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May 19, 2013, 05:01 PM
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Brushless gimbal war 2


3 axis gimbal problems (2 min 20 sec)


Yaw is coupled to roll/pitch when tilted outside a very narrow angle. It used magnetic heading, which seemed to be distorted by the motors. Yaw is a lot of weight & power consumption for something that's always going to need software stabilization. The DT700 rewound with 130 turns of 0.2mm was never perfectly smooth, even at 0.6A.

Eventually, an open source solution to the yaw direction will appear. In the mean time, it's going back to 2 axes.


2 axis brushless gimbal & its limitations (2 min 49 sec)


The tried & true, 2 axis gimbal is revealed. Its limitations are also shown. It uses 0.7A. 2x Turnigy 2205 1350kv 50 turn 0.2mm. At least it's light.


So basically, not knowing the orientation of the roll motor prevents all gimbals from being ideal isolators from all possible movements. The yaw motor does reduce the amount of software stabilization & increase the margins. The magnetic heading is probably not going to be available. It needs to use dead reckoning.


Mixing the motors could be done with a quaternion model or conditional statements. Quaternions are very good at modeling kinematic objects. Fixed point quaternion rotation would be an interesting, pointless project. The right way is probably a matrix.
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