FUSION FREQUENCY

[giannigrondona]

Hi

I am using SENSOR FUSION Library ver 7.0 with FXOS8700 sensor and the algorithm I do intend to use is compass with tilt compension.

I need to run FUSION ALGORITHM at a very low frequency ( 2 HZ) because of consumption issue The sensor reading routines run at faster speed (about about 8 HZ).

I'd like to know if algorithm can work at low speed ( 2HZ)

Thank you

Giovanni Grondona

[lisettelozano]

Hello Giovanni,

Thank you for your patience.

As mentioned before, the Sensor Fusion Library mentioned that the minimum recommended for the FUSION_HZ values is 25Hz in section 5.2 Sample and fusion rate topics in the Sensor Fusion User Manual.

Using the Tilt Compensated Compass at a frequency less than 25Hz can cause accuracy issues (due to noise) and could result in discrepancies in orientation calculations.

For example, the magnetometers have about 1uT of noise and this noise impacts orientation computations. We use Kalman filtering to estimate the orientation by combining measurements from both accelerometer and magnetometer (in this case), in the presence of noise. These filters work better with more samples and hence, 25Hz was determined to give acceptable performance.

I hope this information can be helpful.

Have a great day,

Paulina

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[lisettelozano]

Hello Giovanni, 

By giving a double check to the Sensor Fusion User Guide, it looks like it is a fixed rate use in order to cover the different sensors. I'll need to double check internally if this is something that can be done and provide you more information as soon as I have it. I appreciate your patience on this. 

Have a great day, 

Paulina