Phoebe has pretty much answered the question: she took off from as good an approximation of a horizontal surface as I could come up with, and yet, once airborne, she drifted backwards. This is the polar-opposite of being able to control her flight in a desired direction; if I can stop this drift for a vertical take-off, then I can apply the opposite logic to apply drift for horizontal movement.
First step as always is to have a nosey through Phoebe’s stats from the flight, in particular the x-axis accelerometer output (plus integral for speed), and engage the outer horizontal-speed PIDs to produce the targets for the inner angular PID (which actually drives lateral speed); the unwarranted horizontal movement is stopped by a managed tilt upwards the same direction (i.e. a backwards drift will be stopped by raising Phoebe’s rear blades, and tilting down her forward ones).
But before I get too engrossed, I think Phoebe and I are due some free-play time together!
One last thing – some stats from a separate flight that day showing two things:
First how much effort is required to maintain stable yaw – about 17% more power is applied to the CW blades than to the ACW blades – that surprised me given that in theory at least, the motors and blades are nigh on identical, and the body is well balanced. I’ll have to have a think:
Secondly, a plot of acceleration, speed, and height, all derived from the accelerometer; I’m particularly impressed with the speed and height results, particularly as they are just integrated from the acceleration, and the fact that as the applied power drops, you can see the controlled drop in height as expected. Bodes well for a more automated takeoff. Units on the left at meters per second per second, meters per second or meters for acceleration, speed and height respectively. Units on the right are the motor power between 0 and 1000 (PWM pulse width in microseconds)