The Chinook helicopter has two sets of rotors which rotate in the same direction, leading to 0 yaw. A quadcopter takes the same approach – diagonally opposite blades rotate in the same direction, so both pairs result in 0 yaw.
So how does my bloomin’ quadcopter have yaw problems? I’m bringing this up again as it was a problem in the PID testing; during the first few tests, although the 2 motors started at full hover speed, they slowed down dramatically during the test.
The cause was the yaw PID which I’d forgotten to take out, and once I did, the tests ran consistently at hover speed.
Yet physically there was not yaw to correct – only one diagonal pair of motors was operating and due to the step-ladder, there was no way the quad could rotate around its z axis. And that suggests the yaw sensor is seriously duff.
Next time she’s flying outside, I think I’ll set the yaw rate PID gains to 0 and see what happens – something must have suggested to me I needed them in the first place?