Dual rates and Expo on a quadcopter

[Mikeflight]

Hi, I have just started out with quad-copters (multi-rotors). I have been flying fixed wing for a few years and was wondering if I can use dual rates and expo on my quad to smooth out the sensitivity movements on the sticks?

I have built two quads. One is a 450 size and the latest one I have built is a 250 size. The 450 uses the Pixhawk flight board with 950kv emax motors and it fly's pretty smooth and not too twitchy on the sticks. The small 250 has the NAZE32 full and 2204kv emax motors. In the hover it is nice and still and not twitching about, but is very sensitive to stick movements, which for me makes it harder to control. Can I use dual rates and expo to calm down the controls? It may well be me and my flying style. Are these small racing type quads very sensitive and is this just normal for their size? I don't intend to race the 250 one. It's just for fun and general flying. The 250 is stable and fine in hover, no problem with PID settings that I can see. It is the sensitivity with the 250 that annoys me. So will dual rates and expo help?

Sorry for rambling on a bit but just wanted to give as much information as I can. Don't always get the best weather here in Scotland so being new to multirotors I try and fly on the best days available.

Thanks in advance folks.

Mike.

 

[Snarls]

Hey Mike, yea generally miniquads are more squirrely out of the gate because they are so overpowered. You can add dual rates and expo but it will cut down on the resolution of your control. It is better if your receiver gets the full unfiltered command from the transmitter and then to let the flight controller add the expo or rate. On the Pixhawk that is done more through PIDs, but on the Naze you can set rates and expo explicitly in the Cleanflight/Betaflight configurator.

I'm not sure what the most recent Cleanflight/Betaflight look like, but in the PID Tuning tab you should find Roll, Pitch and Yaw Rate, and in the receiver tab you should find RC Rate and RC Expo. You can set RC Rate and RC Expo similarly to what you would do on your transmitter. If you want to tweak Roll, Pitch, and Yaw rate you can but its a bit more tricky. You can read about that here.

 

[Montiey]

Absolutely! That goes without saying. What firmware is the Naze32 Running? Any reputable firmware will allow you to adjust the expo of the controls.In CleanFlight, look for 'RC Expo' in the first couple of tabs.

However, one thing you should note: With any aircraft controlled by on-board software (such as your quad), it's important to not touch the settings on your transmitter. Make sure your switches are on the right channels, etc, but leave rates & expo to the FC to handle. Chopping the resolution on the TX side leaves a very low resolution for the FC to work with, and your controls will feel very choppy- The same goes for exponential rates.

If you want a "normal" and "crazy" mode to choose from your TX, it can be done, but always keep the highest rate at the normal 100%, and try not to reduce the lowest rate down below, say... 30%?... I really don't know exactly...

Per the standard, you have 1000 uSeconds per channel, in 1 uSecond deviations. You can imagine that if you go down to 0.5% rates, you would only have 5 individual positions on the stick to control your craft with, and of course that would be a terrible experience.

Edit: Dangit, Snarls! How do you type so fast?

 

[Mikeflight]

Thank you Snarls for the reply and help

Thanks Snarls.

Yes I can see what you mean. The flight controller software settings make perfect sense. I should have looked at the settings in Cleanflight first. Will be checking this out, and thanks again

All the best,

Mike

 

[Mikeflight]

Thanks Montiea

Thank you to Montiea This helps enormously. You guys rock.

Mike

 

[PsyBorg]

Expos surely are doable on a quad. If anything I say set expo high and work backwards as you learn. 60% range if doing it in the radio and 45% if you do it on the FC to start.

However I have to question use of dual rates. A major portion of tuning a quad is setting the rates BEFORE tuning pids. Rates have a big effect on how pids work. If you start with high rates and tune your quad and then suddenly swap to low rates you have essentially made it seem like you are flying with too high pids and could potentially put your quad into a bad flying state like the toilet bowl effect when you first start a build and have too high pids on the maiden.

I am not saying this will definitely happen but depending on how tight you tune your pids the potential is there for a bad experience.