Getting a quadcopter stable in the air isn’t trivial. Stability of a quadcopter relies on the harmonious working of all of it’s parts.
Here are three of the major factors that contribute to an quadcopter’s stability:
- Vibration – Vibration will overload the sensor and will provide inaccurate readings. Balancing the propellers significantly reduces vibration which in turn improves stability. Isolating the IMU board from vibration will greater improve stability.
- Propeller choice – Choosing a propeller with a lower pitch will improve the aircrafts stability. A higher pitch propeller displaces a greater amount of air, creating turbulence and causes the aircraft to wobble during hovering. Choosing a lower pitched propeller will reduce the amount of turbulence.
- PID settings – Using a low P and D setting will reduce oscillation but will also create a lethargic aircraft. Using the ArduPirates or ArduCopter code, a “D” setting of 1.2 or lower seems to be the sweet spot for a quadcopter. The “D” setting controls the tolerance of how fast the aircraft will level. A lower setting will allow for a greater pitch or roll before the aircraft tries to recover. It this setting is set to high the aircraft will begin to oscillate. A good test for find an optimal “D” setting is to hover the aircraft 8-10 inches off the ground and then drop the throttle to 25%. If the aircraft begins to overcompensates then the “D” setting is too high. Lower the setting until the aircraft doesn’t overcompensate. The second setting I would adjust is the “P” setting. The “P” setting, is how much power is allocated to keep the aircraft level. A higher setting will cause the aircraft to oscillate. Lower setting will not have enough to keep the aircraft level. This setting is especially important if you plan on taking the aircraft outside. A low setting will be fine for indoor flight, but if you where to take the aircraft outside you will soon find that the wind will turn your aircraft into a kite. A higher “P” setting will be necessary for outdoor flight.