anyone have a link or some reading regarding refdc and pid

[boostd audi]

i thought there was a wiki on the topic, cant seem to find it. anyone have the link?

[gunni]

Here is how I do it.


First set the PID to 0´s to disable wandering.

Then set your refDC table to the highest duty cycle that doesn´t change the minimum boost, i.e if your gate is giving out 0.5bar and 30% doesn´t do anything but 35% gives 0.6bar  then set it to 30%.

Then adjust the duty cycle until you reach the maximum boost you want. You can have a single value throughout the RPM range or you can tailor your max boost curve to suit.

Now when you know this set the RefDC table to the midway between lowest duty cycle and highest for each of the RPM values.

So if you got 30% everywhere as the lowest number and 70% as the highest then all the values would be set to 50%. This is the midpoint from where the Duty cycle will travel to reach it´s target.

Now set the

Boost target vs RPM curve to the lowest value you ever want to run. Say your gate it 0.5 , then set it to 0.6 for instance.

Also set the

Boost PWM max and min values to just a bit more then your known max and min values. So in our case of 30 and 70 set them to 27 and 73%. This allows the PID to just go above max and min to fix overshooting boost for instance.

From here you adjust your PID settings.
This is different for different solenoids so I´ll leave that to testing to find what works for you.

I don´t have a PID tuning strategy yet.

[GintsK]

My way is different: manually find right duty cycle values is very time consuming. I start with low values like 20% for DC and adjust PID. And PID gives me idea about shape and values of DC curve. If overshoots are not desired I set DC curve lower than DC at target. But with same shape.

Always use reasonable overboost protection to be safe.

You will find some readings whan googling for 'PID tuning Motec'.

Gints

[AVP]

@Gunni:

i like the way you propose the boost config.

I have a question: When the refDC is set, If i find the refDC that best suits the target boost that i ultimately want, why should i use the mean instead of just using the refDC that is closer to my value, so as to allow PID to make even smaller adjustments ?

example:

i want 1.9bar overboost till 5500rpm and 1.6bar from 5500 to 7500rpm.

my spool appears: 3800rpm on 3d gear and 3300rpm on 6th gear.

so if i use a refDC of my 3d gear i have say: 60% till 5500 then 50% till 7500

but on 6th gear that refDC will overshoot my boost target due to higher load.

If i keep those values as they are, and just play with PID to compensate, wont that be better than just put all my values at 55% and then allow PID to always correct?

thanks
Vasilis

[gunni]

It´s about what you want.
Are you going to run one boost target ? Or be able to vary it with throttle or 0-5v signal?

If the one boost target without external control then you tune all gears and RefDC to your requirements then use small PID values as that´s all you´ll need to make the fine adjustments.

LOG LOG LOG LOG is going to be your friend.

[AVP]

Unfortunately I cannot run different boost in different gears as the speed sensor in Audi seems to be difficult for vems to read.

Seem to.be getting some odd results from today's runs.

What would the symptom of a torn wastegate membrane be if you ate also trying to control the top chamber of the wastegate?

Either I have something like that or a huge leak. All of a sudden I have spring pressure.boost, no real wooshing and I cannot hear the turbo spooling. I have to check the shaft but I think the turbo is ok. No oil leaks anywhere

[Jamo]

Have you been watching AlexHoy setup on the wiki? he has the speed sensor working now with the stock s2 input

[AVP]

no! link please!

[Jamo]

Really? tut tut 

Only joking http://www.vems.hu/wiki/index.php?page=MembersPage%2FAlexHoy

[AVP]

hmmm interesting

where is the trigger cable?

[AVP]

correction,
is the trigger cable the one looking at the pin?
cause if that is so, mine is completely new, so i doubt i could have issues with the wiring. Unless its the car wirring from the plug thereafter.

also what could the coils have anything to do with it?

[Jamo]

correction,
is the trigger cable the one looking at the pin?
cause if that is so, mine is completely new, so i doubt i could have issues with the wiring. Unless its the car wirring from the plug thereafter.

also what could the coils have anything to do with it?

eh?

your only interested in this section

Also, the speed sensor runs OK. I switched from "Both" to "Rising" (like Marcell recommended), but I also had to double the number of impulses at 100 km/h to 222, although there are actually only 111, so it seems that the sensor catches both rising and falling. Works well regardless, so I'm happy.

---

I seem to have similar problems with the speed sensor, where the needle when driving slowly reacts ok, but when accelerating instead of linearly showing the km/h it actually jumps. My sensor looking at the pin on the flywheel is new, and i will be replacing the rpm sensor as well. BUT i am not sure if the problem will be fixed.

where was the brittle cable in your case? on the sensor bit of the cable, or the car's wiring harness?

thanks

vasilis

23 OCTOBER 2011

1.1.95 Speed signal shows only speeds of up to about 63-65 km/h. Updated to 1.1.96, but the problem remains. Calibration is spot on according to GPS. The car has a Reed-relay with a 2x4 pole magnetic sensor ring (8 field impulses/rev. so with 2 meter circumference 111=100 / 3.6 / (2/8) ). I moved the cable a bit around to take noise into account, but no luck. Also, up to about 1.1.88, it worked as intended, showing higher speeds as well.

Any ideas?

    If you show your config, I can make benchtest on your setup.
    Without your config, the problem reproduction needs more time.

Log file added here (http://www.vems.hu/files/MembersPage/AlexHoy/v3.3_Speed_and_trigger_error.vemslog) There is also a trigger error in it that I am battling with.

The problem is the configuration:

    do not use Both edge setup, except at very low frequency sensor with perfect 50% duty signal
    you have too many pulses, try to use the software divider

[AVP]

the way he is writting it i thought the trigger cable has something to do with it.

i have tried those settings and on mine they didnt work. I havent tried using 222 instead of 112, but i will.

just need to know what the divider is