Sensitivity analysis of a parametric hand exoskeleton designed to match natural human grasping motion

Abstract

This paper describes the simulated analysis of a fully scalable, parametrically designed hand exoskeleton previously developed as part of a stroke rehabilitation program within the Bristol Robotics Laboratory. The device is parametrically designed to match the location and trajectories of the joints within a normal healthy human hand. However, testing of fully scalable designs which can be custom fit to a person using parametric design can be costly, time consuming and potentially hazardous if ill-fitting. Here a method is presented which allows for the performance of a parametric design to be tested. A virtual mechanism with induced manufacturing tolerances is modelled and its interactions with the hand are simulated. The performance can then be assessed by the devices ability to achieve the objective trajectory within the simulation. The results show that for the designed hand exoskeleton, with a manufacturing tolerance of 0.2mm across parts the resulting average trajectory error is less than 0.2 degrees with an average tip error of less than 0.5 mm. The results also demonstrate that for a large tolerance of 1mm across all dimensions, the trajectory error can reach as high as 30.9 degrees. This result justifies the use of parametric design to develop mechanisms matching natural human motion. While the results are for a parametrically scalable hand exoskeleton, it is believed the methodology is applicable to any bio-compatible assistive device. © 2012 Springer-Verlag.