Sunday, October 13, 2013

The TriCopter Maiden Flight

Yes it fly's ...and crashes :-(

I completed a maiden flight last weekend.
The first thing I learnt is the tail servo has to work the opposite way to what you would think.
The rear roter needs to tilt the opposite way to your rudder(Yaw) stick.
            #define YAW_DIRECTION -1
Then recalibrate the throws so the servo doesn't try to travel to far.
           #define TRI_YAW_CONSTRAINT_MIN 1025 // Captured from Mw-WinGUI
           #define TRI_YAW_CONSTRAINT_MAX 1990 // Captured from Mw-WinGUI
           #define TRI_YAW_MIDDLE 1500 // Later adjustment with TX trim
The strange thing is after correcting the YAW direction, the TriCopter developed the dreaded tail roter oscillation. This is a vibration loop starting when the servo twitches on power-up (or any bump to the aircraft) gets picked up by the MultiWii board, sends a correction to the servo and that movement is transferred through the frame starting to whole cycle again. I read a lot of forums and following  information found there I fine tuned the Yaw PID sitting reducing the problem. The final solution appears to be trying another servo or revisit the airframe design. I think the lack of rigidness in the landing gear I fabricated has something to do with it as well.

Other Points
1) Balancing props both off and on the motors is critical (Plenty of video's on YouTube)
2) Set up your TX as Acro with all the Starting points at MAX (+- 100% or more)
Completed the following set with props removed!
3) Calibrate you ESC's, as in Max/Min/Stop (The simple process was not very successful so I've ordered a programming card but eventually would like to flash them with Simon K code)
4) #MinThrottle setup is also important for "panic" decent and board arming. I set mine up so throttle trim needs to be at minimum for Arming (But I can disarm from AUX switch 2)
5) Check pitch and roll are not reversed both with Mw-WinGUI and with motors running.
6) Calibrate the Gyro/Accelerometers
7) Ensure the Barometer has wind and sunlight protection. The 1st piece of foam I used was not dense enough and the Baro output on the MwGUI graph as all over the place.

The 2nd flight

This was much more successful. In ACC mode, after some trimming level flight was achievable.
Enabling BARO and MAG resulted in a beautiful bank toward power-lines and a main road. I panic killed the throttle resulting in a crash. This only collapsed one sife of the fram and broke the props showing how resiliatne Daves design is.
Waiting on new props.........

Screenshot, pictures and hopefully some video to come!

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