44 research outputs found
Toward ‘optimal’ schemes of robot assistance to facilitate motor skill learning
No full textWe investigate whether and on what circumstances physical interaction with a robot may facilitate the acquisition of a novel motor skill. We focus on two different motor tasks: (i) intermanual transfer of cursive handwriting and (ii) acquisition of a putting skill. In the case of handwriting, we found that intermanual transfer is facilitated by forms of interaction that account for the temporal aspects of the movements. In the case of putting, we found that guidance is helpful in improving longitudinal error (a matter of speed accuracy), but not directional error (a matter of position accuracy). Based on these results, we draw some tentative conclusions on which tasks can benefit from guidance, and how robots should be programmed to maximize their effect
Robot-assisted acquisition of a motor skill: Evolution of performance and effort
No full textRobots are widely used to promote the neuromotor recovery of stroke survivors, but it is unclear whether robots might be useful to facilitate the acquisition of novel motor skills. In principle, robots could be used to guide a trainee to experiment the correct movements and/or by preventing him/her from performing incorrect ones (the guidance hypothesis). Here we investigate whether and on what circumstances physical interaction with a robot may facilitate the acquisition of a novel motor skill. We focused on a simulated putting task, consisting of gently hitting an object (e.g. a ball) by means of a tool (the pad, e.g. the golf putter) to move it to a desired final position. A virtual environment, created through a planar robot manipulandum and a computer screen, was used to simulate the physics involved in the putting task. Putting is a redundant task, as the same final position of the ball can be obtained by different combinations of pad velocity, acceleration and point of impact. Two groups of subjects were analyzed: in an assisted group, the robot guided subjects toward the correct movement, whereas a control group performed the task without assistance. In both groups we looked at the subjects' performance and its evolution with exercise at several levels of description, namely: (i) final error (distance between final ball position and center of the target area); (ii) ball velocity just after impact; and (iii) hand position and velocity just before impact. In all cases, we looked at both mean value and variability (variance). We found that guidance is helpful in decreasing longitudinal error (a matter of speed accuracy), but not directional error (a matter of position accuracy). These results are consistent with the notion that guidance can help with the dynamic, but not the geometric components of a task
Robot-assisted intermanual transfer of handwriting skills
No full textWe examined whether intermanual transfer of fine motor skills can be facilitated by training in a virtual environment. We focused on three types of assistance: visual subjects could see a reference template on a computer screen and two variants of haptic assistance. Subjects held a planar robot manipulandum and were required to write isolated cursive letters of an approximate size of 5 cm. Therefore, the task was similar to writing on a horizontal blackboard. The robot generated forces that were directed either towards the reference template (path guidance) or towards the reference trajectory (trajectory guidance). The training protocol consisted of three assisted exercise sessions on three consecutive days. Performance on the following day was tested to assess retention. After training, the improvement in trajectory shape was only significant in trajectory guidance and, to a lesser extent, visual guidance. Path guidance exhibited no significant improvement. These effects were substantially retained one day after the end of training. Similar effects were observed in shape variability. Furthermore, all training modalities caused a reduction in movement duration, but no significant differences were observed among groups. These results suggest that robot assistance may be beneficial for improving intermanual transfer, but inclusion of temporal information in the guidance strategy is essential for learning to take place
Concurrent adaptation to force fields and visual rotations
No full textAn important issue in sensorimotor adaptation is what drives adaptation, and whether different types of perturbations are mediated by different adaptation mechanisms. Here we assess whether any interference is observed among the joint adaptation to visual (i.e. kinematic) and force (i.e. dynamic) perturbations. Subjects adapted their reaching movements to rotations of the display. During adaptation, we perturbed their movements with a rotational force field, whose direction was either the same or the opposite of the visual perturbation (RF and R-F groups). In the two groups, we compared the outcomes of both adaptation modalities. In addition, we analyzed the dynamics of the adaptation processes in terms of a number of linear dynamical models, based on different assumptions. We conclude that the two adaptation processes occur largely in parallel, with little interaction, and exhibit similar time constants, which suggests common underlying memory mechanisms. In addition, we found that subjects in the RF group exhibit a significantly smaller hand compliance, which suggests that the different combinations of disturbances affect the regulation of arm impedance
Adaptive training with full-body movements to reduce bradykinesia in persons with Parkinson’s disease: a pilot study
Get PDFBACKGROUND:
Bradykinesia (slow movements) is a common symptom of Parkinson's disease (PD) and results in reduced mobility and postural instability. The objective of this study is to develop and demonstrate a technology-assisted exercise protocol that is specifically aimed at reducing bradykinesia.
METHODS:
Seven persons with PD participated in this study. They were required to perform whole body reaching movements toward targets placed in different directions and at different elevations. Movements were recorded by a Microsoft Kinect movement sensor and used to control a human-like avatar, which was continuously displayed on a screen placed in front of the subjects. After completion of each movement, subjects received a 0-100 score that was inversely proportional to movement time. Target distance in the next movements was automatically adjusted in order to keep the score around a pre-specified target value. In this way, subjects always exercised with the largest movement amplitude they could sustain. The training protocol was organised into blocks of 45 movements toward targets placed in three different directions and at three different elevations (a total of nine targets). Each training session included a finite number of blocks, fitted within a fixed 40 minutes duration. The whole protocol included a total of 10 sessions (approximately two sessions/week). As primary outcome measure we took the absolute average acceleration. Various aspects of movement performance were taken as secondary outcome measures, namely accuracy (undershoot error), path curvature, movement time, and average speed.
RESULTS:
Throughout sessions, we observed an increase of the absolute average acceleration and speed and decreased undershoot error and movement time. Exercise also significantly affected the relationship between target elevation and both speed and acceleration - the improvement was greater at higher elevations.
CONCLUSIONS:
The device and the protocol were well accepted by subjects and appeared safe and easy to use. Our preliminary results point at a training-induced reduction of bradykinesia
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
Neural correlates of motor learning and performance in a virtual ball putting task
No full textLearning to move skillfully requires that the motor system adjusts motor commands based on ongoing performance, until the task is executed satisfactorily. Robots can be used to emulate motor tasks that involve haptic interaction with objects. These studies may provide useful insights on how humans acquire a novel motor skill. Here we address motor skill learning in a 2D ball putting task, by looking at both kinematic and EEG correlates of learning and performance. Participants grasped the handle of a manipulandum and had to hit a virtual ball in order to put it into a target region (hole). The robot was used to render the contact force with the ball during impact. At every trial, with respect to the initial ball position, the hole appeared in one of three different directions and two distances, selected randomly. The experimental protocol included a total of 300 movements. In movement kinematics we looked at the effects of learning and target distance. In EEG signals, we looked at the effect of learning and the effect of success/failure on the ongoing brain activity. Subjects managed to improve their performance through practice, in all directions and at both target distances. Direction did not affect the performance much, but greater target distance induced greater errors. With regards to the EEG activity, we found that (i) practice led to an increased theta synchronization in the frontal areas; (ii) successful trials were preceded by higher theta synchronization, and alpha and beta desynchronization. These results suggest that EEG signals can be used to monitor the learning process and to predict the outcome (success/failure) of individual trials. These findings open possibilities to develop new schemes to promote and facilitate learning, which integrate EEG and robots
Grasps recognition and evaluation of stroke patients for supporting rehabilitation therapy
Get PDFStroke survivors often suffer impairments on their wrist and hand. Robot-mediated rehabilitation techniques have been proposed as a way to enhance conventional therapy, based on intensive repeated movements. Amongst the set of activities of daily living, grasping is one of the most recurrent. Our aim is to incorporate the detection of grasps in the machine-mediated rehabilitation framework so that they can be incorporated into interactive therapeutic games. In this study, we developed and tested a method based on support vector machines for recognizing various grasp postures wearing a passive exoskeleton for hand and wrist rehabilitation after stroke. The experiment was conducted with ten healthy subjects and eight stroke patients performing the grasping gestures. The method was tested in terms of accuracy and robustness with respect to intersubjects’ variability and differences between different grasps. Our results show reliable recognition while also indicating that the recognition accuracy can be used to assess the patients’ ability to consistently repeat the gestures. Additionally, a grasp quality measure was proposed to measure the capabilities of the stroke patients to perform grasp postures in a similar way than healthy people. These two measures can be potentially used as complementary measures to other upper limb motion tests
A tailored exercise of manipulation of virtual tools to treat upper limb impairment in Multiple Sclerosis
No full textWe developed a robot-assisted rehabilitation protocol, specifically designed to treat cerebellar and motor symptoms in subjects with Multiple Sclerosis. The task consists of controlling a 'virtual' tool (a mass-spring system), under the effect of a resistive force. The exercise is designed in such a way that task difficulty and the degree of resistance are automatically adjusted to the individual patients' impairment. The protocol included a total of eight 40 min training sessions (2 sessions/week), and automatic regulation of difficulty and resistance was repeated at the beginning of each session. Preliminary results suggest that subjects improve their performance, both within and between sessions. Moreover, task difficulty and resistance tend to increase across sessions, indicating that subjects gradually improve their ability to deal with more challenging versions of the task
An Open-Source, Wheelchair Accessible and Immersive Driving Simulator for Training People with Spinal Cord Injury
No full textIndependence is one of the greatest achievements for people with Spinal Cord Injury (SCI). Indeed, mobility represents a big challenge that needs to be addressed, also considering that road accidents are frequently the cause of SCI. Immersive Virtual Reality (VR) combined with a driving simulator may provide a realistic experience, helping users to relearn driving and overcome the traumatic event. The aim of this project was to implement a wheelchair accessible, immersive driving simulator for the training and assessment of SCI people. Here we present a proof of concept of an open-source, VR compatible, driving simulator. The system combines a VR headset with an adaptive driving controller and a VR scenario. Starting from CARLA, an open simulator for autonomous driving, we created driving scenarios designed to fit the needs of SCI rehabilitation. Also, we defined future developments required to create a device usable for the assessment of cognitive and motor abilities.</p
