Asymmetric Dual Arm Approach For Post Stroke Recovery Of Motor Functions Utilizing The EXO-UL8 Exoskeleton System: A Pilot Study

Abstract

In a dual arm therapeutic regime aiming to rehabilitate motor functions post stroke, both the affected arm (paretic) and the unaffected (non-paretic) arm are involved. In this context, the leading idea is that motor functions of the affected arm during a reaching task may be improved if the unaffected arm has already reached the target. As part of this pilot study, one chronic post-stroke patient with weakness and spasticity on his right arm conducted reaching tasks to virtual targets arranged in a 5×3 matrix located parallel to his frontal plane, in two different configurations: (1) affected arm only (without assistance from the exoskeleton); (2) unaffected arm first followed by the affected arm (2a) without, and (2b) with assistance. A force field attracting the wrist of the affected arm to the target was used in the assistive mode. The data post-processing and analysis included task completion time, reachable task space, joint range of motion, human-robot interaction force/torque and power exchange at multiple sensors along the arm-visualized in a series of interaction maps. The data validated the robotic system's basic functionality in facilitating post-stroke unilateral and asymmetric bilateral training. Future work would be expanded to clinical trials with more subjects to be recruited and additional features to be implemented.

Review on Patient-Cooperative Control Strategies for Upper-Limb Rehabilitation Exoskeletons

“…Since the authors developed a dual-arm symmetric system, they also enabled mirroring training modes based on bilateral teleoperation between unimpaired and impaired arms. Additionally, Shen et al (2018) proposed an asymmetric bilateral training using an interactive virtual reality environment.…”

Admittance Control Scheme Comparison of EXO-UL8: A Dual-Arm Exoskeleton Robotic System

“…The development of the dual-arm system enabled symmetric mirror image movement training based on between-arm teleoperation. In addition, asymmetric bilateral training using an interactive virtual reality environment was also developed [16]. In either of the training modes and regardless of the motor control functionality level of the human operator, the exoskeleton arm needs to have high "transparency", which means that it is sensitive enough, in a heuristic way, to not exert unwanted resistance on the human arm (otherwise the human's movement, e.g., redundancy resolution, would be affected [17]), as well as be robust enough to prevent instability in all configurations.…”

“…3, are compared. In Scheme A (the existing control scheme [16]), the human-applied joint torques are calculated from a weighted combination of each sensor's contribution, while in Scheme B, a Kalman Filter is used.…”

Dynamic Model of a Humanoid Exoskeleton of a Lower Limb with Hydraulic Actuators

“…Exoskeletons are also applied in rehabilitation [ 12 , 13 , 14 ]. Cyberdyne (Tsukuba, Japan) made a series of exoskeletons called the Hybrid Assistive Leg (HAL).…”