After Flying the Quad, I did some more looking around the web and started thinking about tuning the KK2.0 board. This is done by adjusting the PI values, which initially seems like a form of dark art. It wasn’t abundantly clear what these values were until I cam across a piece that identified them as the values used for a PID Controller loop. After reading the page the values I was entering made more sense and some of the advice I had found also became more obvious.
The first step was to change the values and see how it flew. All went well and thanks to the easy menus the values were soon changed. The next few days brought wet and windy weather, so no flying was possible to see if the new values were an improvement or not.
It was at this point that the upgrade parts from HobbyKing finally arrived (have I said before how their shipping isn’t the fastest?). With the benefit of hindsight I should have resisted the temptation to upgrade the frame and flown it to check the new PI values, but I didn’t and so the new ESC was installed and the frame made ready.
In order to use the QBrain ESC, we needed to solder on an XT60 power connector, which was trickier than it looked given the nylon connectors tendency to melt. More than one attempt was required.
The numbering of the QBrain ESC outputs differs from what the KK2.0 board uses, so I had to experiment to get the correct orientation and connections. When ordering I also failed to appreciate how much larger the module was compared with the power distribution and KK boards, meaning the well aligned holes in the top plate were of no use requiring some alternative attachments to be used 🙁
It was dark when the changes were finished but undaunted we went outside and powered it up. All seemed good and my calibrating of the ESC was successfully starting all 4 rotors at the same time. Edging the power brought a couple of surprises.
- There was a clear pulsing between the propellers
- The #2 rotor seemed to be producing noticeably less thrust than the others
After these discoveries I did some headscratching and had a look around the web. The QBrain ESC is still a new product and there wasn’t as much help available as I had found for the Plush models it replaced, but the instructions sheet that came with it showed the default timing was set to Medium, not High. Using the ESC Programming Card I changed the settings and then calibrated the ESC again which seemed to cure the pulsing.
When next flying the quad the #2 rotor seemed to be producing more power, but the addition of the GoPro on top meant the whole frame was unbalanced. I’ll try it again without the GoPro and hopefully that will be better balanced.
With hindsight I made too many changes at once. Given my current lack of experience and knowledge I should have changed one aspect and evaluated the results before changing another. It would have been slower, but that’s not always a bad thing.