# Electric Car with Hub Motors



## major (Apr 4, 2008)

Pachinko said:


> I am developing a prototype of electric car that uses 4 in-wheel motors (buying them to a Chinese supplier). And now I have a problem because the Chinese company told me in an e-mail that each motor has its own controller, so I don't know how I am going to coordinate them to produce the differential steering function.
> 
> Do you know how those controllers work exactly, so I can try to solve that problem?


Hi Pac,

Quite simple really. Just run the motors in torque control. Which is the normal way to run an electric motor which propels the car, be a single motor or multiples. The throttle pedal is used to give a torque demand to the controller(s) which then controls the torque output of the motor(s) regardless of the motor speed. So multiple motors can all have the same torque and different speeds. Actually gives much better traction control than the standard mechanical differential where the greased wheel gets all the revs and sets the torque low on the stuck wheel.

Regards,

major


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## Pachinko (Feb 22, 2011)

Thank you for your reply.

So, do you mean that if I put one throttle pedal connected to the 4 controllers and I put this way the same torque on each motor it will work?

I understand what you said about having the same torque on the 4 wheels better than not (something like the TORSEN).But, what will make the motors take different speed when turning?

Thanks for your help.


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## major (Apr 4, 2008)

Pachinko said:


> So, do you mean that if I put one throttle pedal connected to the 4 controllers and I put this way the same torque on each motor it will work?


Yes.



> I understand what you said about having the same torque on the 4 wheels better than not (something like the TORSEN).But, what will make the motors take different speed when turning?


The road will make the wheels and therefore the motors rotate different speeds during turns. The controllers will not care and command each motor to run at the commanded torque, even though they are different speeds. No problem. Done on forklifts all the time (2 wheel drive, 2 motors).

ps...With multiple motors in torque control, it is the road which makes them rotate at the same speed when going straight.


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## Pachinko (Feb 22, 2011)

Ok. Thanks a lot for your reply.

In case I have some other problems I will ask.

Thank you.


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## cyclops2 (Feb 12, 2011)

What happens on sandy spots ? snow in the winter ? hydroplanning in the rain on 1 side only at 70 mph ? 

I really prefer limited slip differentials for directional control during those loss of traction conditions.

I have never driven a non-differential powered car.

I did not forget ice. Nothing works well on ice.


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## DawidvC (Feb 14, 2010)

Torque control on four individually powered motors will give the same effect as 3 limited slip diffs in an ICE powered car. There might be some advantages to the electric system in that its reaction time is inherently faster. On a straight road it will be more like driving a vehicle with locked diffs, only without the wind-up.

Hope that helps.
Dawid


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## major (Apr 4, 2008)

cyclops2 said:


> What happens on sandy spots ? snow in the winter ? hydroplanning in the rain on 1 side only at 70 mph ?
> I did not forget ice. Nothing works well on ice.


Hi cyc,

Yes. Putting one of the wheels on ice would allow it to increase RPM being in torque control. The torque control (simple) was offered up as the solution to cornering. If you want to eliminate wheel spin, like on ice, you would still use the torque control, but implement some higher level sense and control algorithms. But for Pac, just starting out with his build, simple torque control and stay off icy roads would be the way to go.

Regards,

major


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## RoughRider (Aug 14, 2008)

Do the Kellycontrollers controll the speed or the torque?

Or can you switch it?


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## cyclops2 (Feb 12, 2011)

Major

I think a SIMPLE DIY electronic steering differential power to the wheels could be done with a STEERING potentiometer or 2 of them. The purpose being to reduce the torque only to the side the wheel is turning to. 

Obviously the amount of reduction would vary between parking speeds & a violent swing of the steering wheel at 70 mph to avoid a Deer in front of you.

Nissan REALLY screwed up their " Sport Assist PS ratio ". When you floored the gas pedal on the first V6s with it . I almost caused a crash when I floored it to pass on a test drive. The sensitivty increased by some terrifying amount. I guess I missed the head on by .060 ". I spouted off to the terrified salesman next to me. He agreed the car was touchy.

I never bought that year car. Went to a V6 Accord. Far more comfortable in a emergency. 

That is the 1 most dangerous area of any car with powered drive wheels.

If a motor locks up or the drive controller goes insane & shifts into reverse at 70 mph. You are instantly toast with little or NO steering control caused by the skidding wheel on 1 side of the car at 70 mph.

Not far fetched conditions with total computer control.


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## major (Apr 4, 2008)

cyclops2 said:


> I think a SIMPLE DIY electronic steering differential power to the wheels could be done with a STEERING potentiometer or 2 of them. The purpose being to reduce the torque only to the side the wheel is turning to.


Hey cyc,

On the standard automobile with front engine front wheel drive with a standard mechanical differential, don't both front wheels get equal torque when turning a corner? What I proposed is nothing different.

I don't want to get into a debate about this. I doubt wheel motors will become a reality. So it is an academic exercise to me 

Regards,

major


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## cyclops2 (Feb 12, 2011)

Good question.

I only know that the differential is driven by 1 motor for 2 driving wheels.
The differential does automaticly transfer the power to the wheel with the least resistance. 
I have grabbed a raised rear wheel with gloves & then had another person shift the transmission into gear. The other wheel raced up to a maximum speed at idle rpms. There is VERY VERY little force in my hands.

Warning !!!!!!! DO NOT try the same thing with a POSITIVE TRACTION DRIVE AXLE !!!!!!! The POSI differential WILL SLAM EACH WHEEL with full power back and forth VERY VERY RAPIDLY ..It ...WILL....rip the wheel out of your hand !!!!.........It slams full torque to the wheel with the most resistance. 


REALLY well set up POSI rear ends were a delight on snow & ice. 


Rich


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## major (Apr 4, 2008)

major said:


> On the standard automobile with front engine front wheel drive with a *standard* mechanical differential, don't both front wheels get equal torque when turning a corner?





cyclops2 said:


> Good question.


It was a rhetorical question. The answer is yes.


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## cyclops2 (Feb 12, 2011)

If I were DIY the drive axles & differentials. I would try for this make.

The file download site is www.auto.howstuffworks.com/differential6.html


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## Pachinko (Feb 22, 2011)

Hi Major.

Do you know if YONGKANG SUCCESS PERMANENT MAGNETIC MOTOR MANUFACTORY is reliable? Because I'd like to buy their motors and I don't know how I can pay them and if they are reliable enough.

Thank you.


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## major (Apr 4, 2008)

Pachinko said:


> Hi Major.
> 
> Do you know if YONGKANG SUCCESS PERMANENT MAGNETIC MOTOR MANUFACTORY is reliable? Because I'd like to buy their motors and I don't know how I can pay them and if they are reliable enough.
> 
> Thank you.


Hi Pac,

No, I know nothing of the company. I do know that another member of the forum here bought a Chinese BLDC motor and controller package for a single motor installation and had serious problems with the controller to the point where last I heard he was trying to build his own controller for it. When it comes to Chinese products like this, all I can say is buyer beware.

A couple of points:

I was hesitant about replying to your first post because I think wheel motors are a waste of time for on-road EVs. But I didn't know what size EV you were doing. 

Any wheel or hub motor would have to be brushless, AC or BLDC, and therefore must be obtained in a motor/controller package. 

Such motor/controller packages can work well for scooters and motorbikes if applied as intended by the manufacturer.

Any deviation from the norm on installation will require good support from the manufacturer, which is unlikely with a Chinese product.

I know nothing about you or your capabilities or your project. If this is you first attempt into the EV world, I strongly recommend you back off the multiple motor approach and do a common single motor drive. Get your EV legs and then try something more exotic.

Regards,

major


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## cyclops2 (Feb 12, 2011)

Pachinko

Major has given you the very best & most pratical advice possible for what should be your first E V.

I also think a EV bicycle fully completed & running very well, will give you a good basis for a EV conversion of a motorcycle after that.

At that point you will have become experienced in several trades needed to convert a car to electric power.

Or you will say. 
It is not worth so much time & money to not have a 10 year / 100,000 mile reliability.

Conversion CAN cause a terrible amount of personal & public injuries.

Take it a little slower. There is no real rush.

Good luck


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## wherethere42 (Feb 28, 2011)

When rounding a turn in ANY 4 wheeled vehicle the outside tires must make more revolutions due to traveling a longer distance. The inside tires are "taking a short-cut" and travel a shorter distance around the turn. lockers and posi tracs in a differential (round chunk of the axle where the gears are) allow for one tire to free spin around turns but lock both sides if the drive side loses traction and regular "2wd" are really basically 1wd. If you were to take away this action of a free turning wheel and tires on both sides want to make the same revolutions
1. it will be hard to turn, especially AWD
2. your gonna wear out tires quick and unevenly

If you've ever driven anything with the spider gears and carrier all welded together in the axle you would understand this... chirp!chirp!chirp!chirp! around every turn and scared looks from pedestrians in parking lots! haha
Now I dont know alot about EV's and i'm trying to learn so i dont know how awd with elec motors at all four wheels will respond. i would guess similar but you may or may not notice as much depending on the weight of vehicle, torque of the motors and your driving style. the motor may soak up the resistance? seems this will just make all the motors work harder in a turn and you are using power you dont need anyways. anybody tried this, 4 wheels 4 motors?


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## Pachinko (Feb 22, 2011)

Hi guys!

I finally bought the BLDC motors and, as you told me, my first problem right now is the controller. I have some "instructions" (actually it is a sticker with a picture instead of real instructions) where I have the name of each wire, but I don't really know what to do with all the wires (an example is the POWER LOCK wire).

Could you help me with this if I show you this picture?

Thank you very much.


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## Gulah (Feb 24, 2010)

Amazing, this is a great question that I also had, but the doubt still remains, can the Curtis controller, for example, control the motors by torque?


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