4WD system does not work, I chase Mitsu for solution.

[anko]

Looking for stuff like this? ;-)

http://www.myoutlanderphev.com/forum/viewtopic.php?p=23697#p23697

 

[pasquinade]

Hi all,

(in reply to ian4x4) - EDIT: sorry only after re-reading did I understand his comments were more on the motor. At the time I checked that the outlander PHEV motors are full torque at 0 speed, but I forget the exact type now, will try to recover that information.

A while ago I made a small back-of-an-envelope computation and, assuming what I found in some forum pictures (great info, thanks!):

195Nm Stall Torque and 7.065 gearbox for one of the axles and
137Nm Stall Torque and 9.663 gearbox for the other axle

I arrive at (assuming a wheel diameter of 705mm - checked it somewhere) a total of 765kg of forward force (7655N). This means stalling at around 24 degree incline (assuming a weight of around 2tons). Not perfect but better than many cars. If "low gears" switch were available it would be a nice stall torque.

By the way, I am more or less convinced by the above numbers. As a means of checking the result I know the car does 0-120km/h in around 11s, meaning (at a constant acceleration) around 3m/s^2 which implies a constant force of around 6kN. The difference between the two is that torque is not really constant so the average horizontal force is lower (6kN) than the stall force (7.655kN) - just a simple "order of magnitude" sanity check that seems to pass.

I saw some videos of a PHEV going up a very steep metalic structure in Japan, but I'm convinced that that was mostly inertia working....

Hope this is useful...

EDIT 2: sorry, car does 0-120km/h in 11s (not 0-100km/h). Small typo.

 

[anko]

I have done standing starts (several in a row in short time) 17% towing a 1500 kg caravan with 4 adults in the car. It was not fast, but there was no problem either. Based on that, I would think it can do little bit better than 24% without trailer. Of course, if one axle lost grip, it would be a totally different story.

 

[Grigou]

But it does matter. A lot. As you say, in EV mode we have 60 kW available that can / could be distributed over front and rear axles. So, (in theory) we do not have to loose any power. But torque is not limited by the battery, but by the specs of the motors. Like it or not, we loose half of the available torque when one axle has no grip. and the remaining torque may simply not be enough to get going.

It does not matter for me because it's somewhere the same thing. "Somewhere" is an important word in the context of course The angular speed makes the difference.

I agree with the fact that we loose half of the torque when one axle has no grip. It's because I agree that my question is : where is the second half ? The car don't even move for 2 cms !
And why the spinning wheel is not braked ? It should, at least if we don't push any switch ... :?:

 

[ian4x4]

Thanks for your calculations pasquinade

Your reference to wheel diameters made me think of another problem that we may have on soft ground.

Last week when moving an aircraft exhibit we accidently allowed a wheel to go onto the grass. Of course it sank slightly but caused us a lot of effort to move back to the hardstanding. This was mainly as the aircraft wheel (and aircraft) had to rise several inches in it's initial few inches of forward motion.

I was wondering what slope this would be equivalent to, and how it would effect your calculations on the initial moving of the stranded PHEV.

Regards Ian

 

[pasquinade]

Sorry for any mistakes, i'm on my mobile now. Just a clarification about road grade (usually as a percentage or permillage and is shown on road signs) and angle.

Grade [%]=tan(angle)*100

In my post i used angle while it is common to express in grade as anko did. Hence with 24 degrees I mean around 44% grade. Anko's 17% grade imply 10 degrees.

Wikipedia link
https://en.wikipedia.org/wiki/Grade_%28slope%29?wprov=sfla1

Anko, is this what you meant?

EDIT: fixed formula above. multiplication by 100 (to convert to integer percentage) was on the wrong side

 

[anko]

Indeed, you mentioned degrees, not percentage. My bad And yes, 17% is what I meant. I think it is close to what UK people call a "1 in 6 slope"?

Indeed based on my experience, I thought it should be able to do 24% solo. Where your calculations say it can do 44%. So, no surprises there ;-)

Are you sure that steel ramp on the video was more than 44%?

 

[anko]

But it does matter. A lot. As you say, in EV mode we have 60 kW available that can / could be distributed over front and rear axles. So, (in theory) we do not have to loose any power. But torque is not limited by the battery, but by the specs of the motors. Like it or not, we loose half of the available torque when one axle has no grip. and the remaining torque may simply not be enough to get going.

It does not matter for me because it's somewhere the same thing. "Somewhere" is an important word in the context of course The angular speed makes the difference.

I agree with the fact that we loose half of the torque when one axle has no grip. It's because I agree that my question is : where is the second half ? The car don't even move for 2 cms !
And why the spinning wheel is not braked ? It should, at least if we don't push any switch ... :?:

I agree with you that not being able to transfer torque does not necessarily explain why the car doesn't move. In other words: why is half of the torque not enough. I was just trying to explain why we cannot electronically reproduce the effect of a locking center diff, which can transfer torque from one axle to the other ;-)

I wish I could put myself in such a situation easily and test will all possible combinations of 4WD Lock on / off, ASC on / off, Charge on / off and what not and have my tools monitor whats going on .... Just don't know how.

 

[Esparza]

Is not a power or torque problem, just traction. A center lock diff does not split torque or power, just equalize RPM. The problem with taking out the boat with rear axle having traction would disappear if 4wd button makes both axles turn at the same RPM, the front wheels will spin, but rear wheels will push or even spin if one lose traction, but never stay stopped with traction.

In my opinion phev system works very nice once you have started moving, but doesnt work from stop.

 

[phevnor]

@Anko: Perhaps you should provoke a wheel lift making a ramp, simular to this:

Perhaps also tie the car to a three or something that holds it back.
Then try to "drive" an see if it put or to the axel that have both wheel well to the ground.

 

[Trex]

assuming what I found in some forum pictures (great info, thanks!):

195Nm Stall Torque and 7.065 gearbox for one of the axles and
137Nm Stall Torque and 9.663 gearbox for the other axle

You mean like this.


and this.



And I did not think anybody looked at them. :mrgreen:

On my behalf you are indeed welcome.

 

[Trex]

Now it would appear to me we are drifting off topic.

Martinh the starter of this topic said:

The system does not work, ONE! (i have never seen 2) of the front Wheels stars to spinn, you have to push the accelerometer more to get the back Wheel(Always only one) to start pushing. You do not know the front whelle is spinning until the window is covered in mud as you do not hear is spinning, and you can not see on the dash.

That to me is a traction problem IMO. Does anyone not agree?

Then he says,

I heard something about the tyres, and yes, tyres are important, to avoid using special tyres and chains i use 4WD cars.....

I mean this. Does anyone here really think that a 4wd does not need proper tyres to function as a proper 4wd.

and

Sorry!, i forgot to answer.
The PHEV has Nokian Hakka R unstudded Winter tyres 225/50-18, very expensive.

Look up the tread pattern on those tyres. Not good IMO.

And he is pulling a trailer as well. I do not think his PHEV ever had a chance.

This is all just my opinion. I hope MartinH find a answer to his problem. I mean this sincerely.

 

[Trex]

Now we have a video of a some one pulling a boat from the water.

Not MartinH but someone different.

https://youtu.be/H_imGaSZ1B8

Now the first thing I notice with this PHEV is a loss of traction. Front wheels slipping. Creating loss of momentum.

Do we not agree?

So no problem back wheels should get it out.

But we all know he has just lost 1/2 of his power source. Because without a physical prop shaft, tail shaft we cannot transfer the loss of the torque, power, work, energy whatever we want to call it without making major changes to the design of the PHEV.

Do we not agree?

Ok this is where we may beg to differ.

Now this is my opinion.

His first mistake was not having decent tyres. Look at the tread. He is off road (more like on a track :mrgreen: ) relying on his tyres to supply traction.

Decent tyres MAY have helped him stop spinning his front wheels and losing momentum. But we will never know.

His second mistake was not getting into it in the first place. He should have accelerated more to create more momentum.

Ok this is where I hear you say how do you know he did not get into it.?

Because I cannot hear the petrol motor having a decent go at the job.

We hear the petrol motor rev just for a second after he has already lost traction.

We do not see him (hear him ) push that petrol motor to supply the extra torque, energy, through the generator, that is needed to get the most out of the current PHEV.

The PHEV never had a chance.

But that is just my opinion.

 

[pasquinade]

Hi Trex,

I think we might have a Torque vs Power issue:
Torque is physically measured in Nm, or Joule (energy) per radian. Electrically it should be proportional to the current going through the motor, but this is after back emf is included together with internal resistance so not extremely simple to go in to here. Just assume that the max stall torque is the curve we’ve all seen and it occurs for a given amount of electrical power.

Power is physically equivalent to torque times angular velocity and electrically equivalent to current squared times the internal resistance.

Normally, mechanical power (driving the car forward) should be close to electrical power (consumed from the batteries and generator). The difference comes out as wasted heat.

But the detail is in the “close”. It is not exact and heat is inevitable. Notice that when angular velocity (rpm) is 0, mechanical power is 0. So all the electrical power consumed from the battery is being wasted as heat. As a “side-effect” the motor produces a torque (but no mechanical power), which is also in this case the maximum motor torque.

I think I might have been a bit confusing, but this is to say you can have a lot of torque without having a great battery consumption (e.g. with a large enough “perfect” gearbox you can have a AAA battery and a children’s toy motor creating more torque than the PHEV . What you cannot have is a lot of mechanical power (torque times speed) without having a lot of battery consumption (the child toy example will always be extremely slow).

Hope it helps
Ricardo

 

[pasquinade]

Ah, forgot to mention, the motor kicks in to provide more _power_ whenever necessary (which might not be needed at stall to provide max torque)

 

[anko]

...but this is to say you can have a lot of torque without having a great battery consumption

From your own explanation (which I agree with), should you not add "once the motor is spinning"?

Because otherwise, why would you, under some circumstances, have to push the throttle to the point where the ICE kicks in, before you get going? Or do you think this can be prevented at all times?

Maybe the engine only kicks in as a response to "you flooring it to quickly without having a PHEVbox installed".

 

[anko]

A center lock diff does not split torque or power, just equalize RPM.

Not split, but transfer.

If you have an open center diff, power / torque finds the easiest way out, which is through the spinning axle. As soon as you lock the diff, all power / torque is consumed by the axle that has grip. So, by closing the diff power / torque is transferred from the axle without grip to the axle with grip.

Think about the crankshaft of an ICE. Usually, only one side has wheels attached to it. But no (real) power / torque is lost or consumed at the other, freely spinning end of the crank shaft. Indeed because RPM of both sides of the crankshaft are synced. ;-)

 

[Trex]

Hi Trex,

I think we might have a Torque vs Power issue:
Torque is physically measured in Nm, or Joule (energy) per radian. Electrically it should be proportional to the current going through the motor, but this is after back emf is included together with internal resistance so not extremely simple to go in to here. Just assume that the max stall torque is the curve we’ve all seen and it occurs for a given amount of electrical power.

Power is physically equivalent to torque times angular velocity and electrically equivalent to current squared times the internal resistance.

Normally, mechanical power (driving the car forward) should be close to electrical power (consumed from the batteries and generator). The difference comes out as wasted heat.

But the detail is in the “close”. It is not exact and heat is inevitable. Notice that when angular velocity (rpm) is 0, mechanical power is 0. So all the electrical power consumed from the battery is being wasted as heat. As a “side-effect” the motor produces a torque (but no mechanical power), which is also in this case the maximum motor torque.

I think I might have been a bit confusing, but this is to say you can have a lot of torque without having a great battery consumption (e.g. with a large enough “perfect” gearbox you can have a AAA battery and a children’s toy motor creating more torque than the PHEV . What you cannot have is a lot of mechanical power (torque times speed) without having a lot of battery consumption (the child toy example will always be extremely slow).

Hope it helps
Ricardo

Sorry Ricardo,
I am an mechanical and design engineer by trade and have to use electrical equipment in those designs . I certainly know what torque and power is and Amps and Volts back EMF hall sensors, encoders, PLCs, resistors, capacitors, inductors, TRIACS diodes etc. Have used induction motors, stepper motors, brushless motors, torque converters but I still do not know where we have a problem. You need to "quote" me for me to know that. Look on the bottom right of each post.
Regards Trex.

 

[pasquinade]

Hi Trex,

Thanks, I confess email is more my thing, but thanks for the quote button

This is what I was nagging about:

His second mistake was not getting into it in the first place. He should have accelerated more to create more momentum.

Ok this is where I hear you say how do you know he did not get into it.?

Because I cannot hear the petrol motor having a decent go at the job.

We hear the petrol motor rev just for a second after he has already lost traction.

We do not see him (hear him ) push that petrol motor to supply the extra torque, energy, through the generator, that is needed to get the most out of the current PHEV.

And I was trying to say (confusingly I admit) that to have max torque at 0 rpm you do not have max power (as measured in the, sadly unmarked, left power gauge inside). In the past I got bogged down with the wheels stuck and the power gauge was at about 1/4 (pointer pointing left). At the time I wondered why but then I tracked it down to the explanation I gave above. I still believe the PHEV was providing max torque (in another post I try to claim it implies about 765kg of forward force) but this I could not measure. At 1/4 of the gauge the ICE does not need to kick in (in my case I do not remember whether it came on or not since I had other things to worry about

I believe this also replyes to Anko (lets try this quote thing one more time):

From your own explanation (which I agree with), should you not add "once the motor is spinning"?

Because otherwise, why would you, under some circumstances, have to push the throttle to the point where the ICE kicks in, before you get going? Or do you think this can be prevented at all times?

Maybe the engine only kicks in as a response to "you flooring it to quickly without having a PHEVbox installed".

Assuming my memory serves me correctly and gauge was at 1/4 of the way when the PHEV got immobilized at the wheels, I only see the need for the ICE to kick in after the wheels start spinning (either due to forward motion or slippage). In practice I do not remember what the ICE did.

 

[pasquinade]

...but this is to say you can have a lot of torque without having a great battery consumption

From your own explanation (which I agree with), should you not add "once the motor is spinning"?

sorry, in the last post I was not explicit on this part. No, I think what I wrote is correct (perhaps only theoretically ). You can have a lot of torque (in fact for these motors it is max torque) at 0 rpm. This does not require a lot of electrical consumption (power) since mechanical power is 0 (lower bound for electrical power consumed) and only the motor/gearbox characteristics define how wasted heat (electrical power effectively consumed) translates into stall torque (in a loose sense, both are a consequence of the motor characteristics, one does not generate the other as in a thermal engine).

I think the example where a simple AAA battery (minimal power) can generate a great amount of stall torque (but once it gets going it's going to be very very slow) validates the quote above.