Accelerometer uses? Electronics-geek stuff

[2much]

I am nearly an Engineer, and am building a Inertial Navigation system using Micro-Electromechanical Systems accelleromaters and Gyros with GPS updating using Kalman filters.

Will give pitch roll heading basically the full navigation solution, but the MEMS thingys have quite bad drift in the gyros etc which is why I am using the GPS to update its initial position estimates regulary to limit the effect of the drift.

Was going to trail it on my bike depending on how small I get it.

Oh please can I have a play? What a great way to measure the height/angle of your wheelies and stoppies!

[RantyDave]

An idea for use of the data from riding around on a motorbike. Just demostrating the lateral forces:

Eh?

That's just my point, from the perspective of something rigidly mounted on the centre of gravity of the bike+rider there are no lateral forces. All the forces act directly "down" through the wheels. Even when cornering. If it wasn't for riders hanging off (which buggers up our sums by changing the CoG) then you'd be able to calculate the centripetal acceleration acting on a bike purely by looking at it's lean angle.

I'd suggest reversing the operation and calculating lean angle by measuring force acting downwards from the bike's perspective, but that wouldn't work because you'd get false numbers when the bike accelerates in the vertical plane for some other reason - going up a hill, hitting a bump, running over a toddler ... that sort of thing.

We're easily getting into the "needing a piece of paper" territory here. Which means only one thing, needing a pub. Should we reconveine the KB bike telemetry and shit talking project after TCWNR at some point?

Dave

[skelstar]

Could do re: pub. Weds is 'visiting my non-mb mates' night at the moment.

Maybe Newbies ride this month.

Theory: you are right Dave. Peice of paper and workmates and we have worked it out (with your guiding ).

All of the force is directed straight down through the tyres/seat. ie in the vertical plane of the bike (g in pic). We know what the force is due to gravity. So if we drew a vector triangle (see pic), we know two sides v and g, so we can measure the angle. Going up and down hills/slopes will be an issue though. Not too bad on the track though.

[stanko]

You could make a Dynomometer. You can measure rpm, the mass of the bike and the acceleration So you should be able to calculate the horsepower of the engine. its just like a rolling road dyno except instead of accelerating the known mass of the drum you use the mass of the bike. Needs maths that I cant comprehend - but talks cheap!

[skelstar]

Woo, another idea: put a sensor above the back wheel (measuring in the vertical axis) and a sensor on the swing arm (again measuring in the vertical axis). Take the difference between the two signals....shows how the suspension is travelling for suss settings...

[RantyDave]

You could make a Dynomometer.

Absolutely! The maths is easy, the hard part is opening the throttle and leaving it absolutely _pinned_ until you get to max RPM.

"But we were doing a dyno run, officer"

Dave

[sAsLEX]

Woo, another idea: put a sensor above the back wheel (measuring in the vertical axis) and a sensor on the swing arm (again measuring in the vertical axis). Take the difference between the two signals....shows how the suspension is travelling for suss settings...

Linear potientiometer would be a million times easier

[skelstar]

But a potentiometer isnt going to tell you what the whole bike is doing force-wise, only the seat. All bumps/corners are not created equal.

[sAsLEX]

But a potentiometer isnt going to tell you what the whole bike is doing force-wise, only the seat. All bumps/corners are not created equal.

Keep the strapdown INU on the bike and have the potientiometer as well, should be easy to log another signal that needs little maniupulation compared to another accelerometer etc

[skelstar]

True, but if you have two devices (very cheap I think) that are reading with the same magnitude and can be setup exactly the same, then they are easy to compare against each other. Besides, you are going to be using an ADC for the pot or accelerometer anyway. I like avoiding using mechanical devices anyway. These units can be potted in resin and would be near bullet-proof.

[sAsLEX]

Datasheet for said device is here:
http://www.ortodoxism.ro/datasheets/...L150_250_0.pdf

heres my beastie http://www.cloudcaptech.com/crista_imu.htm

[skelstar]

Looks pretty cool. Cost?
Found another chip by freescale that is 3D and is pin configurable for 1.5G,2G,4G, 6G...US$10. Measures 6mm x 6mm.

[sAsLEX]

Looks pretty cool. Cost?
Found another chip by freescale that is 3D and is pin configurable for 1.5G,2G,4G, 6G...US$10. Measures 6mm x 6mm.

No Idea, I aint paying.

[R6_kid:Me]

i've seen a fully done setup for sale on trademe for around $750, had a digital output on it so you could see what was going on at any given time, and also a computer output.

I think some skylines came out with one inbuilt into the dash, so there is a use there. If it works i'll take one. I find stuff like that really interesting, even if i cant really work out what it means

[FlyingDutchMan]

I've been working with an accelerometer at work. Goes +-3G in two axis. Quite a cool little thing, but as discussed ealrier on, its not much good for accurately measuring lean angles. If its static, it can measure them pretty good - but to make sure you've got a good reading, you have to take the ambient temperature into account.