The maiden flight
Please disable all the flight modes, so to leave only the gyroscope active, and arm the quadcopter. Please activate the acceleration stick slowly, and make the quadcopter take off – still paying the highest attention, since you are using the default PID values and it is not said they are correct ones. Within 50 cms from the ground, the air turbulences may significantly influence the flight, therefore be ready to compensate the possible deviations, and as soon as you can let the quadcopter climb more.
In our first flights we used the ANGLE mode, that uses the accelerometer in order to stabilize the flight and make the piloting easier, even for the beginners. The default PID values (P=3.3 I=0.03 D=23 for the ROLL and PITCH and P=6.8 I=0.045 D=0) proved to be good already, but it is possible to further optimize the stability by means of small and focused adjustments.
The flight at very low altitude (20/30 cm from the ground) is affected by the cushion of air created below, that makes the quadcopter drift (hovercraft effect). At a meter of height, the quadcopter is not affected by turbulences and the flight is more regular, but the risks of causing damages in the case of a fall increase; if you see that the quadcopter behaves strangely or that it tends to get too far too quickly, do not panic and slowly reduce the acceleration in order to make it descend.
In the ANGLE mode the flight is more stable, but if you sense a tendency to drift away somewhere, please take care of the accelerometer’s regulation, as previously described.
Once you have obtained a satisfactory stabilization, and only small adjustments of the sticks are needed in order to keep it in position, you may activate the magnetometer and the barometer as well. Please activate the BARO function once you have reached the desired altitude (and you want to keep it); in that moment the reference value will be memorized and you will be able to take away the finger from the throttle stick. You will still have the control via the stick, but if you want to land you will have to disable the function.
PID parameters calibration
The P (Proportional) parameter is the gain, that is to say how much the stabilization sensors intervene; it is important that it is as high as possible, so to have a very stable vehicle that tends to contrast decisively every attitude variation, but it must not be an excessive value, otherwise the vehicle will enter an oscillation state. The I (Integrative) parameter intervenes in the long run to compensate attitude errors, and tries to help the quadcopter to keep the position given by the sticks. The D (Derivative) parameter is influential when some sudden attitude variations occur. By raising this value, the quadcopter is helped in softening the oscillations that occur when there are attitude variations due to sudden maneuvers; but it also compensates the influence of the wind gusts, somehow. Please pay anyway attention to not exaggerate, since too high a value of the D parameter will induce dangerous oscillations.
Presuming to start with an already good set of values, it will be enough to correct them during the flight tests; the PID parameters must be modified, little by little and with extreme patience, with steps of ±0.2 as for P, of ±0.005 as for I and of ±1 as for D. When setting or adjusting the PID parameters, please keep in mind what follows.
- With high P values, the quadcopter has a considerable strength to resist whatever attempt to move it, however excessive values involve oscillations at high frequency and, at most, instability. In the aerobatic flight, higher P values are preferred.
- With low P values, the quadcopter is less resistant to the attitude variations and shows the tendency to drift. During the regular flight, lower P values are preferred.
- With high I values, the capability of keeping the initial position and to reduce the dispersal is increased, but the delay with which it returns to the initial position as a consequence of an attitude variation is increased as well. During the stationary flight, higher values are preferred. If the value for the I parameter is too high, it causes low frequency oscillations.
- Low I values improve the reaction to changes, but they increase the drift and make it difficult to keep the position. During the aerobatic flight lower values are preferred.
- High D values improve the speed with which the disturbances are recovered; too high values induce oscillations. In the aerobatic flight, higher values are preferred.
- With low D values, the oscillations at the return to the initial position are reduced, but the movements are slowed down. During the stationary flight, lower values are preferred.
If you want a clearer idea of the influence of the PID parameters on the quadcopter’s flight, we advice you watch a YouTube video that is a very significant one.
During the calibration of our quadcopter, we slightly corrected the PID values as for the pitch and the roll, in addition to lowering of 50% the PID values for the altitude hold function.
