This paper introduces a newly developed Hand Exoskeleton Rehabilitation Robot (HEXORR). This device has been designed to provide full range of motion (ROM) for all of the hand’s digits. The thumb actuator allows for variable thumb plane of motion to incorporate different degrees of extension/flexion and abduction/adduction. Compensation algorithms have been developed to improve the exoskeleton’s backdrivability by counteracting gravity, stiction and kinetic friction. We have also designed a force assistance mode that provides extension assistance based on each individual’s needs. A pilot study was conducted on 9 unimpaired and 5 chronic stroke subjects to investigate the device’s ability to allow physiologically accurate hand movements throughout the full ROM. The study also tested the efficacy of the force assistance mode with the goal of increasing stroke subjects’ active ROM while still requiring active extension torque on the part of the subject.

(далее…)

Категория: Научные статьи | Нет комментариев »

Background: Hemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients’ gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT’s Anklebot, while unpowered, on gait of chronic stroke sur-vivors during overground and treadmill walking. Methods: Nine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg. Results: The added inertia and friction of the unpowered anklebot had no statis-tically significant effect on spatiotemporal parameters of gait, including paretic and nonparetic step time and stance percen-tage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was grea-ter on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the non-paretic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05). Conclusions: Our results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern. (далее…)

Категория: Научные статьи | Нет комментариев »

Background: Significant progress has been made towards the clinical application of human-machine interfaces (HMIs) based on elec-tromyographic (EMG) pattern recognition for various rehabilitation purposes. Making this technology practical and available to pati-ents with motor deficits requires overcoming real-world challenges, such as physical and physiological changes, that result in vari-ations in EMG signals and systems that are unreliable for long-term use. In this study, we aimed to address these challenges by investigating the stability of time-domain EMG features during changes in the EMG signals and identifying the feature sets that would provide the most robust EMG pattern recognition. Methods: Variations in EMG signals were introduced during physical experi-ments. We identified three disturbances that commonly affect EMG signals: EMG electrode location shift, variation in muscle contrac-tion effort, and muscle fatigue. The impact of these disturbances on individual features and combined feature sets was quantified by changes in classification performance. The robustness of feature sets was evaluated by a stability index developed in this study. Results: Muscle fatigue had the smallest effect on the studied EMG features, while electrode location shift and varying effort le-vel significantly reduced the classification accuracy for most of the features. Under these disturbances, the most stable EMG fea-ture set with combination of four features produced at least 16.0% higher classification accuracy than the least stable set. EMG autoregression coefficients and cepstrum coefficients showed the most robust classification performance of all studied time-domain features. Conclusions: Selecting appropriate EMG feature combinations can overcome the impact of the studied disturbances on EMG pattern classification to a certain extent; however, this simple solution is still inadequate. Stabilizing electrode contact loca-tions and developing effective classifier training strategies are suggested to further improve the robustness of HMIs based on EMG pattern recognition.

(далее…)

Категория: Научные статьи | Нет комментариев »

The choice of non-anthropomorphic kinematic solutions for wearable robots is motivated both by the necessity of improving the ergonomics of physical Human-Robot Interaction and by the chance of exploiting the intrinsic dynamical properties of the robotic structure for an optimal interaction with the human body. Under these aspects, this new class of robotic solutions is potentially advantageous over the one of anthropomorphic robotic orthoses. However, the process of kinematic synthesis of non-antrhopomorphic wearable robots is very complex and difficult to be tackled by human intuition and engineering insight alone. A systematic approach is more useful for this purpose, since it allows to obtain the number of independent kinematic solutions with desired properties. In this perspective, this paper presents a method which enables to list the possible kinematic solutions for wearable robotic orthoses, which generalize the set of solutions of the problem of kinematic synthesis of a non-anthropomorphic wearable robot. This method has been implemented to derive the atlas of topologies of robotic kinematic chains which can be employed to support a 1-DOF human joint.

(далее…)

Категория: Научные статьи | Нет комментариев »

A linear-quadratic-Gaussian regulator is proposed for the torque control of flexible robotic joints with built-in torque sensor. The regulator requires the joint-torque sensor information only and features: (1) a Kalman filter that, beside reducing the noise and evaluating the derivative of the torque sensor measure, is able to estimate all the external and internal torques acting on the joint; 2) a controller that optimizes system stability, responsiveness, accuracy and effort. The regulator is implemented on a flexible joint of a rehabilitation exoskeleton. Simulation and experimental results are provided which demonstrate regulator performance and efficacy.

(далее…)

Категория: Научные статьи | Нет комментариев »