Advancements in power wheelchair joystick technology: Effects of isometric joysticks and signal conditioning on driving performance.

Abstract

An estimated 125,000 Americans with movement disorders that preclude independent mobility in a power wheelchair could benefit from improved control devices. We developed variable gain algorithm (VGA) software for our isometric joystick (IJ) that allows it to emulate a commercially available motion-sensing joystick (MSJ) in performance but retain the unique customizable features of an isometric control. Force sensing algorithm (FSA) software allowed the IJ to function as a simple isometric device. Using a Fitts' Law paradigm, we compared driving performance with floor targets using a standard MSJ and an IJ with both FSA and VGA software in 11 electric power wheelchair users with a variety of impairments. Outcome measures were reaction time (RT), movement time (MT), and driving accuracy (DA). The IJ with FSA had a significantly shorter RT than the MSJ (P < 0.0020). The IJ with FSA had a significantly longer MT than the MSJ to far targets (P < 0.0159). No differences were found between the IJ with VGA and the MSJ with respect to RT or MT. No differences in DA were found among any of the joysticks. VGA software allowed the IJ to function similarly to the MSJ with respect to RT, MT, and DA.