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1.
J Neuroeng Rehabil ; 17(1): 63, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32404174

##### RESUMO

BACKGROUND: Human-likeliness of robot movements is a key component to enable a safe and effective human-robot interaction, since it contributes to increase acceptance and motion predictability of robots that have to closely interact with people, e.g. for assistance and rehabilitation purposes. Several parameters have been used to quantify how much a robot behaves like a human, which encompass aspects related to both the robot appearance and motion. The latter point is fundamental to allow the operator to interpret robotic actions, and plan a meaningful reactions. While different approaches have been presented in literature, which aim at devising bio-aware control guidelines, a direct implementation of human actions for robot planning is not straightforward, still representing an open issue in robotics. METHODS: We propose to embed a synergistic representation of human movements for robot motion generation. To do this, we recorded human upper-limb motions during daily living activities. We used functional Principal Component Analysis (fPCA) to extract principal motion patterns. We then formulated the planning problem by optimizing the weights of a reduced set of these components. For free-motions, our planning method results into a closed form solution which uses only one principal component. In case of obstacles, a numerical routine is proposed, incrementally enrolling principal components until the problem is solved with a suitable precision. RESULTS: Results of fPCA show that more than 80% of the observed variance can be explained by only three functional components. The application of our method to different meaningful movements, with and without obstacles, show that our approach is able to generate complex motions with a very reduced number of functional components. We show that the first synergy alone accounts for the 96% of cost reduction and that three components are able to achieve a satisfactory motion reconstruction in all the considered cases. CONCLUSIONS: In this work we moved from the analysis of human movements via fPCA characterization to the design of a novel human-like motion generation algorithm able to generate, efficiently and with a reduced set of basis elements, several complex movements in free space, both in free motion and in case of obstacle avoidance tasks.

2.
IEEE Trans Neural Syst Rehabil Eng ; 28(5): 1168-1177, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32248115

##### RESUMO

Upper limb functions are severely affected in 23% of the chronic stroke patients, compromising their life quality. To re-enable hand use, providing a degree of functionality and motivating against learned non-use, we propose a robotic supernumerary limb, the SoftHand X (SHX), consisting of a robotic hand, a gravity support system, and different sensors to detect the patient's intent for controlling the robotic hand. In this paper, this novel compensational approach is introduced and experimentally evaluated in stroke patients, assessing its efficacy, usability and safety. Ten patients were asked to perform tasks of a modified Action Research Arm Test with the SHX, by using three input methods. The mARAT scores rated the potentiality of the system. Usability was evaluated with the System Usability Scale, while spasticity before and after use was measured by the modified Ashworth Scale (mAS). Nine patients, not able to perform any tasks without external support, completed the whole experimental procedure using the proposed system with a median score greater than 12/30. Among the three input methods tested, the usability of one was rated as "good" while the other two were rated as "ok". Seven patients exhibited a reduction of the mAS. All nine patients stated that they would use the system frequently. Results obtained suggest that the SHX has the potential to partially compensate severely impaired hand function in stroke patients.

3.
IEEE Int Conf Rehabil Robot ; 2019: 392-397, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31374661

##### RESUMO

Assessing upper limb prostheses and their influence when performing goal-directed activities is essential to compare the quality of different devices and optimize their control settings. Currently available assessments are often subjective, insensitive, and cannot provide a detailed evaluation of prostheses and their usage. The goal of this pilot study was to explore the feasibility of using the Virtual Peg Insertion Test (VPIT) to provide an in-depth assessment of a prosthesis and its functional performance. One transradial amputee performed the goal-directed manipulation task of the VPIT with the sound body side and four different myoelectrically-controlled prostheses. The subject was able to complete the VPIT protocol successfully with technically advanced prosthesis (two out of four devices). The kinematic- and kinetic-based objective evaluation measures extracted from the VPIT were able to capture clear differences between the sound and amputated body side and were able to identify varying movement patterns for different prostheses. Additionally, the outcome measures were sensitive to changes in prosthesis control settings and showed clear trends across measures of subjectively perceived prosthesis quality assessed through a questionnaire. This work demonstrates the general feasibility of objectively evaluating functional prosthesis usage with the VPIT.

##### Assuntos
Amputados , Membros Artificiais , Mãos , Desenho de Prótese , Adulto , Fenômenos Biomecânicos , Feminino , Humanos , Projetos Piloto
4.
IEEE Int Conf Rehabil Robot ; 2019: 963-970, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31374754

##### RESUMO

In literature, much attention has been devoted to the design of control strategies of exoskeletons for assistive purposes. While several control schemes were presented, their performance still has limitations in minimizing muscle effort. According to this principle, we propose a novel approach to solve the problem of generating an assistive torque that minimizes muscle activation under stability guarantees. First, we perform a linear observability and controllability analysis of the human neuromuscular dynamic system. Based on the states that can be regulated with the available measurements and taking advantage of knowledge of the muscle model, we then solve an LQR problem in which a weighted sum of muscle activation and actuation torque is minimized to systematically synthesize a controller for an assistive exoskeleton.We evaluate the performance of the developed controller with a realistic non-linear human neuromusculoskeletal model. Simulation results show better performance in comparison with a well known controller in the literature, in the sense of closed loop system stability and regulation to zero of muscle effort.

##### Assuntos
Exoesqueleto Energizado , Modelos Biológicos , Músculo Esquelético/fisiologia , Junção Neuromuscular/fisiologia , Equipamentos de Autoajuda , Comportamento , Encéfalo/fisiologia , Simulação por Computador , Articulação do Cotovelo/fisiologia , Humanos , Torque , Extremidade Superior/fisiologia
5.
Front Neurorobot ; 13: 39, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31275129

##### RESUMO

The size, weight, and power consumption of soft wearable robots rapidly scale with their number of active degrees of freedom. While various underactuation strategies have been proposed, most of them impose hard constrains on the kinetics and kinematics of the device. Here we propose a paradigm to independently control multiple degrees of freedom using a set of modular components, all tapping power from a single motor. Each module consists of three electromagnetic clutches, controlled to convert a constant unidirectional motion in an arbitrary output trajectory. We detail the design and functioning principle of each module and propose an approach to control the velocity and position of its output. The device is characterized in free space and under loading conditions. Finally, we test the performance of the proposed actuation scheme to drive a soft exosuit for the elbow joint, comparing it with the performance obtained using a traditional DC motor and an unpowered-exosuit condition. The exosuit powered by our novel scheme reduces the biological torque required to move by an average of 46.2%, compared to the unpowered condition, but negatively affects movement smoothness. When compared to a DC motor, using the our paradigm slightly deteriorates performance. Despite the technical limitations of the current design, the method proposed in this paper is a promising way to design more portable wearable robots.

6.
IEEE Trans Neural Syst Rehabil Eng ; 27(7): 1397-1406, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31135365

##### RESUMO

In this paper, we present a novel approach to dynamically describe human upper limb trajectories, addressing the question on whether and to which extent synergistic multi-joint behavior is observed and preserved over time evolution and across subjects. To this goal, we performed experiments to collect human upper limb joint angle trajectories and organized them in a dataset of daily living tasks. We then characterized the upper limb poses at each time frame through a technique that we named repeated-principal component analysis (R-PCA). We found that, although there is no strong evidence on the predominance of one principal component (PC) over the others, the subspace identified by the first three PCs takes into account most of the motion variability. We evaluated the stability of these results over time, showing that during the reaching phase, there is a strong consistency of these findings across participants. In other words, our results suggest that there is a time-invariant low-dimensional approximation of upper limb kinematics, which can be used to define a suitable reduced dimensionality control space for upper limb robotic devices in motion phases.

##### Assuntos
Extremidade Superior/fisiologia , Atividades Cotidianas , Adulto , Algoritmos , Fenômenos Biomecânicos , Eletromiografia , Feminino , Força da Mão/fisiologia , Voluntários Saudáveis , Humanos , Articulações/fisiologia , Masculino , Modelos Teóricos , Análise de Componente Principal , Reprodutibilidade dos Testes , Robótica , Adulto Jovem
7.
J Robot Surg ; 13(4): 585-588, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31062181

##### RESUMO

Uterine fibromatosis is common in women, with an estimated prevalence of up to 15-50% after 35 years. About 80% of women affected by fibromatosis have symptoms and require medical or surgical treatment. Nowadays, the gold standard for the surgical treatment of uterine fibromatosis is the use of minimally invasive surgery. The surgical skills and improvements offered by robotic approach can be relevant in reproductive surgery, in particular in minimally invasive myomectomy. However, the lack of tactile feedback of robotic platform is an important technical drawback that can reduce the accuracy of surgical procedures. Here, we present the design and the preliminary test of the wearable fabric, yielding display wearable haptic interfaces able to generate a real-time tactile feedback in terms of stiffness for applications in gynecologic robotic surgery. We preliminarily tested the device in the simulation of a real scenario of conservative myomectomy with the final purpose of increasing the accuracy and precision during surgery. The future goal is the integration of a haptic device with the commercially available robotic surgical systems with the purpose of improving the precision and accuracy of the surgical operation, thus allowing a better understanding concerning the anatomical relationship of the target structures. This in turn could determine a change in the surgical strategy in some cases, letting some patients selected for a demolitive approach retaining their uterus. This could improve surgical outcomes in fertile women enrolled for minimally invasive surgery for uterine fibroids and may be a facilitation for young gynecological surgeons or during residency teaching plans and learning programs.

##### Assuntos
Procedimentos Cirúrgicos Robóticos/instrumentação , Miomectomia Uterina/métodos , Dispositivos Eletrônicos Vestíveis , Feminino , Fibroma/cirurgia , Humanos , Procedimentos Cirúrgicos Minimamente Invasivos/instrumentação , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Procedimentos Cirúrgicos Robóticos/métodos , Percepção do Tato , Miomectomia Uterina/instrumentação , Neoplasias Uterinas/cirurgia , Útero/cirurgia
8.
IEEE Trans Haptics ; 12(4): 508-520, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31071053

##### RESUMO

Restoring hand function in individuals with upper limb loss is a challenging task, made difficult by the complexity of human hands from both a functional and sensory point of view. Users of commercial prostheses, even sophisticated devices, must visually attend to the hand to know its state, since in most cases they are not provided with any direct sensory information. Among the different types of haptic feedback that can be delivered, particularly information on hand opening is likely to reduce the requirement of constant visual attention. In recent years, there has been a trend of using underactuated, compliant multi-fingered hands as upper limb prostheses, in part due to their simplicity and ease of use attributed to low degree-of-freedom (d.o.f.) actuation. The trend toward underactuation encourages the design of one d.o.f. haptic devices to provide intuitive sensory feedback from the prosthesis. However, mapping the closure of a multi-d.o.f. prosthetic hand to a simple and intuitive haptic cue is not a trivial task. In this paper, we explore the use of a one d.o.f. skin stretch haptic device, the rice haptic rocker, to provide intuitive proprioceptive feedback indicating overall hand closure of an underactuated prosthesis. The benefits and challenges of the system are assessed in multi-tasking and reduced vision scenarios for an object-size discrimination task, in an effort to simulate challenges in daily life, and are compared against the haptic resolution of the device using the just noticeable difference. Finally, an evaluation done with a prosthesis user, in the form of a truncated version of the Activities Measure for Upper Limb Amputees (AM-ULA), shows possible benefits of the addition of haptic feedback in tasks with reduced visual attention.

9.
IEEE Trans Biomed Eng ; 66(1): 138-149, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-29993527

##### RESUMO

OBJECTIVE: Myoelectric hand prostheses have reached a considerable technological level and gained an increasing attention in assistive robotics. However, their abandonment rate remains high, with unintuitive control and lack of sensory feedback being major causes. Among the different types of sensory information, proprioception, e.g., information on hand aperture, is crucial to successfully perform everyday actions. Despite the many attempts in literature to restore and convey this type of feedback, much remains to be done to close the action-perception loop in prosthetic devices. METHODS: With this as motivation, in this paper we introduce HapPro, a wearable, noninvasive haptic device that can convey proprioceptive information for a prosthetic hand. The device was used with an under-actuated, simple to control anthropomorphic robotic hand, providing information about hand aperture by mapping it to the position of a wheel that can run on the user's forearm. Tests with 43 able bodied subjects and one amputee subject were conducted in order to quantify the effectiveness of HapPro as a feedback device. RESULTS: HapPro provided a good level of accuracy for item discrimination. Participants also reported the device to be intuitive and effective in conveying proprioceptive cues. Similar results were obtained in the proof-of-concept experiment with an amputee subject. CONCLUSIONS: Results show that HapPro is able to convey information on the opening of a prosthetic hand in a noninvasive way. SIGNIFICANCE: Using this device for proprioceptive feedback could improve usability of myoelectric prostheses, potentially reducing abandonment and increasing quality of life for their users.

##### Assuntos
Membros Artificiais , Retroalimentação Sensorial/fisiologia , Propriocepção/fisiologia , Robótica/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Adulto , Eletromiografia/instrumentação , Feminino , Antebraço/fisiologia , Mãos/fisiologia , Humanos , Masculino , Desenho de Prótese , Dispositivos Eletrônicos Vestíveis , Adulto Jovem
10.
Conf Proc IEEE Eng Med Biol Soc ; 2018: 3060-3063, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-30441040

##### RESUMO

The Electroencephalogram (EEG) can be considered as the output of a nonlinear system whose dynamics is significantly affected by motor tasks. Nevertheless, computational approaches derived from the complex system theory has not been fully exploited for characterising motor imagery tasks. To this extent, in this study we investigated EEG complexity changes throughout the following categories of imaginary motor tasks of the upper limb: transitive (actions involving an object), intransitive (meaningful gestures that do not include the use of objects), and tool-mediated (actions using an object to interact with another one). EEG irregularity was quantified following the definition of Fuzzy Entropy, which has been demonstrated to be a reliable quantifier of system complexity with low dependence on data length. Experimental results from paired statistical analyses revealed minor topographical changes between EEG complexity associated with transitive and tool-mediated tasks, whereas major significant differences were shown between the intransitive actions vs. the others. Our results suggest that EEG complexity level during motor imagery tasks of the upper limb are strongly biased by the presence of an object.

##### Assuntos
Eletroencefalografia , Extremidade Superior , Encéfalo , Interfaces Cérebro-Computador , Imagens, Psicoterapia
11.
Conf Proc IEEE Eng Med Biol Soc ; 2018: 231-234, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-30440380

##### RESUMO

It is known that brain dynamics significantly changes during motor imagery tasks of upper limb involving different kind of interactions with an object. Nevertheless, an automatic discrimination of transitive (i.e., actions involving an object) and intransitive (i.e., meaningful gestures that do not include the use of objects) imaginary actions using EEG dynamics has not been performed yet. In this study we exploit measures of EEG spectra to automatically discern between imaginary transitive and intransitive movements of the upper limb. To this end, nonlinear support vector machine algorithms are used to properly combine EEG-derived features, while a recursive feature elimination procedure highlights the most discriminant cortical regions and associated EEG frequency oscillations. Results show the significance of $\gamma ( 30 -45$ Hz) oscillations over the fronto-occipital and ipsilateral-parietal areas for the automatic classification of transitive-intransitive imaginary upper limb movements with a satisfactory accuracy of 70.97%.

##### Assuntos
Imagens, Psicoterapia , Máquina de Vetores de Suporte , Eletroencefalografia , Gestos , Movimento
12.
PLoS One ; 13(10): e0205653, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30321204

##### RESUMO

Roughly one quarter of active upper limb prosthetic technology is rejected by the user, and user surveys have identified key areas requiring improvement: function, comfort, cost, durability, and appearance. Here we present the first systematic, clinical assessment of a novel prosthetic hand, the SoftHand Pro (SHP), in participants with transradial amputation and age-matched, limb-intact participants. The SHP is a robust and functional prosthetic hand that minimizes cost and weight using an underactuated design with a single motor. Participants with limb loss were evaluated on functional clinical measures before and after a 6-8 hour training period with the SHP as well as with their own prosthesis; limb-intact participants were tested only before and after SHP training. Participants with limb loss also evaluated their own prosthesis and the SHP (following training) using subjective questionnaires. Both objective and subjective results were positive and illuminated the strengths and weaknesses of the SHP. In particular, results pre-training show the SHP is easy to use, and significant improvement in the Activities Measure for Upper Limb Amputees in both groups following a 6-8 hour training highlights the ease of learning the unique features of the SHP (median improvement: 4.71 and 3.26 and p = 0.009 and 0.036 for limb loss and limb-intact groups, respectively). Further, we found no difference in performance compared to participant's own commercial devices in several clinical measures and found performance surpassing these devices on two functional tasks, buttoning a shirt and using a cell phone, suggesting a functional prosthetic design. Finally, improvements are needed in the SHP design and/or training in light of poor results in small object manipulation. Taken together, these results show the promise of the SHP, a flexible and adaptive prosthetic hand, and pave a path forward to ensuring higher functionality in future.

##### Assuntos
Membros Artificiais , Atividades Cotidianas , Adulto , Idoso , Amputação Traumática , Feminino , Mãos , Humanos , Masculino , Pessoa de Meia-Idade , Desenho de Prótese , Robótica
13.
Front Neurorobot ; 12: 86, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30618707

##### RESUMO

Humans are capable of complex manipulation interactions with the environment, relying on the intrinsic adaptability and compliance of their hands. Recently, soft robotic manipulation has attempted to reproduce such an extraordinary behavior, through the design of deformable yet robust end-effectors. To this goal, the investigation of human behavior has become crucial to correctly inform technological developments of robotic hands that can successfully exploit environmental constraint as humans actually do. Among the different tools robotics can leverage on to achieve this objective, deep learning has emerged as a promising approach for the study and then the implementation of neuro-scientific observations on the artificial side. However, current approaches tend to neglect the dynamic nature of hand pose recognition problems, limiting the effectiveness of these techniques in identifying sequences of manipulation primitives underpinning action generation, e.g., during purposeful interaction with the environment. In this work, we propose a vision-based supervised Hand Pose Recognition method which, for the first time, takes into account temporal information to identify meaningful sequences of actions in grasping and manipulation tasks. More specifically, we apply Deep Neural Networks to automatically learn features from hand posture images that consist of frames extracted from grasping and manipulation task videos with objects and external environmental constraints. For training purposes, videos are divided into intervals, each associated to a specific action by a human supervisor. The proposed algorithm combines a Convolutional Neural Network to detect the hand within each video frame and a Recurrent Neural Network to predict the hand action in the current frame, while taking into consideration the history of actions performed in the previous frames. Experimental validation has been performed on two datasets of dynamic hand-centric strategies, where subjects regularly interact with objects and environment. Proposed architecture achieved a very good classification accuracy on both datasets, reaching performance up to 94%, and outperforming state of the art techniques. The outcomes of this study can be successfully applied to robotics, e.g., for planning and control of soft anthropomorphic manipulators.

14.
IEEE Trans Neural Syst Rehabil Eng ; 25(12): 2407-2417, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29220323

##### RESUMO

Current prosthetic hands are frequently rejected in part due to limited functionality and versatility. We assessed the feasibility of a novel prosthetic hand, the SoftHand Pro (SHP), whose design combines soft robotics and hand postural synergies. Able-bodied subjects ( ) tracked cursor motion by opening and closing the SHP and performed a grasp-lift-hold-release (GLHR) task with a sensorized cylindrical object of variable weight. The SHP control was driven by electromyographic (EMG) signals from two antagonistic muscles. Although the time to perform the GLHR task was longer for the SHP than native hand for the first few trials (10.2 ± 1.4 s and 2.13 ± 0.09 s, respectively), performance was much faster on subsequent trials (~5 s). The SHP steady-state grip force was significantly modulated as a function of object weight ( ). For the native hand, however, peak and steady-state grip forces were modulated to a greater extent (+68% and +91%, respectively). These changes were mediated by the modulation of EMG amplitude and co-contraction. These data suggest that the SHP has a promise for prosthetic applications and point-to-design modifications that could improve the SHP.

##### Assuntos
Membros Artificiais , Força da Mão/fisiologia , Mãos/fisiologia , Músculo Esquelético/fisiologia , Desenho de Prótese/métodos , Adulto , Eletromiografia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Destreza Motora , Contração Muscular/fisiologia , Projetos Piloto , Desempenho Psicomotor , Robótica , Adulto Jovem
15.
J Neuroeng Rehabil ; 14(1): 124, 2017 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-29187203

##### RESUMO

BACKGROUND: Roughly one-quarter of upper limb prosthesis users reject their prosthesis. Reasons for rejection range from comfort, to cost, aesthetics, function, and more. This paper follows a single user from training with and testing of a novel upper-limb myoelectric prosthesis (the SoftHand Pro) for participation in the CYBATHLON rehearsal to training for and competing in the CYBATHLON 2016 with a figure-of-nine harness controlled powered prosthesis (SoftHand Pro-H) to explore the feasibility and usability of a flexible anthropomorphic prosthetic hand. METHODS: The CYBATHLON pilot took part in multiple in-lab training sessions with the SoftHand Pro and SoftHand Pro-H; these sessions focused on basic control and use of the prosthetic devices and direct training of the tasks in the CYBATHLON. He used these devices in competition in the Powered Arm Prosthesis Race in the CYBATHLON rehearsal and 2016 events. RESULTS: In training for the CYBATHLON rehearsal, the subject was able to quickly improve performance with the myoelectric SHP despite typically using a body-powered prosthetic hook. The subject improved further with additional training using the figure-of-nine harness-controlled SHPH in preparation for the CYBATHLON. The Pilot placed 3rd (out of 4) in the rehearsal. In the CYBATHLON, he placed 5th (out of 12) and was one of only two pilots who successfully completed all tasks in the competition, having the second-highest score overall. CONCLUSIONS: Results with the SoftHand Pro and Pro-H suggest it to be a viable alternative to existing anthropomorphic hands and show that the unique flexibility of the hand is easily learned and exploited.

##### Assuntos
Membros Artificiais , Terapia por Exercício/métodos , Exercício Físico/fisiologia , Desenho de Prótese , Mãos , Humanos , Masculino
16.
Conf Proc IEEE Eng Med Biol Soc ; 2017: 398-401, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-29059894

##### RESUMO

We studied the effects of muscle fatigue on the Autonomic Nervous System (ANS) dynamics. Specifically, we monitored the electrodermal activity (EDA) on 32 healthy subjects performing isometric biceps contraction. As assessed by means of an electromyography (EMG) analysis, 15 subjects showed muscle fatigue and 17 did not. EDA signals were analyzed using the recently proposed cvxEDA model in order to decompose them into their phasic and tonic components and extract effective features to study ANS dynamics. A statistical comparison between the two groups of subjects was performed. Results revealed that relevant phasic EDA features significantly increased in the fatigued group. Moreover, a pattern recognition system was applied to the EDA dataset in order to automatically discriminate between fatigued and non-fatigued subjects. The proposed leave-one-subject-out KNN classifier showed an accuracy of 75.69%. These results suggest the use of EDA as correlate of muscle fatigue, providing integrative information to the standard indices extracted from the EMG signals.

##### Assuntos
Fadiga Muscular , Eletromiografia , Resposta Galvânica da Pele , Humanos , Contração Isométrica , Contração Muscular , Músculo Esquelético
17.
Conf Proc IEEE Eng Med Biol Soc ; 2017: 1324-1327, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-29060120

##### RESUMO

Fatigue can be defined as the muscular condition occurring before the inability to perform a task. It can be assessed through the evaluation of the median and mean frequency of the spectrum of the surface electromyography series. Previous studies investigated the relationship between heartbeat dynamics and muscular activity. However, exploitation of such cardiovascular measures to automatically identify muscle fatigue during fatiguing exercises is still missing. To this extent, HRV signals were gathered from 32 subjects during an isometric contraction task, and features defined in the time, frequency and nonlinear domains were investigated. We used surface electromyography to label the occurrence of muscle fatigue. Statistically significant differences were observed by comparing features related to fatigued subjects with the non-fatigued ones. Moreover, a pattern recognition system capable to achieve an average accuracy of 78.24% was implemented. These results confirmed the hypothesis that a relationship between heartbeat dynamics and muscle fatigue might exist.

##### Assuntos
Fadiga Muscular , Eletromiografia , Exercício Físico , Frequência Cardíaca , Humanos , Contração Isométrica , Contração Muscular , Músculo Esquelético
18.
Front Neurorobot ; 11: 41, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28900393

##### RESUMO

Humans are able to intuitively exploit the shape of an object and environmental constraints to achieve stable grasps and perform dexterous manipulations. In doing that, a vast range of kinematic strategies can be observed. However, in this work we formulate the hypothesis that such ability can be described in terms of a synergistic behavior in the generation of hand postures, i.e., using a reduced set of commonly used kinematic patterns. This is in analogy with previous studies showing the presence of such behavior in different tasks, such as grasping. We investigated this hypothesis in experiments performed by six subjects, who were asked to grasp objects from a flat surface. We quantitatively characterized hand posture behavior from a kinematic perspective, i.e., the hand joint angles, in both pre-shaping and during the interaction with the environment. To determine the role of tactile feedback, we repeated the same experiments but with subjects wearing a rigid shell on the fingertips to reduce cutaneous afferent inputs. Results show the persistence of at least two postural synergies in all the considered experimental conditions and phases. Tactile impairment does not alter significantly the first two synergies, and contact with the environment generates a change only for higher order Principal Components. A good match also arises between the first synergy found in our analysis and the first synergy of grasping as quantified by previous work. The present study is motivated by the interest of learning from the human example, extracting lessons that can be applied in robot design and control. Thus, we conclude with a discussion on implications for robotics of our findings.

19.
IEEE Int Conf Rehabil Robot ; 2017: 539-546, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28813876

##### RESUMO

In this paper we present the design of a one degree of freedom assistive platform to augment the strength of upper limbs. The core element is a variable stiffness actuator, closely reproducing the behavior of a pair of antagonistic muscles. The novelty introduced by this device is the analogy of its control parameters with those of the human muscle system, the threshold lengths. The analogy can be obtained from a proper tuning of the mechanical system parameters. Based on this, the idea is to control inputs by directly mapping the estimation of the muscle activations, e.g. via ElectroMyoGraphic(EMG) sensors, on the exoskeleton. The control policy resulting from this mapping acts in feedforward in a way to exploit the muscle-like dynamics of the mechanical device. Thanks to the particular structure of the actuator, the exoskeleton joint stiffness naturally results from that mapping. The platform as well as the novel control idea have been experimentally validated and the results show a substantial reduction of the subject muscle effort.

##### Assuntos
Exoesqueleto Energizado/normas , Reabilitação/instrumentação , Reabilitação/normas , Eletromiografia/instrumentação , Desenho de Equipamento , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Reprodutibilidade dos Testes , Análise e Desempenho de Tarefas , Extremidade Superior/fisiologia
20.
IEEE Trans Haptics ; 10(1): 123-129, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27705863

##### RESUMO

Understanding the mechanisms of human tactual perception represents a challenging task in haptics and humanoid robotics. A classic approach to tackle this issue is to accurately and exhaustively characterize the mechanical behavior of human fingertip. The output of this characterization can then be exploited to drive the design of numerical models, which can be used to investigate in depth the mechanisms of human sensing. In this work, we present a novel integrated measurement technique and experimental set up for in vivo characterization of the deformation of the human fingertip at contact, in terms of contact area, force, deformation, and pressure distribution. The device presented here compresses the participant's fingertip against a flat surface, while the aforementioned measurements are acquired and experimental parameters such as velocity, finger orientation, and displacement (indentation) controlled. Experimental outcomes are then compared and integrated with the output of a 3D finite element (FE) model of the human fingertip, built upon existing validated models. The agreement between numerical and experimental data represents a validation for our approach.

##### Assuntos
Dedos/fisiologia , Tato/fisiologia , Adulto , Simulação por Computador , Feminino , Análise de Elementos Finitos , Humanos , Modelos Biológicos