HeliQuad YAW "problem"

Hello. I’ve been asking regarding my heliquad yaw before and I though I would upload videos of my (possible) problem.

In short, the Heliquad flies well in Stabilize and PosHold and Auto mode. However, I’m seeing something strange with the YAW/collective when I’m armed, but not yet taken off.

I’m linking 2 videos. One shows the yaw and collective input/outputs when the vehicle is disarmed. The yaw and collective works well on all rotors.

DISARMED: https://youtu.be/p71LkC3mZ0k

The second video shows the vehicle armed, but with the motor disconnected (to avoid spinning rotors). In this state, when I YAW fully to the left for a second or 2 the front left and rear right rotor hardly respond to collective. Although, if I YAW to the right this time for a second or 2, the collective seems to start working again.

ARMED: https://youtu.be/Taecr92cJs0

This “problem” only seem to occur when the copter is armed. I don’t know if this is a problem or not since it does fly well in the modes mentioned above.

Any thoughts about this?

When armed, and stationary on the ground, I find you cant read too much into the outputs.

However, in this instance, it sounds as though its working fine to me. When you hold the yaw to the left your Yaw I term builds up. When yawing with a collective quadcopter the yawing torque is introduced by increasing the drag on two of the rotors and reducing the drag on the other two. The drag is reduced by lowering the blade pitch collective, hence why you are seeing the limited movement on two diagonally opposing rotors. Where as, the other two rotors have full range, as they need to increase drag and produce more lift so that the net amount of lift, across all 4 rotors remains unchanged. When you then hold the yaw stick in the opposite direction for a few seconds you are then ‘unwinding’ the I term from one direction and start building it in the other direction so the flight controller remains in the state of trying to yaw, but now in the opposite direction. This causes your other two rotors to become limited in the collective range. The reason it never ‘unwinds’ by itself is because its not actually flying and moving around, so its not seeing the desired response and the error remains high. I hope that makes sense.

In short I think the yaw is working as it should be.

Thank you for the reply. It seems it works as it should even though it has this behaviour when on the ground.

As I say above, the behaviour on the ground is correct. It just seems weird because you ask it to perform a manouver, but it can’t because it isn’t flying. In other words you have it in an artificial environment.