# Independent wheel control



## edin (Sep 16, 2012)

Hi all,

I'm a college student working on a car for the Formula Hybrid competition in the spring. We're building an all wheel drive electric race car and hope to have four-wheel motor control.

It's my understanding that if we have four motors, we need four controllers. I have absolutely no background in electronics, so I apologize for the rather basic questions.

How do you set it up so you can control all of those four motors? Say, for example, we're turning left. We'd want more power going to the right side to help push us around the turn. Or, in acceleration run, we'd want more power going to the rear two wheels.

What resources can you point me to to try and plan how this whole system is going to be set up?

Thanks!
Eric


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## Ivansgarage (Sep 3, 2011)

You might try looking at something like this web site.

http://www.robotmarketplace.com/store.html


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## PStechPaul (May 1, 2012)

That is a very good source for motors, controllers, and other components, but does not really address the OP's question of four wheel independent motor control. I think this will require a separate controller for each wheel, but there must be a way to operate them all from a single operator interface. This might best be accomplished by using direct torque control for each motor, which should drive all four wheels equally even under variable traction. But I think there also needs to be synchronization of speed, because DTC may tend to try to apply higher voltage to a wheel that is slipping, rather than reducing the voltage until the wheel regains a grip on the road surface and contributes to traction. 

It may be worthwhile to steer the vehicle by using adjustable torque and speed differential between the left and right sides. Thus a joystick might be used to apply forward and reverse power either equally or with more or less to the sides for turning. This would also allow for reverse and turning in place (ZTR), although that may not be desireable for a formula hybrid vehicle, which I assume will be for track racing. 

I think this may be a good application for AC motors, and it may be possible to use just two controllers as long as the motors and tires are identical. If a wheel driven by an AC motor loses traction, it will continue to spin at just about the same speed as the other, rather than speed up like an unloaded brushed series DC motor. BLDC motors may also be a good choice. 

The best performance will probably come from excellent control technology utilizing feedback from speed sensors and accelerometers to determine exactly what the vehicle is doing and making millisecond decisions about how to apply power to the motors. Sounds like a cool project, and it should be a great learning experience. I'd advise extensive on-line research as well as hands-on small-scale experience. 

Good luck!


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## aeroscott (Jan 5, 2008)

I was talking with a automation guy about this very thing . He said a canned module for accelerometers and one for stability control . Common in modern cars . The custom part would be interfacing to the motor controllers .


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## domosher (Jul 10, 2011)

for the requirement mentioned I would recomend a microcontroler to monitor stearing wheel position and rpm of each motor and current draw of each motor to determin how much energy and is being properly used this way it will only need one throtle control and 4 digital to analog outputs as well as about 10 analog to digital inputs


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