Isometric Joystick Performance and Error Correction during Computer Access Tasks

Harshal Mahajan, MS1, 2 ; Robert Waaser1, 4 ; Brad E. Dicianno, MD1,2,3 ; Rory A. Cooper, PhD1,2

1 Human Engineering Research Laboratories, VA Pittsburgh Healthcare System
Department of Rehabilitation Science and Technology, University of Pittsburgh
Department of Physical Medicine and Rehabilitation, University of Pittsburgh Medical Center


Many individuals with upper limb impairments or movement disorders find it difficult to use conventional input devices like a mouse or movement joystick for computer access tasks. A specially designed programmable isometric joystick, which requires less dexterity and coordination to operate than a conventional joystick, seems a feasible alternative. The present study explores this feasibility in steering-oriented computer access tasks such as menu navigation. The study also analyzes the effects of a Proportional-Integral-Derivative based correction algorithm on the user’s steering performance while moving a cursor along three paths with varying levels of difficulty. The correction algorithm was shown to significantly decrease the error (p = 0.011) and variability (p =0.01) in cursor movement although the movement offset and trial time were not affected. These encouraging results may permit the development of better control interfaces for individuals with compromised motor control.


isometric joystick, tremor suppression, computer access, steering, rehabilitation


The funding for this research was provided in part by the National Science Foundation, Project EEC 0552351.