Exploring the Stepper Motors on R1200XX

[steveknapp]

Another.

 

http://www.allegromicro.com/datafile/3967.pdf

[RFW]

You can find ICs. A quick google turned up these at $3 per.[/url]

 

Two of those, a PIC, and some glue, you could manually control the motors.

 

Agreed, there are all sorts of stepper drivers out there that can drive stepper motors in single steps, half steps, or micro-step them if you want to get fancy! This eliminates most of the need to understand the gory details of analog motor control design.

 

My post was only intended to get the general principles across.

 

Bob.

[Ken H.]

Agreed, there are all sorts of stepper drivers out there that can drive stepper motors in single steps, half steps, or micro-step them if you want to get fancy! This eliminates most of the need to understand the gory details of analog motor control design.

 

My post was only intended to get the general principles across.

 

Bob.

And THANKS a bunch, it helps! The controller I built uses a UNC5804 stepper controller with a good old 555 generating the pulses. Now the next step (no pun intended!) is to get it interfaced with the stepper on the bike. (Without Marty's 'vote of no confidence' prediction!)

[Marty Hill]

Ken,

 

I was only kidding. I admire your knowledge and desire to learn.

 

I do find it hard to believe that in over 40k on 12GS's that mine were never properly tuned cuz I couldn't park the stepper motors. I'd hate to see some new owners thinking that they couldn't tune their bikes when we know that it can be done and is very easy.

[RFW]

....with a good old 555 generating the pulses.

 

Ah yes! The good old 555. This chip was designed "under the table" at Signetics in the early '70s, because management said they thought it would never sell! It went on to become the largest selling single IC in history! Ooops!

 

Bob.

[steveknapp]

I do find it hard to believe that in over 40k on 12GS's that mine were never properly tuned cuz I couldn't park the stepper motors. I'd hate to see some new owners thinking that they couldn't tune their bikes when we know that it can be done and is very easy.

 

Exactly Marty!

 

I wonder what the real benefit will be of doing this "right".

 

Fun tinkering, yes!

[Timmer]

I wonder what the real benefit will be of doing this "right".

 

Lots of us anal-retentive BMW DIY types will sleep better when we are absolutely certain that our steppers are correctly aligned in step with the TBS, ABS, & BS.

 

Seriously, I think a lot of us just want to know exactly what is going on "under the hood."

[R4ND0M_AX3]

...Seriously, I think a lot of us just want to know exactly what is going on "under the hood."

Put me in the 'exactly' catagory. Best guesses and 'you don't need to worry about that' aren't what I'm about. It's not that I fear something will go wrong. I just crave to fully understand every little sequence of operation for these bikes.

 

This is good stuff. Keep it up.

[artig]

There's probably something I'm misunderstanding, but I just don't see why there is a need to move the stepper motors when doing a TBS at 3 or 4,000rpm.

 

Surely the intention must be to have the best sync possible under normal operating conditions. And under normal operating conditions there is no special parking of stepper motors. If you park the stepper motors while doing the sync, won't the conditions be different from what they will be when you are riding the bike? You can probably get a perfect sync with parked stepper motors, but that perfection may or may not be perfection when the stepper motors are in their normal operating position.

 

Or can someone explain to me what I have misunderstood?

[Ken H.]

I'd hate to see some new owners thinking that they couldn't tune their bikes when we know that it can be done and is very easy.

Oh don't get me wrong Marty, I think you can. I've done it myself. And someone new reading this thread shouldn't be put off.

 

This is as much a quest to understand the operation of the bike better and maybe refine the sync. process, as anything.

[Marty Hill]

Ken,

 

I understand/now a new member will as well.

[Ken H.]

There's probably something I'm misunderstanding, but I just don't see why there is a need to move the stepper motors when doing a TBS at 3 or 4,000rpm.

 

Surely the intention must be to have the best sync possible under normal operating conditions. And under normal operating conditions there is no special parking of stepper motors. If you park the stepper motors while doing the sync, won't the conditions be different from what they will be when you are riding the bike? You can probably get a perfect sync with parked stepper motors, but that perfection may or may not be perfection when the stepper motors are in their normal operating position.

 

Or can someone explain to me what I have misunderstood?

First we have to admit to the fact that the air bypass ports (what the steppers control on the R1200 series and the Large Brass Screws (LBS) control on the R11xx series) effect sync at RPMs other than just idle. E.g. at all RPMs. Some people will say no, and the factory BMW sync procedure for the R11XX series might also lead one to believe no. Because it references them as the idle sync adjustment. But myself (and others) say the air bypass ports DO effect sync at all RPMs, because if for no other reason it's not like they close up or anything when the throttle is opened. And I say you can prove it on an R11XX during a sync procedure - Get the bike at best sync with the cables at say 2000 RPM, then twist one LBS, the sync will change.

 

Further to this train of thought, it is documented by BMW that the R1200 bike dynamically adjust its sync on the fly as we ride. How it knows it is 'in sync' is some speculation, but we know that it does adjust. The only way it can to do so is with the air bypass steppers. If we had steeper motor driven cable adjusters, that would be another method, but thankfully, we don't!

 

So if one is of the mind set that the air bypass port position (how much it is open or closed), as positioned by the steppers, effects / matters above idle, then the next question is where to set all of the affecting adjustments of the bike when doing a sync ourselves?

 

I think there are two key things we are trying to do: One is maximize the auto adjustment range of the air bypass ports. But more importantly we want the air bypass ports initially set the same on both sides when doing a sync. On the R11XX series when doing a proper sync, one of the initial steps is to set the LBSs to the same 1 & ½ (or whatever) turns out. There we are establishing a baseline mechanically equivalent point for both sides, from whence we then make the adjustments to get the desired sync.

 

To me the R1200 is no different. To obtain best possible sync we first have to establish a mechanically equal for both sides baseline point. Where both sides are physically the same. This includes the position of the steppers. If one side’s stepper is at 1/3 of it’s total range, and the other side’s is at 3/4 of its total range, and we adjust sync from there, thus ignoring the discrepancy in the air bypass ports position (and thus the amount of air the ports flow through), we are effectively compensating for one miss-match (the air bypasses) with the wrong adjustment - with the cables.

 

And here is why fundamentally that approach doesn’t work, or at the minimum is less than ideal (on any boxer R11XX or R1200) IMHO: The air bypass ports flow a much smaller % of air into the intake than the throttle butterfly valves. I don’t know what the ratio is, but lets say 90/10. When you try to compensate a miss-match in the small flow path, in the air bypass port, with the large flow path, the butterflies, your ability to accurately compensate is compromised. The butterflies are too course of an adjustment mechanism to accurately compensate for fine errors in the air bypass ports. Not taking this into account is IMHO where some people fail when syncing a boxer motor and as a result it doesn’t run to its full potential smoothness.

 

The R1200 is no different. If the steppers and as a result the air-bypass ports are not in an equal position when you do the sync with the cables, your ‘sync success’ will be less than ideal. Enough to effect the running of the bike? Well maybe, maybe not. How picky are you? But we are talking idealisms here. What’s the best procedure to get the best possible sync?

 

There is a further reason to park the steppers prior to doing the sync with the cables, and that has to do with the stepper / air bypass port’s total adjustment range. They can only move so far when making dynamic adjustments on the fly as we ride. Let me make up a scale to illustrate the problem we may get ourselves into if we sync only with the cables, ignoring the steppers’ positions:

 

Say the steppers have a total mechanical movement range of 1 to 10. Call 1 full closed and 10 full open. For this illustration it doesn’t really matter, but lets say that. Let’s also say that the so-called “parked” position of both of the steppers, as set initial by the dealer diag. equipment, is “5”, mid-point. There is some evidence that it is not mid-point but for now let’s say it is. Now the bike is synced with the cables by the dealer technician and everything is fine. We ride away happy. BUT over time as we ride and as the bike changes, the steppers make sync adjustments and lets say the left one moves to “2” and the right one moves to “6”. The bike remains in sync right? And we continue happily along our way.

 

So 6K goes by in a flash and it’s time for a sync job and this time we decide to do our own sync. HOWEVER we don’t reset both steppers to “5” (because as yet we don’t know how to do so), we just sync the bike using the cable adjustment with the left side stepper currently at “2” and the right one currently at “6”. Yes the bike comes into sync, but we have unknowingly created two problems. One is the earlier mentioned issue of using a course adjustment mechanism (the butterfly’s position via the cable) to compensate for a fine adjustment error (the air bypass port) and the inherent problems with doing so. But we have also potentially, unknowingly created a limit on how far the steppers can move in the future to dynamically on the fly correct for sync errors/changes. Suppose the left side at some future point needs to move 3 steps further closed? It can’t because it’s at “2”. The engine can’t come into full sync on its own now and smoothness and performance suffers as a result. Now of course maybe we luck out and the bike never has to adjust itself to the point where one stepper or the other runs out of adjustment range. But the potential is there. And regardless if this scenario happens or not, the other issue of compensating for air bypass port differences with adjustments to the butterflies remains, also contributing to a boxer that runs less than ideal.

 

To me these are the core reasons why the BMW dealer equipment parks the stepper motors in a fixed and equal position prior to the technician adjusting the cable sync, and why we DIYers need to also learn how to do so.

 

Sorry this is so long winded. But I wanted to get my theory out there. If for no other reason than so some else can poke holes in it!

[steveknapp]

...Seriously, I think a lot of us just want to know exactly what is going on "under the hood."

Put me in the 'exactly' catagory. Best guesses and 'you don't need to worry about that' aren't what I'm about. It's not that I fear something will go wrong. I just crave to fully understand every little sequence of operation for these bikes.

 

This is good stuff. Keep it up.

 

Sure, but you're not getting the "exactly" answer here.

 

If you want to know what the bike is doing, manually controlling the stepper motors is not the answer. Is it?

 

If you want to know more about what the bike is doing, monitor the stepper motors as the bike controlls them. Create an imbalance at idle, does the bike compensate? What happens when the throttle is open? Do they "park"? Do they still try to correct imbalances?

[Ken H.]

If you want to know what the bike is doing, manually controlling the stepper motors is not the answer. Is it?

 

If you want to know more about what the bike is doing, monitor the stepper motors as the bike controls them. Create an imbalance at idle, does the bike compensate? What happens when the throttle is open? Do they "park"? Do they still try to correct imbalances?

Agreed, there are may parts to this puzzle we're trying to figure out. What does the bike do with them dynamically? What does the dealer's system do with them when "parking" them for sync? How can we DIYers move them ourselves in an attempt to duplicate this? Once we can move them, then to where?

 

I'm not saying what I'm talking about at the moment, how to move them and why we need to do so is the whole picture, just one piece of the 'crawl before we walk' puzzle!

 

Somewhere on my list is to build a data recorder to my laptop, connect it to the steppers and go riding! Or someone with more expertise than I in that area step up to the plate and do so!

[steveknapp]

Holes for ya Ken!

 

1: On the R11XX series when doing a proper sync, one of the initial steps is to set the LBSs to the same 1 & ½ (or whatever) turns out.

 

It was? Maybe in one version of the procedure posted on the internet? The BMW procedure as well as most of what I've seen was to loosen the cables to ensure they weren't impacting idle. Then to adjust idle speed and idle sync with the LBS.

 

Only *after* the LBS were adjusted for proper sync, not equal turns, were the cables adjusted. Unless you were futzing with the throttle stop screws, which is a whole different discussion...

 

2: At the end of this, tinkering with the sync and all, how are you going to quantify the improvements? Nothing personal, but there is a psychological factor at play here, spend enough time on something, or buy the "special" piece and a person tends to think it works better.

 

3: You are starting with the conclusion "you need to control the stepper motors for a proper sync" and working your way back with theories of how the bike operates. But you've got no data on what the bike is really doing. Adding onto the above, you're assuming the stepper motors compensate for sync imbalances at higher engine speeds. Is this really true?

 

If you're building some stuff, make something to monitor the stepper motors posistion while they are controlled by the ECU. A counter of some sort would probably work just fine. Or buffer the controls to the stock units and have the buffered outputs drive a second set.

[Ken H.]

Well Steve I know you and I have always been at odds as to the best way to sync a boxer. You believe the BMW procedure on the R11xx series is acceptable, I believe it can and has been be bettered. No point in rehashing all that old ground here I guess.

 

One thing is certain though, even the factory BMW whizzbang, official, approved, signed, sealed and delivered procedure on the R1200 series calls for parking the steppers with the dealer's system prior to doing a sync with the cables. If nothing else I'm trying to DIY duplicate the factory procedure.

[artig]

Thanks, Ken.

 

The part I was missing was that the bike is dynamically trying to adjust sync on the fly while you are riding. I was under the impression that this was only done during idle, and then the stepper motors were left in that position at all other speeds.

 

However, I must say it's not doing a very good job of the sync on the fly. I still get my bike serviced at the dealer every 10,000km, and I assume they are doing a proper sync at that service. This should mean the stepper motors are in an ideal position for full adjustment range. And so the bike should stay in good sync as long as possible. In my experience it stays in good sync no longer than if I do the sync manually, with no adjustment or control over the stepper motors. But with only 3 samples (3 services) it's difficult to say whether there is a definite pattern emerging.

[steveknapp]

If nothing else I'm trying to DIY duplicate the factory procedure.

 

Sure, and I think that's a neat project. But when I pointed out that it might not make any difference in the operation of the bike the response was by in large that people want to know THE TRUTH! How the bike operates, exactly what it's doing.

 

And my point remains that to know how the bike operates requries *observing the bike* then taking action. To DIY the factory service procedure requires a gizmo like you are working on.

 

They are different paths.

 

I must admit I find some irony in the fact that on the oilhead people came up with all these better sync methods to help it run right. On the hexhead, which just runs right to start, people are fighting to replicate the factory method.

 

Did you ever get extra stepper motors? I'm trying to think if there would be some way to drill the housing on the top out so one could observe their movement...

 

The part I was missing was that the bike is dynamically trying to adjust sync on the fly while you are riding.

 

It does? Ken, you know for sure? Or you're assuming it does?

 

[David_S]

I have a hunch the only thing the stepper motors are used for is controlling idle speed. I had my 12GS synced at the dealer during the 600 mile service and was even provided a print out showing the specs were acceptable but when I hooked up my $2.00 sync tool (hoses and ATF) the sync was so far off I had to shut the bike down to prevent the fluid from being sucked into the left TB. This really has nothing to do with this topic other than I have serious doubts that the stepper motors have anything to do with the bike adjusting sync by moving them. If the stepper motors were used to adjust sync all you should have to do is make sure the cables are adjusted correctly and the computer would sync using the stepper motors no?

[Ken H.]

If the stepper motors were used to adjust sync all you should have to do is make sure the cables are adjusted correctly and the computer would sync using the stepper motors no?

One would think. But being as far off as you describe, I would suspect he just blew the sync regardless.

[Ken H.]

people are fighting to replicate the factory method.

Oh I never said I was going to stick with it forever!

 

But one's got to start somewhere figuring it all out!

 

Buy a motorcycle just to ride? Where's the fun in that?? It just begs to be tinkered with!

[Ken H.]

Bob,

 

I guess what I'm not sure of then on an H configuration is what the pulsing sequence is to get the motor to advance a single step at a time. For example if you close 1 & 4 in your diagram doesn't the motor turn continuously?

 

What is the pulsing sequence between the 4 leads to advance it one step at a time, then another, then another, etc...?

[KDeline]

 

Buy a motorcycle just to ride? Where's the fun in that?? It just begs to be tinkered with!

 

I just need to ride to get rid of the headache I've gotten reading all this stuff.