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Unread 25-05-2016, 15:27
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AKA: Scott Libert
FRC #2465 (Kauaibots)
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Re: NavX Calibration Advice

Quote:
Originally Posted by dithier View Post
Our team is starting to work on having our robot align to the target for shooting in the autonomous period and has decided to use the NavX-MXP. We've read that calibration is very important in order to get absolute heading, but I'm a little confused about calibrating the magnetometer based on our robot setup.

We can't use the default yaw axis orientation because of the orientation of our RoboRio and read on the navX website that we can use the OmniMount feature to adjust for this when needing yaw axis readings: http://www.pdocs.kauailabs.com/navx-...ion/omnimount/. Ours is mounted exactly like the picture on that site shows.

However, the magnetometer calibration page doesn't mention how to adjust calibration if the board is not in the expected orientation on the robot. Do we still follow the calibration method outlined on the website and just make sure that we are using it's "new" x,y,z axis when taking data points or is this not necessary? Lastly, should we be doing this calibration while the board is in the robot and the robot is on?
After you've performed the "Omnimount" configuration, and if you want to calibrate the magnetometer, do so using the Magnetometer Calibration tool, using the "new" x,y,z axis orientation - and this should be done while the board is on the robot, and the motors on the robot are *not being energized*. Take care as you perform this calibration to ensure the alignment is as accurate as possible, as this is key to achieving the best results.

Do note that many teams do not find they need the absolute heading data enabled by the magnetometer; instead, most teams use the yaw angle which is based upon fusion of the gyro and accelerometer data, and set the yaw to zero when the robot is in a known orientation relative to the field. So based upon your needs, magnetometer calibration may not be necessary.
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