Closed loop IAC control documentation

Philip Lochner · Post by **Philip Lochner** » Thu Dec 20, 2007 9:53 am

Has anything been written on the MT parameters for closed loop control yet. I'm very keen to give it a try on my Rover V8...

Post by **muythaibxr** » Fri Dec 21, 2007 9:18 am

Mostly a bunch of posts in various threads.

I intend to document it as soon as I get a chance, and it's stopped changing.

The next beta is going to have several significant changes that will require retuning the PID parameters among other things, so I didn't want to document it until it was close to its final form.

Just a note, with stepper IAC motors, the algorithm is a lot more difficult to get working right since steppers move so slow.

Ken

Asteris · Post by **Asteris** » Fri Dec 21, 2007 10:05 am

Did you fixed the problem that it always stays on, whatever setting it uses? Makes my stepper motor get burning hot after 5-10 mins...

Philip Lochner · Post by **Philip Lochner** » Fri Dec 21, 2007 10:22 am

muythaibxr wrote:Just a note, with stepper IAC motors, the algorithm is a lot more difficult

... and that's why us folk who need it to work will appreciate it SO much, thanks Ken

Post by **muythaibxr** » Sat Dec 22, 2007 9:14 am

Asteris wrote:Did you fixed the problem that it always stays on, whatever setting it uses? Makes my stepper motor get burning hot after 5-10 mins...

I don't think that's a problem, as I've got it working on the bench without that problem.

Ken

Post by **muythaibxr** » Sat Dec 22, 2007 9:15 am

Philip Lochner wrote:
muythaibxr wrote:Just a note, with stepper IAC motors, the algorithm is a lot more difficult
... and that's why us folk who need it to work will appreciate it SO much, thanks Ken

heh, I was talking about tuning it.

There might be some mods I can make specific to stepper IAC motors to make them a respond to increased load a little faster... but I have not made those mods yet.

Ken

Asteris · Post by **Asteris** » Sat Dec 22, 2007 12:30 pm

muythaibxr wrote:
Asteris wrote:Did you fixed the problem that it always stays on, whatever setting it uses? Makes my stepper motor get burning hot after 5-10 mins...
I don't think that's a problem, as I've got it working on the bench without that problem.

Ken

From beta 15 and on, IAC controller stays on, whatever settings i use at Idle control. It's obvious, because my stepper motor heats up, even with rpm at 0. This also shows at Realtime display, where the voltage drops at 9-10V (12V/1A AC power supply.

At Beta 14 and previous ones, with setting at IAC stepper Moving only, stepper motor stays cool and voltage is rock steady at 12.2V.

You wanna know what the funny thing is? IAC draws current even when Idle control set to None. And so does firmware 1.02. And B&G 2.870 which i tested.

Post by **muythaibxr** » Sun Dec 23, 2007 12:15 am

Are you talking about warmup only or closed-loop IAC?

Asteris · Post by **Asteris** » Sun Dec 23, 2007 2:27 am

Moving only from 1.02 to beta 14, motor moves, stays cool, voltage at 12.2V.

All other IAC settings (and Moving only at beta 15 and 16), motor moves, but heats up and voltage ripples around 10V.

All other none-IAC settings (on/off, PWM) including None, at all firmwares, motor does not move, but heats up and voltage ripples.

Heating and voltage ripple happens even when Rpm stays at 0.

Post by **muythaibxr** » Sun Dec 23, 2007 7:33 am

EDIT: I found and fixed the bug causing your problem. It'll be in the next beta.

Ken

Asteris · Post by **Asteris** » Sun Dec 23, 2007 7:51 am

I could kiss you if you were here. Thanks a lot...

Asteris · Post by **Asteris** » Thu Dec 27, 2007 12:17 pm

Ken, is this fix implemented at Beta 17 as you said? If yes, I'll go and unhook the ECU from the car to flash and test it...

Post by **muythaibxr** » Thu Dec 27, 2007 1:01 pm

Asteris wrote:Ken, is this fix implemented at Beta 17 as you said? If yes, I'll go and unhook the ECU from the car to flash and test it...

Yes, this and several other fixes are in beta 17... I edited the beta 17 release message to reflect this change as well.

Ken

Asteris · Post by **Asteris** » Thu Dec 27, 2007 2:14 pm

Problem fixed at beta 17. Stepper motor stays dead cool and voltage rock solid at 12.2V. Tomorrow i'll test it on car.

Many thanks.

Asteris · Post by **Asteris** » Sat Dec 29, 2007 4:48 pm

Ok, new problem here.

Testing on the bench, Moving only mode, stepper motor responds fine for a couple of minutes (i change CLT on stim from 0 to 100C, to get IAC step from 100 to 160 steps and back). After those two minutes, and within about 30 seconds, motor starts to loose some pulses, then just makes a hum and won't move and finally stays dead. When i power off and on, it retracts fine, but still stays dead in further commands.

I thought, maybe something overheats real fast, but if i change to Always on mode, it instantly starts to work fine again (tested for another 20 mins or so), so it is not hardware related. Same thing happens at Closed-loop modes.

Seems like IAC controller shuts down after some time, when in Moving only modes. I would use Always on to solve my problem, but stepper motor heats up to 60-70 degrees C and that is in room temperature, don't want to find how high it would reach in the engine compartment. I'll use 15-min IAC till this problem is solved.

Thanks.

Post by **muythaibxr** » Sat Dec 29, 2007 10:54 pm

This doesn't sound like a software problem. It sounds like you may need to jumper the two power resistors on the bottom of the ms2 daughtercard. I kept seeing this problem when testing code until I jumpered them.

Ken

Asteris · Post by **Asteris** » Sun Dec 30, 2007 2:49 am

So, jumping these two resistors, will let me use Moving only all the time? What do these resistors do, reduce the current going to the stepper motor coils? And why should they let the motor work for the first two minutes and then fail?

What is their value? Can i change them with a lower one?

Post by **muythaibxr** » Sun Dec 30, 2007 1:01 pm

Asteris wrote:So, jumping these two resistors, will let me use Moving only all the time? What do these resistors do, reduce the current going to the stepper motor coils? And why should they let the motor work for the first two minutes and then fail?

What is their value? Can i change them with a lower one?

I believe they are current limiting resistors... I don't know why it works for a few minutes then stops with these in, but I do know that for most people with that behavior, it is safe to jumper them.

Ken

Asteris · Post by **Asteris** » Sun Dec 30, 2007 3:58 pm

After jumpering the two big resistors, problem is solved.

So, if now a coil blows inside the stepper motor, IAC controller will short circuit and goes bang, right?

Asteris · Post by **Asteris** » Sun Dec 30, 2007 5:55 pm

Small remark. When Idle set at Closed loop IAC, cranking position steps are Grey. Motor goes to the value taken from PWM cranking position (you can change that if you select PWM closed-loop), but it allows only 1-100 values, where stepper motor may need higher value.

Also Idle Valve closed Duty or Steps (%), doesn't affect operation, motor moves between Idle Open Duty or Steps (%) and Min Duty or Max Steps for PID (%).