Robot-assisted assessment of the effects of self-aligning mechanism on the wrist passive range of motion

Abstract

Axis alignment between human and robot has been a research hotspot in wearable rehabilitation robots and has a significant effects on full natural ranges of motion (ROM) during robot-assisted training exercises. Self-alignment mechanism (SAM) has been extensively applied on the rehabilitation robots to adaptively compensate the axis misalignment between human anatomic and robot mechanical joints. However, the effects of the SAM on the wrist ROM have not been definitely assessed. In this study, we implemented a SAM on a wrist rehabilitation device (WReD II), and the SAM was specially designed to be locked or unlocked to achieve self-alignment function or not according to demands. To assess the effects of SAM on the wrist passive ROM of extension/flexion (E/F), passive training experiments involving 8 healthy participants were conducted by locking or unlocking the SAM respectively. Surface Electromyography (sEMG) was applied to monitor muscle activity during experiments. During the experiments, the wrist passive ROM were measured by applying the robot-assisted assessment technique. Preliminary results show that the means of the passive ROM have a maximum increase of 19.78° in the case with SAM unlocked when compared to the case with SAM locked. Statistical results indicated high test-retest reliability of the passive ROM measurements with intraclass correlation coefficient ICC (2,1) more than 0.82, and standard error of measurement (SEM) less than 3.2°. These findings suggest that the implement of SAM on the rehabilitation robots has great potentials due to its feasibility and reliability to obtain larger natural passive ROM.