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Topic: wheel chair obstacle avoidance (Read 1 time) previous topic - next topic

scott_fx

Hey forum,

my cousin has MS and uses an electric wheel chair when he's at home.  I was talking to his brother today an I guess he's not the best navigator at the house and his walls are showing the pain. 

I'd like to surprise him with an obstacle avoidance feature when i go home for the holidays.

my plan is to use some ultrasonic sensors.  4 total, one on each corner
https://www.adafruit.com/products/981

and possibly simple interface to toggle the system on and off.


the chair is an invacare Pronto M61 w/Sure Step & Standard Pwr. Elev. Seat

the joystick looks like this:


I'm searching the classifieds for a used one that i can test out here in cali so it'll be pretty plug and play when i go home.

my goals are:
safe
obstacle avoidance
be able to turn the system off


im not sure the best way to accomplish this.   Would it be best to hack the donor controller, cut the traces of the joystick and put the arduino in line with that?

thanks for the help

Far-seeker


im not sure the best way to accomplish this.   Would it be best to hack the donor controller, cut the traces of the joystick and put the arduino in line with that?


Assuming a successfully hacked control system, any automatic system that overrides manual control will need to be stringently tested.  Even if it only stops the chair from moving, your cousin will never use it if false posistives or gliches happen more than once in a very long while. 

Instead, I suggest a clearance indication system.  Like having an LED bar graph for each sensor, with each bar representing a small distance like a quarter inch or a centimeter.  The number of lit bars would be the minimum clear distance in the direction of the sensor.  That way your cousin would only need to look in one place to know how much clearance he around his chair. 

Although, if you really think halting the chair is necessary you could also add some microswitchs to use as bump sensors.  This is the same type of system found on most robot vaccums to cause them to backup or turn when they hit a solid object.  If you go this route though, the larger mass and higher speeds will probably mean you'll have to have at least some shock absorbtion (and not for the switches' sakes).  However that combined with momementarily stoping the chair chould be enough to avoid noticable dents and scuffs.

oric_dan

#2
Sep 27, 2012, 12:34 am Last Edit: Sep 27, 2012, 12:43 am by oric_dan(333) Reason: 1
Sounds like a useful project. I can see there is a definite problem knowing
how far the various edges of the wheelchair are from the walls, especially
to the rear and sides.

Rather than completely hacking the wheelchair, which sounds like a serious
amount of work, possibly as an interim step you might develop a system
using 4+ sonars, arranged around the chair, with each giving an auditory
output when the distance measure is below some threshold, like 8-10 inches.
Each sonar could have a distinctive tone signal output. IE, sonars ->
Arduino [signal processing -> beeper.

In general, only one would be signalling at a time. It would help if you
had a means to enable the sonars only when the wheelchair was actually
moving.


scott_fx

thanks for the suggestions guys.  I guess i should first figure out why he's hitting the wall.  if it's just bad driving, or if it's an issue with him manipulating the controls... or if it's an issue with him not being able to sense the space needed to maneuver

scott_fx

been emailing with my cousin (not the one in the wheelchair)  asked him why his brother was running into things.  here is his response:

Quote
The controls on the wheelchair is a joystick that is very sensitive an not too user friendly. I have tried to use it and it jerks around when you start to move the chair. The problem is when you move the joystick slightly the chair does not move so you got to lean more on the joystick and by that time the motor catches up and takes off. One of the main contributing factors is that the two front tires rotate 360 degrees. So it depends on which direction those tires are facing which determines the amount of force needed to get the chair moving.

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