[help needed] VVT Debug fail

[stefanst]

I was trying to log exactly how well VVT is working on the '91 Miata with the VVT engine. But it looks like the debug setting 8 doesn't do anything anymore. I may be doing something wrong of course, but nothing shows up in my log. Other debugs seem to work just fine if that helps with finding the problem. Tune is attached.

[AndreyB]

Looks like that's intended behaviour

Code: Select all

	/**
	 * VVT valve control often uses AUX pid #1
	 */
	DBG_AUX_PID_1 = 7,
	/**
	 * VVT position debugging - not VVT valve control. See AUX pid #1 debug for valve position.
	 */
	DBG_VVT = 8,

See also https://rusefi.com/wiki/index.php?title=Manual:Debug_fields which has some info on which output is what. You want to look at aux pid #1

[AndreyB]

PS: just realized that field value label was misleading. Changing from "VVT PID" to "VVT Input"

https://github.com/rusefi/rusefi/commit/da8195fc2a74dd1f1d18ac8e6b137acf6ed5d20e

[stefanst]

Not sure that's all the problem there is.
With debug set to 8, none of my debug fields in the log recorded anything. All fields (f1-f7, i1-i3) have 0s all day long. According to the Wiki, at least i1 should contain a VVT event counter, whatever this may be.

I'm also half-certain I tried debug setting 7 and didn't get anything. Not 100% though, so I'll report back later today/tonight.

[AndreyB]

And you are right again - it was not counting in NB2 vvt mode. Now it does

https://github.com/rusefi/rusefi/commit/6a9c92c7bb470b0df4f9d029e9f42f3e539afe54

[stefanst]

And yes. I can confirm that "AUX PID 1" does indeed debug the VVT control. Now I just need better PID parameters than what I'm using.

VVT Oscillations

vvt oscillation.png (34.56 KiB) Viewed 7045 times

We have crazy oscillations.
P-I-D
2.000 - 0.005 - 0.000

Any prior art we can look at? Unfortunately I lost my old '03 tune.

[AndreyB]

https://github.com/rusefi/rusefi/blob/master/firmware/config/engines/mazda_miata_vvt.cpp shows mine as

Code: Select all

engineConfiguration->auxPid[0].pFactor = 2;
	engineConfiguration->auxPid[0].iFactor = 0.005;
	engineConfiguration->auxPid[0].dFactor = 0;
	engineConfiguration->auxPid[0].offset = 33;
	engineConfiguration->auxPid[0].minValue = 24;
	engineConfiguration->auxPid[0].maxValue = 44;

[AndreyB]

if you have crazy oscilations how is your VVT position calibration? with VVT plug disconnected what does your VVT position gauge says?

I was suprised to see a huge variabtion in VVT zero position between green and red cars.

[stefanst]

VVT without actuator is just around zero. Also, offset shouldn't really make a difference with a forward-nothing-backup control.
Looks like yesterday I had more stable VVT position. The only change that could possibly have an impact that I can think of is the analog sensor smoothing factor. I sharpened it up- less smoothing. Does that get applied to VVT position?

[AndreyB]

Nope, VVT position is not affected by analog anything.

[stefanst]

More "D" improved the oscillations a lot, especially on a warm engine. The "P" term is still going a bit crazy, essentially dithering around the target, but since our control is fairly slow to react, this seems to work quite well, especially at higher rpms.

One thing I noticed, running the board on the JIMSTIM, the "I"-term is still trying to run away. Meaning if we command a value that can't be reached, it just keeps running into infinity- positive or negative. We need to control this somehow. This is the same problem we are also still seeing with idle control. Maybe just add 2 more fields: "I-term min, max"? We can't use the same min/max as for the absolute output, since we need to be at least able to get to "0" and beyond.