1,720,983 research outputs found
amp; pursue task
No full textCan haptic interaction improve the tracking performance in a fetch & pursue task, similar to clay pigeon shooting? In order to answer this question, we challenged the tracking movements of the subjects by a saddle-like moving force field, with the unstable manifold aligned along the moving target and the stable manifold orthogonal to it. The experimental results show a positive effect, suggesting that the internal model acquired by the subjects for compensating the target-linked haptic disturbance can improve the prediction capability of the subjects based on pure visuo-motor feedback
Adaptive regulation of assistance ‘as needed’ in robot-assisted motor skill learning and neuro-rehabilitation
No full textWe propose a general adaptive procedure to select the appropriate degree of assistance based on a Bayesian mechanism used to estimate psychophysical thresholds. This technique does not need an accurate model of learning and recovery processes. This procedure is validated in the context of a motor skill learning problem (control of a virtual object), in which the controller is used to gradually increase task difficulty as learning proceeds. These automatic adjustments of task difficulty or the degree of assistance can be used to promote not only motor skill learning but also neuromotor recovery
Wrist proprioception: amplitude or position coding?
No full textThis work examines physiological mechanisms underlying the position sense of the wrist, namely the codification of proprioceptive information related to pointing movements of the wrist towards kinesthetic targets. Twenty-four healthy subjects participated to a robot-aided assessment of their wrist proprioceptive acuity to investigate if the sensorimotor transformation involved in matching targets located by proprioceptive receptors relies on amplitude or positional cues. A joint position matching test was performed in order to explore such dichotomy. In this test, the wrist of a blindfolded participant is passively moved by a robotic device to a preset target position and, after a removal movement from this position, the participant has to actively replicate and match it as accurately as possible. The test involved two separate conditions: in the first the matching movements started from the same initial location; in the second one the initial location was randomly assigned. Target matching accuracy, precision and bias in the two conditions were then compared. Overall results showed a consistent higher performance in the former condition than in the latter, thus supporting the hypothesis that the joint position sense is based on vectorial or amplitude coding rather than positional
Characterizing the human-robot haptic dyad in robot therapy of stroke survivors
No full textPurpose – The working hypothesis, on which this paper is built, is that it is advantageous to look at protocols of robot rehabilitation in the general context of human-robot interaction in haptic dyads. The purpose of this paper is to propose a new method to detect and evaluate an index of active participation (AC index), underlying the performance of robot-assisted movements. This is important for avoiding the slacking phenomenon that affects robot therapy. Design/methodology/approach – The evaluation of the AC index is based on a novel technique of assistance which does not use constant or elastic forces but trains of small force impulses, with amplitude adapted to the level of impairment and a frequency of 2 Hz, which is suggested by recent results in the field of intermittent motor control. A preliminary feasibility test of the proposed method was carried out during a haptic reaching task in the absence of visual feedback, for a group of five stroke patients and an equal group of healthy subjects. Findings – The AC index appears to be stable and sensitive to training in both populations of subjects. Originality/value – The main original element of this study is the proposal of the new AC index of voluntary control associated with the new method of pulsed haptic interactio
Wrist Rehabilitation in Chronic Stroke Patients by Means of Adaptive, Progressive Robot-Aided Therapy
No full textParkinson's disease accelerates age-related decline in haptic perception by altering somatosensory integration
No full textThis study investigated how Parkinson’s disease alters haptic perception and the underlying mechanisms of somatosensory and
sensorimotor integration. Changes in haptic sensitivity and acuity (the abilities to detect and to discriminate between haptic
stimuli) due to Parkinson’s disease were systematically quantified and contrasted to the performance of healthy older and young
adults. Using a robotic force environment, virtual contours of various curvatures were presented. Participants explored these
contours with their hands and indicated verbally whether they could detect or discriminate between two contours. To understand
what aspects of sensory or sensorimotor integration are altered by ageing and disease, we manipulated the sensorimotor aspect
of the task: the robot either guided the hand along the contour or the participant actively moved the hand. Active exploration
relies on multimodal sensory and sensorimotor integration, while passive guidance only requires sensory integration of
proprioceptive and tactile information. The main findings of the study are as follows: first, a decline in haptic precision can
already be observed in adults before the age of 70 years. Parkinson’s disease may lead to an additional decrease in haptic
sensitivity well beyond the levels typically seen in middle-aged and older adults. Second, the haptic deficit in Parkinson’s
disease is general in nature. It becomes manifest as a decrease in sensitivity and acuity (i.e. a smaller perceivable range and a
diminished ability to discriminate between two perceivable haptic stimuli). Third, thresholds during both active and passive
exploration are elevated, but not significantly different from each other. That is, active exploration did not enhance the haptic
deficit when compared to passive hand motion. This implies that Parkinson’s disease affects early stages of somatosensory
integration that ultimately have an impact on processes of sensorimotor integration. Our results suggest that the known motor
problems in Parkinson’s disease that are generally characterized as a failure of sensorimotor integration may, in fact, have a
sensory origin
Predicted sensory feedback derived from motor commands does not improve haptic sensitivity
No full textForce-field compensation in a manual tracking task.
No full textThis study addresses force/movement control in a dynamic ‘‘hybrid’’ task: the master sub-task is continuous manual tracking of a target moving along an eight-shaped Lissajous figure, with the tracking error as the primary performance index; the slave sub-task is compensation of a disturbing curl viscous field, compatibly with the primary performance index. The two sub-tasks are correlated because the lateral force the subject must exert on the eight-shape must be proportional to the longitudinal movement speed in order to perform a good tracking. The results confirm that visuo-manual tracking is characterized by an intermittent control mechanism, in agreement with previous work; the novel finding is that the overall control patterns are not altered by the presence of a large deviating force field, if compared with the undisturbed condition. It is also found that the control of interaction-forces is achieved by a combination of arm stiffness properties and direct force control, as suggested by the systematic lateral deviation of the trajectories from the nominal path and the comparison between perturbed trials and catch trials. The coordination of the two sub-tasks is quickly learnt after the activation of the deviating force field and is achieved by a combination of force and the stiffness components (about 80% vs. 20%), which is a function of the implicit accuracy of the tracking task
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