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Mar 20, 2014, 03:04 PM
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brushless gimbal fail








Brushless gimbal fail (0 min 41 sec)



It's not very often that a problem can't be solved, but this one is busted. Using only P & D, the gimbal should stay level. Instead, it's deflecting by a fixed amount. It doesn't matter how fast or slow it's moved. It's deflecting by the same amount.

Because the deflection is always the same amount, it should be possible to compensate it out, without an I term. The I term should only compensate for the variable drift from thermal noise. The fixed rate drift has happened with some designs in the past, but not others.

With the current design, it has been a permanent fixture. The only change was using an I2C buffer. Direct I2C had 0.7ms of latency because it had to use a very slow clockspeed. The I2C buffer can get it down to 0.5ms of latency with no heavy shielding.



So after trying 2 different gyros, reducing the latency to 0.5ms, increasing the gain to 250'/s, the drift was exactly the same. There was no correlation between P & drift.
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