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Heli Hacker's blog
Archive for May, 2010
Posted by Heli Hacker | May 16, 2010 @ 02:08 PM | 5,828 Views
Finished board design for PhuBar 3 using ITG3200 3-axis gyro. Managed to squeeze the board size down to 30x28mm. If I solder cables directly onto the board instead of headers, and use clear shrink wrap instead of an enclosure, the whole thing should be 30x28x7mm, except for where the 5-pin programming connector will stick out from one side.

I added the fifth pin to that connector to supply 3.3v so I can use the TextStar serial terminal for field setup.

I also added connector pads for 2 general-purpose I/O connections plus ground to allow for programming the Propeller to do other functions if desired.

The 3-axis gyro will let me add rudder gyro capability, as well as use cosine-matrix math for more accurate attitude estimation.

Update: I received the boards from BatchPCB on June 1. They look really good - photo below
Posted by Heli Hacker | May 11, 2010 @ 11:13 AM | 5,955 Views
Today I did some vibration testing on my flybarless FireFox "PhuFox" helicopter using the PhuBar and ViewPort to look at the gyro data in real time.

On the graph below, the blue line is the roll rate after smoothing with the digital low-pass filter. The red line is the integrated roll angle. Green is the control signal going to servo #1. The helicopter was sitting on a soft block of egg-crate foam rubber for this test.

On the left side you see no vibration in the signals because the motor is off, but you can see that I moved the aileron stick back and forth to move servo 1.

On the right side of the graph are the same signals except that I throttled the motor up to flight speed. The effect of vibration on the signals is small but visible. The magnitude of this effect on the servo output, when measured, amounted to about 1% of the total servo range of motion. My subjective experience in flying both helicopters is that a moderate level of vibration has no noticeable impact on performance of the PhuBar, thanks to the low-pass filtering.

The change in level of the servo signal you see at t-6 resulted from pausing ViewPort while I throttled up, then I restarted ViewPort. At the higher throttle setting, the pitch curve on my radio sent a higher pitch setting to the receiver and caused all three servos to move to a slightly different position due to the CCPM mixing in the PhuBar.

There are four things that help reject vibration:

1)...Continue Reading