Comparison of Capture Point estimation with human foot placement: Applicability and Limitations

National audienceFor bipeds like humans, taking a step to recover its balance is fundamental. The question that arises is the location where the biped should step. Pratt et al. developed an algorithm to estimate the so-called Capture Point, a point on ground where a robot can step in order to bring itself to a complete stop. The objective of the current work is to test the applicability of the algorithm for the prediction of step location in humans under perturbed state

Balance Recovery Prediction with Multiple Strategies for Standing Humans

International audienceHuman balance recovery from external disturbances is a complex process, and simulating it remains an open challenge. In particular, there still is a need for a comprehensive numerical tool capable of predicting the outcome of a balance perturbation, including in particular the three elementary recovery strategies: ankle, hip and stepping with variable step duration. In order to fill this gap we further developed a previously proposed multiple step balance recovery prediction tool to include the use of the hip strategy and variable step duration. Simulated recovery reactions are compared against observations from different experimental situations from the literature. Reasonable accuracy in terms of step positions and durations were obtained for these different situations using a single set of controller parameters. Moreover, variations in the use of the hip strategy and the step duration between situations were consistent with biomechanical observations. Such a model could be useful to better understand the balance recovery mechanisms, and could also be used to identify potentially hazardous situations

Deriving and Evaluating a Detailed Taxonomy of Game Bugs

Game development has become an extremely competitive multi-billion-dollar industry. Many games fail even after years of development efforts because of game-breaking bugs that disrupt the game-play and ruin the player experience. The goal of this work is to provide a bug taxonomy for games that will help game developers in developing bug-resistant games, game testers in designing and executing fault-finding test cases, and researchers in evaluating game testing approaches. For this purpose, we performed a Multivocal Literature Review (MLR) by analyzing 436 sources, out of which 189 (78 academic and 111 grey) sources reporting bugs encountered in the game development industry were selected for analysis. We validate the proposed taxonomy by conducting a survey involving different game industry practitioners. The MLR allowed us to finalize a detailed taxonomy of 63 game bug categories in end-user perspective including eight first-tier categories: Gaming Balance, Implementation Response, Network, Sound, Temporal, Unexpected Crash, Navigational, and Non-Temporal faults. We observed that manual approaches towards game testing are still widely used. Only one of the approaches targets sound bugs whereas game balancing and how to incorporate machine learning in game testing is trending in the recent literature. Most of the game testing techniques are specialized and dependent on specific platforms

Prenatal Diagnosis of Maternal Serum from Mothers Carrying β-thalassemic Fetus

Background Current study focused on discovering protein biomarkers from the maternal serum of β-thalassemic trait mothers carrying the normal fetus and β-thalassemic major fetus. Method Serum samples from β-thalassemic trait mothers carrying major (N=5) and normal fetuses (N=5) were studied. IVS1-5 thalassemia mutation was common among β-thalassemic trait mothers who were carrying homozygous β-thalassemic fetus (IVS1-5/ IVS1-5 mutation) or normal fetus (no mutation). We employed two-dimensional gel electrophoresis and mass spectrometric analysis to explore differentially expressed maternal serum proteins from thalassemia carrier couples having the same β-thalassemia mutation. Western blotting was performed for one of the identified proteins to validate our data. Results Ten proteins were identified in maternal serum of β-thalassemic trait mothers carrying the β-thalassemic major fetus and normal fetus. Among these, Serotransferrin, Haptoglobin, Alpha-1 anti-trypsin (A1AT), Apo-lipoprotein A1, and Fibrinogen-beta chain were found to be up-regulated in mothers carrying major fetuses and are known to be associated with pregnancy-related disorders. The expression of A1AT was validated through western blotting. Conclusion Proteins identified in the current study from maternal serum are reported to contribute to hereditary disorders. We suggest that these can serve as putative screening markers for non-invasive prenatal diagnosis in β-thalassemic pregnancies

Dynamic simulation of balance recovery : Application to the standing passengers of public transport

La perte d'équilibre chez l'humain est un phénomène courant de la vie quotidienne. Plusieurs causes peuvent être identifiées, dont notamment des perturbations extérieures. Le scénario qui nous intéresse particulièrement est celui des passagers debout dans les transports en commun. La combinaison de plusieurs études accidentologiques fait ressortir un risque de blessure important pour ce type de situations, surtout pour des passagers debout et/ou âgées. Ces incidents en gendrent des blessures qui coûtent très cher au niveau du budget de la santé. La sécurité de ces passagers est donc à l’origine de ce travail. La perte et/ou le rattrapage d’équilibre est une question complexe qui met en jeu un ensemble de phénomènes tels que la perception de la perturbation, le traitement de l’information, la prise de décision et la mise en œuvre d’actions correctrices. Bien que les connaissances théoriques sur chacun de ces phénomènes soient avancées, il n’existe pas, à l’heure actuelle, de modèle global permettant de représenter la réaction des personnes dans des situations aussi concrètes et complexes que celle des passagers debout de transport en commun.Dans ce contexte, l’objectif principal de ce travail était de développer un outil de simulation pour évaluer les risques associés à la perte d’équilibre des passagers de transport en commun.Loss of balance is a common phenomenon in our society resulting in injuries and even deaths each year. Among other common sources of destabilization such as slips or trips from an obstacle, the public transportation vehicles are a major source of balance-related injuries to its passengers. Accidental data suggest that the passenger casualties in these vehicles are common, especially to the standing and the elderly passengers, mainly due to the sudden acceleration/deceleration changes of the vehicle. These injuries as well as associated discomfort may discourage people from using these means of transport resulting in adverse economic and societal effects. In this context, the security of the standing passengers in these vehicles constitutes the main motivation of this work.Recovering balance from an external disturbance is a complex process which involves a set of phenomenon such as the perception of the disturbance, information processing, decision making and its implementation. Even though experimental research in the fields of biomechanics and neurosciences provide us with a fair understanding of these phenomena separately, we are unaware of a global model which represents the reaction of people in response to the external disturbances to their equilibrium. In this context, the objective of this work is to develop such a numerical tool which can be used for the assessment of risks associated with the loss of balance of the standing passengers. The essential feature of this tool is the prediction of the post-disturbance kinematics of the subjects depending upon the disturbance characteristics (magnitude, duration etc.) as well as the active recovery response. Another key feature is the representation of the reaction of different populations, especially the elderly, by integrating age effects in the model. For the development of the tool, mathematical modeling (e.g. simplified body representations) and control ideas are borrowed from the field of biped robotics which explicitly deals with the balance issues of bipeds. Further development is done in view of human balance recovery (BR) characteristics. The resulting BR tool shows reasonable predictive capacity of a human balance recovery response confirmed by the comparison of model predictions with experimental balance recovery data

Validity of Dual-Minima Algorithm for Heel-Strike and Toe-Off Prediction for the Amputee Population

Assessment of gait deficits relies on accurate gait segmentation based on the key gait events of heel strike (HS) and toe-off (TO). Kinematics-based estimation of gait events has shown promise in this regard, especially using the leg velocity signal and gyroscopic sensors. However, its validation for the amputee population is not established in the literature. The goal of this study is to assess the accuracy of lower-leg angular velocity signal in determining the TO and HS instants for the amputee population. An open data set containing marker data of 10 subjects with unilateral transfemoral amputation during treadmill walking was used. A rule-based dual-minima algorithm was developed to detect the landmarks in the shank velocity signal indicating TO and HS events. The predictions were compared against the force platform data for 2595 walking cycles from 239 walking trials. The results showed considerable accuracy for the HS with a median error of −1 ms. The TO prediction error was larger with the median ranging from 35–84 ms. The algorithm consistently predicted the TO earlier than the actual event. Significant differences were found between the prediction accuracy for the sound and prosthetic legs. The prediction accuracy was also affected by the subjects’ mobility level (K-level) but was largely unaffected by gait speed. In conclusion, the leg velocity profile during walking can predict the heel-strike and toe-off events for the transfemoral amputee population with varying degrees of accuracy depending upon the leg side and the amputee’s functional ability level

Simulation dynamique de perte d'équilibre : Application aux passagers debout de transport en commun

Loss of balance is a common phenomenon in our society resulting in injuries and even deaths each year. Among other common sources of destabilization such as slips or trips from an obstacle, the public transportation vehicles are a major source of balance-related injuries to its passengers. Accidental data suggest that the passenger casualties in these vehicles are common, especially to the standing and the elderly passengers, mainly due to the sudden acceleration/deceleration changes of the vehicle. These injuries as well as associated discomfort may discourage people from using these means of transport resulting in adverse economic and societal effects. In this context, the security of the standing passengers in these vehicles constitute the main motivation of this work. Recovering balance from an external disturbance is a complex process which involves a set of phenomenon such as the perception of the disturbance, information processing, decision making and its implementation. Even though experimental research in the fields of biomechanics and neurosciences provide us with a fair understanding of these phenomena separately, we are unaware of a global model which represents the reaction of people in response to the external disturbances to their equilibrium. In this context, the objective of this work is to develop such a numerical tool which can be used for the assessment of risks associated with the loss of balance of the standing passengers. The essential feature of this tool is the prediction of the post-disturbance kinematics of the subjects depending upon the disturbance characteristics (magnitude, duration etc.) as well as the active recovery response. Another key feature is the representation of the reaction of different populations, especially the elderly, by integrating age effects in the model. For the development of the tool, mathematical modeling (e.g. simplified body representations) and control ideas are borrowed from the field of biped robotics which explicitly deals with the balance issues of bipeds. Further development is done in view of human balance recovery (BR) characteristics. The resulting BR tool shows reasonable predictive capacity of a human balance recovery response confirmed by the comparison of model predictions with experimental balance recovery data

Validity of Dual-Minima Algorithm for Heel-Strike and Toe-Off Prediction for the Amputee Population

Assessment of gait deficits relies on accurate gait segmentation based on the key gait events of heel strike (HS) and toe-off (TO). Kinematics-based estimation of gait events has shown promise in this regard, especially using the leg velocity signal and gyroscopic sensors. However, its validation for the amputee population is not established in the literature. The goal of this study is to assess the accuracy of lower-leg angular velocity signal in determining the TO and HS instants for the amputee population. An open data set containing marker data of 10 subjects with unilateral transfemoral amputation during treadmill walking was used. A rule-based dual-minima algorithm was developed to detect the landmarks in the shank velocity signal indicating TO and HS events. The predictions were compared against the force platform data for 2595 walking cycles from 239 walking trials. The results showed considerable accuracy for the HS with a median error of −1 ms. The TO prediction error was larger with the median ranging from 35–84 ms. The algorithm consistently predicted the TO earlier than the actual event. Significant differences were found between the prediction accuracy for the sound and prosthetic legs. The prediction accuracy was also affected by the subjects’ mobility level (K-level) but was largely unaffected by gait speed. In conclusion, the leg velocity profile during walking can predict the heel-strike and toe-off events for the transfemoral amputee population with varying degrees of accuracy depending upon the leg side and the amputee’s functional ability level

Estimation of gait parameters using leg velocity for amputee population.

Quantification of key gait parameters plays an important role in assessing gait deficits in clinical research. Gait parameter estimation using lower-limb kinematics (mainly leg velocity data) has shown promise but lacks validation for the amputee population. The aim of this study is to assess the accuracy of lower-leg angular velocity to predict key gait events (toe-off and heel strike) and associated temporal parameters for the amputee population. An open data set of reflexive markers during treadmill walking from 10 subjects with unilateral transfemoral amputation was used. A rule-based dual-minima algorithm was developed to detect the landmarks in the shank velocity signal indicating toe-off and heel strike events. Four temporal gait parameters were also estimated (step time, stride time, stance and swing duration). These predictions were compared against the force platform data for 3000 walking cycles from 239 walking trials. Considerable accuracy was achieved for the HS event as well as for step and stride timings, with mean errors ranging from 0 to -13ms. The TO prediction exhibited a larger error with its mean ranging from 35-81ms. The algorithm consistently predicted the TO earlier than the actual event, resulting in prediction errors in stance and swing timings. Significant differences were found between the prediction for sound and prosthetic legs, with better TO accuracy on the prosthetic side. The prediction accuracy also appeared to improve with the subjects' mobility level (K-level). In conclusion, the leg velocity profile, coupled with the dual-minima algorithm, can predict temporal parameters for the transfemoral amputee population with varying degrees of accuracy

Simulation de l’effet de l’inertie de la partie supérieure du corps sur la récupération de l’équilibre chez l’homme

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