Author Topic: integration of gryo and blending with accelerometer problems.  (Read 901 times)

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Offline eaydsjjTopic starter

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integration of gryo and blending with accelerometer problems.
« on: August 06, 2011, 11:29:21 AM »
Hi,

I've been going a little crazy lately trying to get the gyro and accelerometer from my idg300 and adxl335. The sensor raw voltage inputs into the analogue module in my compactrio seem fine. However when i integrate the gryo values after taking away the offset and dividing by the sensitivity i don't get the right answers. They seem to always be roughly 2.4 times smaller than they should be.

I have also tested the accelerometer values which seem fine. I divided the raw voltages by the sensivity and then did the arcsin to find the tilt angle. These came out fine but of-course were noisy results.

Does anyone know why the integrated values could be incorrect? I have tried all different types of integrating in labview and it always comes out with the same results.

Also i'm trying to blend the accelerometer and gyro angles to give an accurate angle that doesn't drift and isn't noisy. I'm using the complimentary filter code in labview that can be found on the internet everywhere:

angle = 0.98*(angle + rate*dt) + 0.02*accelerometer angle

By changing the constants (0.98 and 0.002) i can vary how much of each to blend in but i cannot get rid of the drift(i'm multiplying the gyro angle by 2.4 to give a more accurate angle but not feeding it into the integration so it doesn't affect things) If i use a crazy amount of accelerometer angle then the drift is pretty much gone but the results are too noisy to send to a motor. Does anyone have any idea why this is so? It seems to work for other people's examples on the internet.

Here is a link to the same post on the national instruments forum but it has attached my word file with the sensor results from testing. The attachment was too big to attach here.

http://forums.ni.com/t5/LabVIEW/integration-of-gryo-and-blending-with-accelerometer-problems/td-p/1661374

Many thanks for any help any one can give,

Sam

 


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