PDA

View Full Version : Scary :speechless:


Jason C
07-25-2005, 07:11 AM
So as I creep ever-closer to the first of the BMW classes, I've started to look more *in-depth* into the operations of your average "modern" BMW. How these things manage to go down the road without grinding to an irreparable halt, I don't know. And that's the amazing thing, really - when learning more about cars, the oft-heard observation is not "Wow, it's so cool that it works that way!" but more "Damn, I can't believe they actually make all this shit work, and that it don't uselessly leave their owners on the side of the road all the time."

So what kind of madness am I talking about? Here's the BUS SYSTEM structure of our favorite bangle-fied 7-series. It has been posted before:

http://forums.carmudgeons.com/album_pic.php?pic_id=661


And here it is, the legible edition:

http://forums.carmudgeons.com/album_pic.php?pic_id=819



Let's zoom in on the K-CAN S and K-CAN P area (K-CAN stands for Body-Controller Area Network):

http://forums.carmudgeons.com/album_pic.php?pic_id=820

Inside it , we find the following computer modules:

K-CAN S - Body-CAN System
Automobile body main line system

AHM----TRAILER module
BZM----CENTER console operating center
BZMF----CENTER console operating center rear
CIM----CHASSIS integration module
CON----CONTROLLER
DWA----ANTI-Theft alarm system
IHKA----INTEGRATED heating and air conditioning
LM----LIGHT module
PDC----PARK distance control
RDC----TYRE pressure warning system
RLS----RAIN/LIGHT sensor
SH----PARK heating
SHD----SLIDE/TILT sunroof
WIM----WIPER module


K-CAN P - Body-CAN Periphery
Automobile body periphery main line

CAS----CAR access system
HKL----TAILGATE lift
PM----POWER module
SMBF----PASSENGER seat module
SMBFH----PASSENGER seat module rear
SMFA----DRIVER seat module
SMFAH----DRIVER seat module rear
TMBFT----DOOR module passenger door
TMBFTH----DOOR module passenger door rear
TMFAT----DOOR module driver door
TMFATH----DOOR module driver door rear


Those aren't even the fiber-optic networks (that would be MOST and byteflight).

More in the next few months.

"You just ask some of the students here and they'll tell ya - how hard can it be, power window controls? You think, it's a power window - I press the button, it goes up, it goes down. There! That's it. Simple as that. Oh no, it isn't! You got regular up, down, soft up and down, one-touch up and down, you can do it with the turn of the key, the keyfob, anti-trap, disabling anti-trap for the windows AND the moonroof, two different modes when disabling it..." -BMW Instructor

bren
07-25-2005, 09:50 AM
Let me know when they start hiring network admins to work on these things. :)

rumatt
07-25-2005, 10:18 AM
Let me know when they start hiring network admins to work on these things. :)
:lol:

I've wondered for a long time how cars, as well as other things like planes, etc, don't fail more often as their complexity increases.

In the software industry, the complexity of the software produced is well beyond the developers and testers ability to understand it completely and test it fully. Hence, software sucks ass, and crashes all the time.

Why it's not the same for cars, planes, bridges, etc.. I don't know. Maybe just just spend more on testing because problems are more costly to fix than they are in software?

John V
07-25-2005, 10:34 AM
Let me know when they start hiring network admins to work on these things. :)
:lol:

I've wondered for a long time how cars, as well as other things like planes, etc, don't fail more often as their complexity increases.


Redundancy and frequent inspections? I don't know much about planes but I suspect there is a lot of redundancy in the critical control paths.

dredmo
07-25-2005, 10:47 AM
Let me know when they start hiring network admins to work on these things. :)
:lol:

I've wondered for a long time how cars, as well as other things like planes, etc, don't fail more often as their complexity increases.


Redundancy and frequent inspections? I don't know much about planes but I suspect there is a lot of redundancy in the critical control paths.

There is, I worked on them as an avionics tech for four years. The USAF uses double and triple redundant systems on everything. I was a C-5 tech, some of the best years of my life.

The only other thing I would add is that buses, on paper, look deceiving. There is a complex modulation/demodulation scheme involved. It is like a signal heirarchy or route, to put it simply,messages rarely get crossed or interfered with as long as mod/demod and terminations are used correctly.

blee
07-25-2005, 10:54 AM
Don't forget that a software crash in a moving vehicle can be deadly. A software crash in most office environments is just really annoying. My guess is that vehicle systems are actually less complicated than most software packages, that they have some level of redundancy built in, and that they're tested as rigorously as possible during development. After all, it still takes manufacturers over a year to develop a new model; that's enough time to work out the kinks if everyone works hard.

dredmo
07-25-2005, 11:19 AM
Don't forget that a software crash in a moving vehicle can be deadly. A software crash in most office environments is just really annoying. My guess is that vehicle systems are actually less complicated than most software packages, that they have some level of redundancy built in, and that they're tested as rigorously as possible during development. After all, it still takes manufacturers over a year to develop a new model; that's enough time to work out the kinks if everyone works hard.

Right, but theoretically, car computers are fail safe, and individual components should not crash in a way to interfere with other components.... theoretically... :lol:

clyde
07-25-2005, 11:53 AM
Don't forget that the software running in cars is generally running on a known specific set of hardware without competition from other unknown application that may or may not be running (and specifically, running properly) all on top of a bug filled OS (for these purposes, I'm referring to ALL desktop OSs).

FC
07-25-2005, 01:53 PM
Don't forget that the software running in cars is generally running on a known specific set of hardware without competition from other unknown application that may or may not be running (and specifically, running properly) all on top of a bug filled OS (for these purposes, I'm referring to ALL desktop OSs).

Right. It's more like a gaming console.

ff
07-25-2005, 02:12 PM
Don't forget that the software running in cars is generally running on a known specific set of hardware without competition from other unknown application that may or may not be running (and specifically, running properly) all on top of a bug filled OS (for these purposes, I'm referring to ALL desktop OSs).

Excellent point. And the software in your car is (I guess) running on a more simple set of variables and assumptions. The PDC system just has to relay an object's distance back to the computer. If the distance is, say 3 feet, beep once every second. If it's at 2 feet, beep every .5 seconds. It's not like the computer is expected to take any other types of possible signals from the PDC sensors, the way computer software needs to predict what any given user might do next.

Jason C
07-25-2005, 07:18 PM
The PDC system just has to relay an object's distance back to the computer.

That's wrong, the PDC module handles more functions than that (6 separate areas, to be exact). But it's a common mistake to look at a module and say "Gee, it's name is so-and-so, therefore it just does this."