Self-adaptive robot training of stroke survivors for continuous tracking movements

Abstract

BackgroundAlthough robot therapy is progressively becoming an accepted method of treatment for stroke survivors, few studies have investigated how to adapt the robot/subject interaction forces in an automatic way. The paper is a feasibility study of a novel self-adaptive robot controller to be applied with continuous tracking movements.MethodsThe haptic robot Braccio di Ferro is used, in relation with a tracking task. The proposed control architecture is based on three main modules: 1) a force field generator that combines a non linear attractive field and a viscous field; 2) a performance evaluation module; 3) an adaptive controller. The first module operates in a continuous time fashion; the other two modules operate in an intermittent way and are triggered at the end of the current block of trials. The controller progressively decreases the gain of the force field, within a session, but operates in a non monotonic way between sessions: it remembers the minimum gain achieved in a session and propagates it to the next one, which starts with a block whose gain is greater than the previous one. The initial assistance gains are chosen according to a minimal assistance strategy. The scheme can also be applied with closed eyes in order to enhance the role of proprioception in learning and control.ResultsThe preliminary results with a small group of patients (10 chronic hemiplegic subjects) show that the scheme is robust and promotes a statistically significant improvement in performance indicators as well as a recalibration of the visual and proprioceptive channels. The results confirm that the minimally assistive, self-adaptive strategy is well tolerated by severely impaired subjects and is beneficial also for less severe patients.ConclusionsThe experiments provide detailed information about the stability and robustness of the adaptive controller of robot assistance that could be quite relevant for the design of future large scale controlled clinical trials. Moreover, the study suggests that including continuous movement in the repertoire of training is acceptable also by rather severely impaired subjects and confirms the stabilizing effect of alternating vision/no vision trials already found in previous studies.

Can passive arm movement affect adaptation to visuomotor rotation?

“…Therefore, demand for those robotic rehabilitation systems has increased during the past decade. However, because there exist several protocols of robotic rehabilitation, its principal mechanism has not yet been clarified [3], [4].…”

Quantitative assessment based on kinematic measures of functional impairments during upper extremity movements: A review

“…In the literature, this metric was also called by the name of the movement characteristic that it represents "accuracy" (Colombo et al, 2008) (Fig. 2a) or "tracking error" (Vergaro et al, 2010). It's computed as the mean distance from the Euclidean distance between points of the real and theoretical hand trajectories (Celik et al, 2010;Colombo et al, 2007Colombo et al, , 2008Colombo et al, , 2012.…”

Novel kinematic indices for quantifying upper limb ability and dexterity after cervical spinal cord injury

“…This index has been considered a measure of the error in accuracy [10], and in the literature, it was also called as "movement deviation" or "tracking error" [42]. In the reviewed articles, this index has been computed as the mean distance from the Euclidean distance between points of the real and theoretical hand trajectories [8,10,11].…”