Developmental Disabilities Services Division, State of Oklahoma
ABSTRACT
In order to better assess an individual's ability to operate
power mobility, a motorized cart with wheelchair tiedowns and
with the ability to accept many input controls has been developed.
The Turtle Trainer cart allows evaluators to easily determine
an individual's potential for power mobility.
BACKGROUND
Proper operation of power mobility involves many factors such
as vision, cognition, and selection of proper controls. People
unable to self propel a wheelchair can be divided into three categories:
1) Those whom evaluators are sure can operate power mobility
2) Those whom evaluators are unsure whether they can operate power
mobility
3) Those whom evaluators are sure they cannot operate power mobility
( more on this later )
Evaluators have been seeking a quick and accurate way to determine
who in the second group can safely operate a power mobility device.
Until now, evaluating this middle group entailed five choices:
(1) Seating an individual in a power mobility device, not providing
the customized seating possibly used by the individual in his
manual wheelchair, and hoping for an accurate performance.
(2) Take the time to customize the power mobility seating by inflatable
bean bags or other means.
(3) Say it is not possible to evaluate these individuals.
(4) Purchase the individual a power mobility device and hope it
can be operated properly.
(5) Use a computer simulation
While several computer simulations (1,2) have been developed to
determine a potential user's ability to operate power mobility,
it is the author's contention that these simulations are several
steps removed from the reality of a wheelchair moving under the
individuals control. For these reasons, other methods of easily
providing client controlled movement were investigated.
PROJECT DESIGN
Originally, a power base to slip under the rear wheels of a manual
wheelchair was envisioned. But during discussion, therapists thought
that even one inch of added rear height would create too much
of a tilt for some individuals. Therefore a platform large enough
to support all four wheels of the largest wheelchair used at the
school was constructed. To save width, the motors and casters
were placed underneath the platform, and a loading ramp was attached.
Through experimentation, it was determined that operating two
ABEC Fireball wheelchair motors at 6 rather than 24 volts provided
a desired slow, Turtle-paced speed. Acceleration was smooth enough
that variable speed and acceleration were thought unnecessary
and the simple control electronics is comprised of 9 diodes, three
transistors, and three relays. To allow use of a wide variety
of input controls, the electronics were wired to accept Du-It
controls such as a joystick, touch disk, vector scanner, and individual
switches.
Photo 1. Turtle Trainer in use by client, the staff member is
holding the shutdown switch.
To date the Turtle Trainer has been used by several individuals.
The trainer is large enough that the therapist working with a
client was able to sit on it and hold the user control in a variety
of positions to find optimum placement.
By providing the kinesiological input and changing perspectives
not available with computer simulation the Turtle Trainer provides
a truer simulation of power wheelchair control. Although a formal
study has yet to be conducted, evaluations using the Turtle Trainer
should prove more accurate than evaluations using computer simulations.
Even those in the third group ( clients the evaluators are sure
cannot use power mobility ) can use the Turtle Trainer as a switch
control modality for on off movement control instead of controlling
a toy or appliance. In our experience at the school, many clients
in the third group surprise us and we continually look for indicators
of power mobility readiness.
SUMMARY
A powered cart was constructed allowing evaluation of clients
ability to operate power mobility without changing the individuals
seating system.
REFERENCES
(1) Bayer, David M., A Simulation Technique, DU-IT Control Systems
Inc. Shreve, OH.
(2) Tapin, Cathie S., Proceedings of the 12th Annual RESNA conference,
New Orleans, LA. 1989, page 45
(3) DU-IT Control Systems Inc. Shreve, OH.
ACKNOWLEDGEMENTS
The Turtle Trainer was constructed by the Pauls Valley State School
Adaptive Technology Shop from internal funding. The author wishes
to thank the shop personnel for their many suggestions and assistance.
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