KK2 Q&A and Insight Into Tuning Issues from KK Himself

Here are a couple priceless postings along with the links they came from.  This explains a lot!    ...Tiger


Originally Posted by kapteinkuk
The default PI settings where determined with my test multicopters. I forgot one thing: they all use fast SimonK flashed ESCs, so they are, as others has pointed out, too high for normal ESCs.
About the "limit" values. They set the maximum of the available motor power to be used for correction. 100 is 100%. The "I limit" value is also known as "anti wind-up" in PID theory.
The limits is most important on the yaw axis. The prevent a large yaw correction from saturating the motors (giving full or no throttle), causing no control of the roll/pitch axis.
The default values permit 30% ("P Limit" 20 + "I limit" 10) of the motor power to be used to yaw correction, making 70% available for the roll/pitch axis, the most important ones.
You can increase "Yaw P Limit" for faster Yaw response. Note that Yaw response is also limited by the craft itself.
You can increase "Roll/Pitch/Yaw I Limit" for increased heading-hold "memory", that is how far it can deviate and still return to original attitude. Too large memory can cause problems if you have a "blow out" on one of the axis, tries to correct it with opposite control input and then when the blow-out conditions disappear, the craft will try to return to an unknown attitude.
Unless you know what you are doing, leave the limit values as default. Default values has no impact on The PI tuning process.
Also leave the self-level "I gain" and "I limit" at zero. The I part of the self-level algorithm does not work well, this will be fixed later.

Thread link:  http://www.rcgroups.com/forums/showthread.php?t=1675613&page=21


Here are answers to the most important questions about the KK2:
Q&A: (Some of the text is borrowed from other users posts in this thread.)

Q: It lists "Singlecopter 1M 4S", does that mean it could be used on say a Trex450?
A: No, but it is possible to configure the mixer for a heli. I will get me a cheapo 450 and see how well it works as a flybarless controller!

Q: Is it possible to write FW on this controller to use as standalone Camera gimbal like the multiwii?
A: Yes, I will write a camera gimbal FW for it.

Q: How does the low voltage alarm work? I can not see any connections for input V?
A: The Battery voltage input is the unpopulated hole to the left of the yellow component. Connect a cable from battery+ to this hole. The ground return is through Output #1's ground wire. Go to "Misc. Settings", "Alarm 1/10 volts:" to set the threshold. It is in 1/10 volts, so 10.5V is entered as "105". The LVC is only active when battery voltage is below the limit. When it goes above, it stops. Also it beeps faster the lower the voltage is below the limit.

Q: Does the aeroplane mode also include autolevelling? or is that only available for copters?
A: It is available for planes too, but that combination is not tested. I will do it when I get more KK2's

Q: CPPM input mode?
A: I will try to add CPPM mode.

Q: If the gyro can work on 2000 deg/sec, why not make the 2000 deg/sec as the working output? Which solder jumper need to be mod?
A: The 440 deg/sec gives a higher resolution. The jumpers is on a horizontal line below the two black chips at the top. From left to right: X, Y and Z axis. The pads already connected with a trace is 440 deg/sec. Cut this trace and connect (solder a thin wire) the center pad to the opposite pad to get 2000 deg/sec. Be careful not to short out the trace that runs in between the pads.

Q: Why is Autolevel so slow?
A: The autolevel is based only on the ACC. It takes some time before the ACC registers tilt due to the horizontal acceleration of the craft when tilting. It needs some speed to get air resistance and a force on the ACC. Therefore the autolevel works best on draggy crafts. Later I will try to implement a AHRS algorithm, which uses both ACC and gyros to get a immediate tilt angle.

Q: What are the "limit" values in "PI Editor"?
A: About the "limit" values. They set the maximum of the available motor power to be used for correction. 100 is 100%. The "I limit" value is also known as "anti wind-up" in PID theory.
The limits is most important on the yaw axis. The prevent a large yaw correction from saturating the motors (giving full or no throttle), causing no control of the roll/pitch axis.
The default values permit 30% ("P Limit" 20 + "I limit" 10) of the motor power to be used to yaw correction, making 70% available for the roll/pitch axis, the most important ones.
You can increase "Yaw P Limit" for faster Yaw response. Note that Yaw response is also limited by the craft itself.
You can increase "Roll/Pitch/Yaw I Limit" for increased heading-hold "memory", that is how far it can deviate and still return to original attitude. Too large memory can cause problems if you have a "blow out" on one of the axis, tries to correct it with opposite control input and then when the blow-out conditions disappear, the craft will try to return to an unknown attitude.
Unless you know what you are doing, leave the limit values as default. Default values has no impact on The PI tuning process.
Also leave the self-level "I gain" and "I limit" at zero. The I part of the self-level algorithm does not work well, this will be fixed later. (Accelerometers is too slow)

Q: Could you explain in detail how does the Height Dampening and Limit works?
A: "Height Dampening" in "Misc. settings" uses the Z accelerometer to dampen vertical movements caused by wind or tilting the craft. "Height D. Limit" Limits how much power available for dampening. Try 30 for the "Height Dampening" and 10 (10%) for "Height D. Limit".

Q: Why does my Peizo buzzer keep making a beeping noise no matter what values I put on the "Alarm 1/10" voltage settings?
A: You must connect the battery voltage input to the battery. See question 3.

Q: Can I use the KK2 with a cheap HK 4 ch radio?
A: That will be fine but if you want to turn on/off the auto level function you will need to do that at the LCD where as a 5th channel will enable you to do it from your transmitter.

Q: I accidentally adjusted the contrast such that I cannot read the screen now.
Does anyone know how to do a "master reset" to default values?
A: Turn the KK2 off and on again.
push button 4
push button 3 (four times )
push button 4
push button 3
push button 4
push button 1
push button 3 (36 times)
push button 4

Q: In Tricopter configuration the LCD motor layout suggests that all the motors rotate clockwise. Is that correct?
A: On a Tri any combination of CW and CCW can be used, but the best is to have one of CW or CCW and the other two in the other direction.

Q: How to reverse the yaw gyro for a tricopter?
A: Go to the "Mixer Editor" and change the channel (number to the upper right) to 4 where the yaw servo is connected. Then change the "rudder" mix value to -100.

Q: Why that nut job of a ESC calibration sequence?
A: I know that some of you will try to calibrate the ESC with the propellers on, so by requiring to hold down buttons while calibrating, you will probably let go of the buttons and cause the motors to stop when the propellers start to slice through your arms. Also this makes it impossible to leave the ESC calibration on permanently. Why two buttons? In case some buttons get stuck, it will not enter ESC calibration mode accidentally. I see some defeats this by using clothes pins to press the buttons, but I recommend getting help from a friend. Of cource, if you do remove the props, use the clothes pins!

Source for this posting:  http://www.rcgroups.com/forums/showthread.php?t=1675613

Thank You Tiger, That's a lot of good information.

For those of you who have never head of PID loops and are facing the tuning of your new KK2 controller board, you might like to read at least the first part of the PID Wiki here:  http://en.wikipedia.org/wiki/PID_controller 

A full understanding of this stuff and the underlying math is way beyond what you're going to need to know so don't be intimidated by all this.  Still, a basic understanding of the terms and what they represent, might be helpful when you come face to face with these parameters on the KK2 screen.

As the KK2 product matures and more and more people have it in use, a database will no doubt emerge to help you get on target without you having to experiment with tuning at all.  I expect you will eventually be able to look up your airframe on a chart and just plug in the appropriate parameters.

Those of us with a technical background are probably the most excited about this board.  Unlike some other offerings, the designer of this board does not shield you from most of the control parameters that give it its power.  This means that if you are up to the challenge, there is almost nothing you can't do with the board.  This product is extraordinarily well engineered and has more potential applications than anything else I've seen.  Not only does it have more capability, but it is going to eventually outshine the competition because of the extensive level of control it makes available to the user.  Finally we have a powerful controller that will let you have things "your way"!

...Tiger