Magnetometer Accuracy and Calibration problems - Sensor Fusion NXP Libraries

[Dario_]

I am working on a project of a robotic arm that has to be oriented to the north. To perform this task we are using the development kits FRDM-KL25Z, FRDM-STBC-AGM01 (FXAS21002C3, FXOS8700C) and the NXP Sensor Fusion Library v7.0. We are applying the 9-axis Gyro Stabilized Compass algorithm to compensate for magnetic noise from the environment. We are also using the NXP Sensor Fusion Toolbox software at this design stage as a tool to analyze the magnetic noise of the device environment.

I have the following two questions:

1- We are having some magnetic noise problems, as we have 3 stepper motors running during the magnetometer calibration process. To solve this error we are trying to make a structure to distance the sensors from the motors and analyze how it responds. This would be the only way to find a solution to this problem or through the NXP Sensor Fusion software libraries I could modify some configuration parameter to be able to find a better answer to this error?

2-The other query is that we need a precision of the order of 0.5 degrees of pointing to the north. Can we get this precision with these kits, sensors and the Sensor Fusion Library?

Thank you very much for your time.

Best Regards

Darío

[diazmarin09]

Hello Dario,

I hope this response finds you well.

Please note that both devices are obsolete (FXAS2100 and FXOS8700C). You may consider such device status for your future designs.

1. You are correct, such devices are typically used for eCompass applications to measure the earth magnetic fields and find the magnetic north. I am afraid that the stepper motors are, indeed, a source of magnetic noise. I highly recommend to increase the distance between the sensor and the motors.

You may review the documents below for further information:

Layout Recommendations for PCBs Using a Magnetometer Sensor

Calibrating an eCompass in the Presence of Hard- and Soft-Iron Interference

2. There is an application note that mentions how to calculate the Accuracy of Angle Estimation in eCompass and 3D Pointer Applications, please find this document in the following link:

Accuracy of Angle Estimation in eCompass and 3D Pointer Applications

I hope this information helps.

Regards,

David