Multirotor loops and rolls just got easier with OpenPilot
With the latest release of the OpenPilot software version 14.01 come two new features (among others) that when combined, make flipping and rolling a multirotor (MR) even easier. A new flight mode called "Rattitude" is a hybrid of the self levelling "Attitude" and the more aerobatic 'Rate' mode. In "Rattitude" mode as the control stick on the transmitter moves out from the centre, the flight mode of the craft changes from 100% Attitude through to 100% Rate with varying degree of mixture in between. The effect means that letting go of the sticks means the MR will return to self levelling (ie Attitude mode) but you can still throw it around as the control sticks move out from centre, you get the aerobatic response of Rate mode.
Normally you would have to flick a switch to go from Attitude to Rate. In Attitude mode, because it's always trying to self level, to maintain forward flight you have to constantly be holding the stick forward. It feels like you're fighting it to a degree for the whole flight. Also Attitude mode limits the maximum angle of pitch and roll so if you try to roll in Attitude mode, you'll roll to the angle defined as the maximum and not go any further around.
In Rate mode, it goes where you point it. If you roll to 45 degrees, the MR will attempt to hold that angle until you tell it otherwise. Rate mode can be intimidating for the novice pilot as the safety net of self levelling is removed and depending on the settings, Rate mode can fill quite 'slippery' if you're not used to it.
The other new feature in 14.01 is Cruise Control which from my limited reading of the topic attempts to maintain a steady altitude when the MR is turning or banking by slightly increasing the rpm to counter the slight decrease in lift). With Cruise Control comes a 'Max Angle' parameter that when set to 90 degrees, combined with Rattitude mode, means that as the MR rolls past 90 degrees, it automatically spins down the motors. That means the part of the roll when the MR is passing through the inverted (ie the props would normally be pulling it to the ground), the motors are automatically shut down which seems to make for a much tighter roll.
From personal experience I went from rolling and flipping with at least 10m height to doing the same at maybe head height. The first time I tried this combination it was quite weird to hear the motors shut down as it passed through the 90 degree vertical point but they came back up a few milliseconds later. Posts in the OpenPilot forum suggest that setting the Cruise Control Max Angle (CCMA) to 80 degrees and the degrees / second to 360 make for some nice smooth rolls.
The screenshots below show captures from the OPenPilot GCS software version 14.01 and the settings required to change to get this to work. I first tried it on my "beater" quad with a CC3D flight controller and liked it so much I put it on my "nice" quad with a Revo FC and Ov3rquad frame. The video below shows the results from these settings on both my CC3D and Revo controlled quads with CCMA set to 90 degrees and the Rate mode "Degrees / second" setting up at around 450-500.
The next thing I want to try is lowering the CCMA to 80 and deg/sec to 360 for the nice, "natural" roll and then go the other way to CCMA = 100 and deg/sec =720. Maybe with these settings I might get in a few double or triple rolls before hitting the ground.
