Accelerometer to get Position
Accelerometer to get Position
(OP)
My customer wanted us to use an accelerometer to get the curve of the velocity over the position.
We used a 3 axis sensor, with analog output. Here we used a 12 bit ADC.
Now all the effort has been done, but we cant get the exact position of the movement, which is a movement in just one axis. Customer may want to bring new axes in future as well. As we did integration over the acceleration and then over the velocity, we get very diverse results, but none of them matches by far with the real distance which was carried out.
Especially if you put two sensors on the same movement they will surely give very different results.
Now customer wants dearly a result for the position with max 10% error.
We are a little bit clueless what to do to get the exact position, we even envisage in using a different sensor with more precision. But still there would be error at integration, which cant be avoided.
Has anybody some experience with getting position out of acceleration?
I am really thankful to any suggestion.
Regards, Ina
We used a 3 axis sensor, with analog output. Here we used a 12 bit ADC.
Now all the effort has been done, but we cant get the exact position of the movement, which is a movement in just one axis. Customer may want to bring new axes in future as well. As we did integration over the acceleration and then over the velocity, we get very diverse results, but none of them matches by far with the real distance which was carried out.
Especially if you put two sensors on the same movement they will surely give very different results.
Now customer wants dearly a result for the position with max 10% error.
We are a little bit clueless what to do to get the exact position, we even envisage in using a different sensor with more precision. But still there would be error at integration, which cant be avoided.
Has anybody some experience with getting position out of acceleration?
I am really thankful to any suggestion.
Regards, Ina





RE: Accelerometer to get Position
You will save yourself grief if you take a look at some of the articles relative to inertial navigation errors available on the web.
Perhaps you should consider GPS solutions?
Good Luck,
Doug
RE: Accelerometer to get Position
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Accelerometer to get Position
Displacement sensor i cant also use, as everthing should be tiny, work on battery and inside a box full of materials. So a chip solution is desirable.
RE: Accelerometer to get Position
RE: Accelerometer to get Position
Yup. And that's the way it is. Sorry about that. Bob's suggestion may make things better, but equally it could make things worse (imagine what it would say about the displacement of a body in free fall).
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Accelerometer to get Position
1)Do you have a large amount of data showing measured acceleration, accurate velocity and accurate displacement?
2) Is the system well defined? That is, are there constraints on how the thing moves?
3) Is it possible to sense the exact location at some point in the machine's cycle?
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: Accelerometer to get Position
To your questions:
1. Yes we are sampling with 100 Hz. We may try to sample with 1000 Hz. The sampling period is usually 5 seconds.
2. the current movement we are looking into is running in just one axis. It is on a rail.
3. for testing purposes we can sense the exact location. But when it is running we have no influence on the speed, stop movement, backward movement and thats what we need to sense.
RE: Accelerometer to get Position
RE: Accelerometer to get Position
Mike Halloran
Pembroke Pines, FL, USA
RE: Accelerometer to get Position
RE: Accelerometer to get Position
Yes, linear circuits, which do not suffer from sampling error or quantization error.
When they were in vogue, 'tiny' meant something different than it does today. That could be a challenge.
Mike Halloran
Pembroke Pines, FL, USA
RE: Accelerometer to get Position
Regards
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RE: Accelerometer to get Position
Eric Ratliff
http://www.icpdas-usa.com