Force control strategies while driving electric powered wheelchairs with isometric and movement-sensing joysticks

Model System:

Reference Type:

Accession No.:

Journal:

Year, Volume, Issue, Page(s):

Publication Website:

Abstract:

Innovations to control interfaces for electric powered wheelchairs (EPWs) could benefit 220 000 current users and over 125 000 individuals who desire mobility but cannot use a conventional motion sensing joystick (MSJ). We developed a digital isometric joystick (IJ) with sophisticated signal processing and two control functions. In a prior study, subjects’ driving accuracy with our IJ was comparable to using an MSJ. However, we observed subjects using excessive force on the IJ possibly because its rigid post provides no positional feedback. Thus, this paper examines the time-series data recorded in the previous study to characterize subjects’ force control strategies since weakness is a concern. Eleven EPW users with upper limb impairments drove an EPW using an IJ with two different control functions and an MSJ in a Fitts’ law paradigm. Subjects relied upon positional feedback from the MSJ and used appropriate force. In contrast, subjects using the IJ with either control function applied significantly higher force than necessary ( 0 0001 and = 0 0058). Using higher average force Manuscript received August 25, 2006; revised November 28, 2006; accepted December 12, 2006. This work was supported in part by the U.S. Department of Veterans Affairs Rehabilitation Research and Development Service under Grant E1960G, Paralyzed Veterans of America-SCRF under Grant 1738, University of Pittsburgh, Department of Rehabilitation Science and Technology; RERC on Wheeled Mobility, U.S. Department of Education, National Institute on Disability and Rehabilitation Research under Grant H133E990001, and the Rehabilitation Medicine Scientist Training Program NIH K12 under Award (K12HD01097). B. E. Dicianno is with the Human Engineering Research Laboratories (HERL), Pittsburgh, PA 15206 USA, The Department of Physical Medicine and Rehabilitation and with The Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260 USA, and also with the VA Pittsburgh Health Care System, Center of Excellence in Wheelchairs and Associated Rehabilitation Engineering, Pittsburgh, PA 15206 USA (e-mail: diciannob@herlpitt.org). D. M. Spaeth and K. W. Brown are with the Human Engineering Research Laboratories (HERL), Pittsburgh, PA 15206 USA and also with The Department of Rehabilitation Science and Technology, University of Pittsburgh, Pittsburgh PA 15260 USA (e-mail: spaethd@herlpitt.org; brownk@herlpitt.org). R. A. Cooper is with the Human Engineering Research Laboratories (HERL), Pittsburgh, PA 15206 USA, and with The Department of Physical Medicine and Rehabilitation, The Department of Rehabilitation Science and Technology, and with The Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260 USA, and also with the VA Pittsburgh Health Care System, Center of Excellence in Wheelchairs and Associated Rehabilitation Engineering, Pittsburgh, PA 15206 USA (e-mail: rcooper@pitt.edu). S. G. Fitzgerald is with the Human Engineering Research Laboratories (HERL), Pittsburgh, PA 15206 USA and with The Department of Rehabilitation Science and Technology, University of Pittsburgh, Pittsburgh, PA 15260 USA, and also with the VA Pittsburgh Health Care System, Center of Excellence in Wheelchairs and Associated Rehabilitation Engineering, Pittsburgh, PA 15206 USA (e-mail: sgf9@pitt.edu). M. L. Boninger is with the Human Engineering Research Laboratories (HERL), Pittsburgh, PA 15206 USA and The Department of Rehabilitation Science and Technology, and The Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15260 USA and also with the VA Pittsburgh Health Care System, Center of Excellence in Wheelchairs and Associated Rehabilitation Engineering, Pittsburgh, PA 15206 USA (e-mail: boninger@pitt.edu). Digital Object Identifier 10.1109/TNSRE.2007.891394 was correlated with quicker trial times but not associated with accuracy. Lack of positional feedback may result in use of excess isometric force. Modifying control functions, adjusting gain, or providing additional training or feedback might address this problem.

Author(s):

Participating Centers: