Converting disability chair to four wheel drive

Trying to,find out how to tap into signals to the existing two motors, then by using a computer selecting the signal to the faster turning motor feed that info into a dc motor controller for the third motor( transaxle) so that this third motor turns at the same speed. System will need to turn third motor in reverse when original two motors are in reverse.
Complete novice regarding electronics , where do I start.
Any help will be h4atefully received.
Thanks

Tony

Hi @Amk and welcome to the forum!

So, are you trying to use just motors from that disability chair or also a controller?

Maybe you could post a picture of your set up, or draw some schematics?

Anyway, there are plenty of motor controllers here:
https://www.robotshop.com/en/motor-controllers.html

Thank you .

I had hoped to "listen in "to the existing controller, take the instructions to the fastest turning motor and via some sort of switching system run the third motor at the same speed , both forward and in reverse.

If it would be simpler to install a whole new set up the that may be the route to go.

As stated I am ignorant regarding electronics so all help is appreciated.
I have a quick sketch of my original concept.
BUT struggling to see how to attach it? sorry cannot work out if hyperlink? is the way of sending my scanned sketch

Try to upload it directly from your computer:

Scan 12.pdf (763.1 KB)

Thank you the guidance, hopefully rough sketch attached, I had previously tried to copy and paste without success

This was my original concept, see file.

Would it be possible to drive two motors on each channel of the ECU?.

Both left motors on one output and both right on the other.
Through engineering allow one pair of wheels to turn. So that more power to the right wheels induces a left turn and vice versa.

Apologies if my thinking is simplistic, lack of expertise with electronics and dc controls etcScan 13.pdf (388.3 KB)