Comparing Dynamic Hand Rehabilitation Gestures in Leap Motion Using Multi-Dimensional Dynamic Time Warping

We propose and evaluate the use of Multi-dimensional Dynamic Time Warping (MDTW) for comparing dynamic hand rehabilitation gestures that would be performed by a patient (query) relative to hand gestures prepared by a physiotherapist (reference). MDTW enables us to determine how similar or different a query dynamic hand gesture is to a reference one whilst filtering out unwanted sources of error resulting from positional, rotational or speed differences between the query and the reference actions. It produces a minimum-distance value of a warp path after aligning a query dynamic hand gesture with a reference one. A low minimum-distance value implies the two gestures being compared are similar and high minimum-distance value implies the two gestures vary to a greater extent. When we deliberately compare a specific hand gesture with itself, we obtain a minimum-distance value of 0 indicating the similarity is 100. Furthermore, when we compare two closely similar hand gestures i.e. gesture 1 and gesture 4, a minimum-distance value of 35.9 is obtained. However, when we compare two quite different gestures i.e. gesture 2 and gesture 3, a minimum-distance value of 248.5 is obtained. Therefore, a physiotherapist can establish whether a patient performs hand rehabilitation gestures satisfactorily or an adjustment is required based on the minimum-distance values of the warp paths.