The MK is equipped with some of the most modern and sophisticate flight control sensors available, however, if these sensors are not calibrated correctly and accurately, the MK Flight Control Computer will have less than ideal input data to work with and correspondingly poor performance. It is well worth your while to understand and apply the proper calibration procedures. The MK should require very small inputs on lift off (about 1m from the ground) to hold in a steady hover. If you are trying to control the MK with large stick movements then you should look at how the MK is set up.
initial ACC calibration is critical to MK performance. It
basically teaches the FC what is level as well as setting the
accelerometers. If this calibration is not done correctly the MK will perform poorly.
Note: Calibration of the ACC's only needs to be done once or if you have control issues or a software update.
The following procedure is a method that I have learned from others and will ensure proper ACC Calibration. There are certainly other methods that will be less time consuming and once you understand what is being accomplished by calibration, you my very well decide on your own method.
Since it is the propellers that provide thrust to make the MK fly, it is important that the motors and support arms are all on the same plane. (level with each other). If this is accomplished by ensuring the arms are level with each other and the motor shaft are vertical, then the Flight Control computer and the pilot will have less corrections to make and thus the MK will fly level and smooth.
The following calibration procedure will check to make sure the support arms are level with each other as well as calibrate the ACC.
Note: Once again, This process is just the way I set up my calibration, feel free to make changes to this method in order to adjust to your own circumstances.
Selected a table that has adjustable screw type foot pads (if possible) on the bottom in order to make leveling easy. Use playing card or other objects placed under the table legs if the table does not screw type level pads. If the table top has more than one piece, place a firm piece of plywood on the top of the table so that it will a have single surface to level.
Use a bubble level in the center of the table, adjust the table legs until the bubble level is exactly level while looking straight down on it.
I went to the local hardware store a purchased eight pieces of threaded 12 in. x 3/4 in. plastic pipe, eight metal floor flanges, and eight 3/4 in plastic pipe caps. I than pieced together eight stanchions that the arms of the Okto rest on. These stanchions are heavy enough to be moved around on the table top as needed to fit the Okto frame. I found that there is no need to screw down the bases as the metal is heavy enough to keep them from sliding. The threaded caps are adjusted so each stanchion is exactly the same height. See the picture below:
Arm Straightness Check
Once the stanchions are in place, carefully lower each arm of the MK onto the stanchions while at the same time checking to make sure the arms are not bent. Make sure the MK is resting squarely on the stanchion and not the LEDs/cable ties.
Hint: If you find one arm touching a stanchion before the others, make sure the centerpiece bolts are secure. Unless you have had a crash, it is unusual for a boom to be bent. If you visually see a bend, gently bend the arm into position by applying pressure where needed. If the arm is not square with the others, use an open end wrench to twist each arm slightly to bring it back to where it should be to be square and on the same plane.
Also, there is a natural flex in the aluminum tube and a slight degree of error, less than 2 or 3 mm, is acceptable.
If, after this, the MK still veers off to one side, double check arm and motor straightness, and weight distribution.
The micro gyros on the MK are very temperature sensitive and this calibration must be done every flight in order to stabilize gyro temperatures in preparation for flight. This calibration is necessary because the sensors have a series of scattering and temperature dependence (also the resting values of individual axes of the acceleration sensor are different).
1. Place the MK on a stable surface an do not move it. note: the MK does not have to necessarily be perfectly level as the Flight Controller will be using the stored "level" reference made at the time of ACC calibration.
2. After applying power move the throttle up and to the left until the buzzer beeps and the green LED goes out. (The number of beeps corresponds to the setting number.) Remember: only the gyros, are calibrated in this procedure, this does not set level as with the ACC calibration.
This process also powers up other components of the Flight Control board and prepares it for motor start.
Explanation: NickRoll joystick Left Centre = Setting1; Left Up=Setting2, Centre UP=Setting3, etc. Again: keep the throttle-yaw joystick upper left and the Nick-Roll joystick at the same time to any of the positions mentioned above. It also works the other way around, first choose the setting with Nick-Roll, keep the joystick there and calibrate with throttle-yaw.
Now you tilt the board as smoothly as possible to about 45 degrees in direction of the pitch axis. On the scope you check the signal values. The signal of the pitch integral and the pitch acceleration sensor (here red and yellow) should show a significant value.
It is important that the overlaid graphs are identical as far as possible.The same check has to be made on the roll axis (here blue and green):
Then we check the yaw gyro. For this purpose we turn the board around the yaw axis and observe the signal of the gyro. As long as we turn the board there will be a value > 0 which will come back to zero when we stop moving the board.
We check the offset values of the gyros in the virtual display (the values in parenthesis):
For this purpose we click through the buttons in the corresponding menu. The offset values should be around 500 (+-100). In this example the yaw gyro has a problem (178). It must be recalibrated or changed.
Test of the Rx signal In the virtual display we can read the R/C values:
With the R/C control we can adjust the values in the range of ca. -120 to +120.
These instructions are intended to guide you through proper compass calibration of the MK-Mikrokopter series of multi-rotor RC aircraft. The MK must have the proper navigation hardware and software installed.
Additional instructions and video are available on the mikrokopter.com website.
MK-Axis Reference Graph (diag. 1) - The diagram below shows the different MK Axis Lines used in this procedure.
The process also works in older firmware versions, but then without the clicking sound