MotionFX has default bias on gravity with perfect data

[vlad_kost]

Hello,

I am using MotionFX on STM32BlueCoin device. I tested values of linear_acceleration and gravity from MotionFX library, and I have very strange bias on produced values, although I try to feed perfect hardcoded data to the library.

For example I always send MotionFX 6X input data as following, Accelerometer x=0, y=0,z=-9.81, Gyro x=y=z=0

In return, I have strange values on the gravity axis.

 

INFO:__main__:Gravity -> x: 0.0000, y: 0.0000, z: -10.0000
INFO:__main__:Linear Acc -> x: 0.0000, y: 0.0000, z: -0.1890
INFO:__main__:Gravity -> x: 0.0000, y: 0.0000, z: -10.0000
INFO:__main__:Linear Acc -> x: 0.0000, y: 0.0000, z: -0.1890
INFO:__main__:Gravity -> x: 0.0000, y: 0.0000, z: -10.0000
INFO:__main__:Linear Acc -> x: 0.0000, y: 0.0000, z: -0.1890

 

 Why is gravity Z always 10? Shouldn't it be 9.81 in perfect condition? Why linear_acceleration have this strange value of -0.189?

I tried to change many knobs parameters, but I couldn't even change it a bit.

[Federica Bossi]

Hi @vlad_kost ,

It is not a problem of the set parameters but a slight error is expected by the system, the difference is very little.