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Generally, I'm interested in simple (DIY) electric vehicle design problems. I saw some photos of electric vehicles as in the following pic:

4dw diy vehicle

or also you could check this youtube video.

The vehicle is using an independent wheel drive, so it has 4 bicycle hub motors - one for each wheel. How is possible to regulate/sync the motor's RPM/torque in the turns? In the classic one-motor design this is solved by using a differential but how it is solved in an independent wheel drive scenario?

I am also wondering what happens when one wheel temporarily leaves the ground (e.g. in some off-road scenario). Wouldn't it start spinning very fast in the air, without contact with a surface?

As a programmer, I could imagine some Arduino-based "software differential" for the front wheels, which will regulate the RPM on the wheels based on the "steering wheel" angle, but I don't know how to do the same on the rear wheels.

Also, using an Arduino in such projects doesn't sound very "bullet-proof" but a car, especially such an important thing as engine RPM/torque regulation, needs to be "bulletproof" even as a DIY project, so I am not convinced that this would be a reasonable solution.

How it is possible to solve the independent wheel drive problems in the simple DIY world?

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  • $\begingroup$ Some trigonometry, with knowledge of rolling radius, slippage etc $\endgroup$
    – Solar Mike
    Apr 20 '18 at 11:26
  • $\begingroup$ @SolarMike "that trick never works" . I'd recommend strain gauges of some sort with feedback to a global controller which adjusts all 4 motors' drive current until all 4 wheels are at the same strain level. Then add a bunch of "except if" for loss of traction, ... and so on. $\endgroup$
    – Carl Witthoft
    Apr 20 '18 at 14:23
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    $\begingroup$ Just found: arxiv.org/pdf/1803.09411.pdf I thought it could be done "easier", but looks that it really needs some complicated math. The 14DOF model is mind-killer. :( $\endgroup$
    – jm666
    Apr 20 '18 at 15:50
  • $\begingroup$ After many hours of browsing I got some ideas = basically, this question is "too broad". :( I leave the question here - maybe someone could post one big answer with some github-link :), but it really needs to pay attention to many many things - even in the simple DIY (or RC) world. $\endgroup$
    – jm666
    Apr 20 '18 at 18:30
  • $\begingroup$ Hm.. anyone should read this trike build. Even if it is for the 2WD trike, it is an simple solution and it just works. (of course, not "scientifically" correct) :D :). Also found a funny cite: There have always been "experts" that fretted about the lack of a "differential" etc., but even a fairly powerful two wheel pusher trailer never had any adverse affect on a two wheel bike during cornering. $\endgroup$
    – jm666
    Apr 22 '18 at 21:26

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