7G-Tronic & Tiptronic User Notes

[Paul/]

How exactly can you confirm it?

PWM is only an ordinary industry method of encoding an analogue signal as series of digital pulses. No magic.

So to say it's 'key to the operation' in something today doesn't ring true. It's just a ubiquitous method of transmitting analogue information or power.

It sounded out of place to me too as I only knew of it from sound synthesis. So with the caveat that I claim no expertise on the subjects of PWM or transmissions-

The importance of PWM in this transmission is that it's used to control a PWM solenoid valve which regulates the hydraulic pressure on the torque convertor clutch to control slip/lockup.

Extract from MB Vehicle Communication Software Manual for the 722.6 :

PWM SOLENOID VALVE STATUS___CLOSED/SLIP/OPEN
Used on the EGS system. This parameter indicates the state of the electronic transmission control module (ETC) output commands to the PWM (pulse width modulated) solenoid valve.This valve engages the torque converter lockup clutch. The solenoid converts a PWM signal into a corresponding regulated pressure (see SHIFT VALVE DUTY CYCLE for more information).
CLOSED means that the ETC is sending a duty cycle greater than 80% to the PWM solenoid, thus engaging the torque converter lockup clutch.
SLIP means that the ETC is sending a duty cycle between 10 and 80 percent to the PWM solenoid, setting the torque converter lockup clutch to its regulating position.
OPEN means that the ETC is sending a duty cycle of 0 percent to the PWM solenoid, shutting off the torque converter lockup clutch.

SHIFT VALVE DUTY CYCLE_________________0 to 100%
Used on the EGS system. This parameter displays torque converter PWM solenoid duty cycle in percent (not shift valve). The PWM solenoid valve with defined slippage, controls the operating phase of the torque converter lockup clutch. A duty cycle of 80 percent or greatermeans that the torque converter is fully locked up.

Article on PWM Solenoid Theory-
Pulse Width Modulation Solenoid Theory and Operation | TLX Technologies

 

[Dryce]

The importance of PWM in this transmission is that it's used to control a PWM solenoid valve which regulates the hydraulic pressure on the torque convertor clutch to control slip/lockup.

Thanks. Now it becomes *much* clearer.

It's not PWM that is important. It's the control of the solenoid valve that is important. PWM is just the means to control it - and it's a method that is really easy to use with a cheap microcontroller and some suitable hardware for the last 25 to 30 years.

But is that really key?

Other transmissions use variable control valves (they don't need to be PWM) to manage the torque converter lockup.

The venerable 5 speed 722.6 transmission uses one of these solenoid valves to control the torque converter.

 

[Paul/]

Thanks. Now it becomes *much* clearer.

It's not PWM that is important. It's the control of the solenoid valve that is important. PWM is just the means to control it - and it's a method that is really easy to use with a cheap microcontroller and some suitable hardware for the last 25 to 30 years.

But is that really key?

Only key in the sense that if you remove it then it stops working- but I suppose same could be said for most components- even bolts- so I should have just said it's relevant rather than key. Anyway, TBH I wish I hadn't raised the original question- I was hoping the graph might give insight in to the operation from the driver's perspective, but I now know that a driver gains no practical benefit from understanding the role of PWM in the system.

 

[Dash1]

Only key in the sense that if you remove it then it stops working- but I suppose same could be said for most components- even bolts- so I should have just said it's relevant rather than key. Anyway, TBH I wish I hadn't raised the original question- I was hoping the graph might give insight in to the operation from the driver's perspective, but I now know that a driver gains no practical benefit from understanding the role of PWM in the system.

Hi Paul,

I hope you are well.

You sound ever so disappointed Paul. The comments that you raised in your last post - “Anyway, TBH I wish I hadn't raised the original question - I was hoping the graph might give insight in to the operation from the driver's perspective, but I now know that a driver gains no practical benefit from understanding the role of PWM in the system.”

Why on earth should you wish you hadn’t raised such a question, it was perfectly valid, genuine and appropriate under the circumstances. You wanted to know what pw% was. Granted, you are absolutely right, there is no practical advantage whatsoever for you as a driver to know what PWM is, but you did ask that question and I responded and answered accordingly. The overall outcome of this scenario is that you now realise that it is an extremely complex system, and not easily understood.

I don’t wish this to sound unkind here, but from my point of view, I outlined quite clearly from day one that PWM within the TCM’s overall output strategy was in fact the key aspect to the overall control on this sophisticated and very complex electronic/hydraulic transmission system. There is absolutely no other way in which such a complex set of electronic/hydraulic actuators could ever be controlled other that by pulse-width modulation, if they could, then I would know about it. Electronic switching solenoids without pulse width modulation are in a state of either “on” or “off”, there is no in-between, that is not referred to as “control methods”, that is referred to as “switching methods” and they are not the same. In engineering terms, the operation of a pwm solenoid is referred to as “stroking ” the solenoid. To take this control method and process away from this transmission, then it will cease to function - permanently.

I am not interested in the least in what other people perceive this to be, or systems from the past, my point is this, if they lack such understanding of modern engineering systems and technology, well, its their problem, its certainly not mine. It’s like comparing a 25 year old, and yet still reliable, K-Jetronic mechanical fuel injection system to that of the latest generation sequential fuel injection system. They are a million miles apart in terms of technology, don’t get me wrong, they both work very efficiently, yet one is totally and reliant upon the overall control of a computer, the very same principle goes for transmissions, past-to-present, we’ve moved on from the past.

I gave you and dedicated some of my time in the belief that it would in fact help you to understand a little better the quest that you were in fact undertaking. In the circumstances, I have kept it as simple is as possible without going over-the-top into the complexities of every single component individually utilised within the framework of the transmission and its electronic control process. On reflection, and now looking back, I don’t think you were actually looking for that; maybe it’s my own mistake in assuming that’s what you wanted from this. Maybe, in the future, I myself will learn from this experience and I will ask the question next time “What do you actually want to know” before I ever get involved in a thread.

I can only once again commend you for the considerable amount of time, dedication and effort you yourself have put into this, very few people would do that Paul, that’s why I afforded you my time, because of your dedication. Unfortunately, and regrettably, there are some individuals on this forum that don’t seem to appreciate the work and effort you put in to help other forum members understand a process a little better. In their own ignorance, they make silly comments and remarks. I signed off this thread because I had very little else to add, as I believe that the information I gave you was accurate, precisely to-the-point and more than substantial, If that’s not enough, well I’m truly sorry and ever so disappointed.

Anyway, for confirmation purposes, I have attached a link below of the TranX2000 engineering software test manual on the 722.6. I haven’t got the manual for the 7-speed, but it will be the same principles involved. This is just one of the very many transmission test modes available. I have no intension whatsoever of answering any further questions or explaining any of its contents; suffice it to say, this document says it all. All of the electronic/hydraulic valve block solenoids in this transmission operate on the principle of PWM - duty cycle% and not just the torque converter lock up clutch as you and Mr. Dryce are simply implying.

Here’s a very interesting question, and maybe Mr. Dryce would like to come back on here and answer this on your behalf. If I was to introduce a fault in 1-2/4-5 shift valve block solenoids with a shift pressure in the region of between 0-220 psi, and increase their respective resistance from say - 6.5 ohms to 35 ohms when the transmission is at normal operating temperature, what does he think would happen to the transmission?

He comes on this thread as a so-called expert, to hear him talk anyway, and then questions people’s backgrounds and abilities and insults them in the process. It will be very interesting to hear his answer to the question though.

I’ll give him a clue, these pwm solenoids are under test in the TranX2000 manual below, and the answer can be found in the charts attached if he really understands it, somehow, I don’t think that is going to happen –enough said Paul.

My Very Best Regards,


Dash1

TranX2000 Transmission pdf link


http://www.carroautomatico.net/wp-content/uploads/2012/08/Mercedes_722.6.pdf

 

[Dryce]

Here’s a very interesting question, and maybe Mr. Dryce would like to come back on here and answer this on your behalf. If I was to introduce a fault in 1-2/4-5 shift valve block solenoids with a shift pressure in the region of between 0-220 psi, and increase their respective resistance from say - 6.5 ohms to 35 ohms when the transmission is at normal operating temperature, what does he think would happen to the transmission?

Not a scooby.

He comes on this thread as a so-called expert, to hear him talk anyway, and then questions people’s backgrounds and abilities and insults them in the process. It will be very interesting to hear his answer to the question though.

Here's the thing though.

Every so often I end up at a table with technical people and managers to discuss some sort of technical problem in an area I'm not entirely familiar with. And there's usually one or two in the mix who will go on at length and if questioned retort that they have two decades of relevant experience and if really miffed then ask some sort of field specific question to make their point.

They trigger my BS detector.

And so do you. You tickled it before. You've now very close to latching it the on position.

And for the record I have made no claim to being an expert in anything. So don't map your mindset on to mine.

Now why do you think PWM is the only way of controlling a solenoid?

That's not a field specific question to catch you out or misdirect. It's very general not the bluster of your specific exam question. What principle of physics says it's only variable if driven by a PWM signal?

 

[Paul/]

Now why do you think PWM is the only way of controlling a solenoid?

That's not a field specific question to catch you out or misdirect. It's very general not the bluster of your specific exam question. What principle of physics says it's only variable if driven by a PWM signal?

Pending an authoritative answer, I'll run the risk of demonstrating that a little knowledge can be a dangerous thing (for me)-

As I understand it from the link about PWM Solenoid Theory at foot of one of my prev posts, the benefit of PWM is that it provides proportional control of
hydraulic valves, by varying the proportion of time that the valve is fully open and fully closed (with no interim position other than the transient opening and closing), so the hydraulic pressure is directly proportional to the control signal. If instead of PWM control was instead achieved by varying the solenoid's position in increments between 0 and 100%, the complex fluid dynamics of the path through the valve would mean that the hydraulic pressure wouldn't vary in proportion to the control signal.

I'll get ready to get me coat.

 

[Paul/]

If instead of PWM control was instead achieved by varying the solenoid's position in increments between 0 and 100%, the complex fluid dynamics of the path through the valve would mean that the hydraulic pressure wouldn't vary in proportion to the control signal.
QUOTE]

I might have got that entirely wrong, at the very least I've now twigged that PWM can also be used to proportionally control solenoid valve positions (which I now realise was in Dash's explanation)...
http://www.axiomatic.com/pulse-width-modulation.pdf
and there is another benefit of PWM control-


"Static friction, stiction, and hysteresis can cause the control of a hydraulic valve to be erratic and unpredictable. Stiction can prevent the valve spool from moving with small input changes, and hysteresis can cause the shift to be different for the same input signal. In order to counteract the effects of stiction and hysteresis, small vibrations about the desired position are created in the spool. This constantly breaks the static friction ensuring that it will move even with small input changes, and the effects of hysteresis are average out.

Dither is a small ripple in the solenoid current that causes the desired vibration and thereby increases the linearity of the valve.

The amplitude and frequency of the dither must be carefully chosen. The amplitude must be large enough and the frequency slow enough that the spool will respond, yet they must also be small and fast enough not to result in a pulsating output. The optimum dither must be chosen such that the problems of stiction and hysteresis are overcome without new problems being created.​

Dither in the output current is a byproduct of low frequency PWM, as seen above. However, the frequency and amplitude of the dither will be a function of the duty cycle, which is also used to set the output current level. This means that low frequency dither is not independent of current magnitude.​

The advantage of using high frequency PWM is that dither can be generated separately, and then superimposed on top of the output current. This allows the user to independently set the current magnitude (by adjusting the D), as well as the dither frequency and amplitude. The optimum dither, as set by the user, will therefore be constant at all current levels.​

​

 

[Dryce]

And for the record I have made no claim to being an expert in anything. So don't map your mindset on to mine.

Now why do you think PWM is the only way of controlling a solenoid?

That's not a field specific question to catch you out or misdirect. It's very general not the bluster of your specific exam question. What principle of physics says it's only variable if driven by a PWM signal?

I'm withdrawing this question as irrelevant.

That's because on reflection answering it (or requiring it to be answered) doesn't add anything to the context of this thread.

 

[Dash1]

I'm withdrawing this question as irrelevant.

That's because on reflection answering it (or requiring it to be answered) doesn't add anything to the context of this thread.

Hello Dryce,
Thank you for your reply. My apologies for the delay in coming back to you. I do have a very responsible job, which is extremely demanding and it takes up awful lot of my time. It’s very difficult at times for me to just jump on and off this forum and answer any questions that need answering. I do have a life-style outside of work and this forum. However, I am quite prepared to give you some of my time if it helps you understand this process and system a little better.

I’m off work on a day’s holiday today, but out of courtesy, and it really is only out of courtesy, because I don’t believe that I owe you that given the circumstances. The fact that you have withdrawn some of your comments from your last post only contributes further to your own acceptance that you were originally wrong. I’m pretty much sure, in fact I am 99.9% sure that you thought that I was referring to PWM in terms of some form of communications and/or radio frequency/field, well I am not, and I never was, and if you would have taken the time and care to read the posts properly, and as described, then you would have clearly realised that, and well before now. Unfortunately, sometimes it’s a little too late after the event; the damage has already been done.

To be perfectly honest, this has become somewhat of a really tedious task now for me. You were not satisfied with the evidence and facts as they stood and persisted in alternative answers to satisfy your own means. Let me just take this opportunity to say that from my point of view, you invited yourself on to this thread, and you were perfectly entitled to do so and join in with us and contribute to the topic. However, you didn’t do that, what you did do was to shoot me down in flames from the onset. If you would care to take the time and go back and realise what you had said to me, then I think you would accept what the issues are now. As I pointed out in my reply post to your original unwelcome comments at the time, you didn’t even have the courtesy to respond and reply to that post. Had you done so, then I could have answered any questions that you may have had.

I’ll explain to you what I think that you have obviously overlooked here, For all I know, you may very well have an electrical background, but you have clearly not understood the principles involved in the operational process of how these electronic solenoids actually work, so with that in mind, I will basically explain them and you will be able to see exactly what I have already gone through and talked about in many of my posts. In addition to that, at the end of this post, I have attached a photo of a 722.6 valve block conductor plate so you can see what I am actually referring to later on. I really can’t make it much simpler than that I’m afraid. I don’t wish to sound derogatory, but if you can’t grasp the concept from this, then there is something seriously wrong.

These electronic/hydraulic-controlled solenoids are directly seated in the valve block and their electrical contact is made possible with a plate known and referred to as the “conductor” plate. The solenoids are “hard wired” and have two electrical copper/brass terminal connections, one being the “ground”circuit and the other being the 0 to 12-volt “supply”. It is this 0 to 12-volt supply wire, and this wire alone that is actually the subject of the pwm – duty cycle% control. This wire is “pulsed” with the voltage/current anything between 0 to 12-volts and from a duty cycle of between 0% to 100%, - Zero meaning “off” and 12 volts meaning permanently “on”, and varying voltage and current intensities in between depending upon the TCM output strategy at the time to “open/close” or “vary” the solenoids position relative to the time frames initiated and programmed by the TCM module and its strategy upon the drive cycle periods. It really is that simple, its not rocket science, so what don’t you actually understand about that.

If you read my last post, it states quite clearly my position on this. Once again, you failed to grasp this concept, and I can’t be held responsible for that. Please read the last post of mine and many of my other posts, which explains in significant detail the concept of PWM in transmission system control mechanisms. We are actually talking about the principles of electromagnetism here; you must remember that, the question on the physics that you related to in your last post, so I’ll cover those principles just in case you are not familiar with those.

Electromagnetism – It is one of the original basic concepts of the law of physics that follows - current flowing through a simple coil of copper wire, the greater the current flow - the greater the magnetic field, the greater the number of wire turns around the coil – the greater the magnetic field, tubular type solenoids, such as ours in the valve block all still produce magnetic flux fields when energised, the strength of which, in turn, uses the energy into a force and some form of motion, we can utilise and convert this motion into some form of mechanical movement within the solenoid to control the hydraulic pressures. With PWM as our “primary” source of influence, we can also use it in effect to vary our precise control over those solenoids – electronics over hydraulics; this is not a new concept at all, its just been brought up to date to meet the requirements, applications and demands of our needs in the motor industry

With respect, I think that you have become somewhat confused here with the terms of transmission and communication, although early forms of communication were in fact referred to as transmission, but we are talking about a motor vehicle gearbox here, and not transmission/communication waves. The currently used terminology in the automotive industry of a gearbox is referred to as transmission or powertrain. The precision and calculated movement of an electronic solenoid valve, and I do mean precision; under the influence of PWM can only be achieved at this present moment in time. All other avenues of previous control methods and mechanisms over the past decades have been used and proved to be less favourable, effective and of limited choice, especially, when we are talking about the implications of precision control in milliseconds time frames. I could go on forever on this, but I won’t. How many more examples would you actually like to see to be convinced?

In engineering terms, I have more than answered all of the questions in the very many pages that I have written on this thread already, even Paul has provided you with many examples as evidenced in his own posts. The principles that I honestly believe that you are referring to here is in terms of communication - radio waves and are referenced under the basic physics laws behind the wireless communications, which is the EM’s wave’s ability to carry a form of energy and/or information from one point in space (from the sender, for example) to another point (the recipient or the receiver).

The reason that I came to the my conclusion and thought that you had adopted the above thought process, is the very fact of just one key word in the whole of all of your posts put together that stands out, and that word is, “ubiquitous” and I quote “It's just a ubiquitous method of transmitting analogue information or power”- which is exactly right and means that it is present everywhere and at all times. To me, anyway, the only thing that’s everywhere at all times to my mind at this moment in electrical terms is the magnetic field of the earth, satellite or some form of communication/radio waves etc. So what has that got to do with what I am talking about. You have really taken the wrong approach to understanding this, as evidenced in several of your posts.

There is also another aspect of the ubiquity that you have already referenced in your post, and why you ever have made reference to that is beyond me, which once again only confirms what I had already thought, that you were thinking along the wrong lines of approach in understanding what I had said. EM waves, anyway, do play a very important role in our modern society today, and in many other aspects of engineering disciplines and fields, including, mechanical engineering, chemical engineering, computer engineering, to name but a few. Many of the latest cutting and leading-edge developments today prosper and excel in these disciplines alone, such as Microelectromechanical systems (MEMS) high-speed computer chips, medical imaging processes, again, to name a few.

If you were actually honest with yourself, you actually thought that I was referring to the this type of communication and radio frequency process in controlling these solenoid valves, but you were wrong, but you don’t need to answer that, the above comments speak for themselves. How on earth you could have got so confused and come to that conclusion is beyond me, and then to think that I was actually applying that process in my posts on these solenoids operations. There is no mention anywhere in any of my posts whatsoever that this is what I was suggesting.

You have really just misunderstood the situation and blown it out of all proportion. We are not talking about the principles of radio-controlled events such as those in model helicopters and cars here, on the contrary, we are talking about “hard wired” electrical components that so happens to respond to PWM controlled pulsed processes as I have mentioned above. When I say and refer to “hard wired”, I actually mean that the component – the solenoid in this case, is directly connected to the TCM by way of a conductor plate. In other words, a metal conductor plate – copper/brass, that has “continuity” so as to allow current to flow. Other examples of “hard wire” could be in the form of ribbon cable connections, wiring looms, anything that is directly connected from its source to its destination, in our case, the TCM to the solenoid.

Note: To sum up the above then, I will make this absolutely clear, There is no form of any type of transmitter and/or receiver employed in the use of this system, and never likely to be. The transmission solenoids are “hard wired”, and as such, woks on the principle of pwm as I have explained above. In fact, if the truth really were known, you may be surprised to learn that there have been “research and development” programs on this very topic of communication/radio frequency control on several various systems in the automotive industry. However, this will never come to fruition for the very many safety regulations and implication issues put forward by the IEEE, (Institute Electrical Electronics Engineers) and its subsidiary bodies because of the very many “safety critical”issues involved, although there are prototype models vehicles in existence, and that’s all they will remain - prototype. That’s another story though and maybe one day I can explain this in another topic some time.
The question that I originally asked was based upon a genuine failure scenario, not an exam paper, an exam paper would have required an awful lot more detail than I asked for. With the greatest respect, and I don’t wish to offend you, but I knew that you could not possibly answer it, and I will tell you why. The question that you posed to me, and I quote once again, “So how on earth did you make the leap from pw% to a rather odd digression on PWM” This is where you actually went wrong, when you invited yourself on to this thread and asked me to explain that question – That question, and that question alone, does not exist in any form of context that it was ever written, for the simple reason that pw% and pwm are related in context as exactly one and the same, the “m” had inadvertently been omitted from the text. If anyone had known anything about this discipline, then they would have been quite conversant with all its applications in motor vehicle technology, which you failed to acknowledge from day one and in many of the posts to Paul. That is the only reason that I ever asked it, it was never intended to catch you out, so please accept my sincere apologies if it caused you any embarrassment, upset or distress.
And for the record, given the many applications and sophisticated electronic systems now employed in the use of modern motor vehicles, PWM is a preferred choice of operation by many vehicle manufacturers and a very useful tool in the application of control processes on many electrical demands placed upon the modern motor vehicles battery, charging system, lighting system and ancillaries. Yes, even the simplest and most basic function like your courtesy lamp in the vehicle is pulse width modulated. Modern motor vehicle batteries and charging systems would not be able to cope if we returned to the “old-fashioned” method of circuit or component “switching” methods alone, given the amount of heavy current drains placed upon vehicle system found today.
Anyway, I hope this helps to clear up any confusion that you may have had, I just wished now that you would have applied some common sense and logic at the time before you made judgement on me. Asking questions costs absolutely nothing Dryce, and you may very well have learnt something in the process. Please, take my advice; think about something before you commit to writing it. I believe that you owe, at the very least an apology to Paul for what I see as the total unnecessary disturbance of his thread, especially, when you consider all the hard work he himself has put into it. I don’t wish to sound unkind or derogatory here, and I am certainly not interested in any science or physics lessons, so please, don’t insult my intelligence.
I will say this, I bear no grudge or animosity whatsoever towards you personally, and get absolutely no pleasure or satisfaction in sitting here on my day off and writing this, its absolutely unnecessary and a total waste of my time as well. I get very little time anyway with work commitments and the like, but when I do, I sometimes like come on to this site and if I am in a position to help someone, then I will do just that. Contrary to what you may think, I do get a great deal of satisfaction and pleasure in helping other people, fortunately, and thankfully, it’s a trait I would hate to lose. I treat and consider you to be no different to that of any other forum member on here.
This is my last comment on this matter, so you choose whatever you want to say from heron, but I won’t be playing any part or participating in it any further. For me, what started life as a really enjoyable thread, turned in to this fiasco. I originally said to you that your comments would deter people like me from contributing to threads like this, as this is now what we have to contend with because you refused, and may I add, probably from your own lack of knowledge and experience of motor vehicle systems to move on with the times and accept things as they were explained.

Paul,

Please accept my sincere apologies if you think my comments have further disrupted the thread, unfortunately, this is the only problem with Internet forums, at times, when you actually think that you are helping other people like yourself who have a genuine interest in understanding something, we encounter and experience disruptions such as this. Anyway, this post may have served two purposes; you may have learnt some addition information that you didn’t know about.


Best Regards,

Dash1

 

[Acapulco Bill]

@Dash1: Back to the 722.9 - The 722.6 allowed reset of the volatile memory by disconnecting the battery for a few minutes. As the memory in the 722.9 is now non-volatile, is there a way to erase (and preferably permanently), this (what MB calls Adaptive Learning) memory? The 722.9 had a Pre-MY2011 Transmission-CU software update, the Star-based flash erased this learning memory and the transmission performed fantastically. However, coming into heavy traffic, stop lights and parking lots, the memory has stored a LOL (Little Old Lady) shifting pattern and has become lethargically snail-like again. Attempts yo restore performance by accelerating full-throttle repeatedly to 100+ MPH fails to improve shifting performance have been futile.

Am ready to proceed with more drastic solutions such as a full rebuild of the valve body module that comes with a lobotomy of the TCU and it's ludicrous "learning" module to restore correct shifting of the 722.9. Here is one solution:
Weistec Engineering - Products - 722.9 Valve Body and TCU Upgrade

Thanks for your help.