Flat surface joystick

[slomobile]

I recently came across this reddit post asking about a way to control a powerchair or scooter by moving hand over a flat surface like touchpad or touchscreen.
https://www.reddit.com/r/wheelchairs/co ... owerchair/

It makes sense for someone with limited hand dexterity but retained gross arm motor function. The touch point could be a finger if they have that ability, or a button stuck to the hypothenar (the contact point of a karate chop). Touchscreens are available in a wide variety of sizes. The size could be chosen to be at least as large as the comfortable arm range of motion. Additional screen real estate could display whatever the user likes. The surface could double as a table for eating, writing, or computing. Being connected to a small computer the user could capture their available range of motion and custom map it to speed and direction.
For example if your forearm is only comfortable across your body, you could map shoulder rotation, a single quadrant arc usually centered about 45 degrees off of forward, into a 180 degree centered arc representing steering. Elbow extension could be mapped to speed. You could even do it on the cheap without any screen at all. Just a transparent 4 wire analog touch overlay translated into the (X,Y) analog voltages of a joystick. A piece of paper with the user's mapped range of motion could be taped underneath the transparency as a legend.

I don't have the energy to properly follow though with this, so I wanted to throw the idea out to anyone interested. The original reddit poster is in the UK as far as I know.

[Burgerman]

woodygb did this already in a way. He added a BT interface so that people could move the chair around remotely on a touch screen phone. I tried something similar on a DJI drone. My drone allows this on its larger screen or on your phone. ts was terrible as a way to control anything with no feel or positional accuracy. But if its all you can do then better than nothing! Lets put it this way I wouldnt be able to fly a plane or heli that way. And it wouldnt be easy by which I mean accurate or predictable with my small 4x4 camera bot. It would definitely make it drive and go approximately where you wanted though. Going through small gaps? Not so sure. Maybe if you go very slowly and carefully. I think theres already a phone ap if you like that sort of thing that woody used.

[ex-Gooserider]

Technically doable, and not terribly difficult hardware wise. Basically you need to get the surface to output the same sorts of signal that the joystick module expected from the joystick, basically a +/- voltage swing for each axis... Woody's circuit (which I think was posted here, and should be findable w/ the search) did this with an Arduino controlling a couple of digi-pots. Tough part might be the programming of the touch pad to go from user movement to the needed output signals. It might also be essential to have some sort of function to distinguish between movements intended to cause the chair to move, and any OTHER movements...

This is on top of the reservations BM already mentioned about control precision... Not sure how this idea would be better than say a sip + puff control system...

ex-Gooserider