[sdiy] How to explain how negative feedback lowers noise?

chris chris at chrismusic.de
Tue Mar 23 17:13:52 CET 2021


um, not quite. The steering is self-centering, that's right. 

But once you're off-axis with regard to the street you'll hit the curb
eventually. In a straight line.
Unless you're riding on a bobsleigh track, that is...

Chris



On Tue, 23 Mar 2021 16:05:41 +0100 Ben Stuyts <ben at stuyts.nl> wrote:

> Actually :-) the suspension system of a car itself corrects it to a straight line. (Assuming the alignment is in order, of course.) This is due to the positive caster angle of the front suspension. The more a wheel veers to the side, the greater the force to repel it back to the center position will become. As such, it is an excellent example of negative feedback. No human wetware in the loop is needed.
> 
> https://en.wikipedia.org/wiki/Caster_angle <https://en.wikipedia.org/wiki/Caster_angle>
> 
> Ben
> 
> > On 23 Mar 2021, at 14:01, Ian Fritz <ijfritz at comcast.net> wrote:
> > 
> > Or driving a car. If it veers to the right, you steer towards the left to correct it.
> > 
> >> On Mar 23, 2021, at 6:33 AM, thresholdpeople via Synth-diy <synth-diy at synth-diy.org> wrote:
> >> 
> >> Negative feedback is something that's applied to everyone's actions all the time. It also tends to bring systems/attempts to into equilibrium.
> >> 
> >> Something as 'simple' as correcting your walking trajectory: if you see someone else walking toward you perpendicularly and you anticipate that you will both collide, so you adjust.
> >> 
> >> Thermal regulation: you overheat, so your body generates sweat to cool your body. If you cool down too much, your body begins to convulse, shivering to warm the body up through movement.
> >> 
> >> It's also at the core of cybernetics, through which it's applied to many systems- human, natural, machine- and as a consequence through parallels of regulation and understanding of those systems in that way comes the tendency to bundle all those up into one.
> >> 
> >> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> >> 
> >>> On Tuesday, March 23rd, 2021 at 7:55 AM, cheater cheater <cheater00social at gmail.com> wrote:
> >>> 
> >>> Ok but if feedback increases linearity then:
> >>> 
> >>> Without feedback we have less linearity, therefore the original signal
> >>> 
> >>> comes with a bunch of distortion products. Meanwhile the noise can
> >>> 
> >>> keep raising in power longer before it starts clipping. So in that
> >>> 
> >>> case, you're actually increasing noise, while the signal doesn't
> >>> 
> >>> increase, only its distortion products.
> >>> 
> >>> Is this logic correct?
> >>> 
> >>>> On Mon, Mar 22, 2021 at 9:17 PM Gordonjcp gordonjcp at gjcp.net wrote:
> >>>> 
> >>>>> On Mon, Mar 22, 2021 at 06:40:52PM +0100, cheater cheater wrote:
> >>>> 
> >>>>> feedback and not some form of other regulation. What's a simple
> >>>>> 
> >>>>> /physical/ negative feedback?
> >>>> 
> >>>> The throttle on your lawnmower. The throttle cable has a spring that pulls the throttle butterfly in the carb open, and a wire link to a flappy thing beside the cooling fan. The faster the engine goes, the more the cooling fan blows on the flappy thing, which pulls the throttle closed against the spring.
> >>>> 
> >>>> When you hit a big divot of couch grass with the blades the engine revs drop, the cooling fan doesn't blow as hard, and the flappy thing gets pulled in by the spring opening the throttle. As the engine speeds up it blows the flappy thing back again and pulls the throttle shut until the revs settle, with the engine making more power.
> >>>> 
> >>>> Once the blades have chewed their way through the couch grass the engine will rev up freely, the flappy thing will get blown out further, the throttle will close, and the revs will stabilise again.
> >>>> 
> >>>> When you're done you push the throttle to idle relaxing the tension on the spring (your control input) and the flappy thing will blow further out again because the spring isn't holding it, and close the throttle.
> >>>> 
> >>>> --
> >>>> 
> >>>> Gordonjcp
> >>>> 
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