I've just built a tricopter using Tim Nilson's Delrin kit, but I can't get my yaw to work properly. It seems like the servo is only using a very small amount of its travel, and it doesn't feel like it yaws all that quickly as a result. It will also yaw in one direction slightly more easily than the other. I'll try changing the length of the linkage a little to see if I can even it up.
I'm not sure if I've set the linkage up properly. I'm just using both outside holes at the moment. The build instructions were a little light on detail in that regard.
Also my yaw input is reversed. It doesn't matter if I have the 'reverse' box checked under radio setup in mission planner, my yaw control still goes the opposite way to stick input. The stabilise yaw seems to work correctly though. Eg if I yaw the copter with my hand, it will move back to the original heading correctly.
I'm running stock 2.5.4 firmware. on APM1.
Here are a couple of pics
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Having Stb_yaw_P too low will only give you a small amount of travel in the servo, and having Rate_yaw_p too high will give you very jerky movements in the yaw servo.
These are my params, which work reasonably well with 14" arms with 10x4.7s and dt750s on 3s, except for the yaw bounce issue, which is a bug that needs to be fixed.
Rate_pit_p 0.16
Rate_yaw_p 0.14
Stb_pit_p 4
Stb_yaw_p 7
Alright I've somewhat sorted it. I moved the linkage to the other side of the arm, which didn't change anything but it made it the same as the build guide pics.
Here's what happened with a few tests.
with 2.5.4 firmware stock
yaw not reversed in radio setup
tri will spin around to south east and oscillate back and forth about 45 degrees
stick inputs are reversed.
yaw reversed in radio setup
tri will hold its heading and correctly fight changes to the yaw made by hand.
stick inputs are reversed, but yaw returns to centre with no stick input.
2.5.4 firmware with Randy's AP_motorstri.cpp change - Link
yaw not reversed in radio setup
tri will spin around to a heading and oscillate around it.
control inputs are reversed, yaw don't return to centre after stick input
yaw reversed in radio setup
tri will spin around to a heading and oscillate around it.
Control inputs are correct, but yaw doesn't return to centre after stick input
So I've gone to 2.5.4 stock without Randy's change in AP_motorstri.cpp, and just reversed my yaw stick input on my transmitter, and now it's holding its heading correctly, and stick inputs move it in the correct direction.
However it is still only using a small amount of the servo's travel, and not really yawing very fast as a result. Can this be changed at all?
I should add, the servo is a BMS-358DMax on a 5v bec. Its movement is quite jerky. I've tried it on 6v, but it just made it jerkier.
The servo also sounds like it buzzes for a while even when I've stopped the motors.