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scott wrote:
>> ...not to mention traction control... ;-)
>
> Er yeh, that's what I meant by wheel-spin.
ABS turns the brakes off if you brake too hard, traction control turns
the drive off if you accelerate too hard. At least, as far as I know... ;-)
> OOC I looked up the
> instructions for how a dealer fits the "USB Audio" upgrade to my car (I
> was just wondering if the cables were already there and I simply needed
> to fit a suitable plug - sadly not). Anyway, it appears my car has a
> network of fibre optic cables o_O.
Well... less suseptable to EMI and corrosion?
> To fit the upgrade, apparently
> involves ripping out half the car, making some connection to a box of
> opto-electronics in the boot, then fitting a "USB hub" under the drivers
> seat and fitting the USB socket in the centre console, and of course
> fitting cables between all of them. The 250 pound price tag doesn't
> sound so bad now!
LOL! Yeah. Apparently modern cars have quite big wiring looms inside
them now. I remember one guy did some work on his own car, and then had
to pay for an accredited shop to confirm that the airbag detonation
system is still operating within spec.
Seriously though, you'd think they'd just put lots of spare cable in
there so you can add new connections without rearranging half the car...
>> The part I can't figure out is that, as far as I can tell, hooking up
>> a motor that turns the steering wheel in the same direction as you're
>> trying to turn it should generate a positive feedback loop. I can't
>> figure out how turning the wheel doesn't cause the powerful motors to
>> rip the wheel out of your hands and put the car into full lock before
>> snapping the steering column in half...
>
> If you simply program the motor to apply the same torque you are
> applying with your hands to the wheel, then there is no feedback, it
> will just feel like it takes half the force to turn it. Of course in
> reality it is more complex, the multiplier is probably dependant on
> speed, and maybe other factors like how sharp you are turning. And
> maybe there is some limit the torque you apply needs to go above before
> the motor kicks in?
Oh, it's programmable? I thought it was a purely mechanical system...
Even so, how can you "sense" the amount of force the user it putting
into the system seperately from the amount of force the power assist is
putting into it? I can't think of a way of doing that.
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> ABS turns the brakes off if you brake too hard, traction control turns the
> drive off if you accelerate too hard. At least, as far as I know... ;-)
Newer cars can apply the brakes too programmably, it's much faster than
cutting the fuel and more accuracte, and when you are about to skid out
sideways on a slippery road fast reactions are what you need.
> Well... less suseptable to EMI and corrosion?
Yeh the EMI issue is probably the biggest reason, especially now that they
seem to be wanting to put more stuff in the back of the car to keep the
weight distribution 50/50, it means you have long wires which are always bad
from an EMI point of view.
> Seriously though, you'd think they'd just put lots of spare cable in there
> so you can add new connections without rearranging half the car...
Guess it's cheaper not to, and then charge more for people who want to do
stuff afterwards.
> Oh, it's programmable? I thought it was a purely mechanical system...
Older cars it was mechanical, yes, programmable (once!) by the positioning
of the hydraulic valves :-) Newer cars it's all electronic controlling a
motor in software.
> Even so, how can you "sense" the amount of force the user it putting into
> the system seperately from the amount of force the power assist is putting
> into it? I can't think of a way of doing that.
Measure how much the steering column is twisted (ie rotation at one end
minus rotation at the other end) between the steering wheel and where it
connects to the rack/motor/hydraulics. This will be directly proportional
to the torque the driver is applying to the wheel, no matter what the motor
or the wheels are doing.
In mechanical systems, this twist would cause hydraulic valves to open and
assist the rack moving, in electronic systems there is probably just a
strain gauge on the steering column that goes through an ATD to the
software.
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scott wrote:
>> Well... less suseptable to EMI and corrosion?
>
> Yeh the EMI issue is probably the biggest reason.
There would seem to be quite a lot of electronics in a car - especially
a big alternator and a set of sparkplugs. That's gotta kick out a out of
EMI, one would think...
>> Even so, how can you "sense" the amount of force the user it putting
>> into the system seperately from the amount of force the power assist
>> is putting into it? I can't think of a way of doing that.
>
> Measure how much the steering column is twisted (ie rotation at one end
> minus rotation at the other end) between the steering wheel and where it
> connects to the rack/motor/hydraulics. This will be directly
> proportional to the torque the driver is applying to the wheel, no
> matter what the motor or the wheels are doing.
>
> In mechanical systems, this twist would cause hydraulic valves to open
> and assist the rack moving, in electronic systems there is probably just
> a strain gauge on the steering column that goes through an ATD to the
> software.
I was under the impression that the rod is ridig, and therefore can't
twist (only rotate).
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> I was under the impression that the rod is ridig, and therefore can't
> twist (only rotate).
Nothing is perfectly rigid, a strain gauge on the rod will easily pick up
the twist in a rod accurately enough to determine the torque and angle it is
twisted.
On the older style mechanical systems they probably have a special small
section that is a more flexible than the actual rod, that incorporates the
valve design etc.
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scott wrote:
>> I was under the impression that the rod is ridig, and therefore can't
>> twist (only rotate).
>
> Nothing is perfectly rigid, a strain gauge on the rod will easily pick
> up the twist in a rod accurately enough to determine the torque and
> angle it is twisted.
>
> On the older style mechanical systems they probably have a special small
> section that is a more flexible than the actual rod, that incorporates
> the valve design etc.
Mmm, OK.
Presumably you want it to not be *too* flexible though, lest the power
steering mechanism stops working. It would be nice to still be able to
steer. ;-)
Tell me, does this mean that there's no such thing as an inelastic
collission outside of textbooks?
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Invisible <voi### [at] dev null> wrote:
> OOC, how much snow is there in the various other parts of the world
> where POVers are reading this??
Last Wednesday morning we had 12 inches. When I looked outside, my Miata wasn't
much more than a bump in the driveway. Since I live on a side road that usually
doesn't get plowed till late, I turned around and went back to bed. Didn't make
it out until about 3PM. All the roads are now clear, but we still have 8 to 10
inches of snow still on the ground.
Isaac
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Clarence1898 wrote:
> Last Wednesday morning we had 12 inches. When I looked outside, my Miata wasn't
> much more than a bump in the driveway. Since I live on a side road that usually
> doesn't get plowed till late, I turned around and went back to bed. Didn't make
> it out until about 3PM. All the roads are now clear, but we still have 8 to 10
> inches of snow still on the ground.
12 inches. Now that sounds like an actual snowfall.
OOC, where is this?
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> Presumably you want it to not be *too* flexible though, lest the power
> steering mechanism stops working. It would be nice to still be able to
> steer. ;-)
Well yes, I assume we're talking about "flexible" enough to allow a tiny jet
of hydraulic fluid to open under really vigorous steering, not a bit of
rubber that's going to twist through 180 degrees :-)
> Tell me, does this mean that there's no such thing as an inelastic
> collission outside of textbooks?
YOu mean no such thing as an *elastic* collision? No, not at a macroscopic
level. Any collision is going to lose some energy to sound, heat, plastic
deformation etc, some things get pretty close though.
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Invisible <voi### [at] devnull> wrote:
> Clarence1898 wrote:
>
> > Last Wednesday morning we had 12 inches. When I looked outside, my Miata wasn't
> > much more than a bump in the driveway. Since I live on a side road that usually
> > doesn't get plowed till late, I turned around and went back to bed. Didn't make
> > it out until about 3PM. All the roads are now clear, but we still have 8 to 10
> > inches of snow still on the ground.
>
> 12 inches. Now that sounds like an actual snowfall.
>
> OOC, where is this?
Indianapolis. This was the worst snow in about 5 years. Normally we'll get a 6
to 8 inch fall sometime during the winter. So a little worse than usual but not
terrible.
Isaac
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>> OOC, where is this?
>
> Indianapolis. This was the worst snow in about 5 years. Normally we'll get a 6
> to 8 inch fall sometime during the winter. So a little worse than usual but not
> terrible.
Mmm, interesting. My company's HQ is in that state...
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