This is sort of a "final" attempt to make power wheelchairs work better for people. It is the culmination of experience "playing" with robots.

I thought of making a You Tube video showing this wheelchair driving around without a driver claiming a mysterious force was controlling a wheelchair with no one`s intervention. It might get a lot of hits, but wouldn`t do much for CwhatIcanDo Projects.

This culminates my original project, to use existing power wheelchair components to make a robot. I wasn`t interested in wheelchairs at first, but it began to make sense to do things that people could use to make low cost powerful robots, but also to serve handicapped people.

If you`ve followed this website, you can see that I started in chunks, then this project is where it all gets integrated together. The chunks are hooked up together for the first time. This results in an interesting wheelchair.

It operates like a normal wheelchair, though it does prompt the driver with noises, telling the user there are objects in the path.

But this wheelchair has more. The $20 rf remote controlled robot from a wheelchair project was included, so you can move the chair around under your remote command.

And, finally, though somewhat less practical, fully autonomous wheelchair. You can see in the video, I am riding on the chair taking "chair" perspective pictures. I must confess, it was fun having a robot drive me around, but it was also unnerving. That wall coming at me (and my toes) was a little unsettling. Though I can think of many uses for semi-autonomy, I can`t imagine turning this thing loose in a crowd, but hey, more sensors, more software development and who knows?

We are hooking these four circuit boards together. One is the High Power Project Board for the 16X, or 16M2 picAxe microcontroller.

A simple perfboard is used as a "connector" between the connections from inside the joystick controller located in the handrest shaped device you use to steer the wheelchair. It also contains the 5 volt regulator for the logic chips. The controller in the chair supplies the 12v to operate everything.

Another board is removed from an R/C car. Just about any R/C car will do. You are using an H-Bridge to permit you to supply a LOW, A HIGH, or an open circuit. So you won`t use the Motor Drive outputs like the R/C truck used `em. Instead you will supply + or - voltages (relative to 1/2 the 12 volts - Around 5.8 volts.

When you apply higher than +5.8 (around 7 volts) on one wire, the chair goes forward, on the other pin it turns right. When the applied voltage is around 5 volts, the current flows out of the controller and you go back, or turn left. Thus we control the controller. It also allows you to hook things up in parallel. That means you can control the joystick using either the joystick itself (manual) or under R/C control, and one more.

When the chair senses things in front of it (it is more sensitive to the right in my model) it reacts appropriately doing a simple object avoidance procedure, well known by all the simple little tiny robots I`ve built. Basically, this thing is a big giant version of the smaller bots we build around here.

Oh yes, just for fun, I added a 7-watt audio amplifier and speaker to the mix. By taking a feed from a pin that also drives an LED, I get the thing to "show me" and "talk to me" at the same time, so I can use these as signals during development.

I started with a min-Jazzy power chair. I added new batteries and dealt with only the chassis, treating it like a robot.

You can find a series of articles and You Tube videos that deal with building out each of the functions of this automated power chair.

This is the schematic diagram.

This is the latest diagram with all four subsystems in place. You have the modified power board which "floats" held in place only by it`s wires. This allows you to get to the board for programming.

Put everything in the plastic box that came with the 7 watt amplifier kit. I used spacers, nuts and bolts, except for the power board with the picAxe chip. The picAxe development board is heavily modified. So heavily modded, I thought about doing a new board, but hey! I`m a hacker/modder at heart.

This is just to make things more clear. This is everything in the plastic box. The LED flashes and the speaker pops when the Ultrasonics record an event.

Here is the current software for operating the wheelchair. It is like the previous software except for the operating loop that looks for output from the rangefinder and outputs a click or two according to the distance to the object.


; *******************************
; ***** Power Chair Robot *****
; *******************************
; Filename: using18m2.bas
; Date: 03/09/12
; File Version: 2.x
;
; Written by: Jim H
; Function: using nav and drive ctl
; Last Revision: 1
` ------------------------------------------------------------
` Compiler Directives
#picaxe 18m2
` ------------------------------------------------------------
`--------------------------------------------------
` PicAxe 18M2 pin diagram
`==================================================
`(DAC / Touch / ADC / Out / In) C.2 leg 1
`(SRQ / Out) Serial Out / C.3 leg 2
`(In) / Serial In / C.4 leg 3
`(In) old reset is now signal C.5 leg 4
`---------------------------------------
`(gnd) 0v leg 5
`---------------------------------------
`(SRI / Out / In) B.0 leg 6
`(i2c sda /Touch /ADC /Out /In) B.1 leg 7
`(hserin /Touch /ADC /Out / In) B.2 leg 8
`(pwm / Touch / ADC / Out / In) B.3 leg 9
`=======================================
`---- package bottom -- direction up ----------
`=======================================
`(i2c scl / Touch / ADC / Out / In) B.4 leg 10
`(hserout / Touch / ADC / Out / In) B.5 leg 11
`(pwm / Touch / ADC / Out / In) B.6 leg 12
`(Touch / ADC / Out / In) B.7 leg 13
`---------------------------------------
`(vcc) +v leg 14
`---------------------------------------
`(Out / In) C.6 leg 15
`(Out / In) C.7 leg 16
`(Touch / ADC / Out / In) C.0 leg 17
`(Touch / ADC / Out / In) C.1 leg 18
`
`===================================================

`--------------------------------------------------------------


` set motor drivers to known position
` turn all motor enables OFF
symbol in3 = b.7 `FWD/BKWD
symbol en34 = b.2

symbol in1 = b.5 `L/R
symbol en12 = b.3

symbol i2csda = B.1
symbol i2cscl = B.4

symbol runFlag = b6
symbol SRF08SftwRev = b0
symbol LightSens = b2
symbol Range = w2


symbol minAmnt = 30
symbol maxAmnt = 45

` stop everything
low en34,in3,en12,in1, runFlag

` Define i2c slave address for the SRF08
hi2csetup i2cmaster,%11100000,i2cfast,i2cbyte
hi2cout 1,(0) ` cut analog gain to 200 ish

hangTime: `wait to push button to start this thing going
if pinC.5 = 1 then
hi2cout 0,(80) ` Send Ranging command to get range in in
pause 75 ` Wait for ranging to complete
hi2cin 2,(b5, b4) ` Read the Range, Note b5-b4 are w2 high-low bytes

if Range <= minAmnt then
high b.0
else low b.0
end if

if Range > minAmnt AND Range < maxAmnt then
high b.0
else low b.0
end if

goto hangTime
else
goto main
end if


main:
`inline checks of robot condition
`stop, analyze, react appropriately
`make this check so fast it is a blur
`monitor the pb, then start the mover forward until strategy

hi2cout 0,(80) ` Send Ranging command to get range in in
pause 100 ` Wait for ranging to complete
`hi2cin 0,(SRF08SftwRev) ` Read SRF08 Software Revision in b0
hi2cin 1,(LightSens) ` Read the Light Sensor into b2
hi2cin 2,(b5, b4) ` Read the Range, Note b5-b4 are w2 high-low bytes

if Range <= minAmnt then
high b.0
gosub stopFB
gosub stopTurn
`pause 200
gosub moveBackward
pause 200
gosub stopFB
gosub turnLeft
pause 500
gosub stopTurn
else low b.0
end if

if Range > minAmnt AND Range < maxAmnt then
high b.0
gosub turnLeft
pause 350
gosub stopTurn
else low b.0
end if

gosub moveForward
pause 200

goto main



moveForward:
high in3
high en34
pause 10
return

moveBackward:
low in3
high en34
pause 10
return

stopFB: ` stop forward/backward motion
low en34 `drive off
pause 10
return

turnRight:
high in1
high en12
pause 10
return

turnLeft:
low in1
high en12
pause 10
return

stopTurn: ` stop right/left motion
low en12 `drive off
pause 10
return