Robot Programming by Demonstration: Trajectory Learning Enhanced by sEMG-Based User Hand Stiffness Estimation

Trajectory learning is one of the key components of robot Programming by Demonstration approaches, which in many cases, especially in industrial practice, aim at defining complex manipulation patterns. In order to enhance these methods, which are generally based on a physical interaction between the user and the robot, guided along the desired path, an additional input channel is considered in this article. The hand stiffness, that the operator continuously modulates during the demonstration, is estimated from the forearm surface electromyography and translated into a request for a higher or lower accuracy level. Then, a constrained optimization problem is built (and solved) in the framework of smoothing B-splines to obtain a minimum curvature trajectory approximating, in this manner, the taught path within the precision imposed by the user. Experimental tests in different applicative scenarios, involving both position and orientation, prove the benefits of the proposed approach in terms of the intuitiveness of the programming procedure for the human operator and characteristics of the final motion

Combined joint-cartesian mapping for simultaneous shape and precision teleoperation of anthropomorphic robotic hands

There are many applications involving robotic hands in which teleoperation-based approaches are preferred to autonomous solutions. The main reason is that cognitive skills of human operators are desirable in some task scenarios, in order to overcome limitations of robotic hands abilities in dealing with unstructured environments and/or unpredetermined requirements. In particular, in this work we focus on the use of anthropomorphic grasping devices and, specifically, on their teleoperation based on movements of the human operator's hand (the master hand.) Indeed, the mapping of human hand configurations to an anthropomorphic robotic hand (the slave device) is still an open problem, because of the presence of dissimilar kinematics between master and slave that produce shape and/or Cartesian errors - as addressed within our study. In this work, we propose a novel algorithm that combines joint and Cartesian mappings in order to enhance the preservation of both finger shapes and fingertip positions during the teleoperation of the robotic hand. In particular, a transition between the joint and Cartesian mappings is realized on the basis of the distance between the fingertip of the master hands' thumb and the opposite fingers, in which the mapping of the thumb fingertip is specifically addressed. The result of the testing of the algorithm with a ROS-based simulator of a commercially available robotic hand is reported, showing the effectiveness of the proposed mapping

Prenatal diagnosis of X-linked adrenoleukodystrophy associated with isolated pericardial effusion

This is the first reported case of fetal pericardial effusion in association with X-linked adrenoleukodystrophy and hypocortisolism from a nonautoimmune cause. Our hypothesis is that in experienced hands and after accurate genetic counseling, isolated pericardial effusion can constitute an indication for a severe metabolic disease

Fatores ambientais sobre pesos em diferentes idades de ovinos da raça Santa Inês no Nordeste do Brasil.

Com o objetivo de avaliar os efeitos de ambiente sobre as características de crescimento dos cordeiros, foram analisados registros de 4094 cordeiros da raça Santa Inês provenientes de rebanhos dos estados da Paraíba, Ceará e Sergipe, coletados num período de 23 anos (1983 a 2005). Foram avaliados os efeitos da estação, do ano de nascimento, sexo do cordeiro, tipo de nascimento e idade da mãe ao parto sobre os pesos corporais ao nascimento (PN), aos 56 dias de idade (P56), aos 112 dias de idade (P112) e aos 196 dias de idade (P196). Os cordeiros nascidos na estação chuvosa e seca não apresentaram diferenças significativas para PN, P56 e P112, porém no P196 os animais nascidos em estação chuvosa apresentaram pesos maiores. Os cordeiros machos foram mais pesados que as fêmeas em todas as idades estudadas. Cordeiros nascidos de parto simples pesaram mais que os nascidos de parto duplo, entretanto, houve interação significativa entre sexo e tipo de parto em que foi observado que fêmeas nascidas de parto simples tiveram pesos maiores que os machos de parto duplo em todas as idades avaliadas. Desta forma, torna-se evidente a necessidade de inclusão e ajuste destas características, como ferramentas de auxílio na avaliação genética e seleção dos animais visando melhoria no desempenho de ovinos da raça Santa Inês. Environmental factors on weights of different ages of Santa Inês sheep in the Northeasterner of Brazil. Abstract: The aim of this study was to evaluate environmental effects on growth performance in Santa Inês lambs, were using data of 4.094 lambs proceeding from Paraíba, Ceará and Sergipe states, collected over an 23-year period (1983 to 2005). The environmental effects of season of birth (winter or summer), sex of lamb, age of dam at lambing and type of birth (single or twins), were important sources of variation to explain differences in weigth at birth (WB), at 56 (W56), 112 (W112) and 196 (W196) days of age. The lambs born in the rain and dry no observed significant differences for WB,WP112 and W56, but the W196 animals born in the rainr season showed higher weights. Males were heavier than female lambs at all ages. Lambs born as singles were heavier (P < 0.01) than lambs born as twins at all ages, however, there was significant interaction between sex and type of birth, that was observed that females lambs born as single had larger weights than the males of twins in all ages. Adjustment factors for sex of lamb, type of birth and age of ewe at lambing need to be estimated and considered in selection programs to improve growth trait of Santa Inês

Estimação de componentes de variância e parâmetros genéticos para pesos do nascimento aos 196 dias de idade em ovinos Santa Inês por meio de modelo multicaracterística.

Resumo: O trabalho foi conduzido com o objetivo de estimar os componentes de variância e parâmetros genéticos para os pesos ao nascer, 56, 112 e 196 dias de idade em ovinos Santa Inês por meio de um modelo animal em análise multicaracterística. O modelo de análise inclui os efeitos aleatórios genéticos aditivos direto e materno e de ambiente permanente materno. Os efeitos fixos utilizados na análise foram os de grupo contemporâneo e idade da mãe ao parto, como covariável. As herdabilidades diretas estimadas para os pesos ao nascer, 56, 112 e 196 dias de idade foram, respectivamente, 0,17, 0,05, 0,08 e 0,10. Os resultados encontrados indicam que o ganho genético obtido por meio de seleção individual será pequeno. O efeito materno apresentou influência sobre os pesos estudados. Variance components and genetics parameters estimation for birth weight to the 196-days in Santa Inês sheep using multiple-trast model. Abstract: The study was carried out with the objective to stimate the variance components and genetics parameters for birth weights 56, 112 and 196-day in Santa Inês sheep using multiple-trast animal model. The molysis model includes the direct additive and maternal genetic effect and permanent maternal environmental effect. The fixed effects used in molysis were the contemporary group and age of dam lombing, as (co)varience. The estimate direct heritability for the weights at the birth, 56, 112 and 196 days of age were 0,17, 0,05, 0,08 and 0,10 respectively. The found results indicate that the genetic gain obtained through individual selection it will be small. The maternal effect presented influence on the weights studied

Membrane Potential Controls Adipogenic and Osteogenic Differentiation of Mesenchymal Stem Cells

Background: Control of stem cell behavior is a crucial aspect of developmental biology and regenerative medicine. While the functional role of electrophysiology in stem cell biology is poorly understood, it has become clear that endogenous ion flows represent a powerful set of signals by means of which cell proliferation, differentiation, and migration can be controlled in regeneration and embryonic morphogenesis. Methodology/Principal Findings: We examined the membrane potential (Vmem) changes exhibited by human mesenchymal stem cells (hMSCs) undergoing adipogenic (AD) and osteogenic (OS) differentiation, and uncovered a characteristic hyperpolarization of differentiated cells versus undifferentiated cells. Reversal of the progressive polarization via pharmacological modulation of transmembrane potential revealed that depolarization of hMSCs prevents differentiation. In contrast, treatment with hyperpolarizing reagents upregulated osteogenic markers. Conclusions/Significance: Taken together, these data suggest that the endogenous hyperpolarization is a functiona

Principal components analysis based control of a multi-dof underactuated prosthetic hand

<p>Abstract</p> <p>Background</p> <p>Functionality, controllability and cosmetics are the key issues to be addressed in order to accomplish a successful functional substitution of the human hand by means of a prosthesis. Not only the prosthesis should duplicate the human hand in shape, functionality, sensorization, perception and sense of body-belonging, but it should also be controlled as the natural one, in the most intuitive and undemanding way. At present, prosthetic hands are controlled by means of non-invasive interfaces based on electromyography (EMG). Driving a multi degrees of freedom (DoF) hand for achieving hand dexterity implies to selectively modulate many different EMG signals in order to make each joint move independently, and this could require significant cognitive effort to the user.</p> <p>Methods</p> <p>A Principal Components Analysis (PCA) based algorithm is used to drive a 16 DoFs underactuated prosthetic hand prototype (called CyberHand) with a two dimensional control input, in order to perform the three prehensile forms mostly used in Activities of Daily Living (ADLs). Such Principal Components set has been derived directly from the artificial hand by collecting its sensory data while performing 50 different grasps, and subsequently used for control.</p> <p>Results</p> <p>Trials have shown that two independent input signals can be successfully used to control the posture of a real robotic hand and that correct grasps (in terms of involved fingers, stability and posture) may be achieved.</p> <p>Conclusions</p> <p>This work demonstrates the effectiveness of a bio-inspired system successfully conjugating the advantages of an underactuated, anthropomorphic hand with a PCA-based control strategy, and opens up promising possibilities for the development of an intuitively controllable hand prosthesis.</p