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Topic: Using accelerometer to detect driving state(s) (Read 4 times) previous topic - next topic

Fabio Varesano


jraskell

Your scenario isn't nearly as simple as it's being portrayed, and your end goal is going to dictate the best method of reading/detecting braking to accomplish that.

1.0-1.2g braking is likely max braking for most vehicles under ideal conditions.  Dirt roads, dirt on the road, rain, snow, will all have a significant impact on max braking forces.

Most normal driving will also never see anywhere near 1.0-1.2g of braking.  More likely to be around 0.5g for normal daily driving (maybe even less for some people).  So are you looking to detect any normal braking event, or are you looking to detect some sort of emergency stop situation (in which it is assumed that you are braking as hard as possible)  Are you going to be doing anything when this is detected that could be problematic if it's just a case of the person stopping really hard just for the fun of it?

liudr

According to simple law of physics, the static friction is only a small portion of gravity of an object, the factor is called static frictional coefficient. Unless you have some tank tracks or sticky surfaces (spider man), you will not have a static friction that exceeds gravity. So you will not have a deceleration greater than g.

Somebody has something to say about this coefficient for tire on dry road:

http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/frictire.html

As for the braking thing, I think you should ride with an accelerometer and record the entire process of a number of hard breaks, soft breaks and what not so you have data to look at. Without data, I could argue 0.5g is trigger and needs to be at 0.5g+ for 0.1 second and you say different and neither has proof this is what actually happens.

AWOL

Quote
So you will not have a deceleration greater than g.

Brick wall?
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

liudr


Quote
So you will not have a deceleration greater than g.

Brick wall?

OP was talking about braking. There is no collisions involved.

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