Wheel chair abstract
Disclosed is a powered wheel chair with individual motors driving
each of two separate drive wheels. The motors are controlled by
the amount of torque applied to the handrim of the driving wheel.
If the operator pushes on the handrim of the drive wheel, as is
well known, the torque created by such movement is sensed and activates
the drive motor to cause the drive wheel to rotate. The power applied
to the drive motor is controlled by the amount of torque applied
to the handrim such that the conventional control of the wheel chair
is maintained.
Wheel chair claims
I claim:
1. In a powered wheel chair for providing transportation to human
passengers including drive wheels rotatably mounted on said wheel
chair, said drive wheels being independently powered by electric
motors, said improvement comprising:
handrim means flexibly mounted on said wheel chair drive wheels
for providing relative angular displacement to the drive wheels
upon the application of torque thereto;
transducer means, responsive to said relative angular displacement,
for providing an electrical output which is a function of torque
applied to said handrim means; and
controller means, responsive to said transducer means electrical
output, for providing electric power to said electric motors.
2. The apparatus in claim 1 wherein said handrim means is mounted
on each of said drive wheels.
3. The apparatus in claim 2 wherein said transducer means electrical
output is directly proportional to torque applied to said handrim
means.
4. The apparatus in claim 2 wherein said controller means includes
battery means for providing a source of electric power.
5. The apparatus in claim 2 wherein said drive wheel and said handrim
means are mounted to said wheel chair through a common hub, said
hub including said transducer means.
6. The apparatus in claim 2 wherein said transducer means comprises
a potentiometer.
7. The apparatus in claim 2 wherein said transducer means comprises
a magnetic transducer.
8. The apparatus in claim 2 wherein said controller means is manually
adjustable for providing a variable electric power to said electric
motors in response to a given transducer means electrical output.
Wheel chair description
BACKGROUND OF THE INVENTION
The present invention relates to powered wheel chairs for patients
with control over their arms and hands but without the strength
to provide motive power.
Powered wheel chairs are well known in the art and are generally
identified with a joy stick control. By pushing the joy stick forward
both powered wheels run at the same speed and the wheel chair goes
in a straight line. By moving the joy stick towards the left, a
left turn is initiated, etc. For patients who have only the use
of one arm or one appendage the joy stick control must be considered
the present state of the art. However there is a second class of
patients in which the individual has the use of his arms and hands
but, because of his affliction, lacks the strength to provide his
own motive power as in an unpowered wheel chair. In the past, such
individuals have been forced to utilize the joy stick control wheel
chairs which suffer from both controllability and maneuverability
problems in close fitting quarters. The reason for these problems
is that the man-machine interface in the joy stick control lacks
the sensitivity and contains inherent system lags which make precise
positional control very difficult.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a
power wheel chair in which control of the drive motors is provided
by torque applied by the operator to the handrim.
A further object is to provide a powered wheel chair which has
the simplicity of operation comparable to an unpowered wheel chair.
A still further object of the present invention is to provide a
powered wheel chair with precise controllability and maneuverability
characteristics and is capable of being operated by patients with
limited appendage strength.
In accordance with the above and other objects, the handrims are
attached to the drive wheels on each side of the wheel chair, through
a torque transducer which provides a signal in proportion to the
driving torque applied to the handrim. This signal is utilized in
a control circuit to vary the power applied to the wheel chair drive
motor which is connected to the drive wheel. Appropriate elastic
contraints such as a torsional spring and appropriate damping are
built into the flexible connection to prevent undesirable oscillations.
Thus by sitting in the chair and applying a very small forward pressure
on the handrim, the signal generated by the transducer would cause
the drive motor for that wheel to begin operation with the torque
generated by the drive motor in direct proportion to the torque
applied to the handrim. Thus, with very little effort, a patient
with the use of his arms and hands could move forward and precisely
control the position of the wheel chair.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete appreciation of the invention and the attendant
advantages thereof will be more clearly understood by reference
to the following detailed drawings wherein:
FIG. 1 is a perspective view of a powered wheel chair according
to one embodiment of the present invention;
FIG. 2 is a schematic representation illustrating the control transducer;
and
FIG. 3 is a block diagram of the control circuitry in the present
invention .
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Reference is now made to the drawings wherein like reference numerals
designate identical parts throughout the several views. In FIG.
1, a powered wheel chair is shown with drive wheels, 10 and 11 powered
by electric motors 14 and 15, respectively. The motors cause the
drive wheels to rotate through friction drive 17 and 18. A handrim
20 is flexibly mounted around the periphery of the drive wheel such
that it undergoes a small annular displacement relative to the drive
wheel when the operator pushes on the handrim. The battery, control
circuits, and associated wiring are contained in box 22 and are
thus disposed away from the operator.
FIG. 2 schematically represents the control mechanism for the powered
wheel chair. The drive wheel and the handrim 20 are connected to
a central hub 30 through spokes 32 and 34, respectively. Because
of the structural nature of the spokes, when the torque is applied
to the handrim, the spokes will be deflected towards or away from
each other depending on the direction of the applied torque. Angular
position transducer 35 provides a signal indicative of the angular
displacement and controls the torque applied to the drive wheel
10 through friction drive 17 by motor 14. Although transducer 35
has been shown schematically as being connected between two spokes,
it could be included in the hub 30 or in any other manner known
to those skilled in the art. Similarly numerous methods for elastically
mounting the handrim on the drive wheel other than utilizing different
sets of spokes are well known to those of ordinary skill.
FIG. 3 is a blocked diagram showing the velocity controller 40
which provides an electrical output to motor 14 causing drive motion
through friction drives 17. The velocity controller 40 is powered
by battery 42 and controlled by an angular position transducer 35.
Although any number of devices may be utilized to provide an angular
position signal, a simple three-lead potentiometer may be utilized
in one embodiment. The circuitry of velocity controller 40 is well
known to those skilled in the art and upon sensing the change in
resistance in transducer 35 an output will be provided to motor
14 causing drive wheel 10 to rotate in the appropriate direction.
The type of control achieved in this invention is more like a power
assisted steering system rather than total power steering system
in that a degree of feedback (due to the necessity of flexing the
spokes to obtain an initial signal) is provided. The sensitivity
of the system or degree of power assist can be readily varied to
suit the individual patient needs by a simple gain adjustment in
the velocity controller 40. Therefore the effort input required
by the patient would be independent of the actual torque required
to operate the wheel chair over rugs, small inclines, etc. Because
of the elastic constraint of the spokes (or any other structural
mounting system with a handrim), the system is self-centering such
that power is applied to the motor only when the operator pushes
on the handrim. This provides controllability identical to the conventional
manual unpowered wheel chairs. Thus with the Applicant's invention
a wheel chair is provided which has good controllability in tight
quarters and yet minimizes the actual physical exertion required
to operate the wheel chair. The implementation of this wheel chair
system requires little or no additional training for patients and
is readily compatible with patients presently utilizing powered
or unpowered wheel chairs.
Although the invention has been described relative to a specific
embodiment, it is not so limited and many improvements and modifications
thereto will be obvious to those of ordinary skill. Therefore the
scope of the present invention is limited only by the appended claims. |