Rehabilitation Engineering Research Center on Wheeled Mobility
Funding Source: Department of Education, NIDRR-RERC
7/1999-6/2004
RERC on Wheeled Mobility Website: http://www.rercwm.pitt.edu
Projects:
Application of a Commercial Datalogger to Wheelchairs for Rehabilitation Research
Chin-Operated Force-Sensing Joystick
Power Wheelchair Comparison Study
Power Wheelchair Comparison Study: Phase II
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Principal Investigator/s: Rory A. Cooper, PhD
Co-Investigator/s: Songfeng Guo, PhD, & Thomas Corfman, MS
Data collection and data
analysis for all three EPWs have been completed. The data has generated two
journal papers and four conference papers. One journal paper is in progress. A
paper entitled “Influence of wheelchair front caster wheel on the reverse
driving stability” was accepted by Assistive Technology. The relationship
between wheelchair weight distribution, caster wheel trail, caster wheel
orientation, motor back-emf voltage and reverse driving stability were analyzed
in this study. A paper entitled “Analysis of driving backwards in an
electric-powered wheelchair” was accepted by IEEE Transactions on Control
Systems Technology. The paper examined the influences of caster orientations and
driving speeds on the reverse directional stability of electric-powered
wheelchairs. A kinematic model as well as a dynamic model were developed to
simulate the wheelchair motion and conduct a parametric study of different
factors on wheelchair reverse directional stability. A paper entitled
“Characterization of disturbance forces and moments acting on electric powered
wheelchair casters when driving backwards” is in preparation. The force, moment,
caster path/orientation, and speed data has been analyzed and the manuscript is
about 75% done.
Three conference papers were published in 2002 and 2003 annual conference of
RESNA. The titles are “Robust velocity control simulation of a power
wheelchair”, “A study on modeling an electric powered wheelchair”, “Influence of
powered wheelchair backwards driving stability on back-emf”, “Disturbances
induced by wheelchair casters when driving backwards”.
Application of a Commercial Datalogger to Wheelchairs for Rehabilitation Research
Principal Investigator/s: Rory Cooper, PhD
Co-Investigator/s: April Hoover, BS, Rosemarie Cooper, MPT, ATP, Dan Ding, PhD, Michael Dvorznak, BS, Annmarie Kelleher, OTR/L, Shirley Fitzgerald, PhD, BethAnn Kaminski, BA
There is very little information about the actual propulsion behavior of users of wheelchairs. This information is critical to the design of wheelchairs, wheelchair components, battery design/specification, and in studies of risk exposure (e.g., risk of injury due to component failure). The objective of this study is to determine the propulsion characteristics of wheelchair users during unrestricted community activities.
A commercially available datalogger (TFX-11, Onset Computer Corporation) was mounted on each wheelchair and recorded the distance traveled per day, average speed while driving, and distribution of driving over the day. So far three groups of manual wheelchair users have been investigated. Ten users were tested at the 22nd National Veterans Wheelchair Games (NVWG) (Cleveland, OH) and ten users were tested at the 23rd NVWG (Long Beach, CA) to represent an active week of wheelchair use. Nine Pittsburgh, Pennsylvania area users have been tested to represent a typical week of use. Data analysis of these groups is still underway. The data collected from the manual wheelchair users will be compared to the power wheelchair data previously collected. Additional manual wheelchair data will be collected at the 2004 (NVWG) in St. Louis, Missouri and the Pittsburgh area.
Research On the Chin-Operated Force-Sensing Joystick
Principal Investigator/s: Songfeng Guo, PhD, Rory A. Cooper, PhD
Co-Investigator/s: Donald Spaeth, PhD, Dan Ding, PhD
Individuals who sustain a
high-level cervical spinal cord injury (SCI) cannot use hand-operated controls.
The wheelchair industry has developed position-sensing chin joysticks (PCJ) for
driving electric powered wheelchairs (EPW) but these can seldom be used for
other tasks. Cervical vertebrae fusion following SCI may restrict neck motion;
forcing the consumer to move his/her jaw to control speed and steering. Frequent
jaw displacement results in discomfort and may lead to chronic temporo-maxillary
joint irritation. A force-sensing chin joystick (FCJ) operated with force, not
motion, may be a viable alternative without sacrificing proportional control.
A prototype for a force-sensing chin joystick has been designed and fabricated.
The prototype uses strain gages mounted on beam to detect force input from the
user. The beam is mounted rigid into a base and a covering case protects the
strain gage bridges. These mechanical parts are mounted on a support arm to
allow for proper placement of the joystick. A wire connects the stain gage
bridges to a programmable micro controller, which is located in a control box
attached to the side of the wheelchair. The micro controller samples the signal
from the strain gage bridges and processes it using the custom software. The
software was designed with intention that it could be easily changed to fit the
needs of a specific user. For example, the force sensitivity can be altered on a
per axis basis, allowing for symmetrical or asymmetric sensitivity
configurations. The adjusted signal is sent to the wheelchair controller to
drive the EPW. Two publications have been prepared describing this design in
detail: “Development of Compact Chin-Operated Force-Sensing Joystick” has been
accepted for publication in Saudi Journal of Rehabilitation Research and
“Development of Head-Operated, Isometric Controls for Powered Mobility” has been
submitted for review to the 2004 RESNA Conference.
Power Wheelchair Comparison Study
Principal Investigator/s: Rory Cooper, PhD
Co-Investigator/s: Andrew Rentschler, MS, Megan Vitek, BSE, William Ammer, BS
Other Support: PVA
All testing on the power
wheelchair study has been completed. Sections 1,2,3,4,5,6,7,8,9,10, and 14 have
been completed on all fifteen wheelchairs. Information on the methods, results,
discussions, and conclusions for each section can be found on the pitt web site.
Go to www.library.pitt.edu. Under the search PITTCAT heading, select title and
type in “Analysis of the ANSI/RESNA Wheelchair Standards”. Click on unrestricted
access and then scroll to the bottom of the screen and click on
RentschlerAndrew.pdf.
Once the initial testing was completed, all of the power wheelchairs were then
cycled through the two-drum and curb drop machines until a class III failure
occurred that made the wheelchairs inoperable. The Invacare Action Arrow lasted
the longest, with a mean of 2,752,869 equivalent cycles. The E&J Lancer 2000
lasted the shortest, with a mean of 276,981 equivalent cycles. The Invacare
Action Arrow also had the highest value (387 equivalent cycles per dollar), and
lasted the longest until the first occurrence of a failure, as well as the
number of equivalent cycles between failures, consumer repairs, and supplier
repairs.
Power Wheelchair Comparison Study - Phase II
Principal Investigator/s: Rory Cooper, PhD
Co-Investigator/s: Jonathan Pearlman, MSc
A second phase of the power wheelchair comparison was performed on 12 K0010 electric power wheelchairs (EPWs) from four manufacturers: Electric Mobility, Pride Mobility, Golden Technologies, and Invacare. All ANSI/RESNA standards have been completed on all EPWs. Results show that the majority of the wheelchairs (9/12) failed the fatigue testing section, indicating that the expected functional life of these EPWs are less than 3-5 years, the industry standard and goal. Other results of interest were electrical problems (Electric Mobility & Golden Technologies) and stability issues (Pride Mobility). A manuscript describing the results of this work were submitted and accepted into the Archives of Physical Medicine. The reference is:
Pearlman, J.L., Cooper, R.A., Karnawat, J., Cooper R., Boninger, M.L., (2005) Evaluation of the Safety and Durability of Low-cost K0010 Electric Powered Wheelchairs., Archives of Physical Medicine and Rehabilitation December 2005 (Vol. 86, Issue 12, Pages 2361-2370)
Principal Investigator/s: Rory Cooper, PhD
Co-Investigator/s: Amol Karmakar, MSc
The purpose of this study is to compare PAPAW systems from three manufactures: IGlide (Johnson & Johnson), Xtender (Sunrise Medical) and e.motion (Frankmobility Inc.) using the ANSI/RESNA standard testing guidelines. Three models from each of the above mentioned manufactures are being tested (total 9 PAPAW). The sections of the ANSI/RESNA testing that has been completed till date are: 1. Static stability; 2. Dynamic stability; 3.Effectiveness of brakes; 4. Energy consumption; 5.Overall mass, dimension; 6. Speed acceleration; 7. Seating and wheel dimension; and 9. Climatic tests. Section 8, static impact and fatigue strength testing and section 14, power and control systems are currently undergoing. All the PAPAW passed all the sections (except 8 and 14) of ANSI/RESNA standards with minimal differences between them.
There are some commonly occurring problems with each PAPAW system such as: Compatibility and behavior between the three PAPAW systems vary while the Xtender and e.motion are folding type chairs, and the e.motion can adapt to almost any frame with very little modification to chair’s existing frame. The e.motion that has two separate motor systems has a disadvantage of uncontrollable acceleration on downward slopes with no braking action. On occasion e.motion hub batteries lost contact disengaging motor drive to one side causing spinning of the wheelchair. IGlide and Xtender have very identical behavior, with even greater braking control on downhill slopes of IGlide over Xtender.