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Apr 07, 2016, 03:05 PM
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Feiyu mini 3D test 1


Current usage with camera recording at 8.4V:

0.85A with motors not deflected
2.3A with all 3 motors fully deflected

The old pro doesn't work without battery. There's no point in using the power supply umbilical unless you're previewing video. Even then, the power lead should be desoldered. It's easier to use the pro battery in its included spot than carry around an extra gimbal battery.

A dummy battery could go in the pro that would trick it into working without a battery. It probably just needs to see 4.2V on a pin, but no spare battery exists to sacrifice.

Current usage without powering camera at 8.4V:

0.25A with motors not deflected
1A with all 3 motors fully deflected

When powering the camera, a converter reduces current usage for higher voltages. Without powering the camera, the current rises slightly for higher voltages, but with no increase in torque. Minimum current is always 0.25A. The torque seems just high enough, but could go higher without burning out the motors.

Motor control is quite a bit more robust than past gimbals. There's no skipping or studdering. It's like it has encoders giving it motor position, but it doesn't. It's using gyros attached to all 3 motors to gleam phase in addition to orientation. It seems to have an algorithm change which invokes the gyro based encoding when the angles get offset beyond a certain amount. This allows it to recenter instead of studdering.

It was deemed good enough to hard code the mode & speed in the control board, since that was what the home made gimbal used for 3 years. A brand new control board with pure bluetooth control would be used for a vehicle mounted camera.

Mode PWM duty cycle determines 3 modes:
1ms -> heading changes based on PWM. Pitch follows absolute PWM.
1.5ms -> heading follows handle. Pitch is fixed.
2ms -> heading follows handle. Pitch follows absolute PWM.

Should be noted there's no relative pitch control. Pitch tracks the absolute PWM at a very slow speed, creating a long delay from the joystick stopping to the camera stopping. It's obsurdly difficult to aim the pitch with the camera lagging the stick while the yaw has a perfectly good method.

The yaw rate is relative to the PWM duty cycle & stops when the stick stops. Maximum yaw & pitch speeds are quite slow, so there's no point in having a variable speed. Recommend using fixed pitch so there's no question of whether the current pitch is from drifting or the stick being bumped.

On the bench, heading drifts as much as past experience with Invensense gyros. It still does an impressive gyro calibration without being perfectly still during the calibration phase.

The 1st test run with it was a disaster. Yaw reverses direction when the yaw & roll servos trade places, with no evidence of where the dividing line is. Severe gyro drift in roll & pitch accompanies the yaw drift, creating unusable footage. It was just as bad at mixing yaw & roll as the home made gimbal & would oscillate in the 45' position.

The Goog abounds with tales of Feiyu drifting being fixed by firmware updates, but it might require a completely home made solution.

At least it held its pointing direction perfectly when being madly rotated. Could never get the home made gimbal to hold its direction when using I2C over UART.

Feiyu mini 3d test 1 (4 min 27 sec)
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