| Sumario: | OBJECTIVE: 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. DESIGN: 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). RESULTS: 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. CONCLUSIONS: VGA software allowed the IJ to function similarly to the MSJ with respect to RT, MT, and DA.
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