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

[Steepndeep]

Hi

I am with TREX to get back to the original question, "how shall you best drive the car when you want to e.g. pull a boat up a slightly slippery ramp"

I fully agree with TREX that good traction tires are a valuable but sometimes there is a really slippery patch (maybe ice) on one or more tires. How shall you then drive the car? And in order to understand this we need to understand how the car is engineered, and then test in practice.

We know this

It has 4WD with 2 motors and no diffs.
The Emotors have supposedly high torque at low RPM.
It has some software center "diff-lock" which, at least to me, is difficult to understand how it really works. Forget Mitsu advertisement here
It has anti spin which can be tuurned off

Let's take a testcase with 3 wheels on good traction and one "on ice". In my Suzuki with locked center diff I will get the car moving with NO wheelspin, well the wheel on ice spins with exactly twice the speed of the two wheels on the axel with good traction. All motor power goes to the axel with two good wheels. I also can rev the engine to max torque RPM and then use the clutch to get going.

How will this work on the PHEV?? Assuming one fronwheel on ice. And now I am guessing as I have not tested but it should be something like this. Anti spin turned OFF. 4WD lock off.

First the front wheel on ice starts spinning like crazy, even with just lightly pressing the accelerator. I then need to floor the accelerator (I guess) and then hopefully the car gets going with front wheel spinning at the speed of light But that is assuming you can get max torque at 0 RPM on rear motor. Can you really that or is there some security thinking implemented?

Question
Will anti spin help front wheels to get traction? You will not loose any power trying as the front Emotor is useless anyhow in this testcase
How will 4WD lock work?

Any views? Anyone tested?

 

[jaapv]

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.

And do note that these diagrams assume series hybrid mode and SOC>30% (i.e. ICE running)

 

[ian4x4]

I also can rev the engine to max torque RPM and then use the clutch to get going.

This use of engine inertial is not available in the electrically driven PHEV to get going.

I still believe that the 'stationary' torque available is very limited, probably done to protect the motors/drive circuits.

The burning smell of the clutch (or torque converter on automatic) should provide the limit that you use with a conventional engine driven 4x4.

 

[Steepndeep]

This use of engine inertial is not available in the electrically driven PHEV to get going.

Yes I know and that is my point, how to get going when you need max torque?

I still believe that the 'stationary' torque available is very limited, probably done to protect the motors/drive circuits.

Yes, but it would be really nice with an official Mitsu statement. Is there one somewhere?

The burning smell of the clutch (or torque converter on automatic) should provide the limit that you use with a conventional engine driven 4x4

Absolutely

 

[Trex]

I still believe that the 'stationary' torque available is very limited, probably done to protect the motors/drive circuits.

Ok Just one quick comment before I sleep and I will make it to ian4x4 as he has brought this up before.

All good motor drive circuits will have current control using PWM on their individual phases.

Look up a "shunt resistor" "PWM" and 3 phase motor control.

Can someone see if they can find a typical generator graph showing volts and amps.

I will be back tomorrow if no one has helped you out in the meantime.

I think some others here will know where I am going with this.

I need sleep

 

[anko]

I still believe that the 'stationary' torque available is very limited, probably done to protect the motors/drive circuits.

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

 

[ian4x4]

I still believe that the 'stationary' torque available is very limited, probably done to protect the motors/drive circuits.

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

Thanks anko
I have looked at your graphs and explanations again.
On my initial reading I thought you were measuring the 'torque requested' at the ECU, can you explain (simply) to me if this is actual torque, or the 'target' figure requested by the ECU.

It is hard to see, but I did try to expand up the first couple of seconds of your graphs, to get an idea, what was happening.
Under normal circumstances it does appear that the torque (request?) builds up quickly as the car starts to move.

Best Wishes Ian

 

[anko]

It is actuals. Especially interesting is this one, where you can see torque building up to the max in both motors, even before the car starts moving (the brake is released).

It nicely shows difference between torque and power in relation to RPM as well ;-)

 

[ian4x4]

Thanks anko and trex.
I will go away and do some reading.

Something is very wrong when the rear axle (which has more rated torque than the front - 195 / 137 Nm) cannot either spin the wheels or move the car.

I note that the Front Motor Control Unit (or RMCU) decides the final torque command signal and therefore how much current to give the motor(s). The PHEV-ECU derived signal is only a request given to the FMCU and RMCU, could it be this that is being measured on the graph?
Best Wishes Ian

 

[anko]

From memory, I am pretty sure it was actually, not request.

Also, see how the x coordinates differ between front and rear readings? I am quite sure torque request front and right is derived from a single obd request to the PHEV ecu. This would have resulted in matching x coordinates. Actuals take two requests, as they come from two different ecus. This explains the difference in x coordinates.

 

[pasquinade]

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

Hi Ian,

Sorry about the late response, had to do a drawing first

In the figure you see what happens in the case you describe. The front wheel hits an obstacle and if enough force is available will go over it (the center of the wheel will go through the drawn red trajectory).

Since the weight of the car is distributed over the two axles, only half the weight needs to be lifted at a time (note: I think the PHEV is slightly nose heavy). Better would be to go one wheel at a time and then you’d be able to divide the weight by 4, but since I do not want to go into the effect of the differential, lets say you hit the step head on. The back weight will not influence the force needed for the front wheels to go over the obstacle.

Since the front wheel is in contact with the obstacle corner, the force it produces will be tangent to actual motion. Unfortunately the back wheel will produce purely horizontal motion and hence only a fraction of the force will be used to help the vehicle go over the obstacle.

For a wheel diameter d (705mm in the PHEV) and an obstacle height of h, the trajectory tangent of the front wheel (the “slope to go over”) will have an angle relation of:

cos (angle) = (d/2-h)/(d/2)

This angle is important for 2 things:
1 - The total tangent force to be overcome at the front wheels due to gravity (blue arrow) will be W/2*sin(angle)
2 - The back wheel force contributing to lift the front wheel will be only Fb*sin(angle)

Hence the following relation will hold for the minimum forces Ff and Fb required to lift the vehicle:
Ff + Fb*cos(angle) = W/2*sin(angle)

Then we need to take into account the stall torque of the motors, the corresponding gearbox ratios and wheel diameter (d) to get the maximum Ff and Fb forces:

Ff=front_motor_torque/(d/2)*front_gearbox_ratio
Fb=back_motor_torque/(d/2)*back_gearbox_ratio

From here we get the maximum angle the front wheels can climb and going back to the first formula we can check what the maximum step height is. Sorry, too late now for me to pull the calculator, but the outline is here

Long post... hope there are not many errors...

EDIT: first error found. Changed a sin() to a cos() in the Ff + Fb equation.

 

[Trex]

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.

Hi Ricardo,

Are we not forgetting that amps do go up the closer the motor is to stalling. So you need that extra current provided by the generator which is why anko with his trailer had his petrol motor start just going across a drain I think he told us about.

All electric motors have limit to that current increase( in amps) when they stall and quite often show them in their specs for thermal reasons. ie they burn up.

Even ac induction motors from memory had something like double the amount of amps (compared to what they ran at) to start them and get them up to their rated speed and had the old star-delta motor starters for the large 3 phase motors to help protect themselves and the grid for that reason. Now we have soft starters or ac motor drivers.
Regards Trex.

 

[anko]

From memory, I am pretty sure it was actually, not request.

Also, see how the x coordinates differ between front and rear readings? I am quite sure torque request front and right is derived from a single obd request to the PHEV ecu. This would have resulted in matching x coordinates. Actuals take two requests, as they come from two different ecus. This explains the difference in x coordinates.

Now I know for sure, as I just found the little Java program that I wrote and used to probe the OBDII port.

The only thing I got from the PHEV ecu was 'pressure in the brake line', which I used to plot the red vertical lines, which say 'between these lines is where I let go of the brake pedal'.
All other stuff came from front and rear motor ecus. And these only provide actuals, not targets. I have calculated stuff like this:

rear_torque = Integer.parseInt(responseString.substring(i+4, i+8),16)/10 - 1000;
rear_rpm = Integer.parseInt(responseString.substring(i+8, i+12),16) - 20000;
rear_power = (rear_torque * rear_rpm) / 9548.8 ;
rear_speed = rear_rpm * 60 * 2.214 / 7065 ;

Recognise the 9548.8, 2.214 and 7065 factors? :mrgreen:

 

[pasquinade]

Hi Trex,

Are we not forgetting that amps do go up the closer the motor is to stalling. So you need that extra current provided by the generator which is why anko with his trailer had his petrol motor start just going across a drain I think he told us about.

Regards Trex.

Hi Trex,

Yes, stall current depends only on the motor characteristics (and limiting electronics). In case of the PHEV should be easy enough to test using a similar procedure Anko mentioned before: hold the breaks and floor the gas and check what happens. If I remember correctly the power meter (since battery voltage should decrease only slightly, this means around 1/4 of the max Amp output - combined generator + battery) remained at around 1/4 of the gauge (which usually is not enough to start the ICE unless you're low on battery, but the car can consider it a special case and start it anyway).

Hehe, the car is usually driven by my wife (I'm the repairman and weekend dirtroader), but if I get a chance I'll check it today.

Regarding limiting electronics, I hope Mitsubishi did not place these at a low level which would mean lowering the motor's stall torque, but perhaps someone with a winch and a dynamometer might be able to check the real stall torque Or perhaps using the "max step height" method I outlined above...

 

[MartinH]

All, thanks for all interesting teoretical information, also some ideas about tyres.
About my first statement, my standpoint is still:

I will be satisfied, and it will be MY! problem when all 4 wheels is spinning, if not, it is the cars problem. If Mitsu states 4WD, i expect it to be.
I will start checking and change the tyres, or using cains when this happens, not before.

Yesterday had to reverse up with empty trailer, did not have traction to make the job with 2 wheels spinning, had to use the wheel loader
Or do in need to sell this "toy" and go back to my ML to get the job done.

And we are talking about the torque in this electric motors, you can not believe what kind of torque it is unless you experiense, yesterday one, out of 4, wheel of the trailer did not turn(rust on the brakes), i did not notice until i got up in speed, this was with the wheel loader on the trailer!, i did not feel it in the car, i manage to save the tyre after 100m.

 

[anko]

Yesterday had to reverse up with empty trailer, did not have traction to make the job with 2 wheels spinning, ...

Out of curiosity, which wheels were spinning?

And we are talking about the torque in this electric motors, you can not believe what kind of torque it is unless you experiense, yesterday one, out of 4, wheel of the trailer did not turn(rust on the brakes), i did not notice until i got up in speed, this was with the wheel loader on the trailer!, i did not feel it in the car, i manage to save the tyre after 100m.

You overcame friction between 1 of 4 tires of your trailer and the road, while having grip on all 4 wheels of the tow car and using both e-motors. Does that really say anything about expected climbing / towing capacity using one motor / two wheels?

 

[MartinH]

One front and one back, i can not tell right or left, to dangerous to go out and check

What i am trying to tell is that the answer from Mitsu i got to make sure to have the batteries fully charged, to get the most out of the 4WD, is ridiculous, The power and torque from one e-motor is enough pull the car or spin the wheel on almost every surface.
Why only one e-motor?, that can only be the case when one wheel/axel is spinning, and that friction is not cero.

I uses my car very different from most other user, i use my car to work in rough terain and surfaces, not just get ME to work.
Therefore i get into situations many have not experienced, And as i have used my ML for the same puropse for several years, I have one 4WD car working, and one not working as expected.

 

[anko]

One front and one back, i can not tell right or left, to dangerous to go out and check .

Hmmm, kinda cross-axled then. So, that would mean it is definitively not an issue with the rear E-motor itself, right?

 

[maby]

One front and one back, i can not tell right or left, to dangerous to go out and check

What i am trying to tell is that the answer from Mitsu i got to make sure to have the batteries fully charged, to get the most out of the 4WD, is ridiculous, The power and torque from one e-motor is enough pull the car or spin the wheel on almost every surface.
Why only one e-motor?, that can only be the case when one wheel/axel is spinning, and that friction is not cero.

I uses my car very different from most other user, i use my car to work in rough terain and surfaces, not just get ME to work.
Therefore i get into situations many have not experienced, And as i have used my ML for the same puropse for several years, I have one 4WD car working, and one not working as expected.

I don't know how it is sold in Sweden, but the English Outlander PHEV literature makes it very clear that it is not an off-road car - sorry.

 

[jaapv]

All, thanks for all interesting teoretical information, also some ideas about tyres.
About my first statement, my standpoint is still:

I will be satisfied, and it will be MY! problem when all 4 wheels is spinning, if not, it is the cars problem. If Mitsu states 4WD, i expect it to be.
I will start checking and change the tyres, or using cains when this happens, not before.

Yesterday had to reverse up with empty trailer, did not have traction to make the job with 2 wheels spinning, had to use the wheel loader
Or do in need to sell this "toy" and go back to my ML to get the job done.

And we are talking about the torque in this electric motors, you can not believe what kind of torque it is unless you experiense, yesterday one, out of 4, wheel of the trailer did not turn(rust on the brakes), i did not notice until i got up in speed, this was with the wheel loader on the trailer!, i did not feel it in the car, i manage to save the tyre after 100m.

To be honest, I think you are expecting the car to be something it is not. It is a 4WD softroader, not a 4x4 offroader. For that purpose Mitsubishi sells the Pajero, and to a limited extent the Outlander Diesel.
So yes, if you expected the car to perform like a Defender, you bought the wrong car. Whether you were misled would be for a judge to decide, not by an Internet forum.