Re: Automatic Wheelchair Turntable

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Robert L Bass" <robertlbass@xxxxxxxxxxx> wrote in message
news:v-qdncuSIa0wY6DeRVn-ig@xxxxxxxxxxxxxx
> At first I hadn't noticed that this is a scooter rather than a wheelchair.
> The first thing you should do IMO is find a way to ensure that the chair
> cannot be shifted into reverse unless it is in the lowest speed mode.

Reverse and forward use different gear ratios.  The unit backs up much more
slowly than it can go forward (thank God!)

It's not going to be easy to hack into the control panel for the scooter.
If I could somehow automatically sense the surrounding terrain, then I could
figure out some way of determining when a higher speed or an anti-tip
control could be useful.

At first guess, a ring of ultrasonic sensors like those on remote measuring
devices, could tell me something about the surrounding terrain.  If all
sensors indicated objects surrounding the chair, then the speed control
should be set to 2 or 3.   If no nearby objects (like slow-moving
grandmothers), then speed can be set higher.

In fact, the highest speed settings should be rigged sort of like an
automobile speed control.  As soon as you drop speed (the equivalent of
hitting the brakes on a car) the dial would reset itself to low speed.  I
could also try to work with the van's keyfob.  Any time the door is being
opened or closed by remote control, set the speed control down.  Not sure
whether that's doable with modern rolling code wireless remotes - it may be
that I don't actually have to decode the data being sent - just that a car
door opener has been operated nearby.

It might be possible to rig the speed control potentiometer with a DPDT
switch so that there's an automatic setting and a manual setting.  The
automatic settings would be slow and fast and would probably consist of
discrete resistors that approximated the value of the speed control when set
to 2 and 8.  When in close quarters, set to 2, otherwise set to 8.  The
trick now is to figure out how to sense and relay the appropriate conditions
to the microprocessor that would control the resistor selection.

In thinking more about this, a front and rear "range" sensor is really all I
need and it might turn out to be a considerable safety addition to force the
scooter into the lower speed settings whenever there are objects in front or
being the scooter.

It's become pretty obvious why all the scooters I have seen in stores don't
usually have a user-operable speed control and are set to a fairly low
setting.  In fact, it's one of the reasons Dad likes the new scooter so
much - because he can go fast where the terrain warrants it.  Some store
scooters can't make more than 3MPH at top speed.

--
Bobby G.