Hipo AWD project

Technical discussion on converting internal combustion to electric
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Post by tsport100 » Mon, 01 Dec 2008, 03:28

I'd have to agree with JUK about unsprung weight in road cars, there's nothing lightweight about most road car suspension.

While I don't think unsprung weight is super critical in a road car it can't be ignored. To get decent torque in a direct drive induction wheel motor requires a certain amount of ferrous material. When the weight of the friction brakes is removed and the weight of the wheel motor substituted there is in effect no gain in net unsprung weight.

You mention that standard suspension is not designed for 'reaction' torque but it is designed for high brake force loads which I'm sure you'll agree is the same thing.

There’s no new generation of chassis, these Wheel Motors can be retro fitted to current cars with minimal modification and used as either battery EV or either parallel or series hybrid although they are primarily intended for battery EVs.

The proto-type is designed to fit Mitsubishi suspension but it's fairly straight forward to fit to others similar layouts.

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Post by tsport100 » Mon, 01 Dec 2008, 03:35

"actually delivering the kilowatts on a constant basis is still a challenge!"

What exact 'challenge' are referring to? This makes no sense to me at all!

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Post by acmotor » Mon, 01 Dec 2008, 04:09

So is it too soon to get hold of torque, kW and kg data ?

I long for the day when a real hub motor offering is available.
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Post by Electrocycle » Mon, 01 Dec 2008, 04:54

tsport100 wrote: "actually delivering the kilowatts on a constant basis is still a challenge!"

What exact 'challenge' are referring to? This makes no sense to me at all!
generally a battery pack is sized to give the required KWhs for the intended range, and to be capable of supplying the necessary average continuous current.

Delivering full torque at low rpm doesn't require too much battery drain due to the controller's buck conversion.
Once the speed is up, and you still want to deliver that full torque figure at 100km/h plus, you're talking about big current. It's ok for short bursts, but if you want to repeatedly deliver high acceleration at high speeds you'll need a much larger battery pack to handle the current drain.

This is why electric power doesn't work so well for high speed boats, or helicopters, etc which need close to full power on a constant basis.
When you work out the size of battery pack (and motor) required to supply the constant power required, you find that the power to weight ratio is not so good!

I think the real difference is that while an electric motor can deliver many times its rated power figure for a short burst - so can compete with a higher rated ICE in normal road use, an ICE can deliver its full rated power continuously, albeit with reduced life span.

An electric motor capable of supplying 200kw continuously is much heavier than an ICE of the same power (don't forget batteries too!). The electric motor will outlast the ICE, but the ICE will still last plenty long enough for a race season, or a reasonable life span for a performance car.
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Post by tsport100 » Mon, 01 Dec 2008, 06:42

Talk in specifics.

I still don’t get what you are talking about technically.

What sort of EV motor are you talking about? An AC Induction motor draws maximum current at Pull out torque. POT is a specific % of rotor slip, it basically has NOTHING to do with RPM or road speed. Horsepower is Torque x Rpm divided by 5252 so the only difference road speed makes is aero load that increases by the square of speed. But that’s not what you’re talking about is it.

High speed boats, how about something larger? Amongst the fastest and largest ships in the US Navy are aircraft carriers and they have electric propulsion! Nuclear subs ditto. All diesel Locomotives are also powered by electric motors.

As an example of how short lived a ICE is, the Diesel in a locomotive is about 24 times the size of a 5.7lt V-8 car engine but it only make about 10 times the power. The reason is that this engine is designed to produce 3,200 hp continuously, and it lasts for decades. If you continuously ran the engine in your car at full power, you'd be lucky if it lasted a week.

All ICE power measurements are PEAK and they never provide a continuous figure. Basically an engine that converts 75% of the energy it consumes into waste heat will always die of heat fatigue. Most cars can’t even run on a Dyno for any length of time without over-heating. Most cars even today are lucky to last 250,000kms in good condition, by 500,000kms they're junk. By comparison an electric motor can last up to 100,000hrs. If you drive at 60kph for 100,000hrs you’ll cover 6 Million Kms.

As far as batteries go it’s the discharge “C” rating that maters not the overall size of the pack or what the cells are rated at 1C. Cells like those from A123 are rated at 50C, that means 50x the rated current. That’s enough for the Killacycle to put out 500hp do 0-100kms in 0.8 sec and down the quarter in 7.8 sec at 168mph with only a 9kw/hr pack.

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Post by tsport100 » Mon, 01 Dec 2008, 06:49

All I can tell you at the moment is that it weighs 35kg and electrically it's 3 phase AC 400V @ 100A peak and will do 1500rpm @ 100Hz.

The challenge at the moment is actually finding an electric motor dyno facility in Australia large enough to handle it that can also drive it up to 100Hz. Haven't found one so far!

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Post by acmotor » Mon, 01 Dec 2008, 07:39

So does the motor form the rim for the tyre or is that extra weight ?
I'm thinking existing rim + tyre + 35kg will not find favour with department of transport unless you can lose some weight (not personally !)

1500RPM at 100Hz 3 phase so 8 pole.

400V x 100A x 1.73 x .9? ~ 70kW x 4 ~ 280kW peak power for vehicle. What RPM is this peak at ? 750 ?
Peak torque maybe 900Nm ?

All sounds very useable. Image

Ok, I'm digging here. You may not want to spill the beans.

When can I order some ?    
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Post by acmotor » Mon, 01 Dec 2008, 07:52

Dyno is simple.

2 x 75kW VFDs and a 6 or 8 pole induction motor (depending on your peak power revs) Connect the controller DC busses together and one drives, the other regens. Likey to still be 80% efficient. Probably just about run of a 20A 3PO if not then a 32A.

All the voltage and current and kW and torque info is there in front of you. Loggable as well via whatever bus option you chose on controller.
Whole setup maybe $25,000 new. Talk to Danfoss or ABB or ....

BTW, is the 400V at 100Hz the corect v/f so motor is 200V at 50Hz ? if so above would be OK otherwise you will need a higher voltage controller if it is 800V at 100Hz. Image
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Post by tsport100 » Mon, 01 Dec 2008, 09:18

You certainly are digging but most of you're numbers are on the money.

I have found a local (Newcastle) Dyno that can handle up to 150Kw but only at 50Hz. As for 2 x 75Kw industrial inverters there's 3 problems

1) None of the companies with big enough dynos can run variable frequency at this power level
2) There's one in Melb I spoke to that said even if they did run VFD at this power level the RFI makes all readings bar torque and Rpm usless
3) I'm not spending $25,000 just to test output at 100Hz.

We are currently working on an IGBT based inverter to suit so although we can get reliable results up to 50Hz and calculate from there, using out own inverter is probably the best solution to apply full power on a Dyno.

Yes it is 400v at 100Hz.

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Post by Electrocycle » Mon, 01 Dec 2008, 16:05

tsport100 wrote: Talk in specifics.

I still don’t get what you are talking about technically.

What sort of EV motor are you talking about? An AC Induction motor draws maximum current at Pull out torque. POT is a specific % of rotor slip, it basically has NOTHING to do with RPM or road speed. Horsepower is Torque x Rpm divided by 5252 so the only difference road speed makes is aero load that increases by the square of speed. But that’s not what you’re talking about is it.
I'm talking about kilowatts of power.
If your motor is making 200Nm of torque at say 3300rpm (bit over 100km/h after final drive ratio) that's going to be sucking nearly 80kw from the battery. That's 200amps from a 400v battery pack.
This is still only going to be ~55kw at the rear wheels, which makes for a very slow accelerating car once you're up around 100km/h, and could hardly be classed as high performance.
High speed boats, how about something larger? Amongst the fastest and largest ships in the US Navy are aircraft carriers and they have electric propulsion!
These are still displacement vessels, have an "unlimited" supply of cooling water, and don't have much in the way of weight limits for the drive train.
They are also not running flat out under battery power. (submarines run on batteries, but they only get full speed when they're in diesel electric mode.
If you continuously ran the engine in your car at full power, you'd be lucky if it lasted a week.
True, but with very minor cooling upgrades they can handle it for quite a long time. My car's engine was making double its factory rating, and is still going strong, after several years of circuit racing use, mountain road fanging, hillclimbs, etc.
My definition of continuous power in a car is being able to produce full power for at least an hour without issues. Wear may be accelerated, but there is no immediate risk of engine failure.

An electric motor in a car is usually sized so that its nominal rating will handle the average load of normal street use. The peak power might be five times higher to cater for occasional acceleration loads.
If you continuously ran an electric motor at five times its rated power you'd be lucky if it lasted ten minutes - if the battery pack could hold out that long.
Most cars even today are lucky to last 250,000kms in good condition, by 500,000kms they're junk. By comparison an electric motor can last up to 100,000hrs.
no argument on the "normal use" life span comparison.
In high performance use though a limited life span is acceptable. If an engine can last a race season, or even just a race meeting for really serious ones, it's good enough.
The issue with the electric drive system is that one that can handle a race length at a comparable power level is generally too heavy to be usable in a race car.
Cells like those from A123 are rated at 50C, that means 50x the rated current. That’s enough for the Killacycle to put out 500hp do 0-100kms in 0.8 sec and down the quarter in 7.8 sec at 168mph with only a 9kw/hr pack.
Sure an A123 cell can do 50C, but it's going to be flat in less than a minute, which doesn't really count as continuous power in my eyes.

This is exactly why there are successful electric drag vehicles, but not circuit racing vehicles.
An electric motor's only real point of failure is heat. The more power you can pump into it the more it can put out, as long as nothing overheats.
Getting rid of that heat in an electric motor is not easy on a continuous basis, but in applications where it doesn't have time to get too hot you can pump out 40 times their rated power.
This is also why the big old motors with a large thermal mass can make big peak power figures, but newer lighter motors often can't (talking more about DC motors here)


As an interesting experiment, let's specify a motor and battery combo that could compete with my old race car (not the 300+kw one!)

Existing specs:

185kw peak power, with over 160kw available at all times on a race track thanks to the gearbox.

Engine weight 110kg + gearbox 40kg


Wakefield Park has a fairly high full throttle percentage in a car like this, but lets go on the low side and make it about 60% - which means we need about 100kw continuous average power for the race car.
It needs to be able to do it for at least 30 minutes at a time without needing more than 30 minutes cooldown before it can do it again.

What sort of motor, controller and batteries do we need to supply 100kw for 30mins?

Assuming 90% motor and controller efficiency, we'd need over 55Kwhs of battery to last a session on the track.
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Post by acmotor » Mon, 01 Dec 2008, 16:37

?? now I'm confused.
I'm not wishing to be critical but, IMHO, a bit of a reality check ...

You are developing hub motors and building VFD from scratch and you don't have your own dyno test rig ? ... and the thought of $25k bothers you ???? I wish you the best , but how can I take you seriously ?
I'm not trying to be negative - just realistic. The task you have taken on is mamouth.

2 x VFDs, your motor and a standard induction motor as I mentioned and you can test all loads, motor and regen, at any speed with full data logging. In your own workshop. It could be setup within a week and you could get on with a really important R&D job.

If you really have a product, then think big, or chase some funding, before the Chinese run away with it ! ( no patent will protect you )

BTW the guy in Melb is just making lame excuses about RFI. I have set up 75kW VFD on a university wind tunnel with more instrumentation than you could imagine. (Danfoss VLT6000 with standard R3 filers - RFI is not dependent on motor frequency, It is more related to IGBT switching frequency anyway)
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Post by Electrocycle » Mon, 01 Dec 2008, 16:45

why not put the motors in a car and visit any workshop with a chassis dyno.
I can point you in the direction of a Newcastle workshop I've worked with if you like.

Between the controller datalogging and the dyno results, you'll be able to tell a lot about the real world performance of your motor.
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Post by MikeG » Mon, 01 Dec 2008, 17:00

This begs the question, how would you program oversteer characteristics into such a design. As you know, racing vehicles tend to harness oversteer to enhance cornering. Many driving enthusiests ask the same (even in FWD's with lift-off oversteer), so the only way this would interest me is if such a feature was built in. Driving a "mars lander" might be considered to be ultimate in engineering terms, but from a driving point of view it sounds pretty boring (and slow at cornering).

Hence I'd be looking to retain the old-technology AWD system and simply plug the motor into the front diff.

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tsport100 wrote: Make sense?

My full time job is as the owner of a business that has been working on an AC wheel motor project for the past 2 years and I have a patent pending on the subject. These wheel motors DON'T require any suspension modifications. We're also working on a drive system that uses 4 separate inverters and a central controller to drive and brake the 4 induction wheel motors.

What you describe as AC Induction 'slip' is probably best described as passive traction control in either regen or acceleration. For example under acceleration if any individual wheel loses traction relative to the others it will momentarily go faster than the drive frequency being applied and will therefore brake itself automatically until it's speed equals the drive frequency again.

It can also provide the same kind of traction 'balance' during braking (ABS is a modulated anti-lock system so not the same principle) and can provide a passive form of yaw control. I've seen test data from a car fitted with 4x BLDC wheel motors on a skid pan. The matching frequency input on all 4 motors meant that if either of the back wheels lost traction while pitched into a corner then that motor passively braked itself which reduced the yaw rate (i.e stopped the slide). Obviously slightly different with synchronous BLDC instead of asynchronous AC as there's no 'slip' but the reactions would be comparable.

When running separate motors in each wheel you also get a form of passive "brake steer" especially with AC induction as the inside wheels travel a shorter distance they brake slightly and this actually helps turning. The effect can be compared to how a tank of bulldozer with tracks turns, or how a bobcat excavator steers. McLaren had a feature like this years ago in F1 which was manually operated by the drivers via a 4th pedal, of course they started winning too much so it was banned.

I think a 'dumb' parallel system with front and rear differential mounted motors with maybe 5% slip is flawed as unless vehicle pitch is somehow compensated for then the whole system is compromised as I said in a previous post. A circuit for doing this is, believe me, not rocket science.

As a quick example, consider the difference in the size of friction brakes front to rear on any car you care to name. The fronts are ALWAYS bigger and for good reason. If you have ever driven a car with adjustable brake bias you'll realise how poorly it brakes the more rear bias is applied. Having a 'dumb' parallel system tying the front and rear motors together has a similar effect.
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Post by Electrocycle » Mon, 01 Dec 2008, 17:16

you you set up the control system so individual motors for each wheel behave like an AWD system with LSDs I think it'd work pretty much the same, but with higher efficiency and lower weight.

Using oversteer is often a way of overcoming the limitations of the drive train's effect on cornering grip though, so if you can really get all the wheels working to their potential you might not need as much oversteer.
In the end though it's determined by the driver, so the main thing is giving the driver enough control to be able to decide for themselves :)
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Post by tsport100 » Mon, 01 Dec 2008, 17:17

Nothing like a know all Naysayer.

The reality check is this is my business I've had funding for the last 2 years to work on this exclusively and I'm extremely unlikely to tell you my operating budget or justify to you how I spend my budget.

I didn't actually say I was doing everything myself personally did I but I'm hardly likely to tell you who I'm partnering with.

I don't have a grid connection large enough to run a full power test rig in my workshop anyways and just saying "well get one or move" has some extremely practical limitations. It's far more practical to 'rent' time on someone else’s facility rather than reinvent the wheel. Pity you're on the other side of the country otherwise you might want to offer some of you're know all assistance.

You're not comprehending what I said. The test guy from CMG said RFI was a problem as this POWER level, not that the frequency was a problem. From their experience testing with an inverter at 70Kw interferes with their equipment and they can't guarantee any reading bar the basics. And you're prepared to call CMG full of it, I think you'll need to qualify yourself to do that.

BTW what's so hard about building a VFD? I think perhaps you need a bit of a reality check yourself!

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Post by tsport100 » Mon, 01 Dec 2008, 17:33

You don’t adjust your diff settings to fine tune handling!

To adjust the front to back balance of the car can cover any area you can think of from weight balance, front to rear track width, ride height, tire width and compound, springs, shocks, aero etc the list goes on but diff setting is not one commonly used. Most LSDs I believe are not adjustable in the feild and hydraulic active diffs are as rare as hens teeth.

What I'm working on is the electric equal of having 3 active diffs. That’s all I can tell you.

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Post by MikeG » Mon, 01 Dec 2008, 17:36

Don't hub-motor cars do away with the HEAVY disk rotors, and rely on the motors to provide the braking force? Makes sense to me... By loading up the motors for regen, I wonder what sort of braking force can be applied, and if you can impart some sort of active brake control for ABS-like performance.
tsport100 wrote: I'd have to agree with JUK about unsprung weight in road cars, there's nothing lightweight about most road car suspension.

While I don't think unsprung weight is super critical in a road car it can't be ignored. To get decent torque in a direct drive induction wheel motor requires a certain amount of ferrous material. When the weight of the friction brakes is removed and the weight of the wheel motor substituted there is in effect no gain in net unsprung weight.

You mention that standard suspension is not designed for 'reaction' torque but it is designed for high brake force loads which I'm sure you'll agree is the same thing.

There’s no new generation of chassis, these Wheel Motors can be retro fitted to current cars with minimal modification and used as either battery EV or either parallel or series hybrid although they are primarily intended for battery EVs.

The proto-type is designed to fit Mitsubishi suspension but it's fairly straight forward to fit to others similar layouts.
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Post by tsport100 » Mon, 01 Dec 2008, 17:43

You've hit the nail on the head.

Not only can it use regen but DC injection and motor revese independantly on each wheel. The list of features can cover:

-Intelligent ABS (standard ABS is 'dumb')
-Active Stability control
-Active brake force distribution (aka Brake bias)
-Emergency brake assist

to name a few.

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Post by Electrocycle » Mon, 01 Dec 2008, 17:48

active brake control / ABS would be part of the control system.

Regen braking torque is going to be about the same as peak motor torque, although you could allow higher peaks due to the low duty cycle (same as mechanical brakes really - they always rely on thermal mass, and can't dissipate the heat generated on a constant basis.
You don’t adjust your diff settings to fine tune handling!
Actually a lot of people do, but it's usually a set and forget type of adjustment. You either choose a diff with the right sort of ramp rates and clutch preload you need, or you adjust it until it suits your car and driving syle, then leave it alone.
Some race cars change the diff for individual tracks as it can have a big effect on the car's handling. They're either changed by opening up and swapping shims, or many have an adjustment through the center of one axle (unbolt drive shaft, adjust diff, replace drive shaft)
A really tight LSD is no good on sweeping corners, but a loose one will spin the inside wheel when trying to put power down coming out of tight corners.

Electric motors allow for really easy and accurate traction control, and with some steering input to the controller, wheel motors would allow perfect distribution of power.

I think the ideal layout for an electric sports car would be to have a wheel motor on each rear wheel, and most of the batteries / electronics in the front where the engine was (assuming an MX5 / Silvia / Integra like platform)
It'd be possible to maintain good weight distribution, and intelligent control of the motors would give amazing traction and cornering.
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Post by MikeG » Mon, 01 Dec 2008, 17:56

All the power figures for the hub motors are PER WHEEL, right? The power levels sound monsterous and I can only dream of a battery system advanced enough to support this sort of peak power.   Especially in a 4-wheel driven case.

Anything beyond ~100kW per wheel is going to be in supercar territory (if 4WD), and the pricing for batteries and controllers is going to be stratospheric.

Also, be careful with some of the chassis dyno operators in Newcastle. One that uses the name of an ex-GTR touring car driver from the 90's is fairly dodgy from some reports. In fact according to the namesake, he's not a happy camper having sold his name to the business. (this was a few years back, so things may have changed) - Nuff said.

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Post by MikeG » Mon, 01 Dec 2008, 17:59

Sounds good. My only concerns with that approach (and that can be worked around several ways) is that if power is lost for whatever reason, you have no brakes.
tsport100 wrote: You've hit the nail on the head.

Not only can it use regen but DC injection and motor revese independantly on each wheel. The list of features can cover:

-Intelligent ABS (standard ABS is 'dumb')
-Active Stability control
-Active brake force distribution (aka Brake bias)
-Emergency brake assist

to name a few.
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Post by woody » Mon, 01 Dec 2008, 18:11

MikeG wrote: Sounds good. My only concerns with that approach (and that can be worked around several ways) is that if power is lost for whatever reason, you have no brakes.
I think I read in the danfoss manual that it can brake without power. You would need a braking resistor though, since the DC Bus (aka the batteries) is gone.

Some of the drives can run the electronics off a separate 24V supply, which should give you braking in this scenario assuming you have a battery for it.

This is a very interesting thread (even if it's getting a little heated). I think everyone's on the same team still :-)

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Post by acmotor » Mon, 01 Dec 2008, 18:29

My posts stand as they are. Sorry, I don't know it all, but I know enough to idetify notyetmadeium.

If you have a 70kW, 35kg 1500 RPM hub motor (no gearbox I trust) then don't waste time arguing here. That I know all to well. Just get on with it. You have all those control algorithms to work on, that this very topic is about.

If you want some professional advise re dyno, I can help. I am both qualified and experienced in motor control and instrumentation. That very knowledge makes me shudder at your dyno situation.

I did say IMHO.

The commercial need to remain closed shop I understand. Good luck.

I'll wait for some actual product and welcome it totally.

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Post by Gow864 » Mon, 01 Dec 2008, 19:03

Behold! An electric 4WD Image

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Post by tsport100 » Mon, 01 Dec 2008, 19:17

acmotor wrote: Just get on with it.
I do take Sundays off and break for lunch. Image

acmotor wrote:You have all those control algorithms to work on
A system to run 4 wheel motors at a lower power level is already up and running and has been demonstrated on several vehicles. A 70Kw test motor was recently completed and power applied for the 1st time about a month ago.

acmotor wrote: Good luck. I'll wait for some actual product and welcome it totally.
Thanks! Watch for news of a demo vehicle later this year.

BTW I'm not in Newcastle and the Dyno facility I referred to in Newcastle just happens to be the largest available in the state for electric motor load testing and is not related to car testing at all.


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