Sensor Calibration
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.
The
MK will always try to maintain the position it has at the moment of
calibration because it accepts that position as level. After the initial
ACC calibration is accomplished and properly saved, this same "level"
reference is loaded into the MK Flight control as the true level plane
when power is applied. That means, the more it is out-of-level, the more
correction will be needed by the pilot to maintain position. While
performing the calibration, the actual "Setting" (amount of beeps
represents the setting-number) can be chosen.
Accelerometer (ACC) Calibration
Your
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.
What needs to be level?
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.
Setup:
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.
Calibration procedure:
- Remove everything
but the basic MK and landing gear.
- Make sure you are using setting 3 (Easy) as this makes normal
flying easier.
- Turn on the MK/TX and plug it into the MK-tool.
- In MK-Tools - go to the no.3 lcd screen. (green led type readout with number 3 upper right hand corner)
- Make sure the main trims on your TX are in the center or zero.
- Go to your sub-trim menu in your TX and get K2/roll and K3/nick values to zero.
- Now
for the actual calibration. Move the left stick (Throttle/Yaw) to the
upper right corner and hold until the MK beeps. This value is stored in EEPROM
and only needs to be done once, after that, every time you turn on the
MK, the ACC settings are automatically loaded from the EEPROM.
- Test fly the MK in a no wind situation with no gps hold.You
should be able to hold a hover and
trim in the direction you are holding the stick so you can then let the
stick go and the MK will remain in the same place. The MK should stay
pretty much in one spot unless it gets some wind or some stick.
Note: The leveling control starts working from a certain throttle value only.
If,
after this, the MK still veers off to one side, double check arm and motor straightness, and weight distribution.
Gyroscope (Gyro) Calibration
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).
Procedure:
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.
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Stick Position Calibration Chart
The image below shows greater detail of how the sticks are used to select settings and calibration modes:
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.
Test of sensor values in MK-Tool
When
the controller has been successfully programmed, you can check the
sensor values with the MikroKopter tool. For this procedure you connect
the serial converter with the large ribbon cable. The MK (or flight
control board if your testing the board only) must be put in a
horizontal position and switched on, then start the scope option in the
MikroKopter tool (if the scope was already running you should stop it
for a moment to reset the zoom range). We observe here only the first
five analog values. The other analog values can be switched off via the
tab "Scope“ in the MikroKopter tool if the display becomes to difficult
to read.
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.
MK Compass Calibration
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.
Operating Note: Calibration
Important Notes: - When first operated, the MK3Mag needs to
be correctly calibrated! Otherwise the NaviBoard will show you "Err:6
bad compass value".
- Since Version FC:0.84 it is much easier to calibrate the compass with a "clicking sound". This method has the advantage that you doesn't have to hold the Kopter "perfect" horizontally.
- The Nick- and Roll axis refers to the FlightCtrl, and not on the Mixer you use! The arrow of the FlightCtrl shows the Nick axis!
- Calibration should be accomplished outside, away from magnetic influences!
-
Do not calibrate the MK directly next to a house, near power poles or metallic / magnetic surfaces.
-
Take your cell etc. out of your pocket.
- Start Calibration - Initiate
Compass Calibration by holding the transmitter nick/right stick
straight-down and moving the throttle/left stick up-and-left, you will
hear one beep. Compass calibration has now begun.
- Calibrate Nick Axis -
Hold the MK with the front arm pointing north or south (use a compass
or GPS to determine the proper direction, get as close a you can, but,
it doesn’t have to be exact). Now, move the transmitter nick/right stick
to the bottom, you will hear two beeps,
step 2 of the calibration has begun when the clicking sound starts with
each move of the MK. Rotate the MK in the north-south direction so that
the hub of the MK rotation is along the nick axis on diagram 1. The MK is now finding new points of maximum or
minimum values. When the beeping stops, the Nick axis is calibrated.
- Calibrate Roll Axis - Point the MK so that the nose is facing east or west than roll the MK
a few times in the direction of the MK roll axis (diagram 1) so that
the rotation axis or hub is around the X axis as shown on diagram 2. The
rotation is still north/south. Rotate until the buzzer stops beeping
than move the nick/right stick to the bottom. You will hear three beeps
that signal the end of the nick/roll calibration process.
- Calibrate Yaw (Z) Axis - With the nose still facing east, move the nick/right stick down, you will hear four beeps that signals the start of Z Axis calibration. rotate the MK
a few times around the roll axis as indicated on diagram 1 (X axis on
diagram 2). Rotation will remain in north/south orientation until the
buzzer stops beeping.
- End Calibration - Pull the Nick stick down - you will hear one calibration beep that signals the exit of the calibration process.
If the calibration fails (compass still reports "invalid compass value"), you can take a look here: MagnetError
The process also works in older firmware versions, but then without the clicking sound
Watch these videos for demonstration of the method.
