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Author Topic: Actual pre-control in LDRPID  (Read 66427 times)
totti
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« Reply #285 on: November 02, 2019, 07:14:12 AM »

What can I do with overboost? I tried to change kfldrl below 3000rpm to open the wg an avoid oberboost but does not help. Now I measuring again with duty 70 80 and 95 because the air is colder and the turbo is faster a little.
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fukenbroken
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« Reply #286 on: November 02, 2019, 09:29:40 AM »

Ldiata
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totti
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« Reply #287 on: November 02, 2019, 09:40:18 AM »

This is my last log with modified KFLDRL.
I've attached also what the tool generated before.
« Last Edit: November 02, 2019, 09:50:12 AM by totti » Logged
totti
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« Reply #288 on: November 02, 2019, 03:16:20 PM »

I've just put together my previous log when I used my own KFLDIMX and KFLDRL values. What I can see is to prevent overboost around 3000 I need 71% dc before reach the target 1,35 bar. From the latest log my lower dc before reaching the target is 79.6875 and the input for kfldrl is 65.155. The PID output should be under 60 to get around 71% dc from the current KFLDRL table. What I can do is lower kfldimx table values around 2750 and 3000 or give more D.
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totti
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« Reply #289 on: November 03, 2019, 08:41:22 AM »

After hacked the KFLDRL table I could reach a little overboost. Maybe I can lower a little bit more the kfldrl table before 3000rpm
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totti
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« Reply #290 on: November 03, 2019, 11:30:39 AM »

How does it work for others? What is the problem with my tables if I need to modify the drl table to prevent overboost? I don't want to add more Q2. I raised it with 25 percent between 2750 and 4000 with 100 and 200 lde values.
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totti
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« Reply #291 on: November 04, 2019, 02:06:40 PM »

Nobody?   Cry
I analyzed with VisualLogger(very good tool) and what I can see is when the set point is reached the system goes to steady state so it will run from imax because P and D is zero. The LDRPID tool generates the steady state values for KFLDRL. But the problem comes with WOT that the turbo won't be in steady state when reach the set point because it spools and will have overshoot. I thought about to put lower values in KFLDIMX but at this case I'm afraid to have undershoots because IMAX values will generate lower DC values so the turbo cannot reach the required set point in steady state and will have undershoots.
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nyet
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« Reply #292 on: November 04, 2019, 02:10:25 PM »

Yes, you've hit on the fundamental limitation of PIDs. You cannot avoid a small amount of overshoot.
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totti
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« Reply #293 on: November 04, 2019, 02:29:03 PM »

Yes, you've hit on the fundamental limitation of PIDs. You cannot avoid a small amount of overshoot.

I know that overshoot is a "need" of PID. The problem is that I can feel the leak(after the overshoot)(100mbar) during WOT. Does it make sense to add more D?
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totti
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« Reply #294 on: November 05, 2019, 07:07:28 AM »

I had discussions about the Pid. And the suggestion was to lower IMAX values. My problem is with that currently KFLDIMX table has values for different pressure values(for 1,32 bar it will be 73) and KFLDRL table gets this value when the system reached the required pressure(P and D will be 0). The KFLDRL output will be DC value for 1,32 bar in different rpm values. So if I change KFLDIMX to lower values for example 1,32 bar will be 68, KFLDRL table output will be lower to se thre will be undershoot and I cannot raise because Imax limits it.
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totti
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« Reply #295 on: November 06, 2019, 02:46:56 PM »

Maybe I found the problem. I left the spool filter on default value(75mbar/0,1s) but my system can make only ~40mbar/0,1s. I regenerate the DRL table with that and I got lower values below 3000rpm. I will test it tomorrow.
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totti
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« Reply #296 on: November 07, 2019, 11:36:10 AM »

And the results. The problem was the spool config. Now it is work perfectly. Maybe a little bit undershoot. Should I raise DC values a little?
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totti
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« Reply #297 on: November 09, 2019, 07:29:06 AM »

Hi,

Today I was on dyno. The result is not so bad but the PID again was not so good.
What can I do with this overshoot? This feed forward is not working properly with my config.
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