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kriswiner / MPU9250

Arduino sketches for MPU9250 9DoF with AHRS sensor fusion
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How can I get the bias of Acc and Gyro? #39

Open ijunglee opened 8 years ago

ijunglee commented 8 years ago

Hello, I would like to ask that how to get the bias of Acc and Gyro? I'm not really sure for that...... I let the IMU be flat on the table with Z-axis toward up, and then I get the average value of 1000 records of Ax, Ay, Az. The value should be 0, 0, 1, but the values I got are -0.2, -0.06, 0.96. Is the bias of Acc 0.2, 0.06, 0.04? So I have to add 0.2, 0.06, 0.04 to all of values of Ax, Ay and Az. Is this right? Can I use the method to get the bias of Gyro, too? I think it should be 0, 0, 0 deg/sec when it is flat on the table. Thank you very much!

kriswiner commented 8 years ago

What you describe is basically correct I just don't know if the numbers you are quoting are millig or counts or what. As long as they are consistent this procedure should work well. The bias values must be subtracted from the subsequent data. The same procedure can work for the gyro too. Magnetometer is different. You can read about a successful strategy here:

https://github.com/kriswiner/MPU-6050/wiki/Simple-and-Effective-Magnetometer -Calibration

Kris

-----Original Message----- From: ijunglee [mailto:notifications@github.com] Sent: February 4, 2016 9:10 PM To: kriswiner/MPU-9250 Subject: [MPU-9250] How can I get the bias of Acc and Gyro? (#39)

Hello, I would like to ask that how to get the bias of Acc and Gyro? I'm not really sure for that I let the IMU be flat on the table with Z-axis toward up, and then I get the average value of 1000 records of Ax, Ay, Az The value should be 0, 0, 1, but the values I got are -02, -006, 096 Is the bias of Acc 02, 006, 004? So I have to add 02, 006, 004 to all of values of Ax, Ay and Az Is this right? Can I use the method to get the bias of Gyro, too? I think it should be 0, 0, 0 deg/sec when it is flat on the table Thank you very much!

Reply to this email directly or view it on GitHub https://github.com/kriswiner/MPU-9250/issues/39 . https://github.com/notifications/beacon/AGY1qmDNcpWazZV4bJxjIH4eiwmwxSnkks5 phCZFgaJpZM4HUBaj.gif

ijunglee commented 8 years ago

Thanks for your reply and strategy sharing! The numbers I quoted are g (unit of accelerometer). The correct value when the z-axis toward up is (Ax, Ay, Ax) = (0,0,1). By the way, did you use the magnetometer of MPU-9250? I use the LSM9DS0 now and want to change to MPU-9250. What's the difference between the two IMUs? I found that the Magnetometer Scale of MPU-9250 can not be changed, but LSM9DS0 can. Does it affect the result when I use Madgwick AHRS filter? Thank you very much!

kriswiner commented 8 years ago

There is a comparison of these two IMUs at the github repository I linked to.

-----Original Message----- From: ijunglee [mailto:notifications@github.com] Sent: February 4, 2016 11:37 PM To: kriswiner/MPU-9250 Cc: Kris Winer Subject: Re: [MPU-9250] How can I get the bias of Acc and Gyro? (#39)

Thanks for your reply and strategy sharing! The numbers I quoted are g (unit of accelerometer). The correct value when the z-axis toward up is (Ax, Ay, Ax) = (0,0,1). By the way, did you use the magnetometer of MPU-9250? I use the LSM9DS0 now and want to change to MPU-9250. What's the difference between the two IMUs? I found that the Magnetometer Scale of MPU-9250 can not be changed, but LSM9DS0 can. Does it affect the result when I use Madgwick AHRS filter? Thank you very much!

Reply to this email directly or view it on GitHub https://github.com/kriswiner/MPU-9250/issues/39#issuecomment-180236797 . https://github.com/notifications/beacon/AGY1qhd6wdPhZNVXQSYsOjNh7j6XpTDyks5 phEiYgaJpZM4HUBaj.gif