TCC load hysteresis

A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
tobmag
Posts: 206
Joined: Mon Jan 02, 2012 4:22 am

TCC load hysteresis

Post by tobmag »

Lance,

Iver been going thru a lot of the logs I made during the last weeks.
I'm using pwm control for engaging the TCC with a taper of 2sec
What I have found is that when engaging the TCC just below load treshold TCC will disengage after about 1sec meaning its never fully appplied.
Looking on the log you can see that due to the engagemnet of the TCC load will increase slightly and therefor disengage it....

What I can see there is no separate load hysteresis for the TCC

Possible to implement?


BR//Tobmag
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: TCC load hysteresis

Post by Bernard Fife »

Tobmag,

I will have a look.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: TCC load hysteresis

Post by Bernard Fife »

Tobmag,

I recall now that the TCC has time hysteresis only. Load hysteresis could be implemented, but it isn't high on the list.

There are a "Max. TCC Load" ( http://www.msgpio.com/manuals/mshift/V41tune.html#nt ) so it is in a load that is transitional (i.e. if the cruise load is 45 kPa and most of the rest of the time it is 75 to 100 kPa, then setting the load threshold to 60 makes more sense than setting it to either 48 or 72 kPa).
- increase the "TCC Hysteresis Time" ( http://www.msgpio.com/manuals/mshift/V41tune.html#nt ) so that the TCC doesn't cycle on and off. Note that the TCC hysteresis controls the OFF timing, so the TCC can still go on once then off quickly, but after that it will stay off for the specified time. There is some discussion in this here: viewtopic.php?f=4&t=663&p=3592#p3582 .
- increase the averaging ("LOAD Smoothing Factor" - http://www.msgpio.com/manuals/mshift/V41tune.html#gs ) on the load, so that it fluctuates less, resulting in fewer transitions across the threshold.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tobmag
Posts: 206
Joined: Mon Jan 02, 2012 4:22 am

Re: TCC load hysteresis

Post by tobmag »

Lance.

I don’t have any problem with the TCC cycling on-off the problem is that it during the tapering period today set to 2 sec it will disengage after 1sec meaning it was never fully applied and this due to the change in load when the TCC is engaging.

If I set it as you suggest going in a slight incline you will most likely hit the same problem again since you will need to increase load to maintain speed, I think it was discussed in the thread you linked to.

If you have an engine with a lot of torque you can of course set the “max TCC load” very high perhaps over 90kpa but if you have a small low torque engine you will most likely like to have the TCC disengaged earlier.

How will the TCC react in regards of this with the new V5 code if you run like 50/50 TPS/MAP as load?

I have TCC control done by a MSII in my other car (TH700R4) and there I can set the load hysteresis and that works really well.


BR//Tobmag
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: TCC load hysteresis

Post by Bernard Fife »

Tobmag,

That makes sense, I'll come up with something but let me think about it for a bit (the TCC control code is surprisingly complicated, and I don't want to mess it up nor make it more complicated than it has to be).

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tobmag
Posts: 206
Joined: Mon Jan 02, 2012 4:22 am

Re: TCC load hysteresis

Post by tobmag »

Lance.

Sounds good and I'm in no rush either so lets see what you can come up with and as you said lets keep it simple.

BR//Tobmag
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: TCC load hysteresis

Post by Bernard Fife »

Tobmag,

Here is a 'first cut' at this:
Monitor_4134.abs.s19
(72.06 KiB) Downloaded 515 times
GPIO_MShift_4134.ini
(217.63 KiB) Downloaded 522 times
This lets the user set a 'TCC Unlock Hysteresis' value (under TCC Settings/TCC Control Limits), and the TCC won't lock until the value is at the unlock level minus this value. So, for example, if the 'TCC Unlock Above Load' is 90, and the 'TCC Unlock Hysteresis' is 10, then the TCC will unlock if the load is over 90, but won't lock until it is 80 (i.e. 90-10) or less.

TCC Unlock Hysteresis can be from 0 to 25.5 kPa (or %), the default is 5.0.

This isn't true hysteresis, in the sense that it has no memory of whether the limits have been exceeded at any point since the last TCC lock, it only checks if the limit is exceeded at the time the unlock is requested (which is simpler to code).

I have checked this code briefly on my bench, but use it only with great caution.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tobmag
Posts: 206
Joined: Mon Jan 02, 2012 4:22 am

Re: TCC load hysteresis

Post by tobmag »

Lance.

Ive been testing this for a while on the bench and it seems to work fine.
Now the combination of load and time hysteresis should cure this issue, on road testing would ofcourse be better but then looking on my logs
in combination of logs on how my other car is behaving with the TH700R4 Ill say this will do as it is.

BR//Tobmag
Bernard Fife
Posts: 1696
Joined: Fri Apr 04, 2008 1:28 pm

Re: TCC load hysteresis

Post by Bernard Fife »

Tobmag,

Great. This will become the release code shortly then (I just need to update the documentation and code page). Once a few people have tried in in their vehicles, we can refine the TCC behavior further if necessary.

Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it." - George Bernard Shaw
tobmag
Posts: 206
Joined: Mon Jan 02, 2012 4:22 am

Re: TCC load hysteresis

Post by tobmag »

Lance.

Sometimes I think in reverse,
The TCC logic is now almost OK but I did forget a very important thing and that was actually the problem I had.

The scenario is as follows;
You are in a slight incline under acceleration, you are in a gear when TCC can be applied and Load is just below your max load TCC setting.
TCC starts to engage and what now happened is that Load will increase not decrease since you are still accelerating and going uphill…since you were just below your max load TCC setting and now using the PWM mode and about 2sec taper the TCC will be disengaged about “half applied” since now load is above threshold.

Don’t know how to work around this; we need some kind of hysteresis on Load when TCC is applied or can you just add a “max load TCC when applied”?
E.g. you set max Load TCC to 70 that means below this value TCC will be engaged if all other criteria’s are met and then you add a “Max Load TCC applied” and you set this to 80 that will keep TCC locked until you reach this level, one problem I see here is that when you hit 80 TCC disengage and your Load might fall down below 70 engaging the TCC again….but that can be trimmed with these 2 settings since this will be depending a lot on engine size, TC stall speed etc.

I could also see now in TS that we have an indicator for TCC, very nice but would be good if it could change colour as well, makes it easier to see when changing status.

BR//Tobmag
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