2d sensor question - another one - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 24 (permalink) Old 04-30-2015, 11:52 AM Thread Starter
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2d sensor question - another one

After reading countless threads for hours, many about fit and turning radius, have not seen anyone make mention of the big question. Besides allowing for independent compression and rebound adjustment on the fork, does the 2d sensor do anything else? Does it improve the functionality of the DDC automated adjustment of damping characteristics?
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post #2 of 24 (permalink) Old 04-30-2015, 03:37 PM
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Originally Posted by Tahoebrian5 View Post
After reading countless threads for hours, many about fit and turning radius, have not seen anyone make mention of the big question. Besides allowing for independent compression and rebound adjustment on the fork, does the 2d sensor do anything else? Does it improve the functionality of the DDC automated adjustment of damping characteristics?

I think your better question is : Can the average "Joe" rider feel a difference in adding a 2D front fork sensor. Answer, most likely not. You put garbage in, you get garbage out. As in DATA.. However, you can get a "feel good" out of it. Why?

Well, MotoGP... WSBK .. BSS .. AMA pro's .. People like me that use to race 100's of races a year but are too old to be racing, but want every last bit of function out of a already very good street bike...

Me: 53, and raced 40 years in about everything you could want to race. Water, Dirt, asphalt, even tried a little flying ..

So, yes, I can tell the difference. And I am an engineer in 2 fields so I make things the way I want them. If it happens to be 100% plug and play and I can live with it, I dont reinvent the wheel.

I got my turning radius with only a loss of 3mm. I know 99% of people on this forum would never do what I did to resolve my issue, but, there is another way. I just did not want to remove the steering stem and work on it at the time. I will modify my bike any way I chose and it does not bother me a bit. I dont recommend my ways to everyone, as you will need the three T"s ... Time-Tools-Talent .. Without those 3 items, you will be lost.

So as your question beyond fit, there is function. Yes, it works. There was some engineer that set there countless of hours working out the algorithms for the DDC to response within milliseconds so the suspension becomes a working part of the motorcycle and not just some gimmick to sell more bikes against Suzuki and Honda. Yamaha is coming, and may actually be ahead with slide control. 6 axis IMU is the wave of the future i am sure. But for today, it is a linear 150mm potentiometer that reads the ups and downs of the road. Two thumbs up from me.
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post #3 of 24 (permalink) Old 04-30-2015, 04:02 PM Thread Starter
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I'm an engineer also and am very interested to learn the intricacies of how the system works. I have not been able to find very much information other than some very broad statements about stiffening the front for braking, and the rear for acceleration. There has got to be more going on than that. For example, does the DDC analize the sensors to determine if it is beneficial to soften the ride when it senses bumps? What parameters does the race calibration kit allow for adjustment? Can you tell it how much to stiffen or soften for certain events? It seems that with the huge variety of conditions encountered on the street that the 2d sensor would be just as beneficial as on the track.
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post #4 of 24 (permalink) Old 05-01-2015, 12:20 AM
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I'm an engineer also and am very interested to learn the intricacies of how the system works. I have not been able to find very much information other than some very broad statements about stiffening the front for braking, and the rear for acceleration. There has got to be more going on than that. For example, does the DDC analize the sensors to determine if it is beneficial to soften the ride when it senses bumps? What parameters does the race calibration kit allow for adjustment? Can you tell it how much to stiffen or soften for certain events? It seems that with the huge variety of conditions encountered on the street that the 2D sensor would be just as beneficial as on the track.

I have been working on understanding this 2D sensor because for me, as a racer, if I dont understand how something works, I cannot get all of it potential out of it. Some racers can just get on a bike, car, boat, airplane and just start going fast. Someone else sets up the race item, and they go.

Now the understanding every one should have is what works for one person will not work for another. I dont care if it a car or motorcycle.. what works for Rossi does not work for Lorenzo. There is somewhat base line however.

So the first baseline on the suspension is usually 30mm sag. That is a magic starting point and maybe if you weight in at 250 lbs, and you cannot find a spring to accomplish 30mm, you might have to live with 45mm. Just dont try to go 10mm sag. You unload the suspension over a rise, bump or whatever, the tire loses contact patch area.

Ok, I know the answer on a question I saw someone post in one of the other 2D sensor what does it do threads.

Why is 20mm important on the setup of the upper bracket. This bracket is on the fork tube. It can move up and down quite a bit. The answer is part of the picture I have attached to this posting as well. You are working with a 5V potentiometer that moves 150mm per say. This is a linear potentiometer. You have a starting point and an ending point.

CALIB > DONE ! 100% needed. Every time you try to CALIB it better hit DONE and not fail. I know now it is reading the potentiometer on the swing arm, and now my front 2D sensor. The voltage at SAG is a variable that is stored as an integer and used to know when the suspension is going up ( uncompressed ) and down ( compressed ) .. i dont care if your voltage is 1.01010 at SAG, this number is stored in the ECU when CALIB is started, and this process finishes with DONE. Anything else is wrong as in FAIL ..

POINT A is at rest 30mm SAG ( if we are using a baseline here ) Guess what the voltage is on the output signal of the 2D sensor is at 20mm ( there about starting point ) on the fork tube? 1.024 pretty much think that the engineer was shooting for 1.0V @ baseline SAG ( 30mm in my case today )

Now, the suspension needs to unload all the way on the front end... Why? We do wheelies on exit of corners since we have the most awesome S1000RR made today and wheelie control when set right will skim that front tire above the ground 6 inches. Well, the 2D sensor is now at .5V with the suspension unloaded. You do not want it at ZERO I can assure you. The engineer did not write the code to read a zero reading under proper setup and working function. That is NOT point B either. It is more like point C as in it travels the least amount but is so important that the ECU knows when lift is occurring beyond the accellometer telling it that wheelie is in action.

Now, the suspension needs to do it job with the front tire on the ground at what point? Bumps, rises, falls, BRAKING ! This is really where DDC shines.

Point B is anywhere from baseline SAG to bottom of fork.

Another point of interest. The 2D sensor is compressed 1 inch from baseline and guess what the voltage is.... 2.015V ( again see attached picture of how the linear voltage works )

We are at 5V @ 150mm stroke. I have never yet been on the brakes hard enough to compress my fork seal to the bottom of the tube stop.

This is all I know I can write about the sensor at this point. My mind is getting wore out for the day.

I cannot tell you anything about the software that controls DDC as I am pretty sure no on this forum can either. Dagor6 is about the only person I seen posting about the ECU workings in fueling, timing, and other aspects that Bren, OEMtune, Alpha.. are all wacking at each other on whos tuning what EFI the best.. No one fighting about tuning the DDC however and how it works that i have seen.

Really, we take a 2D sensor to the front end. Give the ECU information about travel up and down... DDC is applied in someway that some engineer spent countless hours writing code for.

It works and I wanted it, and I have it now.

Oh, I should note that the attached JPEG is my notes in the bottom right corner. I added those so I could remember what my numbers are couple weeks from now when I check them.
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Last edited by BMW_388; 05-01-2015 at 12:40 AM.
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post #5 of 24 (permalink) Old 05-01-2015, 08:48 AM
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Good info 388. The spec sheet you got that graph from has a lot of very useful info. I have been trying to see if its possible to make a front fork sensor that is a reasonable cost. It would be easy, except it looks like BMW has intentionally made the required resistance a lot lower than what is standard in industry. I feel like I have searched to the end of the internet. What is needed is a Linear Potentiometer with 150mm travel and 1.5k Ohm total resistance (10 ohm/mm). You could maybe use a 200mm travel, with correct resistance. If I could just find that, making a bracket would be cake. If anyone else takes up this quest, let me know. I should be able to make one of these for around $200 in parts.



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Last edited by sqft; 05-01-2015 at 09:04 AM.
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post #6 of 24 (permalink) Old 05-01-2015, 10:25 AM Thread Starter
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I build guitar amplifiers as a hobby. This seems like it should be fairly simple in theory. I'll take a look

Have you seen this..
http://alliancesensors.com/lp-22-ser...-potentiometer

does it have to be exact, meaning there is no calibration feature?

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post #7 of 24 (permalink) Old 05-01-2015, 11:00 AM
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Yes, its very simple in concept. The bike puts out a 5v reference signal, and looks for 0 to 5 v in return to determine position. The one you linked above is typical of whats available. They would be perfect if not for the fact that at 150mm size the ohms are at 5k. It needs to be more like 1.5K ohms, at max resistance.

Take a look at this spec sheet: http://www.2d-datarecording.com/Down...-000-DINA4.pdf

I know enough about electricity to just be dangerous. But maybe there is a way to use a higher resistance pot and still get the required volts output. Seems like it would need some sort of amp tho. From my calculations, I think the bike signal is 5 volts and about 3 microAmps.

Ive thought about going mechanical with some sort of gear or lever reduction, and using a higher ohm rated pot. But the suspension moves so much. What ever it was would take a severe beating, yet need to be incredibly low mass. Probably not practical.

Maybe this needs a new thread?

Last edited by sqft; 05-01-2015 at 11:08 AM.
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post #8 of 24 (permalink) Old 05-01-2015, 12:49 PM Thread Starter
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A circuit could be added to tweak the output. LDR optocouplers are good for this. It would be more elegant to not have to use such things but if it cuts the cost in half it would be worthwhile. I could design a circuit for this. 500 dollars does seem like an awful lot for a part that probably cost fifty to make. Ok, maybe it's more with mounting brackets but still.

Yes, I'm still interested to know more about what can be adjusted on the ecu for DDC parameters and how it works, but I don't mind the derailing of the thread
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post #9 of 24 (permalink) Old 05-01-2015, 01:40 PM
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If you can figure out the electrical side, I can fabricate just about anything.
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post #10 of 24 (permalink) Old 05-01-2015, 03:01 PM
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Spend $20k on a state of the art motorcycle but try and home-brew a solution to an existing $500 plug-and-play part. Makes perfect sense.

I've played with the DDC some in tuning Team Jilly's HP4 track bike. Nobody I've spoken to, so far, understands the control logic or tuning built into the system. I hope to learn more from Nate Kern at RR Fest.

From what I've been able to find out, as it applies to the HP4, the Rain and Sport modes have the same DDC setttings, fairly soft, and the Race and Slick mode have a second set of DDC settings, and they're stiffer. On the whole, the system has the same tuning philosophy as a conventional suspension, with the dynamic adjustment layered on top. For example, the presence of DDC doesn't affect whether or not you need more compression under braking; if you need more, add more. The DDC adjustments then start at that new setting baseline.

As with any motorcycle, the suspension and chassis geometry have to be set correctly. You may have to re-spring the bike to obtain the correct sag numbers. I'd also recommend increasing rear ride height.

In my opinion, the fork position sensor is a must. There are many times where you will want to adjust compression and rebound independently.

The DDC system seems designed to allow a somewhat plush and supple suspension when riding dynamics and forces are low - say going down a straight - but provide additional damping support when forces are increased - hard braking, hard acceleration. These characteristics are very nice for a street bike, but it's hard to see the benefit for a track bike (aside from the ability to interface the system with a GPS and map corner-by-corner settings). Like I said, I hope to learn more.
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