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Mar 17, 2014, 01:49 AM
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Gyro temperature compensation 2

Though taken up & abandoned many times, there is still hope for better gyro stability through temperature compensation. Every gyro datasheet mentions a temperature readout, but no explanation of how to use it.

It depends on how the package was soldered, stresses on the package once soldered. It requires making a unique table for the gyro across a wide range of temperatures. Arducopter doesn't use temperature compensation for the MPU6000, but for a mass produced product like that, it would be really hard to make a table for each unit.

In an effort to make its heading more stable, made a table for the brushless gimbal from room temperature to operational temperature. Since the gyro drift is far below the gyro noise, the table has to be made by averaging many seconds of gyro data.

This one is the ITG3200, which luckily has linear correlation to temperature. The way to use the temperature sensor is to record the temperature corresponding to the center reading. Then for every new gyro reading, calculate the difference between the new temperature & the center temperature & scale it to the amount of center offset.

This algorithm worked nicely. The gimbal held its heading for a much longer time, though it eventually drifted. The aircraft IMU was not so lucky, going from room temperature to operational temp.

Then another test from freezing to operational temp.

The MPU9150 is pretty nonlinear. In the room temperature to operational temperature range, a slope intercept would give a barely useful compensation. Ideally, it would look up where in the curve the center temperature was, then look up the difference in analog value curve between the current temperature & the center temperature. But the 2 tests were inconsistent.
Last edited by Jack Crossfire; Mar 17, 2014 at 01:57 AM.
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