# How to regulate torque/RPM on an IWD vehicle

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

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?

• Some trigonometry, with knowledge of rolling radius, slippage etc Apr 20, 2018 at 11:26
• @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. Apr 20, 2018 at 14:23
• 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. :( Apr 20, 2018 at 15:50
• 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. Apr 20, 2018 at 18:30
• 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. Apr 22, 2018 at 21:26