Magnetometer Calibration - Kauai Labs VMX-pi User Manual

Robotics controller/motion & vision processor

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Reference manual (25 pages)

Table Of Contents

Table of Contents

Guidance

Gyro/Accelerometer Calibration

NOTE: If VMX-pi is moving during startup, this Yaw Offset Calibration may take much longer

than 2 seconds, and may not be calculated at all if the sensor continues moving long enough.

Therefore it is highly-recommended to keep VMX-pi still until initial calibration and Initial Yaw

Offset calibration completes.

On-the-fly Gyro Calibration

In addition to Startup Calibration, during normal operation VMX-pi will automatically re-calibrate

the gyroscope (e.g., to account for ongoing temperature changes) during operation, whenever it

detects 8 seconds of no motion. This process completes after about 7-8 more seconds, and is

completely transparent to the user. Therefore each time VMX-pi is still for approximately 15

seconds, the gyroscopes are re-calibrated "on-the-fly". The purpose of On-the-fly Gyro re-

calibration is to help maintain yaw accuracy when shifts in ambient temperature occur during

operation.

This On-the-fly Gyro Calibration can help deal with cases where the sensor was moving during

Startup Calibration, but note that the yaw is not zeroed at the completion of On-the-fly

Calibration. So once again, it's important to keep the sensor still during Startup Calibration.

Runtime Yaw Zeroing

Your robot software can optionally provide the robot operator a way to reset the yaw angle to

Zero at any time. Please see the documentation for the

The importance of stillness

This is the most important takeaway from this discussion: It is highly-recommended that VMX-pi

be held still during the above Initial Gyro and Initial Yaw Offset calibration periods. In support of

this, VMX-pi indicates when it is calibrating; we recommend you incorporate this information into

your software. Please see the discussion of the navXUI, and the

details on this indication.

VMX-pi onboard orientation sensors require calibration in order to yield optimal results. We

highly recommend taking the time to understand this calibration process – successful calibration

is vital to ensure optimal performance.

Careful and accurate Magnetometer Calibration is crucial in order to yield valid compass

heading, 9-axis heading and magnetic disturbance detection.

Magnetometer Calibration is not typically required for use in many robotics applications,