The “automatic parameter adjustment”(Auto Tune) of APM needs to calculate the delay and feedback of control system. For example, when a plane is wandering from original path, there would be timely difference between calculating and launching signals; the attitude of the plane would be different when the signal arrives. Furthermore, when the correcting signal arrives, the plane would react differently according to different weight, sizes and conditions…. Anyway, it is really complicated. The scientists simplify those problems into Proportional term, Integral term, and Derivative term (PID).
PID manual adjustment
If user would like to adjust PID through Mission Planner, the author suggested resetting three to zero. Tune “P” to overshoot, and tune it down for 15%. Tune “I” to overshoot, and tune it down for 15%. Tune “D” at last.
It takes a lot of patience during tuning process. There are a lot of tuning PID videos on YouTube. The author didn’t complete the PID adjustment perfectly. He suggested beginners hang the UAV in the air and tune PID manually; so the UAV can move freely but not out of control.
PID auto adjustment
Since the new firmware released, APM supports automatic parameter adjustment. The setup process is shown below.
If user plans to use the automatic parameter adjustment, the transmitter needs to equip six channels. For FrSky for example, please take a servo lead (male-male), and connect “CH6” of receiver to “CH7” of APM.
Go to MIX of transmitter to add the channel. Press MENU of the main page of X9D, and press PAGE 5 times to MIXER screen. Select CH6 and press ENT to enter “INSERT MIX CH6”.
The “Source S2” will be highlighted. Press ENT, will flash. Press (-) a few times until “SE” appear in the screen. Select “SF”. Press EXIT to main page.
The page will be as below. The author set the new channel to be controlled by SF (2-way switch at the right).
There is a new channel added. Please recalibrate the transmitter. Connect the APM to computer, start MP, and go to INITAL SETUP->Mandatory Hardware->Radio Calibration. When user adds a new channel or replaces a transmitter/ receiver, remember to recalibrate the transmitter. The process is in Part.06 Firmware Setup
Go to “Flight Modes” of MP, and change one of the flight modes to ALTHOLD mode. Click SAVE MODES.
Go to CONFIG/TUNING->Extended Tuning; change the CH7 to AUTO TURN. Click “Write Params”. (The CH6 of APM doesn’t support auto adjustment. That’s why the author connected CH6 of receiver to CH7 of APM.)
After all preparation, please refer to the video below. Don’t turn off the auto tune (CH7). After landing, APM would lock the throttle, the parameter would be recorded.
In a windless day, the UAV would be nailed in the sky very steadily.
For beginners, the author suggested using default parameters from MP for flying practice. After being familiar with UAV, it would be easier to execute auto tune.
The author shared Common Setting and Function:
Dynamic machine is always with vibration. Vibration would mislead the sensor of auto navigation, and APM could not recognize the correct attitude of UAV. For Multi-Copters, the unbalanced vibration of propellers and motors would also cause bad stability. Many beginners keep focusing on software adjustment - PID, accelerator, or compass calibration - which would not fix vibration.
If the APM was equipped with Data Transmission, it would record all data automatically. User may read the data according to the procedure below, and decrease vibration as possible: balance motors, props, or attaching washers.
After flight, disconnect MP and the UAV. Go to “FLIGHT DATA”->” Telemetry Logs”
Click “Tlog > Kml or Graph”, MP would show Mavlink Log Graph. Select Graph Log, and select the flight data. Flight Data would be at “C:Program Files (x86)Mission PlannerlogsQUADROTOR1” and named accordingly to date and time.
Select the newest flight data. MP would show “Graph This”, please check xacc/ yacc/ zacc.
Mavlink Log Graph would draw the data automatically.
User may zoom in and out by scrolling up and down through mouse wheel. For specific period of time, user may drag a square by left-clicking.
The author shared his own parameters with us.
Start MP, and go to CONFIG/TUNING->Standard Params
RTL Altitude (cm): 1500
RTL Final Altitude (cm): 0 (landing)
RTL loiter time (ms): 50000
Transmitter Fail Safe
It is a very important function supported by transmitter. It is to pre-set APM signal if receiver lost signal from transmitter. UAV is very easily to fly out of the sight, so, remember to set failsafe.
Please refer to the video below. Set X9D failsafe as “No pulese”, which means X9D would stop transmitting when receiver lost signal.
Start MP, go to INITIAL SETUP->Mandatory Hardware->FailSafe. Select a number under 975 at “FS PWM”. Turn off the transmitter, and the CH3 number would become 900; which means the CH3 of APM is lost signal.
The author shared his own parameters with us.
Go to CONFIG/TUNING->Standard Params.
Enable Ground Station Failsafe Enable: Disable
GPS Failsafe Enable: Land
Throttle Failsafe Enable: Enable always RTL
Throttle Failsafe Value: any number under 975
Set the throttle output at 50% in RTL mode once the receiver lost signal. Method 2 is easier, without setting MP.
Please refer to the video below. It’s failsafe setting for X9D and X8R. Remember to set CH5 in RTL mode.