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Torque Vectoring or Traction Control - Twin motors

Posted: Wed, 24 Jul 2013, 10:38
by T2
The Audi R8 e-tron does 0-60mph in 4.8secs which is quite a bit slower than the Tesla cars which can do 3.9secs. How come ?
It has to be in the gear ratio. The Tesla's Vmax is 120mph. For the E-tron it must be about 160mph.

There is an excellent Youtube video posted of the E-tron earlier this year racing around the Nuburgring. Interesting because the driver looks to be quite experienced as he puts it through its paces. The dash camera shows current pegged at 150Amps per motor, I am asuming, until cornering when the needle dives back into the regen area. The speedo goes to 180 but 150mph seems to be the limit.

It's a good lesson in regards to acceleration and top speed which can be applied whether 313Hp or 80Hp is contemplated.

Torque Vectoring or Traction Control - Twin motors

Posted: Thu, 25 Jul 2013, 05:52
by Crash
sorry, why gear ratio, are power, torque and weight the same?

Torque Vectoring or Traction Control - Twin motors

Posted: Thu, 25 Jul 2013, 12:46
by T2
Hi Crash,
     Yes motor torque, power and weight are approximately the same however the total torque at the wheels is not and that is despite the fact of Tesla roadster having only one motor compared to four on the E-tron.

The problem is that the maximum rpm of induction motors of this size are limited to 14000 rpm at which point internal centrifugal forces are likely to build up and cause them to grenade !

The E-tron is probably geared 4:1 to achieve 240mph the Tesla is around 8:1 to achieve 120mph which gives the Tesla a 2:1 advantage right there from a motor point of view.

And then there is the Tesla with a 200Hp motor which is again more than twice the size of each of the 80Hp E-tron motors allowing it to put more torque to the wheels.

Simply put the E-tron is geared for the highest top speed, The Tesla is geared for the best acceleration.     

Torque Vectoring or Traction Control - Twin motors

Posted: Wed, 02 Oct 2013, 22:09
by MasterCATZ
After a way to do quad motors

wanting AWD and a direct electric motor per wheel

with option to switch between FWD RWD AWD of cause :P

Torque Vectoring or Traction Control - Twin motors

Posted: Thu, 03 Oct 2013, 04:06
by Crash
Have discovered my motors (twin AC induction motors, RWD) which are now installed and power cabling done Image have controllers that use the canbus system discussed previously in this thread, so maybe that could be used in managing motor torque for traction control, however microprocessor design and programming is beyond me at present. The motor speed / torque characteristics should work ok for distributing power between the driven wheels, even if it doesn't extract the maximum possible available traction.
If you had 4 motors, one each wheel, going from fwd, rwd and awd would be as simple as turning motors on and off, although it would reduce the rotational inertia of the drive train if there was a clutch disconnect. If you have awd, why would you want to operate as fwd or rwd anyway? Wouldn't you loose around half of your available power.
I'm still keen to try using an arduino or equiv to generate throttle 2 or 4 outputs from a single throttle input, then you could easliy experiment with different sensors and control logic to split torque between 2 or 4 wheel motors.


Torque Vectoring or Traction Control - Twin motors

Posted: Fri, 04 Oct 2013, 00:32
by MasterCATZ

#1 reason would be if its taken to the drag strip at least the rear wheels could have some heat pumped into them

which is the main reason I am wanting to do a 4 motor system so I can eliminate gear box's and use motor RPM to get high end trap speed

#2 reason is IF a motor does die I can switch between FWD / RWD
tho I guess I will have to be able to unlink the motor so wheel can free spin ( in senario where motor welds its self )
maybe I will do a clutch between each motor and wheel which might help with my current brake system deliema

currently thinking of ways to setup breaking system

I was going to have the hand brake applied directly to the motors shaft, but then thought how would I go about with hill starts some form of brake clutch will be needed

you wouldn't want to use the battery life up holding the car in place using motors torque , and you wouldn't want to run the motor before disengaging hand brake in case something broke ..

I am definatly wanting AC system
( imagine regen braking the car at the drag strip :P )
I am wanting to match the car power system to house hold voltage
so the car can also be used as a backup generator :P

14x time now this year powers gone out I have 20 kw grid solar system and no backup power

last night was another time it went out at 11pm .. and I had to get ready for work at 2am .. no water ect ... thankfully showers at work

Torque Vectoring or Traction Control - Twin motors

Posted: Fri, 04 Oct 2013, 04:10
by Crash
had power out myself for two days myself, week before last, reinforcing my own plans for an inverter for backup power.
I don't think the motor controllers are going to drive a household AC system directly, so might be more important to match voltage to standard inverter input.
I'm bemused by the thought of wasting a massive amount of power to do a burnout at the drag strip, but then wanting to recover some power by regen braking. Might be more efficient to get some electric tyre warmers.

Torque Vectoring or Traction Control - Twin motors

Posted: Mon, 18 Nov 2013, 08:27
by Crash
Have got the test project up and running now and the approach works perfectly without spinning the inside wheel, even on loose gravel. That is of course unless you want to spin them.