Results showed that these constants can be estimated with an error of about 5%. After the results obtained for both organs, it can be concluded that the iterative search methodology presented in this thesis allows the \textit{in-vivo} estimation the patient-specific elastic constants of the constitutive biomechanical models that govern the biomechanical behavior of these two organs. / Lago Ángel, MÁ. (2014). A new approach for the in-vivo characterization of the biomechanical behavior of the breast and the cornea [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/44116

<p dir="ltr">Due to biomechanical dynamics are related to the movement patterns and gait characteristics of human people and may provide important insights if mined by deep learning models, we conduct the study the spatial variability of biomechanical dynamics, aiming to evaluate and determine the optimal body location that is of great promise in robust physical activity type detection. Then we have developed a framework for deep learning pruning, aiming to determine the optimal pruning schemes while maintaining acceptable performance. Finally, we have enhanced and boosted the efficient deep learning framework, to co-optimize the accuracy and the continuity during the pruning process.</p>

Tracking human hand motions has raised more attention due to the recent advancements of virtual reality (Rheingold, 1991) and prosthesis control (Antfolk et al., 2010). Surface electromyography (sEMG) has been the predominant method for sensing electrical activity in biomechanical studies, and has also been applied to motion tracking in recent years. While most studies focus on the classification of human hand motions within a predefined motion set, the prediction of continuous finger joint angles and wrist angles remains a challenging endeavor. In this research, a biomechanical knowledge-driven data fusion strategy is proposed to predict finger joint angles and wrist angles. This strategy combines time series data of sEMG signals and simulated muscle features, which can be extracted from a biomechanical model available in OpenSim (Delp et al., 2007). A support vector regression (SVR) model is used to firstly predict muscle features from sEMG signals and then to predict joint angles from the estimated muscle features. A set of motion data containing 10 types of motions from 12 participants was collected from an institutional review board approved experiment. A hypothesis was tested to validate whether adding the simulated muscle features would significantly improve the prediction performance. The study indicates that the biomechanical knowledge-driven data fusion strategy will improve the prediction of new types of human hand motions. The results indicate that the proposed strategy significantly outperforms the benchmark date-driven model especially when the users were performing unknown types of motions from the model training stage. The proposed model provides a possible approach to integrate the simulation models and data fusion models in human factors and ergonomics. / Master of Science / Hand motion tracking is a promising technique for the development of virtual reality and prosthesis. Identifying hand motions based on sensor data is the fundamental step to realize motion tracking. Among all the tracking techniques, surface electromyography (sEMG) is a type of electrical signals that has been proven useful in predicting hand motions in recent years, since sEMG signals can directly reflect muscle activities, and hand motions are controlled by muscle groups. While most studies focus on the classification of human hand motions within a predefined motion set, the prediction of continuous finger joint angles and wrist angles remains a challenging endeavor. In this research, a biomechanical knowledge-driven data fusion strategy was proposed to predict finger joint angles and wrist angles. More specifically, this strategy combined a statistical model with a biomechanical simulation model, and a hypothesis was tested to validate whether adding the biomechanical simulation model would significantly improve the prediction performance. A set of sEMG signals containing 10 types of motions from 12 participants was collected from an institutional review board approved experiment, in order to test the proposed strategy. The results indicate that the proposed strategy significantly outperforms the benchmark statistical models especially when users were performing unknown types of motions from the model training stage. The proposed strategy provides a possible approach to integrate the simulation models and data-driven models in human factors and ergonomics.