Hello,
I'm looking for general advice using the Nine Axis Motion Shield (or the BNO055).
I am wondering about the calibration. There are four outputs about calibration status for the sensor:
- ( 0-3) for the accelerometer
- (0-3) for the mag
- (0-3) for the gyro
- (0-3) for the system overall
I'm wanting to use the sensor for an outdoor mobile robot, but I need the data to be as close to absolute as possible. Following their calibration instructions, I can sometimes get the calibration status of all outputs equal to 3, but it seems like most frequently I can get the sensors to 3, but not the overall system. My output will be something like 3, 3, 3, 0 and the reported Euler Angles don't appear relative to true north. At startup the sensor heading angle is reported with respect to the starting orientation, but as calibration occurs the heading angle should converge to true north. The few times I have gotten all outputs to 3, the sensor seems relative to true north to the extent I need it.
The BNO055 documentation says to discard all values where the sensor isn't fully calibrated and I can't really use the values where the sensor is fully calibrated anyway, because this means the location of the "fixed" frame everything is relative to is moving and changing. I can't seem to get the overall system calibration status to 3 the majority of the time. Why might that be the case? What can I do differently to make the calibration more successful? Any suggestions (other than using a better sensor)?
From the documentation, I know the sensor is also continually calibrating. When I do have full calibration it tends to be much less noisy in the values, but I'll often lose full calibration on the overall system (while retaining it on the sensors). I'm also curious if anyone knows what determines the overall calibration status number.
I'm asking the community, because from what I have seen, the documentation for this sensor is terrible.
EDIT WITH FOLLOWUP QUESTIONS:
If my state is 3, 3, 3, 0 does that mean I can trust the values from each of the sensors but none of the Euler data? Does the system calib represent the quality of their sensor fusion or something? Should I just perform my own EKF off the sensor values to get Euler angles relative to north? I'd prefer not to, but if it works I'm open minded.
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