Hello everybody !
Sorry for my bad english but i have an problem .
I have an friend who has an electrical weelchair because he suffer from both legs paralysis and he cant walk . So , weelchair is broken . The microcontroller who controled the chair is gone. He asked me if it can be done some modification to his chair . He need only forward , backward , left and right .
It is certainly a possible project - its not a trivial project by any means though.
The two motors each need an H-bridge to control them, and for these power levels this isn't trivial (although the motors are 4A rated, the transients will be much more, many tens of amps, and the H-bridges must take this.
Secondly there needs to be considerable attention to safety - a runaway chair could cause severe injury to occupant or innocent bystanders. Commercial chairs and scooters have to pass stringent safety tests and in many countries its a legal requirement that the chair is type-approved.
So realistically I think you need a proper commercial wheelchair motor controller... You may be able to get an exact replacement from a supplier.
I've done adaptions of mobility scooters before for art vehicles - but with these single-motor devices the interface to the controller is a single potentiometer so you can build a user-interface to drive a single voltage with a kill-switch for safety - thus getting all the reliability and safety of the original controller.
Wheel chair controller interfaces may just be two potentiometers but I've not looked at one yet.
If the chair is to be used by somebody, it might be best to get parts off of another junked chair. A simple switch/relay setup might be possible if the motors are simple brushed units.
Based on the pictures, they're brushed DC motors; aygun, take MarkT's advice - you DO NOT want this system to be a run-away. It would be one thing if you were building a robot (even there, I would advocate caution and safety controls), but for a person-carrying chair, you need to take extra-care to make such a system safe. H-bridges to control such motors are available, but without knowing the stall current of the motors, I am hesitant to reccommend any (also, depending on what is needed, such h-bridges can be fairly expensive).
When I get home tonight, I will post a link I have for a place here in the US this guy runs for wheelchair/mobility chair repair - you might be able to get in contact with him for some better advice on what to do...
Just make sure that when you ask for info, let them know what you want to do, and be polite. I can't guarantee that you'll get a response, or if you do if it will be favorable, but it can't hurt to try. That first link also has a message board, so you might want to join and ask around for info and such on there as well.
Basically, you'll want to find the true running and stall currents for the motors, an idea of what kind of h-bridges to buy, or if the control box (or at least, in your pics I thought I saw some kind of control box - I know you mentioned you didn't have one, but what were those boxes and the joysticks for, then?) can be hacked into in some manner for other controls?
Also note that typically, wheelchair/power-chair joysticks aren't connected (the internal pots) in a "standard" manner; be sure to reference a schematic, or create your own, or possible re-wire them. They are generally connected in such a manner so to output a strange "mixed" signal (I don't know how else to put it), rather than a straight x/y signal (maybe its a form of "polar" coordinate output rather than cartesian? Dunno).
Aren't those motor controllers in the middle of the base of the wheelchair, between the two motors? I'll bet you just need to input a control signal to those motor controllers. You can use an Arduino to provide that control signal. You should be able to use a two-axis joystick of some kind for the user to interface with the Arduino.
Thank's very much guys for all the advices . I will keep you informed regarding the project status. I have found somebodz to help me with the programing of the arduino board . The H bridge can it be done very easy . Thank's again everyone .
